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  • richardmitnick 8:01 am on September 6, 2019 Permalink | Reply
    Tags: "Forecasting Solar Storms in Real Time", AGU, CME Scoreboard, , , ,   

    From Eos: “Forecasting Solar Storms in Real Time” 

    From AGU
    Eos news bloc

    From Eos

    30 August 2019
    Jenessa Duncombe

    Predicting when solar storms will hit Earth remains a tricky business. To help, scientists can now submit their forecasts of coronal mass ejections online as they unfold in real time.

    A coronal mass ejection (CME) blasts off from the Sun in these coronagraphs captured on 27 February 2000 by the Solar and Heliospheric Observatory spacecraft. Credit: SOHO ESA & NASA


    The Sun routinely ejects clouds of gas and sends them hurtling through space at several thousand kilometers per hour. At least a few dozen times a year, those clouds head straight for Earth.

    These natural events, called coronal mass ejections (CMEs), crop up when the Sun’s magnetic field becomes tangled and, in righting itself, releases a swarm of charged particles called superheated plasma. Sent at just the right angle toward Earth, these plasma clouds can wreak havoc on our electrical grids, satellites, and oil and gas pipelines.

    Quebec, Canada, for instance, experienced a blackout related to a solar storm on a winter night in 1989. The province went black after a solar storm sent an electric charge into the ground that shorted the electrical power grid. The outage lasted 12 hours, stranding people in elevators and pedestrian tunnels and closing down airports, schools, and businesses.

    Solar storms can threaten our communication and navigation infrastructure. In the past, solar storms interrupted telegraph messages, and future storms could threaten our cellphones, GPS capabilities, and spacecraft.

    With the right kind of warning, utility operators, space crews, and communications personnel can prepare and steer clear of certain activities during solar storms. But once a CME event is spotted leaving the Sun, our best models struggle to forecast when exactly it will arrive.

    To improve forecasts, a group of scientists is taking a community approach: What if researchers working on CME models around the world could post their forecasts publicly, in real time, before the CME reaches Earth?

    The CME Scoreboard, run by the Community Coordinated Modeling Center at NASA Goddard Space Flight Center, does just that. The online portal with 159 registered users acts as a live feed of CME predictions heading for Earth. The portal gives scientists a simple way to compare forecasts, and the log of past predictions presents a valuable data set to assess forecasters’ accuracy and precision.

    Keeping Score

    The AGU Grand Challenges Centennial Collection features the major questions faced by science today. Editors of Space Weather identified CME predictions as one of them, calling the ability to provide them “essential for our society [Space Weather].”

    CME forecasting still lags behind our capabilities to forecast weather systems here on Earth, and the paper highlights several reasons why. Leila Mays, coauthor on the paper and science lead for the CME Scoreboard at NASA Goddard Space Flight Center, said that CME forecasts are lacking in two key areas: Measurements of solar activity are sparse, and the exact physical details driving the Sun are still unclear.

    Despite the need for improvement, people on Earth still rely on CME forecasts, and scientists have myriad ways to supply them. The National Oceanic and Atmospheric Administration and the United Kingdom’s Met Office both release publicly available CME predictions, and individual research groups build their models from scratch. Forecasting models range from data-driven empirical models to physics-based, equation-driven models.

    The models operate independently, perhaps using unique parameters or data inputs, but they all strive for a shared goal: to determine when a CME, or CME’s shock wave, will impact Earth.

    The CME Scoreboard serves as a repository for a wide range of these models. Mays said that scientists tracking solar activity will notice when a CME event explodes from the surface of the Sun, setting down a ticking clock for when the plasma will hit Earth (or miss it altogether). This sets off a flurry of activity, with scientists running their models with parameters from the most recent eruption, including the plasma’s speed, direction, and size. With the numbers crunched, they post their best guess and wait to see what unfolds.

    Ground Truth

    Since the CME Scoreboard’s inception in 2013, scientists have posted 814 arrival time predictions. Some predictions narrowly miss the mark, skirting the real arrival time of the CME by a mere hour or two. But others are days away, trailing the arrival by 30 or more hours.

    Mays said that the forecasts come from over a hundred users and represent 26 unique prediction methods. She said that the interest in the portal has been strong, which she’s not surprised about. The scoreboard merely gives a platform for ad hoc discussions that researchers were already having, spread across listservs and email chains whenever a new CME would appear.

    Pete Riley, a senior research scientist at Predictive Science Inc., knew of the scoreboard but had never contributed. Looking at years of forecasts on the website, he decided to analyze the accuracy and precision of past predictions.

    “I felt like having knowledge in the field but not having a horse in the race, so to speak, I’d be able to do a fairly independent evaluation,” Riley told Eos.

    His study, published in Space Weather in 2018, is the first analysis of the scoreboard data. Riley and his collaborators compared the difference between the projected arrival times and the actual reported times for 32 models. The analysis showed that the forecasts, on average, predicted the CME arrival with a 10-hour error, and they had a standard deviation of 20 hours. Several models performed the best, he said, but only moderately so, and the few that submitted regularly over the 6 years of data analyzed didn’t seem to be improving their forecasts.

    The paper “serves as kind of a ground truth for where we are at currently,” Riley said, as well as laying the foundation for future analysis. Riley made the code accessible so that future forecasts can be tested against the group. Mays said that in the future, the scoreboard may use the information to create a list of automatically updating metrics.

    Although more work lies ahead, Riley said that the future looks bright for more accurate predictions. He points to new space missions that will help fill in blind spots, including NASA’s Parker Solar Probe and nanosatellites called CubeSats that individual research groups deploy.

    NASA Parker Solar Probe Plus named to honor Pioneering Physicist Eugene Parker

    “Space weather is becoming ever more important because as a society, we are so reliant on technology now,” Riley said. With the additional data, he said, “I think it’s promising that in the future we will be able to make predictions more accurate.”

    See the full article here .


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    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 10:57 am on August 28, 2019 Permalink | Reply
    Tags: AGU, Anemic Stars", , , , ,   

    From Eos: “Hunting for Planets Around Old, Anemic Stars” 

    Eos news bloc

    From Eos

    Kimberly M. S. Cartier

    The planetary system depicted here, Kepler-444, formed more than 6 billion years before our Sun was born. Credit: NASA, Tiago Campante/Peter Devine

    The first stars were made of hydrogen and helium. That hasn’t really changed, but each subsequent generation of stars has a bigger fraction of heavy elements like carbon, oxygen, silicon, and iron—elements needed to make planets.

    Heavy elements make up only about 1.3% of the Sun’s mass. Astronomers call these elements metals and abbreviate their abundance with the atomic symbol for iron. Even at that low percentage, the Sun still had enough material to form eight planets, dozens of dwarf planets, and an uncounted number of smaller objects.

    But how low can a star’s metallicity go and still form planets? To answer that question, Ji Wang and his team are turning to the oldest stars in the galaxy: galactic halo stars.

    “Halo stars are the key to understanding planet formation in the very metal-poor regime,” said Wang, an astrophysicist at Ohio State University in Columbus. Wang discussed this project at Extreme Solar Systems IV in Reykjavík, Iceland, on 19 August.

    Hiding in the Halo

    Most stars in the Milky Way galaxy live in one of three places: a compact central bulge, a dense and thin spiral disk, or a diffuse cloudlike halo.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Sometimes, halo stars plunge through the disk at high speeds and from random directions, like a comet streaking in from the cold reaches of the solar system before swooping outward again.

    Those trajectories make halo stars stand out in surveys of stellar motion, like the European Space Agency’s Gaia mission. Halo stars also tend to be older and therefore more chemically primitive than disk stars.

    Wang’s team turned to halo stars to find out how often low-metallicity stars create planets. Of Gaia’s catalog of 1.7 billion stars, the researchers narrowed their search to stars with halolike trajectories that are within about 3,000 light years of us and have less than 10% the amount of metals as the Sun. They narrowed that list to stars bright enough for NASA’s Transiting Exoplanet Survey Satellite (TESS) to observe with high precision.

    NASA/MIT TESS replaced Kepler in search for exoplanets

    During the first half of its mission, TESS searched for planets around about 6,200 of the team’s chemically primitive target stars. The researchers focused on large, short-period objects called hot Jupiters, the type of planet most likely to transit.

    “We didn’t find any planets,” Wang said. “This is okay because, even for the nondetection, we have put a very tight constraint on the occurrence rate around metal-poor stars.”

    The team’s tests showed that TESS could have overlooked roughly half of potential hot Jupiters around these distant stars. On the basis of those statistics, the team calculated that hot Jupiters are born around metal-poor halo stars no more than 0.34% of the time.

    Is It Age or Lack of Metals?

    “This is really cool work. I think it’s a great idea,” Kevin Schlaufman, an astronomer at Johns Hopkins University in Baltimore, Md., commented after the presentation. He pointed out, however, that some recent studies suggest that tidal interactions can make hot Jupiters crash into their stars. “If hot Jupiters are destroyed by tides, it might be the case that old stars, regardless of their metallicity, are unlikely to have a hot Jupiter.”

    One way to resolve that issue, according to Wang, would be to look for metal-poor stars among the younger disk stars. But this would be like looking for a handful of needles in a haystack: Disk stars far outnumber halo stars, and they are mostly metal rich. Finding the few metal-poor stars would be a big task, he said.

    The team estimates that TESS will observe about another 10,000 metal-poor halo stars by the end of next year, which will narrow down how often anemic stars create giant planets, Wang said.

    “With the full sample, we could set a 0.14% upper limit if there are still zero detections,” he said.

    In the meantime, “we can still look for small planets, although with a lower detection efficiency,” Wang said. “There are still a few planets we could detect around these halo stars.”

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 9:35 am on August 20, 2019 Permalink | Reply
    Tags: "Sampling the Space Between the Stars", AGU, ENAs-energetic neutral atoms, , , Heliosheath, , , ,   

    From Eos: “Sampling the Space Between the Stars” 

    From AGU
    Eos news bloc

    From Eos

    19 August 2019
    Mark Zastrow

    Data from the Cassini and Voyager spacecraft reveal new information about the Sun’s magnetic bubble.

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    NASA/Voyager 1

    NASA/Voyager 2

    The basic shape and properties of the heliosphere, the protective magnetic bubble created by the solar wind, shown in this schematic are based on measurements of heliosheath proton distributions from Voyager 1 and 2 (illustrated in the diagram) and of energetic neutral atoms by Cassini. The location of the inner edge of the heliosheath, called the termination shock, is roughly 10 astronomical units (AU; 1 AU is equivalent to the mean Sun-Earth distance of about 150 million kilometers) farther from the Sun where Voyager 1 crossed it compared with Voyager 2, but the location of the outer edge, the heliopause, is about the same distance at along both Voyager trajectories. Red arrows represent the interstellar plasma flow deflected around the heliosphere bubble. Credit: K. Dialynas, S. M. Krimigis, D. G. Mitchell, R. B. Decker and E. C. Roelof

    Charged particles that spew into space as part of the solar wind create a protective magnetic bubble tens of billions of kilometers wide around the solar system. This bubble, called the heliosphere, plows through the harsh cosmic radiation of interstellar space.

    Understanding the physics at the bubble’s edge, called the heliosheath, is not easy. The boundary is in constant flux and pushes out against the broader interstellar magnetic field that permeates our corner of the Milky Way. Only two spacecraft—Voyager 1 and 2, originally launched by NASA in 1977—have ever traversed the frontiers of our local bubble.

    Now Dialynas et al. [Geophysical Research Letters] have combined Voyager data with observations from NASA’s Cassini mission, which orbited Saturn from 2004 to 2017, to gain more insight into this region of space. The researchers recognized that the missions, although launched 20 years apart, had collected complementary data. Voyager 1 and 2 had instruments that measured energetic ions as the craft crossed the heliosheath and exited the solar system. Cassini, meanwhile, was able to remotely observe energetic neutral atoms (ENAs) arriving in all directions from the heliosheath.

    These two phenomena are related: ENAs come from the heliosheath, where fast solar wind protons collide with neutral hydrogen atoms from interstellar space and “steal” an electron from the interlopers. The Voyager probes took in situ measurements of the parent heliosheath proton distributions as they passed through this region. Meanwhile, the protons with newly added electrons become ENAs and zip off in all directions.

    The synergy among the spacecrafts’ observations allowed the researchers to use Voyager data from the heliosheath to ground truth and calibrate ENA data from Cassini, which was more sensitive to lower energetic particles than Voyager was. Together, the spacecraft extended data on the intensity of both ENAs and ions to include a broader range of energies, which gave the team a window into the physics in the heliosheath as the solar wind and interstellar medium press against each other.

    The researchers found that in the energy range considered in their study (>5 kiloelectron volts), lower-energy ions with energies between about 5 and 24 kiloelectron volts played the largest role in maintaining the pressure balance inside the heliosheath. This allowed the team to calculate the strength of the magnetic field and the density of neutral hydrogen atoms in interstellar space—about 0.5 nanotesla and 0.12 per cubic centimeter, respectively.

    On the basis of calculations from Voyager 2 data, the researchers predict that the heliopause, the outer boundary of the heliosheath, is located roughly 18 billion kilometers from the Sun, or 119 times the distance from the Sun to the Earth—right where Voyager 2 found it in November 2018.

    Furthermore, the finding that the lower-energy ions dominate the pressure balance in the heliosheath means that space physicists will have to rethink their assumptions about the energy distribution of such particles in the heliosheath.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 10:41 am on July 17, 2019 Permalink | Reply
    Tags: AGU, , , , , , ,   

    From Eos: “The Cassini Mission May Be Over, but New Discoveries Abound” 

    Eos news bloc

    From Eos

    Sarah Derouin

    NASA/ESA/ASI Cassini-Huygens Spacecraft

    New analysis of high-resolution images shows ring textures and disruptions within Saturn’s rings in unprecedented detail.

    The embedded moon Daphnis creates three waves in Saturn’s rings in this image taken by the spacecraft Cassini during its grand finale. Credit: NASA/JPL-Caltech /Space Science Institute
    After more than a decade observing Saturn, Cassini completed its mission in style—a grand finale sent the spacecraft on almost 2 dozen dives between the planet and the rings before it took its final descent into Saturn’s atmosphere.

    During these ring-grazing trips during summer 2017, Cassini collected high spatial resolution images and spectral and temperature scans of the rings. Years after its crash, researchers are still working with the piles of data Cassini collected, making new discoveries about the ringed planet.

    In a new paper in Science, researchers dove into these high-resolution data, and their synthesis revealed new features inside the rings that hadn’t been seen before. They found sculpted areas within the rings—including banded textures and disturbances from embedded bodies—that can be used to help theorists narrow in on how Saturn and its rings may have formed.

    Ring Disruptions

    During the grand finale, Cassini took high-resolution images of all the rings, from the ring closest to the planet (ring A) to the F ring, one of the most distant. The images are the highest-fidelity images ever to be taken of the rings, and they revealed some surprises to the research team.

    “We found a number of things that are new—a number of structures that we’d never been close enough to see before,” says Matthew Tiscareno, a senior research scientist at the SETI Institute in Mountain View, Calif., and lead author of the paper.

    The team explored disturbances within the rings related to moons or smaller moonlike debris embedded in the rings. The moon Daphnis, for example, leaves a wide trail of disruption in its wake, including a wide gap in the ring and trailing waves of debris.

    These waves, Tiscareno explains, are created by the rings moving at different speeds: The rings orbiting closer to Saturn move at a faster speed than those farther from the planet. This process creates a sheer flow, and “on the outward edge, the ring part, the ring material is falling behind Daphnis and its orbit,” he says.

    This propeller, informally called Bleriot, formed within Saturn’s rings. Propellers are caused by a central moonlet that alters the ring as it orbits around the planet. Credit: NASA/JPL-Caltech/Space Science Institute

    But it’s not just big moons like Daphnis that disrupt the rings. Smaller objects are trying their best to create ring gaps as well, but with less success. “These are objects that are 10 times smaller, which means they’re a thousand times less massive,” says Tiscareno.

    Instead of forming a gap, Tiscareno says these objects form a propeller-shaped disturbance. The swirled structure forms briefly but doesn’t stick around long enough to create a true gap in the ring.

    The researchers knew the propellers existed, so they asked Cassini to perform some targeted flybys to get a closer look.

    “The details of that [propeller] structure [are] telling us exactly how big the moons are at the center of the propeller…about a kilometer across,” says Tiscareno, adding that at that size, it’s not possible to see the actual moon with these image resolutions.

    Ring Textures

    Cassini’s instruments also revealed new details on textures within the rings. “We knew that there were textures before, but we had not seen them as comprehensively,” says Tiscareno. The team noted that the ring textures ranged from strawlike clumps to feathery regions, with sharp edges on their borders.

    One idea for the different textures within the rings is a changing particle composition, says Douglas Hamilton, an astronomer at the University of Maryland who was not involved with the paper. For example, one part of the ring could be more silicate rich, whereas another area has more ice. But Hamilton says the researchers “make a good case” for these textures being caused by something other than composition.

    The team inferred that the sharp borders along the ring textures were not due to a composition change, says Tiscareno, but instead result from the physical properties of the ring particles.

    One physical property might be the roughness of ring particles. Tiscareno explains: Is a ring particle more like a billiard ball or more like a snowball? Roughness can affect not only the reflection of light but also how particles interact with each other. “Do they bounce off of each other, like billiard balls do?” he asks. “Or are they kind of sticky, like a snowball would be?”

    Forming a Ring

    Getting close-up data from Cassini gives researchers information that reaches beyond our nearby ringed planet.

    “Rings are our only natural laboratory to understand disk processes more generally,” says Tiscareno. “And that goes to understanding baby solar systems, which are disk systems where you have massive objects that are embedded in the disk.”

    “We’re seeing massive objects embedded in the rings, and we’re seeing the disk itself doing things that we didn’t expect,” he adds.

    Hamilton says that papers like this help uncover how features like propellers might form. “The theory is our imagination,” Hamilton says. Work like this paper, he adds, allows theoretical researchers to be able to test their models on Saturn’s rings against observed data.

    “[These data are going] to be the basis for 10 years of effort by the entire field in trying to figure out how to make all this [propellers, textures] happen,” says Hamilton.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 8:52 am on July 15, 2019 Permalink | Reply
    Tags: "Seismic Sensors Probe Lipari’s Underground Plumbing", AGU, , ,   

    From Eos: “Seismic Sensors Probe Lipari’s Underground Plumbing” 

    Eos news bloc

    From Eos

    Francesca Di Luccio
    Patricia Persaud
    Luigi Cucci
    Alessandra Esposito
    Guido Ventura
    Robert W. Clayton

    An international team of scientists installed a novel, dense network of 48 seismic sensors on the island of Lipari to investigate the active magma system underground.

    The magma system underneath the island of Lipari, shown here, is connected to a regional fault system formed by tectonic activity rather than to volcanoes like nearby Etna and Stromboli. A research team recently deployed a dense network of seismic sensors to investigate Lipari’s unusual setting. Credit: F. Di Luccio

    Just north of the island of Sicily, near the toe of Italy’s “boot,” a chain of volcanic islands traces a delicate arc in the Mediterranean Sea. This chain, the Aeolian Islands, hosts popular tourist resorts in proximity to some of Earth’s most active and well-known volcanoes, including Etna and Stromboli. Lipari, the largest of these islands, lies just north of the island of Vulcano, for which these eruptive features are named. Lipari is less well characterized than some of the other nearby volcanoes, but one research group is setting out to change this.

    Lipari is located ~80 kilometers north of the well-monitored Etna volcano. The island’s hydrothermal system, in which magma heats the water underground, is not connected to eruptive centers, but, rather, is connected to the regional fault system that delimits the western boundary of the active Ionian subduction zone.

    Lipari holds a unique place in our understanding of the tectonic evolution and hydrothermal activity of volcanoes emplaced in subduction zones. Within the framework of the ring-shaped Aeolian arc, the unexpected NNW–SSE alignment of Lipari and Vulcano has been related to a major regional discontinuity, the Tindari-Letojanni subduction transform edge propagator (STEP) fault, a tear in a tectonic plate that allows one part of the plate to plunge downward while an adjacent part remains on the surface (Figure 1).

    Fig. 1. These tectonic and bathymetric maps show (a) southern Italy and (b) the Aeolian Islands. The bathymetric data are from Ryan et al. [2009]. Major faults are shown as black lines. Regional earthquakes larger than magnitude 3 (black dots) were recorded over the past 3 decades by the permanent Italian seismic network (magenta triangles). Events larger than M 3 that occurred in the time window of the current experiment are shown as cyan stars. The yellow star off the northeastern coast of Sicily shows the location of the 1 November 2018 ML 3.2 earthquake whose waveforms are shown in the left-hand plot of Figure 3. In Figure 1a, blue dashed lines in the Tyrrhenian Sea indicate the isodepths (50, 100, 200, and 300 kilometers) of the slab [Barreca et al., 2014]. Shown in Figure 1b are the locations of Lipari, the Sisifo-Alicudi fault (SAf), and the Tindari-Letojanni STEP fault (STEP-TLf).

    One innovative way to monitor the deep and shallow dynamics of magmatic systems is to deploy dense arrays of seismic sensors over active volcanoes [Hansen and Schmandt, 2015; Ward and Lin, 2017; Farrell et al., 2018]. Thus, to understand Lipari’s unusual setting, we deployed a dense array comprising 48 wireless, self-contained seismic instruments. This is the first time that a dense seismic array has been deployed to investigate a hydrothermal system in the volcanically active Aeolian Islands and the volcanism in the proximity of a STEP fault.

    Transporting the seismic sensors, called nodes, to Lipari required a transatlantic shipment from Louisiana State University (LSU) to Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome, followed by a ferry trip to Lipari. Over the course of 2 days, two crews of two people each placed 48 instruments, spaced ~0.1–1.5 kilometers apart, in a wide variety of locales: with homeowners and hotel owners, at the Lipari observatory, on the sides of streets, and buried in the near surface beneath a few centimeters of soil (Figure 2).

    Fig. 2. Three-dimensional perspective view of a Google Earth map of Lipari Island, which covers an area of about 35 square kilometers. The last eruption on this island was in 1220 CE at Monte Pilato. The locations of the ZLand three-component seismic nodes are shown as yellow triangles. A magenta triangle indicates broadband station ILLI of the Italian permanent seismic network. Site photos taken at selected locations are also shown. The inset shows a detailed map of the hydrothermal area (modified from Cucci et al. [2017]) and the locations of photos A, B, and C, which characterize the hydrothermal alteration.

    Researchers from INGV in Rome, the Department of Geology and Geophysics at LSU, and the Seismological Laboratory of the California Institute of Technology deployed the 48 FairfieldNodal ZLand three-component nodes, which have a 5-hertz corner frequency. The nodes recorded one data point every 4 milliseconds from 16 October to 14 November 2018.

    After their transatlantic voyage from Louisiana to Rome, seismic sensors await a ferry trip to Lipari. Credit: A. Esposito

    Lipari’s Tectonic Neighborhood

    Lipari Island belongs to the Aeolian archipelago, a group of subaerial and submarine volcanoes located in southern Italy between the southern Tyrrhenian Sea back-arc basin and the Calabrian Arc, an orogenic belt affected by late Quaternary extensional tectonics. The NNW–SSE Lipari-Vulcano alignment (Figure 1) coincides with the regional tectonic boundary of the Ionian Sea–Calabrian Arc subduction system that is marked by the Tindari-Letojanni STEP fault [Barreca et al., 2014].

    To the west of the archipelago, the WNW–ESE oriented Sisifo-Alicudi fault accommodates shortening related to the eastern termination of the contractional belt (Figure 1). The Tindari-Letojanni and Sisifo-Alicudi fault systems are characterized by shallow seismicity, at depths of less than 25 kilometers, and recorded earthquakes of M 5.8 or less, including the M 4.7 Ferruzzano earthquake in 1978 [Gasparini et al., 1982].

    The Aeolian volcanoes, emplaced on 15- to 20-kilometer-thick continental crust, are the most recent evidence of the magmatism that started during the Pliocene epoch (5.3–2.6 million years ago). This magmatism started in the central sectors of the Tyrrhenian Sea and migrated southeastward toward the Calabrian Arc.

    From about 1 million years ago to the present time, the volcanoes have been producing magma with calc-alkaline, shoshonitic, and alkaline potassic compositions [De Astis et al., 2003; Barreca et al., 2014]. The geochemical affinity of these rocks and the deep seismicity (reaching depths of 550 kilometers) in the southern Tyrrhenian Sea indicate that the Aeolian Islands represent a volcanic arc related to the subduction and rollback of the Ionian slab beneath the Calabrian Arc [Milano et al., 1994; De Astis et al., 2003].

    Early volcanic activity at Lipari ejected lava and rocks into the air, but today, geothermally heated water is more common. Credit: L. Cucci

    Early volcanic activity on Lipari (150,000 years ago and earlier) was concentrated in the western part of the island and focused along north–south aligned vents. Later on, between 119,000 and 81,000 years ago, the Sant’Angelo and Monte Chirica volcanoes deposited lava and pyroclastics (volcanic material that is forcibly ejected into the air) in the central sector of the island (Figure 2).

    From 42,000 years ago to 1220 CE, the activity was concentrated in the southern and northern sectors. This activity included pyroclastics related to subplinian eruptions, domes, and lava flows. Currently, hydrothermal activity (the expulsion of geothermally heated water) characterizes Lipari, Vulcano, and areas offshore of Panarea and Salina. The Lipari hydrothermal field (approximately 0.5 × 0.15 kilometer; see inset in Figure 2) is located along a north–south striking alteration belt in the western and older sector of the island and is characterized by gypsum-filled veins, normal faults with a prevailing NNW–SSE to north–south strike, and active fumaroles.

    Hydrothermalism on Lipari is not associated with centers of recent volcanic activity (less than 40,000 years old), and fluid pathways are strictly controlled by faults and fractures [Cucci et al., 2017]. Vein networks of gypsum (a type of sulfur mineral) affect the hydrothermal system in the lavas and scorias of the oldest Timponi volcanoes, the overlying pyroclastics of Monte Sant’Angelo, the 27,000-year-old Pianoconte pyroclastic deposits, and the present-day soil (inset in Figure 2). The hydrothermal alteration process has been going on for less than 27,000 years and is still active [Cucci et al., 2017].

    A Mountain of Data

    Fig. 3. Seismograms from two earthquakes at local (left) and regional (right) distances recorded at the Lipari array. Vertical components of the ground velocity are low-pass filtered at 5 and 2 hertz for the ML 3.2 and MW 6.8 magnitude events, respectively, to improve the signal-to-noise ratio. Waveforms at the bottom of each plot are the seismograms of the two events recorded by the permanent broadband seismic station ILLI located on the southern tip of Lipari, as shown in Figure 1b, with numbers in bottom left corners indicating the epicentral distances.

    We collected more than 300 gigabytes of data, which include local, regional, and teleseismic (distant) earthquakes as well as ambient noise and volcanic tremor data. During the period of the experiment, about 50 earthquakes occurred within 100 kilometers of Lipari. Half of these had magnitudes of less than 2, but we also recorded 18 events larger than M 5 that occurred in the region and farther away. In Figure 3, we show two examples of recorded seismic waveforms from an ML 3.2 local earthquake and an Mw 6.8 regional earthquake.

    We aim to investigate in detail the crust and upper mantle beneath Lipari Island using receiver functions to characterize Earth’s structural response near the instrument and regional tomography to construct a three-dimensional image of Earth’s nearby interior. We will also analyze ambient noise and local volcanic tremors.

    We plan to merge the seismic data set with other observables such as geochemical measurements and structural data to get a more robust and complete picture of the tectonic setting. We will apply modern and sophisticated processing and analysis techniques used in seismological studies to the nodal seismic array data.

    The deployment of nodal arrays fills a unique niche in monitoring active volcanoes. In comparison to traditional portable seismic stations, nodal arrays enable a high-quality data set to be obtained over a short deployment period, at lower costs, with easier site selection capabilities, and with easy and quick installation procedures.

    Our collaborative field experiment is the latest vehicle for learning about the seismic structure of Lipari and an excellent approach to linking the unrest at depth to volcanic and hydrothermal activity at the surface in similar settings. This project will contribute to the evaluation of the geohazards of the Mediterranean region, where the African and Eurasian plates converge.


    We thank Comune di Lipari for hosting the experiment and INGV Catania and Lipari Observatory (L. Pruiti) for the logistical support. We are grateful to R. Vilardo and M. Martinelli of the Polo Museale di Lipari, Regione Sicilia; the Hotel Antea; Co.Mark and Tenuta Castellaro; and Alessandro (a grocery store) in Acquacalda for hosting some nodes of the experiment. We thank INGV Roma 1 for funding and supporting the project and the Department of Geology and Geophysics at LSU for supporting this project. A.E. was funded by INGV Osservatorio Nazionale Terremoti (ONT). LSU students R. Ajala and E. McCullison assisted with the deployment setup and preparation of the nodes. Data will be available in November 2020 (2 years after the last instrument was retrieved from the field) by contacting the corresponding author.

    Barreca, G., et al. (2014), New insights in the geodynamics of the Lipari–Vulcano area (Aeolian Archipelago, southern Italy) from geological, geodetic and seismological data, J. Geodyn., 82, 150–167, https://doi.org/10.1016/j.jog.2014.07.003.

    Cucci, L., et al. (2017), Vein networks in hydrothermal systems provide constraints for the monitoring of active volcanoes, Sci. Rep., 7, 46, https://doi.org/10.1038/s41598-017-00230-8.

    De Astis, G., G. Ventura, and G. Vilardo (2003), Geodynamic significance of the Aeolian volcanism (southern Tyrrhenian Sea, Italy) in light of structural, seismological, and geochemical data, Tectonics, 22(4), 1040, https://doi.org/10.1029/2003TC001506.

    Farrell, J., et al. (2018), Seismic monitoring of the 2018 Kilauea eruption using a temporary dense geophone array, Abstract V41B-07 presented at 2018 Fall Meeting, AGU, Washington, D.C., 10–14 Dec.

    Gasparini, G., et al. (1982), Seismotectonics of the Calabrian Arc, Tectonophysics, 84, 267–286, https://doi.org/10.1016/0040-1951(82)90163-9.

    Hansen, S. M., and B. Schmandt (2015), Automated detection and location of microseismicity at Mount St. Helens with a large-N geophone array, Geophys. Res. Lett., 42, 7,390–7,397, https://doi.org/10.1002/2015GL064848.

    Milano, G., G. Vilardo, and G. Luongo (1994), Continental collision and basin opening in southern Italy: A new plate subduction in the Tyrrhenian Sea?, Tectonophysics, 230, 249–264, https://doi.org/10.1016/0040-1951(94)90139-2.

    Ryan, W. B. F., et al. (2009), Global Multi-Resolution Topography synthesis, Geochem. Geophys. Geosyst., 10, Q03014, https://doi.org/10.1029/2008GC002332.

    Ward, K. M., and F.-C. Lin (2017), On the viability of using autonomous three-component nodal geophones to calculate teleseismic Ps receiver functions with an application to Old Faithful, Yellowstone, Seismol. Res. Lett., 88(5), 1,268–1,278, https://doi.org/10.1785/0220170051.

    See the full article here .


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  • richardmitnick 8:25 am on July 15, 2019 Permalink | Reply
    Tags: "Teams Invited to Test Coastal Hyperspectral Imaging Algorithms", AGU, , ,   

    From Eos: “Teams Invited to Test Coastal Hyperspectral Imaging Algorithms” 

    Eos news bloc

    From Eos

    Margaret A. McManus

    Eric Hochberg

    Hyperspectral Remote Sensing of Coastal and Inland Waters Webinar; 28 May 2019

    Hyperspectral imagery collected by NASA’s Coral Reef Airborne Laboratory (CORAL) shows part of Swain Reefs off the eastern coast of Australia. Participants in a webinar last May planned an upcoming technology demonstration of hyperspectral remote sensing algorithms applied to coastal and inland waters. Credit: Eric Hochberg

    Satellite remote sensing using a few discrete wave bands of light, selected to fit the specific application (multispectral imaging), is a well-established means of monitoring the world’s open oceans. Coastal and inland waters are often much more complex, and the methods used to study these waters are more complex as well. These waters have greater sediment and algal loads than the open oceans, and light can reflect off the bottoms of these shallower water bodies, which complicates data analysis.

    Remote sensing of coastal and inland environments requires hyperspectral imaging—simultaneously measuring tens to hundreds of narrow, contiguous wave bands (typically visible through near infrared)—to disentangle multiple confounding signals. Efficient manipulation of large hyperspectral image data volumes, as well as subsequent generation of meaningful and accurate data products, requires sophisticated algorithms, which continue to evolve and improve.

    In May 2018, participants in the Hyperspectral Imaging of Coastal Waters workshop, sponsored by the Alliance for Coastal Technologies (ACT) and the National Oceanic and Atmospheric Administration (NOAA), recommended a technology demonstration of hyperspectral remote sensing algorithms applied to coastal and inland waters. In May 2019, ACT followed up with an introductory webinar to plan the demonstration.

    Thirty-seven individuals participated in the webinar, representing academic and government research institutions, as well as technology developers from around the globe. There were representatives from ACT, seven members of a technical advisory committee established for this demonstration, four individuals and teams already registered to participate in the demonstration, and seven prospective individuals and teams.

    NOAA established ACT in 2001 to bring about fundamental changes in environmental technology innovation and research and in operations practices. ACT achieves its goal through specific technology transition efforts involving both emerging and commercial technologies. Its efforts include the explicit involvement of resource managers, small- and medium-sized firms, world-class marine science institutions, NOAA, and other federal agencies. ACT’s core efforts are as follows:

    technology evaluations for independent verification and validation of technologies
    technology workshops and webinars for capacity and consensus building and networking
    technology information clearinghouses, including an online technologies database

    For the hyperspectral technology demonstration, ACT is inviting individuals and teams with established processing routines and algorithms to work with highly described hyperspectral data sets and corresponding in situ validation data sets. The goal of the demonstration is to evaluate the capabilities and maturities of various algorithms. This exercise is not a research project; rather, it is an opportunity to enhance communication within the community and to advance future applications of hyperspectral remote sensing in coastal waters.

    Three views of the Torres Strait, between Australia and Papua New Guinea, from the CORAL mission illustrate an example of applied hyperspectral data: pseudotrue color image of 12 flightlines were acquired by the Portable Remote Imaging Spectrometer (PRISM) on 12 October 2016 (left); the results of CORAL data processing estimate the probabilities that image pixels are dominated by coral, algae, or sand (middle); and a map of the percentages of coral-dominated pixels in 1 × 1 kilometer grid cells, which enables researchers to fulfill CORAL’s science objective of investigating reef condition in relation to large-scale biogeophysical forcings (right). PRISM data collected for CORAL are freely downloadable.

    Data sets being used in the hyperspectral algorithm technology demonstration characterize kelp forests, coral reefs, harmful algal blooms (including those in inland waters), sea grass, and water quality. It is not required that all individuals and teams work with all data sets. Individuals and teams will select the data sets they are most familiar with, and they are welcome to work with more than one data set or contribute additional data sets that will be made available to all demonstration participants.

    The resulting data products are useful to scientists developing a greater understanding of these natural systems, as well as to resource managers tasked with conservation and decision-making. The data products also support future hyperspectral missions such as NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) and Surface Biology and Geology (SBG).

    The hyperspectral algorithm technology demonstration will be conducted over a 4- to 6-month time frame. The original request for technology was released 20 March 2019. The deadline for individuals and teams to register to participate is 31 August 2019.

    ACT anticipates an additional webinar or in-person workshop in fall 2019. Technology demonstration results will then be shared in a final workshop at the University of Hawai‘i at Mānoa in winter 2020. The overarching goal of the demonstration includes publishing individual project results and synthesis papers on learned best practices. Several manuscripts and a final report are expected to result from these collaborations.

    ACT continues to accept applications to participate in the demonstration. Please contact Thomas Johengen with expressions of interest. ACT will pay for travel costs for one to two members of each team to attend workshops.

    See the full article here .


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  • richardmitnick 7:34 am on July 11, 2019 Permalink | Reply
    Tags: "New Proof That Accretion Disks Align with Their Black Holes", , AGU, , , Bardeen-Petterson alignment, , Blue Waters Cray Linux XE/XK hybrid machine supercomputer, ,   

    From Eos: “New Proof That Accretion Disks Align with Their Black Holes” 

    Eos news bloc

    From Eos

    10 July 2019
    Rachel Crowell

    An image of an accretion disk around a black hole, as seen by an observer nearly edge on to the disk. Credit: NASA GSFC/J. Schnittman

    In 1975, physicist James Bardeen and astrophysicist Jacobus Petterson theorized the existence of a black hole phenomenon that researchers have since been scrambling to show.

    In a study published in the July issue of Monthly Notices of the Royal Astronomical Society, researchers announced that they finally demonstrated Bardeen-Petterson alignment, in which a spinning black hole causes the inner portion of a tilted accretion disk to align with the black hole’s equatorial plane. Finding this effect could change our understanding of how black holes grow and how their presence affects galaxies, according to Sasha Tchekhovskoy, a computational astrophysicist at Northwestern University and colead author of the study.

    In this image, the inner region of the accretion disk (red) aligns with the equatorial plane of the black hole, while the outer disk tilts away. The inner disk (where the black curve dips) is horizontal due to Bardeen-Petterson alignment. Credit: Sasha Tchekhovskoy/Northwestern University and Matthew Liska/University of Amsterdam.

    Powerful Resources Fueled the Simulation

    To accomplish the most detailed and highest-resolution black hole simulation to date, Tchekhovskoy and his team used the Blue Waters supercomputer at the University of Illinois at Urbana-Champaign.

    NCSA U Illinois Urbana-Champaign Blue Waters Cray Linux XE/XK hybrid machine supercomputer

    They also used adaptive mesh refinement, a research method that uses grids that change in response to movements within simulations, and a technique called local adaptive time stepping to bring down the simulation cost by 2 orders of magnitude.

    “It’s very difficult to model the [accretion] disks that show this effect” because they are extremely thin, said Tchekhovskoy. Using graphical processing units instead of central processing units (previously used in similar black hole simulations) enabled the team to “simulate the thinnest disks to date,” Tchekhovskoy said.

    These thin accretion disks have height-to-radius ratios of 0.03, and Tchekhovskoy says the team was surprised to discover that “all of these interesting effects,” including Bardeen-Petterson alignment, appear at that thickness. The thinnest disks simulated prior to this study were more than 1.5 times thicker.

    Cole Miller, an astrophysicist at the University of Maryland in College Park who wasn’t involved with the new study, said he’s impressed with the level of detail in the simulation.

    Unexpected Jets

    “A major surprise of this work is the finding of powerful jets, even in our thin disc accretion system,” the researchers wrote in the study.

    The finding runs counter to the team’s expectation that magnetic fields would rip through the thin accretion disks rather than producing jets, Tchekhovskoy said. Exploring this finding in future work could provide insights into a different phenomenon, he added: why only about 10% of bright, supermassive black holes produce these jets.

    Putting Bardeen-Petterson in Context

    Miller noted that some initial coverage of the new study incorrectly identified John Bardeen, James’s father and a two-time winner of the Nobel Prize in Physics, as one of the two people after which the Bardeen-Petterson effect is named.

    Besides theorizing the Bardeen-Petterson alignment, James Bardeen, now professor emeritus at the University of Washington in Seattle, is also known for formulating (with Stephen Hawking and Brandon Carter) the laws of black hole mechanics. Jacobus Petterson, who died in 1996, was “best known in the astronomical community for his analysis of X-ray binary systems,” according to an obituary written for the American Astronomical Society.

    “This groundbreaking discovery of Bardeen-Petterson alignment brings closure to a problem that has haunted the astrophysics community for more than four decades,” Tchekhovskoy said in a statement.

    “It’s an interesting paper and definitely takes things a step or two beyond previous work,” according to Julian Krolik, an astrophysicist at the University of California, Berkley, who wasn’t involved with the study.

    However, Krolik disagrees about the overall importance of the paper. “It’s not ‘ground-breaking,’ nor does it provide ‘closure.’ ‘Closure’ in this field would mean identification of all the principal mechanisms regulating where the steady-state orientation transition takes place, construction of a method to predict (given relevant disk parameters) the location of this transition, and definition of the boundaries in parameter space separating where alignment is successful and where it isn’t,” Krolik wrote in an email to Eos.

    There is one major question that Krolik said the researchers leave unanswered: why the accretion disk alignment “extends to only a short distance from the black hole, stopping far short of where they expected it to reach.”

    See the full article here .


    Please help promote STEM in your local schools.

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  • richardmitnick 1:14 pm on April 22, 2019 Permalink | Reply
    Tags: "More Than a Million New Earthquakes Spotted in Archival Data", AGU, , Earthquakes in California,   

    From Eos: “More Than a Million New Earthquakes Spotted in Archival Data” 

    From AGU
    Eos news bloc

    From Eos

    19 April 2019
    Katherine Kornei

    By reanalyzing seismic records, researchers found a plethora of tiny earthquakes in Southern California that trace new fault structures and reveal how earthquakes are triggered.

    Little temblors like those detected in the new data are much more numerous than the building-toppling quakes like the one that ripped through San Francisco in 1906. Credit: The U.S. National Archives

    Every 3 minutes. That’s how often an earthquake struck Southern California from 2008 to 2017, new research published in Science shows.

    National Geographic

    Scientists have discovered over 1.6 million previously unknown earthquakes, most of them tiny, by mining seismic records. These results, which constitute the most comprehensive earthquake catalog produced to date, reveal in detail how faults crisscross the Golden State and shed light on how one earthquake triggers others.

    “Having a better earthquake catalog is just like having a better microscope,” said Robert Skoumal, a geophysicist at the U.S. Geological Survey in Menlo Park, Calif., not involved in this study. “We are able to take a closer look at the location of faults, how those faults rupture, and how they interact with each other.”

    Small and Numerous

    A tenet of earthquake science motivated Zachary Ross, a seismologist at the California Institute of Technology in Pasadena, and his collaborators: Earthquake catalogs are always incomplete. That’s because small earthquakes, many of which are too tiny to feel, are always lurking below the limit of detectability. And these little temblors are much more numerous than the building-toppling, highway-churning beasts that make headlines.

    “For every magnitude unit you go down in size, you get about 10 times as many,” said Ross.

    Ross and his colleagues used data from over 500 seismometers in the Southern California Seismic Network to tease out small, previously unrecorded earthquakes.

    They used a technique called template matching, which involves using the seismic waveforms of known earthquakes as templates and then looking for matches in seismic data collected nearby.

    “The shaking that’s recorded…will look almost the same,” said Ross. “They’re seeing all the same rocks as they’re traveling along.”

    Down to the Noise

    “We’re basically at the noise level of the instrumentation.”
    Ross and his team combed through a decade of seismic records using over 280,000 earthquakes as template events. They found over 1.6 million new earthquakes as small as magnitude 0.3. Such low levels of ground shaking can also be caused by construction-related vibrations, ocean waves, and nearby aircraft, said Ross.

    “We’re basically at the noise level of the instrumentation.”

    Using small differences in the arrival times of seismic waves from an earthquake, the scientists calculated the hypocenter of each new event. This information, along with an earthquake’s timing and magnitude, allowed Ross and his colleagues to assemble detailed maps of Southern California’s earthquakes.

    Video by Caltech

    The new earthquake catalog does a far better job of tracing fault lines and revealing how earthquakes trigger others compared with older records, said Ross.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 3:50 pm on March 25, 2019 Permalink | Reply
    Tags: AGU, , , , , WOVO-World Organization of Volcano Observatories   

    From Eos: “Data from Past Eruptions Could Reduce Future Volcano Hazards” 

    From AGU
    Eos news bloc

    From Eos

    Fidel Costa
    Christina Widiwijayanti
    Hanik Humaida

    Optimizing the Use of Volcano Monitoring Database to Anticipate Unrest; Yogyakarta, Indonesia, 26–29 November 2018.

    Java’s Mount Merapi volcano (right), overlooking the city of Yogyakarta, is currently slowly extruding a dome. Mount Merbabu volcano (left) has not erupted for several centuries. Participants at a workshop last November discussed the development and use of a volcano monitoring database to assist in mitigating volcano hazards. Credit: Fidel Costa

    In 2010, Mount Merapi volcano on the Indonesian island of Java erupted explosively—the largest such eruption in 100 years.

    Mount Merapi, viewed from Umbulharjo
    16 April 2014
    Crisco 1492

    Merapi sits only about 30 kilometers from the city of Yogyakarta, home to more than 1 million people. The 2010 eruption forced more than 390,000 people to evacuate the area, and it caused 386 fatalities. In the past few months, the volcano has started rumbling again, and it is currently extruding a dome that is slowly growing.

    Will Merapi’s rumblings continue like this, or will they turn into another large, explosive eruption? Answering this question largely depends on having real-time monitoring data covering multiple parameters, including seismicity, deformation, and gas emissions. But volcanoes can show a wide range of behaviors. A volcanologist’s diagnosis of what the volcano is going to do next relies largely on comparisons to previous cases and thus on the existence of an organized and searchable database of volcanic unrest.

    For over a decade, the World Organization of Volcano Observatories (WOVO) has contributed to the WOVOdat project, which has collected monitoring data from volcanoes worldwide. WOVOdat has grown into an open-source database that should prove very valuable during a volcanic crisis. However, there are many challenges ahead to reaching this goal:

    How do we standardize and capture spatiotemporal data produced in a large variety of formats and instruments?
    How do we go from multivariate (geochemical, geophysical, and geodetic) signals to statistically meaningful indicators for eruption forecasts?
    How do we properly compare periods of unrest between volcanic eruptions?

    Participants at an international workshop last November discussed these and other questions. The workshop was organized by the Earth Observatory of Singapore and the Center for Volcanology and Geological Hazard Mitigation in Yogyakarta. An interdisciplinary group of over 40 participants, including students and experts from more than 10 volcano observatories in Indonesia, the Philippines, Papua New Guinea, Japan, France, Italy, the Caribbean, the United States, Chile, and Singapore, gathered to share their expertise on handling volcano monitoring data, strategize on how to improve on monitoring data management, and analyze past unrest data to better anticipate future unrest and eruptions.

    Participants agreed on the need for a centralized database that hosts multiparameter monitoring data sets and that allows efficient data analysis and comparison between a wide range of volcanoes and eruption styles. They proposed the following actions to optimize the development and use of a monitoring database:

    develop automatic procedures for data processing, standardization, and rapid integration into a centralized database platform
    develop tools for diagnosis of unrest patterns using statistical analytics and current advancement of machine learning techniques
    explore different variables, including eruption styles, morphological features, eruption chronology, and unrest indicators, to define “analogue volcanoes” (classes of volcanoes that behave similarly) and “analogue unrest” for comparative studies
    develop protocols to construct a short-term Bayesian event tree analysis based on real-time data and historical unrest

    Volcano databases such as WOVOdat aim to be a reference for volcanic crisis and hazard mitigation and to serve the community in much the same way that an epidemiological database serves for medicine. But the success of such endeavors requires the willingness of observatories, governments, and researchers to agree on data standardization; efficient data reduction algorithms; and, most important, data sharing to enable findable, accessible, interoperable, and reusable (FAIR) data across the volcano community.

    —Fidel Costa (fcosta@ntu.edu.sg), Earth Observatory of Singapore and Asian School of the Environment, Nanyang Technological University, Singapore; Christina Widiwijayanti, Earth Observatory of Singapore, Nanyang Technological University, Singapore; and Hanik Humaida, Center for Volcanology and Geological Hazard Mitigation, Geological Agency of Indonesia, Bandung

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

  • richardmitnick 1:23 pm on March 22, 2019 Permalink | Reply
    Tags: "New Antenna Design Could Improve Satellite Communications", AGU, Circular polarization of the signal allows for disturbances in the atmosphere that cause the electromagnetic signal to rotate as it travels to and from the ground, Circular polarization of the signal allows the satellite and the ground station to maintain communication even if the satellite rotates relative to the receiver, , The data collected by a satellite are only as good as the signal it sends back to Earth and the signal it sends back is only as good as the antenna that sends it, Turkmen and Secmen design model and fabricate a new type of omnidirectional and circularly polarized slotted antenna that improves on existing designs in a number of ways.   

    From Eos: “New Antenna Design Could Improve Satellite Communications” 

    From AGU
    Eos news bloc

    From Eos

    14 March 2019
    David Shultz

    The new omnidirectional circularly polarized slotted antenna. Credit: Turkmen and Secmen [2018]

    A novel antenna design promises to improve bandwidth and allow for better communication between Earth stations and satellites.

    The data collected by a satellite are only as good as the signal it sends back to Earth, and the signal it sends back is only as good as the antenna that sends it. Modern satellites come equipped with various sorts of antennas, all of which are designed to send and receive data by transmitting and interpreting pulses of electromagnetic radiation. Most satellites operate in a portion of the microwave spectrum known as the Kᵤ band, which spans wavelengths ranging from 1.67 to 2.5 centimeters and frequencies between 12 and 18 gigahertz.

    In a new study, Turkmen and Secmen [Radio Science] design, model, and fabricate a new type of omnidirectional and circularly polarized slotted antenna that improves on existing designs in a number of ways. The word “omnidirectional” is used to describe antennas that transmit their signal isotropically, meaning the pattern of radiation is the same no matter where the receiver is placed relative to the transmitter. Although perfectly isotropic transmission remains impossible, researchers can manipulate the signal in several ways to reduce its directionality. Omnidirectional antennas have several advantages, most notably in their ability to transmit around landforms such as mountains or, in the case of satellites, around the curvature of Earth, allowing researchers to maintain constant contact with the orbiter and detect any faults.

    Similarly, circular polarization of the signal allows the satellite and the ground station to maintain communication even if the satellite rotates relative to the receiver or if disturbances in the atmosphere cause the electromagnetic signal to rotate as it travels to and from the ground.

    Here the authors propose a new antenna designed to create the truest omnidirectional radiation pattern yet. It uses a special waveguide (a hollow structure that controls and aims the electromagnetic radiation) that transitions from a rectangular shape to a cylindrical one (see the image above). Like a sound wave traveling through an organ pipe, the satellite signal propagates through the wave guide, and the unique shape coaxes the signal into a pattern known as the TM01 mode, which also improves the omnidirectionality of the signal.

    To improve the signal’s quality even further, the researchers placed nonidentical antennae array slots in a geometrically symmetric pattern along the waveguide (see the image above). This modification was done to decrease the gain variation in the signal in the azimuthal plane in a wider frequency bandwidth. Gain describes how much a signal is amplified, and low variations in gain are crucial for achieving an omnidirectional radiation pattern. The end result, the researchers say, doubles the bandwidth of the satellite at the 12-gigahertz frequency.

    See the full article here .


    Please help promote STEM in your local schools.

    Stem Education Coalition

    Eos is the leading source for trustworthy news and perspectives about the Earth and space sciences and their impact. Its namesake is Eos, the Greek goddess of the dawn, who represents the light shed on understanding our planet and its environment in space by the Earth and space sciences.

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