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  • richardmitnick 7:58 am on May 10, 2021 Permalink | Reply
    Tags: "Physicists describe new type of aurora", , Space physics, University of Calgary (CS), University of Iowa (US)   

    From University of Iowa (US) with University of Calgary (CA): “Physicists describe new type of aurora” 

    From University of Iowa (US)

    2021.05.06

    Richard Lewis
    Office of Strategic Communication
    319-384-0012
    richard-c-lewis@uiowa.edu

    Discovery comes from reanalysis of two-decade-old video.


    Physicists describe new type of aurora.
    The famed northern and southern lights still hold secrets. In a new study, physicists led by the University of Iowa (US) describe a new phenomenon they call “diffuse auroral erasers,” in which patches of the background glow are blotted out, then suddenly intensify and reappear.

    1
    Diffuse auroral erasers. Credit: David Knudsen via University of Iowa.

    For millennia, humans in the high latitudes have been enthralled by auroras—the northern and southern lights. Yet even after all that time, it appears the ethereal, dancing ribbons of light above Earth still hold some secrets.

    In a new study, physicists led by the University of Iowa report a new feature to Earth’s atmospheric light show. Examining video taken nearly two decades ago, the researchers describe multiple instances where a section of the diffuse aurora—the faint, background-like glow accompanying the more vivid light commonly associated with auroras—goes dark, as if scrubbed by a giant blotter. Then, after a short period of time, the blacked-out section suddenly reappears.

    The researchers say the behavior, which they call “diffuse auroral erasers,” has never been mentioned in the scientific literature. The findings appear in the Journal of Geophysical Research Space Physics.

    Auroras occur when charged particles flowing from the sun—called the solar wind—interact with Earth’s protective magnetic bubble. Some of those particles escape and fall toward our planet, and the energy released during their collisions with gases in Earth’s atmosphere generate the light associated with auroras.

    “The biggest thing about these erasers that we didn’t know before but know now is that they exist,” says Allison Jaynes, assistant professor in the Department of Physics and Astronomy at Iowa and study co-author. “It raises the question: Are these a common phenomenon that has been overlooked, or are they rare?

    “Knowing they exist means there is a process that is creating them,” Jaynes continues, “and it may be a process that we haven’t started to look at yet because we never knew they were happening until now.”


    Diffuse auroral erasers.

    It was on March 15, 2002, that David Knudsen, a physicist at the University of Calgary (CA), set up a video camera in Churchill, a town along Hudson Bay in Canada, to film auroras. Knudsen’s group was a little disheartened; the forecast called for clear, dark skies—normally perfect conditions for viewing auroras—but no dazzling illumination was happening. Still, the team was using a camera specially designed to capture low-level light, much like night-vision goggles.

    Though the scientists saw only mostly darkness as they gazed upward with their own eyes, the camera was picking up all sorts of auroral activity, including an unusual sequence where areas of the diffuse aurora disappeared, then came back.

    Knudsen, looking at the video as it was being recorded, scribbled in his notebook, “pulsating ‘black out’ diffuse glow, which then fills in over several seconds.”

    “What surprised me, and what made me write it in the notebook, is when a patch brightened and turned off, the background diffuse aurora was erased. It went away,” says Knudsen, a Fort Dodge, Iowa, native who has studied aurora for more than 35 years and is a co-author on the study. “There was a hole in the diffuse aurora. And then that hole would fill back in after a half-minute or so. I had never seen something like that before.”

    The note lay dormant, and the video unstudied, until Iowa’s Jaynes handed it to graduate student Riley Troyer to investigate. Jaynes learned about Knudsen’s recording at a scientific meeting in 2010 and referenced the eraser note in her doctoral thesis on diffuse aurora a few years later. Now on the faculty at Iowa, she wanted to learn more about the phenomenon.

    “I knew there was something there. I knew it was different and unique,” says Jaynes, assistant professor in the Department of Physics and Astronomy. “l had some ideas how it could be analyzed, but I hadn’t done that yet. I handed it to Riley, and he went much further with it by figuring out his own way to analyze the data and produce some significant conclusions.”

    2
    Notes written by David Knudsen, a physicist at the University of Calgary, in 2002 make mention of a “pulsating ‘black out’ diffuse glow, which then fills in over several seconds.”

    Troyer, from Fairbanks, Alaska, took up the assignment with gusto.

    “I’ve seen hundreds of auroras growing up,” says Troyer, who is in his third year of doctoral studies at Iowa. “They’re part of my heritage, something I can study while keeping ties to where I’m from.”

    Troyer created a software program to key in on frames in the video when the faint erasers were visible. In all, he cataloged 22 eraser events in the two-hour recording.

    “The most valuable thing we found is showing the time that it takes for the aurora to go from an eraser event (when the diffuse aurora is blotted out) to be filled or colored again,” says Troyer, who is the paper’s corresponding author, “and how long it takes to go from that erased state back to being diffuse aurora. Having a value on that will help with future modeling of magnetic fields.”

    Jaynes says learning about diffuse auroral erasers is akin to studying DNA to understand the entire human body.

    “Particles that fall into our atmosphere from space can affect our atmospheric layers and our climate,” Jaynes says. “While particles with diffuse aurora may not be the main cause, they are smaller building blocks that can help us understand the aurora system as a whole, and may broaden our understanding how auroras happen on other planets in our solar system.”

    Study co-authors are Sarah Jones, from NASA Goddard Space Flight Center (US) and who was part of Knudsen’s team in Churchill, and Trond Trondsen, with Keo Scientific Ltd., who built the camera that filmed the diffuse aurora.

    See the full article here.

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The University of Iowa (US) is a public research university in Iowa City, Iowa. Founded in 1847, it is the oldest and the second-largest university in the state. The University of Iowa is organized into 12 colleges offering more than 200 areas of study and seven professional degrees.

    On an urban 1,880-acre campus on the banks of the Iowa River, the University of Iowa is classified among “R1: Doctoral Universities – Very high research activity”. The university is best known for its programs in health care, law, and the fine arts, with programs ranking among the top 25 nationally in those areas. The university was the original developer of the Master of Fine Arts degree and it operates the Iowa Writer’s Workshop, which has produced 17 of the university’s 46 Pulitzer Prize winners. Iowa is a member of the Association of American Universities, the Universities Research Association, and the Big Ten Academic Alliance.

    Among American universities, the University of Iowa was the first public university to open as coeducational, opened the first coeducational medical school, and opened the first Department of Religious Studies at a public university. The University of Iowa’s 33,000 students take part in nearly 500 student organizations. Iowa’s 22 varsity athletic teams, the Iowa Hawkeyes, compete in Division I of the NCAA and are members of the Big Ten Conference. The University of Iowa alumni network exceeds 250,000 graduates.

     
  • richardmitnick 1:58 pm on March 2, 2017 Permalink | Reply
    Tags: , , Jicamarca Radio Observatory, , , Space physics   

    From Eos: “After Decades, High-Altitude Observations Revived at Jicamarca” 

    AGU bloc

    AGU
    Eos news bloc

    Eos

    3.2.17
    Mark Zastrow

    1
    Dipoles of the telescope at Jicamarca Radio Observatory near Lima, Peru. Construction of the observatory was completed in 1962, around the time this photo was taken. Credit: Alastair Philip Wiper/VIEW

    When the Jicamarca Radio Observatory made its first observations of Earth’s ionosphere in the early 1960s, it was one of the most impressive facilities in the nascent field of space physics. Its massive square array of dipole antennas was laid out in the Peruvian desert east of Lima, nearly 300 meters on each side. The enormous radar facility was designed to probe the ionosphere directly above Earth’s equator; electrons in the ionosphere scatter the radar beams, but a faint return signal gives an indication of their density.

    In its initial observing runs, scientists included measurements at very high altitudes, an exercise meant to map out the space surrounding Earth. They also pushed the facility to its limits, requiring powerful radar pulses from all four of its transmitters and many people to operate them. Soon, however, high-altitude operations were canceled; the last runs occurred in 1965.

    As the facility began to focus on more popular areas of research, the unpublished high-altitude records languished. Many were lost. The details of the observations and analysis—such as which filtering methods, if any, were used—faded away, limiting the surviving data’s usefulness. Eventually, the capability to reproduce them was lost, as transmitters fell offline and Jicamarca focused on targets closer to the ground.

    Today, more than 50 years later, interest in high-altitude observations is on the rise, this time driven by the desire to understand how plasma behaves during geomagnetic storms. Jicamarca remains one of the most important space physics radar facilities, and fortunately, recent upgrades have restored the facility’s ability to carry out high-altitude observations. On 31 May 2016, Jicamarca fired up its transmitters and focused its antennas on high-altitude incoherent scatter in a study conducted by Hysell et al.

    In a 24-hour period of observations, the team found that Jicamarca could profile the electron density up to an altitude of roughly 6300 kilometers. That’s high enough to usefully overlap with data from ground-based magnetometers, which can cover a range from roughly 3000 kilometers to 16,000 kilometers. The data analysis also revealed that different filtering methods did not change the results much, which makes it easier to interpret historical data.

    The authors used just two of Jicamarca’s four transmitters, all of which have been restored to operational status. Even with only two transmitters, the data quality was similar to the 1965 data, with a slightly better dynamic range. The team notes that future observations using all four transmitters will be more sensitive and should push the observatory’s range occasionally up to 10,000 kilometers. (Journal of Geophysical Research: Space Physics, https://doi.org/10.1002/2016JA023569, 2017)

    See the full article here .

    Please help promote STEM in your local schools.

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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.

     
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