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  • richardmitnick 8:54 am on May 2, 2018 Permalink | Reply
    Tags: , , , Chalmers University of Technology, , ,   

    From Chalmers University of Technology: “Flares in the universe can now be studied on earth” 

    Chalmers University of Technology

    02 May 2018

    Tünde Fülöp
    Professor, Department of Physics, Chalmers University of Technology
    +46 72 986 74 40
    tunde.fulop@chalmers.se

    Longqing Yi
    Postdoctoral researcher,Department of Physics,Chalmers University of Technology
    +46 31 772 68 82
    longqing@chalmers.se

    1
    Solar flares are caused by magnetic reconnection in space and can interfere with our communications satellites, affecting power grids, air traffic and telephony. Now, researchers at Chalmers University of Technology, Sweden, have found a new way to imitate and study these spectacular space plasma phenomena in a laboratory environment. Image: NASA/SDO/AIA/Goddard Space Flight Center

    NASA/SDO

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    Longqing Yi
    4
    Tünde Fülöp

    Solar flares, cosmic radiation, and the northern lights are well-known phenomena. But exactly how their enormous energy arises is not as well understood. Now, physicists at Chalmers University of Technology, Sweden, have discovered a new way to study these spectacular space plasma phenomena in a laboratory environment. The results have been published in the renowned journal Nature Communications.

    “Scientists have been trying to bring these space phenomena down to earth for a decade. With our new method we can enter a new era, and investigate what was previously impossible to study. It will tell us more about how these events occur,” says Longqing Yi, researcher at the Department of Physics at Chalmers.

    The research concerns so-called ‘magnetic reconnection’ – the process which gives rise to these phenomena. Magnetic reconnection causes sudden conversion of energy stored in the magnetic field into heat and kinetic energy. This happens when two plasmas with anti-parallel magnetic fields are pushed together, and the magnetic field lines converge and reconnect. This interaction leads to violently accelerated plasma particles that can sometimes be seen with the naked eye – for example, during the northern lights.

    Magnetic reconnection in space can also influence us on earth. The creation of solar flares can interfere with communications satellites, and thus affect power grids, air traffic and telephony.

    In order to imitate and study these spectacular space plasma phenomena in the laboratory, you need a high-power laser, to create magnetic fields around a million times stronger than those found on the surface of the sun. In the new scientific article, Longqing Yi, along with Professor Tünde Fülöp from the Department of Physics, proposed an experiment in which magnetic reconnection can be studied in a new, more precise way. Through the use of ‘grazing incidence’ of ultra-short laser pulses, the effect can be achieved without overheating the plasma. The process can thus be studied very cleanly, without the laser directly affecting the internal energy of the plasma. The proposed experiment would therefore allow us to seek answers to some of the most fundamental questions in astrophysics.

    “We hope that this can inspire many research groups to use our results. This is a great opportunity to look for knowledge that could be useful in a number of areas. For example, we need to better understand solar flares, which can interfere with important communication systems. We also need to be able to control the instabilities caused by magnetic reconnection in fusion devices,” says Tünde Fülöp.

    The study on which the new results are based was financed by the Knut and Alice Wallenberg foundation, through the framework of the project ‘Plasma-based Compact Ion Sources’, and the ERC project ‘Running away and radiating’.

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    Schematic of the proposed setup and relativistic jets generation. a A moderately high-intensity laser pulse (a0 = 5) propagates along the x-direction, and is splitted in half by a micro-sized plasma slab. The laser drives two energetic electron beams on both sides of the plasma surfaces, which generate 100 MG level opposing azimuthal magnetic fields in the middle. Ultrafast magnetic reconnection is observed as the electron beams approach the coronal region (the area within the blue box, where the plasma density decreases exponentially) at the end of the slab. The two insets below show the transverse magnetic fields (black arrows) and longitudinal electric current density (color) at the cross-section marked by the red rectangle (separated by 10λ0) at simulation times t = 24T0 and t = 34T0, respectively. b–e Generation and evolution of the relativistic jet resulting from MR at times 32T0, 35T0, 38T0, and 41T0, respectively. The rainbow color bar shows the transverse momentum P z of the jets formed by the background plasma electrons in b–e, and the blue-red color bar shows the energy of the electron bunch driven by the laser pulse in b, c.

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    Gyrotropy quantification at different times. Square root of quantified pressure tensor agyrotropy Q−−√ in the coronal plasma at simulation time t = 32T0(a), 33T0(b), and 34T0(c). The insets show the value of Q−−√ at the cross-section with longitudinal coordinate x = 26λ0, which is marked by the red rectangles in a–c.

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    Evolution of magnetic fields and magnetic tension force during the reconnection. a–c Static magnetic fields (frequency below 0.8ω0) and d–f z-component of magnetic tension force at simulation time t = 32T0 (a, d), 33T0 (b, e), and 34T0 (c, f). In a–c the transverse (B y , B z ) and longitudinal (B x ) components of magnetic field are presented by the black arrows and color, respectively. The bold white arrows in b show the inflow (horizontal) and outflow (vertical) electric currents that result from Hall reconnection. The black-dashed lines in d–f mark the cross-section where the corresponding magnetic fields (a–c) are shown.

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    Magnetic energy dissipation and the energization of non-thermal electrons. a Field dissipation (E x j x ) and electron density at t = 33T0 in the corona, the insets represent the top and side views of E x j x in the reconnection site (marked by the red box). b Time dependence of total energy increase in electrostatic fields, electrons in the corona, and protons (ΔE+), energy reduction of electromagnetic fields and other electrons (ΔE−), as well as the total energy reduction that includes magnetic field dissipation (ΔE− + ΔEm), inset shows the evolution of static magnetic energy Em and total kinetic energy of electron jets. c Coronal electron spectra from 30T0 to 36T0. d The temporal evolution of the kinetic energy (Ek) and the work done by each electric field component (W x , W y , and W z ) for one representative electron. The inset plane shows the phase-space trajectory (γ − 1 plotted vs. y) of the total 100 tracked electrons, where the blue-dashed line marks the boundary of plasma slab and the trajectory in red represents the case shown in d.

    Text:
    Mia Halleröd Palmgren,
    mia.hallerodpalmgren@chalmers.se

    Translation:
    Joshua Worth, joshua.worth@chalmers.se

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Chalmers University of Technology (Swedish: Chalmers tekniska högskola, often shortened to Chalmers) is a Swedish university located in Gothenburg that focuses on research and education in technology, natural science, architecture, maritime and other management areas

    The University was founded in 1829 following a donation by William Chalmers, a director of the Swedish East India Company. He donated part of his fortune for the establishment of an “industrial school”. Chalmers was run as a private institution until 1937, when the institute became a state-owned university. In 1994, the school was incorporated as an aktiebolag under the control of the Swedish Government, the faculty and the Student Union. Chalmers is one of only three universities in Sweden which are named after a person, the other two being Karolinska Institutet and Linnaeus University.

     
  • richardmitnick 3:18 pm on February 19, 2018 Permalink | Reply
    Tags: , , , , Chalmers receivers at ALMA, Chalmers University of Technology, , ,   

    From Chalmers University of Technology: “Receivers from Chalmers will image the distant universe” 

    Chalmers University of Technology

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    Receivers in the cryostat: ESO/P. Yagoubov

    Each of the 66 telescopes at Alma has now been equipped with Chalmers receivers.

    From March 1, 2018, when the world’s most powerful telescope will target the most distant universe it is equipped with new receivers that have been developed and produced at Chalmers University. The extremely sensitive instruments also provide new opportunities to search for water in space and in our solar system.

    “Being the best in the world is part of our daily life. There are simply no other options if you wish to participate on this level, “says Victor Belitsky, professor and leader of the Research Group for Advanced Receiver Development (GARD) at Chalmers.

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    The ALMA telescope consists of 66 dish antennas located 5000 meters above sea level in Chile on a high plateau in the Andes. The dishes work linked together as one telescope and can make far sharper observations than individual radio telescopes can do.

    Each of the 66 antennas has several receivers for observation at different wavelengths. The Chalmers receivers now being used allow observations of light with a wavelength of between 1.4 and 1.8 millimeters – known as Alma’s Band 5. This is microwave radiation, which can be compared with visible light whose longest wavelengths are around 740 nanometres (less than a thousandth of a millimetre).

    “At these frequencies we can observe cold parts of the universe. For example, regions where stars and planets are formed are of great interest. When ALMA’s dishes work together, you get significantly higher resolution than you can do with current optical telescopes, “says Victor Belitsky, whose research group is part of Onsala Space Observatory at the Department of Space, Earth and Environment.

    • The frequencies that are now accessible can give scientists for example a new understanding of how stars, planets and galaxies are born, he says.

    Perfect timing​

    The receivers were developed by the GARD group (click on the image for a larger version with all names) in a project funded by the EU program EC FP6​ in 2006-2012. The timing proved to be perfect. When the first receivers were ready, new research areas were opening up that specifically required ALMA to be able to observe in Band 5.

    Victor and his colleagues had completed six complete receivers, but to handle the order for a further 73, a team from NOVA (Netherlands Research School for Astronomy) was invited to participate. They integrated GARD’s components in the receiver cassettes.

    “Their effort was important to complete the delivery, but the major challenge was to develop the receiver and manufacture the components. We are delivering to the world’s best and most advanced telescope, and thanks to our knowledge and experience, they have now got the best possible receivers”.

    Cool receivers

    The biggest challenge in the production of receivers for radio telescopes is how to reduce noise from their surroundings and get as clean a signal as possible.

    “The noise sets the limit for how weak signals can be detected. It’s like finding the right station on a regular FM-radio, but a million times more sensitive! So, the more we can reduce different types of noise, the more we increase the possibilities for new discoveries in space”, says Victor Belitsky.

    For example, the receivers operate at -269 degrees Celsius, four degrees above absolute zero, to counteract interference from thermal radiation. The image shows the receivers housed in their cryostat, which is designed to maintain such low temperatures.

    Reducing loss of signal in Earth’s atmosphere is also the reason that the ALMA telescope is located at 5000 meters above sea level, in one of the driest places in the world. There is very little water vapor in the atmosphere above the telescope, which means the Band 5 receivers can look for water in space, both nearby and far away, Victor Belitsky explains.

    “There are many uses for our receivers, both in our solar system and in distant galaxies. It depends on which research applications and topics the Alma Research Committee selects, but we know there is a lot of interest to observe water in our own solar system”.

    Sweden among world leaders​

    Sweden’s success with Alma is not limited to delivering instruments. Swedish researchers were among the most frequent users of the telescopes last year, second only to Japan.

    “Second place! That shows the strength and position of Swedish astronomical research in international terms. With the support of instrumentation, we are at one of the world’s leading positions – both in terms of research and technology. That’s something to be proud of”, says Victor Belitsky.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Chalmers University of Technology (Swedish: Chalmers tekniska högskola, often shortened to Chalmers) is a Swedish university located in Gothenburg that focuses on research and education in technology, natural science, architecture, maritime and other management areas

    The University was founded in 1829 following a donation by William Chalmers, a director of the Swedish East India Company. He donated part of his fortune for the establishment of an “industrial school”. Chalmers was run as a private institution until 1937, when the institute became a state-owned university. In 1994, the school was incorporated as an aktiebolag under the control of the Swedish Government, the faculty and the Student Union. Chalmers is one of only three universities in Sweden which are named after a person, the other two being Karolinska Institutet and Linnaeus University.

     
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