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- Berthomier, M., et al.
(författare)
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Alfven : magnetosphere-ionosphere connection explorers
- 2012
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Ingår i: Experimental astronomy. - Dordrecht : Springer. - 0922-6435 .- 1572-9508. ; 33:2-3, s. 445-489
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Tidskriftsartikel (refereegranskat)abstract
- The aurorae are dynamic, luminous displays that grace the night skies of Earth's high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth's atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The "ideal magnetohydrodynamics" description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfv,n concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.
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| 2. |
- Nakamura, R., et al.
(författare)
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Low- altitude electron acceleration due to multiple flow bursts in themagnetotail
- 2014
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 41:3, s. 777-784
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Tidskriftsartikel (refereegranskat)abstract
- At 10:00 UT on 25 February 2008, Cluster 1 spacecraft crossed the near-midnight auroral zone, at about 2R(E) altitude, while two of the Time History of Events and Macroscale Interactions During Substorms (THEMIS) spacecraft, THD and THE, observed multiple flow bursts on the near-conjugate plasma sheet field lines. The flow shear pattern at THEMIS was consistent with the vortical motion at duskside of a localized flow channel. Coinciding in time with the flow bursts, Cluster 1 observed bursts of counterstreaming electrons with mostly low energies (441eV), accompanied by short time scale (<5s) magnetic field disturbances embedded in flow-associated field-aligned current systems. This conjugate event not only confirms the idea that the plasma sheet flows are the driver of the kinetic Alfven waves accelerating the low-energy electrons but is a unique observation of disturbances in the high-altitude auroral region relevant to the multiple plasma sheet flows. Key Points First observation of multiple flow signatures on near-conjugate flux tubes Low-energy electron profile suggests Alfvenic acceleration due to fast flow Multiple flow bursts are obtained to extend over large radial distance in tail
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