Volume 642, October 2020
|Number of page(s)||11|
|Section||The Sun and the Heliosphere|
|Published online||07 October 2020|
Probing solar flare accelerated electron distributions with prospective X-ray polarimetry missions
Department of Mathematics, Physics & Electrical Engineering, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
2 Space Science Laboratory, University of California, Berkeley, USA
3 School of Physics & Astronomy, University of Glasgow, Glasgow G12 8QQ, UK
Accepted: 18 August 2020
Solar flare electron acceleration is an extremely efficient process, but the method of acceleration is not well constrained. Two of the essential diagnostics, electron anisotropy (velocity angle to the guiding magnetic field) and the high energy cutoff (highest energy electrons produced by the acceleration conditions: mechanism, spatial extent, and time), are important quantities that can help to constrain electron acceleration at the Sun but both are poorly determined. Here, by using electron and X-ray transport simulations that account for both collisional and non-collisional transport processes, such as turbulent scattering and X-ray albedo, we show that X-ray polarization can be used to constrain the anisotropy of the accelerated electron distribution and the most energetic accelerated electrons together. Moreover, we show that prospective missions, for example CubeSat missions without imaging information, can be used alongside such simulations to determine these parameters. We conclude that a fuller understanding of flare acceleration processes will come from missions capable of both X-ray flux and polarization spectral measurements together. Although imaging polarimetry is highly desired, we demonstrate that spectro-polarimeters without imaging can also provide strong constraints on electron anisotropy and the high energy cutoff.
Key words: Sun: flares / Sun: X-rays, gamma rays / Sun: atmosphere / polarization / scattering / acceleration of particles
© ESO 2020
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