Electron trapping and acceleration by kinetic Alfvén waves in solar flares
| Autor: | R. Rankin, I. V. Zimovets, Anton Artemyev |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
010504 meteorology & atmospheric sciences Solar flare Astronomy and Astrophysics Magnetic reconnection Plasma Astrophysics Electron Kinetic energy 01 natural sciences Electromagnetic radiation Computational physics Acceleration Space and Planetary Science Energy cascade Physics::Space Physics 0103 physical sciences Atomic physics 010303 astronomy & astrophysics 0105 earth and related environmental sciences |
| Zdroj: | Astronomy & Astrophysics. 589:A101 |
| ISSN: | 1432-0746 0004-6361 |
| DOI: | 10.1051/0004-6361/201527617 |
| Popis: | Context. Theoretical models and spacecraft observations of solar flares highlight the role of wave-particle interaction for non-local electron acceleration. In one scenario, the acceleration of a large electron population up to high energies is due to the transport of electromagnetic energy from the loop-top region down to the footpoints, which is then followed by the energy being released in dense plasma in the lower atmosphere.Aims. We consider one particular mechanism of non-linear electron acceleration by kinetic Alfven waves. Here, waves are generated by plasma flows in the energy release region near the loop top. We estimate the efficiency of this mechanism and the energies of accelerated electrons.Methods. We use analytical estimates and test-particle modelling to investigate the effects of electron trapping and acceleration by kinetic Alfven waves in the inhomogeneous plasma of the solar corona.Results. We demonstrate that, for realistic wave amplitudes, electrons can be accelerated up to 10−1000 keV during their propagation along magnetic field lines. Here the electric field that is parallel to the direction of the background magnetic field is about 10 to 103 times the amplitude of the Dreicer electric field. The acceleration mechanism strongly depends on electron scattering which is due to collisions that only take place near the loop footpoints.Conclusions. The non-linear wave-particle interaction can play an important role in the generation of relativistic electrons within flare loops. Electron trapping and coherent acceleration by kinetic Alfven waves represent the energy cascade from large-scale plasma flows that originate at the loop-top region down to the electron scale. The non-diffusive character of the non-linear electron acceleration may be responsible for the fast generation of high-energy particles. |
| Databáze: | OpenAIRE |
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