Fluctuating electric field acceleration at a magnetic field null point
Abstract
Release of stored magnetic energy via particle acceleration is a characteristic feature of astrophysical plasmas. In the case of solar flares a large fraction of the flare energy is manifested in the form of fast electrons and protons. Magnetic reconnection is one of the mechanisms for releasing non-potential energy from magnetized plasmas. A collisionless magnetic reconnection scenario could provide both the energy release mechanism and the particle accelerator in flares. We studied particle acceleration consequences from fluctuating electric fields superposed on an X-type magnetic field in collisionless hot solar plasma. This system is chosen to mimic generic features of dynamic reconnection, or the reconnective dissipation of a linear disturbance. Results are compared to particle acceleration from constant electric field superposed on an X-type magnetic field chosen to mimic steady state magnetic reconnection. Time evolution of initially thermal particle distributions are obtained by numerically integrating individual charged particle orbits. A spectrum of frequencies of the electric field is used, representing a turbulent range of waves. The resulting particle distributions have properties that depend on the amplitude and frequency of the electric field. Depending on the timescale for variation of the electric field, electrons and ions are accelerated to different degrees and often have energy distributions of different forms. Protons are accelerated to gamma-ray producing energies and electrons to and above hard X-ray producing energies in timescales of 1 second. The acceleration mechanism is possibly important for solar flares and solar noise storms but is also applicable to all collisionless plasmas.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2008
- Bibcode:
- 2008AGUSMSH43B..05P
- Keywords:
-
- 7519 Flares;
- 7835 Magnetic reconnection (2723;
- 7526);
- 7839 Nonlinear phenomena (4400;
- 6944);
- 7845 Particle acceleration