ACCELERATION, MAGNETIC FLUCTUATIONS, AND CROSS-FIELD TRANSPORT OF ENERGETIC ELECTRONS IN A SOLAR FLARE LOOP
- 7 March 2011
- journal article
- research article
- Published by American Astronomical Society in The Astrophysical Journal Letters
- Vol. 730 (2), L22
- https://doi.org/10.1088/2041-8205/730/2/l22
Abstract
Plasma turbulence is thought to be associated with various physical processes involved in solar flares, including magnetic reconnection, particle acceleration, and transport. Using RHESSI observations and the X-ray visibility analysis, we determine the spatial and spectral distributions of energetic electrons for a flare (GOES M3.7 class, 2002 April 14, 23: 55 UT), which was previously found to be consistent with a reconnection scenario. It is demonstrated that because of the high density plasma in the loop, electrons have to be continuously accelerated about the loop apex of length similar to 2 x 10(9) cm and width similar to 7 x 10(8) cm. Energy-dependent transport of tens of keV electrons is observed to occur both along and across the guiding magnetic field of the loop. We show that the cross-field transport is consistent with the presence of magnetic turbulence in the loop, where electrons are accelerated, and estimate the magnitude of the field line diffusion coefficient for different phases of the flare. The energy density of magnetic fluctuations is calculated for given magnetic field correlation lengths and is larger than the energy density of the non-thermal electrons. The level of magnetic fluctuations peaks when the largest number of electrons is accelerated and is below detectability or absent at the decay phase. These hard X-ray observations provide the first observational evidence that magnetic turbulence governs the evolution of energetic electrons in a dense flaring loop and is suggestive of their turbulent acceleration.This publication has 46 references indexed in Scilit:
- The influence of albedo on the size of hard X-ray flare sourcesAstronomy & Astrophysics, 2010
- Parallel electric field generation by Alfvén wave turbulenceAstronomy & Astrophysics, 2010
- PARTICLE ACCELERATION BY STRONG TURBULENCE IN SOLAR FLARES: THEORY OF SPECTRUM EVOLUTIONThe Astrophysical Journal, 2009
- Birth and evolution of a dense coronal loop in a complex flare regionAstronomy & Astrophysics, 2006
- Problems and progress in flare fast particle diagnosticsAdvances in Space Research, 2005
- Chromospheric Height and Density Measurements in a Solar Flare Observed with RHESSI – I. TheorySolar Physics, 2002
- Particle acceleration and kinematics in solar flares – A Synthesis of Recent Observations and Theoretical Concepts (Invited Review)Space Science Reviews, 2002
- Magnetic turbulence and the transport of energy and particles in tokamaksPlasma Physics and Controlled Fusion, 1997
- The structure and dissipation of forced current sheets in the solar atmosphereThe Astrophysical Journal, 1987
- The deduction of energy spectra of non-thermal electrons in flares from the observed dynamic spectra of hard X-ray burstsSolar Physics, 1971