太阳活动区磁重联过程中电场加速高能电子分布的演化特征

EVOLUTIONARY CHARACTERISTICS OF THE ENERGETIC ELECTRONS ACCELERATED BY ELECTRIC FIELDS IN THE PROCESS OF MAGNETIC RECONNECTION IN SOLAR ACTIVE REGIONS

基于活动区暗条快速上升后其下方电流片重联过程中产生强电场加速电子这一物理过程 ,解包括库仑碰撞和离子声湍动散射的Fokker Planck方程 ,获得电子分布函数的演化特征 .计算结果表明 :( 1 )当电场强度为 1— 1 0V·cm- 1 时 ,在 1 0 - 5— 1 0 - 6s可将电子加速到( 0 .1— 1 )Mev量级 ;( 2 )被加速电子近似呈幂律谱分布 ,其谱指数与耀斑脉冲相微波和硬X射线推断的电子谱指数基本吻合 .

The evolutionary characteristics of the energetic electron distribution are obtained by numerically solving the time dependent Fokker Planck equation with electric field in the presence of ion acoustic waves and Coulomb collisions in solar active regions. The electric field is caused by the reconnecting current sheets formed below a fast ascending filament in active region. It is shown that: (1) the maximum electron energy is about 0.1—1 MeV with the electric field strength around 1 to 10 V/cm after 10 -6 to 10 -5 s; (2) the accelerated electrons approximately exhibit a power spectrum distribution. The calculated power index is basically consistent with the observed power index of electrons derived from the hard X ray and microwave burst in the impulsive phase of solar flare.