脉冲型耀斑中阿尔芬波湍流加速^3He和重离子机制探讨

The Study of the Acceleration Mechanism of the 3He and Heavier Ions by Alfven Tuebulence in the Impulsive Flares

基于在３＿Ｈｅ丰富事件中，高能３＿Ｈｅ和重离子具有相似的幂律谱分布这一观测结 果，通过数值求解Ｆｏｋｋｅｒ－Ｐｌａｎｃｋ方程，探讨经阿尔芬波湍动加速后的离子分布随时间的 演化特征．计算结果表明：加速源区的等离子体密度和阿尔芬波湍动能量密度对粒子能谱 分布起主要作用，如果取加速源区等离子体密度ｎ＝（０１－１）１０～１０ｃｍ－３、磁场强度 Ｂ＝５０－ １００Ｇｓ、湍动能量密度为 ０．４～２ｅｒｇｓｃｍ－３，则在１秒左右的时间内，湍动阿尔芬波能够 将３＿Ｈｅ和重离子加速到１０ ＭｅＶ／ｎｕｃｌｅｏｎ量级，能谱指数为２．０～３．５。理论计算与观测 结果基本一致．

According to the observational similar spectra forms of the energetic 3He and heavier ions in the 3He-rich events, we have solved Fokker-Planck equation numerically to study the evolutional properties of 3He and heavier ions accelerated by Alfven turbulence with time. It's shown that the distribution of the energetic particles is mainly decided by the plasma density and the energy density of Alfven turbulence .If the plasma density, the magnetic field intensity and the energy density of Alfven turbulence are respectively taken (0.1 - 1)1010cm-3 ,50 - 100Gs and 0.4- 2ergscm-3 in the accelerative region, the energy of the accelerated 311e and heavier ions is t.he order of 10MeV/nucleon and the spectrum index is about 2 - 3.5 after is. All of these are basically consistent with the observations.