Stochastic Fermi acceleration in solar flares
Stochastic Fermi acceleration in solar flares
复制标题
太阳耀斑中的随机费米加速
DOI：
10.1086/169233
复制
发表时间：
1990
期刊：
影响因子：
--
通讯作者：
R. Ramaty
中科院分区：
文献类型：
--
作者：
James A. Miller;N. Guessoum;R. Ramaty
计算了太阳耀斑中随机费米加速度产生的非相对论到超相对论能量范围内有效的质子谱。这些光谱是通过数值求解Fokker-Planck方程得到的，其中粒子从加速区逃逸的特征是与能量无关的逃逸时间。除了平衡谱外，还给出了显示平衡方法的随时间能量谱。这些数值平衡谱与以往的蒙特卡罗模拟和近似解析处理结果进行了比较。在对太阳耀斑中介子和中子的产生非常重要的超相对论体系中没有有效的解析解。加速效率与物理参数有关，特别是磁声子波或阿尔芬波中的能量密度，并且从伽马射线观测所隐含的加速时间中对这些能量密度中的任何一个设置了下限。还讨论了逃逸时间的物理解释。参35。
Proton spectra, valid from non- to ultra-relativistic energies, resulting from stochastic Fermi acceleration in solar flares are calculated. These spectra were obtained by numerically solving the Fokker-Planck equation, in which the escape of the particles from the acceleration region is characterized by an energy-independent escape time. In addition to equilibrium spectra, time-dependent energy spectra showing the approach to equilibrium are also presented. These numerical equilibrium spectra are compared with previous results which were obtained either by Monte Carlo simulations or approximate analytical treatments. There are no analytic solutions valid in the transrelativistic regime, which is very important for the production of pions and neutrons in solar flares. The acceleration efficiency is related to physical parameters, in particular the energy density in either magnetosonic or Alfven waves, and a lower limit is placed on either of these energy densities from acceleration times implied by gamma-ray observations. Also discussed is the physical interpretation of the escape time. 35 refs.