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磁重联电流片中的粒子加速
Alternative TitleParticle acceleration in magnetic reconnecting current sheets
李燕
Subtype硕士
Thesis Advisor林隽
2008
Degree Grantor中国科学院研究生院(云南天文台)
Place of Conferral北京
Degree Discipline天体物理
Keyword太阳 磁场重联 粒子加速
Abstract太阳是巨大的高能粒子加速器,能产生高达数十GeV的离子和数十MeV的电子。耀斑是太阳大气中剧烈的能量释放过程,高达10^32-10^33erg的能量在10^2-10^3s时间内释放,10-100keV的电子和大于1MeV的离子包含了其中10%-50%的能量,这意味着加速和能量释放过程密切相关的。加速的电子、质子通过和周围大气的碰撞产生硬X射线和伽玛射线。硬X射线给我们提供了耀斑能量释放过程和粒子加速的机制最重要的信息。所以,粒子加速就成为太阳耀斑最有吸引力的方面之一。 本文分为以下几部分: 第一章, 介绍耀斑观测及其能量释放过程。 第二章, 分析了几种不同的加速机制。 第三章, 采用试验粒子的方法, 研究了在有引导磁场Bz存在的磁重联电流片中, 电子被super-Dreicer电场Ez加速后的运动特征。引导磁场在电流片中被认为是恒定不变的, 但其具有不同的取向, 这种情况直接改变了电子运动轨迹, 使得其沿着不同的路径离开电流片。 在Bz和Ez同向时, 能量较高电子的pitch-angle接近于180度。 相反, 当Bz和Ez反向时, 高能电子pitch-angle接近0度。引导磁场的取向只是使电场有选择地对不同区域的电子进行加速, 但不会影响电子最终的能量分布。粒子能谱是普遍的幂率谱 , 而谱指数的大小依赖于引导磁场的大小、电流片的尺度及磁重联电场的强弱。
Other AbstractThe sun is the most energetic particle accelerator in the solar system, producing ions of up to GeV and electrons of up to tens of MeV. Large solar flares are the most powerful explosions in the solar system, releasing up to 10^32-10^33 ergs in ~10^2-10^3s. The accelerated 20-100keV electrons and the sometimes greater than ~1MeV ions appear to contain ~10%-50% of this energy, indicating that the particle acceleration and energy release processes are intimately linked. Flare-accelerated electrons and ions colliding with the ambient solar atmosphere produce bremsstrahlung hard X-ray and gamma-ray line emission. Hard X-rays can provides us with the most important information required for understanding the energy release process and the mechanism or mechanisms by which particles are energized during flare. So, one of the most fascinating aspects of solar flares is how the particles are accelerating to high energies. This thesis is structured as follow: In chapter one, on the basis of surveying a number of references, we summarized the basic knowledge to flares and energy release mechanism. In chapter two, the acceleration mechanism for non-thermal is recommended. In chapter three, electron acceleration by a super-Dreicer electric field Ez is investigated in the reconnecting current sheet with a guiding magnetic field Bz by applying test particle simulation. The guiding field is assumed constant within an RCS, but it have different direction which change the test particle trajectories and lead to the particles which leave the current sheet following field lines close to the different separatrix. In the presence of Bz parallel to Ez, the pitch-angle of energed particle close to180 degree. In contrast, if Bz anti-parallel to Ez, the pitch-angle close to 0 degree. The electric field will accelerate electron in different region due to the different direction of guiding field, but the effect to the distribution of electron energy is negligible. The energy spectrum of accelerated electron is universal with a power-law spectrum , and the value of spectra index have the relation with the strength of the guiding field, the scale of the current sheet, and the strength of electric field.
Subject Area天文学
Pages71
Language中文
Document Type学位论文
Identifierhttp://ir.ynao.ac.cn/handle/114a53/6602
Collection太阳物理研究组
Recommended Citation
GB/T 7714
李燕. 磁重联电流片中的粒子加速[D]. 北京. 中国科学院研究生院(云南天文台),2008.
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