Scaling of particle acceleration in 3D reconnection at null points
Scaling of particle acceleration in 3D reconnection at null points
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DOI：
10.1051/0004-6361/201014964
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发表时间：
2010-09
影响因子：
6.5
通讯作者：
P. Browning;S. Dalla;D. Peters;J. Smith
中科院分区：
文献类型：
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作者：
P. Browning;S. Dalla;D. Peters;J. Smith
上下文与磁场重联相关的强电场可能是太阳耀斑中观测到的高能质子和电子的原因。有很多证据表明，三维重联在太阳日冕，我们讨论粒子加速在三维重联网站。3D重连的最简单配置是在3D零点处，其中重连可以在脊柱和风扇模式下发生。目标。目的是了解三维磁重联产生的加速粒子的性质，使用测试粒子的方法，从而有助于了解太阳耀斑中高能质子和电子的起源。我们分析了我们以前用来研究质子的磁结构中电子的性质。此外，我们还讨论了粒子性质对重联参数的依赖性，如电场和磁场的强度。方法.提出了一个理论框架，可用于解释粒子加速在三维零点，并显示如何强大的加速度可以出现。我们还使用了测试粒子的方法来计算粒子的轨迹在简单的模型三维重连零。一个修改的指导中心的方法是用于电子，而完整的运动方程是解决质子。结果大多数粒子加速发生时，粒子密切接近脊柱或风扇，我们已经推导出缩放的局部区域的大小，其中发生强加速。比较了质子和电子的能谱，表明加速电子的空间分布不同于质子。可以产生大量被捕获的高能粒子，这些粒子可以被观测为日冕HXR源。加速效果随电场强度增大而增大，随磁场强度增大而减小。结论.质子和电子都可以在3D重连零点处有效地加速。粒子的性质取决于几何形状和场参数，因此，原则上，场的结构可以从粒子的观测性质中推断出来。
Context. The strong electric fields associated with magnetic reconnection are likely to be responsible for the presence of high energy protons and electrons observed in solar flares. There is much evidence for 3D reconnection in the solar corona, and we discuss particle acceleration at 3D reconnection sites. The simplest configuration for 3D reconnection is at a 3D null point, where reconnection can take place in spine and fan modes. Aims. The aim is to understand the properties of accelerated particles generated by 3D magnetic reconnection, using a test particle approach, and thus contribute to understanding the origin of high energy protons and electrons in solar flares. We analyse the properties of electrons in the magnetic configuration we previously used to study protons. In addition, we discuss the dependence of the particle properties on the parameters of the reconnection, such as strengths of electric and magnetic fields. Methods. A theoretical framework is presented which can be used to interpret particle acceleration at 3D null points, and which shows how strong acceleration can arise. We also use a test particle approach to calculate particle trajectories in simple model 3D reconnecting nulls. A modified guiding-centre approach is used for electrons, whilst the full equation of motion is solved for protons. Results. Most particle acceleration takes place when particles closely approach the spine or fan, and we have derived scalings for the sizes of the localised regions in which strong acceleration occurs. The energy spectra of protons and electrons are compared, and it is shown that the spatial distribution of accelerated electrons differs from protons. A significant number of trapped, high-energy particles can be generated, which may be observed as coronal HXR sources. The effectiveness of acceleration increases with the electric-field magnitude, and decreases with magnetic-field magnitude. Conclusions. Both protons and electrons can be effectively accelerated at 3D reconnecting null points. The particle properties depend on the geometry and field parameters, so that, in principle, the field configuration may be inferred from observed properties of particles.