Heavy-ion acceleration and self-generated waves in coronal shocks
Heavy-ion acceleration and self-generated waves in coronal shocks
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DOI：
10.1051/0004-6361/201117507
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发表时间：
2011-11
影响因子：
6.5
通讯作者：
M. Battarbee;T. Laitinen;R. Vainio
中科院分区：
文献类型：
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作者：
M. Battarbee;T. Laitinen;R. Vainio
上下文。目前，日冕物质抛射驱动的激波加速被认为是大型太阳高能粒子事件的主要来源。目标。提供激波加速粒子的太阳风包括大量的离子群，这为加速过程提供了更多的洞察力。我们首次对激波加速的次离子进行了模拟，以详细地探索俘获动力学和加速时间尺度。方法：研究方法。我们用蒙特卡罗方法模拟了小离子(3He2+、4He2+、16O6+和56Fe14+)和质子的扩散激波加速，其中自产生的Alfvenic湍流允许重复激波交叉并加速到高能。结果。我们讨论了少量离子对波的产生，特别是在低波数时的影响，并表明它是显著的。我们发现，最大离子能量是由膨胀通量管中聚焦引起的粒子逃逸和放大的湍流引起的捕获的竞争效应决定的。结果表明，截止能量与粒子荷质比的关系约为(Q/A)1.5。结论。我们认为，要理解日冕激波中次离子的加速，需要进行模拟，使我们能够详细地探索捕获动力学和加速时间尺度，包括湍流捕获边界的演化。我们的结论是，稳态模型不能很好地描述日冕激波中重离子的加速。
Context. Acceleration in coronal mass ejection driven shocks is currently considered the primary source of large solar energetic particle events. Aims. The solar wind, which feeds shock-accelerated particles, includes numerous ion populations, which offer much insight into acceleration processes. We present first simulations of shock-accelerated minor ions, in order to explore trapping dynamics and acceleration timescales in detail. Methods. We have simulated diffusive shock acceleration of minor ions (3He2+, 4He2+, 16O6+ and 56Fe14+) and protons using a Monte Carlo method, where self-generated Alfvenic turbulence allows for repeated shock crossings and acceleration to high energies. Results. We present the effect of minor ions on wave generation, especially at low wavenumbers, and show that it is significant. We find that maximum ion energy is determined by the competing effects of particle escape due to focusing in an expanding flux tube and trapping due to the amplified turbulence. We show the dependence of cut-off energy on the particle charge to mass ratio to be approximately (Q/A)1.5. Conclusions. We suggest that understanding the acceleration of minor ions at coronal shocks requires simulations which allow us to explore trapping dynamics and acceleration timescales in detail, including evolution of the turbulent trapping boundary. We conclude that steady-state models do not adequately describe the acceleration of heavy ions in coronal shocks.