Modelling shock-like injections of solar energetic particles with 3D test particle simulations
Modelling shock-like injections of solar energetic particles with 3D test particle simulations
复制标题
通过 3D 测试粒子模拟模拟太阳高能粒子的冲击式注入
DOI：
10.1051/0004-6361/202245313
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发表时间：
2023
影响因子：
6.5
通讯作者：
Hutchinson A
中科院分区：
文献类型：
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作者：
Hutchinson A
在日冕物质抛射（CME）驱动的冲击中，太阳高能粒子（SEP）加速并注入行星际空间。在1au处测得的强度分布的各种特征归因于激波中径向、纵向和纵向SEP注入的特性。聚焦传输模型通常用于模拟cme冲击时的加速度和随后的传播。测试粒子模拟是另一种方法，但到目前为止，它们只在太阳附近进行瞬时注入。我们为我们的3D测试粒子代码开发了第一个暂时扩展的类冲击注入，并研究了在0.3和1.0 au的冲击下注入的空间特征如何影响观察者的SEP强度和各向异性剖面。方法在考虑三种不同的径向注入函数和两种纵向和纬度注入函数的情况下，对5 MeV单能质子群进行了模拟。我们考虑了一系列散射条件，散射平均自由程值为λ= 0.1 ~ 1.0 au，并确定了六个观测点在不同纵向位置的强度和各向异性剖面。结果径向、纵向和纬向注入函数对SEP强度分布的影响相对较小。强度分布对散射平均自由程值的依赖性也很弱，这与一维聚焦输运模型的结果不同。空间因素，如观察者-激波连接和断开的次数以及激波通过的时间，对SEP强度和各向异性的影响要大得多。持续的各向异性，直到激波通过，在我们的模拟中可以看到。比较瞬时注射和类冲击注射，我们发现注射持续时间和SEP事件持续时间之间的联系非常弱，这与通常的假设不同。
ContextSolar energetic particle (SEP) acceleration and injection into interplanetary space during gradual SEP events is thought to take place at coronal mass ejection (CME)-driven shocks. Various features of measured intensity profiles at 1 au have been attributed to properties of the radial, longitudinal, and latitudinal SEP injections at the shock. Focussed transport models are typically used to model acceleration at a CME-shock and subsequent propagation. Test particle simulations are an alternative approach but so far they have been carried out only with instantaneous injection near the Sun.AimsWe develop the first temporally extended shock-like injection for our 3D test particle code and investigate how the spatial features of injection at a shock affect SEP intensity and anisotropy profiles for observers at 0.3 and 1.0 au.MethodsWe conducted simulations of a monoenergetic population of 5 MeV protons considering three different radial injection functions and two longitudinal and latitudinal injection functions. We considered a range of scattering conditions with scattering mean free path values ranging fromλ= 0.1 − 1.0 au, and determined intensity and anisotropy profiles at six observers at different longitudinal locations.ResultsWe find that the radial, longitudinal, and latitudinal injection functions play a relatively minor role in shaping the SEP intensity profiles. The dependence of intensity profiles on the value of the scattering mean free path is also weak, unlike what is found from 1D focussed transport models. Spatial factors, such as the times of observer-shock connection and disconnection as well as the time of shock passage have a much stronger influence on SEP intensities and anisotropies. Persistent anisotropies, until shock passage, are seen in our simulations. Comparing instantaneous and shock-like injections, we find that the link between the duration of injection and the duration of the SEP event is very weak, unlike what is commonly assumed.