The sources of widespread solar energetic particle events - A comprehensive combined modeling and observational approach

广泛的太阳高能粒子事件的来源 - 综合建模和观测相结合的方法

• 批准号: 399903456
• 负责人: Professor Dr. Bernd Heber, since 1/2021
• 金额: --
• 依托单位: Institut für Experimentelle und Angewandte Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/399903456?language=en
• 关键词: sources; widespread; solar; energetic; particle

Solar Energetic Particle (SEP) are accelerated by magnetic reconnection processes at the Sun and/or by shocks. A subgroup of these SEP events are the so-called widespread events which show extremely wide longitudinal particle spreads in the heliosphere up to 360 degrees. Because of their wide particle distributions, up to longitudes far separated from the parent activity regions at the Sun, these events are of special interest in terms of space weather and the underlying processes need to be identified. Different mechanisms are under discussion: On the one hand, the particle transport, i.e. strong perpendicular diffusion during the outward propagation of the particles may be responsible for the wide spreads. On the other hand, a large injection region, e.g. a wide range, over which the particles enter the open magnetic field regime of the interplanetary medium, could be the reason. Such a large injection region could point to specific magnetic field configurations, however, a larger acceleration region such as a shock would serve as well. As large SEP events often show not only a solar flare but also an accompanying Coronal Mass Ejection (CME), which can drive a shock, such a large acceleration region, apart from the point-like flaring region, might be present. In-situ measurements of SEP events are recorded by a fleet of spacecraft, e.g. situated in the Earth's orbit. To infer the acceleration and injection processes, multi-wavelength remote-sensing observations are employed. To bridge the gap between the injection sites and the in-situ measurements, transport models are used which characterize the particle propagation. As each SEP event is determined by the interplay of acceleration, injection, and transport processes, respectively, a comprehensive and combined analysis is needed to disentangle the different ingredients and to identify the drivers of the extraordinary wide particle spreads. In the proposed study we will focus on near-relativistic widespread electron events observed at 1 AU simultaneously close to Earth as well as at the two STEREO spacecraft. We will use a state of the art transport model to reproduce the multi-spacecraft observations of specific widespread events. By employing a combined observational and modeling approach we will identify the main drivers of the wide spreads for each analyzed event. Furthermore, we investigate if a point source together with strong perpendicular transport can explain such observations or if a certain width of the injection region is needed for all of these extreme events. Finally, we will analyze if different types of widespread events exist or if always a combination of certain processes must be involved.

太阳高能粒子（SEP）是由太阳磁场重联过程和/或激波加速的。这些SEP事件的一个子组是所谓的广泛事件，其显示出在日光层中高达360度的极宽的纵向粒子扩散。由于这些事件的粒子分布范围很广，最远可达1000米，与太阳的母活动区相距甚远，因此在空间天气方面特别令人感兴趣，需要查明其背后的过程。不同的机制正在讨论中：一方面，颗粒传输，即在颗粒向外传播过程中的强烈垂直扩散可能是造成宽传播的原因。另一方面，粒子进入行星际介质的开放磁场区的大注入区域，例如宽范围，可能是原因。如此大的注入区域可以指向特定的磁场配置，然而，更大的加速区域（例如冲击）也可以起作用。由于大的SEP事件往往不仅显示太阳耀斑，而且还伴随着日冕物质抛射（CME），它可以驱动冲击，这样一个大的加速区，除了点状耀斑区，可能存在。SEP事件的现场测量由例如位于地球轨道中的航天器舰队记录。为了推断加速和注入过程，采用了多波长遥感观测。为了弥合注射部位和原位测量之间的差距，使用表征颗粒传播的传输模型。由于每个SEP事件分别由加速，注入和传输过程的相互作用决定，因此需要进行全面和综合的分析，以解开不同的成分，并确定非常宽的颗粒扩散的驱动因素。在拟议的研究中，我们将集中在近相对论性广泛的电子事件，同时在1 Au接近地球，以及在两个STEREO航天器。我们将使用最先进的传输模型来再现特定广泛事件的多航天器观测。通过采用观察和建模相结合的方法，我们将确定每个分析事件的广泛传播的主要驱动因素。此外，我们调查，如果一个点源与强大的垂直运输可以解释这样的观察，或者如果一定宽度的注入区域是需要所有这些极端事件。最后，我们将分析是否存在不同类型的广泛事件，或者是否总是必须涉及某些过程的组合。