Evidence for local particle acceleration in the first recurrent galactic cosmic ray depression observed by Solar Orbiter The ion event on 19 June 2020
Evidence for local particle acceleration in the first recurrent galactic cosmic ray depression observed by Solar Orbiter The ion event on 19 June 2020
复制标题
太阳轨道飞行器观测到的第一次周期性银河系宇宙线凹陷中局部粒子加速的证据 2020 年 6 月 19 日的离子事件
DOI：
10.1051/0004-6361/202140966
复制
发表时间：
2021
影响因子：
6.5
通讯作者：
Aran A
中科院分区：
文献类型：
--
作者：
Aran A
2020年6月中旬，太阳轨道器（SolO）使命任务到达第一个近日点0.51 Au，并开始巡航阶段，大部分原位仪器持续运行。目的我们介绍SolO上的高能粒子探测器（EPD）套件获得的第一个近日点后观察到的第一个质子事件的原位粒子测量。潜在的太阳能和行星际（IP）这些particle.MethodsIon的来源，从20 keV到201 MeV的观测与现有的太阳风数据从无线电和等离子体波（RPW）仪器和磁场数据从磁强计上的SolO评估高能粒子的传输条件和推断可能的加速机制，通过粒子获得能量。我们比较了两次太阳自转的> 17-20 MeV离子计数率测量值，沿着太阳风分析仪（SWA）和RPW仪器提供的太阳风等离子体数据，以推断所观察到的银河宇宙线（GCR）凹陷的起源。结果在各种低速下缺乏观察到的电子事件和速度弥散。能量离子通道和观察到的IP结构指示低能粒子的局部IP源。从粒子强度的各向异性的分析，我们得出结论，低能离子最有可能通过局部二阶费米过程加速。6月19日观测到的GCR下降，以及51.8-1034.0 keV nuc− 1离子增强，是由于太阳风气流相互作用区（SIR）。在下一个太阳自转中观察到类似的GCR下降有利于这种解释，并构成了SolO经常性GCR下降的第一个观察结果。对这个SIR重现时间的分析表明，它与以前在4月和5月测量到的4 He事件的SIR是同一个SIR。最后，我们指出，一个IP结构更复杂的比一个共同的SIR不能被丢弃，主要是由于缺乏太阳风温度测量和缺乏更高的节奏的太阳风速度观测。
ContextIn mid-June 2020, the Solar Orbiter (SolO) mission reached its first perihelion at 0.51 au and started its cruise phase, with most of the in situ instruments operating continuously.AimsWe present the in situ particle measurements of the first proton event observed after the first perihelion obtained by the Energetic Particle Detector (EPD) suite on board SolO. The potential solar and interplanetary (IP) sources of these particles are investigated.MethodsIon observations from ∼20 keV to ∼1 MeV are combined with available solar wind data from the Radio and Plasma Waves (RPW) instrument and magnetic field data from the magnetometer on board SolO to evaluate the energetic particle transport conditions and infer the possible acceleration mechanisms through which particles gain energy. We compare > 17–20 MeV ion count rate measurements for two solar rotations, along with the solar wind plasma data available from the Solar Wind Analyser (SWA) and RPW instruments, in order to infer the origin of the observed galactic cosmic ray (GCR) depressions.ResultsThe lack of an observed electron event and of velocity dispersion at various low-energy ion channels and the observed IP structure indicate a local IP source for the low-energy particles. From the analysis of the anisotropy of particle intensities, we conclude that the low-energy ions were most likely accelerated via a local second-orderFermiprocess. The observed GCR decrease on 19 June, together with the 51.8–1034.0 keV nuc−1ion enhancement, was due to a solar wind stream interaction region (SIR). The observation of a similar GCR decrease in the next solar rotation favours this interpretation and constitutes the first observation of a recurrent GCR decrease by SolO. The analysis of the recurrence times of this SIR suggests that it is the same SIR responsible for the4He events previously measured in April and May. Finally, we point out that an IP structure more complex than a common SIR cannot be discarded, mainly due to the lack of solar wind temperature measurements and the lack of a higher cadence of solar wind velocity observations.