Whistler instability driven by the sunward electron deficit in the solar wind High-cadence Solar Orbiter observations
Whistler instability driven by the sunward electron deficit in the solar wind High-cadence Solar Orbiter observations
复制标题
太阳风中向阳电子亏缺驱动的惠斯勒不稳定性高节奏太阳轨道飞行器观测
DOI：
10.1051/0004-6361/202140970
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发表时间：
2021
影响因子：
6.5
通讯作者：
Bercic L
中科院分区：
文献类型：
--
作者：
Bercic L
太阳风电子以电子热通量的形式将能量携带到行星际空间，在太阳风加速的能量平衡中起着重要的作用。热通量存储在由膨胀、库仑碰撞和场-粒子相互作用形成的复杂的电子速度分布函数（VDFs）中。驱动动力学不稳定性，并产生具有准-平行于背景磁场的方向。MethodsWe相结合的高节奏测量的电子俯仰角分布函数和电磁波提供的太阳轨道器在其第一轨道。我们的案例研究是基于一个突发模式的数据间隔从静电分析仪系统（SWA-EAS）的距离为112 RS（0.52 Au）从太阳，在此期间，几个哨声波包被检测到太阳轨道器的无线电和等离子体波（RPW）instrument.ResultsThe向阳赤字创造动力学条件下，准平行哨声波变得不稳定。我们通过太阳风观测直接测试我们对这些波存在的预测。我们发现哨声波是准平行的，几乎是圆偏振的，传播远离太阳，正好与一个明显的向阳赤字的电子VDF。满足回旋共振条件的电子移动的方向相反的波的传播方向，与能量对应的那些与向阳deficiency.ConclusionsWe的结论，向阳赤字作为准平行的哨声波在太阳风的源。共振电子的准线性扩散倾向于填补赤字，导致总电子热通量的减少。
ContextSolar wind electrons play an important role in the energy balance of the solar wind acceleration by carrying energy into interplanetary space in the form of electron heat flux. The heat flux is stored in the complex electron velocity distribution functions (VDFs) shaped by expansion, Coulomb collisions, and field-particle interactions.AimsWe investigate how the suprathermal electron deficit in the anti-strahl direction, which was recently discovered in the near-Sun solar wind, drives a kinetic instability and creates whistler waves with wave vectors that are quasi-parallel to the direction of the background magnetic field.MethodsWe combined high-cadence measurements of electron pitch-angle distribution functions and electromagnetic waves provided by Solar Orbiter during its first orbit. Our case study is based on a burst-mode data interval from the Electrostatic Analyser System (SWA-EAS) at a distance of 112RS(0.52 au) from the Sun, during which several whistler wave packets were detected by Solar Orbiter’s Radio and Plasma Waves (RPW) instrument.ResultsThe sunward deficit creates kinetic conditions under which the quasi-parallel whistler wave becomes unstable. We directly test our predictions for the existence of these waves through solar wind observations. We find whistler waves that are quasi-parallel and almost circularly polarised, propagating away from the Sun, coinciding with a pronounced sunward deficit in the electron VDF. The cyclotron-resonance condition is fulfilled for electrons moving in the direction opposite to the direction of wave propagation, with energies corresponding to those associated with the sunward deficit.ConclusionsWe conclude that the sunward deficit acts as a source of quasi-parallel whistler waves in the solar wind. The quasilinear diffusion of the resonant electrons tends to fill the deficit, leading to a reduction in the total electron heat flux.