Thermal Electron Behavior in Obliquely Propagating Whistler Waves: MMS Observations in the Solar Wind

2021 ◽  
Vol 48 (14) ◽  
Author(s):  
Z.‐Y. Liu ◽  
B. Wang ◽  
Q.‐G. Zong ◽  
S. T. Yao ◽  
C. J. Pollock ◽  
...  
2021 ◽  
Author(s):  
Alfredo Micera ◽  
Andrei Zhukov ◽  
Rodrigo A. López ◽  
Maria Elena Innocenti ◽  
Marian Lazar ◽  
...  

<p>Electron velocity distribution functions, initially composed of core and strahl populations as typically encountered in the near-Sun solar wind and as recently observed by Parker Solar Probe, have been modeled via fully kinetic Particle-In-Cell simulations. It has been demonstrated that, as a consequence of the evolution of the electron velocity distribution function, two branches of the whistler heat flux instability can be excited, which can drive whistler waves propagating in the direction parallel or oblique to the background magnetic field. First, the strahl undergoes pitch-angle scattering with oblique whistler waves, which provokes the reduction of the strahl drift velocity and the simultaneous broadening of its pitch angle distribution. Moreover, the interaction with the oblique whistler waves results in the scattering towards higher perpendicular velocities of resonant strahl electrons and in the appearance of a suprathermal halo population which, at higher energies, deviates from the Maxwellian distribution. Later on, the excited whistler waves shift towards smaller angles of propagation and secondary scattering processes with quasi-parallel whistler waves lead to a redistribution of the scattered particles into a more symmetric halo. All processes are accompanied by a significant decrease of the heat flux carried by the strahl population along the magnetic field direction, although the strongest heat flux rate decrease is simultaneous with the propagation of the oblique whistler waves.</p>


2019 ◽  
Vol 878 (1) ◽  
pp. 41 ◽  
Author(s):  
Yuguang Tong ◽  
Ivan Y. Vasko ◽  
Anton V. Artemyev ◽  
Stuart D. Bale ◽  
Forrest S. Mozer

Solar Physics ◽  
2017 ◽  
Vol 292 (3) ◽  
Author(s):  
Rajesh Kumar Rai ◽  
Swati Sharma ◽  
R. P. Sharma

1996 ◽  
Vol 101 (A12) ◽  
pp. 27555-27564 ◽  
Author(s):  
D. Lengyel-Frey ◽  
R. A. Hess ◽  
R. J. MacDowall ◽  
R. G. Stone ◽  
N. Lin ◽  
...  

2021 ◽  
Author(s):  
Matthieu Kretschmar ◽  
Thomas Chust ◽  
Daniel Graham ◽  
Volodya Krasnosekskikh ◽  
Lucas Colomban ◽  
...  

<p>Plasma waves can play an important role in the evolution of the solar wind and the particle velocity distribution functions in particular. We analyzed the electromagnetic waves observed above a few Hz by the Radio Plasma Waves (RPW) instrument suite onboard Solar Orbiter, during its first orbit, which covered a distance from the Sun between 1 AU and 0.5 AU.  We identified the majority of the detected waves as whistler waves with frequency around  0.1 f_ce and right handed circular polarisation. We found these waves to be mostly aligned or anti aligned with the ambient magnetic field, and rarely oblique. We also present and discuss their direction of propagation and the variation of the waves' properties with heliocentric distance.</p>


2021 ◽  
Vol 923 (2) ◽  
pp. 216
Author(s):  
S. T. Yao ◽  
Q. Q. Shi ◽  
Q. G. Zong ◽  
A. W. Degeling ◽  
R. L. Guo ◽  
...  

Abstract The role of whistler-mode waves in the solar wind and the relationship between their electromagnetic fields and charged particles is a fundamental question in space physics. Using high-temporal-resolution electromagnetic field and plasma data from the Magnetospheric MultiScale spacecraft, we report observations of low-frequency whistler waves and associated electromagnetic fields and particle behavior in the Earth’s foreshock. The frequency of these whistler waves is close to half the lower-hybrid frequency (∼2 Hz), with their wavelength close to the ion gyroradius. The electron bulk flows are strongly modulated by these waves, with a modulation amplitude comparable to the solar wind velocity. At such a spatial scale, the electron flows are forcibly separated from the ion flows by the waves, resulting in strong electric currents and anisotropic ion distributions. Furthermore, we find that the low-frequency whistler wave propagates obliquely to the background magnetic field ( B 0), and results in spatially periodic magnetic gradients in the direction parallel to B 0. Under such conditions, large pitch-angle electrons are trapped in wave magnetic valleys by the magnetic mirror force, and may provide free perpendicular electron energy to excite higher-frequency whistler waves. This study offers important clues and new insights into wave–particle interactions, wave generation, and microscale energy conversion processes in the solar wind.


2021 ◽  
Author(s):  
Laura Bercic ◽  

<div> <div> <div> <p>The solar coronal plasma which escapes the Sun’s gravity and expands through our solar system is called the solar wind. It consists mainly of electrons and protons, carries the Sun’s magnetic field and, at most heliocentric distances, remains weakly-collisional. Due to their small mass, the solar wind electrons have much higher thermal velocity than their positively charged counterpart, and play an important role in the solar wind energetics by carrying the heat flux away from the Sun. Their velocity distribution functions (VDFs) are complex, usually modeled by three components. While the majority of electrons belong to the low-energetic thermal Maxwellian core population, some reach higher velocities, forming either the magnetic field aligned strahl population, or an isotropic high-energy halo population. This shape of the electron VDF is a product of the interplay between<br>Coulomb collisions, adiabatic expansion, global and local electro-magnetic fields and turbulence.<br>In this work we focus on the effects of local electro-magnetic wave activity on electron VDF, taking advantage of the early measurements made by the novel heliospheric Solar Orbiter mission. The high- cadence sampling of 2-dimensional electron VDFs by the electrostatic analyser SWA-EAS, together with the EM wave data collected by the seach-coil magnetometers and electric-field antennas, part of</p> </div> </div> </div><div> <div> <div> <p>the RPW instrument suit, allow a direct investigation of the wave-particle energy and momentum exchange. We present the evolution of the electron VDF in the presence of quasi-parallel and oblique whistler waves, believed to be responsible for scattering the strahl and creating the halo population (Verscharen et al. 2019; Micera et al. 2020).</p> </div> </div> </div>


1982 ◽  
Vol 6 (3) ◽  
pp. 192-198
Author(s):  
Zhang Zhen-da ◽  
Huang You-ran ◽  
Li Xiao-qing

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