Authors: Ilya Kuzichev (New Jersey Institute of Technology, Center for Solar-Terrestrial Research, Newark, NJ, USA), Ivan Vasko (Space Sciences Laboratory, University of California, Berkeley, CA, USA), Lynn B. Wilson III (NASA Goddard Space Flight Center, Heliophysics Science Division, Greenbelt, MD, USA), Joseph Torsiello (New Jersey Institute of Technology, Center for Solar-Terrestrial Research, Newark, NJ, USA), Anton Artemyev (Department of Earth, Planetary, and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA, USA))

Whistler waves (right-hand polarized electromagnetic waves with frequencies well above local proton cyclotron frequency, but below local electron cyclotron frequency) in the solar wind and at the interplanetary shocks have drawn a lot of attention due to their potential role in the heat flux regulation and electron scattering that results in formation of typical solar wind electron velocity distribution functions (eVDF) [1,2]. Modern satellite measurements provided conclusive evidence that whistler waves are generated locally via the so-called whistler heat flux instabilities [3,4]. Such experimental successes have driven theoretical and modelling efforts to understand the influence of the locally generated whistler waves on the particles, which demonstrated, in particular, different roles played by parallel, anti-parallel, and oblique waves [1,2,5]. But so far, observational evidence for oblique and anti-parallel whistler waves in the solar wind is rather scarce, majority of the observed whistlers are parallel. At the same time, eVDF observations often demonstrate that hot electrons have temperature anisotropy that might drive the generation of anti-parallel whistler waves. In this report, we present the results of the linear stability analysis of a large dataset of eVDFs observed by the Wind spacecraft.

1.Kuzichev et al. 2019 APJ, https://doi.org/10.3847/1538-4357/ab3290

2.Micera et al. 2020 ApJL, https://doi.org/10.3847/2041-8213/abc0e8

3.Tong et al. 2019 ApJL, https://doi.org/10.3847/2041-8213/aaf734

4.Tong et al. 2019 ApJ, https://doi.org/10.3847/1538-4357/ab1f05

5.Vasko et al. 2020 PoP, https://doi.org/10.1063/5.0003401
This work has been supported by NSF Grant AGS-1502923 and NASA grant HGI-O 80NSSC21K0581.