Kinetic-scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere

Daniel Vech (1, 2) , Justin C. Kasper (1, 3) , Kristopher G. Klein (4) , Jia Huang (1) , Michael L. Stevens (3) , Christopher H.K. Cheng (5) , Anthony W. Case (3) , Kelly E. Korreck (3) , Stuart D. Bale (6) , Trevor A. Bowen (6) , Phyllis L Whittlesey (6) , Roberto Livi (6) , Davin E Larson (6) , David Malaspina (3) , Marc Pulupa (6) , John Bonnell (6) , Peter Harvey (6) , Keith Goetz (7) , Thierry Dudok de Wit (8) , Robert Macdowall (9)

1 CLaSP - Department of Climate and Space Sciences and Engineering
2 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
3 Smithsonian Astrophysical Observatory
4 LPL - Lunar and Planetary Laboratory [Tucson]
5 School of Physics and Astronomy [London]
6 UC Berkeley - University of California [Berkeley]
7 UMN - University of Minnesota [Twin Cities]
8 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
9 GSFC - NASA Goddard Space Flight Center

In this work, we present the first results from the flux angle (FA) operation mode of the Faraday Cup instrument on board the Parker Solar Probe (PSP). The FA mode allows rapid measurements of phase space density fluctuations close to the peak of the proton velocity distribution function with a cadence of 293 Hz. This approach provides an invaluable tool for understanding kinetic-scale turbulence in the solar wind and solar corona. We describe a technique to convert the phase space density fluctuations into vector velocity components and compute several turbulence parameters, such as spectral index, residual energy, and cross helicity during two intervals when the FA mode was used in PSP's first encounter at 0.174 au distance from the Sun.

Keywords: Heliosphere; Interplanetary turbulence; Solar wind; Magnetohydrodynamics; Alfven waves

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]; Solar and Stellar Astrophysics [astro-ph.SR]

Daniel Vech, Justin C. Kasper, Kristopher G. Klein, Jia Huang, Michael L. Stevens, et al.. Kinetic-scale Spectral Features of Cross Helicity and Residual Energy in the Inner Heliosphere. The Astrophysical Journal Supplement, 2020, 246 (2), pp.52. ⟨10.3847/1538-4365/ab60a2⟩. ⟨insu-02942545⟩