Observations of Non-Thermal Structure in the Proton Velocity Distribution Function Using Proton Beams Below 0.3 AU from Parker Solar Probe and at 1 AU with Wind

B. L. Alterman , J. C. Kasper , M. L. Stevens , A. W. Case , K. E. Korreck , D. E. Larson , R. Livi , P. L. Whittlesey , J. Huang , K. G. Klein , M. Martinović (1) , S. D. Bale , M. Pulupa , D. Malaspina , J. W. Bonnell , K. Goetz , P. Harvey , Thierry Dudok de Wit (2) , R. J. Macdowall , J. Verniero , A. Tenerani , O. Alexandrova (3) , B. Maruca , L. Matteini (3)

1 Observatoire de Paris
2 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
3 LESIA (UMR_8109) - Laboratoire d'études spatiales et d'instrumentation en astrophysique

Solar wind protons regularly deviate from local thermodynamic equilibrium (LTE). Non-LTE features of the VDF can provide sources of free energy that drive instabilities. One such source of free energy is an excess temperature parallel to the local magnetic field, which may include a non-zero proton heat flux. We characterize this excess temperature with two drifting proton populations, one Maxwellian and one bi-. We compare proton beam and core measurements at two locations. At 1 AU, we report more than 20 years of measurements with the Wind/SWE Faraday cups. Below 0.3 AU, we also report their radial variation using measurements from the Parker Solar Probe SWEAP and Fields instruments.

Keywords: General or miscellaneous; MAGNETOSPHERIC PHYSICS; SOLAR PHYSICS; ASTROPHYSICS; ASTRONOMY; SPACE PLASMA PHYSICS; SPACE WEATHER

Domains: Sciences of the Universe [physics]

B. L. Alterman, J. C. Kasper, M. L. Stevens, A. W. Case, K. E. Korreck, et al.. Observations of Non-Thermal Structure in the Proton Velocity Distribution Function Using Proton Beams Below 0.3 AU from Parker Solar Probe and at 1 AU with Wind. American Geophysical Union, 2019, San Francisco, United States. 15 pp. ⟨insu-03562468⟩