Radial Evolution of Non-Maxwellian Electron Populations Derived from Quasi-thermal Noise Spectroscopy: Parker Solar Probe Observations
Authors/Creators
- 1. Shenzhen Key Laboratory of Nuclear and Radiation Safety, Institute for Advanced Study in Nuclear Energy & Safety, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, People's Republic of China
- 2. Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, People's Republic of China
- 3. Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA
- 4. Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Space Physics, Solar-Terrestrial Center of Excellence, Brussels, Belgium
- 5. Center for Space Radiation (CSR), Earth and Life Institute—Climate Sciences (ELI-C), Université Catholique de Louvain, Louvain–la-Neuve, Belgium
- 6. LESIA, Observatoire de Paris, Meudon, France
- 7. Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450, USA
- 8. Mullard Space Science Laboratory University College London, Holmbury St. Mary, Dorking RH5 6NT, UK
Description
Understanding the transport of energy within space plasmas, particularly in the solar wind, remains a complex
challenge. Accurate measurement of electron temperatures and their nonthermal characteristics is crucial for
comprehending energy transport properties in plasmas. Quasi-thermal-noise (QTN) spectroscopy has emerged as a
dependable tool for precise electron parameters assessment as it is less susceptible to spacecraft effects than particle
detectors. In this study, we apply a QTN spectroscopy fitting method to analyze data from the Parker Solar Probe
FIELDS radio instrument obtained during Encounters 2 through 13, under unbiased antenna conditions. We use the
kappa function to characterize the electron velocity distribution and employ a fitting technique to derive the
changes in each parameter across heliocentric distances ranging from 12 Rs to 76 Rs. Specifically, we find that the
electron density scales as ne ∝ r−2.09±0.04 and the Te ∝ r−0.65±0.02 . The distribution of the kappa index has three
distinct regions as a function of radial distance from the Sun. Furthermore, we conduct a statistical analysis of solar
wind energy flux which we finds follows a power-law relationship wtotal ∝ r−1.92±0.04 .
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