Solar Wind Impact on ENAs From Earth's Subsolar Magnetosheath. Issue 11 (10th November 2022)

• Record Type: Journal Article
• Authors: Starkey, M. J.; Dayeh, M. A.; Fuselier, S. A.; Petrinec, S. M.; McComas, D. J.; Ogasawara, K.; Szalay, J. R.; Schwadron, N. A.; Sokół, J. M.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-11-10
• Subjects: Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2022JA030965
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: As the solar wind (SW) crosses Earth's bow shock, it is heated and decelerated, resulting in a hot and dense magnetosheath ion population. This increases the probability of charge exchange between a magnetosheath proton and a geocoronal Hydrogen atom, which produces energetic neutral atoms (ENAs). These ENAs propagate away from the magnetosheath carrying information about the inherent properties of the progenitor plasma. In this work, ENA fluxes from the subsolar magnetosheath, observed by the Interstellar Boundary Explorer, are compared to SW conditions. These comparisons reveal that the passband‐weighted average differential flux of ENAs is strongly influenced by the SW density, and that ENA spectra flatten with increasing SW speed and temperature, and steepen with increasing SW density. In addition, there is evidence from ENA spectra for different interplanetary magnetic field configurations that most of the ENAs observed by Interstellar Boundary Explorer come from the specularly reflected proton population in the magnetosheath. Plain Language Summary: The solar wind (SW) is a high speed flow of charged particles continuously ejected from the Sun and moves radially away. As the SW reaches Earth, it is heated and decelerated across Earth's bow shock and enters a hot and dense region known as the magnetosheath. The heated SW can then exchange electrons with the surrounding geocoronal neutral atoms and produce energetic neutral atoms (ENA). ENAs travel away from the magnetosheath, unaffected by Earth's magnetic field, and are detected by ENA imagers on the Interstellar Boundary Explorer spacecraft. This work analyzes ENA signals from Earth's magnetosheath and identifies relationships between their energy distributions and SW properties (i.e., temperature, speed, and density). Average ENA energy distributions are compared for different SW conditions, and the heating mechanisms at Earth's BS are identified. Key Points: Energetic neutral atom (ENA) spectral index from the subsolar magnetosheath correlates well with upstream solar wind speed, density, and temperature ENA spectra from the magnetosheath are representative of their local progenitor ion populations ENA magnetosheath spectra provide evidence of specularly reflected protons