DOE OSTI · 3005620
Spectral Properties of Globally Distributed ENA Fluxes across Diverse Regions of the Heliosphere
Abstract
This study analyzes energetic neutral atom (ENA) spectral properties across distinct regions of globally distributed flux (GDF) sky maps, using Interstellar Boundary Explorer data from a full solar cycle, corrected for time dispersion. By time-shifting the data to the heliosheath using GDF source distances from D. B. Reisenfeld et al., we achieve a more accurate representation of heliosheath GDF energy spectra. We quantify ENA spectral characteristics, heliosheath line-of-sight-integrated proton pressure, and heliosheath proton temperature, comparing these to solar wind properties at 1 au and interplanetary scintillation-derived solar wind data. Our findings show that the spectral index is generally anticorrelated with heliosheath proton temperature and pressure, except in the central tail, where a partial positive correlation is observed. The lowest spectral index values occur when high-latitude heliosheath regions are dominated by fast solar wind from polar coronal holes. The south pole exhibits the flattest energy spectra due to plasma heating from both fast solar wind and a late-2014 pressure pulse. The central tail shows shorter variability (5–6 yr) for spectral index and heliosheath proton temperature, while proton pressure follows the 11 yr solar cycle. Most spectral shapes exhibit a “knee” distribution, peaking during solar maximum, with an “ankle” shape observed only at the south pole during solar cycle transitions. Asymmetry in proton pressure in the lobes is driven by the draping effect of the local interstellar magnetic field. This study provides insights into the energetic properties of GDF across the heliosphere, enhancing our understanding of the heliospheric environment.
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Kim, Thomas K. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:0000000162820803), Reisenfeld, Daniel Brett [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:0000000318749450), Zirnstein, Eric J. [Princeton Univ., NJ (United States)] (ORCID:0000000172400618), Janzen, Paul H. [Univ. of Montana, Missoula, MT (United States)], Merrill, Asher S. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); Univ. of Utah, Salt Lake City, UT (United States)], Noh, Sung Jun [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); New Mexico Consortium, Los Alamos, NM (United States)] (ORCID:0000000280327833), Walia, Nehpreet Kaur [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); New Mexico Consortium, Los Alamos, NM (United States)] (ORCID:0000000272965288), Chen, Yue [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)], Guo, Fan [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:0000000343153755), Osthus, Dave Allen [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:000000024681091X), Beesley, Lauren Joann [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)], Shin, Dae-Kyu [Space Environment Laboratory, Seoul (Korea, Republic of)], Sokół, Justyna M. [Southwest Research Institute, San Antonio, TX (United States)] (ORCID:0000000241733601), Bzowski, Maciej [Polish Academy of Sciences (PAS), Warsaw (Poland)] (ORCID:0000000339572359), Kubiak, Marzena A. [Polish Academy of Sciences (PAS), Warsaw (Poland)] (ORCID:0000000252049645), Porowski, Czeslaw [Polish Academy of Sciences (PAS), Warsaw (Poland)] (ORCID:0000000182524104), Funsten III, Herbert O. [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)] (ORCID:0000000268171039). 2025-10-09. Spectral Properties of Globally Distributed ENA Fluxes across Diverse Regions of the Heliosphere. https://doi.org/10.3847/1538-4357%2Fae0183
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