Redefining SAR Arc Generation: The Competing Roles of Magnetospheric and Ionospheric Energy Injection
Abstract Stable auroral red (SAR) arcs are luminous subauroral emissions produced by the collisional excitation of oxygen atoms during geomagnetically active times. While traditionally attributed to inner magnetospheric electron heating, recent observations and simulations challenge the exclusivity of this mechanism. Here, we resolve the ionospheric origin of SAR arcs using multi‐instrument observations and numerical simulations during the March 2015 geomagnetic storm. Both magnetospheric heat flux and ion‐neutral frictional heating, driven by subauroral plasma flows, independently generate SAR arcs with intensities surpassing background airglow by hundreds of Rayleighs. While thermal electron impact dominates red‐line emissions in both cases, the vertical structures diverge: frictional heating localizes emissions to altitudes of 250–400 km, whereas magnetospheric heating extends emissions above ∼280 km with broader altitudinal coverage. These results redefine SAR arc generation as a product of competing magnetospheric and ionospheric energy pathways, advancing our understanding of cross‐scale interactions in geospace.
Authors
- Yongliang Zhang (ORCID: https://orcid.org/0000-0003-4851-1662)
- Jun Liang (ORCID: https://orcid.org/0000-0002-4590-2978)
- C. R. Martinis (ORCID: https://orcid.org/0000-0002-1085-7871)
- J. Wroten (ORCID: https://orcid.org/0000-0001-7188-3793)
- Libo Liu (ORCID: https://orcid.org/0000-0001-5773-0184)
- Jing Liu (ORCID: https://orcid.org/0000-0002-6584-0647)
- Wenbin Wang (ORCID: https://orcid.org/0000-0002-6287-4542)
- Yao Chen (ORCID: https://orcid.org/0000-0001-6449-8838)
- Yifan Lu (ORCID: https://orcid.org/0009-0001-4053-853X)
- Tru H. Cao (ORCID: https://orcid.org/0009-0000-2960-6717)
Institutions
- NSF National Center for Atmospheric Research (US)
- Boston University (US)
- NSF NCAR High Altitude Observatory (US)
- Shandong University (CN)
- University of Calgary (CA)
- Chinese Academy of Sciences (CN)
- Johns Hopkins University Applied Physics Laboratory (US)
- Institute of Space Sciences (ES)
- Institute of Geology and Geophysics (CN)
- Geological Exploration Institute of Shandong Zhengyuan (CN)
Publication Details
- Journal
- AGU Advances
- Published
- 2025-11-24
- DOI
- https://doi.org/10.1029/2025av001881
- Citations
- 1
- Primary Topic
- Ionosphere and magnetosphere dynamics
- Type
- article
- Field-Weighted Citation Impact
- 1.15
Funders
- National Science Foundation
- National Natural Science Foundation of China
- Natural Science Foundation of Shandong Province