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- Title
The Contribution of Plasma Sheet Bubbles to Stormtime Ring Current Buildup and Evolution of Its Energy Composition.
- Authors
Sciola, A.; Merkin, V. G.; Sorathia, K.; Gkioulidou, M.; Bao, S.; Toffoletto, F.; Pham, K.; Lin, D.; Michael, A.; Wiltberger, M.; Ukhorskiy, A.
- Abstract
The formation of the stormtime ring current is a result of the inward transport and energization of plasma sheet ions. Previous studies have demonstrated that a significant fraction of the total inward plasma sheet transport takes place in the form of bursty bulk flows, known theoretically as flux tube entropy‐depleted "bubbles." However, it remains an open question to what extent bubbles contribute to the buildup of the stormtime ring current. Using the Multiscale Atmosphere Geospace Environment Model, we present a case study of the 17 March 2013 storm, including a quantitative analysis of the contribution of plasma transported by bubbles to the ring current. We show that bubbles are responsible for at least 50% of the plasma energy enhancement within 6 RE during this strong geomagnetic storm. The bubbles that penetrate within 6 RE transport energy primarily in the form of enthalpy flux, followed by Poynting flux and relatively little as bulk kinetic flux. Return flows can transport outwards a significant fraction of the plasma energy being transported by inward flows, and therefore must be considered when quantifying the net contribution of bubbles to the energy buildup. Data‐model comparison with proton intensities observed by the Van Allen Probes show that the model accurately reproduces both the bulk and spectral properties of the stormtime ring current. The evolution of the ring current energy spectra throughout the modeled storm is driven by both inward transport of an evolving plasma sheet population and by charge exchange with Earth's geocorona. Plain Language Summary: The formation of the ring current is one of the defining features of the near‐Earth space response to solar storms. While it is known that the plasma that constitutes the ring current originates from Earth's magnetic tail, the relative roles of different transport processes remains unclear. In this study, we utilize numerical modeling to investigate ring current buildup for a specific solar storm, and find that flows that are medium‐scale relative to the system size and referred to as plasma "bubbles," are responsible for at least half of the total buildup of ring current plasma. Our analysis also shows that the bubbles displace some of the background plasma on their way Earthward, which is important when calculating their net contribution to the ring current. The modeled ring current energy spectrum is in good agreement with spacecraft observations, and the evolution of the energy spectrum is driven by both an evolving plasma population in the tail and by energy‐dependent charge exchange. The ability to accurately model the complex interactions between the ring current and Earth's geospace system is critical for understanding the full impacts of solar storms. Key Points: Global geospace model shows that bubbles contribute at least half of the total ring current energy during the 17 March 2013 stormThe model accurately reproduces the observed ring current intensity and spatial distribution across a broad energy range (10–100 keV)The evolution of the modeled ring current ion energy composition is due to both an evolving source population and energy‐dependent losses
- Subjects
MAGNETIC storms; CHARGE exchange; STORMS; EARTH currents; POPULATION transfers; BUBBLES
- Publication
Journal of Geophysical Research. Space Physics, 2023, Vol 128, Issue 11, p1
- ISSN
2169-9380
- Publication type
Article
- DOI
10.1029/2023JA031693