| Autor: |
Sorathia, K. A., Shumko, M., Sciola, A., Michael, A., Merkin, V. G., Gallardo‐Lacourt, B., Henderson, M. G., Lin, D., Bao, S., Garretson, J., Ukhorskiy, A. Y. |
| Předmět: |
|
| Zdroj: |
Geophysical Research Letters; 8/28/2024, Vol. 51 Issue 16, p1-10, 10p |
| Abstrakt: |
We present the first global geospace simulation to reproduce auroral giant undulations (GUs). To identify their magnetospheric drivers, we employ the MAGE (Multiscale Atmosphere‐Geospace Environment) model in a case study of a geomagnetic storm for which there were spacecraft‐ and ground‐based observations of GUs. The model reproduces the spatial and temporal scales of the GUs as well as the presence of duskside subauroral polarization streams (SAPS) and plasmapause undulations. Based on our modeling, we are able to identify the magnetospheric drivers of GUs as mesoscale ring current injections which, after drifting westward, create inverted regions of flux‐tube entropy (FTE) and subsequent interchange instability. Outward‐protruding interchange fingers disrupt shielding of the inner magnetosphere, creating longitudinally localized ripples in magnetospheric convection equatorward of the magnetospheric instability, which structure the plasmapause and duskside diffuse precipitation. While not causal, SAPS and plasmapause undulations are a consequence of the unstable magnetospheric configuration. Plain Language Summary: The visually dazzling display of the aurora during active periods is caused primarily by the precipitation of energetic electrons from the magnetosphere into the ionosphere. The auroral oval plays host to a variety of morphological features, or auroral forms, that are a reflection of magnetospheric processes and therefore a powerful tool for understanding the cross‐scale processes that bind together different geospace domains. Unlocking that power, however, requires an understanding of how magnetospheric processes are reflected in the aurora. Despite decades of study, that understanding has remained elusive, primarily due to limited in situ measurements and uncertainty in the magnetic mapping connecting them to the ionosphere. Only recently have new global geospace models emerged that can provide this understanding. In this letter we identify the magnetospheric driver of auroral giant undulations (GUs), wave‐like trains of undulations that form on the equatorward edge of the diffuse aurora with typical spatial scales of 100 km. We show that GUs are the consequence of a "buoyancy imbalance" formed during the buildup of the ring current and the subsequent disruption of the ionospheric current systems that typically shield the inner magnetosphere. Key Points: We present the first global geospace simulation to reproduce auroral giant undulations (GUs)Model shows GUs result from localized under‐shielding as a consequence of interchange instability during the buildup of the ring currentInterchange‐unstable regions drive ripples in magnetospheric convection, structuring the plasmapause and duskside diffuse precipitation [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Plný text