Journal Article

MMS Observations of a Compressed, Strongly Driven Magnetopause During the 2024 Mother's Day Storm

Fuselier, Stephen A, Sun, Weijie, Genestreti, Kevin J, Øieroset, Marit, Marshall, Andy, Burch, Jim L, Chen, Li‐Jen, Vines, Sarah K, Burkholder, Brandon, Trattner, Karlheinz J, Phan, Tai D, Torbert, Roy B, Shuster, Jason R, Gurram, Harsha, Rice, Rachel C, Gershman, Daniel J, Lindberg, Martin, Gomez, Roman G, Beedle, Jason M. H, Cantwell, Kelly

2025

Overview

From 10 to 12 May 2024, a series of coronal mass ejections led to one of the strongest geomagnetic storms of the century, referred to as the Mother's Day or Gannon Storm. MMS's position on the dayside magnetosphere on 11 May provided observations of a strongly driven and compressed ∼7RE $\\left(\\sim 7\\ {R}_{E}\\right)$ reconnecting magnetopause. Because of the driving conditions, the magnetopause became saturated with O+ ${O}^{+}$ outflows that dominated the mass density of the plasma environment. In the reconnecting magnetopause, MMS observes signatures of parallel electron heating on the magnetopause's magnetosheath side, but anomalous and significant electron cooling, especially from the perpendicular electron temperature on the magnetosphere side, possibly driven by additional mechanisms besides reconnection. Even with the strong driving and O+ ${O}^{+}$ outflows, we find an expected (0.19±0.04) $(0.19\\pm 0.04)$ normalized reconnection rate for the primary exhaust, indicating insensitivity to these conditions. The unnormalized rate, however, is atypically large and scales with the driving conditions.

• Publisher: John Wiley & Sons, Inc
• Subject: Charged particles / Coronal mass ejection / Driving conditions / Electric fields / Electron energy / Electron heating / Energy / Geomagnetic storms / Magnetic fields / Magnetic storms / Magnetopause / Magnetosheath / Magnetospheres / Outflow / Plasma / Storms