Multi-Instrument Characterization of Magnetospheric Cold Plasma Dynamics in the June 22, 2015 Geomagnetic Storm

Area of Science:

• Space Physics
• Plasma Physics
• Geophysics

Background:

• Geomagnetic storms significantly impact Earth's magnetosphere.
• Understanding plasma density variations is crucial for space weather prediction.

Purpose of the Study:

• To compare magnetospheric plasma mass and electron density observations.
• To analyze these densities during a geomagnetic storm event (June 22, 2015).

Main Methods:

• Utilized Equatorial plasma mass density from geomagnetic field line resonances (FLRs) via Van Allen Probes and ground-based magnetometers (EMMA, CARISMA).
• Employed in situ electron density from Van Allen Probes' plasma wave data using the Neural-network-based Upper hybrid Resonance Determination algorithm.
• Validated observations using plasmapause test particle simulations.

Main Results:

• Observed an order of magnitude density decrease ~1 day after the Dst minimum, followed by partial recovery and another decrease.
• Ground and in situ FLR-derived plasma mass densities showed good agreement at L ~ 4.
• Spacecraft measurements indicated higher densities than ground observations for L < ~3, potentially due to spacecraft motion.

Conclusions:

• Magnetospheric plasma density exhibits significant dynamic changes following geomagnetic storms.
• The study validates FLR-derived mass density measurements and highlights discrepancies at lower L-shells.
• Average ion mass varies between ~1 amu in the plasmasphere and ~2-3 amu in the plasmatrough.