Eastward transients in the dayside ionosphere. II. A parallel-plate capacitorlike effect

Area of Science:

• Space Physics
• Atmospheric Science
• Geophysics

Background:

• Geospace storms significantly impact Earth's magnetosphere and ionosphere.
• Previous studies often interpret cusp region electrodynamics in terms of poleward-moving auroral forms.

Purpose of the Study:

• To investigate chorus-wave-driven energetic particle precipitation during a geospace storm.
• To analyze associated ionospheric phenomena, including electric field enhancements and turbulence.
• To contextualize these observations within dayside ionosphere dynamics and compare them with a similar event during a superstorm.

Main Methods:

• Observation of energetic particle precipitation on closed magnetic field lines.
• Radar detection of meter-scale turbulence and ionospheric electric field enhancements.
• Comparison of events from April 2023 and May 2024 geospace storms.

Main Results:

• Observed chorus-wave-driven energetic particle precipitation on closed magnetic field lines.
• Detected simultaneous ionospheric impact ionization and strong electric field enhancements.
• Identified fast, eastward-moving electric field structures equatorward of the ionospheric cusp in both events.
• Associated these structures with turbulent Hall currents, challenging existing cusp electrodynamics models.

Conclusions:

• Transient eastward electrodynamic bursts in the dayside ionosphere may be a common feature of geomagnetic storms.
• These bursts challenge conventional explanations focusing on poleward-moving forms.
• The findings suggest wave-particle interactions or proton precipitation contribute to these phenomena.