Multi‐Scale Density Structures in the Plasmaspheric Plume During a Geomagnetic Storm
Abstract
Evolution of large‐scale and fine‐scale plasmaspheric plume density structures was examined using space‐ground coordinated observations of a plume during the 7–8 September 2015 storm. The large‐scale plasmaspheric plume density at Van Allen Probes A was roughly proportional to the total electron content (TEC) along the satellite footprint, indicating that TEC distribution represents the large‐scale plume density distribution in the magnetosphere. The plasmaspheric plume contained fine‐scale density structures and subauroral polarization streams (SAPS) velocity fluctuations. High‐resolution TEC data support the interpretation that the fine‐scale plume structures were blobs with ∼300 km size and ∼500–800 m/s in the ionosphere (∼3,000 km size and ∼5–8 km/s speed in the magnetosphere), emerging at the plume base and drifting to the plume. The short‐baseline Global Navigation Satellite System receivers detected smaller‐scale (∼10 km in the ionosphere, ∼100 km in the magnetosphere) TEC gradients and their sunward drift. Fine‐scale density structures were associated with enhanced phase scintillation index. Velocity fluctuations were found to be spatial structures of fine‐scale SAPS flows that drifted sunward with density irregularities down to ∼10 s of meter‐scale. Fine‐scale density structures followed a power law with a slope of ∼−5/3, and smaller‐scale density structures developed slower than the larger‐scale structures. We suggest that turbulent SAPS flows created fine‐scale density structures and their cascading to smaller scales. We also found that the plume fine‐scale density structures were associated with whistler‐mode intensity modulation, and localized electron precipitation in the plume. Structured precipitation in the plume may contribute to ionospheric heating, SAPS velocity reduction, and conductance enhancements.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Mar 01, 2022
- Source ID
- 10.1029/2021ja030230
Entities
People
- Anthea J. Coster
- Carlos Martinis
- J. L. Semeter
- J. M. Ruohoniemi
- Jerry Goldstein
- Nozomu Nishitani
- Qianli Ma
- Sebastijan Mrak
- Shun-Rong Zhang
- Simon Shepherd
- Wen Li
- Yukitoshi Nishimura
Organizations
- Air Force Office of Scientific Research
- Alfred P. Sloan Foundation
- Boston University
- Dartmouth College
- Massachusetts Institute of Technology
- Nagoya University
- National Aeronautics and Space Administration
- National Science Foundation
- Southwest Research Institute
- Virginia Tech