Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning
Abstract
We present high‐resolution Resolute Bay Incoherent Scatter Radar (RISR) measurements in the cusp region during an IMF southward turning. The simultaneous RISR‐N and RISR‐C operation provided 3‐D observations of the dayside polar region, and offered an opportunity to identify the cusp dynamics and polar cap patch formation. Associated with the IMF southward turning, the F‐region density and temperature increased in the cusp, and the increase was particularly evident in the topside ionosphere. The high‐density plasma drifted into the polar cap by an enhanced poleward convection, and became a polar cap patch. The patch plasma was initially dominated by density originating in the cusp, and then later the subauroral ionospheric plasma also contributed to the density enhancement. Weak upflows were present but their contribution within the RISR altitude range was minor. We suggest that the patch source region switches due to dynamic variations of the cusp precipitation and convection from lower latitudes. RISR also detected a flow vortex embedded in the large‐scale convection, which is likely a poleward moving auroral form (PMAF) signature. Joule heating peaked in the cusp E and lower F‐regions. The F‐region Pedersen conductivity increased more than the Hall conductivity, and the high conductivity region extended poleward associated with the patch density enhancement. A 1‐D cusp simulation reproduced the density and temperature enhancements by soft electron precipitation, indicating the importance of soft electron precipitation for the cusp dynamics and the initial part of the patch formation.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- May 01, 2021
- Source ID
- 10.1029/2020ja029090
Entities
People
- A. Otto
- Anthea J. Coster
- B. Sadler
- Nozomu Nishitani
- R. G. Gillies
- Roger H Varney
- Shun-Rong Zhang
- Yukitoshi Nishimura
Organizations
- Air Force Office of Scientific Research
- Athabasca University
- Boston University
- Canada Foundation for Innovation
- Massachusetts Institute of Technology
- Nagoya University
- National Aeronautics and Space Administration
- National Science Foundation
- SRI International
- Sunnybrook Research Institute
- University of Alaska System
- University of Calgary
- University of New Hampshire
- University of Saskatchewan