Cusp Dynamics and Polar Cap Patch Formation Associated With a Small IMF Southward Turning. Issue 5 (17th May 2021)

• Record Type: Journal Article
• Authors: Nishimura, Y.; Sadler, F. B.; Varney, R. H.; Gilles, R.; Zhang, S. R.; Coster, A. J.; Nishitani, N.; Otto, A.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 5(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-17
• Subjects: ARTEMIS -- conductanceDMSP -- SuperDARN -- total electron content (GPS TEC); Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA029090
• Languages: English
• ISSNs: 2169-9380

Abstract

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. Key Points: The simultaneous Resolute Bay Incoherent Scatter Radar (RISR)‐N and RISR‐C operation gave 3‐D observations of the cusp dynamics and polar cap patch formation Horizontal and meridional profiles of the cusp density, temperature, velocity, conductance, and Joule heating are presented The patch formation, propagation, and time‐dependent contributions of the cusp and subauroral sources are found