Azimuthal flow bursts in the inner plasma sheet and possible connection with SAPS and plasma sheet earthward flow bursts. Issue 6 (5th June 2015)

• Record Type: Journal Article
• Authors: Lyons, L. R.; Nishimura, Y.; Gallardo‐Lacourt, B.; Nicolls, M. J.; Chen, S.; Hampton, D. L.; Bristow, W. A.; Ruohoniemi, J. M.; Nishitani, N.; Donovan, E. F.; Angelopoulos, V.
• Is Part Of: Journal of geophysical research. Volume 120:Issue 6(2015:Jun.)
• Page Start: 5009
• Page End: 5021
• Publication Date: 2015-06-05
• Subjects: flow bursts -- SAPS -- plasma sheet -- streamers -- aurora -- convection; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2015JA021023
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: We have combined radar observations and auroral images obtained during the Poker Flat Incoherent Scatter Radar Ion Neutral Observations in the Thermosphere campaign to show the common occurrence of westward moving, localized auroral brightenings near the auroral equatorward boundary and to show their association with azimuthally moving flow bursts near or within the subauroral polarization stream (SAPS) region. These results indicate that the SAPS region, rather than consisting of relatively stable proton precipitation and westward flows, can have rapidly varying flows, with speeds varying from ~100 m/s to ~1 km/s in just a few minutes. The auroral brightenings are associated with bursts of weak electron precipitation that move westward with the westward flow bursts and extend into the SAPS region. Additionally, our observations show evidence that the azimuthally moving flow bursts often connect to earthward (equatorward in the ionosphere) plasma sheet flow bursts. This indicates that rather than stopping or bouncing, some flow bursts turn azimuthally after reaching the inner plasma sheet and lead to the bursts of strong azimuthal flow. Evidence is also seen for a general guiding of the flow bursts by the large‐scale convection pattern, flow bursts within the duskside convection being azimuthally turned to the west, and those within the dawn cell being turned toward the east. The possibility that the SAPS region flow structures considered here may be connected to localized flow enhancements from the polar cap that cross the nightside auroral poleward boundary and lead to flow bursts within the plasma sheet warrants further consideration. Key Points: Westward moving brightenings near the auroral equatorward boundary are common and are associated with azimuthally moving flow bursts near or within SAPS region Azimuthal flow bursts connect to earthward plasma sheet flow bursts