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Found 2 entries in the Bibliography.

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An examination of the source of decameter-scale irregularities in the geomagnetically disturbed mid-latitude ionosphere

We present first results from a study of the plasma instability mechanism responsible for the small-scale (\~10 m) ionospheric density irregularities commonly observed by the Super Dual Auroral Radar Network (SuperDARN) HF radars in the vicinity of Sub Auroral Polarization Streams (SAPS) during periods of geomagnetic disturbance. A focus is placed on the mid-latitude region of the ionosphere over North America where recent expansion of the SuperDARN network allows for extensive direct comparisons with total electron content (TEC) measurements from a dense network of ground-based GPS receivers. The TEC observations indicate that high-speed SAPS channels and the associated small-scale irregularities are typically located within the mid-latitude ionospheric trough. The Millstone Hill Incoherent Scatter Radar (ISR), operating in campaign mode in support of the NASA Van Allen Probes mission, provided measurements of F region ion/electron density, velocity, and temperature suitable for identifying potential mechanisms of plasma instability during a SAPS event that extended over 12 hours of magnetic local time (MLT) on 2 February 2013. Previous work has indicated that the density gradients associated with the poleward wall of the mid-latitude trough can produce small-scale irregularities due to the gradient drift instability during quiet periods by cascade from larger-scale structures. In this study we demonstrate that the gradient drift instability is a viable source for the direct generation of the small-scale irregularities observed by SuperDARN radars in the mid-latitude ionosphere during geomagnetically disturbed conditions.

Thomas, Evan; Yan, Jingye; Zhang, Jiaojiao; Baker, Joseph; Ruohoniemi, Michael; Hoskawa, Keisuke; Erickson, Philip; Coster, Anthea; Foster, John;

Published by:       Published on: 08/2014

YEAR: 2014     DOI: 10.1109/URSIGASS.2014.6929853

Ionosphere; Plasmas; SUPERDARN; Van Allen Probes

Storm time observations of plasmasphere erosion flux in the magnetosphere and ionosphere

Plasmasphere erosion carries cold dense plasma of ionospheric origin in a storm-enhanced density plume extending from dusk toward and through the noontime cusp and dayside magnetopause and back across polar latitudes in a polar tongue of ionization. We examine dusk sector (20 MLT) plasmasphere erosion during the 17 March 2013 storm (Dst ~ -130 nT) using simultaneous, magnetically aligned direct sunward ion flux observations at high altitude by Van Allen Probes RBSP-A (at ~3.0 Re) and at ionospheric heights (~840 km) by DMSP F-18. Plasma erosion occurs at both high and low altitudes where the subauroral polarization stream flow overlaps the outer plasmasphere. At ~20 UT, RBSP-A observed ~1.2E12 m-2 s-1 erosion flux, while DMSP F-18 observed ~2E13 m-2 s-1 sunward flux. We find close similarities at high and low altitudes between the erosion plume in both invariant latitude spatial extent and plasma characteristics.

Foster, J.; Erickson, P.; Coster, A.; Thaller, S.; Tao, J.; Wygant, J.; Bonnell, J;

Published by: Geophysical Research Letters      Published on: 02/2014

YEAR: 2014     DOI: 10.1002/2013GL059124

Van Allen Probes