Physics
Scientific paper
Sep 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002jgra..107.1241g&link_type=abstract
Journal of Geophysical Research (Space Physics), Volume 107, Issue A9, pp. SIA 1-1, CiteID 1241, DOI 10.1029/2001JA000158
Physics
2
Magnetospheric Physics: Plasma Convection, Ionosphere: Auroral Ionosphere (2704), Ionosphere: Plasma Convection, Ionosphere: Particle Precipitation, Ionosphere: Ionospheric Irregularities
Scientific paper
Small-scale ionospheric irregularities and auroral precipitation are common features of the auroral ionosphere, but their spatial association has not been examined on global scales. In this paper, we compare electron and ion precipitation from individual passes of the Defense Meteorological Satellite Program (DMSP) spacecraft with concurrent observations of ionospheric irregularities and plasma convection from the Northern Hemisphere component of the Super Dual Auroral Radar Network (SuperDARN). Because of the nature of the DMSP orbits and the spatial resolution of the SuperDARN measurements these comparisons have been limited to the dusk and postdawn sectors and spatial dimensions greater than ~100 km. We have found that the SuperDARN radars generally observe ionospheric irregularities over a greater latitudinal extent than the DMSP satellites observe particle precipitation. Specifically, ionospheric irregularities are observed both equatorward and poleward of the convection reversal boundary (CRB) in the dawn and dusk sectors, whereas particle precipitation is only observed equatorward of the CRB. Under conditions where the radars can detect the true equatorward boundary of the irregularities, they are observed to extend equatorward of the particle precipitation. Both irregularities and particle precipitation expand equatorward with increasing geomagnetic activity, and there is evidence that precipitation regions with higher energy flux are associated with regions of stronger sunward convection. These results suggest that SuperDARN can provide a coarse determination of the auroral-oval position that will complement measurements with optics and particle detectors. More importantly, they demonstrate the spatial relationships between precipitation, electric fields, and ionospheric irregularities that result from the electrical coupling between the magnetosphere and ionosphere and the dependence of ionospheric plasma instabilities on the ionospheric electric field and precipitation-induced electron-density gradients.
Barnes Robin J.
Greenwald Raymond A.
Ruohoniemi Michael J.
Shepherd Simon G.
Sotirelis Thomas S.
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