Drift of Auroral Absorption and Ionospheric Convection

Details Drift of Auroral Absorption and Ionospheric Convection Drift of Auroral Absorption and Ionospheric Convection

Dec 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmsm54a..04m&link_type=abstract

American Geophysical Union, Fall Meeting 2004, abstract #SM54A-04

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Computation

2455 Particle Precipitation, 2463 Plasma Convection, 2704 Auroral Phenomena (2407), 2716 Energetic Particles, Precipitating

Scientific paper

We develop a method for quasi-continuous monitoring of the particle precipitation regions using the cosmic noise absorption (CNA) data from an imaging riometer. The method does not require vast computational resources nor does it involve excessive manual sifting through the data. The horizontal absorption drift velocity is estimated from the regression lines to positions of the maxima in the two-dimensional absorption intensity images for each individual region of enhanced CNA (absorption patches). The absorption drift velocity estimates from a 7x7-beam Imaging Riometer for Ionospheric Studies (IRIS) in Kilpisjarvi are compared with the electrojet plasma flows deduced from magnetic perturbations recorded by the Kilpisjarvi magnetometer as well as with the tristatic ion drift velocities in the F region (for one event) measured by the EISCAT radar facility within the IRIS field of view (FoV). A reasonable agreement was found between the directions of absorption drift and ionospheric convection both in point-by-point comparisons and in terms of direction reversal timings. The absorption patches of lower intensity appear to have smaller drift velocities and to be associated with weaker magnetic perturbations. Based on our observations, we interpret the relatively slow motions of the auroral absorption as associated with the ExB drift of the entire magnetic flux tube as opposed to the gradient-curvature drift of energetic electrons injected into the ionosphere at the substorm onset. Since the absorption intensity in beam 16 of IRIS, the beam closest to that of EISCAT at 90 km, was found to correlate well with the height-integrated Hall conductivity due to particle precipitation inferred from the EISCAT density measurements, we also assess the conductivity gradient effects on the agreement between the convection measurements by different techniques by considering the gradients of the absorption intensity within the IRIS FoV.

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