Effects of Magnetostorms on the Plasmaspheric Density Distribution

Bodo Reinisch, Xueqin Huang, Paul Song, Ivan Galkin, Grigori Khmyrov
Environmental, Earth, and Atmospheric Sciences Department
Center for Atmospheric Research, University of Massachusetts Lowell

Robert Benson, Shing Fung, James Green
NASA Goddard Space Flight Center

Application of the radio sounding technique to the magnetosphere has provided
unprecedented capability of remotely measuring the global plasma density in
the plasmasphere. The Radio Plasma Imager (RPI) on IMAGE conducts echo radio
sounding experiments producing plasmagrams that display echo amplitudes as
function of virtual range and frequency. These plasmagrams show different
types of echo traces resulting from X, O, and Z mode wave propagation. The
identification of the wave modes requires careful analysis. Angle of arrival
measurements together with the echo trace characteristics reveal two classes
of echoes, direct and field-aligned propagation (FAP) echoes. From the FAP
echo traces the plasma density distribution along the field line from
hemisphere to hemisphere can be calculated. Each of such profiles can be
derived every 2 min during the satellite flight. With the measurements before
a storm, we derive the plasma density distribution during quiet times from 
L = 2.2 to L = 4. After the storm, we observed that the densities dropped to 
a small fraction of the quiet time values in the region L > 2.3, indicating
that during the storm the plasmapause had moved to L = 2.2 and flux tubes
outside of L = 2.3 were depleted. Afterward, the plasmasphere underwent a
recovery phase to refill the plasma in the depleted flux tubes, indicating a
plasma flow from the ionosphere. From the observations, the refilling of the
plasmasphere lasted less than 28 hours.   

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To be presented at the 10th International Ionospheric Effects Symposium
Alexandria, Virginia, USA, May 7-9, 2002.