|
|
 |
|
|
Ann. Geophys., 24, 873-885, 2006
www.ann-geophys.net/24/873/2006/
© European Geosciences Union 2006
STARE velocity at large flow angles: is it related to the ion acoustic speed?
M. V. Uspensky1, A. V. Koustov2, and S. Nozawa3
1Finnish Meteorological Institute, Erik Palminin Aukio 1, P.O. Box 503, Helsinki FIN-00101, Finland
2Institute of Space and Atmospheric Studies, University of Saskatchewan, 116 Science Place, Saskatoon, S7N 5E2, Canada
3Solar-Terrestrial Environment Laboratory, Nagoya University, Chikusa-ku, Nagoya 464-01, Japan
Abstract. The electron drift and ion-acoustic speed in the E region inferred
from EISCAT measurements are compared with concurrent STARE radar velocity
data to investigate a recent hypothesis by Bahcivan et al. (2005), that the
electrojet irregularity velocity at large flow angles is simply the product
of the ion-acoustic speed and the cosine of an angle between the electron
flow and the irregularity propagation direction. About 3000 measurements
for flow angles of 50°–70° and electron drifts of 400–1500 m/s are
considered. It is shown that the correlation coefficient and the slope of
the best linear fit line between the predicted STARE velocity (based solely
on EISCAT data and the hypothesis of Bahcivan et al. (2005)) and the measured
one are both of the order of ~0.4. Velocity predictions are somewhat
better if one assumes that the irregularity phase velocity is the
line-of-sight component of the E×B drift scaled down by a
factor ~0.6 due to off-orthogonality of irregularity propagation
(nonzero effective aspect angles of STARE observations).
Full Article in PDF (1479 KB) |
|
|
