|
|
 |
|
|
Ann. Geophys., 20, 501-509, 2002
www.ann-geophys.net/20/501/2002/
© European Geosciences Union 2002
A case study of HF radar spectral width in the post midnight magnetic local time sector and its relationship to the polar cap boundary
E. E. Woodfield1, J. A. Davies1, P. Eglitis2, and M. Lester1
1Department of Physics and Astronomy, University of Leicester, Leicester, LE17RH, UK
2Swedish Institute of Space Physics, Uppsala Division, Box 537, S-751 21 Uppsala, Sweden, and The Finnish Meteorological Institute, P. O. Box 503, Fin-00101 Helsinki, Finland
Correspondence to: E. E. Woodfield
(Emma.Woodfield@ion.le.ac.uk)
Abstract. The aim of this paper is
to advance the current understanding of the spectral width parameter observed
by coherent high frequency (HF) radars. In particular, we address the
relationship of a frequently observed gradient, between low ( < 200 m/s) and
high ( > 200 m/s) spectral width, to magnetospheric boundaries. Previous
work has linked this gradient in the spectral width, in the nightside sector of
magnetic local time, to the Polar Cap Boundary (PCB), and also to the boundary
between the Central Plasma Sheet (CPS) and the Plasma Sheet Boundary Layer (PSBL).
The present case study investigates the former by comparison with the 630.0 nm
optical emission. No suitable data were available to test the second of the two
hypotheses. It is found that during the interval in question the spectral width
gradient is within the region of the 630.0 nm optical emission. A comparison of
coherent and incoherent scatter radar data is also conducted, which indicates
that values of high spectral width are typically collocated with elevated
F-region electron temperatures. We conclude that the high spectral width region
in the interval under study is associated with particle precipitation and also
that the spectral width gradient is not a reliable method for locating the PCB.
Key words. Ionosphere (auroral
ionosphere; ionospheric irregularities)
Full Article in PDF (991 KB) |
|
|
