FM-CW Radar Observation of the Electric Fields Penetrating into the Low Latitude Ionosphere at the Time of SC

Details FM-CW Radar Observation of the Electric Fields Penetrating into the Low Latitude Ionosphere at the Time of SC FM-CW Radar Observation of the Electric Fields Penetrating into the Low Latitude Ionosphere at the Time of SC

Dec 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufmsm31a0311i&link_type=abstract

American Geophysical Union, Fall Meeting 2006, abstract #SM31A-0311

Physics

2788 Magnetic Storms And Substorms (7954), 4455 Nonlinear Waves, Shock Waves, Solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, 7900 Space Weather, 7944 Ionospheric Effects On Radio Waves

Scientific paper

When SC(geomagnetic sudden commencement) occurs, the intensity of the geomagnetic field increases rapidly in low latitude region. In addition, PI(preliminary impulse) and following MI(main impulse) electric field penetrate into the polar ionosphere from the magnetosphere[Tamao,1964 ; Araki,1994], and propagate to the low latitude ionosphere instantly [Kikuchi et al.,1978 ; Kikuchi and Araki,1979]. In order to detect ionospheric electric fields, we have built an FM-CW radar(HF radar) in Sasaguri, Fukuoka (geomagnetic latitude=23.2 degree, geomagnetic longitude=199.6 degree). FM-CW radar observation started in 2002 using a doppler mode. Using this mode, we can observe short period(few seconds) phenomenon caused by penetration of electric field from the magnetosphere to the ionosphere. By using the FM-CW radar at 10 s sampling, we can measure the vertical drift velocity v of the ionosphere and its altitude. The IGRF model is used to estimate magneticfield B at Sasaguri. The ionospheric electric field E is derived by the relational expression of E=-v*B. Using the above method, we estimated the intensity of ionospheric electric field at the time of SC. For example, intensity of PI electric field was 0.16 mV/m (westward) and MI was 0.69 mV/m (eastward) in dayside at Nov.4, 2003. In the case of nightside, PI was 0.23mV/m (eastward) and MI was 1.01 mV/m (westward) at Jan.21, 2005. In this study, using data from the FM-CW radar and SYM-H(H component of the midlatitude symmetric disturbance index), we plotted the intensity of the electric field versus the magnetic field intensity at the time of SC (MI). There is a positive correlation between the intensity of the MI electric field and SC amplitude. Further we examined the magnetic local time(MLT) dependence of the intensity of the electric field at the time of MI. In addition, we will compare the intensity of the MI electric field and solar wind parameters at the time of SC.

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