HR: 1340h
AN: SM43A-1145    [Abstracts]
TI: Monitoring Auroral Electrojet from Polar Cap Stations
AU: * Tan, A
EM: ATAN@aamu.edu
AF: Alabama A&M University, 4900 Meridian st., Huntsville, AL 35762 United States
AU: Lyatsky, W
EM: lyatsky@cspar.uah.edu
AF: Alabama A&M University, 4900 Meridian st., Huntsville, AL 35762 United States
AU: Lyatskaya, S
EM: lyatsky@usa.com
AF: Alabama A&M University, 4900 Meridian st., Huntsville, AL 35762 United States
AB: The auroral electrojet AL and AE geomagnetic activity indices are important for monitoring geomagnetic substorms. In the northern hemisphere these indices are derived from measurements at a set of geomagnetic observatories located in the auroral zone. In the southern hemisphere the major portion of the auroral zone is located on the ocean; this does not allow us to derive the auroral electrojet indices in the same way. We showed that monitoring the auroral electrojet is possible from magnetic field measurements at polar cap stations. For this purpose we used hourly values of geomagnetic field variations at four polar cap stations, distributed along polar cap boundary and occupying a longitudinal sector of about 14 hours, and calculated mean values of the total magnetic field disturbance T = (X2 + Y2 + Z2)1/2 where X, Y, and Z are geomagnetic field components measured at these polar cap stations. The set of the obtained values were called the T index. This index has a clear physical mining: it is the summary of geomagnetic disturbance in all three components averaged over the polar cap boundary. We found that correlation coefficients for the dependence of the T index on both AL and AE indices are as high as ~0.9 and higher. The high correlation of the T index with the AL and AE indices takes place for any UT hour when the stations were located at the night side. The T index further shows good correlation with solar wind parameters: the correlation coefficient for the dependence of the T index on the solar wind-geomagnetic activity coupling function is ~0.8 and higher, which is close to the correlation coefficient for AL index. The T index may be especially important in the cases when ground-based measurements in the auroral zone are impossible as in the southern hemisphere.
DE: 2435 Ionospheric disturbances
DE: 2722 Forecasting
DE: 2788 Storms and substorms
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting