HR: 0800h
AN: SA51A-0236    [Abstracts]
TI: Cross-Wavelet Spectrum Analysis of the Ring Currents Using Magnetic Records from Multiple Low-Latitude Stations
AU: * Xu, Z
EM: xuzhonghua_99@yahoo.com
AF: Utah State University, Center for Atmospheric and Space Sciences 4405 Old Main Hill, Logan, UT 84322-4405, United States
AU: Zhu, L
EM: zhu@cc.usu.edu
AF: Utah State University, Center for Atmospheric and Space Sciences 4405 Old Main Hill, Logan, UT 84322-4405, United States
AU: Sojka, J J
EM: sojka@cc.usu.edu
AF: Utah State University, Center for Atmospheric and Space Sciences 4405 Old Main Hill, Logan, UT 84322-4405, United States
AU: Kokoszka, P
EM: piotr@math.usu.edu
AF: Utah State University, Mathematics and Statistics Department, Logan, UT 84322-3900, United States
AB: Ground magnetic disturbances in equatorial regions are directly connected to the spatial and temporal variations of the ring currents, which have both the symmetric and asymmetric components, as well as many local-time dependent M-I currents. In this study, we applied the wavelet analysis technique, which is especially appropriate for the data with impulsive and time-dependent spectrum features, to the magnetic records from multiple low- latitude stations in order to study the dynamic behaviors of the symmetric and asymmetric parts of the ring currents for both quiet and storm conditions. First, we decomposed the magnetic records into various details in wavelet spectrum domain and systematically studied the temporal and frequency properties of the magnetic disturbances for various geomagnetic and seasonal conditions. Then we performed cross-wavelet spectrum analysis on the data from multiple stations in both UT and LT time frames in order to separate and elucidate the effects of the symmetric and asymmetric parts of the ring currents. Our results show that slow time-varying components of the ring currents are largely globally symmetric and during quiet times, the magnetic effect of this symmetric part is comparable to that of the asymmetric (or local-time dependent) part. During storm times, the magnetic disturbances associated with both the symmetric and asymmetric parts of the ring currents increase significantly, but the increase of the symmetric current is much larger than that of the asymmetric current and it becomes dominant during storm times. Our results also indicate that there are substantial residues of the magnetic effects of local-time dependent currents left in the Dst index and this further proves that the Dst is not an ideal index for the description of the symmetric ring current.
DE: 2409 Current systems (2721)
DE: 2415 Equatorial ionosphere
DE: 2778 Ring current
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting