HR: 1340h
AN: SH23A-0315    [Abstracts]
TI: Solar Trans-Equatorial Magnetic Flux Ropes and Their Possible Relation to Geomagnetic Storms
AU: * Sun, W
EM: sun@jupiter.gi.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks 903 Koyukuk Ave, Fairbanks, AK 99775-7320 United States
AU: Saito, T
EM: saitots@nifty.com
AF: Saito Space Physics, Taihaku 2-6-29 Taihaku-ku, Sendai, 982-021 Japan
AU: Akasofu, S
EM: sakasofu@iarc.uaf.edu
AF: International Arctic Research Center, University of Alaska Fairbanks PO Box 757340, Fairbanks, AK 99775-7340 United States
AU: Deehr, C
EM: cdeehr@gi.alaska.edu
AF: Geophysical Institute, University of Alaska Fairbanks 903 Koyukuk Ave, Fairbanks, AK 99775-7320 United States
AU: Fry, C
EM: gfry@expi.com
AF: Exploration Physics International, Suite 37-105 6275 University Drive NW, Huntsville, AL 35806 United States
AU: Dryer, M
EM: Murray.Dryer@noaa.gov
AF: Geophysical Institute, University of Alaska Fairbanks 903 Koyukuk Ave, Fairbanks, AK 99775-7320 United States
AU: Dryer, M
EM: Murray.Dryer@noaa.gov
AF: Exploration Physics International, Suite 37-105 6275 University Drive NW, Huntsville, AL 35806 United States
AU: Dryer, M
EM: Murray.Dryer@noaa.gov
AF: NOAA/Space Environment Center, 325 Broadway, Boulder, CO 80305 United States
AB: Some solar sunspot groups in the northern and southern hemispheres are linked by magnetic flux tubes (transequatorial magnetic flux tubes), which have been observed to brighten prior to the onset of geomagnetic storms. We have examined several of these events and linked the meridional orientation of the flux tube to satellite observations of the IMF and solar wind plasma near Earth. On October 19, 1998, the IMF and solar plasma observed by the satellite ACE showed intense disturbances followed by a weak shock. The high IMF magnitude and low density indicated the arrival of a magnetic flux rope with helical magnetic configuration. However, the time variations of IMF Bx, By and Bz components indicate that the helical magnetic configuration was not a flux rope lying in the equatorial plane, but perpendicular to it in the meridional plane. We were able to simulate the ACE observations by using the three-dimensional HAF (Hakamada-Akasofu-Fry) solar wind model, combined with a flux rope model in the solar meridional plane. The simulation also shows that the weak shock leading to a storm sudden commencement around 18 UT on October 18, 1998 was caused by a corotating interaction region (CIR). No flares and no coronal mass ejections (CMEs) were observed as the source of the interplanetary disturbances for several days before the event, but there were active sunspot groups in both the northern and southern hemispheres. Although there were no observations to confirm possible activation of the flux in this particular case, we have found several other similar cases in which the trans-equatorial flux brightened a few days before geomagnetic storms.
DE: 2102 Corotating streams
DE: 2139 Interplanetary shocks
DE: 2164 Solar wind plasma
DE: 2722 Forecasting (7924, 7964)
DE: 2788 Magnetic storms and substorms (7954)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005