HR: 1330h
AN: SM42A-0594    [PDF]
TI: IMF control of the theta aurora and substorm onset location in the conjugate hemispheres
AU: * Ostgaard, N
EM: nikost@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Mende, S B
EM: mende@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Frey, H U
EM: hfrey@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Immel, T J
EM: immel@ssl.berkeley.edu
AF: Space Sciences Laboratory, University of California, Berkeley, 7 Gauss Way, Berkeley, CA 94720-7450 United States
AU: Frank, L A
EM: louis-frank@uiowa.edu
AF: Department of physics and astronomy, University of Iowa, 405 Van Allen Hall, Iowa City, IA 52242-1479 United States
AU: Sigwarth, J B
EM: john-sigwarth@uiowa.edu
AF: Department of physics and astronomy, University of Iowa, 405 Van Allen Hall, Iowa City, IA 52242-1479 United States
AB: Based on simultaneous imaging data from IMAGE FUV and Polar VIS Earth Camera, we examine the IMF control of the occurrence and location of auroral features in the conjugate hemispheres. The imaging data have revealed that transpolar arcs during northward IMF can exist in one hemisphere but not in the other. We attribute this occurrence of non-conjugate theta aurora to the sign of the IMF $B_x$ component, which controls the hemisphere in which lobe reconnection is favored. Examining auroral substorm onsets in the conjugate hemispheres, we find that the onset locations are displaced in one hemisphere compared to the other, meaning they have different geomagnetic coordinates (e.g., apex, CGM). We find that the relative displacement of onset locations in the conjugate hemispheres are controlled by ratio of $B_y$/$B_z$ or the IMF clock-angle. These results indicate that the magnetic tensions force is acting on open magnetic field lines before reconnecting in the magnetotail. This leads to a twisted magnetotail and can explain why conjugate field lines have different geomagnetic coordinates in the northern and southern hemispheres.
DE: 2740 Magnetospheric configuration and dynamics
DE: 2776 Polar cap phenomena
DE: 2784 Solar wind/magnetosphere interactions
DE: 2788 Storms and substorms
SC: SPA - Magnetospheric Physics [SM]
MN: 2003 Fall Meeting