HR: 15:25h
AN: SM53C-08    [Abstracts]
TI: Properties of magnetic merging at the magnetopause inferred from dayside 557.7-nm all-sky images
AU: * Maynard, N C
EM: nelson.maynard@atk.com
AF: ATK Mission Research, 589 West Hollis St.; Suite 201, Nashua, NH 03061 United States
AU: Burke, W J
EM: william.burke2@hanscom.af.mil
AF: Air Force Research Laboratory, 29 Randolph Road, Hanscom AFB, MA 01731 United States
AU: Ebihara, Y
EM: ebihara@nipr.ac.jp
AF: National Institute of Polar Research, Kaga 1-9-10 Itabashiku, Tokyo, 173-8515 Japan
AU: Ober, D M
EM: daniel.ober@atk.com
AF: ATK Mission Research, 589 West Hollis St.; Suite 201, Nashua, NH 03061 United States
AU: Wilson, G R
EM: gordon.wilson@atk.com
AF: ATK Mission Research, 589 West Hollis St.; Suite 201, Nashua, NH 03061 United States
AU: Winningham, J D
EM: david@cluster.space.swri.edu
AF: Southwest Research Institute, P.O. Drawer 28510, San Antonio, TX 78228 United States
AU: Balogh, A
EM: a.balogh@ic.ac.uk
AF: Imperial College Space and Astrophysics Group, Blackett Laboratory Exhibition Road, London, SW7 2BW United Kingdom
AU: Farrugia, C J
EM: charlie.farrugia@unh.edu
AF: EOS, University of New Hampshire, Morse Hall, Durham, NH 03824 United States
AU: Singer, H J
EM: howard.singer@noaa.gov
AF: Space EDnvironment Center, NOAA, Boulder, CO 80303 United States
AU: Ejiri, M
AF: National Institute of Polar Research, Kaga 1-9-10 Itabashiku, Tokyo, 173-8515 Japan
AU: Fazakerley, A
EM: anf@mssl.ucl.ac.uk
AF: Mullard Space Science Laboratory, Dorking, Surrey, RH5 6NT United Kingdom
AU: Reme, H
EM: henri.reme@cesr.fr
AF: CESR, 9 Ave Colonel Roche Cedex, Toulouse, 31029 France
AU: Andre, M
EM: ma@irfu.se
AF: Swedish Institute of Space Physics, Uppsala Division, Box 537, Uppsala, SE-751 21 Sweden
AB: We combine {\it in situ} measurements from Cluster with high-resolution 557.7 nm all-sky images from South Pole to investigate the spatial and temporal evolution of merging on the dayside magnetopause. Variations of 557.7 nm emissions were observed at a 6 s cadence at South Pole on April 29, 2003, at a time when significant changes in the Interplanetary Magnetic Field (IMF) clock angle were reaching the magnetopause. Electrons energized at merging sites are plausible sources for 557.7 nm cusp emissions. At the same time Cluster was crossing the pre-noon cusp in the Northern Hemisphere. The combined observations confirm results of a previous study that high-latitude merging events can occur at multiple sites simultaneously and vary asynchronously on time scales of 30 s to 3 min. Under prevailing IMF $B_Y$ and $B_Z$ negative conditions, the optical patterns are consistent with a scenario in which merging occurs primarily at high latitudes at positions dictated by the IMF clock angle. The intensity of the emissions, and probably the merging rate, appear to vary with changes in both IMF $B_X$ and dynamic pressure of the solar wind. Significant $B_X$ affects the lag-times of merging in the two hemispheres. Cluster observations set the merging lag times for Northern Hemisphere sites while the post- noon optical emissions set times of Southern Hemisphere merging. Matching optical signatures with clock-angle, $B_X$, and dynamic pressure variations provides new insights about interplanetary control of temporal-spatial variability of dayside merging.
DE: 2407 Auroral ionosphere (2704)
DE: 2724 Magnetopause, cusp, and boundary layers
DE: 2736 Magnetosphere/ionosphere interactions
DE: 2784 Solar wind/magnetosphere interactions
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting