Physics
Scientific paper
Feb 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009jgra..11402209b&link_type=abstract
Journal of Geophysical Research, Volume 114, Issue A2, CiteID A02209
Physics
1
Magnetospheric Physics: Solar Wind/Magnetosphere Interactions, Magnetospheric Physics: Substorms, Magnetospheric Physics: Auroral Phenomena (2407), Magnetospheric Physics: Magnetotail, Magnetospheric Physics: Energetic Particles: Precipitating
Scientific paper
Substorm energetics has been shown to have two components, the ``loading-unloading'' component releasing energy previously stored in the tail and the ``directly driven'' component dissipating simultaneously fed solar wind energy. Previous studies disagree about the relative importance of each process. The SI12 spectral imager onboard the IMAGE satellite provides images of the Doppler-shifted Lyman α auroral emission at 121.8 nm every 2 min. It has been used to determine the auroral intensity during substorms, which may be compared to the solar wind characteristics and interplanetary magnetic field components before and/or after substorm onsets. In this study, we analyze 256 substorms between June 2000 and December 2002, which satisfy criteria relative to the viewing conditions. We compare the mean nightside intensity during the expansion phase with the magnetic open flux, the epsilon parameter, and other coupling functions (used as proxies of transfer of solar wind energy to the magnetosphere) integrated over the growth phase or the expansion phase. The mean auroral intensity during the expansion phase correlates well with coupling functions integrated over the growth phase. We also find that the correlation between the auroral precipitation during the expansion phase and the coupling functions integrated over the expansion phase is lower but still significant. This implies that, even though both mechanisms contribute to the energy precipitated during substorms, the loading-unloading process is statistically dominant.
Blockx C.
Coumans Valérie
Gérard Jean-Claude
Hubert Bernard
Meurant Mathieu
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