Physics
Scientific paper
Feb 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012jgra..11702218j&link_type=abstract
Journal of Geophysical Research, Volume 117, Issue A2, CiteID A02218
Physics
Atmospheric Composition And Structure: Airglow And Aurora, Ionosphere: Auroral Ionosphere (2704), Magnetospheric Physics: Auroral Phenomena (2407), Magnetospheric Physics: Cusp, Magnetospheric Physics: Solar Wind/Magnetosphere Interactions
Scientific paper
In the cusp, the equatorward boundary of the auroral 6300 Å[OI] red line emission can be used as a proxy for the dayside open/closed field line boundary (OCB). In this paper we perform a statistical study based on ground-based optical data from Longyearbyen, Svalbard, covering a period of 15 auroral seasons from 1995 to 2009 (northern hemisphere, winter conditions), concentrating on the time period close to magnetic noon in the dayside part of the auroral oval. Acquiring the OCB latitude from these data, we have compared it to a variety of solar wind coupling functions and geomagnetic indices. The OCB is, according to our findings, located at 75.4 degrees MLAT. The diurnal movement of the OCB latitude follows the poleward edge of the Feldstein auroral oval, confirming the notion that its poleward part is on open field lines. A causal relationship between the latitudinal location of the OCB and the solar cycle is demonstrated. A dependency is clearly seen between the negative Bz component of the interplanetary magnetic field and the OCB latitude. However, when plotting the OCB latitude as function of coupling functions where the solar wind velocity also is taken into account, better correlations are obtained. We are in this work not able to find previously used coupling functions that clearly distinguishes themselves from the others with respect to correlation coefficients. Good correlations with geomagnetic indices such as AE, PC and SYM/H, suggests that both processes at the magnetopause and in the magnetotail are needed in order to best understand the latitudinal location of the dayside OCB.
Johnsen M. G.
Lorentzen Dag A.
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