RESEARCH GEOPHYSICAL LETTERS, VOL. 32, L14112, doi:10.1029/2005GL023197, 2005
A systematic study of effects of solar wind density on auroral electrojets
J.-H. Shue,1,2 Y. Kamide,3 and P. T. Newell2
Received 9 April 2005; revised 26 May 2005; accepted 24 June 2005; published 29 July 2005.
[1] The subject of effects of solar wind density (Np) on auroral electrojets has recently received increasing attention. For ``unbiased'' events in which only Np varied significantly but other solar wind parameters were relatively constant, we calculated rates of change of the auroral electrojets per unit change of Np (dAU/dNp and dAL/dNp). Here we report that the distribution of dAU/dNp and dAL/dNp binned by the Z component of interplanetary magnetic field (IMF) shows a butterfly pattern. The rates are found to be small for northward IMF. As the southward IMF becomes larger, the distribution bifurcates one branch extending to positive rates and the other to negative rates. Although it has been commonly believed that the enhanced Np increases the auroral electrojets, the enhanced Np can also decrease the auroral electrojets with a 49% probability.
Citation: Shue, J.-H., Y. Kamide, and P. T. Newell (2005), A systematic study of effects of solar wind density on auroral electrojets, Geophys. Res. Lett., 32, L14112, doi:10.1029/ 2005GL023197.
1. Introduction
[2] Auroral electrojets are a channel of electric currents flowing along the auroral oval. Their development is controlled by magnetic reconnection between the Earth's magnetic field and southward interplanetary magnetic field (IMF) and also by compression of the magnetosphere by solar wind density (Np) and velocity. A sudden increase in Np compresses the entire magnetosphere and energizes particles along magnetic field lines which then collide with molecules and atoms of the upper atmosphere, creating spectacular auroras [Craven et al., 1986; Zhou and Tsurutani, 2001; Shue et al., 2002] and enhancing the auroral electrojets [Burch, 1972; Iijima, 1973; Kokubun et al., 1977; Shue and Kamide, 1998, 2001; Zesta et al., 2000]. [3] Increases/decreases in the auroral electrojets are commonly described by the AU and AL indices, which are deriv...
Shue_DensityandElectorjets_2005GL023197