A high time resolution study of interplanetary parameter correlations with AE

Abstract

Using the earth‐orbiting spacecraft IMP‐8, we have performed a high time‐resolution (2.5‐min) study of the linear cross‐correlations of a quantitative indicator of magnetospheric substorm activity, the auroral electrojet (AE) index, with several interplanetary (IP) parameters. The present study includes all available satellite data (from an eight‐month period) rather than selecting a small number of substorm events, or a relatively small number of chosen days. Prior published studies have suggested that geomagnetic activity is related to a variety of solar wind parameters: solar wind speed (V); north‐south magnetic field component (Bz); total interplanetary magnetic field (IMF) strength (B); and various combinations of these parameters. Very recently, a new parameter, ϵ(= VB² sin4(θ/2)ℓo²), has been suggested as a superior predictor of substorm activity. The other major preferred correlator with geomagnetic activity is VBs, where Bs is the southward (Bz < 0) component of the IMF. Substantial discussion has ensued as to which parameter is the "best" predictor of substorm activity. The present non‐selective, high‐resolution analysis reveals that VBs generally reaches a higher peak correlation than ϵ (0.6 vs 0.54). Both parameters reach a peak correlation at the same lag time (with AE lagging the IP parameters by ∼40 min.), but VBs also appears to have a preferable qualitative lag profile shape for AE prediction purposes.

Reconstruction and Prediction of Variations in the Open Solar Magnetic Flux and Interplanetary Conditions

“…The southward IMF orientation in GSM occurs for 50% of the time (Hapgood et al, 1991). The DP2 or "directly driven" currents respond to IMF variations with a lag of a few minutes (Nishida, 1968), whereas the larger DP1 or "storage-release system" currents are enhanced during substorm expansion phases following a lag of typically one hour (e.g., Baker et al, 1981). The high latitude auroral currents link to the magnetospheric ring current via the Region-2 field-aligned currents, as shown in Figure 2.…”

Influence of the IMF azimuthal component on magnetospheric substorm dynamics.

“…Energy transference from the solar wind to the magnetosphere is most efficient when the IMF is directed southward (FAIRFIELD and CAHILL, 1966;ROSTOKER and FALTHAMMAR, 1967). Investigations of the relationship between the solar wind parameters and the level of geomagnetic activity have attached importance to those parameters, which include the IMF southward component and the solar wind velocity (FOSTER et al, 1971;CAAN et al, 1977;PERREAULT and AKASOFU, 1978;MAEZAWA, 1979;CLAUER et al, 1981;BAKER et al, 1981;MURAYAMA, 1982;HOLZER and SLAVIN, 1982;MAEZAWA and MURAYAMA, 1985). The effects of the IMF azimuthal component on geomagnetic activity were studied by PUDOVKIN et al (1970), MURAYAMA and HAKAMADA (1975), MURAYAMA et al (1980), and METLYAEV et al (1982, but their results were rather puzzling.…”

Ionospheric and geomagnetic responses to changes in IMF &lt;i&gt;B&lt;sub&gt;Z&lt;/sub&gt;&lt;/i&gt;: a superposed epoch study

“…These include the cross polar cap potential (the ionospheric signature of the voltage across the magnetosphere) (Reiff et al, 1981;Doyle and Burke, 1983;Wygant et al, 1983;Cowley, 1984;Reiff and Luhmann, 1986); the patterns of the associated high-latitude F-region ionospheric flows (Heelis, 1984;Heppner and Maynard, 1987;Etemadi et al, 1988) and E-region currents (Nishida, 1968;Friis-Christiansen et al, 1985); field aligned currents (Iijima et al, 1978); the average size of the polar cap (Holzworth and Meng, 1984), the occurrence of global geomagnetic activity (e.g. Schatten and Wilcox, 1967;Arnoldy, 1971;Berthelier, 1976;Baker et al, 1981Baker et al, , 1983Clauer et al, 1981;Bargatze et al, 1985;Scurry and Russell, 1991), including magnetospheric substorms (Rostoker and Falthammer, 1967;Caan et al, 1977;Meloni et al, 1982;Samson and Young, 1986); the occurrence of reconnection signatures such as flux transfer events (Berchem and Russell, 1984) and high speed flow streams at the magnetopause (Scurry et al, 1994); the energy deposition into the high-latitude ionosphere and thermosphere (Akasofu, 1981;Bargatze et al, 1986;Weiss et al, 1992); and the global pattern of winds in the neutral thermosphere (Killeen et al, 1985).…”