Evidence for OI 630.0 nm dayglow variations over low latitudes during onset of a substorm

Abstract

Observations of OI 630.0 nm dayglow intensity from Mt. Abu (magnetic latitude (MLAT): 16.2°N; magnetic longitude (MLONG): 148°E) at two different directions corresponding to two different magnetic latitudes (MLATZenith: 16.2°N and MLAT20°Elevation: 22.2°N) revealed nearly simultaneous intensity enhancements on 2 February 2002 (Ap = 19) during 0554–0635 universal time (UT) (1124–1205 Indian Standard Time (IST); IST = UT + 5.5 h). This feature is found to be absent on a typical control day (3 February 2002; Ap = 4). The dayglow enhancements were concomitant with enhancements in the E-region zonal electric field inferred from deviations of the northward component of magnetic field (ΔH) obtained from a meridional chain of magnetometers encompassing the dip equatorial and low-latitude regions. Simultaneous positive bay signatures in ΔH were also recorded at all stations along the 210° magnetic meridian (MM) in the afternoon sector (∼1454–1535 magnetic local time). The changes in the solar wind parameters including the dawn-to-dusk component of IEF and ram pressure are found negligible during 0554–0635 UT. However, the variations in the auroral electrojet and ring current indices indicate the presence of a substorm during 0554–0635 UT. Sudden enhancements in the energetic particle fluxes measured by the Los Alamos National Laboratory (LANL) 1991–080 satellite at geosynchronous altitude provide evidence for the onset of the expansion phase of a magnetospheric substorm. Therefore, the present investigation adduces the response of 630.0 nm dayglow intensities over low latitudes corresponding to the onset of the expansion phase of an auroral/magnetospheric substorm.