Abstract
Abstract. Measurements of OI 630.0 nm thermospheric dayglow emission by means of the Dayglow Photometer (DGP) at Mt. Abu (24.6° N, 73.7° E, dip lat 19.09° N), a station under the crest of Equatorial Ionization Anomaly (EIA), reveal day-to-day changes in the shapes of the diurnal profiles of dayglow intensity variations. These shapes have been characterized using the magnetometer data from equatorial and low-latitude stations. Substantial changes have been noticed in the shapes of the dayglow intensity variations between 10:00–15:00 IST (Indian Standard Time) during the days when normal and counter electrojet events are present over the equator. It is found that the width (the time span corresponding to 0.8 times the maximum dayglow intensity) of the diurnal profile has a linear relationship with the integrated electrojet strength. Occasional deviation from this linear relationship is attributed to the presence of substantial mean meridional wind.Key words. Ionosphere (equatorial ionosphere; ionosphere – atmosphere interactions; ionospheric disturbances)
Highlights
The low and equatorial thermosphere-ionosphere system (TIS) is known for multifarious geophysical processes uniquely characteristic to this particular region
The shapes of the normalized dayglow intensity variations depicted on the right panel (d–f) have a moderate “flat” region at noontime
It is of interest to note that the overall shapes of the dayglow intensity variations for all the days depicted on the left panel are similar, whereas the shapes of the curves on the right panel resemble each other
Summary
The low and equatorial thermosphere-ionosphere system (TIS) is known for multifarious geophysical processes uniquely characteristic to this particular region. Most of the experimental studies regarding the low-latitude TIS were based primarily on ground-based radio probing, magnetometer and in situ rocket and satellite borne measurements. With the advent of the Dayglow Photometer (DGP) (Narayanan et al., 1989; Sridharan et al, 1992a), it has become possible to carry out airglow observations even during daytime. DGP is operated to monitor the OI 630.0 nm dayglow emission, which emanates from the altitude region centered ∼ 220 km during daytime with a typical semi-thickness of ∼ 60–70 km (Hays et al, 1978; Solomon and Abreu, 1989)
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