Ionospheric electron temperatures near dawn

Abstract

Solar dependence of electron and ion temperatures (Te and Ti) in the ionosphere is studied using RPA data onboard SROSS C2 at an altitude of ∼500 km and 77°E longitude during early morning hours (04:00–07:00 LT) for three solar activities: solar minimum, moderate and maximum during winter, summer and equinox months in 10°S–20°N geomagnetic latitude. In winter the morning overshoot phenomenon is observed around 06:00 LT (Te enhances to ∼4000 K) during low-solar activity and to Te ∼ 3800 K, during higher solar activity. In summer, it is observed around 05:30 LT, but the rate of Te enhancement is higher during moderate solar activity (∼2700 K/hr) than the low-solar activity (∼1700 K/hr). During equinox, this phenomenon is delayed and is observed around 06:00 LT (∼4200 K) during all three activities.In winter, the Ti shows an enhancement (∼2300 from ∼700 K) around 06:00 LT during low-solar activity but during other activities, it raise smoothly with the progress of the morning. In summer, Ti increases at a rate of 260 K/hr during low and moderate activities and with half the rate (∼130 K/hr) during high-solar activity. And in equinox months, the Ti is lower during high-solar activity than in low-solar activity.