Local-time, seasonal and solar cycle variation of Nitric Oxide radiative emission over Indian longitude sector
We study the local-time, seasonal and solar cycle variations of Nitric Oxide (NO) infrared radiative emission, as observed by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the NASA’s Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) satellite, over Indian longitude sector. It covers nineteen (January 2002-December 2020) years of NO radiative emission data in the altitude region of 100–155 km. The NO volume emission rate (VER) shows a strong local-time variation with maximum and minimum, respectively, during local-noon and local-midnight. The peak altitude of NO VER decreases by about 18 km from the midnight to the lowest altitude of 117 km at noon. The mean NO VER also undergoes a significant change between the day and night. The mean daytime NO VER is more than double the night-time counterpart. The seasonal variation of peak NO VER shows a maximum during the month of December and a minimum during March. The peak altitude is maximum during September and minimum during June unlike the peak NO VER. The lowest peak altitude, maximum VER and maximum intensity are observed during winter. The relative change in NO VER between the winter and the summer seasons, peaks around 116 km, increases with altitude above 108 km. The long-term trend of NO VER/intensity shows a clear solar cycle variation with higher values during the higher solar activity periods. The NO intensity exhibits a strong correlation with sunspot number (SSN), F10.7 solar index and Lyman-α during both 23rd and 24th solar cycles, although the peak VER does not coincide with the peak SSN.
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Advances in Space Research
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