Abstract
Abstract. In this study, we analyse the climatology of ionosphere over Nepal based on GPS-derived vertical total electron content (VTEC) observed from four stations as defined in Table 1: KKN4 (27.80∘ N, 85.27∘ E), GRHI (27.95∘ N, 82.49∘ E), JMSM (28.80∘ N, 83.74∘ E) and DLPA (28.98∘ N, 82.81∘ E) during the years 2008 to 2018. The study illustrates the diurnal, monthly, annual, seasonal and solar cycle variations in VTEC during all times of solar cycle 24. The results clearly reveal the presence of equinoctial asymmetry in TEC, which is more pronounced in maximum phases of solar cycle in the year 2014 at KKN4 station, followed by descending, ascending and minimum phases. Diurnal variations in VTEC showed the short-lived day minimum which occurs between 05:00 to 06:00 LT (local time) at all the stations considered, with diurnal peaks between 12:00 and 15:00 LT. The maximum value of TEC is observed more often during the spring equinox than the autumn equinox, with a few asymmetries. Seasonal variation in TEC is observed to be a manifestation of variations in solar flux, particularly regarding the level of solar flux in consecutive solstices.
Highlights
Total electron content (TEC) is a crucial parameter of ionosphere comprising high concentrations of electrons and ions formed under the ionization of extreme ultraviolet (EUV) radiation and solar X-rays
The vertical total electron content (VTEC) plots reveal a growth from dawn to a highest value of about 5 to 98 TEC units (TECU) after the daylight hours, and it decreases to the lowest value prior to dusk, with a time difference of ±1 to 2 h
This paper investigates the diurnal, monthly, seasonal and solar cycle variations in VTEC at four mid–low latitude stations, namely KKN4 (27.80◦ N, 85.27◦ E), GRHI (27.95◦ N, 82.49◦ E), JMSM (28.80◦ N, 83.74◦ E) and DLPA (28.98◦ N, 82.81◦ E) in Nepal
Summary
Total electron content (TEC) is a crucial parameter of ionosphere comprising high concentrations of electrons and ions formed under the ionization of extreme ultraviolet (EUV) radiation and solar X-rays. Parwani et al (2019) studied the latitudinal variation in ionospheric TEC in the northern hemispheric region and found that the diurnal TEC has a higher value in low latitudes than in mid and high latitudes and in the seasonal variation maximum in spring and autumn than in summer and winter. We present, for the first time, characteristics of ionosphere in Nepal, such as the diurnal, annual, seasonal and solar cycle dependence of TEC on the local ionospheric conditions, using GPS TEC data obtained from the four GPS stations of KKN4, GRHI, JMSM and DLPA (see Table 1).
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