Diurnal and seasonal variations of <i>hm</i>F2 deduced from digitalionosonde over New Delhi and its comparison with IRI 2001

Abstract

Abstract. Using digital ionosonde observations at a low mid-latitude station, New Delhi (28.6 • N, 77.2 • E, dip 42.4 • N), we have derived hourly monthly values of hmF2 (the real height corresponding to the peak electron density in the F2-region), employing both the Dudeney (1983) and Bilitza (1990) Bilitza (1990) formulations reveal more or less a similar diurnal trend of hmF2, with higher values around midnight and lower during sunrise, in all the seasons. It is also noted that the hmF2 shows a larger variability around midnight than by daytime, in all the seasons. Further, the study shows that median values of observed hmF2, using both formulations, are somewhat larger than those predicted by the IRI, in all seasons and at all local times. During summer, the IRI values agree comparatively well with the observations, especially during daytime. Major discrepancies occur when the IRI underestimates observed hmF2 for local times from about 14:00 LT to 18:00 LT and 04:00 LT to 05:00 LT during winter and equinox, where the percentage deviation of the observed hmF2 values with respect to the IRI model varies from 15 to 25%. The difference between the model and observations, outside this time period, remains less than 20% during all the seasons.

NmF2 and hmF2 measurements at 95° E and 127° E around the EIA northern crest during 2010–2014

“…The diurnal maximum hmF2 is observed before noon in June solstice and around noon in equinox. These results are also consistent with the earlier observations (Mayr and Mahajan 1971;Sethi et al 2004). The probable cause of the June-December solstice asymmetry may be the summer to winter interhemispheric neutral winds which would move the ionization along and up the magnetic field lines towards the equator in June solstice and down the field lines towards the pole in December solstice.…”

Variations in Electron Content Ratio and Semi-thickness Ratio during LSA and MSA periods and some Cyclone Genesis Periods using COSMIC satellite observations

“…(Dabas et al, 1980;Gulyaeva, 2007), large magnitude earthquake (Hsiao et al, 2009;Singh et al, 2010) and thunderstorm activity (Rai et al, 2006), etc. Some earlier studies (e.g., DasGupta et al, 2007;Sethi et al, 2004;Sethi and Dabas, 2006;Sripathi, 2012) have unfolded so many interesting characteristic of Indian-equatorial ionosphere. Though, the traditional ground-based measurements (e.g., Sethi and Mahajan, 2002;Sun et al, 2012) are sufficient to determine the bottom-side ionospheric behaviour, the modern space-based measurements (Aragon-Angel et al, 2009) are essential to attest the topside variability in precise manner (Reinisch and Huang, 1998).…”

IRI-2001 model predictions compared with ionospheric data observed at Brazilian low latitude stations

“…Abdu et al, 1996;Batista et al, 1996;Souza et al, 2003;Sethi et al, 2004;Batista and Abdu, 2004). It is well known that IRI is an empirical ionospheric model based on experimental observations of the ionospheric plasma either by ground or in-situ measurements.…”