An empirical model of ionospheric total electron content (TEC) near the crest of the equatorial ionization anomaly (EIA)

Abstract

We present a geomagnetic quiet time (Dst > À50 nT) empirical model of ionospheric total electron content (TEC) for the northern equatorial ionization anomaly (EIA) crest over Calcutta, India. The model is based on the 1980-1990 TEC measurements from the geostationary Engineering Test Satellite-2 (ETS-2) at the Haringhata (University of Calcutta, India: 22.58°N, 88.38°E geographic; 12.09°N, 160.46°E geomagnetic) ionospheric field station using the technique of Faraday rotation of plane polarized VHF (136.11 MHz) signals. The ground station is situated virtually underneath the northern EIA crest. The monthly mean TEC increases linearly with F 10.7 solar ionizing flux, with a significantly high correlation coefficient (r = 0.89-0.99) between the two. For the same solar flux level, the TEC values are found to be significantly different between the descending and ascending phases of the solar cycle. This ionospheric hysteresis effect depends on the local time as well as on the solar flux level. On an annual scale, TEC exhibits semiannual variations with maximum TEC values occurring during the two equinoxes and minimum at summer solstice. The semiannual variation is strongest during local noon with a summer-to-equinox variability of 50-100 TEC units. The diurnal pattern of TEC is characterized by a pre-sunrise (0400-0500 LT) minimum and near-noon (1300-1400 LT) maximum. Equatorial electrodynamics is dominated by the equatorial electrojet which in turn controls the daytime TEC variation and its maximum. We combine these long-term analyses to develop an empirical model of monthly mean TEC. The model is validated using both ETS-2 measurements and recent GNSS measurements. It is found that the present model efficiently estimates the TEC values within a 1-r range from the observed mean values.

Cometary plasma response to interplanetary corotating interaction regions during 2016 June–September: a quantitative study by the Rosetta Plasma Consortium

“…TEC is defined as the total number of free thermal electrons present in a column of one meter squared cross section along a path between a radio transmitter and a receiver. This is an important ionospheric state parameter (see Browne et al 1956;Evans 1956;Chakraborty & Hajra 2008;Hajra 2012;Hajra et al 2016a, and references therein). While large latitudinal/longitudinal variations were observed, peak TEC increases varied around 80-100 per cent during the CIRs.…”

A New Global Total Electron Content Empirical Model

“…Huang et al [8] created a one-hour ionospheric TEC prediction model for a single station by using Back Propagation (BP) artificial neural network algorithm optimized by a genetic algorithm. Hajra et al [9] developed a single-station ionospheric TEC empirical model using TEC observations over the Calcutta station in India from 1980 to 1990. Jakowski [10] suggested an empirical ionospheric TEC model NTCM-EU suitable for Europe by using the non-linear least squares method.…”

Storm Time Total Electron Content Modeling Over African Low‐Latitude and Midlatitude Regions

“…Recently, EOF analysis was used for the first time to model TEC during geomagnetic storms, and it was found that modeling results agree with observed TEC quite well for storms with nonsignificant ionospheric response while positive and negative storm responses were not sufficiently captured (Uwamahoro & Habarulema, 2015). Multiregression analysis-based methods have been developed and applied to ionospheric modeling during geomagnetically quiet and disturbed conditions, and results agree with observations quite well (Feng et al, 2016;Hajra et al, 2016;Kutiev & Muhtarov, 2001, 2003Li et al, 2016;Mukhtarov et al, 2013). However, the failure to accurately capture positive and negative ionospheric responses was reported for some geomagnetic storms considered for validation (e.g., Mukhtarov et al, 2013).…”

“…Toward a better understanding of TEC response during geomagnetic storms, TEC modeling during storm conditions is of utmost importance for ionospheric studies and satellite applications. Different TEC models have long been developed and applied for ionospheric studies during both geomagnetically quiet and disturbed conditions (e.g., Chen et al, 2015;Dabbakuti & Ratnam, 2016Ercha et al, 2012Ercha et al, , 2015Feng et al, 2016;Habarulema et al, 2007Habarulema et al, , 2010Habarulema et al, , 2011Hajra et al, 2016;Kakinami et al, 2009;Li et al, 2016;Mao et al, 2005Mao et al, , 2008Mukhtarov et al, 2013;Uwamahoro & Habarulema, 2015;Watthanasangmechai et al, 2012). Findings about the performance of climatological models such as the International Reference Ionosphere (IRI) have shown that, on average, TEC is predicted quite well during geomagnetically quiet conditions although for some cases, IRI model underestimates or overestimates TEC magnitude (e.g., Adewale et al, 2011;Akala et al, 2013;Kenpankho et al, 2011;Rathore et al, 2015).…”