Nighttime enhancements in TEC near the crest of northern equatorial ionization anomaly during low solar activity period

Abstract

Enhancement in nighttime total electron content (TEC) near the crest of equatorial ionization anomaly at Bhopal (Geog. 23. 2°N, 77.4°E, and MLAT 14.2°N) has been studied for the solar minimum period March 2005-November 2006. TEC data recorded by GPS Ionospheric Scintillation and TEC Monitor (GISTM) GSV4004A receiver is used for the study and results are presented in the paper. More than 10% increase in TEC with respect to background content is considered for analysis. Out of total 138 enhancements, 65 observed during pre midnight hours and 73 during post midnight hours. It is observed that nighttime enhancement in TEC at Bhopal occurs in all seasons; it is more frequent during summer, less during equinox and least during winter months. The enhancement in nighttime TEC can be observed both in geomagnetic disturbed time and in quiet time. We found that mean peak amplitude for pre-midnight TEC enhancement are more in equinox and less in winter, while in postmidnight TEC enhancement it is highest in summer and less in winter. Post-midnight enhancements have smaller peak amplitude as compared to pre-midnight. Also the most probable values for pre-and post-midnights are 4.4 TECU and 2.17 TECU respectively. The percentage occurrence of nighttime TEC enhancement does not show any dependence on solar activity whereas the peak amplitude depends on solar activity. The percentage occurrence of nighttime TEC enhancement decreases as the magnetic activity increases whereas there is no such dependency found with peak amplitude. It is also observed that majority of nighttime TEC enhancements are occurred without scintillation. The localised nighttime TEC enhancements near the crest of equatorial ionization anomaly region have been observed most of the nights during the period of study.

Observations of poleward-propagating large-scale traveling ionospheric disturbances in southern China

“…This leads to severe dissipation of LSTIDs, even if they were traveling during the night. Strong nighttime enhancements in TEC are usually observed at low latitudes during both disturbed and quiet times (Unnikrishnan et al, 2002;Jain et al, 2011), and dissipation of LSTIDs due to ion drag has previously been reported by Tsugawa et al (2004) and Ding et al (2012).…”

A case study of postmidnight enhancement in F‐layer electron density over Sanya of China

“…Such identifications have been taken by Jain et al . [], Pavlov and Pavlova [], and Pirog et al . [].…”

“…Each enhancement event was identified by the presence of a relative nighttime maximum of electron density. Such identifications have been taken by Jain et al [2011], Pavlov and Pavlova [2007], and Pirog et al [2011]. Category type B was introduced by Young et al [1970].…”

“…Lots of investigations have been conducted extensively to study the nighttime enhancements either in total electron content [e.g., Arendt and Soicher , ; Titheridge , ; Young et al ., ; Davies et al ., ; Balan and Rao , , ; Balan et al ., ; Horvath , ; Unnikrishnan et al ., ; Chen et al ., ; Jain et al ., ; Trivedi et al ., ] or in critical frequency (foF2) or peak electron density (NmF2) of the F2 layer [ Farelo et al ., ; Tsagouri and Belehaki , ; Mikhailov et al ., ; Pavlov and Pavlova , ; Yakovets et al ., ; Pezzopane et al ., ; Pirog et al ., ] or in both of them [ Essex and Klobuchar , ; Jakowski et al ., ; Gordienko et al ., ]. Moreover, observations from incoherent scatter radars [ Pavlov and Pavlova , ], tomographic images [ Dabas and Kersley , ], and radio occultations [ Luan et al ., ; He et al ., ] have also been analyzed to reveal features and physical processes involved in the enhancement phenomena.…”

Impacts of solar activity on performance of the IRI-2012 model predictions from low to mid latitudes

“…The ionosphere, being a complex physical system, exhibits different features like diurnal, seasonal, and spatial variability. The distribution and characteristics of TEC over low, mid, and high latitudes have been investigated by several authors (Rama Rao et al 2006;Yizengaw et al 2007;Liu et al 2008;Bagiya et al 2009;Jain et al 2011;Zou et al 2011;Sojka et al 2012;Kumar et al 2012). The latitudinal variation of the TEC is mostly dictated by the phenomenon of EIA (Kumar and Singh 2009;Venkatesh et al 2011).…”