Latitudinal and Seasonal Investigations of Storm-Time TEC Variation

Abstract

The ionosphere responds markedly and unpredictably to varying magnetospheric energy inputs caused by solar disturbances on the geospace. Knowledge of the impact of the space weather events on the ionosphere is important to assess the environmental effect on the operations of ground-and space-based technologies. Thus, global positioning system (GPS) measurements from the international GNSS service (IGS) database were used to investigate the ionospheric response to 56 geomagnetic storm events at six different latitudes comprising the northern and southern hemispheres in the Afro-European sector. Statistical distributions of total electron content (TEC) response show that during the main phase of the storms, enhancement of TEC is more pronounced in most of the seasons, regardless of the latitude and hemisphere. However, a strong seasonal dependence appears in the TEC response during the recovery phase. Depletion of TEC is majorly observed at the high latitude stations, and its appearance at lower latitudes is seasonally dependent. In summer hemisphere, the depletion of TEC is more pronounced in nearly all the latitudinal bands. In winter hemisphere, enhancement as well as depletion of TEC is observed over the high latitude, while enhancement is majorly observed over the mid and low latitudes. In equinoxes, the storm-time TEC distribution shows a fairly consistent characteristic with the summer distribution, particularly in the northern hemisphere.

A Year‐Long Comparison of GPS TEC and Global Ionosphere‐Thermosphere Models

“…Solar zenith angle-dependent photoionization by solar extreme ultraviolet (EUV) radiation is the largest source of electrons in the dayside ionosphere (Hargreaves, 1992;Roble, 1995). As such, there are variations in TEC by season (Adimula et al, 2016;Mannucci, 2005;Mendillo et al, 2005;Tsurutani, 2004;Wright, 1963), latitude (Liu, Zhao, et al, 2009), local time (Scherliess et al, 2008), and the solar cycle and rotation period (Fejer et al, 1979;Forbes et al, 2000;. Energetic particles from the solar wind and other geomagnetic events constitute another important source of TEC, especially at higher latitudes (Buonsanto, 1999;Fuller-Rowell et al, 2006;Mendillo, 2006;Tsurutani et al, 2009;Zhu & Ridley, 2014).…”

Solar Hysteresis Pattern and Spectral Components in TEC Time Series (GPS and TIE‐GCM) of the Quadrilaterally Coupled Geomagnetic Conjugate Low‐Latitude Stations

“…The solar radiation reaching the different layers of the ionosphere under quiet geomagnetic conditions has the greatest influence on daytime ionospheric variations (Hargreaves, 1992; Rishbeth, 1998). Although the amount of incoming solar radiation varies throughout the year depending on local time, seasons, latitude, and longitude, ionospheric electrodynamics responds in accordance by altering the temperature, wind effect, and thermospheric neutral density composition (e.g., Adimula et al., 2016; Fejer et al., 1979; Forbes et al., 2000; Mendillo et al., 2005; Schunk & Nagy, 1978; Zhao et al., 2009). Earlier research has examined ionospheric variation over a single station and a data set of a few years or a part of the solar cycle.…”