Simultaneous radio and optical observations of the mid-latitude atmospheric response to a major geomagnetic storm of 6–8 April 2000

Time delay and duration of ionospheric total electron content responses to geomagnetic disturbances

“…The generated TADs propagate from high-to low-latitudes, even to the opposite hemisphere. The neutral winds perturbations associated with TADs can bring the plasma upward/downward along the magnetic field lines, resulting in ionospheric fluctuations, which are termed as large scale traveling ionospheric disturbances (LSTIDs), attracting attention from observation and model studies (e.g., Afraimovich et al, 2002;Lee et al, 2004;Ding et al, 2007;Lei et al, 2008). LSTIDs, with horizontal velocities between 400 and 1000 m/s and periods in the range of 30 min to 3 h, are most likely the manifestations of atmospheric gravity waves launched by high latitude sources (Hunsucker, 1982).…”

Geomagnetic storms and their ionospheric effects observed at the equatorial anomaly crest in the Indian Region

“…The reason for decrease in the [O]/[N 2 ] ratio is a heating of the lower part of the thermosphere (100-140 km) in the high latitudes due to deposition of st energy therein. The significant role of an increase in vibrationally excited oxygen that may lead to strong intensification of the O + +N 2 reaction and so to a significant reduction in the electron content has also been reported by several authors (Pavlov, 1994;Pavlov and Buonsano, 1997;Afraimovich et al, 2002). Several mechanisms have been reported as a possible source of positive ionospheric storm effects.…”

“…The LS AGWs transport gas from high latitudes to low and equatorial latitudes with increased temperature and increased N 2 density leading to a decrease in the [O]/[N 2 ] ratio and an increase in the recombination coefficient caused by the higher temperature (Buonsanto, 1999). Afraimovich et al (2002) reported LS TIDs associated with the storm of 6-7 April 2000 that caused a decrease in foF 2 and TEC over Almaty, a mid-latitude station in Russia. LS AGWs transport from high latitudes associated with the April storm might have reached to low latitude of Ahmedabad and decreased foF 2 due to storm-induced advection of gas with a depleted [O]/[N 2 ] ratio.…”

“…Ionospheric storms represent an extreme form of space weather, which can have significant adverse effects on increasingly sophisticated ground and space based technological systems of our society (Lasˇtovicka, 2002). The significant changes in the key ionospheric F-layer parameters, such as the critical frequency of the F2-layer (foF 2 ), the virtual height of the F-layer (h 0 F), the peak height of the F2-layer (h p F 2 ), the maximum electron density of the F2-layer (N max F2), and the total electron content (TEC), and in the ground based magnetometer records associated with magnetic storms have been reported on both a regional and a global basis (Rajaram et al, 1971;Batista et al, 1991;Yeh et al, 1992;Walker and Wong, 1993;Sojka et al, 1994;Sobral et al, 2001;Afraimovich et al, 2002;Lasˇtovicka, 2002;Blagoveshchensky et al, 2003). The ionospheric effects are dependent on the time of storm occurrence and intensity (Titheridge and Buonsanto, 1988), as well as on the latitude of the station and its location in the summer or in the winter hemisphere (Essex et al, 1981;Scho¨del et al, 1974).…”

Global pattern of the ionospheric response to large-scale internal gravity waves

“…Recently the techniques for studying TID effects in total electron content involving GPS observations have undergone significant development (Ho et al, 1998;Afraimovich et al, 2000Afraimovich et al, , 2001Afraimovich et al, , 2002Leonovich et al, 2004;Tsugawa et al, 2004;Afraimovich et al, 2005). The advantage of these observations is in very dense network of GPS receivers, especially in Northern America, Europe and Japan.…”