Effects of solar and geomagnetic activity on the occurrence of equatorial plasma bubbles over Hong Kong

Abstract

In the present study, the occurrence and characteristics of equatorial plasma bubble (EPB) has been analyzed using the GPS data from continuously operating reference stations network over Hong Kong during 2001–2012. The analysis found maximum EPB occurrences during the equinoctial months and minimum EPB occurrences during the December solstice throughout 2001–2012 except during the solar minimum in 2007–2009. The maximum EPB occurrences were observed in June solstice during 2007–2008, whereas for 2009, EPB occurrences were quite higher for June solstice but slightly smaller than the March equinox. The seasonal maximum in EPB occurrences have been discussed in terms of plasma density seed perturbation caused by gravity waves as well as the post sunset F‐layer rise due to the pre‐reversal enhancement of zonal electric field. Generally, EPB occurrences are found to be more prominent during nighttime hours (19:00–24:00 h) than daytime hours. The day and nighttime EPB occurrences were inferred and found to vary linearly with solar activity and have an annual correlation coefficient (R) of ~ 0.92 with F10.7 cm solar flux and ~0.88 with sunspot number. Moreover, the impact of solar activity on EPB occurrences is found to be dependent on seasons with maximum during the equinox (R = 0.80) and minimum during the summer season (R = 0.68). The detail study of EPB occurrences during two typical cases of geomagnetic storms on 6 November and 24 November 2001 found that the storm on 24 November triggered the EPB occurrence whereas storm on 6 November suppressed the EPB occurrence. The enhancement/suppression of EPB occurrences during storms periods is a consequence of a storm‐induced prompt penetration electric field as well as disturbance dynamo electric field effects associated with the main phase of the geomagnetic storm.

Occurrence characteristics of ionospheric irregularities over Indian low latitude region Varanasi during ascending phase of solar cycle 24

“…Apart from the nighttime scintillation occurrences, the daytime scintillation occurrences have also been observed all through the period 2009-2014 with relatively small values as compared to nighttime. Similar diurnal occurrences of irregularities were reported by previous workers [Rama Rao et al 2006, Nishioka et al 2008, Singh et al 2016, Kumar et al 2016. The development of post sunset irregularities is governed by mainly two parameters: evening F-layer drift as well as precursor gravity waves in seeding the instability.…”

“…Using the numerical simulation, [Maruyama 1988] showed that the role of inter-hemispheric neutral winds, which is directed from summer hemisphere to winter hemisphere, is to increase the Pedersen conductivity and thereby reducing the growth rate of the R-T instability. This asymmetry is expected to arise by the difference in inter-hemispheric neutral winds strength during two equinoxes [Nishioka et al 2008, Maruyama et al 2009, Mungufeni et al 2016, Kumar et al 2016. The results reported over Indonesia indicated that, asymmetric meridional winds during vernal and autumn equinox periods over Indonesia may provide asymmetric growth of the irregularity and leading to the equinoctial asymmetry [Maruyama et al 2009].…”

“…solar minimum year 2009. The seasonal maximum occurrences of ionospheric irregularities can be mainly controlled by two parameters: (i) one is post-sunset rise of F-layer (or vertical drift) due to pre-reversal enhancement (PRE) and (ii) other is seed perturbation in plasma density induced by gravity waves (GWs) which is originated from troposphere [Tsunoda 2010, Kumar et al 2016, Kumar 2017. During solar minimum period, the vertical drift due to PRE is less significant and seed perturbation can play significant role to manage the seasonal variation of ionospheric irregularities.…”

Improved characterization and modeling of equatorial plasma depletions

“…The occurrence of EPBs depends on many factors such as local time, longitude, season, solar cycle and geomagnetic activity (e.g. Huang et al, 2002;Burke et al, 2004;Magdaleno et al, 2012Magdaleno et al, , 2017Cherniak and Zakharenkova, 2016;Kumar et al, 2016b). Although EPBs are mainly equatorial phenomena, they can extend to higher latitudes along the magnetic field lines (e.g.…”

Statistical analysis of low-latitude spread F observed over Puer, China, during 2015–2016

“…At equatorial region, some studies (Bowman 1998;Sobral et al 2002;Su et al 2006;Ray and DasGupta 2007) found that the geomagnetic activity tended to suppress the generation of ESF. However, some researches have suggested that the dependence of magnetic activity varied with latitude, longitude, season and the phase of storm (Sahai et al 2005;Sobral et al 2002;Becker-Guedes et al 2004;Li et al 2010;Kumar et al 2016). Whalen (2002) reported that there was an inverse relationship between the occurrence of ESF and Kp index during equinoxes and December solstice, but no correlation in June solstice.…”