On the effects of geomagnetic storms and pre storm phenomena on low and middle latitude ionospheric F2

Abstract

This paper presents some features of the ionospheric response observed in equatorial and mid-latitudes region to two strong geomagnetic storms, occurring during Oct. 19-23, 2001 and May 13-17, 2005 and to understand the phenomena of pre-storm that lead to very intense geomagnetic storms. The result point to the fact that pre-storm phenomena that leads to intense ionospheric storm are; large southward turning of interplanetary magnetic field Bz, high electric field, increase in flow speed stream, increase in proton number density, high pressure ram and high plasma beta. The magnitude of Bz turning into southward direction from northward highly depends upon the severity of the storm and the variation in F2 layer parameter at the time of geomagnetic storm are strongly dependent upon the storm intensity. A detailed analysis of the responses of the ionosphere shows that during the storm periods, foF2 values depleted simultaneously both in the equatorial and mid latitude. Observation also shows that low to moderate variations in ionospheric F2 at the pre-storm period may signal the upcoming of large ionospheric disturbances at the main phase. The ionospheric F2response for low and mid latitude does not show any significant differences during the storm main phase and the prestorm period. The ionospheric response during the pre-storm period is thought very puzzling. The period is observed to be depleted throughout with low-moderate effect across all the stations in the low and mid latitude.

Preliminary Results From the Latin American Giant Observatory Space Weather Simulation Chain

“…This is shown in Figure , where the time evolution of Δ Ξ 1 − 2 is displayed at both sites for May of 2005. We have selected this particular month because the strong geomagnetic storm on 13–17 May 2005, generated intense disturbances in the GF (see, e.g., Adekoya et al, ; Bisi et al, ; Galav et al, ). Three particular cases are shown: the total flux secondary particles, Δ Ξ 1 − 2 , the muon flux and the neutron flux .…”

Ionospheric and Solar Wind Variation during Magnetic Storm Onset and Main Phase at Low- and Mid-latitudes

“…From the early hour of 5 April the storm emerged with a moderate to weak amplitude activity up to around 12:00 UT on 6 April. Following this is the period expected to be dominated by sudden storm commencement phenomena (Balasis et al 2006, Adekoya et al 2012a, but the decrease in the westward ring current encircling the earth did not significantly enhanced the H component (little energy is entering into the earth magnetosphere). However, the Dst value was observed to be -6 nT around the onset period, which indicates that the storm is not preceded by SSC.…”

“…This corresponds to the increase in solar wind flow speed to a peak value of 1107 km/s. On the Dst plot is the picture of the sudden positive increase known as the sudden storm commencement (SSC), which is generally recently known as the SSC (see Balasis et al 2006, Mikhailov and Perrone 2009, Adekoya et al 2012a) and spans 12:00-17:00 UT. This period is observed to be a turning point for the flow speed increase, as well as the southward orientation of IMF Bz (Fig.…”

“…Such effects have been reproduced by coupled models of the ionosphere-thermosphere system. Adekoya et al (2012a) had demonstrated that investigations into the origin and nature of SSC on the ionospheric F-region have continued to engage the attention of scientists who constitute the space weather community. Some of these include Prölss (1995), Mikhailov and Perrone (2009), Laštoviþka (2007, 2008), and Danilov (2013).…”

The response of the ionosphere over Ilorin to some geomagnetic storms

“…There are many previous and recent studies on the Ionospheric behaviour during geomagnetic storms (e.g. Skinner and Wright, 1955;Woodman, 1970;Low and Roelof, 1973;Turunen and Rao, 1980;Adeniyi, 1986;Abdu et al, 1995;Sastri, 1988;Radicella and Adeniyi, 1999;Mansilla, 2004;Kumar et al, 2005;Dabas et al, 2006;Burns et al, 2007;Adebesin, 2008;Adekoya et al, 2012;Joshua et al, 2013a,b;etc.). These studies have shown that; geomagnetic storms affect the distribution of electron density in the ionosphere.…”