American Journal of Astronomy and Astrophysics 2014; 2(6): 61-65 Published online December 19, 2014 (http://www.sciencepublishinggroup.com/j/ajaa) doi: 10.11648/j.ajaa.20140206.11 Geomagnetic disturbances and its impact on ionospheric critical frequency (foF2) at high, mid and low latitude region Roshni Atulkar 1, * , Shivangi Bhardwaj 2 , Prakash Khatarkar 2 , Purushottam Bhawre 2 , P. K. Purohit 1 1 National Institute of Technical Teachers’ Training and Research, Bhopal (MP), India 2 Space Science Laboratory, Barkatullah University, Bhopal (MP), India Email address: roshniatulkar@gmail.com(R. Atulkar) To cite this article: Roshni Atulkar, Shivangi Bhardwaj, Prakash Khatarkar, Purushottam Bhawre, P. K. Purohit. Geomagnetic Disturbances and Its Impact on Ionospheric Critical Frequency (foF2) at High, Mid and Low Latitude Region. American Journal of Astronomy and Astrophysics. Vol. 2, No. 6, 2014, pp. 61-65. doi: 10.11648/j.ajaa.20140206.11 Abstract: A geomagnetic storm is a major disturbance of Earth's magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth. During solar and geomagnetic activities, critical frequency of F2 layer (foF2) varies in a great extent. In this Study, our main aim is to examine the effect of solar and geomagnetic activities on the critical frequency (foF2) during January 2014 to April 2014 respectively. One magnetic intense storm occurred on 19 February with (Dst -112) and other moderate storm occurred on 12 April 2014 with (Dst -80). In our study, we have analyzed these effects on critical frequency of F2 layer for ionospheric monitoring. We have used ionospheric data at Low, mid and high latitude station. The absorption and ionization of the ionospheric medium depends on solar activity. The value of foF2 increased from their normal value at all the three latitudes. This is due to geomagnetic storms that occurred around the same time. A very interesting feature that can be seen in the figures is that the increase of foF2 at Low latitude is much more intense as compare to high and mid latitude. Comparison among all the latitudes shows that the values of foF2 at high latitude are quite less as compared to low and mid latitude. We have found that the effect of solar and geomagnetic storm disturbances is strongest at the low latitude and weakest at the high latitude during the geomagnetic storm time. Keywords: Geomagnetic Disturbance, Critical Frequency, Ionosphere, Storm 1. Introduction The continuous nuclear fusion process inside the sun, emit electromagnetic radiation. Earth’s magnetosphere, thermosphere and ionosphere are mostly affected by these electromagnetic radiations. Geomagnetic storms are created when the Earth's magnetic field captures ionized particles carried by the solar wind due to coronal mass ejections or coronal holes at the Sun. a geomagnetic storm is caused by a solar wind shock wave which typically strikes the Earth's magnetic field 24 to 36 hours after the event. Although there are different types of disturbances noted at the Earth surface, the disturbances can be characterized as a very slowly varying magnetic field, with rise times as fast as a few seconds, and pulse widths of up to an hour. The rate of change of the magnetic field is a major factor in creating electric fields in the Earth, geomagnetic storm phenomena associated with the variability of the sunspot cycle, and each sunspot cycle is typically ~11 years in duration. The frequency of geomagnetic storms increase and decreases depends on the sunspot cycle. During the Geomagnetic storm, ionospheric critical frequency foF2 become unstable, fragment and disappear. These ionospheric effects are dependent on the time of storm and intensity as well as the latitude of a station and its location in the summer or in the winter hemisphere (Batista et al.1991). Thermospheric-ionospheric view associated with positive and negative storm effects (Prolss 1993). The storm enhanced density (SED) described by Foster 1993), at mid latitude, storm enhanced plasma densities (SEDs) are observed during periods of enhanced geomagnetic activity. These bands of largely increased density structures, caused by storm-time electric fields that transport plasma from low to mid latitudes (Foster et al., 2002).Although low latitude ionospheric weather phenomenon is related to variations in the E×B plasma drift, which is prominent during the daytime. The ionization lifts upward near the dip equator and in concert with the parallel motion down the field lines creates the equatorial ionization anomaly. The largest density values occur in the ionization anomaly peaks with day to day