Effects of geomagnetic storm on middle latitude ionospheric F2 during storm of 2-6 April 2004

606-616A study of the intense geomagnetic storm on 2-6 April 2004 has been carried out using ionospheric data obtained from ionosonde station in the mid-latitude stations with emphasis on the F2 region. Ionospheric storms represent an extreme form of space weather with important effects on ground and space-based technological systems. These phenomena are driven by highly variable solar and magnetospheric energy inputs to the Earth's upper atmosphere. The mid-latitude ionospheric stations are classified into two, depending on their geographic coordinates and ionospheric storm variation (i.e. positive and negative phases of ionospheric storm). The low-mid latitude are characterized with geographic latitude between 20°N< low-mid ≤ 36°N, while high-mid latitude are >36°N. The ionospheric storms are classified as positive storms (P-storm) or negative storms (N-storm) depending on whether maximum electron density variation is positive or negative following the onset of geomagnetic storms (small fluctuations of less than ±20% are neglected). The ionospheric storm produced at low-mid latitude was observed to be negative (N) ionospheric storm at the main phase, and also the declining phase of Dst was simultaneously depleted. The recovery phase is more pronounced with positive (P) ionospheric storm with noticeable effect than the initial and main phase. The D(foF2) response of high-mid latitude was observed with positive storm in the main phase. The initial phase responded with severe negative ionospheric storm compared to low-mid latitude with positive ionospheric storm. During the main phase of the geomagnetic storm, positive and negative phases of ionospheric storm prevailed in the daytime and at night