Structuring of intermediate scale equatorial spread F irregularities during intense geomagnetic storm of solar cycle 24. Issue 7 (19th July 2016)

• Record Type: Journal Article
• Authors: Kakad, B.; Gurram, P.; Tripura Sundari, P. N. B.; Bhattacharyya, A.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 7(2016:Jul.)
• Page Start: 7001
• Page End: 7012
• Publication Date: 2016-07-19
• Subjects: equatorial ionosphere -- ESF structuring -- geomagnetic storm; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022635
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Here we examine the structuring of equatorial plasma bubble (EPB) during intense geomagnetic storm of solar cycle (SC) 24 that occurred on 17 March 2015 using spaced receiver scintillation observations on a 251 MHz radio signal, recorded by a network of stations in Indian region. As yet, this is the strongest geomagnetic storm ( D s t min ∼−223nT) that occurred in present SC. Present study reveals that the structuring of equatorial spread F (ESF) irregularities was significantly different on 17 March as compared to quiet days of corresponding month. ESF irregularities of intermediate scale (100 m to few kilometers) are observed at unusually higher altitudes (≥ 800 km) covering wider longitudinal‐latitudinal belt over Indian region. A presence of large‐scale irregularity structures with stronger Δ N at raised F peak with small‐scale irregularities at even higher altitudes is observed. It caused strong focusing effect ( S 4 >1) that prevails throughout premidnight hours at dip equatorial station Tirunelveli. Other observational aspect is that zonal irregularity drifts over low‐latitude station Kolhapur exhibited a large deviation of ∼230 m/s from their average quiet time pattern. During this geomagnetic storm, two southward turnings of significant strength ( B Z ≤−15 nT) occurred at 11.4 IST (Indian standard time) and 17.9 IST. The later southward turning of interplanetary magnetic field (IMF) B Z resulted in a large eastward prompt penetration electric field (PPEF) close to sunset hours in Indian longitude. Estimates of PPEF obtained from real‐time ionospheric model are too low to explain the observed large upliftment of F region in the post sunset hours. Possible reason for observed enhanced PPEF‐linked effects is discussed. Key Points: Intermediate scale (100 m to few kilometers) ESF irregularities at unusually higher altitude Large‐scale structures with stronger Δ N near raised equatorial F peak A large deviation of 230 m/s in low‐latitude F region zonal irregularity drift