Characteristics of Large Scale Ionospheric Irregularities over Delhi

Abstract

The Faraday fading records obtained at Delhi for 40 MHz transmissions from satellite BE-B for the period October 1964 to March 1969 and from satellite BE-C for the period May 1965 to March 1969 have been utilized for studying the characteristics of large scale ionospheric irregularities. To estimate the size of the irregularities, the irregularity height was assumed to be around 350 km based on a previous study, in which Faraday fading records taken simultaneously at Delhi and Kurukshetra were utilized. The present study reveals that: (i) during low solar activity, the frequency of occurrence is small during daytime and high during night-time, while during high solar activity the frequency of occurrence shows no preference; (ii) during low solar activity the horizontal sizes vary from 50 to 700 km, the most common size being about 175 km, while during high solar activity, the sizes vary from 5 to 300 km, the most common size being about 25 km; and (iii) the electron content of the irregularities varies from 1.0 x 10¹³ to 1.3 x 10¹⁶ m^-2 being 0.1 to 35% of the background electron content during low solar activity and from 4 x 10¹⁴ to 1.2 x 10¹⁶ m^-2, being 0,03 to 12% of the background content during high solar activity.