Solar Zenith Angle Dependence of Ionospheric Absorption during Different Epochs of the Solar Cycle

Abstract

Cos <img src='/image/spc_char/lembda.gif' border=0> variation of absorption for the period 1972-80 over Udaipur (24°35'N) is presented. The working frequencies are in the range 2-4.1 MHz. The cos <img src='/image/spc_char/lembda.gif' border=0> variation of absorption follows expressions <i>A</i> = <i>A</i>₁ + <i>B</i>₁cos<i>ⁿ</i> <img src='/image/spc_char/lembda.gif' border=0> and <i>A</i> = <i>B’</i>₁ cos<i>ⁿ</i> <img src='/image/spc_char/lembda.gif' border=0> for low and high solar activity periods, respectively. The cos <img src='/image/spc_char/lembda.gif' border=0> index values have also been found to be different during the minimum and maximum periods of the solar activity. The results have been discussed.