Probing low-latitude ionosphere using the giant metrewave radio telescope

Abstract

The Earth’s ionosphere forms a 3-Dimensional phase screen (particularly for signals having frequencies below1 GHz) in the upper atmosphere, susceptible to solar activities. Electron density fluctuations in the ionosphere change over time due to solar activity and spatially due to the Earth’s magnetic field. Situated hundreds of kilometers above the Earth’s surface, this plasma region holds great significance in global applications, depending on the frequency of the signals used. While the ionosphere acts as a reflective medium for radio frequencies ranging from 3 kHz to 30 MHz, enabling long-distance communication worldwide, its behavior differs for other frequency ranges. For frequencies between 30 MHz and 3 GHz, the ionosphere primarily acts as a refractive medium, which can cause signal attenuation; and thus cause degradation of the signal, received by the ground based receivers which can be Global navigation satellite system (GNSS) base systems or radio telescope arrays, depending on their sensitivity.