Studying the Diurnal Ionospheric Distortions in the Southern Hemisphere

In Summer 2023, I worked at the Low-Frequency Cosmology Lab (LoCo), a radio astronomy lab at ASU. I had the opportunity to work under Prof. Judd Bowman to study the Ionospheric Distortions using a telescope called Experiment to Detect the Global EoR Signature (EDGES). EDGES is a telescope located at the Murchison Radio-astronomy Observatory (MRO) in Western Australia. 

Before diving into the conducted research, let’s get a grasp of what exactly is the Ionosphere and why it’s worth studying. Ionosphere is a part of the Earth's atmosphere, located somewhat between the thermosphere. It ranges from 50 to 500 km above sea level. Just like the name suggests, it is the ionized part of the atmosphere that contains a high concentration of ions and free electrons. The ionosphere plays a crucial role in radio communication and the transmission of electromagnetic signals, including radio waves.

The ionization in the ionosphere is primarily caused by solar radiation, particularly the high-energy ultraviolet (UV) and X-ray radiation from the Sun. When this solar radiation interacts with the neutral atoms and molecules in the upper atmosphere, it can strip electrons from these particles, creating positively charged ions and free electrons. 

The global 21-cm from the Epoch of Reionization is expected to be extremely weak (∼100 mK) in comparison to the synchrotron emission and Galactic foregrounds emissions (∼10⁴ K). Beyond this, the diurnal ionospheric fluctuations cause structures in the residuals of daily spectra. In this project, we used the data from EDGES to statistically model the effects of ionosphere in low radio frequencies (50-100 MHz).