Strong ionospheric activity at the MWA site associated with plasma bubble measured by GNSS

Abstract The Earth’s ionosphere refracts radio signals, shifting the apparent position of radio sources. Wide-field measurements with a radio interferometer can measure the ionospheric distortion. The Murchison Widefield Array (MWA) has the ability to capture ionospheric structures that are smaller than $100\:$km in extent. We report unusually strong ionospheric activity in MWA data during a magnetic storm on 2023 December 1. The duct-like structure (roughly $50\: {\rm km} \times {>}100\:$km) passes through the MWA field-of-view with a velocity of ${\sim}100\:\mathrm{m}\:\mathrm{s}^{-1}$. The offsets of the apparent position of the radio source are more than $1^{\circ }$ in the MWA observation data at around $180\:$MHz. By comparing the total electron content (TEC) data obtained from the global navigation satellite systems’ receiver network, we have found that the TEC fluctuations represented by a high rate of TEC change index coincided with the strong ionospheric activity observed by the MWA. This result suggests that unusual ionospheric signatures detected by the MWA could be caused by plasma bubbles extending across Western Australia during a magnetic storm.