[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-04] Detecting the plasma bubble at Western Australia in the MWA data

★Invited Papers

*吉浦 伸太郎¹、大塚 雄一²、Trott Cathryn³、Null Dev³、西谷 望²、高橋 慶太郎⁴、西岡 未知⁴、Perwitasari Septi⁵、新堀 淳樹² (1.国立天文台、2.宇宙地球環境研究所、3.カーティン大学、4.熊本大学、5.情報通信研究機構)

キーワード：プラズマバブル、電離層、全球測位衛星システム、 Murchison Widefield Array

In this talk, we report the detection of a plasma bubble feature using astronomical radio images. During a magnetic storm on 2023 December 1, Total Electron Content (TEC) maps derived from Global Navigation Satellite Systems (GNSS) data revealed the propagation of the plasma bubble over Western Australia. The significant turbulence in the ionosphere not only disturb the GPS data but also impacts radio astronomical observations. In particular, for radio interferometers consisting of multiple antennas, ionospheric distortions introduce severe errors in the phase of observed data. Consequently, the apparent positions of astronomical sources shift and vary on short time scales. We found the significant distortion of radio sources in MWA data on 2023 December 1. The Murchison Widefield Array (MWA) is a low-frequency radio interferometer located in Western Australia. With its exceptionally wide field of view (approximately 20 deg x 20 deg), the MWA can simultaneously measure the positional shifts of multiple radio sources. Our analysis reveals a duct like structure with a size of roughly 50 km (east-west) propagating across the field of view with a velocity of roughly 100 m/s. The rate of TEC change index shows significant TEC fluctuations at the same time. These results strongly suggest that the duct-like structure is caused by a plasma bubble extending across Western Australia. Furthermore, one of the bright radio source inside the duct was observed to split into multiple components exhibiting rapid time variability. We interpret this phenomenon as diffraction caused by small-scale structures within the plasma bubble.