Institute for Space-Earth Environmental Research, Nagoya University, Chikusa-ku, Nagoya, 464-8601, Japan.
National Institute of Information and Communications Technology, Koganei, Tokyo, 184-8795, Japan.
Sci Rep. 2023 May 22;13(1):6450. doi: 10.1038/s41598-023-33603-3.
Equatorial plasma bubbles are a phenomenon of plasma density depletion with small-scale density irregularities, normally observed in the equatorial ionosphere. This phenomenon, which impacts satellite-based communications, was observed in the Asia-Pacific region after the largest-on-record January 15, 2022 eruption of the Tonga volcano. We used satellite and ground-based ionospheric observations to demonstrate that an air pressure wave triggered by the Tonga volcanic eruption could cause the emergence of an equatorial plasma bubble. The most prominent observation result shows a sudden increase of electron density and height of the ionosphere several ten minutes to hours before the initial arrival of the air pressure wave in the lower atmosphere. The propagation speed of ionospheric electron density variations was ~ 480-540 m/s, whose speed was higher than that of a Lamb wave (~315 m/s) in the troposphere. The electron density variations started larger in the Northern Hemisphere than in the Southern Hemisphere. The fast response of the ionosphere could be caused by an instantaneous transmission of the electric field to the magnetic conjugate ionosphere along the magnetic field lines. After the ionospheric perturbations, electron density depletion appeared in the equatorial and low-latitude ionosphere and extended at least up to ±25° in geomagnetic latitude.
赤道等离子体气泡是一种等离子体密度亏缺的现象，伴有小规模密度不规则性，通常在赤道电离层中观测到。这种现象会影响基于卫星的通信，在 2022 年 1 月 15 日汤加火山爆发有记录以来最大的一次爆发后，在亚太地区观测到了这种现象。我们利用卫星和地面电离层观测结果表明，汤加火山喷发引发的气压波可能导致赤道等离子体气泡的出现。最显著的观测结果表明，在气压波最初到达低层大气之前的几十分钟到几小时内，电离层中的电子密度和高度会突然增加。电离层电子密度变化的传播速度约为 480-540 米/秒，其速度高于对流层中兰姆波 (~315 米/秒) 的速度。北半球的电子密度变化比南半球大。电离层的快速响应可能是由于电场沿磁力线瞬时传输到磁共轭电离层引起的。电离层扰动后，赤道和低纬电离层出现电子密度亏缺，并至少延伸到地磁纬度±25°。
