15:00 〜 15:15
[PEM13-06] Ionospheric irregularities and scintillations during the geomagnetic storm on 15 January 2022
キーワード：電離圏不規則構造、電離圏シンチレーション、地磁気嵐
On 15 January 2022, various ionospheric disturbances were observed over Japan. Some of them appeared to be associated with the volcanic eruption of Hunga Tonga-Hunga Ha'apai. On the other hand, since a moderate geomagnetic storm commenced on 14 January 2022 was going on at the same time, it is important to distinguish the effects of the volcanic eruption and the geomagnetic storm.
We used GNSS total electron contents (TECs) and its temporal fluctuation represented by rate of TEC index (ROTI) derived from GNSS data from GEONET (GNSS Earth Observation Network). Besides the traveling ionospheric disturbances (TIDs) seen in high-pass filtered (detrended) TEC (dTEC) coinciding with atmospheric waves believed to be emitted from the volcanic eruption, multiple band-like regions with ROTI enhancement was started to be observed from 10 UT on 15 January 2022. They extended in the NW-SW direction and apparently moved westward. The structures were not aligned with the TIDs seen in dTEC. In the region of ROTI enhancement, enhancement in TEC was also observed. Stripes of sharp TEC depletions were embedded in the region. This looks similar to the storm-enhanced density (SED) or storm-induced plasma stream (SIPS) observed in the geomagnetic storms.
At the same time, strong scintillation in GNSS signals were observed over Ishigaki Island (24.4N, 124.1E), Japan. A number of TEC depletions embedded in TEC enhancements were observed. Scintillations were observed for almost all the GNSS satellite in view which indicates that the irregularities were distributed over a wide area.
Although it is still unknown that these ionospheric irregularities were due to the geomagnetic storm or combined effects with other sources, this event is important both for understanding the mechanisms of the ionospheric irregularities and for evaluating their effects on GNSS applications.
We used GNSS total electron contents (TECs) and its temporal fluctuation represented by rate of TEC index (ROTI) derived from GNSS data from GEONET (GNSS Earth Observation Network). Besides the traveling ionospheric disturbances (TIDs) seen in high-pass filtered (detrended) TEC (dTEC) coinciding with atmospheric waves believed to be emitted from the volcanic eruption, multiple band-like regions with ROTI enhancement was started to be observed from 10 UT on 15 January 2022. They extended in the NW-SW direction and apparently moved westward. The structures were not aligned with the TIDs seen in dTEC. In the region of ROTI enhancement, enhancement in TEC was also observed. Stripes of sharp TEC depletions were embedded in the region. This looks similar to the storm-enhanced density (SED) or storm-induced plasma stream (SIPS) observed in the geomagnetic storms.
At the same time, strong scintillation in GNSS signals were observed over Ishigaki Island (24.4N, 124.1E), Japan. A number of TEC depletions embedded in TEC enhancements were observed. Scintillations were observed for almost all the GNSS satellite in view which indicates that the irregularities were distributed over a wide area.
Although it is still unknown that these ionospheric irregularities were due to the geomagnetic storm or combined effects with other sources, this event is important both for understanding the mechanisms of the ionospheric irregularities and for evaluating their effects on GNSS applications.