17:15 〜 18:45
[PEM12-P21] The Significant ionospheric depletion and related HF communication effects after the 2022 Tonga volcano eruption
キーワード：the 2022 Tonga volcano eruption, the ionospheric depletion , HF communication
The extreme Tonga volcano eruption on 15 January 2022 triggered profound and prolonged disturbances in the atmosphere and the ionosphere. This study focuses on the large-scale depletion of the ionosphere after this event and the resulting impact on shortwave communication.
Firstly, the large scale anomalous structure of the ionosphere over the epicentre of the volcano is analyzed by using ground-based and radio occultation (RO) GNSS data. The observations from ground-based GNSS data showed that the ionospheric TEC began to deplete significantly 45 minutes after the eruption, with a depletion amplitude of more than 10 TECU. The depletion diffusion range is ~40°×40° in latitude and longitude, and the duration is more than 10 hours. In addition, the COSMIC RO observations showed that the electron density decreased significantly after the volcano mainly above 250 km in altitude and lasted for more than 10 hours. The reason for the large-scale depletion of ionosphere may be due to the extreme explosion blowing molecular particles from the lower altitudes to the upper atmosphere, changing the thermosphere composition, reducing the ratio of atomic and molecular density (such as [O]/[N2]), and further increasing the plasma loss rate in the ionosphere.
The HF radio data (WSPRnet) showed that in the hours following the eruption around the Australia and New Zealand, the numbers of shortwave communications below 14 MHz decreased slightly compared to the background days, and the numbers of communications above 18 MHz decreased significantly.
Then, a three-dimensional ionospheric grid data was established before and after the volcanic eruption data assimilation technology. To evaluate the influence of the ionosphere on shortwave communication, we designed four typical communication links. Based on the 3-D ray tracing technique, we analyze the changes of radio wave propagation and the influence of communication frequency on each link before and after volcanic eruption.
Simulation of ray tracing showed that within 16 hours after the volcano, the MUF (Maximum Usable Frequency) and the OWF (Optimum Working Frequency) of the four links in the area around the volcano are significantly reduced, with the amplitude of about 5-7 MHz and 3-5 MHz.
Since satellite communications were severely hampered by the severe damage to infrastructure following the eruption, shortwave communication will become more important. But if people want to use it effectively, it is very important to adjust the communication strategy according to the ionospheric state in time.
Firstly, the large scale anomalous structure of the ionosphere over the epicentre of the volcano is analyzed by using ground-based and radio occultation (RO) GNSS data. The observations from ground-based GNSS data showed that the ionospheric TEC began to deplete significantly 45 minutes after the eruption, with a depletion amplitude of more than 10 TECU. The depletion diffusion range is ~40°×40° in latitude and longitude, and the duration is more than 10 hours. In addition, the COSMIC RO observations showed that the electron density decreased significantly after the volcano mainly above 250 km in altitude and lasted for more than 10 hours. The reason for the large-scale depletion of ionosphere may be due to the extreme explosion blowing molecular particles from the lower altitudes to the upper atmosphere, changing the thermosphere composition, reducing the ratio of atomic and molecular density (such as [O]/[N2]), and further increasing the plasma loss rate in the ionosphere.
The HF radio data (WSPRnet) showed that in the hours following the eruption around the Australia and New Zealand, the numbers of shortwave communications below 14 MHz decreased slightly compared to the background days, and the numbers of communications above 18 MHz decreased significantly.
Then, a three-dimensional ionospheric grid data was established before and after the volcanic eruption data assimilation technology. To evaluate the influence of the ionosphere on shortwave communication, we designed four typical communication links. Based on the 3-D ray tracing technique, we analyze the changes of radio wave propagation and the influence of communication frequency on each link before and after volcanic eruption.
Simulation of ray tracing showed that within 16 hours after the volcano, the MUF (Maximum Usable Frequency) and the OWF (Optimum Working Frequency) of the four links in the area around the volcano are significantly reduced, with the amplitude of about 5-7 MHz and 3-5 MHz.
Since satellite communications were severely hampered by the severe damage to infrastructure following the eruption, shortwave communication will become more important. But if people want to use it effectively, it is very important to adjust the communication strategy according to the ionospheric state in time.