17:15 〜 18:45
[PEM15-P02] The performance evaluation of three dimentional ionospheric tomography based on GNSS-TEC observation with ionozonde data assimilation
キーワード：電離圏、トモグラフィ、イオノゾンデ、3次元変分法
The ionosphere is constantly undergoing variationsinfluenced by solar activity and the lower layers of the atmosphere. The distribution of electron density in the ionosphere leads to phenomena such as reflection, absorption, and delay of radio waves. Particularly, radio waves in the L-band, commonly used in GPS satellite positioning, experience delays in the ionosphere, contributing to positioning errors. Therefore, for the advanced utilization of satellite positioning, it is essential to investigate the effects of the ionosphere.
Ssessanga et al. (2021) developed 3-D ionospheric tomography based on GNSS-TEC observation with ionosonde data assimilation, which can analyze 3-D ionospheric electron density distributions. This analysis realizes near-realtime monitoring of the ionosphere and is expected to improve performance in satellite positioning or other applications. However, the specific performance of this analysis has not yet been evaluated in detail. Therefore, in this study, we evaluated the performance of this analysis by comparison with other data that are independent of this analysis.
By comparing the ionospheric peak density and altitudes derived from long-term incoherent scatter radar observations by the MU radar and the 3-D tomography, when ionosonde observations near the analysis point are not influenced by ionospheric events such as Es layer or spreading of ionospheric traces, we found that peak-density altitudes from the tomography analysis distributed approximately ±30km of the actual altitudes from the MU radar observations.
Another comparison was conducted between the ionosonde parametersthat come from manual and automatic scaling. The parameters from the automatic scaling are used by the near-real-time tomography analysis while the parameters from the manual scaling are considered the determined value. We found that the automatic scaling well detects the occurrence of the Es layers. For the detection of spread-F phenomena, however, the performance of the automatic scaling is limited to that of the manual scaling. Careful attention should be taken in using near-real-time tomography when spread-F phenomena may exist.
In the presentation, based on the results of the performance evaluation in this study, we discuss recent development of the 3-D ionospheric tomography analysis.
Ssessanga et al. (2021) developed 3-D ionospheric tomography based on GNSS-TEC observation with ionosonde data assimilation, which can analyze 3-D ionospheric electron density distributions. This analysis realizes near-realtime monitoring of the ionosphere and is expected to improve performance in satellite positioning or other applications. However, the specific performance of this analysis has not yet been evaluated in detail. Therefore, in this study, we evaluated the performance of this analysis by comparison with other data that are independent of this analysis.
By comparing the ionospheric peak density and altitudes derived from long-term incoherent scatter radar observations by the MU radar and the 3-D tomography, when ionosonde observations near the analysis point are not influenced by ionospheric events such as Es layer or spreading of ionospheric traces, we found that peak-density altitudes from the tomography analysis distributed approximately ±30km of the actual altitudes from the MU radar observations.
Another comparison was conducted between the ionosonde parametersthat come from manual and automatic scaling. The parameters from the automatic scaling are used by the near-real-time tomography analysis while the parameters from the manual scaling are considered the determined value. We found that the automatic scaling well detects the occurrence of the Es layers. For the detection of spread-F phenomena, however, the performance of the automatic scaling is limited to that of the manual scaling. Careful attention should be taken in using near-real-time tomography when spread-F phenomena may exist.
In the presentation, based on the results of the performance evaluation in this study, we discuss recent development of the 3-D ionospheric tomography analysis.