3:00 PM - 3:15 PM
[PEM11-21] Observation of the Doppler frequency shift of the HF wave transmitted by an ionosonde
Keywords:observation, Doppler frequency shift, ionosonde, equatorial spread F, cross-correlation, replica
Navigation satellite systems are now used in a wide variety of applications and are known to suffer from ionospheric disturbances such as the post-sunset equatorial spread F (ESF). For forecasting post-sunset ESF, the potential of ionosondes is assessed and the vertical plasma drift velocity is reported to correlate with the post-sunset ESF with a criterion of 30 m/s for high probability of occurrence. The difference between two consecutive ionograms is used to estimate the velocity [1]. However, the velocity can also be measured directly as the Doppler frequency shift of the wave reflected from the ionosphere [2]. An example of such an observation is shown as below.
The Doppler frequency shift of the pulse train transmitted by the Chung-Li ionosonde [3] starting at 19:00 on January 18, 2024 (UT) is analyzed as shown in the figure. A heat map of the absolute values of the summed cross-correlations between the received samples and the model replicas is plotted against the Doppler frequency shift multiplied by the replicas (horizontal axis) and the relative time of flight (vertical axis). A course resolution of 2 Hz of the Doppler frequency shift is shown. This resolution can resolve the 30 m/s vertical velocity, when the ionosphere reflects the 10 MHz vertical incident wave. It is straightforward to obtain a more accurate estimate of the Doppler frequency shift according to the signal-to-noise ratio of the samples using the maximum likelihood method.
[1] P. Abadi, U. A. Ahmad, Y. Otsuka, P. Jamjareegulgarn, A. Almahi, S. Perwitasari, S. Supriadi, W. Harjupa, and R. R. Septiawan, `Assessing the potential of ionosonde for forecasting post-sunset equatorial spread F: an observational experiment in Southeast Asia,’ Earth Planets Space, vol. 75, 2023.
[2] T. Iwamoto, M. Konishi, N. Ikeda, and S. Kameoka, `Observation of Doppler frequency shift and time of flight of a temporally modulated HF wave propagating through ionosphere,’ the Japan Geoscience Union Meeting 2022, Chiba, Japan, May 2022.
[3] K.-J. Ke, C.-L. Su, R.-M. Kuong, H.-C. Chen, H.-S. Lin, P.-H. Chiu, C.-Y. Ko, and Y.-H. Chu, `New Chung-Li Ionosonde in Taiwan: System Description and Preliminary Results,’ Remote Sensing, vol. 14, 2022.
Figure caption:
A heat map of the absolute values of the summed cross-correlations between the received samples of the pulse train transmitted starting at 19:00 on January 18, 2024 (UT) and the model replicas is plotted against the Doppler frequency shift multiplied by the replicas (horizontal axis) and the relative time of flight (vertical axis).
The Doppler frequency shift of the pulse train transmitted by the Chung-Li ionosonde [3] starting at 19:00 on January 18, 2024 (UT) is analyzed as shown in the figure. A heat map of the absolute values of the summed cross-correlations between the received samples and the model replicas is plotted against the Doppler frequency shift multiplied by the replicas (horizontal axis) and the relative time of flight (vertical axis). A course resolution of 2 Hz of the Doppler frequency shift is shown. This resolution can resolve the 30 m/s vertical velocity, when the ionosphere reflects the 10 MHz vertical incident wave. It is straightforward to obtain a more accurate estimate of the Doppler frequency shift according to the signal-to-noise ratio of the samples using the maximum likelihood method.
[1] P. Abadi, U. A. Ahmad, Y. Otsuka, P. Jamjareegulgarn, A. Almahi, S. Perwitasari, S. Supriadi, W. Harjupa, and R. R. Septiawan, `Assessing the potential of ionosonde for forecasting post-sunset equatorial spread F: an observational experiment in Southeast Asia,’ Earth Planets Space, vol. 75, 2023.
[2] T. Iwamoto, M. Konishi, N. Ikeda, and S. Kameoka, `Observation of Doppler frequency shift and time of flight of a temporally modulated HF wave propagating through ionosphere,’ the Japan Geoscience Union Meeting 2022, Chiba, Japan, May 2022.
[3] K.-J. Ke, C.-L. Su, R.-M. Kuong, H.-C. Chen, H.-S. Lin, P.-H. Chiu, C.-Y. Ko, and Y.-H. Chu, `New Chung-Li Ionosonde in Taiwan: System Description and Preliminary Results,’ Remote Sensing, vol. 14, 2022.
Figure caption:
A heat map of the absolute values of the summed cross-correlations between the received samples of the pulse train transmitted starting at 19:00 on January 18, 2024 (UT) and the model replicas is plotted against the Doppler frequency shift multiplied by the replicas (horizontal axis) and the relative time of flight (vertical axis).