Presentation Information
[PEM12-P27]Calculation of propagation paths and attenuation during propagation of ordinary and extraordinary waves in the ionosphere
*Abe Shota1, Hiroyuki Nakata1, Hiroyo Ohya1 (1.Graduate School of Science and Engineering, Chiba University)
Keywords:
HF radio wave,Ordinary mode,Extraordinary mode,ray-tracing
When radio waves propagate through the ionosphere, the refractive index, determined by the distribution of electron density, results in variable radio wave propagation path. Additionally, the radio waves propagating through the ionosphere undergo attenuation due to collisions between particles. This attenuation arises from the movement of electrons in the plasma, driven by the radio wave's electric field, leading to collisions with neutral particles and ions in the ionosphere. In this study, we have calculated the propagation paths and attenuation of HF (High Frequency) radio waves, considering the influence of geomagnetic field.
In calculating the propagation paths of radio waves, the ray-tracing method was employed. Considering the influence of geomagnetic field, radio waves in the ionosphere propagate in two modes: Ordinary mode (O-mode) and Extraordinary mode (X-mode). We conducted calculations for the propagation paths of both modes. To validate these calculations, we used critical frequencies obtained from ionosondes by the National Institute of Information and Communications Technology (NICT). The difference in the critical frequencies of O-mode and X-mode is half the cyclotron frequencies and the calculated difference was approximately 0.7MHz. This value corresponds to a value obtained by ionosonde measurements. This consistency suggests the accuracy of the derived difference between O-mode and X-mode. Additionally, the annual variation is revealing a consistent trend in higher frequencies in equinoctial seasons, and lower in solstice seasons. However, the critical frequencies derived from calculations tended to be higher. It is necessary to confirm whether the discrepancies in critical frequency are attributed to the IRI and MSIS model or other factors.
We also conducted calculations of attenuation of radio waves propagating through the ionosphere. The primary factor of this attenuation is collisions between particles and can be calculated by integrating the absorption coefficient κ along the propagation path. Anticipating the comparison with HF Doppler observations, we calculated the attenuation occurring during propagation between transmission and reception points, specifically between Chofu and Sugadaira. The simulation results showed that the attenuation in the ionosphere during the daytime in equinoctial seasons is significant, with the approximate value of 30 dB.
In summary, we calculated the propagation path considering the influence of geomagnetic field and compared the critical frequency obtained from the ionosonde with the calculated critical frequencies. The results showed that the variation trends were consistent. In addition, we calculated temporal variation of the attenuation in the ionosphere, and obtained the simulation results that the attenuation in the ionosphere is larger during the daytime in equinoctial seasons.
In the presentation, detailed examinations of propagation characteristics for each mode and calculating the received signal strength from ionospheric attenuation, will be discussed.
In calculating the propagation paths of radio waves, the ray-tracing method was employed. Considering the influence of geomagnetic field, radio waves in the ionosphere propagate in two modes: Ordinary mode (O-mode) and Extraordinary mode (X-mode). We conducted calculations for the propagation paths of both modes. To validate these calculations, we used critical frequencies obtained from ionosondes by the National Institute of Information and Communications Technology (NICT). The difference in the critical frequencies of O-mode and X-mode is half the cyclotron frequencies and the calculated difference was approximately 0.7MHz. This value corresponds to a value obtained by ionosonde measurements. This consistency suggests the accuracy of the derived difference between O-mode and X-mode. Additionally, the annual variation is revealing a consistent trend in higher frequencies in equinoctial seasons, and lower in solstice seasons. However, the critical frequencies derived from calculations tended to be higher. It is necessary to confirm whether the discrepancies in critical frequency are attributed to the IRI and MSIS model or other factors.
We also conducted calculations of attenuation of radio waves propagating through the ionosphere. The primary factor of this attenuation is collisions between particles and can be calculated by integrating the absorption coefficient κ along the propagation path. Anticipating the comparison with HF Doppler observations, we calculated the attenuation occurring during propagation between transmission and reception points, specifically between Chofu and Sugadaira. The simulation results showed that the attenuation in the ionosphere during the daytime in equinoctial seasons is significant, with the approximate value of 30 dB.
In summary, we calculated the propagation path considering the influence of geomagnetic field and compared the critical frequency obtained from the ionosonde with the calculated critical frequencies. The results showed that the variation trends were consistent. In addition, we calculated temporal variation of the attenuation in the ionosphere, and obtained the simulation results that the attenuation in the ionosphere is larger during the daytime in equinoctial seasons.
In the presentation, detailed examinations of propagation characteristics for each mode and calculating the received signal strength from ionospheric attenuation, will be discussed.