5:15 PM - 7:15 PM
[MTT37-P09] Visualization of shape and motion of Sporadic E using data from ultra-dense GNSS receiver network
Keywords:ionosphere, sporadic E, GNSS
Sporadic E (Es) is known as a thin layer in the ionospheric E region at around 100 km altitude, in which the electron density increases suddenly and locally. When Es occurs, VHF radio waves, which normally propagate through the ionosphere, are reflected, leading to anomalous long-distance propagation. This can cause unintended interference between unwanted distant signals and desired signals from nearby radio sources. Es has been observed using ionosondes since 1950’s. In recent years, the occurrence of Es is monitored by anomalous long-distance propagation of VHF signals used for maritime and aeronautical navigations. In this study, we aim to visualize the spatial distribution and dynamics of Es by utilizing an ultra-dense GNSS receiver network in Japan. Although previous studies have already employed GNSS-based observations to detect Es, the limited number of data points resulted in imaging with relatively low spatial resolution, making it difficult to accurately capture the structure and motion of Es.
Considering such a situation, this study visualized Es using data from the ichimill GNSS receiver network, which is operated by SoftBank Corp. at more than 3,300 locations across Japan. Specifically, we analyzed an Es event that occurred on July 4, 2022, by mapping the electron density disturbance index, known as the Rate of TEC Index (ROTI), derived from the total electron content (TEC) obtained from the ichimill GNSS receiver network. When mapping the ROTI data, the altitude of electron density disturbances was assumed to be 100 km, enabling us to visualize the spatial structure of Es. As a result, we not only revealed the spatial scale and moving speed of Es but also succeeded in tracking the motion of Es in the two-dimensional fashion.
In particular, the speed of Es, determined through both longitude cross-sectional analysis and direct 2D tracking, was found to be approximately 105 m/s in both the cases. Additionally, the observed Es patches showed a spatial scale of approximately 70 km in both the east-west and north-south directions. The moving direction of Es was found to change over time: initially, Es drifted northward or northwestward, but just before its disappearance, its direction shifted toward the northeast. Furthermore, the motional characteristics of Es, as visualized in this study, were found to be generally consistent with numerical simulations of metal ion accumulation based on neutral wind data from the GAIA model (Andoh et al., 2023). These results demonstrate that the ultra-dense GNSS receiver network enables detailed visualization of both the morphology and motional characteristics of Es.
In the poster presentation, we plan to present the temporal variations of the spatial scale and speed of Es, as well as the results of analyses of other events and statistics. Additionally, we will compare the current findings with the predictions of numerical simulation of Andoh et al. (2023).
The SoftBank’s GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the “Consortium to utilize the SoftBank original reference sites for Earth and Space Science”.
Considering such a situation, this study visualized Es using data from the ichimill GNSS receiver network, which is operated by SoftBank Corp. at more than 3,300 locations across Japan. Specifically, we analyzed an Es event that occurred on July 4, 2022, by mapping the electron density disturbance index, known as the Rate of TEC Index (ROTI), derived from the total electron content (TEC) obtained from the ichimill GNSS receiver network. When mapping the ROTI data, the altitude of electron density disturbances was assumed to be 100 km, enabling us to visualize the spatial structure of Es. As a result, we not only revealed the spatial scale and moving speed of Es but also succeeded in tracking the motion of Es in the two-dimensional fashion.
In particular, the speed of Es, determined through both longitude cross-sectional analysis and direct 2D tracking, was found to be approximately 105 m/s in both the cases. Additionally, the observed Es patches showed a spatial scale of approximately 70 km in both the east-west and north-south directions. The moving direction of Es was found to change over time: initially, Es drifted northward or northwestward, but just before its disappearance, its direction shifted toward the northeast. Furthermore, the motional characteristics of Es, as visualized in this study, were found to be generally consistent with numerical simulations of metal ion accumulation based on neutral wind data from the GAIA model (Andoh et al., 2023). These results demonstrate that the ultra-dense GNSS receiver network enables detailed visualization of both the morphology and motional characteristics of Es.
In the poster presentation, we plan to present the temporal variations of the spatial scale and speed of Es, as well as the results of analyses of other events and statistics. Additionally, we will compare the current findings with the predictions of numerical simulation of Andoh et al. (2023).
The SoftBank’s GNSS observation data used in this study was provided by SoftBank Corp. and ALES Corp. through the framework of the “Consortium to utilize the SoftBank original reference sites for Earth and Space Science”.