11:00 AM - 11:15 AM
[G06-4-02] 3-D Tomography of Daytime Mid-latitude Sporadic-E from GNSS Data
We study ionospheric irregularities caused by daytime midlatitude sporadic-E (Es) in Japan using 3-D (three-dimensional) ionospheric tomography. Es is a thin layer of unusually high ionization that appears at the altitude of ~100 km. In previous studies, we imaged the Es patches on 2-D maps over Japan (Maeda & Heki, 2014 Radio Sci.; 2015 EPS) using changes in the ionospheric Total Electron Content (TEC) observed with Japanese GNSS receiver array, GEONET. They found that Es usually show frontal structure extending hundreds of kilometers predominantly in east-west.
Using the slant TEC residuals as an input, we estimate the electron density anomalies within >2000 small blocks with dimensions of a few tens of kilometers over a region of 300 x 500 km. We applyed a certain continuity constraint to stabilize the solution. We considered the distribution of GNSS line-of-sights to know which area will be properly resolved, and performed checkerboard resolution tests with synthesized data before using the actual observation data.
We select two examples of clear Es irregularities, i.e. Case 1 over the Kanto District at ~8 UT on 21 May 2010, and Case 2 over the Kyushu District at ~4 UT on 22 May 2010. They are first studied by Maeda & Heki (2014) and Maeda & Heki (2015), respectively. We confirmed that the positive electron density anomalies showed frontal shapes extending east-west at the E region altitude. In the first case, Es patch slowly moved southward, and it moved rather rapidly northward in the second case. One interesting feature in their 3-D structures is that positive anomalies expand upward and northward in Case 1, and upward and southward in Case 2. The results suggest that the extension direction of the upward continuation of Es patches might be controlled by their horizontal drift directions.
Using the slant TEC residuals as an input, we estimate the electron density anomalies within >2000 small blocks with dimensions of a few tens of kilometers over a region of 300 x 500 km. We applyed a certain continuity constraint to stabilize the solution. We considered the distribution of GNSS line-of-sights to know which area will be properly resolved, and performed checkerboard resolution tests with synthesized data before using the actual observation data.
We select two examples of clear Es irregularities, i.e. Case 1 over the Kanto District at ~8 UT on 21 May 2010, and Case 2 over the Kyushu District at ~4 UT on 22 May 2010. They are first studied by Maeda & Heki (2014) and Maeda & Heki (2015), respectively. We confirmed that the positive electron density anomalies showed frontal shapes extending east-west at the E region altitude. In the first case, Es patch slowly moved southward, and it moved rather rapidly northward in the second case. One interesting feature in their 3-D structures is that positive anomalies expand upward and northward in Case 1, and upward and southward in Case 2. The results suggest that the extension direction of the upward continuation of Es patches might be controlled by their horizontal drift directions.