## 2 Data  
In this study, measurements from ionosondes, the ground-based Global Navigation Satellite Systems (GNSS) network, and the CHAMP and ROCSAT-1 satellites are utilized to study the occurrence of midlatitude plasma depletions over Eastern Asia under the influence of the magnetic storm on 16 July 2003. The geophysical conditions during this storm are described by the solar wind velocity, interplanetary magnetic field (IMF) Bz component, au-roral electrojet (AE) index, and geomagnetic indices (i.e., SYM-H and Kp). A meridional chain of ionosondes along the longitude of \(\sim\)135\({}^{\circ}\)E over Japan can be used to identify spread F and obtain the F2 layer critical frequency (foF2) from ionograms. From middle latitudes to low latitudes, they are Wakkanai (WK545: 45.4\({}^{\circ}\)N, 141.7\({}^{\circ}\)E), Kokubunji (TO536: 35.7\({}^{\circ}\)N, 139.5\({}^{\circ}\)E), Yamagawa (YG431: 31.2\({}^{\circ}\)N, 130.6\({}^{\circ}\)E), and Okinawa (OK426: 26.7\({}^{\circ}\)N, 128.2\({}^{\circ}\)E). The detailed location information of ionosonde stations is given in Table 1. Manually scaled parameters (i.e., foF2) with 1 h intervals were kindly provided by the National Institute of Information and Communications Technology (NICT) in Japan. We also manually checked the ionospheric parameter foF2, which are in good agreement with the NICT results. Moreover, we manually identified spread F with a 1 h sampling interval. Note that the local time in our analysis refers to the Japanese Standard time (JST = UT + 9 h), where UT is universal time. Data derived from the ground-based GNSS network can help characterize ionospheric density and disturbances [34]. First, the total electron content (TEC) is calculated through multiple steps using the dual-frequency carrier phase and pseudorange, which can be found in the detailed work of previous work [35; 36]. Then, the TEC was further processed to obtain the rate of TEC change index (ROTI) and the detrended TEC products. The ROTI is defined as the standard deviation of the rate of the TEC change over 5 min. Details of the method used to obtain the ROTI were described by [PERSON] et al. [37]. Here, the two-dimensional global maps of ROTI indices, provided by the Institute for Space-Earth Environmental Research (ISEE) at Nagoya University, are used to detect the existence of ionospheric F-region irregularities on a global scale [38; 39]. The detrended TEC products were produced by subtracting the background TEC using a 15 min running window [16]. In this study, the detrended TEC maps produced by the NICT are used to identify MSTIDs over Japan. To detect EPBs over Eastern Asia, the ROCSAT-1 and CHAMP satellites are also included in this study. The ROCSAT-1 satellite is in a near-circular orbit at an altitude of \(\sim\)600 km with a 35\({}^{\circ}\) inclination, which can provide the in situ ion density (Ni), and plasma drift at a sampling cadence of 1 s via the Ionospheric Plasma and Electrodynamics Instrument (IPEI) payload and the retarding potential analyzer (RPA) [1; 40]. The CHAMP satellite is in a circular, near-polar orbit with an inclination of 87.3\({}^{\circ}\), and an initial altitude of \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Station (Abbr.)** & **Geographic Latitude** & \
\begin{tabular}{c} **Geographic** \\ **Longitude** \\ \end{tabular} &
\begin{tabular}{c} **Geomagnetic** \\ **Latitude** \\ \end{tabular} \\ \hline Wakkanai (WK545) & 45.4\({}^{\circ}\)N & 141.7\({}^{\circ}\)E & 40.5\({}^{\circ}\)N \\ Kokubunji (TO536) & 35.7\({}^{\circ}\)N & 139.5\({}^{\circ}\)E & 30.0\({}^{\circ}\)N \\ Yamagawa (YG431) & 31.2\({}^{\circ}\)N & 130.6\({}^{\circ}\)E & 26.1\({}^{\circ}\)N \\ Okinawa (OK426) & 26.7\({}^{\circ}\)N & 128.2\({}^{\circ}\)E & 21.2\({}^{\circ}\)N \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Coordinates of ionosonde stations used in this study. Geomagnetic latitude are obtained from the International Geomagnetic Reference Field (IGRF)-2005 magnetic field model. 450 km.