报告主题：Observations in Southeast Asia and numerical simulations of equatorial plasma bubbles
报告人：Dr. Tatsuhiro Yokoyama
Equatorial spread F (ESF) is a well-known phenomenon in the equatorial ionoshperic F region. As it causes severe scintillation in the amplitude and phase of radio signals, it is important to understand and forecast the occurrence of ESF from a space weather point of view. Ionospheric observation with the 47-MHz Equatorial Atmosphere Radar (EAR) in West Sumatra, Indonesia (0.20S, 100.32E, 10.36S dip latitude) has been conducted since 2001, and its unique observational data has been obtained for more than one solar cycle. Along with the EAR observations, Southeast Asia Low-latitude Ionospheric Network (SEALION) project by NICT started in 2003 for the purpose of monitoring and forecasting ESF. The SEALION consists of multiple ionosondes, GPS receivers and several other instruments in the Southeast Asian region. On the other hand, since late 1970s, numerical simulations have been powerful tools to study the fully nonlinear evolution of EPBs, which cannot be wholly understood from theoretical predictions. The most recent model, High-Resolution Bubble (HIRB) model, could reproduce very turbulent structures inside EPBs such as bufurcation, zonal asymmetry, and two-component power law spectral characteristics. Future collaboration with observations and modeling studies are expected.
Dr. Tatsuhiro Yokoyama completed his doctor degree at Kyoto University in 2004. Then, he has kept working in ionospheric research field in Nagoya University, Japan, Cornell University, USA, NASA Goddard Space Flight Center, USA, National Institute of Information and Communications Technology, Japan.
In November 2018, Dr. Tatsuhiro Yokoyama was appointed as Associate Professor at Research Institute for Sustainable Humanosphere, Kyoto University, Japan.
SCIENTIFIC ACTIVITIES AND ACHIEVEMENTS
1. A dedicated study of low to middle latitude ionosphere by utilizing numerical models and radar/rocket/satellite observations, especially on ionospheric irregularities and disturbances
2. Development of numerical models for ionospheric irregularities and disturbances by utilizing FORTRAN high performance parallel computing
3. Clarification of plasma instabilities and electrodynamical coupling process between ionospheric E and F regionswith numerical models
4. Radar observation of ionospheric field-aligned irregularities (FAI) in association with mid-latitude sporadic-E layer and equatorial spread F