One of the major questions in the Sun-Earth connected system is "How are mass, momentum, and energy from the Sun transported within the magnetosphere and ionosphere/upper atmosphere?" One of the critical issues in this general theme is to understand the causality between solar activities and near-Earth space's disturbances.
 Until now, however, it is not clear how the physical quantities in the magnetosphere and ionosphere/upper atmosphere response to the passage of solar wind disturbances associated with solar activities. To improve our understanding for the field of the Sun-Earth connection, we need interdisciplinary research (i.e., solar physics, magnetospheric physics, and ionospheric/upper atmospheric physics) through the examination of physical quantities (i.e., temperature and density of the space plasma, magnetic and electric field, solar/aurora images) measured in space and/or on the ground.
 The main research subjects are as follows: (1) solar eruption, (2) connection between solar and geomagnetic storms, (3) near-Earth space's responses to solar disturbances, (4) magnetosphere-ionosphere/upper atmosphere coupling, (5) empirical space weather forecasting, etc.