Seminar & Lecture

Development of space weather research－A new approach to the substorm onset issue

Designated Assistant Professor Tzu-Fang Chang

Institute for Space‐Earth Environmental Research (ISEE), NAGOYA UNIVERSITY (NU) JAPAN

2019/3/21 14:10 R.48218 –2nd floor of Composite Building

Magnetospheric storms and substorms are the main manifestations of what are nowadays known as the “space weather” which has a practical impact on modern technology systems and our activities on Earth. Various spacecraft have been investigating the space environment around the Earth to explore the effects of substorms and storms－the THEMIS (Time History of Events and Macroscale Interactions during Substorms) and the ERG (Exploration of energization and Radiation in Geospace) missions for example. In particular, substorms are disturbances in the Earth's magnetosphere that causes energy to be released from the "tail" of the magnetosphere to the high-latitude ionosphere. The enhancement in electron fluxes during substorms can be a few orders greater than the pre-onset conditions. Since a fierce debate on substorm onset triggering has persisted for a long time, it highlights a pressing need for a better understanding of substorms in developing the space weather research. Two categories of substorm onset initiation models have been proposed－the Near-Earth Neutral Line model and the Current Disruption model. After the launch of the THEMIS quintet, some notable results even reported a new scenario – plasma intrusion to the inner plasma sheet. Thus starting a further exploration of substorms is inevitable. We will put forth a proposal to settle one of the center issues in dispute, the definition of substorm onset, by investigating the auroral streamers.

Long-lasting radial IMF events and their influence of dayside magnetosphere

Dr. Gilbert Pi

Faculty of Mathematics and Physics, Charles University Prague, Czech Republic

2019/3/15 14:00 R.4811B –2nd floor of Composite Building

Long-lasting radial interplanetary magnetic field (IMF) events are one of the special solar wind conditions. These events are usually accompanied with low density, weak magnetic field strength, low temperature, and low fluctuations of each solar wind parameters; however, the unique IMF orientation can cause numerous interesting features in the dayside magnetosphere. When the radial magnetic field transits through the bow shock, the magnetic field will be enhanced in all components. After that, Bx will divert to the Y and Z components and form an asymmetric Bz polarization in the Northern and Southern Hemispheres near the magnetopause. This asymmetry will lead the dayside reconnections occur at different locations and create a complex structure of magnetopause and its boundary sublayers. These sublayers of (1) the inner part of the low-latitude boundary layer (LLBL) on closed magnetic field lines; (2) the outer LLBL on open field lines; (3) the inner part of the magnetosheath boundary layer (MSBL) formed by dayside reconnection in the Southern Hemisphere; and (4) the outer MSBL resulting from lobe reconnection in the Northern Hemisphere are identified by observation.