[Title]
Living with a star: physics of the Sun and space weather

[Speaker]
Dr Hiroaki Isobe (Engineering Department)

[Date/Time]
Saturday, 29 April, 2006; 7:30-9:30pm

[Venue]
Seminar room, No1. Newnham Terrace, Darwin College

[Abstract]
Regardless whether you are aware of or not, you are living with a star, the Sun. Though it is the closest and most familar star for all the life on the Earth, the nature of the Sun is still full of mystery.
The sun seen in the visible light is quiet and steady, without any prominent structure except for sunspots. On the other hand, X-ray obervations from spacecrafts have revealed that the upper atmosphere of the Sun (solar corona)is very active, full of explosions called solar flares.
Solar flares are the most energetic explosion in the solar system, and their energy comes from the magnetic field around sunspots. Similar explosive phenomena by the magnetic field also occur in stars, galaxies and blackholes, and hence modern astronomers believe that the universe is full of "flares". Understanding the physics of the Sun is, therefore, the basis toward deeper understanding of our universe.
Another aspect of current solar physics research is to investigate the influence of magnetic activities in the Sun on the Earth and human activities. When large solar flares occur, intense X-rays and energetic particles are pruduced, and enormous amount of plasma (electrically charged gas) is ejected to the space. The ejected plasma hits and disturbs the magnetic field of the Earth, which causes so called geo-magnetic storms and aurorae. The X-rays and energetic particle damage the sattellites, and if an astronaut is working outside the space craft, he/she may be exposed to lethal radioactivity. In the era when more and more people explore and use the space, it is essential to predict when solar flares occur and how energetic they are. This is called "space weather forecast", now one of the most important topics in solar physics.
In this seminar, I will show beautiful images and movies from recent solar observations, and try to explain the amazing figure of the Sun and the frontier of the solar physics.