How the solar wind controls the two states of the Earth’s magnetosphere

Abstract: The magnetosphere exists due to the interaction of the solar wind with the Earth’s magnetic field. It is defined as the cavity around the Earth that is protected from the solar wind and forms a long tail on the anti-sunward side of the Earth. The solar wind is a highly ionized gas that is continuously released by the sun and spreads deep into space. It carries with it the Sun’s own magnetic field, the IMF. Depending on the direction of the IMF, the Earth’s magnetosphere is either closed (northward IMF) or partly connected to the solar wind (southward IMF) due to a process called magnetic reconnection through which the solar wind’s energy can be transferred into the magnetosphere. The direction of the IMF has a strong impact on a phenomenon that we can observe with our own eyes on the night sky in the northernmost (and southernmost) regions of the Earth, the aurora. The aurora appears along a large oval around the magnetic north (and south) pole in the boundary region between atmosphere and magnetosphere. This boundary region acts as a load of the magnetospheric current system which is driven by the solar wind-magnetosphere interaction. Studying the aurora gives us an understanding of the solar wind-magnetosphere coupling for different IMF conditions. During southward IMF, the large amount of transferred solar wind energy is periodically released through magnetic substorms which cause most spectacular and dynamic auroral displays. Under northward IMF conditions the aurora is weak but forms a complicated pattern where poleward regions that are usually void of aurora fill with auroral arcs. The two different states of the magnetosphere can also be studied with help of magnetosphere models showing a huge difference in its topology which may explain both, the occurrence of substorms and auroral arcs poleward of the auroral oval.

The lecture will be held in English.

Purpose: The candidate's teaching skills will be assessed by an evaluation committee. The committee consists of:

• Prof. Gunnar Karlsson, chairman
• Prof. Martin Norgren, teacher representative
• Mariana Dalarsson, student representative