Coronal Weather Report







Modeling the Sun's Magnetic Field

The many manifestations of the solar cycle described on the previous page are related to changes in the Sun's magnetic field. Why it is important to study the Sun's magnetic field? Besides the fact that it is interesting to study things we do not understand completely, it is also important that we develop a better understanding of the Sun's magnetic field because it directly affects our lives on Earth.

Solar scientists are working to develop computer programs which will model the Sun's magnetic field, thus helping them to better understand it. These programs allow us to visualize magnetic field lines in the upper atmosphere, or corona, of the Sun.

Magnetic field data from the surface of the Sun (for example, sunspots) are used as initial input for the simulations. By working to understand the processes necessary to generate a realistic model of the Sun's coronal magnetic field scientists will have a better overall understanding of how magnetic field generated in the Sun leads to coronal eruptions and disturbed space weather.

When coronal magnetic field loops remain closed the hot gas is trapped. However, if the magnetic field lines expand or open up, coronal gas and magnetic field is expelled into interplanetary space, sometimes in the direction of Earth. The Sun releases large amounts of magnetic energy in solar flares and coronal mass ejections. Explosive events which expel magnetized gas into space are called coronal mass ejections, or CMEs for short. This image was taken by the SOHO solar spacecraft and shows a CME about to explode off the northeast limb of the Sun. Click on the image to see a movie of seveal coronal mass ejections leaving the Sun.. (Here is a tutorial about the difference between CME's and solar flares.)

Image Credit: SOHO

The modeled cornoal magnetic field lines shown below suggest what may be happening to the real coronal magnetic field during a CME like the one above. In this picture, only the coronal fields that have opened up between the time represented on the left, and that on the right, are shown. The magnetic field lines which did not change between the times of the two images have not been drawn.

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