Coronal Weather Report







Observing the Sun's Magnetic Field

Although there are no iron filings on the Sun to outline the magnetic field for us, there are other ways to know it is there. Spots on the surface of the Sun are one sign of the magnetic field. The Sun's magnetic field hinders the usual boiling motion which mixes the hot and cool gasses in the photosphere. In the strong magnetic regions the cooler gas becomes trapped, and appears as a dark spot on the solar surface.

Image Credit: Big Bear Solar Observatory

Image Credit: SOHO

Solar observers take advantage of the fact that light is affected by strong magnetic fields to generate magnetic maps of the Sun's surface, called magnetograms. The image to the left is a magnetogram taken by an instrument on the SOHO solar satellite. This image shows areas of magnetic activity on the Sun. Magnetic field indicated by the color black is pointed in the opposite direction of that indicated by the color white.

Another method of spotting magnetic field on the Sun is by observing the gas in the upper atmosphere. The gas follows the magnetic field much like the iron filings did in the previous example. The image to the right was taken by the TRACE solar satellite. By looking at images like this, with bright gaseous loops, it is easy to see that there is magnetic field everywhere on the Sun!

Image Credit: TRACE

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