The solar corona

The above image shows an active region observed on 2 February 2007 by the (EIS) Extreme Ultraviolet Imaging Spectrometer on board Hinode.

The EIS is effectively a solar speed camera. it is now possible to pinpoint the source of eruptions during solar flares and to find new clues about the heating processes of the corona.

The speed camera is a spectrometer, an instrument that splits the light coming from solar plasma, a tenuous and highly variable gas, into its distinct colours (or spectral lines), providing detailed information about the plasma. The velocity of the gases in a solar feature is measured by the Doppler effect - the same effect that is used by police radars to detect speeding motorists.