On the left is an image of a total solar eclipse on February 26, 1998. The image on the right is a computer model of the sun's magnetic field as it would appear on the same day. The bright coronal regions in the eclipse image correspond to locations in the corona where the solar magnetic field is shaped like loops (i.e. closed) as seen in the model image on the right. These magnetic loops act to trap the solar atmosphere so that greater amounts of material are located in these regions causing them to appear brighter. The darker regions in the eclipse image are locations where the solar corona escapes the sun to form the solar wind, which fills the solar system. The magnetic field lines in these darker regions are drawn out into the solar system (as seen in the model image on the right) and become part of the solar wind.
The image on the left is of the solar corona seen in visible light in an artificial eclipse image taken on November 1, 2003 with the K-Coronameter at Mauna Loa in Hawaii. The light from the solar disk is ~ 1 million times brighter than the corona therefore the white light corona can only be seen in ‘eclipsed’ images. Visible light images of the corona allow scientists to map the density structure of the corona and are ideal observations for tracking a form of solar activity known as coronal mass ejections. The corona can be detected out to great distances (more than 10 million miles) when viewed in visible light from telescopes in space.
The image on the right is of the solar corona seen in extreme ultraviolet (EUV) light taken by the Extreme ultraviolet Imaging Telescope (EIT) on the SOHO spacecraft. In this type of light, scientists can view the corona against the solar disk. No artificial eclipse is needed because the solar disk is dark in EUV wavelengths. EUV images allow the scientists to study the temperature and density structure of the corona and track features as they rotate across the disk of the sun. These observations are ideal for studying solar flares and other coronal disturbances.
Source: HAO, LASCO, EIT Science teams /NASA
This picture was made by combining 3 images of the solar corona. The inner green image shows the very low corona in extreme ultraviolet (EUV) wavelengths as seen against the solar disk. EUV observations are ideal for studying the temperature and density of the corona and for observing events like solar flares. The blue/white images show the inner and outer corona as seen in visible light. Visible light images allow scientists to study the density structure of the corona and are ideal for observing events like coronal mass ejections. The corona can be observed out to great heights in visible light (more than 10 million miles) but multiple telescopes are needed to observe over a wide range of heights because the brightness of the corona changes rapidly with height. The EUV image was taken by the Extreme ultraviolet Imaging Telescope on the SOHO spacecraft, the inner blue/white image of the inner corona was taken by the K-coronameter on Mauna Loa in Hawaii, and the blue/white image of the outer corona was taken by the LASCO C2 coronagraph on the SOHO spacecraft. The earth would be a tiny dot in this image.