MDI spots a developing active region on the far side of the Sun
This sequence of images from SOHO's MDI instrument clearly illustrates the value of being able to 'see' through the Sun.
1 March 2001: MDI's view of the near side of the Sun for this date gives no hint of any unusual activity.
15 March 2001: 14 days later (half of a solar rotation) clear evidence for strong activity on the far side of the Sun is apparent.
28 March 2001: Another half solar rotation later, a large active region is visible on the near side of the Sun. This region, which is now known as AR 9393, hosts the largest sunspot group to occur in 10 years.
11 April 2001: Another two weeks pass by and MDI's view of the far side of the Sun shows that AR 9393 is still bubbling away.
24 April 2001: From this recent view of the near side of the Sun AR 9393 is still clearly active.
These images have been extracted from an animation, constructed with MDI images, which shows the movement of active regions across the near- and far-side of the Sun. The animation (available in mpeg or Quicktime format) covers the period 1 March 2001 to 24 April 2001.
Some background information for these images: