MDI spots a developing active region on the far side of 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:
The images are whole-Sun maps of magnetic activity. They are shown in the so-called 'Carrington coordinate system' which is normally used for solar observations. The map extent is from south pole to north pole in an equal-area projection. The solar equator and each 60 degrees of longitude are marked.
The near side (Earthside) images are smoothed versions of magnetic flux as measured by MDI. The images are shown to 70 degrees from the disk centre.
The far side images are maps of wave speed variations - faster wave speeds are identified by a darker colour. These darker regions indicate locations where there is an accumulation of magnetic field near the surface. The far side images can only be created out to 50 degrees from the far side disk centre as (un)seen from Earth.