The birth of number 18
Late April 29,  we could witness the birth of a sunspot which made already some fuzz before it even got a name. With an amazing speed the baby became an adult with a complex magnetic configuration. May 1 and May 2 turned out to be its glory days.
Nederlandstalige versie / Version franaise posted: May 6, 2004
Fragment of the weekly bulletin from April 26 until May 2:
On April 29, a sunspot group labeled with number 18 (NOAA 0601) suddenly popped up from nowhere and has grown really fast to a beta-configuration. The evolution of this group could be nicely seen in an MDI-movie. Its entry was made by a B2.2 flare on April 30 at 22:12 UT at S11W21. The group was the source of two complex active periods, on May 1 and May 2. The largest flares to be respectively a C9.5 and a C8.3.

SOHO/MDI shows the magnetic structure of the solar surface. The black and white spots denote a local high concentration of magnetic field, pointing in (black) or out (white) the surface. In fact, the picture is a color coded figure representing the polarities of each region. A sunspot (visible in white light) or an active region (highlighted region in EUV, like in  SOHO/EIT images) is linked to these kind of black and/or white fields.

The strength of mingling of the two polarities in a sunspot is expressed by a greek letter. Sunspot 18 got the label 'beta' as it has both positive and negative magnetic polarities, with a simple and distinct division between the black and white regions. Although some period between May 2 and May 3, number 18 was almost dressed like a real member of the beta-delta clan as some black (white) stips intruded into the white (black) region.

Click on the picture to see the SOHO/MDI movie about the birth, life and disappearing on the west limb of sunspot group 18.