This movie is shows a sequence of magnetograms taken over 6 days in
1996 July when a particularly impressive active region emerged at the
surface of the Sun. The data were obtained by the MDI instrument on the
SOHO spacecraft, and consist of line-of-sight magnetic field
measurements every 96 minutes. Upgoing magnetic fields are represented
by whiter shades, downgoing fields by darker shades, with grey
representing weak fields. The display chosen saturates at 500 Gauss.
The images have been deprojected and solar rotation has been removed.
the flux seems to emerge in the center of the region and then spread
out, positive flux to the leading edge of the region and negative flux
to the trailing edge of the region.
A delta spot (positive and negative
fields within the same sunspot penumbra) develops and produces an
X-class flare on July 9 (the first flare of this size for several
Also note how the simple dipole present for days prior to the
abrupt onset of emergence is affected: the negative pore is quickly
cancelled by newly-emerged positive flux, while the positive pore starts
moving rapidly and becomes the leading spot of the region.
This region was remarkable for several things:
MDI is an optical telescope
operated by Stanford University.
SOHO is a joint ESA/NASA satellite mission to study the Sun.