Enormous X-Ray Solar Flare Seen By SOHO

http://www.esa.int/export/esaCP/SEMY...D_index_2.html

Enormous X-ray solar flare seen by SOHO
European Space Agency
October 28, 2003

[SOHO image]

The huge solar event of The third most powerful solar X-ray
28 October 2003 flare on record, a remarkable X17.2
category explosion, erupted from sunspot 10486 on Tuesday, 28 October
2003. This is the second largest X-ray flare ever seen by the
ESA/NASA SOHO spacecraft, after the major X20 solar flare of April
2001. Regular observations of X-ray flares began in the 1970s.

This explosion hurled a "coronal mass ejection" (CME) almost directly
toward Earth, which could trigger bright aurorae when the material
reaches us in about a day.

The Earth was immediately affected by intense X-ray radiation, which
ionised the upper layers of the atmosphere, causing serious disruption
to radio communications.

The high-energy particles that followed (called a 'proton storm') could
upset satellites by interfering with their electronics systems and
damaging exposed components. During these storms, astronauts are
advised to reduce exposure, particularly during spacewalks.

Our atmosphere protects people on the Earth, but passengers and crews
on commercial jets at high latitudes could receive exposure equivalent
to a normal medical chest X-ray.

The CME associated with this flare is larger than the Sun itself and is
one of the most dramatic halo CMEs ever recorded by SOHO. The material
ejected by this CME is travelling towards Earth at 2145 kilometres per
second (7.5 million km/h), as compared to a "normal" speed for these
events of 400 kilometres per second (1.5 million km/h). This is a very
fast one!

This image is from SOHO's LASCO coronagraph, a telescope that uses a
disc to block the Sun's bright surface, revealing the faint solar
corona, stars, planets and "sungrazing" comets. In other words, a
coronagraph produces an artificial solar eclipse.