A huge sunspot, thirteen-times larger than the surface
area of the Earth and growing, has now rotated with the Sun
to face our planet. The sunspot, which is the largest of the
current solar cycle, is also the largest to appear in a

The area of the Sun, designated AR 9393, has been a prolific
generator of stormy solar activity, hurling clouds of
electrified gas towards Earth, producing four explosions,
called flares, and spawning storms of high-speed particles in

The largest of the four flares occurred at 4:57 a.m. EST on
Thursday, March 29, and was rated as an X-class flare, the
most potent designation. The other three flares were rated M-
class, second only to the X-class. An eruption near AR 9393
hurled a cloud of electrified, magnetic gas towards Earth on
Wednesday. This eruption, called a Coronal Mass Ejection may
cause auroral displays and magnetic storm activity when it
impacts the Earth’s magnetic field sometime Friday. Another
Earthbound CME associated with the X-class flare was seen at
5:26 a.m. EST March 29 and is expected to arrive on Saturday.

“Sunspots with complex magnetic field structures like those
in AR 9393 can generate big flares, and sure enough, we just
had a powerful X-class flare from this area,” said Dr. Joseph
Gurman, at NASA’s Goddard Space Flight Center, Greenbelt, MD,
project scientist for the Solar and Heliospheric Observatory
(SOHO) spacecraft. SOHO is one of a fleet of sun-observing
spacecraft now tracking this region and its activity.

Sunspots are darker areas on the visible surface of the Sun
caused by a concentration of distorted magnetic fields. The
strong magnetic field slows the flow of heat from the Sun’s
interior and keeps sunspots slightly cooler than their
surroundings, causing them to appear dark. The number of
sunspots increases and decreases as the Sun’s 11-year cycle
of stormy activity rises and falls. Violent solar activity is
believed to be caused by the release of magnetic energy, and
powerful solar eruptions and flares often occur near the
enhanced magnetic field of sunspots.

Solar flares, among the solar system’s mightiest eruptions,
are tremendous explosions in the Sun’s atmosphere, capable of
releasing as much energy as a billion megatons of TNT. Caused
by the sudden release of magnetic energy, in just a few
seconds flares can accelerate solar particles to very high
velocities and heat solar material to tens of millions of

Coronal mass ejections are clouds of electrified magnetic gas
weighing billions of tons, hurled into space at speeds of 12
to 1,250 miles per second. Depending on the orientation of
the magnetic fields carried by the ejection cloud, solar
explosions cause magnetic storms by interacting with Earth’s
magnetic field, distorting its shape and accelerating
electrically charged particles trapped within.

Severe solar weather is often heralded by dramatic auroral
displays, but magnetic storms are occasionally harmful,
potentially affecting satellites, radio communications and
power systems.

Coronal Mass Ejections and flares can produce storms of high-
velocity particles. The ejections are believed to produce
longer particle storms than flares, storms that sometimes
last for days, as they plow through the slower solar wind at
supersonic speeds, creating a shock wave that accelerates
electrically charged particles.

The SOHO project is an international cooperative program
between NASA and the European Space Agency in the framework
of the international Solar Terrestrial Science Program.

Movies and images of this solar activity will be broadcast
today on NASA Television, which is broadcast on satellite GE-
2, transponder 9C, C-band, located at 85 degrees West
longitude. The frequency is 3880 MHz, with vertical
polarization and monaural audio at 6.8 MHz.