New technique provides the first full view of the far side of thesun (Forwarded)

News Service
Stanford University
Stanford, California

Contact:
Mark Shwartz, News Service
(650) 723-9296

Comment:
Phil Scherrer, Department of Physics
(650) 723-1504

March 13, 2006

New technique provides the first full view of the far side of the sun
By Mark Shwartz

The hidden face of the sun is fully visible for the first time, thanks to
a new technique developed at Stanford University.

Only half of the sun -- the near side -- is directly observable. The far
side always faces away from Earth and is therefore out of view. But the
new technology allows anyone with a computer to download images of the
entire solar surface -- an important advance with practical applications,
say researchers, because potentially damaging solar storms that form on
the far side now can be detected days, or even weeks, before they wreak
havoc on Earth.

"Sunspots, solar flares and other active regions on the surface of the sun
emit radiation that can interfere with orbiting satellites,
telecommunications and power transmission," says Philip Scherrer, research
professor in the Department of Physics. "This new method allows more
reliable warning of magnetic storms brewing on the far side that could
rotate with the sun and threaten the Earth."

It takes about 27 days for the sun to rotate on its axis, so an active
region that forms on the far side can remain hidden for up to 13 days and
surprise Earth-bound observers when it finally rotates into view. That's
what happened in October 2003, when active regions from the back side
suddenly appeared on the eastern edge of the sun, spewing X-rays,
ultraviolet radiation and high-energy particles into space. "We were not
able to make a public prediction about the intensity of that activity,
because at the time we could only image about a quarter to a third of the
far side," Scherrer says. "The new method allows us to see the entire far
side, including the poles."

SOHO mission

Scherrer and his Stanford colleagues study the sun using data from the
Solar and Heliospheric Observatory (SOHO), a research satellite launched
in 1995 by NASA and the European Space Agency. On board SOHO is the
Michelson Doppler Imager (MDI), an electronic instrument that creates
images of the sun's interior by measuring the velocity of sound waves
produced by hot, bubbling gases that well up to the surface -- a technique
called acoustic helioseismology.

"Helioseismology works on the same principle as medical ultrasound, which
can create an image of a fetus inside a pregnant woman," Scherrer
explains. "In this case, we're looking through a star with sound waves."

Positioned about 1 million miles above Earth, the SOHO satellite always
faces the visible side of the sun. In 2000 and 2001, scientists Charles
Lindsey and Doug Braun -- now at NorthWest Research Associates Inc. --
developed two techniques that resulted in the first pictures of the sun's
back side. However, both techniques had limitations. One method only
produced images near the center of the far side, while the other was
restricted to views at the edges. To get a complete image, researchers
would have to combine both methods, but that proved to be a major
technical challenge.

The problem was finally overcome last summer when a new computer algorithm
was developed by the Stanford SOHO/MDI team in collaboration with Kenneth
Oslund, an undergraduate at the California Institute of Technology. Their
work resulted in the MDI Farside Graphics Viewer, which displays the first
full images of the far side of the sun. The viewer is available online at
http://soi.stanford.edu/press/farside_Feb2006/web/

Solar max

"This new method is a vast improvement," Scherrer says. "It should be
especially important during the next solar maximum, which should begin in
2011, when solar activity will be at its peak."

He points out that during the last "solar max," which lasted from 2000 to
2003, solar storms temporarily knocked out power in the northern parts of
Sweden and Canada and destroyed a satellite that was used to verify credit
card payments at numerous gas stations in the United States. Air
transportation also can be disrupted when solar radiation interferes with
the operation of Global Positioning System satellites, or when aircraft
that take shortcuts over the North Pole have to take longer routes to
prevent passengers and crew from being exposed to intense X-ray radiation.

"Our goal is to give pilots and air traffic controllers a day or two
notice of a possible solar event," Scherrer says, adding that missions to
Mars and other planets also can be affected when solar storms interfere
with satellite communications to Earth. Last week, researchers at the
National Center for Atmospheric Research in Colorado released new computer
models predicting that the next solar cycle will be 30 to 50 percent
stronger than last time.

In 2008, SOHO is scheduled to be replaced by NASA's Solar Dynamics
Observatory (SDO), a more advanced satellite designed to provide new data
about the magnetic forces inside the sun that drive the 11-year solar
cycle. Stanford, the University of Colorado and the Lockheed Martin Corp.
will lead the SDO research effort.

"With cell phones and other devices, we've gotten more and more dependent
on the space environment, so there are real economic reasons for missions
like SOHO and SDO," Scherrer says.

-30-

Editor Note:

Videos and high-resolution images of the far side of the sun are available
at
http://sohowww.nascom.nasa.gov/

Relevant Web URLs:

* Stanford Solar Center
http://solar-center.stanford.edu/
* Solar and Heliospheric Observatory (SOHO)
http://sohowww.nascom.nasa.gov/