Lindsay Renick Mayer June 18, 2003<br />Goddard Space Flight Center<br />(Phone: 301-286-7646)<br /><br /><br />Release: 03-66<br /><br /><br />SPACECRAFT TRIO PEEKS AT SECRET RECIPE FOR STORMY SOLAR <br />WEATHER<br /><br /><br /> A three-spacecraft collaboration recorded for the first <br />time the entire initiation process of a high-speed eruption <br />of electrified gas from the Sun, providing clues about the <br />Sun's secret recipe for stormy weather. The April 21, 2002 <br />observation confirmed the predominant scenario for how these <br />eruptions, called Coronal Mass Ejections, are blasted from <br />the Sun.<br /><br /><br />The three spacecraft involved were NASA's Reuven Ramaty High <br />Energy Solar Spectroscopic Imager (RHESSI), which takes <br />pictures of flaring regions using the Sun's high-energy X-<br />rays and gamma rays; NASA's Transition Region and Coronal <br />Explorer (TRACE), which makes images using ultraviolet light <br />from the Sun; and the Solar and Heliospheric Observatory <br />(SOHO) spacecraft, a collaboration between NASA and the <br />European Space Agency.<br /><br /><br />"This was the first time that we have been able to identify <br />and study in detail the region on the Sun where the <br />initiation and acceleration of a coronal mass ejection <br />occurs," said Dr. Peter Gallagher, research scientist for <br />RHESSI and SOHO at NASA's Goddard Space Flight Center, <br />Greenbelt, Md., and lead author of two papers on this <br />research. "We now have a better understanding of how the <br />energy release above the surface of the Sun relates to the <br />ejection of material, perhaps allowing some real-time <br />forecasts." The results are being presented today during a <br />meeting of the American Astronomical Society's Solar Physics <br />Division in a press conference at the Johns Hopkins <br />University Applied Physics Laboratory, Laurel, Md.<br /><br /><br />Coronal Mass Ejections (CME) are often associated with solar <br />flares. A flare is a giant explosion in the solar atmosphere <br />that spews radiation and results in the heating of solar gas <br />and the acceleration of particles to nearly the speed of <br />light. Both events can be initiated in a matter of seconds, <br />making their joint observations difficult to coordinate. <br /><br /><br />The twisting and snapping of magnetic field lines on the Sun, <br />called magnetic reconnection, seem to cause CMEs and solar <br />flares. When these fields snap from the buildup of magnetic <br />energy, plasma is heated and particles are accelerated, <br />resulting in massive explosions and emitting radiation <br />ranging from radio waves to X-rays. <br /><br /><br />Frequently, a CME and flare will burst from the same region <br />of the Sun nearly simultaneously. Just like the debate over <br />whether the chicken or the egg came first, solar researchers <br />discuss whether flares cause CMEs or the reverse, or if they <br />are more loosely associated. <br /><br /><br />The April 21, 2002 observation confirmed the predominant <br />scenario for high-speed CMEs (those moving at one million to <br />5 million miles per hour or 1.6 million to 8 million km/hr.). <br />This is where solar magnetic fields act like a lid, holding <br />down a blob of gas (CME) that is trying to rise. Somehow, the <br />magnetic lid opens, possibly as a result of magnetic <br />reconnection and the generation of a flare, and then the CME <br />rises from the Sun, dragging the magnetic fields with it. <br />Magnetic reconnection continues to energize the associated <br />flare for over 12 hours.<br /><br /><br />All three spacecraft played vital roles in confirming that <br />this was the process. First, RHESSI saw a gradually <br />increasing burst of X-rays announcing the start of the flare. <br />TRACE observed the CME in the extreme ultraviolet as it began <br />to rise from the Sun. Several minutes later, RHESSI saw a <br />burst of high energy X-rays under the erupting CME, and TRACE <br />saw a similar explosion of ultraviolet rays, both indicating <br />a large flare. SOHO then captured the CME as it continued <br />moving away from the Sun.<br /><br /><br />"Each of these spacecraft is quite complementary," said <br />Gallagher. "It's only through their coordination in this <br />observation that we're now able to understand the predominant <br />scenario for these fast, large coronal mass ejections and the <br />associated flares."<br /><br /><br />The current results feed into the decades-old controversy <br />over whether solar flares cause coronal mass ejections, or <br />vice versa. While the first signs of the flare occur before <br />the CME liftoff, the bulk of the flare energy is released <br />later, after the CME has already been accelerated. The two <br />phenomena are revealed to be merely different aspects of the <br />same event, according to the team. For images and more <br />information, refer to:<br /><br /><br />http://www.gsfc.nasa.gov/topstory/2003/0617rhessicme.html