From: Jet Propulsion Laboratory
Posted: Wednesday, January 30, 2002
University of New Hampshire scientists are among those who will study data from the National Aeronautics and Space Administration's HESSI satellite, to be launched Feb. 5 from Cape Canaveral Air Force Station in Florida.
Originally scheduled for launch in July of 2000, the HESSI project has been plagued by numerous delays, most of which were related to difficulties in preparing the Pegasus launch vehicle.
The High Energy Solar Spectroscopic Imager will study gigantic explosions in the atmosphere of the Sun with a unique kind of vision, producing the first high-fidelity X-ray movies of solar flares and their high energy emissions.
Within the gigantic flare explosions, magnetic fields twist, snap and recombine, blasting particles to almost the speed of light, firing solar gas to tens of millions of degrees. This action causes the solar atmosphere to sizzle with high-energy X-rays and gamma rays and accelerate proton and electron particles into the solar system. Radiation and particles from solar flares sometimes affect orbiting spacecraft, interfering with communications and astronaut activities.
To understand what triggers a solar flare and how it explosively releases energy, scientists must identify the different kinds of particles being accelerated, locate the regions where the acceleration occurs and determine when the particles get accelerated. The most direct tracer of these accelerated particles is the X-ray and gamma ray radiation that they produce as they travel through the solar atmosphere.
The UNH project involves using data from HESSI to measure the polarization of solar flare X-rays. The university's Institute for the Study of Earth, Oceans, and Space (EOS) was awarded a three-year, $225,000 NASA grant to conduct this work.
"These measurements should provide important insights into the geometry of the particle acceleration process in flares," says Research Associate Professor Mark McConnell, principal investigator, who is working on the project with Professor Jim Ryan. "In other words, are the particles explosively accelerated in all directions at once or are they somehow accelerated largely in one direction -- or beamed -- guided by the intense magnetic fields at the flare site? Furthermore, if they are beamed, how tightly are they beamed?"
Polarization measurements are difficult to make, and past efforts have met with only limited success. The results from earlier efforts (more than 20 years ago) have been rather controversial, says McConnell, with no clear results. HESSI provides a unique opportunity to make the high-quality polarization measurements that are needed.
"The HESSI mission is designed to provide the clearest picture yet of what takes place during a solar flare," he says. "The polarization measurements are part of the larger effort to describe what is going on. Only when we have a clear and detailed picture of what happens during a solar flare will we be able to develop accurate models that explain how and why it takes place. It is part of the often slow scientific process that leads to a better understanding of the solar flare phenomenon."
Since HESSI is designed to look at solar flares, getting up during the current solar maximum period is important to the success of the mission. The solar maximum represents the peak of the Sun's 11-year cycle. During the peak period, which lasts for as long as one or two years, the Sun's magnetic fields are more turbulent and solar flares erupt more often.
Media Contact: Sharon Keeler, UNH News Bureau, 603-862-1566; firstname.lastname@example.org
NOTE TO EDITORS: You can reach Mark McConnell, research associate professor in UNH's Institute for the Study of Earth, Oceans, and Space at 603-862-2047 or by email at email@example.com. Launches are subject to last-minute changes. Check the NASA Web site at http://spacescience.nasa.gov.
// end //