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.

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Media Contact: Sharon Keeler, UNH News Bureau, 603-862-1566;
sharon.keeler@unh.edu

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
mark.mcconnell@unh.edu. Launches are subject to last-minute
changes. Check the NASA Web site at
http://spacescience.nasa.gov.