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NMSU-developed satellite instrumentation gathers data from unusual solar event

As far as solar events go, the moderate flare erupting from the sun on May 17 should have been rather unremarkable. But the unexpected hour-long blast of high-energy particles showering the globe made it extraordinary.

Man standing beneath sun with arms crossed
Steve Stochaj, NMSU professor of electrical and computer engineering, has been involved with the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) since 1987 (NMSU photo by Darren Phillips)

Fortunately, physicists and astronomers have the data from this highly unusual event to examine and analyze due to satellite instrumentation that was developed and tested at New Mexico State University as part of a worldwide collaboration beginning more than two decades ago.

The burst of solar particles from the eruption traveled at nearly the speed of light and reached Earth about 20 minutes after the light from the flare. Although the flare was at least 10 times less powerful than the largest flares, the particles emanating from it were so energetic that when they collided with atoms in the Earth's atmosphere, they caused a shower of particles to cascade toward Earth's surface in what is called a ground level enhancement (GLE). GLEs are quite rare ? only 70 have been detected within the past 100 years and they are usually associated with giant solar flares. The last GLE occurred in 2006. This occurrence indicates that the sun is entering the active phase of its regular 11-year cycle.

Information from the event was measured with instrumentation placed on the European satellite, PAMELA, short for Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics ? a project that has involved Steve Stochaj, NMSU professor of electrical and computer engineering, since 1987.

At that time, Stochaj and scientists in Italy began developing instruments to be placed on a satellite with the objective to measure high-energy cosmic ray particles. The instrumentation was to be placed on a NASA satellite, but when funding and other issues interfered with that plan, the instrumentation was instead placed on PAMELA, launched in 2006. Today, PAMELA is conducted by a collaboration led by Italy and Russian with German and Swedish institutes and American collaborators at the University of New Hampshire and NMSU.

The instruments for the satellites were tested at NMSU on high-altitude balloons through NMSU's Physical Science Laboratory, which conducts balloon tests for NASA.

"We've been highly vested in the project since the beginning," said Stochaj, an astrophysicist whose interest in developing the instruments earned him a place on the electrical engineering faculty.

The core of the PAMELA instrumentation is a magnetic spectrometer, a physics detector that measures certain aspects of cosmic particles.

"The instruments are very good at detecting cosmic ray particles, but they are also detecting solar particles," said Stochaj. "Satellites, for solar studies, are good at detecting low-energy particles and ground-based monitors are good at detecting high-energy particles. The PAMELA measurements fill in the gap between these measurements and provide information that has never been collected before."

Only the early data has been seen so far, but scientists have hopes that as more observations are analyzed they will be able to learn more about the May 17 onslaught of solar protons and figure out why this moderate solar event triggered a GLE when larger bursts of solar protons in January and March of this year did not.

NMSU, along with the University of New Hampshire and the Goddard Space Flight Center are funded to examine solar physics for the PAMELA mission through the National Science Foundation's Solar, Heliospheric, and Interplanetary Environment (SHINE) program.

The first explicit PAMELA research directed at solar physics was initiated by former NMSU physics doctoral student and Stochaj advisee, Ulisse Bravar, now a faculty member at UNH and that institution's principal investigator for the PAMELA mission. He is also, incidentally, a pilot for American Airlines?earning a pilot's license while a student at NMSU.

Bravar graduated from NMSU in 2001 with a doctoral degree in physics and in 2002 with a master's degree in electrical engineering, but continues to collaborate with Stochaj on the PAMELA research. Three physics and two astronomy students have earned advanced degrees at NMSU based on PAMELA-related research. Approximately a dozen electrical engineering students have worked on instrumentation components.

Scientists who study high-energy particles from the sun had been watching for a sizable active region on the sun since the 2006 GLE. On May 5, a sunspot as big as about 15 Earths appeared on the left side of the sun as it rotated into view. It remained inactive for two weeks until just before it rotated out of view on the right side of the sun, when it erupted.

"These huge explosions on the sun throw out energy and particles into the solar system and the Earth gets hit, which can cause numerous problems to society," said Stochaj. "They have taken out satellites, interrupted communications, and they can introduce voltage spikes on the ground that can blow out electrical transformers and interrupt our power supply. It's important to be able to predict when they might occur so that we can protect our assets and infrastructure.

"It's also nice to know how the sun works," he added.