On May 17, 2012 an M-class flare exploded from the sun. The eruption also shot out a burst of solar particles traveling at nearly the speed of light that reached Earth about 20 minutes after the light from the flare. The particles sent out on May 17 were so fast and energetic that when they collided with atoms in Earth’s atmosphere, they caused a shower of particles to cascade down toward Earth’s surface.
Ground level Enhancement is quite rare. Fewer than 100 events have been observed in the last 70 years. The joint Russian/Italian mission PAMELA, short for Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, simultaneously measured the particles from the sun that caused the GLE. Solar particles have been measured before, but PAMELA is sensitive to the very high-energy particles that reach ground level at Earth.
“Usually we would expect this kind of ground level enhancement from a giant coronal mass ejection or a big X-class flare,” says Georgia de Nolfo, a space scientist who studies high speed solar particles at NASA’s Goddard Space Flight Center in Greenbelt, Md. “So not only are we really excited that we were able to observe these particularly high energy particles from space, but we also have a scientific puzzle to solve”.
The path to this observation began on Saturday, May 5, when a large sunspot rotated into view on the left side of the sun. The sunspot was as big as about 15 Earths, a fairly sizable active region, though by no means as big as some of the largest sunspots that have been observed on the sun. Scientists who study high-energy particles from the sun had been keeping their eye out for just such an active region because they had seen no GLEs since December of 2006.
The PAMELA mission, which had focused on cosmic rays from outside our galaxy, could now be used to observe solar particles.
Most of the time the showers are not the solar energetic particles themselves, but the resultant debris of super-fast particles slamming into atoms in Earth’s atmosphere.
PAMELA is a space-borne experiment of the Wizard collaboration, which is an international collaboration between Italian, Russian, German and Swedish institutes, realized with the main support of the Italian and Russian Space Agencies.
Keywords:- PAMELA mission, NASA, Ground level Enhancement, M-class flare exploded from the sun, Solar particles to Earth.
