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Solar 'Fireworks' Signal New Space Weather Mystery

View of solar flare from SOHO LASCO view of coronal mass ejection blasting into space

Images Above: After the first sign of the January flare, a storm of energetic protons impacted Earth just 15 minutes later as opposed to the usual timeline of a few hours. Left: The Extreme ultraviolet Imaging Telescope (EIT) instrument on SOHO shows the flare erupting, then the camera getting peppered by solar particles soon after. Right: SOHO's Large Angle and Spectrometric Coronagraph (LASCO) instrument blocks out the corona to watch the coronal mass ejection streaming out into space. Credit: NASA / ESA


Animation of sunspot producing a flare Image Left:Solar flares are caused by the solar magnetic field. In this animation, magnetic field lines stretch and twist over sunspots on the solar surface, storing energy that can be released as a flare when the lines "snap open." Click on image for animation or download print resolution stills. Credit: NASA/Walt Feimer




RHESSI data overlaid on TRACE solar image Image Right:The RHESSI data overlaid on a TRACE image shows gamma-rays (blue) and X-rays (red) thrown off by the hottest part of the flare. The gamma rays are made by energetic protons at the Sun. Credit: NASA

The origin of the protons is imprinted in their energy spectrum (as measured by ACE and other spacecraft), which matches the energy spectrum of gamma-rays thrown off by the flare (as measured by RHESSI). "This is surprising", says Lin, "because in the past we believed that the protons making gamma-rays at the flare were produced locally and the ones at the Earth were produced instead by shock acceleration in interplanetary space. The similarity of the spectra suggests that they are the same."

Solar flares and coronal mass ejections (CMEs), associated giant clouds of plasma in space, are the largest explosions in the solar system. They are caused by the buildup and sudden release of magnetic stress in the solar atmosphere above the giant magnetic poles we see as sunspots. The TRACE and the Solar and Heliospheric Observatory (SOHO) spacecraft are devoted to observing the Sun and identifying the root causes of flares and CMEs, with an eye toward forecasting them.

Extreme closeup of a sunspot from TRACE spacecraft Image Left:The TRACE spacecraft identified one possible source of the magnetic stress that causes flares: sunspots that rotate, storing energy in the magnetic field. Credit: NASA/LMSAL

"We do not yet know how to predict the flow of energy into and through these large flares", says Dr. Richard Nightingale of the Lockheed Martin Solar and Astrophysics Laboratory in Palo Alta, Calif., "but instruments like TRACE give us new clues with each event we observe." TRACE has identified a possible source of the magnetic stress that causes solar flares. The sunspots that give off the very largest ("X-class") flares appear to rotate in the days around the flare. "This rotation stretches and twists the magnetic field lines over the sunspots", says Nightingale. "We have seen it before every X-flare that TRACE has observed since it was launched and more than half of all flares in that time."

Astronaut Michael E. Lopez-Alegria, STS-113 mission specialist, works on the ISS. Image Right:Solar flares and CMEs are the largest explosions in the solar system. They are caused by the buildup and sudden release of magnetic stress in the solar atmosphere above the giant magnetic poles we see as sunspots. CMEs can cause magnetic storms affecting communication systems, power grids and astronauts in space. Credit: NASA



+ Press Release

Bill Steigerwald
NASA Goddard Space Flight Center