STEREO Panoramic Images Improve Solar Storm Tracking

"The new view from the STEREO spacecraft will greatly improve our ability to forecast the arrival time of severe space weather," said Dr Russell Howard of the Naval Research Laboratory, Washington, the Principal Investigator of STEREO's Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI). "Previous imagery did not show the front of a solar disturbance as it travelled towards Earth, so we had to make estimates of when the storm would arrive. These estimates were uncertain by a day or so. With STEREO, we can track the front from the sun all the way to Earth, and forecast its arrival within a couple of hours."

The panoramic views are created by combining images from the SECCHI suite of instruments, including the Heliospheric Imager on both spacecraft - built in the UK by the University of Birmingham and CCLRC's Rutherford Appleton Laboratory.

Professor Keith Mason, Chief Executive of PPARC said, "Despite frequent observations over the last decade many questions remain unanswered about the nature of the Sun-Earth relationship and the way in which solar disturbances travel away from the sun. These new panoramic images illustrate the relationship from an entirely new perspective."

The instruments on board the STEREO spacecraft allow scientists to track a type of solar disturbance called a Coronal Mass Ejection (CME) from its birth at the sun towards Earth. CME's are violent eruptions of electrically charged gas, called plasma, from the sun's atmosphere. A CME cloud can contain billions of tons of plasma and move at a million miles per hour. As the CME cloud ploughs through the solar system, it slams into the slower solar wind, a thin stream of plasma constantly blowing from the sun. The collision with the solar wind generates a shock that accelerates electrically charged particles in the solar wind, causing radiation storms that can disrupt sensitive electronics on satellites and cause cancer in unshielded astronauts.

Professor Richard Harrison from CCLRC's Rutherford Appleton Laboratory is Principal Investigator for the HI instruments. He comments, "The combination of data from the instruments onboard STEREO have meant a dramatic improvement in the level of accuracy of solar storm prediction, illustrating how space research really can impact on operations on Earth."

A CME cloud is also laced with magnetic fields and CMEs directed our way smash into Earth's magnetic field. If the CME magnetic fields have the proper orientation, they dump energy and particles into Earth's magnetic field, causing magnetic storms that can overload power line equipment. Satellite and utility operators can take precautions to minimize CME damage, but they need an accurate forecast of when the CME will arrive.

Dr Chris Davis, a member of the UK STEREO team from CCLRC's Rutherford Appleton Laboratory said, "Every new image from STEREO provides us with further detail about the properties of CME's forever adding to our knowledge. It is exciting to think that the best images, providing a 3D view of the Sun, are yet to come."

The two observatories will orbit the sun, one slightly ahead of Earth and one slightly behind, separating from each other by approximately 45 degrees per year. Just as the slight offset between your eyes provides you with depth perception, this separation of the spacecraft will allow them to take 3-D images and particle measurements of the sun. Scientists will use the 3-D views to discover new details about the structure of CME clouds, and to see how that structure evolves as the clouds move through space. The first 3-D views are expected in April.