A far-side powerful flare erupted and triggered a huge and long-lasting proton storm that flew past the STEREO Behind spacecraft on Labor Day, Sept. 1, 2014. The storm was so strong that it temporarily confused the star trackers on both STEREO spacecraft. The "snowstorm effect" that you see was caused by high-energy particles hitting the spacecraft's detectors in the SECCHI instrument's extreme ultraviolet and inner coronagraph telescopes (EUVI and COR1). The moment when the star tracker on Behind resets is evident when the spacecraft starts rolling. The spacecraft uses SECCHI's guide telescope to keep locked on the Sun, but depends on the star tracker to determine its roll angle. Once the star tracker came back online, the spacecraft almost immediately moved back to its correct orientation. Credit: STEREO/NASA.
November 24, 2009: Sometimes you really can believe your eyes. That's what NASA's STEREO (Solar Terrestrial Relations Observatory) spacecraft are telling researchers about a controversial phenomenon on the sun known as the "solar tsunami."
Years ago, when solar physicists first witnessed a towering wave of hot plasma racing along the sun's surface, they doubted their senses. The scale of the thing was staggering. It rose up higher than Earth itself and rippled out from a central point in a circular pattern millions of kilometers in circumference. Skeptical observers suggested it might be a shadow of some kind—a trick of the eye—but surely not a real wave.
"Now we know," says Joe Gurman of the Solar Physics Lab at the Goddard Space Flight Center. "Solar tsunamis are real."
The twin STEREO spacecraft confirmed their reality in February 2009 when sunspot 11012 unexpectedly erupted. The blast hurled a billion-ton cloud of gas (a "CME") into space and sent a tsunami racing along the sun's surface. STEREO recorded the wave from two positions separated by 90 degrees, giving researchers an unprecedented view of the event...
No one has been able to observe Jupiter and its moons for some time as it is too close to the Sun, but that did not stop the STEREO (Behind) COR1 coronagraph from capturing it and its four major moons over a 30-hour period (March 15-16, 2009). If you look carefully, you can identify three of its moons close to Jupiter, and even discern how their positions change as the movie progresses. Those with keen eyes can see the fourth moon, Callisto, as a fainter object well to the right of the others. These four moons are known as the Galilean moons, because they were first discovered by Galileo Galilei in 1610. Jupiter itself is largely saturated in the movie, to bring out the moons and the faint solar corona. The solid dark green area on the right is the coronagraph?s occulting disk that blocks out the Sun and some of its bright atmosphere to that our instrument can see fainter structure just beyond the Sun. The thin, white line inside of that indicates the actual size of the Sun. By coincidence, a coronal mass ejection is seen blasting a white cloud of charged particles out into space during much of the clip. We have not seen many solar storms of late as the Sun is near its low point in its solar activity cycle.