Spectacular prominence eruption seen by the STEREO Ahead spacecraft on 23 July 2022. This eruption was on the far side of the Sun, and did not impact either STEREO Ahead or Earth.
CME rate plot for both STEREO A and B counts/day (duty-cycle corrected) vs carrington rotation thru 2019-03 (A) and 2014-09 (B).
Sungrazing Comet observed by COR 1 - 2016-05-01
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.
STEREO (Behind) captured this magnificent coronal mass ejection (associated with an M-class flare) that flung a long stream of plasma into space (Aug. 24, 2014). We have combined a view of the Sun in extreme UV light with a broader visible light view of the Sun's corona. It is interesting to note that a lot of the plasma, lacking sufficient kinetic energy to break free from the Sun's gravity, was pulled back into the Sun. Credit: STEREO/NASA.
Three powerful X-class flares were released by active region AR1748 during just 24 hours between May 13-14, 2013, followed up by yet another X-class flare on May 15 (not shown). This movie, from the STEREO Behind observatory, located on the far side of the Sun, shows not only the three X-flares (seen as brief flahses) and their associated coronal mass ejections, but also quite a bit of other activity on the side of the Sun not visible from Earth. The active region producing the flares is near the upper-right edge of the Sun as seen in by STEREO Behind in the 304 Angstrom line of Helium (orange) by the EUVI telescope. Surrounding the Sun is the solar atmosphere revealed by another instrument, STEREO's COR1 coronagraph.
Like looking down the barrel of a cannon, the STEREO Behind spacecraft caught the Sun throwing a massive coronal mass ejection (CME) directly at it on March 5, 2013. Here are two movies showing the event as seen in the emission line at 195 Angstroms of highly ionized iron by the Extreme Ultraviolet Imager (EUVI, green), and in scattered white light by the inner (COR1, blue) and outer (COR2, red) coronagraphs. The event starts with a strong flare right in the active region right in the center of the Sun as seen from STEREO Behind, but which was hidden behind the limb for Earth-based telescopes. The associated CME then is seen as a halo around the Sun passing through the COR1 and COR2 fields of view, reaching the spacecraft itself two days later on March 7, where it was seen by the in situ particle and magnetic field instruments. While this solar blast was not pointed at Earth, it did include the planet Mars in its path. This prompted NASA to place the Curiosity rover on Mars in standby mode to wait out the storm.
A massive prominence is shown erupting in this movie made of combined EUVI and COR1 images from the STEREO Ahead spacecraft. In orange is the Sun as seen in the emission line of helium at 304 Angstroms. Prominences emit strongly at this wavelength, and are clearly visible at various locations around the rim, in particular the massive one in the lower-left limb at the start of the movie. At higher heights above the limb, images taken by the COR1 inner coronagraph are shown in green. At the beginning of the movie, a small but rapid eruption can be seen near the top. This eruption may have been the final trigger for the eruption of the eruption of the prominence, which was close to erupting in any case.
A large prominence swirled and twisted above the Sun's surface before breaking away and launching itself into space (Oct. 6-7, 2012). This image and movie are a combination of the Sun itself, observed in extreme UV light (from the STEREO Ahead spacecraft) and STEREO's view of the corona in white light taken by its COR1 instrument. Prominences are clouds of cooler plasma that hover above the Sun, tethered by unstable magnetic forces, which often break away or fade within days or weeks. The movie covers one day of activity.
A very large and bright prominence erupted off the surface of the Sun around 19:00 UT on August 31, 2012 and just kept going. This video from the STEREO Behind spacecraft shows the prominence and the coronal mass ejection (CME) in which its is embedded as it leaves the Sun (orange, EUVI) and travels through the fields of view of COR1 (green), COR2 (red), and HI1 (blue) telescopes before it finally disappears from HI1 around the end of September 2, still clearly visible more than two days after it erupted. While CMEs are routinely seen in the Heliographic Imager (HI) telescopes, it's very rare for prominences to stay visible for so long. The HI1 field of view ranges from 4 to 24 degrees away from the Sun. To get a sense of scale, we know the Sun is roughly 860,000 miles wide-and look how far the prominence holds together. And this CME is so bright, it initially saturates the COR1 telescope.
Also visible in the movie is the planet Venus, which appears as a bright spot on the right side of the COR2 field. Venus is extremely bright and its image is saturated on the COR2 detector. It also creates a couple of artifacts in the movie due to internal reflections within the HI1 telescope. The first of these artifacts is a loop-like feature near the position of the planet on the left side of the HI1 field. The second is a large bubble-like feature on the opposite side of the HI1 image--this is more easily seen at the start of the movie. Both of these artifacts are explained on our website at http://stereo.gsfc.nasa.gov/artifacts/artifacts_reflections.shtml