For the second day in a row, an active region on the sun has erupted with a coronal mass ejection (CME), blasting a beautifully dynamic magnetic bubble of energetic plasma in the direction of Earth. It is powering through interplanetary space at a breakneck speed of 1,360 kilometers per second (that’s over 3 million miles per hour!)
A NASA spacecraft — one of two solar satellites called the Solar-Terrestrial Relations Observatory (STEREO) that are orbiting the sun in opposite directions — watched the CME expand and get launched into interplanetary space from a perfect vantage point.
On June 13, AR1504 erupted, producing a M1 class flare that was accompanied by a CME. According to Spaceweather.com, that CME will hit Venus on June 15th, Earth on June 16th and Mars on June 19th. Today’s CME, launched from the same location, is predicted to also slam into the Earth’s magnetic field on June 16, potentially generating a geomagnetic storm.
If the conditions are just right, a CME’s magnetic field can compress and distort the magnetic field of our planet, called the magnetosphere. If the rotation of the CME’s magnetic field is aligned just right, it may become “geoeffective,” causing the CME’s field to connect with the Earth’s magnetic field.
Should this occur, a geomagnetic storm may result, causing the injection of energetic solar particles into the magnetosphere and a rapid release of stored energy. The result is often spectacular displays of aurorae at high latitudes and potentially some interference to modern technology. Communication interference may occur and, during extreme geomagnetic storms, airliners may be directed away from polar regions and electrical surges in national power grids may be detected.
STEREO “A” — for “ahead” as it is ahead of Earth’s orbit — imaged the sun from the side with its coronagraph, tracking the CME’s evolution (top). A coronagraph creates a fake eclipse with a disk inside the instrument so the obscuring light from the sun can be blocked. The beautiful intricate structure of the sun’s atmosphere — or corona — and any structures like a CME can then be photographed.
Active region 1504 (or AR1504) is a magnetically intense region that is crackling with flares and it has rotated in our direction. Powerful arcs of magnetic field are protruding deep from within the solar body, pushing back the hot outer layers of the sun’s photosphere, exposing the cooler, (comparatively) dark interior. A beautiful complex of sunspots is the result — shown in the NASA Solar Dynamics Observatory image, below.
As we become more technologically sophisticated we become more vulnerable to geomagnetic storms, but with the help of missions such as STEREO, the SDO and the long-lived Solar and Heliospheric Observatory (SOHO), we are getting better at predicting a CME’s impact and its potential effects on our magnetosphere.
Watch a cool SDO video of AR1504 pop off a series of flares:
Images: Top: A series of observations from STEREO A tracking the AR1504 CME (NASA). Middle: An SDO view of sunspots in the solar photosphere — through the 4500A filter (NASA/SDO)