Solar activity sometimes stays trapped close to the Sun’s surface — but sometimes it breaks free in enormous ejections of hot plasma. What determines whether a solar flare stays confined or is followed by a catastrophic eruption? A new study reveals clues.
A Flare Conundrum
False-color H-alpha image of an active region on the Sun’s surface. The Earth is provided in the corner for scale. Click to enlarge. [Dutch Open Telescope]During the rise of the Sun’s 11-year solar cycle, its surface transitions from quiet calm to a roiling environment containing active regions — temporary areas where the strong and complex magnetic field is disturbed. These active regions release magnetic energy in the form of solar flares, the largest of which are often — but not always — associated with coronal mass ejections (CMEs), significant expulsions of hot plasma and magnetic fields into interstellar space.
At the height of the solar cycle, when active regions are more common, the Sun expels around three CMEs per day — and the most violent of these can disrupt radio transmissions on Earth, damage satellites in orbit, and even produce power outages. To predict these catastrophic eruptions, it’s critically important that we better understand the ...