The "corpse" of a sunspot exploded Monday (April 11), triggering a mass ejection of solar material that is headed in Earth's direction.
The explosion comes courtesy of a dead sunspot called AR2987, according to SpaceWeather.com (opens in new tab). The sunspot explosion released loads of energy in the form of radiation, which also led to a coronal mass ejection (CME) — explosive balls of solar material — both of which could spur more intense northern lights in Earth's upper atmosphere. The material in that CME is likely to impact Earth on April 14, according to SpaceWeather.
Sunspots are dark regions on the surface of the sun. They are caused by intense magnetic flux from the sun's interior, according to the Space Weather Prediction Center (opens in new tab). These spots are temporary and can last anywhere from hours to months. The idea of a "dead" sunspot is more poetic than scientific, said Philip Judge, a solar physicist at the High Altitude Observatory at the National Center for Atmospheric Research (NCAR), but the convection of the sun breaks these spots apart, leaving in their wake magnetically-disturbed bits of quiet solar surface.
"Occasionally," Judge wrote Live Science in an email, "sunspots can 'restart,' with more magnetism appearing later (days, weeks) at the same region, as if a weakness was made in the convection zone, or as if there is an unstable region under the surface that is particularly good at generating magnetic fields beneath."
Related: Strange new type of solar wave defies physics
Whatever the future of AR2987, the sunspot let out a C-class solar flare at 5:21 Universal Time Monday (April 11). Such flares happen when the plasma and magnetic fields above the sunspot give way under stress; they accelerate outward, Judge said, because they would run into dense material if they went downward toward the sun's interior.
C-class flares are fairly common and rarely cause any impacts on Earth directly. Sometimes, as with today's eruption, solar flares can trigger coronal mass ejections, which are huge eruptions of plasma and magnetic fields from the sun that travel outward into space at millions of miles per hour. C-class solar flares rarely trigger CMEs, according to SpaceWeatherLive (opens in new tab), and when they do, the CMEs are usually slow and weak.
When CMEs hit the magnetic field surrounding Earth, the charged particles within the ejection can travel down the magnetic field lines that emanate from the North and South Poles and interact with the gases in the atmosphere, releasing energy in the forms of photons and creating the shifting, dazzling curtains known as the aurora — the northern and southern lights.
During quiet times on the sun's surface, a stream of particles known as the solar wind is enough to trigger the aurora in the polar regions. During a large CME, the greater disturbance to the planet's magnetic field means that the aurora may appear over a much broader range. A so-called cannibal CME raced toward Earth at the end of March, triggering auroras in Canada, the northern U.S., and New Zealand, Space.com reported.
The CME released Monday might yield a minor (G1) geomagnetic storm on April 14, meaning that there could be minor impacts on satellite operations and weak fluctuations in the power grid, according to SpaceWeather. The aurora may become visible at lower latitudes than usual, as far south as northern Michigan and Maine.
All of this activity is fairly par for the course for the sun, according to the Solar Influences Data Analysis Center, part of the Royal Observatory of Belgium. It's a time of increased activity for our nearest star, which goes through periods of quiet and activity known as solar cycles. The sun is currently in Solar Cycle 25, the 25th since formal observations began in 1755. The number of sunspots during this cycle is on the upswing and is expected to peak in 2025, which means more opportunities for solar storms — and auroras.
Strong geomagnetic storms were also observed on Sunday (April 10). But according to the Solar Influences Data Analysis Center, there have been no other Earth-directed CMEs observed in the past 24 hours other than the one spit out by AR2987's remnants.
Originally published on Live Science.