About 40 years ago, solar physicists discovered raging plasma storms in the Sun’s atmosphere, though the mechanism behind the storms wasn’t understood. Using data from the Swedish Solar Telescope (SST) and NASA’s Solar Dynamics Observatory (SDO), a team led by Eamon Scullion of Trinity College Dublin has created an explanation for these storms. The research was presented Tuesday (June 24) at the 2014 National Astronomy Meeting in Portsmouth.
We’re all familiar with the water cycle on Earth: water is heated by the Sun and evaporates; cools and condenses into clouds at high altitudes; then precipitates back down to the surface in the form of rain. As it turns out, the Sun has a similar process, though much more severe and terrifying because it uses huge amounts of electrically-charged gas known as plasma instead of tiny droplets of water.
Thanks to technology like the SST and SDO, scientists have learned that weather on the Sun can fluctuate due to interaction with the magnetic field. Unlike on Earth, solar storms involve “drops” of plasma the size of Ireland hurdling down from the Sun’s corona at a breakneck speed of 200,000 kilometers per hour. These storms can be so severe that the downpour resembles a waterfall. Recently, Scullion’s team was able to determine that this plasma cycles through the Sun very similarly to how water cycles on Earth.
Image credit: E. Scullion/SST
”Showers of 'rain' and waterfalls on the Sun are quite something, though I wouldn't recommend taking a stroll there anytime soon,” Scullion quipped in a press release. “But the parallels with weather on Earth are both striking and surprising.”
In order to get the dense plasma up into the corona, it must be evaporated quickly. Scullion’s team postulates that this evaporation is caused by powerful explosive solar flares. When clouds of plasma cool and condense enough due to fluctuations with the Sun’s magnetic field, a process Scullion’s team describes as ‘catastrophic cooling’, plasma falls back down to the surface, creating a loop called a coronal arcade. After studying high-resolution images of a plasma ‘waterfall’ captured by the SST in the summer of 2012, the researchers were able to link solar flares with coronal rain.
Physicists have long been confounded by how the temperature of the Sun’s corona would be heated, and Scullion’s research may provide that answer. The cycle of solar flares and and coronal rain may regulate the corona’s temperature, which ranges from about 5000 Kelvin near the surface, up to over 1,000,000 K further out.
What exactly do these raging, loopy coronal storms look like? Check it out: