Scientists identify mechanism that could feed solar explosions

Coronal Mass Ejections (CMEs) are violent solar explosions capable of propelling up to 10 billion tons of the Sun’s atmosphere – at a million miles an hour – out through the corona and into space.

Such ejections may take as little as 18 hours to reach Earth. When they do, the emissions have the potential to generate geomagnetic storms, which could interfere with radio transmissions, induce large currents in power lines and oil pipelines and seriously disrupt spacecraft.

Clearly, predicting such ejections in a timely manner would go a long way in helping to prevent or mitigate damage from the violent solar explosions. 

Fortunately, researchers from Lockheed Martin, the Harvard-Smithsonian Center for Astrophysics, Kyoto University and the National Center for Atmospheric Research recently discovered a turbulent convective flow system in solar “quiescent” prominences.

The flow system is apparently suspended in the corona – the Sun’s outer atmosphere –  and points to a mechanism by which hot coronal plasma (and presumably magnetic flux) are injected upwards into the coronal cavity system.

Coronal cavities are essentially large magnetic flux ropes suspended in the corona, typically in the polar regions of the Sun. These flux ropes all eventually erupt in the form of CMEs that can impact the interplanetary and terrestrial space environments.

“How these large flux ropes erupt is a poorly understood fundamental process in the science of space weather. Our discovery points to a way in which intermittent ‘bubbles’ in solar prominences can inject new mass and magnetic flux into the flux ropes, thus slowly building up their magnetic buoyancy over time,” explained Dr. Thomas Berger, lead author of the Nature paper, and solar physicist at the Lockheed Martin Solar and Astrophysics Lab at the ATC.

“These ‘bubbles’, which can be as wide as several Earth diameters, are analogous to the blobs of material in a Lava Lamp that are heated by a light from below, become buoyant, and rise to the top to deposit their energy, then drop back down again. By this mechanism coronal cavity flux ropes could grow slowly until they are able to exceed the ‘tethering’ forces of overlying magnetic fields and thus erupt as CMEs.”

According to Berger, the above-mentioned discovery could eventually help scientists establish a predictive tool for the eruption of CMEs based on the rate of observed flux injection.

“The discovery is [also] significant because it revises the common view that the magnetic field in the corona dominates the gas pressure and allows only simple, laminar, flows along magnetic field lines.

“It is apparent that our understanding of basic forces at work in the corona must be revised to include turbulent motions that can deform the magnetic field lines and produce novel flow and mixing systems,” he added.

Additional data, images and videos can be viewed here.