The Sun is surrounded by an aura of plasma called the corona, which is millions of degrees in temperature, significantly hotter than the “surface” of the star. Solar physicists have been trying to better understand this peculiar feature, and have now created the most realistic coronal loops in the lab.
The team from the California Institute of Technology (Caltech) was able to create ropes of plasma 1.5 meters (5 feet) long, which behaved like the solar coronal loops at a smaller scale. Their research was published in the journal Geophysical Research Letters.
Plasma around the Sun is moved by our star’s strong magnetic fields, and coronal loops are a special interaction where arches of plasma erupt from the solar surface. The scientists were able to recreate a loop with a magnetic strapping field, which is what researchers believe anchors the arches to the surface of the Sun.
The strength of the strapping field diminishes as material moves away from the Sun, and the plasma can break free at high altitude. These eruptions are known as solar flares and coronal mass ejections (CMEs), and they accelerate plasma away from the Sun at up to 3,200 kilometers (2,000 miles) per second.
When the lab rope moved to a critical height beyond the peak strapping field region, the plasma was accelerated, just like the predicted acceleration from CMEs.
A real coronal loop (left) compared to one simulated in the lab (right). P. Bellan/Caltech
“Studying coronal mass ejections is challenging, since humans do not know how and when the Sun will erupt. But laboratory experiments permit the control of eruption parameters and enable the systematic explorations of eruption dynamics,” said graduate student Bao Ha, lead author of the study.
“While experiments with the same eruption parameters are easily reproducible, the loop dynamics vary depending on the configuration of the strapping magnetic field.”
The accelerated plasma is responsible for geomagnetic storms that occasionally affect our planet. The most intense ones can be very damaging, with countries like the US having to put in place a plan for how to deal with the consequences of major storms.
“This potential for causing havoc – which only increases the more humanity relies on satellites for communications, weather forecasting, and keeping track of resources – makes understanding how these solar events work critically important,” said senior author Professor Paul Bellan in a statement.
The setup took more than three years to design, construct, and test. The researchers now plan to study the magnetic field within the erupting loop, and also hope to understand the waves emitted by the plasma breaking free.