Solar storms can rain a deluge of charged particles on our planet, creating spectacular aurorae but also damaging satellites and electronics. Scientists have now discovered that these storms also have the opposite effect – they can drain the upper atmosphere above the Earth of almost all its charge.
The discovery, published in the journal Radio Science, is based on observations of the solar storm that reached Earth on February 19, 2014. A network of satellites and geomagnetic observatories observed an increase in charged particles like ions and electrons above Greenland, but they also showed wide regions completely devoid of electric charge.
The international team of researchers found that these “electrically empty” areas were between 500 to 1,000 kilometers (300 to 600 miles) across and remained depleted of electrons for several days after the storm.
"We don't know exactly what causes the depletion," co-author Attila Komjathy, from NASA’s Jet Propulsion Laboratory, said in a statement. "One possible explanation is that electrons are recombining with positively charged ions until there are no excess electrons. There could also be redistribution – electrons being displaced and pushed away from the region, not only horizontally but vertically."
The Sun is constantly emitting a stream of electrically charged particles, the so-called solar wind. But sometimes there is an excess in this stream due to activities in the Sun, like coronal mass ejections that erupt solar plasma into space at incredible speeds.
All these particles, whether slow-moving or very fast, interact with the Earth’s magnetic field. Depending on their mass and velocity, some are deflected, some can reach the upper atmosphere and create northern lights, and some get trapped in the Van Allen Belts.
There are many factors that influence the type of particles and interactions above our planet. Understanding how the Sun shapes Earth’s space weather is crucial to guarantee the safety of astronauts as well as the satellites that keep us connected.
The latest discovery could also help with radio communication in the Arctic, which is plagued by interferences and almost started World War Three!
Solar eruption seen by NASA's Solar Dynamics Observatory on September 26, 2014. NASA