The Sun Produced a Powerful Interplanetary Shockwave—And It Shook the Whole Solar System

A NASA mission has observed an interplanetary shock produced by the sun and taken high-resolution measurements of the phenomena for the first time.

This shock is the result of streams of charged particles that are emitted by the sun—what's known as the "solar wind." The solar wind can travel at different speeds, and when a faster stream overtakes a slower stream, this can create a shockwave, according to a paper published in the Journal of Geophysical Research Space Physics.

Interplanetary shocks are described as "collisionless" meaning that the particles involved do not transfer their energy by knocking into one another. Instead, they transfer their energy via electromagnetic fields.

"An interplanetary shock is a shock wave that propagates through the solar system," Ian Cohen, lead author of the study from the Applied Physics Laboratory at Johns Hopkins University in Maryland, told Newsweek. "Shocks are physical processes created when a faster object moves through a slower one. An example is when a supersonic jet moves faster than the speed of sound in air."

"In the case of the interplanetary shock, we have faster flowing solar wind—a constant stream of particles from the sun—catching up with slower solar wind and creating a shock wave," he said. "These types of shocks are 'collisionless' because the particles involved in the shock—i.e. the solar wind particles—primarily interact with the electric and magnetic fields and not in billiard-ball-like collision with other particles."

These kinds of "collisionless shocks" are found throughout the universe and are associated with some of the most energetic particles known in astrophysics, which are produced by objects such as black holes and supernovae, according to the study.

Understanding interplanetary shocks can help to cast light on some of the larger phenomena in the universe. However, detecting one is no easy feat because it requires fortuitous timing and placement.

Nevertheless, NASA's Magnetospheric Multiscale Mission (MMS) has been attempting to do just that since being launched in 2015.

The mission involves four identical spacecraft equipped with high-resolution instruments, which lie just a few miles apart from each other. These devices can measure electrons (negatively charged subatomic particles) and ions (charged atoms or molecules) traveling at high speed.

For example, one instrument—known as the Fast Plasma Investigation—can measures ions and electrons whizzing by the spacecraft at a rate of up to six times per second, which is fast enough to identify a passing shockwave moving at high-speed.

Finally, after four years in space, the MMS spacecraft got lucky by being in the right place and time to measure an interplanetary shock as it sped past.

On January 8, 2018, the four spacecraft identified two collections of ions originating from the solar wind, which provided evidence of a powerful interplanetary shock wave, according to an analysis conducted by an international team of scientists.

"The MMS instruments were able to obtain high temporal-resolution measurements of the ions and electrons involved in the shock as well as the electric and magnetic fields," Cohen said.

The authors of the study say that these measurements could have significant implications for our understanding of the cosmos.

"Interplanetary shocks have been known of and investigated since pretty early in the Space Age and we have a fairly good theoretical understanding of how the physics in these shocks works," Cohen said. "However, these new measurements are unique because they are the highest temporal-resolution observations of particles in an interplanetary shock ever obtained and have confirmed the existence of solar wind ions reflecting off of the shock surface; this was previously theorized and inferred from previous measurements, but no instruments have ever measured fast enough to actually see these before.

"In general, understanding the very small-scale physics of these shocks has far-reaching implications because collisionless shocks occur all over the universe and play a large role in the fundamental physical process of particle acceleration," he said.

Despite the difficulty in detecting this single shock, the authors are confident of detecting more in the near future, particularly weaker ones.

This article was updated to include additional comments from Ian Cohen.

NASA, MMS
Artist's illustration of the MMS mission. NASA
The Sun Produced a Powerful Interplanetary Shockwave—And It Shook the Whole Solar System | Tech & Science