For the first time in human history, we have visible evidence of an "interplanetary shock".
Starting at the sun, these shocks continually release streams of charged particles called the solar wind. Solar wind typically comes in two types " slow and fast. When a fast stream of solar wind overtakes a slower stream, it creates a shock wave. Like a boat moving through a river creates a wave, the wave then spreads out across the solar system, a NASA statement says.
These shocks are found everywhere in the universe from distant stars to supernovae and black holes.
This phenomenon was captured by the Magnetospheric Multiscale mission (MMS) on 8 January 2019. The MMS mission, a group of four spacecrafts orbiting the Earth in a tight formation, was launched in 2015. Their coordinated movement allows researchers to observe and map interplanetary shock waves in 3-D space. The study also collects information on magnetic fields around the Earth, how and where they overlap and the energy released when two such magnetic field lines intersect, in a process known as magnetic reconnection.
MMS observes reconnection from right here in Earth's very own protective magnetic space environment, the magnetosphere. By studying reconnection in this local, natural laboratory, MMS can help us understand reconnection elsewhere in the universe as well, like in the atmosphere of the sun and other stars, in the vicinity of black holes and neutron stars, and at the boundary between our solar system's heliosphere and interstellar space.
Solar wind that is the cause of the planetary shocks. Image credit: NASA/YouTube
These spacecraft are fitted with high-resolution instruments that help them 'see what no other spacecraft can.' These instruments helped in taking measurements of the shock waves.
One instrument suite in particular that aided the measurements is the Fast Plasma Investigation suite. It measures ions and electrons around the spacecraft at up to 6 times per second. Since speeding shock waves could pass the spacecraft in a mere half-second, the high-speed sampling capability of this instrument is essential to catching such shock wave events.
When scientists look at data collected from that same day the shock recorded by MMS, they noticed a clump of ions picked up from the solar wind. Shortly after, they noticed a second clump of ions, created by ions already in the area that had bounced off the shock as it passed by. Analyzing this second population, the scientists found evidence to support a theory of energy transfer first proposed in the 1980s.
Since the four MMS spacecraft were separated by only 19 kilometres at the time of the shock, the scientists could also see small-scale irregular patterns in the shock, which is still pending further study.
The findings from this event has been published in the Journal of Geophysical Research.