Data that have recently been received and evaluated in December 2020 from the Voyager Mission reveals that the spacecraft encountered dynamics that have been hypothesized, but never before observed. Voyager 1 is now about 152 astronomical units (AU) from Earth, and Voyager 2 is about 126 AU and both are in interstellar space; they’re moving at an average velocity of 36,208 mph, and are on different trajectories. The one-way communication time (light speed) is about 21 and 17 hours, respectively.
The hypothesis has been that shock waves accelerate electrons and other particles. The two Voyagers both detected bursts of cosmic ray electrons which were accelerated by shock waves originating from coronal mass ejections (CME) from the Sun. (CME can travel at a million miles an hour, but even at these speeds, it takes more than a year for the shock waves to reach the Voyagers.) These electron bursts are accelerated along magnetic field lines within the interstellar medium, and travel at nearly the speed of light.
The University of Iowa’s IowaNow site reported on Dec. 3, 2020: “The electron bursts were followed by plasma wave oscillations caused by lower-energy electrons arriving at the Voyagers’ instruments days later — and finally, in some cases, the shock wave itself as long as a month after that.”
This is very much like the experience when watching fireworks, lightning, or a rocket launch from several miles away — first you see the light, then some seconds or minutes later, you hear the sound. In these examples, the light is like the electron bursts, and the sound is like the shock wave. (In the case of artillery fire — even with blanks — the shock wave is felt, not just heard). [A compilation of shock waves was put together in this video https://www.youtube.com/watch?v=EZHDUFucc-g]
“`What we see here specifically is a certain mechanism whereby when the shock wave first contacts the interstellar magnetic field lines passing through the spacecraft, it reflects and accelerates some of the cosmic ray electrons,’ says Don Gurnett, professor emeritus in the Department of Physics and Astronomy and the study’s corresponding author. ‘We have identified through the cosmic ray instruments these are electrons that were reflected and accelerated by interstellar shocks propagating outward from energetic solar events at the Sun. That is a new mechanism.’
“The discovery could help physicists better understand the dynamics underpinning shock waves and cosmic radiation that come from flare stars (which can vary in brightness briefly due to violent activity on their surface) and exploding stars. The physics of such phenomena would be important to consider when sending astronauts on extended lunar or Martian excursions, for instance, during which they would be exposed to concentrations of cosmic rays far exceeding what we experience on Earth.
“The physicists believe these electrons in the interstellar medium are reflected off of a strengthened magnetic field at the edge of the shock wave and subsequently accelerated by the motion of the shock wave. The reflected electrons then spiral along interstellar magnetic field [IMF] lines, gaining speed as the distance between them and the shock increases.” https://now.uiowa.edu/2020/12/voyager-spacecraft-detect-new-type-solar-electron-burst
