February 20, 2013
Cassini Catches Solar Wind, Helps NASA Study Particle Acceleration
Michael Harper for redOrbit.com — Your Universe Online
As it floats around the planet Saturn, the Cassini spacecraft recently got a front row seat to what NASA astronomers are calling an “unusual strong blast of solar wind.” Shortly after this “wind” blew by, Cassini began detecting particles which had been accelerated to ultra-high energies. Particles which are accelerated this much are usually found surrounding far away supernovas.This is good news for the Cassini team, as NASA now says it plans to take this opportunity and study these particles up close. As these supernova explosions happen so far away from the Earth, astronomers might not get another chance to observe this particle acceleration so soon.
According to NASA, this strong blast of solar wind has resulted in a shockwave around Saturn´s magnetic field. Meanwhile, Cassini floats nearby, ready to collect as much data as it can. The Cassini mission is a joint effort by the European Space Agency (ESA), the Italian Space Agency (ASI), and NASA. Together, the team has compiled some of their early findings and published a report this week in the journal Nature Physics which confirms that different types of shockwaves are better at accelerating particles than others. Previously, it had not been thought that this was the case.
Adam Masters of the Institute of Space and Astronautical Science (ISAS) in Japan is leading this study and has said these accelerated particles may have come from the strongest shockwave ever experienced at Saturn.
"Cassini has essentially given us the capability of studying the nature of a supernova shock in situ in our own solar system, bridging the gap to distant high-energy astrophysical phenomena that are usually only studied remotely," said Masters in a statement.
Shockwaves occur frequently in the universe, following explosions of stars or the aforementioned solar wind. When pieces of debris are hurled away from a supernova explosion, they create shockwaves in their path. Solar winds create a different kind of shock. As particles are carried away from the sun in these solar winds, they interact with the magnetic fields of planets, as recently happened with Saturn.
These shocks are called bow shocks.
According to NASA, the way a magnetic field is oriented, either quasi-parallel or quasi-perpendicular, and the strength of the shock all play a part in determining particle acceleration. In some situations, these particles are accelerated to the speed of light. These hyper-accelerated particles could be the source of cosmic rays, which are high energy particles found all over the Milky Way.
Astronomers are particularly interested in the quasi-parallel shockwaves which emanate from forward-facing magnetic fields. These quasi-parallel shockwaves could be found in the supernova remnants. With any luck, the Cassini team will be able to pick out particles from these shockwaves and investigate them more closely.