High-energy X-ray bursts from low-energy plasma

phys.org | 2/19/2019 | Staff
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Solar flares shouldn't produce X-rays, but they do. Why? The one-size-fits-all approach to electron collisions misses a lucky few that lead to an intense X-ray burst. Scientists thought there were too many electron-scattering collisions in such cold plasmas for electrons to be accelerated to high energy and radiate X-rays. While most of the electrons in a cold plasma collide before they can accelerate, it's possible that a few don't collide. These particles are like warriors who endure a sequence of deadly battles but survive each encounter and develop experience to have a better chance of surviving the next one.

For a long time, scientists have observed X-rays and energetic particles in solar flares and other situations where the plasma is supposed to be too collisional for these phenomena to occur. X-rays might also occur in lightning and certain fusion energy devices. Astrophysical jets might produce high-energy particle beams (gamma rays). The team's discovery shows that scientists need to take detailed statistics of collisions into account. A one-size-fits-all approach misses the lucky few electrons that do not collide and accelerate to attain large kinetic energy.

Scientists - Burst - X-rays - Laboratory - Plasma

Scientists observed a burst of X-rays from a laboratory plasma jet. This burst was unexpected because the plasma jet was relatively cold and thus highly collisional. A simple way to think about a cold, collisional plasma is that there is too much friction for electrons to be accelerated to high energy and radiate X-rays because friction corresponds to collisions that scatter electrons. While the great majority of electrons in a cold plasma collide before they can accelerate to high energy, it's possible that a lucky few don't. Collisions are quantified statistically by the mean free path, which is the distance over which a particle has a two-thirds chance of colliding and so losing all its...
(Excerpt) Read more at: phys.org
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