Simnett, G. M. and M. G. Haines, On the Production of Hard X-Rays in Solar Flares, Sol. Phys., 130, 253-263 (1990) (ADS)
(click on the image for a larger version)
If a beam of particles from the corona could be an explanation for the
chromospheric effects of a flare during the impulsive phase (a strong and
still controversial
hypothesis), then the beam might as well be made of protons or neutrals.
This would represent an alternative to the standard thick-target
model, which envisions an electron beam.
The main argument against having more massive particles involved
this would be the time scales, since if non-relativistic, they
might have transport time inconsistent with the observed time
variations.
But, if such an idea were possible, then the interaction of the beam
in the chromosphere could produce charge separations and one would get
the hard X-ray emissions from locally accelerated electrons.
Note the electrical potential Φ appearing in the chromosphere.
This cartoon thus represents a clear step forward in our view of the
thick-target model, in envisioning chromospheric acceleration.
If a beam of particles from the corona could be an explanation for the chromospheric effects of a flare during the impulsive phase (a strong and still controversial hypothesis), then the beam might as well be made of protons or neutrals. This would represent an alternative to the standard thick-target model, which envisions an electron beam. The main argument against having more massive particles involved this would be the time scales, since if non-relativistic, they might have transport time inconsistent with the observed time variations. But, if such an idea were possible, then the interaction of the beam in the chromosphere could produce charge separations and one would get the hard X-ray emissions from locally accelerated electrons. Note the electrical potential Φ appearing in the chromosphere. This cartoon thus represents a clear step forward in our view of the thick-target model, in envisioning chromospheric acceleration.