On the origin of the hard X-ray pulsations during solar flares

The quasiperiodic pulsations of flare hard X-rays may result from magnetohydrodynamic oscillations of the initial energy-release site near the top of the flare loop. The rising gas-kinetic pressure there will produce a magnetic trap about two arcsec in diameter. MHD oscillations in the trap triggered by the impulsive energy release will modulate the flux of fast electrons, which will interact with the sense atmosphere at the flare-loop footpoints. As a result the intensity of the hard X-rays emitted there will pulsate. The pulsation period, quality, and modulation depth convey information on the parameters of the initial energy-release region.