ON THE TRANSPORT AND ACCELERATION OF SOLAR-FLARE PARTICLES IN A CORONAL LOOP

The turbulent environment of a flaring solar coronal loop directly affects the population of particles to be accelerated or already accelerated. These particles, electrons or protons, are responsible for the emission of hard X-rays and gamma-rays. The turbulence in the loop serves to diffuse the particles in both real and momentum space. Under the assumption of a uniform turbulent MHD wave field within the loop, we discuss the behavior of a particle distribution as it interacts with the turbulence, including particle precipitation to the footpoints of the loop and the evolution of the energy distribution as the particles undergo second-order stochastic acceleration. Two cases are discussed in detail: (1) particles spatially diffusing within the loop and precipitating with minimal acceleration in the short time scale of an impulsive event and (2) particles diffusing in both real and momentum space in a long duration event. Collisional losses due to ambient electrons are included. The gamma-ray flare of 1982 June 3 is modeled, and good agreement is obtained between predicted and observed time profiles if the loop length is 10(5) km with an intrinsic spatial diffusion time of 100-450 s. It follows that the production of high-energy neutrons and pi mesons extends over a time scale of 1000 s as observed.