Acceleration of 0.29 to 0.5MeV protons by interplanetary shocks
Abstract
The availability of high time resolution spacecraft data has made possible in situ and detailed study of plasma processes in the interplanetary medium. One important process that has received a lot of attention is the energization of charged particles due to interaction with traveling interplanetary shock waves. The specific goal of this study is to make use of observed magnetic fields, plasma density and velocity, and initial particle trajectories calculated from real spacecraft orientations in a timereversed computer simulation which follows particles through a single complete interaction with a shock in order to predict the angular distribution of energetic protons (0.290.5 MeV). This study is fully threedimensional and unique in that real conditions for specific shocks outside the Earth's magnetosphere are simulated, and the results are compared to observations for each particular shock. Energy gains and losses calculated in the simulation are used to predict the amount of enhancement in each sector, assuming an isotropic ambient medium and a relationship between energy and particle number that is based on a power law. This study is a test of single encounter shock drift acceleration for two real shocks: 1974 day 312 (θ_{Bn}=68°) and 1979 day 95 (θ_{Bn}=54°). The first is clearly a quasiperpendicular shock while the second has the long rise time associated with an energetic storm particle event with a shock spike just at the time of shock passage features, i.e., the observed angular distributions in the lowestenergy proton channel of the IMP 8 spacecraft for sectors which interacted with the shock. The 1974 day 312 shock is an example of the model correctly predicting the observations, and the shock spike of the 1979 day 95 shock offers a good base for comparison with the day 312 shock.
 Publication:

Journal of Geophysical Research
 Pub Date:
 June 1988
 DOI:
 10.1029/JA093iA06p05525
 Bibcode:
 1988JGR....93.5525K
 Keywords:

 Interplanetary Medium;
 Particle Acceleration;
 Proton Energy;
 Shock Waves;
 Computerized Simulation;
 Interplanetary Magnetic Fields;
 Magnetic Effects;
 Mathematical Models;
 Particle Trajectories;
 Plasma Density;
 Astrophysics;
 Interplanetary Physics: Interplanetary shocks