Spatial structure of flare‐associated perturbations in the solar wind simulated by a two‐dimensional numerical MHD model

TLDR: In this paper, the authors investigated the dynamic behavior of flare-associated disturbances using a time-dependent two-dimensional MHD numerical model for a one-fluid solar wind with adiabatic expansion.

Abstract: The dynamic behavior of flare-associated disturbances has been investigated using a time-dependent two-dimensional MHD numerical model for a one-fluid solar wind with adiabatic expansion. Simulations of the development and propagation of perturbations have been performed between 18 R/sub S/ and 226 R/sub S/ (where R/sub S/ = solar radius) in an angular sector of the equatorial plane of the sun 90/sup 0/ wide. Several test computations have been carried out with different initial pulse characteristics. These pulses are set arbitrarily at the inner boundary assuming that a shock wave is already formed. The parameters are the velocity of the shock front, the angular width of the perturbation, and its time duration at 18 R/sub S/. It is shown that in every case the time delay between 18 R/sub S/ and 226 R/sub S/ depends on the total amount of energy released by the prototype flare (hence in the pulse). This dependence is stronger with the initial velocity than with the angular width. Also it appears that the shock wave propagates according to a power law of time: R = at/sup b/. After a relatively short time the expansion of the wave is dominated by the internal energy so that themore » longitudinal extent of the perturbation at 1 AU seems to be only a function of the time elapsed after the arrival of the front shock at this distance. The existence of a reverse shock which is formed after a few hours is shown to last a time long enough to reach 1 AU. Its longitudinal extension is limited to the area around the flare central meridian where the pressure gradient induced by the initial condition is strong enough.« less