Prompt particle acceleration around moving X-point magnetic field during impulsive phase of solar flares

We present a model for high-energy solar flares to explain prompt proton and electron acceleration, which occurs around moving X-point magnetic field during the implosion phase of the current sheet. We derive the electromagnetic fields during the strong implosion phase of the current sheets, which is driven by the converging flow derived from the magnetohydrodynamic equations. It is shown that both protons and electrons can be promptly (within 1 second) accelerated to approximately 70 MeV and approximately 200 MeV, respectively. This acceleration mechanism can be applicable for the impulsive phase of the gradual gamma ray and proton flares (gradual GR/P flare), which have been called two-ribbon flares

太陽フレアにおける電流ループ合体を示すコロナ爆発

We present a model for high-energy solar flare explosions driven by 3-dimensional X-type current loop coalescence. The 3-dimensional X-type loop coalescence, where two crossed fluxtubes interact in one point, is a fundamentally new process as compared to the 1-D and 2-D cases studied earlier. It is shown that, following the strong plasma collapse due to pinch effect, a point-like plasma explosion can be driven and also fast magnetosonic shock waves can be excited;We found that the conditions in the area producing the remarkable flare bursts of 21 May 1984 were indeed such that the many flare spikes could have been due to 3-D explosive X-type current loop coalescence. We also show, by studing the conding the conditions of shock formation in a Gamma ray flare, that the time delay of γ-rays from the impulsive phase could be the time needed for the shock formation in the flaring region.We draw some general conclusions on the question why certain flares do emit γ-rays in the Mev energy range, and why other, apparently important and large flares, do not. We accentuate the fact that a well-developed high-energy flare has three phases of particle acceleration

太陽の捩じれた磁気ループでのリング状のエネルギー解放

We investigate the magnetohydrodynamic (MHD) instability of the magnetic loop in association with the solar flare. We use \u27safety factor\u27 q to describe the local twist of the magnetic loop where low q value means the strong twist, then it becomes more unstable for the MHD instability.We present the q profile on the equilibrium for two types which may correspond to small and large flare. One type corresponding to small flare is the slim cylindrical untwisted magnetic loop in initial stage. When the tube is twisted, low q region is localized around the axis of the center of the loop. We conclude that the localized low q region must be ring shaped. The energy release by MHD instability can be localized with the ring shaped region. The other type is barrel shaped untwisted magnetic loop which may correspond to the large flare. After the twist, low q region is wide along the axis. The MHD instability is caused on the whole magnetic loop, therefore the energy release is global

小さい高エネルギーフレアにおけるX型電流ループ合体による粒子加速

We studied the acceleration conditions in the small but fairly energetic flare of May 21, 1984 at 13:26 UT. The most pronounced aspect of this flare was a series of 13 microwave / x-ray spikes, each lasting for about 0.1s. A previous study has shown that each of these was due to a series of successive sudden formations of small plasma knots of high energy particles. Each of these knots lost its energy in about 50 ms. In the present study we show that these knots can originate by the process of x-type (3-D) flux tube coalescence. The predicted rise time (30 to 50 ms) and energy are in good agreement with the observationally derived parameters

3次元X型電流ループ合体による高エネルギーフレア爆発

The coronal explosion, discovered by De Jager and Boelee (1984), and interpreted by them as manifestations of plasma streaming out of the flare kernels, can also be interpreted as signatures of current loop coalesscence in the flaring region

磁気島の爆発的合体過程の粒子加速

An explosive reconnection process associated with the nonlinear evolution of the coalescence instability is found through studies of the electromagnetic particle simulation. The explosive coalescence is a process of magnetic collapse, in which we find the magnetic and electrostatic field energies and temperatures (ion temperature in the coalescing direction, in particular) explode toward the explosion time to as (t_0 - t)^, (t_0 - t)^, and (t_0 - t)^, respectively.Single-peak, double-peak, and triple-peak structures of magnetic energy, temperature, and electrostatic energy, respectively, are observed on the simulatton as overshoot amplitude oscillations and these features are theoretically explained. Rapid acceleration of particles binormal to the magnetic field and electric field becomes possible

磁気島の爆発的合体過程の流体モデル

Magnetohydrodynamic simulation of the explosive coalescence of magnetic islands is carried out. This result is in agreement with the electromagnetic particle simulation. A theoretical model to describe this process observed in our computer simulations is presented. The theory describes the magnetic collapse and is based on a self-similar solution to the two-fluid plasma equations, as the simulation exhibits temporal self-similarity. The master equation for the scale factor takes a from of the orbital equation in a Sagdeev potential

非線形電磁流体波による強制的磁気再結合

Forced magnetic reconnection induced by magnetohydrodynamic (MHD) waves may account for the triggering of explosive solar activities such as flares. Reconnection in a neutral sheet plasma can be driven by the ponderomotive force associated with nonlinear MHD waves accompanying plasma vortex motion. The nonlinear stage of forced reconnection by MHD waves is simulated with a MHDparticle-code: Some conditions for fast reconnection are discussed with applications to solar flares

磁場の収縮時における爆発的静電場と粒子加速

It is shown that ion streams across the magnetic field moving with electrons cause explosive transverse electrostatic field during magnetic collapse such as coalescence instability of current loops. The electrostatic field can explosively accelerate ions and electrons perpendicular both to the magnetic field and ion streams. Ions and electrons are almost simultaneously accelerated to the opposite direction, respectively. The results obtained here well explain the simulation results of collisionless coalescence instability of current loops. The simultaneous acceleration mechanism of ions and electrons is applied to the origin of explosive high energy varticles in cosmic plasmas

太陽紅炎の形成及び振動の動的モデル

We investigate a dynamical model of prominence formation in a current sheet at the boundary between two regions of opposite magnetic polarity. Coupled nonlinear equations describing the temporal compression and condensation of plasma in the current sheet are set up as a natural extension of the usual equations for current sheet collapse (Imshennik and Syrovatskii, 1967). It is shown that under certain conditions the current sheet undergoes a nonlinear oscillation during the compression. The thermal instability with cooling is driven by a density enhancement produced during the current sheet formation stage