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

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

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

Meteor radiant mapping with MU radar

The radiant point mapping of meteor showers with the MU radar by using a modified mapping method originally proposed by Morton and Jones (1982) was carried out. The modification is that each meteor echo was weighted by using the beam pattern of the radar system. A preliminary result of the radiant point mapping of the Geminids meteor shower in 1989 is presented

Log-aesthetic Curves as Similarity Geometric Analogue of Euler's Elasticae

In this paper we consider the log-aesthetic curves and their generalization which are used in CAGD. We consider those curves under similarity geometry and characterize them as stationary integrable flow on plane curves which is governed by the Burgers equation. We propose a variational formulation of those curves whose Euler-Lagrange equation yields the stationary Burgers equation. Our result suggests that the log-aesthetic curves and their generalization can be regarded as the similarity geometric analogue of Euler's elasticae

A theory of the electric quadrupole contribution to resonant x-ray scattering: Application to multipole ordering phases in Ce_{1-x}La_{x}B_{6}

We study the electric quadrupole (E2) contribution to resonant x-ray scattering (RXS). Under the assumption that the rotational invariance is preserved in the Hamiltonian describing the intermediate state of scattering, we derive a useful expression for the RXS amplitude. One of the advantages the derived expression possesses is the full information of the energy dependence, lacking in all the previous studies using the fast collision approximation. The expression is also helpful to classify the spectra into multipole order parameters which are brought about. The expression is suitable to investigate the RXS spectra in the localized f electron systems. We demonstrate the usefulness of the formula by calculating the RXS spectra at the Ce L_{2,3} edges in Ce_{1-x}La_{x}B_{6} on the basis of the formula. We obtain the spectra as a function of energy in agreement with the experiment of Ce_{0.7}La_{0.3}B_{6}. Analyzing the azimuthal angle dependence, we find the sixfold symmetry in the \sigma-\sigma' channel and the threefold onein the \sigma-\pi' channel not only in the antiferrooctupole (AFO) ordering phase but also in the antiferroquadrupole (AFQ) ordering phase, which behavior depends strongly on the domain distribution. The sixfold symmetry in the AFQ phase arises from the simultaneously induced hexadecapole order. Although the AFO order is plausible for phase IV in Ce_{1-x}La_{x}B_{6}, the possibility of the AFQ order may not be ruled out on the basis of azimuthal angle dependence alone.Comment: 12 pages, 6 figure

太陽フレアーにおける融合不安定

Double sub-peak structures in the quasi-periodic oscillations found in the time profiles of two solar flares on 1980 June 7 and 1982 November 26 are well explained in terms of the coalescence instability of two current loops. This interpretation is supported by the observations of two microwave sources and their interaction for the November 26 flare. The difference of both sub-peak structures and time scales between the two flares are discussed from the viewpoint of different plasma parameters in our computer simulations