arXiv subjects

Sanae-I. Itoh

Publications and source records attributed to Sanae-I. Itoh.

4 recordsLinked to original sources

arXiv2009

Shear flow effects on double tearing mode global magnetic reconnection

The dynamics of a global reconnection in the presence of a poloidal shear flow which is located in between magnetic islands is investigated. Different linear regimes are identified according to the value of the resistivity and the distance between the low-order resonant surfaces. It is found that the presence of a small shear flow affects and significantly delays the global reconnection processes. It is shown that this delay is linked to a breaking of symmetry imposed by the existence of the shear flow and the generation of a mean poloidal flow in the resistive layers.

physics.plasm-ph↗

arXiv2003

Statistics for transition of a plasma turbulence with multiple characteristic scales

Subcritical transition of an inhomogeneous plasma where turbulences with different characteristic space-time scales coexist is analyzed with methods of statistical physics of turbulences. We derived the development equations of the probability density function (PDF) of the spectrum amplitudes of the fluctuating electro-static potential. By numerically solving the equations, the steady state PDFs were obtained. Although the subcritical transition is observed when the turbulent fluctuations are ignored, the PDF shows that the transition is smeared out by the turbulent fluctuations. It means that the approximation ignoring the turbulent fluctuations employed by traditional transition theories could overestimate the range where hysteresis is observed and statistical analyses are inevitably needed.

physics.plasm-ph↗

arXiv2002

Transition Probability to Turbulent Transport Regime

Transition phenomena between thermal noise state and turbulent state observed in a submarginal turbulent plasma are analyzed with statistical theory. Time-development of turbulent fluctuation is obtained by numerical simulations of Langevin equation which contains hysteresis characteristics. Transition rates between two states are analyzed. Transition from turbulent state to thermal noise state occurs in entire region between subcritical bifurcation point and linear stability boundary.

physics.plasm-ph↗

arXiv2002

Stochastic Transition between Turbulent Branch and Thermodynamic Branch of an Inhomogeneous Plasma

Transition phenomena between thermodynamic branch and turbulent branch in submarginal turbulent plasma are analyzed with statistical theory. Time-development of turbulent fluctuation is obtained by numerical simulations of Langevin equation which contains submarginal characteristics. Probability density functions and transition rates between two states are analyzed. Transition from turbulent branch to thermodynamic branch occurs in almost entire region between subcritical bifurcation point and linear stability boundary.

physics.plasm-ph↗