T. Watanabe

Nonlinear Gyrokinetic Simulation of the Magnetosphere‐Ionosphere Feedback Coupling

T. Watanabe, K. Fujita, S. Maeyama

Abstract A nonlinear gyrokinetic simulation is applied to the magnetosphere‐ionosphere (M‐I) coupling system to investigate spontaneous growth of auroral structures and electron acceleration self‐consistently. Perturbations of electron density, potential and field‐aligned current in the auroral ionosphere develop through the feedback instability, resulting …

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Energy exchange between electrons and ions driven by ITG–TEM turbulence

T. Kato, H. Sugama, T. Watanabe

In this study, the energy exchange between electrons and ions in trapped-electron-mode (TEM) and mixed ion temperature gradient (ITG)–TEM turbulence is investigated using gyrokinetic simulations. The energy exchange in TEM turbulence is primarily composed of the cooling of electrons associated with perpendicular …

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Growth of Auroral Structures, Vortex Formation, Turbulence Transition, and Energy Cascade in Alfvénic Magnetosphere‐Ionosphere Coupling

T. Watanabe, Koji Fujita, S. Maeyama

Abstract Magnetohydrodynamic simulations of the Alfvénic magnetosphere‐ionosphere (M‐I) coupling reveal a comprehensive picture of nonlinear development of the feedback instability, demonstrating spontaneous growth of auroral structures of density and current enhancements, vortex formation, turbulence transition, and energy cascade. Turbulent energy spectra consistent …

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Energy exchange between electrons and ions driven by ITG-TEM turbulence

T. Kato, H. Sugama, T. Watanabe

In this study, the energy exchange between electrons and ions in ITG TEM turbulence is investigated using gyrokinetic simulations. The energy exchange in TEM turbulence is primarily composed of the cooling of electrons associated with perpendicular drift and the heating of ions …

A kinetic energy and entropy preserving scheme for compressible magnetohydrodynamics

Takashi Shiroto, T. Watanabe

This paper extends the kinetic energy and entropy preserving (KEEP) scheme, which was originally designed for compressible fluid dynamics, to include compressible magnetohydrodynamics (MHD). In MHD, the magnetic energy included in the total energy equation is consistent with that derived from the …

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Application of field-aligned coordinates to a spectral reduced MHD code for simulation of ballooning mode turbulence

Ayumi Takano, T. Watanabe

To realize simulation of ballooning mode turbulence with high spatial resolution, the field-aligned coordinates are applied to a spectral reduced magnetohydrodynamics (rMHD) code which was originally developed by means of the cylindrical coordinates. A new computational scheme using a poloidal mode number …

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Comprehensive gyrokinetic study of eigenstate transitions in fast ion-driven electrostatic drift instabilities

Byoung-Woo Kang, H. Sugama, T. Watanabe, M. Nunami

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Convective Growth of Auroral Arcs Through the Feedback Instability in a Dipole Geometry

Tomohiko Sakaki, T. Watanabe, S. Maeyama

Abstract Auroral dynamics in the magnetosphere‐ionosphere (M‐I) coupling system with the dipole magnetic field is investigated by means of a novel simulation code developed with flux coordinates where a set of the reduced magnetohydrodynamic (MHD) and the two‐fluid equations for the M‐I …

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Time evolutions of information entropies in a one-dimensional Vlasov–Poisson system

K. Maekaku, H. Sugama, T. Watanabe

A one-dimensional Vlasov–Poisson system is considered to elucidate how the information entropies of the probability distribution functions of the electron position and velocity variables evolve in the Landau damping process. Considering the initial condition given by the Maxwellian velocity distribution with the …

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Time evolutions of information entropies in a one-dimensional Vlasov-Poisson system

K. Maekaku, H. Sugama, T. Watanabe

A one-dimensional Vlasov-Poisson system is considered to elucidate how the information entropies of the probability distribution functions of the electron position and velocity variables evolve in the Landau damping process. Considering the initial condition given by the Maxwellian velocity distribution with the …

Energy exchange between electrons and ions in ion temperature gradient turbulence

H. Sugama, T. Watanabe, M. Nunami

Microturbulence in magnetic confined plasmas contributes to energy exchange between particles of different species as well as the particle and heat fluxes. Although the effect of turbulent energy exchange has not been considered significant in previous studies, it is anticipated to have …

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Overview of multiscale turbulence studies covering ion-to-electron scales in magnetically confined fusion plasma

S. Maeyama, N. T. Howard, J. Citrin, T. Watanabe et autres

Abstract Turbulent transport in magnetically confined fusion plasma has conventionally been analyzed at the ion gyroradius scale based on the microturbulence theory. However, ion-scale turbulence analysis sometimes fails to predict the turbulent transport flux observed experimentally. Microturbulence at the electron gyroradius scale …

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