We revisit the characteristics of stable, damped modes originating from the Landau damping by employing a discretized gyrokinetic Vlasov simulation and also eigenvalue analysis in an unsheared slab geometry. By comparing results between gyrokinetic simulation and an eigenvalue analysis, we found that there exists a critical collisionality βc⋆ at which the Case-van Kampen (CvK) modes are damped down to the analytically estimated Landau damping rate and an eigenmode consistent with Landau's theory emerges. Consequently, the recurrence phenomenon disappears so that the Landau damping can be properly reproduced. The critical collisionality βc⋆ depends on the resolution in velocity space; i.e., a higher (lower) resolution requires a lower (higher) collisionality, while tends to zero (βc⋆→0) as Δv→0. It is found through a reduced model that even in the collisionless case with marginally stable CvK modes, the linear mode coupling between unstable and stable/damped components through a tertiary mode and the resultant energy transfer can be properly calculated such that the stable/damped mode persists as an eigenstate.

We propose an innovative temperature control technology wherein a heat capacity change upon lock and key binding is applied. A proof-of-principle calculation is performed using a three-dimensional integral equation theory of a statistical mechanics of fluid (Ornstein-Zernike theory coupled by HNC closure). Logical correctness of the temperature control technology is verified by this calculation. The performance of the heat pump is discussed. In addition, a more effective condition of the heat pump is also discussed to improve the performance.Currently, variety of temperature control (heating and cooling) technologies exist: vapor compression heat pump [1,2], adsorption refrigerating cycle [3,4], adiabatic demagnetization [5,6], magnetocaloric effect [7,8], and laser cooling [9,10], etc. These technologies are applied as air conditioners or experimental apparatuses. Recently, biological functions are drawn upon in some science areas to create new technologies. For example, water purification and drug synthesis make use of biological functions. In this study, we propose an innovative temperature control technology by drawing upon lock and key principle, a one of biological functions. The proposed temperature control technology is a newly proposed heat pump system which utilizes the heat capacity change upon lock and key binding. A proof-of-principle calculation is performed by using a three-dimensional integral equation theory [11][12][13][14] of a statistical mechanics of fluid. Logical correctness of the temperature control technology (the heat pump) is verified by the calculation. The performance of the heat pump is the one of the most considerable things. Therefore, the performance of the heat pump is discussed. In addition, a more effective condition of the heat pump is also discussed to improve the performance.We illustrate the newly proposed heat pump system in Fig. 1. Fig. 1(a) shows a schematic of the heat pump system. There, small spheres forming the solvent exist in the box. The solvent is a sim-*

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Kinetic damping in linear gyrokinetic (GK) Vlasov simulations is found to exhibit a bifurcation at the collisionality β c = β c , above which, i.e. β c > β c , the damping is represented by a Landau eigenmode in velocity space, while below which, i.e. β c < β c , by the phase mixing of a finite number of marginally stable, discretized Case-van Kampen eigenmodes. The latter causes a recurrence that restricts the damping and then the energy transfer from wave to particles within a finite recurrence time. In order to address whether the stabilization effect due to such stable damped modes on unstable modes via mode coupling can be evaluated in long timescale GK simulations, we introduced a triad model consisting of stable and unstable modes incorporated with a tertiary vortex flow. We identified β c numerically and found that the stabilization effect works properly beyond the recurrence time even in the phase mixing regime across β c = β c . In plasma turbulence, stable modes play an important role in absorbing fluctuating free energy as a sink, which leads to saturation. Such a phenomenon commonly exists in various linear and nonlinear mode coupling processes. For example, nonlinear energy cascades occur through a three-wave coupling in drift wave turbulence. On the other hand, the unstable ion temperature gradient (ITG) mode is suppressed by the linear mode coupling produced by an externally imposed static vortex flow or magnetic island, forming a global ITG structure with the same growth rates and frequencies [1]. Mode coupling mediates the underlying suppression mechanisms of unstable modes by the dissipation effect of stable modes. Such stable modes originate from various damping processes. They are characterized by collisional (viscous) damping in a fluid model while they result from Landau damping and the so-called finite Larmor radius (FLR) effects in the kinetic system. Hence, Landau damping is crucial in energy transfer processes because it predominantly affects the fluctuation dynamics in both linear and nonlinear regimes.However, in collisionless gyrokinetic (GK) simulations, Landau damping exhibits different time evolutions depending on the choice of the initial distribution in velocity space due to the appearance of marginally stable Case-van Kampen (CvK) eigenmodes in the discretized velocity space. Namely, we observe a marginal behavior with neither growth nor damping for a random noise distribution. On the other hand, a damping accompanied by the recurrence phenomenon occurs for the Maxwellian author's e-mail: paul@center.iae.kyoto-u.ac.jp distribution [2], where damping is terminated within a finite time determined by the mesh size v. Consequently, the damping rate averaged over a timescale longer than the recurrence time becomes zero. Such damping with recurrence has been found to result not from Landau damping as a discrete eigenmode but from the phase mixing of a finite number of CvK eigenmodes. This is in contrast to the unstable ITG mode, which is always found to be an eigenmode of the GK Vla...

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