 Publication Date:
 NSFPAR ID:
 10312802
 Journal Name:
 The Astrophysical Journal
 Volume:
 923
 Issue:
 2
 ISSN:
 0004637X
 Sponsoring Org:
 National Science Foundation
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A heat flux in a high $\unicode[STIX]{x1D6FD}$ plasma with low collisionality triggers the whistler instability. Quasilinear theory predicts saturation of the instability in a marginal state characterized by a heat flux that is fully controlled by electron scattering off magnetic perturbations. This marginal heat flux does not depend on the temperature gradient and scales as $1/\unicode[STIX]{x1D6FD}$ . We confirm this theoretical prediction by performing numerical particleincell simulations of the instability. We further calculate the saturation level of magnetic perturbations and the electron scattering rate as functions of $\unicode[STIX]{x1D6FD}$ and the temperature gradient to identify the saturation mechanism as quasilinear. Suppression of the heat flux is caused by oblique whistlers with magneticenergy density distributed over a wide range of propagation angles. This result can be applied to high $\unicode[STIX]{x1D6FD}$ astrophysical plasmas, such as the intracluster medium, where thermal conduction at sharp temperature gradients along magneticfield lines can be significantly suppressed. We provide a convenient expression for the amount of suppression of the heat flux relative to the classical Spitzer value as a function of the temperature gradient and $\unicode[STIX]{x1D6FD}$ . For a turbulent plasma, the additional independent suppression by the mirror instability is capable of producing large total suppression factors (severalmore »

In this study, we investigate and develop scaling laws as a function of external nondimensional control parameters for heat and momentum transport for nonrotating, slowly rotating and rapidly rotating turbulent convection systems, with the end goal of forging connections and bridging the various gaps between these regimes. Two perspectives are considered, one where turbulent convection is viewed from the standpoint of an applied temperature drop across the domain and the other with a viewpoint in terms of an applied heat flux. While a straightforward transformation exist between the two perspectives indicating equivalence, it is found the former provides a clear set of connections that bridge between the three regimes. Our generic convection scalings, based upon an InertialArchimedean balance, produce the classic diffusionfree scalings for the nonrotating limit (NRL) and the slowly rotating limit (SRL). This is characterized by a freefalling fluid parcel on the global scale possessing a thermal anomaly on par with the temperature drop across the domain. In the rapidly rotating limit (RRL), the generic convection scalings are based on a CoriolisInertialArchimedean (CIA) balance, along with a local fluctuatingmean advective temperature balance. This produces a scenario in which anisotropic fluid parcels attain a thermal wind velocity and wheremore »

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