Abstract
The turbulent thermal convection on the Sun is an example of an irreversible non-equilibrium phenomenon in a quasi-steady state characterized by a continuous entropy production rate. Here, the statistical features of a proxy of the local entropy production rate, in solar quiet regions at different timescales, are investigated and compared with the symmetry conjecture of the steady-state fluctuation theorem by Gallavotti and Cohen. Our results show that solar turbulent convection satisfies the symmetries predicted by the fluctuation relation of the Gallavotti and Cohen theorem at a local level.
Highlights
Non-equilibrium dynamical systems are quite ubiquitous in nature, and are due to non-conservative forces acting on open systems, which imply a continuous dissipation generally transferred to other systems in the form of heat
We have investigated the validity of the symmetries predicted by the Gallavotti–Cohen fluctuation relation for non-equilibrium systems in the case of the solar turbulent convection by studying the statistics of the local vertical heat flux at different timescales
We show that the probability density functions (PDFs) of the local vertical heat flux are clearly non-Gaussian, asymmetric and have a non-zero mean value, which confirms that there is a spontaneous production of entropy on the solar turbulent convection
Summary
Non-equilibrium dynamical systems are quite ubiquitous in nature, and are due to non-conservative forces acting on open systems, which imply a continuous dissipation generally transferred to other systems (thermostats) in the form of heat. Because the fluctuation relation of GC theorem (GCFR) deals with the statistical features of a variable related to the phase space contraction rate, it has been assumed to be valid in the case of flux quantities, J (e.g., heat, energy or momentum flux) [10]. In this case the FR can be equivalently written, as follows, π ( Jτ = J ). By using these observations, we can evaluate the vertical heat flux from the solar surface temperature and the vertical velocity and use it as a proxy of the entropy production rate, or more generally, the phase space contraction rate [5,13]
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