Non-Equilibrium Transitions of Heliospheric plasma

Recent advances in Space Physics theory have established the connection between non-extensive Statistical Mechanics and space plasmas by providing a theoretical basis for the empirically derived kappa distributions commonly used to describe the phase space distribution functions of these systems [1]. The non-equilibrium temperature and the kappa index that govern these distributions are the two independent controlling parameters of non-equilibrium systems [1-3]. The significance of the kappa index is primarily given by its role in identifying the non-equilibrium stationary states, and measuring their "thermodynamic distance" from thermal equilibrium [4], while its physical meaning is connected to the correlation between the system's particles [5]. For example, analysis of the IBEX high Energetic Neutral Atom spectra [6] showed that the vast majority of measured kappa indices are between ~1.5 and ~2.5, consistent with the far-equilibrium "cavity" of minimum entropy discovered by Livadiotis & McComas [2]. Spontaneous procedures that can increase the entropy, move the system gradually toward equilibrium, that is the state with the maximum (infinite) kappa index. Other external factors that may decrease the entropy, move the system back to states further from equilibrium where the kappa indices are smaller. Newly formed pick-up ions can play this critical role in the solar wind and other space plasmas. We have analytically shown that their highly ordered motion can reduce the average entropy in the plasma beyond the termination shock, inside the inner heliosheath [7]. Non-equilibrium transitions have a key role in understanding the governing thermodynamical processes of space plasmas. References 1. Livadiotis, G., & McComas, D. J. 2009, JGR, 114, 11105. 2. Livadiotis, G., & McComas, D. J. 2010a, ApJ, 714, 971. 3. Livadiotis, G., & McComas, D. J. 2010c, in AIP Conf. Proc. 9, Pickup Ions Throughout the Heliosphere and Beyond, ed. J. LeRoux, V. Florinski, G. P. Zank, & A. Coates (Melville, NY: AIP), 70. 4. Livadiotis, G., & McComas, D. J. 2010b, PhyS, 82, 035003. 5. Livadiotis, G., & McComas, D. J. 2011, ApJ, Invariant kappa distribution in space plasmas out of equilibrium, in press. 6. Livadiotis, G., McComas, D. J., Dayeh, M. A., Funsten, H. O., Schwadron, N. A. 2011, ApJ.., 734, 1. 7. Livadiotis, G., & McComas, D. J. 2011, ApJ, The influence of pick-up ions on space plasma distributions, in press.