Unified Alfven Wave Turbulence Based Model for Energy and Particle Transport in Solar Corona and Heliosphere

Abstract

The existing Alfven Wave Turbulence Based Solar Atmosphere Model (AWSoM) as used in the SWMF framework of the University of Michigan to simulate the Solar Corona and Inner Heliosphere (i.e. to 1 AU heliocentric distance) meets an ideological problem while compared with the equations for turbulence usually employed in modeling the outer heliosphere (i.e. beyond 1 AU). While for the turbulence in the outer heliosphere the energy difference (the difference between the averaged kinetic and magnetic energy densities) is used as one of the Reynolds-averaged quantity describing the local state of turbulence, the present AWSoM model lacks the energy difference at all.  Besides an evident inconsistency between the models of turbulence, employing the different sets of variables below and beyond 1 AU, to have a full description of turbulence is important by two reasons, both relating to the charged particle transport producing the radiation hazards in space. First, for simulation both solar energetic particle and galactic cosmic rays at 1 AU a computational domain should extend at least to 2-3 AU. Second, even if below 1 AU the energy difference effect on turbulence might be negligible and not necessary to be included into the turbulence model, it is still needed to calculate transport coefficients for the high energy charged particles in the turbulent magnetic field. To evaluate it from the averaged quantities characterizing the turbulence, both the total energy density and the said energy difference are needed.  In the presented research, an extra equation for the energy difference in introduced and solved in such way that at small heliocentric distances the turbulence model reduces to that used in the AWSoM with no loss in generality. On the other hand at larger heliocentric distances it becomes very close (if not identical) to the typical outer heliosphere model. In addition to averaged energetic characteristics of turbulence we evaluate the correlation spatial scales for directions parallel and perpendicular to the averaged interplanetary magnetic field was well as the transport coefficients for high-energy charged particles