Cosmic Ray Transport in Heliospheric Magnetic Structures. I. Modeling Background Solar Wind Using the Cronos Magnetohydrodynamic Code

Abstract

The transport of energetic particles such as Cosmic Rays is governed by the properties of the plasma being traversed. While these properties are rather poorly known for galactic and interstellar plasmas due to the lack of in situ measurements, the heliospheric plasma environment has been probed by spacecraft for decades and provides a unique opportunity for testing transport theories. Of particular interest for the 3D heliospheric transport of energetic particles are structures such as corotating interaction regions (CIRs), which, due to strongly enhanced magnetic field strengths, turbulence, and associated shocks, can act as diffusion barriers on the one hand, but also as accelerators of low energy CRs on the other hand as well. In a two-fold series of papers we investigate these effects by modeling inner-heliospheric solar wind conditions with a numerical magnetohydrodynamic (MHD) setup (this paper), which will serve as an input to a transport code employing a stochastic differential equation (SDE) approach (second paper). In this first paper we present results from 3D MHD simulations with our code CRONOS: for validation purposes we use analytic boundary conditions and compare with similar work by Pizzo. For a more realistic modeling of solar wind conditions, boundary conditions derived from synoptic magnetograms via the Wang-Sheeley-Arge (WSA) model are utilized, where the potential field modeling is performed with a finite-difference approach (FDIPS) in contrast to the traditional spherical harmonics expansion often utilized in the WSA model. Our results are validated by comparing with multi-spacecraft data for ecliptical (STEREO-A/B) and out-of-ecliptic (Ulysses) regions. Subject headings: magnetohydrodynamics (MHD) -shock waves -solar windmethods: numerical -Sun: heliosphere -Sun: magnetic fields

CESE‐HLL Magnetic Field‐Driven Modeling of the Background Solar Wind During Year 2008

“…At the same time, comparisons between simulated results and multipoint spacecraft data have also been implemented by a variety of studies. Some of these studies take advantage of special constellation of spacecraft to test a model's ability to reproduce certain phenomena (e.g., Broiles et al, ; Wiengarten et al, ). Other studies are aimed to generally assess model's validity beyond the L1 point, such as at the position of other planets (e.g., Shiota et al, ), inside the Earth's orbit (e.g., Pahud et al, ) and away from the ecliptic plane (e.g., Jian et al, ).…”

EUHFORIA: European heliospheric forecasting information asset

“…The quantity around which the empirical model is built is the solar wind speed v, and is obtained through a given function of the magnetic field properties: v = v(f, d). Several different forms for specifying the wind speed have been presented in the literature (e.g., Arge & Pizzo, 2000;Arge 2003;Riley et al, 2001;Owens et al, 2008;Detman et al, 2006;Wiengarten et al, 2014;McGregor et al, 2011).…”

Cosmic-Ray Transport in Heliospheric Magnetic Structures. II. Modeling Particle Transport through Corotating Interaction Regions

“…As pointed out in the first paper of this series (Wiengarten et al 2014, hereinafter Paper I), the understanding and appropriate modeling of the transport of energetic charged particles in turbulent magnetic fields remains one of the longstanding challenges in astrophysics and space physics. Despite the progress achieved during recent years (for recent reviews, see, e.g., Giacalone 2013;Schlickeiser 2015;Snodin et al 2016), the corresponding theories have not yet matured into a coherent, (self-)consistent, and generally accepted state.…”