Comparison of different analytic heliospheric magnetic field configurations and their significance for the particle injection at the termination shock

Scherer, K.; Fichtner, H.; Effenberger, Frederic; Burger, R. A.; Wiengarten, T.

doi:10.1051/0004-6361/200913638

Cited by 7 publications

(5 citation statements)

References 41 publications

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“…This is implemented by having the mass flux depend on the radial velocity by introducing a transition function f(v r ) [see Scherer et al, 2010] …”

Section: Remaining Mhd Quantitiesmentioning

confidence: 99%

“…[37] We introduced an improvement to be in agreement with Ulysses data [McComas et al, 2000], which showed for solar minimum conditions that the mass flux associated with high-speed streams is about half the one of low-speed streams. This is implemented by having the mass flux depend on the radial velocity by introducing a transition function f(v r ) [see Scherer et al, 2010] defined as…”

Section: Remaining Mhd Quantitiesmentioning

confidence: 99%

“…[4] Several authors have suggested modifications of both fields [Jokipii and Kota, 1989;Smith and Bieber, 1991;Schwadron, 2002;Burger and Hitge, 2004;Burger et al, 2008;Schwadron et al, 2008], which have been quantitatively compared in a study by Scherer et al [2010]. Although very useful for many purposes, these analytical representations of the HMF cannot be used to reproduce actual measurements in sufficient detail at any given time in the solar activity cycle.…”

Section: Introductionmentioning

confidence: 99%

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MHD simulation of the inner‐heliospheric magnetic field

et al. 2013

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[1] Maps of the radial magnetic field at a heliocentric distance of 10 solar radii are used as boundary conditions in the MHD code CRONOS to simulate a three-dimensional inner-heliospheric solar wind emanating from the rotating Sun out to 1 AU. The input data for the magnetic field are the result of solar surface flux transport modeling using observational data of sunspot groups coupled with a current-sheet source surface model. Among several advancements, this allows for higher angular resolution than that of comparable observational data from synoptic magnetograms. The required initial conditions for the other MHD quantities are obtained following an empirical approach using an inverse relation between flux tube expansion and radial solar wind speed. The computations are performed for representative solar minimum and maximum conditions, and the corresponding state of the solar wind up to the Earth's orbit is obtained. After a successful comparison of the latter with observational data, they can be used to drive outer-heliospheric models.

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“…This is implemented by having the mass flux depend on the radial velocity by introducing a transition function f(v r ) [see Scherer et al, 2010] …”

Section: Remaining Mhd Quantitiesmentioning

confidence: 99%

Section: Remaining Mhd Quantitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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MHD simulation of the inner‐heliospheric magnetic field

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“…In the case F s = 0 the HMF reduces to the standard Parker spiral magnetic field. For a quantitative comparison of different HMF configurations, see Scherer et al (2010).…”

Section: An Example For the New Diffusion Tensormentioning

confidence: 99%

A Generalized Diffusion Tensor for Fully Anisotropic Diffusion of Energetic Particles in the Heliospheric Magnetic Field

Effenberger

Fichtner

Scherer

et al. 2012

ApJ

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The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e. one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the transformation for the diffusion tensor from this local to a global frame, in which the Parker transport equation for energetic particles is usually formulated and solved. Particularly, we generalize the transformation formulas to allow for an explicit choice of two principal local perpendicular diffusion axes. This generalization includes the 'traditional' diffusion tensor in the special case of isotropic perpendicular diffusion. For the local frame, we motivate the choice of the Frenet-Serret trihedron which is related to the intrinsic magnetic field geometry. We directly compare the old and the new tensor elements for two heliospheric magnetic field configurations, namely the hybrid Fisk and the Parker field. Subsequently, we examine the significance of the different formulations for the diffusion tensor in a standard 3D model for the modulation of galactic protons. For this we utilize a numerical code to evaluate a system of stochastic differential equations equivalent to the Parker transport equation and present the resulting modulated spectra. The computed differential fluxes based on the new tensor formulation deviate from those obtained with the 'traditional' one (only valid for isotropic perpendicular diffusion) by up to 60% for energies below a few hundred MeV depending on heliocentric distance.

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“…When F S is equal to one, the HMF is most region the HMF is a Parker spiral, while the field structure r evident. For a comparison of the different HMF models, see the recent paper by Scherer et al (2010).…”

Section: The Heliospheric Magnetic Field Structure During Solar Minimummentioning

confidence: 99%

POSSIBLE EVIDENCE FOR A FISK-TYPE HELIOSPHERIC MAGNETIC FIELD. I. ANALYZINGULYSSES/KET ELECTRON OBSERVATIONS

Sternal¹,

Engelbrecht²,

Burger³

et al. 2011

ApJ

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The propagation of energetic charged particles in the heliospheric magnetic field is one of the fundamental problems in heliophysics. In particular, the structure of the heliospheric magnetic field remains an unsolved problem and is discussed as a controversial topic. The first successful analytic approach to the structure of the heliospheric magnetic field was the Parker field. However, the measurements of the Ulysses spacecraft at high latitudes revealed the possible need for refinements of the existing magnetic field model during solar minimum. Among other reasons, this led to the development of the Fisk field. This approach is highly debated and could not be ruled out with magnetic field measurements so far. A promising method to trace this magnetic field structure is to model the propagation of electrons in the energy range of a few MeV. Employing three-dimensional and time-dependent simulations of the propagation of energetic electrons, this work shows that the influence of a Fisk-type field on the particle transport in the heliosphere leads to characteristic variations of the electron intensities on the timescale of a solar rotation. For the first time it is shown that the Ulysses count rates of 2.5-7 MeV electrons contain the imprint of a Fisk-type heliospheric magnetic field structure. From a comparison of simulation results and the Ulysses count rates, realistic parameters for the Fisk theory are derived. Furthermore, these parameters are used to investigate the modeled relative amplitudes of protons and electrons, including the effects of drifts.

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Comparison of different analytic heliospheric magnetic field configurations and their significance for the particle injection at the termination shock

Cited by 7 publications

References 41 publications

MHD simulation of the inner‐heliospheric magnetic field

MHD simulation of the inner‐heliospheric magnetic field

A Generalized Diffusion Tensor for Fully Anisotropic Diffusion of Energetic Particles in the Heliospheric Magnetic Field

POSSIBLE EVIDENCE FOR A FISK-TYPE HELIOSPHERIC MAGNETIC FIELD. I. ANALYZINGULYSSES/KET ELECTRON OBSERVATIONS

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