Comparison of the fisk magnetic field with the standard parker IMF: consequences for diffusion coefficients

Kobyliński, Zbigniew

doi:10.1016/s0273-1177(01)00098-9

Cited by 9 publications

(6 citation statements)

References 15 publications

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“…where tan É ¼ ÀB / B 2 r þ B 2 À Á 1/2 and tan ¼ B /B r . Note that Alania & Dzhapiashvili (1979), Alania (2002), and Kobylinski (2001) give a similar result, but with tan É ¼ ÀB /B r . The relevant angles are shown in Figure 6.…”

Section: Fisk-parker Hybridmentioning

confidence: 63%

“…Between this latitude and the one labeled II in the figure, one would expect a mixture of a region where footpoint motion occurs by means of diffusive reconnection, and another by means of ordered motion. The former leads to a Parker-type field, and the latter to a Fisk-type field ( Kobylinski 2001). At lower latitudes than the one labeled III, the field will be Parker-like.…”

Section: The Fisk-parker Hybrid Field: a Solar-cycle Dependent Approachmentioning

confidence: 91%

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A Fisk‐Parker Hybrid Heliospheric Magnetic Field with a Solar‐Cycle Dependence

Burger

Krüger

Hitge

et al. 2008

ApJ

112

126

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We present a refinement of the Fisk-Parker hybrid field of Burger and Hitge which now includes a region bordering the solar rotational equator where magnetic field footpoint motion occurs only through diffusive reconnection. The hybrid field, therefore, only occurs above a certain latitude in a given hemisphere, and in the equatorial region the field is a pure Parker field. We also propose a simple qualitative model for the solar cycle dependence of the hybrid field, taking into account changes in the tilt angle of the heliospheric current sheet and the latitudinal extend of the polar coronal hole on the photosphere and on the source surface over the course of a solar activity cycle. We find that the amplitude of magnetic field fluctuations for assumed solar minimum parameters would not be observable above the background noise (see Roberts and coworkers). We also show that for these parameters, periodicities associated with differential footpoint motion would be barely distinguishable from rigid rotation at the solar equatorial rate. We point out that the question of periodicities in magnetic field data is perhaps more complicated than previously thought. We confirm the result of Burger and Hitge that a Fisk-type heliospheric magnetic field provides a natural explanation for the observed linear relationship between the amplitude of the recurrent cosmic-ray variations and the global latitude gradient (see Zhang). We show that this relationship holds for helium, protons, and electrons. Moreover, we show that the constant of proportionality is larger when qA > 0 than when qA < 0, as inferred from observations by Richardson and coworkers.

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Section: Fisk-parker Hybridmentioning

confidence: 63%

Section: The Fisk-parker Hybrid Field: a Solar-cycle Dependent Approachmentioning

confidence: 91%

A Fisk‐Parker Hybrid Heliospheric Magnetic Field with a Solar‐Cycle Dependence

Burger

Krüger

Hitge

et al. 2008

ApJ

112

126

View full text Add to dashboard Cite

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“…formation from field-aligned to spherical coordinates (Alania & Dzhapiashvili 1979;Kobylinski 2001) yields the tensor used in equation 4.…”

Section: Modulation Modelmentioning

confidence: 99%

The Effect of a Fisk-Type Heliospheric Magnetic Field on Cosmic-Ray Modulation

Burger

Hitge

2004

ApJ

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The Fisk model of the heliospheric magnetic field (HMF) has proved to be quite difficult to implement in three-dimensional numerical modulation codes. We have developed a divergence-free Fisk-Parker hybrid HMF that is easier to implement and that should be a reasonable approximation for the case when field lines open into the heliosphere both in the polar coronal holes and at low latitudes. To study the effects of this hybrid field on galactic cosmic rays, we solve the three-dimensional steady state Parker transport equation numerically, covering the entire model heliosphere. We find that latitudinal cosmic-ray gradients are reduced as expected, but only during epochs when particles are drifting from the polar regions of the heliosphere toward the ecliptic plane. We investigate 26 day recurrent variations of both protons and electrons and find that the amplitude of these variations are directly proportional to the latitudinal intensity gradient, independent of species, in agreement with observational studies. In the absence of drifts in the code, electrons and protons obey different but still linear relationships.

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“…He was able to derive analytical expressions that generalize the Parker field correspondingly. Subsequent analytical investigations [Zurbuchen et al, 1997;Kobylinski, 2001;Schwadron, 2002;Schwadron et al, 2008] have quantified the complex structure of this so-called Fisk-field and its deviations from the Parker field, and numerical simulations have revealed that the original choice of parameters by Fisk [1996] represented an extreme, which has recently been confirmed via a study of the consequences of the Fisk-field for cosmic ray modulation [Sternal et al, 2011].…”

Section: Introductionmentioning

confidence: 98%

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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Comparison of the fisk magnetic field with the standard parker IMF: consequences for diffusion coefficients

Cited by 9 publications

References 15 publications

A Fisk‐Parker Hybrid Heliospheric Magnetic Field with a Solar‐Cycle Dependence

A Fisk‐Parker Hybrid Heliospheric Magnetic Field with a Solar‐Cycle Dependence

The Effect of a Fisk-Type Heliospheric Magnetic Field on Cosmic-Ray Modulation

MHD simulation of the inner‐heliospheric magnetic field

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