Eccentric geomagnetic dipole potential

Winch, D. E.

doi:10.1016/0032-0633(68)90137-2

Cited by 3 publications

(1 citation statement)

References 12 publications

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“…An asymmetric photospheric field also affects the largescale structure of the solar coronal magnetic field. We have investigated this by computing the potential-field source-surface (PFSS) model of the coronal field (Wang & Sheeley, 1992) between the solar surface and the coronal source surface at 2.5 solar radii, using the magnetic field of the two-dipole model as an inner boundary condition. The coronal magnetic field corresponding to the average two-dipole model for the three minima is depicted in Figure 5, where we have also included the MWO photospheric field observed during Carrington rotation 1910 in year 1996, as a typical example of photospheric magnetic field distribution during solar minimum.…”

Section: Introductionmentioning

confidence: 99%

Two-dipole model of the asymmetric Sun

Zieger

Мурсула

2020

J. Space Weather Space Clim.

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The large-scale photospheric magnetic field is commonly thought to be mainly dipolar during sunspot minima, when magnetic fields of opposite polarity cover the solar poles. However, recent studies show that the octupole harmonics contribute comparably to the spatial power of the photospheric field at these times. Also, the even harmonics are non-zero, indicating that the Sun is hemispherically asymmetric with systematically stronger fields in the south during solar minima. We present here an analytical model of two eccentric axial dipoles of different strength, which is physically motivated by the dipole moments produced by decaying active regions. With only four parameters, this model closely reproduces the observed large-scale photospheric field and all significant coefficients of its spherical harmonics expansion, including the even harmonics responsible for the solar hemispheric asymmetry. This two-dipole model of the photospheric magnetic field also explains the southward shift of the heliospheric current sheet observed during recent solar minima.

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Section: Introductionmentioning

confidence: 99%

Two-dipole model of the asymmetric Sun

Zieger

Мурсула

2020

J. Space Weather Space Clim.

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Eccentric dipole coefficients and magnetic centres

James

1970

Planetary and Space Science

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The geomagnetic eccentric dipole: facts and fallacies

Lowes

1994

Geophysical Journal International

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S U M M A R YThe geomagnetic field is sometimes approximated as that of a single dipole displaced from the geocentre, i.e. by an eccentric dipole. By investigating how the field can be represented exactly by a spherical harmonic (multipole) series at a displaced origin, it is shown how this eccentric dipole depends on the choice of criterion of best fit. In particular it is explained how, in some approximations, the 'best' eccentric dipole need not be parallel to, or have the same magnitude as, the geocentric dipole, despite the physical invariance of the true dipole moment to change of origin. Finally, the reader is warned about attempts to give physical significance to the position of the eccentric dipole.

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Eccentric geomagnetic dipole potential

Cited by 3 publications

References 12 publications

Two-dipole model of the asymmetric Sun

Two-dipole model of the asymmetric Sun

Eccentric dipole coefficients and magnetic centres

The geomagnetic eccentric dipole: facts and fallacies

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