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Dipole model of the Earth's magnetic field

About: Dipole model of the Earth's magnetic field is a research topic. Over the lifetime, 2756 publications have been published within this topic receiving 83021 citations.


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Journal ArticleDOI
TL;DR: In this paper, the authors present a review of the present observational picture of the magnetic field, which is needed to understand the problems of how to properly interpret the observations, and also include a brief review of how the Sun's magnetic field is measured.
Abstract: Solar activity is basically caused by the interaction between magnetic fields, solar rotation and convective motions. Detailed mapping of the Sun's rapidly varying magnetic field helps one to understand the mechanisms of solar activity. Observations in recent years have revealed unexpected and intriguing properties of solar magnetic fields, the explanation of which has become a challenge to plasma physicists. The review deals primarily with how the Sun's magnetic field is measured, but it also includes a brief review of the present observational picture of the magnetic field, which is needed to understand the problems of how to properly interpret the observations.

54 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method for consistent reconstruction of coronal magnetic field and the coronal density structure with the help of a newly developed optimization scheme, which can be used to solve the equations of magnetohydrostatics.
Abstract: We undertake a first attempt towards a consistent reconstruction of the coronal magnetic field and the coronal density structure. We consider a stationary solar corona which has to obey the equations of magnetohydrostatics. We solve these equations with help of a newly developed optimization scheme. As a first step we illustrate how tomographic information can be included into the reconstruction of coronal magnetic fields. In a second step we use coronal magnetic field infor- mation to improve the tomographic inversion process. As input the scheme requires magnetic field measurements on the photosphere from vector-magnetographs and the line-of-sight integrated den- sity distribution from coronagraphs. We test our codes with well-known analytic magnetohydrostatic equilibria and models. The program is planned for use within the STEREO mission. The solar magnetic field is an important quantity which couples the solar interior, the photosphere and the atmosphere. The quasi stationary coronal magnetic field configuration is an interesting and challenging topic on its own right. But even to understand basic processes like coronal mass ejections and flares it is important to understand the quiescent magnetic configuration out of which these dynamic phenomena arise. Unfortunately the coronal magnetic field cannot be measured di- rectly, but it has to be reconstructed from photospheric measurements. A magnetic field reconstruction of the solar corona has to be consistent with the observed spa- tial variation of the coronal plasma (density, pressure, temperature) often elongated along the magnetic field. Here we are mainly interested in long-living structures which are time- independent in first order. We also concentrate on closed magnetic configurations where a stationary plasma flow (solar wind) does not significantly contribute to the force balance. Such configurations are static equilibria and have to obey the magnetohydrostatic equations (MHS). As the magnetic field B and the density distribution N are physically closely related their model reconstruction should also be linked as much as possible. In this paper we attempt to show how this can be achieved. We propose variational principles which if they can be solved should give a consistent model for an isother-

54 citations

Journal ArticleDOI
TL;DR: In this article, the authors used multiple dipoles in 2.5D MPD simulations to increase the size of the mini-magnetosphere for only small increases in the magnitude of the total magnetic field.
Abstract: [1] Initial two-dimensional (2-D) MHD simulations indicated that mini-magnetospheres can form around magnetic anomalies on the surface of the Moon but required magnetic field strengths at 100 km above the surface an order of magnitude larger than in situ measurements. Modeling the lunar magnetic anomalies with multiple dipoles in 2.5-D MPD simulations inflates the size of the mini-magnetospheres for only small increases in the magnitude of the total magnetic field. Multiple dipoles increase the lateral distance over which solar wind plasma is held off the surface. This extended magnetic field geometry inflates the mini-magnetosphere by inhibiting fluid flow within the shock region. With multiple dipoles, a mini-magnetosphere will form with magnetic field magnitudes smaller than the lower limit for a single dipole. These results indicate that the higher order moments of the anomalous magnetic fields play a significant role in deflecting the solar wind and determining the size and shape of the mini-magnetosphere.

54 citations

Journal ArticleDOI
TL;DR: In this paper, the vector potential for a solenoidal magnetic field is calculated as the sum of a Laplacian part and a current-carrying part, where the only requirements are the divergence freeness of the L 1 and L 2 magnetic fields and the sameness of their normal field component on the bounding surface of the considered volume.
Abstract: To quantify changes of the solar coronal field connectivity during eruptive events, one can use magnetic helicity, which is a measure of the shear or twist of a current-carrying (non-potential) field. To find a physically meaningful quantity, a relative measure, giving the helicity of a current-carrying field with respect to a reference (potential) field, is often evaluated. This requires a knowledge of the three-dimensional vector potential. We present a method to calculate the vector potential for a solenoidal magnetic field as the sum of a Laplacian part and a current-carrying part. The only requirements are the divergence freeness of the Laplacian and current-carrying magnetic field and the sameness of their normal field component on the bounding surface of the considered volume.

54 citations

Journal ArticleDOI
TL;DR: Cosmic ray anisotropy direction during solar proton events compared with concurrent interplanetary magnetic field vector direction, using Pioneer 6 data as mentioned in this paper, using Pioneer data sets.
Abstract: Cosmic ray anisotropy direction during solar proton events compared with concurrent interplanetary magnetic field vector direction, using Pioneer 6 data

54 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202312
202220
20181
201751
201656
201546