How to Calculate the Magnetic and Electric Field

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Discussion Overview

The discussion focuses on calculating the magnetic and electric fields around celestial bodies such as the Sun and planets, exploring theoretical frameworks and real-world applications. It includes considerations of vector potentials and electric potentials, as well as specific challenges related to modeling these fields over time.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant requests a real-world example of calculating the magnetic and electric fields around the Sun or a planet, referencing specific equations for these fields.
  • Another participant notes that to use the provided equations, one must first determine the values of the vector potential, \(\vec{A}\), and the electric potential, \(\phi\).
  • A further contribution questions how to solve for \(\vec{A}\) and \(\phi\) for a planet or star modeled as a dipole or current loop, mentioning that the equations may only be valid every 11 years due to polarity reversals, and points out that Earth's magnetic North Pole is not fixed.
  • A participant shares a link to a paper titled "Mathematical Modeling of Earth’s Magnetic Field," which may provide additional context or methodologies.
  • Another participant inquires about a list of Gaussian coefficients from the IAGA and IGRF, indicating a need for historical data related to magnetic field modeling.
  • A later reply mentions a footnote regarding NASA's shutdown, which may affect access to certain resources or data.

Areas of Agreement / Disagreement

Participants express various viewpoints on the complexities of calculating magnetic and electric fields, with no consensus reached on specific methods or solutions. Multiple competing views remain regarding the modeling of these fields and the implications of polarity changes.

Contextual Notes

The discussion highlights limitations related to the assumptions necessary for modeling, the dependence on accurate definitions of vector and electric potentials, and the unresolved nature of certain mathematical steps in the calculations.

Who May Find This Useful

Researchers and students interested in astrophysics, geophysics, and electromagnetic theory may find this discussion relevant, particularly those exploring magnetic field modeling and its applications in celestial contexts.

Philosophaie
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Could someone show me a real world example of how to calculate the Magnetic and Electric Field around the Sun or a Planet.
\vec{B} = \nabla * \vec{A} = (B_x, B_y,B_z)
\vec{E} = -\nabla*\phi-\frac{\partial \vec{A}}{\partial t} = (E_x,E_y,E_z)
 
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For these equations you must first know the value of the vector potential, \vec{A}, and the electric potential, \phi.
 
How do you solve for ##\vec{A}## and ##\phi## for a planet or star acting like a dipole or current loop? For the sun the equations only are valid every 11 years or so because the polarity reverses. Also the Earth does not have a true North North Pole it is somewhere in Siberia.
 
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Does anyone know where there is a list by date of Gaussian coefficients from the IAGA and IGRF(more recent then 2000).
They look like this ##g^m_n## and ##h^m_n##
 
See footnote 2; but NASA is shutdown this week.
 

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