Can the Axisymmetric Poisson Equation for Magnetostatics be Solved?

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SUMMARY

The discussion focuses on solving the axisymmetric Poisson equation for magnetostatics, specifically the equation \(\frac{1}{x}\frac{d}{dx} \left( x \frac{dy(x)}{dx} \right) = -C^2 y(x)\). Participants concluded that by rescaling variables, the equation can be transformed into a form resembling the zeroth order Bessel function differential equation. This transformation allows for the identification of solutions by adjusting the constant term \(C^2\) appropriately. The method discussed effectively simplifies the problem and provides a pathway to finding particular solutions.

PREREQUISITES
  • Understanding of differential equations, particularly second-order linear equations.
  • Familiarity with Bessel functions and their properties.
  • Knowledge of variable rescaling techniques in mathematical physics.
  • Basic concepts of magnetostatics and related equations.
NEXT STEPS
  • Study the properties and applications of Bessel functions, focusing on zeroth order solutions.
  • Explore variable rescaling methods in solving differential equations.
  • Investigate the physical implications of the axisymmetric Poisson equation in magnetostatics.
  • Learn about numerical methods for solving differential equations that do not have analytical solutions.
USEFUL FOR

Physicists, mathematicians, and engineers working on magnetostatics problems, particularly those dealing with differential equations and Bessel functions.

Wiemster
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For a magnetostatics problem I seek the solution to the following equation

\frac{1}{x}\frac{d}{dx} \left( x \frac{dy(x)}{dx} \right) = -C^2 y(x)

(C a real constant) or equivalently

x \frac{d^2 y(x)}{dx^2} + \frac{dy(x)}{dx} + C^2 x y(x)=0

It seems so simple, but finding a particular solution beats me...is this solvable?
 
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If you rescale variables to get rid of the C^2 it looks like you could get it into the form of the differential equation for a zeroth order Bessel function. The general equation for a Bessel function is:

x^2 \frac{d^2 y}{dx^2} + x \frac{dy}{dx} + (x^2 - \alpha^2)y = 0

So with alpha = 0, you could divide out an x (or equivalently mutliply your equation by one) and it matches your equation - you just need to scale out the constant. i.e., somehow you want to scale that last term such that C^2xy \rightarrow xy with the other terms remaining unchanged.
 
That's great! Thank you very much...works like a charm!
 

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