Waveform produced by a collapsing magnetic field

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SUMMARY

The discussion centers on the electromagnetic (EM) radiation produced by an electron that instantaneously stops, leading to a collapse of its magnetic field. Participants reference the Lienard-Wiechert potentials and Dirac delta functions to analyze the implications of infinite acceleration and its effects on the emitted radiation. The conversation highlights the complexities of calculating the resulting waveform, emphasizing that the radiation field is intricately linked to the electron's abrupt deceleration and the resultant energy distribution. Key insights include the necessity of considering finite acceleration to avoid oversimplification and the importance of Fourier analysis in understanding the emitted radiation spectrum.

PREREQUISITES
  • Understanding of Lienard-Wiechert potentials
  • Familiarity with electromagnetic wave theory
  • Knowledge of Dirac delta functions in physics
  • Basic principles of special relativity and acceleration
NEXT STEPS
  • Study the Lienard-Wiechert potentials in detail
  • Learn about the implications of Dirac delta functions in electromagnetic theory
  • Explore Fourier analysis techniques for waveforms
  • Investigate the effects of finite acceleration on radiation emission
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Physicists, electrical engineers, and students studying electromagnetic theory, particularly those interested in radiation from charged particles and relativistic effects.

  • #31
Wow o_O

To try to begin to understand your method I drew a picture, I wondered if it agrees with what you had in mind (or whether it's completely off :wink:)? The red line is the worldline of the charge, and at ##t' = 0##, its 4-velocity is parallel to the ##t'## axis, so the charge is instantaneously at rest at this time in ##S'##. Also, the vector ##R## joining this event to ##E## is null, and thus parallel to the yellow lightcones.

1609627805563.png

How does that look?
 
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  • #32
That's it. Thanks - I was planning to draw a Minkowski diagram myself, but got side-tracked with the simplification stuff.

Looking at that, I wonder if I've got the wrong sign on my solution for ##v##, since it should be negative. I'll have a look tomorrow.
 
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  • #33
Constant proper acceleration is also among the more complicated examples. Even Pauli got it wrong (not so Sommerfeld, but this has been overlooked for some time). I think the resolution of the paradox that apparently there seems to be no radiation is given by Griffiths in

https://arxiv.org/abs/1405.7729
https://aapt.scitation.org/doi/10.1119/1.4875195
https://doi.org/10.1119/1.4906577 (Erratum)

Also in this case there are singular contributions to the fields, because the speed of the particle goes asymptotically to ##c##, and these conributions solve the problem.
 

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