Synchrotron radiation

Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity ( $a ⊥ v$ ). It is produced artificially in some types of particle accelerators or naturally by fast electrons moving through magnetic fields. The radiation produced in this way has a characteristic polarization, and the frequencies generated can range over a large portion of the electromagnetic spectrum.^[1]

Synchrotron radiation is similar to bremsstrahlung radiation, which is emitted by a charged particle when the acceleration is parallel to the direction of motion. The general term for radiation emitted by particles in a magnetic field is gyromagnetic radiation, for which synchrotron radiation is the ultra-relativistic special case. Radiation emitted by charged particles moving non-relativistically in a magnetic field is called cyclotron emission.^[2] For particles in the mildly relativistic range (≈85% of the speed of light), the emission is termed gyro-synchrotron radiation.^[3]

In astrophysics, synchrotron emission occurs, for instance, due to ultra-relativistic motion of a charged particle around a black hole.^[4] When the source follows a circular geodesic around the black hole, the synchrotron radiation occurs for orbits close to the photosphere where the motion is in the ultra-relativistic regime.

Synchrotron radiation from a bending magnet

^ "What is synchrotron radiation?". NIST. 2010-03-02.
^ Monreal, Benjamin (Jan 2016). "Single-electron cyclotron radiation". Physics Today. 69 (1): 70. Bibcode:2016PhT....69a..70M. doi:10.1063/pt.3.3060.
^ Chen, Bin. "Radiative processes from energetic particles II: Gyromagnetic radiation" (PDF). New Jersey Institute of Technology. Retrieved 10 December 2021.
^ Brito, João P. B.; Bernar, Rafael P.; Crispino, Luís C. B. (11 June 2020). "Synchrotron geodesic radiation in Schwarzschild–de Sitter spacetime". Physical Review D. 101 (12): 124019. arXiv:2006.08887. Bibcode:2020PhRvD.101l4019B. doi:10.1103/PhysRevD.101.124019. ISSN 2470-0010. S2CID 219708236.

[1] "What is synchrotron radiation?". NIST. 2010-03-02.

[2] Monreal, Benjamin (Jan 2016). "Single-electron cyclotron radiation". Physics Today. 69 (1): 70. Bibcode:2016PhT....69a..70M. doi:10.1063/pt.3.3060.

[3] Chen, Bin. "Radiative processes from energetic particles II: Gyromagnetic radiation" (PDF). New Jersey Institute of Technology. Retrieved 10 December 2021.

[4] Brito, João P. B.; Bernar, Rafael P.; Crispino, Luís C. B. (11 June 2020). "Synchrotron geodesic radiation in Schwarzschild–de Sitter spacetime". Physical Review D. 101 (12): 124019. arXiv:2006.08887. Bibcode:2020PhRvD.101l4019B. doi:10.1103/PhysRevD.101.124019. ISSN 2470-0010. S2CID 219708236.

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