Blandford-Znajek process as Alfvénic superradiance

Sousuke Noda, Yasusada Nambu, Takuma Tsukamoto, Masaaki Takahashi

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5 Citations (Scopus)


The superradiant scattering of Alfvén waves (Alfvénic superradiance) in a forcefree magnetosphere is discussed to reveal the relationship between the Blandford-Znajek (BZ) process and superradiance. For simplicity, we consider a four-dimensional rotating black string spacetime of which each z=const slice is a Banãdos-Teitelboim-Zanelli solution as an analogy of the equatorial plane of the Kerr spacetime. Then, it is confirmed that the condition for Alfvénic superradiance coincides with that for the BZ process, and the wave amplification can be very large due to a resonant scattering for some parameter sets of the wave frequency and the angular velocity of the magnetic field line. Moreover, by analysis of the Poynting flux, we first show that the BZ process can be interpreted as the long wavelength limit of Alfvénic superradiance.

Original languageEnglish
Article number023003
JournalPhysical Review D
Issue number2
Publication statusPublished - Jan 3 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)


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