Gyrokinetics, as a reduced kinetic theory derived from adiabaticity, provides a general framework for the long-term dynamics of magnetized plasmas. While its validity limits are stated in terms of formal expansion parameters, more quantitative test of such is not widely mentioned even if it existed. Here we show, by detailed analyses of the Hamiltonian map with a test particle model, that gyrokinetic theory rests on the inherent nature of particle dynamics as a boundary layer problem. For low-frequency fluctuations, we demonstrate the existence of a frequency-independent threshold in the normalized amplitude, below which gyrokinetics is generally applicable. However, this threshold becomes sensitive to wave parameters in the high-frequency regime, which raises concerns about the generality of high-frequency gyrokinetic theory. Further analyses indicate that constructing a reduced kinetic equation based on superadiabaticity is not feasible. These findings contribute to a deeper understanding of the basic physics behind gyrokinetic theory.

Validity of gyrokinetic theory in magnetized plasmas

Zonca F.;
2024-01-01

Abstract

Gyrokinetics, as a reduced kinetic theory derived from adiabaticity, provides a general framework for the long-term dynamics of magnetized plasmas. While its validity limits are stated in terms of formal expansion parameters, more quantitative test of such is not widely mentioned even if it existed. Here we show, by detailed analyses of the Hamiltonian map with a test particle model, that gyrokinetic theory rests on the inherent nature of particle dynamics as a boundary layer problem. For low-frequency fluctuations, we demonstrate the existence of a frequency-independent threshold in the normalized amplitude, below which gyrokinetics is generally applicable. However, this threshold becomes sensitive to wave parameters in the high-frequency regime, which raises concerns about the generality of high-frequency gyrokinetic theory. Further analyses indicate that constructing a reduced kinetic equation based on superadiabaticity is not feasible. These findings contribute to a deeper understanding of the basic physics behind gyrokinetic theory.
File in questo prodotto:
File Dimensione Formato  
Validity of gyrokinetic theory in magnetized plasmas.pdf

accesso aperto

Tipologia: Versione Editoriale (PDF)
Licenza: Creative commons
Dimensione 3.83 MB
Formato Adobe PDF
3.83 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.12079/79287
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 1
social impact