ROBUSTLY UNSTABLE EIGENMODESOF THE MAGNETOSHEARING INSTABILITY IN ACCRETION DISK

松元, 亮治

Matsumoto, Ryōji

The stability of nonaxisymmetric perturbations in dierentially rotating astrophysical accretion disksis analyzed by fully incorporating the properties of shear flows. We verify the presence of discrete unstableeigenmodes with complex and pure imaginary eigenvalues, without any artificial disk edge boundaries,unlike Ogilvie & Pringle(1996)'s claim. By developing the mathematical theory of a non-self-adjointsystem, we investigate the nonlocal behavior of eigenmodes in the vicinity of Alfv´en singularities at!D = ±!A, where !D is the Doppler-shifted wave frequency and !A = kkvA is the Alfv´en frequency.The structure of the spectrum of discrete eigenmodes is discussed and the magnetic field and wavenumberdependence of the growth rate are obtained. Exponentially growing modes are present even in a regionwhere the local dispersion relation theory claims to have stable eigenvalues. The velocity field created byan eigenmode is obtained, which explains the anomalous angular momentum transport in the nonlinearstage of this stability.

https://opac.ll.chiba-u.jp/da/curator/900020205/

https://opac.ll.chiba-u.jp/da/curator/900020205/matsumoto_0007246.pdf

プレプリント

publisher