Free and forced oscillations of a flux tube

Abstract

view Abstract Citations (26) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Free and forced oscillations of a flux tube Wilson, P. R. Abstract The free oscillations of a magnetic flux tube of finite dimension, embedded in a nonmagnetic plasma, which may be in uniform motion relative to the tube, are studied for models in which energy may propagate laterally away from the tube. Although solutions obtained using the thin tube approximation yield both real and complex frequencies, the numerical solutions for effectively thick tubes all exhibit real frequencies and imaginary external wavenumbers. Thus the waves propagate parallel to e flux tube with constant amplitude and are evanescent in the transverse direction. The same general formulation permits the study of the oscillations set up by an oscillatory disturbance applied at a point on the axis of the tube. Here it is found that for weak or moderately intense tubes the wave amplitudes decrease along the tube away from the disturbance as wave energy leaks away from the tube in the transverse direction. Intense tubes, however, tend to focus the wave energy along the tube, and the wave amplitude increases away from the disturbance. It is suggested that this effect may be relevant for photospheric flux tubes. Publication: The Astrophysical Journal Pub Date: December 1981 DOI: 10.1086/159519 Bibcode: 1981ApJ...251..756W Keywords: Magnetic Flux; Magnetoplasmadynamics; Photosphere; Solar Oscillations; Sunspots; Forced Vibration; Free Vibration; Magnetohydrodynamic Flow; Oscillating Flow; Stellar Models; Wave Propagation; Astrophysics full text sources ADS |