The five-minute period oscillation in magnetically active regions

✍ Scribed by A. G. Michalitsanos

• Book ID: 104646929
• Publisher: Springer
• Year: 1973
• Tongue: English
• Weight: 804 KB
• Volume: 30
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00156172

✦ Synopsis

The magnetohydrodynamic frequency-wavelength relation, derived by McLellan and Winterberg (1968), has been evaluated for an isothermal atmosphere. In particular, the effect which an inclined magnetic field and a finite horizontal wavelength have on the critical sonic and internalgravity cut-off frequencies has been examined, in which it has been assumed that the magnetic field vector, wave vector, and gravity vector are coplanar. It is shown that the frequency band in which vertical wave propagation is impossible in the non-magnetic photosphere, becomes smaller when an inclined uniform magnetic field is introduced, and that low frequency magnetically coupled internalgravity waves do not propagate vertically if the horizontal wavelengths associated with this mode are greater than a critical wavelength which decreases with field strength.

It is also demonstrated that an inclined magnetic field will inhibit the resonance that occurs at the critical frequency cog in the non-magnetic atmosphere which is a result consistent with recent observations of the 'wiggly line structure' in active regions.