Solar magneto-atmospheric waves. Interim report

Technical Report · Mon Nov 17 04:00:00 EST 1975

OSTI ID:7075431

Thomas, J H; Nye, A H; Clark, A Jr

The linearized theory of magneto-atmospheric waves (involving the combined restoring forces due to buoyancy, compressibility, and magnetic field) is developed for the case of a horizontal magnetic field which may vary with height. The convective stability of the basic atmosphere is considered, and it is shown that a nonuniform horizontal magnetic field may be destabilizing as well as stabilizing. A detailed model of a sunspot penumbra is studied in order to identify the mode of running penumbral waves. It is found that penumbral waves may be identified with magneto-atmospheric waves of the plus type that are vertically trapped at photospheric levels. An exact analytical solution for magneto-atmospheric wave modes is found in the case of an isothermal atmosphere permeated by a uniform horizontal magnetic field, without making the usual short-wavelength approximation. This solution is applied to an idealized model of the low-corona-chromosphere transition region as a model for flare-induced coronal waves. The exact solution mentioned above is also used in conjunction with a simple two-layer model of a sunspot penumbra to study further the mode of running penumbral waves. The lowest plus eigenmode of the model is in good agreement with observations of penumbral waves.

• Research Organization: Rochester Univ., N.Y. (USA). Dept. of Mechanical and Aerospace Sciences
• OSTI ID: 7075431
• Report Number(s): AD-A-046291
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHROMOSPHERE
COMPRESSIBILITY
CONVECTIVE INSTABILITIES
HYDROMAGNETIC WAVES
INSTABILITY
MAGNETIC FIELDS
MECHANICAL PROPERTIES
PLASMA INSTABILITY
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR CORONA
SUNSPOTS
WAVE PROPAGATION