Magnetoatmospheric oscillations in sunspot umbrae

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/169566· OSTI ID:6159668

Hasan, S S ^[1]

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1. Indian Institute of Astrophysics, Bangalore (India)

The nature of umbral oscillations is investigated using an empirical model for the sunspot umbra, based on the model of Maltby et al. (1986). Approximating the sunspot as a thick flux tube of circular cross section, the axisymmetric normal modes of magnetoatmospheric waves were determined, and a diagnostic diagram was generated for different field strengths. The diagram shows the existence of avoided crossings in the solution of magnetoatmospheric modes in a sunspot atmosphere. It was found that, for low values of the radial wavenumber k, corresponding to observed oscillations, a simple global classification is not possible. The oscillations in the low photosphere and below are of either fast or mixed type, but tend to acquire a slow or acoustic character above the temperature minimum. 61 refs.

• OSTI ID: 6159668
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 366; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
ENERGY
HYDROMAGNETIC WAVES
KINETIC ENERGY
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETOACOUSTIC WAVES
MATHEMATICAL MODELS
OSCILLATIONS
PHOTOSPHERE
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STAR MODELS
STARSPOTS
STELLAR ACTIVITY
SUNSPOTS