Sunspot umbral oscillations in the photosphere and low chromosphere

Journal Article · Mon Jul 15 04:00:00 EDT 1985 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/163338· OSTI ID:5266177

Lites, B W; Thomas, J H

Velocity oscillations in sunspot umbrae were measured simultaneously in two spectral lines, one formed in the low photosphere and the other formed in the low chromosphere, just above the temperature minimum. The power spectrum of velocity in each spectral line shows the presence of both 5 minute and 3 minute oscillations. The coherence spectrum and phase spectrum between the velocities in the two lines show that the 3 minute umbral oscillation has the character of a coherent, vertically standing wave in the photosphere. Also, the kinetic energy density of the 3 minute oscillation is found to be at least 5 times greater in the low photosphere than in the low chromosphere. These results indicate that the fundamental 3 minute umbral oscillation is caused by a photospheric resonance rather than a chromospheric resonance. Multiple peaks in the power spectrum of chromospheric velocity at periods near 3 minutes may be caused by the additional effect of a chromospheric resonance. The umbral 5 minute oscillations are coherent between the two heights, with a small, positive phase difference between the low photosphere and low chromosphere, much the same as in the quiet Sun. A negative phase difference at frequencies around 2 mHz suggests the presence of gravity waves in the umbra.

• Research Organization: National Solar Observatory
• OSTI ID: 5266177
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 294:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CHROMOSPHERE
DATA
EXPERIMENTAL DATA
INFORMATION
MAIN SEQUENCE STARS
NUMERICAL DATA
OSCILLATIONS
PHOTOSPHERE
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SPECTRA
STARS
STARSPOTS
STELLAR ACTIVITY
SUN
SUNSPOTS
VELOCITY