Dynamics of the solar photosphere. I. Two-dimensional spectroscopy of mesoscale phenomena.

Details Dynamics of the solar photosphere. I. Two-dimensional spectroscopy of mesoscale phenomena. Dynamics of the solar photosphere. I. Two-dimensional spectroscopy of mesoscale phenomena.

Aug 1997

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997a%26a...324..704s&link_type=abstract

Astronomy and Astrophysics, v.324, p.704-712

Astronomy and Astrophysics

Astrophysics

42

Sun: Atmosphere, Granulation, Photosphere, Oscillations, Convection, Hydrodynamics

Scientific paper

We address the "mesogranulation" phenomenon by analyzing a spectral time series, taken at disk center with a two-dimensional spectroscopy device and covering a period of 4 hours. This tunable device was composed by a Fabry-Perot interferometer mounted in tandem with an Universal Birefringent Filter (UBF). We calculate spatial power spectra, spatio-temporal k-ω power, phase difference and coherence spectra at different low photospheric levels, in order to investigate the nature of the mesoscale phenomena. At the lowest levels, mesostructures appear as a part of an extended distribution of granular sizes without further distinction from granulation. Here, the plasma flows are driven by convection. On the other hand, a different mesoscale phenomenon emerges at levels as high as approximately 200-300km above τ_5000_=1, at medium spatial (k=~0.5...2Mm^-1^) and medium temporal (ν=~0.5...1mHz) frequencies. This phenomenon is distinct from convection by its non-convective phase difference values ({PHI}_v-I_=~-30°, {PHI}_v-v_<0°) and by its different propagation character (almost horizontal propagation). By these properties, the mesoscale phenomena in the higher photosphere can be identified as internal gravity waves in the solar atmosphere.

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