Is mesogranulation a distinct regime of convection?

Details Is mesogranulation a distinct regime of convection? Is mesogranulation a distinct regime of convection?

Mar 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992a%26a...256..652s&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 256, no. 2, p. 652-659.

Astronomy and Astrophysics

Astronomy

32

Solar Convection (Astronomy), Solar Granulation, Fourier Transformation, Photosphere, Power Spectra, Solar Atmosphere, Time Series Analysis, Wave Propagation

Scientific paper

We investigate the dynamics of the mesogranulation phenomenon by analyzing spatially 2D spectral time series taken at disk center and cos Theta = 0.8. After a 3D Fourier transformation, we integrate the power and crosspower spectra in azimuth, and calculate k - omega power, phase difference, and cross-power spectra. The spatial power spectra are compared with those obtained from numerical simulations of stationary cell patterns. In the deepest atmospheric layers the V - I phase difference spectra reveal a uniform regime of convective motions at frequencies below the Lamb mode. The power spectra exhibit at all levels a significant distinction between supergranulation and convective patterns of smaller scales. On the other hand, the 'mesogranulation' phenomenon cannot be identified as an independent convective regime in the deep photosphere, distinct from granulation. Rather, the mesostructures that appear to emerge in the middle photosphere and temperature minimum seem to be a product of the overshoot driving only the largest elements of an extended distribution of granular sizes while the smaller elements have already died out at a lower level.

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