Investigation on the Possible Coupling Between Coronal Variability and Photospheric Dynamics

Details Investigation on the Possible Coupling Between Coronal Variability and Photospheric Dynamics Investigation on the Possible Coupling Between Coronal Variability and Photospheric Dynamics

Dec 2008

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufmsh41a1601a&link_type=abstract

American Geophysical Union, Fall Meeting 2008, abstract #SH41A-1601

Physics

2164 Solar Wind Plasma, 7509 Corona, 7549 Ultraviolet Emissions, 7811 Discontinuities (2109), 7863 Turbulence (4490)

Scientific paper

Density fluctuations are observed with the Ultraviolet Coronagraph Spectrometer - UVCS - operating onboard the SOHO spacecraft in the solar corona plasma of the regions of the low-latitude streamers and where the slow solar wind is accelerated. The results of the Fourier analysis, performed on solar minimum data, show that the coronal density fluctuations are dominated by discontinuities with a minimum temporal scale consistent with the lifetime of the photospheric supergranulation cells, thus suggesting a possible coupling of the variability of the solar corona and the dynamics of photospheric supergranulation. The spectral power derived on the basis of a Fourier analysis decreases with frequency as ν-2 from 10 to 100 μ Hz, in the frequency range where the supergranular motions mainly contribute to the photospheric intensity background, as observed for instance with VIRGO/SOHO. The fit of the low-frequency coronal spectra, performed according to the Harvey (1985) approach, yields a time constant of about 9×104 s, consistent with the time scales of the supergranulation regime in the solar noise. Furthermore, the degree of persistency of the density variations observed in the outer corona, derived by applying the Hurst analysis, is consistent with that inferred by Nesis et al. (1994), who investigated the dynamics of the solar granulation, by analyzing the photospheric intensity oscillations. The present results thus imply that the processes underlying the photospheric dynamics and coronal variability show common characteristics.

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