RAPID FLUCTUATIONS IN THE LOWER SOLAR ATMOSPHERE

The Rapid Oscillations in the Solar Atmosphere instrument reveals solar atmospheric fluctuations at high frequencies. Spectra of variations of the G-band intensity (I-G) and Ca II K-line intensity (I-K) show correlated fluctuations above white noise to frequencies beyond 300 mHz and 50 mHz, respectively. The noise-corrected G-band spectrum for f = 28-326 mHz shows a power law with exponent -1.21 +/- 0.02, consistent with the presence of turbulent motions. G-band spectral power in the 25-100 mHz (UHF) range is concentrated at the locations of magnetic bright points in the intergranular lanes and is highly intermittent in time. The intermittence of the UHF G-band fluctuations, shown by a positive kurtosis kappa, also suggests turbulence. Combining values of I-G, I-K, UHF power, and kappa reveals two distinct states of the solar atmosphere. State 1, including almost all the data, is characterized by low I-G, I-K, and UHF power and kappa approximate to 6. State 2, including only a very small fraction of the data, is characterized by high I-G, I-K, and UHF power and kappa approximate to 3. Superposed epoch analysis shows that the UHF power peaks simultaneously with spatio-temporal I-G maxima in either state. For State 1, I-K shows 3.5 minute chromospheric oscillations with maxima occurring 21 s after I-G maxima implying a 150-210 km effective height difference. However, for State 2 the I-K and I-G maxima are simultaneous; in this highly magnetized environment sites of G-band and K-line emission may be spatially close together.