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Rapid Fluctuations in the Lower Solar Atmosphere  

John K Lawrence   Submitted: 2011-11-23 16:01

The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument revealssolar atmospheric fluctuations at high frequencies. Spectra of variations ofthe G-band intensity (IG) and CaII K-line intensity (IK) show correlatedfluctuations above white noise to frequencies beyond 300 mHz and 50 mHz,respectively. The noise-corrected G-band spectrum for f = 28 - 326 mHz shows apower law with exponent -1.21 pm, 0.02, consistent with the presence ofturbulent motions. G-band spectral power in the 25 - 100 mHz ('UHF') range isconcentrated at the locations of magnetic bright points in the intergranularlanes and is highly intermittent in time. The intermittence of the UHF G-bandfluctuations, shown by a positive kurtosis {kappa}, also suggests turbulence.Combining values of IG, IK, UHF power, and {kappa}, reveals two distinctstates of the solar atmosphere. State 1, including almost all the data, ischaracterized by low IG, IK, and UHF power and {kappa} approx 6. State 2,including only a very small fraction of the data, is characterized by high IG,IK, and UHF power and {kappa} approx 3. Superposed epoch analysis shows thatthe UHF power peaks simultaneously with spatio-temporal IG maxima in eitherstate. For State 1, IK shows 3.5 min chromospheric oscillations with maximaoccurring 21 s after IG maxima implying a 150 - 210 km effective heightdifference. However, for State 2 the IK and IG maxima are simultaneous; in thishighly magnetized environment sites of G-band and K-line emission may bespatially close together.

Authors: J.K. Lawrence, A.C. Cadavid, D.J. Christian, D.B. Jess and M. Mathioudakis
Projects: National Solar Observatory (Sac Peak)

Publication Status: 2011 ApJ, 743, L24
Last Modified: 2011-11-24 02:52
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