Physics
Scientific paper
Sep 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aspc..184..136n&link_type=abstract
Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations, ASP Conference Series vol.184, p. 136-140. Eds
Physics
1
Mhd Waves, Magnetic Oscillations, Sunspots, Magnetic Fields
Scientific paper
We report on the spatial distribution of magnetic oscillatory power and phase angles between velocity and magnetic signals as observed with the Michelson Doppler Imager. The dataset is 151.25arcsec x 151.25arcsec containing sunspot from Dec 2, 1997 with a temporal sampling interval of 60 seconds and spatial sampling of 0.605arcsec. Simultaneously observed continuum intensity and surface velocity accompany the magnetic information. We focus on three frequency regimes: 0.5-1.0, 3.0-3.5 and 5.5-6.0 mHz corresponding roughly to timescales of magnetic evolution, p-modes and the 3 minute resonant sunspot oscillation. Significant low frequency magnetic power is found in lower flux pixels, 100-300 Gauss, in a striking ring with filamentary structure surrounding sunspot. Five minute oscillatory magnetic power peaks in extended regions of flux 600-800 Gauss. The 3 minute oscillation is observed in sunspot umbra in pixels whose flux measures 1300-1500 Gauss. Phase angles of -90° between velocity and magnetic flux in the 3.0-3.5 and 5.5-6.0 mHz regimes suggest the MHD oscillations are magnetoacoustic in nature.
Bush Rock I.
Norton Andrew
Tarbell Ted D.
Ulrich Richard K.
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