FORMATION OF THE PENUMBRA AND START OF THE EVERSHED FLOW

ABSTRACT We studied the variations of line of sight photospheric plasma flows during the formation phase of the penumbra around a pore in active region NOAA 11490. We used a high spatial, spectral, and temporal resolution data set acquired by the Interferometric BIdimensional Spectrometer operating...

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Bibliographic Details
Published in:The Astrophysical journal 2016-07, Vol.825 (1), p.75-75
Main Authors: Murabito, M., Romano, P., Guglielmino, S. L., Zuccarello, F., Solanki, S. K.
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CHROMOSPHERE
Formations
GALAXIES
INCLINATION
MAGNETIC FIELDS
MAGNETIC FLUX
NOAA
Penumbras
PHOTOSPHERE
PLASMA
Porosity
RED SHIFT
RESOLUTION
SATELLITES
Solar observatories
SPECTROMETERS
SUN
Sun: chromosphere
Sun: magnetic fields
Sun: photosphere
SUNSPOTS
SURFACES
TELESCOPES
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Summary:ABSTRACT We studied the variations of line of sight photospheric plasma flows during the formation phase of the penumbra around a pore in active region NOAA 11490. We used a high spatial, spectral, and temporal resolution data set acquired by the Interferometric BIdimensional Spectrometer operating at the NSO/Dunn Solar Telescope as well as data taken by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory satellite (SDO/HMI). Before the penumbra formed we observed a redshift of the spectral line in the inner part of the annular zone surrounding the pore as well as a blueshift of material associated with opposite magnetic polarity farther away from the pore. We found that the onset of the classical Evershed flow occurs on a very short timescale (1 to 3 hr) while the penumbra is forming. During the same time interval we found changes in the magnetic field inclination in the penumbra, with the vertical field actually changing sign near the penumbral edge, while the total magnetic field showed a significant increase, about 400 G. To explain these and other observations related to the formation of the penumbra and the onset of the Evershed flow we propose a scenario in which the penumbra is formed by magnetic flux dragged down from the canopy surrounding the initial pore. The Evershed flow starts when the sinking magnetic field dips below the solar surface and magnetoconvection sets in.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/825/1/75