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Streaming Magnetic Features near Sunspots

Published online by Cambridge University Press:  14 August 2015

Dale Vrabec
Dale Vrabec*
Affiliation:
San Fernando Observatory and Space Physics Laboratory, The Aerospace Corporation, Los Angeles, Calif., U.S.A.

Abstract

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Observations prompted by Sheeley's discovery of outflowing CN bright points from sunspots have established that there occur small moving magnetic features (MMF's) near sunspots. These MMF's exhibit a highly ordered pattern of movement directly related to the associated sunspot. The observations are consistent with the concept of magnetic flux outflow (MFO), a process whereby net magnetic flux of the same polarity as the sunspot is transferred from a decaying sunspot to the surrounding magnetic network. Small magnetic flux concentrations are apparently convected outward by a velocity cell centered on the sunspot. Doppler spectroheliograms have provided evidence for such systematic outward velocities extending as far as 10000 to 20000 km beyond the outer edge of the penumbra of some sunspots, which is comparable to the extent of MFO. While MFO is best observed by means of time-lapse movies of the magnetic fields, it is also manifested morphologically on individual magnetograms by features that resemble moats (or bays) and wreaths around only those sunspots where MFO is present. Two examples of magnetic features streaming toward and into rapidly forming sunspots are described, providing evidence for the occurrence of magnetic flux inflow (MFI) associated with the growth phase of sunspot development. It is, therefore, likely that MFI and MFO are basic aspects of the evolutionary development of sunspots. Observational and instrumental aspects relevant to the investigation of MMF's are described in the Appendix.

Type
Part VI: Evolution of Chromospheric Fine Structures
Information
Symposium - International Astronomical Union , Volume 56: Chromospheric Fine Structure , 1974 , pp. 201 - 231
Copyright
Copyright © Reidel 1974 

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