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Title: Evolution of the magnetic field inclination in a forming penumbra

We describe the evolution of the magnetic and velocity fields in the annular zone around a pore a few hours before the formation of its penumbra. We detected the presence of several patches at the edge of the annular zone, with a typical size of about 1''. These patches are characterized by a rather vertical magnetic field with polarity opposite to that of the pore. They correspond to regions of plasma upflow up to 2.5 km s{sup –1} and are characterized by radially outward displacements with horizontal velocities up to 2 km s{sup –1}. We interpret these features as portions of the pore magnetic field lines returning beneath the photosphere being progressively stretched and pushed down by the overlying magnetic fields. Our results confirm that the penumbra formation results from changes in the inclination of the field lines in the magnetic canopy overlying the pore, until they reach the photosphere.
Authors:
 [1] ; ; ; ;  [2] ;  [3]
  1. INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania (Italy)
  2. Dipartimento di Fisica e Astronomia-Sezione Astrofisica, Università di Catania, Via S. Sofia 78, I-95123 Catania (Italy)
  3. INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (Italy)
Publication Date:
OSTI Identifier:
22351527
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 784; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; EVOLUTION; MAGNETIC FIELDS; PHOTOSPHERE; PLASMA; SUN; VELOCITY