INVESTIGADORES
LOPEZ FUENTES Marcelo Claudio
artículos
Título:
The magnetic helicity budget of solar active regions from the photosphere to magnetic clouds
Autor/es:
C. H. MANDRINI; P. DÉMOULIN; L. VAN DRIEL-GESZTELYI; L. M. GREEN; M. C. LÓPEZ FUENTES
Revista:
ASTROPHYSICS AND SPACE SCIENCE
Editorial:
Kluwer Academic Publishers
Referencias:
Año: 2004 vol. 290 p. 319 - 344
ISSN:
0004-640X
Resumen:
We have analyzed the long-term evolution of two active regions (ARs)
from their emergence through their decay using observations from several
instruments on board SoHO (MDI, EIT and LASCO) and Yohkoh/SXT. We have
computed the evolution of the relative coronal magnetic helicity
combining data from MDI and SXT with a linear force-free model of the
coronal magnetic field. Next, we have computed the injection of helicity
by surface differential rotation using MDI magnetic maps. To estimate
the depletion of helicity we have counted all the CMEs of which these
ARs have been the source, and we have evaluated their magnetic helicity
assuming a one to one correspondence with magnetic clouds with an
average helicity contain. When these three values (variation of coronal
magnetic helicity, injection by differential rotation and ejection via
CMEs) are compared, we find that surface differential rotation is a
minor contributor to the helicity budget since CMEs carry away at least
10 times more helicity than the one differential rotation can provide.
Therefore, the magnetic helicity flux needed in the global balance
should come from localized photospheric motions that, at least
partially, reflect the emergence of twisted flux tubes. We estimate that
the total helicity carried away in CMEs can be provided by the
end-to-end helicity of the flux tubes forming these ARs. Therefore, we
conclude that most of the helicity ejected in CMEs is generated below
the photosphere and emerges with the magnetic flux.