INVESTIGADORES
MANDRINI Cristina Hemilse
congresos y reuniones científicas
Título:
Helicity analysis for expanding magnetic clouds: a case study
Autor/es:
NAKWACKI, M.S.; DASSO, S.; MANDRINI, C.H.; DÉMOULIN, P.
Lugar:
Whistler, Canadá
Reunión:
Congreso; Solar Wind 11-SOHO 16; 2005
Resumen:
Magnetic Clouds (MCs) are the interplanetary counterpart
of coronal mass ejections (CMEs). They transport
to the interplanetary medium the magnetic flux and helicity
released in CMEs by the Sun. At 1 AU from the
Sun, MCs are generally modeled as static flux ropes, i.e.,
considering them as rigid bodies traveling through the
solar wind. However, the velocity profile of some MCs
presents clear signatures of a significant expansion while
observed in situ by a spacecraft in the heliosphere. We
present here an analysis of the magnetic structure of an
expanding magnetic cloud observed during the raising
phase of solar cycle 23 by the spacecraft Wind. We consider
a dynamical model, based on a self-similar behavior
for the cloud radial velocity. We assume a free expansion
for the cloud, and a cylindrical linear force free field (i.e.,
the Lundquists field) as the initial conditions for its magnetic
configuration. We derive theoretical expressions for
the magnetic flux, across a surface perpendicular to the
cloud axis, and for the magnetic helicity per unit length
along the tube using the self-similar model. Finally, we
compute these magnitudes fitting the free parameters of
the expanding model to in situ magnetic observations,
and compare them with those obtained from the linear
force free static model.