T. Amari et al., Three-dimensional solutions of magnetohydrodynamic equations for prominence magnetic support: Twisted magnetic flux rope, ASTROPHYS J, 518(1), 1999, pp. L57-L60
The search for a background magnetic configuration favorable for prominence
support has been given a great deal of attention for several decades. The
most recent theoretical studies seem to agree that a promising candidate fo
r the support of the dense and cooler prominence material, which fulfills s
everal of the theoretical and observational requirements such as twist, she
ar along the neutral line, and dips, is a magnetic flux rope. The most conv
incing models take an infinitely long periodic configuration that consists
of a linear constant-alpha force-free magnetic field. These models, however
, assume values of a that are close to its maximum possible value. In this
Letter, we report our recent results, which show that it is indeed possible
to produce a configuration that consists of a twisted magnetic flux tube e
mbedded in an overlaying, almost potential, arcade such that high electric
currents (and therefore values of alpha) are confined to the inner twisted
magnetic flux rope. We present two MHD processes-corresponding to two diffe
rent types of boundary conditions-that produce such a configuration. Our re
sults show that the process associated variations of B-z at the photospheri
c level by applying an electric field involving diffusion is much more effi
cient for creating a structure with more twist and dips.