5 research outputs found
Measurements of magnetic fields in solar prominences
Magnetic fields can be measured, in solar prominences, by means of two different basic mechanisms that are responsible for the introduction (or the reduction) of a given amount of polarization in spectral lines: these are the Zeeman effect and the Hanle effect. Through the splitting of the magnetic components of a spectral line, the Zeeman effect is capable of introducing a certain amount of circular polarization across the line profile. The Hanle effect consist of a modification of the linear polarization that is induced in spectral lines by the anisotropic illumination of the prominence plasma by the photospheric radiation field. These two effects are briefly discussed
The modulation of SiO maser polarization by Jovian planets
Searching for planets in the atmosphere of AGB stars is difficult, due to
confusion with the stellar wind and pulsations. The aim here is to provide a
complementary strategy for planet search in such a dense environment. The
polarization properties of SiO masers, especially their circular polarization,
are, under certain conditions, good tracers for rapid magnetospheric events. A
Jovian planet with a magnetosphere whose dipole axis is misaligned with its
rotation axis, naturally provides such conditions. Here I present several
models showing that the polarization will be periodically modulated.
Single-dish monitoring with a sufficiently dense time sampling and a carefully
calibrated polarimeter, in combination with VLBI observations, are suited to
detect and locate a periodic modulation of the circular maser polarization due
to a precessing Jovian magnetosphere. The phenomenon will be rare, because a
favourable arrangement of maser and magnetosphere is needed, otherwise the
polarization may be below the detection threshold, especially if the maser is
unsaturated. Linear polarization, though exhibiting a qualitatively similar
modulation, is likely to suffer more from confusion due to beam dilution, even
in VLBI observations