Several recently
published Faraday rotation measures (RM) derived using the novel RM synthesis
technique are likely in error. If a set of polarimetric observations contains a
large gap in the wavelength coverage, the rotation measure determination is sometimes ambiguous;
this is also true even when two long wavelength ranges are observed but are
separated by a wide gap. Essentially, there are 180° ambiguities in the observed
Position Angle of the electric polarisation vector between the two
wavelength ranges; these ambiguities are not resolved because the extent of wavelengths^{2} covered, within each of the two ranges, is too small to uniquely determine the
RM in isolation.We find that
unphysical “Faraday ghosts” can be mathematically constructed with a np ambiguity (±180° times an integer) at predictable polarization position
angles when using only two wavelength ranges separated by a gap, as a function
of the width of the gap (Equation (4)). Our computations suggest an
empirical correlation between an observational gap between two wavelength ranges and the appearance of
“Faraday ghosts”.

A new interpolation method for rotation
and divergence free fields is presented. It is based on a suitable choice of a tricubic
interpolation scheme and reaches an accuracy of third order in grid size (Δx). With the interpolation method it is possible
to increase the accuracy with a factor of gridsize/distance with respect to the trilinear
interpolation method using exactly the same data points. Simulations for several
distances of dipoles (r) to the interpolation
area show that the maximum relative deviation is approximately 3(Δx/r)^{3} ppm.

Abstract:
New observational data related to the X1.1/2N solar flare of 17 July 2004 were investigated and compared with some old data for other powerful flares and non-flare regions. Observations were carried out with the Echelle spectrograph of the Kyiv University Astronomical Observatory. The Stokes I ± V profiles of several metallic lines with different effective Lande factors geff have been analyzed including the FeI 5434.5 line with very low magnetic sensitivity (g_{eff} = –0.014). The obvious evidences of the emissive Zeeman effect were found as in lines with great and middle Lande factors as in FeI 5434.5 line. On the basis of all analyzed data one can conclude that upper magnetic field limit in flares can reach 70 - 90 kG, i.e. about more order higher than the well-known magnetic fields in great sunspots. The possible physical nature of such superstrong fields is discussed.

Abstract:
Synergistic interactions between specific magnetic field intensities and chemical concentrations are challenging biophysical phenomena. Planarian were exposed to one of five different concentrations of melatonin and to a “geomagnetic”—patterned 7 Hz amplitude modulated magnetic field for 6 min once per hour for 8 hr during six successive nights. The peak average strengths were within the range (50 nT) or outside the range (200 nT) derived by the equation. As predicted by a resonance equation planarian displayed highly statistically significant decreased relative activity within the 50 nT, 10^{–7} to 10^{–6} M melatonin conditions compared to lower or higher concentrations. The effect explained about 30% of the variance in these changes of activity. Activity of planarian exposed to the same melatonin concentrations but to the 200 nT field did not differ significantly from each other or from those exposed to the 50 nT field in concentrations of melatonin <10^{–7} M or >10^{–6} M. These results suggest the existence of non-linear, “narrow-band” mechanisms involving the numbers of molecules within a distance determined by the boundary of the organism and the intensity of naturally-patterned magnetic fields derived from energy rather than force-based resonances.

Abstract:
Recently
torsion fields were introduced in CP-violating cosmic axion a^{2}-dynamos
[Garcia de Andrade, Mod Phys Lett A, (2011)] in order to obtain Lorentz
violating bounds for torsion. Here instead, oscillating axion solutions of the
dynamo equation with torsion modes [Garcia de Andrade, Phys Lett B (2012)] are
obtained taking into account dissipative torsion fields. Magnetic helicity
torsion oscillatory contribution is also obtained. Note that the torsion presence
guarantees dynamo efficiency when axion dynamo length is much stronger than the
torsion length. Primordial axion oscillations due to torsion yield a magnetic
field of 10^{9} G at Nucleosynthesis epoch. This is obtained due to a
decay of BBN magnetic field of 10^{15} G induced by torsion. Since
torsion is taken as 10^{–20} s^{–1}, the dynamo efficiency is
granted over torsion damping. Of course dynamo efficiency is better in the
absence of torsion. In the particular case when the torsion is obtained from
anomalies it is given by the gradient of axion scalar [Duncan et al., Nuclear Phys B 87, 215] that a
simpler dynamo equation is obtained and dynamo mechanism seems to be efficient
when the torsion helicity, is negative while magnetic field decays when the
torsion is positive. In this case an extremely huge value for the magnetic
field of 10^{15} Gauss is obtained. This is one order of magnitude
greater than the primordial magnetic fields of the domain wall. Actually if one
uses t_{DW} ~ 10^{-}^{4} sone obtains B_{DW} ~ 10^{22} Gwhich is a
more stringent limit to the DW magnetic primordial field.

To answer the queries concerning penetrability of ~1 μT,
physiologically patterned, time-varying magnetic fields through the cranium,
the proportions of attenuation through thicknesses and densities of ~3 times
that of the human skull were measured directly. There was no reduction in the
intensity of the magnetic field when two 2 cm thick dried pine boards
(4.3×10^{3} kg·m^{-}^{3}) were placed between
the pairs of solenoids separated by the approximate width of the skull.
Although volumes of water containing intracellular concentrations of ions did
not attenuate the field intensity, placement of 290 cm^{2} of 2 mm sheets of duct metal
reduced the amplitude by 25%. Spectra comparisons showed a clear congruence in
profiles between direct measurement of the applied field and the original
computer-generated pattern. These results indicate there is little validity to
claims that weak, time-varying magnetic fields applied in this manner are
eliminated or significantly attenuated by the human skull.

Abstract:
Cool stars like the Sun harbor convection zones capable of producing substantial surface magnetic fields leading to stellar magnetic activity. The influence of stellar parameters like rotation, radius, and age on cool-star magnetism, and the importance of the shear layer between a radiative core and the convective envelope for the generation of magnetic fields are keys for our understanding of low-mass stellar dynamos, the solar dynamo, and also for other large-scale and planetary dynamos. Our observational picture of cool-star magnetic fields has improved tremendously over the last years. Sophisticated methods were developed to search for the subtle effects of magnetism, which are difficult to detect particularly in cool stars. With an emphasis on the assumptions and capabilities of modern methods used to measure magnetism in cool stars, I review the different techniques available for magnetic field measurements. I collect the analyses on cool-star magnetic fields and try to compare results from different methods, and I review empirical evidence that led to our current picture of magnetic fields and their generation in cool stars and brown dwarfs.

Abstract:
The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundary conditions must be obtained from measurements of the magnetic field vector in the solar photosphere. This approach is currently of large interests, as accurate measurements of the photospheric field become available from ground-based (for example SOLIS) and space-born (for example Hinode and SDO) instruments. If we can obtain accurate force-free coronal magnetic field models we can calculate the free magnetic energy in the corona, a quantity which is important for the prediction of flares and coronal mass ejections. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma.

Abstract:
In this review we give an overview about the current state-of-knowledge of the magnetic field in sunspots from an observational point of view. We start by offering a brief description of tools that are most commonly employed to infer the magnetic field in the solar atmosphere with emphasis in the photosphere of sunspots. We then address separately the global and local magnetic structure of sunspots, focusing on the implications of the current observations for the different sunspots models, energy transport mechanisms, extrapolations of the magnetic field towards the Corona, and other issues.

Magnetic field can be
amplified and twisted near a supermassive black hole residing in a galactic
nucleus. At the same time magnetic null points develop near the horizon. We
examine a large-scale oblique magnetic field near a rotating (Kerr) black hole
as an origin of magnetic layers, where the field direction changes abruptly in
the ergosphere region. In consequence of this, magnetic null points can develop
by purely geometrical effects of the strong gravitational field and the
frame-dragging mechanism. We identify magnetic nulls as possible sites of
magnetic reconnection and suggest that particles may be accelerated efficiently
by the electric component. The situation we discuss is relevant for starving nuclei of
some galaxies which exhibit episodic accretion events, namely, Sagittarius A^{*} black hole in our Galaxy.