Observed variations of the magnetic field strength in sunspot umbrae consist of intrinsic oscillations and ``false'' oscillations due to time-dependent opacity effects. Here we present an approach intended for the separation of these components. We develop a mathematical formalism based on the analytical solution of the MHD equations including

One of the instruments developed for the Advanced Technology Solar Telescope (ATST) site survey is a non-redundant array of six scintillometers known as a ShaBaR (SHAdow BAnd Ranging) system, developed by J. Beckers. The ShaBaR provides an estimate of Cn2(h), the turbulence structure function, in the Earth's atmosphere. We can use the estimate of

The Equivalence Theorem is commonly used to calculate perturbatively amplitudes involving gauge bosons at energy scales higher than gauge boson masses. However, when the scalar sector is strongly interacting the theory is non-perturbative. We show that the Equivalence Theorem holds in the large N limit at next-to-leading order by calculating the

We determine the inclinations of the vector magnetic field and flow velocity in a sunspot penumbra by interpreting full Stokes profiles of three infrared lines observed with the Tenerife Infrared Polarimeter. It is shown that analyses based on one-component atmospheres deliver flow velocities which are more horizontal than the average magnetic

High-resolution observations of quiescent filaments point out that their fine structure is made of small-scale threads or fibrils. These fibrils can be represented as thin loops having cool tops, i.e. the prominence material, while the rest of the loop displays coronal temperatures. Then, the stacking of these thin loops in the vertical and

In order to determine what ground-based proxies are best for evaluating solar irradiance variation before the advent of space observations, it is necessary to test these proxies against space observations. We have tested sunspot number, total sunspot area, and sunspot umbral area against the Nimbus-7 measurements of total solar irradiance variation