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Interferometric observations of the Sun with ALMA provide valuable diagnostic tools for studying the small-scale dynamics of the solar atmosphere. Estimations of the observability of the small-scale dynamics as a function of spatial…
The Sun is the primary source of energy for Earth and one of the main external drivers of its climate. Solar irradiance -- the radiative power emitted by the Sun and received at 1-AU -- varies on all observable timescales. It is measured as…
The ideal magnetohydrodynamic torus instability can drive the eruption of coronal mass ejections. The critical threshold of magnetic field strength decay for the onset of the torus instability occurs at different heights in different solar…
The solar activity in the current, that is, the 24-th, sunspot cycle is analyzed. Cyclic variations in the sunspot number (SSN) and radiation fluxes in various spectral ranges have been estimated in comparison with the general level of the…
We use helioseismic data obtained over two solar cycles to determine whether there are changes in the near-surface shear layer (NSSL). We examine this by determining the radial gradient of the solar rotation rate. The radial gradient itself…
The aim of this work is to provide new insights on the dynamics associated to the resonances which arise as a consequence of the coupling of the effect due to the oblateness of the Earth and the Solar Radiation Pressure (SRP) effect for an…
The variation of the solar diameter is the subject of hot debates due to the possible effect on Earth climate and also due to different interpretations of long period solar variabilities, including the total solar irradiance. We shortly…
The radiative and particulate loss of mass by the Sun, -9.13*10^-14 Solar masses per year or more causes the orbits of the planets to expand at the same rate, and their periods to lengthen at twice this rate. Unfortunately, under the…
The power spectrum of magnetic-field fluctuations in the fast solar wind ($V_{\rm SW}> 500 \mbox{ km} \mbox{ s}^{-1}$) at magnetohydrodynamic (MHD) scales is characterized by two different power laws on either side of a break frequency…
The millimeter/submillimeter wavelength polarization of Sgr A* is known to be variable in both magnitude and position angle on time scales down to a few hours. The unstable polarization has prevented measurements made at different…
The aim of this paper is to study the latitudinal variation in the solar rotation in soft X-ray corona. The time series bins are formed on different latitude regions of the solar full disk (SFD) images that extend from 80 degree South to 80…
Solar astrometry deals with the accurate measumerent of the solar diameter, and in general with the measurement of the shape of the Sun. During the last decades several techniques have been developed to monitor the radius and the irradiance…
The precise shape of the Sun is sensitive to the influence of gravity, differential rotation, local turbulence and magnetic fields. It has been previously shown that the solar shape exhibits asphericity that evolves with the 11-year cycle.…
Solar activity and helioseismology show the limitation of the standard solar model and call for the inclusion of dynamical processes in both convective and radiative zones. We concentrate here on the radiative zone and first show the…
Oscillation properties are usually measured by fitting symmetric Lorentzian profiles to the power spectra of Sun-like stars. However the line profiles of solar oscillations have been observed to be asymmetrical for the Sun. The physical…
Precise stellar masses and radii can be determined using asteroseismology, but their accuracy must be tested against independent estimates. Using radii derived from Gaia DR2 parallaxes, we test the accuracy of asteroseismic radii for a…
The determination of the cutoff frequency in real solar observations under different local physical conditions is an important and insufficiently explored aspect of waves in solar physics. This work utilizes the near ultraviolet (NUV)…
Long-term variations of solar differential rotation and sunspot activity are investigated through re-analyzing the data on parameters of the differential rotation law obtained by Makarov, Tlatov, and Callebaut (1997), Javaraiah, Bertello,…
The solar atmosphere displays a sharp temperature gradient, starting from spicules in the chromosphere at $2 \times 10^4$ K, outward into the corona exceeding $10^6$ K. Plasma turbulence produced by the transverse motion of magnetic fields…
We study the properties of line bisectors in the spectrum of the Sun-as-a-star, as observed using the Integrated Sunlight Spectrometer (ISS) of the SOLIS project. Our motivation is to determine whether changes in line shape, due to magnetic…