We investigate p-mode absorption in a sunspot using SOHO/MDI high-resolution Doppler images. The Doppler power computed from a three and a half hour data set is used for studying the absorption in a sunspot. The result shows an enhancement in absorption near the umbral-penumbral boundary of the sunspot. We attempt to relate the observed absorption with the magnetic field structure of the sunspo...

We analyze the famous Wolf’s sunspot numbers. We discovered that the distribution of the sunspot number fluctuations is a mixture of the BHP distribution with the Gaussian distribution.

Although the Sun's torsional oscillation is believed to be driven by the Lorentz force associated with the sunspot cycle, this oscillation begins 2-3 yr before the sunspot cycle. We provide a theoretical explanation of this with the help of a solar dynamo model having a meridional circulation penetrating slightly below the bottom of the convection zone, because only in such dynamo models does t...

We have recovered the sunspot observations made by David E. Hadden during 1890–1931 from Alta, Iowa. We have digitized the available data published by Hadden in different astronomical journals. This data series have been analyzed and compared with the standard sunspot number series. Moreover, we provide additional information on two great sunspot groups, previously not described, that originate...

Sunspot equilibrium and lottery equilibrium are two stochastic solution concepts for nonstochastic economies. We compare these concepts in a class of completely finite, (possibly) nonconvex exchange economies with perfect markets, which requires extending the lottery model to the finite case. Every equilibrium allocation of our lottery model is also a sunspot equilibrium allocation. The convers...

The sunspot number time series was used to examine different methods of the periodogram as a spectrum estimator. The periodogram was used as the benchmark to compare the results of the sunspot cycle period estimate to the modified periodogram, the Blackman-Tukey method of periodogram smoothing, the Welch-Bartlett method of periodogram averaging and the Multitaper method. The Welch-Bartlett meth...

In the present work a statistical investigation of the spatial distribution of longitudinal coordinates of sunspot data has been carried out. For the analysis the maximal area of umbra plus penumbra of sunspot groups has been taken into account. Spatial distributions of longitudinal coordinates of sunspot data are obtained in diierent coordinate systems (e.g. Carrington, equatorial and diierent...

The unusually long 4th solar cycle has recently been proposed by Usoskin et al. (2001) to be composed of two cycles. They argue that a weak and short cycle might have been lost in sparse sunspot data at the end of the 18th century. Here we check this hypothesis in different ways. First, we consider the sunspot number record in greater detail and compare in a statistical sense the sunspot observ...

In the present work, we introduce and explain a method of solution of the radiative transfer equation based on a thin cloud model. The efficiency of this method to retrieve dynamical chromospheric parameters from Stokes I profiles of Ca II 854.2 nm line showing spectral emission is investigated. The analyzed data were recorded with the Crisp Imaging Spectro-Polarimeter (CRISP) at Swedish 1-m So...