We investigate the direct contribution of strong, sunspot-like magnetic fields to helioseismic wave travel-time shifts via two numerical forward models, a 3D ideal MHD solver and MHD ray theory. The simulated data cubes are analyzed using the traditional time-distance center-to-annulus measurement technique. We also isolate and analyze the direct contribution from purely thermal perturbations t...

The umbral regions of sunspots and pores in the solar photosphere are generally dominated by $3$~mHz oscillations, which due to $p$-modes penetrating magnetic region. In these locations, wave power is also significantly reduced with respect quiet Sun. However, here we study a pore where oscillations umbra not only comparable, or even larger than that Sun, but main dominant frequency as expected...

We use 2D numerical simulations and eikonal approximation, to study properties of MHD waves traveling below the solar surface through the magnetic structure of sunspots. We consider a series of magnetostatic models of sunspots of different magnetic field strengths, from 10 Mm below the photosphere to the low chromosphere. The purpose of these studies is to quantify the effect of the magnetic fi...

Sunspots are the subject of interest to many astronomers and solar physicists. Sunspot observation, analysis and classification form an important part of furthering the knowledge about the Sun. Sunspot classification is a manual and thus very labor intensive process that could be automated if it can be successfully learned by a machine. This paper deals with data mining approaches to the proble...

Aims. We study the visibility of sunspots and its influence on observed values of sunspot region parameters. Methods. We use Virtual Observatory tools provided by AstroGrid to analyse a sample of 6862 sunspot regions. By studying the distributions of locations where sunspots were first and last observed on the solar disk, we derive the visibility function of sunspots, the rate of magnetic flux ...

In order to understand the influence of magnetic fields on the propagation properties of waves, as derived from different local helioseismology techniques, forward modeling of waves is required. Such calculations need a model in magnetohydrostatic equilibrium as initial atmosphere to propagate oscillations through it. We provide a method to construct such a model in equilibrium for a wide range...

Based on observations obtained with the Solar and Heliospheric Observatory SOHO joint observing program for velocity fields in sunspot regions, we have detected 3 min transition region umbral oscillations in NOAA 8156. Simultaneous recordings of O V λ629 and N V λ1238, λ1242 with the SUMER instrument give the spatial distribution of power in the 3 min oscillations, both in intensity and line-of...

Helioseismology observations from space missions SOHO and Hinode have provided tremendous amount of new information about thermodynamic properties and dynamics of plasma in the solar interior. The helioseismic diagnostics are based on measuring oscillation frequencies and travel times of acoustic waves excited by turbulent convection in subsurface layers. These diagnostics give us new insights ...