Search Publications
Measuring the solar meridional flow from perturbations of eigenfunctions of global oscillations
Roth, M.; Schad, A.; Timmer, J.
We present a new concept to infer the meridional flow in the deep solar interior from global oscillation data. This concept is based on the estimation of the coupling strengths of p-mode eigenfunctions mediated by the meridional flow. We illustrate the performance of the method using simulations and present first inversion results of a large-scale…
Dynamics of the solar magnetic field from SOHO/MDI
Benevolenskaya, E. E.
The investigation of the dynamics of magnetic fields from small scales to the large scales is very important for the understanding of the nature of solar activity. It is also the base for producing adequate models of the solar cycle with the purpose to predict the level of solar activity. Since December 1995 the Michelson Doppler Imager (MDI) on b…
The interior of the Sun in 3-D: Beyond the spherical Sun picture
Mathis, S.
With all the results now obtained by global helioseismology, it is clear that we have to go beyond the classical spherical modelling of the Sun. In this way, it is now necessary to draw a picture that takes into account internal dynamical processes such as rotation, magnetic field, and waves from the core to the surface. This is a challenging task…
Internal magnetic fields inferred from helioseismic data
Larson, T. P.; Antia, H. M.; Basu, S. +1 more
Measuring the internal solar magnetic fields and how they change over the course of a solar cycle is one of the key aims of helioseismology. We present the results of attempts to model the global mode splitting coefficients over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large-scale magnetic field. The firs…
A new code for Fourier-Legendre analysis of large datasets: First results and a comparison with ring-diagram analysis
Thompson, M. J.; Roth, M.; Doerr, H. -P. +2 more
Fourier-Legendre decomposition (FLD) of solar Doppler imaging data is a promising method to estimate the sub-surface solar meridional flow. FLD is sensible to low-degree oscillation modes and thus has the potential to probe the deep meridional flow. We present a newly developed code to be used for large scale FLD analysis of helioseismic data as p…
Quantitative solar spectroscopy
Wilhelm, K.
Quantitative solar spectroscopy must be based on calibrated instrumentation. The basic requirement of a calibration, i.e., a comparison between the instrument under test and a primary laboratory standard through appropriate procedures, will be briefly reviewed, and the application to modern space instruments will be illustrated. Quantitative measu…
Local helioseismology and the active Sun
Schunker, H.
The goal of local helioseismology is to elicit three-dimensional information about the sub-surface (or far-side) structure and dynamics of the Sun from observations of the helioseismic wave field at the surface. The physical quantities of interest include flows, sound-speed deviations and magnetic fields. However, strong surface magnetic fields in…
Advances in solar rotation rate inferences: Unstructured grid inversions and improved rotational splittings
Eff-Darwich, A.; Korzennik, S. G.; García, R. A.
We present a new inversion methodology that adapts the inversion grid in both radius and co-latitude to the data set and solves the inversion problem through an iterative procedure. This method was tested on state-of-the-art global mode frequency splittings to assess the solar interior rotation rate and its temporal variation. We also explore the …
The acoustic and magnetic solar cycle
Komm, R.
The frequency variation of global modes provides information about the solar structure and the rotation rate of the solar interior. The solar-cycle variation of the rotation rate, the so-called torsional oscillation, extends throughout the convection zone. Alternating bands of faster- and slower-than-average rotation move from mid-latitudes toward…
Observational results from active region seismology
González Hernández, I.
Active regions are one of the most observed features in the solar surface. High-resolution solar telescopes on ground and space have revealed the fine configuration of umbra and penumbra of sunspots with amazing detail. However, the subsurface structure of sunspots and active regions remains, for the most part, unknown. Thanks to the development o…