Sensitivity of time-distance helioseismic measurements to spatial variation of oscillation amplitudes I. Observations and a numerical model
نویسنده
چکیده
It is well known that the observed amplitude of solar oscillations is lower in sunspots than in quiet regions of the Sun. We show that this local reduction in oscillation amplitudes combined with the phase-speed filtering procedure in time-distance helioseismic analyses could be a source of systematic errors in the range of 5 40% in the measured travel-time anomalies of acoustic waves around sunspots. Removing these travel time artifacts is important for correctly inferring the subsurface structure of sunspots. We suggest an empirical correction procedure and illustrate its usage for a small sunspot. This work utilizes data from MDI/SOHO. Subject headings: Sun: helioseismology — Sun: magnetic fields — Sun: oscillations — sunspots
منابع مشابه
Sensitivity Analysis of Spatial Sampling Designs for Optimal Prediction
In spatial statistic, the data analyzed which is correlated and this correlation is due to their locations in the studied region. Such correlation that is related to distance between observations is called spatial correlation. Usually in spatial data analysis, the prediction of the amount of uncertain quantity in arbitrary 4locations of the area is considered according to attained observations ...
متن کاملField Measurements and 3D Numerical Modeling of Hydrodynamics in Chabahar Bay, Iran
As the first phase of a series of monitoring and modeling studies of Iranian coastal areas, Chabahar Bay, located on the north coast of the Gulf of Oman, was under a comprehensive monitoring and modeling study in 2006-2007. The study included an extensive one-year field measurements program to help understanding the ongoing processes in the bay and provide inputs or boundary conditions and vali...
متن کاملنوسانات آزاد زمین
This work is a study of the Earths free oscillations considering a merge of solid and liquid model. At the turn of 19th century Geophysicists presented the theory of the free oscillations for a self-gravitating, isotropic and compressible sphere. Assuming a steel structure for an Earth size sphere, they predicted a period of oscillation of about 1 hour. About 50 years later, the free oscillat...
متن کاملInvestigation of the effect of source distance and scattering medium on spatial resolution and contrast of Gamma camera images [Persian]
By identifying the effect of any parameter such as distance, attenuation and scattering on the Line Spread Function (LSF), one can compensate the quantitative and qualitative destructive effect of such parameters by deconvolution method. Using a 99mTC line source, this study was performed on a single head ADAC SPECT system operating in planar mode. Variation of FWTM and FWHM and LSFs as a...
متن کاملBuoyancy Term Evolution in the Multi Relaxation Time Model of Lattice Boltzmann Method with Variable Thermal Conductivity Using a Modified Set of Boundary Conditions
During the last few years, a number of numerical boundary condition schemes have been used to study various aspects of the no-slip wall condition using the lattice Boltzmann method. In this paper, a modified boundary condition method is employed to simulate the no-slip wall condition in the presence of the body force term near the wall. These conditions are based on the idea of the bounce-back ...
متن کامل