Computing Travel Time in Time-Distance Helioseismology
نویسندگان
چکیده
منابع مشابه
Surface Magnetism Effects in Time-Distance Helioseismology
Recent observations of helioseismic holography revealed that magnetic fields that are inclined relative to the line-of-sight direction could cause systematic variations in measured acoustic phase shifts (hereafter, “inclined magnetic field effect”), and that the presence of surface magnetic field may shift the phases and impair the coherence of acoustic waves (known as “showerglass effect”), th...
متن کاملAnalytical models for Cross-correlation signal in Time-Distance Helioseismology
In time-distance helioseismology, the time signals (Doppler shifts) at two points on the solar surface, separated by a fixed angular distance are crosscorrelated, and this leads to a wave packet signal. Accurately measuring the travel times of these wave packets is crucial for inferring the sub-surface properties in the Sun. The observed signal is quite noisy, and to improve the signal-tonoise ...
متن کاملThe sign of temperature inhomogeneities deduced from time-distance helioseismology
Inhomogeneities in wave propagation conditions near and below the solar surface have been detected by means of time-distance helioseismology. Here we calculate the effect of temperature inhomogeneities on the travel times of sound waves. A temperature increase, e.g. in active regions, not only increases the sound speed but also lengthens the path along which the wave travels because the expansi...
متن کاملImaging the Solar Tachocline by Time-Distance Helioseismology
The solar tachocline at the bottom of the convection zone is an important region for the dynamics of the Sun and the solar dynamo. In this region, the sound speed inferred by global helioseismology exhibits a bump of approximately 0.4% relative to the standard solar model. Global helioseismology does not provide any information on possible latitudinal variations or asymmetries between the North...
متن کاملTime-distance Helioseismology with the Mdi Instrument: Initial Results
In time-distance helioseismology, the travel time of acoustic waves is measured between various points on the solar surface. To some approximation, the waves can be considered to follow ray paths that depend only on a mean solar model, with the curvature of the ray paths being caused by the increasing sound speed with depth below the surface. The travel time is aaected by various inhomogeneitie...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 1998
ISSN: 0004-637X
DOI: 10.1086/311309