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Deep-Focusing Time-Distance HelioseismologyMuch progress has been made by measuring the travel times of solar acoustic waves from a central surface location to points at equal arc distance away. Depth information is obtained from the range of arc distances examined, with the larger distances revealing the deeper layers. This method we will call surface-focusing, as the common point, or focus, is at the surface. To obtain a clearer picture of the subsurface region, it would, no doubt, be better to focus on points below the surface. Our first attempt to do this used the ray theory to pick surface location pairs that would focus on a particular subsurface point. This is not the ideal procedure, as Born approximation kernels suggest that this focus should have zero sensitivity to sound speed inhomogeneities. However, the sensitivity is concentrated below the surface in a much better way than the old surface-focusing method, and so we expect the deep-focusing method to be more sensitive. A large sunspot group was studied by both methods. Inversions based on both methods will be compared.
Document ID
20010073393
Document Type
Conference Paper
Authors
Duvall, T. L., Jr. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Jensen, J. M. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Kosovichev, A. G. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Birch, A. C. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Fisher, Richard R.
Date Acquired
August 20, 2013
Publication Date
January 5, 2001
Subject Category
Solar Physics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.