helioseismology

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helioseismology

(heel-ee-oh-sÿz-mol -ŏ-jee) The study of the Sun's interior by the observation of solar oscillations. First detected in 1960 by measuring the Doppler shifts of Fraunhofer lines at several points on the Sun's disk away from active regions, the oscillations are a rhythmic rise and fall of regions of the solar photosphere (and lower chromosphere) several thousand kilometers in diameter. They have periods of about 5 minutes, persist at any one point for less than half an hour, and attain a maximum velocity of about 0.5 km s–1. The oscillations are thought to be produced by the outward propagation of low-frequency sound waves, generated by turbulence in the convective zone, and by analyzing their global occurrence over an extended period of time it is possible to build up a picture of the Sun's interior.

Instruments used in the observation of solar oscillations include grating spectrographs, narrow-band interference filter (Lyot filter, magneto-optical filter, or Fabry–Perot interferometer) imagers, and Michelson interferometers – notably the Fourier tachometer, which has been in operation since 1985 and simultaneously monitors more than 60 000 points on the Sun's disk. A number of collaborative programs have been established, for example the Global Oscillations Network Group (GONG). These are complemented by continuous monitoring by the helioseismology instrument on ESA's spacecraft, the Solar Heliospheric Observatory (SOHO).

helioseismology

[‚hē·lē·ō‚sīz′mäl·ə·jē]
(astronomy)
The analysis of wave motions of the solar surface to determine the structure of the sun's interior.
References in periodicals archive ?
At present, helioseismic measurements (see [section]6) indicate that the degree of solar oblateness may be slightly smaller [288, 289], but the general feature remains.
Along with many of the structural ([section]) and helioseismic ([section]) lines of evidence, they are amongst the simplest to visualize.
It has a 48-year-long heritage of spaceborne solar instruments including the Soft X-ray Telescope on the Japanese Yohkoh satellite, the Michelson Doppler Imager on the ESA/NASA Solar and Heliospheric Observatory, the solar telescope of NASA's Transition Region and Coronal Explorer, the Focal Plane Package on the Japanese Hinode satellite, the Solar X-ray Imagers on GOES-N, -O and -P, the Extreme Ultraviolet Imager instruments on NASA's twin STEREO spacecraft, and the Helioseismic and Magnetic Imager and the Atmospheric Imaging Assembly on NASA's Solar Dynamics Observatory.
The immense amount of data collected during our research requires a powerful HPC solution capable of ingesting and analyzing data quickly and with precision," said Phil Scherrer, principal investigator, Helioseismic and Magnetic Imager, Stanford University.
The solar scientists used the Stanford-operated Helioseismic and Magnetic Imager (HMI) - an instrument onboard NASA's Solar Dynamics Observatory satellite - to track solar waves in much the way seismologists would study seismic movements beneath the surface of the Earth.
Second, solar helium levels are inherently linked to the gaseous models of the Sun [16-18] and the application of theoretical findings to the interpretation of helioseismic results [19-23].
Moreover, the SDO Helioseismic and Magnetic Imager (HMI), combined with a computational model of full-sphere flux-transport on the Sun, and global coronal field modeling, revealed the long-distance magnetic connections with fair fidelity.
Numerical Simulation of Scattering of Helioseismic MHD Waves by Sunspots
Helioseismic analysis of the Sun has revealed that sound waves travel faster within sunspots relative to the photosphere [42,43].
Washington, August 17 ( ANI ): Researchers have used the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory satellite to obtain what they believe is the definitive and baffling answer about the slightly flattened surface of the sun.
The ATC has a 47-year-long heritage of spaceborne solar instruments including the Soft X-ray Telescope on the Japanese Yohkoh satellite, the Michelson Doppler Imager on the ESA/NASA Solar and Heliospheric Observatory, the solar telescope on NASA's Transition Region and Coronal Explorer, the Solar X-ray Imager on the GOES-N, O and P environmental satellites, the Focal Plane Package on Hinode, an Extreme Ultraviolet Imager on each of the two spacecraft in NASA's Solar Terrestrial Relations Observatory, and the Atmospheric Imaging Assembly and Helioseismic Magnetic Imager on NASA's Solar Dynamics Observatory.
Two RAD6000 radiation-hardened computers aboard NASA's Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager payloads will process large volumes of scientific data and manage the satellite's directional orientation.