Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002apj...572..663k&link_type=abstract
The Astrophysical Journal, Volume 572, Issue 1, pp. 663-673.
Astronomy and Astrophysics
Astronomy
27
Sun: Activity, Sun: Helioseismology, Sun: Magnetic Fields, Sun: Oscillations
Scientific paper
We present the first attempt at localizing in latitude the temporal variation of mode energy, energy supply rate, and lifetime of global acoustic modes. We use Global Oscillation Network Group (GONG) and Michelson Doppler Imager data analyzed with the GONG peak-fitting algorithm to measure mode width and amplitude of individual (l, n, m) modes. While measured amplitude and width values are inherently noisier than frequency measurements, it is possible to use the (m/l) dependence of these mode parameters to extract their variation in latitude. With the currently analyzed data sets, we construct maps in time and latitude of acoustic mode energy, lifetime (inverse of mode width), and energy supply rate covering the rising phase of the current solar cycle from the previous minimum to the current maximum. We find that the energy and width of global modes vary in latitude as well as in time and that the variation is clearly related to the distribution of magnetic flux. After removing the average quantity, the residual mode width shows a linear correlation with magnetic activity with a correlation coefficient of 0.88, while the corresponding residual mode energy is anticorrelated with magnetic activity with a correlation coefficient of -0.90. These mode parameters derived from global p-modes respond to the local distribution of surface magnetic activity. The energy supply rate shows no correlation with the latitudinal distribution of magnetic activity within the limits of the current measurements. We estimate the variation of global mode energy in response to an individual magnetic feature, such as a plage, and find that the global mode energy and the mode lifetime are reduced by about 40% by an active region compared to the quiet Sun.
Hill F. F.
Howe Rachel
Komm Rudi
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