Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000apj...543..472k&link_type=abstract
The Astrophysical Journal, Volume 543, Issue 1, pp. 472-485.
Astronomy and Astrophysics
Astronomy
33
Sun: Activity, Sun: Evolution, Sun: Interior, Sun: Oscillations
Scientific paper
We present measurements of mode width, Γ, and mean square velocity power, 2>, derived from all currently processed 108 day Global Oscillation Network Group (GONG) time series and discuss their implications for p-mode excitation and damping. Assuming stochastic excitation, we estimate the energy per mode, E, and the energy supply rate, dE/dt. For modes with l=9-150, the mean square velocity power and the mode energy peak at about 3.15 mHz reaching values of 2>~1.4×103 cm2 s-2 and E~2.2×1028 ergs. The energy supply rate reaches a maximum value of dE/dt~2.5×1023 ergs s-1 near 3.6 mHz. The mode width shows the familiar ``plateau'' between 2.5 and 3.1 mHz with a ``dip'' near 2.9 mHz, which is strongest for l~40. This dip is most prominent during solar cycle minimum and disappears with increasing magnetic activity. The energy supply rate decreases on average by about 2.7% from the previous activity minimum to the currently highest level of activity. The solar cycle variation of dE/dt shows no frequency dependence, which is in marked contrast to the other mode parameters. The mode parameters are adequately represented by power laws in several frequency ranges, for example, dE/dt~ν6.89+/-0.07 for 2.4 mHz<=ν<3.0 mHz and dE/dt~ν-5.62+/-0.27 for 3.75 mHz<=ν<4.5 mHz. The solar cycle variation of these parameters can then be expressed as changes of a few percent in the power-law exponents and multipliers. Our results agree reasonably well with previous studies of Birmingham Solar-Oscillations Network and Big Bear Solar Observatory data.
Hill F. F.
Howe Rachel
Komm Rudolf W.
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