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[1.14] Width and Energy of Solar P-Modes Observed by GONG

R. Komm, R. Howe, F. Hill (NSO)

We present mode width, \Gamma, and mean-square velocity power, < v² >, derived from all currently processed 108-day 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 < v² > \,\approx\, 1.4 \; 10³~cm²~s^-2 and E \,\approx\, 2.2 \; 10²⁸~ergs. The energy supply rate reaches a maximum value of dE / dt \,\approx\, 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 \approx 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 ~ \nu^{6.89 \pm 0.07} for 2.4 \leq \nu < 3.0~mHz and dE / dt ~\nu^{-5.62 \pm 0.27} for 3.75 \leq \nu < 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 BiSON and BBSO data.

The author(s) of this abstract have provided an email address for comments about the abstract: komm@noao.edu

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