Solar Physics Division Meeting 2000, June 19-22
Session 1. Helioseismology, Magnetic Fields, Chromosphere and Transition Region
Display, Chair: C. U. Keller, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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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 ~ \nu6.89 \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.

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