1. LoHCo Meeting – Tucson, December 13, 2005
Lifetimes of high-l solar p-modes from time-distance analysis: GONG and TON data
Olga Burtseva (NSO/GONG)
contributors & collaborators:
Shukur Kholikov (NSO/GONG),
Sasha Serebryanskiy (UBAI, Uzbekistan),
Dean-Yi Chou, Oleg Ladenkov (Tsing-Hua U, Taiwan)
LoHCo Meeting – Tucson, December 13, 2005

2. Outline Introduction Data analysis
Lifetime measurements based on time-distance technique
Results from TON and GONG data
Conclusions and future work

3. Motivation
Lifetime of the solar p-modes is related to their excitation and damping mechanisms in the solar interior
Line widths of the p-mode peaks in power spectrum can not be determined precisely in high-l domain
Time-distance technique can allow us to determine lifetimes of high-l solar acoustic waves more precisely

4. Time-distance technique (T. Duvall, 1993)
Acoustic waves propagating inside the Sun arrive at the solar surface in different travel times and at different distances from the original point
The modes with the same angular phase velocity /l have approximately the same ray path. They form a wave packet
Points r1 and r2 of appearance of the wave packet on the solar surface should correlate

5. Idea of the study
The amplitude of the cross-correlation function decreases exponentially with the number of skips
This phenomenon is interpreted as the dissipation of solar p-mode power (D.-Y.Chou et al., 2001)

6. Data
Intensity images Velocity images
K Ca II 3934 A Ni I 6768 A

7. Data analysis Remapping of each image into sin(), coordinates.
Correction for the solar surface rotation.
Filtering by the 15-frame running mean.
Producing the SHT coefficients time series.
Filtering with a Gaussian function of FWHM=2mHz, centered at a frequency 0.
Phase velocity filtering to isolate wave packets characterized by the central frequency 0 and the degree l0.
Reconstruction of the images back to the space-time domain.
Computing of cross-correlation functions of the wave packets.
Determination of parameters of the cross-correlation functions by fitting them to a Gabor wavelet.

8. Method of lifetime measurements
In the absence of dispersion of the wave packet:
A – amplitude en – travel time of one skip n – number of skips Т – lifetime
Effect of dispersion of the waves makes the lifetimes shorter and we do attempt to take it into account:

9. Results from TON data
Lifetimes of wave packets characterized by 0 = mHz and degrees l0 =
After correction for the dispersion effect lifetimes of the waves with l= increases by factor 1.5–2.
For the waves with l= the difference of the lifetimes with and without correction for the dispersion is negligible.

10. Results from TON and GONG data

11. Conclusions and future work
The lifetime decreases with frequency and degree, that is consistent with results from analysis of the spectral line profile
It seems that effect of dispersion is more significant for the wave packets with l  400
After considering dispersion, the lifetimes of l=100 at   3.5 mHz are close to the values from the spectral line profile (Jefferies et al., 1991)
Errors and fluctuations of the lifetime values are greater in the case of considering dispersion as the determination of the width is less accurate than the amplitude, that needs to be improved
Should we use A2 instead of A ?!