1. Variations of Solar Acoustic Radius from GONG low-L data
Shukur Kholikov
NSO/GONG

2. Outline Auto-correlation analysis Data: GONG, BISON, VIRGO/SPM
Large separation or acoustic radius measurements
Results
Meridional flows from SH zonal modes
Conclusions and future work

3. ACF

4. Large separations from GONG frequencies

5. Large separations from BISON frequencies

6. Large separations from ACF L= 0, 2

7. Travel times:
GONG

8. Correlation with the activity

9. Relative changes of acoustic radius: MDI, GONG

10. Relative changes of acoustic radius: BISON

11. Relative changes of acoustic radius: VIRGO/SPM

12. Conclusions Precise measurements of large separation
Possibly we may estimate change of upper reflection boundary during the activity cycle
Applicable to astroseismology, stellar activity

13. Meridional travel time differences using GONG (m=0) SH time series

14. Average CCF
T=1 gong month
∆=17º
=3 mHz

15. Comparison travel time differences
Directly from velocity images
From M=0 SH coefficients
From reconstructed images using all-L SH coefficients

16. Average travel time differences