1. Ivana Poljančić Physics Department University of Rijeka, Croatia ipoljancic@phy.uniri.hr IHY-ISWI Regional Meeting Heliophysical phenomena and Earth's environment 7-13 September 2009, Šibenik, Croatia

2. IHY-ISWI Regional Meeting Heliophysical phenomena and Earth's environment 7-13 September 2009, Šibenik, Croatia...with R. Brajsa 1, D. Ruzdjak 1, D. Hrzina 2, R. Jurdana-Sepi ć 3, H. Wöhl 4, W. Otruba 5 1 Hvar Observatory, Faculty of Geodesy, University of Zagreb 2 Zagreb Astronomical Observatory, Croatia 3 Department of Physics, University of Rijeka, Croatia 4 Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany 5 Solar Observatory Kanzelhöhe, Austria

3. Solar differential rotation - Scientific context  one of the fundamental properties of the Sun as the star  observational constraint on theoretical models of the rotating convection zone  MHD dinamo -> solar magnetic activity Results for the time period 1874 – 1976:  dependence of solar rotation on time (Brajša et al. 2006)  relationship between the solar rotation and activity (Brajša et al. 2007) -> to extend 1977 - present

4. Motivation and aims 1. Greenwich Photoheliographic results (GPR) ->  1874 – 1976 2. Solar Optical Observing Network (SOON), United States Air Force (USAF), National Oceanic and Atmospheric Administration (NOAA) -> 1977 - present  data in almost the same format  the aim is to check the precision of the second data set and compare it with the first one

5. Data sets  Positions of sunspot groups :  GPR  SOON/USAF/NOAA  A comparison with other data sets: Kanzelhöhe data, drawings (1947 – present)  To identify sunspot groups we also used:  Debrecen Photoheliographic Data (1977 - present)

6. Data selection for test 1972: GPR & Kanzelhöhe 1993: SOON/USAF/NOAA & Kanzelhöhe  aproximately the same phases of different solar cycles  mostly isolated single H and J sunspot groups (Zürich types)

7. Methods  determining positions and angular velocities of selected sunspot groups from the digitized Solar Observatory Kanzelhöhe drawings  comparing the determined Kanzelhöhe sunspot group coordinates and angular velocities with those from GPR (1972) and SOON/USAF/NOAA (1993)  Sungrabber: a special software for determination of tracer’s positions in full disk solar images

8. Sungrabber  images in the several graphical formats (jpg, gif, bmp...)  for different purposes (determination of tracer’s heliographic coordinates in full disk solar images)  Hrzina et al., 2007 (www.zvjezdarnica.hr/sungrabber) Kanzelhöhe drawing (25th Jan. 1993)

9. Sungrabber  Seetings -> Coordinate system, Zero Point, Date and Time

10. Sungrabber  Input -> Sun’s limb, Daily parallel, New Object

11. Sungrabber  Input -> New Object; File -> Save

12. Sungrabber

13. Number of analysed sunspot groups Zürich types sunspot groups Year Number of analysed sunspot groups Observer 1Observer 2 Single H and J 197245 1993136 Complex 197212- 199316-

14. Results – Single H and J sunspot groups (GPR vs. Kanz. & SOON vs. Kanz., heliographic coordinates) Year limit of CMD  L (deg)  B (deg) Obs. 1Obs. 2Obs. 1Obs. 2 1972 All 0,4790,4290,2310,285 60 0,3710,3250,2600,310 40 0,3420,2590,2720,370 1993 All 0,8510,8470,6120,648 60 0,7640,7840,6090,680 40 0,6940,8560,6260,770  L,  B – difference between Kanzelhöhe and other data sets longitude (latitude)

15. Results – Single H and J sunspot groups (GPR vs. Kanz. & SOON vs. Kanz., angular velocities) Year limit of CMD  (deg/day) Obs. 1Obs. 2 1972 All 0,5660,386 60 0,4950,326 40 0,5380,321 1993 All 0,9190,909 60 0,8400,778 40 0,6970,977  – difference between Kanzelhöhe and other data sets angular velocities

16. Results – Complex sunspot groups (heliographic coordinates & angular velocities) Year limit of CMD  L (deg)  B (deg)  (deg/day) 1972 All 1,0740,5241,357 60 1,1060,5571,285 40 0,9860,5591,022 1993 All 1,0750,6031,385 60 0,9450,6071,285 40 0,8950,5941,022 Results: Observer 1

17. Difference between the two observers (Average absolute deviation) Year limit of CMD  L (deg)  B (deg)  (deg/day) 1972 All 0,1440,1240,153 60 0,1880,1680,227 40 0,2060,1290,338 1993 All 0,1220,0770,149 60 0,1010,0790,145 40 0,0970,0790,140

18. Conclusions  With the assumption of constant reliability of Kanzelhöhe drawings –> SOON/USAF/NOAA data are somewhat less precise then GPR  the precision of the second data set (SOON/USAF/NOAA ) is still suitable for the investigation of long term measurments of solar rotation as a global parameter of the Sun as the star  future work:  to reduce more data and to include further data sets  to apply the residual methods (one  value per year) on SOON/USAF/NOAA  temporal variations and relationship with the level of solar activity

19. Acknowledgements This work is sponsored by the Air Force Office of Scientific Research, Air Force Material Command, USAF, Under grant member FA8655-07-1-3093. Also, the research leading to the results presented here has partly received funding from European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 218816.

20. Acknowledgements Finally, we are thankfull to E. Cliver and N. Gopalswamy for usefull suggestions and discussions. Thank you for your attention!