Ivana Poljan č i ć Physics Department U niversity of Rijeka , C roatia ipoljancic@phy.uniri.hr

1. A COMPARISON OF SUNSPOT POSITION MEASURMENTS FROM DIFFERENT DATA SETS IvanaPoljančić 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. ...with R. Brajsa1, D. Ruzdjak1, D. Hrzina2, R. Jurdana-Sepić3, H. Wöhl4, W. Otruba5 1Hvar Observatory, Faculty of Geodesy, University of Zagreb 2Zagreb Astronomical Observatory, Croatia 3Department of Physics, University of Rijeka, Croatia 4Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany 5Solar Observatory Kanzelhöhe, Austria 7-13 September 2009, Šibenik, Croatia IHY-ISWI Regional Meeting Heliophysical phenomena and Earth's environment

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 IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

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 IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

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) IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

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) IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

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 IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

8. Sungrabber Kanzelhöhe drawing (25th Jan. 1993) • 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)

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 IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

14. Results – Single H and J sunspot groups (GPR vs. Kanz. & SOON vs. Kanz., heliographic coordinates) DL, DB – difference between Kanzelhöhe and other data sets longitude (latitude) IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

15. Results – Single H and J sunspot groups (GPR vs. Kanz. & SOON vs. Kanz., angular velocities) Dw– difference between Kanzelhöhe and other data sets angular velocities IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

16. Results – Complex sunspot groups (heliographic coordinates & angular velocities) Results: Observer 1 IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

17. Difference between the two observers (Average absolute deviation) IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

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 D value per year) on SOON/USAF/NOAA • temporal variations and relationship with the level of solar activity IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

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. IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets

20. Acknowledgements Finally, we are thankfull to E. Cliver and N. Gopalswamy for usefull suggestions and discussions. Thank you for your attention! IHY-ISWI Regional Meeting, Šibenik, 2009 - A comparison of sunspot position measurments from different data sets