A COMPARISON OF SUNSPOT
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A COMPARISON OF SUNSPOT POSITION MEASURMENTS FROM DIFFERENT DATA SETS. Ivana Poljan č i ć Physics Department U niversity of Rijeka , C roatia [email protected] IHY-ISWI Regional Meeting Heliophysical phenomena and Earth's environment. 7-13 September 2009, Šibenik, Croatia.

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Ivana Poljan č i ć Physics Department U niversity of Rijeka , C roatia [email protected]

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A COMPARISON OF SUNSPOT

POSITION MEASURMENTS

FROM DIFFERENT

DATA SETS

IvanaPoljančić

Physics Department

University of Rijeka, Croatia

[email protected]

IHY-ISWI Regional Meeting

Heliophysical phenomena

and Earth's environment

7-13 September 2009, Šibenik, Croatia


...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


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


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


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


    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


    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


    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)


    Sungrabber

    • Seetings -> Coordinate system, Zero Point, Date and Time


    Sungrabber

    • Input -> Sun’s limb, Daily parallel, New Object


    Sungrabber

    • Input -> New Object; File -> Save


    Sungrabber


    Number of analysed sunspot groups

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


    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


    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


    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


    Difference between the two observers

    (Average absolute deviation)

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


    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


    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


    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


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