ivana poljančić physics department university of rijeka, croatia [email protected] ihy-iswi...
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Ivana Poljančić
Physics DepartmentUniversity of Rijeka, Croatia
[email protected] IHY-ISWI Regional Meeting Heliophysical phenomena and Earth's environment
7-13 September 2009, Šibenik, Croatia
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
3 Department of Physics, University of Rijeka, Croatia
4Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany
5Solar Observatory Kanzelhöhe, Austria
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
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
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)
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)
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
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)
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
Zürich types
sunspot groups
Year
Number of analysed sunspot groups
Observer 1 Observer 2
Single H and J
1972 4 5
1993 13 6
Complex1972 12 -
1993 16 -
Results – Single H and J sunspot groups(GPR vs. Kanz. & SOON vs. Kanz., heliographic
coordinates)
Yearlimit
of CMD
L (deg) B (deg)
Obs. 1 Obs. 2 Obs. 1 Obs. 2
1972
All 0,479 0,429 0,231 0,285
60 0,371 0,325 0,260 0,310
40 0,342 0,259 0,272 0,370
1993
All 0,851 0,847 0,612 0,648
60 0,764 0,784 0,609 0,680
40 0,694 0,856 0,626 0,770
L, B – difference between Kanzelhöhe and other data sets longitude (latitude)
Results – Single H and J sunspot groups(GPR vs. Kanz. & SOON vs. Kanz., angular velocities)
Yearlimit
of CMD
(deg/day)
Obs. 1 Obs. 2
1972
All 0,566 0,386
60 0,495 0,326
40 0,538 0,321
1993
All 0,919 0,909
60 0,840 0,778
40 0,697 0,977
– difference between Kanzelhöhe and other data sets angular velocities
Results – Complex sunspot groups(heliographic coordinates & angular velocities)
Yearlimit of
CMDL (deg)
B (deg)
(deg/da
y)
1972
All 1,074 0,524 1,357
60 1,106 0,557 1,285
40 0,986 0,559 1,022
1993
All 1,075 0,603 1,385
60 0,945 0,607 1,285
40 0,895 0,594 1,022
Results: Observer 1
Difference between the two observers(Average absolute deviation)
Yearlimit of
CMDL (deg)
B (deg)
(deg/da
y)
1972
All 0,144 0,124 0,153
60 0,188 0,168 0,227
40 0,206 0,129 0,338
1993
All 0,122 0,077 0,149
60 0,101 0,079 0,145
40 0,097 0,079 0,140
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
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.
Acknowledgements
Finally, we are thankfull to E. Cliver and N. Gopalswamy for usefull suggestions and discussions.
Thank you for your attention!