Abstract
Various parameters describing the dynamics of G-band bright points (GBPs) were derived from G-band images, acquired by the Dutch Open Telescope (DOT), of a quiet region close to the disk center. Our study is based on four commonly used diagnostics (effective velocity, change in the effective velocity, change in the direction angle, and centrifugal acceleration) and two new ones (rate of motion and time lag between recurrence of GBPs). The results concerning the commonly used parameters are in agreement with previous studies for a comparable spatial and temporal resolution of the used data. The most probable value of the effective velocity is ∼ 0.9 km s−1, whereas we found a deviation of the effective velocity distribution from the expected Rayleigh function for velocities in the range from 2 to 4 km s−1. The change in the effective velocity distribution is consistent with a Gaussian one with FWHM=0.079 km s−2. The distribution of the centrifugal acceleration exhibits a highly exponential nature (a symmetric Gaussian centered at the zero value). To broaden our understanding of the dynamics of GBPs, two new parameters were defined: the real displacement between their appearance and disappearance (rate of motion) and the frequency of their recurrence at the same locations (time lag). For ∼ 45 % of the tracked GBPs, their displacement was found to be small compared to their size (the rate of motion smaller than one). The locations of the tracked GBPs mainly cover the boundaries of supergranules representing the network, and there is no significant difference in the locations of GBPs with small (m<1) and large (m>2) values of the rate of motion. We observed a difference in the overall trend of the obtained distribution for the values of the time lag smaller (slope of the trend line being −0.14) and greater (−0.03) than ∼ 7 min. The time lags mostly lie within the interval of ∼ 2 – 3 min, with those up to ∼ 4 min being more abundant than longer ones. Results for both new parameters indicate that the locations of different dynamical types of GBPs (stable/farther traveling or with short/long lifetimes) are bound to the locations of more stable and long-living magnetic field concentrations. Thus, the disappearance/reappearance of the tracked GBPs cannot be perceived as the disappearance/reappearance of their corresponding magnetic field concentrations.
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Acknowledgements
The Technology Foundation STW in the Netherlands financially supported the development and construction of the DOT and follow-up technical developments. The DOT has been built by instrumentation groups of Utrecht University and Delft University (DEMO) and several firms with specialized tasks. The DOT is located at Observatorio del Roque de los Muchachos (ORM) of Instituto de Astrofísica de Canarias (IAC). DOT observations on 19 October 2005 have been funded by the OPTICON Trans-national Access Programme and by the ESMN-European Solar Magnetic Network – both programs of the EU FP6. The authors thank P. Sütterlin for the DOT observations and R. Rutten for the data reduction. This work was supported by the Slovak Research and Development Agency under the contract No. APVV-0816-11. We acknowledge support by the project VEGA 2/0108/12. We are indebted to an anonymous reviewer whose comments improved the paper substantially.
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Bodnárová, M., Utz, D. & Rybák, J. On Dynamics of G-Band Bright Points. Sol Phys 289, 1543–1556 (2014). https://doi.org/10.1007/s11207-013-0428-z
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DOI: https://doi.org/10.1007/s11207-013-0428-z