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* News 04/04/20 * The archive is using a new backend database. This has thrown up a few SQL errors in the last few days. If you have any issues please email adavey@nso.edu with either the number of eprint you are trying to edit or a link to your preprint.

Manifestations of bright points observed in G-band and Ca II H by Hinode/SOT  

Yanxiao Liu   Submitted: 2018-09-21 03:06

An algorithm was developed for identifying and tracking a magnetic bright point, or bright point (BP) for short, observed in both the photosphere (G-band) and chromosphere (Ca II H), as well as for pairing a photospheric BP (PBP) with its conjugate chromospheric BP (CBP). Two sets of data observed by Hinode/SOT in the quiet Sun near the disk center were analyzed. About 278 PBP-CBP pairs were identified and tracked. Lifetimes of both the PBPs and CBPs follow an exponential distribution with average lifetimes of 174 s and 163 s, respectively. We found that the differences in appearance time, in disappearance time and in lifetime of the two kinds of BPs all follow Gaussian distributions,which may indicate that the mechanisms of PBP and CBP formation/disintegration are different. However, the lifetimes of PBPs and CBPs are positively correlated with one another, with a correlation coefficient of 0.8. Furthermore, we calculated the horizontal displacement between the PBP and its conjugate CBP, which follows a Gaussian function with an average and standard deviation of (67.7 ± 38.5) km. We also calculated the amplitude of the flux tube shape change which might be caused by MHD waves propagating along the flux tube, and found that it follows an exponential distribution very well.

Authors: Yanxiao Liu, Ning Wu, Jun Lin
Projects: Hinode/SOT

Publication Status: RAA(published)
Last Modified: 2018-09-21 15:31
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Studies of Isolated and Non-isolated Photospheric Bright Points in an Active Region Observed by the New Vacuum Solar Telescope  

Yanxiao Liu   Submitted: 2018-03-25 22:15

Properties of photospheric bright points (BPs) near an active region have been studied in TiO λ 7058 ? images observed by the New Vacuum Solar Telescope of the Yunnan Observatories. We developed a novel recognition method that was used to identify and track 2010 BPs. The observed evolving BPs are classified into isolated (individual) and non-isolated (where multiple BPs are observed to display splitting and merging behaviors) sets. About 35.1% of BPs are non-isolated. For both isolated and non-isolated BPs, the brightness varies from 0.8 to 1.3 times the average background intensity and follows a Gaussian distribution. The lifetimes of BPs follow a lognormal distribution, with characteristic lifetimes of (267 ? 140) s and (421 ? 255) s, respectively. Their size also follows log-normal distribution, with an average size of about (2.15 ? 0.74) ? 104 km2 and (3.00 ? 1.31) ? 104 km2 for area, and (163 ? 27) km and (191 ? 40) km for diameter, respectively. Our results indicate that regions with strong background magnetic field have higher BP number density and higher BP area coverage than regions with weak background field. Apparently, the brightness/size of BPs does not depend on the background field. Lifetimes in regions with strong background magnetic field are shorter than those in regions with weak background field, on average.

Authors: Yanxiao Liu, Yongyuan Xiang, Robertus Erdélyi, Zhong Liu, Dong Li, Zongjun Ning, Yi Bi,Ning Wu, and Jun Lin
Projects: New Vacuum Solar Telescope (NVST)

Publication Status: Accepted for publication in ApJ
Last Modified: 2018-03-28 11:37
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Manifestations of bright points observed in G-band and Ca II H by Hinode/SOT
Studies of Isolated and Non-isolated Photospheric Bright Points in an Active Region Observed by the New Vacuum Solar Telescope

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