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Multi-wavelength study of Network Bright Points near the limb

Georgakilas, A. A. and Christopoulou, E. B. and Koutchmy, S. (2001) Multi-wavelength study of Network Bright Points near the limb. Solar Physics, 202 (2). pp. 241-258. ISSN 0038-0938. doi:10.1023/a:1012202330676.

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We analyze the morphology of network bright points (NBPs), their relation to fine dark mottles and their temporal variations, using observations of a quiet region near the polar solar limb, obtained during the solar minimum. For our analysis we used an image-processing method for the selection and identification of NBPs. Further we constructed 'maximum power frequency' maps computing the power spectrum for each pixel of a field and selecting the frequency of maximum spectral power as the most representative oscillating frequency for this pixel. The morphological analysis of our data indicates that the enhancement of NBPs is part of a complicated process that is responsible for the formation of mottles. The analysis of the lifetimes of NBPs indicates that although the general patterns of NBPs remain constant for time intervals larger than an hour, the lifetime of individual bright points is of the order of 16 min. Furthermore, our results indicate an association of the lifetime of NBPs with that of mottles. From the analysis of temporal variations we confirm that the power of NBPs is smaller than the corresponding power for intra-network points at both the 3-min and the 5-min oscillating modes and in both the Mg b₁−0.4 Å and the continuum. Our analysis revealed enhanced power in the 7-min range, which is theoretically considered a candidate frequency for transverse waves related to NBPs at the base of the chromosphere (Kalkofen, 1997). However, we consider more likely that this period is related to the evolution of individual NBPs.

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Additional Information:© 2001 Kluwer Academic Publishers. Received 16 February 2001; accepted 5 June 2001. Based on observations made with the NSO/SPO Dunn Solar Telescope (DST) supported by AURA (NSF-USA). We would like to thank Dr R. N. Smartt, the T.A.C. of NSO/SP and the staff of the Sacramento Peak Observatory for their warm hospitality and their help in getting the observations. A part of this work was performed thanks to a visit of E.C. and A.G. to the Institut d’ Astrophysique de Paris, CNRS. This work was partially supported by NSF grant ATM-9726147. We would like to thank the referee for his/her positive criticism, which led to a substantial improvement of the paper.
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Subject Keywords:Temporal Variation; Transverse Wave; Power Spectrum; General Pattern; Maximum Power
Issue or Number:2
Record Number:CaltechAUTHORS:20200103-161550178
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Official Citation:Georgakilas, A., Christopoulou, E. & Koutchmy, S. Multi-wavelength study of Network Bright Points near the limb*. Solar Physics 202, 241–258 (2001) doi:10.1023/A:1012202330676
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100516
Deposited By: Tony Diaz
Deposited On:05 Jan 2020 03:46
Last Modified:16 Nov 2021 17:54

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