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Flows, flares, and formation of umbrae and light bridges in BBSO region No. 1167

Zirin, Harold and Wang, Haimin (1990) Flows, flares, and formation of umbrae and light bridges in BBSO region No. 1167. Solar Physics, 125 (1). pp. 45-60. ISSN 0038-0938. doi:10.1007/bf00154778.

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We present high-resolution observations of the large active region BBSO No. 1167 (Boulder No. 5060) which cast new light on the structure of sunspot regions. We obtained excellent data, highlighted by videomagnetograms (VMG) obtained with our 65-cm telescope, which give unprecedented spatial resolution, about 0.5′' for much of two 11-hr periods. This permitted us to see details of the field evolution and flows in the AR. The Hα filtergrams and D3 filtergrams permit study of these magnetic changes compared to spots and chromospheric structure. The region was a huge but simple active region (CMP July 2, 1988) in which we observed rapid flux emergence for several days. Because the new flux generally matched the old, there were few large flares. However, there were 14 flares on June 28 and 29, mostly in two sites. The first site was a δ spot which already existed when the active region appeared on the east limb. This site showed little change of magnetic structure during our observing period. The second site is an area disturbed by new flux emergence, which included a δ spot which formed and disappeared in two days, and a rapidly moving p spot. Flares ocurring at one site almost always produced footpoints at the other. The delay between flash phases of the same flare at the two sites ranges from 40 to 160 s. The magnetograms show complex fine structure, with some closely interwined regions of opposite polarity. In a region of new flux emergence, positive (leading polarity) flux flows along elongated channels immersed in the negative flux. Moving magnetic features occur around all of the spots. We point out other interesting aspects of this large region: (1) While there is extensive penumbra around the main umbrae, there is also significant penumbra apparently unrelated to any spot. These unusual penumbrae are either due to flux returning to the surface, flux left behind by the moving umbra, or associated with pores that appear and disappear. (2) We observed umbrae to move faster than the accompanying penumbrae, and concluded that penumbrae are not a simple extension of the umbra. (3) We found that combining spots of the same polarity do not completely merge, but are always separated by a thin light bridge. This means that the emerging flux loops are discrete entities.

Item Type:Article
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URLURL TypeDescription
Wang, Haimin0000-0002-5233-565X
Additional Information:© 1990 Kluwer Academic Publishers. Provided by the NASA Astrophysics Data System. Received 30 June 1989; Revised 28 July 1989. We are indebted to the staff at BBSO for their assistance in obtaining the data. This work has been supported by NSF under grant ATM-8513577 and NASA under grant NGL 05002034.
Funding AgencyGrant Number
NASANGL 05 002 034
Subject Keywords:Flare; Flux Emergence; Large Flare; East Limb; Flux Loop
Issue or Number:1
Record Number:CaltechAUTHORS:20200520-154601329
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Official Citation:Zirin, H., Wang, H. Flows, flares, and formation of umbrae and light bridges in BBSO region No. 1167. Sol Phys 125, 45–60 (1990).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103371
Deposited By: Tony Diaz
Deposited On:20 May 2020 22:54
Last Modified:16 Nov 2021 18:20

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