Flares Associated with the 1960 November Event and the Flare Nimbus Phenomenon

Ellison, M. A.; McKenna, Susan; Reid, J. H.

doi:10.1093/mnras/122.6.491

Cited by 17 publications

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“…Further to the preliminary report (Ellison, McKenna, and Reid, 1960b) described above in Section 2.1, Ellison, McKenna, and Reid (1961a) presented five examples of a phenomenon associated with Class 3 and Class 3 + flares which they called the flare nimbus. This was defined to be:…”

Section: The Flare Nimbusmentioning

confidence: 98%

“…The phenomena accompanying events 2 -3 are already described in Section 1.1. Ellison, McKenna, and Reid (1961a) presented in their paper photographic examples of the nimbus event of 16 July 1959 taken from the McMath records as well as of the four nimbi recorded in the Cape records while commenting that, although the nimbus phenomenon was Ellison, McKenna, and Reid (1961a). less conspicuous in photographic records than on the original 35 mm films, its general aspect was clearly visible in the photographic reproductions provided.…”

Section: The Flare Nimbusmentioning

confidence: 99%

“…less conspicuous in photographic records than on the original 35 mm films, its general aspect was clearly visible in the photographic reproductions provided. Here Figure 4 and Figure 5, taken from Ellison, McKenna, and Reid (1961a), present drawings of the development of the flare emission filaments (flare ribbons) that characterized the flares of 10 and 12 November (the approximate positions of the outer boundary of the nimbus is in each case indicated by dashed lines from the time of its first certain appearance).…”

Section: The Flare Nimbusmentioning

confidence: 99%

“…Table 1 (also reproduced from Ellison, McKenna, and Reid, 1961a) summarizes for the above mentioned five cases, characteristic properties of the flare nimbus, namely their times of beginning, greatest visibility and maximum diameter in relation to associated flare times Top right, indication of the N-S direction across the active region followed during photometry (see Section 2.2). Sunspots are shown as dotted regions.…”

Section: The Flare Nimbusmentioning

confidence: 99%

“…The trapped particles are assumed to be 'mirrored' between points of reflection in the chromosphere. Reproduced from Ellison, McKenna, and Reid (1961a). described by Boischot (1958) usually: begins near the time of flare maximum in Hα, endures for several hours, is characterized by its smoothness in intensity, reaches maximum 20 -30 minutes after the start of the emission, and its typical source dimensions are of the order of ∼ 7 -12 arcmin (or 3.1 -5.3 × 10 5 km). Also there is evidence for the early ascent of the radio source into the corona.…”

Section: Figurementioning

confidence: 99%

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Discovery in 1960 of the Flare Nimbus Phenomenon and Changes with Time in Its Interpretation

McKenna‐Lawlor

2011

Sol Phys

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During the International Geophysical Year (IGY, 1957(IGY, /1958) Dunsink Observatory near Dublin in Ireland was a World Data Centre for Solar Activity. In this circumstance, Hα Lyot Heliograph records secured on a daily basis between 07:00 -14:00 UT at the Cape of Good Hope (then an integral link in a network of similar instruments contributing during the IGY to global monitoring of solar chromospheric activity) were routinely sent to Dunsink for analysis and dissemination. The investigations carried out at Dunsink on these data resulted, inter alia, in the discovery of the Flare Nimbus phenomenon. The nimbus comprises a dark expanding halo seen in the plage regions around major flares at, or within a few minutes of, the time of flare maximum intensity in Hα light. It reaches its greatest extent about 30 minutes after flare maximum. Its maximum dimensions (estimated visually) lie in the range 2 -4 × 10 5 km and its duration ranges from ∼ 1 -2 hours. Within the nimbus the striation pattern is either completely destroyed or loses its pre-flare configuration. An account of this phenomenon and its interpretation appeared primarily, although not exclusively, in the locally produced Dunsink Observatory Publications which are not now easily accessible to the world community of solar researchers. Also, at around the time when the nimbus was first identified and recorded in Lyot Heliograph data at several observatories, techniques in solar physics shifted towards high resolution narrow field observations. Under these conditions no further examples of the nimbus were recorded and the subject has remained dormant over several decades. The present paper again places the scientific results obtained with regard to the nimbus in the public domain, together with an account of the evolution within the scientific community of an explanation of this phenomenon. It is suggested here for the first time, in the light of present day data concerning coronal mass ejections (CMEs) and coronal dimming, that the nimbus provides a signature of CME-related reorganization of the magnetic field in the chromosphere (such that the transverse magnetic field component decreases and transforms into the line of sight component as the vector field stretches out). Coronal dimming provides a complementary signature of CME-related mass depletion in the corona.

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Section: The Flare Nimbusmentioning

confidence: 98%

Section: The Flare Nimbusmentioning

confidence: 99%

Section: The Flare Nimbusmentioning

confidence: 99%

Section: The Flare Nimbusmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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