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Allen, Maxwell J.; Oluseyi, Hakeem M.; Walker, Arthur B. C.; Hoover, Richard B.; Barbee, Troy W.

doi:10.1023/a:1004955129119

Cited by 14 publications

(7 citation statements)

References 32 publications

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“…The observational consequences of this are profound. It has been observed by several authors (Allen et al 1997;Kankelborg et al 1996Kankelborg et al , 1997Brosius et al 1996;Wang and Sheeley 1995) that the magnitude of the lower transition region emission at the footpoints of several coronal structures is consistent with the inferred conductive flux from the corona. It has also been observed that there are many fewer coronal structures than are necessary to account for the thousands of network elements observed at transition region temperatures (Feldman and Laming 1994).…”

Section: Heating the Lower Transition Regionsupporting

confidence: 81%

“…These conduction type lukewarm loops may provide, then, an energy source for the observed lower transition region network elements that are not obviously associated with coronal structures. We have pointed out previously (Allen et al 1997 ;Kankelborg et al 1996Kankelborg et al , 1997) that the chromosphere/ corona interface at the footpoints of polar plumes and XBPs may make a signiÐcant, perhaps dominant, contribution to the energy emitted by the local network in the lower transition region, contrary to the views expressed by a number of authors. In the present paper we show that it is possible that the interface between structures at subcoronal temperatures and the chromosphere can make a signiÐcant contribution to the energy emitted by the lower transition region in the quiet Sun.…”

Section: Discussionmentioning

confidence: 71%

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Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Oluseyi

Walker

Santiago

et al. 1999

ApJ

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In the present work we undertake a study of the quasi-static loop model and the observational consequences of the various solutions found. We obtain the most general solutions consistent with certain initial conditions. Great care is exercised in choosing these conditions to be physically plausible (motivated by observations). We show that the assumptions of previous quasi-static loop models, such as the models of Rosner, Tucker, & Vaiana (RTV) and Veseckey, Antiochos, & Underwood, (VAU) are not necessarily valid for small loops at transition region temperatures. We Ðnd three general classes of solutions for the quasi-static loop model, which we denote radiation-dominated loops, conduction-dominated loops, and classical loops. These solutions are then compared with observations. Departures from the classical scaling law of RTV are found for the solutions obtained. It is shown that loops of the type that we model here can make a signiÐcant contribution to lower transition regions emission via thermal conduction from the upper transition region.

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Section: Heating the Lower Transition Regionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 71%

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Oluseyi

Walker

Santiago

et al. 1999

ApJ

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“…MSSTA observations indicated that most plumes have a unipolar magnetic structure with electron densities of 1 × 10 8 cm −3 at 1.05 R and 2 × 10 7 cm −3 at 1.5 R . No conclusive answer on flows in plumes could be obtained by Allen et al (1997).…”

Section: Coronal Holes Polar Plumes and The Fast Solar Windmentioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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“…Polar plumes (PP) are bright individual features seen in polar coronal holes (DeForest et al 1997), and sometimes in coronal holes that extend to equatorial heights (Allen et al 1997). They can also appear in groups.…”

Section: Radio -Euvmentioning

confidence: 99%

Comparison of 87 GHz solar polar structures with EUV and soft X-ray emission

Pohjolainen

Portier-Fozzani

Ragaigne

2000

Astron. Astrophys. Suppl. Ser.

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Abstract. Polar radio brightenings at 87 GHz (3.5 mm) are compared for the first time with features seen in EUV and soft X-rays. The data consist of nearly simultaneous full disk images and maps from Metsähovi Radio Observatory, SOHO/EIT, and Yohkoh/SXT on 9 selected days near the solar minimum (1996)(1997).The observed radio brightenings corresponded to various features seen in EUV, such as diffuse or localized intensity enhancements (e.g., bright points and bases of polar plumes), and intensity depressions of varying sizes (e.g., coronal holes). Some of these features were also visible in soft X-rays. The visibility of radio bright coronal holes seemed to depend on how much of the polar area was exposed, due to the variation of the B 0 -angle.The observed radio depressions near the solar poles were very well correlated with coronal holes and other EUV and/or soft X-ray intensity drops. More than half of the coronal holes, or coronal hole-like intensity drops in EUV and soft X-rays, had radio brightenings inside them. Therefore coronal holes do not have uniform radio brightness at 87 GHz.Many of the bright points seen at lower latitudes in the EIT and SXT images had no, or just faint, counterparts in the millimeter radio maps. It appears that for an EUV bright point to show up at 87 GHz it has to be bright and/or spatially large also in soft X-rays.

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Untitled

Cited by 14 publications

References 32 publications

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Observation and Modeling of the Solar Transition Region. II. Identification of New Classes of Solutions of Coronal Loop Models

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

Comparison of 87 GHz solar polar structures with EUV and soft X-ray emission

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