A concentric ellipse multiple-arch system in the solar corona

Saito, K.; Hyder, C. L.

doi:10.1007/bf00147121

Cited by 34 publications

(16 citation statements)

References 7 publications

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“…The earliest analyses were of white-light eclipse data (Waldmeier 1941, p. 234;Waldmeier 1970;Saito & Hyder 1968;Saito & Tandberg-Hanssen 1973). The dense core sometimes seen within the cavity in white light is a prominence/filament, and early studies concluded that cavities were more likely to be visible when associated with quiescent filaments away from active regions and that their visibility was related to their size and the orientation of the filament axis relative to the line of sight (Waldmeier 1970).…”

Section: Cavity Observations To Datementioning

confidence: 98%

“…A few quantitative estimates of this density depletion were made from these eclipse observations, with estimates of 80% or higher (Saito & Hyder 1968;Saito & Tandberg-Hanssen 1973). These estimates should be considered with great caution, however, as they use low-resolution eclipse photographs to estimate coronal brightness and from this determine coronal density, and they use highly simplified model assumptions of coronal morphology.…”

Section: Cavity Observations To Datementioning

confidence: 99%

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The Calm before the Storm: The Link between Quiescent Cavities and Coronal Mass Ejections

Gibson¹,

Foster²,

Burkepile³

et al. 2006

ApJ

165

151

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Determining the state of the corona prior to CMEs is crucial to understanding and ultimately predicting solar eruptions. A common and compelling feature of CMEs is their three-part morphology, as seen in white-light observations of a bright expanding loop, followed by a relatively dark cavity, and finally a bright core associated with an erupting prominence/filament. This morphology is an important constraint on CME models. It is also quite common for a three-part structure of loop, cavity, and prominence core to exist quiescently in the corona, and this is equivalently an important constraint on models of CME-precursor magnetic structure. These quiescent structures exist in the low corona, primarily below approximately 1.6 R , and so are currently observable in white light during solar eclipses, or else by the Mauna Loa Solar Observatory Mk4 coronameter. We present the first comprehensive, quantitative analysis of white-light quiescent cavities as observed by the Mk4 coronameter. We find that such cavities are ubiquitous, as they are the coronal limb counterparts to filament channels observed on the solar disk. We consider examples that range from extremely long-lived, longitudinally extended polar-crown-filament-related cavities to smaller cavities associated with filaments near or within active regions. The former are often visible for days and even weeks at a time and can be identified as long-lived cavities that survive for months. We quantify cavity morphology and intensity contrast properties and consider correlations between these properties. We find multiple cases in which quiescent cavities directly erupt into CMEs and consider how morphological and intensity contrast properties of these cases differ from the general population of cavities. Finally, we discuss the implications that these observations may have for the state of the corona just prior to a CME, and more generally for the nature of coronal MHD equilibria.

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Section: Cavity Observations To Datementioning

confidence: 98%

Section: Cavity Observations To Datementioning

confidence: 99%

The Calm before the Storm: The Link between Quiescent Cavities and Coronal Mass Ejections

Gibson¹,

Foster²,

Burkepile³

et al. 2006

ApJ

165

151

View full text Add to dashboard Cite

show abstract

“…However, observations in the coronal green and red lines (Waldmeier, 1970) and in the white light corona during eclipses (Saito and Hyder, 1968;Saito and Tandberg-Hanssen, 1973) have shown that cavities have significantly lower densities (~<108 cm -3) than the surrounding corona. Therefore the observed flux increase could not be due entirely to a temperature increase, i.e., there must also have been an accompanying increase in the density.…”

Section: (8)mentioning

confidence: 99%

Coronal X-ray enhancements associated with H? filament disappearances

Webb¹,

Krieger²,

Rust³

1976

Sol Phys

125

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A survey of soft X-ray images from Skylab has revealed a class of large-scale transient X-ray enhancements in the lower corona which are typically associated with the disappearance of Ha filaments away from active regions. Contemporary with the Ha filament disappearance, X-r@ emitting structures appeared at or near the filament location with shape and size resembling the filament. Eventually these structures faded, but the filament cavity was no longer obvious. Typically the peak of the X-ray event lagged the end of the filament disappearance by tens of minutes. The durations of the coronal X-ray enhancements were considerably longer than the associated Ha filament disappearances. Major flare effects, such as chromospheric brightenings, typically were not associated with these X-ray events.One event analyzed quantitatively had a peak temperature between 1.8 and 2.7 x 106 K, achieved a peak density of ~ 109 cm -3 and resulted in an enhancement in the plasma pressure over the conditions of the preexisting coronal cavity of at least a factor of 7. The mass of the coronal X-ray emitting material was about 10% that of the preexisting filament and the thermal energy of the coronal event was on the order of 1029 erg, about 10% of the mechanical energy of the Ha filament eruption. The event appeared to cool by radiative losses and not by thermal conduction. It is likely that the coronal enhancements are caused by heating of an excess of previously cooler material, either from the filament itself, or by compression of coronal material by a changing magnetic field.

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“…This region is referred to as the prominence cavity or filament cavity. Exterior to the tunnel of coronal arches, white light eclipse images, x-ray images and white light images from experiments on solar satellites have shown that a helmet-like configuration caps the tunnel of coronal arches (Saito and Hyder 1968;Tandberg-Hanssen 1995).…”

Section: Introductionmentioning

confidence: 98%

Filament Thread-like Structures and Their Small-amplitude Oscillations

Lin

2010

Space Sci Rev

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Thanks to gradually improving observational capabilities, both from space and ground-based observatories, it is now generally accepted that thin threads (width ∼200 km) constitute the building blocks of solar filaments and prominences. At ultra-small scales, high quality image sequences show a non-static picture of filaments and reveal that their oscillatory behavior is an important dynamic feature of these structures. Filament seismology sheds light on the internal magnetic structures of filaments and their interactions with surrounding solar regions. Understanding the overall magnetic topology of solar filaments and prominences including their small-scale thread-like structures is essential in interpretation and understanding of their oscillations. For this reason we aim here to present an update of the dynamic and spatial structures of prominences and filaments as inferred from high resolution observations in the past decennia. Some constraints in high resolution observations are addressed. Our review focuses mainly on the observational aspects and aims to summarize recent oscillation studies of individual filament threads and groups of threads. Finally, some theoretical interpretations of oscillations of filament threads and the inferred physical conditions of filament plasma are also discussed.

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A concentric ellipse multiple-arch system in the solar corona

Cited by 34 publications

References 7 publications

The Calm before the Storm: The Link between Quiescent Cavities and Coronal Mass Ejections

The Calm before the Storm: The Link between Quiescent Cavities and Coronal Mass Ejections

Coronal X-ray enhancements associated with H? filament disappearances

Filament Thread-like Structures and Their Small-amplitude Oscillations

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