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

Oluseyi, Hakeem M.; Walker, Arthur B. C.; Santiago, David I.; Hoover, Richard B.; Barbee, Troy W.

doi:10.1086/308113

Cited by 15 publications

(32 citation statements)

References 60 publications

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“…The basic input of the theory is the reasonable assumption that the coronal structures are created from the evolution and re-organization of a relatively cold plasma flow [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] emerging from the sub-coronal region (between the solar surface and the visible corona) and interacting with the ambient magnetic field anchored inside the solar surface. During the process of trapping and accumulation, a part of the kinetic energy of the flow is converted to heat by viscous dissipation and the coronal structure is born hot and bright.…”

Section: Introductionmentioning

confidence: 99%

Formation and primary heating of the solar corona: Theory and simulation

et al. 2001

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An integrated Magneto-Fluid model, that accords full treatment to the Velocity fields associated with the directed plasma motion, is developed to investigate the dynamics of coronal structures. It is suggested that the interaction of the fluid and the magnetic aspects of plasma may be a crucial element in creating so much diversity in the solar atmosphere. It is shown that the structures which comprise the solar corona can be created by particle (plasma) flows observed near the Sun's surface -the primary heating of these structures is caused by the viscous dissipation of the flow kinetic energy.

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Section: Introductionmentioning

confidence: 99%

Formation and primary heating of the solar corona: Theory and simulation

et al. 2001

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“…Recent results have also shown that simple scaling laws may not be universally applicable, not holding for some loop classes such as cool transition region loops (Oluseyi et al 1999a(Oluseyi et al , 1999b or Ñaring loops (Garcia 1998), while and Aschwanden, Nightengale, & Alexander (2000a) have also highlighted inconsistencies associated with scaling law relationships. The EUV instruments on board SOHO and particularly T RACE have further added to our ability to measure coronal plasma properties in addition to studying the morphology of solar features, a fact that is clearly highlighted in Aschwanden et al (1999Aschwanden et al ( , 2000aAschwanden et al ( , 2000b.…”

Section: Introductionmentioning

confidence: 99%

The Extreme‐Ultraviolet Structure and Properties of a Newly Emerged Active Region

Gallagher

Phillips

Lee

et al. 2001

ApJ

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The structure and properties of a newly emerged solar active region (NOAA Active Region 7985) are discussed using the Coronal Diagnostic Spectrometer (CDS) and the Extreme-Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory. CDS obtained high-resolution EUV spectra in the 308È381 and 513È633 wavelength ranges, while EIT recorded full-disk EUV images in A A the He II (304 Fe IX/X (171 Fe XII (195 and Fe XV (284 bandpasses. Electron density mea-A ), A ), A ), A ) surements from Si IX, Si X, Fe XII, Fe XIII, and Fe XIV line ratios indicate that the region consists of a central high-density core with peak densities of the order of 1.2 ] 1010 cm~3, which decrease monotonically to D5.0 ] 108 cm~3 at the active region boundary. The derived electron densities also vary systematically with temperature. Electron pressures as a function of both active region position and temperature were estimated using the derived electron densities and ion formation temperatures, and the constant pressure assumption was found to be an unrealistic simpliÐcation. Indeed, the active region is found to have a high-pressure core (1.3 ] 1016 cm~3 K) that falls to 6.0 ] 1014 cm~3 K just outside the region. CDS line ratios from di †erent ionization stages of iron, speciÐcally Fe XVI (335.4and Fe XIV A ) (334.4 were used to diagnose plasma temperatures within the active region. Using this method, peak A ), temperatures of 2.1 ] 106 K were identiÐed. This is in good agreement with electron temperatures derived using EIT Ðlter ratios and the two-temperature model of Zhang et al. The high-temperature emission is conÐned to the active region core, while emission from cooler (1È1.6) ] 106 K lines originates in a system of loops visible in EIT 171 and 195 images. Finally, the three-dimensional geometry of the A active region is investigated using potential Ðeld extrapolations from a Kitt Peak magnetogram. The combination of EUV and magnetic Ðeld extrapolations extends the "" core-halo ÏÏ picture of active region structure to one in which the core is composed of a number of compact coronal loops that conÐne the hot, dense, high-pressure core plasma while the halo emission emerges from a system of cooler and more extended loops.

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“…Two aspects of this event's evolution hint at TCR as its formation mechanism. First, these two individual loop structures, both in close proximity to one another, likely share a footpoint rooted in the center of a supergranulation cell (Oluseyi et al 1999a(Oluseyi et al , 1999b. The convergence of these footpoints leads to propagating brightenings that fill these two loop structures until the full non-potential structure is formed.…”

Section: B August 05mentioning

confidence: 99%

“…First, it has been shown that the QS network at EUV temperatures is dominated by crowded loop structures with one footpoint rooted in the network lanes (Feldman et al 1999;Oluseyi et al 1999aOluseyi et al , 1999bWarren & Winebarger 2000). The close proximity of such loops and the sharing of footpoints elevate such structures as prime candidates for the TCR process.…”

Section: General Commentsmentioning

confidence: 99%

“…However, the formation of intense, bright QS network non-potential events has not yet been observed, but if it is, it may be directly dependent on the morphology and evolution of network cell structuring (Chesny et al 2013). Explosive activity at cool temperatures could be inherent in the QS network where bundles of loop footpoints interact stochastically (Oluseyi et al 1999b) and provide an environment conducive to flaring activity (Hughes et al 2003). The potential for small QS network cool loops to initiate flaring activity (Chesny et al 2013) suggests that identifying the full ensemble of cool, non-potential structures would allow us to explore the physics of non-potential field formation across broad spatial, temporal, thermal, density, and magnetic energy scales.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic Flaring Non-Potential Fields on Quiet Sun Network Scales

Chesny

Oluseyi

Orange³

2016

ApJ

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We report on the identification of dynamic flaring non-potential structures on quiet Sun (QS) supergranular network scales. Data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory allow for the high spatial and temporal resolution of this diverse class of compact structures. The rapidly evolving nonpotential events presented here, with lifetimes <10 minutes, are on the order of 10″ in length. Thus, they contrast significantly with well-known active region (AR) non-potential structures such as high-temperature X-ray and EUV sigmoids (>100″) and micro-sigmoids (>10″) with lifetimes on the order of hours to days. The photospheric magnetic field environment derived from the Helioseismic and Magnetic Imager shows a lack of evidence for these flaring non-potential fields being associated with significant concentrations of bipolar magnetic elements. Of much interest to our events is the possibility of establishing them as precursor signatures of eruptive dynamics, similar to notions for AR sigmoids and micro-sigmoids, but associated with uneventful magnetic network regions. We suggest that the mixed network flux of QS-like magnetic environments, though unresolved, can provide sufficient free magnetic energy for flaring non-potential plasma structuring. The appearance of non-potential magnetic fields could be a fundamental process leading to self-organized criticality in the QS-like supergranular network and contribute to coronal heating, as these events undergo rapid helicial and vortical relaxations.

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

Cited by 15 publications

References 60 publications

Formation and primary heating of the solar corona: Theory and simulation

Formation and primary heating of the solar corona: Theory and simulation

The Extreme‐Ultraviolet Structure and Properties of a Newly Emerged Active Region

Dynamic Flaring Non-Potential Fields on Quiet Sun Network Scales

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