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

Abstract

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.

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

“…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.…”

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

“…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.…”

Dynamic Flaring Non-Potential Fields on Quiet Sun Network Scales

“…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.…”

“…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.…”

“…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.…”