Atmospheric Imaging Assembly Observations of Coronal Loops: Cross-Field Temperature Distributions

Polito

Janvier

et al. 2016

ApJ

116

111

We investigate the occurrence of slipping magnetic reconnection, chromospheric evaporation, and coronal loop dynamics in the 2014 September 10 X-class flare. The slipping reconnection is found to be present throughout the flare from its early phase. Flare loops are seen to slip in opposite directions towards both ends of the ribbons. Velocities of 20-40 km s −1 are found within time windows where the slipping is well resolved. The warm coronal loops exhibit expanding and contracting motions that are interpreted as displacements due to the growing flux rope that subsequently erupts. This flux rope existed and erupted before the onset of apparent coronal implosion. This indicates that the energy release proceeds by slipping reconnection and not via coronal implosion. The slipping reconnection leads to changes in the geometry of the observed structures at the IRIS slit position, from flare loop top to the footpoints in the ribbons. This results in variations of the observed velocities of chromospheric evaporation in the early flare phase. Finally, it is found that the precursor signatures including localized EUV brightenings as well as non-thermal X-ray emission are signatures of the flare itself, progressing from the early phase towards the impulsive phase, with the tether-cutting being provided by the slipping reconnection. The dynamics of both the flare and outlying coronal loops is found to be consistent with the predictions of the standard solar flare model in 3D.

Section: Flare Evolutionmentioning

confidence: 99%

Section: Flare Evolutionmentioning

confidence: 99%

Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-CLASS Solar Flare

Polito

Janvier

et al. 2016

ApJ

116

111

“…However, the presence of a variety of emission lines originating at different temperatures within one filter bandpass makes the temperature responses of the AIA EUV filters (Fig. 2) highly multithermal in nature (e.g., O'Dwyer et al 2010;Del Zanna et al 2011c;Schmelz et al 2013). This behaviour is also reflected in the responses of the 131 Å and 94 Å filters used for flare observations.…”

Section: Overviewmentioning

confidence: 99%

SLIPPING MAGNETIC RECONNECTION DURING AN X-CLASS SOLAR FLARE OBSERVED BYSDO/AIA

Janvier

Aulanier

et al. 2014

ApJ

136

158

We present SDO/AIA observations of an eruptive X-class flare of July 12, 2012, and compare its evolution with the predictions of a 3D numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the AIA 131Å observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km s −1 along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flare loops. A DEM analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a CME observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the "standard solar flare model in 3D". This model matches the observations well, reproducing both the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour.

“…The differential emission measure (DEM) indicates the amount of emission from plasmas at a specific temperature. As such, it can reflect the properties, such as the coronal heating mechanism, and was intensively investigated for variety of solar structures and events (e.g., Del Zanna 2013b; Del Schmelz et al 2013Schmelz et al , 2011bSchmelz et al ,a, 2009Hannah & Kontar 2012;Winebarger et al 2012;O'Dwyer et al 2011;Brooks et al 2012Brooks et al , 2011Reale et al 2009;Siarkowski et al 2008;Parenti & Vial 2007;Schmelz & Martens 2006;Lanzafame et al 2005Lanzafame et al , 2002Judge et al 1997;Thompson 1990;Fludra & Sylwester 1986;Sylwester et al 1980;Craig 1977;Craig & Brown 1976). The properties of emission in the core of an active region have been studied by Warren et al (2011), Tripathi et al (2011), and Viall & Klimchuk (2011, and typically found to be multithermal.…”

Section: Introductionmentioning

confidence: 99%

Differential emission measure analysis of active region cores and quiet Sun for the non-Maxwellianκ-distributions

Mackovjak

Dzifčáková

2014

A&A

Context. The non-Maxwellian κ-distributions have been detected in the solar wind and can explain intensities of some transition region lines. Presence of such distributions in the outer layers of the solar atmosphere influences the ionization and excitation equilibrium and widens the line contribution functions. This behavior may be reflected on the reconstructed differential emission measure (DEM). Aims. We aim to investigate the influence of κ-distributions on the reconstructed DEMs. Methods. We perform DEM reconstruction for three active region cores and a quiet Sun region using the Withbroe-Sylwester method and the regularization method. Results. We find that the reconstructed DEMs depend on the value of κ. The DEMs of the active region cores show similar behavior with decreasing κ, or an increasing departure from the Maxwellian distribution. For lower κ, the peaks of the DEMs are typically shifted to higher temperatures and the DEMs themselves become more concave. This is caused by the less steep high-temperature slopes for lower κ. However, the low-temperature slopes do not change significantly even for extremely low κ. The behavior of the quiet-Sun DEM distribution is different. It becomes progressively less multithermal for lower κ with the EM-loci plots that indicate near-isothermal plasma for κ = 2. Conclusions. The κ-distributions can influence the reconstructed DEMs. The slopes of the DEM, however, do not change with κ significantly enough to produce different constraints on the heating mechanism in terms of frequency of coronal heating events.