The High‐Temperature Response of the<i>TRACE</i>171 A and 195 A Channels

Phillips, K. J. H.; Chifor, C.; Landi, E.

doi:10.1086/430128

Cited by 24 publications

(17 citation statements)

References 12 publications

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“…Warren & Reeves (2001) and Gallagher et al (2002) reported very similar bright and diffuse emission from TRACE 195 Å loops associated with X-class flares, which was interpreted as being due to the Fe xxiv contribution of plasma at a temperature of 15-20 MK. Phillips et al (2005) further confirmed that the Fe xxiv line emission is the dominant contributor to emission in the TRACE 195 Å channel for flare associated high temperature features (such as hot LT emission). These bright EUV loops showed a large-scale contraction.…”

Section: The First Phasesupporting

confidence: 57%

Magnetic Reconnection During the Two-Phase Evolution of a Solar Eruptive Flare

Joshi

Veronig

Cho

et al. 2009

ApJ

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We present a detailed multi-wavelength analysis and interpretation of the evolution of an M7.6 flare that occurred near the southeast limb on 2003 October 24. Pre-flare images at TRACE 195 Å show that the bright and complex system of coronal loops already existed at the flaring site. The X-ray observations of the flare taken from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) spacecraft reveal two phases of the flare evolution. The first phase is characterized by the altitude decrease of the X-ray looptop (LT) source for ∼11 minutes. Such a long duration of the descending LT source motion is reported for the first time. The EUV loops, located below the X-ray LT source, also undergo contraction with similar speed (∼15 km s −1 ) in this interval. During the second phase the two distinct hard X-ray footpoint (FP) sources are observed which correlate well with UV and Hα flare ribbons. The X-ray LT source now exhibits upward motion as anticipated from the standard flare model. The RHESSI spectra during the first phase are soft and indicative of hot thermal emission from flaring loops with temperatures T > 25 MK at the early stage. On the other hand, the spectra at high energies (ε 25 keV) follow hard power laws during the second phase (γ = 2.6-2.8). We show that the observed motion of the LT and FP sources can be understood as a consequence of three-dimensional magnetic reconnection at a separator in the corona. During the first phase of the flare, the reconnection releases an excess of magnetic energy related to the magnetic tensions generated before a flare by the shear flows in the photosphere. The relaxation of the associated magnetic shear in the corona by the reconnection process explains the descending motion of the LT source. During the second phase, the ordinary reconnection process dominates describing the energy release in terms of the standard model of large eruptive flares with increasing FP separation and upward motion of the LT source.

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Section: The First Phasesupporting

confidence: 57%

Magnetic Reconnection During the Two-Phase Evolution of a Solar Eruptive Flare

Joshi

Veronig

Cho

et al. 2009

ApJ

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“…Thus, for our present analysis we obtain a loop temperature of T = 1.5 ± 0.6 MK, which is within TRACE's temperature response for the 171 Å channel, and towards the central portion of the 195 Å channel's temperature response curve (Aschwanden 2004;Phillips et al 2005). Nevertheless, the visibility of the coronal loop in both the 171 Å and 195 Å bandpasses, in addition to a derived loop temperature within the TRACE instrument's temperature response function, suggests that the loop under investigation is in hydrostatic equilibrium (Andries et al 2005).…”

Section: Application Of Coronal Seismologysupporting

confidence: 81%

TRACE observations of driven loop oscillations

Ballai

Jess²,

Douglas

2011

A&A

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Aims. On 13 June 1998, the TRACE satellite was fortuitously well placed to observe the effects of a flare-induced EIT wave in the corona, and its subsequent interaction with coronal magnetic loops. In this study, we use these TRACE observations to corroborate previous theoretical work, which determined the response of a coronal loop to a harmonic driver in the context of ideal magnetohydrodynamics, as well as estimate the magnetic field strength and the degree of longitudinal inhomogeneity. Methods. Loop edges are tracked, both spatially and temporally, using wavelet modulus maxima algorithms, with corresponding loop displacements from its quiescent state analysed by fitting scaled sinusoidal functions. The physical parameters of the coronal loop are subsequently determined using seismological techniques. Results. The studied coronal loop is found to oscillate with two distinct periods, 501 ± 5 s and 274 ± 7 s, which could be interpreted as belonging to the fundamental kink mode and first harmonic, or could reflect the stage of an overdriven loop. Additional scenarios for explaining the two periods are listed, each resulting in a different value of the magnetic field and the intrinsic and sub-resolution properties of the coronal loop. When assuming the periods belong to the fundamental kink mode and its first harmonic, we obtain a magnetic field strength inside the oscillating coronal loop of 2.0 ± 0.7 G. In contrast, interpreting the oscillations as a combination of the loop's natural kink frequency and a harmonic EIT wave provides a magnetic field strength of 5.8 ± 1.5 G. Using the ratio of the two periods, we find that the gravitational scale height in the loop is 73 ± 3 Mm. Conclusions. We show that the observation of two distinct periods in a coronal loop does not necessarily lead to a unique conclusion. Multiple plausible scenarios exist, suggesting that both the derived strength of the magnetic field and the sub-resolution properties of the coronal loop depend entirely on which interpretation is chosen. The interpretation of the observations in terms of a combination of the natural kink mode of the coronal loop, driven by a harmonic EIT wave seems to result in values of the magnetic field consistent with previous findings. Other interpretations, which are realistic, such as kink fundamental mode/first harmonic and the oscillations of two sub-resolution threads result in magnetic field strengths that are below the average values found before.

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“…Fe ix and Fe x lines dominate the emission in 171 Å TRACE images, making them most sensitive to temperatures of 1-2 MK. Phillips et al (2005) have demonstrated that the 171 Å filter also has a hightemperature response due to continuum and Fe xx contributions.…”

Section: Overview Of the Event And Observing Instrumentsmentioning

confidence: 98%

The early phases of a solar prominence eruption and associated flare: a multi-wavelength analysis

Chifor¹,

Mason²,

Tripathi³

et al. 2006

A&A

Self Cite

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Aims. We aim to examine the precursor phases and early evolution of a prominence eruption associated with a M4-class flare and a partial halo coronal mass ejection (CME) observed on 2005 July 27. Our main goal is to investigate the precursor eruption signatures observed in EUV, X-ray and microwave emission and their relation to the prominence destabilisation. Methods. We perform a multi-wavelength study of the prominence morphology and motion using high-cadence and spatial resolution EUV 171 Å images from the TRACE satellite. The high-temperature flare radiative emission in soft and hard X-rays are analysed through imaging and spectral modeling with RHESSI. Complementary microwave images (17 GHz and 34 GHz) from NoRH are also investigated.Results. The activation of the filament proceeds from one anchored footpoint. We observe "pre-eruption" brightenings in X-ray and EUV images, close to the erupting footpoint of the prominence, being temporally correlated to the point when the prominence first enters a slow-rise phase, and then an accelerated fast-rise phase. The brightness temperature (T b ) of the prominence at 34 GHz is increasing during the eruption. We also find very good correlation between the prominence height-time profile and the spatially integrated soft X-ray (SXR) emission. Conclusions. We discuss the observed precursor brightenings with respect to possible mechanisms that might be responsible for the prominence destabilisation and acceleration. Our observations suggest that reconnection events localised beneath the erupting footpoint may eventually destabilise the entire prominence, causing the eruption.

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The High‐Temperature Response of theTRACE171 A and 195 A Channels

Cited by 24 publications

References 12 publications

Magnetic Reconnection During the Two-Phase Evolution of a Solar Eruptive Flare

Magnetic Reconnection During the Two-Phase Evolution of a Solar Eruptive Flare

TRACE observations of driven loop oscillations

The early phases of a solar prominence eruption and associated flare: a multi-wavelength analysis

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