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Hudson, H. S.; Khan, J. I.; Lemen, J. R.; Nitta, N.; Uchida, Yutaka

doi:10.1023/a:1022904125479

Cited by 119 publications

(102 citation statements)

References 39 publications

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“…The event was associated with a very strong intensity enhancement, with the electron temperature in the wave estimated to be ∼2-4 MK, and the Mach number of the shock estimated to be ∼1.1-1.3 (these estimates are dependent on the assumed coronal ambient temperature). Hudson et al (2003) concluded that the observations were consistent with the interpretation of the X-ray emission front as the signature of a coronal shock wave at a low Mach number. The cause of the shock wave was hypothesized to be due to plasma motions that began at a relatively small distance from the flare core, with this conclusion due to the close association between the excitation of the wave and the beginning of the impulsive phase of the flare.…”

Section: Euv and X-ray Signatures Of Coronal Bright Frontssupporting

confidence: 83%

“…The next observation of an X-ray wave was made by Hudson et al (2003), with an Xray wave associated with an X-class flare and Type II, III, and IV radio bursts. In this event, a large loop structure to the north of the flare core is observed to explode outwards, with the wave appearing to emanate from this location.…”

Section: Euv and X-ray Signatures Of Coronal Bright Frontsmentioning

confidence: 99%

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Large-scale Bright Fronts in the Solar Corona: A Review of “EIT waves”

2010

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"EIT waves" are large-scale coronal bright fronts (CBFs) that were first observed in 195Å images obtained using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory (SOHO). Commonly called "EIT waves", CBFs typically appear as diffuse fronts that propagate pseudo-radially across the solar disk at velocities of 100-700 km s −1 with front widths of 50-100 Mm. As their speed is greater than the quiet coronal sound speed (c s ≤200 km s −1 ) and comparable to the local Alfvén speed (v A ≤1000 km s −1 ), they were initially interpreted as fast-mode magnetoacoustic waves (v f = (c 2 s + v 2 A ) 1/2 ). Their propagation is now known to be modified by regions where the magnetosonic sound speed varies, such as active regions and coronal holes, but there is also evidence for stationary CBFs at coronal hole boundaries. The latter has led to the suggestion that they may be a manifestation of a processes such as Joule heating or magnetic reconnection, rather than a wave-related phenomena. While the general morphological and kinematic properties of CBFs and their association with coronal mass ejections have now been well described, there are many questions regarding their excitation and propagation. In particular, the theoretical interpretation of these enigmatic events as magnetohydrodynamic waves or due to changes in magnetic topology remains the topic of much debate.

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Section: Euv and X-ray Signatures Of Coronal Bright Frontssupporting

confidence: 83%

Section: Euv and X-ray Signatures Of Coronal Bright Frontsmentioning

confidence: 99%

Large-scale Bright Fronts in the Solar Corona: A Review of “EIT waves”

2010

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“…See also Fig. 3 in Hudson et al 2003). Later a wave-like signature, inferred to be the direct observation of a shock wave seen in soft X-rays (Khan & Hudson 2000;Hudson et al 2003) was observed (indicated by the white arrow in Fig.…”

Section: Yohkoh Soft X-ray Telescope Imagesmentioning

confidence: 85%

“…Here we refer to the M-class flare as "Flare 1" and the X-class flare as "Flare 2". Some aspects of Flare 2 and phenomena associated with it have already been examined and reported elsewhere (e.g., Khan & Hudson 2000;Klassen et al 2001;Hudson et al 2003). In this paper we concentrate on aspects related to the shrinking and expanding coronal loops associated with Flare 2.…”

Section: Observationsmentioning

confidence: 88%

Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Khan¹,

Fletcher²,

Nitta

2006

A&A

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We report what we believe are the first direct and unambiguous observations of simultaneous coronal magnetic flux loop shrinkage and expansion during the decay phase of a solar flare. The retracting and expanding loops were observed nearly face-on (i.e., with the loop major axis approximately orthogonal to the line of sight) in emission in imaging data from the Yohkoh Soft X-ray Telescope (SXT). The retracting loop is observed to shrink with a speed of 118 ± 66 km s −1 . The faint outward moving loop-like feature occurred ∼200 above the shrinking loop during the time of the shrinking loop. We estimate the speed of the outward moving loop was ∼129 ± 74 km s −1 . We interpret the shrinking loop and simultaneous outward moving loop as direct evidence for reconnected magnetic field lines during a flare.

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“…These manifestations occur in tandem to the large-scale front which is essentially the EUV wave. Moreover, EUV waves are frequently associated with phenomena observed in other wavelength domains such as Moreton waves in the chromospheric Hα (e.g., Thompson et al, 2000;Warmuth et al, 2001) and He I 10830 A lines (e.g., Vršnak et al, 2002), and in the corona in Soft X-rays (SXRs) (e.g., Khan and Aurass, 2002;Hudson et al, 2003;Warmuth, Mann, and Aurass, 2005) microwaves (e.g., Warmuth et al, 2004;White and Thompson, 2005) and in the metric-range (e.g., Vršnak et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

On the Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode (Invited Review)

2012

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A major, albeit serendipitous, discovery of the SOlar and Heliospheric Observatory mission was the observation by the Extreme Ultraviolet Telescope (EIT) of large-scale Extreme Ultraviolet (EUV) intensity fronts propagating over a significant fraction of the Sun's surface. These so-called EIT or EUV waves are associated with eruptive phenomena and have been studied intensely. However, their wave nature has been challenged by non-wave (or pseudo-wave) interpretations and the subject remains under debate. A string of recent solar missions has provided a wealth of detailed EUV observations of these waves bringing us closer to resolving their nature. With this review, we gather the current state-of-art knowledge in the field and synthesize it into a picture of an EUV wave driven by the lateral expansion of the CME. This picture can account for both wave and pseudo-wave interpretations of the observations, thus resolving the controversy over the nature of EUV waves to a large degree but not completely. We close with a discussion of several remaining open questions in the field of EUV waves research.

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Cited by 119 publications

References 39 publications

Large-scale Bright Fronts in the Solar Corona: A Review of “EIT waves”

Large-scale Bright Fronts in the Solar Corona: A Review of “EIT waves”

Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

On the Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode (Invited Review)

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