Toward magnetic field dissipation during the 23 July 2002 solar flare measured with Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) and Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

Zharkova, V. V.; Zharkov, S.; Ipson, Stanley S.; Benkhalil, A.

doi:10.1029/2004ja010934

Cited by 22 publications

(9 citation statements)

References 45 publications

(88 reference statements)

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“…Indeed, the results of our preliminary analysis suggest that abrupt and permanent magnetic changes are more prevalent in the ribbons, although the picture is still quite complex, perhaps due to the continuing flux emergence in the region. Further analysis making use of known methods (Sudol and Harvey, 2005;Zharkova, Zharkov, Ipson et al, 2005) and now available HMI vector magnetic data is needed to understand the variability of magnetic-field changes in seismic sources and this flare in general.…”

Section: Discussionmentioning

confidence: 99%

Properties of the 15 February 2011 Flare Seismic Sources

et al. 2012

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The first near-side X-class flare of the Solar Cycle 24 occurred in February 2011 and produced a very strong seismic response in the photosphere. One sunquake was reported by Kosovichev (2011) followed by the discovery of a second sunquake by Zharkov et al (2011). The flare had a two-ribbon structure and was associated with a flux rope eruption and a halo coronal mass ejection (CME) as reported in the CACTus catalogue. Following the discovery of the second sunquake and the spatial association of both sources with the locations of the feet of the erupting flux rope (Zharkov et al 2011) we present here a more detailed analysis of the observed photospheric changes in and around the seismic sources. These sunquakes are quite unusual, taking place early in the impulsive stage of the flare, with the seismic sources showing little hard X-ray (HXR) emission, and strongest X-ray emission sources located in the flare ribbons. We present a directional time--distance diagram computed for the second source, which clearly shows a ridge corresponding to the travelling acoustic wave packet and find that the quake at the second source happened about 45 seconds to one minute earlier than the first source. Using acoustic holography we report different frequency responses of the two sources. We find strong downflows at both seismic locations and a supersonic horizontal motion at the second site of acoustic wave excitation.Comment: 15 pages, 5 figures, accepted for publication by Solar Physic

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Section: Discussionmentioning

confidence: 99%

Properties of the 15 February 2011 Flare Seismic Sources

et al. 2012

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“…Later, when high-cadence longitudinal (line-of-sight) photospheric magnetic field measurements became available from NASA's Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SoHO) satellite and the National Solar Observatory's Global Oscillations Network Group (GONG) ground-based network, the evidence for flare-related magnetic changes in the photosphere became clearer. Based on 1-min MDI longitudinal data, Zharkova (1999, 2001) reported sudden and permanent decreases in magnetic flux near X-class flares near magnetic neutral lines, and Zharkova et al (2005) found a permanent and significant increase in magnetic flux near the neutral line of a region during another X-class flare observed near the limb. Using 1-min GONG longitudinal magnetograms, Sudol and Harvey (2005) characterized the spatial distribution, strength, and rate of change of permanent field changes associated with 15 X-class flares by tracing the field changes pixel by pixel.…”

Section: Introductionmentioning

confidence: 96%

Photospheric and Coronal Observations of Abrupt Magnetic Restructuring in Two Flaring Active Regions

Petrie

2016

Sol Phys

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For two major X-class flares observed by the Solar Dynamics Observatory (SDO) and the Solar TErrestrial RElations Observatory Ahead (STEREO-A) spacecraft when they were close to quadrature, we compare major, abrupt changes in the photospheric magnetic vector field to changes in the observed coronal magnetic structure during the two flares. The Lorentz force changes in strong photospheric fields within active regions are estimated from time series of SDO Helioseismic and Magnetic Imager (HMI) vector magnetograms. These show that the major changes occurred in each case near the main neutral line of the region and in two neighboring twisted opposite-polarity sunspots. In each case the horizontal parallel field strengthened significantly near the neutral line while the azimuthal field in the sunspots decreased, suggesting that a flux rope joining the two sunspots collapsed across the neutral line with reduced magnetic pressure because of a reduced field twist component. At the same time, the coronal extreme ultraviolet (EUV) loop structure was observed by the Atmospheric Imaging Assembly (AIA) onboard SDO and the Extreme Ultraviolet Imager (EUVI) on STEREO-A to decrease significantly in height during each eruption, discontinuous changes signifying ejection of magnetized plasma, and outward-propagating continuous but abrupt changes consistent with loop contraction. An asymmetry in the observed EUV loop changes during one of the flares matches an asymmetry in the photospheric magnetic changes associated with that flare. The observations are discussed in terms of the wellknown tether-cutting and breakout flare initiation models.

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“…In consequence, plasma can escape from the corona and it was reported by Thompson et al (2000) that extended intensity depletions seen in EUV light during representative events mapped out the apparent footprints of CMEs contemporaneously observed in white-light coronagraph data. Also it was demonstrated (Zarro et al, 1999) that the possible explanation that coronal dimming is due to a local cooling effect (see, e.g., Chertok and Grechnev, 2003) is not supported by the observations since dimmings were simultaneously recorded within the same spatial location at different wavelengths (Attrill et al, 2008 and references therein). Spectral data confirm that dimming is due to mass loss Sterling, 2001, 2003;Harra et al, 2007).…”

Section: Coronal Mass Ejections and Coronal Dimmingmentioning

confidence: 95%

“…It was later argued by Zhang et al (2002) that loss of equilibrium within a magnetic coronal structure may trigger both a CME and a flare. Thereafter, Andrews (2003) demonstrated that only 60% of flares of M-class and higher are associated with CMEs.…”

Section: The Initiation Of Cmes and Flaresmentioning

confidence: 98%

Discovery in 1960 of the Flare Nimbus Phenomenon and Changes with Time in Its Interpretation

McKenna‐Lawlor

2011

Sol Phys

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During the International Geophysical Year (IGY, 1957(IGY, /1958) Dunsink Observatory near Dublin in Ireland was a World Data Centre for Solar Activity. In this circumstance, Hα Lyot Heliograph records secured on a daily basis between 07:00 -14:00 UT at the Cape of Good Hope (then an integral link in a network of similar instruments contributing during the IGY to global monitoring of solar chromospheric activity) were routinely sent to Dunsink for analysis and dissemination. The investigations carried out at Dunsink on these data resulted, inter alia, in the discovery of the Flare Nimbus phenomenon. The nimbus comprises a dark expanding halo seen in the plage regions around major flares at, or within a few minutes of, the time of flare maximum intensity in Hα light. It reaches its greatest extent about 30 minutes after flare maximum. Its maximum dimensions (estimated visually) lie in the range 2 -4 × 10 5 km and its duration ranges from ∼ 1 -2 hours. Within the nimbus the striation pattern is either completely destroyed or loses its pre-flare configuration. An account of this phenomenon and its interpretation appeared primarily, although not exclusively, in the locally produced Dunsink Observatory Publications which are not now easily accessible to the world community of solar researchers. Also, at around the time when the nimbus was first identified and recorded in Lyot Heliograph data at several observatories, techniques in solar physics shifted towards high resolution narrow field observations. Under these conditions no further examples of the nimbus were recorded and the subject has remained dormant over several decades. The present paper again places the scientific results obtained with regard to the nimbus in the public domain, together with an account of the evolution within the scientific community of an explanation of this phenomenon. It is suggested here for the first time, in the light of present day data concerning coronal mass ejections (CMEs) and coronal dimming, that the nimbus provides a signature of CME-related reorganization of the magnetic field in the chromosphere (such that the transverse magnetic field component decreases and transforms into the line of sight component as the vector field stretches out). Coronal dimming provides a complementary signature of CME-related mass depletion in the corona.

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Toward magnetic field dissipation during the 23 July 2002 solar flare measured with Solar and Heliospheric Observatory/Michelson Doppler Imager (SOHO/MDI) and Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI)

Cited by 22 publications

References 45 publications

Properties of the 15 February 2011 Flare Seismic Sources

Properties of the 15 February 2011 Flare Seismic Sources

Photospheric and Coronal Observations of Abrupt Magnetic Restructuring in Two Flaring Active Regions

Discovery in 1960 of the Flare Nimbus Phenomenon and Changes with Time in Its Interpretation

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