RHESSI observations of long-duration flares with long-lasting X-ray loop-top sources

Kołomański, S.; Mrozek, Tomasz; Bąk-Stęślicka, Urszula

doi:10.1051/0004-6361/201016176

Cited by 9 publications

(11 citation statements)

References 45 publications

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“…Here, we investigate the kinematic evolution of CMEs associated with long duration flares of slow rising phase (slow LDEs). This group of flares is characterized not only by a long decay but also by long rising phase, which may last more than 30 minutes (Hudson and McKenzie, 2000;Bak-Stȩślicka and Jakimiec, 2005;Bak-Stȩślicka, Mrozek, and Ko lomański, 2011). Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) analysis of several slow LDEs is presented in our previous article (Bak-Stȩślicka, Mrozek, and Ko lomański, 2011).…”

Section: Introductionmentioning

confidence: 99%

Coronal Mass Ejections Associated with Slow Long Duration Flares

2013

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It is well known that there is a temporal relationship between coronal mass ejections (CMEs) and associated flares. The duration of the acceleration phase is related to the duration of the rise phase of a flare. We investigate CMEs associated with slow long duration events (LDEs), i.e. flares with the long rising phase. We determined the relationships between flares and CMEs and analyzed the CME kinematics in detail. The parameters of the flares (GOES flux, duration of the rising phase) show strong correlations with the CME parameters (velocity, acceleration during main acceleration phase, and duration of the CME acceleration phase). These correlations confirm the strong relation between slow LDEs and CMEs. We also analyzed the relation between the parameters of the CMEs, i.e. a velocity, an acceleration during the main acceleration phase, a duration of the acceleration phase, and a height of a CME at the end of the acceleration phase. The CMEs associated with the slow LDEs are characterized by high velocity during the propagation phase, with the median equal to 1423 km s −1 . In half of the analyzed cases, the main acceleration was low (a < 300 m s −2 ), which suggests that the high velocity is caused by the prolonged acceleration phase (the median for the duration of the acceleration phase is equal 90 minutes). The CMEs were accelerated up to several solar radii (with the median ≈ 7 R ), which is much U. Bak-Stȩślicka is a visiting scientist at High Altitude Obsevatory, NCAR, Boulder, USA.U. Bak-Stȩślicka ( ) · S. Kołomański · T. Mrozek

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Section: Introductionmentioning

confidence: 99%

Coronal Mass Ejections Associated with Slow Long Duration Flares

2013

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“…The plasma temperature decreased much slower than by thermal conduction only, even during the X-ray decay phase, suggesting at later stages additional energy release is required (e.g. Ko lomański et al 2011) to explain the long lasting X-ray loop emission. For the limb event (Flare 1), we do see a decrease in loop altitude before the peak in X-ray emission of roughly 2 ′′ ≃ 1.4 Mm, which is comparable in magnitude to the decrease in loop width but overall, the largest changes occurred for the X-ray loop volume, not the X-ray loop position.…”

Section: Summary and Discussionmentioning

confidence: 98%

Temporal Variations of X-Ray Solar Flare Loops: Length, Corpulence, Position, Temperature, Plasma Pressure, and Spectra

Jeffrey

Kontar

2013

ApJ

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The spatial and spectral properties of three solar flare coronal X-ray loops are studied before, during and after the peak X-ray emission. Using observations from the Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we deduce the temporal changes in emitting X-ray length, corpulence, volume, position, number density and thermal pressure. We observe a decrease in the loop length, width and volume before the X-ray peak, and an increasing number density and thermal pressure. After the X-ray peak, volume increases and loop corpulence grows due to an increasing width. The volume variations are more pronounced than the position variations, often known as magnetic line contraction. We believe this is the first dedicated study of the temporal evolution of X-ray loop lengths and widths. Collectively, the observations also show for the first time three temporal phases given by peaks in temperature, X-ray emission and thermal pressure, with minimum volume coinciding with the X-ray peak. Although the volume of the flaring plasma decreases before the peak in X-ray emission, the relationship between temperature and volume does not support simple compressive heating in a collapsing magnetic trap model. Within a low β plasma, shrinking loop widths perpendicular to the guiding field can be explained by squeezing the magnetic field threading the region. Plasma heating leads to chromospheric evaporation and growing number density, producing increasing thermal pressure and decreasing loop lengths as electrons interact at shorter distances and we believe after the X-ray peak, the increasing loop corpulence.

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“…They are the long-lived cusp-shaped loop-top sources. The presence of a source of energy could prolong the decay phase up to from several hours to more than one day (see, for example, Isobe et al 2002;Ko lomański et al 2011b, and references therein). Therefore, there is a need to identify which of the mechanisms operates in a given case.…”

Section: Introductionmentioning

confidence: 99%

Quasi-periodic pulsations in a solar flare with an unusual phase shift

Kupriyanova

Kashapova

Doorsselaere

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Two kinds of processes could occur during the flare decay phase: processes of energy release or processes of energy relaxation. Quasi-periodic pulsations (QPPs) of the broadband emission are a good tool for the verification of mechanisms. We aim to study the processes during the decay phase of the X-class solar flare SOL2014-03-29T17:48. The observations in X-ray, microwave, and extreme ultraviolet (EUV) bands are exploited to study the fine temporal, spatial, and spectral structures of the flare. The periods, amplitudes, and phases of both the fluxes and physical parameters (emission measure, temperature) are studied using standard methods of correlation, Fourier, and wavelet analyses. It is found that the source of the QPPs is associated with the uniform post-flare loop. The X-ray source is located at the top of the arcade. QPPs with the similar characteristic time scales of P ≈ 74-80 s are found in the X-ray (3-25 keV) and microwave (15.7 GHz) emissions. Besides, QPPs with the same period are found in the time profiles of both the temperature (T e ) and emission measure (E M). The QPPs in temperature and the QPPs in emission measure demonstrate anti-phase behavior. The analysis reveals the quasi-periodic process of energy relaxation, without any additional source of energy during the decay phase. The periods of the QPPs are in a good agreement with second harmonic of standing slow magneto-acoustic wave in the arcade which could be triggered by a Moreton wave initiated by the flare in the direct vicinity of the arcade.

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RHESSI observations of long-duration flares with long-lasting X-ray loop-top sources

Cited by 9 publications

References 45 publications

Coronal Mass Ejections Associated with Slow Long Duration Flares

Coronal Mass Ejections Associated with Slow Long Duration Flares

Temporal Variations of X-Ray Solar Flare Loops: Length, Corpulence, Position, Temperature, Plasma Pressure, and Spectra

Quasi-periodic pulsations in a solar flare with an unusual phase shift

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