Preface

Ren, Lin; Dennis, B. R.; Benz, A. O.; Harvey, J. W.; Engvold, O.; Švestka, Z.

doi:10.1007/s11207-004-0827-2

Cited by 513 publications

(571 citation statements)

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“…Because of its particular location (at the limb) and its peculiar orientation (with the line connecting the footpoints approximately perpendicular to the equator) the flare-loop system observed during the main phase of the flare allowed us to study the evolution of some physical parameters and to compare them with those provided by models. We observed the loop system in the EUV range using TRACE (Handy et al 1999) images at 195 Å, in X-rays by RHESSI (Lin et al 2002) in the 3-6 keV, 6-12 keV, 12-25 keV and 30-80 keV bands and in the radio band, at 17 and 34 GHz.…”

Section: Discussionmentioning

confidence: 99%

Evolution of an eruptive flare loop system

Romano

Zuccarello

Fletcher

et al. 2009

A&A

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Context. Flares, eruptive prominences and coronal mass ejections are phenomena where magnetic reconnection plays an important role. However, the location and the rate of the reconnection, as well as the mechanisms of particle interaction with ambient and chromospheric plasma are still unclear. Aims. In order to contribute to the comprehension of the above mentioned processes we studied the evolution of the eruptive flare loop system in an active region where a flare, a prominence eruption and a CME occurred on August 24, 2002. Methods. We measured the rate of expansion of the flare loop arcade using TRACE 195 Å images and determined the rising velocity and the evolution of the low and high energy hard X-ray sources using RHESSI data. We also fitted HXR spectra and considered the radio emission at 17 and 34 GHZ. Results. We observed that the top of the eruptive flare loop system initially rises with a linear behavior and then, after 120 mn from the start of the event registered by GOES at 1-8 Å, it slows down. We also observed that the heating source (low energy X-ray) rises faster than the top of the loops at 195 Å and that the high energy X-ray emission (30-40 keV) changes in time, changing from footpoint emission at the very onset of the flare to being coincident during the flare peak with the whole flare loop arcade. Conclusions. The evolution of the loop system and of the X-ray sources allowed us to interpret this event in the framework of the Lin & Forbes model (2000), where the absolute rate of reconnection decreases when the current sheet is located at an altitude where the Alfvén speed decreases with height. We estimated that the lower limit for the altitude of the current sheet is 6 × 10 4 km. Moreover, we interpreted the unusual variation of the high energy HXR emission as a manifestation of the non thermal coronal thick-target process which appears during the flare in a manner consistent with the inferred increase in coronal column density.

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Section: Discussionmentioning

confidence: 99%

Evolution of an eruptive flare loop system

Romano

Zuccarello

Fletcher

et al. 2009

A&A

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“…RHESSI (Lin et al 2002) not only provides high resolution spatially integrated spectra but it is possible to obtain feature integrated spectra, i.e. spectra from individual sources, using imaging spectroscopy techniques (Battaglia & Benz 2006).…”

Section: Introductionmentioning

confidence: 99%

Kappa distribution and hard X-ray emission of solar flares

Kašparová¹,

Karlický²

2009

A&A

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Aims. We investigate whether the so-called kappa distribution, often used to fit electron distributions detected in situ in the solar wind, can describe electrons producing the hard X-ray emission in solar flares. Methods. Using Ramaty High Energy Solar Spectroscopic imager (RHESSI) flare data we fit spatially-and feature-integrated spectra, assuming a kappa distribution for the mean electron flux spectrum. Results. We show that a single kappa distribution generally cannot describe spatially integrated X-ray emission composed of both footpoint and coronal sources. In contrast, the kappa distribution is consistent with mean electron spectra producing hard X-ray emission in some coronal sources.

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“…Electrons accelerated in association with jets have been detected in space Article published by EDP Sciences . Another diagnostic of fast electrons is bremsstrahlung X-ray emission which can be observed with the Reuven Ramaty High Energy Spectroscopic Imager, (RHESSI: Lin et al 2002). However until now no evidence of hard X-ray emission has been observed directly from the jet in the corona.…”

Section: Introductionmentioning

confidence: 99%

Hard X-ray emission from a flare-related jet

Bain¹,

Fletcher²

2009

A&A

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Aims. We aim to understand the physical conditions in a jet event which occurred on the 22nd of August 2002, paying particular attention to evidence for non-thermal electrons in the jet material. Methods. We investigate the flare impulsive phase using multiwavelength observations from the Transition Region and Coronal Explorer (TRACE) and the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) satellite missions, and the ground-based Nobeyama Radioheliograph (NoRH) and Radio Polarimeters (NoRP). Results.We report what we believe to be the first observation of hard X-ray emission formed in a coronal jet. We present radio observations which confirm the presence of non-thermal electrons present in the jet at this time. The evolution of the event is best compared with the magnetic reconnection jet model in which emerging magnetic field interacts with the pre-existing coronal field. We calculate an apparent jet velocity of ∼500 km s −1 which is consistent with model predictions for jet material accelerated by the J × B force resulting in a jet velocity of the order of the Alfvén speed (∼100-1000 km s −1 ).

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Preface

Cited by 513 publications

References 0 publications

Evolution of an eruptive flare loop system

Evolution of an eruptive flare loop system

Kappa distribution and hard X-ray emission of solar flares

Hard X-ray emission from a flare-related jet

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