Preflare conditions, changes and events

Martin, Sara

doi:10.1007/bf00156861

Cited by 93 publications

(33 citation statements)

References 68 publications

(30 reference statements)

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“…(6) Filament darkening and widening Martin (1980) pointed out that among many preflare precursors, the most typical one is the filament darkening and widening, as illustrated by Figure 11. Generally a flare would occur 1 hour after the appearance of such features (Bruzek, 1951).…”

Section: (4) Radio Noise Stormsmentioning

confidence: 99%

Coronal Mass Ejections: Models and Their Observational Basis

Chen

2011

Living Rev. Solar Phys.

681

530

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Coronal mass ejections (CMEs) are the largest-scale eruptive phenomenon in the solar system, expanding from active region-sized nonpotential magnetic structure to a much larger size. The bulk of plasma with a mass of ∼ 10 11 -10 13 kg is hauled up all the way out to the interplanetary space with a typical velocity of several hundred or even more than 1000 km s -1 , with a chance to impact our Earth, resulting in hazardous space weather conditions. They involve many other much smaller-sized solar eruptive phenomena, such as X-ray sigmoids, filament/prominence eruptions, solar flares, plasma heating and radiation, particle acceleration, EIT waves, EUV dimmings, Moreton waves, solar radio bursts, and so on. It is believed that, by shedding the accumulating magnetic energy and helicity, they complete the last link in the chain of the cycling of the solar magnetic field. In this review, I try to explicate our understanding on each stage of the fantastic phenomenon, including their pre-eruption structure, their triggering mechanisms and the precursors indicating the initiation process, their acceleration and propagation. Particular attention is paid to clarify some hot debates, e.g., whether magnetic reconnection is necessary for the eruption, whether there are two types of CMEs, how the CME frontal loop is formed, and whether halo CMEs are special.

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Section: (4) Radio Noise Stormsmentioning

confidence: 99%

Coronal Mass Ejections: Models and Their Observational Basis

Chen

2011

Living Rev. Solar Phys.

681

530

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“…A small fraction of flares do occur in so-called "spotless" regions (Dodson & Hedeman 1970;Martin 1980), and largescale filament eruptions with flare-like properties can happen anywhere on the quiet Sun (e.g., Harvey et al 1986). It is not yet possible to predict the time or location of a solar flare.…”

Section: Flare Developmentmentioning

confidence: 99%

An Observational Overview of Solar Flares

et al. 2011

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We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.

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“…Bumba & Křiviský (1959), who introduced the term "preflares", were the first to address this topic. Reviews of early studies for such flare precursors can be found in Martin et al (1980) and Van Hoven & Hurford (1984).…”

Section: Introductionmentioning

confidence: 99%

X-ray precursors to flares and filament eruptions

Chifor¹,

Tripathi²,

Mason³

et al. 2007

A&A

103

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Aims. To study preflare X-ray brightenings as diagnostics of the destabilisation of flare-associated erupting filaments/prominences. Methods. We combine new observations from the Transition Region and Coronal Explorer (TRACE) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), as well as revisit events reported in the literature to date, in order to scrutinise the preflare activity during eight flare-associated filament eruptions. Results. The preflare activity occurs in the form of discrete, localised X-ray brightenings observed between 2 and 50 min before the impulsive phase of the flare and filament acceleration. These transient preflare brightenings are situated on or near (within 10 of) the polarity inversion line (PIL), coincident with emerging and/or canceling magnetic flux. The filaments begin to rise from the location of the preflare brightenings. In five out of eight events, the preflare brightenings were observed beneath the filament channel, close to the filament footpoint first observed to rise. Both thermal and nonthermal hard X-ray emissions during the preflare enhancement were detected with RHESSI, suggesting that both plasma heating and electron acceleration occurred at this time. The main energy release during the impulsive phase of the flare is observed close to (within 50 of) the preflare brightenings. The fast-rise phase of the filament eruption starts at the same time as the onset of the main flare or up to 5 min later. Conclusions. The preflare brightenings are precursors to the flare and filament eruption. These precursors represent distinct, localised instances of energy release, rather than a gradual energy release prior to the main flare. The X-ray precursors represent clearly observable signatures in the early stages of the eruption. Together with the timing of the filament fast-rise at or after the main flare onset, the X-ray precursors provide evidence for a tether-cutting mechanism initially manifested as localised magnetic reconnection being a common trigger for both flare emission and filament eruption.

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Preflare conditions, changes and events

Cited by 93 publications

References 68 publications

Coronal Mass Ejections: Models and Their Observational Basis

Coronal Mass Ejections: Models and Their Observational Basis

An Observational Overview of Solar Flares

X-ray precursors to flares and filament eruptions

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