A Theory of Chromospheric Flares

Giovanelli, R. G.

doi:10.1038/158081a0

Cited by 277 publications

(124 citation statements)

References 3 publications

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“…have been considered as manifestation of magnetic reconnection processes (Giovanelli 1946;Gold & Hoyle 1960;Priest 1981;Parker 1988;Forbes 1991;Priest & Forbes 2000) resulting from the formation of a current sheet formed by magnetic flux 6. Integrated intensity in the blue wing of Ly 11, Ly 10, Ly 9, Ly 7, Ly 6 and S vi in the region of the explosive event (5 pixels along the slit) for the all analysed dataset.…”

Section: Discussionmentioning

confidence: 99%

Temporal evolution of different temperature plasma during explosive events

Madjarska¹,

Doyle²

2002

A&A

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Abstract. High cadence observations (10 s exposure time) obtained with the SUMER spectrometer on-board SoHO in the Ly 6 (20 000 K) and S vi (200 000 K) lines reveal new insight on the nature of explosive events. A time delay in the response of the S vi line with respect to the Ly 6 line has been observed, with the Ly 6 line responding with about 20-40 s earlier. A temporal series obtained with 30 s exposure time and covering the entire Lyman series plus O i, C ii and S vi (temperature range from 15 000 to 200 000 K) has also been explored showing the response of all these lines during transient phenomena. New common features linking explosive events and blinkers were found. During explosive events, the central intensity increases between 1.6 and 2.0 times the pre-event value while the same range of intensity increase was already reported during blinker phenomena. On the other hand the maximum intensity increase in Ly 6 was only 13%.

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Section: Discussionmentioning

confidence: 99%

Temporal evolution of different temperature plasma during explosive events

Madjarska¹,

Doyle²

2002

A&A

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“…Following observational results, theoretical studies began to focus on the role of magnetic field in producing a flare. Giovanelli (1946) first pointed out that a neutral point where the magnetic field takes an X-type configuration could be the site of energy release during a flare. He proposed that the electric current may be dissipated at the neutral point.…”

Section: Introductionmentioning

confidence: 99%

Solar Flares: Magnetohydrodynamic Processes

Shibata

Magara

2011

Living Rev. Solar Phys.

762

647

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This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10 32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

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“…Schindler et al 1988Schindler et al , 1991, hence should lead to particle acceleration. Actually, the concept of magnetic reconnection was first introduced in order to explain the possible generation of high energy particles in flares (Giovanelli 1946).…”

Section: Introductionmentioning

confidence: 99%

Particle acceleration at a reconnecting magnetic separator

Threlfall

Neukirch

Parnell

et al. 2015

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Context. While the exact acceleration mechanism of energetic particles during solar flares is (as yet) unknown, magnetic reconnection plays a key role both in the release of stored magnetic energy of the solar corona and the magnetic restructuring during a flare. Recent work has shown that special field lines, called separators, are common sites of reconnection in 3D numerical experiments. To date, 3D separator reconnection sites have received little attention as particle accelerators. Aims. We investigate the effectiveness of separator reconnection as a particle acceleration mechanism for electrons and protons. Methods. We study the particle acceleration using a relativistic guiding-centre particle code in a time-dependent kinematic model of magnetic reconnection at a separator. Results. The effect upon particle behaviour of initial position, pitch angle, and initial kinetic energy are examined in detail, both for specific (single) particle examples and for large distributions of initial conditions. The separator reconnection model contains several free parameters, and we study the effect of changing these parameters upon particle acceleration, in particular in view of the final particle energy ranges that agree with observed energy spectra.

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A Theory of Chromospheric Flares

Cited by 277 publications

References 3 publications

Temporal evolution of different temperature plasma during explosive events

Temporal evolution of different temperature plasma during explosive events

Solar Flares: Magnetohydrodynamic Processes

Particle acceleration at a reconnecting magnetic separator

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