On magnetic field stochasticity and nonthermal line broadening in solar flares

Antonucci, E.; Rosner, R.; Tsinganos, K.

doi:10.1086/163960

Cited by 36 publications

(33 citation statements)

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“…In particular, it is possible that reconnection takes place in localized regions scattered throughout the flaring loop. This picture is consistent with coronal loops whose magnetic field lines become twisted by photospheric motions, leading then to local reconnection, with consequent magnetic energy dissipation throughout the loop (Antonucci, Rosner, and Tsinganos, 1986;Parker, 1987). Plasma is ejected at the Alfven speed from a localized site, where magnetic reconnection occurs (Sweet, 1969;Parker, 1983).…”

Section: Non-thermal Line Broadeningssupporting

confidence: 66%

“…Flows with velocities within 100-500 km s " ' are consistent with motions which are predominantly ascensional, since blue-shifts are not observed in flares occurring beyond approximately 60 deg in longitude (Antonucci, Gabriel, and Dennis, 1984;Tanaka, 1986). Such upflows are associated both spatially and temporally with an impulsive heating of the chromosphere.…”

Section: Impulsive Phase Blue-shifts and Chromospheric Evaporationmentioning

confidence: 77%

“…The properties of the soft X-ray line blue-shifts derived from studies of the impulsive phase of a large sample of flares strongly suggest that blue-shifts are evidence for chromospheric evaporation (Antonucci etal., 1982;Tanaka etal., 1982b;Antonucci and Dennis, 1983;Antonucci, Gabriel, and Dennis, 1984;Tanaka, 1986). Flows with velocities within 100-500 km s " ' are consistent with motions which are predominantly ascensional, since blue-shifts are not observed in flares occurring beyond approximately 60 deg in longitude (Antonucci, Gabriel, and Dennis, 1984;Tanaka, 1986).…”

Section: Impulsive Phase Blue-shifts and Chromospheric Evaporationmentioning

confidence: 99%

“…If the upflowing material due to chromospheric evaporation plays a dominant role in the formation of the thermal coronal plasma in flares, we expect a mass and energy balance between the evaporating material and the soft X-ray coronal source. Moreover, since density and temperature of the evaporating plasma cannot be directly measured due to the blending of the temperature diagnostic lines emitted from the evaporating and coronal plasmas, we can only assert that mass and energy balance can be ensured for plausible values of such quantities: that is, densities of the order of 1-2 x 10" cm" 3 , and temperatures of 1-2 x 10 7 K (Antonucci etal, 1982;Antonucci, Gabriel, and Dennis, 1984). Densities derived from mass balance represent lower limits, mainly because of the unresolved geometry of the flare region.…”

Section: Impulsive Phase Blue-shifts and Chromospheric Evaporationmentioning

confidence: 99%

“…factors derived for soft X-ray loops in non-flaring conditions on the basis of scaling law considerations (Martens, van den Oord, Hoyng, 1985) and for active regions in the phase immediately preceding the flare onset by studying the flow velocities in the reconnection sites (Antonucci, Rosner, and Tsinganos, 1986).…”

mentioning

confidence: 99%

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Solar Flare Spectral Diagnosis: Present and Future

Antonucci

1989

International Astronomical Union Colloquium

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Abstract. New perspectives in solar diagnosis have been opened in recent years with the advent of high-resolution soft X-ray spectroscopy for plasmas forming at temperatures above 10 7 K. The spectra obtained with the soft X-ray spectrometers flown during the last solar maximum on the major space missions dedicated to flares have allowed detailed studies of the hydrodynamic response of coronal loops to impulsive energy deposition and of the formation of the high-temperature plasma as a consequence of such dynamic effects. These studies are possible since high-resolution spectrometers give an accurate measure of both line intensities and profiles in important spectral regions, covering the emission of highly ionized heavy ions, which allow a direct determination of most of the crucial plasma parameters in the flare region. In response to the impulsive energy release in the flare region, while the intensity of soft X-ray lines increases, line profiles show large non-thermal broadenings and strong blue-asymmetries.There have been important contributions in the understanding of the formation of the flare hightemperature plasma, as an effect of the hydrodynamic response of the solar atmosphere to impulsive chromospheric heating. On the other hand, the attempts to investigate the primary energy release and transport, on the basis of the soft X-ray spectral data, have not yet been entirely successful. Significant differences in the emitted spectra are expected at the very onset of flares for different energy deposition and transport processes, but the sensitivity of the present experiments is still insufficient to detect with good statistics the early stage of flares and, therefore, to allow a reliable discrimination. It is expected that future experiments with higher sensitivity will be of great importance for relating with less ambiguity the observed flare evolution in soft X-rays to the primary energy deposition in the flaring coronal loops.

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Section: Non-thermal Line Broadeningssupporting

confidence: 66%

Section: Impulsive Phase Blue-shifts and Chromospheric Evaporationmentioning

confidence: 77%