High-resolution solar flare X-ray spectra

Doschek, G. A.; Kreplin, R. W.; Feldman, U.

doi:10.1086/183096

Cited by 98 publications

(50 citation statements)

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“…The first of these, flown in the 1960s and 1970s, observed the prominent spectral lines due to the H-like and He-like ions. The next generation of spectrometers in the late 1970s and early 1980s was flown on the U.S. Navy P78-1 (SOLFLEX, SOLEX; Doschek, Kreplin, and Feldman, 1979), the NASA Solar Maximum Mission (X-ray Polychromator (XRP) Acton et al, 1980, cf. the Japanese Hinotori spacecraft (SOX1, SOX2; Tanaka et al, 1982). These allowed the time evolution of temperatures, emission measures, flows and turbulent velocities to be studied and related to current theories of solar flares.…”

Section: Overview Of the X-ray Line Observations At 1-7åmentioning

confidence: 99%

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

et al. 2017

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We review the presence and signatures of the non-equilibrium processes, both non-Maxwellian distributions and non-equilibrium ionization, in the solar transition region, corona, solar wind, and flares. Basic properties of the non-Maxwellian distributions are described together with their influence on the heat flux as well as on the rates of individual collisional processes and the resulting optically thin synthetic spectra. Constraints on the presence of highenergy electrons from observations are reviewed, including positive detection of non-Maxwellian distributions in the solar corona, transition region, flares, and wind. Occurrence of non-equilibrium ionization is reviewed as well, especially in connection to hydrodynamic and generalized collisional-radiative modelling. Predicted spectroscopic signatures of non-equilibrium ionization depending on the assumed plasma conditions are summarized. Finally, we discuss the future remote-sensing instrumentation that can be used for detection of these non-equilibrium phenomena in various spectral ranges.

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Section: Overview Of the X-ray Line Observations At 1-7åmentioning

confidence: 99%

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

et al. 2017

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“…In general, the analysis indicated that during the onset phase of flares the nonthermal mass motions were largest. From then on they continuously decreased until late in the decay phase when they attained some minimum value (Doschek, Kreplin, & Feldman 1979;Antonucci, Gabriel, & Dennis 1984). In the case of large flares, nonthermal mass motions were typically 150 km s À1 near flare onset and later near the end of the decay phase they decrease to '60 km s À1 .…”

Section: Earlier Observations Of Line Shifts and Widths In Solar Flarmentioning

confidence: 99%

Mass Motions and Plasma Properties in the 10⁷K Flare Solar Corona

Landi

Feldman

Innes

et al. 2003

ApJ

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In the present work, we analyze Solar Ultraviolet Measurement of Emitted Radiation (SUMER) observations of a solar limb flare that occurred on 1999 May 9. The analyzed data cover a time span of around 6.4 hr, during which an M-7.6 flare erupted and decayed in the field of view. Two selected regions along the SUMER slit have been considered for quantitative analysis. The main purpose of the present analysis is to measure the mass motions and the nonthermal velocities of the postflare plasmas and their temporal evolution. To achieve this we use lines having formation temperatures in the 2:5 Â 10 6 to 2 Â 10 7 K range from which we derive net mass motions and nonthermal velocities and compare them with the properties of the surrounding plasma not affected by the flare activity. To understand the physical conditions of the flaring plasma and of the surrounding material, we derive electron temperature, electron density, and emission measures of the emitting plasma. We find that bulk motions, initially of the order of several hundreds of kilometers per second in both directions, decay within 10 minutes from the flare onset; nonthermal velocities decay to preflare values of around 30 km s À1 in less than 2 hr from the maximum value of around 100 km s À1 at flare onset. The measured electron density does not seem to change during activity, while the flare plasma temperature steadily decays to preflare values. The temperature evolution is consistent with a radiatively cooling plasma, although the uncertainties associated to the measurement of the variation of thermal energy of the flare plasma prevent a definitive conclusion on possible continuous heating of the flaring plasma.

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“…Blue-shifted components of a few hundred km s −1 have been reported in the X-ray wavelength range from SOLFLEX (cf. Doschek et al 1979), the Solar Maximum Mission (SMM) X-ray polychromator (XRP) Bent Crystal Spectrometer (BCS) (cf. Antonucci et al 1982), and from the Bragg Crystal Spectrometer (BCS) on YOHKOH (see, e.g., Bentley et al 1994).…”

Section: Introductionmentioning

confidence: 99%

The 22 May 2007 B-class flare: new insights fromHinodeobservations

Zanna¹,

Mitra-Kraev²,

Bradshaw

et al. 2010

A&A

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We present multi-wavelength observations of a small B-class flare which occurred on the Sun on 2007 May 22. The observations include data from Hinode, GOES, TRACE and the Nobeyama Radioheliograph. We obtained spatially and spectrally-resolved information from the Hinode EUV Imaging Spectrometer (EIS) during this event. The temporal and temperature coverage of the EIS observations provides new insights into our understanding of chromospheric evaporation and cooling. The flare showed many "typical" features, such as brightenings in the ribbons, hot (10 MK) loop emission and subsequent cooling. We also observed a new feature, strong (up to 170 km s −1 ) blue-shifted emission in lines formed around 2-3 MK, located at the footpoints of the 10 MK coronal emission and within the ribbons. Electron densities at 2 MK in the kernels are high, of the order of 10 11 cm −3 , suggesting a very narrow layer where the chromospheric evaporation occurs. We have run a non-equilibrium hydrodynamic numerical simulation using the HYDRAD code to study the cooling of the 10 MK plasma, finding good agreement between the predicted and observed temperatures, densities and ion populations. Line blending for some potentially useful diagnostic lines for flares, which are observed with Hinode/EIS, is also discussed.

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High-resolution solar flare X-ray spectra

Cited by 98 publications

References 0 publications

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Mass Motions and Plasma Properties in the 10⁷K Flare Solar Corona

The 22 May 2007 B-class flare: new insights fromHinodeobservations

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High-resolution solar flare X-ray spectra

Cited by 98 publications

References 0 publications

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Nonequilibrium Processes in the Solar Corona, Transition Region, Flares, and Solar Wind (Invited Review)

Mass Motions and Plasma Properties in the 107K Flare Solar Corona

The 22 May 2007 B-class flare: new insights fromHinodeobservations

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Mass Motions and Plasma Properties in the 10⁷K Flare Solar Corona