Analysis of the August 7, 1972 white light flare: Its spectrum and vertical structure

Machado, M. E.; Rust, David M.

doi:10.1007/bf00155084

Cited by 66 publications

(26 citation statements)

References 24 publications

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“…They concluded that Paschen or H − continuum radiation were not likely to be responsible for the emission, and instead proposed the presence of a slightly warmer layer (≈150 K) in the photosphere. Hudson et al (2010) compared the three observations of WLF Balmer continua presented by Hiei (1982), Neidig (1983), and Machado & Rust (1974). Their spectral signatures varied from the clear presence of a Balmer jump to one that was shifted toward longer wavelengths and to its complete absence.…”

Section: Introductionmentioning

confidence: 99%

Suppression of Hydrogen Emission in an X-class White-light Solar Flare

Prochazka

Milligan

Allred

et al. 2017

ApJ

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We present unique NUV observations of a well-observed X-class flare from NOAA 12087 obtained at Ondřejov Observatory. The flare shows a strong white-light continuum but no detectable emission in the higher Balmer and Lyman lines. RHESSI and Fermi observations indicate an extremely hard X-ray spectrum and γ-ray emission. We use the RADYN radiative hydrodynamic code to perform two type of simulations. One where an energy of 3 • 10 11 erg cm −2 s −1 is deposited by an electron beam with a spectral index of ≈ 3 and a second where the same energy is applied directly to the photosphere. The combination of observations and simulations allow us to conclude that the white-light emission and the suppression or complete lack of hydrogen emission lines is best explained by a model where the dominant energy deposition layer is located in the lower layers of the solar atmosphere rather than the chromosphere.

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Section: Introductionmentioning

confidence: 99%

Suppression of Hydrogen Emission in an X-class White-light Solar Flare

Prochazka

Milligan

Allred

et al. 2017

ApJ

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“…Boyer et al 1985;Ding et al 1999;Chen & Ding 2006) presumably due to radiative back-warming, and the generation of WL emission in the higher temperature regions of the upper chromosphere (e.g. Machado & Rust 1974;Hudson 1972) have been made. The major observational challenge here is to have simultaneous HXR, UV, and WL images with sufficiently high angular resolution.…”

Section: Introductionmentioning

confidence: 99%

Height structure of X-ray, EUV, and white-light emission in a solar flare

Battaglia

Kontar

2011

A&A

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Context. The bulk of solar flare emission originates from very compact sources located in the lower solar atmosphere and observable at a broad range of wavelengths such as near optical, UV, EUV, soft and hard X-rays, and gamma-rays. Nevertheless, very few spatially resolved imaging observations have been performed to determine the structure of these compact regions. Aims. We investigate the above-the-photosphere heights of hard X-ray (HXR), EUV, and white-light (6173 Å) continuum sources in the low atmosphere and the corresponding densities at these heights. By considering the collisional transport of solar energetic electrons, we also determine where and how much energy is deposited and compare these values with the emissions observed in HXR, EUV, and the continuum. Methods. Simultaneous EUV/continuum images from AIA/HMI on-board SDO and HXR RHESSI images are compared to study a well-observed gamma-ray limb flare. Using RHESSI X-ray visibilities, we determine the height of the HXR sources as a function of energy above the photosphere. Co-aligning AIA/SDO and HMI/SDO images with RHESSI, we infer, for the first time, the heights and characteristic densities of HXR, EUV, and continuum (white-light) sources in the flaring footpoint of the magnetic loop. Results. We find 35-100 keV HXR sources at heights of between 1.7 and 0.8 Mm above the photosphere, below the 6173 Å continuum emission that appears at heights 1.5−3 Mm and the peak of EUV emission originating near 3 Mm. Conclusions. The EUV emission locations are consistent with energy deposition from low energy electrons of ∼12 keV occurring in the top layers of the fully ionized chromosphere/low corona and not by 20 keV electrons that produce HXR footpoints in the lower neutral chromosphere. The maximum of white-light continuum emission appears between the HXR and EUV emission, presumably in the transition between ionized and neutral atmospheres, implying that it consists of free-bound and free-free continuum emission. We note that the energy deposited by low energy electrons is sufficient to explain the energetics of both the optical and UV emissions.

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“…On the 3-27 (Neidig 1983), Sept. 10, 1974(Hiei 1982Aug. 7, 1972 (Machado andRust 1974). Io refers to the intensity in the bright windows of the spectrum adjacent to the flare.…”

Section: -26mentioning

confidence: 99%

“…The spectra in white light flares, is characteristic of chromospheric densities (electron density 1-5 x 10 _3 cm-3; see Machado and Rust 1974;Neidig and Wiborg 1984;Zirin 1983). Nevertheless, it is by no means certain that the emission underlying the Balmer continuum and extending to longer wavelengths is due to Hfb emission in general (the 24 April flare, which shows a Paschen jump, is a good candidate for an event dominated in the visible and infrared by Hfb emission).…”

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confidence: 99%