On the behaviour of the hydrogen Lyman series in flares

Feiter, L. D. De; Švestka, Z.

doi:10.1007/bf00154078

Cited by 4 publications

(2 citation statements)

References 11 publications

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“…A coarse estimate of the electronic density n e and the population N 1 is obtained from the quantum number of the lastresolvable Lyman line (De Feiter &Švestka 1975). With a quantum number higher than 14 in this case, n e must be smaller than 10 13 cm −3 and N 1 smaller than 10 20 cm −3 .…”

Section: Physical Characteristics Of the Flarementioning

confidence: 99%

Flare observation of the Sun as a star by SUMER/SOHO in the hydrogen Lyman continuum

Lemaire

Gouttebroze

Vial

et al. 2004

A&A

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Abstract. During the execution of the programme "Sun as a star", while the SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and Heliospheric Observatory) slit was collecting the scattered radiation from the telescope mirror far away from the solar disk image, a class X5.3/3b flare erupted on the solar disk, on 25 August 2001. During the first phase of the flare a relative increase of a few percent was detected at the head of the hydrogen Lyman continuum. After correction from the instrumental parameters, the relative signal increase is 70% at the head of the Lyman continuum (910 Å), and 190% in the C  904 Å multiplet. Accounting for the area of the flare region, the local increase of the radiance of the Lyman continuum and of the C  lines is estimated to be a factor of several thousands. We compare this result with other solar observations and models.

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Section: Physical Characteristics Of the Flarementioning

confidence: 99%

Flare observation of the Sun as a star by SUMER/SOHO in the hydrogen Lyman continuum

Lemaire

Gouttebroze

Vial

et al. 2004

A&A

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“…Radiation from Ly𝛼 photoionises Ca from all levels present other than the ground state, and the higher energy radiation from higher Lyman lines can photoionise Ca to Ca from all Ca levels in this model. In reality, higher Lyman lines, significantly Stark-broadened by the flaring atmosphere, will create a quasi-continuum from a point between Ly𝛿 and the Lyman continuum (De Feiter & Švestka 1975), further enhancing the photoionisation of Ca from what is presented here.…”

Section: Methodsmentioning

confidence: 68%

On the Importance of Ca II Photoionisation by the Hydrogen Lyman Transitions in Solar Flare Models

Osborne,

Heinzel,

Kašparová

et al. 2021

Preprint

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The forward fitting of solar flare observations with radiation-hydrodynamic simulations is a common technique for learning about energy deposition and atmospheric evolution during these explosive events. A frequent spectral line choice for this process is Ca 854.2 nm due to its formation in the chromosphere and substantial variability. It is important to ensure that this line is accurately modeled to obtain the correct interpretation of observations. Here we investigate the importance of photoionisation of Ca to Ca by the hydrogen Lyman transitions; whilst the Lyman continuum is typically considered in this context in simulations, the associated bound-bound transitions are not. This investigation uses two RADYN flare simulations and reprocesses the radiative transfer using the Lightweaver framework which accounts for the overlapping of all active transitions. The Ca 854.2 nm line profiles are found to vary significantly due to photoionisation by the Lyman lines, showing notably different shapes and even reversed asymmetries. Finally, we investigate to what extent these effects modify the energy balance of the simulation and the implications on future radiation-hydrodynamic simulations. There is found to be a 10-15% change in detailed optically thick radiative losses from considering these photoionisation effects on the calcium lines in the two simulations presented, demonstrating the importance of considering these effects in a self-consistent way.

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