Emission lines of H2 in the extreme-ultraviolet solar spectrum

Jordan, C.; Brueckner, G. E.; Bartoe, J. D. F.; Sandlin, G. D.; Vanhoosier, M. E.

doi:10.1086/156651

Cited by 46 publications

(49 citation statements)

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“…However, in the umbra the atmosphere is very cool, making it possible to form a substantial fraction of H 2 . Observations of the fluorescent H 2 lines in the ultraviolet have confirmed its presence in the chromosphere above sunspots (Jordan et al 1978;Bartoe et al 1979;Innes 2008), while atmospheric models of the sunspot umbra predict a molecular hydrogen population of up to 10%, peaking near the height of continuum formation (Maltby et al 1986).…”

Section: The Magnetohydrostatic Equilibrium Of Sunspots and The Role mentioning

confidence: 98%

On Molecular Hydrogen Formation and the Magnetohydrostatic Equilibrium of Sunspots

Jaeggli¹,

Lin²,

Uitenbroek³

2012

ApJ

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We have investigated the problem of sunspot magnetohydrostatic equilibrium with comprehensive IR sunspot magnetic field survey observations of the highly sensitive Fe i lines at 15650 Å and nearby OH lines. We have found that some sunspots show isothermal increases in umbral magnetic field strength which cannot be explained by the simplified sunspot model with a single-component ideal gas atmosphere assumed in previous investigations. Large sunspots universally display nonlinear increases in magnetic pressure over temperature, while small sunspots and pores display linear behavior. The formation of molecules provides a mechanism for isothermal concentration of the umbral magnetic field, and we propose that this may explain the observed rapid increase in umbral magnetic field strength relative to temperature. Existing multi-component sunspot atmospheric models predict that a significant amount of molecular hydrogen (H 2 ) exists in the sunspot umbra. The formation of H 2 can significantly alter the thermodynamic properties of the sunspot atmosphere and may play a significant role in sunspot evolution. In addition to the survey observations, we have performed detailed chemical equilibrium calculations with full consideration of radiative transfer effects to establish OH as a proxy for H 2 , and demonstrate that a significant population of H 2 exists in the coolest regions of large sunspots.

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Section: The Magnetohydrostatic Equilibrium Of Sunspots and The Role mentioning

confidence: 98%

On Molecular Hydrogen Formation and the Magnetohydrostatic Equilibrium of Sunspots

Jaeggli¹,

Lin²,

Uitenbroek³

2012

ApJ

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“…Many H 2 lines are enhanced in specific regions of the sunspot umbra, excited by fluorescence from H I Lyα (Jordan et al 1978;. Complicated flow geometries, including dual flows with supersonic speeds, have been detected in the sunspot transition region (Brynildsen et al , 2004.…”

Section: Sunspots and Sunspot Plumesmentioning

confidence: 99%

“…The chromospheric network structure of the quiet Sun and of active regions near the centre of the disk are the most prominent features in this image Fleck and Deubner (1989) postulated a "magic height" between 880 km and 1200 km at which the oscillatory behaviour of the chromosphere changed dramatically. Studies of the H I Lyman continuum (Wilhelm and Kalkofen 2003) and the C II 133.5 nm multiplet (Judge et al 2003) both indicated a heating of the upper chromosphere by magnetic effects and not by acoustic waves. However, Gallagher et al (1999) found indications of heating by acoustic shocks even in the transition region near 2.5 × 10 5 K. Evidence for atmospheric gravity waves was found from TRACE observations (Rutten and Krijger 2003).…”

Section: Chromospheric Oscillationsmentioning

confidence: 99%

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

et al. 2007

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In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical considerations on the heating of the corona and the generation of the solar wind.

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“…The 1119.10 Å line is about 60 % as bright as the strongest 1-4 Werner line at 1164 Å. The H 2 is believed to be formed just above the temperature minimum at around 4200 K. Its strength is expected to correlate with the O VI intensity, as well as with the chromosphere structure in and above the H 2 region (Jordan et al 1978).…”

Section: Introductionmentioning

confidence: 94%

SUMER-Hinode observations of microflares: excitation of molecular hydrogen

Innes

2007

A&A

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Context. Concentrations of H 2 have been detected by SUMER in active region plage. The H 2 is excited by O VI line emission at 1031.94 Å which, although not observed, must be brightening along with the observed transition region line, Si iii 1113.24 Å.Aims. We investigate the excitation of H 2 and demonstrate the association between the observed H 2 emission and footpoints of X-ray microflares. Methods. We have made co-ordinated observations of active region plage with the spectrometer SUMER/SoHO in lines of H 2 1119.10 Å and Si iii 1113.24 Å and with XRT/Hinode X-ray and SOT/Hinode Ca II filters.Results. In six hours of observation, six of the seven H 2 events seen occurred near a footpoint of a brightening X-ray loop. The seventh is associated with an unusually strong Si iii plasma outflow.Conclusions. Microflare energy dissipation heats the chromosphere, reducing its opacity, so that O VI microflare emission is able to reach the lower layers of the chromosphere and excite the H 2 .

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Emission lines of H2 in the extreme-ultraviolet solar spectrum

Cited by 46 publications

References 0 publications

On Molecular Hydrogen Formation and the Magnetohydrostatic Equilibrium of Sunspots

On Molecular Hydrogen Formation and the Magnetohydrostatic Equilibrium of Sunspots

Observations of the Sun at Vacuum-Ultraviolet Wavelengths from Space. Part II: Results and Interpretations

SUMER-Hinode observations of microflares: excitation of molecular hydrogen

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