H2 emission in the solar atmosphere

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

doi:10.1093/mnras/187.3.463

Cited by 25 publications

(39 citation statements)

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“…These measurements are consistent with earlier estimates (e.g. Jordan et al 1978;Bartoe et al 1979;Tian et al 2009), suggesting a lower opacity of the chromosphere above sunspot umbrae.…”

Section: Line Optical Thicknesssupporting

confidence: 92%

A steady-state supersonic downflow in the transition region above a sunspot umbra

Straus

Fleck

Andretta

2015

A&A

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We investigate a small-scale (∼1.5 Mm along the slit), supersonic downflow of about 90 km s ). Consequently, this implies a substantial mass flux (∼5×10 −7 g cm −2 s −1 ), which would evacuate the overlying corona on timescales close to 10 s. We interpret these findings as evidence of a stationary termination shock of a supersonic siphon flow in a cool loop that is rooted in the central umbra of the spot.

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“…These measurements are consistent with earlier estimates (e.g. Jordan et al 1978;Bartoe et al 1979;Tian et al 2009), suggesting a lower opacity of the chromosphere above sunspot umbrae.…”

Section: Line Optical Thicknesssupporting

confidence: 92%

A steady-state supersonic downflow in the transition region above a sunspot umbra

Straus

Fleck

Andretta

2015

A&A

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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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“…More recently an active region EUV atlas in the range from 230Å to 450Å was obtained with the SERTS (Solar EUV Rocket Telescope and Spectrometer) rocket experiment (Thomas & Neupert 1994). Emission lines of molecular hydrogen, which are present in sunspot spectra, have been measured and/or predicted by Bartoe et al (1979). Brooks et al (1999) have presented a spectral line list in the ranges 308Å to 381Å and 513Å to 633Å based on measurements of the normal incidence channel (NIS) of the SOHO/CDS instrument (Coronal Diagnostic Spectrometer, Harrison et al 1995).…”

Section: Earlier Spectral Atlasesmentioning

confidence: 99%

“…Squares and circles point to line lists published on SUMER observations, circles to Curdt et al (1997) and squares to Feldman et al (1997), respectively. Diamonds point to the older lists of Kelly (1987), Cohen et al (1978), Sandlin et al (1986), and Bartoe et al (1979). We have checked the line lists in this order and emphasize that marks are not meant in a sense of "first identification by", but, on the contrary, in general are pointing to the most recent list.…”

Section: Line Identificationmentioning

confidence: 99%

The SUMER spectral atlas of solar-disk features

Curdt

Brekke

Feldman

et al. 2001

A&A

289

294

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Abstract.A far-ultraviolet and extreme-ultraviolet (FUV, EUV) spectral atlas of the Sun between 670Å and 1609Å in the first order of diffraction has been derived from observations obtained with the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory). The atlas contains spectra of the average quiet Sun, a coronal hole and a sunspot on the disk. Different physical parameters prevalent in the bright network (BN) and in the cell interior (CI) -contributing in a distinct manner to the average quiet-Sun emission -have their imprint on the BN/CI ratio, which is also shown for almost the entire spectral range. With a few exceptions, all major lines are given with their identifications and wavelengths. Lines that appear in second order are superimposed on the first order spectra. These lines are clearly marked in the atlas. The spectra include emissions from atoms and ions in the temperature range 6 × 10 3 K to 2 × 10 6 K, i.e., continua and emission lines emitted from the lower chromosphere to the corona. This spectral atlas, with its broad wavelength coverage, provides a rich source of new diagnostic tools to study the physical parameters in the chromosphere, the transition region and the corona. In particular, the wavelength range below 1100Å as observed by SUMER represents a significant improvement over the spectra produced in the past. In view of the manifold appearance and temporal variation of the solar atmosphere, it is obvious that our atlas can only be a -hopefully typical -snapshot. Brief descriptions of the data reduction and calibration procedures are given. The spectral radiances are determined with a relative uncertainty of 0.15 to 0.30 (1σ) and the wavelength scale is accurate to typically 10 mÅ. The atlas is also available in a machine readable form.

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H2 emission in the solar atmosphere

Cited by 25 publications

References 0 publications

A steady-state supersonic downflow in the transition region above a sunspot umbra

A steady-state supersonic downflow in the transition region above a sunspot umbra

On Molecular Hydrogen Formation and the Magnetohydrostatic Equilibrium of Sunspots

The SUMER spectral atlas of solar-disk features

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