Millimeter radiation from a 3D model of the solar atmosphere

Loukitcheva, M.; White, S. M.; Solanki, S. K.; Fleishman, G. D.; Carlsson, Mats

doi:10.1051/0004-6361/201629099

Cited by 39 publications

(45 citation statements)

References 49 publications

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“…Preliminary results from advanced numerical models (e.g., those computed with the Bifrost model; Gudiksen et al 2011see also Carlsson et al 2016 and references therein) of quiet-Sun conditions indicate that the Mg II h2v feature forms in the middle chromosphere over a range of heights from 600 to 2000 km with a peak around 1400 km (Leenaarts et al 2013b). Synthetic observables calculated from the Bifrost at a wavelength of 1.3 mm, near that reported here, suggest that the radiation mostly originates at similar heights, with a peak at 1150 km (Loukitcheva et al 2017). While the diagnostics are formed in roughly the same region of the atmosphere, it is unclear whether there are systematic differences in formation height along individual lines of sight.…”

Section: Resultssupporting

confidence: 78%

A First Comparison of Millimeter Continuum and Mg ii Ultraviolet Line Emission from the Solar Chromosphere

Bastian

Chintzoglou

Pontieu

et al. 2017

ApJL

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We present joint observations of the Sun by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS). Both millimeter/submillimeter-λ continuum emission and ultraviolet (UV) line emission originate from the solar chromosphere and both have the potential to serve as powerful and complementary diagnostics of physical conditions in this enigmatic region of the solar atmosphere.The observations were made of a solar active region on 2015 December 18 as part of the ALMA science verification effort. A map of the Sun's continuum emission was obtained by ALMA at a wavelength of 1.25 mm (239 GHz). A contemporaneous map was obtained by IRIS in the Mg II h doublet line at 2803.5 Å. While a clear correlation between the 1.25 mm brightness temperature T B and the Mg II h line radiation temperature T rad is observed, the slope is <1, perhaps as a result of the fact that these diagnostics are sensitive to different parts of the chromosphere and that the Mg II h line source function includes a scattering component. There is a significant difference (35%) between the mean T B (1.25 mm) and mean T rad (Mg II). Partitioning the maps into "sunspot," "quiet areas," and "plage regions" we find the relation between the IRIS Mg II h line T rad and the ALMA T B regiondependent. We suggest this may be the result of regional dependences of the formation heights of the IRIS and ALMA diagnostics and/or the increased degree of coupling between the UV source function and the local gas temperature in the hotter, denser gas in plage regions.

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Section: Resultssupporting

confidence: 78%

A First Comparison of Millimeter Continuum and Mg ii Ultraviolet Line Emission from the Solar Chromosphere

Bastian

Chintzoglou

Pontieu

et al. 2017

ApJL

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“…The spatial resolution of the simulations is subarcsecond, and so it is not straightforward to compare their results with the much poorer spatial resolution of the single-dish data. They find average brightness temperatures of 5000 K at 230 GHz and 6200 K at 94 GHz, corresponding to effective heights above the photosphere of about 1150 km at 230 GHz and 1600 km at 94 GHz (Loukitcheva et al, 2017). Earlier simulations of inter-network quiet-Sun regions by Wedemeyer-Böhm et al (2007) found even lower average brightness temperatures.…”

Section: Solar Brightness Temperaturesmentioning

confidence: 92%

“…The ALMA values are consistent with previous data, but with much smaller uncertainty due to the large number of values involved in our assessment. Loukitcheva et al (2015Loukitcheva et al ( , 2017 use state-of-the-art radiative hydrodynamic simulations of the solar chromosphere (from the Bifrost code; Carlsson et al, 2016) to predict brightness temperatures at millimeter wavelengths. The spatial resolution of the simulations is subarcsecond, and so it is not straightforward to compare their results with the much poorer spatial resolution of the single-dish data.…”

Section: Solar Brightness Temperaturesmentioning

confidence: 99%

Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping

et al. 2017

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The Atacama Large Millimeter-submillimeter Array (ALMA) radio telescope has commenced science observations of the Sun starting in late 2016. Since the Sun is much larger than the field of view of individual ALMA dishes, the ALMA interferometer is unable to measure the background level of solar emission when observing the solar disk. The absolute temperature scale is a critical measurement for much of ALMA solar science, including the understanding of energy transfer through the solar atmosphere, the properties of prominences, and the study of shock heating in the chromosphere. In order to provide an absolute temperature scale, ALMA solar observing will take advantage of the remarkable fast-scanning capabilities of the ALMA 12 m dishes to make single-dish maps of the full Sun. This article reports on the results of an extensive commissioning effort to optimize the mapping procedure, and it describes the nature of the resulting data. Amplitude calibration is discussed in detail: a path that utilizes the two loads in the ALMA calibration system as well as sky measurements is described and applied to commissioning data. Inspection of a large number of single-dish datasets shows significant variation in the resulting temperatures, and based on the temperature distributions we derive quiet-Sun values at disk center of 7300 K at λ = 3 mm and 5900 K at λ = 1.3 mm. These values have statistical uncertainties of order 100 K, but systematic uncertainties in the temperature scale that may be significantly larger. Example images are presented from two periods with very different levels of solar activity. At a resolution of order 25 ′′ , the 1.3 mm wavelength images show temperatures on the disk that vary over about a 2000 K range. Active regions and plage are amongst the hotter features while a large sunspot umbra shows up as a depression and filament channels are relatively cool. Prominences above the solar limb are a common feature of the single-dish images.

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“…Поскольку масштаб мелкомасштабной структуры внутри заданного куба много меньше размеров куба, то получаемое при таком построении распределение параметров атмосферы спокойного Солнца, практически, не нарушает общности расчетов. При расчете теплового тормозного миллиметрового излучения применялся алгоритм, использованный в [16].…”

Section: Doi: 1031725/0552-5829-2019-403-406unclassified

Solar Radioradius in Mm Range and Modern Chromosphere Models

Topchilo¹,

Loukitcheva²,

Nagnibeda³

et al. 2019

Proceedings of the 23rd All-Russia Conference on Solar and Solar-Terrestrial Physics

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The radioradius of the Sun is an important and suitable observational feature that connected with structure of the atmosphere. Its value in millimeter and submillimeter range defines the chromospheres height (limb extension). Numerous measurements of the solar radioradius provide ample opportunities for testing models of a solar atmosphere comparing observational and model values. Special interest causes a millimeter-submillimeter range of wavelengths, radiation in which is completely defined by chromosphere. In the presented work model calculation of radioradius for spatially-non-uniform 3D models of chromosphere by means of program Bifrost for a cube 24×24×17 Mm with spatial resolution of 48 km across and 19-100 km on a vertical is executed. Values of radioradius were calculated for set of wavelengths from operating range of ALMA radiointerferometer. Comparison of observational and modelling values shows that the measured values of radioradius significantly surpass calculated on the used numerical model. In the considered range the measured radioradius changes from 7" up to 24" while model calculation gives the values which are not exceeding 3". Such strong discrepancy requires additional research.

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Millimeter radiation from a 3D model of the solar atmosphere

Cited by 39 publications

References 49 publications

A First Comparison of Millimeter Continuum and Mg ii Ultraviolet Line Emission from the Solar Chromosphere

A First Comparison of Millimeter Continuum and Mg ii Ultraviolet Line Emission from the Solar Chromosphere

Observing the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA): Fast-Scan Single-Dish Mapping

Solar Radioradius in Mm Range and Modern Chromosphere Models

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