Spicule Dynamics over a Plage Region

The Culgoora magnetograph (Ramsay et al., 1970) produces simultaneous filtergrams in opposite circular polarizations at a wavelength selected by a filter bandwidth 0.005 nm (Ramsay et al., 1970). In the blue wing of the 610.27 nm line of CaI, regions of magnetic fields in strong or weak plages are very obvious in one or other polarization, depending on polarity, even before subtraction; in one polarization they are bright, but almost invisible in the other. They are more difficult to discern at equal intervals from the line centre in the other wing (Figure 1). When subtractions are carried out to yield magnetograms of the same sense, the two magnetograms from opposite wings give results which appear to be much the same. An example is shown in Figure 2. Similar results are obtained over a wide range of positions in the wings of the 610.27 nm line.

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The multi-thermal chromosphere

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937117 ◽

2020 ◽

Vol 634 ◽

pp. A56 ◽

Cited By ~ 4

Author(s):

J. M. da Silva Santos ◽

J. de la Cruz Rodríguez ◽

J. Leenaarts ◽

G. Chintzoglou ◽

B. De Pontieu ◽

...

Keyword(s):

Thermal Structure ◽

Low Frequency ◽

Solar Chromosphere ◽

Quiet Sun ◽

Average Brightness ◽

Near Ultraviolet ◽

Plage Region ◽

Hydrogen Ionization ◽

Two Parameters ◽

Average Brightness Temperature

Context. Numerical simulations of the solar chromosphere predict a diverse thermal structure with both hot and cool regions. Observations of plage regions in particular typically feature broader and brighter chromospheric lines, which suggests that they are formed in hotter and denser conditions than in the quiet Sun, but also implies a nonthermal component whose source is unclear. Aims. We revisit the problem of the stratification of temperature and microturbulence in plage and the quiet Sun, now adding millimeter (mm) continuum observations provided by the Atacama Large Millimiter Array (ALMA) to inversions of near-ultraviolet Interface Region Imaging Spectrograph (IRIS) spectra as a powerful new diagnostic to disentangle the two parameters. We fit cool chromospheric holes and track the fast evolution of compact mm brightenings in the plage region. Methods. We use the STiC nonlocal thermodynamic equilibrium (NLTE) inversion code to simultaneously fit real ultraviolet and mm spectra in order to infer the thermodynamic parameters of the plasma. Results. We confirm the anticipated constraining potential of ALMA in NLTE inversions of the solar chromosphere. We find significant differences between the inversion results of IRIS data alone compared to the results of a combination with the mm data: the IRIS+ALMA inversions have increased contrast and temperature range, and tend to favor lower values of microturbulence (∼3−6 km s−1 in plage compared to ∼4−7 km s−1 from IRIS alone) in the chromosphere. The average brightness temperature of the plage region at 1.25 mm is 8500 K, but the ALMA maps also show much cooler (∼3000 K) and hotter (∼11 000 K) evolving features partially seen in other diagnostics. To explain the former, the inversions require the existence of localized low-temperature regions in the chromosphere where molecules such as CO could form. The hot features could sustain such high temperatures due to non-equilibrium hydrogen ionization effects in a shocked chromosphere – a scenario that is supported by low-frequency shock wave patterns found in the Mg II lines probed by IRIS.

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Simulation of Solar Magnetoconvection

Symposium - International Astronomical Union ◽

10.1017/s0074180900133339 ◽

2003 ◽

Vol 210 ◽

pp. 157-167 ◽

Cited By ~ 14

Author(s):

A. Vögler ◽

S. Shelyag ◽

M. Schüssler ◽

F. Cattaneo ◽

T. Emonet ◽

...

Keyword(s):

Numerical Methods ◽

Radiative Transfer ◽

Transfer Test ◽

Parallel Computers ◽

Plage Region ◽

First Results ◽

Non Local ◽

Efficient Parallelization

We present a new 3D MHD code for the simulation of solar magnetoconvection. The code is designed for use on parallel computers and in the choice of methods emphasis has been laid on efficient parallelization. We give a description of the numerical methods and discuss the non-local and non-grey treatment of the radiative transfer. Test calculations underlining the importance of non-grey effects and first results of the simulation of a solar plage region are shown.

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Physical properties of bright Ca II K fibrils in the solar chromosphere

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037572 ◽

2020 ◽

Vol 637 ◽

pp. A1 ◽

Cited By ~ 2

Author(s):

Sepideh Kianfar ◽

Jorrit Leenaarts ◽

Sanja Danilovic ◽

Jaime de la Cruz Rodríguez ◽

Carlos José Díaz Baso

Keyword(s):

Physical Properties ◽

Local Thermodynamic Equilibrium ◽

Broad Band ◽

Active Regions ◽

Line Of Sight ◽

Solar Chromosphere ◽

Line Profiles ◽

Surrounding Atmosphere ◽

Plage Region ◽

Non Local

Context. Broad-band images of the solar chromosphere in the Ca II H&K line cores around active regions are covered with fine bright elongated structures called bright fibrils. The mechanisms that form these structures and cause them to appear bright are still unknown. Aims. We aim to investigate the physical properties, such as temperature, line-of-sight velocity, and microturbulence, in the atmosphere that produces bright fibrils and to compare those to the properties of their surrounding atmosphere. Methods. We used simultaneous observations of a plage region in Fe I 6301-2 Å, Ca II 8542 Å, Ca II K, and Hα acquired by the CRISP and CHROMIS instruments on the Swedish 1 m Solar Telescope. We manually selected a sample of 282 Ca II K bright fibrils. We compared the appearance of the fibrils in our sample to the Ca II 8542 Å and Hα data. We performed non-local thermodynamic equilibrium inversions using the inversion code STiC on the Fe I 6301-2 Å, Ca II 8542 Å, and Ca II K lines to infer the physical properties of the atmosphere. Results. The line profiles in bright fibrils have a higher intensity in their K2 peaks compared to profiles formed in the surrounding atmosphere. The inversion results show that the atmosphere in fibrils is on average −100 K hotter at an optical depth log(τ500 nm) = −4.3 compared to their surroundings. The line-of-sight velocity at chromospheric heights in the fibrils does not show any preference towards upflows or downflows. The microturbulence in the fibrils is on average 0.5 km s−1 higher compared to their surroundings. Our results suggest that the fibrils have a limited extent in height, and they should be viewed as hot threads pervading the chromosphere.

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Stratification of canopy magnetic fields in a plage region

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038754 ◽

2020 ◽

Vol 642 ◽

pp. A210

Author(s):

Roberta Morosin ◽

Jaime de la Cruz Rodríguez ◽

Gregal J. M. Vissers ◽

Rahul Yadav

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Field Strength ◽

Numerical Models ◽

Lower Boundary ◽

Field Approximation ◽

Weak Field ◽

Field Vector ◽

Plage Region ◽

The Magnetic Field

Context. The role of magnetic fields in the chromospheric heating problem remains greatly unconstrained. Most theoretical predictions from numerical models rely on a magnetic configuration, field strength, and connectivity; the details of which have not been well established with observational studies for many chromospheric scenarios. High-resolution studies of chromospheric magnetic fields in plage are very scarce or non existent in general. Aims. Our aim is to study the stratification of the magnetic field vector in plage regions. Previous studies predict the presence of a magnetic canopy in the chromosphere that has not yet been studied with full-Stokes observations. We use high-spatial resolution full-Stokes observations acquired with the CRisp Imaging Spectro-Polarimeter (CRISP) at the Swedish 1-m Solar Telescope in the Mg I 5173 Å, Na I 5896 Å and Ca II 8542 Å lines. Methods. We have developed a spatially-regularized weak-field approximation (WFA) method, based on the idea of spatial regularization. This method allows for a fast computation of magnetic field maps for an extended field of view. The fidelity of this new technique has been assessed using a snapshot from a realistic 3D magnetohydrodynamics simulation. Results. We have derived the depth-stratification of the line-of-sight component of the magnetic field from the photosphere to the chromosphere in a plage region. The magnetic fields are concentrated in the intergranular lanes in the photosphere and expand horizontally toward the chromosphere, filling all the space and forming a canopy. Our results suggest that the lower boundary of this canopy must be located around 400 − 600 km from the photosphere. The mean canopy total magnetic field strength in the lower chromosphere (z ≈ 760 km) is 658 G. At z = 1160 km, we estimate ⟨B∥⟩ ≈ 417 G. Conclusions. In this study we propose a modification to the WFA that improves its applicability to data with a worse signal-to-noise ratio. We have used this technique to study the magnetic properties of the hot chromospheric canopy that is observed in plage regions. The methods described in this paper provide a quick and reliable way of studying multi layer magnetic field observations without the many difficulties inherent to other inversion methods.

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Solar Decimetre Radio Bursts

Australian Journal of Physics ◽

10.1071/ph630008 ◽

1963 ◽

Vol 16 (1) ◽

pp. 8 ◽

Cited By ~ 4

Author(s):

RF Mullaly ◽

T Krishnan

Keyword(s):

High Resolution ◽

Burst Activity ◽

Radio Interferometer ◽

The Sun ◽

Radio Bursts ◽

Solar Burst ◽

Brightness Temperatures ◽

Plage Region ◽

East West ◽

Eastern Half

High resolution studies (2' of arc beam) were made with the east�west arm of the Christiansen radio interferometer for about 50 21�cm solar burst events during 1958-1961. The burst sources were always closely associated in position with already existing radio plage regions of the Sun's slowly varying decimetre radiation. They had sizes of from 2 to 5' of arc, never exceeded but often approached in size their parent plage region, and showed no major movements during their development. Brightness temperatures ranged up to 2 X 109 OK (mostly between 107 and 108 OK). More bursts were observed near the Sun's centre than near the limb, and more on the western than on the eastern half. There was also a curious "gap" of 30� longitude on the eastern half of the Sun with virtually no burst activity.

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Investigations of the MnI 539.47 nm and MnI 542.04 nm lines in solar plages

Serbian Astronomical Journal ◽

10.2298/saj0570115v ◽

2005 ◽

pp. 115-121 ◽

Cited By ~ 3

Author(s):

Istvan Vince ◽

O. Gopasyuk ◽

S. Gopasyuk ◽

Oliver Vince

Keyword(s):

Line Profile ◽

Equivalent Width ◽

Surface Coverage ◽

Solar Surface ◽

Activity Cycle ◽

Full Width ◽

Half Maximum ◽

Line Profiles ◽

Plage Region ◽

Magnetic Filed

We observed the MnI 539.47 nm and 542.04nm line profiles in the quiet photosphere and plage regions in 1998 and 2001, and measured the full widths at half maximum, equivalent widths and depths of these profiles. The relative changes of the MnI 539.47 nm line parameters, normalized to the values obtained for quiet photosphere, as a function of magnetic field strength in plages is analyzed. We found, for plage region observed in 1998, that both the equivalent width and the depth of the line profile decrease with increasing strength of magnetic filed in plage at a rate of 9x10?4 /Gauss, but the full width at half maximum does not show any significant regular changes. Based on these results, the variations of the MnI 539.47 nm spectral line in solar flux with activity cycle could be explained by the variation of solar surface coverage with plages. For observations in 2001, the equivalent width and the depth of this line profile also decrease with increasing strength of magnetic filed in plage, but there are significant differences in the behavior of line parameters in comparison with the 1998 values. Comparison of changes of the MnI 539.47 nm line parameters with the parameters of the MnI 542.04 nm line in 1998 shows a clear discrepancy between them. On the contrary, in 2001 the full widths at half maximum and the equivalent widths of these two lines behaved in a similar fashion. .

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