scholarly journals The structure of the lower solar chromosphere in undisturbed and active regions

1968 ◽  
Vol 35 ◽  
pp. 255-258 ◽  
Author(s):  
E. Dubov
Keyword(s):  
Active Regions ◽  
Brightness Distribution ◽  
Solar Chromosphere ◽  
Image Brightness ◽  
Observational Material ◽  
Birefringent Filter ◽  
Doppler Shifts

As observational material in this work we used spectroheliograms taken with the Crimean solar tower telescope in K232 and Hα filtergrams taken with the chromospheric telescope in Simeis. The Hα birefringent filter was so adjusted, that by tuning the last polaroid we could take filtergrams in the centre of Hα or combined filtergrams in the two wings at Hα ± 0·5 Å. So the effect of Doppler shifts on image-brightness distribution was diminished. We compared the brightness distribution with that of spectroheliograms.

Synoptic Magnetic Fields Measurements of the Solar Chromosphere from SOLIS/VSM at NSO

2018 ◽  
Vol 13 (S340) ◽  
pp. 91-92
Author(s):  
Sanjay Gosain ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind Speed ◽  
Active Regions ◽  
Field Measurements ◽  
Solar Observatory ◽  
Solar Chromosphere ◽  
Polar Regions ◽  
National Solar Observatory ◽  
Perspective Effect ◽  
Stokes Polarimetry

AbstractFull disk magnetic field measurements of the photosphere and chromosphere have been performed at National Solar Observatory (NSO), USA for many decades. Here we briefly describe recent upgrades made to this synoptic observing program. In particular, we present the full Stokes polarimetry observations made using the chromospheric Ca II 854.2 nm spectral line. These new observations have the potential to probe vector nature of magnetic field in the chromosphere above the active regions and provide improved estimates of magnetic free-energy, which is released during flares and coronal mass ejections (CMEs). We emphasize that these observations could improve estimates of polar fields, as compared to photospheric observations, due to magnetic field expansion in higher layers and perspective effect near the polar regions. The global coronal potential field models and solar wind speed estimates depend critically on polar field measurements.

scholarly journals Filter Magnetograph Measurements at Meudon Observatory

1993 ◽  
Vol 141 ◽  
pp. 199-202
Author(s):  
Audouin Dollfus ◽  
Jacques Moity
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Observational Studies ◽  
Neutral Line ◽  
Active Regions ◽  
Transverse Magnetic ◽  
Birefringent Filter ◽  
Solar Active Regions

SummaryWe report observational studies of solar active regions n°6150 and n°6850 during cycle 22. Observations were carried out with a tunable monochromatic birefringent filter coupled with a line-shifter and a Stokesmeter as well as with a spectro-magnetograph, both at Meudon Observatory. AR n°6150 is typical of emerging flux regions, while AR n° 6850, with a complex preceding δ-spot, exhibits characteristic configurations of the transverse magnetic field for flaring activity: shear along the neutral line, and curvature coupled with anomalous Evershed mass motions.

scholarly journals Flare activity and spotgroup development

1968 ◽  
Vol 35 ◽  
pp. 311-317 ◽  
Author(s):  
V. Bumba ◽  
L. Křivský ◽  
M. J. Martres ◽  
I. Soru-Iscovici
Keyword(s):  
Magnetic Fields ◽  
Active Regions ◽  
Flare Activity ◽  
Activity Rate ◽  
Observational Material

The flare activity of all active regions having ten or more flares from August 1959 until December 1961 was investigated. We constructed flare-activity curves drawn with the aid of Kleczek's q-index. The characteristic magnetic situation on the Mt. Wilson synoptic charts of photospheric magnetic fields in which the flare-rich active regions developed is described. A flare activity rate ‘quantization’ was found. From the CSSAR magnetic observational material we studied the reorganization of the magnetic fields of active regions which correlated with sudden changes in the rate of flare activity.

Evidence on Chromospheric Structure from Observations of Solar Brightness Distribution at Millimetre Wavelengths

1978 ◽  
Vol 3 (4) ◽  
pp. 256-259 ◽  
Author(s):  
N. R. Labrum
Keyword(s):  
Brightness Distribution ◽  
Aperture Synthesis ◽  
The Other ◽  
Solar Chromosphere ◽  
Quiet Sun ◽  
Preliminary Discussion ◽  
Eclipse Observation ◽  
Solar Brightness ◽  
Chromospheric Structure ◽  
Important Test

Observations of the distribution of millimetre-wavelength brightness over the quiet Sun provide an important test of models of the solar chromosphere. The author and colleagues have recently carried out two investigations of the quiet-Sun brightness at 3 mm wavelength — one by means of a total eclipse observation (Labrum et al. 1978) and the other by aperture synthesis with a two-element interferometer (Archer et al. 1978). I present here a preliminary discussion of these and other measurements of millimetre-wavelength brightness distributions and of their interpretation in terms of chromospheric structure.

scholarly journals Joint Discussion 3 Solar active regions and 3D magnetic structure

2006 ◽  
Vol 2 (14) ◽  
pp. 139-168
Author(s):  
Debi Prasad Choudhary ◽  
Michal Sobotka
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Large Scale ◽  
Focal Point ◽  
Active Regions ◽  
Theoretical Modelling ◽  
Solar Chromosphere ◽  
Origin And Evolution ◽  
Solar Active Regions ◽  
The Magnetic Field

AbstractKeeping in view of the modern powerful observing tools, among othersHinode(formerlySOLAR-B),STEREOand Frequency-Agile Solar Radiotelescope, and sophisticated modelling techniques, Joint Discussion 3 during the IAU General Assembly 2006 focused on the properties of magnetic field of solar active regions starting in deep interior of the Sun, from where they buoyantly rise to the coronal heights where the site of most explosive events are located. Intimately related with the active regions, the origin and evolution of the magnetic field of quiet Sun, the large scale chromospheric structures were also the focal point of the Joint Discussion. The theoretical modelling of the generation and dynamics of magnetic field in solar convective zone show that the interaction of the magnetic field with the Coriolis force and helical turbulent convection results in the tilts and twists in the emerging flux. In the photosphere, some of these fluxes appear in sunspots with field strengths up to about 6100 G. Spectro-polarimetric measurements reveal that the line of sight velocities and magnetic field of these locations are found to be uncombed and depend on depth in the atmosphere and exhibit gradients or discontinuities. The inclined magnetic fields beyond penumbra appear as moving magnetic features that do not rise above upper photospheric heights. As the flux rises, the solar chromosphere is the most immediate and intermediary layer where competitive magnetic forces begin to dominate their thermodynamic counterparts. The magnetic field at these heights is now measured using several diagnostic lines such as CaII854.2 nm, HI656.3 nm, and HeI1083.0 nm. The radio observations show that the coronal magnetic field of post flare loops are of the order of 30 G, which might represent the force-free magnetic state of active region in the corona. The temperatures at these coronal heights, derived from the line widths, are in the range from 2.4 to 3.7 million degree. The same line profile measurements indicate the existence of asymmetric flows in the corona. The theoretical extrapolation of photospheric field into coronal heights and their comparison with the observations show that there exists a complex topology with separatrices associated to coronal null points. The interaction of these structures often lead to flares and coronal mass ejections. The current MHD modelling of active region field shows that for coronal mass ejection both local active region magnetic field and global magnetic field due to the surrounding magnetic flux are important. Here, we present an extended summary of the papers presented in Joint Discussion 03 and open questions related to the solar magnetic field that are likely to be the prime issue with the modern observing facilities such asHinodeandSTEREOmissions.

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

2020 ◽  
Vol 637 ◽  
pp. A1 ◽  
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.

scholarly journals A total sky cloud detection method using real clear sky background

2015 ◽  
Vol 8 (12) ◽  
pp. 13073-13098 ◽  
Author(s):  
J. Yang ◽  
Q. Min ◽  
W. Lu ◽  
Y. Ma ◽  
W. Yao ◽  
...  
Keyword(s):  
Detection Algorithm ◽  
Brightness Distribution ◽  
Detection Methods ◽  
Cloud Detection ◽  
Image Brightness ◽  
Clear Sky ◽  
Sensitivity Tests ◽  
Thin Cloud ◽  
Distribution Sensitivity ◽  
Solar Position

Abstract. The brightness distribution of sky background is usually non-uniform, which creates many problems for traditional cloud detection methods including the failure of thin cloud detection in total sky images and significantly reducing retrieval accuracy in the circumsolar and near-horizon regions. This paper describes the development of a new cloud detection algorithm, named "clear sky background differencing (CSBD)", which is accomplished by differencing the original image and the corresponding clear sky background image using the images' green channel. First, a library of clear sky background images with a variety of solar elevation angles needs to be developed. The image rotation and image brightness adjustment algorithms are applied to ensure the two images being differenced have the same solar position and similar brightness distribution. Sensitivity tests show, as long as the positions of the sun in the two images are the same, the cloud detection results are satisfactory. Several experimental cases show that the CSBD algorithm obtains good cloud recognition results visually, especially for thin clouds.

scholarly journals Chromospheric K CaII telescope of Baikal Astrophysical Observatory. New light

2019 ◽  
Vol 5 (2) ◽  
pp. 133-147
Author(s):  
Любовь Лоптева ◽  
Lyubov Lopteva ◽  
Галина Кушталь ◽  
Galina Kushtal ◽  
Владимир Прошин ◽  
...  
Keyword(s):  
Large Scale ◽  
Spectral Characteristics ◽  
Optical Path ◽  
Continuous Operation ◽  
Solar Chromosphere ◽  
Optical Scheme ◽  
High Contrast ◽  
Birefringent Filter ◽  
Telescope Optics ◽  
Full Disk

In recent years, most results of CaII studies of the solar chromosphere in H and K lines have been based on observations with narrow passband filters. The Baikal Observatory’s full-disk chromospheric telescope for the K CaII line with a birefringent filter (BF) has again been included in observation programs of the Sun Service Station and scientific research. We analyze the methods of telescope and modernized birefringent filter adjustment. After many years of continuous operation, a pressing need arose to replace the damaged parts of the chromospheric telescope. Optics and mechanics of the entire telescope have been cleaned and readjusted. Wavefront interferograms of the teleobjective lens and of the whole telescope show that wavefront distortions of the entire optical path are within 0.25 λ. We present an optical scheme and discuss optical-physical characteristics of BF elements. The interference prefilter and UV polarizers have been replaced, and passbands of BF tunable stages have been adjusted. The BF spectral characteristics provide a fairly high contrast of monochromatic images of large-scale phenomena. Unfortunately, with a collimator and Sony Cyber-Shot DSC-S85 camera, mounted on the telescope, the theoretical resolution of the 180-mm telescope is not realized. We have therefore calculated two optical schemes of telescope changes for possible improvement in spatial resolution.

scholarly journals Chromospheric K CaII telescope of Baikal Astrophysical Observatory. New light

2019 ◽  
Vol 5 (2) ◽  
pp. 116-128
Author(s):  
Любовь Лоптева ◽  
Lyubov Lopteva ◽  
Галина Кушталь ◽  
Galina Kushtal ◽  
Владимир Прошин ◽  
...  
Keyword(s):  
Large Scale ◽  
Spectral Characteristics ◽  
Optical Path ◽  
Continuous Operation ◽  
Solar Chromosphere ◽  
Optical Scheme ◽  
High Contrast ◽  
Birefringent Filter ◽  
Telescope Optics ◽  
Full Disk

In recent years, most results of CaII studies of the solar chromosphere in H and K lines have been based on observations with narrow passband filters. The Baikal Observatory’s full-disk chromospheric telescope for the K CaII line with a birefringent filter (BF) has again been included in observation programs of the Sun Service Station and scientific research. We analyze the methods of telescope and modernized birefringent filter adjustment. After many years of continuous operation, a pressing need arose to replace the damaged parts of the chromospheric telescope. Optics and mechanics of the entire telescope have been cleaned and readjusted. Wavefront interferograms of the teleobjective lens and of the whole telescope show that wavefront distortions of the entire optical path are within 0.25 λ. We present an optical scheme and discuss optical-physical characteristics of BF elements. The interference prefilter and UV polarizers have been replaced, and passbands of BF tunable stages have been adjusted. The BF spectral characteristics provide a fairly high contrast of monochromatic images of large-scale phenomena. Unfortunately, with a collimator and Sony Cyber-Shot DSC-S85 camera, mounted on the telescope, the theoretical resolution of the 180-mm telescope is not realized. We have therefore calculated two optical schemes of telescope changes for possible improvement in spatial resolution.

Sign in / Sign up

Export Citation Format

Share Document