scholarly journals The multi-thermal chromosphere

2020 ◽  
Vol 634 ◽  
pp. A56 ◽  
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.

The solar chromosphere and corona: Quiet Sun

1977 ◽  
Vol 25 (9) ◽  
pp. 893-894
Author(s):  
Carole Jordan
Keyword(s):  
Solar Chromosphere ◽  
Quiet Sun

QUIET-SUN INTENSITY CONTRASTS IN THE NEAR-ULTRAVIOLET AS MEASURED FROM SUNRISE

2010 ◽  
Vol 723 (2) ◽  
pp. L154-L158 ◽  
Author(s):  
J. Hirzberger ◽  
A. Feller ◽  
T. L. Riethmüller ◽  
M. Schüssler ◽  
J. M. Borrero ◽  
...  
Keyword(s):  
Quiet Sun ◽  
Near Ultraviolet

scholarly journals Modeling the quiet Sun cell and network emission with ALMA

2020 ◽  
Vol 640 ◽  
pp. A57 ◽  
Author(s):  
C. E. Alissandrakis ◽  
A. Nindos ◽  
T. S. Bastian ◽  
S. Patsourakos
Keyword(s):  
Electron Temperature ◽  
Brightness Temperature ◽  
Absolute Calibration ◽  
Solar Chromosphere ◽  
Temperature Structure ◽  
Cell Interior ◽  
Network Cell ◽  
Quiet Sun ◽  
Millimeter Wavelengths ◽  
Cell Segregation

Observations of the Sun at millimeter wavelengths with the Atacama Large Millimeter/submillimeter Array (ALMA) offer a unique opportunity to investigate the temperature structure of the solar chromosphere. In this article we expand our previous work on modeling the chromospheric temperature of the quiet Sun, by including measurements of the brightness temperature in the network and cell interiors, from high-resolution ALMA images at 3 mm (Band 3) and 1.26 mm (Band 6). We also examine the absolute calibration of ALMA full-disk images. We suggest that the brightness temperature at the center of the solar disk in Band 6 is ∼440 K above the value recommended by White et al. (2017, Sol. Phys., 292, 88). In addition, we give improved results for the electron temperature variation of the average quiet Sun with optical depth and the derived spectrum at the center of the disk. We found that the electron temperature in the network is considerably lower than predicted by model F of Fontenla et al. (1993, ApJ, 406, 319) and that of the cell interior considerably higher than predicted by model A. Depending on the network/cell segregation scheme, the electron temperature difference between network and cell at τ = 1 (100 GHz) ranges from ∼660 K to ∼1550 K, compared to ∼3280 K predicted by the models; similarly, the electron temperature, Te ratio ranges from ∼1.10 to 1.24, compared to ∼1.55 of the model prediction. We also found that the network/cell Te(τ) curves diverge as τ decreases, indicating an increase of contrast with height and possibly a steeper temperature rise in the network than in the cell interior.

scholarly journals Transient brightenings in the quiet Sun detected by ALMA at 3 mm

2020 ◽  
Vol 638 ◽  
pp. A62 ◽  
Author(s):  
A. Nindos ◽  
C. E. Alissandrakis ◽  
S. Patsourakos ◽  
T. S. Bastian
Keyword(s):  
Solar Atmosphere ◽  
Power Law ◽  
Small Scale ◽  
Solar Chromosphere ◽  
Average Intensity ◽  
Quiet Sun ◽  
Brightness Temperatures ◽  
Weak Preference ◽  
Thermal Origin ◽  
First Time

Aims. We investigate transient brightenings, that is, weak, small-scale episodes of energy release, in the quiet solar chromosphere; these episodes can provide insights into the heating mechanism of the outer layers of the solar atmosphere. Methods. Using Atacama Large Millimeter/submillimeter Array (ALMA) observations, we performed the first systematic survey for quiet Sun transient brightenings at 3 mm. Our dataset included images of six 87″ × 87″ fields of view of the quiet Sun obtained with angular resolution of a few arcsec at a cadence of 2 s. The transient brightenings were detected as weak enhancements above the average intensity after we removed the effect of the p-mode oscillations. A similar analysis, over the same fields of view, was performed for simultaneous 304 and 1600 Å data obtained with the Atmospheric Imaging Assembly. Results. We detected 184 3 mm transient brightening events with brightness temperatures from 70 K to more than 500 K above backgrounds of ∼7200 − 7450 K. All events showed light curves with a gradual rise and fall, strongly suggesting a thermal origin. Their mean duration and maximum area were 51.1 s and 12.3 Mm2, respectively, with a weak preference of appearing at network boundaries rather than in cell interiors. Both parameters exhibited power-law behavior with indices of 2.35 and 2.71, respectively. Only a small fraction of ALMA events had either 304 or 1600 Å counterparts but the properties of these events were not significantly different from those of the general population except that they lacked their low-end energy values. The total thermal energies of the ALMA transient brightenings were between 1.5 × 1024 and 9.9 × 1025 erg and their frequency distribution versus energy was a power law with an index of 1.67 ± 0.05. We found that the power per unit area provided by the ALMA events could account for only 1% of the chromospheric radiative losses (10% of the coronal ones). Conclusions. We were able to detect, for the first time, a significant number of weak 3 mm quiet Sun transient brightenings. However, their energy budget falls short of meeting the requirements for the heating of the upper layers of the solar atmosphere and this conclusion does not change even if we use the least restrictive criteria possible for the detection of transient brightenings.

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.

The Solar Chromosphere and Corona: Quiet Sun

1976 ◽  
Vol 27 (9) ◽  
pp. 408-408
Author(s):  
W M Glencross
Keyword(s):  
Solar Chromosphere ◽  
Quiet Sun

scholarly journals Prognostic factors of cardiovascular death in patients with ischemic stroke in the long-term follow up

2016 ◽  
Vol 7 (3-4) ◽  
pp. 97-103
Author(s):  
A. V Fonyakin ◽  
L. A Geraskina ◽  
V. A Shandalin
Keyword(s):  
Ischemic Stroke ◽  
Sinus Rhythm ◽  
Recurrent Stroke ◽  
Low Frequency ◽  
Holter Monitoring ◽  
Multivariate Regression Analysis ◽  
Cardiovascular Death ◽  
Increased Risk ◽  
Two Parameters

In a prospective observational non-interventional study included 148 patients with ischemic stroke at the age of 60 (52; 68) years, with sinus rhythm. At the end of the acute stroke period (21-22 days) was performed Holter monitoring with the assessment of arrhythmias and heart rate variability (HRV). Duration of prospective follow-up was 35 (28; 40) months. We register all cases of cardiovascular death (CD), including death due to recurrent stroke, myocardial infarction (MI), sudden CD (SCD), acute heart failure (AHF), pulmonary embolism. During follow up CD was registered in 15 (10%) patients: in 7 patients - due to recurrent stroke, 2 patients - due to acute MI, in 3 - due to AHF, 3 patients - due to SCD. On multivariate regression analysis in sinus rhythm revealed significant association with the development of CD following factors: age over 67 years, male gender, involvement insula in the area of ischemic damage, supraventricular extrasystoles (more than 54 extrasystoles per day), ventricular arrhythmias, bradyarrhythmias, reduced power range of high-frequency (HF) less than 39 ms2 and low frequency less than 180 ms2 HRV. Separately from the number of these factors with increased risk of fatal complications was significantly associated only two parameters: the involvement insula in the cerebral infarct area (p

scholarly journals Observational study of chromospheric heating by acoustic waves

2020 ◽  
Vol 642 ◽  
pp. A52
Author(s):  
V. Abbasvand ◽  
M. Sobotka ◽  
M. Švanda ◽  
P. Heinzel ◽  
M. García-Rivas ◽  
...  
Keyword(s):  
Energy Flux ◽  
Acoustic Waves ◽  
Acoustic Energy ◽  
Solar Chromosphere ◽  
Echelle Spectrograph ◽  
Quiet Sun ◽  
Non Local ◽  
Radiative Losses ◽  
Semi Empirical

Aims. Our aim is to investigate the role of acoustic and magneto-acoustic waves in heating the solar chromosphere. Observations in strong chromospheric lines are analyzed by comparing the deposited acoustic-energy flux with the total integrated radiative losses. Methods. Quiet-Sun and weak-plage regions were observed in the Ca II 854.2 nm and Hα lines with the Fast Imaging Solar Spectrograph (FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and in the Hα and Hβ lines with the echelle spectrograph attached to the Vacuum Tower Telescope on 2018 December 11 and 2019 June 6. The deposited acoustic energy flux at frequencies up to 20 mHz was derived from Doppler velocities observed in line centers and wings. Radiative losses were computed by means of a set of scaled non-local thermodynamic equilibrium 1D hydrostatic semi-empirical models obtained by fitting synthetic to observed line profiles. Results. In the middle chromosphere (h = 1000–1400 km), the radiative losses can be fully balanced by the deposited acoustic energy flux in a quiet-Sun region. In the upper chromosphere (h >  1400 km), the deposited acoustic flux is small compared to the radiative losses in quiet as well as in plage regions. The crucial parameter determining the amount of deposited acoustic flux is the gas density at a given height. Conclusions. The acoustic energy flux is efficiently deposited in the middle chromosphere, where the density of gas is sufficiently high. About 90% of the available acoustic energy flux in the quiet-Sun region is deposited in these layers, and thus it is a major contributor to the radiative losses of the middle chromosphere. In the upper chromosphere, the deposited acoustic flux is too low, so that other heating mechanisms have to act to balance the radiative cooling.

scholarly journals Improved Functionality of Integration-Deficient Lentiviral Vectors (IDLVs) by the Inclusion of IS2 Protein Docks

Pharmaceutics ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1217
Author(s):  
Marina Cortijo-Gutiérrez ◽  
Sabina Sánchez-Hernández ◽  
María Tristán-Manzano ◽  
Noelia Maldonado-Pérez ◽  
Lourdes Lopez-Onieva ◽  
...  
Keyword(s):  
Transgene Expression ◽  
Low Frequency ◽  
Nuclear Gene ◽  
Lentiviral Vectors ◽  
Sequence Element ◽  
Strand Breaks ◽  
Expression Levels ◽  
Potential Applications ◽  
Two Parameters ◽  
Positive Effect

Integration-deficient lentiviral vectors (IDLVs) have recently generated increasing interest, not only as a tool for transient gene delivery, but also as a technique for detecting off-target cleavage in gene-editing methodologies which rely on customized endonucleases (ENs). Despite their broad potential applications, the efficacy of IDLVs has historically been limited by low transgene expression and by the reduced sensitivity to detect low-frequency off-target events. We have previously reported that the incorporation of the chimeric sequence element IS2 into the long terminal repeat (LTR) of IDLVs increases gene expression levels, while also reducing the episome yield inside transduced cells. Our study demonstrates that the effectiveness of IDLVs relies on the balance between two parameters which can be modulated by the inclusion of IS2 sequences. In the present study, we explore new IDLV configurations harboring several elements based on IS2 modifications engineered to mediate more efficient transgene expression without affecting the targeted cell load. Of all the insulators and configurations analysed, the insertion of the IS2 into the 3′LTR produced the best results. After demonstrating a DAPI-low nuclear gene repositioning of IS2-containing episomes, we determined whether, in addition to a positive effect on transcription, the IS2 could improve the capture of IDLVs on double strand breaks (DSBs). Thus, DSBs were randomly generated, using the etoposide or locus-specific CRISPR-Cas9. Our results show that the IS2 element improved the efficacy of IDLV DSB detection. Altogether, our data indicate that the insertion of IS2 into the LTR of IDLVs improved, not only their transgene expression levels, but also their ability to be inserted into existing DSBs. This could have significant implications for the development of an unbiased detection tool for off-target cleavage sites from different specific nucleases.

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.

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