scholarly journals 3-D numerical simulations of coronal loops oscillations

2009 ◽  
Vol 27 (10) ◽  
pp. 3899-3908 ◽  
Author(s):  
M. Selwa ◽  
L. Ofman
Keyword(s):  
Active Regions ◽  
External Source ◽  
Coronal Loops ◽  
Velocity Perturbation ◽  
Impulsive Excitation ◽  
Kink Mode ◽  
Parametric Studies ◽  
Field Lines ◽  
Significant Distance

Abstract. We present numerical results of 3-D MHD model of a dipole active region field containing a loop with a higher density than its surroundings. We study different ways of excitation of vertical kink oscillations by velocity perturbation: as an initial condition, and as an impulsive excitation with a pulse of a given position, duration, and amplitude. These properties are varied in the parametric studies. We find that the amplitude of vertical kink oscillations is significantly amplified in comparison to horizontal kink oscillations for exciters located centrally (symmetrically) below the loop, but not if the exciter is located a significant distance to the side of the loop. This explains why the pure vertical kink mode is so rarely observed in comparison to the horizontally polarized one. We discuss the role of curved magnetic field lines and the pulse overlapping at one of the loop's footpoints in 3-D active regions (AR's) on the excitation and the damping of slow standing waves. We find that footpoint excitation becomes more efficient in 3-D curved loops than in 2-D curved arcades and that slow waves can be excited within an interval of time that is comparable to the observed one wave-period due to the combined effect of the pulse inside and outside the loop. Additionally, we study the effect of AR topology on the excitation and trapping of loop oscillations. We find that a perturbation acting directly on a single loop excites oscillations, but results in an increased leakage compared to excitation of oscillations in an AR field by an external source.

Formation of solar coronal loops through magnetic reconnection in an emerging active region

2021 ◽  
Author(s):  
Zhenyong Hou ◽  
Hui Tian ◽  
Hechao Chen ◽  
Xiaoshuai Zhu ◽  
Jiansen He ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Emission Measure ◽  
Three Dimensional ◽  
Transverse Field ◽  
Power Spectral Analysis ◽  
Active Regions ◽  
Building Blocks ◽  
Coronal Loops ◽  
Field Lines

<p>Coronal loops are building blocks of solar active regions (ARs). However, their formation is not well understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge to the solar atmosphere. Observations in the EUV passbands of SDO/AIA clearly show the newly formed loops following magnetic reconnection within a vertical current sheet. Formation of the loops is also seen in the Hα images taken by NVST. The SDO/HMI observations show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ~0.5 km s<sup>-1</sup> before the apparent formation of coronal loops. During the formation of coronal loops, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. We have reconstructed the three-dimensional magnetic field structure through a magnetohydrostatic model, which shows field lines consistent with the loops in AIA images. Numerous bright blobs with a width of ~1.5 Mm appear intermittently in the current sheet and move upward with apparent velocities of ~80 km s<sup>-1</sup>. We have also identified plasma blobs moving to the footpoints of the newly formed large loops, with apparent velocities ranging from 30 to 50 km s<sup>-1</sup>. A differential emission measure analysis shows that the temperature, emission measure and density of the bright blobs are 2.5-3.5 MK, 1.1-2.3×10<sup>28</sup> cm<sup>-5</sup> and 8.9-12.9×10<sup>9</sup> cm<sup>-3</sup>, respectively. Power spectral analysis of these blobs indicates that the magnetic reconnection is inconsistent with the turbulent reconnection scenario.</p>

Influence of Magnetic Fields on Solar Hydrodynamics: Experimental Results

1977 ◽  
Vol 36 ◽  
pp. 143-180 ◽  
Author(s):  
J.O. Stenflo
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
General Problem ◽  
Solar Rotation ◽  
Active Regions ◽  
Physical Conditions ◽  
Dynamic Phenomena

It is well-known that solar activity is basically caused by the Interaction of magnetic fields with convection and solar rotation, resulting in a great variety of dynamic phenomena, like flares, surges, sunspots, prominences, etc. Many conferences have been devoted to solar activity, including the role of magnetic fields. Similar attention has not been paid to the role of magnetic fields for the overall dynamics and energy balance of the solar atmosphere, related to the general problem of chromospheric and coronal heating. To penetrate this problem we have to focus our attention more on the physical conditions in the ‘quiet’ regions than on the conspicuous phenomena in active regions.

REDUCED MULTIREFERENCE COUPLED-CLUSTER METHOD AND ITS APPLICATION TO THE PYRIDYNE DIRADICALS

2008 ◽  
Vol 07 (04) ◽  
pp. 805-820 ◽  
Author(s):  
XIANGZHU LI ◽  
JOSEF PALDUS
Keyword(s):  
Molecular Geometry ◽  
External Source ◽  
Cluster Method ◽  
Coupled Cluster ◽  
Triplet States ◽  
Correlation Effects ◽  
Spin Multiplicity ◽  
Triplet Splitting ◽  
Singlet And Triplet States

The reduced multireference (RMR) coupled-cluster (CC) method with singles and doubles (RMR CCSD) that employs a modest-size MR CISD wave function as an external source for the most important (primary) triples and quadruples in order to account for the nondynamic correlation effects in the presence of quasidegeneracy, and which is further perturbatively corrected for the remaining (secondary) triples, RMR CCSD(T), is employed to compute the molecular geometry and the energy of the lowest-lying singlet and triplet states, as well as the corresponding singlet–triplet splitting, for all possible isomers of the m, n-pyridyne diradicals. A comparison is made with earlier results that were obtained by other authors, and the role of the multireference effects for both the geometry and the spin multiplicity of the lowest state, as described by the RMR-type methods, is demonstrated on the example of 2,6- and 3,5-pyridynes.

AXITURB: A Full Computer Implementation of the NASA Design Procedure for Axial-Flow Turbines

1993 ◽  
Author(s):  
P. C. Lu ◽  
Chen-Ying Wang
Keyword(s):  
Alkali Metals ◽  
Axial Flow ◽  
Design Procedure ◽  
Rankine Cycle ◽  
Eutectic Alloys ◽  
Singular Case ◽  
Cycle Space ◽  
Power Turbine ◽  
Parametric Studies

Abstract A recent task to design a Rankine-cycle space-power turbine system employing eutectic alloys of alkali metals prompted the present authors to re-examine the NASA design procedure for axial-flow turbines, as outlined by Glassman and Futral (and based on works of Stewart) in 1963. After clarifying the role of the singular case of a single-stage turbine, and organizing the procedure in clear steps, a computer program AXITURB was written. The present paper reports essentially the success of AXITURB in performing parametric studies of NaK and CsK turbines (using 78.4% and 23.1%, respectively, of potassium by weight), after re-generating all the reported NASA designs for turbines employing pure Na, K and Cs. An outline of design steps is also given. AXITURB has been put in public domain. Its heavily commented source code in FORTRAN is available to designers for adaption or modification.

scholarly journals Evidence for Open Field Lines from Active Regions: Short Communication

1980 ◽  
Vol 91 ◽  
pp. 261-261
Author(s):  
K. V. Sheridan
Keyword(s):  
Open Field ◽  
Subject Matter ◽  
Short Communication ◽  
Active Regions ◽  
Theoretical Physics ◽  
University Of Colorado ◽  
Solar Active Regions ◽  
The Subject ◽  
Field Lines ◽  
Sydney Australia

A paper that has considerable relevance of the subject matter of this symposium is the following: “Evidence for Extreme Divergence of Open Field Lines from Solar Active Regions,” by G. A. Dulk (Division of Radiophysics, CSIRO, Sydney, Australia and Department of Astro-Geophysics, University of Colorado, Boulder, Colorado), D. B. Melrose (Department of Theoretical Physics, University of Sydney, Australia) and S. Suzuki (Division of Radiophysics, CSIRO, Sydney, Australia).

scholarly journals ACTIVITY OF COURTS IN THE KHANTY-MANSIYSK AUTONOMOUS OKRUG TO STRENGTHEN THE LABOR DISCIPLINE OF THE SOVIET SOCIETY IN THE EARLY 1940s

2021 ◽  
pp. 51-58
Author(s):  
Aleksandr A. Kaвurkin
Keyword(s):  
Labor Policy ◽  
Soviet Society ◽  
Criminal Cases ◽  
Labor Discipline ◽  
The Social ◽  
Territorial Structure ◽  
Working Day ◽  
Second World ◽  
Significant Distance

The article reflects the peculiarities of implementing the penal and labor policy by the Soviet party and state bodies, including judicial ones in the Ostyako-Vogulsky, later Khanty-Mansiysk National Okrug, their interrelation in the early 1940s. The stages of evolving and forming the administrative-territorial structure in the region are also touched upon. The relevance of the stated topic is noted. In the conditions of the Second World War and on the eve of the Great Patriotic War in the USSR, there were noticeable changes in the social policy of the state, which were conditioned by the needs of the country’s defense. It is known that in the 1930s tensions in international relations increased, there was a threat of an attack on the USSR. Due to this in 1940s the transition to an 8-hour working day and a 7-day working week was carried out in all regions of the country. In the same year, a law was adopted on the judicial responsibility up to imprisonment for unauthorized leave, absenteeism and tardiness as a result of which criminal penalties and the role of punitive, including judicial, bodies were strengthened in the country. The article notes that in the harsh northern conditions, taking into account the vast territory of the district, a significant distance separating settlements from each other, the lack of proper transport links between settlements, it was impossible to properly and promptly ensure proper consideration of criminal cases, which did not allow the territorial judicial authorities of the Ostyak-Vogul (Khanty-Mansiysk) National Okrug to make correct and balanced decisions in a timely manner. However, the judicial authorities of the district played an important role in strengthening labor discipline in the region in the early 1940s.

scholarly journals Origins and Function of VL30 lncRNA Packaging in Small Extracellular Vesicles: Implications for Cellular Physiology and Pathology

Biomedicines ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1742
Author(s):  
Stefania Mantziou ◽  
Georgios S. Markopoulos
Keyword(s):  
Extracellular Vesicles ◽  
Active Regions ◽  
Regulatory Elements ◽  
Binding Motif ◽  
Regulatory Sequences ◽  
Chromosomal Distribution ◽  
Non Coding Rna ◽  
Rna Biology ◽  
And Function

Long non-coding RNAs (lncRNAs) have emerged during the post-genomic era as significant epigenetic regulators. Viral-like 30 elements (VL30s) are a family of mouse retrotransposons that are transcribed into functional lncRNAs. Recent data suggest that VL30 RNAs are efficiently packaged in small extracellular vesicles (SEVs) through an SEV enrichment sequence. We analysed VL30 elements for the presence of the distinct 26 nt SEV enrichment motif and found that SEV enrichment is an inherent hallmark of the VL30 family, contained in 36 full-length elements, with a widespread chromosomal distribution. Among them, 25 elements represent active, present-day integrations and contain an abundance of regulatory sequences. Phylogenetic analysis revealed a recent spread of SEV-VL30s from 4.4 million years ago till today. Importantly, 39 elements contain an SFPQ-binding motif, associated with the transcriptional induction of oncogenes. Most SEV-VL30s reside in transcriptionally active regions, as characterised by their distribution adjacent to candidate cis-regulatory elements (cCREs). Network analysis of SEV-VL30-associated genes suggests a distinct transcriptional footprint associated with embryonal abnormalities and neoplasia. Given the established role of VL30s in oncogenesis, we conclude that their potential to spread through SEVs represents a novel mechanism for non-coding RNA biology with numerous implications for cellular homeostasis and disease.

INTERNET PROSUMPTION IN THE ASPECT OF ENTERPRISE COMPETITIVENESS

2021 ◽  
Vol 22 (2) ◽  
pp. 53-66
Author(s):  
Maria Kocot
Keyword(s):  
External Source ◽  
Original Model ◽  
The Internet ◽  
Technological Changes ◽  
Market Position ◽  
Modern Enterprise ◽  
Production And Consumption ◽  
New Knowledge ◽  
Enterprise Competitiveness

The article focuses on presenting the role of internet prosumption as a source of competitivenessof a modern enterprise. The boundaries between production and consumption processes areblurring. The prosumption relationship will be strengthened thanks to the progressive technological changes, especially the development of the Internet. Internet prosumers, by expressing their opposition to standardized production, become a reservoir of “new knowledge”. which in turn becomes the seed of innovation of all kinds. These activities lead to the expansion of the group of satisfied customers, consolidation of the company’s market position and, as a result, an increase in its competitiveness. The aim of the article is to present the importance of internet prosumption as a source of enterprise competitiveness. The analysis was summed up in the original model, which indicated that establishing a pro-consumer system becomes an external source of competitiveness. The article highlights the role of the Internet and ICT as a catalyst for effective communication between the consumer and the provider.

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