Diagnosing chromospheric magnetic field through simultaneous spectropolarimetry in Hα and Ca II 854.2 nm

2019 ◽  
Vol 15 (S354) ◽  
pp. 46-52
Author(s):  
K. Nagaraju ◽  
K. Sankarasubramanian ◽  
K. E. Rangarajan
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Opposite Polarity ◽  
Point Of View ◽  
Current Understanding ◽  
Small Scale ◽  
Preliminary Results

AbstractMeasurement of magnetic field in this layer is challenging both from point of view of observations and interpretation of the data. We present in this work about spectropolarimetric observations of a pore, simultaneously in Ca ii (CaIR) at 854.2 nm (CaIR) and H α (656.28 nm). The observed region includes a small scale energetic event (SSEE) taking place in the region between the pore and the region which show opposite polarity to that of pore at the photosphere. The energetic event appears to be a progressive reconnection event as shown by the time evolution of the intensity profiles. Closer examination of the intensity profiles from the downflow regions suggest that the height of formation of CaIR is higher than that of Hi α, contrary to the current understanding about their height of formation. Preliminary results on the inversion of Stokes-I and V profiles of CaIR are also presented.

scholarly journals Numerical Simulation of the Time Evolution of Small-Scale Irregularities in the F-Layer Ionospheric Plasma

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
O. V. Mingalev ◽  
G. I. Mingaleva ◽  
M. N. Melnik ◽  
V. S. Mingalev
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Ionospheric Plasma ◽  
Debye Length ◽  
Small Scale ◽  
System Of Equations ◽  
Applied Model ◽  
Positive Ions ◽  
F Region ◽  
Small Scale Irregularity

Dynamics of magnetic field-aligned small-scale irregularities in the electron concentration, existing in the F-layer ionospheric plasma, is investigated with the help of a mathematical model. The plasma is assumed to be a rarefied compound consisting of electrons and positive ions and being in a strong, external magnetic field. In the applied model, kinetic processes in the plasma are simulated by using the Vlasov-Poisson system of equations. The system of equations is numerically solved applying a macroparticle method. The time evolution of a plasma irregularity, having initial cross-section dimension commensurable with a Debye length, is simulated during the period sufficient for the irregularity to decay completely. The results of simulation indicate that the small-scale irregularity, created initially in the F-region ionosphere, decays accomplishing periodic damped vibrations, with the process being collisionless.

scholarly journals Small scale observation of magnetopause motion: preliminary results of the INTERBALL project

1997 ◽  
Vol 15 (5) ◽  
pp. 562-569 ◽  
Author(s):  
J. Safrankova ◽  
G. Zastenker ◽  
Z. Nemecek ◽  
A. Fedorov ◽  
M. Simersky ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Resolution ◽  
Simultaneous Measurement ◽  
Small Scale ◽  
Satellite Measurements ◽  
Preliminary Results ◽  
Plasma Device ◽  
First Results ◽  
The Magnetic Field ◽  
Interball Project

Abstract. Two satellites of the INTERBALL project were launched on 3 August 1995. The main goals of the present paper are (1) to give a brief information about the VDP plasma device onboard the INTERBALL-1 satellite, (2) to present the Faradays cup data taken in different magnetospheric regions and (3) to expose first results of the two satellite measurements of the magnetopause motion. The presented data illustrate magnetopause crossings as seen by two satellites when separated by about ~ 1000 km. This separation combined with the Faraday's cup time resolution allows to estimate the velocity of the magnetopause and to reconstruct a possible structure of the boundary. Simultaneous measurement of the magnetic field supports the interpretation of the observed ion fluxes as a signature of the wavy motion of the boundary.

scholarly journals Three-dimensional magnetic field structure of a flux-emerging region in the solar atmosphere

2019 ◽  
Vol 632 ◽  
pp. A112 ◽  
Author(s):  
Rahul Yadav ◽  
Jaime de la Cruz Rodríguez ◽  
Carlos José Díaz Baso ◽  
Avijeet Prasad ◽  
Tine Libbrecht ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Surface ◽  
Free Field ◽  
Opposite Polarity ◽  
Field Vector ◽  
Small Scale ◽  
Maximum Height ◽  
Horizontal Magnetic Field ◽  
Point Separation ◽  
The Magnetic Field

We analyze high-resolution spectropolarimetric observations of a flux-emerging region (FER) in order to understand its magnetic and kinematic structure. Our spectropolarimetric observations in the He I 10830 Å spectral region of a FER were recorded with GRIS at the 1.5 m aperture GREGOR telescope. A Milne–Eddington-based inversion code was employed to extract the photospheric information of the Si I spectral line, whereas the He I triplet line was analyzed with the Hazel inversion code, which takes into account the joint action of the Hanle and the Zeeman effects. The spectropolarimetric analysis of the Si I line reveals a complex magnetic structure near the vicinity of the FER, where a weak (350–600 G) and horizontal magnetic field was observed. In contrast to the photosphere, the analysis of the He I triplet presents a smooth variation of the magnetic field vector (ranging from 100 to 400 G) and velocities across the FER. Moreover, we find supersonic downflows of ∼40 km s−1 appearing near the foot points of loops connecting two pores of opposite polarity, whereas strong upflows of 22 km s−1 appear near the apex of the loops. At the location of supersonic downflows in the chromosphere, we observed downflows of 3 km s−1 in the photosphere. Furthermore, nonforce-free field extrapolations were performed separately at two layers in order to understand the magnetic field topology of the FER. We determine, using extrapolations from the photosphere and the observed chromospheric magnetic field, that the average formation height of the He I triplet line is ∼2 Mm from the solar surface. The reconstructed loops using photospheric extrapolations along an arch filament system have a maximum height of ∼10.5 Mm from the solar surface with a foot-point separation of ∼19 Mm, whereas the loops reconstructed using chromospheric extrapolations reach around ∼8.4 Mm above the solar surface with a foot-point separation of ∼16 Mm at the chromospheric height. The magnetic topology in the FER suggests the presence of small-scale loops beneath the large loops. Under suitable conditions, due to magnetic reconnection, these loops can trigger various heating events in the vicinity of the FER.

scholarly journals SMA observations of polarized dust emission in solar-type Class 0 protostars: Magnetic field properties at envelope scales

2018 ◽  
Vol 616 ◽  
pp. A139 ◽  
Author(s):  
Maud Galametz ◽  
Anaëlle Maury ◽  
Josep M. Girart ◽  
Ramprasad Rao ◽  
Qizhou Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Dust Emission ◽  
Point Of View ◽  
Continuum Emission ◽  
Small Scale ◽  
Theoretical Point ◽  
Multiple Systems ◽  
Linearly Polarized ◽  
Solar Type ◽  
The Magnetic Field

Aims. Although from a theoretical point of view magnetic fields are believed to play a significant role during the early stages of star formation, especially during the main accretion phase, the magnetic field strength and topology is poorly constrained in the youngest accreting Class 0 protostars that lead to the formation of solar-type stars. Methods. We carried out observations of the polarized dust continuum emission with the SMA interferometer at 0.87 mm to probe the structure of the magnetic field in a sample of 12 low-mass Class 0 envelopes in nearby clouds, including both single protostars and multiple systems. Our SMA observations probed the envelope emission at scales ~600 − 5000 au with a spatial resolution ranging from 600 to 1500 au depending on the source distance. Results. We report the detection of linearly polarized dust continuum emission in all of our targets with average polarization fractions ranging from 2% to 10% in these protostellar envelopes. The polarization fraction decreases with the continuum flux density, which translates into a decrease with the H2 column density within an individual envelope. Our analysis show that the envelope-scale magnetic field is preferentially observed either aligned or perpendicular to the outflow direction. Interestingly, our results suggest for the first time a relation between the orientation of the magnetic field and the rotational energy of envelopes, with a larger occurrence of misalignment in sources in which strong rotational motions are detected at hundreds to thousands of au scales. We also show that the best agreement between the magnetic field and outflow orientation is found in sources showing no small-scale multiplicity and no large disks at ~100 au scales.

scholarly journals Solar Magnetoconvection

1990 ◽  
Vol 138 ◽  
pp. 191-211
Author(s):  
Å. Nordlund ◽  
R. F. Stein
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Time Evolution ◽  
Large Scale ◽  
Stratified Medium ◽  
Small Scale ◽  
Surface Magnetic Field ◽  
The Hierarchical Structure ◽  
Surface Manifestation

As a prelude to discussing the interaction of magnetic fields with convection, we first review some general properties of convection in a stratified medium. Granulation, which is the surface manifestation of the major energy carrying convection scales, is a shallow phenomenon. Below the surface, the topology changes to one of filamentary cool downdrafts, immersed in a gently ascending isentropic background. The granular downflows merge into more widely separated downdrafts, on scales of mesogranulation and super-granulation.The local topology and time evolution of the small scale, kilo Gauss, network and facular magnetic field elements are controlled by convection on the scale of granulation. The topology and time evolution of larger scale magnetic field concentrations are controlled by the hierarchical structure of the horizontal components of the large scale velocity field. In sunspots, the small scale magnetic field structure determines the energy balance, the systematic flows and the waves. Below the surface, the small scale structure of the magnetic field may change drastically, with little observable effect at the surface. We discuss results of some recent numerical simulations of sunspot magnetic fields, and some mechanisms that may be relevant in determining the topology of the sub-surface magnetic field. Finally, we discuss the role of active region magnetic fields in the global solar dynamo.

scholarly journals General features of the linear crystalline morphology of accretion disks

2021 ◽  
Vol 75 (3) ◽  
Author(s):  
Giovanni Montani ◽  
Brunello Tirozzi ◽  
Nakia Carlevaro
Keyword(s):  
Magnetic Field ◽  
Vertical Gradient ◽  
Point Of View ◽  
Small Scale ◽  
Partial Differential ◽  
Differential Problem ◽  
Radial Magnetic Field ◽  
Kummer Functions ◽  
Magnetic Profile ◽  
Variable Separation Method

Abstract In this paper, we analyze the so-called Master Equation of the linear backreaction of a plasma disk in the central object magnetic field, when small scale ripples are considered. This study allows to single out two relevant physical properties of the linear disk backreaction: (i) the appearance of a vertical growth of the magnetic flux perturbations; (ii) the emergence of sequence of magnetic field O-points, crucial for the triggering of local plasma instabilities. We first analyze a general Fourier approach to the solution of the addressed linear partial differential problem. This technique allows to show how the vertical gradient of the backreaction is, in general, inverted with respect to the background one. Instead, the fundamental harmonic solution constitutes a specific exception for which the background and the perturbed profiles are both decaying. Then, we study the linear partial differential system from the point of view of a general variable separation method. The obtained profile describes the crystalline behavior of the disk. Using a simple rescaling, the governing equation is reduced to the second-order differential Whittaker equation. The zeros of the radial magnetic field are found by using the solution written in terms Kummer functions. The possible implications of the obtained morphology of the disk magnetic profile are then discussed in view of the jet formation. GraphicAbstract

scholarly journals Spatio-temporal variability of the photospheric magnetic field

2010 ◽  
Vol 6 (S274) ◽  
pp. 204-206
Author(s):  
A. Vecchio ◽  
M. Laurenza ◽  
D. Meduri ◽  
V. Carbone ◽  
M. Storini
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Empirical Mode Decomposition ◽  
Temporal Variability ◽  
Solar Magnetic Field ◽  
Temporal Dynamics ◽  
Heliographic Latitude ◽  
Preliminary Results ◽  
Mode Decomposition ◽  
Spatio Temporal

AbstractThe spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak synoptic magnetic maps covering ~28 yr. For each heliographic latitude the field has been analyzed through the Empirical Mode Decomposition, in order to investigate the time evolution of the various characteristic oscillating frequencies. Preliminary results are discussed.

ABOUT UNIFORMITY OF THE PHENOMENOLOGY AND THE MATHEMATICAL DESCRIPTION OF SO-CALLED « JOINED» ACTION OF HAZARDS AND COMBINED TOXICITY (ON THE EXAMPLE OF A COMBIBATION OF THE FLUORIDE AND THE STATIC MAGNETIC FIELD)

2016 ◽  
pp. 13-20
Author(s):  
B. A. Katsnelson ◽  
M. P. Sutunkova ◽  
N. A. Tsepilov ◽  
V. G. Panov ◽  
A. N. Varaksin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Static Magnetic Field ◽  
Point Of View ◽  
Whole Body ◽  
Surface Model ◽  
Combined Toxicity ◽  
Fluoride Solution ◽  
Adverse Action ◽  
Biochemical Indices ◽  
And Control

Sodium fluoride solution was injected i.p. to three groups of rats at a dose equivalent to 0.1 LD50 three times a week up to 18 injections. Two out of these groups and two out of three groups were sham-injected with normal saline and were exposed to the whole body impact of a 25 mT static magnetic field (SMF) for 2 or 4 hr a day, 5 times a week. Following the exposure, various functional and biochemical indices were evaluated along with histological examination and morphometric measurements of the femur in the differently exposed and control rats. The mathematical analysis of the combined effects of the SMF and fluoride based on the a response surface model demonstrated that, in full correspondence with what we had previously found for the combined toxicity of different chemicals, the combined adverse action of a chemical plus a physical agent was characterized by a tipological diversity depending not only on particular effects these types were assessed for but on the dose and effect levels as well. From this point of view, the indices for which at least one statistically significant effect was observed could be classified as identifying (I) mainly single-factor action; (II) additive unidirectional action; (III) synergism (superadditive unidirectional action); (IV) antagonism, including both subadditive unidirectional action and all variants of contradirectional action.

scholarly journals No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Evgeny Mikhailov ◽  
Daniela Boneva ◽  
Maria Pashentseva
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Point Of View ◽  
Accretion Discs ◽  
Wide Range ◽  
Astrophysical Objects ◽  
Alpha Effect ◽  
The Stability ◽  
The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

scholarly journals A New Measure of Complementarity in Market Basket Data

2021 ◽  
Vol 16 (4) ◽  
pp. 670-681
Author(s):  
Radosław Puka ◽  
Stanislaw Jedrusik
Keyword(s):  
Large Data ◽  
Point Of View ◽  
Detailed Data ◽  
Market Basket ◽  
Economic Theories ◽  
Empirical Verification ◽  
Preliminary Results ◽  
Research Fields ◽  
It Systems ◽  
Real Market

Modern IT systems collect detailed data on each activity, transaction, forum entry, conversation and many other areas. The availability of large data volumes in the business, industry and research fields opens up new opportunities for the empirical verification of various economic theories and laws. The analysis of big datasets in turn allows us to look at many issues from a new point of view and see the dependencies that are otherwise difficult to derive. In this paper, we propose a new measure for dependencies between goods in market basket data. The introduced measure was inspired by the well-known microeconomic concept of complementarity. Due to its similar properties to those of complementarity, the new measure was called basket complementarity (b-complementarity). B-complementarity not only measures the strength of dependencies between goods but also measures the direction of these dependencies. The values of the proposed measure can be relatively easily calculated using market basket data. This paper also presents a simple example illustrating this new concept, areas of possible application (e.g., in e-commerce) and preliminary results of searching for goods that meet the criteria of basket complementarity in real market basket data.

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