scholarly journals Physical variability of the magnetic field of some stars

2021 ◽  
pp. 143-146
Author(s):  
V. D. BYCHKOV ◽  
L. V. BYCHKOVA ◽  
J. MADEY
Keyword(s):  
Magnetic Field ◽  
Magnetic Behavior ◽  
Red Dwarfs ◽  
Time Periods ◽  
The Magnetic Field

The magnetic behavior of red dwarfs shows a change in physical magnetic field parameters in time periods of months-years. We investigate whether a similar variability is possible in stars of other types.

Impurity-Induced Magnetic Anomalies in the Slightly Diluted Low Anisotropy A2Fe1-xInxCl5·H2O, (A=K, Rb) Antiferromagnets: An Overview

1998 ◽  
Vol 12 (18) ◽  
pp. 1781-1793 ◽  
Author(s):  
Fernando Palacio ◽  
Javier Campo ◽  
M. Carmen Morón ◽  
Armando Paduan-Filho ◽  
Carlos C. Becerra
Keyword(s):  
Magnetic Field ◽  
Phase Diagram ◽  
Solid Solutions ◽  
Magnetic Phase ◽  
Magnetic Phase Diagram ◽  
Magnetic Behavior ◽  
Magnetic Anomalies ◽  
Small Perturbations ◽  
The Magnetic Field

The phase diagram of low anisotropy antiferromagnets contains regions where small perturbations in the structure can induce rich interesting physical phenomenology that is still to be fully understood. This paper reviews the anomalies observed in site-diluted antiferromagnets in two regions of the magnetic phase diagram: the region where the magnetic field is very low, normally less than 10 Oe, and the spin-flop region. Although the observed phenomena is quite general, the magnetic behavior of the solid solutions A 2 Fe 1-x In x Cl 5· H 2 O , (A=K, Rb) is used to exemplify such anomalies.

scholarly journals Numerical modeling of statistical moments in a galactic dynamo problem with nonlinearity

2020 ◽  
pp. 172-179
Author(s):  
Д.А. Грачев ◽  
С.А. Елистратов
Keyword(s):  
Magnetic Field ◽  
Numerical Modeling ◽  
Field Strength ◽  
Stochastic Model ◽  
Characteristic Time ◽  
Statistical Moments ◽  
Small Magnetic Field ◽  
Time Periods ◽  
Field Approaches ◽  
The Magnetic Field

Рассматривается нелинейная модификация стохастической модели галактического динамо, в рамках которой коэффициент, отвечающий за турбулентную диффузию, полагается случайным процессом с обновлением. Показано, что при малых значениях напряженности магнитного поля его статистические моменты ведут себя примерно так же, как и в линейной модели (в частности, продемонстрировано наличие эффекта перемежаемости). Получены оценки для характерных времен выхода моментов на стабилизацию, которая наступает по мере приближения поля к равновесному значению. Проведено сопоставление результатов численного эксперимента, полученных при усреднении различных объемов выборки независимых случайных реализаций поля. In this paper we consider a nonlinear modification of a stochastic model of the galactic dynamo in which the coefficient of turbulent diffusion is assumed to be a random process with renewal. It is shown that, in the case of small magnetic field strength, its statistical moments behave almost in the same manner as in the linear model; it is also shown that the intermittency effect exists. The characteristic time periods of moment stabilization are estimated when the magnetic field approaches its equilibrium. The numerical results obtained by averaging various samplings of its independent random implementations are compared.

scholarly journals Distance Scaling Method for Accurate Prediction of Slowly Varying Magnetic Fields in Satellite Missions

2016 ◽  
Author(s):  
P. P. Zacharias ◽  
E. G. Chatzineofytou ◽  
S. T. Spantideas ◽  
C. N. Capsalis
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Power Law ◽  
Near Field ◽  
Magnetic Behavior ◽  
Field Measurements ◽  
Scaling Method ◽  
Magnetic Signature ◽  
The Magnetic Field

Abstract. In the present work, the determination of the magnetic behavior of localized magnetic sources from near field measurements is examined. The distance power law of the magnetic field fall-off is used in various cases to accurately predict the magnetic signature of an EUT consisting of multiple AC magnetic sources. Therefore, parameters concerning the location of the observation points (magnetometers) are stud ied towards this scope. The results clearly show that these parameters are independent of the EUT's size and layout. Additionally, the techniques developed in the present study enable the placing of the magnetometers close to the EUT, thus achieving high SNR. Finally, the proposed method is verified by real measurements, using a mobile phone as an EUT.

scholarly journals On unsteady hydromagnetic flows of a dusty viscous fluid between two oscillating plates

1989 ◽  
Vol 2 (1) ◽  
pp. 13-31 ◽  
Author(s):  
Lokenath Debnath ◽  
A. K. Ghosh
Keyword(s):  
Magnetic Field ◽  
Early Stage ◽  
Fluid Velocity ◽  
Fluid Motion ◽  
Unsteady Motion ◽  
Spherical Particles ◽  
Lower Plate ◽  
Time Period ◽  
Time Periods ◽  
The Magnetic Field

A study is made of the unsteady motion of an incompressible viscous conducting fluid with embedded small spherical particles bounded by two infinite rigid non-conducting plates. The operational method derives exact solutions for the fluid and the particle velocities and the wall shear stress. The quantitative evaluation of these results is considered when the two plates oscillate in phase but with different frequencies. The results are shown graphically for different values of the time period of oscillations of the plates which represent the cases: (i) the lower plate oscillates with time period less than the upper, (ii) both the plates oscillate with the same time period, (iii) the lower plate oscillates with time period greater than the upper. The magnetic field damps the fluid motion for all values of the time period of oscillations of the plates. When the time periods are small, i.e., when the plates oscillate with high frequency, the fluid motion is retarded by the particles. However, when the plates oscillate with larger time periods (smaller frequencies), the fluid velocity is increased by the presence of the particles at the early stage of the motion, and this effect persists until the equilibrium is reached when the particles exert their influence to resist the flow. The drag on the plate, which is evaluated numerically for the lower plate oscillating with large time period, depends on the ratio of the time periods of the oscillating plates. If the ratio of the time periods is not equal to unity, the drag on the plate, irrespective of the values of the magnetic field, oscillates with larger amplitude compared to its value when the ratio of the time periods is equal to unity. Further, for the ratio of the time periods less than or equal to unity and for any fixed values of the magnetic field, the drag increases by the presence of the particles after a time t≈1.2 which is the upper time limit for the non-equilibrium stress-value to exist. In a similar situation, a reverse effect, i.e., the decrease of the drag with increasing particle concentration, is found for the ratio of the time periods being greater than unity.

scholarly journals Large magnetodielectric coupling in the vicinity of metamagnetic transition in 6H−perovskite Ba3GdRu2O9

2022 ◽  
Author(s):  
Sonu Chhillar ◽  
Kaustav Mukherjee ◽  
C. S. Yadav
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
Magnetic Behavior ◽  
Magnetic Interactions ◽  
Metamagnetic Transition ◽  
Lower Temperature Side ◽  
Lower Temperature ◽  
Transition Complex ◽  
The Magnetic Field ◽  
Temperature Side

Abstract The 6H-perovskites Ba3RRu2O9 (R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of 4d - 4f magnetic interactions. Here, we have reported a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba3GdRu2O9. The signature of long-range antiferromagnetic (AFM) ordering at ~14.8 K (TN) is evident from the magnetization and heat capacity studies. The TN shifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magnetization at 2 K shows three metamagnetic transitions with the opening of small hysteresis in different regions. A new transition at T1 emerges after the onset of the first metamagnetic transition. Complex magnetic behavior is observed in different magnetic field regions whereas these field regions themselves vary with the temperature. Dielectric response recorded at zero and 80 kOe field exhibits the development of MD coupling well above TN. The MD coupling (~ 4.5 % at 10 K) is enhanced by 25 % as compared to the Dy counterpart. Effect of complex magnetic behavior is also conveyed in the MD results where the maximum value of MD coupling is observed in the vicinity of 10 K (onset of T1) and near the second metamagnetic transition. Our investigation suggests that both Gd and Ru moments align simultaneously at TN. Short-range magnetic correlations are possibly responsible for MD coupling above TN.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

Materials for Electron Beam Information Storage

1969 ◽  
Vol 27 ◽  
pp. 152-153 ◽  
Author(s):  
D. E. Speliotis
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Recent Literature ◽  
Electron Beams ◽  
Information Storage ◽  
The Subject ◽  
The Magnetic Field

The interaction of electron beams with a large variety of materials for information storage has been the subject of numerous proposals and studies in the recent literature. The materials range from photographic to thermoplastic and magnetic, and the interactions with the electron beam for writing and reading the information utilize the energy, or the current, or even the magnetic field associated with the electron beam.

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