Transverse tangential component of the magnetic field of a defect

Abstract. We present a theory of trapped ion motion in the magnetotail current sheet with a constant dawn–dusk component of the magnetic field. Particle trajectories are described analytically using the quasi-adiabatic invariant corresponding to averaging of fast oscillations around the tangential component of the magnetic field. We consider particle dynamics in the quasi-adiabatic approximation and demonstrate that the principal role is played by large (so called geometrical) jumps of the quasi-adiabatic invariant. These jumps appear due to the current sheet asymmetry related to the presence of the dawn–dusk magnetic field. The analytical description is compared with results of numerical integration. We show that there are four possible regimes of particle motion. Each regime is characterized by certain ranges of values of the dawn–dusk magnetic field and particle energy. We find the critical value of the dawn–dusk magnetic field, where jumps of the quasi-adiabatic invariant vanish.

Download Full-text

Jump conditions for pressure anisotropy and comparison with the Earth's bow shock

Nonlinear Processes in Geophysics ◽

10.5194/npg-8-167-2001 ◽

2001 ◽

Vol 8 (3) ◽

pp. 167-174 ◽

Cited By ~ 11

Author(s):

D. F. Vogl ◽

H. K. Biernat ◽

N. V. Erkaev ◽

C. J. Farrugia ◽

S. Mühlbachler

Keyword(s):

Magnetic Field ◽

Tangential Component ◽

Bow Shock ◽

Jump Conditions ◽

Plasma Parameters ◽

Pressure Anisotropy ◽

Threshold Conditions ◽

Wind Spacecraft ◽

Earth’S Bow Shock ◽

The Magnetic Field

Abstract. Taking into account the pressure anisotropy in the solar wind, we study the magnetic field and plasma parameters downstream of a fast shock, as functions of upstream parameters and downstream pressure anisotropy. In our theoretical approach, we model two cases: a) the perpendicular shock and b) the oblique shock. We use two threshold conditions of plasma instabilities as additional equations to bound the range of pressure anisotropy. The criterion of the mirror instability is used for pressure anisotropy p \\perp /p\\parrallel > 1. Analogously, the criterion of the fire-hose instability is taken into account for pressure anisotropy p \\perp /p\\parrallel < 1. We found that the variations of the parallel pressure, the parallel temperature, and the tangential component of the velocity are most sensitive to the pressure anisotropy downstream of the shock. Finally, we compare our theory with plasma and magnetic field parameters measured by the WIND spacecraft.

Download Full-text

Analysis of the distribution, rotation and scale characteristics of solar wind switchbacks: comparison between the first and second encounters of Parker Solar Probe

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/ac49e4 ◽

2022 ◽

Author(s):

Mingming Meng ◽

Ying Liu ◽

Chong Chen ◽

Rui Wang

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Coronal Holes ◽

Minimum Variance ◽

Tangential Component ◽

Magnetic Field Rotation ◽

Anticlockwise Rotation ◽

Scale Characteristics ◽

Field Lines ◽

The Magnetic Field

Abstract The S-shaped magnetic structure in the solar wind formed by the twisting of magnetic field lines is called a switchback, whose main characteristics are the reversal of the magnetic field and the significant increase in the solar wind radial velocity. We identify 242 switchbacks during the first two encounters of Parker Solar Probe (PSP). Statistics methods are applied to analyze the distribution and the rotation angle and direction of the magnetic field rotation of the switchbacks. The diameter of switchbacks is estimated with a minimum variance analysis (MVA) method based on the assumption of a cylindrical magnetic tube. We also make a comparison between switchbacks from inside and the boundary of coronal holes. The main conclusions are as follows: (1) the rotation angles of switchbacks observed during the first encounter seem larger than those of the switchbacks observed during the second encounter in general; (2) the tangential component of the velocity inside the switchbacks tends to be more positive (westward) than in the ambient solar wind; (3) switchbacks are more likely to rotate clockwise than anticlockwise, and the number of switchbacks with clockwise rotation is 1.48 and 2.65 times of those with anticlockwise rotation during the first and second encounters, respectively; (4) the diameter of switchbacks is about 10^5 km on average and across five orders of magnitude (10^3 – 10^7 km).

Download Full-text

Strong electromagnetic pulses generated in high-intensity short-pulse laser interactions with thin foil targets

Laser and Particle Beams ◽

10.1017/s026303461700074x ◽

2017 ◽

Vol 35 (4) ◽

pp. 677-686 ◽

Cited By ~ 9

Author(s):

P. Rączka ◽

J.-L. Dubois ◽

S. Hulin ◽

V. Tikhonchuk ◽

M. Rosiński ◽

...

Keyword(s):

Magnetic Field ◽

Short Pulse ◽

Thin Foil ◽

Tangential Component ◽

Laser Target ◽

Electromagnetic Pulses ◽

Target Interaction ◽

Short Pulse Laser ◽

Comparison Of The Results ◽

The Magnetic Field

AbstractMeasurements are reported of the target neutralization current, the target charge, and the tangential component of the magnetic field generated as a result of laser–target interaction by pulses with the energy in the range of 45–92 mJ on target and the pulse duration from 39 to 1000 fs. The experiment was performed at the Eclipse facility in CELIA, Bordeaux. The aim of the experiment was to extend investigations performed for the thick (mm scale) targets to the case of thin (μm thickness) targets in a way that would allow for a straightforward comparison of the results. We found that thin foil targets tend to generate 20–50% higher neutralization current and the target charge than the thick targets. The measurement of the tangential component of the magnetic field had shown that the initial spike is dominated by the 1 ns pulse consistent with the 1 ns pulse of the neutralization current, but there are some differences between targets of different types on sub-ns scale, which is an effect going beyond a simple picture of the target acting as an antenna. The sub-ns structure appears to be reproducible to surprising degree. We found that there is in general a linear correlation between the maximum value of the magnetic field and the maximum neutralization current, which supports the target-antenna picture, except for pulses 100s of fs long.

Download Full-text

Study of the Possibility of Estimating the Size of the Fractional-Dimensional Surface Layer by Electromagnetic Methods

Materials Science Forum ◽

10.4028/www.scientific.net/msf.945.932 ◽

2019 ◽

Vol 945 ◽

pp. 932-937 ◽

Cited By ~ 1

Author(s):

I.R. Kuzeev ◽

V.Yu. Pivovarov

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Plate Thickness ◽

Tangential Component ◽

Surface Layers ◽

Electromagnetic Methods ◽

Internal Structures ◽

First Time ◽

The Magnetic Field

It is known that the surface of a solid body and its volume part are different forms of the same substance. There is a hypothesis about the presence of a transition fractional-dimensional layer, which is the "limiter" of the volume from the surface. It is assumed that this layer is able to store information about changes in the surface and internal structures of the solid. The origin of defects, leading to destruction, in most cases begins in the surface and surface layers of the metal. In this regard, the existence of fractional-dimensional layer as a subsurface structure, which has information about the properties of the whole solid, is of particular importance in the detection of possible critical defects. In order to test this hypothesis, an experiment was conducted based on measuring the magnetic field strength of a steel plate (25x25x2 mm) when its thickness was changed. With the help of sandpaper, one side of the plate was swamped, and the second remained unchanged. The measurements of the magnetic field strength components were carried out on both sides with the plate thickness decreasing by 0.08-0.1 mm from 2.0 to 0.3 mm. Applying a linear approximation to the obtained dependence of the average tangential component of the magnetic field on the plate thickness, it was found that the extrapolated approximation line comes to a point close to zero (0.01 mm). It was assumed that the value 0.01 determines the preliminary value of the fractional-dimensional layer. Such an experiment was carried out for the first time, so the results obtained so far will undoubtedly become the basis for further research in this area.

Download Full-text

Application of coercimetry to assess the functional properties of materials

MATEC Web of Conferences ◽

10.1051/matecconf/202134602040 ◽

2021 ◽

Vol 346 ◽

pp. 02040

Author(s):

Vladimir Kostin ◽

Danila Ksenofontov ◽

Olga Vasilenko ◽

Alexander Byzov

Keyword(s):

Magnetic Field ◽

Coercive Force ◽

Comparative Study ◽

Functional Properties ◽

Ferromagnetic Materials ◽

Tangential Component ◽

Upper Limit ◽

Properties Of Materials ◽

Magnetic Resistance ◽

The Magnetic Field

The purpose of this work is a comparative study of the possibilities of various types of coercimeters to assess the functional properties of ferromagnetic materials. Conducted research have shown that the limitation of the maximum measured value of the coercive force using an attached transducer with a U-shaped electromagnet is due to the lower value of the magnetic resistance of the tested workpiece. The upper limit of measurements of the coercive force using a two-pole transducer is determined by the magnitude of the tangential component of the magnetic field only by the possibility of magnetizing the tested object.

Download Full-text

Solution for jump conditions at fast shocks in an anisotropic magnetized plasma

Journal of Plasma Physics ◽

10.1017/s002237780000893x ◽

2000 ◽

Vol 64 (5) ◽

pp. 561-578 ◽

Cited By ~ 23

Author(s):

N. V. ERKAEV ◽

D. F. VOGL ◽

H. K. BIERNAT

Keyword(s):

Magnetic Field ◽

Mach Number ◽

Tangential Component ◽

Magnetized Plasma ◽

Normal Velocity ◽

Jump Conditions ◽

Plasma Parameters ◽

Closure Relation ◽

Pressure Anisotropy ◽

The Magnetic Field

We study the magnetic field and plasma parameters downstream of a fast shock as functions of normalized upstream parameters and the rate of pressure anisotropy (defined as the ratio of perpendicular to parallel pressure). We analyse two cases: with the shock (i) perpendicular and (ii) inclined with respect to the magnetic field. The relations on the fast shock in a magnetized anisotropic plasma are solved taking into account the criteria for the mirror instability and firehose instability bounding the pressure anisotropy downstream of the shock. Our analysis shows that the parallel pressure and the parallel temperature as well as the tangential component of the velocity are the parameters that are most sensitive to the rate of pressure anisotropy. The variations of the other parameters, namely density, normal velocity, tangential component of the magnetic field, perpendicular pressure, and perpendicular temperature are much less pronounced, in particular when the perpendicular pressure exceeds the parallel pressure. The variations of all parameters increase substantially for a very low rate of anisotropy, which is bounded by the firehose instability in the case of inclined shocks. Using the criterion for mirror instability as a closure relation for the jump conditions at the fast shock, we obtain the plasma parameters and the magnetic field downstream of the shock as functions of the Alfvén Mach number. For each Alfvén Mach number, the criterion for mirror instability determines the minimum jumps in such parameters as density, tangential magnetic field component, parallel pressure, and temperature, and determines the maximum values of the velocity components and the perpendicular temperature. Ideal anisotropic magnetohydrodynamics (MHD) has wide applications for space plasma physics. Observations of the field and plasma behaviour in the solar wind as well as in the Earth's magnetosheath have highlighted the need for an MHD model where the plasma pressure is treated as a tensor.

Download Full-text

Observing the galactic magnetic field

Symposium - International Astronomical Union ◽

10.1017/s0074180900101251 ◽

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.

Download Full-text

Evolution of Large-Scale Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100024945 ◽

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.

Download Full-text

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

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.

Download Full-text