HAWC+/SOFIA Polarimetry in L1688: Relative Orientation of Magnetic Field and Elongated Cloud Structure

Two-dimensional numerical computations were carried out for natural convection of air in a vertical cylindrical container with and without a gravitational field under a gradient of a magnetic field. The magnetic field and the magnetizing force were induced in the cylinder area and the strength and the vectors of the magnetizing force were dependent on the axial location of the electric coil. Sample computations were carried out by changing the relative orientation of an electric coil and container. In a gravitational field, air in a cylindrical container was driven by both gravitational and magnetizing forces. On the other hand, the air flow was induced by the magnetizing force even in a non-gravitational field. Flow pattern and the heat transfer rate greatly depended on the axial position of the electric coil under both gravitational and non-gravitational fields.

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The relative orientation between the magnetic field and gas density structures in non-gravitating turbulent media

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3078 ◽

2020 ◽

Vol 499 (4) ◽

pp. 4785-4792

Author(s):

Bastian Körtgen ◽

Juan D Soler

Keyword(s):

Magnetic Field ◽

Molecular Clouds ◽

Relative Orientation ◽

Local Magnetic Field ◽

Gas Formation ◽

Initial Magnetization ◽

The Galaxy ◽

Dynamical Time ◽

Isothermal Gas ◽

The Magnetic Field

ABSTRACT Magnetic fields are a dynamically important agent for regulating structure formation in the interstellar medium. The study of the relative orientation between the local magnetic field and gas (column-) density gradient has become a powerful tool to analyse the magnetic field’s impact on the dense gas formation in the Galaxy. In this study, we perform numerical simulations of a non-gravitating, isothermal gas, where the turbulence is driven either solenoidally or compressively. We find that only simulations with an initially strong magnetic field (plasma-β < 1) show a change in the preferential orientation between the magnetic field and isodensity contours, from mostly parallel at low densities to mostly perpendicular at higher densities. Hence, compressive turbulence alone is not capable of inducing the transition observed towards nearby molecular clouds. At the same high initial magnetization, we find that solenoidal modes produce a sharper transition in the relative orientation with increasing density than compressive modes. We further study the time evolution of the relative orientation and find that it remains unchanged by the turbulent forcing after one dynamical time-scale.

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Using Herschel and Planck observations to delineate the role of magnetic fields in molecular cloud structure

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935779 ◽

2019 ◽

Vol 629 ◽

pp. A96 ◽

Cited By ~ 19

Author(s):

Juan D. Soler

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Molecular Clouds ◽

Thermal Emission ◽

Relative Orientation ◽

Young Stellar Objects ◽

Circular Statistics ◽

Stellar Objects ◽

Submillimeter Wavelengths ◽

The Magnetic Field

We present a study of the relative orientation between the magnetic field projected onto the plane of sky (B⊥) on scales down to 0.4 pc, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the distribution of gas column density (NH) structures on scales down to 0.026 pc, derived from the observations by Herschel in submillimeter wavelengths, toward ten nearby (d < 450 pc) molecular clouds. Using the histogram of relative orientation technique in combination with tools from circular statistics, we found that the mean relative orientation between NH and B⊥ toward these regions increases progressively from 0°, where the NH structures lie mostly parallel to B⊥, with increasing NH, in many cases reaching 90°, where the NH structures lie mostly perpendicular to B⊥. We also compared the relative orientation between NH and B⊥ and the distribution of NH, which is characterized by the slope of the tail of the NH probability density functions (PDFs). We found that the slopes of the NH PDF tail are steepest in regions where NH and B⊥ are close to perpendicular. This coupling between the NH distribution and the magnetic field suggests that the magnetic fields play a significant role in structuring the interstellar medium in and around molecular clouds. However, we found no evident correlation between the star formation rates, estimated from the counts of young stellar objects, and the relative orientation between NH and B⊥ in these regions.

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The relation between the column density structures and the magnetic field orientation in the Vela C molecular complex

Astronomy and Astrophysics ◽

10.1051/0004-6361/201730608 ◽

2017 ◽

Vol 603 ◽

pp. A64 ◽

Cited By ~ 33

Author(s):

J. D. Soler ◽

P. A. R. Ade ◽

F. E. Angilè ◽

P. Ashton ◽

S. J. Benton ◽

...

Keyword(s):

Magnetic Field ◽

Molecular Complex ◽

Column Density ◽

Relative Orientation ◽

Field Orientation ◽

Filamentary Structure ◽

Magnetic Field Orientation ◽

Physical Scale ◽

The Magnetic Field ◽

High Column

We statistically evaluated the relative orientation between gas column density structures, inferred from Herschel submillimetre observations, and the magnetic field projected on the plane of sky, inferred from polarized thermal emission of Galactic dust observed by the Balloon-borne Large-Aperture Submillimetre Telescope for Polarimetry (BLASTPol) at 250, 350, and 500 μm, towards the Vela C molecular complex. First, we find very good agreement between the polarization orientations in the three wavelength-bands, suggesting that, at the considered common angular resolution of 3.́0 that corresponds to a physical scale of approximately 0.61 pc, the inferred magnetic field orientation is not significantly affected by temperature or dust grain alignment effects. Second, we find that the relative orientation between gas column density structures and the magnetic field changes progressively with increasing gas column density, from mostly parallel or having no preferred orientation at low column densities to mostly perpendicular at the highest column densities. This observation is in agreement with previous studies by the Planck collaboration towards more nearby molecular clouds. Finally, we find a correspondencebetween (a) the trends in relative orientation between the column density structures and the projected magnetic field; and (b) the shape of the column density probability distribution functions (PDFs). In the sub-regions of Vela C dominated by one clear filamentary structure, or “ridges”, where the high-column density tails of the PDFs are flatter, we find a sharp transition from preferentially parallel or having no preferred relative orientation at low column densities to preferentially perpendicular at highest column densities. In the sub-regions of Vela C dominated by several filamentary structures with multiple orientations, or “nests”, where the maximum values of the column density are smaller than in the ridge-like sub-regions and the high-column density tails of the PDFs are steeper, such a transition is also present, but it is clearly less sharp than in the ridge-like sub-regions. Both of these results suggest that the magnetic field is dynamically important for the formation of density structures in this region.

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The Skew of Polar Crown X-ray Arcades

International Astronomical Union Colloquium ◽

10.1017/s0252921100048041 ◽

1998 ◽

Vol 167 ◽

pp. 430-433 ◽

Cited By ~ 4

Author(s):

A.H. McAllister ◽

A.J. Hundhausen ◽

D. Mackay ◽

E. Priest

Keyword(s):

Magnetic Field ◽

Differential Rotation ◽

Flux Distribution ◽

Numerical Models ◽

Relative Orientation ◽

Axial Component ◽

Field Observations ◽

X Ray ◽

One To One ◽

The One

AbstractThe one-to-one relationship between the chirality of filament channels and the skew (relative orientation) of the overlying coronal arcades can be coupled with the predictions for the axial component of polar crown filaments based on past magnetic field observations to predict the skew of polar crown arcades in the recent cycle 22. We have surveyed the actual skew as seen in the Yohkoh SXT images over the declining phase of cycle 22 and found a result opposite to that expected. The SXT arcades have been compared with numerical models to show that while some of this result can be explained by flux distribution around switchbacks, other mechanisms such as differential rotation are also needed.

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What are we learning from the relative orientation between density structures and the magnetic field in molecular clouds?

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731049 ◽

2017 ◽

Vol 607 ◽

pp. A2 ◽

Cited By ~ 34

Author(s):

J. D. Soler ◽

P. Hennebelle

Keyword(s):

Magnetic Field ◽

Molecular Clouds ◽

Relative Orientation ◽

The Magnetic Field

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Statistics on the relative orientation between magnetic fields and filaments hosting Planck Galactic Cold Clumps

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003594 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 104-104

Author(s):

D. Alina ◽

I. Ristorcelli ◽

L. Montier ◽

M. Juvela

Keyword(s):

Magnetic Field ◽

Statistical Analysis ◽

Magnetic Fields ◽

Column Density ◽

Evolutionary Process ◽

Bimodal Distribution ◽

Relative Orientation ◽

The Magnetic Field ◽

Preferential Alignment ◽

High Column

AbstractWe present a statistical analysis of the relative orientation between the plane-of-sky magnetic field and the filaments associated with the Galactic Cold Clumps. We separated polarization parameters components of the filaments and their background using thin optical medium assumption, the filaments were detected using the Rolling Hough Transform algorithm and we separated the clump and the filament contributions in our maps. We found that in high column density environments the magnetic fields inside the filaments and in the background are less likely to be aligned with each other. This suggests a decoupling between the inner and background magnetic fields at some stage of filamentsâ€™ evolution. A preferential alignment between the filaments and their inferred magnetic fields is observed in the whole selection if the clumpsâ€™ contribution is subtracted. Interestingly, a bimodal distribution of relative orientation is observed between the filamentary structures of the clumps and the filaments’ magnetic field. Similar results are seen in a subsample of nearby filaments. The relative orientation clearly shows a transition from parallel to no preferential and perpendicular alignment depending on the volume densities of both clumps and filaments. Our results confirm a strong interplay between the magnetic field and filamentary structures during their formation and evolutionary process.

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Large magnetoresistance in oxide based ferromagnet / superconductor spin switches

MRS Proceedings ◽

10.1557/proc-0887-q11-02 ◽

2005 ◽

Vol 887 ◽

Author(s):

V. Peña ◽

N. Nemes ◽

C. Visani ◽

J. Garcia-Barriocanal ◽

F. Bruno ◽

...

Keyword(s):

Magnetic Field ◽

Giant Magnetoresistance ◽

Relative Orientation ◽

Length Scale ◽

Magnetoresistance Effect ◽

Superconducting Layer ◽

Spin Polarized ◽

Ferromagnetic Layers ◽

Parallel Configuration

ABSTRACTWe report large magnetoresistance (in excess of 1000%) in ferromagnet / superconductor / ferromagnet structures made of La0.7Ca0.3MnO3 and YBa2Cu3O7 in the current in plane (CIP) geometry. This magnetoresistance has many of the ingredients of the giant magnetoresistance of metallic superlattices: it is independent on the angle between current and magnetic field, depends on the relative orientation of the magnetization in the ferromagnetic layers, and takes very large values. The origin is enhanced scattering at the F/S interface in the anti parallel configuration of the magnetizations. Furthermore, we examine the dependence of the magnetoresistance effect on the thickness of the superconducting layer, and show that the magnetoresistance dies out for thickness in excess of 30 nm, setting a length scale for the diffusion of spin polarized quasiparticles.

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Dust properties and magnetic field geometry towards LDN 1570

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314011545 ◽

2012 ◽

Vol 10 (H16) ◽

pp. 385-385

Author(s):

C. Eswaraiah ◽

G. Maheswar ◽

A. K. Pandey

Keyword(s):

Magnetic Field ◽

Field Structure ◽

Material Flows ◽

Magnetic Field Structure ◽

Cloud Structure ◽

Photometric Observations ◽

Field Geometry ◽

Formation And Evolution ◽

Field Lines ◽

The Magnetic Field

AbstractWe have performed both optical linear polarimetric and photometric observations of an isolated dark globule LDN 1570 aim to study the dust polarizing and extinction properties and to map the magnetic field geometry so as to understand not only the importance of magnetic fields in formation and evolution of clouds but also the correlation of the inferred magnetic field structure with the cloud structure and its dynamics. Dust size indicators (RV and λmax) reveal for the presence of slightly bigger dust grains towards the cloud region. The inferred magnetic field geometry, which closely follows the cloud structure revealed by Herschel images, suggest that the cloud could have been formed due to converging material flows along the magnetic field lines.

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Magnetic-field strengths from optical polarization data

Symposium - International Astronomical Union ◽

10.1017/s0074180900101263 ◽

1967 ◽

Vol 31 ◽

pp. 381-383

Author(s):

J. M. Greenberg

Keyword(s):

Magnetic Field ◽

Optical Polarization ◽

Polarization Data ◽

Term Model ◽

Source Of Information ◽

Field Strengths

Van de Hulst (Paper 64, Table 1) has marked optical polarization as a questionable or marginal source of information concerning magnetic field strengths. Rather than arguing about this–I should rate this method asq+-, or quarrelling about the term ‘model-sensitive results’, I wish to stress the historical point that as recently as two years ago there were still some who questioned that optical polarization was definitely due to magnetically-oriented interstellar particles.

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