Role of the magnetic field on the formation of solar type stars

2018 ◽  
Vol 14 (A30) ◽  
pp. 119-119
Author(s):  
Valeska Valdivia ◽  
Anaëlle J. Maury ◽  
Patrick Hennebelle
Keyword(s):  
Magnetic Field ◽  
Gravitational Collapse ◽  
Dust Emission ◽  
Stokes Parameters ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Solar Type ◽  
3D Topology ◽  
The Magnetic Field

AbstractMagnetic fields play a key role during the gravitational collapse of dense protostellar cores. In recent years mm and sub-mm observations of dust polarized emission have been used to unveil the morphology of the magnetic field, but this method relies on the assumption that non-spherical dust grains are well aligned with the magnetic field.Using non-ideal MHD numerical simulations, we study the evolution of the magnetic field during the gravitational collapse. We use the state-of-the-art radiative transfer code POLARIS to compute the Stokes parameters and produce synthetic observations of mm/submm polarized dust emission. We compare the results obtained using the radiative torques (RAT) mechanism to the results obtained by assuming that grains are perfectly aligned to constrain how well polarized dust emission traces the magnetic field orientation.The complexity of the magnetic field produces a mild depolarization. The depolarization observed in the inner regions is rather caused by a decrease of the dust alignment efficiency and it cannot be reproduced by just scaling down the polarisation degree obtained for a uniform efficiency. We find that the magnetic field orientation is well constrained by the polarized dust emission as long as its 3D topology remains organized.

The role of the magnetic field in a translucent molecular cloud

2018 ◽  
Vol 14 (A30) ◽  
pp. 108-108
Author(s):  
Georgia Panopoulou
Keyword(s):  
Magnetic Field ◽  
Molecular Cloud ◽  
Quantitative Estimate ◽  
Molecular Clouds ◽  
Dust Emission ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Cloud Evolution ◽  
The Magnetic Field

AbstractTranslucent molecular clouds represent a vastly underexplored regime of cloud evolution in terms of the effect of the magnetic field. Their pristine nature renders them ideal for investigating the initial properties of the magnetic field, prior to the onset of star formation. Using starlight polarimetry, we map the plane-of-sky magnetic field orientation throughout 10 sq. degrees of the Polaris Flare translucent molecular cloud. We provide the first quantitative estimate of the magnetic field strength in this type of system. By combining our measurements with the high-resolution Herschel dust emission map, we find a preferred alignment between filaments and the observed magnetic field. Our results support the presence of a strong magnetic field in this system (Panopoulou et al. 2016).

On the absence of plasma wave emissions and the magnetic field orientation in the distant magnetosheath

1994 ◽  
Vol 21 (24) ◽  
pp. 2761-2764 ◽  
Author(s):  
F. V. Coroniti ◽  
E. W. Greenstadt ◽  
S. L. Moses ◽  
B. T. Tsurutani ◽  
E. J. Smith
Keyword(s):  
Magnetic Field ◽  
Plasma Wave ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
The Magnetic Field

scholarly journals The Magnetic Field of the Crab as Revealed by New, High Resolution, Multi-Band Radio Images

1990 ◽  
Vol 140 ◽  
pp. 79-80
Author(s):  
M. F. Bietenholz ◽  
P. P. Kronberg
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Crab Nebula ◽  
Radio Observations ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
The Crab Nebula ◽  
The Magnetic Field ◽  
Made In ◽  
Multi Band

We present and describe recent radio observations of the Crab Nebula, which allow us to determine the magnetic field orientation and depolarization at unprecedented resolution. The observations were made in 1987-1988 using all four configurations of the VLA, at 1410,1515,4625, and 4885 MHz. The resulting maps were all convolved with a clean beam of 1.8″ × 2.0″, elongated in P.A. 80°, and the residuals added back in.

Effect of Processing Variables on The Magnetic Field Orientation of Liquid Crystalline Thermosets

1999 ◽  
Vol 559 ◽  
Author(s):  
Derek M. Lincoln ◽  
Elliot P. Douglas
Keyword(s):  
Magnetic Field ◽  
Liquid Crystalline ◽  
Fractional Factorial Design ◽  
Fractional Factorial ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Liquid Crystalline Epoxy ◽  
Processing Variables ◽  
Degree Of Orientation ◽  
The Magnetic Field

ABSTRACTWe have investigated the effect of various processing variables on the magnetic field orientation of a liquid crystalline epoxy. By using a modified fractional factorial design, we created an empirical model which can be used to predict the degree of orientation as a function of these variables. The model predicts the correct qualitative trends, namely that orientation increases with increasing magnetic field strength, increases with increasing time in the field, and decreases with increasing B-staging. The model also reveals some surprising effects of B-staging on the degree of orientation.

A New Model to Describe the Magnetic Structure of CMEs

2020 ◽  
Author(s):  
Nada Al-Haddad ◽  
Noé Lugaz
Keyword(s):  
Magnetic Field ◽  
Flux Rope ◽  
Challenging Problem ◽  
New Paradigm ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
The Past ◽  
Current Paradigm ◽  
The Magnetic Field

<p>The structure of coronal mass ejections (CMEs) has been the center of numerous studies over the past few decades. Defining the magnetic field orientation locally and globally has proven to be a challenging problem, due to the limited nature of observations that we have, as well as our reliance on the current paradigm of highly-twisted flux ropes. Studies suggest that not all CMEs measured <em>in situ </em>fit within the simple twisted and well-organized flux rope topology. Additionally, many of the events that can be well fitted by existing static flux rope models, do not have as simple a structure as that assumed by the models. This is clear from remote observations and multi-spacecraft measurements. With the wealth of data that we have today, as well as the affluence of research and analysis performed over the last 40 years, it is dues time to present an alternative paradigm, that better represents those data. In this work, we discuss this new paradigm and the literature leading to it. </p>

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

2017 ◽  
Vol 603 ◽  
pp. A64 ◽  
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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