scholarly journals Effects of an Intrinsic Magnetic Field on Ion Loss From Ancient Mars Based on Multispecies MHD Simulations

2020 ◽  
Vol 125 (2) ◽  
Author(s):  
R. Sakata ◽  
K. Seki ◽  
S. Sakai ◽  
N. Terada ◽  
H. Shinagawa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Intrinsic Magnetic Field ◽  
Mhd Simulations

CHOICE OF CONDITIONS FOR MHD SIMULATIONS ABOVE THE ACTIVE REGION, ALLOWING THE STUDY OF THE SOLAR FLARE MECHANISM

2021 ◽  
Vol 44 ◽  
pp. 92-95
Author(s):  
A.I. Podgorny ◽  
◽  
I.M. Podgorny ◽  
A.V. Borisenko ◽  
N.S. Meshalkina ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Solar Flare ◽  
Magnetic Energy ◽  
Solar Radius ◽  
Computational Domain ◽  
Mhd Simulations ◽  
Flare Energy ◽  
Numerical Instabilities ◽  
The Magnetic Field

Primordial release of solar flare energy high in corona (at altitudes 1/40 - 1/20 of the solar radius) is explained by release of the magnetic energy of the current sheet. The observed manifestations of the flare are explained by the electrodynamical model of a solar flare proposed by I. M. Podgorny. To study the flare mechanism is necessary to perform MHD simulations above a real active region (AR). MHD simulation in the solar corona in the real scale of time can only be carried out thanks to parallel calculations using CUDA technology. Methods have been developed for stabilizing numerical instabilities that arise near the boundary of the computational domain. Methods are applicable for low viscosities in the main part of the domain, for which the flare energy is effectively accumulated near the singularities of the magnetic field. Singular lines of the magnetic field, near which the field can have a rather complex configuration, coincide or are located near the observed positions of the flare.

scholarly journals Effects of a Weak Intrinsic Magnetic Field on Atmospheric Escape From Mars

2018 ◽  
Vol 45 (18) ◽  
pp. 9336-9343 ◽  
Author(s):  
Shotaro Sakai ◽  
Kanako Seki ◽  
Naoki Terada ◽  
Hiroyuki Shinagawa ◽  
Takashi Tanaka ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Atmospheric Escape ◽  
Intrinsic Magnetic Field

scholarly journals Constraint on ion–neutral drift velocity in the Class 0 protostar B335 from ALMA observations

2018 ◽  
Vol 615 ◽  
pp. A58 ◽  
Author(s):  
Hsi-Wei Yen ◽  
Bo Zhao ◽  
Patrick M. Koch ◽  
Ruben Krasnopolsky ◽  
Zhi-Yun Li ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Drift Velocity ◽  
Large Scale ◽  
Ambipolar Diffusion ◽  
Neutral Drift ◽  
Neutral Gas ◽  
Mhd Simulations ◽  
Ambipolar Drift ◽  
Velocity Drift ◽  
The Magnetic Field

Aims. Ambipolar diffusion can cause a velocity drift between ions and neutrals. This is one of the non-ideal magnetohydrodynamics (MHD) effects proposed to enable the formation of large-scale Keplerian disks with sizes of tens of au. To observationally study ambipolar diffusion in collapsing protostellar envelopes, we compare here gas kinematics traced by ionized and neutral molecular lines and discuss the implication on ambipolar diffusion. Methods. We analyzed the data of the H13CO+ (3–2) and C18O (2–1) emission in the Class 0 protostar B335 obtained with our ALMA observations. We constructed kinematical models to fit the velocity structures observed in the H13CO+ and C18O emission and to measure the infalling velocities of the ionized and neutral gas on a 100 au scale in B335. Results. A central compact (~1′′–2′′) component that is elongated perpendicular to the outflow direction and exhibits a clear velocity gradient along the outflow direction is observed in both lines and most likely traces the infalling flattened envelope. With our kinematical models, the infalling velocities in the H13CO+ and C18O emission are both measured to be 0.85 ± 0.2 km s−1 at a radius of 100 au, suggesting that the velocity drift between the ionized and neutral gas is at most 0.3 km s−1 at a radius of 100 au in B335. Conclusions. The Hall parameter for H13CO+ is estimated to be ≫1 on a 100 au scale in B335, so that H13CO+ is expected to be attached to the magnetic field. Our non-detection or upper limit of the velocity drift between the ionized and neutral gas could suggest that the magnetic field remains rather well coupled to the bulk neutral material on a 100 au scale in this source, and that any significant field-matter decoupling, if present, likely occurs only on a smaller scale, leading to an accumulation of magnetic flux and thus efficient magnetic braking in the inner envelope. This result is consistent with the expectation from the MHD simulations with a typical ambipolar diffusivity and those without ambipolar diffusion. On the other hand, the high ambipolar drift velocity of 0.5–1.0 km s−1 on a 100 au scale predicted in the MHD simulations with an enhanced ambipolar diffusivity by removing small dust grains, where the minimum grain size is 0.1 μm, is not detected in our observations. However, because of our limited angular resolution, we cannot rule out a significant ambipolar drift only in the midplane of the infalling envelope. Future observations with higher angular resolutions (~0. ′′1) are needed to examine this possibility and ambipolar diffusion on a smaller scale.

scholarly journals Plastic Deformation Influence on Intrinsic Magnetic Field of Austenitic Biomaterials

2016 ◽  
Vol 67 (6) ◽  
pp. 407-413
Author(s):  
Milan Smetana ◽  
Klára Čápová ◽  
Vladimír Chudáčik ◽  
Peter Palček ◽  
Monika Oravcová
Keyword(s):  
Magnetic Field ◽  
Plastic Deformation ◽  
Austenitic Steel ◽  
Medical Practice ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Intrinsic Magnetic Field ◽  
Fluxgate Sensor ◽  
Non Destructive Evaluation ◽  
Non Destructive

Abstract This article deals with non-destructive evaluation of austenitic stainless steels, which are used as the biomaterials in medical practice. Intrinsic magnetic field is investigated using the fluxgate sensor, after the applied plastic deformation. The three austenitic steel types are studied under the same conditions, while several values of the deformation are applied, respectively. The obtained results are presented and discussed in the paper.

Martian Atmospheric Evolution: Implications of an Ancient Intrinsic Magnetic Field

Astrobiology ◽  
2002 ◽  
pp. 203-217 ◽  
Author(s):  
Helmut Lammer ◽  
Willibald Stumptner ◽  
Gregorio J. Molina-Cuberos
Keyword(s):  
Magnetic Field ◽  
Atmospheric Evolution ◽  
Intrinsic Magnetic Field
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