Long-term evolution of crustal neutron star magnetic fields

1994 ◽  
Vol 433 ◽  
pp. 780 ◽  
Author(s):  
V. A. Urpin ◽  
G. Chanmugam ◽  
Yeming Sang
Keyword(s):  
Neutron Star ◽  
Magnetic Fields ◽  
Long Term Evolution ◽  
Term Evolution

scholarly journals Reconstructing solar magnetic fields from historical observations

2019 ◽  
Vol 627 ◽  
pp. A11
Author(s):  
I. O. I. Virtanen ◽  
I. I. Virtanen ◽  
A. A. Pevtsov ◽  
L. Bertello ◽  
A. Yeates ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Active Regions ◽  
Long Term Evolution ◽  
Photospheric Magnetic Field ◽  
Solar Magnetic Fields ◽  
Term Evolution ◽  
Large Scale Field

Aims. The evolution of the photospheric magnetic field has only been regularly observed since the 1970s. The absence of earlier observations severely limits our ability to understand the long-term evolution of solar magnetic fields, especially the polar fields that are important drivers of space weather. Here, we test the possibility to reconstruct the large-scale solar magnetic fields from Ca II K line observations and sunspot magnetic field observations, and to create synoptic maps of the photospheric magnetic field for times before modern-time magnetographic observations. Methods. We reconstructed active regions from Ca II K line synoptic maps and assigned them magnetic polarities using sunspot magnetic field observations. We used the reconstructed active regions as input in a surface flux transport simulation to produce synoptic maps of the photospheric magnetic field. We compared the simulated field with the observed field in 1975−1985 in order to test and validate our method. Results. The reconstruction very accurately reproduces the long-term evolution of the large-scale field, including the poleward flux surges and the strength of polar fields. The reconstruction has slightly less emerging flux because a few weak active regions are missing, but it includes the large active regions that are the most important for the large-scale evolution of the field. Although our reconstruction method is very robust, individual reconstructed active regions may be slightly inaccurate in terms of area, total flux, or polarity, which leads to some uncertainty in the simulation. However, due to the randomness of these inaccuracies and the lack of long-term memory in the simulation, these problems do not significantly affect the long-term evolution of the large-scale field.

scholarly journals The long-term evolution of neutron star merger remnants - I. The impact of r-process nucleosynthesis

2014 ◽  
Vol 439 (1) ◽  
pp. 744-756 ◽  
Author(s):  
S. Rosswog ◽  
O. Korobkin ◽  
A. Arcones ◽  
F.- K. Thielemann ◽  
T. Piran
Keyword(s):  
Neutron Star ◽  
Long Term Evolution ◽  
Term Evolution ◽  
R Process ◽  
The Impact

scholarly journals Long-term evolution of a magnetic massive merger product

2020 ◽  
Vol 495 (3) ◽  
pp. 2796-2812
Author(s):  
F R N Schneider ◽  
S T Ohlmann ◽  
Ph Podsiadlowski ◽  
F K Röpke ◽  
S A Balbus ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
White Dwarfs ◽  
Massive Stars ◽  
Thermal Relaxation ◽  
Long Term Evolution ◽  
Critical Surface ◽  
Single Star ◽  
Strong Magnetic Fields ◽  
Term Evolution

ABSTRACT About 10 per cent of stars more massive than ${\approx}1.5\, {\mathrm{M}}_{\odot }$ have strong, large-scale surface magnetic fields and are being discussed as progenitors of highly magnetic white dwarfs and magnetars. The origin of these fields remains uncertain. Recent three-dimensional (3D) magnetohydrodynamical simulations have shown that strong magnetic fields can be generated in the merger of two massive stars. Here, we follow the long-term evolution of such a 3D merger product in a 1D stellar evolution code. During a thermal relaxation phase after the coalescence, the merger product reaches critical surface rotation, sheds mass and then spins down primarily because of internal mass readjustments. The spin of the merger product after thermal relaxation is mainly set by the co-evolution of the star–torus structure left after coalescence. This evolution is still uncertain, so we also consider magnetic braking and other angular momentum-gain and -loss mechanisms that may influence the final spin of the merged star. Because of core compression and mixing of carbon and nitrogen in the merger, enhanced nuclear burning drives a transient convective core that greatly contributes to the rejuvenation of the star. Once the merger product relaxed back to the main sequence, it continues its evolution similar to that of a genuine single star of comparable mass. It is a slow rotator that matches the magnetic blue straggler τ Sco. Our results show that merging is a promising mechanism to explain some magnetic massive stars and it may also be key to understand the origin of the strong magnetic fields of highly magnetic white dwarfs and magnetars.

scholarly journals Long-term evolution of CFS-unstable neutron stars and the role of differential rotation on short time-scales

2018 ◽  
Vol 482 (3) ◽  
pp. 3045-3057 ◽  
Author(s):  
A I Chugunov
Keyword(s):  
Neutron Star ◽  
Time Scales ◽  
Differential Rotation ◽  
Time Scale ◽  
Evolution Equations ◽  
Long Term Evolution ◽  
Cooling Power ◽  
Term Evolution ◽  
Short Time

Abstract I consider differential rotation, associated with radiation-driven Chandrasekhar–Friedman–Schutz (CFS) instability, and respective observational manifestations. I focus on the evolution of the apparent spin frequency, which is typically associated with the motion of a specific point on the stellar surface (e.g. polar cap). I start from long-term evolution (on the time-scale when instability significantly changes the spin frequency). For this case, I reduce the evolution equations to one differential equation and I demonstrate that it can be directly derived from energy conservation law. This equation governs the evolution rate through a sequence of thermally equilibrium states and it provides linear coupling for the cooling power and rotation energy losses via gravitational wave emission. In particular, it shows that differential rotation does not affect long-term spin-down. In contrast, on short time-scales, differential rotation can significantly modify the apparent spin-down, if we examine a strongly unstable star with a very small initial amplitude for the unstable mode. This statement is confirmed by considering a Newtonian non-magnetized perfect fluid and dissipative stellar models as well as a magnetized stellar model. For example, despite the fact that the widely applied evolution equations predict effective spin to be constant in the absence of dissipation, the CFS-unstable star should be observed as spinning-down. However, the effects of differential rotation on apparent spin-down are negligible for realistic models of neutron star recycling, unless the neutron star is non-magnetized, the r-mode amplitude is modulated faster than the shear viscosity dissipation time-scale, and the amplitude is large enough that spin-down can be measured on a modulation time-scale.

scholarly journals LONG TERM EVOLUTION OF MAGNETIC TURBULENCE IN RELATIVISTIC COLLISIONLESS SHOCKS

2008 ◽  
Vol 17 (10) ◽  
pp. 1769-1775 ◽  
Author(s):  
PHILIP CHANG ◽  
ANATOLY SPITKOVSKY ◽  
JONATHAN ARONS
Keyword(s):  
Magnetic Fields ◽  
Magnetic Energy ◽  
Analytic Form ◽  
Long Term Evolution ◽  
Particle Distributions ◽  
Particle In Cell ◽  
Magnetic Turbulence ◽  
Term Evolution ◽  
Simple Analytic Form

We study the long term evolution of magnetic fields generated by an initially unmagnetized collisionless relativistic e+e- shock. Our 2D particle-in-cell numerical simulations show that downstream of such a Weibel-mediated shock, particle distributions are approximately isotropic, relativistic Maxwellians, and the magnetic turbulence is highly intermittent spatially, non-propagating, and decaying. Using linear kinetic theory, we find a simple analytic form for these damping rates. Our theory predicts that the overall magnetic energy decays as (ωp t)-q with q ~ 1, which compares favorably with simulations, but predicts overly rapid damping of short-wavelength modes. The magnetic trapping of particles within the magnetic structures may be the origin of this discrepancy. We conclude that initially unmagnetized relativistic shocks in electron-positron plasmas are unable to form persistent downstream magnetic fields. These results put interesting constraints on synchrotron models for the prompt and afterglow emission from GRBs.

scholarly journals Long-term evolution of the neutron-star spin period of SXP 1062

2013 ◽  
Vol 556 ◽  
pp. A139 ◽  
Author(s):  
R. Sturm ◽  
F. Haberl ◽  
L. M. Oskinova ◽  
M. P. E. Schurch ◽  
V. Hénault-Brunet ◽  
...  
Keyword(s):  
Neutron Star ◽  
Long Term Evolution ◽  
Spin Period ◽  
Term Evolution

scholarly journals The long-term evolution of neutron star merger remnants – II. Radioactively powered transients

2014 ◽  
Vol 439 (1) ◽  
pp. 757-770 ◽  
Author(s):  
Doron Grossman ◽  
Oleg Korobkin ◽  
Stephan Rosswog ◽  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Long Term Evolution ◽  
Term Evolution
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