Today, the origin of the magnetic field of stars and planets is explained by the dynamo effect. Since Cowling’s anti-dynamo theorem has forbidden a purely axisymmetric dynamo, scientists are all convinced today that ...Today, the origin of the magnetic field of stars and planets is explained by the dynamo effect. Since Cowling’s anti-dynamo theorem has forbidden a purely axisymmetric dynamo, scientists are all convinced today that the fluid flow in the core of a star cannot be laminar, so it is turbulent. However, we will see in this study that the configuration in which the conductive fluid contained in the core of a star is in rapid rotation around an axis of symmetry is the one that best explains the origin of the magnetic field of stars and planets. It also explains why certain types of stars have very intense magnetic fields. Indeed, we will show here that the magnetic field of stars and planets is created by the electric current generated by the rotational movement of charged fluid particles as in an electromagnet. The lines of this magnetic field are channelled by the solid paramagnetic seed which plays the role of magnetic core in the cores of planets and stars. The seed is composed mainly of Iron and Nickel on the planets and of solid helium-3 in the stars. In this work, we will use this model of rapidly rotating fluids to introduce a new way to ionize a neutral gas and maintain it in a plasma state for indefinitely large time scales, to present a new technique for generating very intense magnetic fields, to establish a new magnetic nucleation process and to propose a new type of nuclear fusion reactor in which the plasma is perpetually rapidly rotating.展开更多
We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the ...We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 tr level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 MG, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.展开更多
Rotochemical heating originates in the deviation from beta equilibrium due to spin-down compression, which is closely related to the dipole magnetic field. We numerically calculate the deviation from chemical equilibr...Rotochemical heating originates in the deviation from beta equilibrium due to spin-down compression, which is closely related to the dipole magnetic field. We numerically calculate the deviation from chemical equilibrium and thermal evolution of neutron stars with decaying magnetic fields. We find that the power-law long term decay of the magnetic field slightly affects the deviation from chemical equilibrium and surface temperature. However, the magnetic decay leads to older neutron stars that could have a different surface temperature with the same magnetic field strength. That is, older neutron stars with a low magnetic field (10^8 G) could have a lower temper- ature even with rotochemical heating in operation, which probably explains the lack of other observations on older millisecond pulsars with higher surface temperature, except millisecond pulsar J0437-4715.展开更多
We calculate the mass-radius relationship of quark stars with the magnetized density- dependent quark mass model in this work, considering two magnetic field geometries: a statistically isotropic, tangled field and a...We calculate the mass-radius relationship of quark stars with the magnetized density- dependent quark mass model in this work, considering two magnetic field geometries: a statistically isotropic, tangled field and a force-free configuration. In both cases, magnetic field production decreases in the case of maximum quark star mass. Furthermore, a tangled, isotropic magnetic field has a relatively smaller impact on the mass and radius, compared to the force-free configuration, which implies that the geometry of the interior magnetic field is at least as important as the field strength itself when the influ- ence of the strong magnetic field on the mass and radius is assessed.展开更多
We investigate the effects of strong magnetic fields upon the large-scale properties of neutron and protoneutron stars. In our calculations, the neutron star mat- ter was approximated by pure neutron matter. Using the...We investigate the effects of strong magnetic fields upon the large-scale properties of neutron and protoneutron stars. In our calculations, the neutron star mat- ter was approximated by pure neutron matter. Using the lowest order constrained vari- ational approach at zero and finite temperatures, and employing AV18 potential, we present the effects of strong magnetic fields on the gravitational mass, radius, and gravitational redshift of neutron and protoneutron stars. It is found that the equation of state for a neutron star becomes stiffer with an increase of magnetic field and tem- perature. This leads to larger values of the maximum mass and radius for the neutron stars.展开更多
β decay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ^67Ni(β-)^67Cu and ^62Mn(β-)^62Fe are investigated as examples. The results show that a weak ...β decay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ^67Ni(β-)^67Cu and ^62Mn(β-)^62Fe are investigated as examples. The results show that a weak magnetic field has little effect on β decay but a strong magnetic field (B 〉 10^12G) increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process.展开更多
In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates ...In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 10^5 - 10^13g on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 10^13 to 10^18 G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.展开更多
The influences of electron screening (ES) and electron energy correction (EEC) are investigated by superstrong magnetic field (SMF). We also discuss in detail the discrepant factor between our results and those ...The influences of electron screening (ES) and electron energy correction (EEC) are investigated by superstrong magnetic field (SMF). We also discuss in detail the discrepant factor between our results and those of Fushiki, Gudmundsson and Pethick (FGP) in SMF. The results show that SMF has only a slight effect on ES when B 〈 10^9 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B 〉 10^9 T . For instance, due to SMF the ES potential may be increased about 23.6% and the EEC may be increased about 4 orders of magnitude at ρ/μe = 1.0 × 10^6 mol/cm^3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP's when B 〈 10^9 T . But the difference will be increased with increasing SMF.展开更多
We study the effect of strong magnetic fields on the structure of neutron star. We find that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the ...We study the effect of strong magnetic fields on the structure of neutron star. We find that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the star's mass and radius are negligible; if the field is as large as that estimated from the scalar virial theorem, then considerable effects will be induced. The maximum mass of the star will be increased substantially while the central density is greatly reduced. The radius of a magnetic star can be larger by about 10% ~ 20% than a nonmagnetic star of the same mass.展开更多
I present a novel mechanism to boost magnetic field amplification of newly born neutron stars in core collapse supernovae.In this mechanism,that operates in the jittering jets explosion mechanism and comes on top of t...I present a novel mechanism to boost magnetic field amplification of newly born neutron stars in core collapse supernovae.In this mechanism,that operates in the jittering jets explosion mechanism and comes on top of the regular magnetic field amplification by turbulence,the accretion of stochastic angular momentum in core collapse supernovae forms a neutron star with strong initial magnetic fields but with a slow rotation.The varying angular momentum of the accreted gas,which is unique to the jittering jets explosion mechanism,exerts a varying azimuthal shear on the magnetic fields of the accreted mass near the surface of the neutron star.This,I argue,can form an amplifying effect which I term the stochastic omega(Sω) effect.In the common αω dynamo the rotation has constant direction and value,and hence supplies a constant azimuthal shear,while the convection has a stochastic behavior.In the Sω dynamo the stochastic angular momentum is different from turbulence in that it operates on a large scale,and it is different from a regular rotational shear in being stochastic.The basic assumption is that because of the varying direction of the angular momentum axis from one accretion episode to the next,the rotational flow of an accretion episode stretches the magnetic fields that were amplified in the previous episode.I estimate the amplification factor of the Sω dynamo alone to be ≈ 10.I speculate that the Sω effect accounts for a recent finding that many neutron stars are born with strong magnetic fields.展开更多
We report on the near-infrared polarimetric observations of RCW 120 with the 1.4 m IRSF telescope.The starlight polarization of the background stars reveals for the first time the magnetic field of RCW 120.The global ...We report on the near-infrared polarimetric observations of RCW 120 with the 1.4 m IRSF telescope.The starlight polarization of the background stars reveals for the first time the magnetic field of RCW 120.The global magnetic field of RCW 120 is along the direction of 20°,parallel to the Galactic plane.The field strength on the plane of the sky is 100 ± 26 μG.The magnetic field around the eastern shell shows evidence of compression by the H Ⅱ region.The external pressure(turbulent pressure+ magnetic pressure) and the gas density of the ambient cloud are minimum along the direction where RCW 120 breaks out,which explains the observed elongation of RCW 120.The dynamical age of RCW 120,depending on the magnetic field strength,is~1.6 Myr for field strength of100 μG,older than the hydrodynamic estimates.In direction perpendicular to the magnetic field,the density contrast of the western shell is greatly reduced by the strong magnetic field.The strong magnetic field in general reduces the efficiency of triggered star formation,in comparison with the hydrodynamic estimates.Triggered star formation via the "collect and collapse" mechanism could occur in the direction along the magnetic field.Core formation efficiency(CFE) is found to be higher in the southern and eastern shells of RCW 120 than in the infrared dark cloud receiving little influence from the H Ⅱ region,suggesting increase in the CFE related to triggering from ionization feedback.展开更多
The general relativistic frame dragging effect on the properties,such as the moments of inertia and the radiiof gyration of fast rotating neutron stars with a uniform strong magnetic field,is calculated accurate to th...The general relativistic frame dragging effect on the properties,such as the moments of inertia and the radiiof gyration of fast rotating neutron stars with a uniform strong magnetic field,is calculated accurate to the first orderin the uniform angular velocity.The results show that compared with the corresponding non-rotating static sphericalsymmetric neutron star with a weaker magnetic field,a fast rotating neutron star(millisecond pulsar)with a strongermagnetic field has a relative smaller moment of inertia and radius of gyration.展开更多
We first present the multicolor photometry results of the rapidly rotating magnetic star HD 345439 using the Nanshan One-meter Wide-field Telescope.From the photometric observations,we derive a rotational period of 0....We first present the multicolor photometry results of the rapidly rotating magnetic star HD 345439 using the Nanshan One-meter Wide-field Telescope.From the photometric observations,we derive a rotational period of 0.7699±0.0014 day.The light curves of HD 345439 are dominated by the double asymmetric S-wave feature that arises from the magnetic clouds.Pulsating behaviors are not observed in Sector 41 of the Transiting Exoplanet Survey Satellite.No evidence is found of the occurrence of centrifugal breakout events neither in the residual flux nor in the systematic variations at the extremum of the light curve.Based on the hypothesis of the Rigidly Rotating Magnetosphere model,we restrict the magnetic obliquity angleβand the rotational inclination angle i so that they satisfy the approximate relationβ+i≈105°.The color excess,extinction,and luminosity are determined to be E_((B-V))=0.745±0.016 mag,A_(V)=2.31±0.05 mag,and log(L/L_(⊙))=3.82±0.1 dex,respectively.Furthermore,we derive the effective temperature as T_(eff)=22±1 kK and the surface gravity as log g=4.00±0.22.The mass M=-7.24_(-1.24)^(+1.75)M_(⊙),radius R=4.44_(-1.93)^(+2.68)R_(⊙),and age τ_(age)=23.62_(-21.97)^(+4.24) Myr are estimated from the Hertzsprung-Russell diagram.展开更多
Magnetic topology has been a key to the understanding of magnetic energy release mechanism. Based on observed vector magnetograms, we have determined the threedimensional (3D) topology skeleton of the magnetic field...Magnetic topology has been a key to the understanding of magnetic energy release mechanism. Based on observed vector magnetograms, we have determined the threedimensional (3D) topology skeleton of the magnetic fields in the active region NOAA 10720. The skeleton consists of six 3D magnetic nulls and a network of corresponding spines, fans, and null-null lines. For the first time, we have identified a spiral magnetic null in Sun's corona. The magnetic lines of force twisted around the spine of the null, forming a 'magnetic wreath' with excess of free magnetic energy and resembling observed brightening structures at extraultraviolet (EUV) wavebands. We found clear evidence of topology eruptions which are referred to as catastrophic changes of topology skeleton associated with a coronal mass ejection (CME) and an explosive X-ray flare. These results shed new lights on the structural complexity and its role in explosive magnetic activity. The concept of flux rope has been widely used in modelling explosive magnetic activity, although their observational identity is rather obscure or, at least, lacking of necessary details up to date. We suggest that the magnetic wreath associated with the 3D spiral null is likely an important class of the physical entity of flux ropes.展开更多
Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the high...Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the higher coronal magnetic field intensity may correspond to.To try to further reveal the relationship between coronal green line brightness and magnetic field intensity,we use the 2 D coronal images observed by Yunnan Observatories Greenline Imaging System(YOGIS) of the 10 cm Lijiang coronagraph and the coronal magnetic field maps calculated from the current-free extrapolations with the photospheric magnetograms taken by Helioseismic and Magnetic Imager(HMI) on board the Solar Dynamics Observatory(SDO) spacecraft.In our analysis,we identified the coronal loop structures and construct two-dimensional maps of the corresponding magnetic field intensity in the plane of the sky(POS) above the limb.We derive the correlation coefficients between the coronal brightness and the magnetic field intensity for different heights of coronal layers.We further use a linear combination of a Gaussian and a quadratic profile to fit the correlation coefficients distribution,finding a largest correlation coefficient of 0.82 near 1.1 R(solar radii) where is almost the top of the closed loop system.For the small closed loop system identified,the correlation coefficient distributions crossing and covering the loop are calculated.We also investigate the correlation with extended heliocentric latitude zones and long period of one whole Carrington Rotation,finding again that the maximum correlation coefficient occurs at the same height.It is the first time for us to find that the correlation coefficients are high(all are larger than 0.8) at the loop-tops and showing poor correlation coefficients with some fluctuations near the feet of the coronal loops.Our findings indicate that,for the heating of the low-latitude closed loops,both DC(dissipation of currents) and AC(dissipation of Alfvén and magnetosonic waves) mechanisms should act simultaneously on the whole closed loop system while the DC mechanisms dominate in the loop-top regions.Therefore,in the distributions of the correlation coefficients with different heights of coronal layers,for both large-and small-scale latitude ranges,the coefficients can reach their maximum values at the same coronal height of 1.1 R,which may indicate the particular importance of the height of closed loops for studying the coupling of the local emission mechanism and the coronal magnetic fields,which maybe helpful for studying the origin of the low-speed solar wind.展开更多
Many models of gamma-ray bursts suggest a common central engine; a black hole of several solar masses accreting matter from a disk at an accretion rate from 0.01 to 10 M⊙s^-1, the inner region of the disk is cooled b...Many models of gamma-ray bursts suggest a common central engine; a black hole of several solar masses accreting matter from a disk at an accretion rate from 0.01 to 10 M⊙s^-1, the inner region of the disk is cooled by neutrino emission and large amounts of its binding energy are liberated, which could trigger the fireball. We improve the neutrino- dominated accreting flows by including the effects of magnetic fields. We find that more than half of the liberated energy can be extracted directly by the large-scale magnetic fields in the disk, and it turns out that the temperature of the disk is a bit lower than the neutrino-dominated accreting flows without magnetic field. Therefore, the outflows are magnetically-dominated rather than neutrino dominated. In our model, the neutrino mechanism can fuel some GRBs (not the brightest ones), but cannot fuel X-ray flares. The magnetic processes (both BZ and electromagnetic luminosity from a disk) are viable mechanisms for most of GRBs and their following X-ray flares.展开更多
文摘Today, the origin of the magnetic field of stars and planets is explained by the dynamo effect. Since Cowling’s anti-dynamo theorem has forbidden a purely axisymmetric dynamo, scientists are all convinced today that the fluid flow in the core of a star cannot be laminar, so it is turbulent. However, we will see in this study that the configuration in which the conductive fluid contained in the core of a star is in rapid rotation around an axis of symmetry is the one that best explains the origin of the magnetic field of stars and planets. It also explains why certain types of stars have very intense magnetic fields. Indeed, we will show here that the magnetic field of stars and planets is created by the electric current generated by the rotational movement of charged fluid particles as in an electromagnet. The lines of this magnetic field are channelled by the solid paramagnetic seed which plays the role of magnetic core in the cores of planets and stars. The seed is composed mainly of Iron and Nickel on the planets and of solid helium-3 in the stars. In this work, we will use this model of rapidly rotating fluids to introduce a new way to ionize a neutral gas and maintain it in a plasma state for indefinitely large time scales, to present a new technique for generating very intense magnetic fields, to establish a new magnetic nucleation process and to propose a new type of nuclear fusion reactor in which the plasma is perpetually rapidly rotating.
基金Supported by the National Natural Science Foundation of China though Grants 10173021, 10433030,10773003 and 10778601supported by the Ministry of Science and Technology of the People’s Republic of China through Grant 2007CB815406
文摘We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 tr level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 MG, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.
基金funded by the National Natural Science Foundation of China (NSFC, No. 11347108)the Fundamental Research Funds for the Central Universities (No. 2014QC014)the key program project of the Joint Fund of Astronomy by NSFC and the Chinese Academy of Sciences (No. 11178001)
文摘Rotochemical heating originates in the deviation from beta equilibrium due to spin-down compression, which is closely related to the dipole magnetic field. We numerically calculate the deviation from chemical equilibrium and thermal evolution of neutron stars with decaying magnetic fields. We find that the power-law long term decay of the magnetic field slightly affects the deviation from chemical equilibrium and surface temperature. However, the magnetic decay leads to older neutron stars that could have a different surface temperature with the same magnetic field strength. That is, older neutron stars with a low magnetic field (10^8 G) could have a lower temper- ature even with rotochemical heating in operation, which probably explains the lack of other observations on older millisecond pulsars with higher surface temperature, except millisecond pulsar J0437-4715.
基金funded by the National Natural Science Foundation of China (Grant Nos. 11547021, 11347108 and 11003005)
文摘We calculate the mass-radius relationship of quark stars with the magnetized density- dependent quark mass model in this work, considering two magnetic field geometries: a statistically isotropic, tangled field and a force-free configuration. In both cases, magnetic field production decreases in the case of maximum quark star mass. Furthermore, a tangled, isotropic magnetic field has a relatively smaller impact on the mass and radius, compared to the force-free configuration, which implies that the geometry of the interior magnetic field is at least as important as the field strength itself when the influ- ence of the strong magnetic field on the mass and radius is assessed.
基金The project supported by National Natural Science Foundation of China under Grant Nos.10347008 and 10778719the Scientific Research Fund of the Education Department of Sichuan Province under Grant No.2006A079the Science and Technological Foundation of China West Normal University
文摘这篇论文显示出那超级强壮的磁场(例如那些磁铁艺术) 能在中子星的外壳中多次增加精力产生率。这结果无疑不仅影响冷却中子星和中子星观察的 X 光检查光明而且中子的进化担任主角。
基金supported financially by the Center for Excellence in Astronomy and Astrophysics (CEAA-RIAAM)
文摘We investigate the effects of strong magnetic fields upon the large-scale properties of neutron and protoneutron stars. In our calculations, the neutron star mat- ter was approximated by pure neutron matter. Using the lowest order constrained vari- ational approach at zero and finite temperatures, and employing AV18 potential, we present the effects of strong magnetic fields on the gravitational mass, radius, and gravitational redshift of neutron and protoneutron stars. It is found that the equation of state for a neutron star becomes stiffer with an increase of magnetic field and tem- perature. This leads to larger values of the maximum mass and radius for the neutron stars.
基金Project suoported by the National Natural Science Foundation of China (Grant No 10347008).
文摘β decay in the strong magnetic field of the crusts of neutron stars is analysed by an improved method. The reactions ^67Ni(β-)^67Cu and ^62Mn(β-)^62Fe are investigated as examples. The results show that a weak magnetic field has little effect on β decay but a strong magnetic field (B 〉 10^12G) increases β decay rates obviously. The conclusion derived may be crucial to the research of late evolution of neutron stars and nucleosynthesis in r-process.
基金Project supported by the National Natural Science Foundation of China (Grant No 10347008).
文摘In this paper electron capture on iron group nuclei in crusts of neutron stars in a strong magnetic field is investigated. The results show that the magnetic fields have only a slight effect on electron capture rates in a range of 10^5 - 10^13g on surfaces of most neutron stars, whereas for some magnetars the magnetic fields range from 10^13 to 10^18 G. The electron capture rates of most iron group nuclei are greatly decreased, reduced by even four orders of magnitude due to the strong magnetic field.
基金supported by the Natural Science Foundation of Hainan Province,China (Grant No.109004)the Scientific Research and Foundation of Hainan Provincial Education Department,China (Grant No.Hjkj2010-42)the Special Foundation of Institutions for Higher Education of Sanya (Grant No.YD09047)
文摘The influences of electron screening (ES) and electron energy correction (EEC) are investigated by superstrong magnetic field (SMF). We also discuss in detail the discrepant factor between our results and those of Fushiki, Gudmundsson and Pethick (FGP) in SMF. The results show that SMF has only a slight effect on ES when B 〈 10^9 T on the surfaces of most neutron stars. Whereas for some magnetars, SMF influence ES greatly when B 〉 10^9 T . For instance, due to SMF the ES potential may be increased about 23.6% and the EEC may be increased about 4 orders of magnitude at ρ/μe = 1.0 × 10^6 mol/cm^3 and T9 = 1. On the other hand, the discrepant factor shows that our results are in good agreement with FGP's when B 〈 10^9 T . But the difference will be increased with increasing SMF.
基金STA foundation and the National Natural Science Foundation of China.
文摘We study the effect of strong magnetic fields on the structure of neutron star. We find that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the star's mass and radius are negligible; if the field is as large as that estimated from the scalar virial theorem, then considerable effects will be induced. The maximum mass of the star will be increased substantially while the central density is greatly reduced. The radius of a magnetic star can be larger by about 10% ~ 20% than a nonmagnetic star of the same mass.
基金supported by a grant from the Israel Science Foundation
文摘I present a novel mechanism to boost magnetic field amplification of newly born neutron stars in core collapse supernovae.In this mechanism,that operates in the jittering jets explosion mechanism and comes on top of the regular magnetic field amplification by turbulence,the accretion of stochastic angular momentum in core collapse supernovae forms a neutron star with strong initial magnetic fields but with a slow rotation.The varying angular momentum of the accreted gas,which is unique to the jittering jets explosion mechanism,exerts a varying azimuthal shear on the magnetic fields of the accreted mass near the surface of the neutron star.This,I argue,can form an amplifying effect which I term the stochastic omega(Sω) effect.In the common αω dynamo the rotation has constant direction and value,and hence supplies a constant azimuthal shear,while the convection has a stochastic behavior.In the Sω dynamo the stochastic angular momentum is different from turbulence in that it operates on a large scale,and it is different from a regular rotational shear in being stochastic.The basic assumption is that because of the varying direction of the angular momentum axis from one accretion episode to the next,the rotational flow of an accretion episode stretches the magnetic fields that were amplified in the previous episode.I estimate the amplification factor of the Sω dynamo alone to be ≈ 10.I speculate that the Sω effect accounts for a recent finding that many neutron stars are born with strong magnetic fields.
基金supported by the National Key Research & Development Program of China (2017YFA0402702)the general Grant Nos. 11903083, 12173090, U2031202, 11873093, 11873094 from the National Natural Science Foundation of Chinathe science research grants from the China Manned Space Project with No. CMS-CSST2021-B06。
文摘We report on the near-infrared polarimetric observations of RCW 120 with the 1.4 m IRSF telescope.The starlight polarization of the background stars reveals for the first time the magnetic field of RCW 120.The global magnetic field of RCW 120 is along the direction of 20°,parallel to the Galactic plane.The field strength on the plane of the sky is 100 ± 26 μG.The magnetic field around the eastern shell shows evidence of compression by the H Ⅱ region.The external pressure(turbulent pressure+ magnetic pressure) and the gas density of the ambient cloud are minimum along the direction where RCW 120 breaks out,which explains the observed elongation of RCW 120.The dynamical age of RCW 120,depending on the magnetic field strength,is~1.6 Myr for field strength of100 μG,older than the hydrodynamic estimates.In direction perpendicular to the magnetic field,the density contrast of the western shell is greatly reduced by the strong magnetic field.The strong magnetic field in general reduces the efficiency of triggered star formation,in comparison with the hydrodynamic estimates.Triggered star formation via the "collect and collapse" mechanism could occur in the direction along the magnetic field.Core formation efficiency(CFE) is found to be higher in the southern and eastern shells of RCW 120 than in the infrared dark cloud receiving little influence from the H Ⅱ region,suggesting increase in the CFE related to triggering from ionization feedback.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10647116 and 10575140 and the China Postdoctoral Science Foundation under Grant No. 2005037175
文摘在一致强壮的磁场的旋转中子星的性质和变丑是计算的。磁场将弄软中子星物质的状态的方程并且在旋转中子星的结构上做明显的效果。如果磁场是超级的强壮(B = 10 ~(17 ) T ) ,团,半径,和变丑将有效地变得更小。
基金National Natural Science Foundation of China under Grant Nos.10647116 and 10575140the China Postdoctoral Science Foundation under Grant No.2005037175
文摘The general relativistic frame dragging effect on the properties,such as the moments of inertia and the radiiof gyration of fast rotating neutron stars with a uniform strong magnetic field,is calculated accurate to the first orderin the uniform angular velocity.The results show that compared with the corresponding non-rotating static sphericalsymmetric neutron star with a weaker magnetic field,a fast rotating neutron star(millisecond pulsar)with a strongermagnetic field has a relative smaller moment of inertia and radius of gyration.
基金The project supported by National Natural Science Foundation of China under Grant No.10778719the Scientific Research Fund of the Education Department of Sichuan Province under Grant No.2006A079the Science and Technological Foundation of China West Normal University
文摘铁组原子核上的 Gamow 出纳转变的电子俘获在中子星的外壳在一个强壮的磁场被调查。结果证明磁场与磁场的范围在电子俘获率上有仅仅细微效果( 10 <SUP>9</SUP>~ 10 <SUP>13</SUP> G )在大多数中子星的表面上,而为某磁铁磁场变化的艺术是 10 <SUP>13</SUP>~ 10 <SUP>18</SUP> G ,大多数铁组原子核的电子俘获率将极大地被降低并且可以甚至被减少溢出由强壮的磁场的 3 个数量级。
基金the generous support of the Natural Science Foundation of Xinjiang No.2021D01C075the National Natural Science Foundation of China under grants U2031204,12163005 and 11863005+5 种基金the science research grants from the China Manned Space Project with Nos.CMS-CSST-2021-A08 and CMS-CSST-2021-A10the science research grants from National Key R&D Program of China(2022YFE0126200)National Major Scientific Project built by the Chinese Academy of Sciencesprovided by the National Development and Reform Commissionprovided by the NASA Explorer Programoperated by the Association of Universities for Research in Astronomy,Inc.,under NASA contract NAS 526555。
文摘We first present the multicolor photometry results of the rapidly rotating magnetic star HD 345439 using the Nanshan One-meter Wide-field Telescope.From the photometric observations,we derive a rotational period of 0.7699±0.0014 day.The light curves of HD 345439 are dominated by the double asymmetric S-wave feature that arises from the magnetic clouds.Pulsating behaviors are not observed in Sector 41 of the Transiting Exoplanet Survey Satellite.No evidence is found of the occurrence of centrifugal breakout events neither in the residual flux nor in the systematic variations at the extremum of the light curve.Based on the hypothesis of the Rigidly Rotating Magnetosphere model,we restrict the magnetic obliquity angleβand the rotational inclination angle i so that they satisfy the approximate relationβ+i≈105°.The color excess,extinction,and luminosity are determined to be E_((B-V))=0.745±0.016 mag,A_(V)=2.31±0.05 mag,and log(L/L_(⊙))=3.82±0.1 dex,respectively.Furthermore,we derive the effective temperature as T_(eff)=22±1 kK and the surface gravity as log g=4.00±0.22.The mass M=-7.24_(-1.24)^(+1.75)M_(⊙),radius R=4.44_(-1.93)^(+2.68)R_(⊙),and age τ_(age)=23.62_(-21.97)^(+4.24) Myr are estimated from the Hertzsprung-Russell diagram.
基金the National Natural Science Foundation of China
文摘Magnetic topology has been a key to the understanding of magnetic energy release mechanism. Based on observed vector magnetograms, we have determined the threedimensional (3D) topology skeleton of the magnetic fields in the active region NOAA 10720. The skeleton consists of six 3D magnetic nulls and a network of corresponding spines, fans, and null-null lines. For the first time, we have identified a spiral magnetic null in Sun's corona. The magnetic lines of force twisted around the spine of the null, forming a 'magnetic wreath' with excess of free magnetic energy and resembling observed brightening structures at extraultraviolet (EUV) wavebands. We found clear evidence of topology eruptions which are referred to as catastrophic changes of topology skeleton associated with a coronal mass ejection (CME) and an explosive X-ray flare. These results shed new lights on the structural complexity and its role in explosive magnetic activity. The concept of flux rope has been widely used in modelling explosive magnetic activity, although their observational identity is rather obscure or, at least, lacking of necessary details up to date. We suggest that the magnetic wreath associated with the 3D spiral null is likely an important class of the physical entity of flux ropes.
基金supported by the National Natural Science Foundation of China under grants 11873090, 12173086, 11873092, U2031148the CAS “Light of West China” Program。
文摘Two-dimensional(2 D) solar coronal magnetogram is difficult to be measured directly until now.From the previous knowledge,a general relation has been noticed that the brighter green-line brightness for corona,the higher coronal magnetic field intensity may correspond to.To try to further reveal the relationship between coronal green line brightness and magnetic field intensity,we use the 2 D coronal images observed by Yunnan Observatories Greenline Imaging System(YOGIS) of the 10 cm Lijiang coronagraph and the coronal magnetic field maps calculated from the current-free extrapolations with the photospheric magnetograms taken by Helioseismic and Magnetic Imager(HMI) on board the Solar Dynamics Observatory(SDO) spacecraft.In our analysis,we identified the coronal loop structures and construct two-dimensional maps of the corresponding magnetic field intensity in the plane of the sky(POS) above the limb.We derive the correlation coefficients between the coronal brightness and the magnetic field intensity for different heights of coronal layers.We further use a linear combination of a Gaussian and a quadratic profile to fit the correlation coefficients distribution,finding a largest correlation coefficient of 0.82 near 1.1 R(solar radii) where is almost the top of the closed loop system.For the small closed loop system identified,the correlation coefficient distributions crossing and covering the loop are calculated.We also investigate the correlation with extended heliocentric latitude zones and long period of one whole Carrington Rotation,finding again that the maximum correlation coefficient occurs at the same height.It is the first time for us to find that the correlation coefficients are high(all are larger than 0.8) at the loop-tops and showing poor correlation coefficients with some fluctuations near the feet of the coronal loops.Our findings indicate that,for the heating of the low-latitude closed loops,both DC(dissipation of currents) and AC(dissipation of Alfvén and magnetosonic waves) mechanisms should act simultaneously on the whole closed loop system while the DC mechanisms dominate in the loop-top regions.Therefore,in the distributions of the correlation coefficients with different heights of coronal layers,for both large-and small-scale latitude ranges,the coefficients can reach their maximum values at the same coronal height of 1.1 R,which may indicate the particular importance of the height of closed loops for studying the coupling of the local emission mechanism and the coronal magnetic fields,which maybe helpful for studying the origin of the low-speed solar wind.
基金Supported by the National Natural Science Foundation of China.
文摘Many models of gamma-ray bursts suggest a common central engine; a black hole of several solar masses accreting matter from a disk at an accretion rate from 0.01 to 10 M⊙s^-1, the inner region of the disk is cooled by neutrino emission and large amounts of its binding energy are liberated, which could trigger the fireball. We improve the neutrino- dominated accreting flows by including the effects of magnetic fields. We find that more than half of the liberated energy can be extracted directly by the large-scale magnetic fields in the disk, and it turns out that the temperature of the disk is a bit lower than the neutrino-dominated accreting flows without magnetic field. Therefore, the outflows are magnetically-dominated rather than neutrino dominated. In our model, the neutrino mechanism can fuel some GRBs (not the brightest ones), but cannot fuel X-ray flares. The magnetic processes (both BZ and electromagnetic luminosity from a disk) are viable mechanisms for most of GRBs and their following X-ray flares.