A mechanism is presented for generating high speed particles in Herbig-Haro flow coming from accretion disks associated with protostars.The disks are threaded with weak magnetic field lines,in which the magnetorotatio...A mechanism is presented for generating high speed particles in Herbig-Haro flow coming from accretion disks associated with protostars.The disks are threaded with weak magnetic field lines,in which the magnetorotational instability results in magnetohydrodynamic turbulence.Then the turbulent waves accelerate the thermal particles out of the accretion disks to a few hundred kilometres per second,forming the high speed particles of optical jets in star-forming regions.展开更多
Two-fluid magnetohydrodynamic equations are applied to dark molecular clouds that are composed of neutrals mixed with minor charged particles,weakly ionized gas systems.The result shows the temperatures are higher at ...Two-fluid magnetohydrodynamic equations are applied to dark molecular clouds that are composed of neutrals mixed with minor charged particles,weakly ionized gas systems.The result shows the temperatures are higher at the cloud edges than at their inner regions,the cause of which is that the cloud potential,released as clouds contract particularly at their edges,along with some dissipated rotational kinetic energy is converted into thermal.The cloud contracting is due to the loss of the magnetic field that threads it through ambipolar diffusion.Nevertheless,without the support of the magnetic and the centrifugal forces in the direction of the magnetic Held assumed to be parallel to the cloud rotating axis,the cloud collapses in that direction when its mass is over the Jeans mass.展开更多
In dense molecular clouds the grains become the main charged particles.When the hydrogen gas density reaches as high as nH=10^(11)cm^(-3) and the grains are assumed to be small polycyclic aromatic hydrocarbons(PAHs),t...In dense molecular clouds the grains become the main charged particles.When the hydrogen gas density reaches as high as nH=10^(11)cm^(-3) and the grains are assumed to be small polycyclic aromatic hydrocarbons(PAHs),the lower hybrid drift instability develops,leading to the creation of anomalous electric conductivity,which makes the magnetic Reynold's number of the system R_(M)~1 indicating the dissipation of magnetic fields.When the gas density continues to go up and over10^(11)cm_(-3),the collision frequency between PAHs and gas particles becomes larger than the plasma frequency,resulting in the collision process being dominant.In that case the magnetic field also dissipates because R_(M)~1 is still kept.展开更多
Massive stars often tend to be in cluster when they form in molecular clouds,and bipolar molecular outflows occur during the forming process of stars.On the basis of newly observed bipolar molecular outflows associate...Massive stars often tend to be in cluster when they form in molecular clouds,and bipolar molecular outflows occur during the forming process of stars.On the basis of newly observed bipolar molecular outflows associated with massive stars,three properties are proposed to statistically identify massive stars whether in cluster or not as the driving engines of the flows.For clustering massive stars with some exceptions,their outflow collimation factors are generally poor and less than two,and the correlations of the flow momentum rate and the mass flow rate with the central source bolometric luminosity deviate the ones for selected well-resolved 16 flows.展开更多
A new acceleration and emission mechanism is presented for wisps in the crab nebula.It is suggested that the energy of ultra-relativistic electrons comes mainly from Langmuir wave turbulence acceleration and synchrotr...A new acceleration and emission mechanism is presented for wisps in the crab nebula.It is suggested that the energy of ultra-relativistic electrons comes mainly from Langmuir wave turbulence acceleration and synchrotron absorption acceleration,then they give rise to synchrotron emission.Langmuir wave turbulence acceleration is the dominant mechanism atε≤ε*,while synchrotron absorption acceleration is more important atε>ε*.The energy diffusion equation is investigated for ultra-relativistic electrons undergoing different acceleration and derive power-law solution.In wisp 1 region,the synchrotron emission spectra are obtained,and they are x-rays,optical but not radio.The results are consistent with observations.展开更多
文摘A mechanism is presented for generating high speed particles in Herbig-Haro flow coming from accretion disks associated with protostars.The disks are threaded with weak magnetic field lines,in which the magnetorotational instability results in magnetohydrodynamic turbulence.Then the turbulent waves accelerate the thermal particles out of the accretion disks to a few hundred kilometres per second,forming the high speed particles of optical jets in star-forming regions.
文摘Two-fluid magnetohydrodynamic equations are applied to dark molecular clouds that are composed of neutrals mixed with minor charged particles,weakly ionized gas systems.The result shows the temperatures are higher at the cloud edges than at their inner regions,the cause of which is that the cloud potential,released as clouds contract particularly at their edges,along with some dissipated rotational kinetic energy is converted into thermal.The cloud contracting is due to the loss of the magnetic field that threads it through ambipolar diffusion.Nevertheless,without the support of the magnetic and the centrifugal forces in the direction of the magnetic Held assumed to be parallel to the cloud rotating axis,the cloud collapses in that direction when its mass is over the Jeans mass.
文摘In dense molecular clouds the grains become the main charged particles.When the hydrogen gas density reaches as high as nH=10^(11)cm^(-3) and the grains are assumed to be small polycyclic aromatic hydrocarbons(PAHs),the lower hybrid drift instability develops,leading to the creation of anomalous electric conductivity,which makes the magnetic Reynold's number of the system R_(M)~1 indicating the dissipation of magnetic fields.When the gas density continues to go up and over10^(11)cm_(-3),the collision frequency between PAHs and gas particles becomes larger than the plasma frequency,resulting in the collision process being dominant.In that case the magnetic field also dissipates because R_(M)~1 is still kept.
文摘Massive stars often tend to be in cluster when they form in molecular clouds,and bipolar molecular outflows occur during the forming process of stars.On the basis of newly observed bipolar molecular outflows associated with massive stars,three properties are proposed to statistically identify massive stars whether in cluster or not as the driving engines of the flows.For clustering massive stars with some exceptions,their outflow collimation factors are generally poor and less than two,and the correlations of the flow momentum rate and the mass flow rate with the central source bolometric luminosity deviate the ones for selected well-resolved 16 flows.
文摘A new acceleration and emission mechanism is presented for wisps in the crab nebula.It is suggested that the energy of ultra-relativistic electrons comes mainly from Langmuir wave turbulence acceleration and synchrotron absorption acceleration,then they give rise to synchrotron emission.Langmuir wave turbulence acceleration is the dominant mechanism atε≤ε*,while synchrotron absorption acceleration is more important atε>ε*.The energy diffusion equation is investigated for ultra-relativistic electrons undergoing different acceleration and derive power-law solution.In wisp 1 region,the synchrotron emission spectra are obtained,and they are x-rays,optical but not radio.The results are consistent with observations.
