分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yuming Wang
Xianyong Bai
Changyong Chen
Linjie Chen
Xin Cheng
Lei Deng
Linhua Deng
Yuanyong Deng
Li Feng
Tingyu Gou
Jingnan Guo
Yang Guo
Xinjun Hao
Jiansen He
Junfeng Hou
Huang Jiangjiang
Zhenghua Huang
Haisheng Ji
Chaowei Jiang
Jie Jiang
摘要： Solar Ring (SOR) is a proposed space science mission to monitor and study the Sun and inner heliosphere from a full 360{\deg} perspective in the ecliptic plane. It will deploy three 120{\deg}-separated spacecraft on the 1-AU orbit. The first spacecraft, S1, locates 30{\deg} upstream of the Earth, the second, S2, 90{\deg} downstream, and the third, S3, completes the configuration. This design with necessary science instruments, e.g., the Doppler-velocity and vector magnetic field imager, wide-angle coronagraph, and in-situ instruments, will allow us to establish many unprecedented capabilities: (1) provide simultaneous Doppler-velocity observations of the whole solar surface to understand the deep interior, (2) provide vector magnetograms of the whole photosphere - the inner boundary of the solar atmosphere and heliosphere, (3) provide the information of the whole lifetime evolution of solar featured structures, and (4) provide the whole view of solar transients and space weather in the inner heliosphere. With these capabilities, Solar Ring mission aims to address outstanding questions about the origin of solar cycle, the origin of solar eruptions and the origin of extreme space weather events. The successful accomplishment of the mission will construct a panorama of the Sun and inner-heliosphere, and therefore advance our understanding of the star and the space environment that holds our life.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Large-scale solar eruptive activities have a close relationship with coronal magnetic flux ropes. Previous numerical studies have found that the equilibrium of a coronal flux rope system could be disrupted if the axial magnetic flux of the rope exceeds a critical value, so that the catastrophe occurs, initiating the flux rope to erupt. Further studies discovered that the catastrophe does not necessarily exist: the flux rope system with certain photospheric flux distributions could be non-catastrophic. It is noteworthy that most previous numerical studies are under the ideal magnetohydrodynamic (MHD) condition, so that it is still elusive whether there is the catastrophe associated with the critical axial flux if magnetic reconnection is included in the flux rope system. In this paper, we carried out numerical simulations to investigate the evolutions of coronal magnetic rope systems under the ideal MHD and the resistive condition. Under the ideal MHD condition, our simulation results demonstrate that the flux rope systems with either too compact or too weak photospheric magnetic source regions are non-catastrophic versus varying axial flux of the rope, and thus no eruption could be initiated; if there is magnetic reconnection in the rope system, however, those flux rope systems could change to be capable of erupting via the catastrophe associated with increasing axial flux. Therefore, magnetic reconnection could significantly influence the catastrophic behaviors of flux rope system. It should be both the magnetic topology and the local physical parameters related to magnetic reconnection that determine whether the increasing axial flux is able to cause flux rope eruptions.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we use a newly compiled sample of ultra-compact structure in radio quasars and strong gravitational lensing systems with quasars acting as background sources to constrain six spatially flat and non-flat cosmological models ($\Lambda$CDM, PEDE and DGP). These two sets of quasar data (the time-delay measurements of six strong lensing systems and 120 intermediate-luminosity quasars calibrated as standard rulers) could break the degeneracy between cosmological parameters ($H_0$, $\Omega_m$ and $\Omega_k$) and therefore provide more stringent cosmological constraints for the six cosmological models we study. A joint analysis of the quasar sample provides model-independent estimations of the Hubble constant $H_0$, which is strongly consistent with that derived from the local distance ladder by SH0ES collaboration in the $\Lambda$CDM and PEDE model. However, in the framework of a DGP cosmology (especially for the flat universe), the measured Hubble constant is in good agreement with that derived from the the recent Planck 2018 results. In addition, our results show that zero spatial curvature is supported by the current lensed and unlensed quasar observations and there is no significant deviation from a flat universe. For most of cosmological model we study (the flat $\Lambda$CDM, non-flat $\Lambda$CDM, flat PEDE, and non-flat PEDE models), the derived matter density parameter is completely consistent with $\Omega_m\sim 0.30$ in all the data sets, as expected by the latest cosmological observations. Finally, according to the the statistical criteria DIC, although the joint constraints provide substantial observational support to the flat PEDE model, they do not rule out dark energy being a cosmological constant and non-flat spatial hypersurfaces.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Yuming Wang
Xianyong Bai
Changyong Chen
Linjie Chen
Xin Cheng
Lei Deng
Linhua Deng
Yuanyong Deng
Li Feng
Tingyu Gou
Jingnan Guo
Yang Guo
Xinjun Hao
Jiansen He
Junfeng Hou
Huang Jiangjiang
Zhenghua Huang
Haisheng Ji
Chaowei Jiang
Jie Jiang
摘要： Solar Ring (SOR) is a proposed space science mission to monitor and study the Sun and inner heliosphere from a full 360{\deg} perspective in the ecliptic plane. It will deploy three 120{\deg}-separated spacecraft on the 1-AU orbit. The first spacecraft, S1, locates 30{\deg} upstream of the Earth, the second, S2, 90{\deg} downstream, and the third, S3, completes the configuration. This design with necessary science instruments, e.g., the Doppler-velocity and vector magnetic field imager, wide-angle coronagraph, and in-situ instruments, will allow us to establish many unprecedented capabilities: (1) provide simultaneous Doppler-velocity observations of the whole solar surface to understand the deep interior, (2) provide vector magnetograms of the whole photosphere - the inner boundary of the solar atmosphere and heliosphere, (3) provide the information of the whole lifetime evolution of solar featured structures, and (4) provide the whole view of solar transients and space weather in the inner heliosphere. With these capabilities, Solar Ring mission aims to address outstanding questions about the origin of solar cycle, the origin of solar eruptions and the origin of extreme space weather events. The successful accomplishment of the mission will construct a panorama of the Sun and inner-heliosphere, and therefore advance our understanding of the star and the space environment that holds our life.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： To better understand the physical processes associated with Jovian decametric (DAM) radio emissions, we present the statistical study of DAMs and inferred characteristics of DAM sources based on multi-view observation from Wind and STEREO spacecraft. The distribution of the apparent rotation speed of DAMs derived from multiple spacecraft suggests that the rotation speed of Io-related DAMs is in range of 0.15-0.6{\Omega}_J and that of non-Io-DAMs is between 0.7-1.2{\Omega}_J. Based on the method of Wang et al. (2020), we locate the sources of the DAMs and infer their emission angles and associated electron energies. The statistical results show that the DAM source locations have three preferred regions, two in the southern hemisphere and one in the northern hemisphere, which is probably caused by the non-symmetrical topology of Jupiter's magnetic field. The difference between Io-DAM source footprints and Io auroral spots changes with the Io's position in longitude, consistent with the previous results from Hess et al. (2010), Bonfond et al. (2017) and Hinton et al. (2019). In addition, the emission angles for non-Io-DAMs are smaller than that for Io-DAMs from the same source regions and all the emission angles range from 60{\deg} to 85{\deg}. Correspondingly, the electron energy is mainly distributed between 0.5 and 20 keV.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We investigate a generalized form of the phenomenologically emergent dark energy model, known as generalized emergent dark energy (GEDE), introduced by Li and Shafieloo [Astrophys. J. {\bf 902}, 58 (2020)] in light of a series of cosmological probes and considering the evolution of the model at the level of linear perturbations. This model introduces a free parameter $\Delta$ that can discriminate between the $\Lambda$CDM (corresponds to $\Delta=0$) or the phenomenologically emergent dark energy (PEDE) (corresponds to $\Delta=1$) models, allowing us to determine which model is preferred most by the fit of the observational datasets. We find evidence in favor of the GEDE model for Planck alone and in combination with R19, while the Bayesian model comparison is inconclusive when Supernovae Type Ia or BAO data are included. In particular, we find that $\Lambda$CDM model is disfavored at more than $2\sigma$ CL for most of the observational datasets considered in this work and PEDE is in agreement with Planck 2018+BAO+R19 combination within $1\sigma$ CL.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we use a newly compiled sample of ultra-compact structure in radio quasars and strong gravitational lensing systems with quasars acting as background sources to constrain six spatially flat and non-flat cosmological models ($\Lambda$CDM, PEDE and DGP). These two sets of quasar data (the time-delay measurements of six strong lensing systems and 120 intermediate-luminosity quasars calibrated as standard rulers) could break the degeneracy between cosmological parameters ($H_0$, $\Omega_m$ and $\Omega_k$) and therefore provide more stringent cosmological constraints for the six cosmological models we study. A joint analysis of the quasar sample provides model-independent estimations of the Hubble constant $H_0$, which is strongly consistent with that derived from the local distance ladder by SH0ES collaboration in the $\Lambda$CDM and PEDE model. However, in the framework of a DGP cosmology (especially for the flat universe), the measured Hubble constant is in good agreement with that derived from the the recent Planck 2018 results. In addition, our results show that zero spatial curvature is supported by the current lensed and unlensed quasar observations and there is no significant deviation from a flat universe. For most of cosmological model we study (the flat $\Lambda$CDM, non-flat $\Lambda$CDM, flat PEDE, and non-flat PEDE models), the derived matter density parameter is completely consistent with $\Omega_m\sim 0.30$ in all the data sets, as expected by the latest cosmological observations. Finally, according to the the statistical criteria DIC, although the joint constraints provide substantial observational support to the flat PEDE model, they do not rule out dark energy being a cosmological constant and non-flat spatial hypersurfaces.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： It is widely accepted that coronal magnetic flux ropes are the core structures of large-scale solar eruptive activities, which inflict dramatic impacts on the solar-terrestrial system. Previous studies have demonstrated that varying magnetic properties of a coronal flux rope system could result in a catastrophe of the rope, which may trigger solar eruptive activities. Since the total mass of a flux rope also plays an important role in stabilizing the rope, we use 2.5-dimensional magnetohydrodynamic (MHD) numerical simulations in this letter to investigate how a flux rope evolves as its total mass varies. It is found that an unloading process that decreases the total mass of the rope could result in an upward (eruptive) catastrophe in the flux rope system, during which the rope jumps upward and the magnetic energy is released. This indicates that mass unloading processes could initiate the eruption of the flux rope. Moreover, when the system is not too diffusive, there is also a downward (confined) catastrophe that could be caused by mass loading processes, via which the total mass accumulates. The magnetic energy, however, is increased during the downward catastrophe, indicating that mass loading processes could cause confined activities that may contribute to the storage of energy before the onset of coronal eruptions.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： In this paper, we present a model-independent approach to calibrate the largest quasar sample. Calibrating quasar samples is essentially constraining the parameters of the linear relation between the $\log$ of the ultraviolet (UV) and X-ray luminosities. This calibration allows quasars to be used as standardized candles. There is a strong correlation between the parameters characterizing the quasar luminosity relation and the cosmological distances inferred from using quasars as standardized candles. We break this degeneracy by using Gaussian process regression to model-independently reconstruct the expansion history of the Universe from the latest type Ia supernova observations. Using the calibrated quasar dataset, we further reconstruct the expansion history up to redshift of $z\sim 7.5$. Finally, we test the consistency between the calibrated quasar sample and the standard $\rm{\Lambda}CDM$ model based on the posterior probability distribution of the GP hyperparameters. Our results show that the quasar sample is in good agreement with the standard $\rm{\Lambda}CDM$ model in the redshift range of the supernova, despite of mildly significant deviations taking place at higher redshifts. Fitting the standard $\rm{\Lambda}CDM$ model to the calibrated quasar sample, we obtain a high value of the matter density parameter $\Omega_m = 0.382^{+0.045}_{-0.042}$, which is marginally consistent with the constraints from other cosmological observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Large-scale solar eruptive activities have a close relationship with coronal magnetic flux ropes. Previous numerical studies have found that the equilibrium of a coronal flux rope system could be disrupted if the axial magnetic flux of the rope exceeds a critical value, so that the catastrophe occurs, initiating the flux rope to erupt. Further studies discovered that the catastrophe does not necessarily exist: the flux rope system with certain photospheric flux distributions could be non-catastrophic. It is noteworthy that most previous numerical studies are under the ideal magnetohydrodynamic (MHD) condition, so that it is still elusive whether there is the catastrophe associated with the critical axial flux if magnetic reconnection is included in the flux rope system. In this paper, we carried out numerical simulations to investigate the evolutions of coronal magnetic rope systems under the ideal MHD and the resistive condition. Under the ideal MHD condition, our simulation results demonstrate that the flux rope systems with either too compact or too weak photospheric magnetic source regions are non-catastrophic versus varying axial flux of the rope, and thus no eruption could be initiated; if there is magnetic reconnection in the rope system, however, those flux rope systems could change to be capable of erupting via the catastrophe associated with increasing axial flux. Therefore, magnetic reconnection could significantly influence the catastrophic behaviors of flux rope system. It should be both the magnetic topology and the local physical parameters related to magnetic reconnection that determine whether the increasing axial flux is able to cause flux rope eruptions.
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