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Time Evolution of the Turnover Frequency for Diagnosis of the Coronal Magnetic Field

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chinese Journal of Astronomy and Astrophysics 2006年第1期6卷 113-119页

作者： Guang-Li Huang purple mountain observatory Chinese Academy of Sciences Nanjing 210008

Two impulsive microwave bursts observed by Owens-Valley Solar Arrays （OVSA） are studied. The fast time variation of the turnover frequency in these bursts is quite different from the constant value in the earlier conclusion. The observational turnover frequencies are consistent with the calculations using the non-thermal gyrosynchrotron radiation model. We find the turnover frequency may play an important role for calculating the coronal magnetic field on the basis of Dulk and Marsh＇s approximations.

关键词： Sun： radio radiation -- Sun： corona- Sun： magnetic fields

Near-Infrared Observations of the Massive Star Forming Region IRAS 23151+5912

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chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 284-298页

作者： Xue-Peng Chen Yong-Qiang Yao purple mountain observatory chinese academy of sciences, Nanjing 210008 purple mountain observatory Chinese Academy of Sciences Nanjing 210008

Near-infrared images and K-band spectroscopy of the massive star-formingregion IRAS 23151+5912 are presented. The JHK′ images reveal an embedded infrared clusterassociated with infrared nebula, and the H_2 (2.12 μm) narrowband image provides for the first timeevidence of outflow activity associated with the cluster. That the cluster is young can be shown bythe high percentage of infrared excess sources and the outflow activity. We suggest an age of thecluster of ～ 10~6 yr. Eight young stars are found in the bright nebular core around IRAS23151+5912. By the color-magnitude diagrams of the cluster, we found five high-mass YSOs and fourintermediate-mass YSOs in the cluster. Eight H_2 emission features are discovered in the region witha scattered and non-axisymmetric distribution, indicating the existence of multiple outflows drivenby the cluster. Diffuse H_2 emission detected to the north and to the west of the cluster mayresult from UV leakage of the cluster. Brγ, H_2, and CIV emission lines are found in the K-bandspectrum of the brightest source, NIRS 19, indicating the presence of envelope, stellar wind, andshock in the circumstellar environment. We have estimated an O7-O9 spectral type for the centralmassive YSO (20 ～ 30 solar mass), with an age of less than 1 x 10~6 yr.

关键词： infrared radiation stars: formation ISM: individual: IRAS 23151 + 5912 ISM: jets and outflows

The simulation of GCRs at near earth interplanetary locations for radioprotection

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Science China(Physics,Mechanics & Astronomy) 2010年第9期53卷 1739-1745页

作者： BAO Gang purple mountain observatory,chinese academy of sciences,Nanjing 210008,China purple mountain observatory Chinese Academy of Sciences Nanjing China

The interplanetary radiation environment is detrimental to space missions,giving rise to cumulative damage to both astronauts and payloads and enhanced background levels in detectors.Therefore,there is a pressing need for a reliable simulation of these harmful effects for risk assessment and shielding optimization in manned space missions.We have modeled the interaction processes of the two most abundant galactic cosmic ray particle fluxes(protons and helium nuclei) using the Geant4 toolkit for a given space vehicle model.The total energy deposited due to protons and helium nuclei is calculated in this work,and the energy deposited due to the secondary particles generated by this radiation is also estimated.

关键词： radioprotection simulation Geant4 cosmic rays

Multiwavelength study of low-luminosity 6.7-GHz methanol masers

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Research in Astronomy and Astrophysics 2011年第2期11卷 137-155页

作者： Yuan-Wei Wu,Ye Xu and Ji Yang purple mountain observatory,chinese academy of sciences,Nanjing 210008,China purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China

We present results of 13CO（1-0）,C18O（1-0）,and HCO＋（1-0） map observations and N2H＋（1-0） single point observations directed towards a sample of nine low-luminosity 6.7-GHz masers.N2H ＋ line emission has been detected from six out of nine sources,C18O line emission has been detected from eight out of nine sources,and HCO ＋ and 13CO emission has been detected in all sources.In particular,a ＂blue profile＂ of the HCO ＋ spectrum,a signature of inflow,is found towards one source.From integrated intensity emission maps,we identified 17 cores in the sample.Among them,nine cores are closely associated with low-luminosity methanol masers.For these cores,we derive the column densities,core sizes,masses and molecular abundances.Comparison of our results with similar molecular line surveys towards the southern sky methanol masers indicates that linewidths of our sample,including only the low-luminosity masers,are smaller than the sample that includes both lowand high-luminosity masers.For the maser associated cores,their gas masses have the same order of magnitude as their virial masses,indicating that these cores are gravitationally bound systems.In addition,we have found from our observations that the low-luminosity methanol masers tend to coexist with H2O masers and outflows rather than with OH masers.

关键词： masers -- ISM： abundances -- ISM： molecules -- stars： formation

Disorder effects in NbTiN superconducting resonators

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chinese Physics B 2024年第2期33卷 482-486页

作者：吕伟涛支强胡洁李婧史生才 purple mountain observatory Chinese Academy of SciencesNanjing 210034China GEPI Observatoire de ParisPSL UniversitéCNRSParis 75014France

Disordered superconducting materials like NbTiN possess a high kinetic inductance fraction and an adjustable critical temperature, making them a good choice for low-temperature detectors. Their energy gap(D), critical temperature(T_(c)),and quasiparticle density of states(QDOS) distribution, however, deviate from the classical BCS theory due to the disorder effects. The Usadel equation, which takes account of elastic scattering, non-elastic scattering, and electro–phonon coupling,can be applied to explain and describe these deviations. This paper presents numerical simulations of the disorder effects based on the Usadel equation to investigate their effects on the △, Tc, QDOS distribution, and complex conductivity of the NbTiN film. Furthermore, NbTiN superconducting resonators with coplanar waveguide(CPW) structures are fabricated and characterized at different temperatures to validate our numerical simulations. The pair-breaking parameter α and the critical temperature in the pure state T_(c)^(P) of our NbTiN film are determined from the experimental results and numerical simulations. This study has significant implications for the development of low-temperature detectors made of disordered superconducting materials.

关键词： effects of disorder NbTiN superconducting film Usadel equation complex conductivity superconducting resonator

Statistical study of EUV and X-ray transient brightenings

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Research in Astronomy and Astrophysics 2010年第7期10卷 696-706页

作者： Jing-Wei Li Hui Li purple mountain observatory Chinese Academy of Sciences Nanjing 210008 China

Using the visual inspection and base difference method and data from the X-ray Telescope （XRT） onboard Hinode and TRACE with improved spatial and temporal resolution, we selected 48 X-ray transient brightenings （XTBs） and 237 EUV transient brightenings （ETBs） to study the connection between these two types of transient brightenings （TBs）. These ETBs and XTBs have smaller areas （8.42 Mm^2 and 36.3 Mm^2, respectively, on average） and shorter durations （9.0 min and 6.9 min, respectively, on average） than previous studies. These XTBs show three types of morphological structure： point-like, single-loop and multiple-loop. We find only 20% of the ETBs have corresponding XTBs while the other 80% have no X-ray signatures at all. This is presumably due to the small amount of released energy, which is not enough to heat the plasma to coronal temperatures which produce X-ray emission rather than being due to the limitation of spatial resolution and temperature sensitivity of the X-ray instrument. These small ETBs may significantly contribute to the coronal heating.

关键词： Sun X-rays, gamma rays -- Sun UV radiation -- Sun corona

The Gyrosynchrotron Radiation Spectrum in a Nonuniform Source

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chinese Journal of Astronomy and Astrophysics 2006年第2期6卷 260-264页

作者： Ai-Hua Zhou purple mountain observatory Chinese Academy of Sciences Nanjing 210008

Effects of the energy spectral index δ, low energy cutoff E0 and number density N of energetic electrons on gyrosynchrotron spectrum are investigated for a model source with a nonuniform magnetic field. It is found that the flux density SVT of the x-mode and o-mode systematically increase with increasing E0, N and with decreasing δ. The peak frequency of the spectrum, vp, also systematically increases as increasing E0 and N, but it may not depend on δ. The gyrosynchrotron radiation in the nonuniform case is polarized predominately in the x-mode at v ≥ 3 GHz. A sense reversal of circular polarization also occurs but at much lower frequencies （v ≤ 3 GHz）. The reversal frequency also increases with increasing E0 and N, but it perhaps is independent of δ.

关键词： Sun： flares - Sun： radio radiation

First Digit Distributions of Gamma-Ray Bursts

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Research in Astronomy and Astrophysics 2024年第5期24卷 70-75页

作者： Hou-Yu Lai Jun-Jie Wei purple mountain observatory Chinese Academy of SciencesNanjing 210023China School of Astronomy and Space sciences University of Science and Technology of ChinaHefei 230026China

The occurrence of the first significant digits from real world sources is usually not equally distributed,but is consistent with a logarithmic distribution instead,known as Benford’s law.In this work,we perform a comprehensive investigation on the first digit distributions of the duration,fluence,and energy flux of gamma-ray bursts (GRBs) for the first time.For a complete GRB sample detected by the Fermi satellite,we find that the first digits of the duration and fluence adhere to Benford’s law.However,the energy flux shows a significant departure from this law,which may be due to the fact that a considerable part of the energy flux measurements is restricted by lack of spectral information.Based on the conventional duration classification scheme,we also check if the durations and fluences of long and short GRBs (with duration T_(90)>2 s and T_(90)≤2 s,respectively) obey Benford’s law.We find that the fluences of both long and short GRBs still agree with the Benford distribution,but their durations do not follow Benford’s law.Our results hint that the long–short GRB classification scheme does not directly represent the intrinsic physical classification scheme.

关键词： (stars:)gamma-ray burst general-methods statistical-astronomical databases miscellaneous

Suprathermal particle events observed by WIND spacecraft in interplanetary space during 1995―1999 and their classification

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Science China(Technological sciences) 2008年第9期51卷 1542-1553页

作者： SUN LingPeng1,2, WU DeJin1 & WANG DeYu1 1 purple mountain observatory, chinese academy of sciences, Nanjing 210008, China 2 Graduate School of chinese academy of sciences, Beijing 100049, China purple mountain observatory Chinese Academy of Sciences Nanjing China Graduate School of chinese academy of sciences Beijing China

Fifty-five suprathermal particle events were selected from WIND observations between 1995 and 1999. Based on systematic analysis on the observational characteristics of these events a two-parameter (the rising time and the flux ratio of electrons to protons in each event) classification method was proposed to classify these events. The three clas-sified classes are (1) impulsive electron events with the flux ratio of electrons to protons being bigger than 1 and rising time being shorter than 200 min, (2) impulsive proton events with the flux ratio being smaller than 1 and rising time being shorter than 200 min, and (3) gradual proton events with the flux ratio being smaller than 1 and the rising time being longer than 200 min. In the past, "impulsive solar electron events" were under in-tense research. However, because the selection standards of their velocity dispersions or pitch-angle distributions were inadequate, statistical surveys of selected events were dif-ferent from each other and even some conclusions were not consistent with the theory, for example, the relation of type-III solar radio bursts to the "impulsive solar electron events". The first class of impulsive electron events are associated with type-III radio bursts and with clear velocity dispersions; therefore they ought to originate from the Sun. The second class of the events, which have short continuance time and usually are not associated with type-III radio bursts and without velocity dispersion, are still far away from inter-planetary shocks and most of them do not one-to-one correspond to corrotating interact-ing regions (CIRs); such events are possible results of local interplanetary magnetic field reconnection or electromagnetic disturbances. Finally, about 2/3 gradual proton events of the third class occur with interplanetary shocks, the delay times of which are almost equal to the rising time. Some of these events can be understood as particle accelerations by shocks.

关键词： suprathermal particles solar wind plasma solar eruptive activity interplanetary active regions