Solar energetic particles intensity variations associated with a tilted-dipole 3D corotating interaction region

The effect of a tilted-dipole three-dimensional corotating interaction region(CIR)on the transport and acceleration of solar energetic particles(SEPs)is studied.In this work,we discussed how the particle intensity longitudinal and radial dependence might be influenced by the background structures.Moreover,we investigate how the spectral index distribution is modulated by the CIR structure We use the focused transport equation(FTE)to describe the propagation and acceleration of SEPs in a tilt-dipole 3D CIR,generated by the high-resolution 3D magnetohydrodynamic(MHD)model.The forward stochastic differential method is used to solve the FTE.The protons with theE~(-4.4)spectrum from 0.5 to 15 MeV are injected uniformly at the heliographic equator of 0.15 AU.Physical quantities are extracted along each interplanetary magnetic field(IMF)line to show the results.In the tilted-dipole CIR background,if injected from the solar equator at the inner boundary,particles in the slow flow are transported to higher latitudes due to the extension of the IMF lines to higher latitudes.The longitudinal patterns of the particles are dominated by the density of IMF lines.The focusing effect modulates the longitudinal variation of the particle intensity and gives rise to new longitudinal intensity peaks.The adiabatic effect largely increases the intensity fluctuation along the longitude.The structure of the solar wind can also lead to the difference of the indexαin the empirical functionI_(max)=kR~(-α),describing the radial variation of peak intensity according to our simulation.Under the influence of the CIR structure,the indexαvaries from 1.9 to 3.4 at 0.3-1.0 AU.The variation of the solar wind speed should be considered when estimating the radial dependence of the SEP peak intensity.The spectra indices rise near the CIR boundaries and drop near the stream interface(SI).The adiabatic effect makes the spatial variability of the spectral index larger.The spectral index could be similar at different radial distances in the CIR structure.

Does regional air–sea coupling improve the simulation of the summer monsoon over the western North Pacific in the WRF4 model?

A new regional coupled ocean–atmosphere model,WRF4-LICOM,was used to investigate the impacts of regional air–sea coupling on the simulation of the western North Pacific summer monsoon(WNPSM),with a focus on the normal WNPSM year 2005.Compared to WRF4,WRF4-LICOM improved the simulation of the summer mean monsoon rainfall,circulations,sea surface net heat fluxes,and propagations of the daily rainband over the WNP.The major differences between the models were found over the northern South China Sea and east of the Philippines.The warmer SST reduced the gross moist stability of the atmosphere and increased the upward latent heat flux,and then drove local ascending anomalies,which led to the increase of rainfall in WRF4-LICOM.The resultant enhanced atmospheric heating drove a low-level anomalous cyclone to its northwest,which reduced the simulated circulation biases in the stand-alone WRF4 model.The local observed daily SST over the WNP was a response to the overlying summer monsoon.In the WRF4 model,the modeled atmosphere exhibited passive response to the underlying daily SST anomalies.With the inclusion of regional air–sea coupling,the simulated daily SST–rainfall relationship was significantly improved.WRF4-LICOM is recommended for future dynamical downscaling of simulations and projections over this region.

Metallicity and star formation activities of the interacting system Arp 86 from observations with MOS on the Xinglong 2.16m telescope

We present an analysis of the metallicity and star formation activities of H II regions in the interacting system Arp 86, based on the first scientific observations using mulri-object spectroscopy with the 2.16 m telescope at the Xinglong Observing Station. We find that the oxygen abundance gradient in Arp 86 is flatter than that in normal disk galaxies, which confirms that gas inflows caused by tidal forces during encounters can flatten the metallicity distributions in galaxies. The companion galaxy NGC 7752 is currently experiencing a galaxy-wide starburst with a higher star for- marion rate surface density than the main galaxy NGC 7753, which can be explained in that the companion galaxy is more susceptible to the effects of interaction than the primary. We also find that the galaxy 2MASX J23470758＋2926531 has similar abun- dance and star formation properties to NGC 7753, and may be a part of the Arp 86 system.

Distribution of O^(+)and O_(2)^(+) fluxes and their escape rates in the near-Mars magnetotail:A survey of MAVEN observations

Tailward ion outflows in the Martian-induced magnetotail are known to be one of the major channels for Martian atmospheric escape.On the basis of nearly 6.5 years of observations from the Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we investigate the statistical distribution of tailward and Marsward fluxes of heavy ions(i.e.,O^(+),and O_(2)^(+))in the near-Mars magnetotail and explore their characteristic responses to the corotating interaction region(CIR),solar wind dynamic pressure,and local magnetic field intensity.Our results show that the tailward fluxes of oxygen ions and molecular oxygen ions in the magnetotail are significantly greater than their Marsward fluxes and that the tailward flux of molecular oxygen ions is generally larger than that of oxygen ions.Furthermore,the tailward ion flux distribution exhibits dependence on the CIR,solar wind dynamic pressure,and local magnetic field strength in a manner stronger than the Marsward ion flux distribution.According to the distribution of tailward ion fluxes,we calculate the corresponding escape rates of heavy ions and show that when the CIR occurs,the total escape rates of oxygen ions and molecular oxygen ions increase by a factor of~2 and~1.2,respectively.We also find that the escape rates of heavy ions increase with the enhancement of solar wind dynamic pressure,whereas the overall effect of the local magnetic field is relatively weak.Our study has important implications for improved understanding of the underlying mechanisms responsible for the Martian atmospheric escape and the evolution of the Martian atmospheric climate.

Flow resistance in the channel-bar landscape of large alluvial rivers

Accurate approaches for estimating flow resistance in large alluvial rivers are fundamental for simulating discharge,sediment transport,and flood routing.However,methods for estimating riverbed resistance and additional resistance in the channel-bar landscapes remain poorly investigated.In this study,we used in situ river bathymetry,sediment,and hydraulic data from the Shashi Reach in the Yangtze River to develop a semi-empirical approach for calculating flow resistance.Our method quantitatively separates flow resistance into riverbed resistance and additional resistance and shows high accuracy in terms of deviation ratio(~20%),root-mean-square error(~0.008),and geometric standard deviation(~3).Additional resistance plays a dominant role under low-flow conditions but a secondary role under high flows,primarily due to the reduction in momentum exchange in channel-bar regions as discharge increases.Riverbed resistance first decreases and then increases,which might be attributed to bedform changes in the lower and transitional flow regimes as flow velocity increases.Overall,our findings further the understanding of dynamic changes in flow resistance in the channel-bar landscapes of large river systems and have important implications for riverine ecology and flood management.

A DISCRETE MODEL WITH INTERACTION BETWEEN THE BUDWORM AND ITS PREDATOR IN A CIRCULAR REGION

We consider a discrete model with interaction between the budworm and its predator in aeircular region. The number and properties of steady solutions, and the asymptotic behaviour ofunsteady solution are discussed.

Estimation of the radiation backgrounds in the CEPC vertex detector

Background The Circular Electron-Positron Collider(CEPC)is aimed for precision measurements of the Higgs boson properties and the electroweak parameters.The achievable precision will be largely dependent on the controlled level of radiation backgrounds,which requires an optimized design of the interaction region to assure the optimal performance of both the accelerator and the detectors.Purpose In this article,the latest results on the radiation backgrounds are reported based on the accelerator parameters and the detector design presented in the CEPC conceptual design reports.Method For the different sources of radiation backgrounds,simulation steps consisting of generation,tracking,and detector simulation were performed.Radiation backgrounds from the processes of synchrotron radiation,pair production,radiative Bhabha scattering,beam gas Bremsstrahlung scattering,and beam thermal photon scattering were considered for the accel-erator operating at the different centre-of-mass energies(HZ threshold,WW threshold,and Z pole).Possible mitigation methods of masks and/or collimators were introduced to suppress the radiation backgrounds,together with the careful opti-mization of the interaction region design.With the improved tracking methods during simulation,the accuracy and reliability of the results were improved.In addition,the radiation backgrounds on the CEPC vertex detector were estimated,and the pair-production was found to be the most important source.Result In the worst case of operation at the Z pole,the vertex detector would have to withstand a total ionization dose of 5.6 Mrad per year and a non-ionization energy loss(shown in 1 MeV neutron equivalent)of 1.06×10^(13)n_(eq)/cm^(2)per year.