A normalized statistical study of Earth’s cusp region based on nine-years of Cluster measurements

Nine years(2001–2009)of data from the Cluster spacecraft are analyzed in this study of the Earth’s mid-and high-altitude(2–9RE)cusp.Properties of the cusp region,and its location and size in the Solar Magnetic coordinate system,are studied statistically.The survey shows that(1)the relationships between X and Z are nearly linear for the poleward,equatorward boundaries and the center of the cusp;(2)the relationship between cusp width in the X direction and Z can be expressed by a quadratic function;(3)the cusp region is almost dawn-dusk symmetric for the cusp width in the X direction.Based on topology information,a new normalized statistical methodology is developed to organize the measurements of cusp crossings to obtain distributions of magnetic field and plasma parameters in the XZ plane.The statistical results show that(1)Bx is mostly negative and Bz is always negative;(2)proton velocity is found to be positive for Vx and Vz at low altitudes,while Vx and Vz are negative on the equator side and negative Vx and positive Vz on the pole side at high altitudes;(3)proton density is higher on the equator side than on the pole side.Results reported here will be useful in suggesting directions for future cusp research.

Study on Daily ET Based on SEBAL Model in a Typical Watershed of the Loess Plateau of China

Under the double impact of global climate change and human intervention, surface evapotranspiration (ET), as an important part of hydrological cycle, is affecting watershed land-use planning and economic development. The Loess Plateau is mostly arid and semi-arid areas and its ecological environment is fragile. Drought and soil erosion not only reflects the regional climate change, but also human social activities and ecosystems. In particular, these processes are directly related to the thermal and water gradients exchange in the soil-vegetation-atmosphere system. Luoyugou watershed, a typical Loess Plateau watershed, is selected for this study. Estimating ET through SEBAL (Surface Energy Balance Algorithm for Land) model demonstrates that the SEBAL model in the watershed is more applicable. At the same time, ET seasonal variation is got, combined with the corresponding periods of the land-use changes for analysis. The results show that ET in the Northwest of the basin is higher than the East on the spatial distribution, especially in the high vegetation coverage area. Land use changes significantly in the watershed over the past 20 years, mainly transferring from sloping terraces to the terraces and woodland. ET significantly increased area accounts for 47.6% of the total area in the valley, however, conspicuously reduced area accounts for 13.2%. The daily ET of different land use types had significant differences with the ET of water land and wood land was the largest. It is important that this study on the ET distribution can aid policy and decision makers for land use planning and environmental construction in Luoyugou watershed.

Validation of the use of THEMIS-B and THEMIS-C as a near-Earth solar wind monitor

Two THEMIS(Time History of Events and Macroscale Interactions during Substorms)spacecraft,B and C,began orbiting the Moon in 2011 and have since provided routine measurements of the plasma conditions in the lunar orbit.In this study,we systematically compare these measurements in near-Earth space with solar wind measurements obtained from the Lagrangian 1(L1)point and propagated to the Earth,including measurements in the OMNI database and from the Wind spacecraft.A statistical comparison between THEMIS data and data from the OMNI database from September 2011 to December 2017 showed that the Y and Z components of the magnetic field and the flow speed are generally consistent between the two data sets.The ion number density and the dynamic pressure measured by THEMIS in near-Earth space are lower than those in the OMNI database,suggesting possible variation in the solar wind environment while propagating from the L1 point to near-Earth space.We further show two examples in which near-Earth solar wind measurements are applied in calculating the magnetopause location and in quantifying the magnetic field response to interplanetary shocks.Both examples suggest that using solar wind data from near-Earth space achieves better results than using solar wind data from the L1 point.These results provide validation of THEMIS-B and THEMIS-C as an alternative monitor of the near-Earth solar wind environment.

Astrocytes in Post-traumatic Stress Disorder

Although posttraumatic stress disorder(PTSD)is on the rise,traumatic events and their consequences are often hidden or minimized by patients for reasons linked to PTSD itself.Traumatic experiences can be broadly classified into mental stress(MS)and traumatic brain injury(TBI),but the cellular mechanisms of MS-or TBI-induced PTSD remain unknown.Recent evidence has shown that the morphological remodeling of astrocytes accompanies and arguably contributes to fearful memories and stressrelated disorders.In this review,we summarize the roles of astrocytes in the pathogenesis of MS-PTSD and TBIPTSD.Astrocytes synthesize and secrete neurotrophic,proand anti-inflammatory factors and regulate the microenvironment of the nervous tissue through metabolic pathways,ionostatic control,and homeostatic clearance of neurotransmitters.Stress or trauma-associated impairment of these vital astrocytic functions contribute to the pathophysiological evolution of PTSD and may present therapeutic targets.