A Fabry-Perot interferometer,funded by the Meridian Project in China,was deployed at the Xinglong station(40.2°N,117.4°E) of the National Astronomical Observatories in Hebei Province,China.The instrument has been operating since April 2010,measuring mesospheric and thermospheric winds.The first observational data of winds at three heights in the mesosphere and thermosphere were analyzed,demonstrating the capacity of this instrument to aid basic scientific research.The wavelengths of three airglow emissions were OH892.0,OI 557.7,and OI 630.0 nm,which corresponded to heights of 87,98,and 250 km,respectively.Three 38-day data sets of horizontal winds,from April 5,2010 to May 12,2010,show clear day-to-day variations at the same height.The minimum and maximum meridional winds at heights of 87,98,and 250 km were-16.5 to 8.7 m/s,-24.4 to 15.9 m/s,and-43.6 to 1.5 m/s.Measurements of zonal winds were-5.4 to 7.6 m/s,2.3 to 23.0 m/s,and-22.6 to 49.3 m/s.The average data from the observations was consistent with the data from HWM93.The wind data at heights of 87 and 98 km suggest a semi-diurnal oscillation,clearly consistent with HWM93 results.Conversely there was a clear discrepancy between the observations and the model at 250 km.In general,this Fabry-Perot interferometer is a useful ground-based instrument for measuring mesospheric and thermospheric winds at middle latitudes.
We have studied 172 field-aligned currents(FACs) cases observed by the ClusterII satellites when they crossed the plasma sheet boundary layer(PSBL) in the magnetotail from July to October 2001.We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index.The main results indicated the followings:1) In the different geomagnetic activity levels,the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity.2) The density of FACs in PSBL increased monotonically with Kp index.In the storm main phase,the density of FACs increased dramatically,the maximum FACs approximately equaled 19.05 nA m 2 while Kp equaled 5.3) The variation of FACs density in PSBL was consistent with the variation of the Kp index.However,when AE<800 nT,FACs density in PSBL increased with increasing AE,and when AE>800 nT,it decreased with increasing AE.Therefore,our results suggested that the FACs density in PSBL had a closer correlation with Kp index.
The north-south component B_z of the Interplanetary Magnetic Field(IMF) and solar wind dynamic pressure P_d are generally treated as the two main factors in the solar wind that determine the geometry of the magnetosphere.By using the 3D global MHD simulations,we investigate the effect of the Interplanetary Electric Field(IEF) on the size and shape of magnetopause quantitatively. Our numerical experiments confirm that the geometry of the magnetopause are mainly determined by P_d and B_z,as expected.However,the dawn-dusk IEFs have great impact on the magnetopause erosion because of the magnetic reconnection,thus affecting the size and shape of the magnetopause.Higher solar wind speed with the same B_z will lead to bigger dawn-dusk IEFs,which means the higher reconnection rate,and then results in more magnetic flux removal from the dayside. Consequently,the dayside magnetopause moves inward and flank magnetopause moves outward.
This paper presents the Interplanetary Magnetic Field (IMF) observations at 0.72 AU measured by Venus Express (VEX) and 1 AU by Advanced Composition Explorer (ACE) in 2007.The distributions of daily averages of B are lognormal in both locations.The multiscale structure of the magnetic field fluctuations was described by studying the increments of B over a range scales from 10 min to 21.3 hours.All the Probability Distribution Functions (PDFs) can be described quantitatively by Tsallis distribution function.On the ecliptic plane from 0.72 AU to 1 AU,the entropy index q increases with distance over all scales,indicating the intermittency of turbulence is growing.The widths of the PDFs at 0.72 AU are larger than those at 1 AU at all scales,which indicating the turbulence at 0.72 AU is more intense than that at 1 AU.This helps us understand the nature and development of the magnetic field fluctuations.
