Characteristics And Modeling Research Into The Ionospheric Upflows At Various Geomagnetic Activity Levels

The ionospheric plasma comes from the photoelectric ionization by the solar ultraviolet as well as extreme ultraviolet,heating by the thermal electron and proton precipitating from the magnetosheath through the open magnetic field lines and from the magnetotail reconnection area.However,it is a comparatively complicated problem that the compositions of the magnetospheric plasma.Although substantial details suggest that the solar wind plasma input and ionspheric upflow ions are the two dominant plasma sources,there still remain fundamental questions about the proportionality of the two and the transport pathes.So far,a consentient view suggests the ionospheric upflows and outflows as the quite important composition,but it is still not clear to astrophysicist on the upflow magnitude and spatial distribution characteristics.Consequently,our researches into the referred questions are rather frame and essential to understand the ionspheric cold plasma heating and acceleration mechanisms.Using the observations from TEAMS instrument onboard FAST satellite from March 2000 to October 2005,which exactly located on the decline phase of solar cycle 23,the following points are individually investigated from the perspectives of geomagnetic disturbance,ions energy,ions mass charge ratio based on the UFI definition in this paper.?).The ions upflow source regions and the disturbance-variations.?).Hemispheric distribution characteristics of upflow intensities(including rate and energy flux)and hemispheric asymmetry of disturbance-variations.?).Variations on upflow intensity between ions with various energies.?).Variations between ions with different masses.?).The mechanisms for ions heating and acceleration,will be discussed after individually building the empirical models for upflow intensities.A slice of conclusions are made in our paper,some of them are consistent with previous studies,such as intensity enhancement by the geomagnetic disturbance,steady upflow source regions,dawn-dusk and noon-midnight asymmetries of upflow rates,the intensity of H+exceeding sharply than these of O+,increasement with increasing altitude and solar cycle positive-correlation.And,couples of new characteristics are stated,such as hemispheric asymmetry of distrubance-enhancement,'cold upflows' and 'thermal upflows' from the dayside high and nightside auroral magnetic latitudes,respectively,disturbance-enhancement inconsistency between high and low enegy level ions,increasing fraction of upflow O+ during disturbed times.In addition,the comparisons are made on the intensities of dayside cusp currents and auroral field-aligned currents by discussing the day-night asymmetry of upflow rate.Various influence factors and heating mechanisms are examined at alternative altitudes.Our results show clear evidences for the unequal disturbance-enhancement between the two hemispheres to every mass and energy level ions,which is called hemispheric asymmetry of upflow rate disturbance-enhancement.By comparing the source regions of various energy level ions,low energy(80-1keV)ones are found to transported upwards top on the dayside polar cap region,which is called 'cold upflows',and high energy(1-12keV)ones do that from the nightside auroral acceleration area,which is called 'thermal upflows'.The phenomenon evidently indicates the dominant heating sources from energetic particles precipitated from the magnetosheath and the magnetotail,but the low energy ions are only constrained to upflow through the open field lines while the other high energy ones could jump into the loss cones of closed field line in the magnetotail.There also exists significant inconsistency on disturbance enhancements that the increasements are more impressive to high energy upflowing ions.By a comprehensive analysis of upflow intensities for all geomagnetic activity levels and each mass,the rates on the nightside aurora are calculated 20-40%larger than those on the dayside cusp.This day-night asymmetry probably explains the weaker cusp current intensity than the aurora field-aligned currents.About the different ion heating and acceleration mechanisms at alternative altitudes,the energy dissipating on high altitude ion heating,usually>2RE,is generally provided by the solar wind input and magnetotail reconnection energy injection,while the dissipation on low altitude ion heating and acceleration,2000-4200 km in this study,is considered to be positively correlated to the solar EUV and UV fluxes.Impressively,the seasonal variations are not clearly found,disregarding the exact pitch angle extents for ions beams and conics,respectively.Finally,although future improvements are in urgent need,the empirical regression models built for simulating FAST altitude ions upflow spatial distribution characteristics have already shown practicable capability on simulating steady upflow source regions,the upflow rate's disturbance-enhancement as well as its dawn-dusk asymmetry.