Characteristics Of High-Latitude Ionosphere And The Dynamics Of Its Coupling With Magnetosphere

Due to solar EUV radiation,the upper atmosphere on Earth begins to get ionized and transforms into ionosphere above the height of 60 km.The ionosphere at high latitude is vulnerable to solar wind,interplanetary magnetic field and a variety of local occurred dynamic processes,which lead to aurora,magnetic disturbances and even the high latitudinal ionospheric disturbances in quiet days.Moreover,the ionospheric electron density are easily affected by some physical processes such as the energetic particle precipitation,neutral wind and electron field drift,etc.The polar ionosphere and magnetosphere tightly couple together by the existence of convection electric fields,particle precipitation and field-aligned currents,which plays an important role in the solar-wind-magnetosphere-ionosphere and thermosphere coupling process.The ionosphere scale height is regarded as one of the key ionospheric parameters for its intrinsic connection to variations of the ionosphere electron density profile and the gradient change of electron density in ionosphere,which are related to ionospheric dynamics,ionospheric plasma temperature,ionospheric plasma composition,etc.Though a lot of work have been done about variations of the ionospheric scale height,knowledge of the behavior of polar HmF2 is still insufficient.In order to deeply understand the characteristics of polar ionosphere and the mechanism of polar ionosphere-plasmasphere-magnetosphere coupling,we have done several studies as shown below:(1)Based on a large number of observations from EISCAT ESR radar,we propose and validate a new method for calculating the ionosphere HmF2 at high latitudes,by adopting a least square method to fit the electron density profile above the F2 layer peak to derive the HmF2.(2)Based on observations between 1997 and 2008 from the EISCAT ESR radar,we first obtain the statistical characteristics of the polar ionosphere HmF2 changing over local time(LT),season and solar activity under conditions of geomagnetic quiet days(Kp?2)and geomagnetic disturbed days(2<Kp?5)in a complete solar cycle,respectively.Based on non-linear fitting,we also establish an empirical model of the polar ionosphere in quiet days.Moreover,we obtain the linear correlation coefficients between the polar ionosphere HmF2 and the Kp index through linear regression calculations.(3)During the energetic ion injection event,we discover a new production mechanism of SAPS based on conjugate observations of DMSP F13 and NOAA 15 satellites.That is,the downward FACs in the outer boundary of the ring current(RC)flowing into the subauroral ionosphere,can cause strong SAPS.(4)We establish a model of magnetic flux tube convection on the geomagnetic equatorial plane.By comparing with GPS TEC,we found that the calculated drift trajectory is highly consistent with the SED plume,which verifies the rationality of the model.