| Summary: | 碩士 === 國立中央大學 === 太空科學研究所 === 97 === In this thesis we use the S4 data of GPS L1 scintillations received by FORMOSAT-3/COSMIC satellites and the field-aligned electron precipitation data measured by the DMSP satellites in auroral region to study the distribution of scintillation events at high latitude ionosphere. We discuss how the changes of geomagnetic field disturbance (specified by Kp), auroral electrojet current (represented by AE) and energetic precipitating electron flux, will affect the spatial distribution as well as the intensity level of ionospheric scintillations. We choose the data of the 2007 summer and winter, and of the highlight period of a magnetic storm on May 23 for analyses. The main results of the analysis are summarized as follows.
From statistical analyses we found: (1) the morphology of the intensity distribution of scintillation (represented by S4 index) is approximately coincident with that of auroral electron (30eV ~30keV) precipitation flux in the magnetic local time versus magnetic latitude coordinate frame (MLT-MLAT). The scintillation phenomenon is most pronounced in the local time sector from sunset to the midnight regardless of seasons. However the strength of scintillation in the summer is generally stronger than that in the winter. (2) As Kp increases, strong scintillation events span wider MLT-MLAT region. (3)The distribution and intensity of scintillation respond most sensitively to the change of AE. As AE increases the morphology of strong scintillations expands to both high and low latitudes. Strong scintillation can be seen from the sunset to the post midnight hours.
Furthermore, by comparison of the simultaneous measurements of S4 with energetic (1-10keV) precipitating electrons during the expansion phase (06-14 UT) of the May 23 storm we found that the occurrence and variations of strong scintillation events are greatly affected by the distribution and dynamics of auroral precipitating electrons.
|
|---|
