| dc.description.abstract | The research investigates the diurnal, monthly, and annual variations of Midlatitude Electron Density Enhancement (MEDE) from 2007 to 2010 using FORMOSAT-3/COSMIC (F3/C) GPS occultation electron density profiles. The results indicate that MEDE exhibits effects related to local time, season, solar activity, and geomagnetic latitude. MEDE is more pronounced during nighttime to early morning, with the most significant occurrence at 0500 LT (local time), whereas it is less observable during the daytime. During the equinoxes, MEDE is evident in both hemispheres across various longitudes; during solstices, it is more prominent in the winter hemisphere. This may be due to the anomalous increase in electron density over the Weddell Sea and Okhotsk Sea in the summer hemisphere, making MEDE less noticeable. The distribution of MEDE is most evident around geomagnetic latitudes of ±40°N. The F2 layer peak electron density typically occurs at altitudes of 250-350 km, with the MEDE phenomenon becoming more pronounced at higher altitudes, suggesting the involvement of upper ionospheric plasma dynamics. The ionospheric electron density is proportional to solar activity; however, MEDE is relatively less apparent during high solar activity periods. By analyzing the electron density profiles from 0200 to 0500 LT at different longitudes and normalizing the electron density at various altitudes, we can explore the temporal variation of the latitude-altitude profile of MEDE, as well as the effects of magnetic declination and equatorial offset. Comparing the F3/C electron density profiles with the Horizontal Wind Model (HWM 14) results reveals that the formation of MEDE is primarily due to the downward diffusion of plasmaspheric plasma, influenced by neutral winds, resulting in different density distributions at various longitudes. | en_US |