Variability of ionospheric foF2 in the low latitude (Hainan) and comparisons with the high latitude
Abstract
Variability of the ionospheric F2-layer characteristics is of great importance to improve the daily ionospheric forecasting. Using the data from February 2002 to December 2010 observed with DPS-4 ionosonde in the low latitude station (Hainan), variability of the important ionospheric parameter (foF2) for different solar phases are statistically studied. Two methods are used to investigate the variability of ionospheric parameters: EOF (Empirical Orthogonal Function) analysis and the daily deviations from monthly-median values. For the EOF analysis, the first 4 dominant modes can explain more than 99% of the foF2 variance and the first 4 principle components have obvious physical meaning respectively. Generally the first principle component represents well the climatologic or average diurnal variation and the others are the supplement for the 1st one and represent the anomaly from average diurnal variation, such as foF2 peak at midnight in equinox at high solar activity. Their EOF coefficients all show obvious seasonal and solar cycle variations. Generally the EOF coefficients of the first 2 EOF modes show solar cycle well and have good linear relation with 10.7-cm solar radio flux and the others show seasonal, semiannual and annual variations. It is notable that about two-week period can be seen in all EOF coefficients. The data reconstructions are also done with first 4 EOF modes to investigate how much they can represent the observation data and the possible origin of the deviation. For the daily deviations from monthly-median values, the results show that the deviations have obvious diurnal, seasonal and solar cycle variation. Generally there is stronger deviation at nighttime than in the daytime and in equinox than in summer and winter. The biggest deviation occurs at about 0300 LT or at sunset generally. The variability of foF2 decreases from high solar activity to low solar activity. Comparisons of ionospheric variability between the low latitude (Hainan) and the high latitude (Irkutsk) in the East-Asia zone are also done.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.2132W