共查询到4条相似文献,搜索用时 0 毫秒
1.
O.A. Maltseva N.S. MozhaevaT.V. Nikitenko 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Modern use and study of the auroral region needs to attract a wider class of models for describing conditions of radio wave propagation in the ionosphere. In this paper the possibilities of the International Reference Ionosphere model, well-proven and widespread in the mid-latitudes, are investigated in the high latitude zone. Model and measured values of the critical frequency foF2 for two mid-latitude stations (Juliusruh and Goosebay) and four high-latitude ones (Loparskaya, Sodankyla, Sondrestrom, Thule) are compared. Deviations of medians, variations from day to day and solar activity trends seemed to be similar for both areas. This similarity is irrespective of the RZ12 index. Special attention is paid to the TEC parameter and its determination using 6 versions of models, a new version of the model IRI2010 (IRI-Plas) among them. It is shown that the IRI-Plas model significantly improves the definition of TEC in contrast to the versions of IRI2007 and the new model NeQuick. The use of the median of the experimental equivalent slab thickness, together with the current values of the TEC, increases by a factor of two the agreement between calculated and measured foF2 values as compared with the variations from day to day. This allows foF2 to be defined in near-real time. 相似文献
2.
Arun Kumar Singh Rupesh M. Das Shailendra Saini 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(11):3558-3567
The solar cycle variation and seasonal changes significantly affects the ionization process of earth’s ionosphere and required to be monitored in real time basis for regional level refinement of existing models. In view of this, the present study has been carried out by using the ionospheric Total Electron Content (TEC) data observed with the help of Global Ionospheric Scintillation and TEC monitoring (GISTM) system installed at Indian Antarctic Research Station, “Maitri” [70°46′00″S 11°43′56″E] during the ascending phase of 24th solar cycle. The daily values of solar extreme ultraviolet (EUV) flux (0.1–50?nm wavelength), 10.7?cm radio flux F10.7 and Sunspot number (SSN) has been taken as a proxy to represent the solar cycle variation to correlate with TEC. The linear regression results revels better correlation of TEC with EUV flux rather than F10.7 and SSN. Also, the EUV and TEC show better agreement during summer as compared to winter and equinox period. Correlation between TEC and EUV appears significantly noticeable during ten internationally defined quiet days of each month (stable background geophysical condition) as compared to the overall days (2010–2014). Further, saturation effect has been observed on TEC values during the solar maxima year 2014. The saturation effects are more prominent during the night hours of winter and equinox season due to transportation losses manifested by the equator-ward direction of meridional wind. 相似文献
3.
A.O. Adewale E.O. OyeyemiU.D. Ofuase 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The observed ionospheric F2 critical frequency (foF2) values over a South Africa mid-latitude station, Grahamstown, (geographic coordinates: 33.3°S, 26.5°E), were analysed and compared with International Reference Ionosphere (IRI) model, using the CCIR (Comite´ Consultatif International des Radio communications) and URSI (Union Radio-Scientifique Internationale) coefficients, during four geomagnetically disturbed days in the year 2000. These days are April 5, May 23, August 10 and September 15. The data were analysed for five days around the storm day. Comparisons between the IRI-2001 predicted foF2 values, using both CCIR and URSI coefficients and the observed values are shown with their root-mean-square error (RMSE) and the relative deviation module mean (rdmm) for the various storm periods. The CCIR option performed more accurately than the URSI option. 相似文献
4.
Man-Lian Zhang Weixing WanLibo Liu Baiqi Ning 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
In this paper, latitudinal profiles of the vertical total electron content (TEC) deduced from the dual-frequency GPS measurements obtained at ground stations around 120°E longitude were used to study the variability of the equatorial ionization anomaly (EIA). The present study mainly focuses on the analysis of the crest-to-trough TEC ratio (TEC-CTR) which is an important parameter representing the strength of EIA. Data used for the present study covered the time period from 01 January, 1998 to 31 December, 2004. An empirical orthogonal function analysis method is used to obtain the main features of the TEC-CTR’s diurnal and seasonal variations as well as its solar activity level dependency. Our results showed that: (1) The diurnal variation pattern of the TEC-CTR at 120°E longitude is characterized by two remarkable peaks, one occurring in the post-noon hours around 13–14 LT, and the other occurring in the post-sunset hours around 20–21 LT, and the post-sunset peak has a much higher value than the post-noon one. (2) Both for the north and south crests, the TEC-CTR at 120°E longitude showed a semi-annual variation with maximum peak values occurring in the equinoctial months. (3) TEC-CTR for the north crest has lower values in summer than in winter, whereas TEC-CTR for the south crest does not show this ‘winter anomaly’ effect. In other words, TEC-CTR for both the north and south crests has higher values in the northern hemispheric winter than in the northern hemispheric summer. (4) TEC-CTR in the daytime post-noon hours (12–14 LT) does not vary much with the solar activity, however, TEC-CTR in the post-sunset hours (19–21 LT) shows a clear dependence on the solar activity, its values increasing with solar activity. 相似文献