The present work is a comparative study between the foF2 variabilities for two equatorial regions (Ouagadougou: lat.</span><span style="font-family:""> </span><span style="font...The present work is a comparative study between the foF2 variabilities for two equatorial regions (Ouagadougou: lat.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">12</span><span style="white-space:nowrap;font-family:Verdana;">°</span></span><span style="font-family:Verdana;">21'</span><span style="font-family:Verdana;">N;long. </span><span style="font-family:""><span style="font-family:Verdana;">1</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;">30'</span><span style="font-family:Verdana;">E, dip.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">1.43</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;"> in Africa</span><span style="font-family:Verdana;"> and Huancayo: Lat.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">12</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;">S</span><span style="font-family:Verdana;">;Long.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">75</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;">12'W</span><span style="font-family:Verdana;"> in America) during solar cycles 20 and 21 minima and maxima phases under geomagnetic extreme conditions (quiet and disturb). Profiles from these two stations are very similar for all the seasons over the solar cycles. However, measured data from Huancayo station are higher than those from Ouagadougou station during winter with a reverse phenomenon for summer. Th展开更多
In this paper we report on the foF2 variabilities for two equatorial regions (Ouagadougou: Lat. 12.4°N;Long. 358.5°E, Dip. 1.43°S;and Manila: Lat. 14°36'15.12''N;Long. 120°58'5...In this paper we report on the foF2 variabilities for two equatorial regions (Ouagadougou: Lat. 12.4°N;Long. 358.5°E, Dip. 1.43°S;and Manila: Lat. 14°36'15.12''N;Long. 120°58'55.92''E;Dip. 0.6°S) during solar cycles 20 and 21 minima and maxima phases. Many previous works have argued on the diurnal and seasonal variation of foF2 for different solar events conditions for latitudinal position. But there are few investigations for Africa equatorial region longitudinal variation. The present paper’s goal is to outline possible similarity in foF2 behavior between variations for better understanding of physical process lead to some observed phenomenon in Asia-Africa equatorial sector. The F-layer critical frequency (foF2) data observed from the two equatorial ionosonde stations have been used for the present comparative study. The results show significant similarity between the critical frequency (foF2) seasonal variations over the time intervals 1976-1996. During day-time measured data from Manila station are higher than those from Ouagadougou station. That may lie in that Manila is closer to equatorial ionization crest region. During solar minimum phase, the longitudinal variation of foF2 shows two crossing points (11:00 UT and 22:00 UT) between the foF2 profiles form the two stations for all seasons regardless of the solar cycle. However during intense solar activity condition, the number of crossing-point between measured data from Manila and Ouagadougou stations varies by seasons and solar cycle. This phenomenon may be due to the compilations of severe activities (storms, coronal mass ejection, heliosheet fluctuations) during the solar maximum phases.展开更多
There is strong correlation among the ionospheric longitudinal structures of wavenumber-3(WN3),wavenumber-4(WN4),and eastward-propagating diurnal tides with zonal wave numbers s = 2 and 3(DE2 and DE3) in the upper atm...There is strong correlation among the ionospheric longitudinal structures of wavenumber-3(WN3),wavenumber-4(WN4),and eastward-propagating diurnal tides with zonal wave numbers s = 2 and 3(DE2 and DE3) in the upper atmosphere.The total electron content derived from the Global Ionospheric Maps of the Jet Propulsion Laboratory is used to deduce the latitudinally total electron content(ITEC) in the low-latitude ionosphere,and TIDE/TIMED observations are employed to obtain zonal and meridian winds of the mesopause and lower thermosphere.Through Fourier transformation,various ionospheric longitudinal harmonic components and tidal patterns are derived from the ionospheric and upper-atmospheric observations,and we compare the annual/inter-annual variations in ionospheric harmonic components WN3 and WN4 with those in atmospheric tides(DE2 and DE3).It is found that the annual and inter-annual variations in WN3 and WN4 are consistent with those in DE2 and DE3 zonal wind components respectively,while they are inconsistent with those in the meridian components.We then decompose the harmonic components into "tidal patterns",finding that the "DE2" and "DE3" patterns are the main parts of WN3 and WN4 respectively.Their annual and inter-annual variations are similar to those of atmospheric tidal patterns(DE2 and DE3).Complex correlation results show that correlation between the ionospheric "DE2" in WN3 and the atmospheric tidal DE2 zonal wind component is quite strong in the Northern Hemisphere,while that between the ionospheric "DE3" in WN4 and the atmospheric tidal DE3 zonal wind component is much stronger at low latitudes.At the same time,the contribution of the meridian wind component is very weak.Above all,the atmospheric tidal DE2 and DE3 patterns are important factors of the ionospheric WN3 and WN4 structures.展开更多
文摘The present work is a comparative study between the foF2 variabilities for two equatorial regions (Ouagadougou: lat.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">12</span><span style="white-space:nowrap;font-family:Verdana;">°</span></span><span style="font-family:Verdana;">21'</span><span style="font-family:Verdana;">N;long. </span><span style="font-family:""><span style="font-family:Verdana;">1</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;">30'</span><span style="font-family:Verdana;">E, dip.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">1.43</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;"> in Africa</span><span style="font-family:Verdana;"> and Huancayo: Lat.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">12</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;">S</span><span style="font-family:Verdana;">;Long.</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">75</span><span style="white-space:nowrap;font-family:Verdana;">°</span><span style="font-family:Verdana;"></span><span style="font-family:Verdana;"></span></span><span style="font-family:Verdana;">12'W</span><span style="font-family:Verdana;"> in America) during solar cycles 20 and 21 minima and maxima phases under geomagnetic extreme conditions (quiet and disturb). Profiles from these two stations are very similar for all the seasons over the solar cycles. However, measured data from Huancayo station are higher than those from Ouagadougou station during winter with a reverse phenomenon for summer. Th
文摘In this paper we report on the foF2 variabilities for two equatorial regions (Ouagadougou: Lat. 12.4°N;Long. 358.5°E, Dip. 1.43°S;and Manila: Lat. 14°36'15.12''N;Long. 120°58'55.92''E;Dip. 0.6°S) during solar cycles 20 and 21 minima and maxima phases. Many previous works have argued on the diurnal and seasonal variation of foF2 for different solar events conditions for latitudinal position. But there are few investigations for Africa equatorial region longitudinal variation. The present paper’s goal is to outline possible similarity in foF2 behavior between variations for better understanding of physical process lead to some observed phenomenon in Asia-Africa equatorial sector. The F-layer critical frequency (foF2) data observed from the two equatorial ionosonde stations have been used for the present comparative study. The results show significant similarity between the critical frequency (foF2) seasonal variations over the time intervals 1976-1996. During day-time measured data from Manila station are higher than those from Ouagadougou station. That may lie in that Manila is closer to equatorial ionization crest region. During solar minimum phase, the longitudinal variation of foF2 shows two crossing points (11:00 UT and 22:00 UT) between the foF2 profiles form the two stations for all seasons regardless of the solar cycle. However during intense solar activity condition, the number of crossing-point between measured data from Manila and Ouagadougou stations varies by seasons and solar cycle. This phenomenon may be due to the compilations of severe activities (storms, coronal mass ejection, heliosheet fluctuations) during the solar maximum phases.
基金supported by the KIP Pilot of the Chinese Academy of Sciences (KZCX2-YW-123)the National Natural Science Foundation of China (40974090 and 40636032)the National Basic Research of China (2006CB806306)
文摘There is strong correlation among the ionospheric longitudinal structures of wavenumber-3(WN3),wavenumber-4(WN4),and eastward-propagating diurnal tides with zonal wave numbers s = 2 and 3(DE2 and DE3) in the upper atmosphere.The total electron content derived from the Global Ionospheric Maps of the Jet Propulsion Laboratory is used to deduce the latitudinally total electron content(ITEC) in the low-latitude ionosphere,and TIDE/TIMED observations are employed to obtain zonal and meridian winds of the mesopause and lower thermosphere.Through Fourier transformation,various ionospheric longitudinal harmonic components and tidal patterns are derived from the ionospheric and upper-atmospheric observations,and we compare the annual/inter-annual variations in ionospheric harmonic components WN3 and WN4 with those in atmospheric tides(DE2 and DE3).It is found that the annual and inter-annual variations in WN3 and WN4 are consistent with those in DE2 and DE3 zonal wind components respectively,while they are inconsistent with those in the meridian components.We then decompose the harmonic components into "tidal patterns",finding that the "DE2" and "DE3" patterns are the main parts of WN3 and WN4 respectively.Their annual and inter-annual variations are similar to those of atmospheric tidal patterns(DE2 and DE3).Complex correlation results show that correlation between the ionospheric "DE2" in WN3 and the atmospheric tidal DE2 zonal wind component is quite strong in the Northern Hemisphere,while that between the ionospheric "DE3" in WN4 and the atmospheric tidal DE3 zonal wind component is much stronger at low latitudes.At the same time,the contribution of the meridian wind component is very weak.Above all,the atmospheric tidal DE2 and DE3 patterns are important factors of the ionospheric WN3 and WN4 structures.
