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Comparative Study of the Geomagnetic Activity Effect on foF2 Variation as Defined by the Two Classification Methods at Dakar Station over Solar Cycle Phases
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作者 Sibri Alphonse Sandwidi Doua Allain Gnabahou Frédéric Ouattara 《International Journal of Geosciences》 2020年第8期501-517,共17页
This paper aims to establish a comparison between both geomagnetic activity classification methods on foF2 diurnal variation over solar cycle phases. It concerns first a comparison of geomagnetic activity occurrences ... This paper aims to establish a comparison between both geomagnetic activity classification methods on foF2 diurnal variation over solar cycle phases. It concerns first a comparison of geomagnetic activity occurrences according to both classification methods;and second the geomagnetic effect on foF2 diurnal variation profiles as defined for the equatorial latitudes. The occurrences of the different disturbed geomagnetic activities (recurrent activity (RA), shock activity (SA) and fluctuant activity (FA)) according to both classifications (ancient classification (AC) and new classification (NC)) have been studied at Dakar ionosonde station (Lat: 14.8°N;Long: 342.6°E). Regarding both classifications, the RA occurs more during the decreasing phase. And it’s observed that the RA occurs the most during the increasing phase for the AC and during the minimum phase for the NC. The maximum gap of occurrence (<img src="Edit_e4627ea9-9a9a-4473-9017-202d04a16377.bmp" alt="" /><span><span style="font-family:Verdana;">) between both classifications is <span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">&#45</span></span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">11.1%</span><span style="font-family:Verdana;"> (for the negative value which is observed during the increasing phase) and </span><span style="font-family:Verdana;">+16.74%</span><span style="font-family:Verdana;"> (for the positive one which is observed during the decreasing phase). The occurrence of the SA in relation with both classifications is the lowest during the minimum phase and the maximum occurrence is observed during the maximum and decreasing phases, for the AC, with a value close to </span><span style="font-family:Verdana;">37%</span><span style="font-family:Verdana;"> and for the NC at the maximum phase with a percentage of </span><span style="font-family:Verdana;">54.47%</span><span><span style="font-family:Verdana;">. The maximum gap of occurrence (</span><img src="Edit_20fa141b-ecee-4e06-8024-144ba0969395.bmp" alt="" /></span></span><span style="font-family:Verdana;">) between both classifications is <span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">&#45</span></span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">17.85%</span><span style="font-family:Verdana;"> (for the negative value which is observed at maximum phase) and </span><span style="font-family:Verdana;">+13.53%</span><span style="font-family:Verdana;"> (for the positive one which is observed during the decreasing phase). For both classifications, the FA occurs the least during the minimum phase and the most during the maximum phase for the AC and at maximum and decreasing phases with percentage values of occurrence of roughly </span><span style="font-family:Verdana;">37%</span><span><span style="font-family:Verdana;"> for the NC. The maximum gap of occurrence (</span><img src="Edit_eecb8939-783e-4d43-b92c-80c528c1890b.bmp" alt="" /><span style="font-family:Verdana;"></span></span></span><span style="font-family:Verdana;">) between both classifications is <span style="font-size:10.0pt;font-family:;" "=""><span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">&#45</span></span>10% (for the negative value which is observed during the decreasing phase) and </span><span style="font-family:;" "=""><span style="font-family:Verdana;">+20.11%</span><span style="font-family:Verdana;"> (for the positive one which is observed during the maximum phase). foF2 diurnal profiles throughout solar cycle phases concerning the AC and the NC have been compared. The FA diurnal profiles don’t present a difference. The RA and the SA present a difference during minimum and increasing phases and the least at maximum and decreasing phases.</span></span></span> 展开更多
关键词 Geomagnetic Activity Classification Method Solar cycle phases foF2 Diurnal Profile
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Comparative Study of foF2 during Quiet Geomagnetic Activity with URSI and CCIR Predictions during the Phase Minimum of Solar Cycle 22
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作者 Moustapha Konaté Abidina Diabaté +2 位作者 Kadidia Nonlo Drabo Emmanuel Nanéma Frédéric Ouattara 《Journal of Applied Mathematics and Physics》 2022年第12期3562-3571,共10页
This paper investigates the performance of the latest International Reference Ionosphere model to predict the critical frequency at low latitudes in the African region. The variability of the critical frequency of the... This paper investigates the performance of the latest International Reference Ionosphere model to predict the critical frequency at low latitudes in the African region. The variability of the critical frequency of the F2 layer of the ionosphere (foF2) is studied for the different seasons of the phase minimum of solar cycle 22 during quiet geomagnetic activity at the Ouagadougou station. The data used are those provided by the ionosonde and the predictions of the two subprograms: International Radio Consultative Committee (CCIR) and International Radio-Scientific Union (URSI) of the 2016 version of the International Reference Ionosphere model. This study shows that, in general, URSI and CCIR of the IRI-2016 model are able to reproduce fairly well the variability of the critical frequency of the F2 layer of the ionosphere at low latitudes during the phase minimum at the Ouagadougou station. However, the model shows an almost homogeneous overestimation of the foF2 during the four seasons studied. The good response is observed between 0700 TL and 1900 TL for the available data. The agreement between the subroutine responses and the observed results is between reasonable and poor. The best match state response is obtained in winter with the CCIR subroutine. These results show that there is a need to improve both CCIR and URSI subroutines of the IRI-2016 model in low latitudes in the African region. 展开更多
关键词 FOF2 IRI IONOSONDE Quiet Time Periods Solar cycle phase Minimum
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Statistical Study of the Occurrence of Coronal Mass Ejections (CMEs) from 1996 to 2018 (Solar Cycles 23-24)
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作者 Salfo Kaboré Abdoul Kader Segda +1 位作者 Aristide Marie Frédéric Gyébré Frédéric Ouattara 《Journal of Modern Physics》 2024年第12期2238-2255,共18页
The objective of this article was to carry out a statistical study of the occurrences of CMEs from solar cycles 23 and 24 and to deduce interpretations as a contribution to a greater understanding of heliosphere dynam... The objective of this article was to carry out a statistical study of the occurrences of CMEs from solar cycles 23 and 24 and to deduce interpretations as a contribution to a greater understanding of heliosphere dynamics. Thus, from the statistical examination of the occurrences according to the phases it appeared that solar cycle 23 (SC23) counted 13207 occurrences of CMEs while 16510 were counted for solar cycle 24 (SC24). These occurrences of CMEs are correlated to the sunspot cycle because in each of these cycles we would note the predominance of the phase maximum (1478 for SC23 and 2338 for SC24) over the ascending phases (550 for SC23 and 1559 for the SC24) and descending (1197 for the SC23 and 1178 for the SC24) and these predominate on the minimum phase (206 for the SC23 and 834 for the SC24). However, the percentages per phase in each cycle show that SC23 was only predominant over SC24 at the maximum phase (43.08% for SC23 and 39.57% for SC24). From this correlation, some authors therefore suggest that the toroidal magnetic field would be the cause of the ejections of these CMEs. The annual statistical examination confirms the correlation with the sunspot cycle but nevertheless reveals in the descending phase of SC23 two unusual peaks in 2005 and 2007 and a drop-in sunspot activity of 42% from SC23 to SC24 while that we would note an increase in the activity of CME occurrences of 36% at SC24, thus suggesting that CMEs can occur without the toroidal magnetic field being the cause, particularly from the coronal holes. The seasonal statistical examination shows for its part that out of the total of 29717 occurrences of CMEs of the two cycles that spring (28%) was the most active than summer (25%) and summer over autumn (24%) and finally autumn over winter (23%) thus revealing that: The ascending phase of the cycle was only the most active during the winter seasons in spring and the descending phase only during the rest of the seasons. Finally, the monthly statistical examination of the occurrences of CMEs corroborates the seasonal statistical examination by the presence of two maximum peaks (May and October) and two minimum peaks (February and August). 展开更多
关键词 CMES OCCURRENCE Solar cycle phase of the Solar cycle SEASONS MONTHS
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Arg-X Protease-Sensitive in Supramolecular Structures of Interphase Cell Nucleus during Growth Morphogenesis Mature Germs of Wheat 被引量:1
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作者 Ivanov Ruslan Vafina Gulnara Ivanova Evilina 《Journal of Life Sciences》 2012年第12期1351-1355,共5页
Abstract: In the present study was investigated Arg-X protease-sensitive in supramolecular-genome compartments (nucleoplasm, chromatin, nuclear matrix), during the period of the transcriptional activation of chroma... Abstract: In the present study was investigated Arg-X protease-sensitive in supramolecular-genome compartments (nucleoplasm, chromatin, nuclear matrix), during the period of the transcriptional activation of chromatin when the growth processes was initiated in the mature germs of winter and transformed from it spring wheat. The germs have been separated from endosperm from 0 h (air-dry seed) up to 21 h in each 3 h after the start of seeds soaking. Cell nucleus have been allocated from germs and cleared, and then from them supramolecular-genome compartments were extracted by increasing ionic strength of solution. The Arg-X (tryptase) activity was assessed by cleavage of Arg-X bonds in the arginine-enriched protein protamine in all nuclear fractions. In the present study have shown what Arg-X protease-sensitives zones can be located on the supramolecular structures of chromatin matrix in processes of realization of ontogenetic programs of development in mature germs of the winter and transformed from it spring wheat. Arg-X protease-sensitive can translocate and coordinated in heteropolymer structures on the same genetic matrix. Questions of epigenetic mechanisms are discussed. 展开更多
关键词 Arg-Xprotease-sensitive Gl phase of cell cycle supramolecular structures cell nuclei spring and winter wheat.
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Effect of Exogenous bFGF on the Proliferation of Human Adenoid Cystic Carcinoma ACC-2 Cells
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作者 丁蕾 朱声荣 +1 位作者 谢三祥 吴祥冰 《Journal of Huazhong University of Science and Technology(Medical Sciences)》 SCIE CAS 2008年第2期227-229,共3页
To observe the effects of basic fibroblast growth factor (bFGF) on human adenoid cystic carcinoma ACC-2 cell line proliferation and ERK, cyclin D1/p21^waf/cip1 signaling pathways, human adenoid cystic carcinoma cel... To observe the effects of basic fibroblast growth factor (bFGF) on human adenoid cystic carcinoma ACC-2 cell line proliferation and ERK, cyclin D1/p21^waf/cip1 signaling pathways, human adenoid cystic carcinoma cells (ACC-2) were cultured and the influence of bFGF of different concentrations on cell proliferation was determined by MTT. Protein was detected by immuno-precipitation and ERK activity by using ERK agent kit. p-ERK1/2 and down-stream cyclin D1, p21^waf/cip1 expression were detected by Western blotting and the interfering role of mitogen protein-activated kinase (MEK) suppressor U0126 in the afore-mentioned indicators was examined. MTT demonstrated ACC-2 cell proliferation was substantially enhanced by bFGF, immuo-precipitation displayed ERK activity was up-regulated by bFGF, and immuno-imprinting also showed p-ERK1/2, cyclin D1 expression was greatly enhanced and p21^waf/cip1 expression was inhibited by bFGE U0126 suppressed the effect of bFGF. It is concluded that bFGF can promote the proliferation of human adenoid cystic carcinoma ACC-2 cells, and its pathways are associated with the up-regulated activity and expression of p-ERK1/2, inhibited p21waf/cip1 expression and enhanced cyclin D1 expression. 展开更多
关键词 basic fibroblast growth factor adenoid cystic carcinoma extracellular signal-regulated kinase cell cycle phase protein D1
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Ringing cancellation in Carr-Purcell-Meiboom-Gill-type sequences
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作者 Shin Utsuzawa Marcus Donaldson Yi-Qiao Song 《Magnetic Resonance Letters》 2022年第4期233-242,共10页
We propose a four-step phase cycling scheme that can cancel ringings from both the excitation and the refocusing pulses in Carr-Purcell-Meiboom-Gill(CPMG)measurements.It allows accurate measurements of the first echo ... We propose a four-step phase cycling scheme that can cancel ringings from both the excitation and the refocusing pulses in Carr-Purcell-Meiboom-Gill(CPMG)measurements.It allows accurate measurements of the first echo with short echo spacing tE,yielding improved precision of porosity,permeability,and fluid type identification in porous media study,at a cost of~25%signal reduction.In our example,we achieved tE=100 ms on a 6.8 MHz unilateral NMR sensor without using a Q-switch.These methods can be integrated in all nuclear magnetic resonance(NMR)protocols using CPMG,such as relaxation(T1,T2)and diffusion measurements,and do not require additional hardware(e.g.,Qswitches)to cancel ringing(although it can be used with a Q-switch to further reduce residual ringing). 展开更多
关键词 CPMG Ringing cancellation phase cycling
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Contribution of the International Reference Ionosphere-2016 Model in the Evidence of the Winter Anomaly
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作者 Moustapha Konaté Raoul Ilboudo +2 位作者 Kadidia Nonlo Drabo Emmanuel Nanéma Frédéric Ouattara 《Open Journal of Applied Sciences》 CAS 2022年第11期1749-1757,共9页
This study is a contribution to the estimation of the winter anomaly in the F2 layer of the ionosphere at low latitudes. The aim is to study the variability of the virtual height (hmF2) of the F2 region of the ionosph... This study is a contribution to the estimation of the winter anomaly in the F2 layer of the ionosphere at low latitudes. The aim is to study the variability of the virtual height (hmF2) of the F2 region of the ionosphere through the predictions of the latest International Reference Ionosphere model (IRI-2016). The present work allows analyzing the temporal evolution of hmF2 according to the different phases of three (3) solar cycles during the quiet geomagnetic activity to estimate the seasonal anomaly at the Ouagadougou station. The analysis of the seasonal profiles shows that the variability of hmF2 is: 1) strongly linked to the solar cycle activity, 2) dependent on the season and 3) variable from one cycle to the next for the same phase. It appears that hmF2 increases during the ascending phase to reach its maximum value at the phase maximum. During the descending phase, it decreases until the phase minimum where it finds its minimum value. The difference between winter and summer on the hmF2 values for each phase of the cycle is obtained at the phase minimum and is estimated to be at least 16 km. In low latitudes, solar irradiation is greater in summer than in winter. From this study, hmF2 values are larger in winter compared to summer indicating an anomaly in the virtual height of the F2 layer of the ionosphere through the predictions of IRI-2016 at the Ouagadougou station. 展开更多
关键词 Winter Anomaly IRI hmF2 Quiet Day Solar cycle phases
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foF2 Diurnal Variability at African Equatorial Stations:Dip Equator Secular Displacement Effect
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作者 Doua A.Gnabahou Frederic Ouattara +1 位作者 Emmanuel Nanema Francois Zougmore 《International Journal of Geosciences》 2013年第8期1145-1150,共6页
The paper goal is to analyze the variability of foF2 at African equatorial stations and the effect of dip angle on this variability. The gap between the dip angle of Dakar and Ouagadougou is superior to that between D... The paper goal is to analyze the variability of foF2 at African equatorial stations and the effect of dip angle on this variability. The gap between the dip angle of Dakar and Ouagadougou is superior to that between Djibouti and Ouagadougou. The trend of the dip angle at Ouagadougou and Dakar decreases while that of Djibouti increases. The relative position of the station with respect to the equator and the trend sign explains the difference observed in foF2 variability at Dakar station and at the two other stations. At Djibouti and Ouagadougou, foF2 exhibits noon bite out profile during all solar cycle phases while at Dakar observed profile is dome or plateau during the maximum and the predominance afternoon peak for the other solar cycle phases. 展开更多
关键词 Dip Angle FOF2 Diurnal Variability Solar cycle phase
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Statistical Study of foF2 Diurnal Variation at Dakar Station from 1971 to 1996:Effect of Geomagnetic Classes of Activity on Seasonal Variation at Solar Minimum and Maximum
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作者 Ali Mahamat Nour Ouattara Frederic +3 位作者 Zerbo Jean Louis Gyebre Aristide Marie Frederic Nanema Emmanuel Zougmore Francois 《International Journal of Geosciences》 2015年第3期201-208,共8页
The statistical study of F2 layer critical frequency at Dakar station from 1971 to 1996 is carried out. This paper shows foF2 statistical diurnal for all geomagnetic activities and all seasons and that during solar ma... The statistical study of F2 layer critical frequency at Dakar station from 1971 to 1996 is carried out. This paper shows foF2 statistical diurnal for all geomagnetic activities and all seasons and that during solar maximum and minimum phases. It emerges that foF2 diurnal variation graphs at Dakar station exhibits the different types of foF2 profiles in African EIA regions. The type of profile depends on solar activity, season and solar phase. During solar minimum and under quiet time condition, data show?the signature of a strength electrojet that is coupled with intense counter electrojet in the afternoon. Under disturbed conditions,?mean intense electrojet is observed in winter?during fluctuating and recurrent activities. Intense counter electrojet is seen under fluctuating and shock activities in all seasons coupled with strength electrojet in autumn. In summer?and spring under all geomagnetic activity condition, there is intense counter electrojet. During solar maximum, in summer and spring there is no electrojet under geomagnetic activity conditions.?Winter shows a mean intense electrojet. Winter and autumn are marked by the signature of the reversal electric field. 展开更多
关键词 foF2 Diurnal Variation Solar cycle phases Geomagnetic Activity Classes Seasonal Effects E Region Electric Currents
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Determination of inter-satellite relative position using X-ray pulsars 被引量:1
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作者 Da-jun FENG Lu-ping XU +1 位作者 Hua ZHANG Shi-bin SONG 《Journal of Zhejiang University-Science C(Computers and Electronics)》 SCIE EI 2013年第2期133-142,共10页
Pulsars are rapidly rotating neutron stars that generate pulsed electromagnetic radiation.A new method for intersatellite relative position determination between a global navigation satellite system(GNSS) and spacecra... Pulsars are rapidly rotating neutron stars that generate pulsed electromagnetic radiation.A new method for intersatellite relative position determination between a global navigation satellite system(GNSS) and spacecraft using X-ray pulsars is proposed in this paper.The geometric model of this method is formulated,and two different resolution algorithms are introduced and analyzed.The phase cycle ambiguity resolution is investigated,and a new strategy is proposed and formulated.Using the direct vector parameters of the pulsar,geometric dilution of precision(GDOP) is studied.It is shown that this method has advantages of simplicity and efficiency,and is able to eliminate the clock errors.The analytical results are verified numerically via computer simulations. 展开更多
关键词 Pulsar navigation Position determination phase cycle ambiguity Geometric dilution of precision(GDOP)
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