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1.
利用全球203个电离层测高仪台站的F_2层临界频率(f_oF_2)和E层临界频率(f_oE),以及美国喷气推进实验室(JPL)提供的电离层总电子含量(TEC)地图数据统计分析了电离层春秋分(March Equinox and September Equinox,ME and SE)不对称的特点.基于电离层参量随年积日(Day of Year,DoY)和太阳活动指数F_(10.7)变化的傅里叶级数模型,对f_oF_2、f_oE及TEC数据分别进行最小二乘法拟合,将电离层参量归算到低太阳活动(F_(10.7)=80)、中等太阳活动(F_(10.7)=150)和高太阳活动(F_(10.7)=200)水平.该方法定量分离了实际观测数据中包含的电离层参量随季节和太阳活动的变化,因而得到了更为定量、精确的电离层春秋分不对称性特征.分析了不同地方时(LT)的春秋分不对称性指数(Asymmetry Index,AI)和春秋分差值Δ(=ME-SE)的全球分布特征与太阳活动依赖性.结果表明,foE日出时全球主要表现为9月分点值高于3月分点值,午后春秋分不对称性几乎消失,而日落时则反转为3月分点值高于9月分点值;f_oF_2日出时除少数地区外也主要表现为9月分点值高于3月分点值,而其他时段则相反;TEC日出时低太阳活动时的全球及中高太阳活动时的低纬地区表现为9月分点值高于3月分点值,而其他时段则相反.fo_E春秋分不对称性受太阳活动影响较弱,而f_oF_2和TEC的春秋分不对称随太阳活动有明显的变化,其3月分点值相对于9月分点值增加.计算了F_2层峰高(h_mF_2)处对应的氧氮浓度比([O]/[N_2],由大气模型NRLMSISE-00计算得到)和h_mF_2的春秋分不对称性,提取了TEC年变化的幅度及相位信息.氧氮浓度比和h_mF_2的春秋分不对称性能够部分解释电离层的春秋分不对称性,而TEC春秋分不对称的全球分布特征可以用TEC年变化的相位的全球分布解释. 相似文献
2.
GPS（Global Positioning System）周跳是一种GPS信号异常现象.研究发现一定仰角以上的GPS周跳与电离层闪烁有关,是强电离层闪烁造成的GPS载波信号短时失锁现象,因此其可作为表征电离层闪烁效应的参量.本文通过分析由中国低纬度地区GPS台站原始观测数据提取的GPS周跳发生率与地方时、季节、太阳活动以及磁活动之间的关系,开展电离层闪烁效应与这几种参量之间关系的模式化研究.研究结果表明：（1）周跳发生率存在着地方时分布,发生时段主要在日落19：00LT后到午夜02：00LT之前,发生次数在22：00LT左右达到极大,然后缓慢减少,这一变化特点可以用自变量为地方时的Chapman函数形式来描述;（2）周跳发生率存在年变化特点,主要发生在年积日45~135天（春分季节）和225~315天（秋分季节）,可以通过高斯函数来描述每个分季闪烁效应的变化特点;（3）可以利用太阳辐射指数F10.7作为描述周跳随太阳活动周变化的参量,根据周跳随太阳活动周的变化特点,我们使用一个以F10.7为自变量的三次函数来描述这种变化;（4）电离层闪烁与磁活动的关系比较复杂,由于大多数情况下表现为磁活动对电离层闪烁的抑制作用,在本研究中使用一个以地磁活动指数Ap为自变量的的平方根函数来拟合这种变化. 相似文献
3.
本文利用通量管积分方法,对磁南北半球分别沿磁力线积分,研究背景电离层南-北半球不对称以及中性风场和磁偏角随经度的变化对广义瑞利-泰勒不稳定性和电离层不规则结构生成和发展的影响.结果表明,通量管积分广义瑞利-泰勒不稳定性线性增长率存在显著的半球不对称,南北半球不对称的中性风场是导致电离层不规则结构呈南北分布不对称的重要因素;随经度变化的中性风场和磁偏角对瑞利-泰勒不稳定性的经度变化有重要影响,它们可能是导致不规则结构出现率经度变化的主要控制因素. 相似文献
4.
本文利用北京地区的北京台（BJI）和北京十三陵台（BMT）的地磁场X、Y和Z分量时均值数据,研究了1960年至2013年期间该地区地磁场Sq强度的季节变化和长期变化.结果表明：（1）BJI台和BMT台的地磁场Sq不仅变幅相近,而且具有一致的地方时变化、季节变化、太阳活动周变化和长期变化.（2）BJI台和BMT台Sq强度的逐月变化,其中ASq（X）主要表现为春秋增强而冬夏减弱的季节变化.ASq（Y）呈现出夏季增强的半年变化.ASq（Z）变化较为复杂.虽然在5月和9月出现减小,但是总体来看,其变化曲线也具有夏季增强的半年变化特征.同时,Sq强度与太阳活动F107指数之间存在明显的正相关关系,具有一致的11年太阳活动周变化和长期变化,反映出了Sq与太阳活动之间的密切关系.（3）BJI台和BMT台Sq强度差值dASq表明,在大多数年份,两个台站的Sq强度之差一般不超过±2 nT,同时没有明显的季节或年周期变化特征.在2000年和2001年太阳活动高年,dASq出现显著增强,最大可达12.3 nT.反映出了北京地区Sq场强度梯度的剧烈扰动与太阳活动之间的密切关系,意味着在太阳活动高年,Sq电离层发电机电流的局部结构可能发生了明显的改变. 相似文献
5.
利用球冠谐分析法对2009年我国35个绝对观测地磁台站的Sq太阳静日变化进行内外源场分离,反演得到三个劳埃德季节(冬季D,分点E,夏季J)相应的内、外源等效电流体系,结果表明Sq外源电流体系在该区域D、E、J三个季节的电流涡中心强度分别为56.2 kA、137.7 kA、137.9 kA,电流涡中心位置的地方时由冬季的1124LT前移至夏季的约1030LT;Sq内源电流体系在该区域D、E、J三个季节的电流涡中心强度分别为21.1 kA、63.4 kA、72.7 kA,电流涡中心位置的地方时由冬季的1100LT前移至夏季的约1000LT. 相似文献
6.
使用COSMIC掩星和垂测仪,探测2011—2012年北京地区电离层临界频率数据,比较不同探测手段获取的电离层特征参量随地方时和地磁季节相关性的变化。研究表明:2组数据具有较好的相关性;标准偏差随地方时变化,日出时6:00 LT开始增大,日落时16:00LT到次高值,19:00LT达最大值后开始下降;标准偏差随地磁季节变化,夏季最小,冬季最大。分析认为,电子密度在垂直和水平方向上的梯度变化,造成掩星反演误差增大,可能导致了数据相关性在不同地磁季节和地方时刻的相应变化。 相似文献
7.
本文利用DMSP卫星测量数据和傅里叶分解和重构方法,研究了地磁平静期顶部电离层总离子密度(Ni)经度结构的多重波数特征及波数4的年变化、逐年变化、地方时差异和随倾角的变化.傅里叶分解和重构的结果表明,顶部电离层平均Ni的经度结构中同时含有以波数1至波数4为主的多重分量,不同波数分量的幅度和相位各不相同.对波数4分量的分析表明,波数4的幅度在春秋季最强,北半球夏季高于冬季;随太阳活动水平增强,波数4分量的幅度增高,至太阳活动高年幅度达到最高,此后随太阳活动水平降低而减小,与F10.7呈正相关;春秋季和北半球夏季波数4分量在傍晚最强,晚上和上午次之,黎明最弱,从09LT到21LT,波数4的相位依次滞后,暗示向东移动.分析还发现,日落期间波数4幅度依赖倾角,春秋季随倾角的变化呈双峰结构,两个极大出现在倾角±18°附近,暗示赤道等离子体喷泉效应对顶部电离层经度结构的控制作用. 相似文献
8.
为构建赤道-低纬电离层不规则结构和闪烁活动出现率的理论模型,本文根据分析赤道-低纬电离层的广义Rayleigh-Taylor(R-T)不稳定性得到的三维线性增长率的表达式,计算分析了线性增长率随地方时的变化特征.并选取计算得到的每日增长率的极大值表征每日的线性增长率,分析增长率随季节、太阳活动和地理经度的变化特征以及逐日变化特征,建立三维广义R-T不稳定性线性增长率的理论统计特征模型,发现增长率表现出显著的随地方时、季节、太阳活动和地理经度以及逐日变化特征.通过比较分析增长率的变化特征与不规则结构和闪烁活动的变化特征,发现三维广义R-T不稳定性的线性增长率能较好地反映不规则结构和闪烁活动随季节、太阳活动、地理经度以及逐日变化规律.本文建立的R-T不稳定性的三维线性增长率的统计特征模型可用于构建赤道-低纬电离层不规则结构和闪烁出现率的理论形态特征模型. 相似文献
9.
用1957~2006年间515个主相单步发展的磁暴事件,分析东亚扇区4个中低纬台站的电离层扰动类型及电离层暴开始时间,得到该地区电离层暴随纬度、季节和地方时的分布规律.研究表明,中纬区负暴明显,低纬区正暴明显;夏季负暴比正暴多,冬季正暴比负暴多,春秋季正负暴分布表现出明显的纬度差异.在东亚扇区,中纬区负暴开始时间主要分布在夜间及清晨时段,且在正午至午后时段极少发生.低纬区正暴开始时间主要发生在白天时段,且在夜间18~21 LT时段也易发生正暴.中低纬电离层正相暴平均延迟时间在10 h以内,负相暴平均延迟时间在10 h以上,且中纬区延迟时间明显比低纬区短.电离层暴延迟时间与磁暴主相开始时间对应的地方时很相关,正相暴对白天发生的磁暴比对晚上发生的磁暴响应快些,而负相暴正好相反.但电离层暴延迟时间与磁暴强度之间并没有十分明显的依赖关系. 相似文献
10.
本文采用欧洲22个台站的电离层F2层峰值电子密度NmF2，分析了其逐日变化分量的相关距离S，着重研究了S的周日变化、季节变化及其随太阳活动和地磁活动的变化.首先用指数型函数模式来拟合任意两站间电离层逐日变化的相关系数R随间距d的变化，由此估算出逐日变化的相关距离S.详细研究了S在不同的季节（春季、夏季、秋季和冬季），不同的地磁活动（平静和扰动）及不同的太阳活动（低、中和高）随世界时的变化（周日变化）.结果表明：（１）S的范围一般为400～1600 km；（２）S值在白天比夜间大；（３）S值具有季节变化，夏季最大，冬季最小，春秋季差异不大；（４）S值在地磁扰动时比平静时大；（５）当太阳活动低时，S值在日落到正午间要比太阳活动中或高时明显偏小，而在正午到日落间则与太阳活动中或高时差异不大.根据以上结果，我们认为：（１） 太阳辐射对电离层逐日变化的影响是大尺度的，并在白天和太阳活动高时大于晚上和太阳活动低时；（２） 地磁活动的影响也是大尺度的；（３）气象活动的影响是相对小尺度的，且逐日变化具有季节性.本文从相关尺度分析的角度，证实了电离层逐日变化来源于太阳辐射、地磁活动和气象活动因素的论断. 相似文献
11.
《Journal of Atmospheric and Solar》2008,70(5):756-763
This paper deals with the diurnal and seasonal variations of height of the peak electron density of the F2-layer (hmF2) derived from digital ionosonde measurements at a low–middle-latitude station, New Delhi (28.6°N, 77.2°E, dip 42.4°N). Diurnal and seasonal variations of hmF2 are examined and comparisons of the observations are made with the predictions of the International Reference Ionosphere (IRI-2001) model. Our study shows that during both the moderate and low solar activity periods, the diurnal pattern of median hmF2 reveals a more or less similar trend during all the seasons with pre-sunrise and daytime peaks during winter and equinox except during summer, where the pre-sunrise peak is absent. Comparison of observed median hmF2 values with the IRI during moderate and low solar activity periods, in general, reveals an IRI overestimation in hmF2 during all the seasons for local times from about 06 LT till midnight hours except during summer for low solar activity, while outside this time period, the observed hmF2 values are close to the IRI predictions. The hmF2 representation in the IRI model does not reproduce pre-sunrise peaks occurring at about 05 LT during winter and equinox as seen in the observations during both the solar activity periods. The noontime observed median hmF2 values increase by about 10–25% from low (2004–2005) to high solar activity (2001–2002) during winter and equinox, while the IRI in the same time period and seasons shows an increase of about 10–20%. During summer, however, the observed noontime median hmF2 values show a little increase with the solar activity, as compared to the IRI with an increase of about 12%. 相似文献
12.
XiaoHua Mo DongHe Zhang Larisa Goncharenko ShunRong Zhang YongQiang Hao Zuo Xiao JiaZheng Pei Akimasa Yoshikawa HaDuyen Chau 《中国科学:地球科学(英文版)》2017,60(4):776-785
The present paper investigates the asymmetrical variability of the location of the north and the south equatorial ionization anomaly (EIA) crests in the East-Asian sector, along with their association with simultaneous observations of equatorial electrojet (EEJ) strength, geomagnetic activity index, and solar flux index during the 2002–2003 sudden stratospheric warming (SSW) event. Analysis of these observations indicates the existence of a large-scale quasi 16-day periodic meridional movement in both EIA crests, and also reveals a strong correlation between the quasi 16-day oscillation in geomagnetic latitudes of the EIA crest and EEJ strength. The latitude of the northern/southern EIA crest and the EEJ strength indicate that obvious synchronous periodic oscillations were in-phase in the northern and southern hemisphere when the SSW occurred. In addition, it is also found that both the EIA crest location and amplitude of the periodic movement of the EIA locations exhibit hemispheric asymmetry. The amplitude of the periodic movement of the EIA location in the southern hemisphere is larger than that of the northern hemisphere, and the southern EIA crest is further off from the equator than the north one. Understanding these asymmetries requires a combination of mechanisms that involve at least trans-equator meridional winds and the position of a sub-solar point; however, potential disturbances in neutral winds associated with the SSW may additionally complicate the equatorial ionospheric dynamics. 相似文献
13.
Longitudinal and local time variations in the structure of the equatorial anomaly under high solar activity in the equinox are considered according to the Intercosmos-19 topside sounding data. It is shown that the anomaly begins to form at 0800 LT, when the southern crest is formed. The development of the equatorial anomaly is associated with well-known variations in the equatorial ionosphere: a change in the direction of the electric field from the west to the east, which causes vertical plasma drift W (directed upward) and the fountain effect. At 1000 LT, both anomaly crests appear, but they become completely symmetrical only by 1400 LT. The average position of the crests increases from I = 20° at 1000 LT to I = 28° at 1400 LT. The position of the crests is quite strong, sometimes up to 15°, varies with longitude. The foF2 value above the equator and the equatorial anomaly intensity (EAI) at 1200–1400 LT vary with the longitude according to changes in the vertical plasma drift velocity W. At this time, four harmonics are observed in the longitudinal variations of W, foF2, and EAI. The equatorial anomaly intensity increases to the maximum 1.5–2 h after the evening burst in the vertical plasma drift velocity. Longitudinal variations of foF2 for 2000–2200 LT are also associated with corresponding variations in the vertical plasma drift velocity. The equatorial anomaly intensity decreases after the maximum at 2000 LT and the crests decrease in size and shift towards the equator, but the anomaly is well developed at midnight. On the contrary, after midnight, foF2 maxima in the region of the anomaly crests are farther from the equator, but this is obviously associated with the action of the neutral wind. At 0200 LT, in contrast to the morning hours, only the northern crest of the anomaly is clearly pronounced. Thus, in the case of high solar activity during the equinoxes, a well-defined equatorial anomaly is observed from 1000 to 2400 LT. It reaches the maximum at 2000 LT. 相似文献
14.
本文利用GPS-CHAMP高分辨率的掩星探测数据,考察了E_S层不规则结构随地理经度和随季节、倾角磁纬与太阳活动的变化特征.研究发现,E_S层不规则结构的经度变化以波数1~5分量为主,呈现出多重波数特征.在低纬度带存在显著的波数4分量,其幅度存在季节依赖,在夏季和秋季明显高于春季和冬季.E_S层不规则结构出现率随倾角磁纬的变化表现为赤道区和中纬度区较低,低纬区和极区较高.E_S层不规则结构出现率的季节变化和年均值的逐年变化表现为夏季出现最频繁,秋季次之,冬春季最弱,随太阳活动水平的减弱而降低. 相似文献
15.
《Journal of Atmospheric and Solar》2007,69(8):947-954
The GPS-derived total electron content (TEC) and NmF2 are measured at the Chung-Li ionosonde station (24.9°N, 121°E) in order to study the variations in slab thickness (τ) of the ionosphere at low-latitudes ionosphere during 1996–1999, corresponding to half of the 23rd solar cycle. This study presents the diurnal, seasonal, and solar flux variations in τ for different solar phases. The seasonal variations show that the average daily value is greater during summer and the reverse is true during equinox in the equatorial ionization anomaly (EIA) region. Moreover, the τ values are greater during the daytime (0800–1600 LT) and nighttime (2000–0400 LT) for summer and winter, respectively. The diurnal variation shows two abnormal peaks that appear during the pre-sunrise and post-sunset hours. The peak values decrease as the sunspot number increases particularly for the pre-sunrise peak. Furthermore, the variation in the F-peak height (hpF2) indicates that a thermospheric wind toward the equator leads to an increase in hpF2 and an enhancement in τ during the pre-sunrise period. Furthermore, the study shows the variations of τ values for different geophysical conditions such as the geomagnetic storm and earthquake. A comprehensive discussion about the relation between τ and the geophysical events is provided in the paper. 相似文献
16.
The equatorial ionospheric anomaly in electron content from solar minimum to solar maximum for South East Asia 总被引：1，自引：0，他引：1
Median hourly, electron content-latitude profiles obtained in South East Asia under solar minimum and maximum conditions have been used to establish seasonal and solar differences in the diurnal variations of the ionospheric equatorial anomaly (EIA). The seasonal changes have been mainly accounted for from a consideration of the daytime meridional wind, affecting the EIA diffusion of ionization from the magnetic equator down the magnetic field lines towards the crests. Depending upon the seasonal location of the subsolar point in relation to the magnetic equator diffusion rates were increased or decreased. This led to crest asymmetries at the solstices with (1) the winter crest enhanced in the morning (increased diffusion rate) and (2) the same crest decaying most rapidly in the late afternoon (faster recombination rate at lower ionospheric levels). Such asymmetries were also observed, to a lesser extent, at the equinoxes since the magnetic equator (located at about 9○N lat) does not coincide with the geographic equator. Another factor affecting the magnitude of a particular electron content crest was the proximity of the subsolar point, since this increased the local ionization production rate. Enhancements of the EIA took place around sunset, mainly during the equinoxes and more frequently at solar maximum, and also there was evidence of apparent EIA crest resurgences around 0300 LST for all seasons at solar maximum. The latter are thought to be associated with the commonly observed, post-midnight, ionization enhancements at midlatitudes, ionization being transported to low latitudes by an equatorward wind. The ratio increases in crest peak electron contents from solar minimum to maximum of 2.7 at the equinoxes, 2.0 at the northern summer solstice and 1.7 at northern winter solstice can be explained, only partly, by increases in the magnitude of the eastward electric field E overhead the magnetic equator affecting the [E×B] vertical drifts. The most important factor is the corresponding increase in ionization production rate due to the increase in solar radiation flux. The EIA crest asymmetries observed at solar maximum were less significant, and this is probably due to the corresponding increase in ionization densities leading to an increase of the retarding effect of ion-drag on the daytime meridional winds. 相似文献
17.
利用气象、电离层和气候卫.星联合观测系统COSMIC掩星2007-2013年探测资料,分析了120°E经线附近电离层E层区域(70~140km)闪烁指数的季节、地方时和空间变化.结果表明强电离层闪烁主要集中在磁纬度±30°内,夏季达到最大,冬季其次,春季最小.闪烁峰值大小与太阳辐射有关,但北半球夏冬季闪烁峰值大于南半球观测结果,秋半球闪烁峰值大于春半球观测结果.地磁高纬地区较强闪烁现象出现在地方时傍晚之后,午夜前后达到最大值.地磁中纬和低纬区域日出后即出现较为明显的闪烁现象,一直持续至夜间甚至凌晨,分别约在中午和傍晚前达到最大值.磁赤道区闪烁现象通常始于地方时日出后,最大值发生在傍晚1800LT左右.电离层E区的闪烁峰值大都集中110km高度,但高纬地区的峰值高度略有降低.此外,太阳和地磁活动的增强一定程度上会抑制E层闪烁现象.相关研究结果有利于分析E层不规则结构及物理形成机制,同时为电离层区域闪烁模型的建立提供有用的信息. 相似文献
18.
《Journal of Atmospheric and Solar》2002,64(3):307-313
The virtual (or minimum) height of the F-region (h′F), recorded over a number of solar cycles for 11 equatorial and mid-latitude ionosonde stations, was used to deduce the hemispheric (i.e. southern or northern hemisphere) character of equatorial stations. The semi-annual median monthly height (h′F) variations consist of two components: major local summer maximum and winter sub-maximum (about 5 percent of the summer maximum). This hemispheric pattern was most consistently observed for equatorial stations (within 5° of the geomagnetic equator) in a period centred on the local midnight (21-03 LT) but was also present, to a lesser extent, at mid-latitude stations and at other time intervals. It is evident that the physical parameter h′F defines the hemispheric character of an equatorial station which has different (sometimes opposite) geographic and geomagnetic latitudes.There is a sharp transition in the latitudinal character of the stations on both sides of the equator leading to hypothesis that the equal maxima in h′F in December and June solstices are observed at a near-equator position labelled as ionosonde deduced equator (IDE). Such a signature was observed for an American equatorial (both geographic and geomagnetic) station Talara (Peru) which is an experimental support of the hypothesis. The IDE can be another useful parameter characterising the equatorial ionosphere. This finding reveals a new application of the standard ionosonde data in defining the geophysical character of equatorial stations, being an important contribution to space climatology. 相似文献
19.
Ionospheric electron content (IEC) observed at Delhi (geographic co-ordinates: 28.63°N, 77.22°E; geomagnetic co-ordinates: 19.08°N, 148.91E; dip Latitude 24.8°N), India, for the period 1975/80 and 1986/89 belonging to an ascending phase of solar activity during first halves of solar cycles 21 and 22 respectively have been used to study the diurnal, seasonal, solar and magnetic activity variations. The diurnal variation of seasonal mean of IEC on quiet days shows a secondary peak comparable to the daytime peak in equinox and winter in high solar activity. IECmax (daytime maximum value of IEC, one per day) shows winter anomaly only during high solar activity at Delhi. Further, IECmax shows positive correlation with F10.7 up to about 200 flux units at equinox and 240 units both in winter and summer; for greater F10.7 values, IECmax is substantially constant in all the seasons. IECmax and magnetic activity (Ap) are found to be positively correlated in summer in high solar activity. Winter IECmax shows positive correlation with Ap in low solar activity and negative correlation in high solar activity in both the solar cycles. In equinox IECmax is independent of Ap in both solar cycles in low solar activity. A study of day-to-day variations in IECmax shows single day and alternate day abnormalities, semi-annual and annual variations controlled by the equatorial electrojet strength, and 27-day periodicity attributable to the solar rotation. 相似文献
20.
Heejun Kim Kyoungwook Min Jaeheung Park Jaejin Lee Ensang Lee Hyosub Kil Vitaly P. Kim Sunmie Park 《Journal of Atmospheric and Solar》2006,68(18):2107-2118
In this paper, we report the results of our comparison study between satellite measurements and the International Reference Ionosphere (IRI) model on the seasonal and longitudinal changes of the low-latitude nighttime topside ionosphere during the period of solar maximum from June 2000 to July 2001. Satellite measurements were made by KOMPSAT-1 and DMSP F15 at 685 km altitude and 840 km altitude, respectively. The results show that the IRI2001 model gives reasonable density estimations for the summer hemisphere and the March equinox at both altitudes. However, the observed wintertime densities are smaller than the predictions of the IRI2001 model, especially at a higher (840 km) altitude, manifesting strong hemispheric asymmetries. The observed electron temperatures generally reside between the two estimations of IRI2001, one based on the Aeros–ISIS data and the other based on Intercosmos, and the latter estimation better represents the observations. With more or less monotonic increase with latitude, the temperature profiles of the IRI2001 model do not predict the enhancement seen around 15° magnetic latitude of the winter hemisphere. Longitudinal variation, probably caused by the zonal winds, is seen in all seasons at both altitudes, while the IRI2001 model does not show a large variation. The observed density and temperature show significant changes according to the F10.7 values in the whole low-latitude region from 40°S to 40°N geomagnetic latitude. The effect is manifested as increases in the density and temperature, but not in the hemispheric asymmetry or in the longitudinal variation. 相似文献