共查询到17条相似文献，搜索用时 203 毫秒
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本文通过对1960年以来全球磁纬度40°N至50°N内测高仪台站的观测数据进行研究,提取了电离层F2层临界频率（foF2）的潮汐,揭示了其变化特征及可能的形成原因.研究发现,周日和半日的迁移潮汐分量（即DW1和SW2）强度最大,并且显示出明显的年变化和半年变化.周日潮汐的3波分量（即DE3）作为典型的非迁移潮汐分量,相对较弱,显示出微弱的半年变化.在冬季,DW1和SW2与太阳活动指数（F107）呈现正相关性,其相关系数分别大于0.88和0.65.相反,在夏季,DW1和SW2与太阳活动指数呈现负相关性,特别是SW2,其相关系数在6月份达到-0.72.在相对于纬向均值的归一化处理之后,上述潮汐强度和太阳活动指数之间的正/负相关性被显著增强/削弱.其中,归一化后的夏季DW1和SW2与太阳活动指数的相关系数达到-0.8.更加深入的讨论显示出上传的大气潮汐波动可能是电离层潮汐除了太阳辐射之外的重要驱动源,并且这种驱动机制在SW2中更加强烈. 相似文献
2.
本文利用地磁台站和卫星磁场数据,对平流层爆发性增温(Sudden Stratospheric Warming,SSW)期间赤道电集流(Equatorial Electrojet,EEJ)中太阴半日潮汐的经度变化进行了统计学分析.结果显示,SSW期间秘鲁和印度扇区的EEJ中太阴半日潮汐明显增强,且存在显著的经度差异.秘鲁扇区的EEJ中太阴半日潮汐达到峰值的时间要早于印度扇区,进一步分析发现峰值时间的经度差异与太阳活动和准两年振荡相位有关.此外,SSW期间秘鲁扇区EEJ的太阴半日潮汐峰值强度比印度扇区高.对比不同经度带背景磁场的强度与太阴半日潮汐的峰值幅度的关系,可以看出SSW期间EEJ太阴半日潮汐峰值幅度的经度差异与背景磁场强度有关,但也存在其他物理过程的影响. 相似文献
3.
本文利用2001至2010年间CHAMP(CHallenging Minisatellite Payload)卫星标量磁力仪(Overhauser Magnetometer)观测的磁场数据,反演得到电离层霍尔(Hall)电流,并且对极区电离层Hall电流的特征进行了统计学研究.研究主要关注平静期,即重联电场小于2 mV·m~(-1)条件下,在磁纬60°至90°范围内的Hall电流在不同太阳活动、季节、磁经度、磁地方时等条件下的变化特征.研究发现:Hall电流具有明显的经度差异,在南北半球呈现显著一波经度结构,而且南北半球反相,即北半球电流密度呈现峰-谷-峰结构,而南半球呈现谷-峰-谷结构.Hall电流密度的经度结构与太阳活动紧密相关,太阳活动高年经度差异最大,太阳活动中年经度差异次之,太阳活动低年经度差异最小.研究发现,在磁地方时为10-14MLT的白天,影响Hall电流的因素主要是太阳辐射;而磁地方时为21-03MLT的夜晚,除了电导率的影响之外,可能存在其他的重要的物理过程影响着Hall电流的经度分布.本文还研究了与电流相关的焦耳热的经度分布情况,发现其在南北半球分别呈现单峰、单谷结构,经度差异亦十分明显. 相似文献
4.
本文利用最大熵谱分析方法处理了电离层赤道异常北峰Okinawa站的f0F2行星波周期的振荡.比较同一期间相近经度链上的南北半球观测到的低热层中性大气运动,发现较短周期的2-5日波,尤其是在南北半球的夏季期间（北半球7-8月前后,南半球1-2月前后）,其纬向风与赤道异常振荡强弱及周期变化具有良好的同步对应性.对于较长周期的中性风振荡,只要其幅度相当大,也会在赤道异常的振荡中有所对应.从而提供证据说明中性风的行星波振荡是赤道异常的行星波振荡的驱动源. 相似文献
5.
本文利用Swarm卫星2015—2016年高精度的磁场矢量数据,将晨昏地方时扇区高纬场向电流(Field-Aligned Currents,FACs)事件按极性和电流密度分为四类,并首次比较研究了四类FACs事件的时空分布特征及其影响因素,研究发现:极性正常事件(晨侧靠极侧电流元向下流入电离层,靠赤道侧电流元向上流出电离层,昏侧电流极性相反,即传统意义上的R1和R2FACs)发生率约为70%,其中R1FACs强于R2事件的发生率为R1FACs弱于R2的3~5倍;极性异常事件(与传统的R1和R2FACs流向相反,两片电流元定义为R1*和R2*FACs)发生率约占30%,其中R1*R2*的1.5~2.5倍.进一步分析发现极性正常事件主要发生在南向IMF Bz期间,与重联电场相关性较好,净电流密度随着重联电场和电离层电导率的增加而增加.其中R1R2*事件通常发生在IMF By<0期间,昏侧事件主要发生在IMF By>0期间,而R1*相似文献
6.
本文利用CHAMP卫星以及全球电离层-热层模型(GITM)来研究太阳活动低年(2007—2009年)中纬热层大气质量密度(ρ)的经度结构变化.结果如下:(1)ρ存在明显的经度单波结构(单峰和单谷),且南北半球反相,波峰和波谷随着地方时增加而向东移动;(2)模拟表明离子拖曳效应在ρ结构差异的形成中起到了重要的作用,欧亚地区电子密度经度差异性较弱,不足以影响ρ经度分布,导致该地区ρ经度差异不明显;(3)在磁中纬地区,太阳天顶角的经度差异可达20°~30°,太阳光加热的经度不均匀性是导致ρ经度差异的另一个主要原因. 相似文献
7.
平流层爆发性增温(SSW)期间,低层大气温度场和风场等的剧烈变化会直接影响潮汐和风剪切作用.此举可能会导致电离层Es的相应变化.本文以2009年1月事件为例,分析了SSW期间Es层的响应.首先,在排除太阳活动和地磁活动对Es层影响的前提下,分析了昆明站附近MLT区域行星波和潮汐波的波动特性,发现此期间存在显著的2日行星波,并伴有日潮汐减弱和半日潮汐增强等波动现象;随后,分析相应时间段内Es层的变化特性发现,重庆和昆明站附近Es层强度明显减弱,且其高度显著抬升.这一现象与低层大气的波动变化具有同步性.最后,通过模拟经典风剪切理论下Es层金属离子的汇聚过程和运动轨迹,再现了SSW期间Es层与低层大气波动的耦合演化过程.该分析结果为研究低层-中层-高层大气的耦合过程提供了一种新的思路. 相似文献
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本文利用2014年9月到2017年8月全球高时空分辨率TEC数据对北半球四个经度带电离层中纬槽的发生率和槽极小位置的变化进行了统计研究.基于Kp指数,我们引入了一个包含地磁活动变化历史效应的地磁指数(Kp 9)来分析中纬槽位置变化与地磁活动水平的关系.通过与其他地磁活动指数的对比,发现槽极小纬度与Kp 9指数的相关性最好.此外,本文重点分析了中纬槽发生率及槽极小纬度的经度差异、季节变化、地方时变化以及与地磁活动强度等的关系.结果表明,中纬槽的发生率与经度关系不大,主要受到季节、地方时与地磁活动的影响.午夜中纬槽发生率在夏季较低,其随地方时的变化则呈现出负偏态分布的特点,在后半夜发生率更高,而地磁活动增强对中纬槽的发生具有明显的促进作用.对于槽极小纬度,其在四个经度带的分布差异不大,但月变化各不相同,其中-120°经度带呈单峰分布,在夏季槽极小纬度更高,而0°经度带夏季槽极小纬度更低.槽极小的位置显著依赖于地磁活动、地方时以及季节变化.一般说来,地磁活动越强,中纬槽纬度越低.中纬槽位置随地方时的变化有明显的季节差异,冬季昏侧槽极小纬度随地方时变化较快,弱地磁活动条件下22∶00 LT前即达到最低纬度,其后位置几乎保持不变,而两分季槽极小纬度从昏侧至午夜都在降低,夏季槽极小纬度从昏侧连续下降至03∶00 LT左右. 相似文献
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E. L. Afraimovich I. K. Edemsky S. V. Voeykov Yu. V. Yasukevich I. V. Zhivetiev 《Geomagnetism and Aeronomy》2010,50(1):79-95
The morphology of medium-scale traveling wave packets is for the first time presented based on the total electron content
(TEC), measured at the global network of GPS receivers (up to 1500 stations) during the long period (from 1998 to 2007) and
at the GPS/GEONET dense Japan network (1220 stations) in 2008—2009. In the time domain, these packets are chains of narrowband
TEC variations (trains) with a duration of about 1—2 h, a total duration of up to 6 h, and a variation period of 10—30 min.
In the winter Northern Hemisphere, traveling wave packets are observed mostly 3 h after the passage of the morning solar terminator.
In the equinox they appear after the passage of the solar terminator without a pronounced delay or advance. In summer traveling
wave packets are registered 1.5—2 h before the appearance of the evening solar terminator at the observation point when the
solar terminator passes in the magnetically conjugate region. The spatial structure of traveling wave packets is characterized
by a high degree of anisotropy and coherence at a distance larger than ten wavelengths (the wavelength is 100—300 km). A high
quality of the oscillatory system and synchronization with the appearance of the solar terminator at the observation point
and in the magnetically conjugate region indicate that the generation of traveling wave packets by the solar terminator is
of the MHD nature. Our results for the first time experimentally confirm the hypothesis that the solar terminator generates
ion sound waves, proposed by Huba et al. [2000b]. 相似文献
12.
The zone of anomalous diurnal variations in foF2, which is characterized by an excess of nighttime foF2 values over daytime ones, has been distinguished in the Southern Hemisphere based on the Intercosmos-19 satellite data.
In English literature, this zone is usually defined as the Weddell Sea anomaly (WSA). The anomaly occupies the longitudes
of 180°–360° E in the Western Hemisphere and the latitudes of 40°–80° S, and the effect is maximal (up to ∼5 MHz) at longitudes
of 255°–315° E and latitudes of 60°–70° S (50°–55° ILAT). The anomaly is observed at all levels of solar activity. The anomaly
formation causes have been considered based on calculations and qualitative analysis. For this purpose, the longitudinal variations
in the ionospheric and thermospheric parameters in the Southern Hemisphere have been analyzed in detail for near-noon and
near-midnight conditions. The analysis shows that the daytime foF2 values are much smaller in the Western Hemisphere than in the Eastern one, and, on the contrary, the nighttime values are
much larger, as a result of which the foF2 diurnal variations are anomalous. Such a character of the longitudinal effect mainly depends on the vertical plasma drift
under the action of the neutral wind and ionization by solar radiation. Other causes have also been considered: the composition
and temperature of the atmosphere, plasma flows from the plasmasphere, electric fields, particle precipitation, and the relationship
to the equatorial anomaly and the main ionospheric trough. 相似文献
13.
场向电流在不同的等离子体区之间传递能量、动量和质量,是磁层与电离层之间的关键耦合过程.本文利用CHAMP卫星高精度的空间磁场测量数据,研究亚暴期间极区电离层场向电流的统计学分布特征.研究表明场向电流的大小与所在位置呈现明显的日夜和晨昏不对称性,具体为：（1）场向电流的大小与亚暴极光电急流指数（AL）密切相连,AL愈大,电流愈强,亚暴期间电流强度相对平静期来说可增加约5倍,昏侧和夜侧电流强度与AL指数的相关性较好,晨侧和白天侧两者相关性较差;（2）电流的峰值密度所在位置与AL指数的相关性不高,昏侧电流所处纬度低于晨侧,而夜晚电流所处纬度低于白天侧. 相似文献
14.
V. M. Mishin A. D. Bazarzhapov V. V. Mishin U. Sukhbaatar M. Förster 《Geomagnetism and Aeronomy》2011,51(7):937-945
A model of alignment of the field-aligned current generator system in the disturbed magnetosphere is proposed. It has been
found that Pedersen currents in the disturbed ionosphere of the auroral oval are meridional. They connect oppositely directed
field-aligned currents (FACs) of two adjacent Iijima and Potemra (IP) regions. This supplements the dominant concept of currents
in the literature, in which a substorm current wedge plays a major role. During the considered substorm, graphs have been
obtained of changes in FAC intensities in each of the three Iijima and Potemra regions of the Northern Hemisphere. These new
data suggest that during a disturbance, the Region 1 FAC and the sum of regions 2 and 0 FACs remain equal. The equality means
that these three generators form a unified system. Inequalities of intensities between two FACs of different sign simultaneously
observed in the dawn and dusk sectors have also been detected in each IP region. A conceptual model is proposed for the formation
of this dawn-dusk asymmetry. In the model, in addition to FACs that close up in the ionosphere of the Northern Hemisphere,
FACs connecting the two hemispheres are also presented. The conclusion is justified that the global magnetospheric dynamo
operates as a voltage generator under relatively quiet (average) conditions, as during storms. 相似文献
15.
Longitudinal variation in E- and F-region ionospheric trends 总被引：1，自引：0，他引：1
A novel technique is used to examine northern hemisphere midlatitude longitudinal variations in ionospheric long-term trends. Differences in hour-by-hour monthly median ionospheric parameters between equilatitudinal observatory pairs are analysed for long-term trends, thus eliminating at source the large solar cycle and geomagnetic variability that normally hinders ionospheric trend calculations. The results confirm the finding of Bremer [1998. Trends in the ionsopheric E- and F-regions over Europe. Annales Geophysicae 16, 698–996] that there are longitudinal variations in the F-region altitude trend across Europe, but suggest the influence of a stationary wave-like feature between 3°W and 104°E. Possible causes such as scaling errors, insufficient account of changes in ionisation underlying the F-region, varying gravity wave fluxes, and secular change in the geomagnetic field are ruled out. The data suggest that the longitudinal variation may reflect long-term changes in a large-scale stationary feature induced via non-migrating tides induced by latent heat release in the troposphere.Significant differences in the long-term trend of E-region peak plasma frequency between observatories were also found. These E-region differential trends varied with solar zenith angle reaching over 0.3 MHz per decade between Juliusruh and Moscow at midday in summer. 相似文献
16.
O. V. Kozyreva N. G. Kleimenova A. E. Levitin J. Watermann 《Geomagnetism and Aeronomy》2006,46(5):622-634
Based on the observations in six pairs of almost conjugate high-latitude stations in the Arctic and Antarctic regions, the spectral and spatial-temporal structures of long-period geomagnetic pulsations (f = 2–5 mHz) during the magnetic storm of April 16–17, 1999, which is characterized by a high (up to 20 nPa) solar wind dynamic pressure, have been studied. It has been indicated that the magnetic storm sudden commencement is accompanied by a symmetrical excitation of np pulsations near the dayside polar cusps with close amplitudes. Under the conditions when IMF B z > 0 and B y < 0, strong magnetic field variations with the periods longer than 15–20 min were observed only in the northern polar cap. When IMF B z and B y became close to zero, geomagnetic pulsation bursts in both hemispheres were registered simultaneously but differed in the spectral composition and spatial distribution. In the Northern Hemisphere, pulsations were as a rule observed in a more extensive latitude region than in the Southern Hemisphere. In the Northern Hemisphere, the oscillation amplitude maximum was observed at higher latitudes than in the Southern Hemisphere. The pulsation amplitude at geomagnetic latitude lower than 74° was larger in the Arctic Regions than in the Antarctic Regions. This can be explained by sharply different geographic longitudes in the polar cap and latitudes in the auroral zone, which results in a different ionospheric conductivity affecting the amplitude of geomagnetic pulsations. 相似文献
17.
利用ISEE－1和ISEE-2飞船观测的磁场数据，分析了地球内磁层场向电流的统计特征，包括场向电流的空间（L值和地方时）分布；流进和流出电离层的场向电流随地方时的变化；场向电流发生率与地磁活动水平（以AL指数表征）、行星际磁场（IMF）Bz的关系，电流强度和密度随地磁活动水平的变化等．发现，场向电流大都发生在夜间，且集中在L为6-10区域内，场向电流发生率，强度和密度随地磁活动增强而增大，行星际磁场南向时的发生率远远高于北向时的发生率．这些结果表明，内磁层场向电流的产生是太阳风和磁层、电离层间电动耦合增加的结果． 相似文献