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1.
A hypothesis about the effect of the tropospheric source on the longitudinal distributions of the equatorial plasma bubbles observed in the topside ionosphere was proposed earlier. It was supposed that this influence is transferred mainly by the thermospheric winds modulated by the DE3 tropospheric tidal waves. This conclusion was based on the discovered high degree correlation (R ? 0.79) between the variations of the longitudinal distribution of the plasma bubbles and the neutral atmospheric density. In this work, the hypothesis of the effect of the thermospheric tidal waves on the plasma bubbles at the stage of their generation is subjected to further verification. With this purpose, the longitudinal distributions of the frequency of the plasma bubble observations at the different ionospheric altitudes (~600 km, ROCSAT-1; ~1100 km, ISS-b) are analyzed; their principal similarity is revealed. Comparative analysis of these distributions with the longitudinal profile of the deviations of the zonal thermospheric wind (~400 km, CHAMP) modulated by the DE3 tidal wave is carried out; their considerable correlation (R ? 0.69) is revealed. We conclude that the longitudinal variations of the zonal wind associated with DE3 tidal waves can effect the longitudinal variations in the appearance frequency of the initial “seeding” perturbations, which further evolve into the plasma bubbles. 相似文献
2.
本文利用GCITEM-IGGCAS模式,从电动力学耦合作用和直接上传两种作用方式,详细模拟研究了DE2潮汐4种Hough波模分量对电离层的影响.我们将不同种类的Hough波模分别输入到模式当中作为底层边界条件,驱动模式模拟得到电离层的电子密度变化,从中分离两种作用机制的响应进行分析.模拟结果发现电离层对DE2的4种Hough波模的响应都表现为半年变化,波峰出现在春季和秋季,波谷则出现在冬季和夏季.一天的变化特性上,赤道对称波模的响应出现明显的4个峰值和谷值,其他3种波模响应主要表现为一个峰值和谷值.4种波模当中赤道对称波模对电离层的作用最为明显,占据主导地位,对电离层的影响表现为波动效应,其中3波分量的响应最强,主要由电动力学作用控制.其他3种波模对电离层则是削弱作用.本研究可以帮助我们更深刻的理解非迁移潮汐对电离层的作用方式和效果. 相似文献
3.
This work presents a new examination of the hypothesis regarding the equatorial origin of low He+ density plasma depletions (or subtroughs). For this purpose, we have conducted a detailed comparative analysis of longitudinal variations in the occurrence probabilities of subtroughs in both hemispheres and variations in the occurrence probabilities of equatorial F-region irregularities (EFIs), equatorial spread F (RFS and ESF), and equatorial plasma bubbles (EPBs). Taking into consideration the seasonal dependence and some peculiarities of magnetic field variations in different hemispheres, a conclusion has been reached regarding the similarity between longitudinal statistical occurrences of subtroughs and equatorial ionospheric F-region irregularities. In addition, another piece of evidence in favor of the similarity of the nature of the above-mentioned phenomena has been obtained. We have got a confirmation once again that low He+ density depletions (or subtroughs) can be rightfully considered as equatorial plasma “bubbles,” which can be observed at altitudes of the topside ionosphere as depletions in the He+ density. 相似文献
4.
L. N. Sidorova 《Geomagnetism and Aeronomy》2008,48(1):56-65
A consistent patter, indicating that subtroughs in the He+ density and plasma bubbles can be considered as phenomena of the same origin, has been obtained within the scope of the existent model of equatorial plasma bubbles. The study has been performed based on the measurements of the ISS-b satellite, which flew during the period of high solar activity. The conclusion has been made based on a comparative analysis of the characteristics of subtroughs with the parameters of the known equatorial phenomena. (1) The similarity of the LT variations in the latitude of the minimums of subtroughs in the He+ density has been revealed. (2) It has been displayed that the variations in the averaged depth of subtroughs change from season to season similarly to the LT variations in the average velocity of the equatorial vertical plasma drift. (3) Good correlation (R = 0.67) between the occurrence probability of subtroughs and equatorial spread F statistics, constructed as the functions of LT and month, has been obtained. (4) The obtained velocity of the possible rise of plasma irregularities (observed as regions depleted in He+) is in good agreement with the ionosonde, satellite, and radar measurements of the equatorial plasma bubble velocities of the same period. (5) It has been indicated that plasma irregularities, reaching the altitudes of the topside ionosphere in the low-latitude and midlatitude regions during high solar activity, are most observable as depleted regions (subtroughs) of He+ density. 相似文献
5.
The possible causes of the strong ionospheric day-to-day variability under the influence of processes in the geospace, troposphere, and lithosphere are considered based on the data of the critical frequency of the F2 layer of the ionosphere at two observation stations. It is shown that even in the absence of powerful events, the ionosphere is influenced both “from above” and “from below”; in this case, the ionosphere can respond to an external action as an open nonlinear dissipative system. 相似文献
6.
G. L. Gdalevich A. Kh. Depueva N. I. Izhovkina V. D. Ozerov 《Geomagnetism and Aeronomy》2010,50(1):69-78
The results of the Cosmos-900 satellite observ ations of plasma density inhomogeneities in the geomagnetic equator region
and the longitudinal distributions of the equatorial spread-F, according to the Intercosmos-19 satellite data are presented. It is show n that the dependence of radiosignal propagation
in the ionosphere on geophysical parameters is related to development of the electrostatic instability of the inhomo-geneous
ionospheric plasma. The longitudinal dependence of the spread-F, can reflect the influence of the energetic sources, located outside the ionospheric layer that scatters a radio pulse, on
the ionosphere. The manifestation of the longitudinal effect in the equatorial spread-F, in the Atlantic region can be explained by the influence of the cone instability on the plasma electrodynamics in the South
Atlantic geomagnetic anomaly. 相似文献
7.
《Journal of Atmospheric and Solar》2007,69(3):351-361
Chung Park (1938–2003) was a true pioneer of magnetosphere–ionosphere coupling research. During a short career at Stanford University that began in 1970 and ended in 1981, he wrote seminal papers on several topics. Using ground-based whistler data, he was the first to demonstrate experimentally that day-side upward ion flow from the mid-latitude ionosphere was sufficient to maintain the night-time ionosphere. He made the only measurements to date of longitudinally localized drainage of significant quantities of plasmaspheric plasma into the underlying ionosphere during a period of enhanced convection activity. He pioneered in demonstrating the presence at ionospheric heights of geophysically important electric fields that originate in the troposphere in thunderstorm centers. He cooperated in a unique study of the guidance of whistler-mode waves by field-aligned density irregularities (ducts) in the magnetosphere. Park provided unique observational data on nonlinear wave–particle interaction processes such as: (i) the development of sidebands during the injection of whistler-mode waves from Siple, Antarctica, and (ii) the mysterious whistler precursor phenomenon. Today, in spite of the several decades that have elapsed since his work, Park's early findings remain cornerstones of our understanding of magnetosphere–ionosphere coupling processes. Some of his later studies of non-linear magnetospheric wave–particle interaction phenomena have stirred lively debate, and today remain relevant to a number of topics in space plasma wave research. 相似文献
8.
Atmospheric waves influence the dynamics and energetic budget of the upper atmosphere. Using the continuous HF Doppler sounder,
we study the wave activity in the ionosphere during tropospheric convective storms in western and central part of the Czech
Republic. The study is focused on acoustic-gravity waves in the period range 2–30 minutes. We discuss possible methods of
distinguishing the waves emitted by meteorological sources from waves of different origin, particularly waves of geomagnetic
origin. In two cases out of twenty-five analysed, we found waves in the infrasonic period range which might be generated by
exceptionally intense meteorological activity in the troposphere. The results differ considerably from those previously obtained
in North America. In the central part of the United States, infrasonic waves were frequently observed during convective storms.
As a possible reason, we discuss different intensity and dynamics of weather systems in both regions. 相似文献
9.
本文利用SWARM A和C双星高精度的矢量磁场数据研究了不同季节高纬地区场向电流(FACs)随地磁经度和地方时的变化情况.研究发现:在南北半球,FACs存在明显的经度变化,南半球FACs的变化强度大约是北半球的1.2～3.2倍.利用潮汐谱分析法我们发现FACs中占主导的非迁移潮汐分量为DW2和D0.在春秋和夏季半球,DW2波更为明显.D0波可用太阳光照的经度变化来解释,向阳侧靠近磁极的经度带比远离磁极的经度带有更强的太阳光照射.DW2波则与地磁场强度和地磁倾角等因素有关.全球电离层与热层模型计算的FACs中D0波占主导,且中性风和对流电场对D0波的贡献几乎相当. 相似文献
10.
I. V. Karpov F. S. Bessarab O. P. Borchevkina K. A. Artemenko A. I. Klopova 《Geomagnetism and Aeronomy》2018,58(4):509-522
The results of numerical experiments on the modeling of thermospheric and ionospheric disturbances under conditions of sudden stratospheric warming are presented to study the possible mechanisms of such disturbances. Local disturbances caused by a planetary wave with zonal wave number s = 1 and internal gravity waves (IGWs) propagating from the disturbed region in the stratosphere are taken into account as sources of disturbances. It is shown that the inclusion of an additional source of thermospheric disturbances caused by mesospheric variations of atmospheric parameters with IGW periods over the region of sudden stratospheric warming leads to significant changes in the parameters of the thermosphere and ionosphere, including a change in the global structure of the distributions of the gas components of the thermosphere and a shift in maximum concentrations of atomic oxygen to low latitudes of the Southern Hemisphere; there is an increase in the mean values, the diurnal and semidiurnal variations of the ion concentration in the F region of the ionosphere. These features of changes in the parameters of the thermosphere and ionosphere occurred with insignificant disturbances of tidal variations in the thermosphere. 相似文献
11.
N. I. Izhovkina 《Geomagnetism and Aeronomy》2011,51(3):342-347
The density and temperature of the plasma electron component and wave emission intensity in the topside ionosphere were measured
by the INTERCOSMOS-19 satellite. In the subauroral ionosphere, a decrease in the plasma density correlates with an increase
in the plasma electron component temperature. In this case, the additional increase in the electron component temperature
was measured in regions with increased plasma density gradients during the substorm recovery phase. In a linear approximation,
the electromagnetic wave growth increments are small on electron fluxes precipitating in the auroral zone. It has been indicated
that Bernstein electromagnetic waves propagating in the subauroral topside ionosphere can intensify in regions with increased
plasma density gradients on electron fluxes orthogonal to the geomagnetic field, which are formed when plasma is heated by
decaying electrostatic oscillations of the plasma electron component. This can be one of the most important factors responsible
for the intensification of auroral kilometric radiation. 相似文献
12.
当喷泉效应较弱而双峰结构发展不充分的时候,可能在赤道异常区仅能够观测到一个电子密度的峰值,称之为单峰现象.本文利用CHAllenging Minisatellite Payload卫星在2001-2010年的电子密度数据给出了单峰的发生规律,单峰在地方时早上08：00-10：00和下午16：00-19：00发生率高,发生位置在经度上呈现多波数分布,尤其在10：00-18：00明显：在分季时多呈现四波,而在冬至季时以三波为主.单峰发生多的经度,正好对应着双峰的结构特征较弱之处.究其原因,是非迁移潮的DE2和DE3分量调制了背景风场和大气发电机电场,在电场和喷泉效应减弱的经度,双峰结构难以形成时,就会表现为单峰结构.本文扩展了对单峰现象的地方时、季节和经度分布等规律的了解,明确了非迁移潮在其中施加的影响,由此,单峰同双峰现象一样可以用于研究非迁移潮对热层-电离层的作用. 相似文献
13.
本文根据考虑大气热传导和黏滞的重力波复色散关系,采用传输函数的概念,基于重力波的线性理论,构建了用于研究对流层内重力波激发源与电离层响应之间的传输函数数值模式.在相空间中讨论了传输函数振幅的分布特性,并以地面单位脉冲源为例,分析了从地面到300 km高空的响应,得到了物理量的时空分布特征.结果表明：（1）对内重力波的传播而言,大气相当于一个滤波器,只有波动周期在15～30 min,水平波长在200～450 km之间的重力波扰动才最容易到达300 km电离层高度;（2）电离层的响应主要在与地面的激发源之间相隔较远的水平距离上发生;（3）黏滞和热传导系数在低层对上传重力波的影响较小,随着高度的增加它们对重力波的影响越来越大;（4）在低层计算的波动频率与Row理论的计算结果比较一致,然而到了高层却相差较大. 相似文献
14.
参量衰减不稳定性(Parametric Decay Instability,PDI)在大功率高频(High frequency,HF)电波与电离层等离子体相互作用的过程中扮演着十分重要的角色,本文采用广义Zakharov方法对常规的等离子体流体力学方程组进行相应处理后,并在近似实际的电离层背景和电波传播模型下,构建了高频电波加热电离层激发PDI的数值计算模型.模拟结果发现:在毫秒量级的时间尺度上,大功率高频电波在寻常波(Ordinary wave,O波)反射点高度附近激发出了朗缪尔波(Langmuir wave)和离子声波(Ion-Acoustic wave)两种等离子体静电波模,模拟中产生的朗缪尔波和离子声波相应波数为5~11rad·m~(-1),结果与利用色散关系求出的理论值4~7 rad·m~(-1)近似一致,密度扰动幅值从10~6m~(-3)量级指数级增长到了10~(10)m~(-3)量级,直至能显著影响与"低频"密度背景相关的等离子体频率后,出现了等离子体"空穴"结构以及朗缪尔波被"俘获"现象,在扰动空间内的小尺度静电场幅值最高能达到100 V·m~(-1)量级,最终造成一种强烈的局地化"空穴"湍流现象.本文的研究有助于深入理解PDI的物理机制,对研究大功率高频电波与电离层等离子体之间复杂的非线性相互作用也有着非常重要的意义. 相似文献
15.
Water vapor plays an important role in the global climate system. A clear relationship between water vapor and solar activity can explain some physical mechanisms of how solar activity influences terrestrial weather/climate changes. To gain insight of this possible relationship, the atmospheric precipitable water vapor (PWV) as the terrestrial climate response was observed by ground-based GPS receivers over the Antarctic stations. The PWV changes analyzed for the period from 2003 to 2008 coincided with the declining phase of solar cycle 23 exhibited following the solar variability trend. Their relationship showed moderate to strong correlation with 0.45 < R 2 < 0.93 (p < 0.01), on a monthly basis. This possible relationship suggests that when the solar-coupled geomagnetic activity is stronger, the Earth’s surface will be warmer, as indicated by electrical connection between ionosphere and troposphere. 相似文献
16.
《Continental Shelf Research》2006,26(12-13):1469-1480
The generation of internal waves in the partially mixed estuaries is examined. The numerical experiments consider the barotropic tidal currents interacting with isolated obstacles in an open channel. The bottom boundary layer and longitudinal salinity gradient are included. Internal lee (arrested) waves are excited when the accelerating barotropic tidal current approaches the first-mode internal wave speed. The arrested waves are amplified, and are subsequently released when the decelerating tidal current falls below the first-mode internal wave speed. The power input from the barotropic tidal energy into internal wave energy is calculated. It is on the order of 10−2 W/m2, and is comparable to the estimated interior dissipation rate. This suggests that the tidally generated internal waves could be a significant energy source for mixing in the halocline. 相似文献
17.
Analytical and numerical analysis of tides and salinities in estuaries; part I: tidal wave propagation in convergent estuaries 总被引：2，自引：2，他引：0
Leo C. van Rijn 《Ocean Dynamics》2011,61(11):1719-1741
Analytical solutions of the momentum and energy equations for tidal flow are studied. Analytical solutions are well known
for prismatic channels but are less well known for converging channels. As most estuaries have a planform with converging
channels, the attention in this paper is fully focused on converging tidal channels. It will be shown that the tidal range
along converging channels can be described by relatively simple expressions solving the energy and momentum equations (new
approaches). The semi-analytical solution of the energy equation includes quadratic (nonlinear) bottom friction. The analytical
solution of the continuity and momentum equations is only possible for linearized bottom friction. The linearized analytical
solution is presented for sinusoidal tidal waves with and without reflection in strongly convergent (funnel type) channels.
Using these approaches, simple and powerful tools (spreadsheet models) for tidal analysis of amplified and damped tidal wave
propagation in converging estuaries have been developed. The analytical solutions are compared with the results of numerical
solutions and with measured data of the Western Scheldt Estuary in the Netherlands, the Hooghly Estuary in India and the Delaware
Estuary in the USA. The analytical solutions show surprisingly good agreement with measured tidal ranges in these large-scale
tidal systems. Convergence is found to be dominant in long and deep-converging channels resulting in an amplified tidal range,
whereas bottom friction is generally dominant in shallow converging channels resulting in a damped tidal range. Reflection
in closed-end channels is important in the most landward 1/3 length of the total channel length. In strongly convergent channels
with a single forward propagating tidal wave, there is a phase lead of the horizontal and vertical tide close to 90o, mimicking a standing wave system (apparent standing wave). 相似文献
18.
Cléa Araújo da Silva Pedro Walfir M. Souza-FilhoSuzan W.P. Rodrigues 《Continental Shelf Research》2009
The northern Brazilian coast, east of the Amazon River is characterized by several macrotidal estuarine systems that harbor large mangrove areas with approximately 7600 km2. The Marapanim Estuary is influenced by macrotidal regime with moderate waves influence. Morphologic units were investigated by using remote sensing images (i.e., Landsat-7 ETM+, RADARSAT- 1 Wide and SRTM) integrated with bathymetric data. The modern sedimentary deposits were analyzed from 67 cores collected by Vibracore and Rammkersonde systems. Analysis of morphology and surface sedimentary deposits of the Marapanim River reveal they are strongly influenced by the interaction of tidal, wave and fluvial currents. Based on these processes it was possible to recognize three distinct longitudinal facies zonation that revels the geological filling of a macrotidal estuary. The estuary mouth contain fine to medium marine sands strongly influenced by waves and tides, responsible for macrotidal sandy beaches and estuarine channel development, which are characterized by wave-ripple bedding and longitudinal cross-bedding sands. The estuary funnel is mainly influenced by tides that form wide tidal mudflats, colonized by mangroves, along the estuarine margin, with parallel laminations, lenticular bedding, root fragments and organic matter lenses. The upstream estuary contains coarse sand to gravel of fluvial origin. Massive mud with organic matter lenses, marks and roots fragments occur in the floodplain accumulates during seasonal flooding providing a slowly aggrading in the alluvial plain. This morphologic and depositional pattern show easily a tripartite zonation of a macrotidal estuary, that are in the final stage of filling. 相似文献
19.
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
20.
The earth's ionosphere possesses plasma properties at altitudes above 80 km where the collisions of charged particles with the neutral gas gradually lose their dominating influence. The ionosphere can be characterized as a weakly ionized low- and low-temperature plasma of great homogeneity with respect to the spatial scales of most of the processes of interest. The basic properties of the ionospheric plasma are presented in Section 2.1. The role of thermal fluctuations and their use in a powerful diagnostic technique -- the incoherent scatter technique -- are reviewed in Section 2.2. Plasma instabilities of natural cause, occurring in different altitude regions, are briefly discussed in Sections 2.3 and 2.4. The major part of this article is devoted to active experiments in the ionospheric plasma, as initiated by powerful electromagnetic waves transmitted from the ground, and their theoretical understanding (Section 3). Nonlinear effects caused by strong electromagnetic waves are numerous, but they can be traced to either of two nonlinearity mechanisms, thermal or ponderomotive. Thermal nonlinearities in a homogeneous wave field are briefly sketched in Section 3.1. Thermal nonlinearities in an inhomogeneous wave field, having their origin in pressure gradient forces and resulting in two different types of density irregularities, both aligned with the magnetic field, are treated in Section 3.2. Ponderomotive nonlinearities have their source in the convective derivative in the electron momentum equation which gives rise to a force that pushes plasma from high to low wave intensity. Specific phenomena caused by ponderomotive action are Langmuir turbulence and stimulated electromagnetic emissions (SEE). Both these phenomena are presently the subjects of intensive experimental and theoretical investigations, and they are described at some length in Section 3.3. 相似文献