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本文尝试结合非相干散射雷达和GPS TEC观测数据提取等离子体层总电子含量(PTEC).我们首先描述所用的技术方法,然后具体利用了Millstone Hill台站的观测数据研究该地区上空等离子体层总电子含量(PTEC)的变化情况.我们采用变化标高的Chapman函数对非相干散射雷达测得的电子浓度剖面数据进行拟合,然后通过对剖面积分得到100 km到1000 km高度范围的电离层总电子含量.GPS提供的TEC数据为高度达20200 km的总电子含量,两者之差可近似看成等离子体层的电子含量.本文分别选取太阳活动高年(2000, 2002年)和太阳活动低年(2005,2008年)Millstone Hill台站的静日数据进行研究.结果表明,等离子体层电子含量及其所占GPS TEC的比例具有明显的周日变化.PTEC含量在白天高于夜间,而所占GPS TEC的百分比,夜间明显高于白天.太阳活动高年所选月份等离子体层电子含量在4~14 TECU (1TECU=1016el/m2) 范围内变化,夜间所占比例可达60%左右.太阳活动低年所选月份等离子体层电子含量在3~7 TECU范围内变化,所占比例夜间最高可达80%左右.我们所得到的结果与前人基于其它观测手段所得结果在变化趋势上一致,在量级上也大致相当.因此,这从一个侧面证明了我们所用方法的可靠性.非相干散射雷达能够探测包括F2层峰值以下及以上高度的电子浓度,利用这一设备所观测得到的资料来推算电离层电子含量将比前人基于电离层垂测仪观测资料进行的推算更具真实性,由此得到的等离子体层电子含量也将更为接近真实情况. 相似文献
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利用曲靖非相干散射雷达2017-2018年春夏季观测数据首次分析了电离层日间150~450km电子温度的地方时与高度变化特征及其与电子密度的相关性.发现hmF2及以上的电子温度在日出日落时具有两个峰值,在11∶00-16∶00LT之间变化较小,高度越高午后上升的时间越早;从150km开始迅速增加,在约220km达到最大值,然后开始降低,在约300~350km达到最小值,最后单调上升;200km以下电子温度与电子密度成正相关(主要由热传导控制),200~450km之间存在明显的反相关(光电离过程占主导),电子-离子温度差与电子密度对数之间存在近似线性关系,电子温度逐日变化与光电离因子的变化趋势相似,这种相关性在中午与午后更明显;以上结果与其他非相干散射雷达观测和电离层模型计算结果基本一致,但也存在一些差别,需要结合更多数据深入分析. 相似文献
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北京MST雷达是子午工程建设的国内仅有的两部MST雷达之一,为研究其在中间层-低热层MLT区域的探测能力以及数据可靠性,本文应用北京MST雷达2012、2013两年高模式数据,从数据获取率、与廊坊流星雷达测风对比以及风场时空分布特征三个方面进行初步分析.结果是:(1)数据获取率日变化特征为:白天65~100km均可获取数据,数据获取率的高值区主要集中在70~80km,最大值可达80%;夜间主要集中在80~100km,数据获取率在30%及以下.表明该MST雷达白天可以探测到电离层D层和E层低层,夜间D层消失,只探测到E层低层.季节变化特征为:夏季白天可获取数据的时间和高度区间都比较大,春季次之,冬季最小.夏季白天以及日落后1h内可探测到120km.(2)对北京MST雷达与廊坊流星雷达2012年5月份、80~100km高度区间测量的水平风进行对比分析,二者测风结果在时空分布上有很好的一致性,表明MST雷达探测数据是可靠的.(3)2012年和2013年相应月份平均的纬向风、经向风时空分布特征有较高的一致性,并与HWM07模式结果也基本一致.上述初步分析结果表明,北京MST雷达对中间层-低热层60~120km高度区域已具备较强的探测能力,所得结果将可用于MLT过程揭示与驱动因子研究,并可与该高度上其他探测手段作综合研究. 相似文献
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在极区电离层模式中,考虑了软电子沉降引起的电离,并对差分方法的应用提出了改进意见.模拟了不同特征的沉降电子对极区电离层的影响,发现平均能量低的电子束能够形成明显的电离层F层,平均能量较高的电子束能使得最大电离的高度下移,形成明显的E层,甚至其电子浓度高于F层.将电子沉降的卫星测量结果作为电离层模型的输入,所得F层临频与观测结果符合较好.通过分析中山站电离层统计结果,综合电子沉降在极隙区的分布特征和上述模拟结果,认为中山站磁中午现象主要由电子沉降所致. 相似文献
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利用闪电作为辐射源来探测电离层D层是近年来国外学者研究的热点.本文基于江淮流域六站同步闪电观测站网,实现了一种利用闪电双极性窄脉冲事件（Narrow Bipolar Events,NBE）来探测电离层D层等效高度的方法.基于此方法,对两次分别发生在日出和日落阶段的雷暴分析结果显示,上述两个阶段D层反射高度变化特征呈现显著的不对称性：日出期间D层反射高度随时间线性降低速率为5.9 km/h;而日落期间D层反射高度随时间线性递增速率为8.6 km/h.综合日间太阳耀斑期间D层反射高度剧烈波动的观测事实,与日出、日落期间D层特征变化,结果表明太阳辐射电离中性大气分子的电子生成机制在日间D层电子密度变化中占主导地位.本文结果展现了利用NBE事件监测电离层D层变化特征的可行性,这一方法与基于地闪回击波形的D层探测方法结合在一起,有望把现有具有闪电事件定位和电磁波波形记录能力的闪电观测站网扩展为实时对电离层D层时空变化监测的网络. 相似文献
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在基于GPS数据提取电离层总电子含量(TEC)的过程中,电离层薄壳高度的选择对解算电离层垂直TEC的精度有很大的影响.但由于不可能获得一个真实的从电离层D层到GPS卫星高度的电子密度剖面,关于电离层薄壳高度的选择一直是基于GPS数据解算电离层TEC方法中关注的一个问题.本文利用等离子体GCPM模型,对太阳活动高年(2002)和太阳活动低年(2008)情况下电离层有效薄壳高度的选择进行了仿真计算.结果表明,最佳的薄壳高度在2002年为560 km,而在2008年为695 km.通过对全球八个具有代表性地点的仿真计算,揭示了有效薄壳高度更复杂的变化特点.在白天,最佳薄壳的高度变化不大(500 km至750 km);但在夜晚,最佳薄壳高度变化范围很大,甚至可以超过2000 km.此外,本文还对不同卫星仰角的情况下斜向TEC转换为垂直TEC的误差进行了分析,结果表明:随着卫星仰角的增加,薄壳模型带来的转换误差基本上是单调减少的.因而,在实际应用中,尽可能地采用大仰角的卫星数据有助于提高解算的电离层垂直TEC的精度.最后,对全球不同地点的电离层TEC的仿真研究表明,在电子密度水平梯度较大的地区,应用电离层薄壳模型时会导致电子密度较高处的TEC被高估,而电子密度较低处的TEC被低估,在分析基于GPS数据提取的电离层TEC空间变化时要认识到这一点. 相似文献
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利用极区电离层自洽模型,考虑沉降电子引起的电离,计算了极区电离层的高度积分电导率和F层电子浓度,模拟了不同能谱分布的沉降电子对极区电离层的影响.研究发现不同能谱分布沉降电子对电离层电导率的影响不大,在能通量一定的情况下,平均能量是影响电导率大小的决定因素.而能谱对F层电子密度影响较大,随着平均能量的增加,能谱对电子浓度的影响越显著.在平均能量大于1 keV（甚至更低）时,修正的麦克斯韦分布谱能明显地增强F层电子浓度. 相似文献
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Tamara L. Gulyaeva 《Acta Geophysica》2007,55(2):253-266
Variations of the upper boundary of the ionosphere (UBI) are investigated based on three sources of information: (i) ionosonde-derived
parameters: critical frequency foF2, propagation factor M3000F2, and sub-peak thickness of the bottomside electron density profile; (ii) total electron content (TEC) observations from signals
of the Global Positioning System (GPS) satellites; (iii) model electron densities of the International Reference Ionosphere
(IRI*) extended towards the plasmasphere. The ionospheric slab thickness is calculated as ratio of TEC to the F2 layer peak electron
density, NmF2, representing a measure of thickness of electron density profile in the bottomside and topside ionosphere eliminating the
plasmaspheric slab thickness of GPS-TEC with the IRI* code. The ratio of slab thickness to the real thickness in the topside ionosphere is deduced making use of a similar ratio
in the bottomside ionosphere with a weight Rw. Model weight Rw is represented as a superposition of the base-functions of local time, geomagnetic latitude, solar and magnetic activity.
The time-space variations of domain of convergence of the ionosphere and plasmasphere differ from an average value of UBI
at ∼1000 km over the earth.
Analysis for quiet monthly average conditions and during the storms (September 2002, October–November 2003, November 2004)
has shown shrinking UBI altitude at daytime to 400 km. The upper ionosphere height is increased by night with an ‘ionospheric
tail’ which expands from 1000 km to more than 2000 km over the earth under quiet and disturbed space weather. These effects
are interposed on a trend of increasing UBI height with solar activity when both the critical frequency foF2 and the peak height hmF2 are growing during the solar cycle. 相似文献
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本文用日本电离层探测卫星ISS-b的资料,假设F2层峰顶以上电离层中各类离子随高度呈扩散平衡分布,得到了太阳活动高年（1978年8月-1979年8月）确定顶外电离层电子密度剖面形状的一个重要参数,即O+-H+离子过渡高度hT的一些变化特征.指出hT的日变化特性主要受电离层中O+离子的产生与复合作用的控制.太阳活动高年在不同纬度和所有经度区域,平均说来日间hT为大约1500-2500km变化,而夜间位于800-1400km,冬夜甚至接近中性氢、氧原子的化学平衡高度.过渡高度也表现出明显的纬度关系,在接近±20°的磁赤道地区,hT基本上不随纬度变化;但在大于±30°磁纬区域hT随纬度很快增加.义中还就hT随时间和地磁（或地理）纬度变化的机制作了简要讨论. 相似文献
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《Journal of Atmospheric and Solar》2007,69(7):817-825
Measurements from the Global Positioning System (GPS) satellites provide a valuable source of information about the ionosphere in the form of ray-path integrations of electron density. Total electron content (TEC) through the ionosphere can be estimated for specific satellite-to-ground paths using the two GPS frequencies and knowledge of the dispersive properties of the ionosphere. One approach used is the ionospheric imaging tool Multi Instrument Data Analysis System (MIDAS), which uses differential phase data from a number of GPS satellites and receivers to create an ionospheric movie of electron density. This paper addresses the accuracy with which MIDAS images the electron density at the F-layer peak. Firstly, the image accuracy is tested using a simulation of the imaging technique, representative of 1 year of data. Experimental GPS phase data are then used to image the electron density during a period of disturbed geomagnetic activity during April 2002. The images are compared to independent measurements from three ionosondes located across Europe and confirm the underestimate in peak electron density that was found in the simulation. Regardless of the peak density errors the vertical TEC in the images remains accurate. The accuracy of the imaged peak electron density is shown to improve across the image when measurements from ionosondes are included in the inversion process. 相似文献
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The measurements of an increase in the total electron content (TEC) of the ionosphere during solar flares, obtained based
on the GPS data, indicated that up to 30% of TEC increments corresponded to the ionospheric regions above 300 km altitude
in some cases, and TEC increased mainly below altitudes of 300 km in other cases. The theoretical model of the ionosphere
and plasmasphere was used to study the obtained effects. The altitude-time variations in the charged particle density in the
ionospheric region from 100 to 1000 km were used depending on the solar flare spectrum. An analysis of the modeling results
indicated that an intensification of the flare UV emission in the 55–65 and 85–95 nm spectral ranges results in a pronounced
increase in the electron density in the topside ionosphere (above 300 km). The experimental dependences of the ionospheric
TEC response amplitude on the localization and peak power of flares on the Sun in the X-ray range, obtained based on the GPS
data, are also presented in the work. 相似文献
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The measurements of variations in the total electron content of the Earth’s ionosphere along the GPS satellite signal propagation path are described. The signal parameters were measured at a network of receivers at three distant sites: Sura (Vasilsursk), Zelenodolsk, and Kazan. They are arranged along the geomagnetic latitude of the Sura Facility under short-wave radio irradiation of the ionosphere. One feature of the experiment is the crossing of a disturbed region by the radio path between a GPS satellite and Vasilsursk. This resulted from the angular sizes of the Sura array pattern; the radio paths between a GPS satellite and Zelenodolsk and a GPS satellite and Kazan did not cross. Variations in the total electron content of up to 0.15?0.3 TECU were revealed at all three sites during four experimental campaigns (March 2010, March 2013, May 2013, and November 2013). The lateral scale of an ionospheric disturbance stimulated by a high-power radio wave and the velocity of its west-to-east propagation along the geomagnetic latitude were 30–60 km and 270–350 m/s, respectively. A decrease in the total electron content (down to 0.55 TECU) was recorded along the Kazan–Zelenodolsk–Vasilsurks line, which is connected with the solar terminator transit; the lateral scale of the related ionospheric inhomogeneities was ~65–80 km. 相似文献
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Summary Wave diagnostics of several alternatives of a constructed model of the daytime and night ionosphere of the mid geomagnetic latitudes were carried out in the ULF range of electromagnetic waves. The altitude profiles of local wave parameters of the ionosphere, the wavelengths and wave attenuation, were analysed at a fixed frequency. The frequency dependence of the amplitude and polarization characteristics of the total wave at the Earth's surface were also analysed in dependence on the frequency-amplitude spectrum of geomagnetic pulsations. The effect of the low regions of the ionosphere (h<100 km) was tested on the damping of the propagating wave and on the frequency-amplitude and polarization characteristics of the wave at the Earth's surface. 相似文献
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利用COSMIC掩星2009年电子密度剖面数据,筛选数据进行网格划分,网格内数据统计平均,基于球谐函数计算模型值,分析电离层中低纬度地区最大电子密度的地磁季节变化、昼夜测分布相对变化,及地磁活动对电子密度的分布影响.结果表明,最大电子密度昼测值明显高于夜测值,在中纬度部分区域增大明显.电子密度昼测值在地磁活动期间高度150-550 km中低纬度范围为正相扰动,随纬度变化存在区域差异,随高度增加,扰动加强. 相似文献
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本文利用1996年的电离层数字测高仪DPS-4所测的f0F2、f0E以及美国NOAA和DMSP卫星观测估算的半球功率指数和午夜极光区赤道侧边界纬度等资料,考察中山站电离层的极区特征。结果表明,在太阳和地磁宁静环境下,冬季极夜磁正午中山站处于极隙区中心时,电离层内的电离密度达全天的最大值;上、下午各有数小时间隔位极光带内时,高能粒子的电离作用也很重要;夜间进入极差区后,电子密度则很低。夏季极昼时,太阳EUV辐射的电离效应使电离层电离密度比冬季值大许多,而且,日变化的最大值时间也提前了1~2h,强磁扰时,极隙区和极光带均向低纬侧移动;中山站上空的电子密度会大幅度下降。在中等扰动环境下情况要加复杂：磁正午前后极隙区内软粒子沉降的电离强度有所减小,而上、下午极光区的高能粒子电离则有较大增加。 相似文献
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A theory of the generation of plasma density irregularities with virtually no aspect sensitivity, in the lower ionosphere at high latitudes, by electron drifts aligned with the geomagnetic field, is presented. The theory is developed through fluid equations in which the destabilising mechanism involves positive feedback from electron collisional heating. When field aligned electron drift speeds exceed a few km s–1, this effect destabilises waves with wavelengths in excess of a few tens of metres in the lower E-region, where collisional effects are sufficiently large. Furthermore, the threshold conditions are almost independent of the wave propagation direction and the unstable waves propagate at speeds well below the ion acoustic speed. The role that this new instability may play in recent radar backscatter observations of short scale irregularities propagating in directions close to that of the geomagnetic field, in the lower E-region is also considered. 相似文献