2009年1月强爆发性增温期间突发E(Es)层的响应

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.     

平流层爆发性增温期间赤道电集流中太阴潮汐的经度变化统计学研究

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.     

基于COSMIC资料分析电离层F层不规则体结构

根据电离层不规则体的产生会导致周围电子浓度发生起伏变化的原理,利用2007年COSMIC掩星系统的TEC数据,通过平滑滤波得到TEC的扰动值ΔTEC的变化,利用其研究F层不规则体的时空变化特征.统计结果表明:扰动较大的掩星事件主要发生在磁纬±20°之间和高纬地区,春季和秋季带状分布较为明显,不同经度地区较强扰动的掩星事件的分布也有不同特征;较强ΔTEC的掩星事件主要发生在地方时午夜前和午夜后两个时段,发生的高度主要在250~400km范围内.这些结果与已知的F层不规则体的时空分布特征较为一致,说明利用TEC的扰动量来分析电离层F层不规则体结构是可行的.     

中国廊坊(39.4°N,116.7°E)中间层和低热层潮汐的季节变化

本文利用中国廊坊站(39.4°N,116.7°E)流星雷达在2012年4月1日至2013年3月31日期间的水平风场观测数据,分析了廊坊上空中间层和低热层(MLT,80~100 km)大气纬向风、经向风潮汐的季节变化特征.研究表明:廊坊MLT区域周日潮汐和半日潮汐波动比较显著,有明显的季节变化特征.周日潮汐振幅在88 km以下为半年变化,极大值位于2-3月和10月,极小值位于冬、夏季;在88 km以上为周年变化,振幅冬末春初最强,夏季最弱.周日潮汐相位在秋、冬季比春、夏季提前.半日潮汐主要呈现半年变化,在5月和9月最强,冬、夏季最弱.半日潮汐相位在春、夏季比秋、冬季提前.此外,廊坊风场潮汐的观测结果与WACCM4模式模拟结果进行比较,结果表明两者的主要特征相似,在细节上有显著区别.与40°N附近其他站点风场潮汐观测结果的比较结果表明中纬度MLT风场潮汐有显著的随经度变化特性.     

南极中山站F-lacuna特征分析

F-lacuna是高纬极区电离层测高仪频高图上经常出现的一种F层回波描迹部分或全部消失的现象,直接影响电离层参数的标定,其表征的电离层物理过程尚未定论.利用南极中山站测高仪频高图数据,本文统计分析了Flacuna在不同太阳风速度水平下的发生频率,主要对2012年2月15日一次F2-lacuna观测实例的粒子沉降及电离层特性进行了分析.观测特征表明,F2-lacuna发生期间,电离层电子总含量TEC明显减小,昭和站SuperDARN高频雷达观测到的中山站上空电离层Bragg后向散射增强,但对应来自磁层的电子和离子沉降并不明显.这可能是由磁层亚暴引起的极区电离层电流体系扰动,触发电离层F-B不稳定性,产生沿场向排列的小尺度不规则体,其热效应导致F2层密度减小,F2-lacuna出现.     

冬季强、弱平流层增温事件的发生与春季最后增温事件爆发早晚的联系

利用1958~2012年NCEP-NCAR逐日再分析资料,对平流层冬季强、弱爆发性增温事件(SSW)的发生和春季最后增温事件(SFW)爆发的早晚进行了统计、对比和合成分析.结果表明,冬季SSW事件的强、弱以及发生与否,可关系到后期春季SFW事件爆发的早晚.具体地,在发生(未发生)冬季强SSW事件之后的春季,SFW事件的爆发趋于偏晚(早);而在冬季弱SSW事件之后的春季,出现SFW事件爆发早和爆发晚的几率相当.对比冬季强、弱SSW过程中环流以及行星波活动异常的演变发现,在冬季强SSW事件爆发约30天之后,平流层会出现相反的强极涡(强极夜急流)型异常环流,伴随的行星波活动强度的负异常可持续到SSW爆发后约45天;不同的是,冬季弱SSW事件所伴随的环流异常持续时间短,不存在后期的强极涡型环流异常和行星波活动的显著异常.为了进一步证实冬季强SSW事件的发生对春季SFW事件爆发早晚的可能影响,针对冬季强、弱SSW年以及无增温事件发生的普通年份分别进行了合成分析,平均而言,在有强SSW事件(无SSW事件)发生年的冬季月份,热带外平流层行星波活动异常偏强(弱),极夜急流和平流层极涡异常偏弱(强),但在后期的春季月份,行星波活动则异常偏弱(强),平流层极涡异常偏强(弱).在有冬季弱SSW事件发生年的后期春季,平流层极夜急流以及极涡的强度无显著异常,与气候平均状况接近.     

利用COSMIC掩星探测分析120°E经线附近电离层E层闪烁指数变化

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.     

不同地磁扰动事件期间全球电离层的扰动形态分析

利用全球电离层台站提供的观测数据，分析 了5次不 同类型磁暴事件期间全球电离层F2层f0F2和hmF2的扰动变化. 主要结果 表明：对于延迟型主相磁暴S（C）和S（E），中高纬电离层首先会出现明显的正相扰动，随 后是明显延迟的负相扰动，负相扰动覆盖范围广，甚至扩展到低纬区, 且持续时间很长, 恢 复及其缓慢，其中S（C）型的扰动更为明显; 对于非延迟型主相磁暴S（A）、S（B）和 S（D ），高纬电离层正相扰动持续时间较短甚至不出现，中高纬电离层负相扰动的出现、发展和 恢复也相对较快; 磁暴主相强度的大小会对电离层负相扰动的强度、发展和持续时间产生一 定的影响; 高纬电离层扰动在非延迟型主相磁暴恢复相期间会出现明显的地方时效应，地方 时效应随纬度的降低而增强，并且会明显影响到中低纬电离层的扰动；电离层扰动从高纬到 低纬的变化趋势为：f0F2的扰动由负相向正相转化，hmF2的增加由全天出现趋向于只存在于夜间，反映了不同扰动物理机制的作用.     

1990年3月21日磁暴期间的电离层响应

利用美、欧、日等国非相干散射雷达观测的离子速度,高纬地磁站链1 min分辨率H分量及多站地面电离层垂测h'F等多种资料,对高低纬电离层的磁层耦合响应进行事例分析.除常规地磁资料外,极光区两雷达站对F层离子速度的测量是考察高纬电离层对流的很有效手段.本次中强磁暴期间赤道环电流指数Dst的最小值为-136 nT,但其最大的离子速度却超过2500 m/s,双对流圈的西旋则约为30°.从此次事件中极光区两雷达站离子速度的连续观测,得出了物理上合理的电离层对流形态,此图象得到地磁站链记录的有力支持.本事例的中低纬电离层响应再次确认了磁层扰动从高纬向中低纬穿透的事实.此外,Arecibo非相干散射雷达站资料又进一步证明:在同一经度链附近,磁暴期夜间电离层垂测h'F的多站突增现象是东向扰动电场从高纬穿透到中低纬,再通过E×H垂直向上的等离子漂移,使F层底部上升的结果.本文用高、低纬台站的多种观测资料较好地分析了该典型电离层物理现象.     

1989年3月特强磁暴期间的电离层暴

用欧亚大陆地面电离层垂测站资料考察1989年3月12～16日磁暴期间的电离层暴形态及其发展变化. 特强磁暴引发的电离层暴是全球性的,但自磁层沉降的高能粒子对热层低部的加热程度及区域分布不同,因而各经度链区域内电离层暴的特征也有所差异. 本文研究表明,与理论推断对照,欧洲地区内F2层最大电子密度NmaxF2(或f0F2)并不出现正暴现象,而负暴自高纬向低纬的发展则与典型的热层环流结果相符. 此外,此磁暴过程期间在中低纬区存在明显的波动过程. 在亚洲高纬地区,磁暴初期13日有约10 h的正暴,而负暴过程则与欧洲地区类似,但不太清晰;且无波动现象. 磁暴期间,同一经度链的中低纬地区,夜间常发生多站同时的h′F突增. 本文再次证实这是一般磁暴期间常出现的普遍现象.     

On the synchronism in the events within the core and on the surface of the earth: the changes in the organic world and in the polarity of the geomagnetic field in the phanerozoic

The data on geomagnetic reversals are compared with the changes in the organic world and with the lower-mantle plumes. The times of the formation of plumes and the times of their appearance on the Earth’s surface relate to the intervals characterized by the different frequencies of geomagnetic reversals, i.e., there is no interrelation between the formation of plumes and the frequency of the changes in the geomagnetic field polarity. At the same time, a certain synchronism is observed between the frequency of the geomagnetic reversals and the boundaries of the biostratigraphic ages, i.e., the changes in the organic world in the long-period range. A hypothesis is proposed, which explains the change in the sign of the geomagnetic field by the combined effect of the irregular rotation of the internal core relative to the mantle and the changes in the slope angle of the axis of the Earth’s rotation, which, in turn, results in synchronous events on the Earth’s surface: the rates of changes in the organic world.     

On the maintenance of the axisymmetric part of the flow in the atmosphere

Summary The maintenance of the axisymmetric component of the flow in the atmosphere is investigated by means of a steady-state, quasi-geostrophic formulation of the meteorological equations. It is shown that the meridional variations in the time-averaged axisymmetric variables can be expressed as the sum of three contributions, one being due to the eddy heat transport, another to the eddy momentum transport, and a third to the convective-radiative equilibrium temperature which enters the problem through the specification of a Newtonian form of diabatic heating. The contributions by the large scale eddies are evaluated through the use of observed values for the eddy heat and momentum transports.The contributions from each of the three forcing mechanisms to the temperature and zonal wind fields are invstigated individually and found to be of about equal importance. The sum of the three contributions are also presented for the temperature, the zonal wind, the stream function associated with the mean meridional circulation and the corresponding vertical motion. Although the results fail to reproduce the main observed features of the lower stratosphere, they are found to be in good agreement with observations in the middle latitude troposphere. At any pressure level, for example, the computed mean zonal wind has a jet-like profile and the axis of the jet is found to slope to the south with height, as observed in the atmosphere.Based in part on a thesis submitted by the first author as partial fulfillment of the requirements for the Ph.D. degree at the University of Michigan. — Publication No. 194 from the Department of Meteorology and Oceanography, The University of Michigan.     

On the gravimetric undulations of the geoid and the deflections of the vertical

Summary The author mentions the aims of the World-wide gravity project he established in the Ohio State University in Columbus, in 1950. He outlines the practical procedure of the gravimetric computations of the undulationsN and the vertical deflection components and and emphasizes that only by the global international cooperation and additional gravity observations at sea carried out during the last decade it has been possible to gather to Columbus the needed gravity material. Since there exist still large gravimetrically unsurveyed areas it is of vital significance to study what gravity anomalies are best to be used for these regions. The given figures concerning the accuracy of theN, and , estimated theoretically and obtained in practice, indicate that in the gravimetrically well surveyed parts of the world like in Europe and the United States we can get gravimetrically on basis of existing gravity material theN-values with accuracy of about 5–10 meters, and and with the accuracy of about 1. The geoid undulationsN are already computed in Columbus for more than 6000 points of the northern hemisphere. The sample maps show the interesting geoid of Europe and vicinity between the latitudes 60° and 30° and longitude 5° W and 30° E, drafted on basis of more than 1000N-values computed at the corners of 1°×1° squares. It is interesting to realize that the geoid undulations in all this area are positive, the extreme values being between 40 and 50 meters. The geophysical significance of the geoid maps of this kind is pointed out.     

太平洋中部地磁台11年周期变化的研究

综合APIA、HONOLULU、PAMATAI 3个地磁台三分量的11年周期变化的形态后,可定性地提出该变化源于内场。如内源为核幔边界的电涡流,则其中心点应位于3台之间。     

Magnetic stratigraphy of the Ordovician in the lower reach of the Kotuy River: the age of the Bysy-Yuryakh stratum and the rate of geomagnetic reversals on the eve of the superchron

Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary.     

On the variation in the geomagnetic dipole over the geological history of the Earth

The global database on the paleointensity, containing determinations of the virtual dipole moment (VDM) for a stable (normal) regime of the geomagnetic field in a time interval of up to 3.5 Ga, is supplemented by new VDM determinations and analyzed. The field generation process started no later than 3–3.5 Ga (earlier data are absent) at the stage of the Earth’s core formation. Since that time, the dipole value has differed from its present value by no more than an order of magnitude, and the deviations that have already been detected tend toward smaller values. The distribution of VDM values in the time interval 0–400 Ma is bimodal, which apparently reflects the presence of two different generation levels of the geomagnetic field distinguished by a relatively large value (close to the present field value) and a relatively small value (approximately half as large as the present value). The total duration of decreased VDM values appreciably exceeds that of increased VDM values (179.1 and 28.6 Myr, respectively). On the whole, data on the paleointensity do not contradict the hypothesis about the dipole nature of the field over the last 400 Myr; however, the number of determinations at high paleolatitudes is too small to draw decisive conclusions on the validity (or invalidity) of the dipole field approximation based solely on paleointensity data.     

Comparison Between the Nutations of the Planet Mars and the Nutations of the Earth

The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth.     

Evolutionary Changes in the Configuration of the Magnetic Field of the Solar Corona in the Epoch of the Minimum

Geomagnetism and Aeronomy - The evolution of the magnetic configuration in the solar corona is studied. The curvature of the K-corona helmets obtained from an analytical approximation of the...