北半球电离层中纬槽发生率及其槽极小位置变化的统计研究

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.     

Field-aligned plasma diffusive fluxes in the topside ionosphere from radio occultation measurements by CHAMP

O⁺ field-aligned diffusive velocities and fluxes in the topside ionosphere have been calculated from electron density profiles retrieved from CHAMP radio occultation (RO) measurements. The velocities and fluxes from January 2002 to December 2003 at low- and mid-latitudes have been statistically analyzed. The results show that daytime diffusive fluxes changed gradually from downward to upward as altitude increases. The largest values of the upward diffusive fluxes and velocities occurred at around ±25° geomagnetic latitude. During solstices the plasma fluxes in the winter hemisphere were larger than those in the summer hemisphere.     

Geomagnetic field fluctuations near Kharkov,which accompanied rocket launches from the Baikonur site

The observations of the geomagnetic field variations in the range of periods 1–1000 s, which accompanied the launches of 65 Soyuz and Proton rockets from the Baikonur site in 2002–2006, have been analyzed. The measurements were performed near Kharkov (the distance from the launching site is R ≈ 2100 km). Three groups of disturbances, with delays of 6–7, 30–70, and 70–130 min dependent on the time of day, have been revealed. The disturbance duration was 10–30, 50–70, and 45–70 min, respectively. Periods of 3–6, 6–12, and 6–12 min, respectively, predominated in the geomagnetic pulsations. The amplitudes of these pulsations reached 3–6 nT. The physical model of the observed geomagnetic disturbances, which generally agrees with the measurements, has been proposed.     

Anomalous night-time peaks in diurnal variations of NmF2 close to the geomagnetic equator: A statistical study

We present a study of anomalous night-time NmF2 peaks, ANNPs, observed by the La Paz, Natal, Djibouti, Kodaikanal, Madras, Manila, Talara, and Huancayo–Jicamarca ionosonde stations close to the geomagnetic equator. It is shown for the first time that the probabilities of occurrence of the first and second ANNPs depend on the geomagnetic longitude, and there is a longitude sector close to 110° geomagnetic longitude where the first and second ANNPs occur less frequently in comparison with the longitude regions located close to and below about 34° geomagnetic longitude and close to and above about 144° geomagnetic longitude. The found frequencies of occurrence of the ANNPs increase with increasing solar activity, except of the Djibouti and Kodaikanal ionosonde stations, where the probability of the first ANNP occurrence is found to decrease with increasing solar activity from low to moderate solar activity, and except of the Natal ionosonde station, where the frequencies of occurrence of the first and second ANNPs decrease with increasing solar activity from moderate to high solar activity. We found that the occurrence probabilities of ANNPs during geomagnetically disturbed conditions are greater than those during geomagnetically quiet conditions. The ANNP probabilities are largest in summer and are lowest in winter for the La-Paz, Talara, and Huancayo–Jicamarca sounders. These probabilities are lowest in summer for the Djibouti, Madras, and Manila ionosonde stations, and in spring for the Kodaikanal sounder. The maximums in the probabilities are found to be in autumn for the Djibouti, Madras, and Manila ionosonde stations, and in winter for the Kodaikanal sounder.     

欧洲地区电离层峰值电子密度逐日变化的相关距离研究

本文采用欧洲22个台站的电离层F^₂层峰值电子密度N_mF^₂,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.     

foF2月中值太阳循环变化及单站谱模型研究

利用我国9个电离层观测站第21和22太阳周大约20年的foF2月中值数据,分析太阳活动和地磁活动对电离层foF2的影响,结果显示白天和夏季夜间foF2和太阳黑子数R之间存在着明显非线性关系,并且随着纬度的降低逐渐增强.当回归分析加入地磁Ap指数时,多重回归模型与实测值误差进一步减小,说明同时考虑太阳活动和地磁活动的非线性影响能够更好地描述foF2的变化.基于foF2与太阳黑子数R及地磁指数Ap之间的非线性统计关系,利用Fourier级数建立9个单站谱模型,并与国际参考电离层IRI进行了比较,精度有一定提高.     

Variations in the ULF index of geomagnetic pulsations during strong magnetic storms

The level of wave geomagnetic activity in the morning, afternoon, and nighttime sectors during strong magnetic storms with Dst varying from ?100 to ?150 nT has been statistically studied based on a new ULF wave index. It has been found out that the intensity of geomagnetic pulsations at frequencies of 2–7 mHz during the magnetic storm initial phase is maximal in the morning and nighttime sectors at polar and auroral latitudes, respectively. During the magnetic storm main phase, wave activity is maximal in the morning sector of the auroral zone, and the pulsation intensity in the nighttime sector is twice as low as in the morning sector. It has been indicated that geomagnetic pulsations excited after substorms mainly contribute to a morning wave disturbance during the magnetic storm main phase. During the storm recovery phase, wave activity develops in the morning and nighttime sectors of the auroral zone; in this case nighttime activity is also observed in the subauroral zone.     

基于ZH-1卫星探测的太阳活动低年顶部电离层不规则结构的时空特征

利用ZH-1卫星2019、2020年的原位电子密度观测数据,对卫星观测范围,即地理纬度南北65°之间午夜后顶部电离层的不规则结构进行研究,得到如下结果.(1)午夜后顶部电离层不规则结构集中区主要分布在地磁赤道、中纬度以及较高纬度区,白天赤道异常峰值区为不规则结构的谷值区.(2)不同纬度区不规则结构随地理经度分布呈现出明...     

Interhemispheric comparison of TDIM E- and F-region ionospheres on 14 January 1988

The USU time-dependent ionospheric model (TDIM) simulated the northern (winter) and southern (summer) ionospheres as they responded to the changing solar wind and geomagnetic activity on 14 January 1988. This period began with moderately disturbed conditions, but as the IMF turned northward, the geomagnetic activity decreased. By 1400 UT, the IMF B_y component became strongly negative with B_z near zero; and eventually B_z turned southward. This began a period of intense activity as a magnetic storm developed. The magnetospheric electric field and auroral electron precipitation drivers for these simulations were obtained from the Naval Research Laboratories (NRL) Magnetohydrodynamic (MHD) magnetospheric simulation for this event.The F-region ionospheric simulations contrast the summer–winter hemispheres. Then, the difference in how the two hemispheres respond to the geomagnetic storm is related to the differences in magnetospheric energy deposition in the two hemispheres. This also emphasizes the role played by the E-region in the magnetosphere–ionosphere (M–I) coupling and subsequent lack of conjugacy in the two hemispheres. The F-region’s response to the changing geomagnetic conditions also demonstrates a striking lack of conjugacy. This manifests itself in a well-defined ionospheric morphology in the summer hemisphere and a highly irregular morphology in the winter hemisphere. These differences are found to be associated with the differences in the magnetospheric electric field input.     

Features of the latitudinal distribution of the annual variation of the geomagnetic field level and circumpolar current system in 1964

The results of investigations of the latitudinal distribution of annual variation of the geomagnetic field level in the seasons of 1964 (International Quiet Sun Year) using the data from 95 world magnetic observatories located at various longitudes in the latitude range 83° N–90° S are reported. The latitudinal features of the X, Y, and Z components of the geomagnetic field have been analyzed. It has been shown that the amplitudes (summer-winter differences) of the annual variation are maximal in the polar regions, decrease continuously to zero towards the equator, and are identical for both the Northern and Southern hemispheres with a half-year delay (local summer). The amplitudes of the equinox-winter difference in the equinox periods are smaller than those in summer, but are manifested simultaneously in the Northern and Southern hemispheres. An equivalent circumpolar current system has been constructed, which is responsible for the annual variation of the geomagnetic field level. Its parameters have been determined.     

Mean thermospheric winds observed from Halley,Antarctica

Thermospheric winds on a total of 237 nights have been studied for the effects due to geomagnetic activity, solar flux, and season. The observations have been made from 1988 to 1992 by a Fabry-Perot interferometer (FPI) operating at Halley (75.5^°S, 26.6^°W), Antarctica. This is the first statistical study of thermospheric winds near the southern auroral zone. The main factor affecting the wind velocities is the geomagnetic activity. Increases in activity cause an increase in the maximum equatorward wind, and cause the zonal wind in the evening to become more westward. Smaller changes in the mean wind occur with variations in season and solar flux. The small variation with solar flux is more akin to the situation found at mid-latitudes than at high latitudes. Since the geomagnetic latitude of Halley is only 61^°, it suggests that the variability of the wind with solar flux may depend more on geomagnetic than geographic latitude. These observations are in good agreement with the empirical Horizontal Wind Model (HWM90). However, comparisons with predictions of the Vector Spherical Harmonic Model (VSH) show that for low geomagnetic activity the predicted phases of the two components of the wind closely resemble the observations but the modelled amplitudes are too small by a factor of two. At high geomagnetic activity the major differences are that modelled zonal velocity is too westward in the evening and too eastward after 04 UT. The modelled ion densities at the F-region peak are a factor of up to 9 too large, whilst the predicted mean value and diurnal variation of the altitude of the peak are significantly lower than those observed. It is suggested that these differences result from the ion loss rate being too low, and an inaccurate model of the magnetic field.     

Seasonal features in the spread-F probability near midnight over Moscow

Using the data of Moscow station for 1975–1985, the seasonal features in the dependence of the spread-F probability P near midnight on the levels of solar and geomagnetic activity have been analyzed. It has been found that the P dependence on solar activity is most substantial in winter and fall, the P dependence on geomagnetic activity is maximal during equinoxes, and the P dependence on solar activity prevails in summer but is much weaker than in winter and fall. Based on the qualitative analysis of the known mechanisms of the midlatitude spread-F, the regression equation, which shows the P dependence on the solar activity level and thermospheric parameters (temperature and density) at a fixed average level of geomagnetic activity, has been obtained. In this equation the character of the seasonal changes in P is determined by the thermospheric parameters, the relative contribution of which depends on solar activity. The found dependence of the character of the P seasonal variations on the solar activity level has been interpreted based on this equation.     

全球电离层VLF电场功率谱特征

分析2006年3月至2009年2月DEMETER卫星VLF电场功率谱数据发现,卫星高度上全球电离层电场功率谱有以下特征:高纬度区域电场辐射强度平均高于低纬度区域,几个地磁场异常区相应的电场辐射增强;全球电场功率谱,向阳侧强于夜侧,大陆强于海洋,夏季强于分点季,冬季最弱;不同频段的电场功率谱特征有显著差异,某些频段的功率...     

foF2月中值太阳循环变化及单站谱模型研究

利用我国9个电离层观测站第21和22太阳周大约20年的f_oF₂月中值数据,分析太阳活动和地磁活动对电离层f_oF₂的影响,结果显示白天和夏季夜间f_oF₂和太阳黑子数R之间存在着明显非线性关系,并且随着纬度的降低逐渐增强．当回归分析加入地磁Ap指数时,多重回归模型与实测值误差进一步减小,说明同时考虑太阳活动和地磁活动的非线性影响能够更好地描述f_oF₂的变化．基于f_oF₂太阳黑子数R及地磁指数Ap之间的非线性统计关系,利用Fourier 级数建立9个单站谱模型,并与国际参考电离层IRI进行了比较,精度有一定提高．     

On the long-term change of ionospheric parameters

Independent of the possible sources (solar activity, geomagnetic activity, greenhouse effect, etc.) of a global change in the upper atmosphere, it is the sign of a long-term trend of temperature that might reveal the cause of a global change.Long-term change of temperature in the F region of the ionosphere has been studied and is assumed to be expressed in terms of thickness of the bottomside F2 layer characterized by the difference between height of the maximum electron density of the F2 layer hmF2 and altitude of the lower boundary of the F region represented by h′F. Using the difference of two ionospheric parameters has the advantage that it reduces the effect of changes resulting from alteration of equipment and scaling personnel. In this study, in summer only night values of the difference hmF2−h′F and in winter both day and night values have been taken into account considering that h′F might indicate the lower boundary of the F region in these periods. The study of the behaviour of hmF2−h′F taking separately the stations and determining yearly the mean measure (trend) of the variation of hmF2−h′F with solar and geomagnetic activities found that this difference increases significantly with enhanced solar activity, but trends of the solar activity effect exerted on this difference themselves do not practically change with increasing sunspot number. Further, hmF2−h′F decreases only insignificantly with growing geomagnetic activity. Trends of the geomagnetic activity effect related to hmF2−h′F change only insignificantly with increasing Ap; however, trends of the geomagnetic activity effect decreased with increasing latitude.As a result of this investigation it has been found that hmF2−h′F regarded as thickness of the bottomside F2 layer shows an effect of the change of solar activity during the last three solar cycles, indicating temperature change in the upper atmosphere to be expected on the basis of changing solar activity. Furthermore, though a long-term variation of solar activity considering only years around solar activity minima is relatively small, the difference hmF2−h′F indicates a trend opposing the change of solar activity; that is, it decreases slightly during the first three 20, 21, 22 solar cycle minima (1964–1986), but decreases more abruptly according to the change of solar activity towards the minimum of solar cycle 23 (1986–1996), thus also indicating variation of temperature in the F region. However, this variation cannot be explained by the change of solar and geomagnetic activities alone, but assumes some other source (e.g. greenhouse gases) too.     

太阳和地磁活动对磁赤道地区低热层NO密度的影响研究

利用SNOE卫星1998年3月11日至2000年9月30日共计935天观测的NO密度和太阳软X射线数据,分析了低热层NO的时空分布特征及其对太阳和地磁活动的响应,得出了以下结论:NO密度从96.67 km开始增加,大约在105～110 km高度达到最大,随后开始减小;同一高度处一般夏季期间最大,冬季次之,春秋分季最小;密度峰值大小变化范围约为(0.5～1.5)×10⁸ mol/cm³,峰值高度基本分布在107 km和113 km高度处,且不随太阳活动变化,平均值约为107 km;NO密度与太阳软X射线及地磁Ap指数的相关系数在不同高度存在0、1和2天的最佳延迟时间,而同太阳软X射线的统计关系在不同高度和季节存在"线性"、"放大"和"饱和"现象;从统计和事件分析结果来看,太阳活动对磁赤道地区低热层NO密度的气候尺度变化的影响远大于地磁活动,但地磁活动对NO短期变化贡献非常明显.     

Pc1 geomagnetic pulsations as a potential hazard of the myocardial infarction

The analysis of 85,800 events (1979–1981) of Moscow ambulance calls, related to the myocardial infarction (MI), demonstrates a seasonal variation with the profound summer minima and winter maxima. Similar results were obtained by analyzing the 25-year (1970–1995) statistical monthly data on the death from infarction in Bulgaria. The estimated high correlation coefficient (0.84) between Moscow and Bulgarian data suggests a common reason. There is a great number of clinical and statistical studies confirming that the MI number rises during geomagnetic disturbances, which have a maximum of occurrence near equinox, not in winter. In order to explain this contradiction we suggest that one of the critical additional factors, which affect a human cardiovascular system, could be geomagnetic Pc1 pulsations at frequencies comparable with the human heart beat rate. The MI variations as well as the Pc1 pulsations exhibit a summer minimum. The comparative analysis of the Moscow ambulance MI data and Pc1 pulsations recorded at the geophysical observatory in Borok is presented. It is shown that in about 70% of the days when an anomalously great number of ambulance calls (AMI) has been registered Pc1 pulsations have been recorded. In the winter season the probability of the simultaneous AMI and Pc1 occurrence was 1.5 times larger than their accidental coincidence. Moreover, it was found that the effects of magnetic storms and Pc1 in AMI were much higher in winter than in summer. We suggest that the seasonal variation of the production of the pineal hormone melatonin leads to a winter instability in the human organisms and increases the sensitivity of the patient to the “negative” influence of Pc1 geomagnetic pulsations in winter.     

日冕绿区与地磁扰动間的某些問題

一、引言地磁場扰动的原因,至今仍是地球物理学者与天体物理学者所共同关切的問題.有許多理由說明太阳是使地磁产生扰动的主要根源.一般說来,在任何时期內,太阳活动愈強,地磁活动也愈強.然而,即使是在太阳活动最弱的年份,地磁場也可能产生不小的扰动.既然在太阳活动低年,作为太阳活动标誌的黑子数很少,那么,使地磁产生扰动的根源又是什么呢?对于这个問題,20多年以前提出了所謂M区来做答案.     

Changes in geomagnetic activity and global temperature during the past 40 years

The purpose of this study is to investigate the effect of geomagnetic activity (used as a measure of solar wind parameters) on the variability of large-scale climate patterns and on changes in the global temperature. We show that positive statistically significant correlations between global temperature and the distribution of surface temperature over Eurasia, the East and Equatorial Pacific and over the North Atlantic for the period 1966?C2009 correspond to large-scale climate patterns defined by climate indices. We found very similar positive correlations between geomagnetic activity and the distribution of surface temperature in the mentioned regions. As an effect of geomagnetic storms, energetic particles penetrate from the magnetosphere into the region of the stratospheric polar vortex. The increase of temperature and pressure can be observed over northern Canada. The vortex shifts towards Europe, rotates counter-clockwise and the wind blows from the polar region over Greenland southwards. It diverts the warm flow proceeding northward over the Atlantic, eastward along the deep Icelandic low extending as far as the Barents Sea and takes part in warming Eurasia. The strengthened zonal flow from Siberia cools the western Pacific with the impact on the warming of the equatorial and eastern Pacific when also a distinct 1976?C78 climate shift occurred. Processes in the Atlantic and Pacific play a significant role and a time delay (wind forcing over the previous 1?C4 yr) appears to be the most important for the relocation of the oceanic gyres. Results showing statistically significant relations between time series for geomagnetic activity, for the sum of climate indices and for the global temperature help to verify findings concerning the chain of processes from the magnetosphere to the troposphere.