Reflection of the solar wind parameters in the CR geomagnetic cutoff rigidity before a strong magnetic storm in November 2003

The time variations in the CR geomagnetic cutoff rigidity and their relation to the interplanetary parameters and the Dst index during a strong magnetic storm of November 18–24, 2003, have been analyzed. The Tsyganenko (Ts03) model of a strongly disturbed magnetosphere [Tsyganenko, 2002a, 2002b; Tsyganenko et al., 2003] have been used to calculate effective geomagnetic thresholds with the help of the method for tracing CR particle trajectories in the magnetospheric magnetic field. The geomagnetic thresholds have been calculated using the method of global spectrographic survey (GSS), based on the data from the global network of CR stations, and the results have been compared with the effective geomagnetic cutoff rigidities. The daily anisotropy of effective geomagnetic thresholds during the Dst variation minimum have been estimated. The relation of the theoretical and experimental geomagnetic thresholds, obtained using the GSS method, to the interplanetary parameters and Dst variation is analyzed. The Dst variations, IMF B _z , and solar wind density are most clearly defined in the geomagnetic thresholds during this storm. The correlation between B _y and experimental geomagnetic thresholds is higher than such a correlation between this parameter and theoretical thresholds by a factor 2–3, which suggests that a real dawn-dusk asymmetry during this storm was stronger than such an asymmetry represented by the Ts03 model.     

Components of geomagnetic variations with tidal wave frequencies

This work studies regular variations caused by the effect of O ₁ and M ₂ tidal waves on magnetospheric current systems. The response to the tidal effect has been calculated using the magnetic field paraboloid model. A model of origination of the geomagnetic variations with O ₁ and M ₂ tidal wave periods has been developed. The values of such variations, which originate as a result of tidal deformations of the current system in the magnetosphere, are 0.2÷0.9 nT. The calculated values coincide in magnitude with the processed geomagnetic data obtained at the Paratunka geophysical observatory.     

Effects in cosmic rays in March 1991

Using the spectrographic global survey method, variations in the rigidity spectrum and anisotropy of galactic cosmic rays (March 1991) have been studied using data from ground-based observations of cosmic rays (CR) at the worldwide network of stations. Variations in geomagnetic cutoff rigidity (GCR) have been calculated. The paper also presents latitudinal GCR variations at certain moments of the considered period for different geomagnetic field disturbance levels. Calculation results of GCR variations have been compared with those of effect of the westward current flowing with a strength proportional to the latitude cosine along parallels on the sphere, for different radii of the current ring in the dipole field.     

Dynamics of Cosmic-Ray Cutoff Rigidity and Magnetospheric Parameters during Different Phases of the Storm of November 20, 2003

Geomagnetism and Aeronomy - The correlations between variations in the geomagnetic cutoff rigidity of cosmic rays and the Dst and Kp geomagnetic indices and solar-wind and IMF parameters are...     

Correlation of the Cosmic-Ray Cutoff Rigidity with Heliospheric and Geomagnetic-Activity Parameters at Different Phases of a Magnetic Storm in November 2004

Geomagnetism and Aeronomy - The correlation of the variations in geomagnetic cutoff rigidity of cosmic rays ΔR with the interplanetary medium parameters and geomagnetic activity indices Dst...     

Influence of the Solar Wind and Geomagnetic Activity Parameters on Variations in the Cosmic Ray Cutoff Rigidity during Strong Magnetic Storms

Geomagnetism and Aeronomy - The correlation between the variations of geomagnetic cutoff rigidity ΔR and interplanetary parameters and the Dst index of geomagnetic activity during one moderate...     

地磁平静期间磁层高能粒子非垂直地磁截止刚度研究

地磁截止刚度是定量衡量地球磁场对高能粒子屏蔽效应的参数,描述了高能粒子穿越磁层到达指定观测点的带电粒子刚度阈值.人们一直研究垂直方向上的截止刚度,但对作为方向函数的截止刚度,缺少详细研究.我们使用单粒子方法,倒向追踪粒子的运动状态,计算了近地空间不同投掷角度的高能粒子地磁截止刚度,研究发现:(1)天顶方向或者垂直方向的...     

Spectrographic analysis of events in cosmic rays in October–November 2003

Based on the multiplied neutron registration with the Magadan neutron monitor, the parameters of the spectrum of variations in the cosmic ray hardness and variation in geomagnetic cutoff rigidity for Forbush decreases and intensity increases, related to registration at a level of solar cosmic ray observation, have been determined using the spectrographic method. Results of an analysis indicate that the spectral index (represented in the power form) increases for Forbush decreases and decreases for increases in CR intensity. In the analyzed cases, geomagnetic cutoff rigidity decreases for intensity increases and Forbush decreases.     

Geomagnetic cutoff rigidities of cosmic rays in a model of the bounded magnetosphere with the ring current

The cosmic ray geomagnetic cutoff rigidities are obtained by analytical calculations within an axisymmetric model of bounded magnetosphere, the magnetic field of which is created by the dipole field of the Earth and by two spheres located beyond the Earth with the currents that flow along the parallels and have a value proportional to the cosine of latitude. The inner sphere models the ring current flowing in the westerly direction; the outer sphere simulates the currents over the magnetopause, which flow in the easterly direction. The analytical results of calculations of variations in the geomagnetic cutoff rigidity for different levels of geomagnetic disturbances are given. The results are compared with the results of analytical calculations within the model of unbounded magnetosphere (when the outer sphere is absent).     

Magnetospheric effects of cosmic rays. 1. Long-term changes in the geomagnetic cutoff rigidities for the stations of the global network of neutron monitors

Vertical geomagnetic cutoff rigidities are obtained for the stations of the global network of neutron monitors via trajectory calculations for each year of the period from 1950 to 2020. Geomagnetic cutoff rigidities are found from the model of the Earth’s main field International Geomagnetic Reference Field (IGRF) for 1950–2015, and the forecast until 2020 is provided. In addition, the geomagnetic cutoff rigidities for the same period are obtained by Tsyganenko model T89 (Tsyganenko, 1989) with the average annual values of the Kp-index. In each case, the penumbra is taken into account in the approximation of the flat and power spectra of variations of cosmic rays. The calculation results show an overall decrease in geomagnetic cutoff rigidities, which is associated with the overall decrease and restructuring of the geomagnetic field during the reporting period, at almost all points.     

Cosmic ray geomagnetic cutoff rigidities in the magnetic field of two empirical models during a strong disturbance in November 2003: A comparison of models

Cosmic ray (CR) fluxes, which penetrate into the Earth??s magnetosphere and atmosphere from the interplanetary space, are an important factor of space weather. The geomagnetic field allows or forbids CR particles to enter into a given point in the magnetosphere depending on their energy. The geomagnetic cutoff rigidity regulates the distribution of CR fluxes in the magnetosphere. The geomagnetic cutoff rigidity (geomagnetic threshold) determination accuracy is closely related to the accuracy of the magnetospheric model used in calculations. Using a method for tracing of charged CR particle trajectories in the magnetic field of a model magnetosphere, we obtained geomagnetic thresholds for two magnetosphere empirical models (Ts01 and Ts04), constructed based on the same initial database. The Ts01 model describes the middle magnetosphere for certain conditions in the solar wind and interplanetary field. The Ts04 model pays the main attention to describing the large-scale evolution of magnetospheric currents during a storm. The theoretically obtained geomagnetic thresholds have been compared with experimental thresholds, calculated using the spectrographic global survey method based on data from the global network of CR stations. The study has been performed for the period of a strong geomagnetic storm that occurred in November 2003.     

甘肃嘉峪关、瓜州地电场日变化与地电暴差异机理分析

通过甘肃省嘉峪关台地磁场观测资料,研究嘉峪关台、瓜州台磁静日地电场日变化的时频特征波;由地电场分钟值观测数据的时序叠加残差方法,研究嘉峪关、瓜州山的地电暴变化。结果表明:(1)两台地电场静日变化以两次起伏变化为主,无相位差,但两台之间日变幅差异较大;(2)地电场分量变化与地磁场正交分量变化显著相关;地电场与地磁场日变波形不同,极值时间有差异。2个台存在很明显的高频成分,在去除了高频变化后,其优势周期也相同,从大到小依次为12 h、8 h、24 h。地磁场H分量因存在磁暴影响,故高频变化较多,在去除了磁暴影响后,其优势周期从大到小依次为24 h、12 h、8 h;(3)当电磁暴扰动剧烈时,两台可以较清晰地记录到地电暴的完整变化。在发生电磁暴时,地电场与地磁场的相关性明显降低,且不同台、不同测向之间的变化幅度也不尽相同。两台东分量E_Y暴日的日变幅较静日明显增大,磁暴期间Y分量变化率与地电场东分量E_Y观测数据显著相关,由此说明:两台日变幅的不同与台站台址电导率有关,太阳风引起的电离层活动是引起了地电场日变化主因。引起电暴的原因可能不同于引起日变化的原因,主要是两台之间及不同测向之间的浅、深层电阻率和地质构造等诸多因素的结果。     

Correlations between SAR arc intensity and solar and geomagnetic activity

We present a study of statistical relationships between SAR arc intensities acquired by the Pacific Northwest Laboratory Photometer Network during 1978–1988 and solar and geomagnetic activity indices Dst, F10.7, and Kp by use of the method of multiple regression analysis. We found significant correlations between intensity and all of the indices involved. In the present work we show for the first time that the partial correlation coefficients depend on the time offset, t, between the time of SAR arc intensity observations and the onset of the geomagnetic storm recovery phase, with the largest correlations being observed when 8 d t d 16 h. It is also shown that there are significant differences between partial correlation coefficients calculated for SAR arcs associated with strong (Dst_min > −100 nT) and weak (Dst_min > −100 nT) geomagnetic storms. We observe also that the multiple correlation coefficients for strong storms are much larger than for weak ones. We found that the variations in the electron temperature, T_e, in the SAR arc region are not mainly produced by variations in the electron density of the ionosphere but are strongly driven by the additional heating of the electron gas due to an interaction of the ring current ions and the plasmaspheric electrons. As a result, variations of T_e in the SAR arc region with characteristic time scales from several minutes to several hours are stipulated by time variations of ring current parameters.     

2018年云南通海MS5.0和墨江MS5.9地震前地磁垂直强度极化异常时空特征研究

利用云南11个地磁台站的秒采样观测数据,计算和分析了地磁垂直强度极化值Y_zh在2019年8月13日、14日通海M_S5.0地震前及2019年9月8日墨江M_S5.9地震前的时空变化特征。研究表明,地磁台站Y_zh值的幅度在震前会出现同步增强现象。而与以往的极化震例研究相比,Y_zh值的高值异常在震前出现时间要更早些,可能会在震前2~5个月出现,距发震时间越近,产生的异常幅值可能越大,异常持续时间也越长。同时,研究还发现2次地震主要发生在异常空间等值线的高值区内,尤其在零值阈值线附近,这可能对今后发震地点的预测有一定的指示意义。对比异常产生时段内的D_st指数,认为该高值异常并非由空间电流体系所引起。     

Comparison of standard and digital observation at the Geomagnetic Adolf Schmidt Observatory Niemegk

For more than 4 yr the geomagnetic field has continuously been recorded by means of 3 proton magnetometers (F, X. Y) at Niemegk Observatory (1 value/min on punched tape). With this observation material, for all 7 geomagnetic components hourly means are calculated. The preliminary hourly means forF, Y, andX are published in the monthly report. As a rule, their comparison with the observatory data is satisfactory. Only with great geomagnetic activity (K ₁7) what was the case especially in 1982 relatively often, deviations in the hourly means up to 30 nT occurred. Obviously, during great magnetic disturbances the scanning rate of 1 min is not sufficient. In case of quick data variations, however, small technical defects in the electronic circuit can occur. Besides, these great differences could also be explained by errors which could be conditioned by the standard observational and processing methodology.     

两次4.0级地震前高邮台和盐城台地磁谐波振幅比异常分析

使用江苏地区9个地磁台站2009年1月~2016年10月的分钟值数据,计算得到各台站的地磁谐波振幅比时间序列变化曲线。分析发现,2012年7月20日高邮4.9级地震、2016年10月20日射阳4.4级地震前,高邮台和盐城台地磁谐波振幅比YZH_x和YZH_y分别出现了长短周期不同步的异常变化。其异常特征表现为:(1)异常的长期变化形态为"下降—转折—恢复",在恢复过程中出现不同步现象,异常持续时间近3年,异常幅度为0.02~0.17;(2)YZH_y向的异常幅度大于YZH_x向,同时,2次地震主震的主压应力方向为EW向,存在异常幅度较大方向与主压应力方向一致的特点。     

On the 18-day quasi-periodic oscillation in the ionosphere

The presence and persistence of an 18-day quasi-periodic oscillation in the ionospheric electron density variations were studied. The data of lower ionosphere (radio-wave absorption at equivalent frequency near 1 MHz), middle and upper ionosphere (critical frequencies f₀E and f₀F2) for the period 1970–1990 have been used in the analysis. Also, solar and geomagnetic activity data (the sunspot numbers Rz and solar radio flux F10.7 cm, and a_N index respectively) were used to compare the time variations of the ionospheric with the solar and geomagnetic activity data. Periodogram, complex demodulation, auto- and cross-correlation analysis have been used. It was found that 18-day quasi-periodic oscillation exists and persists in the temporal variations of the ionospheric parameters under study with high level of correlation and mean period of 18–19 days. The time variation of the amplitude of the 18-day quasi-periodic oscillation in the ionosphere seems to be modulated by the long-term solar cycle variations. Such oscillations exist in some solar and geomagnetic parameters and in the planetary wave activity of the middle atmosphere. The high similarities in the amplitude modulation, long-term amplitude variation, period range between the oscillation of investigated parameters and the global activity of oscillation suggests a possible solar influence on the 18-day quasi-periodic oscillation in the ionosphere.     

Preliminary study on the source field mode of geomagnetic six-month-period variations

The monthly means of north component X of geomagnetic field from 16 observatories during 1984–1988 were analyzed using the Sompi spectral analysis technique Most of these observatories are located in China. The analysis of the semiannual variations indicates that the latitude has no apparent effect on the X component. This clearly implies that the source field mode of semiannual variations cannot simply be described by using the p ₁ ⁰ mode. Using the p ₁ ⁰ mode to estimate the inductive scale lengthC in the semiannual period, the value ofC at each observatory would be biased significantly. The purpose of this study is to find which kind of modes is optimal for estimating the values ofC corresponding to the semiannual variations. The results show that a composite mode, involving five terms P _n ⁰ (n = 1,, 5), might be a reasonable and acceptable one     

Variations of the upper atmosphere air density and electron density during geomagnetic disturbances

The variations of the upper atmosphere air density during geomagnetic disturbances have been investigated by many authors. According to the analysis of satellite orbits, in most cases an increase in the air density may be observed when the indexA _phas a maximum. Having ionospheric data from stations in Europe, Asia and Australia we might be able to study the global behaviour of the electron density in theF ₂ region during such geomagnetic disturbances when an increase of the air density had been observed. In these cases we found, that at the peak of the ionospheric layer, the electron density decreased 0–3 days later than theA _pmaximum.     

Response of the high-latitude polar ionosphere to changes in the orientation of the Poynting vector near the Earth orbit relative to the geomagnetic moment orientation

The effect of the mutual orientation of the Poynting vector P of the electromagnetic energy density in the solar wind and the vector M of the Earth’s magnetic moment (taking into account its orbital and diurnal motions) on the geomagnetic activity has been examined for the first time using the measurements of the solar wind parameters on the Earth orbit in 1963–2005. The component P _m of the vector P along the vector M is shown to have a pronounced annual variation with the extrema in November and May and a diurnal variation with the extrema at ∼6 and 18 UT. The phases of the variations are shown to be determined only by the geometric parameters and are independent of the sign of the sector structure of the interplanetary magnetic field. The experimental data on the planetary and high-latitude geomagnetic activity, which is a response to changes in the orientation of P relative to M, are presented. The power of the sources of the electromagnetic energy of the solar wind during strong geomagnetic disturbances is also estimated.