极光沉降粒子能量与AE、Dst指数的相关分析

对NOAA的POES系列极轨卫星观测得到的1978年以来近30年的极光沉降粒子半球能量的估算值EPI(Estimated Power Input)数据进行了分析,结果表明,极光沉降粒子有显著的春秋分峰值的年变化特征,并且有冬季半球沉降能量较大的南北半球不对称性.对EPI的时均值Pa与地磁指数AE、Dst的相关分析得到,Pa与AE的相关系数为0.76,Pa与Dst的相关系数为-0.55.把南北半球的时均值SPa,NPa数据分别与AE,Dst指数做相关,发现SPa与AE的相关性稍高于NPa的,SPa和NPa与Dst的相关性近似.当时延τ=0时,AE与Pa的相关最好,表明全球极光沉降粒子和极光电集流的变化同步;当Dst滞后于Pa,时延τ=1~2 h,Pa与Dst的相关最好,并且时延τ为6～8 h,Pa与Dst的相关都好于无时延的水平.     

Phase shift (time) between storm-time maximum negative excursions of geomagnetic disturbance index Dst and interplanetary Bz

The evolutions of severe geomagnetic storms (D_st<−200 nT) during solar cycle 23 were examined. For each storm, certain timing landmarks (starting of increases of interplanetary total field B, its B_z component, D_st changes, etc.) were noted and from these, various antecedence intervals were calculated. It was noticed that the various delays varied in a very wide range from storm to storm. Thus, some storms had a warning of only 4 h at the ACE location, while others had a warning of up to 30 h. These variations do not depend upon the Sun–Earth transit time. Also, faster interplanetary structures do not necessarily give quicker or stronger D_st evolutions, though larger negative B_z seems to give stronger negative D_st, but not necessarily earlier.     

Difference in the air temperatures between the years of solar activity maximum and minimum and its mechanism

Based on large set of observational data (for ∼100 years), it has been demonstrated that the air temperature at midlatitudes in the years close to solar activity maximum is on average higher than in other years by DT = 0.11–0.15 degrees at many meteorological stations. The DT parameter is negative and smaller in magnitude near the equator and poles. A correct (in the energetic sense) physical mechanism by which solar and geomagnetic activities affect the ground level air temperature has been proposed.     

极光沉降粒子能量与AE、Dst指数的相关分析

对NOAA的POES系列极轨卫星观测得到的1978年以来近30年的极光沉降粒子半球能量的估算值EPI(Estimated Power Input)数据进行了分析,结果表明,极光沉降粒子有显著的春秋分峰值的年变化特征,并且有冬季半球沉降能量较大的南北半球不对称性.对EPI的时均值Pa与地磁指数AE、D_st的相关分析得到,Pa与AE的相关系数为0.76,Pa与D_st的相关系数为-0.55.把南北半球的时均值SPa,NPa数据分别与AE,D_st指数做相关,发现SPa与AE的相关性稍高于NPa的,SPa和NPa与D_st的相关性近似.当时延τ=0时,AE与Pa的相关最好,表明全球极光沉降粒子和极光电集流的变化同步;当D_st滞后于Pa,时延τ=1~2 h,Pa与D_st的相关最好,并且时延τ为6～8 h,Pa与D_st的相关都好于无时延的水平.     

Mismatch between variations of solar indices, stratospheric ozone and UV-B observed at ground

In solar cycles 22–23, all solar indices showed maxima near 1990 and 2000 and minima in 1996. The maximum to minimum variation was only 1–2% in the UV range 240–350 nm. Dobson ozone intensities did not show any clear relationship with solar cycle and ozone variations were less than 10%. The UV-B (295–325 nm) observed at ground by Brewer spectrophotometers at some locations had variations of 50–100% for 295–300 nm, and 20–50% for 305–325 nm. The maxima were in different years at different locations (even with separations of only 300 km), did not match with the solar cycle, and were far too large to be explained on the basis of ozone changes (1% decrease of ozone is expected to cause 2% increase of UV-B). Thus, if the data are not bad, the UV-B changes do not match with solar activity or ozone changes and must be mostly due to other local effects (clouds, etc.?). When data are averaged over wide geographical regions, UV-B variation ranges are smaller (10–20%, probably because localised, highly varying cloud effects get filtered out), and are roughly as expected from ozone variations.     

Seasonal,longitudinal, and latitudinal differences in air pressure over Russia during the solar activity maximum and minimum years

Using a large set of observational data (for ～50–100 years) obtained at 333 meteorological stations in Russia, we have shown that there is a clearly expressed differential pressure DP in the years of maximum and minimum solar activity by months and seasons, and by latitude and longitude. The values of the parameter DP were observed to be especially large at high latitudes U = 62.5°–67.5° in the longitude range D = 30°–50° in March (DP = ?4.45 ± 0.5 mbar) and in September (DP = 2.49 ± 0.21 mbar). We have concluded that the solar and geomagnetic activities can control the development of internal instabilities of the atmosphere and thus affect the climate.     

Global lightning formation at a minimum and maximum of solar activity according to the observations of the Schumann resonance on the Kola Peninsula

On the basis of the two-component measurements of the atmospheric noise electromagnetic field on the Kola Peninsula, a change in the first Schumann resonance (SR-1) as an indicator of global lightning formation is studied depending on the level of galactic cosmic rays (GCRs). It is found that the effect of GCRs is most evident during five months: in January and from September to December; in this case the SR-1 intensity in 2001 was higher than the level of 2007 by a factor of 1.5 and more. This effect almost disappears when the regime of the Northern Hemisphere changes into the summer regime. It is assumed that an increase in the GCR intensity results in an increase in the lightning occurrence frequency; however, the probability that the power of each lightning stroke decreases owing to an early disruption of the charge separation and accumulation processes in a thundercloud increases; on the contrary, a decrease in the GCR intensity decreases lightning stroke occurrence frequency and simultaneously increases the probability of accumulating a higher energy by a thundercloud and increasing the lightning power to the maximum possible values.     

Relationships between hydrosedimentary processes and occurrence of mercury-resistant bacteria (merA) in estuary mudflats (Seine, France)

The Seine estuary (France) is one of the world's macrotidal systems that is most contaminated with heavy metals. To study the mercury-resistant bacterial community in such an environment, we have developed a molecular tool, based on competitive PCR, enabling the quantification of Gram-negative merA gene abundance. The occurrence of the Gram-negative merA gene in relation with the topology (erosion/deposit periods) and the mercury contamination of three contrasted mudflats was investigated through a multidisciplinary approach and compared with a non-anthropized site (Authie, France). The higher abundance of the Gram-negative merA gene in the Seine estuary mudflats indicates a relationship between the degree of anthropization and the abundance of the merA gene in the mudflat sediments. In the Seine mudflats, the maxima of abundance are always located in fresh sediment deposits. Therefore, the abundance is closely related with the hydrosedimentary processes, which thus seem to be determining factors in the occurrence of the Gram-negative merA gene in the surface sediments of the Seine's mudflat.     

The zonal E×B plasma drift effects on the low latitude ionosphere electron density at solar minimum near equinox

The F2-layer peak density, NmF2, and peak altitude, hmF2, which were observed by 12 ionospheric sounders during the 20 September 1964 geomagnetically quiet time period at solar minimum are compared with those calculated by the three-dimensional time-dependent theoretical model of the Earth's low and middle latitude ionosphere and plasmasphere. The modeled NmF2 are also compared with those measured during the geomagnetically quiet time periods of 12–15, 18–21, and 26 September 1964 to take into account observed day-to-day ionospheric variability. Major features of the data are reproduced by the model if the corrected HWM90 neutral wind is used. The changes in NmF2 due to the zonal E×B plasma drift are found to be less than 20% in the daytime low latitude ionosphere. The model, which does not take into account the zonal E×B plasma drift, underestimates night-time NmF2 up to the maximum factor of 2 at low geomagnetic latitudes. The night-time increase of NmF2 caused by the zonal E×B plasma drift is less pronounced at −20° and 20° geomagnetic latitudes in comparison with that between −10° and 10° geomagnetic latitude. The longitude dependence of the calculated night-time low latitude influence of the zonal E×B plasma drift on NmF2 is explained in terms of the longitudinal asymmetry in B (the eccentric magnetic dipole is displaced from the Earth's center and the Earth's eccentric tilted magnetic dipole moment is inclined with respect to the Earth's rotational axis), and the variations of the wind induced plasma drift and the meridional E×B plasma drift in geomagnetic longitude. The difference between the hmF2 values calculated by including the effect of zonal E×B drift and that obtained when it is excluded does not exceed 19 km in the low latitude ionosphere. Over the geomagnetic equator the zonal E×B plasma drift produces the maximum increase in the electron density by a factor of 1.06–1.48 and 1.05–1.30 at 700 and 1000 km altitude, respectively, and this increase is not significant above about 1500 km. Changes in the vertical electron content, VEC, caused by the zonal E×B plasma do not exceed 16% during the day, while the value of the night-time VEC is increased up to a factor of 1.4 due to this drift. The maximum effects of the zonal E×B plasma drift on the night-time electron density derived from the model results corresponding to solar minimum and maximum are quite comparable.     

The Polar Cap (PC) indices: Relations to solar wind parameters and global magnetic activity

The polar geomagnetic activity resulting from solar wind–magnetosphere interactions can be characterized the Polar Cap (PC) indices, PCN and PCS. PC index values are derived from polar magnetic variations calibrated on a statistical basis such that the index approximate values in units of mV/m of the interplanetary “geo-effective” (or “merging”) electric field (E_M) conveyed by the solar wind. The timing and amplitude relations of the PC index to solar wind plasma and magnetic field parameters are reported. The solar wind effects are parameterized in terms of the geo-effective electric field (E_M) and the dynamical pressure (P_DYN). The PC index has a delayed and damped response to E_M variations and display saturation-like effects for E_M values exceeding 10 mV/m. Steady or slowly varying levels of solar wind dynamical pressure have little or no impact on the PC index above the effects related to E_M for which the solar wind velocity is also a factor. Sharp increases in the dynamical pressure generate impulsive variations in the PC index comprising a initial negative impulse of 5–10 min duration followed by a positive impulse lasting 10–20 min. Typical amplitudes of both the negative and the positive impulses are 0.2–0.5 units. A sharp decrease in the pressure produces the inverse sequence of pulses in the PC index. Auroral substorm activity represented by the AL index level has a marked influence on the average PC/E_M level at the transition from very quiet (AL0 nT) to disturbed conditions while more or less disturbed conditions (AL<−100 nT) have no systematic effect on the average PC/E_M values. At distinct substorm events the PC/E_M ratio has a minimum (0.8) in the pre-onset phase at around 20 min before substorm onset. The average ratio gradually increases in the expansion phase to reach a maximum value (1.1) at around 40 min after substorm onset (or 20 min after the largest (negative) peak in AL). At substorm recovery during the next 2 h the PC/E_M ratio decreases. Finally, we report on the application of polar magnetic variations to model the disturbance storm time (Dst) index development during magnetic storms by using the PC index as a source function to quantify the energy input to the ring current representing accumulated storm energy and characterized by the Dst index.     

Long-period geomagnetic pulsations caused by the solar wind negative pressure impulse on 22 March 1979 (CDAW-6)

An analysis is made of the long-period geomagnetic pulsations as recorded at seven Norilsk meridian stations ( = 162°, latitudinal range: 61°–71°N) following abrupt magnetospheric expansion during the storm of 22 March 1979 caused by a rapid decrease in solar wind density. As with the time interval following an abrupt contraction at the time of sudden storm commencement, there exist two types of pulsations in the pulsation spectra: latitude-independent (T>400 s) and latitude-dependent (T<200 s) pulsations. The first pulsation type is interpreted in terms of forced pulsations associated with magnetopause oscillations. The oscillation period is determined by plasma density in the boundary layer and by the radius of the magnetosphere (T ^1/2R⁴). The latitudinal dependence of the period, amplitude and polarization of the second-type pulsations is in agreement with the resonance mechanism of their origin.     

安大略萨德伯里附近的近场(震源距<30km)地震动衰减

使用距震源30km以内发生在安大略萨德伯里附近12个震级MN1.0~3.1的地方浅源地震的3个台站记录资料研究了近场地震动衰减。这对在北美洲东部进行地震动预测方程的研究和依据区域地震观测资料推断震源参数具有重要意义。我们得到了距震源25~30km内地震动高频(3~10Hz)水平分量以大约R-1.3的几何扩散率衰减(这里R为震源距)的结果。这与Atkinson(2004)确定的及Atkinson与Boore(2006)的预测方程中使用的几何扩散率一致。在这个距离范围内的地震动垂直分量似乎以R-1.1略低些的速率衰减。     

Time evolution of cosmic-ray intensity and solar flare index at the maximum phase of cycles 21 and 22

Analysis of the time series into trigonometric series allows the investigation of cosmic-ray (CR) intensity variations in a range of periodicities from a few days to 1 year. By this technique the amplitude and the phase of all observed fluctuations can be given. For this purpose, daily CR intensity values recorded at Climax Neutron Monitor station for the time intervals 1979–1982 and 1989–1991, which correspond to the epochs of maximum activity for solar cycles 21 and 22, respectively, have been studied. The data analysis revealed the occurrence of new periodicities, common or not, in the two solar maxima. A search of our results was done by a power spectral analysis determining independently possible systematic periodic or quasi-periodic variations. Based on the fact that during these maxima the CR intensity tracks the solar flare index better than the sunspot number, the same analysis was performed on these data, which are equivalent to the total energy emitted by the solar flares. Both analyses result in periodicities with different probability of occurrence in different epochs. Occurrence at peaks of 70, 56, 35, 27, 21 and 14- days were observed in all time series, while the periods of 140–154 and 105 days are reported only in the 21st solar maximum and are of particular importance. All of the short-term periods except of those at 27 and 154-days are recorded for first time in CR data, but they had already been observed in the solar activity parameters. Moreover, each parameter studied here has a very different power spectrum distribution in periods larger than 154 days. The possible origin of the observed variations in terms of the CR interaction in the upper atmosphere and the solar cavity dynamics is also discussed here.     

Studying correlations between the coronal hole area,solar wind velocity,and local magnetic indices in the Canadian region during the decline phase of cycle 23

Geomagnetic disturbances in the Canadian region are compared with their solar and heliospheric sources during the decline phase of solar activity, when recurrent solar wind streams from low-latitude coronal holes were clearly defined. A linear correlation analysis has been performed using the following data: the daily and hourly indices of geomagnetic activity, solar wind velocity, and coronal hole area. The obtained correlation coefficients were rather low between the coronal hole areas and geomagnetic activity (0.17–0.48), intermediate between the coronal hole areas and the solar wind velocity (0.40–0.65), and rather high between the solar wind velocity and geomagnetic activity (0.50–0.70). It has been indicated that the correlation coefficient values can be considerably increased (by tens of percent in the first case and about twice in the second case) if variations in the studied parameters related to changes in the ionosphere (different illumination during a year) and variations in the heliolatitudinal shift of the coordinate system between the Earth, the Sun, and a spacecraft are more accurately taken into account.     

The dynamics of phytoplankton, bacteria and heterotrophic flagellates at two Banks near Magdeburg in the River Elbe (Germany)

The main objectives of this study were to describe the seasonal standing stock dynamics of phytoplankton, bacterioplankton and heterotrophic flagellates in the highly eutrophic River Elbe (Germany), and to compare the seasonal patterns observed with other streams. Emphasis was placed on examining and assessing abiotic and biotic controlling factors influencing the structure and dynamics of the riverine plankton. All the physico-chemical and biological parameters determined were within the range or somewhat higher (in the case of phytoplankton abundance and biomass) than reported for other large streams. The underwater light conditions resulting from atypically short phytoplankton growth periods of about 6 months per year and the low phytoplankton carbon to chl a ratio of 23 were identified as a major limiting factor for phytoplankton development in the River Elbe. The seasonal distribution pattern of bacterioplankton indicated probable tight trophodynamical coupling both with phytoplankton and with heterotrophic flagellates, whereas heterotrophic flagellates showed a more trophic link with bacterial densities. Although approximately constant DOC and DON levels throughout the year sustained bacterial growth rates, during the phytoplankton growing season an increase of bacterial standing stocks was observed. Although the left-bank sampling site of the Elbe is strongly influenced by the tributaries Mulde and Saale containing higher concentrations of chloride, nitrogen nutrients, heavy metals and organic pollutants, no clear differences were observed between the two sides of the river concerning the biological parameters measured. Possible reasons and the slightly higher phytoplankton abundance and diversity at the right bank are discussed.     

Quiet-condition hmF2, NmF2, and B0 variations at Jicamarca and comparison with IRI-2001during solar maximum

We use the measurements of the Jicamarca digisonde to examine the variations in F2 layer peak electron density (NmF2), its height (hmF2), and the F2 layer thickness parameter (B₀) near the dip equator. The hourly ionograms during geomagnetic quiet-conditions for a 12-month period close to the maximum solar activity, April 1999–March 2000, are used to calculate the monthly averages of these parameters, for each month. The averages are compared with the International Reference Ionosphere (IRI)-2001 model values. The results show that the higher hmF2 values during daytime, associated with the upward velocity, are mainly responsible for the greater values of NmF2 and B₀; while the nighttime lower hmF2, related to the downward velocity, are responsible for the smaller NmF2 and B₀. For daytime, hmF2 and NmF2 are correlated with the solar activity in the equinoctial and summer months. The hmF2 and B₀ peaks at sunset with an associated sharp decrease in NmF2 are presented in the equinoctial and summer months, but not in the winter months. Comparison of the measured hmF2 values with the International Radio Consultative Committee (CCIR) maps used in IRI-2001 (IRI-CCIR) reveals an IRI overestimate in hmF2 during daytime. The most significant discrepancy is that the IRI-CCIR does not model the post-sunset peak in hmF2. For the NmF2 comparison, the values obtained from both the CCIR and URSI maps are generally close to the observed values. For the B₀ comparison, the highest discrepancy between the observation and the Gulyaeva option (IRI-Gulyaeva) is the location of the annual maximum for the daytime values, also the winter daytime predictions are too low. Additionally, the significant negative difference between the observation and the B₀-table option (IRI-B₀-table) provides a slightly better prediction, except for 0400–1000 LT when the model significantly overestimates. The post-sunset peak in B₀ at some months is predicted by neither the IRI-Gulyaeva nor the IRI-B₀-table options.