Solar rhythms in the characteristics of the Arctic frontal zone in the North Atlantic

Long-term changes of the Arctic frontal zone characteristics near the south-eastern coasts of Greenland were considered, the NCEP/NCAR reanalysis data being used. It was found that in the cold half of the year the temperature gradients in the layer 1000–500 hPa in the region under study reveal strong ∼10-yr and ∼22-yr periodicities that seem to be related to solar activity cycles. The results obtained suggest the influence of solar activity and cosmic ray variations on the structure of the temperature field of the troposphere resulting in the changes of the temperature contrasts in the Arctic frontal zone that, in turn, may affect the intensity of cyclogenesis at middle latitudes. The detected effects seem to indicate an important part of frontal zones in the mechanism of solar activity and cosmic ray variation influence on the development of extratropical baric systems. It is suggested that the variations of the temperature gradients revealed in the Arctic frontal zone are due to the radiative forcing of cloudiness changes which may be associated with geomagnetic activity and cosmic ray variations.     

Stratospheric polar vortex as a possible reason for temporal variations of solar activity and galactic cosmic ray effects on the lower atmosphere circulation

Possible reasons for the temporal instability of long-term effects of solar activity (SA) and galactic cosmic ray (GCR) variations on the lower atmosphere circulation were studied. It was shown that the detected earlier ∼60-year oscillations of the amplitude and sign of SA/GCR effects on the troposphere pressure at high and middle latitudes (Veretenenko and Ogurtsov, Adv.Space Res., 2012) are closely related to the state of a cyclonic vortex forming in the polar stratosphere. The intensity of the vortex was found to reveal a roughly 60-year periodicity affecting the evolution of the large-scale atmospheric circulation and the character of SA/GCR effects. An intensification of both Arctic anticyclones and mid-latitudinal cyclones associated with an increase of GCR fluxes at minima of the 11-year solar cycles is observed in the epochs of a strong polar vortex. In the epochs of a weak polar vortex SA/GCR effects on the development of baric systems at middle and high latitudes were found to change the sign. The results obtained provide evidence that the mechanism of solar activity and cosmic ray influences on the lower atmosphere circulation involves changes in the evolution of the stratospheric polar vortex.     

Regional and temporal variability of solar activity and galactic cosmic ray effects on the lower atmosphere circulation

In this work we studied the spatial and temporal structure of long-term effects of solar activity (SA) and galactic cosmic ray (GCR) variations on the lower atmosphere circulation as well as possible reasons for the peculiarities of this structure. The study revealed a strong latitudinal and regional dependence of SA/GCR effects on pressure variations in the lower troposphere which seems to be determined by specific features of baric systems formed in different regions. The temporal structure of SA/GCR effects on the troposphere circulation at high and middle latitudes is characterized by a roughly 60-year periodicity which is apparently due to the epochs of the large-scale atmospheric circulation. It is suggested that a possible mechanism of long-term effects of solar activity and cosmic ray variations on the troposphere circulation involves changes in the evolution of the polar vortex in the stratosphere of high latitudes, as well as planetary frontal zones.     

Time series modeling and analysis of trends of daily averaged ionospheric total electron content

A 10.7 cm solar radio flux F10.7, geomagnetic planetary equivalent amplitude (Ap index), and period variations were considered in this paper to construct a linear model for daily averaged ionospheric total electron content (TEC). The correlation coefficient of the modeled results and International GNSS Service (IGS) observables was approximately 0.97, which implied that the model could accurately reflect the realistic variation characteristics of the daily averaged TEC. The influences of the different factors on TEC and its characteristics at different latitudes were examined with this model. Results show that solar activity, annual and semiannual cycles are the three most important factors that affect daily averaged TEC. Solar activity is the primary determinant of TEC during periods with high solar activity, whereas periodic factors primarily contribute to TEC during periods with minimum solar activity. The extent of the influences of the different factors on TEC exhibits obvious differences at varying latitudes. The magnitude of the semiannual variation becomes less significant with the increase in latitude. Furthermore, a geomagnetic storm causes an increase in TEC at low latitudes and a decrease at high latitudes.     

Long-term changes in indices of geomagnetic activity at the auroral station Sodankylä

Here we compare the traditional analog measure of geomagnetic activity, Ak, with the more recent digital indices of IHV and Ah based on hourly mean data, and their derivatives at the auroral station Sodankylä. By this selection of indices we study the effects of (i) analog vs. digital technique, and (ii) full local-time vs. local night-time coverage on quantifying local geomagnetic activity. We find that all other indices are stronger than Ak during the low-activity cycles 15–16 suggesting an excess of very low scalings in Ak at this time. The full-day indices consistently depict stronger correlation with the interplanetary magnetic field strength, while the night-time indices have higher correlation with solar wind speed. The Ak index correlates better with the digital indices of full-day coverage than with any night-time index. However, Ak depicts somewhat higher activity levels than the digital full-day indices in the declining phase of the solar cycle, indicating that, due to their different sampling rates, the latter indices are less sensitive to high-frequency variations driven by the Alfvén waves in high-speed streams. On the other hand, the night-time indices have an even stronger response to solar wind speed than Ak. The results strongly indicate that at auroral latitudes, geomagnetic indices with different local time coverage reflect different current systems, which, by an appropriate choice of indices, allows studying the century-scale dynamics of these currents separately.     

Evolution of Dst index,cosmic rays and global temperature during solar cycles 20–23

We have studied conditions in interplanetary space, which can have an influence on galactic cosmic ray (CR) and climate change. In this connection the solar wind and interplanetary magnetic field parameters and cosmic ray variations have been compared with geomagnetic activity represented by the equatorial Dst index from the beginning 1965 to the end of 2012. Dst index is commonly used as the solar wind–magnetosphere–ionosphere interaction characteristic. The important drivers in interplanetary medium which have effect on cosmic rays as CMEs (coronal mass ejections) and CIRs (corotating interaction regions) undergo very strong changes during their propagation to the Earth. Because of this CMEs, coronal holes and the solar spot numbers (SSN) do not adequately reflect peculiarities concerned with the solar wind arrival to 1 AU. Therefore, the geomagnetic indices have some inestimable advantage as continuous series other the irregular solar wind measurements. We have compared the yearly average variations of Dst index and the solar wind parameters with cosmic ray data from Moscow, Climax, and Haleakala neutron monitors during the solar cycles 20–23. The descending phases of these solar cycles (CSs) had the long-lasting solar wind high speed streams occurred frequently and were the primary contributors to the recurrent Dst variations. They also had effects on cosmic rays variations. We show that long-term Dst variations in these solar cycles were correlated with the cosmic ray count rate and can be used for study of CR variations. Global temperature variations in connection with evolution of Dst index and CR variations is discussed.     

New index of long-term variations of galactic cosmic ray intensity

We find that the soft rigidity spectrum of the Galactic Cosmic Ray (GCR) intensity variations for the maximum epoch and the hard rigidity spectrum for the minimum epoch calculated based on the neutron monitors experimental data (1960–2002) are related with the various dependence of the diffusion coefficient on the GCR particle’s rigidity for different epoch of solar activity. This dependence is stronger in the maximum epoch than in the minimum epoch of solar activity, and is provided by the essential temporal rearrangements of the structure of the Interplanetary Magnetic Field (IMF) turbulence from the maxima to minima epoch of solar activity. We also show that the rigidity spectrum of GCR intensity variations is harder for the effective rigidities ∼(10–15) GV (by neutron monitors data), than for the effective rigidities ∼(25–30) GV (by neutron monitors and muon telescopes data). A general scenario of GCR modulation versus solar activity is settled on the essential temporal rearrangements of the structure of the IMF turbulence. Therefore, the temporal changes of the power law rigidity spectrum exponent can be considered as a vital (new) index to explain the 11-year variations of the GCR intensity. We assume that ∼(70–80)% of the changes of the amplitudes of the 11-year variations of GCR intensity is related with the changes of the IMF turbulence versus solar activity.     

Dependence of E-sporadic layer response on solar and geomagnetic activity variations from its ion composition

The aim of this paper is to consider an influence of solar and geomagnetic activity level variations on frequency and stochastic parameters of mid-latitude ionosphere sporadic-E layer. Critical frequency of sporadic-E layer, foEs, relative excess of sporadic ionization over monthly median values, foEs − foEm/foEm, and probability of Es layer appearance, PEs, are considered. It has been found that sporadic-E layer parameters response to solar and geomagnetic activity level variations can be both positive (foEs and PEs values are increase) and negative (foEs and PEs values are decrease). In particular, sporadic-E layers response to solar and geomagnetic activity variations are different depending upon layer intensity. It is suggested that revealed differences may be associated with dissimilarity of the layers ion composition (high-intensive layers are composed from metallic ions and low intensive composed from molecular ions).     

Effect of geomagnetic disturbances on physiological parameters: An investigation on aviators

Over the last years the potential effect that the geomagnetic activity may have on human physiological parameters (such as heart rate, arterial diastolic and systolic pressure) is being widely investigated with irrefutable results. As it is suggested, human health can be affected by solar activity and related geophysical changes. In this study a group of 4018 Slovak aviators was examined from January 1, 1994 to December 31, 2002, covering periods with high solar and geomagnetic activity. Specifically, medical data of mean values of arterial diastolic and systolic blood pressure, which were registered during the medical examinations of the Slovak aviators, were related to daily variations of Dst and Ap geomagnetic indices. All subjects were men (from 18 to 60 years old) in good health. Statistical significance levels (p-values) of the effect of geomagnetic activity on the aforementioned parameters up to three days before and three days after the geomagnetic event were established using the statistical method ANalysis Of VAriance (ANOVA). Statistical analysis of the arterial blood pressure variations for different levels of geomagnetic activity revealed that geomagnetic changes are connected to variations of the human physiological parameters.     

27-day variations of the galactic cosmic ray intensity and anisotropy in the minimum of the 23rd solar activity cycle

We study the 27-day variations of the solar wind velocity, galactic cosmic ray (GCR) intensity and anisotropy in the last minimum epoch of solar activity (2007–2009, A < 0). The average amplitude of the 27-day variation of the galactic cosmic ray anisotropy (A27A) in the current minimum epoch of solar activity (2007–2009, A < 0) is lesser than in previous positive polarity period as it is expected from the drift theory. So, polarity dependence rule for the 27-day variation of the GCR anisotropy is fully kept. It is a universal principle for the amplitudes of the 27-day variation of the GCR anisotropy. At the same time, the average amplitude of the 27-day variation of the GCR intensity (A27I) remains at the same level as for previous minimum epoch 1995–1997 (A > 0) showing by the same token an violation of its polarity dependence rule established earlier. We assume that this phenomenon could be generally related with the well established 27-day variation of the solar wind velocity being in anti-correlation with the similar changes of the 27-day variation of the GCR intensity. Generally, a character of the heliolongitudinal asymmetry of spatial large-scale structure of the solar wind velocity (SWV) established in the recent minimum epoch, preferentially pronounces in the behavior of the 27-day variation of the GCR intensity than anisotropy. The formation of the 27-day variation of the GCR anisotropy preferentially takes place in a restricted disk like local vicinity in the helioequatorial region, whilst the 27-day variation of the GCR intensity is formed in the global three dimensional vicinity of the heliosphere.     

Is the North Atlantic Oscillation modulated by solar and lunar cycles? Some evidences from Hurst autocorrelation analysis

Several studies have suggested that the Sun and Moon cycles affect the Earth climatic dynamics. Nevertheless, there is a long-standing controversy whether solar variability and tides can significantly generate climate change, and how this may occur. Spectral analysis of climatic indices has provided only indirect evidences of the effects of solar–tidal periodicities in the Earth climate. This work addresses the issue by considering the dynamics of the daily North Atlantic Oscillation index over the period from 1950 to 2009. In contrast to previous studies, this work proposes that external cycles can be detected in the autocorrelation dynamics rather than in the raw North Atlantic Oscillation index series. Here, the R/S-scaling analysis is used to quantify, via the so-called Hurst exponent, the presence of autocorrelations along the studied years. Fourier analysis scan of the autocorrelation series thus show two prominent spectral components near (±3%) the lunar tidal 4.425 and the solar 11 years cycles. Intermediate spectral components near 6.4, 7.75 and 8.9 years are proposed to be, at least partially, a result of energy capture from internal mechanisms into cycles resulting from the nonlinear resonance of the fundamental solar–tidal cycles. The dominant effect of the solar variability is clarified by showing that in about 70% of the studied period the sunspot number and the Hurst exponent phases are synchronized, indicating that a higher solar activity enhances the North Atlantic Oscillation index predictability.     

低平流层温度对银河系宇宙线强度变化的响应

选用芬兰中子堆监测站从lop年7月至1989年3月的宇宙线强度月平均曲线数据,和在相对应期间我国境内海拉尔等4个高空气象观测站的30hPa和100hPa等位势高度上常规气温观测月平均资料,经统计分析,取得初步结果:低平流层气温与银河系宇宙线辐射强度之间呈现负相关的特性;与银河系宇宙线辐射强度峰区和谷区相对应会在低平流层中引起幅值为2-3℃的温度变化;不同纬度观测站所得观测数据表明,上述增温幅值随纬度降低而减少。      

An empirical model of electron temperature for low and middle latitudes in the 100–200 km height region

An empirical model of electron temperature (T_e) for low and middle latitudes is proposed in view of IRI. It is constructed on the basis of experimental data obtained at 100 to 200 km by probe and incoherent scatter methods. Below 150 km the model gives two T_e values: one from incoherent scatter data and another from probe measurements. The model can be used for all seasons for quiet geomagnetic conditions (Kp not greater 3) and at almost all levels of solar activity (F_10.7 between 70 and 200). It is presented in an analytical form that allows one to calculate T_e profiles for different latitudes, longitudes and at any season (day). Depending on geomagnetic latitude and solar zenith angle, electron temperature distributions are presented for two heights along with T_e profile variations during the day (at middle latitudes).     

Solar, geomagnetic and cosmic ray intensity changes, preceding the cyclone appearances around Mexico

Recently it has been suggested that there exist specific changes in the cosmic ray intensity and some solar and geomagnetic parameters during the days, preceding the hurricane appearances over the North Atlantic Ocean. To understand better these phenomena, data for all hurricanes born not only over the Atlantic but also over the Pacific waters in the last 55 years that hit the Mexican borders were elaborated. As basic hurricane parameters the maximum rotational velocity and the estimated total energy were used. To avoid any interference all hurricanes, overlapping the preceding ones with more than 20 days were not included. Then the behavior of the cosmic ray (CR) intensity, the sunspot (SS) numbers, and the geomagnetic parameters (AP) and (KP) in 35 days prior and 20 days after the cyclone start were investigated. The CR, SS, AP and KP showed much more intensive disturbances in the periods preceding and following the hurricane appearance. For SS this disturbance gradually increase with the hurricane strength. A characteristic peak in the CR intensity appears before the hurricane start. But its place varies between 5 and 20 days before that start. Specific changes were observed in the SS. For major hurricanes they begins sometimes more than 20 days in advance. The AP and the KP show series of bursts, spread over the whole period of 30 preceding days. The obtained results from the performed correlational analysis are enough interesting to motivate a further statistical analysis with more precise techniques: in particular a common periodicity of 30 years found in the number of tropical storms landing into Mexico, the averaged rotational wind velocity and the ACE must be studied in connection with the solar Hale cycle. Using coherence wavelet spectral analysis we present a comparative study between one terrestrial and one cosmophysical phenomena that presumable influence hurricanes development: African dust outbreaks versus cosmic rays for all North Atlantic tropical cyclones. It is shown that the cosmophysical influence cannot be considered as a negligible effect.     

Occurrence rate of SAR arcs during the 23rd solar activity cycle

The occurrence rate of SAR arcs during 1997–2007 has been analyzed based on the photometric observations at the Yakutsk meridian (Maimaga station, corrected geomagnetic coordinates: 57°N, 200°E). SAR arcs appeared in 114 cases (∼500 h) during ∼370 nights of observations (∼3170 h). The occurrence frequency of SAR arcs increases to 27% during the growth phase of solar activity and has a clearly defined maximum at a decline of cycle 23. The SAR arc registration probability corresponds to the variations in geomagnetic activity in this solar cycle. The dates, intervals of UT, and geomagnetic latitudes of SAR arc observations at the Yakutsk meridian are presented.     

Solar polar magnetic field dependency of geomagnetic activity semiannual variation indicated in the Aa index

Three major hypotheses have been proposed to explain the well-known semiannual variation of geomagnetic activity, maxima at equinoxes and minima at solstices. This study examined whether the seasonal variation of equinoctial geomagnetic activity is different in periods of opposite solar magnetic polarity in order to understand the contribution of the interplanetary magnetic field (IMF) in the Sun-Earth connection. Solar magnetic polarity is parallel to the Earth’s polarity in solar minimum years of odd/even cycles but antiparallel in solar minimum years of even/odd cycles. The daily mean of the aa, Aa indices during each solar minimum was compared for periods when the solar magnetic polarity remained in opposite dipole conditions. The Aa index values were used for each of the three years surrounding the solar minimum years of the 14 solar cycles recorded since 1856. The Aa index reflects seasonal variation in geomagnetic activity, which is greater at the equinoxes than at the solstices. The Aa index reveals solar magnetic polarity dependency in which the geomagnetic activity is stronger in the antiparallel solar magnetic polarity condition than in the parallel one. The periodicity in semiannual variation of the Aa index is stronger in the antiparallel solar polar magnetic field period than in the parallel period. Additionally, we suggest the favorable IMF condition of the semiannual variation in geomagnetic activity. The orientation of IMF toward the Sun in spring and away from the Sun in fall mainly contributes to the semiannual variation of geomagnetic activity in both antiparallel and parallel solar minimum years.     

Solar cosmic rays in the near Earth space and the atmosphere

Solar energetic particles (SEPs) constitute a distinct population of energetic charged particles, which can be often observed in the near Earth space. SEP penetration into the Earth’s magnetosphere is a complicated process depending on particle magnetic rigidity and geomagnetic field structure. Particles in the several MeV energy range can only access to periphery of the magnetosphere and the polar cap regions, while the GeV particles can arrive at equatorial latitudes. Solar protons with energies higher than 100 MeV may be observed in the atmosphere above ∼30 km, and those with energies more than 1 GeV may be recorded even at the sea level. There are some observational evidences of SEP influence on atmospheric processes. Intruding into the atmosphere, SEPs affect middle atmosphere odd-nitrogen and ozone chemistry. Since spatial and temporal variations of SEP fluxes in the near Earth space are controlled by solar activity, SEPs may present an important link between solar activity and climate. The paper outlines dynamics of SEP fluxes in the near Earth space during the last decades. This can be useful for tracing relationship between SEPs and atmospheric processes.     

Statistical analysis of the occurrence rate of geomagnetic storms during solar cycles 20–24

This study examines the occurrences rate of geomagnetic storms during the solar cycles (SCs) 20–24. It also investigates the solar sources at SCs 23 and 24. The Disturbed storm time (Dst) and Sunspot Number (SSN) data were used in the study. The study establishes that the magnitude of the rate of occurrences of geomagnetic storms is higher (lower) at the descending phases (minimum phases) of solar cycle. It as well reveals that severe and extreme geomagnetic storms (Dst < -250 nT) seldom occur at low solar activity but at very high solar activity and are mostly associated with coronal mass ejections (CMEs) when occurred. Storms caused by CME + CH-HSSW are more prominent during the descending phase than any other phase of the solar cycle. Solar minimum features more CH-HSSW- associated storms than any other phase. It was also revealed that all high intensity geomagnetic storms (strong, severe and extreme) are mostly associated with CMEs. However, CH-HSSW can occasionally generate strong storms during solar minimum. The results have proven that CMEs are the leading cause of geomagnetic storms at the ascending, maximum and the descending phases of the cycles 23 and 24 followed by CME + CH-HSSW. The results from this study indicate that the rate of occurrence of geomagnetic storms could be predicted in SC phases.     

Assessing the relationship between solar activity and some large scale climatic phenomena

The nature of the climatic response to solar variability is assessed over a long-time scale. The wavelet analysis applied to paleoclimatic proxy data of large scale atmospheric phenomena (North Atlantic Oscillation, Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation and Southern Oscillation Index) has revealed coherence between the climatic oscillations and the solar phenomena (the cosmogenic isotope ¹⁰Be and the Total Solar Irradiance) preferentially with periods of Schwabe, Hale and Yoshimura–Gleissberg cycles that may reflect a modulation of solar activity.     

Estimation of Galactic Cosmic Ray exposure inside and outside the Earth’s magnetosphere during the recent solar minimum between solar cycles 23 and 24

The evidently low solar activity observed between solar cycles 23 and 24 during the years 2008–2010 led to a substantial increase in the Galactic Cosmic Ray (GCR) intensity in comparison with preceding solar minima. As the GCRs consist of highly-ionizing charged particles having the potential to cause biological damage, they are a subject of concern for manned missions to space. With the enhanced particle fluxes observed between 2008 and 2010, it is reasonable to assume that the radiation exposure from GCR must have also increased to unusually high levels. In this paper, the GCR exposure outside and inside the Earth’s magnetosphere is numerically calculated for time periods starting from 1970 to the end of 2011 in order to investigate the increase in dose levels during the years 2008–2010 in comparison with the last three solar minima. The dose rates were calculated in a water sphere, used as a surrogate for the human body, either unshielded or surrounded by aluminium shielding of 0.3, 10 or 40 g/cm².