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The dynamics of the intensity of cosmic rays is known to be different on the ascending and descending branches of the 11-year solar cycle, i.e., hysteresis phenomena are observed. Recently, it has been obtained that at shorter intervals on the scale of magnetic storms there are also signs of hysteresis in dependences of cosmic ray cutoff rigidities R (geomagnetic thresholds) on heliosphere and geosphere parameters. R is the rigidity below which a particle flux is cut off due to geomagnetic shielding. In this paper, we have analyzed the dependence of the geomagnetic storm index Dst and the variation of the ΔR thresholds on interplanetary magnetic field (IMF) and solar wind (SW) parameters during the two-step magnetic storm on September 7–8, 2017. We have found hysteresis phenomena in the following paired series: (1) dependences of Dst on SW and IMF parameters, and (2) dependences of ΔR on SW and IMF parameters. We have established that the dependence curves in the storm descending phase (main phase) and ascending phase (recovery phase) do not coincide — hysteresis loops are formed. A specific feature of the storm under study is the second lowering of Dst in the recovery phase. The hysteresis pattern reflects this specific storm dynamics, forming two hysteresis loops in response to the two Dst drops.

The geomagnetic cutoff rigidity of cosmic rays (CRs) is the main factor regulating the arrival of CR particles at a given point on Earth's surface or inside the magnetosphere. To study the relationship between cutoffs and near-Earth space parameters, we have selected the strongest magnetic storm that occurred on March 8–11, 2012 during the CAWSES-II interval, recommended by SCOSTEP for detailed studies of solar-terrestrial relations. We have found the geomagnetic cutoffs by two methods: 1) by trajectory calculations in the magnetic field of the perturbed magnetosphere according to the Ts01 model and 2) by the spectrographic global survey method according to the data from the world network of neutron monitors. The largest drop in the cutoffs (−1.1 GV) obtained by the latter method was observed during the recovery phase of the storm. Apparently, this is due to the influence of the supersubstorms that occurred at that time. The analysis has shown that the closest connection of variations in the cutoffs can be traced with the geomagnetic activity index Dst, which indicates the determining contribution of the ring current to the transport of CRs. In addition, we have found a significant connection with the electromagnetic field parameters (with the Bz component of the interplanetary magnetic field and the azimuthal component of the electric field Ey). The dynamic solar wind parameters practically do not control variations in CR geomagnetic cutoff rigidities.

Recent epidemiological studies suggest a link between transport magnetic fields (MF) and certain adverse health effects. We performed measurements in workplaces of engineers on Russian DC and Swiss AC powered (16.67 Hz) electric trains using a computer based waveform capture system with a 200 Hz sampling rate. MF in DC and AC trains show complex combinations of static and varying components. The most probable levels of quasistatic MF (0.001-0.03 Hz) were in the range 40 microT. Maximum levels of 120 microT were found in DC powered locomotives. These levels are much higher than the geomagnetic field at the site of measurements. MF encountered both in DC and AC powered rail systems showed irregular temporal variability in frequency composition and amplitude characteristics across the whole frequency range studied (0-50 Hz); however, more than 90% of the magnetic field power was concentrated in frequencies

Relationships between different parameters of the geomagnetic activity and medical statistical data on myocardial infarction were investigated anew, because previous results in this field have been often inconsistent. The data are daily numbers of myocardial infarction incidence rates (15,543 cases) and number of deaths for infarction (3,065 cases), abstracted from registries of the 14 biggest hospitals of St. Petersburg (1989-1990). The analysis showed a statistically significant increase in myocardial infarction rate during big geomagnetic disturbances, defined by the days of the descending phase of cosmic ray Forbush decreases. An overall estimation of the average increase in infarction incidence rate during big geomagnetic storms, (10.5 +/- 1.2)%, has been computed by taking into account previous results [1-3]. In contrast, morbidity data did not show any significant correlation with geomagnetic disturbances. It was found also that the infarction incidence rate appears to be rather constant from Monday to Friday and to decrease sharply by a factor approximately 1.25 on Saturday-Sunday and mid-week festivities. This effect is associated with different exposure during work days and week-ends to man-made magnetic field environment mainly produced by electrified transport. Such effect was not observed in mortality data. The results and their methodological aspects are placed in the context of studies on possible health effects of low frequency magnetic fields both natural and man-made origin.

The study was inspired by earlier results that displayed influence of variable natural geomagnetic field (0.005-10 Hz range-ultra-low frequencies) on circulatory system, indicated possible correlation between industrial ultra-low frequency fields and prevalence of myocardial infarction. The authors conducted unique measurements of ultra-low frequency fields produced by electric engines. The results were compared with data on morbidity among railway transport workers. The findings are that level of magnetic variations in electric locomotive cabin can exceed 280 micro Tesla, whereas that in car sections reaches 50 micro Tesla. Occurrence of coronary heart disease among the locomotive operators appeared to be 2.0 + 0.2 times higher than that among the car section operators. Higher risk of coronary heart disease in the locomotive operators is associated with their increased occupational magnetic load.

The present analysis was stimulated by previous findings on the possible influence of natural ultralow-frequency (ULF; 0.001-10 Hz) geomagnetic field variations on the cardiovascular system and indications of an effect of man-made ULF magnetic fields on the rate of myocardial infarction. In the present study, we considered the occupational health hazards of the strongest ULF magnetic fields in densely populated urban areas. Measurements of ULF magnetic field fluctuations produced by trains powered by DC electricity were performed by means of a computer-based, highly sensitive, three-component magnetometer. We found that the magnitude of magnetic field pulses inside the driver's cab of electric locomotives (ELs) could be > or = 280 microT in the horizontal component perpendicular to the rails and up to approximately 130 microT in the vertical component, and, in the driver's compartment of electric motor unit (EMU) trains, they were approximately 50 and 35 microT, respectively. We have investigated the relationships between the occupational exposure to ULF magnetic field fluctuations produced by electric trains and cardiovascular diseases (CVDs) among railroad workers in the former Soviet Union. We have analyzed medical statistical data for a period of 3 years for approximately 45,000 railroad workers and 4,000 engine drivers. We have also analyzed 3 years of morbidity data for three subgroups of engine drivers (approximately 4,000 in each group) operating different types of trains. We find that EL drivers have a twofold increase in risk (2.00 +/- 0.27) of coronary heart diseases (CHDs) compared with EMU drivers. Because our analysis of major CVDs shows that the examined subpopulations of drivers can be considered to have had equal exposure to all known risk factors, the elevated CHD risk among EL drivers could be attributed to the increased occupational exposure to ULF magnetic fields.

The effect of man-made electromagnetic fluctuations and strong geomagnetic disturbances on human pathology-data from St. Petersburg (Russia, 1981) is analyzed. The most remarkable effect is the 7-day variation of the ambulance-call data for myocardial infarction, that show a decrease in pathology-rate (70%) during week-ends and public holidays. Results of measurement of man-made electromagnetic fluctuations in the frequency range 0.005-10 Hz in 1991 and 1994 show a big decrease in electromagnetic noise during week-ends. We suggest that very big 7-day variation in infarction rates is connected with the decrease of electromagnetic noise during Saturdays-Sundays. This phenomenon is responsible for the very big 7-day variation in infarction rate. The myocardial infarction rate cleaned up by meteorological and social effects show the increasing by a factor 1.14 during geomagnetic storms.

Investigations were carried out to correlate the frequency of cardiovascular catastrophes (daily mortality rate of patients with ischemic heart disease), heliogeomagnetic activity (solar radiation in the wave band 10.7 cm, H, D and Z components of the geomagnetic field), synchronization and desynchronization of circaseptidian rhythms, and total number of cardiovascular catastrophes in different seasons. The raw data sets were treated with due account of the discrete pattern of random sequences and noise in the medical data set, finite analysis interval and informativity of the derivatives of the parameters used. The occurrence of cardiovascular catastrophes showed circaseptidian rhythms whose level depended on the above three factors. The results obtained are discussed with respect to possible synchronization and desynchronization of endogenous biorhythms by time cues, relating them to the mechanism of human adaptation to the environment.