Giorgio Villoresi

Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996– 1997): 3. Geomagnetic effects and coupling functions

We present the results of a ship survey conducted from Italy to Antarctica and back during the 1996-1997 solar minimum measuring the latitude variation in the neutron component of cosmic radiation at sea level. High-energy atmospheric neutrons were detected by a 3NM-64 and thermalized atmospheric neutrons were detected by two bare BF 3 counters. Discussions of the internal consistency of the data and the stability of the detectors, investigations of meteorological effects, and data corrections are presented in two companion papers. In this paper we compute updated vertical cutoff rigidities corrected for the penumbra effect, and we estimate apparent cutoff rigidities, which take into account the contribution of nonvertically incident particles to the counting rate. When comparing cosmic ray intensities observed in the same place, a small forward-backward effect is found and explained as the effect of an asymmetric shielding structure around the monitor. Latitude dependencies (i.e., neutron intensities versus cutoff rigidity) and associated coupling functions are computed for both monitors and compared. The NM latitude dependence obtained for the 1996-1997 solar minimum is found to be almost identical to that obtained by other authors in the previous solar minimum. The absence of the so-called crossover effect when comparing coupling functions of subsequent solar minima is discussed also on the basis of cosmic ray intensity changes observed by neutron monitor stations.

Monitoring and forecasting of great solar proton events using the neutron monitor network in real time

Obtaining online information on the onset of great solar energetic particle (SEP) events from real-time data of the neutron monitor network (NMN) is considered and the corresponding algorithm and program are proposed. Determination of the particle energy spectrum outside the atmosphere at different moments of the flare is considered on the basis of coupling functions method. The spectra defined in diffusion and kinetic approaches are compared. Using this information, the time of the SEP ejection into solar wind, the energy spectrum of a SEP event in the source inside the solar corona, and the SEP diffusion coefficient in the interplanetary space during the flare can be estimated. In this work, the significant possibility of the expected SEP fluxes and the energy spectrum forecasting on the early part of the increasing SEP intensity (about 20-30 min after the onset) is considered. Available satellite data in real-time scale combined with real time-data from neutron monitors (NM) are used for extrapolation of this forecast to the region of very small energy particles. The method is checked on the SEP event of September 1989. It is important to note that the accuracy of the developed method sufficiently increases with the increasing dangerous level of the SEP event. The method is not CPU damaging and can run in real time, providing inexpensive means of SEP prediction.

Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996–1997): 1. Methodology and data quality assurance

During the 1996–1997 austral summer, a 3NM-64 neutron monitor was operated on board the ship Italica to record cosmic ray neutron intensities in ocean areas from Italy to Antarctica and back. Two bare BF3 counters also measured the flux of thermalized neutrons. The main purpose of this research was the determination of an accurate latitude curve of cosmic ray nucleonic intensity during solar minimum to be used for obtaining the coupling function appropriate for this phase of solar cycle. Accuracy was achieved through reliable instrumentation and proper control of the experiment and by determining and applying for the first time all corrections, for (1) changes in vertical atmospheric mass column, by taking into account wind effect; (2) oscillations of the ship produced by sea roughness; (3) atmospheric temperature changes; (4) primary cosmic ray temporal variations including north–south asymmetry; and (5) temporal variations in the cosmic ray east–west effect, caused by asymmetric shielding on the ship. In this paper we describe the experiment, present the complex procedure of data reduction which was required for the survey data, evaluate the intensity changes produced by primary cosmic ray temporal variations, correct the data for meteorological effects, and present the “fully corrected” daily values of neutron intensity as a function of threshold rigidity. Several independent tests are applied to evaluate the quality of the “fully corrected” data and to determine their residual statistical uncertainty. In two companion papers, all meteorological effects are investigated in detail, geomagnetic effects are evaluated, and coupling functions are computed.

Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996–1997): 2. Determination of meteorological effects

In this paper we present an analysis of meteorological effects influencing the counting rate of a standard cosmic ray NM-64 neutron monitor and bare neutron counters used during the latitude survey performed in 1996–1997 from Italy to Antarctica and back. In particular, we determine for the first time the influence of the Bernoulli effect on the evaluation of atmospheric mass and the effect of sea state strength on neutron counting rate, by using data recorded during the long period spent in the Antarctic region (vertical cutoff rigidity Rcp ≤ 1 GV). Atmospheric absorption coefficients have been computed accurately for the Antarctic region, as well as at different cutoff rigidities by combining previous findings together with our determinations at Rcp ≤ 1 GV and Rcp = 6.2 GV. We also estimate the temperature effect on the NM-64 counting rate by using the sea level temperature during the expedition and the vertical distribution data of atmospheric temperature measured by satellites. Data corrections for all meteorological effects are discussed.

Hysteresis between solar activity and cosmic rays during cycle 22: the role of drifts, and the modulation region

Abstract Our studies of the neutron monitor observatories data with different cut-off rigidities during solar cycle 22 have made it possible to investigate the hysteresis character of the relationship between the variations in solar activity and in galactic cosmic ray intensity. This effect arises from the delay of interplanetary processes (responsible for cosmic ray modulation) with respect to the initiating solar processes, which correspond to some effective solar wind velocity and shock waves propagation. It gives the possibility to determine the effective dimension of modulation region in depending on the effective energy of galactic cosmic rays. In addition to our previous investigations of cosmic ray—solar activity hysteresis phenomenon made in the frame of convection-diffusion model, we now try to take into account drifts that change sign in periods of solar magnetic field reversal. From comparisons with experimental data on long-term cosmic ray variation in cycle 22, we determine the role of convection-diffusion and drifts in global modulation, and the effective dimension of the modulation region.

Time lag between cosmic rays and solar activity: solar minimum of 1994–1996 and residual modulation

Abstract Using neutron monitor (NM) data of stations with different cut-off rigidities, we calculate the rigidity dependence of the galactic cosmic ray long-term variation near the last solar minimum (sunspot number W ≤ 40, January 1994–January 1997). In the framework of a model for the global cosmic ray modulation in the heliosphere, taking into account the time-lag of processes in interplanetary space relative to processes on the Sun using data on solar activity-cosmic ray hysteresis effects, we estimate the radial dimension of the modulation region, the radial diffusion coefficient, the cosmic ray intensity outside of the heliosphere, and the residual cosmic ray modulation depending on primary cosmic ray particle rigidity.

Health Effects among Engine Drivers: Possible Association with Occupational Exposure to Magnetic Fields from DC Electrified Transport

The initial interest on possible health hazard from exposure to low-frequency, low-intensity magnetic fields (MFs) was mainly concentrated on MFs from power transmission lines (50/60 Hz). Elevated risks of diseases such as leukemia, brain tumor, and male breast cancer have been identified in a variety of professions. Values of risk factors are often 2 or 3 times higher than for residential studies. However, more recently, electrified transportation modes have also come under consideration. A 2-fold increased risk for leukemia mortality has been observed in line and shunting yard drivers of the Swiss Federal Railways with respect to train attendants and station managers.1 An analysis made in Sweden revealed that railway engine drivers and train staff have increased risk in some specific kind of cancer, as leukemia2 and brain tumor,3 though the total cancer incidence (all tumors included) among railway engine drivers was lower than in the general Swedish population. An other study4 on Swedish railway personnel showed that engine drivers had a higher than expected frequency of chromosomal aberrations. A study on workers of Swiss Railways5 showed that exposure to 16.7 Hz MFs may alter the urinary 6-hydroxymelatonin sulfate excretion in humans. There are indications on possible hazards of MFs from electric railways also for people living nearby. For instance in two studies conducted in USA and Germany it was found that sudden infant deaths are clustered near electric railroads.6

Exposure Metrics of Magnetic Fields from Electrified Transport

Biological and epidemiological studies indicate that possible bioeffects of magnetic fields (MFs) could be related to a variety of different exposure metrics.1 For instance, the effects might:

Long-term cosmic ray/solar activity hysteresis phenomenon and properties of solar wind for the last 200 years

On the basis of cosmic ray (CR) neutron monitor data of the station Climax (University of Chicago, P.I. Prof. J. A. Simpson), as well as of solar activity (SA) data for 1953–1997 (about 4 solar cycles), the CR/SA hysteresis phenomenon is investigated. We consider the time lag between the processes in the interplanetary space responsible for CR modulation and the corresponding processes on the Sun. By these results we estimate the average dimension of the Heliosphere and CR modulation parameters, over about 4 solar cycles. The results obtained for the last 4 cycles are used for determining the long-term CR variations during 1750–1970 on the basis of solar activity data (the last 18 years are used to compare the observed and expected CR intensities).

Magnetic Field Monitoring on Board of DC Electrified Transport in Russia

During the last few decades the intensity level of electromagnetic field (EMF) environment has dramatically increased: devices generating EMFs have proliferated in industrial plants, public transportation systems, homes, etc. This new situation is often described as “EM pollution” or “EM smog”. One of the main components of EM pollution is the magnetic field (MF) produced by electrified transport.