Ionization effect of solar protons in the Earth atmosphere – Case study of the 20 January 2005 SEP event

The cosmic ray ground level enhancement on January 20, 2005 is among the largest recorded events in the history of cosmic ray measurements. The solar protons of MeV energies cause an excess of ionization in the atmosphere, specifically over polar caps following major solar disturbances. The ionization effect in the Earth atmosphere is obtained for various latitudes on the basis of solar proton energy spectra, reconstructed from GOES 11 measurements and subsequent full Monte Carlo simulation of cosmic ray induced atmospheric cascade. The estimation of ionization rates is based on a numerical model for cosmic ray induced ionization. The evolution of atmospheric cascade is performed with the CORSIKA 6.52 code using FLUKA 2006b and QGSJET II hadron interaction models. The atmospheric ion rate ionization is explicitly obtained for 40°N, 60°N and 80°N latitudes. The time evolution of obtained ion rates is presented. It is demonstrated that ionization effect is negative for 40°N and small for 60°N, because of accompanying Forbush decrease. The ionization effect is significant only in sub-polar and polar atmosphere during the major ground level enhancement of 20 January 2005.     

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.     

Analytical approach to cosmic ray ionization by nuclei with charge Z in the middle atmosphere – Distribution of galactic CR effects

The effects of galactic and solar cosmic rays (CR) in the middle atmosphere are considered in this work. A new analytical approach for CR ionization by protons and nuclei with charge Z in the lower ionosphere and middle atmosphere is developed in this paper. For this purpose the ionization losses (dE/dh) according to the Bohr–Bethe–Bloch formula for the energetic charged particles are approximated in three different energy intervals. More accurate expressions for energy decrease E(h) and electron production rate profiles q(h) are derived. The obtained formulas allow comparatively easy computer programming. The integrand in q(h) gives the possibility for application of adequate numerical methods – such as Romberg method or Gauss quadrature, for the solution of the mathematical problem. On this way the process of interaction of cosmic ray particles with the upper, middle and lower atmosphere will be described much more realistically. Computations for cosmic ray ionization in the middle atmosphere are made. The full CR composition is taken into account: protons, Helium (α-particles), light L, medium M, heavy H and very heavy VH group of nuclei.     

Statistical analysis of the Thunderstorm Ground Enhancements (TGEs) detected on Mt. Aragats

Starting from 2008 experimental facilities of the Aragats Space Environmental Center (ASEC) routinely measure time series of secondary cosmic ray fluxes. At these years of the minimum of solar activity we analyze the new high-energy phenomena in the terrestrial atmosphere. Namely, Thunderstorm Ground Enhancements (TGEs) and Extensive Cloud Showers (ECSs). Several new particle detectors were designed and fabricated having lower energy threshold to detect particle fluxes from the thunderclouds; some of them have possibility to distinguish charged and neutral fluxes. During 2008–2012 years ASEC detectors located at Aragats, Nor Amberd and Yerevan were detected ∼300 TGE enhancements. Amplitude of majority of them is less than 5%; however, 13 TGEs have amplitude exceeding 20%. The maximal value of observed enhancement was 271% (September 19, 2009). The paper summarizes five-years study of the TGEs on Aragats. The statistical analysis revealing the month and day-of-time distributions of TGE events, as well as the amplitude and event duration diagrams are presented.     

Solar proton events recorded in the stratosphere during cosmic ray balloon observations in 1957–2008

Long-term balloon observations have been performed by the Lebedev Physical Institute since 1957 up to the present time. The observations are taken several times a week at the polar and mid latitudes and allow us to study dynamics of galactic and solar cosmic ray as well as secondary particle fluxes in the atmosphere and in the near-Earth space. Solar energetic particles (120) – mostly protons – (SEP) events with >100 MeV proton intensity above 1 cm⁻² s⁻¹ s⁻¹ were recorded during 1958–2006. Before the advent of the SEP monitoring on spacecraft these results constituted the only homogeneous series of >100 MeV SEP events. The SEP intensities and energy spectra inferred from the Lebedev Physical Institute observations are consistent with the results taken in the adjacent energy intervals by the spacecraft and neutron monitors. Joint consideration of the SEP events series recorded by balloons and by neutron monitors during solar cycles 20–23 makes it possible to restore the probable number of events in solar cycle 19, which was not properly covered by observations. Some correlation was found between duration of SEP event production in a solar cycle and sunspot cycle characteristics.     

Mid 19th century minimum of galactic cosmic ray flux inferred from Ti in Allegan meteorite

Measurements of ⁴⁴Ti activity in meteorites show that the galactic cosmic ray (GCR) intensity has been declining in the interplanetary space during the past three centuries and has a component of cyclic variation, with periodicity of about 87 years [Taricco, C., Bhandari, N., Cane, D., et al. Galactic cosmic ray flux decline and periodicities in the interplanetary space during the last 3 centuries revealed by ⁴⁴Ti in meteorites. J. Geophys. Res. 111, A08102, 2006.]. In order to verify these results, we have measured ⁴⁴Ti activity in Allegan meteorite which fell in 1899 and in some other meteorites with better precision. The measurements confirm low cosmic ray flux and consequently high solar activity near the middle of 19th century.     

Preliminary validation of computational procedures for a new atmospheric ionizing radiation (AIR) model.

A new computational procedure to determine particle fluxes in the Earth's atmosphere is presented. The primary cosmic ray spectrum has been modeled through an analysis of simultaneous proton and helium measurements made on high altitude balloon flights and spacecraft. An improved global fit to the data was achieved through applying a unique technique utilizing the Fokker-Plank equation with a non-linear rigidity-dependent diffusion coefficient. The propagation of primary particles through the Earth's atmosphere is calculated with a three-dimensional Monte Carlo transport program called FLUKA. Primary protons and helium nuclei (alphas) are generated within the rigidity range of 0.5 GV-20 TV uniform in cos2 theta. For a given location, primaries above the effective cutoff rigidity are transported through the atmosphere. Alpha particles are initially transported with a separate package called HEAVY to simulate fragmentation. This package interfaces with FLUKA to provide interaction starting points for each nucleon originating from a helium nucleus. Results from this calculation are presented and compared to measurements.     

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.     

Empirical model of cosmic ray spectrum in energy interval 1 MeV–100 GeV during 11-year solar cycle

The galactic cosmic rays (GCR) are the main ionization source at altitude of ∼3–35 km in the atmosphere. For high latitude anomalous cosmic ray (ACR) component has also a significant influence on the atmospheric ionization. We propose an empirical model for differential spectra D(E) of galactic and anomalous cosmic rays in energy interval 1 MeV–100 GeV during solar cycle. In the model data are used which cover three solar cycles: 20, 22 and 23. The LEAP87, IMAX92, CAPRICE94, AMS98 and BESS experimental spectra for protons and alpha particles are fitted to the proposed empirical model. The modulated GCR differential spectra are compared with force-field approximation to the one-dimensional transport equation and with solutions of two-dimensional cosmic ray transport equation. For experimental spectra, the calculation of the model parameters is performed by Levenberg–Marquardt algorithm, applied to the special case of least squares. Algorithm that combines the rapid local convergence of Newton–Raphson method with globally convergent method for non-linear systems of equations is applied for theoretically obtained differential spectra. The described programmes are realized in algorithmic language C++. The proposed model gives practical possibility for investigation of experimental data from measurements of galactic cosmic rays and their anomalous component.     

The brief history of experimental research of cosmic ray variations in Yakutia

Some unknown historical facts of cosmic ray studies in the north-east of the former Soviet Union related to the Yakutsk scientific group are reported for the benefit of the international scientific community. It focuses on the founders of Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of Siberian Branch of Russian Academy of Sciences. A chronology of measurements of cosmic ray intensity variations since 1949 in Yakutia (Sakha Republic; NE Siberia) is given. In particular, for the first time the data of the first solar cosmic ray event registered at Yakutsk (GLE04), with a small ionization chamber S-2 (volume: 20 L) are presented. Moreover, the data of the large ionization chamber ASK-1 (volume: 950 L) for the 1953–2003 period useful for specialists in the field of cosmic ray variations are also shown.     

The Tien-Shan mountain cosmic ray station of the Ionosphere Institute of Kazakhstan Republic

The mountain cosmic ray (CR) station of the Ionosphere Institute of Kazakhstan Republic (CR station Alma-Ata B, 43.1N latitude, 76.6E longitude, geomagnetic rigidity cutoff 6.69 GV) is a center for an experimental study of the non-stationary processes caused by cosmic rays of different origin in the interplanetary and near-Earth space, so as their influence on the state of the Earth’s magnetosphere and the upper atmosphere layers. This paper summarizes efforts performed over the years by the Almaty CR group till its present status.     

Periodic variations of ionization rate in the low and middle atmosphere

The cosmic ray ionization source functions which were obtained using a simplified extensive air shower model are used to calculate the eleven year cycle, seasonal and diurnal variations of ionization rate in the low and middle atmosphere. The ionization source function, as a function of the penetrating depth and the energy of cosmic ray particles, is the ionization rate per unit depth for a unit flux of incoming cosmic ray particles with certain energy.The calculation of the eleven year cycle variation of ionization rate in the low and middle atmosphere due to the modulation of galactic cosmic ray intensity by solar activity shows that the amplitude is larger at a higher magnetic latitude and is generally larger at higher altitudes. The relative amplitude of fluctuation of the ionization peak value (at altitudes near 15 km) is up to 45% in the magnetic polar region. The ionization rate, due to the seasonal variation of the atmospheric density, varies from several per cent below the ionization peak to several tens per cent above the peak. This seasonal variation of ionization rate reaches 35% at 70 km. The diurnal variation of atmospheric densities caused by atmospheric tidal oscillation can produce a diurnal variation of the ionization rate to an amplitude of several per cent at altitudes above 40 km. The diurnal oscillation is less than 1% below 35 km.     

宇宙线变化特征在强地磁暴预报中的应用

利用宇宙线中子探测数据定性分析了地面宇宙线多台站之间的相互联系以及大磁暴与宇宙线之间的响应关系. 以Irkutsk和Oulu宇宙线台站为例, 运用小波去噪技术提高数据的稳定性. 结果表明, 相同世界时条件下, 两站宇宙线通量相关性在事件发生时较高; 而相同地方时条件下, 相关性则在平静期较高. 进一步采用相同地方时条件对不同宇宙线台站的通量在平静期和扰动期的相对变化进行分析, 选取2004年7月强地磁暴典型事例进行直观分析, 发现大地磁暴前Irkutsk和Oulu台站的宇宙线相对通量发生明显差异, 可以尝试作为强地磁暴宇宙线先兆特征. 通过对2001年3月至2005年5月的强磁暴和中强磁暴进行统计, 得到与强地磁暴相关的适当宇宙线相对差异阈值. 将得到的阈值对2005年9月至2011年12月所有强磁暴及中强磁暴进行验证, 总成功率达到87.5%, 误报率为35.7%, 结果较好.      

History of cosmic ray research in Finland

The history of cosmic ray research in Finland can be traced back to the end of 1950s, when first ground-based cosmic ray measurements started in Turku. The first cosmic ray station was founded in Oulu in 1964 performing measurements of cosmic rays by a muon telescope, which was later complemented by a neutron monitor. Since the 1990s, several research centers and universities, such as The Finnish Meteorological Institute, Helsinki University of Technology, University of Oulu, University of Turku and University of Helsinki have been involved in space science projects, such as SOHO, AMS, Cluster, Cassini, BepiColombo, etc. At the same time, ground-based cosmic ray measurements have reached a new level, including a fully automatic on-line database in Oulu and a new muon measuring underground site in Pyhäsalmi. Research groups in Helsinki, Oulu and Turku have also extensive experience in theoretical investigations of different aspects of cosmic ray physics. Cosmic ray research has a 50-year long history in Finland, covering a wide range from basic long-running ground-based observations to high-technology space-borne instrumentation and sophisticated theoretical studies. Several generations of researchers have been involved in the study ensuring transfer of experience and building the recognized Finnish research school of cosmic ray studies.     

On transmissivity of low energy cosmic rays in disturbed magnetosphere

Access of low energy cosmic rays to any position on the Earth depends on the state of the magnetosphere. Anisotropy of cosmic rays, deduced from the neutron monitor network, must assume the variable transmissivity of the magnetosphere especially during the geomagnetic disturbances. We illustrate that computations based on different available models of geomagnetic field during selected strong geomagnetic disturbances in 2003 and 2004 imply different profiles of cut-off rigidities in time, different transmissivity functions and different asymptotic directions. Using of cosmic ray records by neutron monitors at middle and low latitudes during geomagnetically active periods, in addition to cosmic ray anisotropy in interplanetary space deduced from high and low energy cosmic ray ground based measurements, may be used for checking validity of geomagnetic field models.     

Cosmic ray measurements in High Tatra mountains: 1957–2007

Lomnický Štít (LS, situated at High Tatra mountain, 2634 m above sea level, in the direction of 49.40°N, 20.22°E; geomagnetic vertical cut-off rigidity for cosmic rays ∼4 GV) is a relevant place for cosmic ray studies. After a brief review of the LS research history we present a selection of the results based on the measurements performed by the neutron monitor located at that site. In particular, the characteristics of quasi-periodicities and the diurnal variability amplitude and phase obtained from those data are discussed.     

Applications and usage of the real-time Neutron Monitor Database

A high-time resolution Neutron Monitor Database (NMDB) has started to be realized in the frame of the Seventh Framework Programme of the European Commission. This database will include cosmic ray data from at least 18 neutron monitors distributed around the world and operated in real-time. The implementation of the NMDB will provide the opportunity for several research applications most of which will be realized in real-time mode. An important one will be the establishment of an Alert signal when dangerous solar cosmic ray particles are heading to the Earth, resulting into ground level enhancements effects registered by neutron monitors. Furthermore, on the basis of these events analysis, the mapping of all ground level enhancement features in near real-time mode will provide an overall picture of these phenomena and will be used as an input for the calculation of the ionization of the atmosphere. The latter will be useful together with other contributions to radiation dose calculations within the atmosphere at several altitudes and will reveal the absorbed doses during flights. Moreover, special algorithms for anisotropy and pitch angle distribution of solar cosmic rays, which have been developed over the years, will also be set online offering the advantage to give information about the conditions of the interplanetary space. All of the applications will serve the needs of the modern world which relies at space environment and will use the extensive network of neutron monitors as a multi-directional spectrographic detector. On top of which, the decreases of the cosmic ray intensity – known as Forbush decreases – will also be analyzed and a number of important parameters such as galactic cosmic ray anisotropy will be made available to the users of NMDB. A part of the NMDB project is also dedicated to the creation of a public outreach website with the scope to inform about cosmic rays and their possible effects on humans, technological systems and space-terrestrial environment. Therefore, NMDB will also stand as an informative gate on space research through neutron monitor’s data usage.     

Heavy particle fluxes in Salyut space station orbit

Results of a detailed analysis of heavy ion fluences measured on the Salyut and MIR orbital stations from 1978 to 1990 are presented. The analysis has made use of new models that describe the cosmic ray fluxes and their transition through the magnetosphere. The penetration of solar cosmic ray particles to the orbit, the increase of the (ScCr)/Fe flux ratio in the orbit, and the occurrences of 200–500 MeV/nucl heavy nuclei in <30° latitudes have been analyzed.     

Primary mass discrimination of high energy cosmic rays using PNN and k-NN methods

Probabilistic neural network (PNN) and k-Nearest Neighbors (k-NN) methods are widely used data classification techniques. In this paper, these two methods have been used to classify the Extensive Air Shower (EAS) data sets which were simulated using the CORSIKA code for three primary cosmic rays. The primaries are proton, oxygen and iron nuclei at energies of 100?TeV–10?PeV. This study is performed in the following of the investigations into the primary cosmic ray mass sensitive observables. We propose a new approach for measuring the mass sensitive observables of EAS in order to improve the primary mass separation. In this work, the EAS observables measurement has performed locally instead of total measurements. Also the relationships between the included number of observables in the classification methods and the prediction accuracy have been investigated. We have shown that the local measurements and inclusion of more mass sensitive observables in the classification processes can improve the classifying quality and also we have shown that muons and electrons energy density can be considered as primary mass sensitive observables in primary mass classification. Also it must be noted that this study is performed for Tehran observation level without considering the details of any certain EAS detection array.     

Relationships between neutron fluxes and rain flows

Registration of secondary cosmic ray neutrons is a convenient tool for investigation of primary cosmic ray variations and meteorological effects as well. At present a large network of neutron monitors exists, providing the studies of cosmic ray variations related to the interplanetary conditions and geomagnetic activity. At the same time cosmic ray variations may be caused by some atmospheric processes. In this connection, using the data from standard and lead-free neutron monitors, and gamma and muon detectors, we studied relations between rain flows and neutron, gamma and ionization component behavior. To explain observable results the calculations of neutron and gamma absorption and albedo neutron spectra have been performed on the basis of universal software package FLUKA-2006. In this study we used hourly data on the neutron flux, corrected for barometric pressure and data from local meteorological stations. It was shown that secondary neutron radiation, recorded by lead-free NM, and gamma radiation as well are strongly effected by meteorological factors. The neutron component behavior depends on the moisture content in the soil, and above its surface.