Variation Of Cosmic Ray Intensity Research Articles

North–South Asymmetry of Solar Diurnal Variations of Cosmic-Ray Intensity Throughout the Period 1975 – 2013

Hourly cosmic-ray intensities, recorded by 15 neutron monitor detectors in both Earth hemispheres, have been analyzed according to the interplanetary magnetic field (IMF) polarity sense (Toward (T) or Away (A)) to examine the asymmetry of solar diurnal variations (amplitudes and phases) during the time interval from 1975 to 2013. The vertical geomagnetic cut-off rigidity of these detectors is \(R_{\mathrm{o}} \leq 13~\mbox{GV}\). Previously, the north–south asymmetries of cosmic-ray intensity, between the northern and southern sectors with respect to the neutral sheet, have been studied for different periods to give an explanation as regards the cosmic ray flow in the direction parallel to the rotation axis of the Earth. The observed cosmic ray asymmetries between the two sectors were related to a corresponding N–S asymmetry of solar activity. Our results showed that during the years of minima and maxima solar activity cycles, asymmetric of latitudinal southward or northward gradients have been observed at both hemispheres. In addition, the southward and northward cosmic ray latitudinal gradients were frequently observed at stations on both hemispheres during the active period of the northern and/or southern hemispheres of the Sun. On the other hand, the differences in the solar diurnal (T–A) vectors show that the time of maximum depends on latitude at the point of observation. In addition, when the interplanetary magnetic field IMF was directed away from the Sun north of the current sheet, the northern solar diurnal vectors (T–A) shifted to later hours. Moreover, when the solar magnetic field is reversed, the phase of solar diurnal (T–A) vectors changed from 1 to 11 h, and from 3 to 9 h for northern and southern observations, respectively.

THE TEMPERATURE EFFECT IN SECONDARY COSMIC RAYS (MUONS) OBSERVED AT THE GROUND: ANALYSIS OF THE GLOBAL MUON DETECTOR NETWORK DATA

ABSTRACT The analysis of cosmic ray intensity variation seen by muon detectors at Earth's surface can help us to understand astrophysical, solar, interplanetary and geomagnetic phenomena. However, before comparing cosmic ray intensity variations with extraterrestrial phenomena, it is necessary to take into account atmospheric effects such as the temperature effect. In this work, we analyzed this effect on the Global Muon Detector Network (GMDN), which is composed of four ground-based detectors, two in the northern hemisphere and two in the southern hemisphere. In general, we found a higher temperature influence on detectors located in the northern hemisphere. Besides that, we noticed that the seasonal temperature variation observed at the ground and at the altitude of maximum muon production are in antiphase for all GMDN locations (low-latitude regions). In this way, contrary to what is expected in high-latitude regions, the ground muon intensity decrease occurring during summertime would be related to both parts of the temperature effect (the negative and the positive). We analyzed several methods to describe the temperature effect on cosmic ray intensity. We found that the mass weighted method is the one that best reproduces the seasonal cosmic ray variation observed by the GMDN detectors and allows the highest correlation with long-term variation of the cosmic ray intensity seen by neutron monitors.

Cosmic Ray Daily Variation on Anomalous Days

The Characteristics of the daily variation of cosmic ray intensity on different types of anomalous days have been studied by using data of Neutron Monitors. It is observed that Cosmic Ray intensity remains statistically low during the period of 1996-1998 on both Beijing and Moscow Neutron Monitor stations. These data are subjected to Harmonic Analysis and Fourier Techniques for entire period of consideration that is 1996-2006. The amplitude and phase of diurnal and semidiurnal anisotropies on these stations particularly on Anomalous days have been discussed. The occurrence of these events are dominated during solar activity minimum years. The number of days of occurrence is more anti-correlated with solar cycle.

Effect of near-earth thunderstorms electric field on the intensity of ground cosmic ray positrons/electrons in Tibet

Monte Carlo simulations are performed to study the correlation between the ground cosmic ray intensity and near-earth thunderstorms electric field at YBJ (located at YangBaJing, Tibet, China, 4300m a. s. l.). The variations of the secondary cosmic ray intensity are found to be highly dependent on the strength and polarity of the electric field. In negative fields and in positive fields greater than 600V/cm, the total number of ground comic ray positrons and electrons increases with increasing electric field strength. And these values increase more obviously when involving a shower with lower primary energy or a higher zenith angle. While in positive fields ranging from 0 to 600V/cm, the total number of ground comic ray positrons and electrons declines and the amplitude is up to 3.1% for vertical showers. A decrease of intensity occurs in inclined showers within the range of 0−500V/cm, which is accompanied by smaller amplitudes. In this paper, the intensity changes are analyzed, especially concerning those decreasing phenomena in positive electric fields. Our simulation results could be helpful in understanding the decreases observed in some ground-based experiments (such as the Carpet air shower array and ARGO-YBJ), and also be useful in understanding the acceleration mechanisms of secondary charged particles caused by an atmospheric electric field.

An estimation of the yield and response functions for the mini neutron monitor

AbstractThe present study estimates the yield and response functions of the mini neutron monitor (miniNM). This relatively new cosmic ray detector is the mobile version of the standard NM64. It can be use not only to calibrate the NM64 but also to study the modulation processes. Due to its portability, the miniNM can be easily placed in a suitable location to measure secondary particles, which give information about the intensity variations of galactic and solar cosmic rays. In order to perform these modulation studies with miniNMs, it is crucial to know their sensitivity to detect secondary cosmic ray flux, i.e., we must know their yield function. A previous study found that miniNM and NM64 have slightly different response functions. This work analyzes the observed counting rate ratio (miniNM to NM64) and gives for the first time an useful expression for the yield function of the miniNM. The results found here will allow to interpret the new measurements with this mobile neutron monitor. For comparison, a brief summary of the NM64 yield functions reported by other authors is presented.

Study of the Cosmic-Ray Modulation During the Passage of ICMEs and CIRs

We compare the cosmic-ray response to interplanetary coronal mass ejections (ICMEs) and corotating interaction regions (CIRs) during their passage in near-Earth space. We study the relative importance of various structures/features identified during the passage of the ICMEs and CIRs observed during Cycle 23 (1995 – 2009). The identified ICME structures are the shock front, the sheath, and the CME ejecta. We isolate the shock arrival time, the passage of the sheath region, the arrival of ejecta, and the end time of their passage. Similarly, we isolate the CIR arrival, the associated forward shock, the stream interface, and the reverse shock during the passage of a CIR. For the cosmic-ray intensity, we utilize the data from high counting rate neutron monitors. In addition to neutron monitor data, we utilize near-simultaneous and same time-resolution data of interplanetary plasma and field, namely the solar-wind velocity, the interplanetary magnetic field (IMF) vector, and its variance. Further, we also utilize some derived interplanetary parameters. We apply the method of the superposed-epoch analysis. As the plasma and field properties are different during the passage of different structures, both in ICMEs and CIRs, we systematically vary the epoch time in our superposed-epoch analysis one by one. In this way, we study the role and effects of each of the identified individual structures/features during the passage of the ICMEs and CIRs. Relating the properties of various structures and the corresponding variations in plasma and field parameters with changes of the cosmic-ray intensity, we identify the relative importance of the plasma/field parameters in influencing the amplitude and time profiles of the cosmic-ray intensity variations during the passage of the ICMEs and CIRs.

Solar cycle and 27-day variations of the diurnal anisotropy of cosmic rays during the solar cycle 23

The diurnal anisotropy of cosmic-ray intensity observed over the period 1997–2006, which coincides with the solar cycle 23, has been analyzed using cosmic ray data from Athens and Oulu neutron monitor stations. In this analysis it was observed that the time of the diurnal variation maximum shifted to earlier hours than the corotation direction from 1997 to 2000, where the polarity state of the magnetic field was positive ( $qA > 0$ ) and to later hours from 2001 to 2006 where the polarity state was negative ( $qA < 0$ ). Moreover the 27-day variation of the cosmic-ray diurnal anisotropy in connection with the 27-day variation of the interplanetary magnetic field has been studied. In this study six groups of ten Bartel rotations each one have been analyzed (2232–2241, 2249–2258, 2275–2284, 2286–2295, 2328–2337, 2356–2365). It is remarkable that the 27-day variation of cosmic- ray intensity is characterized by the well known sector structure and it is well correlated with the $B_{XY}$ component of the interplanetary magnetic field. These findings during the last solar cycle confirm once again the close relation of the diurnal variation of cosmic ray intensity and the interplanetary magnetic field.

Diurnal anisotropy of cosmic rays during intensive solar activity for the period 2001–2014

The diurnal variation of cosmic ray intensity, based on the records of two neutron monitor stations at Athens (Greece) and Oulu (Finland) for the time period 2001 to 2014, is studied. This period covers the maximum and the descending phase of the solar cycle 23, the minimum of the solar cycles 23/24 and the ascending phase of the solar cycle 24.These two stations differ in their geographic latitude and magnetic threshold rigidity. The amplitude and phase of the diurnal anisotropy vectors have been calculated on annual and monthly basis.From our analysis it is resulted that there is a different behaviour in the characteristics of the diurnal anisotropy during the different phases of the solar cycle, depended on the solar magnetic field polarity, but also during extreme events of solar activity, such as Ground Level Enhancements and cosmic ray events, such as Forbush decreases and magnetospheric events. These results may be useful to Space Weather forecasting and especially to Biomagnetic studies.

Impulsive event probability in the radiocarbon record in VIII - XI centuries

The abundance of cosmogenic isotopes in natural samples is the main source of information about past variations of cosmic ray intensity, in the solar activity and in the strength of the geomagnetic field. Sharp increases could originate from powerful impulsive events such as solar flares, gamma-rays from supernova explosions and gamma-ray bursts. A significant increase in the radiocarbon record has been detected recently in tree rings around AD 775 [1]. Both large solar proton event (SPE) [2] and gamma-ray burst (GRB) in our Galaxy [3] are favored as a source. However, either of the explanations faces difficulties of low event rate because of detection of a similar peak around AD993 [4], [5]. What is more, we know other similar result [6]. We carried out a statistical analysis of these three data sets. It is shown that AD 775 event differs fundamentally from AD 993 and AD 1006 events, because the last two can be explained without the assumption of the impulsive event.

Short-Term Variations of Cosmic-Ray Intensity During the Recent Deep Solar Minimum and the Previous Four Solar Minima: A Wavelet Analysis

The recent, unusual solar cycle and solar minima between Cycles 23 and 24 have been studied extensively. Wavelet analysis of hourly cosmic-ray intensity during the last five solar minima reveals a number of short-term variations with few temporal shifts in the periods. This study suggests that deviations with a one-solar-rotation period and its harmonics are small during the recent minimum. However, deviations are considerably larger during the other minima. Analysis also demonstrates that the behavior of active regions is nearly the same during the minima of Cycles 19, 20, 21, and 22. The results also suggest that regions outside the streamer stalk are significantly larger in the recent solar minimum as opposed to the other minima.

Study of Cosmic-Ray Modulation During the Recent Unusual Minimum and Mini-Maximum of Solar Cycle 24

After a prolonged and deep solar minimum at the end of Cycle 23, the current Solar Cycle 24 is one of the lowest cycles. These two periods of deep minimum and mini maximum are separated by a period of increasing solar activity. We study the cosmic-ray intensity variation in relation with the solar activity, heliospheric plasma and field parameters, including the heliospheric current sheet, during these three periods (phases) of different activity level and nature: (a) a deep minimum, (b) an increasing activity period and (c) a mini maximum. We use neutron monitor data from stations located around the globe to study the rigidity dependence on modulation during the two extremes, i.e., minimum and maximum. We also study the time lag between the cosmic-ray intensity and various solar and interplanetary parameters separately during the three activity phases. We also analyze the role of various parameters, including the current sheet tilt, in modulating the cosmic-ray intensity during the three different phases. Their relative importance and the implications of our results are also discussed.

2-D Modelling of Long Period Variations of Galactic Cosmic Ray Intensity

A new two-dimensional (2-D) time dependent model describing long-period variations of the Galactic Cosmic Ray (GCR) intensity has been developed. New approximations for the changes of the magnitude B of the Interplanetary Magnetic Field (IMF), the tilt angle δ of the Heliospheric Neutral Sheet (HNS) and drift effects of the GCR particles have been included into the model. Moreover, temporal changes of the exponent γ expressing the power law - rigidity dependence of the amplitudes of the 11-year variation of the GCR intensity have been added. We show that changes of the expected GCR particle density precedes changes of the GCR intensity measured by the Moscow Neutron (MN) monitor by about 18 months. So ∼18 months can be taken as an effective delay time between the expected intensity caused by the combined influence of the changes of the parameters implemented in the time-dependent 2-D model and the GCR intensity measured by neutron monitors during the 21 cycle of solar activity.

Rigidity spectrum of the long-period variations of the galactic cosmic ray intensity in different epochs of solar activity

We investigate character of correlations between the rigidity spectrum exponent γ of the 11-year variations of the Galactic Cosmic Ray (GCR) intensity and the exponent v of the Power Spectral Density (PSD) of the Interplanetary Magnetic Field (IMF) turbulence in period 1968-2012 using data of the IMF and carefully selected neutron monitors. We show that a clear inversely correlation between γ and v is observed when a resonance frequency range f1-f2 of the IMF turbulence (using for calculation of v), are determined taking into account changes of the solar wind velocity Vsw and strength B of the IMF versus solar activity. We assume that an essential contribution to the scattering of GCR particles in the heliosphere is setting up generally by the turbulence of By and Bz components of the IMF. Therefore, in this paper we use the exponents vy and vz of PSD of the By and Bz components of the IMF turbulence. Generally, both γ and v can be accepted as the essential proxies to study GCR propagation near earth orbit in heliosphere for the rigidity range of GCR particles to which neutron monitors and ground muon telescopes respond

Mini neutron monitor measurements at the Neumayer III station and on the German research vessel Polarstern

Neutron monitors (NMs) are ground-based devices to measure the variation of cosmic ray intensities, and although being reliable they have two disadvantages: their size as well as their weight. As consequence, [1] suggested the development of a portable, and thus much smaller and lighter, calibration neutron monitor that can be carried to any existing station around the world [see 2; 3]. But this mini neutron monitor, moreover, can also be installed as an autonomous station at any location that provides ’’office” conditions such as a) temperatures within the range of around 0 to less than 40 degree C as well as b) internet and c) power supply. However, the best location is when the material above the NM is minimized. In 2011 a mini Neutron Monitor was installed at the Neumayer III station in Antarctica as well as the German research vessel Polarstern, providing scientific data since January 2014 and October 2012, respectively. The Polarstern, which is in the possession of the Federal Republic of Germany represented by the Ministry of Education and Research and operated by the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research and managed by the shipping company Laeisz, was specially designed for working in the polar seas and is currently one of the most sophisticated polar research vessels worldwide. It spends almost 310 days a year at sea usually being located in the waters of Antarctica between November and March while spending the northern summer months in Arctic waters. Therefore, the vessel scans the rigidity range below the atmospheric threshold and above 10 GV twice a year. In contrast to spacecraft measurements NM data are influenced by variations of the geomagnetic field as well as the atmospheric conditions. Thus, in order to interpret the data a detailed knowledge of the instrument sensitivity with geomagnetic latitude (rigidity) and atmospheric pressure is essential. In order to determine the atmospheric response data from the Neumayer III station here we will perform comparisons to other polar stations, resulting in an atmospheric pressure coefficient of 7.5‰/hPa, while the rigidity dependence will be determined experimentally by utilizing several latitude scans. Thereby, the atmospheric pressure and temperature correction will be discussed in more detail and the results of the latitude scan performed between October 2012 and March 2013 will be presented. Moreover, we will show that this latitude scan can also be described by using the yield function of [4].

27-day variation of the GCR intensity based on corrected and uncorrected for geomagnetic disturbances data of neutron monitors

We study 27-day variations of the galactic cosmic ray (GCR) intensity for 2005–2008 period of the solar cycle #23. We use neutron monitors (NMs) data corrected and uncorrected for geomagnetic disturbances. Besides the limited time intervals when the 27-day variations are clearly established, always exist some feeble 27-day variations in the GCR intensity related to the constantly present weak heliolongitudinal asymmetry in the heliosphere. We calculate the amplitudes of the 27-day variation of the GCR intensity based on the NMs data corrected and uncorrected for geomagnetic disturbances. We show that these amplitudes do not differ for NMs with cut-off rigidities smaller than 4-5 GV comparing with NMs of higher cut-off rigidities. Rigidity spectrum of the 27-day variation of the GCR intensity found in the uncorrected data is soft while it is hard in the case of the corrected data. For both cases exists definite tendency of softening the temporal changes of the 27-day variation's rigidity spectrum in period of 2005 to 2008 approaching the minimum of solar activity. We believe that a study of the 27-day variation of the GCR intensity based on the data uncorrected for geomagnetic disturbances should be carried out by NMs with cut-off rigidities smaller than 4-5 GV.

Определение плотности температурных коэффициентов для мюонов в атмосфере

When studying variations of cosmic ray intensity, by the use of muon telescopes located deep in the atmosphere it is necessary to take into account changes in atmospheric parameters, mainly pressure and temperature. The density distribution of temperature coefficients of the atmosphere muon intensity needs to be estimated from observations. To this purpose, the method of principal components regression and meth-ods of projection to latent structures (PLS-1 and PLS-2). We used data of continuous recording of muons, as well as Novosibirsk 2004–2010 aerological data. As shown by comparing results, PLS-2 method allows us to esti-mate the density distribution of muon intensity temperature coefficients with minimal errors.

Rigidity Dependence of the Long-Term Variations of Galactic Cosmic-Ray Intensity in Relation to the Interplanetary Magnetic-Field Turbulence: 1968 – 2002

We studied the relationship between the power-law exponent γ on the rigidity R of the spectrum of galactic cosmic-ray (GCR) intensity variation (δD(R)/D(R)∝R −γ ) and the exponents ν y and ν z of the power spectral density (PSD) of the B y and B z components of the interplanetary magnetic field (IMF) turbulence (PSD∼f −ν , where f is the frequency). We used the data from neutron monitors and IMF for the period of 1968 – 2002. The exponents ν y and ν z were calculated in the frequency interval Δf=f 2−f 1=3×10−6 Hz of the resonant frequencies (f 1=1×10−6 Hz, f 2=4×10−6 Hz) that are responsible for the scattering of GCR particles with the rigidity range detected by neutron monitors. We found clear inverse correlations between γ and ν y or ν z when the time variations of the resonant frequencies were derived from in situ measurements of the solar wind velocity U sw and IMF strength B during 1968 – 2002. We argue that these inverse relations are a fundamental feature in the GCR modulation that is not restricted to the analyzed years of 1968 – 2002.

Evidence for Planetary Forcing of the Cosmic Ray Intensity and Solar Activity Throughout the Past 9400 Years

Paleo-cosmic-ray (PCR) records based on cosmogenic 10Be and 14C data are used to study the variations in cosmic-ray intensity and solar activity over the past 9400 years. There are four strong correlations with the motion of the Jovian planets; the probability of occurring by chance being < 10−5. They are i) the PCR periodicities at 87, 350, 510, and 710 years, which closely approximate integer multiples of half the Uranus–Neptune synodic period; ii) eight periodicities in the torques calculated to be exerted by the planets on an asymmetric tachocline that approximate the periods observed in the PCR; iii) the maxima of the long-term PCR variations are coincident with syzygy (alignment) of the four Jovian planets in 5272 and 644 BP; and iv) in the time domain, the PCR intensity decreases during the first 60 years of the ≈ 172 year Jose cycle (Jose, Astron. J. 70, 193, 1965) and increases in the remaining ≈ 112 years in association with barycentric anomalies in the distance between the Sun and the center of mass of the solar system. Furthermore, sunspot and neutron-monitor data show that three anomalous sunspot cycles (4th, 7th, and 20th) and the long sunspot minimum of 2006 – 2009 CE coincided with the first and second barycentric anomalies of the 58th and 59th Jose cycles. Phase lags between the planetary and heliospheric effects are ≤ five years. The 20 largest Grand Minima during the past 9400 years coincided with the latter half of the Jose cycle in which they occurred. These correlations are not of terrestrial origin, nor are they due to the planets’ contributing directly to the cosmic-ray modulation process in the heliosphere. Low cosmic-ray intensity (higher solar activity) occurred when Uranus and Neptune were in superior conjunction (mutual cancellation), while high intensities occurred when Uranus–Neptune were in inferior conjunction (additive effects). Many of the prominent peaks in the PCR Fourier spectrum can be explained in terms of the Jose cycle, and the occurrence of barycentric anomalies.

A real-time multichannel detector system for large-scale environmental radiation survey

In this work, we established a real-time multichannel detector system for large-scale environmental radiation survey. The system consists of a Berkeley Lab cosmic-ray detector for the measurement of muons, a moderated He detector for neutrons, a NaI(Tl) as well as a HPGe spectrometer for terrestrial gamma rays, and a high pressure ionization chamber, which responses to both cosmic rays and terrestrial gamma rays. The measured data of these five detector channels as well as signals from a global position system are acquired and displayed by a LabVIEW program on a notebook computer every one minute (10 min for HPGe and 20 min for NaI(Tl) gamma-ray spectrometers). The advantage and merit of this multichannel detector system have been demonstrated by test runs with the equipment set up both on a train and on a bus to show in real time the variation of cosmic-ray intensity as a function of altitude and the gamma-ray dose rates as well as the relative concentrations of the natural radioactive elements over a large survey area. This real-time multichannel detector system was originally developed for natural background radiation measurements for popular science education to general public, however, due to the specific features of each detector of the system it appears to be an ideal system for radiation survey over a large radiation polluted or contaminated area resulted from a severe nuclear accident, such as Fukushima Dai-Ichi Nuclear Power Plant accident.

A study on the various types of arrhythmias in relation to the polarity reversal of the solar magnetic field

Over the last few years, various researches have reached the conclusion that cosmic ray variations and geomagnetic disturbances are related to the condition of the human physiological state. In this study, medical data concerning the number of incidents of different types of cardiac arrhythmias for the time period 1983–1992, which refer to 1902 patients in Tbilisi, Georgia, were used. The smoothing method and the Pearson r-coefficients were used to examine the possible effect of different solar and geomagnetic activity parameters and cosmic ray intensity variations on the different types of arrhythmias. The time interval under examination was separated into two different time periods, which coincided with the polarity reversal of the solar magnetic field occurred in the years 1989–1990, and as a result, a different behavior of all the above-mentioned parameters as well as of the different types of arrhythmias was noticed during the two time intervals. In addition, changing of polarity sign of the solar magnetic field was found to affect the sign of correlation between the incidence of arrhythmias and the aforementioned parameters. The primary and secondary maxima observed in the solar parameters during the solar cycle 22, also appeared in several types of arrhythmias with a time lag of about 5 months.