Harmonics of Daily Variations in Cosmic-Ray Intensity

The high/low amplitude anisotropic wave-train events (HAE/LAE) in cosmic-ray intensity have been investigated during the period 1991-94, using the neutron monitor data for different latitudes. In all, 16 HAE and 13 LAE cases have been studied. An inter-comparison of the first three harmonics during these events has been made so as to understand the basic reason causing the occurrence of these types of events. It has been observed that the phase of diurnal anisotropy shifts towards earlier hours for HAEs; similarly, it shifts towards earlier hour as compared to 18-Hr direction for LAEs. For semi-diurnal anisotropy phase remains statistically the same for both HAE as well as for LAE. Further in case of tri-diurnal anisotropy phase is evenly distributed for both types of events. The interplanetary magnetic field and solar-wind plasma parameters during these events are also investigated. It has been also observed that HAE/LAEs are weakly dependent on solar-wind velocity.     

Unusually low-amplitude anisotropic wave-train events of cosmic ray intensity during 1981–1994

Investigation has been made for unusually low-amplitude anisotropic wave train events (LAE) for cosmic ray intensity data of Deep River neutron monitoring station during the period 1981–94. It has been observed that the phase of diurnal anisotropy remains in the same co-rotational direction for most of the LAEs while the phase shifts to early hours for some of the LAEs in diurnal anisotropy. During minimum solar activity, LAEs have been observed to be dominant. Solar wind plasma (SWP) parameters, inter-planetary magnetic field and various features at solar disk have also been studied. The amplitude remains low continuously for most of the days while the phase shifts to earlier hours. Occurrence of LAE is independent of the nature of interplanetary magnetic field (IMF).     

Third harmonics of cosmic ray intensity on quiet days at Deep River Neutron Monitoring Station

The cosmic ray (CR) intensity data recorded in Deep River Neutron Monitoring Station have been investigated on quietest days (QD) for third harmonics of daily variation during solar cycles 21 and 22. It has been observed that in spite of abrupt change in the amplitude and phase of tri-diurnal anisotropy in CR intensity, the amplitude is quite significant throughout the period of investigation with larger amplitude during the years 1980 and 1985. Thus, tri-diurnal anisotropy clearly shows 11-year variation at the mid latitude neutron monitoring station.      

利用羊八井中子监测器研究宇宙线的太阳日周期变化

通过对宇宙线周期变化研究可以得到宇宙线产生和传播区域的重要信息,是宇宙线长期研究的重要热点问题。利用位于西藏羊八井(地磁截止刚度:14.1 GeV) 的中子监测器2006 至2011年的观测数据,研究宇宙线的太阳日周期变化。在对中子监测器观测数据进行气压修正后,通过Lomb-Scargle 傅立叶变换法对修正后的数据进行周期分析,发现宇宙线计数率存在超过地球公转运动Compton-Getting 效应的太阳日周期变化,该周期变化可能是地球公转效应和宇宙线传播物理过程调制效应以及剩余气象效应的叠加。计算分析了1 日周期信号的振幅和初相位随时间的变化,发现1 日周期变化的初相位存在较为明显的年周期变化规律,这可能是地球公转和自转合成运动的结果;1 日周期变化幅度在2010 年后出现增大趋势。这些结果对宇宙线周期变化和各向异性的研究具有重要参考意义。With the study of the cosmic rays' solar diurnal variation we can get the important information about Cosmic Ray's production and propagation. It's important issues of cosmic rays' studies. We analyze the temporal variation of cosmic rays rate observed with the Yangbajing neutron monitor during 2006 to 2011, and nd semidiurnal and diurnal period signals included in the rates of cosmic rays with vertical rigidity equal to 14.1 GV. We have checked the time dependence of the phase and the amplitude of semidiurnal and diurnal anisotropy, and nd that the phase of diurnal signal varies yearly, it could be a synthetic movement of the earth's rotation and revolution. The amplitude before 2010 is obvious smaller than that after 2010. These results are of great reference value for studying the anisotropy and time variation of cosmic rays.     

Climatologies of tides at mid-latitudes in the lower thermosphere

Summary Time variations of the semi-diurnal and diurnal tides observed at Budrio (45°N, 12°E) in the wind structure of the lower thermosphere ((80÷110) km) throughout the period 1976–1990 are herewith represented as monthly contours of both amplitudes and phasesvs. height. The semi-diurnal tide has more marked seasonal variations, showing amplitudes generally larger than the diurnal ones ((10÷30) m/svs. (5÷15) m/s). The vertical wavelengths are longer in summer than in winter, at least below 100 km. Agreement with new numerical models for semi-diurnal tide at 50°N appears to be satisfactory.     

PROPAGATION EFFECTS OF SOLAR COSMIC RAYS

Computer calculations have been made on the dimensional solution to the anisotropic diffusion convection equation for solar cosmic rays propagating in an uniform and unbounded interplanetary medium. This paper presents the results calculated by means of Jokipii's diffusion coefficients. Discussion is restricted to the influences of solar wind convection on the rise to maximum times and on the peak intensities of solar cosmic ray events with solar corotation effect taken into consideration. The model well explains the asymmetrical variations of the propagation charateristics of the events with solar longitudes of their parents flares relative to the interplanetary magnetic field lines passing through the earth, and the theoretical curves of the rise times fit satisfactorily the observations of solar events ranging from relativistic to about 30 MeV medium energies.     

Solar diurnal anisotropy measured using muons in GRAPES-3 experiment in 2006

The GRAPES-3 experiment at Ooty contains a large-area (560 m²) tracking muon detector. This detector consists of 16 modules, each 35 m² in area, that are grouped into four supermodules of 140 m² each. The threshold energy of muons is sec(θ) GeV along a direction with zenith angle θ and the angular resolution of the muon detector is 6°. Typically, it records ~4×10⁹ muons every day. The muon detector has been operating uninterruptedly since 2001, thus providing a high statistics record of the cosmic ray flux as a function of time over one decade. However, prior to using these data, the muon rate has to be corrected for two important atmospheric effects, namely, variations in atmospheric pressure and temperature. Because of the near equatorial location of Ooty (11.4°N), the seasonal variations in the atmospheric temperature are relatively small and shall be ignored here. Due to proximity to the equator, the pressure changes at Ooty display a dominant 12 h periodic behaviour in addition to other seasonal changes. Here, we discuss various aspects of a novel method for accurate pressure measurement and subsequent corrections applied to the GRAPES-3 muon data to correct these pressure-induced variations. The pressure-corrected muon data are used to measure the profile of the solar diurnal anisotropy during 2006. The data, when divided into four segments, display significant variation both in the amplitude (~45%) and phase (~42 m) of the solar diurnal anisotropy during 2006, which was a period of relatively low solar activity.     

基于小波变换的1—10TeV宇宙线周期变化研究

利用小波变换, 结合折叠周期分析方法, 对羊八井宇宙线观测站Tibet AS γ阵列1998年4—6月的实验记录数据进行了周期分析, 发现 TeV和10 TeV宇宙线流强观测数据中包含0.5 和1 d周期变化, 其信噪比分别达到10和6. TeV宇宙线0.5 和1 d周期变化的最大变化幅度分别约为0.3%和0.5%, 10 TeV宇宙线约为0.4%和0.7%. We use the technique of wavelet analysis and epoch folding methods to search for the superimposed periodic signals of 1—10 TeV cosmic ray in the data obtained with Tibet Ⅱ/HD AS Array for April to June of 1998. Solar time semi diurnal and diurnal variations have been detected with about signal noise ratio 10 and 6 for the 1 TeV and 10 TeV cosmic ray flux respectively. The semi diurnal variations are of an amplitude 0.3%, a phase 0.9 for 1 TeV cosmic ray and 0.4%, 0.9 for 10 TeV. The diurnal variations are of amplitude 0.5%, 0.7%, and phase 0.8 for 1 TeV and 10 TeV cosmic ray respectively.     

What Laboratory-Produced Plasma Structures Can Contribute to the Understanding of Cosmic Structures Both Large and Small

The tradition of the classical 1901 work by Birkeland [1] on aurora phenomena by laboratory terrella experiments was resumed by Alfvén [2], Cowling [3], Ferraro et al. [4], and by Bennett [5] in his terrella experiments. In 1954 [6] when experimenters accidentally produced in the laboratory structures later identified as diamagnetic vortex filaments, and in 1961 [7] when filaments, later identified as current-carrying paramagnetic plasma vortex structures (which are both electric motors and dynamos), were observed in the Z and theta-pinch experiments, this tradition was being further reestablished. It has been successfully argued [6], [8], [11], [20] that both of these types of vortices are force-free minimum-free-energy structures that spontaneously spring to life as readily as do thousands of spherical bubbles and water droplets during the splash of a breaking water wave. The Birkeland aurora filaments are a hybrid combination of these two basic types (paramagnetic and diamagnetic) of plasma vortices. It is to be expected that such structures on a cosmic scale play an important role in the cosmos, and indeed they do in the formation of galaxies, stars, binary stars, solar systems, solar prominences, solar flares, solar wind, comet tails, cosmic "strings" in the Crab nebula, string-like galactic clusters, expansion of the Universe, giant galactic jets, cosmic rays, sunspots, vortex rolls in sunspot penumbra, twinkling of radio stars by the density fluctuations in the ionosphere, turbulence at the interface between the solar wind and the earth's magnetosphere, etc.     

宇宙线福布什下降期间羊八井云量的变化

进入地球大气中的宇宙线强度发生变化,可能导致气候,比如云量的变化. 利用羊八井中子监测器在2003—2004年观测到3次宇宙线福布什下降,在这期间同时记录了观测站点上空的云量变化. 通过对宇宙线福布什下降期间羊八井上空云量的统计分析发现,宇宙线福布什下降期间云量增加,即云量对宇宙线福布什下降表现出明显的负响应. 这表明,宇宙线福布什下降期间,低纬度薄云层地区云量增加,与其他观测结果相一致.     

Behavior of the cosmic-ray vector anisotropy before interplanetary shocks

The behavior of the galactic cosmic ray density and vector anisotropy during geomagnetic storms with sudden storm commencements has been investigated based on the global survey data. It is shown that the average anisotropy significantly increases directly before a sudden storm commencement; the larger the subsequent Forbush decrease, the larger the increase in anisotropy. The averaged values of the CR anisotropy and density start to be affected by the shock wave approximately 5 h before its arrival. Changes in the anisotropy direction (especially for west Forbush sources) can be observed much earlier.     

Mechanism of proton anisotropic velocity distribution in the solar wind

Although it has been long that spacecraft observed the anisotropy of velocity protons in the solar wind, there is still not a reasonable explanation. In this paper we try to give an explanation from the diffusion plateau of protoncyclotron resonance predicted by the quasi-linear theory for the resonance between the protons and the parallel propagating waves. We consider the effect of dispersion relation on diffusion plateau and notice that the diffusion plateau we have got by using cold plasma dispersion relation accords with the density contours in the velocity phase space detected at 0.3 AU in fast solar wind. For explaining proton distributions obtained in the fast solar wind from 0.7 AU to 1 AU hot plasma dispersion relation should be considered. We also give a theoretical relation of proton thermal anisotropy A and plasma parameter β.     

Diurnal and Eleven- Year Variations of Neutron Component of Cosmic Rays

Cosmic ray ground observations are used together with the method of coupling coefficients to determine, by spectrographic method, the features of the variational primary energy spectrum of diurnal and eleven-year variations of neutron component of cosmic rays. It is found that the variational energy spectrum responsible for both types of variations can be best described by a constant spectrum up to an upper effective rigidity boundary. The upper cut-off effective rigidity boundary for the variational energy spectrum of diurnal variation was found to change from 105 GV at maximum solar activity to 15.85 GV at minimum solar activity. For Eleven-year variation, R_max was found to have a value of about 20 GV which changes slighly with solar activity due to the change of the coupling coefficients with solar activity.     

Investigation of geoeffective and non-geoeffective CMEs according to data from the URAGAN muon hodoscope

Coronal mass ejections are the brightest manifestations of solar activity. Dozens of coronal mass ejections are observed daily during periods of higher solar activity. They directly affect cosmic ray fluxes that carry information on plasma clouds, including clouds moving toward the Earth. Several aspects of geoeffective and non-geoeffective coronal mass ejections, observed with the ground-based URAGAN muon hodoscope operated as part of the NEVOD experimental complex at MEPhI, are discussed. The anisotropy of cosmic ray muon fluxes recorded during coronal mass ejections in 2014 and 2015 is investigated.     

Far-out surface science: radiation-induced surface processes in the solar system

Interplanetary space is a cosmic laboratory for surface scientists. Energetic photons, ions and electrons from the solar wind, together with galactic and extragalactic cosmic rays, constantly bombard surfaces of planets, planetary satellites, dust particles, comets and asteroids. Many of these bodies exist in ultrahigh vacuum environments, so that direct particle–surface collisions dominate the interactions. In this article, we discuss the origins of the very tenuous planetary atmospheres observed on a number of bodies, space weathering of the surface of asteroids and comets, and magnetospheric processing of the surfaces of Jupiter's icy satellites. We emphasize non-thermal processes and the important relationships between surface composition and the gas phase species observed. We also discuss what laboratory and computational modeling should be done to support the current and future space missions––e.g. the Genesis mission to recover solar wind particles, the Cassini mission to probe Saturn, the Europa Lander mission to explore the subsurface ocean hypothesis, and the Pluto/Kuiper Express to sample the outer reaches of the solar system.     

Forbush decreases in the 19th solar cycle

The 19th solar cycle was characterized by abnormally high solar activity; unfortunately, the possibilities of observing it were limited. Ground-based observations of cosmic rays and geomagnetic activity are among the few types of continuous measurements that allow statements about the events of 19th cycle and their comparison with events of other cycles. Comparison of the events in cosmic rays with solar and geomagnetic activities shows that the number and strength of magnetic storms in the 19th cycle correspond to an abnormally high number of sunspots. However, large Forbush decreases were lacking in this cycle. The most powerful ICMEs of the 19th cycle were generally weaker than the greatest ones in later periods.     

On the heliosphere characteristics important for galactic cosmic rays in the phase of minimum solar activity

Various heliospheric parameters important for the behavior of cosmic rays, i.e., the solar wind velocity, heliospheric magnetic field, and heliospheric current sheet during epochs of the minimum of solar cycles 20?C24 are discussed. Main features and regularities of the behavior of these parameters and their interrelations are considered.     

Cosmic ray studies with the L3-cosmics program at CERN

The L3 detector at the CERN electron-positron collider had a muon spectrometer which was employed during the last years of LEP operation for cosmic ray studies. The results of this program include a precise muon spectrum and charge ratio between 20 GeV and 3 TeV, a limit on TeV primary antiprotons from a study of the Moon’s shadow, the (possible) observation of a are signal from a fixed position in the northern hemisphere through muons, a solar anisotropy of 200 GeV protons, and other results. Negative limits on muons associated with known H.E. gamma sources or gamma bursts, the search for anomalous H.E. interaction or decay events such as reported from the Kolar Gold Fields, and a search for muons correlated with a solar are are also noted.     

Observation by an air-shower array in Tibet of the multi-TeV cosmic-ray anisotropy due to terrestrial orbital motion around the Sun

We report on the solar diurnal variation of the galactic cosmic-ray intensity observed by the Tibet III air shower array during the period from 1999 to 2003. In the higher-energy event samples (12 and 6.2 TeV), the variations are fairly consistent with the Compton-Getting anisotropy due to the terrestrial orbital motion around the Sun, while the variation in the lower-energy event sample (4.0 TeV) is inconsistent with this anisotropy. This suggests an additional anisotropy superposed at the multi-TeV energies, e.g., the solar modulation effect. This is the highest-precision measurement of the Compton-Getting anisotropy ever made.     

North-South anisotropy during the quasi-stationary modulation of galactic cosmic rays

Summary High-speed solar-wind streams coming from coronal holes produce, in the interplanetary space, a quasi-stationary modulation of galactic cosmic rays. The Rome cosmic-ray group has analysed this modulation taking into account not only the charged-particle isotropic intensity but also the North-South anisotropy (A _NS), derived from ground-based measurements. The obtained results for the period October 1964–December 1987 are summarized. Data from the Bartels solar rotation no. 2034 (May 23–June 18, 1982) are used to illustrate theA _NS phenomenology. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.