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1.
《New Astronomy》2013
The primary processing of the neutron monitor data includes all the necessary actions and procedures that each cosmic ray station follows in order to provide the worldwide neutron monitor network with good quality data. One of the main corrections of the primary data is the pressure correction due to the barometric effect. The barometric effect induces variations to the measured data of the neutron monitors which are related to the variations of the local atmospheric pressure of the stations. This correction requires the definition of the barometric coefficient which is calculated experimentally. The accurate calculation of the coefficient is a prerequisite for the quality of the data. This paper presents the implementation of an online tool which calculates the barometric coefficient of a cosmic ray station, by taking advantage of the fact that most stations publish their data on the Neutron Monitor Data Base. 相似文献
2.
M.F. Tolba 《Planetary and Space Science》1979,27(4):355-364
The expected diurnal waves with different harmonics in cosmic ray intensity arising from the semidiurnal anisotropy, due to the geometrical inclination of the Earth's axis, are calculated for different cosmic ray stations. The sensitivity of these waves to the exponent n of the latitude dependence function cosn λ for the semidiurnal anisotropy is investigated. The amplitudes of the geometrical tridiurnal waves for high latitude stations show a great sensitivity to n and, therefore, it is concluded that its value can be determined precisely from the tridiurnal wave rather than from the semidiurnal waves observed at different latitudes. Available data from high latitude neutron monitors were used to determine n and it was found as 2±0.4, which is of higher accuracy than the previously determined values. The present results are consistent with either the density gradient or loss cone models of the semidiurnal anisotropy. Furthermore, they show that the geometrical tridiurnal waves have a very small amplitude and can be neglected in any analysis concerning tridiurnal variations in cosmic ray intensity. 相似文献
3.
The variations in the form of the cosmic-ray fluctuation power spectrum as an interplanetary shock wave approaches the Earth have been calculated for different values of cosmic ray anisotropy. The relevant experimental estimates of the power spectra are inferred from the data of cosmic ray detection with the ground-based neutron monitors at cosmic-ray stations. A comparison between the theoretical and experimental estimates has demonstrated an important role of the cosmic ray anisotropy spectrum in the generation of the power spectrum as the latter is rearranged before the interplanetary medium disturbances. 相似文献
4.
Richard E. Lingenfelter 《Astrophysics and Space Science》1973,24(1):83-94
The limitations on the nature of cosmic ray acceleration regions and processes, as deduced from cosmic ray measurements and propagation studies, are reviewed. The power requirements for these acceleration regions are estimated from measurements of the local cosmic ray energy density, anisotropy and spallation-deduced pathlength. Possible constraints on the acceleration spectrum of the cosmic rays and on a charge dependence of the acceleration process, implied by the measured cosmic ray spectrum and composition, are considered. Various suggested sources and processes of cosmic ray acceleration are discussed in the light of these limitations.Astrophysics and Space Science Review Paper. 相似文献
5.
Yu. I. Fedorov 《Kinematics and Physics of Celestial Bodies》2017,33(2):63-78
The propagation of galactic cosmic rays in heliospheric magnetic fields is studied. An approximate solution to the cosmic ray transport equation has been derived on the basis of a method that takes into account the small value of anisotropy of particle angular distribution. The spatial and energy distributions of the cosmic ray intensity and anisotropy have been investigated, and estimates of cosmic ray energy flux have been carried out. 相似文献
6.
Identifying the precursors (pre-increases or pre-decreases) of a geomagnetic storm or a Forbush decrease is of great importance since they can forecast and warn of oncoming space weather effects. A wide investigation using 93 events which occurred in the period from 1967 to 2006 with an anisotropy A xy >1.2% has been conducted. Twenty-seven of the events revealed clear signs of precursors and were classified into three categories. Here we present one of the aforementioned groups, including five Forbush decreases (24 June 1980, 28 October 2000, 17 August 2001, 23 April 2002, and 10 May 2002). Apart from hourly cosmic ray intensity data, provided by the worldwide network of neutron monitor stations, data on solar flares, solar wind speed, geomagnetic indices (Kp and Dst), and interplanetary magnetic field were used for the analysis of the examined cosmic ray intensity decreases. The asymptotic longitudinal cosmic ray distribution diagrams were plotted using the “ring of stations” method. Results reveal a long pre-decrease up to 24 hours before the shock arrival in a narrow longitudinal zone from 90° to 180°. 相似文献
7.
《New Astronomy》2016
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. 相似文献
8.
In this paper are described a new neutron spectrometer which operate in the Concordia station (Antarctica, Dome C) since December 2015. This instrument complements a network including neutron spectrometers operating in the Pic-du-Midi and the Pico dos Dias. Thus, this work present an analysis of cosmic ray induced-neutron based on spectrometers operated simultaneously in the Pic-du-Midi and the Concordia stations during a quiet solar activity. The both high station platforms allow for investigating the long period dynamics to analyze the spectral variation and effects of local and seasonal changes, but also the short term dynamics during solar flare events. A first part is devoted to analyze the count rates, the spectrum and the neutron fluxes, implying cross-comparisons between data obtained in the both stations. In a second part, measurements analyses were reinforced by modeling based on simulations of atmospheric cascades according to primary spectra which only depend on the solar modulation potential. 相似文献
9.
The sector polarity of the interplanetary magnetic field has been inferred daily for the period 1971–1973, using ground level cosmic ray observations. The method depends on the sectors directed towards and away from the Sun being associated with different characteristic variations of the cosmic ray north-south asymmetry. The analysis has a simple basis. The difference between the north and south daily mean intensities of directional telescopes at a single observing station is determined and its value relative to the 27-day average is calculated. The sign (negative or positive) of the value thus derived corresponds to the sector polarity on a daily basis. Good (~76%) agreement is obtained between the polarities inferred indirectly by the present method and those observed directly with the spacecraft magnetometers. We therefore suggest that cosmic ray observations can be used for inferring the sector polarity of the magnetic field in interplanetary space. 相似文献
10.
The propagation of solar cosmic rays in interplanetary space is considered based on the kinetic equation. The expression for cosmic ray density under instantaneous particle injection by a point-like source is obtained. The set of a differential equation system for harmonics of cosmic ray distribution function is obtained starting from the kinetic equation. The cosmic ray transport equation, taking into account the presence of the second harmonic of particle angular distribution, is derived and the solution of this equation is obtained. 相似文献
11.
The dependence of the maximum energy cosmic rays can reach via diffusive shock acceleration in AGN jets on flow speeds is discussed. It is shown that in highly inclined termination shocks where the speed of the de Hoffman-Teller frame is crucial, a good independent knowledge of the jet speed is required to properly assess the extent of the cosmic ray spectrum. 相似文献
12.
The mass composition of high energy cosmic rays depends on their production, acceleration, and propagation. The study of cosmic ray composition can therefore reveal hints of the origin of these particles. At the South Pole, the IceCube Neutrino Observatory is capable of measuring two components of cosmic ray air showers in coincidence: the electromagnetic component at high altitude (2835 m) using the IceTop surface array, and the muonic component above ∼1 TeV using the IceCube array. This unique detector arrangement provides an opportunity for precision measurements of the cosmic ray energy spectrum and composition in the region of the knee and beyond. We present the results of a neural network analysis technique to study the cosmic ray composition and the energy spectrum from 1 PeV to 30 PeV using data recorded using the 40-string/40-station configuration of the IceCube Neutrino Observatory. 相似文献
13.
In this work the galactic cosmic ray modulation in relation to solar activity indices and heliospheric parameters during the years 1996??C?2010 covering solar cycle 23 and the solar minimum between cycles 23 and 24 is studied. A new perspective of this contribution is that cosmic ray data with a rigidity of 10 GV at the top of the atmosphere obtained from many ground-based neutron monitors were used. The proposed empirical relation gave much better results than those in previous works concerning the hysteresis effect. The proposed models obtained from a combination of solar activity indices and heliospheric parameters give a standard deviation <?10?% for all the cases. The correlation coefficient between the cosmic ray variations of 10?GV and the sunspot number reached a value of r=?0.89 with a time lag of 13.6±0.4 months. The best reproduction of the cosmic ray intensity is obtained by taking into account solar and interplanetary indices such as sunspot number, interplanetary magnetic field, CME index, and heliospheric current sheet tilt. The standard deviation between the observed and calculated values is about 7.15?% for all of solar cycle 23; it also works very well during the different phases of the cycle. Moreover, the use of the cosmic ray intensity of 10?GV during the long minimum period between cycles 23 and 24 is of special interest and is discussed in terms of cosmic ray intensity modulation. 相似文献
14.
The origin of cosmic rays is one of the long-standing mysteries in physics and astrophysics. Simple arguments suggest that a scenario of supernova remnants (SNRs) in the Milky Way as the dominant sources for the cosmic ray population below the knee could work: a generic calculation indicates that these objects can provide the energy budget necessary to explain the observed flux of cosmic rays. However, this argument is based on the assumption that all sources behave in the same way, i.e. they all have the same energy budget, spectral behavior and maximum energy. In this paper, we investigate if a realistic population of SNRs is capable of producing the cosmic ray flux as it is observed below the knee. We use 21 SNRs that are well-studied from radio wavelengths up to gamma-ray energies and derive cosmic ray spectra under the assumption of hadronic emission. The cosmic ray spectra show a large variety in their energy budget, spectral behavior and maximum energy. These sources are assumed to be representative for the total class of SNRs, where we assume that about 100–200 cosmic ray emitting SNRs should be present today. Finally, we use these source spectra to simulate the cosmic ray transport from individual SNRs in the Galaxy with the GALPROP code for cosmic ray propagation. We find that the cosmic ray budget can be matched well for these sources. We conclude that gamma-ray emitting SNRs can be a representative sample of cosmic ray emitting sources. In the future, experiments like CTA and HAWC will help to distinguish hadronic from leptonic sources and to further constrain the maximum energy of the sources and contribute to producing a fully representative sample in order to further investigate the possibility of SNRs being the dominant sources of cosmic rays up to the knee. 相似文献
15.
The non-diffusive transport of an anisotropic pulse of cosmic ray charged particles in an inhomogeneous medium with a regular magnetic field is considered. Both the angle particle distribution in a source and the angle dependence of a detector response as well as the time dependent particle injection from the source into the medium are comprised. The temporal dependences of the particle number and of the detected particle intensity are demonstrated at various distances from the source. It is shown that the temporal profiles are strongly dependent on the anisotropy value and they have dissimilar behaviour for different asymptotic direction of detector. 相似文献
16.
The flux rate of cosmic rays incident on the Earth’s upper atmosphere is modulated by the solar wind and the Earth’s magnetic
field. The amount of solar wind is not constant due to changes in solar activity in each solar cycle, and hence the level
of cosmic ray modulation varies with solar activity. In this context, we have investigated the variability and the relationship
of cosmic ray intensity with solar, interplanetary, and geophysical parameters from January 1982 through December 2008. Simultaneous
observations have been made to quantify the exact relationship between the cosmic ray intensity and those parameters during
the solar maxima and minima, respectively. It is found that the stronger the interplanetary magnetic field, solar wind plasma
velocity, and solar wind plasma temperature, the weaker the cosmic ray intensity. Hence, the lowest cosmic ray intensity has
good correlations with simultaneous solar parameters, while the highest cosmic ray intensity does not. Our results show that
higher solar activity is responsible for a higher geomagnetic effect and vice versa. 相似文献
17.
18.
The role of nearby galactic sources, the supernova remnants, in formation of observed energy spectrum and large-scale anisotropy of high-energy cosmic rays is studied. The list of these sources is made up based on radio, X-ray and gamma-ray catalogues. The distant sources are treated statistically as ensemble of sources with random positions and ages. The source spectra are defined based on the modern theory of cosmic ray acceleration in supernova remnants while the propagation of cosmic rays in the interstellar medium is described in the frameworks of galactic diffusion model. Calculations of dipole component of anisotropy are made to reproduce the experimental procedure of “two-dimensional” anisotropy measurements. The energy dependence of particle escape time in the process of acceleration in supernova remnants and the arm structure of sources defining the significant features of anisotropy are also taken into account. The essential new trait of the model is a decreasing number of core collapse SNRs being able to accelerate cosmic rays up to the given energy, that leads to steeper total cosmic ray source spectrum in comparison with the individual source spectrum. We explained simultaneously the new cosmic ray data on the fine structure of all particle spectrum around the knee and the amplitude and direction of the dipole component of anisotropy in the wide energy range 1 TeV–1 EeV. Suggested assumptions do not look exotic, and they confirm the modern understanding of cosmic ray origin. 相似文献
19.
Solar circumstances have been evaluated for January 28, 1967, the date of an observed ground level enhancement of cosmic rays
which was not preceded by observation of a suitably great Hα flare. On the visible solar hemisphere, a bright subflare at
S23° E19° occurred in appropriate time association with the cosmic ray event, and was accompanied by weak X-ray enhancement
and radio frequency emission. If this flare, alone, or in combination with other minor flares observed on the visible hemisphere
on January 28 was the source of the energetic cosmic rays recorded on that date, then current thinking regarding the characteristics
of cosmic ray flares must be modified.
An initial study of probable circumstances on the invisible hemisphere did not lead to the immediate recognition of amajor center of activity as the probable source of a cosmic ray flare. Further evaluation of all centers of activity on the invisible
hemisphere identified one region, McMath Plage No. 8687, 64° beyond the west limb, as the most plausible, possible site for
the cosmic ray flare on January 28, 1967. The location of this region is in accord with the source-position deduced in Lockwood's
analysis (1968) of the cosmic ray event. This center of activity could not have been more than 5 days old on January 28, 1967.
The interval of major activity in the region was confined primarily to the invisible hemisphere. The occurrence of an ‘isolated’
major flare in the region on February 13, 1967 is discussed. The present study exemplifies the partial nature of solar observations
which are limited to the visible hemisphere.
The possible role of exceptional geomagnetic calm, 1963–1967, in permitting atypical cosmic ray enhancements, as on January
28, 1967, is mentioned. 相似文献
20.
In the present work the cosmic ray data of three different neutron monitoring stations, Deep River, Inuvik, and Tokyo, located
at different geomagnetic cutoff rigidities and altitudes have been harmonically analyzed for the period 1980–95 for a comparative
study of diurnal semi-diurnal and tri-diurnal anisotropies in cosmic ray intensity in connection with the change in interplanetary
magnetic field Bz component and solar wind velocity on 60 quietest days. It is observed that the amplitudes of all the three
harmonics increase during the period 1982–84 at all the stations during the high speed solar wind stream epoch and remain
low during the declining phase of the stream. The amplitudes of the three harmonics have no obvious characteristics associated
with the time variation of magnitude of the Bz component. The phases of all the three harmonics have no time variation characteristics
associated with solar wind velocity and Bz.
Published in Astrofizika, Vol. 49, No. 4, pp. 651–664 (August 2006). 相似文献