Cosmic Ray Intensity Fluctuations Research Articles

The galactic cosmic ray intensity fluctuations during perturbations of the solar wind in early November 2021

In order to develop methods for predicting negative manifestations of space weather, the dynamics of fluctuations in the intensity of galactic cosmic rays during geophysical disturbances in early November 2021 is studied. The obtained results point to the possibility of real-time short-term space weather forecasting based on the measurement data of the Russian national ground-based network of cosmic ray stations.

Forecast of Intense Geomagnetic Storms in February-March 2023, Based on Measurements of Galactic Cosmic Ray Intensity Fluctuations

Forecast of Intense Geomagnetic Storms in February-March 2023, Based on Measurements of Galactic Cosmic Ray Intensity Fluctuations

Shape of spectrum of galactic cosmic ray intensity fluctuations

The impact of solar wind plasma on fluxes of galactic cosmic rays (CR) penetrating from the outside into the heliosphere with energies above ~1 GeV leads to temporal variations in the CR intensity in a wide frequency range. Cosmic rays being charged particles, their modulation occurs mainly under impacts of the interplanetary magnetic field.
 It is well known that the observed spectrum of interplanetary magnetic field (IMF) fluctuations in a wide frequency range ν from ~10–7 to ~10 Hz has a pronounced falling character and consists of three sections: energy, inertial, and dissipative. Each of them is described by the power law PIMF(ν)~ν–α, while the IMF spectrum index α increases with increasing frequency. The IMF fluctuations in each of these sections are also characterized by properties that depend on their nature.
 Also known are established links between fluctuation spectra of the interplanetary magnetic field and galactic cosmic rays in the case of modulation of the latter by Alfvén or fast magnetosonic waves. The theory predicts that fluctuation spectra of cosmic rays should also be described by the power law PCR(ν)~ν–γ. However, the results of many years of SHICRA SB RAS research into the nature and properties of cosmic ray intensity fluctuations based on data from neutron monitors at stations with different geomagnetic cut-offs RC from 0.5 to 6.3 GV show that the observed spectrum of fluctuations in galactic cosmic ray intensity in the frequency range above 10–4 Hz becomes flat, i.e. it is similar to white noise. This fact needs to be realized and explained.
 This paper reports the results of research into the shape of the spectrum of galactic cosmic ray intensity fluctuations within a frequency range ν from ~10–6 to ~1 Hz and compares them with model calculations of white noise spectra, using measurement data from the neutron monitor of the Apatity station. A possible physical explanation has been given for the observed shape of the cosmic ray fluctuation spectrum on the basis of the known mechanisms of their modulation in the heliosphere.

О форме спектра флуктуаций интенсивности галактических космических лучей

The impact of solar wind plasma on fluxes of galactic cosmic rays (CR) penetrating from the outside into the heliosphere with energies above ~1 GeV leads to temporal variations in the CR intensity in a wide frequency range. Cosmic rays being charged particles, their modulation occurs mainly under impacts of the interplanetary magnetic field.
 It is well known that the observed spectrum of interplanetary magnetic field (IMF) fluctuations in a wide frequency range ν from ~10–7 to ~10 Hz has a pronounced falling character and consists of three sections: energy, inertial, and dissipative. Each of them is described by the power law PIMF(ν)~ν–α, while the IMF spectrum index α increases with increasing frequency. The IMF fluctuations in each of these sections are also characterized by properties that depend on their nature.
 Also known are established links between fluctuation spectra of the interplanetary magnetic field and galactic cosmic rays in the case of modulation of the latter by Alfvén or fast magnetosonic waves. The theory predicts that fluctuation spectra of cosmic rays should also be described by the power law PCR(ν)~ν–γ. However, the results of many years of SHICRA SB RAS research into the nature and properties of cosmic ray intensity fluctuations based on data from neutron monitors at stations with different geomagnetic cut-offs RC from 0.5 to 6.3 GV show that the observed spectrum of fluctuations in galactic cosmic ray intensity in the frequency range above 10–4 Hz becomes flat, i.e. it is similar to white noise. This fact needs to be realized and explained.
 This paper reports the results of research into the shape of the spectrum of galactic cosmic ray intensity fluctuations within a frequency range ν from ~10–6 to ~1 Hz and compares them with model calculations of white noise spectra, using measurement data from the neutron monitor of the Apatity station. A possible physical explanation has been given for the observed shape of the cosmic ray fluctuation spectrum on the basis of the known mechanisms of their modulation in the heliosphere.

Cosmic ray fluctuations parameter as indicator of interplanetary "magnetic cork"

It is established, that the main contribution into dynamics of galactic cosmic ray intensity fluctuations (GCR) in a vicinity of magnetic "cork" from a shock gives a nonrandom, non-Gauss component of GCR intensity. An occurrence of correlated fluctuations is caused by following circumstance: due to laws of conservation the probability that the cosmic ray particles reflected from a magnetic cork (in the expanding magnetic field) will undergo collimations, becomes considerable. The collimation will be manifested in focusing of particles into the anisotropic beams. In this case, observations should show "scintillations" of celestial sphere in cosmic rays i.e. the" HALO" effect. Similar scintillations are the indicator of interplanetary magnetic cork. The algorithm of detection of GCR scintillations is realized in real time using "Cyber-FORSHOCK" robotized system.

Effect of random nature of cosmic ray sources – Supernova remnants – on cosmic ray intensity fluctuations, anisotropy, and electron energy spectrum

The random nature of sources (the supernova remnants) leads to the fluctuations of cosmic ray intensity in space and time. We calculate the expected fluctuations in a flat-halo diffusion model for particles with energies from 0.1 to 10 3 TeV. The data on energy spectra and anisotropy of very high energy protons, nuclei and electrons, and the astronomical data on supernova remnants, the potential sources of cosmic rays, are used to constrain the value of the cosmic-ray diffusion coefficient and its dependence on energy.

An Analysis of Polar Coronal Hole Evolution: Relations to Other Solar Phenomena and Heliospheric Consequences

We use observations of the green corona low-brightness regions to construct a time series of a polar coronal hole area from 1939 to 1996, covering 5 solar cycles. We then perform a power-spectral analysis of the monthly data time series. Several persistent significant periodicities appear in the spectra, which are related with those found in solar magnetic flux emergence, geomagnetic storm sudden commencements and cosmic-ray flux at Earth. Of particular importance are the peak at around 1.6–1.8 yr recently found in cosmic-ray intensity fluctuations, and the peak at around 1 yr, also identified in coronal hole magnetic flux variations. Additional interesting features are the peaks close to 5 yr, 3 yr and the possible peak at around 30 yr, that were also found in other solar and interplanetary phenomena. Our results stress the physical connection between the solar magnetic flux emergence and the interplanetary medium dynamics, in particular the importance of coronal hole evolution in the structuring of the heliosphere.

Galactic cosmic ray fluctuations during solar cycles 22 and 23 at high altitude neutron monitors

Abstract Cosmic ray detectors installed at high magnetic cutoff rigidity and mountain elevation are only a few. It is therefore important to have reliable data for active monitors with these characteristics. The Mexico City 6-NM64 has been in continuos operation since 1990. It is located at an altitude of 2274 m above sea level and has a vertical magnetic cutoff rigidity of 8.2 GV for the 1990 epoch (Shea and Smart, 1997). In this work we make a study of the cosmic ray intensity fluctuations observed in Mexico City and compare it with other mountain altitude neutron monitors of the american sector during the years 1990–1999. The period comprises the maximum and declining phase of solar cycle 22 and the beginning of cycle 23. Evolution of important variation periodicities compared with solar activity indicators are presented. We have also constructed a new solar activity index based on the measured hard x-rays flux.

Исследование флуктуации интенсивности космических лучей в стратосфере, вызываемых процессами на Солнце

Исследование флуктуации интенсивности космических лучей в стратосфере, вызываемых процессами на Солнце

Les blackouts ionosphériques observés en terre adélie en 1957 et 1958

During the IGY continuous vertical incidence ionosonde records were obtained at Terre Adélie by the Expéditions Polaires Françaises in collaboration with the Group Ionosphère of CNET. Excellent hourly and, during World Days, quarter hourly, ionograms were obtained during the entire twenty-four month period from January, 1957 to December, 1958. From an examination of the numerous ionograms, the occurrences of complete blackouts was noted at Terre Adélie, which is well within the southern auroral zone and only a few hundred kilometers from the south magnetic pole. Correlation of these high absorption periods was sought with other geophysical phenomena; e.g. local and planetary magnetic indices, cosmic ray fluctuations, proton events, solar radio and ultraviolet bursts and with ionospheric blackouts found at northern high latitude stations. Several conclusions were found: (a) the occurrence, duration and intensity of blackouts in Terre Adélie correlates rather poorly with local magnetic character figures as deduced from the station magnetograms; (b) observed blackouts correlate much better with planetary magnetic character figures, Kp or Ap; (c) good correlation exists with cosmic ray intensity fluctuations both the total component (recorded at Limeil-Brevannes) or the nucleonic component (recorded at Pic du Midi and Kerguelen). Antarctic blackouts in most cases coincide with the main, negative, phase of cosmic ray storms. It was also found that a definite relationship exists between the few proton events which we investigated and the most intense blackouts; the proton events occurred prior to the blackouts. An excellent correlation was noted between the blackouts found at Terre Adélie and those observed at Little America, Thule, Barrow, Churchill, Ottawa, etc. Thus, with the exception of partial absorption of small duration, polar blackouts seem to be global polar phenomena being particularly intense in the auroral zones. Suggestions are made regarding the probable mechanism responsible for producing the polar high absorption periods and their precursors.

Unusual Cosmic-Ray Intensity Fluctuations Observed at Southern Stations during October 21-24, 1957

ABS>Observations are repoated from four southern stations of cosmic-ray intensity fluctuations during the period October 21-24, 1957. These fluctuaions exhibit unusual featares which suggest the existence of a shont-lived sed highly directional anisotropy of the primary rsdiation during the period immediately preceding a Forbush-type decrease. (auth)

Cosmic-Ray Intensity Fluctuations at Sea Level

Geomagnetic and atmospheric influences on sea-level cosmic radiation have been studied at Berkeley, California (95-m elevation, 44\ifmmode^\circ\else\textdegree\fi{} N geomagnetic latitude). The hard (20-cm lead absorber) and total intensities were measured with wide-angle triple-coincidence counter telescopes, and fluctuations of intensity were compared statistically with changes of barometric pressure, pressure-altitude, and temperature of the lower stratosphere. The atmospheric coefficients found by Duperier were verified for the 100-millibar region, but radiosonde data were not complete enough to permit calculations for higher strata of the atmosphere. The hard and total intensity data, corrected to constant barometric pressure, were examined for fluctuations that could be correlated with geomagnetic disturbances. No apparent cosmic-ray changes accompanied any of seven geomagnetic sudden commencements. Of eighteen magnetic storm periods occurring over eight months, only four appeared definitely to be accompanied by cosmic-ray intensity decreases. No increases of intensity occurred during these periods. Of the four decreases observed, two were unusual in that the decrease occurred an appreciable time before the measurable geomagnetic disturbance (May 27 and June 25, 1951). These two events occurred during times of very great sunspot activity, but only a loose genetic relationship could be established between the sunspot behavior and the prestorm cosmic-ray decreases.

The semi-diurnal component of cosmic ray intensity at Bandung (Java)

Observations at Bandung (Java) of cosmic ray intensity by means of a S t e i n k e-ionization-apparatus during 1939 and 1940 show a semi-diurnal component in opposite phase to the semi-durnal component of the barometer. On closer inspection it may be interpreted as a superposition of a normal barometereffect (opposite phase) and a a same phase component that can be explained as a result of the semi-diurnal movement of the meson-producing layer in the atmosphere (theory of P e k e r i s; N i c o l s o n and S a r a b h a i). So it appears to confirm the results of R a u and R e g e n e r concerning cosmic ray intensity fluctuations under 40 m water in the lake Constance.