SMALL COSMIC-RAY INCREASES MEASURED AT GROUND LEVEL, SEPTEMBER 3, 1960, JULY 18 AND JULY 20, 1961

1962 ◽  
Vol 40 (5) ◽  
pp. 540-549 ◽  
Author(s):  
B. G. Wilson ◽  
D. C. Rose ◽  
Margaret D. Wilson
Keyword(s):  
Cosmic Ray ◽  
Ground Level ◽  
Strong Impact ◽  
Impact Zone ◽  
Limited Data ◽  
Neutron Monitors ◽  
Small Magnitude ◽  
Cosmic Ray Intensity ◽  
Interplanetary Magnetic Fields ◽  
The Impact

Three small increases in cosmic-ray intensity, observed in high counting rate neutron monitors in Canada, are described and the results examined in relation to the impact zone effect with particular reference to recent studies by McCracken. Pronounced impact zone effects were observed during the July 18, 1961, event, the largest of these three increases, while the September 3, 1960, event showed no such effects. Considerations of the state of the interplanetary magnetic fields at these times show that these results are consistent with McCracken's explanations. The sharp rise to maximum of the July 20, 1961, increase would suggest strong impact zone effects, but such conclusions that can be drawn from the limited data and the small magnitude of the increase suggest that it does not conform with the usual pattern.

scholarly journals Unusual decrease of the cosmic ray intensity in May 2019 on the background of the minima solar activity

2021 ◽  
pp. 73-80
Author(s):  
Liudmila Trefilova ◽  
Pavel G. Kobelev ◽  
Anatoly V. Belov ◽  
Eugenia A. Eroshenko ◽  
Anaid A. Melkumyan ◽  
...  
Keyword(s):  
Solar Activity ◽  
Cosmic Rays ◽  
Active Regions ◽  
Cosmic Ray ◽  
Ground Level ◽  
Neutron Monitors ◽  
Cosmic Ray Intensity ◽  
The Earth ◽  
24Th Cycle ◽  
Field Lines

In May 2019 there was a long and sloping decreasing of cosmic ray’s intensity (up to ~4%), which was observed on neutron monitors. Despite this was a small decreasing compared to quasi-eleven-period variation, it stands out well in 24th cycle of solar activity. According to LASCO/SOHO and STEREO-A data from spectrometer in different UHF bands and from coronograph, there was a series of CMEs which affected on modulation of cosmic rays by creating a series of Forbush decrea - sing, which didn’t restore. This series was connected to two active regions on sun and began on April 30 from “reversed halo” CME. This CME didn’t reach the earth, but led to significant additional modulation of cosmic rays, mostly on east side. Later there was a series of smaller CMEs on May 1-6, which also didn’t reach the earth, but were gradually approaching to Earth. Recent CMEs on 8-9 and 12-13 created a normal Forbush decreasing. In May 2019, cosmic rays shown again, that they can collect information about distant objects of geliosphere and transmit it to Earth. The ground-level detectors sometimes can observe an interaction of interplanetary distur- bances, which didn‘t reach the earth. East CMEs are especially effective, because they closing magnetic field lines beyond the orbit of earth and can interfere the restoring of cosmic ray’s intensity.

INTERPLANETARY AND SOLAR PLASMA PARAMETERS OF THE 14 JULY 2000 GROUND LEVEL ENHANCEMENT

2003 ◽  
Vol 12 (02) ◽  
pp. 337-344 ◽  
Author(s):  
S. S. AL-THOYAIB
Keyword(s):  
Rapid Change ◽  
Cosmic Ray ◽  
Ground Level ◽  
Low Energy ◽  
Neutron Monitors ◽  
Ground Level Enhancement ◽  
Plasma Parameters ◽  
Cosmic Ray Intensity ◽  
The Difference ◽  
Galactic Cosmic Ray

The ground level enhancement (GLE) of 14 July 2000 observed in the cosmic ray intensity has been examined. The event was recorded only by neutron monitors. It has a complex intensity-time structure. The northern hemisphere stations (Thule, Goose Bay, and Oulu) recorded abrupt increases earlier by 10 minutes than those in the southern hemisphere. Due to the difference in sensitivity at rigidity less than ~3 GV, the considered detectors recorded different increases in count rates relative to galactic cosmic ray background. This paper presents the study of GLE associated with the X5.7 solar flare. The rapid change of arriving particles were anisotropic during the onset of the event; it become isotropic during the declining phase of the event, where only low energy protons remained. In addition, the observations of energetic solar particles and interplanetary parameters have been examined.

Solar Flare Increase of Cosmic Ray Intensity on November 22, 1977

1978 ◽  
Vol 3 (3) ◽  
pp. 238-241 ◽  
Author(s):  
A. G. Fenton ◽  
K. B. Fenton ◽  
J. E. Humble
Keyword(s):  
Solar Flares ◽  
Average Rate ◽  
Sunspot Cycle ◽  
Cosmic Ray ◽  
Ground Level ◽  
Solar Cycles ◽  
Neutron Monitors ◽  
Cosmic Ray Intensity ◽  
The Past ◽  
The World

Solar flares for which protons of relativistic energies reach Earth are rare events compared with the number in which non-relativistic protons are produced. For instance, Shea and Smart (1978) have listed 139 proton events for the interval 1955-69 of which 17 were GLE’s (i.e. “ground level events” detected by the world network of cosmic ray neutron monitors). We have tentatively identified a further 11 GLE’s in the interval 1970-1977, of which 3 were in 1977 in the sunspot cycle which commenced about mid-1976 (cycle 21). Thus the average rate over the past two solar cycles has been a little over one per year.

Daily variation of cosmic rays during quiet and disturbed periods in 1965 and 1966

1968 ◽  
Vol 46 (10) ◽  
pp. S819-S822
Author(s):  
Pekka J. Tanskanen
Keyword(s):  
Daily Variation ◽  
Cosmic Ray ◽  
Ecliptic Plane ◽  
Neutron Monitors ◽  
Monthly Basis ◽  
Cosmic Ray Intensity ◽  
Variable Amplitude ◽  
Ecliptic Latitude ◽  
Streaming Velocity ◽  
Corrected Data

Data from super neutron monitors at Deep River, Churchill, Resolute, and Alert have been used to study the daily variation of cosmic-ray intensity during 1965 and 1966. Intensities have been examined on a daily, weekly, and monthly basis as a function of the asymptotic direction of vertically incident 7.5-BeV particles. The data have been analyzed in an earth-centered solar-ecliptic coordinate system in which daily (due to the earth's rotation) and seasonal (due to the inclination of the earth's axis to the ecliptic plane) variations of the asymptotic directions are considered.During undisturbed periods the daily variation has been examined by applying a digital filter to the pressure-corrected data and also to the data after subtraction of a variable-amplitude Parker–Axford theoretical diurnal variation. Particular attention has been paid to the dependence of the observed daily variation on the solar-ecliptic latitude of the asymptotic direction.Seventy-three percent of the weeks considered in 1965 and 1966 give the phase of the first harmonic in a direction 85° ± 35 °E. Sixty percent of the weekly periods show a daily variation as a function of solar-ecliptic latitude which is in agreement with the Parker–Axford "streaming-velocity" theory. During Forbush decreases the diurnal phase shifts towards earlier hours and the amplitude increases to two to three times the predecrease level.

THE SUN AS A SOURCE OF COSMIC RAYS OF INTERMEDIATE ENERGIES

1959 ◽  
Vol 37 (11) ◽  
pp. 1207-1215
Author(s):  
J. Katzman
Keyword(s):  
Cosmic Rays ◽  
Cosmic Ray ◽  
The Sun ◽  
Relative Importance ◽  
Cosmic Ray Intensity ◽  
Intermediate Energies ◽  
Narrow Angle ◽  
The Impact ◽  
Impact Zones

The cosmic ray intensity as measured with an extremely narrow-angle telescope, 1.2 × 10−3 steradians, and with 96 inches of lead as absorber for the period 1 January 1955 to 31 December 1958 shows an increase of 20%. This increase is attributed to particles coming from the sun. It is shown that the change in hour of maximum of the first and second harmonics can be explained by a change in the relative importance of the impact zones. This phenomenon is attributed to a change in the number and polarity of sunspots.

scholarly journals Variations of Interplanetary Parameters and Cosmic-Ray Intensities

1980 ◽  
Vol 91 ◽  
pp. 393-398
Author(s):  
A. Geranios
Keyword(s):  
Solar Flare ◽  
Recovery Time ◽  
Propagation Speed ◽  
Cosmic Ray ◽  
Interplanetary Shocks ◽  
Fast Solar Wind ◽  
Neutron Monitors ◽  
Cosmic Ray Intensity ◽  
Cosmic Ray Modulation ◽  
Modulation Region

Observations of cosmic ray intensity depressions by earth bound neutron monitors and measurements of interplanetary parameter's variations aboard geocentric satellites in the period January 1972-July 1974 are analysed and grouped according to their correlation among them. From this analysis of about 30 cases it came out that the majority of the depressions correlates with the average propagation speed of interplanetary shocks as well as with the amplitude of the interplanetary magnetic field after the eruption of a solar flare. About one fourth of the events correlates with corotating fast solar wind streams. As the recovery time of the shock-related depressions depends strongly on the heliographic longitude of the causitive solar flare, it seems that the cosmic ray modulation region has a corotative-like feature.

The long-term variation of the cosmic radiation

1968 ◽  
Vol 46 (10) ◽  
pp. S903-S906 ◽  
Author(s):  
J. A. Lockwood ◽  
W. R. Webber
Keyword(s):  
Neutron Monitor ◽  
Cosmic Radiation ◽  
Cosmic Ray ◽  
Solar Modulation ◽  
Neutron Monitors ◽  
Cosmic Ray Intensity ◽  
Direct Measurements ◽  
Term Variation ◽  
Primary Cosmic Radiation

The variation in the cosmic-ray intensity recorded by neutron monitors from 1958 to 1965 has been investigated to deduce the form of the solar modulation of the cosmic radiation. The observed changes in the intensity at the neutron monitor stations, averaged over quarter-year periods, were compared with changes calculated using modulation functions depending upon energy, rigidity, and velocity × rigidity. These calculations were based upon the revised differential response functions deduced by Lockwood and Webber (1967). The variance between the observed and calculated changes in the neutron monitor intensities at different stations was minimized to determine the best form of the solar modulation function. We find that the change of the primary cosmic radiation, deduced from the change in the neutron monitor intensity as well as from direct measurements of the primary flux, can be described by a modulation of the form exp(–K/P) in the rigidity range 0.5 < P < 50 GV. The change between 1959 and 1965 can be fitted with K = 1.94 ± 0.09 and between 1963 and 1965 with K = 0.36 ± 0.05.

Cosmic Ray Transient Variations Observed from the Earth

1994 ◽  
Vol 11 (2) ◽  
pp. 110-125 ◽  
Author(s):  
M. L. Duldig
Keyword(s):  
Human Activity ◽  
Cosmic Ray ◽  
Ground Level ◽  
Neutron Monitors ◽  
Detection Techniques ◽  
The Earth ◽  
Periodic Fluctuations ◽  
Transient Variations ◽  
Underground Muon ◽  
Ground Level Enhancements

AbstractCosmic ray transient variations are signatures of the underlying solar processes which affect the heliomagnetic structure. They can be found in the data from surface systems, such as neutron monitors and muon telescopes, and from shallow underground muon telescopes. Although sometimes observable at all latitudes, the global distribution of the effects is important in determining the structures and causes. Three transient variation types are known, namely Forbush decreases, ground level enhancements, and quasi-periodic fluctuations. The latter category includes some variations which are, perhaps, too long-lived to be considered truly transient. In this review, the detection techniques and background of cosmic ray research are followed by a summary of some observations in each transient category. The heliomagnetic structures and dynamics inferred from such transients are discussed together with the possible impact such events can have on human activity.

Testing the Impact of Coronal Mass Ejections on Cosmic Ray Intensity Modulation with Algorithm selected Forbush Decreases

2020 ◽  
Author(s):  
O Okike ◽  
O C Nwuzor ◽  
F C Odo ◽  
E U Iyida ◽  
J E Ekpe ◽  
...  
Keyword(s):  
Coronal Mass Ejections ◽  
Cosmic Ray ◽  
Forbush Decreases ◽  
Cosmic Ray Intensity ◽  
Event Identification ◽  
Diurnal Anisotropy ◽  
Current Article ◽  
Galactic Cosmic Ray ◽  
The Impact ◽  
The Relationship

Abstract The relationship between coronal mass ejections (CMEs) and Forbush decreases (FDs) has been investigated in the past. But selection of both solar events are difficult. Researchers have developed manual and automated methods in efforts to identify CMEs as well as FDs. While scientists investigating CMEs have made significant advancement, leading to several CME catalogues, including manual and automated events catalogues, those analyzing FDs have recorded relatively less progress. Till date, there are no comprehensive manual FD catalogues, for example. There are also paucity of Automated FD lists. Many investigators, therefore, attempt to manually select FDs which are subsequently used in the analysis of the impact of CMEs on galactic cosmic ray (GCR) flux depressions. However, some of the CME versus FD correlation results might be biased since manual event identification is usually subjective, unable to account for the presence of solar-diurnal anisotropy which characterizes GCR flux variations. The current article investigates the relation between CMEs and FDs with emphasis on accurate and careful Forbush event selection.

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