Cosmic Ray Intensity in Interplanetary Space

The daily variation of cosmic ray intensity at low latitudes can under certain conditions be associated with an anisotropy of primary radiation. During 1957-8, this anisotropy had an energy spectrum of variation of the form aϵ -0.8±0.3 and corresponded to a source situated at an angle of 112 ± 10° to the left of the earth-sun line. The daily variation which can be associated with a local source situated along the earth-sun line has an energy spectrum of variation of the form aϵ 0 . Increases in east-west asymmetry and the associated daily variation for east and west directions can be explained by the acceleration of cosmic ray particles crossing beams of solar plasma in the neighbourhood of the earth. For beams of width 5 x 10 12 cm with a frozen magnetic field of the order of 10 -4 G, a radial velocity of about 1.5 x 108 cm/s is required. The process is possible only if the ejection of beams takes place in rarefied regions of inter planetary space which extend radially over active solar regions. An explanation of Forbush, type decreases observed at great distances from the earth requires similar limitation on the plasma density and conductivity of regions of interplanetary space. The decrease of east-west asymmetry associated with world-wide decreases of intensity and with SC magnetic storms is consistent with a screening of the low-energy cosmic ray particles due to magnetic fields in plasma clouds.

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39. The anisotropy of primary cosmic radiation and the electromagnetic state in interplanetary space

Symposium - International Astronomical Union ◽

10.1017/s0074180900237959 ◽

1958 ◽

Vol 6 ◽

pp. 377-385

Author(s):

V. Sarabhai ◽

N. W. Nerurkar ◽

S. P. Duggal ◽

T. S. G. Sastry

Keyword(s):

Experimental Data ◽

Cosmic Rays ◽

Cosmic Radiation ◽

Interplanetary Space ◽

Daily Variation ◽

Cosmic Ray ◽

The Sun ◽

Cosmic Ray Intensity ◽

Daily Variations ◽

Primary Cosmic Radiation

Study of the anisotropy of cosmic rays from the measurement of the daily variation of meson intensity has demonstrated that there are significant day-today changes in the anisotropy of the radiation. New experimental data pertaining to these changes and their solar and terrestrial relationships are discussed.An interpretation of these changes of anisotropy in terms of the modulation of cosmic rays by streams of matter emitted by the sun is given. In particular, an explanation for the existence of the recently discovered types of daily variations exhibiting day and night maxima respectively, can be found by an extension of some ideas of Alfvén, Nagashima, and Davies. An integrated attempt is made to interpret the known features of the variation of cosmic ray intensity in conformity with ideas developed above.

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Eisenmeteorite als Raumsonden für die Untersuchung des Intensitätsverlaufes der kosmischen Strahlung während der letzten Milliarden Jahre

Zeitschrift für Naturforschung A ◽

10.1515/zna-1962-0508 ◽

1962 ◽

Vol 17 (5) ◽

pp. 422-432 ◽

Cited By ~ 2

Author(s):

H. Voshage

Keyword(s):

Interplanetary Space ◽

Cosmic Ray ◽

Gas Production ◽

Rare Gas ◽

Rare Gases ◽

Production Rates ◽

Cosmic Ray Intensity ◽

Long Time ◽

History Of ◽

Exposure Ages

The use of iron meteorites for the establishment of possible long-time variations (108 —109 years) of the cosmic ray intensity in interplanetary space is based upon the study of the production rates of nuclides which are formed by the interaction of cosmic ray particles with nuclei in meteorites. Mass spectrometric measurements of the isotopic composition of meteoritic potassium * are combined with data on cosmogenic rare gases and other elements to give K41-K40-exposure ages and rare gas production rates. The K41-K40-exposure ages are larger than the exposure ages obtained from the study of short-lived activities (e. g. Cl36, A39), by a factor 1.3 to 1.8. This result indicates that the cosmic ray intensity increased during the bombardment history of the meteorites. The data, for example, are consistent with the following assumptions: 1) The cosmic ray intensity was constant during most of the bombarding time and increased by a factor of about 1.5 only a few million years ago. 2) The intensity rose as I(t) =I0 e— γt with —1.1·10-9 ≦ γ ≦ —0.6 · 10-9 a–1. The consequences of this result for the interpretation of meteorite data are discussed.

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Semidiurnal Anisotropy of Galactic Cosmic Ray Intensity

Canadian Journal of Physics ◽

10.1139/p71-006 ◽

1971 ◽

Vol 49 (1) ◽

pp. 34-48 ◽

Cited By ~ 12

Author(s):

G. Subramanian

Keyword(s):

Energy Spectrum ◽

Counting Rate ◽

Interplanetary Space ◽

Cosmic Ray ◽

Cosmic Ray Intensity ◽

The Earth ◽

Positive Exponent ◽

Semidiurnal Variation ◽

Using Data ◽

Galactic Cosmic Ray

The semidiurnal variation of galactic cosmic ray intensity is investigated using data from mainly high counting rate neutron and meson monitors during 1964–1968. It is shown that in order to explain the observed semidiurnal variation it is necessary that an anisotropy of cosmic ray intensity be present in interplanetary space. The energy spectrum and the asymptotic latitude dependence of the anisotropy are then determined. The energy spectrum has a positive exponent close to + 1 for the power law in energy. The strength of the anisotropy decreases more rapidly than cosλ with increasing asymptotic latitude λ, both cos2λ and cos3λ being acceptable. The distribution of cosmic ray intensity in the range of heliolatitudes ± 7.25° at the orbit of the earth, obtained using data from the Ottawa neutron monitor, does not support the explanation of the semidiurnal variation based on the models of Subramanian and Sarabhai or Lietti and Quenby.

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Prediction of galactic cosmic ray intensity variation for a few (up to 10-12) years ahead on the basis of convection-diffusion and drift model

Annales Geophysicae ◽

10.5194/angeo-23-3003-2005 ◽

2005 ◽

Vol 23 (9) ◽

pp. 3003-3007 ◽

Cited By ~ 5

Author(s):

L. I. Dorman

Keyword(s):

Interplanetary Space ◽

Intensity Variation ◽

Cosmic Ray ◽

Particle Energy ◽

Cosmic Ray Intensity ◽

Convection Diffusion ◽

Drift Model ◽

Galactic Cosmic Ray ◽

Near Future

Abstract. We determine the dimension of the Heliosphere (modulation region), radial diffusion coefficient and other parameters of convection-diffusion and drift mechanisms of cosmic ray (CR) long-term variation, depending on particle energy, the level of solar activity (SA) and general solar magnetic field. This important information we obtain on the basis of CR and SA data in the past, taking into account the theory of convection-diffusion and drift global modulation of galactic CR in the Heliosphere. By using these results and the predictions which are regularly published elsewhere of expected SA variation in the near future and prediction of next future SA cycle, we may make a prediction of the expected in the near future long-term cosmic ray intensity variation. We show that by this method we may make a prediction of the expected in the near future (up to 10-12 years, and may be more, in dependence for what period can be made definite prediction of SA) galactic cosmic ray intensity variation in the interplanetary space on different distances from the Sun, in the Earth's magnetosphere, and in the atmosphere at different altitudes and latitudes.

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On the heliolatitudinal variation of the galactic cosmic-ray intensity. Comparison with Ulysses measurements

Annales Geophysicae ◽

10.5194/angeo-21-1341-2003 ◽

2003 ◽

Vol 21 (6) ◽

pp. 1341-1345 ◽

Cited By ~ 1

Author(s):

G. Exarhos ◽

X. Moussas

Keyword(s):

Solar Wind ◽

Cosmic Rays ◽

Interplanetary Space ◽

Cosmic Ray ◽

Solar Wind Plasma ◽

Simple Method ◽

Cosmic Ray Intensity ◽

Interplanetary Physics ◽

Diffusion Convection ◽

Galactic Cosmic Ray

Abstract. We study the dependence of cosmic rays with heliolatitude using a simple method and compare the results with the actual data from Ulysses and IMP spacecraft. We reproduce the galactic cosmic-ray heliographic latitudinal intensity variations, applying a semi-empirical, 2-D diffusion-convection model for the cosmic-ray transport in the interplanetary space. This model is a modification of our previous 1-D model (Exarhos and Moussas, 2001) and includes not only the radial diffusion of the cosmic-ray particles but also the latitudinal diffusion. Dividing the interplanetary region into "spherical magnetic sectors" (a small heliolatitudinal extension of a spherical magnetized solar wind plasma shell) that travel into the interplanetary space at the solar wind velocity, we calculate the cosmic-ray intensity for different heliographic latitudes as a series of successive intensity drops that all these "spherical magnetic sectors" between the Sun and the heliospheric termination shock cause the unmodulated galactic cosmic-ray intensity. Our results are compared with the Ulysses cosmic-ray measurements obtained during the first pole-to-pole passage from mid-1994 to mid-1995.Key words. Interplanetary physics (cosmic rays; interplanetray magnetic fields; solar wind plasma)

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Anisotropy of transient variations of cosmic-ray intensity

Canadian Journal of Physics ◽

10.1139/p68-371 ◽

1968 ◽

Vol 46 (10) ◽

pp. S871-S874

Author(s):

Masami Wada ◽

Hiroo Komori

Keyword(s):

Angular Distribution ◽

Interplanetary Space ◽

Principal Direction ◽

Cosmic Ray ◽

Distribution Functions ◽

Present Calculation ◽

Cosmic Ray Intensity ◽

The Earth ◽

Rotation Of The Earth ◽

Transient Variations

The angular distribution of the anisotropy of cosmic rays in interplanetary space is generally assumed to follow a cosine function. In the case of the daily variation, the source direction lies essentially in the equatorial plane. In the present calculation, the following three points were taken into account: (1) the latitude of the principal direction, (2) the angular distribution functions, and (3) the increases in flux of cosmic-ray particles. The response functions, the asymptotic directions, and the variation spectra are also involved in the calculation. Because of the rotation of the earth with respect to the source direction, which is fixed at the 12-h meridian, the daily variations are obtained. The variations include higher harmonics if the angular distribution is other than a simple cosine function.Comparing the calculated curves with observed data, the anisotropy in the space outside the geomagnetic field can be estimated with parameters such as the source direction in latitude and longitude, the half-width of the angular distribution, and the amplitude and exponent of the variation spectrum, which are all time-dependent. An increase which occurred on 24 March 1966 was analyzed.

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CHANGES IN THE DIURNAL HOUR OF MAXIMUM OF THE COSMIC-RAY INTENSITY

Canadian Journal of Physics ◽

10.1139/p61-174 ◽

1961 ◽

Vol 39 (10) ◽

pp. 1477-1485

Author(s):

J. Katzman

Keyword(s):

Solar System ◽

Interplanetary Space ◽

Geomagnetic Latitude ◽

Cosmic Ray ◽

Cosmic Ray Intensity ◽

Latitude Belt

The diurnal hour of maximum of the meson component changed progressively at Ottawa, Canada, from 10 hr 44 min to 14 hr 40 min during the period January 1955 to December 1960 while the nucleon component changed from 12 hr 12 min to 15 hr 16 min for the same period. This evidence favors the 22-year cycle in the diurnal hour of maximum that was first suggested by Thambyahpillai and Elliot, for stations within a geomagnetic latitude belt between 58.1° N. and 48.1° S. The diurnal hour of maximum at Churchill changed from 14 hr 40 min to 15 hr 24 min during the period April 1957 to December 1960 for the meson component and from 15 hr 12 min to 15 hr 52 min for the nucleon component. Although the change was for a later hour the indication of a 22-year cycle at Churchill is not impressive. At Resolute the diurnal hour of maximum is dominated by the varying magnetic masses in interplanetary space. It is shown that the anisotropy varies both in magnitude and direction depending on the conditions that exist in the solar system.

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43. On the variations of the primary cosmic ray intensity

Symposium - International Astronomical Union ◽

10.1017/s0074180900237996 ◽

1958 ◽

Vol 6 ◽

pp. 420-427

Author(s):

E. N. Parker

Keyword(s):

Solar Activity ◽

Interplanetary Space ◽

Particle Density ◽

Sunspot Cycle ◽

Forbush Decrease ◽

Cosmic Ray ◽

Abrupt Onset ◽

Cosmic Ray Intensity ◽

Solar Origin ◽

Quantitative Development

To construct a model for producing the observed variation in the cosmic ray intensity we consider primarily the Forbush decrease and the general decrease of the cosmic ray intensity during years of solar activity. These are larger variations than the diurnal and 27-day variations and require more drastic assumptions; thus they will better serve to establish a unique model.It is assumed that the sun does not emit cosmic ray particles except during the time of a solar flare. Thus, decreases in the cosmic ray intensity are to be interpreted as a solar effect which inhibits the arrival of galactic cosmic ray particles at earth. Since the intensity of low rigidity primary cosmic ray particles is observed to vary more than the intensity at higher rigidities, the inhibition has generally been assumed to be caused by magnetic fields.The necessary depression of the cosmic ray intensity requires both a barrier, to impede their arrival, and a removal mechanism within the barrier, to prevent eventual statistical equilibrium (with uniform particle density). Quantitative development indicates that a heliocentric magnetic dipole, a heliocentric cavity in the galactic field (Davis, Phys. Rev.100, 1440, 1955), and a heliocentric interplanetary cloud barrier (Morrison, Phys. Rev.101, 1397, 1956) all encounter serious difficulties in explaining the observed effects, one reason being the ineffective removal that is available.It is shown that a geocentric magnetic cloud barrier does not encounter these difficulties: it is proposed that during the years of solar activity the terrestrial gravitational field captures magnetic gas of solar origin from interplanetary space, which is then supported by the geomagnetic field; the removal by absorption by the earth is sufficiently effective that only a relatively thin barrier need be maintained; the occasional capture of new magnetic material accounts for the abrupt onset of the Forbush decreases, and the slow decay (0·5 years) of the captured fields for the smooth variation of the mean cosmic ray intensity with the sunspot cycle.

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