Enhanced isotropic cosmic ray intensity waves during cosmic ray storms

Duggal, S. P.; Pomerantz, M. A.

doi:10.1029/ja084ia12p07382

Cited by 5 publications

(1 citation statement)

References 24 publications

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“…In the present paper we are studying waves with a period of 27 days in the cosmic ray north-south anisotropy because of an interest in how such waves may contribute to the isotropic cosmic ray intensity waves which were detected by Duggal and Pomerantz [1979]; these isotropic waves, with a periodicity of 27 days, are observed at north and south polar and also equatorial-viewing stations as a persistent wavelike pattern with a large peak to peak amplitude (about 3% in 1978). These isotropic intensity waves have been studied using data from the Mawson Station, which is an underground cosmic ray telescope in Antarctica which has operated since 1982 [Jacklyn and Pomerantz, 1983;Jacklyn et al, 1984Jacklyn et al, , 1987.…”

Section: Paper Number 92ja01663mentioning

confidence: 99%

Waves in the cosmic ray north‐south anisotropy with periods of 27 days, 1 year, and 11 years

Swinson¹,

Yasue²

1992

J. Geophys. Res.

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We use data from 1971 to 1989 from the Nagoya cosmic ray muon telescope to look at waves in the cosmic ray north-south anisotropy. The GG component of the Nagoya data is used because it is particularly sensitive to the north-south anisotropy. The presence of waves with a period of 27 days is demonstrated through most of the period. For each 27-day solar rotation the 27 daily values for the GG component have been harmonically analyzed to determine the amplitude of the best fit sine wave to the data. When these GG 27-day amplitudes are plotted for each solar rotation during the 19-year period, it becomes apparent that there is a very marked annual modulation of these amplitudes; the annual variation is greatest at solar maximum, and is also an I l-year modulation of the effect. The cosmic ray north-south anisotropy arises from the By x VNR, anisotropy resulting from the interaction of the y component of the interplanetary magnetic field (IMF), By and VN R, the radial heliocentric cosmic ray density gradient. We have also determined the daily average values for By from 1971 to 1987, and for each 27-day solar rotation these daily values have also been harmonically analyzed to obtain the best fit sine wave of period 27 days. When the amplitudes of the 27-day By waves are plotted for each solar rotation, an annual wave and an I l-year wave are also found; the behavior is very similar in nature to the behavior of the waves in the Nagoya GG data. These two sets of data have been compared with the values of a, the tilt of the heliospheric neutral sheet, which is available for most of the solar rotations between 1971 and 1989. The largest annual waves in the amplitude of the 27-day GG waves appear to coincide with relatively rapid excursions in the tilt of the neutral sheet. The annual mean of the amplitudes as well as the range (highest to lowest) in the amplitudes for the 27-day waves in the GG component and in the By component have been determined for each year; in each case there is a periodicity of about 11 years comparable to the solar activity periodicity.

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Section: Paper Number 92ja01663mentioning

confidence: 99%

Waves in the cosmic ray north‐south anisotropy with periods of 27 days, 1 year, and 11 years

Swinson¹,

Yasue²

1992

J. Geophys. Res.

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Remarkable anisotropic cosmic‐ray intensity oscillation

Duggal¹,

Pomerantz²,

Tsao³

1980

Geophysical Research Letters

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A large cosmic ray intensity wave in which a single oscillation of the galactic flux with a peak‐to‐peak amplitude of about 4% and a period of approximately 27 hours, occurred on October 27‐28, 1977. This unusual intensity profile was not associated with a classical Forbush decrease. Harmonic analysis in Universal Time of data from a global distribution of stations revealed that in each case the diurnal vector on October 27 differs significantly from those on other days before and after the event. Furthermore, the amplitude of the wave follows the relationship R1(i) = Aeαμ(i) where A and α(=1) are constants and μ(i) in the cosine of the angle between the direction of anisotropy and the asymptotic direction of viewing. The mechanism which produced this unusual oscillation is not yet understood.

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Observation of pronounced isotropic variations of cosmic ray intensity during August–September 1979

Venkatesan¹,

Volk²,

Agrawal³

1981

J. Geophys. Res.

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A study of the cosmic ray intensity data from high‐latitude stations reveals an isotropic variation of ∼30‐day periodicity and a peak‐to‐peak amplitude of 10% during the two months August–September 1979. Such an unusual modulation of cosmic ray intensity has not been observed before. It is clear that the variation is worldwide and in view of no significant north‐south asymmetry, we have to visualize the modulation region responsible for the effect to be extremely large. The rigidity spectra of the variation is found to be similar to that of Forbush decreases. The results are discussed in terms of solar activity. No obvious physical mechanism is readily seen, to account for this intensity variation.

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Enhanced isotropic cosmic ray intensity waves during cosmic ray storms

Cited by 5 publications

References 24 publications

Waves in the cosmic ray north‐south anisotropy with periods of 27 days, 1 year, and 11 years

Waves in the cosmic ray north‐south anisotropy with periods of 27 days, 1 year, and 11 years

Remarkable anisotropic cosmic‐ray intensity oscillation

Observation of pronounced isotropic variations of cosmic ray intensity during August–September 1979

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