Diurnal variation of cosmic ray intensity I. Two approaches to the study

Journal Article · Wed Nov 01 04:00:00 EST 1978 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA083iA11p05139· OSTI ID:6468139

Sari, J W; Venkatesan, D; Lanzerotti, L J; Maclennan, C G

The investigation has been carried out over the past two decades by either of two approaches: the traditional Fourier series method and the more recently introduced power spectral method. A comparison of the two approaches is essential to the proper understanding of the results derived from them. The present study, for the first time, adopts both approaches for investigating the data from the Sulfur Mountain super neutron monitor for the period of mid-December 1965 to April 1966 (extending over five solar rotations), when interplanetary magnetic field data from Pioneer 6 were also available. Problems relating to the analyses of both data sets on a day-to-day basis and on a statistical basis over a number of days are discussed. The power spectral analysis method cannot provide information on the phase of the diurnal variation or information on the diurnal amplitude on a day-to-day basis. This method provides excellent estimates of the diurnal anisotropy amplitude provides a measure of the ambient anisotropy amplitude. The Fourier series method can yield reliable measures of the amplitude and phase on a day-to-day basis, provided the time series is reasonably stationary. This method cannot estimate the ambient anisotropy amplitude which, for small amplitudes, contributes to large uncertainties in the Fourier coefficients. We find that there is a general agreement between the observed diurnal variation and that predicted theoretically. However, for most of the periods examined the ratio of the perpendicular diffusion coefficient to the parallel diffusion coefficient is rather small (K/sub 1//K < or approx. =0.1). As such the diurnal variation amplitude is generally most sensitive to the interplanetary field direction and the solar wind velocity and not to the calculated values of the diffusion coefficients. Further tests of the theory are discussed.

• Research Organization: Calspan Corporation, Buffalo, New York 14221
• OSTI ID: 6468139
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 83:A11; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics &amp; Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
COSMIC RADIATION
DAILY VARIATIONS
DIFFUSION
FOURIER TRANSFORMATION
INTEGRAL TRANSFORMATIONS
INTERPLANETARY MAGNETIC FIELDS
IONIZING RADIATIONS
MAGNETIC FIELDS
MATHEMATICS
RADIATIONS
STATISTICS
TRANSFORMATIONS
VARIATIONS