EarthRef.org Reference Database (ERR) -- Ahluwalia 2000

We have studied the data strings for the limiting rigidity (Rc) for the galactic cosmic ray (GCR) solar diurnal anisotropy, the interplanetary magnetic field (IMF) intensity (B), and the planetary index Ap for the period 1963 to 1998. The study covers three sunspot number (SSN) cycles (20, 21, 22). Our analysis brings out some of the steady state characteristics of the long term changes in Rc and other data strings and their interrelationships. Among other things, we relate the observed changes in Rc values to changes in B which are not related to SSN; the largest value of Rc occurs near 1982 when B has a high value 3 years away from SSN maximum for cycle 21. Rc bears a linear correlation with B and Ap but shows a low correlation with the power in the low frequency turbulence in IMF. The fit parameters with Ap data may be used to compute the values of Rc when in situ measurements of B do not exist; they may be applied to the cosmic ray data (available since 1937) to compute the amplitude and the phase of the diurnal anisotropy and to estimate more accurately the values of the key heliospheric transport parameters at high GCR rigidities near earth's orbit. ¿ 2000 American Geophysical Union We have studied the data strings for the limiting rigidity (Rc) for the galactic cosmic ray (GCR) solar diurnal anisotropy, the interplanetary magnetic field (IMF) intensity (B), and the planetary index Ap for the period 1963 to 1998. The study covers three sunspot number (SSN) cycles (20, 21, 22). Our analysis brings out some of the steady state characteristics of the long term changes in Rc and other data strings and their interrelationships. Among other things, we relate the observed changes in Rc values to changes in B which are not related to SSN; the largest value of Rc occurs near 1982 when B has a high value 3 years away from SSN maximum for cycle 21. Rc bears a linear correlation with B and Ap but shows a low correlation with the power in the low frequency turbulence in IMF. The fit parameters with Ap data may be used to compute the values of Rc when in situ measurements of B do not exist; they may be applied to the cosmic ray data (available since 1937) to compute the amplitude and the phase of the diurnal anisotropy and to estimate more accurately the values of the key heliospheric transport parameters at high GCR rigidities near earth's orbit. ¿ 2000 American Geophysical Union