Cosmic rays represent one of the longer data bases for studying the temporal variation of solar activity. The availability of continuous data records during several solar cycles from a neutron monitor is important for a wide variety of investigations of the cosmic ray modulation. For example, data from neutron monitors are essential for evaluating the extent of the modulation of high energy cosmic-rays and possible asymmetries in this modulation from cycle to cycle: these data also serve as a baseline for lower-energy cosmic-ray gradient measurements and help to understand the propagation of energetic particles in solar cosmic-ray events. This grant will continue the operation of the cosmic-ray neutron monitors at Mt. Washington and Durham and continue studies which relate these ground-based cosmic-ray observations to near earth cosmic ray telescope data from the IMP series of spacecraft and similar data at large distances from the earth acquired from Pioneers 10 and 11 and Voyagers 1 and 2. Mt. Washington is the only high latitude neutron monitor providing continuous data coverage over almost three solar cycles, the data from that station have been used as standard indicators of the energetic cosmic-ray flux at earth by balloon and satellite experiments on a worldwide basis. Currently many other groups request the data as a time base for spacecraft and balloon measurements. The inclusion of these ground-based observations provides an essential additional dimension to the spacecraft measurements. The grant will support the following specific problems using the Mt. Washington and spacecraft data described above: (1) the cosmic ray intensities at earth and at heliocentric distances beyond 15 Astronomical Unit (AU) during the recovery phase of the current modulation cycle; (2) the integral and differential radial cosmic-ray gradients 45 AU; (3) latitudinal intensity gradients; (4) the effect of the heliospheric boundary upon the cosmic-ray intensity; (5) other studies, to include the phase-lag effects during the decreasing and increasing portions of different solar cycles, a comparison of the cosmic-ray modulation in the last three solar cycles particularly at periods of minimum modulation, the Forbush-type decrease of February 6, 1986, and (6) the acceleration, injection and propagation of the protons in the May 7, 1978 and February 16, 1984 solar cosmic ray events.
