This grant will support both research and continued operations of two neutron monitors at Climax, Colorado and Haleakala, Hawaii. The research will investigate the physics of the electrodynamical processes in three dimensions in the inner heliosphere, with special emphasis on the solar-terrestrial region. For instance, the PI's neutron monitors have discovered that as the Ulysses spacecraft travels towards the Sun's polar regions, the recurrent 26-day modulation continues to be seen to extremely high latitudes, beyond the extent of the magnetic field and plasma structures (previously thought to control these variations). The neutron monitors continued their measurements of these same variations, implying the mechanism for recurrent modulation must be a global, large-scale phenomenon, extending throughout the inner heliosphere. This mechanism will be pursued over the next few years. Further, the PI has the longest running neutron monitor records, covering more than two solar magnetic cycles. This will enable further exploration of the role of gradient drifts in the modulation of galactic cosmic rays, which reach the top of the atmosphere. The PI will continue long-term studies of the apparent bimodal character of cosmic ray modulation through the next solar minimum. Finally, the PI will continue support and upgrade of the two neutron monitors.
