Cosmic rays in the dynamic heliosphere
Potgieter, Marius S.
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he relation between the dynamics of the heliosphere, its shape and geometry, so lar activity and cosmic ray variations is addressed. The global features of the helio sphere influence what happens inside its boundaries on a variety of time-scales. Galactic and anomalous cosmic rays are the messengers that convey vital information on global heliospheric changes in the manner that they respond to th ese changes. By observing neutral and charged particles, including cosmic rays, over a wide range of energies on various spacecraft and at Earth, a better understanding is gained about heliospheric phenomena including space weather and space climate. Causes of cosmic ray modulation and variability in the heliosphere are reviewed, with emphasis on the 11-year and 22-year solar activity cycles, step-modul ation, charge-sign dependent modulation and particle drifts. Advances in this field will be highlighted such as the ef fects of the solar wind terminati on shock and the heliosheath on cosmic ray variability, also related to important recent observations in the heliosheath by the two Voyager spacecraft