Solar cycle induced variations of the outer heliospheric structures

The solar wind undergoes complicated but typical changes during the solar activity cycle which are especially strongly pronounced in the inner heliosphere. In the outer heliosphere, as the main surviving solar cycle feature, a periodic variation of the solar wind dynamical pressure has been recognized by the VOYAGER‐1/2 spacecraft. We model this long‐periodic variation of the solar wind dynamical pressure with time‐dependent inner boundary conditions in our two‐dimensional 5‐fluids code. Only after running more than 8 activity cycles do the interface boundary layers start carrying out periodic breathings in constant phase lags with respect to the solar activity cycle. Especially the pick‐up ions and the anomalous cosmic rays, which are dynamically coupled to the low energy H‐atom and proton fluids, activate new interaction modes and store a longtime history of the past 2–3 solar cycles. This memory effect influences the analysis of energetic neutral atoms (ENA's) from the heliospheric interface regions.