Authors: Paria Abouhamzeh (Department of Space Science, University of Alabama in Huntsville), Bingbing Wang (The Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville), Gary Zank ( Department of Space Science, University of Alabama in Huntsville)

In the outer heliosphere, turbulence is primarily driven by the presence of newly formed pickup ions (PUIs). The driving rate of PUIs is the product of the free energy of a single PUI and the rate at which PUIs are created. The commonly adopted model by Zank et al. (1996) assumes that the free energy of PUI is the same for both parallel and antiparallel propagating turbulence providing that the solar wind velocity is perpendicular to the heliospheric magnetic field (HMF). However, at high latitudes, the solar wind velocity and HMF are not quasi-perpendicular, thus a more general latitudinal dependent form for free energy should be applied. Additionally, the ionization rate of neutral atoms, which governs the creation rate of PUIs, exhibits a significant dependence on latitude. This latitudinal dependence is strongest during solar minimum and weakest during solar maximum. In this study, we investigate the time and latitudinal dependence in the driving of turbulence by PUIs over a few solar cycles. Our findings provide a crucial component for investigating the evolution of turbulence in the heliosphere by solving 2D turbulence transport models.