  The solar cycle and its associated magnetic activity are the main drivers
behind changes in the interplanetary environment and the Earth's upper
atmosphere (commonly referred to as space weather). These changes have a direct
impact on the lifetime of space-based assets and can create hazards to
astronauts in space. In recent years there has been an effort to develop
accurate solar cycle predictions (with aims at predicting the long-term
evolution of space weather), leading to nearly a hundred widely spread
predictions for the amplitude of solar cycle 24. A major contributor to the
disagreement is the lack of direct long-term databases covering different
components of the solar magnetic field (toroidal vs.\ poloidal). Here we use
sunspot area and polar faculae measurements spanning a full century (as our
toroidal and poloidal field proxies), to study solar cycle propagation, memory,
and prediction. Our results substantiate predictions based on the polar
magnetic fields, whereas we find sunspot area to be uncorrelated to cycle
amplitude unless multiplied by area-weighted average tilt. This suggests that
the joint assimilation of tilt and sunspot area is a better choice (with aims
to cycle prediction) than sunspot area alone, and adds to the evidence in favor
of active region emergence and decay as the main mechanism of poloidal field
generation (i.e. the Babcock-Leighton mechanism). Finally, by looking at the
correlation between our poloidal and toroidal proxies across multiple cycles,
we find solar cycle memory to be limited to only one cycle.
