  The thermal and magnetic histories of planetesimals provide unique insights
into the formation and evolution of Earth's building blocks. These histories
can be gleaned from meteorites by using numerical models to translate measured
properties into planetesimal behaviour. In this paper, we present a new 1D
planetesimal thermal evolution and dynamo generation model. This magnetic field
generation model is the first of a differentiated, mantled planetesimal that
includes both mantle convection and non-eutectic core solidification. We have
improved fundamental aspects of mantle heat transport by including a more
detailed viscosity model and stagnant lid convection parametrisations
consistent with internal heating. We have also added radiogenic heating from
$^{60}Fe$ in the metallic Fe-FeS core. Additionally, we implement a combined
thermal and compositional buoyancy flux, as well as the latest magnetic field
scaling laws to predict magnetic field strengths during the planetesimal's
thermal evolution until core solidification is complete. We illustrate the
consequences of our model changes with an example run for a 500 km radius
planetesimal. These effects include more rapid erosion of core thermal
stratification and longer duration of mantle convection compared to previous
studies. The additional buoyancy from core solidification has a marginal effect
on dynamo strength, but for some initial core sulfur contents it can prevent
cessation of the dynamo when mantle convection ends. Our model can be used to
investigate the effects of individual parameters on dynamo generation and
constrain properties of specific meteorite parent bodies. Combined, these
updates mean this model can predict the most reliable and complete magnetic
field history for a planetesimal to date, so is a valuable tool for deciphering
planetesimal behaviour from meteorite properties.
