I am sorry. Not really. I am missing something. Some thinking about it may help. The clue is in those charged particles? Thanks for trying.
Hazel, the issue is the stream of charged particles (ions) coming from the sun, which are very reactive because they want to acquire or lose an electron in order to become neutral. These ions would be very likely to break chemical bonds in any complex molecules that were forming on the the early Earth, which would make it hard for life to start.
However charged particles that enter a magnetic field experience a force, at right angles to the direction they are travelling, which bends their path. The presence of the Earth's magnetic field (which arises from electric currents in the conductive, liquid core of the planet) deflects these solar ions away from the surface. So the magnetic field is a sort of protective force field for the Earth, sheltering it from the bombardment.
If the Earth did not have such a core, it is reasonable to think life would have found it either harder to get started or completely impossible.
Edited by exchemist, 29 October 2018 - 10:56 AM.