What type of force cause an object to accelerate? ?

ANY force causes an object to accelerate, just as long as there are not
some other forces on the object that cancel out the first one.

Are you looking for the answer ... an "UNBALANCED" force ?
That's a very poor way to describe it, because there's no such thing
as a balanced or unbalanced force.  The thing that's balanced or
unbalanced is a GROUP of forces, not a single force.

it supports the magnetic field

Explanation:

That inner core supports the magnetic field created through the outer core, which appears to protect living beings from dangerous solar radioactivity.