Consider what we know about Earth's Magnetosphere,
it's caused by the earth having molten iron that's spinning in the core inducing a similar effect as a dynamo where you can pass current through an iron metal wound up and form an electromagnet only in the core the spinning effect generates those free electrons.
With that in mind and the fact that Mars has a weak almost considered no Magnetosphere due to the fact its core has cooled off mainly because it's a smaller planet so it lost its heat quicker, and without a molten core you lose your Magnetosphere.
But what if one is needed to make Mars fully terraformed to Earth-like conditions, safe from harmful UV rays and Solar Winds from destroying electronic devices and stripping the planet of its atmosphere. What if you have a free floating satellite acting as the Magnetosphere.
For this to work first thing is to have the satellite always be sun facing which can be achieved with the right orbital trajectory set. This saves the task of having to fully surround the planet with satellites. Secondly, the satellites would be strong electromagnets which would deflect the harmful UV rays and solar flares and act basically as an electromagnet always sun facing. With a few of them depending on the range of each satellite magnetic field you can have a honeycomb setup that would form an Artificial Magnetosphere for the planet.
The only thing to consider is how to provide each with enough power to run on its own. It will likely have it's own power bank and possibly always sun facing could mean if the electronics can work under such a strong magnetic field they can charge using the sunlight and using the battery also possibly only needing then a smaller amount of recharge from the surface which can be sent as concentrated lasers to a receiver that converts the laser to electrical power thereby charging the deficit required.