Is this an Earth science question and does it belong in that forum?
The source of tides on Earth is the gravitational interaction between the fluid elements of the Earth and the rest of the universe. By far the largest component of this interaction comes from the moon.
The source of geomagnetism lies on the core of the earth. Since the core is at least partly fluid there is some gravitational interaction between this fluid and the rest of the universe. This interaction is different and separate from the interaction producing the ocean tides.
Is this what you are talking about?