Question

what evidence do we have that earth has a magnetic field surrounding the planet?

Explanation:

Key evidence for Earth's magnetic field includes compass needles aligning with magnetic north (a direct effect of the field), the auroras (caused by charged particles from the sun being deflected by the magnetic field into the atmosphere), and the protection of Earth's atmosphere from solar wind erosion (a function of the magnetic field's shielding effect).

Answer:

Compass needles aligning with magnetic north, the occurrence of auroras, and the shielding of Earth from solar wind are key evidence of Earth's surrounding magnetic field.