Answer:
The Earth's molten iron core
Step-by-step explanation:
The Earth's magnetic field is mainly due to the convection current flowing in its molten iron core. It is considered to be a great conductor of electricity and is also dubbed as an "invisible river." If people were to study the magnetic field, they have to follow the movement of the molten iron that flows about thousands of miles every hour. The magnetic field is so strong that it can pass through the earth's core, crust and even reach the space (although it becomes weaker at this point).