Temperature is a property of mass and gravity. Bigger mass has stronger gravity therefore greater energy density/temperature. The sun is just a hot mass due to its large mass compared to earth mass

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Earth's magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in the Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.

Why can't scientist use same principle to produce electricity? Make a model of molten iron core to produce magnetic fores?

Sunlight/AC in the atmosphere moves around earth at 1000 miles per hour at the equator, this creates a current/emf in the atmosphere, this emf causes so called magnetic field of earth. it makes campus point to north and navigates birds.