The sun emits a stream of energetic electrons and protons called the solar wind. These particles frequently get caught up in the earth's magnetic field, traveling in spiral paths that take them toward the north or south magnetic poles. When they head northward and collide with atoms in the earth's upper atmosphere, those atoms emit light we know as the aurora borealis, or northern lights. These particles also interfere with radio reception. Why do they emit radio waves?

The sun emits a stream of energetic electrons and protons called the solar wind. When they head northward and collide with atoms in the earth's upper atmosphere, those atoms emit light we know as the aurora borealis, or northern lights. They emit radio waves because the spiraling electric charges are accelerating and thus producing changing electric and magnetic fields which results in the charges emitting electromagnetic waves

Explanation:

Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field. EM waves are composed of oscillating magnetic and electric fields.
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.
Electromagnetic waves are electric and magnetic fields traveling through empty space with the speed of light
A charged particle oscillating about an equilibrium position is an accelerating charged particle. If its frequency of oscillation is, then it produces an electromagnetic wave with the same oscillating frequency
Electromagnetic radiation is made when an atom absorbs energy. The absorbed energy causes one or more electrons to change their location within the atom. When the electron returns to its original position they produce an EM wave.
Electromagnetic waves have properties of speed, wavelength, and frequency