Narrow‐band Jovian kilometric radiation: A new radio component

Abstract

We describe a new component of Jupiter's radio spectrum. This component emits in a very narrow bandwidth (≤ 40 kHz) near 100 kHz. Its waveform is a very smooth and gradual rise and subsequent fall in intensity over typically two hours. The emission is polarized with left‐hand polarization associated with the Jovian northern magnetic hemisphere and righthand with the south. The most interesting feature of the emission is its deviation from a strict System III rotation period repetition rate. The emission source of this narrow‐band component clearly rotates slower by 3‐5% than all other forms of Jovian radio emission. Propagation considerations coupled with this observed lack of corotation point to a source region near the magnetic equatorial plane at the outer ‘edge’ (8‐9 R J ) of the Io plasma torus.