The interaction of the solar wind with comet Shoemaker--Levy 9 leading to the formation of the cometary magnetosphere and its interaction with the Jovian bow shock is simulated using a one dimensional hybrid code. The mass loading of the solar wind by the cometary ions leads to the formation of a bow shock behind which the plasma density is 2--3 cm-3 and the electron temperature is 4 eV. The interaction of this system with the Jovian bow shock yields local enhancements of the magnetic field and the plasma density by factors of 4--5 and the electron temperature by 2--3. ¿ American Geophysical Union 1994