Excitation of Jovian Seismic Waves by the Shoemaker-Levy 9 Cometary Impact
Résumé
The kinetic energy released by the collision of the comet Shoemaker-Levy 9 with Jupiter is expected to be between 1020 J and 1023 J. This energy will excite seismic waves, which will propagate within Jupiter. These seismic waves are computed by summing normal modes of degree ℓ up to 1400 and frequency ν up to 10 mHz. The excitation amplitudes are obtained using a model of the blast wave induced by the explosion of the comet. Keeping in mind the possible detection of the waves with an IR camera, we examine the thermal signature of the global modes and transient waves excited by the impact. We show that the excitation of surface waves and normal modes will produce a directly observable signal for strong impacts only. An impact with an energy greater than 2.8 × 1021 J will produce a 10-mHz frequency P wave with associated peak-to-peak temperature fluctuations greater than 0.01 K at the antipode. Surface waves with frequencies less than 3 mHz will give rise to fluctuations everywhere in excess of 0.01 K for impacts greater than 9 × 1022 J. Lower energy impacts will not be directly detectable, the signal-to-noise ratio on a single pixel of the camera being too low. Stacking methods might enable the detection of P waves generated by impacts with energies as low as 7.25 × 1020 J at Δ = 90° and of surface waves generated by impacts as low as 1.4 × 1021 J. High-frequency monitoring of the temperature in the jovian troposphere daring at least 2 hr after each impact, and low-frequency monitoring during the remaining observation time may provide unique information on the inner structure of Jupiter, including the core and the discontinuity due to the possible plasma phase transition of hydrogen.