Excitation of Jovian normal modes by an impact source

Abstract

Abstract. We estimated the amplitudes of Jovian normal modes excited by a near-surface impact. The planet is modeled as a self-gravitating fluid sphere, and the impact source is approximated by a single force or a point pressure source. The effects of rotation are not included. An impact of a comet with a radius of 3 km and momentum Mv=6.8xl0 23 gcm/s is modeled as a point source 100 km below the Jovian surface, assumed to be at 1 bar. The peak-to-peak amplitudes of displacement and velocity of disturbance with a period of 700 s are approximately 2.1 m and 1.9 cm/s, respectively, at a distance of 90° from the impact. An amplification of a factor of about 25 occurs near the antipode. This estimate is not sensitive to the assumptions on the density distribution above· the surface. The amplitude in the higher altitude can be significantly higher. At shorter periods (100 to 200 s), the amplitudes depend on the source depth. For an impact with Mv=10 23 g-cm/s, and for a source depth of about 20 to 50 km, the amplitude and the particle velocity at a distance of 90° are of the order of 100 m, and 3 m/s, respectively. The pressure change at a depth of 20 to 50 km is of the order of 20 dyne/cm2, or about 2xl0· 6 of the ambient pressure at a depth of 40 km.

Planetary Seismology

“…Due to the large energies involved, the impact of the Shoemaker-Levy 9 comet was such an event. In that case, signal amplitudes were theoretically predicted for different impactor masses (Kanamori, 1993;Marley, 1994). For an impact with an energy > 10 21 J, peak-topeak temperature fluctuations greater than $0.01 K were expected for 10-mHz frequency P waves, while surface waves below 3 mHz were expected to generate fluctuations in excess of 0.01 K for impacts >2 Â 10 21 J .…”

Memoirs of a Giant Planet

“…We follow the first approach here. Second, the momentum delivery also exerts a force on the fluid and drives oscillations (Kanamori 1993;Lognonne et al 1994;Dombard & Boughn 1995). We call the former 'explosion' excitation, and the latter 'momentum punch'.…”

Tidal capture of a primordial black hole by a neutron star: implications for constraints on dark matter

“…e.g. [30,32]): where g(r) = M (r)/r 2 is the gravitational acceleration, M ′ (r) = 4πr 2 ρ and κ = ρdP/dρ is the incompressibility. In the notation of Ref.…”