Decreased values of cosmic dust number density estimates in the Solar System

摘要: Experiments to investigate the effect of impacts on side-walls dust detectors such as present NASA/ESA Galileo/Ulysses instrument are reported. Side walls constitute 27% internal area these instruments, and increase field view from 140° 180°. Impact cosmic particles onto Al side was simulated by firing Fe particles, 0.5–5 μm diameter, 2–50 km s^(−1), an plate, simulating targets Galileo Ulysses instruments. Since wall affect rise time target ionization signal, degree which particle fluxes overestimated varies with velocity. Side-wall at velocities 2–20 km s^(−1) yield times 10–30% longer than for direct impacts, so that derived impact velocity is reduced a factor ∼2. Impacts 20–50 ∼10 relative data. This would result in serious overestimates flux intersecting km s^(−1). Taking into account differences laboratory calibration geometry we obtain following percentages previous incident number density values [Grun et al., 1992. The detector. Space Sci. Rev. 60, 317–340]: 55% 2 10 400% 70 We predict individual masses ∼10–90% when side-wall occur underestimated ∼10–^(102)∼10–102 can be identified data their unusually short times. used new revised [Kruger 2000. A cloud Ganymede maintained hypervelocity interplanetary micrometeoroids. Planet. 48, 1457–1471; 2003. Impact-generated clouds surrounding Galilean moons. Icarus 164, 170–187] satellite densities 9.4×^(10−5), 9.9×^(10−5), 4.1×^(10−5), 6.8×^(10−5) m^(−3) 1 radius Io, Europa, Ganymede, Callisto, respectively. Additionally, detected mission found 1.6×^(10−4), 7.9×^(10−4), 3.2×^(10−5), 7.9×^(10−4) heliocentric distances 0.7, 1, 2, 3, 5 AU, Work Burchell al. [1999b. Acceleration conducting polymer-coated latex projectiles experiments. J. Phys. D: Appl. 32, 1719–1728] suggests low-density “fluffy” encountered will not significantly our results—further useful confirm this.