Interstellar dust flux measurements by the Galileo dust instrument between the orbits of Venus and Mars

[i] We present an analysis of the data obtained by the Galileo in situ dust instrument for interstellar dust (ISD). Between December 1989 and the end of 1993, three orbit segments were favorable for the detection of ISD at less than 3 AU heliocentric distance. After removing background events from the data sample, which were mostly due to interplanetary dust impactors, we infer that the flux of ISD grains between 0.7 AU and 3 AU is about 4 x 10 -5 m -2 s -1 . This result is compatible with the ISD flux of 3 × 10 -5 m -2 s -1 (grain size 0.4 μm) derived from the Cassini measurements at about 1 AU. Using a new concept called ISD β spectroscopy, we are able to estimate at different locations in the inner solar system the ISD flux alteration resulting from the competing effects of radiation pressure and gravitation. In particular, we confirm results of previous Ulysses dust data analysis showing that radiation pressure prevents smaller ISD grains (radius smaller than 0.3 μm) from reaching the innermost region of the solar system. Furthermore, our analysis shows the relevance of gravitational focusing in the dynamics of bigger ISD grains (micron-sized grains). The Galileo measurements were performed 10 years before the Cassini measurements. Thus the available ISD data now cover almost a full 11-year solar cycle. Nonetheless, the flux of ISD grains with radius bigger than 0.4 μm shows no significant temporal variation. This suggests that the dynamics of these ISD grains is not influenced much by the interaction with the time-dependent solar magnetic field.

[1]  H. Fechtig,et al.  Discovery of Jovian dust streams and interstellar grains by the Ulysses spacecraft , 1993, Nature.

[2]  G. Gruen,et al.  Dynamics of Micrometeoroids , 1980 .

[3]  E. Grün,et al.  Penetration of the heliosphere by the interstellar dust stream during solar maximum , 2003 .

[4]  Eberhard Grün,et al.  Identification of “small” dust impacts in the Ulysses dust detector data , 1993 .

[5]  E. Grün,et al.  Calibration of the Galileo/Ulysses dust detectors with different projectile materials and at varying impact angles , 1989 .

[6]  Hugo Fechtig,et al.  Collisional balance of the meteoritic complex , 1985 .

[7]  M. Landgraf.  Modeling the motion and distribution of interstellar dust inside the heliosphere , 1999, astro-ph/9906300.

[8]  E. Grün,et al.  The flux of interstellar dust observed by Ulysses and Galileo , 1995 .

[9]  A. Heck,et al.  Analysis of the sensor characteristics of the Galileo dust detector with collimated Jovian dust stream particles , 1999 .

[10]  E. Grün,et al.  The Galileo Dust Detector , 1992 .

[11]  E. Grün,et al.  Deflection of the local interstellar dust flow by solar radiation pressure. , 1999, Science.

[12]  Gregor E. Morfill,et al.  Interstellar dust in the heliosphere , 1994 .

[13]  W. Kratschmer,et al.  Dust in the local interstellar wind , 1999 .

[14]  H. Rosenbauer,et al.  The Ulysses neutral gas experiment: Determination of the velocity and temperature of the interstellar neutral helium , 1993 .

[15]  Gregor E. Morfill,et al.  The Ulysses dust experiment , 1992 .

[16]  M. Stübig.  New insights in impact ionization and in time-of-flight mass spectroscopy with micrometeoroid detectors by improved impact simulations in the laboratory , 2002 .

[17]  Sascha Kempf,et al.  Cassini between Venus and Earth: Detection of interstellar dust , 2003 .

[18]  B. Gustafson.  Physics of Zodiacal Dust , 1994 .

[19]  Mark J. Matney,et al.  Synthesis of Observations , 2001 .

[20]  Mihaly Horanyi,et al.  CHARGED DUST DYNAMICS IN THE SOLAR SYSTEM , 1996 .

[21]  M. Landgraf,et al.  Aspects of the mass distribution of interstellar dust grains in the solar system from in situ measurements , 1999 .