| 1. |
- Sorriso-Valvo, Luca, et al.
(författare)
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Intermittency in plasma turbulence
- 2001
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Ingår i: Planetary and Space Science. - 0032-0633 .- 1873-5088. ; 49:12, s. 1193-1200
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Wurz, Peter, et al.
(författare)
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Particle populations in Mercury's magnetosphere
- 2001
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Ingår i: Planetary and Space Science. - 0032-0633 .- 1873-5088. ; 49:14-15, s. 1643-1653
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Tidskriftsartikel (refereegranskat)abstract
- Observations by Mariner 10 during its first and third flybys showed that Mercury possesses an intrinsic magnetic field resulting in a small magnetosphere that can keep the solar wind from directly interacting with the planet's surface under usual conditions. Since Mercury occupies a large fraction of its magnetosphere, regions of trapped charged particles in the inner magnetosphere, the plasmasphere and the energetic radiation belts, would all be absent. During the first flyby, energetic particle bursts were detected and interpreted as hermean substroms analogous to the terrestrial magnetosphere. Moreover, during this flyby, ULF waves and field-aligned currents were detected in the data. Earth-based observations of Na, K, and Ca populations in the exosphere strongly suggest the existence of dynamic magnetospheric processes at high latitudes interacting with the planet's surface.
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| 3. |
- Krüger, H., et al.
(författare)
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Four years of Ulysses dust data: 1996-1999
- 2001
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Ingår i: Planetary and Space Science. - 1873-5088. ; 49:13, s. 1303-1324
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Tidskriftsartikel (refereegranskat)abstract
- The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse(/i=79°, perihelion distance 1.3 AU, aphelion distance 5.4 AU).Between January /1996 and December /1999 the spacecraft was beyond 3 AUfrom the Sun and crossed the ecliptic plane at aphelion in May /1998. Inthis 4-yr period 218 dust impacts were recorded with the dust detectoron board. We publish and analyse the complete data set of both raw andreduced data for particles with masses10-16-10-8g. Together with 1477 dust impactsrecorded between launch of Ulysses and the end of /1995 publishedearlier (Grün et al., Planet. Space Sci. 43 (/1995a) 971;Krüger et al., Planet. Space Sci. 47 (/1999b) 363), a data set of1695 dust impacts detected with the Ulysses sensor between October /1990and December /1999 is now available. The impact rate measured between1996 and 1999 was relatively constant with about 0.2 impacts per day.The impact direction of the majority of the impacts is compatible withparticles of interstellar origin, the rest are most likelyinterplanetary particles. The observed impact rate is compared with amodel for the flux of interstellar dust particles. The flux of particlesseveral micrometres in size is compared with the measurements of thedust instruments on board Pioneer 10 and Pioneer 11 beyond 3 AU (Humes,J. Geophys. Res. 85 /(1980) 5841). Between 3 and 5 AU, Pioneer resultspredict that Ulysses should have seen 5 times more (~10mum sized)particles than actually detected.
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| 4. |
- Krüger, H., et al.
(författare)
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One year of Galileo dust data from the Jovian system: 1996
- 2001
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Ingår i: Planetary and Space Science. - 1873-5088. ; 49:13, s. 1285-1301
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Tidskriftsartikel (refereegranskat)abstract
- The dust detector system onboard Galileo has recoding dust impacts incircumjovian space since the spacecraft was injected into a bound orbitabout Jupiter in December 1995. This is the sixth in a series of papersdedicated to presenting Galileo and Ulysses dust data. We present datafrom the Galileo dust instrument for the period January to December 1996when the spacecraft completed four orbits about Jupiter (G1, G2, C3 andE4). Data were obtained as high-resolution realtime science data orrecorded data during a time period of 100 days, or via memory read-outsduring the remaining times. Because the data transmission rate of thespacecraft is very low, the complete data set (i.e. all parametersmeasured by the instrument during impact of a dust particle) for only 2%(5353) of all particles detected could be transmitted to Earth; theother particles were only counted. Together with the data for 2883particles detected during Galileo's interplanetary cruise and publishedearlier, complete data of 8236 particles detected by the Galileo dustinstrument from 1989 to 1996 are now available. The majority ofparticles detected are tiny grains (about 10nm in radius) originatingfrom Jupiter's innermost Galilean moon Io. These grains have beendetected throughout the Jovian system and the highest impact ratesexceeded 100min-1. A small number of grains has been detectedin the close vicinity of the Galilean moons Europa, Ganymede andCallisto which belong to impact-generated dust clouds formed by (mostlysubmicrometer sized) ejecta from the surfaces of the moons (Krügeret al., /1999e. Nature 399, 558). Impacts of submicrometer to micrometersized grains have been detected throughout the Jovian system andespecially in the region between the Galilean moons.
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| 5. |
- Lindblad, Bertil Anders
(författare)
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A long-term high-resolution study of the visual activity curve of the Perseid meteor stream 1953-1983
- 2000
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Ingår i: Planetary and Space Science. - 1873-5088. ; 48:10, s. 905-909
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Tidskriftsartikel (refereegranskat)abstract
- Perseid and sporadic meteor hourly rates and magnitudes observed in 1953-1983 by a team of visual observers at the Onsala Space Observatory, Sweden, are analysed. A high-resolution study of the zenithal hourly rates of bright Perseid meteors /(m<=2.5) versus solar longitude has been made using a step length of /0.05° in solar longitude. The present study, which is based on 147 Perseid hourly rates, observed between solar longitudes /138.70°-/141.65° (equinox 2000) covers the period of maximum Perseid activity. Somewhat surprisingly it reveals a multi-peak structure of the Perseid maximum with at least four separate peaks in the activity curve of bright Perseids. The first peak located at /139.38° corresponds to the crossing of the nodal plane of the parent comet, the second at /139.68° is the so-called ``new'' Perseid maximum, the third peak at /140.20° is the ``old'' or ``traditional'' maximum of the shower, while the fourth peak although less intense than the previous three peaks indicates a well-defined activity maximum centred on /140.78°. It is interesting to note that, for bright Perseids, the nodal maximum is of the same intensity as the ``new'' and ``old'' maxima, but is of a somewhat shorter duration than these two maxima. A similar study of the activity curve of all observed Perseid meteors (i.e. independent of apparent magnitude) shows the same multi-peak structure, but with slightly less pronounced peaks. In a previous study of the Perseid activity curve based on 605 photographic Perseid orbits obtained in various two-station programs 1937-1985 the multi-peak structure can be recognised in a number versus solar longitude diagram (Lindblad and Porubcan, /1994. Planet Space Sci. 42, 117-122.). The various peaks in the photographic data are located at the same solar longitudes as in the visual data. This agreement between the results of the present long-term visual study and a long-term photographic study of the Perseid activity curve strongly supports our conclusions as to the multi-peak structure of the Perseid shower.
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| 6. |
- Mileikowsky, C, et al.
(författare)
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Risks threatening viable transfer of microbes between bodies in our solar system
- 2000
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Ingår i: PLANETARY AND SPACE SCIENCE. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0032-0633. ; 48:11, s. 1107-1115
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Tidskriftsartikel (refereegranskat)abstract
- A fraction of the number of ejecta expelled from a planet by comet or asteroid impacts end up landing on another planet. If microorganisms were living in the ground before impact, they would be transported inside ejecta to the target planet. During that p
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