Computer Science
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd..10e..36g&link_type=abstract
Progress in Planetary Exploration Missions, 26th meeting of the IAU, Joint Discussion 10, 21-22 August 2006, Prague, Czech Repub
Computer Science
Scientific paper
In many theoretical investigations the normal modes of the linearized equations of rotation are computed, yielding both the periods and the eigenspaces of three librations. The modern view of internal structure of the planet takes into account a complex two- or three-layer model. For a planet with a solid inner core and a liquid outer core, there are four rotational normal modes. This numbers is reduced to two for a planet without inner core, and to one for a planet without liquid core. All types of modes are result of non-coincidence of rotation axes and of the main inertia moments of mantle, outer and inner core. For the Earth and the nearest planets - Mars and Moon - there is a wide spectrum of observations and theoretical speculations about parameters of the planet's deep interior. For instance, the most interesting data on dynamics and internal structure of the Moon are already accumulated as a result of the different observations and space experiments. The Japanese space experiments Lunar A, SELENE-missions, Luna Glob (Russia) planed for 2007 - 2012 years will contribute significantly to the information about the Moon: qualitative parameter Q, Love number k[2], core's radius R[c], core's density etc. In a case of free rotation of the two- or three-layer planet the two or four modes in its polar motion might be observed. The evaluations of the periods were made: periods of the Free Core Nutation (FCN) were obtained for Mercury (P[FCN] = 597 yrs) and first time for Venus (P[FCN] = 1534 yrs). For the Moon the period of Free Inner Core Nutation (FICN) P[FICN]= 515 - 634 yrs and the period of Inner Core Wobble (ICW) P[ICW]= 101 - 108 yrs were computed for different models of the lunar core. The main tendency of behavior of two new periods (P [FICN ]and P[ICW]) is preliminary revealed: a) the FICN-period decreases both with the increasing of the core's radius and of the thick of fluid shell; b) conversely, the ICW-period have the direct ratio to radius of a core and thickness of a liquid layer.
Gusev Alexander A.
Kitiashvili Irina
Petrova Natalia
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