Abstract
The inner core rotates under the influence of inertial, frictional, electromagnetic and gravity torques. When its symmetry axis is inclined by an angle to the mantle symmetry axis, calculation shows the gravity restoring torque to be 2.50 x 1024cos01sin01N m, several orders of magnitude larger than the other torques combined. Investigation of its rotational dynamics under this torque shows that it can have two modes of steady precession. One mode involves a slow precession in space and is presumably ruled out because of the nearly diurnal relative motion required with respect to the outer core. The second steady precessional mode involves a rapid, nearly diurnal prograde motion in space and hence is slow in the mantle frame. Because the inner core is a good electrical conductor and because of its large rotational energy it is likely to have a strong interaction with the main magnetic field. In particular, if it is in the second steady precessional mode it may be carrying magnetic fields bodily for periods of several thousand years (its magnetic diffusion time) and the ‘dipole wobble’ of the main field, seen in historical measurements, and apparently extending into the palaeomagnetic record, may be a reflection of the influence of this motion on the outer core dynamo.
Highlights
Em artigo anterior (M (h.uk,. 1985) admitiu-se quc o campo geomagnitico possa resultar da rotaEao de cargas elictricas diltrenciadas cxistcntcs no n[clco terestre
Precession in thc rolalion ol lhe inncrcorc secms lo induce a Preccssion of the {comrgnetic fictd q ith I period of .rhourl.lx l{)'lorad/s. fhis vrlue corrc\pond{ to an cbngation of l.2 \ l0-D ofthe.prolatc spheroid of rhc inncr corc
O centro esti desviado de 5o,9 do polo geogrifico, o que pode significar que o eixo do momento cin6tico do manto n6o coincide exactamente com a posigeo m6dia (?) do eixo do momento cintitico do nfcleo interior
Summary
A velocidade angular absaluta 6 medida em relagdo a um referencial que. antigamente. se designava por "estrelas fixas". A velocidade angular absaluta 6 medida em relagdo a um referencial que. Esse referencial absoluto parece dever ligar-se ao conjunto das massas do Universo. A rotaqeo duma esfera em ktrno do cenlro e a correspondente conservaqi0 do moorento cindtico devcm relacionar-se com este rcferencial absoluto Por s€u lado' a rotaEeo dc cargas cldctricas que vai produzir utn culrrpo mag;dtico deve scr refcrida ao rclcrencial cnr quc for medido o campo. Visto quc cste dcpcndc apenas do movinrcnto rclativo das cargas electrlcas'. Podc tl ndclco extcrit>r e admilir-sc o nriclco quc o interi()r giram ttldos conl a mcsna vclocidadc angulur' Flsta vclocirlade corrcsptlntlc a umu rl)taqio conrplcta enr cada dia sidcrul. Pcla conscrvagittt do nlomcnlo cineltico' dcvcrii scr' na austncia dc biniirios aPlicados
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