Dipole model of the Earth's magnetic field (MLAT), or geomagnetic latitude, formula_10 is measured northwards from the equator (analogous to geographic latitude) and is related to formula_9 by formula_12. In this case, the radial and azimuthal components of the magnetic field (the latter still in the formula_9 direction, measured from the axis of the north pole) are given by formula_14 formula_15 formula_16 where formula_17 in this case has units of Earth radii (formula_18). Invariant latitude is a parameter that describes where a particular magnetic field line touches the surface of the Earth. It is given by formula_19 or formula_20 where formula_21 is the invariant latitude and formula_22
The Longest Voyage The Longest Voyage "The Longest Voyage" is a science fiction short story by American writer Poul Anderson. It won the Hugo Award for Best Short Story in 1961. On a distant world the age of exploration is beginning. A party of daring explorers attempts to circumnavigate their world. In unknown waters they encounter an island civilization which claims to have a prophet who fell from the stars. "The Longest Voyage" won the 1961 Hugo Award for Best Short Story. Gardner Dozois, upon selecting "The Longest Voyage" for inclusion in his 2000 anthology "Explorers: SF Adventures to Far Horizons", said that