This question has arisen from the Carl Friedrich Gauss’ statement that the Earth could be modeled, concerning his calculations about the earth’s magnetic potential, as a big magnet, himself having stated it literally as follows:
“By experiments made in the year 1832 (Intensitas, Art. 21) the magnetic moment of a magnet bar, of a pound weight, was found to be, according to the same absolute unity, = 100877000. […] Thus 8464 trillions of such magnet bars, with parallel magnetic axes, would be required to replace in external space the magnetic influence of the earth. Supposing the magnetism of the earth to be uniformly distributed throughout its volume, it would hence be equal to eight such bars (more exactly 7.831) for every cubic meter.” From: Scientific Memoirs, Selected from the Transactions of Foreign Academies of Science and Learned Societies, and from Foreign Journals: Volume 2, by Richard Taylor. (Source: PDF BOOK FILE available on Google Books. This text was published as a translation to English from the original Latin or German version)
Also we can read in a thesis by Keith Dawson, downloadable from the Internet:
“We ought to believe, however I could not confirm it, that the magnet bar used by Gauss was of almost one foot in length and weighing nearly one pound”. (Source: THE EARLY HISTORY OF ELECTRO-MAGNETIC TELEGRAPH INSTRUMENTS, Thesis by Keith Dawson)
And we learn, from italian astronomer Padre Secchi, that such magnet bars were made of steel and were magnetized to saturation. (Source: L'unité des forces physiques, by Secchi, downloadable from Gallica)
Gauss used non-conventional and some sort of intricated unities for his calculation, and I’ve been unable to come across the conversion to Tesla or even to Gauss of the Gauss’ primitive measurements. Unable as I’ve been to calculate the “magnetic moment,” as stated by Gauss, of “such a 1 pound magnet bar,” I thought perhaps there will be someone with the necessary skills and patience in this community to evaluate the correctness of the Gauss assumptions relating the Earth’s magnetic strength, and its actual conversion to Tesla. And then, perhaps make an evaluation of how accurate were Gauss’ calculations.
That said, every time I search for the Earth magnetic field it’s always depicted as weak, thing that is certainly true in its surface, but the real strength in its axis, where it could be considered as uniform and where its strength will be the highest, is always omitted!
