The Trouvelot astronomical drawings manual — John Shaqi
The Trouvelot astronomical drawings manualTrouvelot, E. L. (Etienne Leopold)
Science
The Trouvelot astronomical drawings manual
Trouvelot, E. L. (Etienne Leopold)
Astronomy -- Pictorial works
Auroral phenomena generally accompany the extraordinary perturbations in
the oscillations of the magnetic needle, which are commonly called
"magnetic storms," and the greater the auroral displays, the greater are
the magnetic perturbations. Not only is the needle subject to unusual
displacements during an aurora, but its movements seem to be
simultaneous with the pulsations and waving motions of the delicate
auroral streamers in the sky. When the aurora sends forth a coruscation,
or a streamer in the sky, the magnetic needle responds to it by a
vibration. The inference that the auroral phenomena are connected with
terrestrial magnetism is further supported by the fact that the centre
of the corona is always situated exactly in the direction of that point
in the heavens to which the dipping needle is directed.
It has been found that the aurora is a periodical phenomenon, and that
its period corresponds very closely with those of the magnetic needle
and Sun-spots. The years which have the most Sun-spots and magnetic
disturbances have also the most auroras. There is an almost perfect
similarity between the courses of the three sets of phenomena, from
which it is concluded that the aurora is connected in some mysterious
way with the action of the Sun, as well as with the magnetic condition
of the earth.
A very curious observation, which has been supposed to have some
connection with this subject, was made on Sept. 1st, 1859, by Mr.
Carrington and Mr. Hodgson, in England. While these observers, who were
situated many miles from one another, were both engaged at the same time
in observing the same Sun-spot, they suddenly saw two luminous spots of
dazzling brilliancy bursting into sight from the edge of the Sun-spot.
These objects moved eastward for about five minutes, after which they
disappeared, having then traveled nearly 34,000 miles. Simultaneously
with these appearances, a magnetic disturbance was registered at Kew by
the self-registering magnetic instruments. The very night that followed
these observations, great magnetic perturbations, accompanied by
brilliant auroral displays, were observed in Europe. A connection
between the terrestrial magnetism and the auroral phenomena is further
proved by the fact that, before the appearance of an aurora, the
magnetic intensity of our globe considerably increases, but diminishes
as soon as the first flashes show themselves.
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