The magnetosphere of Jupiter is the cavity created in the solar wind by
the planet's immensely strong magnetic field. Extending up to seven
million kilometers in the Sun's direction and almost to the orbit of
Saturn in the opposite direction, Jupiter's magnetosphere is the
largest and most powerful of any planetary magnetosphere in the Solar
System, and by volume the largest known continuous structure in the
Solar System after the heliosphere. Wider and flatter than the Earth's
magnetosphere, Jupiter's is stronger by an order of magnitude, while
its magnetic moment is roughly 18,000 times larger. The existence of
Jupiter's magnetic field was first inferred from observations of radio
emissions at the end of 1950s and was directly observed by the Pioneer
10 spacecraft in 1973. Jupiter's internal magnetic field is generated
by electrical currents flowing in the planet's outer core, which is
composed of metallic hydrogen. Volcanic eruptions on Jupiter's moon Io
eject large amounts of sulfur dioxide gas into space, forming a large
torus around the planet. Jupiter's magnetic field forces the torus to
rotate with the same angular velocity and direction as the planet's
rotation. The torus in turn loads the magnetic field with plasma, in
the process stretching it into a pancake-like structure called a
magnetodisk. In effect, Jupiter's magnetosphere is shaped by Io's
plasma and its own rotation, rather than by the solar wind like Earth's
magnetosphere.
Read the rest of this article:
<http://en.wikipedia.org/wiki/Magnetosphere_of_Jupiter>
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Today's selected anniversaries:
1467:
Troops under Stephen III of Moldavia defeated the forces of Matthias
Corvinus of Hungary in present-day Baia, Romania.
<http://en.wikipedia.org/wiki/Battle_of_Baia>
1791:
The first ten amendments to the United States Constitution,
collectively known as the United States Bill of Rights, were ratified.
<http://en.wikipedia.org/wiki/United_States_Bill_of_Rights>
1864:
American Civil War: Union troops essentially destroyed the Army of
Tennessee, one of the largest Confederate forces, at the Battle of
Nashville.
<http://en.wikipedia.org/wiki/Battle_of_Nashville>
1942:
World War II: The Americans engaged Imperial Japanese forces at the
Battle of Mount Austen, the Galloping Horse, and the Sea Horse in the
hills near the Matanikau River area on Guadalcanal during the
Guadalcanal Campaign.
<http://en.wikipedia.org/wiki/Battle_of_Mount_Austen%2C_the_Galloping_Horse%2C_and_the_Sea_Horse>
1964:
The six-month long Canadian Great Flag Debate effectively ended when
the Canadian House of Commons voted to replace the de facto national
flag of Canada, the Canadian Red Ensign, with an official one designed
by historian George Stanley, the Maple Leaf Flag .
<http://en.wikipedia.org/wiki/Flag_of_Canada>
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Wiktionary's word of the day:
pensive (adj):
1. Having the appearance of deep, often melancholic thinking.
2. Looking thoughtful, especially from sadness
<http://en.wiktionary.org/wiki/pensive>
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Wikiquote quote of the day:
It appears that mind, as manifested by the capacity to make choices, is
to some extent inherent in every atom. The universe as a whole is also
weird, with laws of nature that make it hospitable to the growth of
mind. I do not make any clear distinction between mind and God. God is
what mind becomes when it has passed beyond the scale of our
comprehension.
--Freeman Dyson
<http://en.wikiquote.org/wiki/Freeman_Dyson>