Far Side of the Sun
Explanation:
You may think it's impossible to see
through the Sun, but maps of
the Sun's far side
are now made routinely by instruments on board the
sun-staring SOHO spacecraft.
This is one such map from April 12.
At right, is a map projection of calculated magnetic field strengths on
the Earth-facing solar hemisphere with yellow and red indicating high
magnetic fields characteristic of solar active regions.
At left is a similar map of the solar hemisphere opposite planet Earth,
which shows the large active region AR9393 as the 27-day
solar rotation carried it across
the
far side.
The largest sunspot group in a decade,
AR9393 was easily seen
as it tracked across the Sun's Earth-facing hemisphere in late March.
When AR9393 swung around
to
the Sun's far side, SOHO's
Michelson
Doppler Interferometer
(MDI) instrument continued to map its position
by measuring changes
in
motions caused by
solar
sound waves - transmitted through the Sun and
influenced by the active region's strong magnetic fields.
Known as
helioseismology, analyzing
solar sound waves is like
using seismological records of earthquakes to probe the
interior of the Earth.
On the Sun, sound waves are produced by turbulent convection
cells seen on the surface as
dynamic solar granules.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
