PHYSICS NEWS UPDATE A digest of physics news items prepared by Phillip F. Schewe, AIP Publ

PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 155  December 13, 1993

THE HUBBLE SPACE TELESCOPE REPAIR MISSION has been
successful.  Space Shuttle astronauts installed a module (COSTAR)
to correct the optical aberration in Hubble's main mirror.  It also
received several new gyroscopes, new solar panels, and an upgraded
wide-field planetary camera.  (The New York Times, 10 Dec.)

PRINCETON'S TFTR TOKAMAK HAS PRODUCED 5.6
MEGAWATTS OF POWER from fusion reactions.  The previous
record power output for a fusion reactor was 1.7 megawatts at the
Joint European Torus (JET) in 1991.  The high power at Princeton
(as with JET) was made possible by using tritium.  Deuterium-tritium
reactions result in the emission of neutrons with an energy of 17.6
MeV, whereas deuterium-deuterium reactions---the ones studied at
Princeton until last week---release only 3.2 MeV of surplus energy.
The trouble with tritium is that it is radioactive and has to be
produced artificially.  The short burst of fusion at TFTR lasted only
about one second; furthermore, despite the high power output more
energy was put into initiating the fusion than was gotten out of it.
(The Washington Post, 11 Dec.)

SOLAR WIND SPEEDS are twice as great (800 km/sec) at a latitude
of 45 degrees south as in the plane of the ecliptic, new Ulysses
measurements show.  The Ulysses spacecraft, on its way toward a
point beneath the sun's southern pole, does not look at the 5000-K
photosphere, the sun we see with our eyes, but rather at the much
hotter (millions of K) corona; it studies the magnetic fields and the
particles cast out by the sun in a part of the solar system where no
probe has ever been before.  Ulysses scientists (Ed Smith of JPL and
others), who spoke at last week's meeting of the American
Geophysical Union in San Francisco, have discovered that shock
waves, set up when certain fast gusts of solar wind overtake slower
gusts, can accelerate ionized atoms that have entered the solar system
from the interstellar medium.  It was previously thought that these
"anomalous cosmic rays" originated only in the outer precincts of the
solar system.

MANTLE PLUMES CONTAIN RECYCLED OCEAN CRUST AND
SEDIMENT, William M. White of Cornell University reported at the
AGU meeting.  Mantle plumes are the upwellings of hot rock that
originate either at the boundary between the mantle and the core 2900
km below the surface, or at a convective boundary (if one exists)
between the upper and lower mantle, which seismic measurements
suggest may be located 660 km below the surface.  Measurements of
the lead-to-cerium ratio in volcanic rock originating from plumes in
the Society Islands, which include Tahiti, led White's team to
conclude that some of the material must have been part of the ocean
floor in the past.  These findings suggest a picture whereby ocean
slabs sink very deeply into the mantle, only to re-emerge on the
surface as material in mantle plumes.  Earlier this year, Jon D.
Woodhead of Australian National University and his colleagues made
a similar conclusion through analysis of oxygen isotope ratios from
igneous rocks studied in a volcanic region near Pitcairn Island.

THE FIRST OBSERVED TRANSIT OF MERCURY across the sun's
corona was recorded by the x-ray satellite Yokhoh.  A series of
pictures show the tiny planet below the limb of the sun and
silhouetted against the bright x-ray glow of the corona.  (Science, 19
Nov.)