Number 167, March 3, 1994 by Phillip F. Schewe and Ben Stein
CORONAL MASS EJECTIONS VS. SOLAR FLARES . John Gosling of Los Alamos
believes that many strong solar phenomena such as geomagnetic storms and
shock waves in the solar wind are actually a result of coronal mass ejections
(CME's) and not solar flare activity. During a CME up to 10**16 grams of
matter from the corona (the very hot region above the sun's surface) are
thrown out into space at speeds up to 1200 km/sec. The appearance of CME's,
like that of other solar phenomena, is related to the 11-year solar cycle,
and indeed some CME's and flares (and other eruptions) appear at nearly
the same time. Gosling contends, however, that a careful analysis of the
intensity, energy, and temporal characteristics of many prominent events
in the solar-terrestrial environment shows that they are caused by CME's,
not by flares. CME's are poorly understood, Gosling says, because they
are difficult to measure, particularly Earth-bound ejections (those which
would have the greatest effect on the near-Earth space environment) which
proceed amid the glare of sunlight. (Nature, 17 Feb. 1994.)
SEARCHING FOR ANTIPROTON DECAY is harder than searching for proton decay.
Proton stability can be studied by using vast underground tanks of fluids;
such experiments have pushed the proton's measured lifetime to at least
10**32 years. Antiprotons, in contrast, must be created artificially at
accelerators and can be stored in comparatively small numbers. The most
stringent previous antiproton lifetime limit was 3.4 months. Now scientists
at Fermilab has established new higher limits for a variety of possible
decay modes, such as 1848 years for antiproton decay into a positron plus
a photon and 554 years for decay into a positron and a pion. Theorists
expect that the lifetime of the proton and antiproton would be identical,
but this has to be confirmed experimentally. (S. Geer et al., UPCOMING
ARTICLE in Physical Review Letters, 14 Mar. 1994.)
DETERMINING THE NATURE OF CHEMICAL BONDS AT NEAR-ATOMIC RESOLUTION in
the interfaces of inorganic solids is now possible using a combination
of electron microscopy techniques. First, columns of atoms at an interface
are imaged at sub-nm resolution using scanning transmission electron microscopy
(STEM). Then information about the electronic states of atoms in the column
are obtained through a technique known as electron energy-loss spectroscopy
(EELS), in which a beam of electrons is sent down a specified column, after
which the energy spectrum of the scattered electrons is measured. Philip
Batson of IBM images layers of silicon atoms at a silicon-silicon dioxide
interface and can deduce the chemical bonding states for silicon atoms
from layer to layer. Meanwhile, David Muller at Cornell maps columns of
carbon atoms between a diamond film and a silicon substrate. He finds that
the carbon bonding states change between columns over a distance of less
than 1 nm and that the diamond grows on an amorphous carbon layer, ruling
out other proposed scenarios. This technique is likely to be a useful tool
for studying and controlling properties of inorganic thin films as well
as grain boundaries in metals and ceramics (Nature, 23/30 Dec. 1993). Furthermore,
the combined use of STEM and EELS should result in the ability to map the
presence of trace elements at a level of 10 parts per million in 10-nm-wide
regions. (Science News, 26 Feb. 1994.)
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