Energetic electrons: an ozone killer?

Energetic electrons: An ozone killer?

High-energy electrons riding the earth's magnetic field lines,40,000 kilometers above the surface of the planet, have already been implicated in the malfunctions and failures of several satellites. Now, scientists from the Los Alamos (N.M.) National Laboratory propose that these electrons rain down from their high-flying orbits and possibly contribute to the loss of stratospheric ozone over Antarctica each year (SN: 5/23/87, p.326). Scientists are concerned with stratospheric ozone because it protects life on earth by absorbing harmful ultraviolet radiation from the sun.

Large populations of these electrons regularly appeared inthe earth's magnetosphere every 27 days from late 1981 to 1984, a time that corresponds to a minimum in the 11-year cycle of sunspot activity. In recent years, as the solar cycle builds toward a maximum, the Los Alamos scientists have measured smaller, less periodic fluxes of these electrons, which travel at nearly the speed of light.

Most of the electrons remain trapped in the magnetosphere,but a small portion of them could precipitate out near the earth's poles and penetrate as far down into the atmosphere as 40 km above the surface, Los Alamos's Dan Baker reported at a recent meeting in Baltimore of the American Geophysical Union. These electrons would then ionize air molecules and in turn produce odd nitrogen compounds, which catalytically remove ozone from the stratosphere. In support of this theory, Baker points to a correlation between the years of greatest ozone loss and largest electron fluxes.

Researchers are unsure of the source of the acceleratedelectrons. In one proposed mechanism, solar winds energize electrons already present in the earth's magnetosphere. A rival theory relies on electrons that originate outside the magnetosphere and are accelerated by Jupiter's magnetic field.