It was recognized at the very outset of the space age that a complete description and understanding of plasmas in space would only be achieved if electric fields (from DC to high frequencies) could be measured together with the particle fluxes and the magnetic fields. Professor Forrest Mozer, an eminent and groundbreaking space physics member of AGU, is the recipient of the 2018 John Adam Fleming Medal. Professor Mozer invented and pioneered the flight of the spherical double-probe techniques that revolutionized experimental space plasma research, techniques that are continuing to make major advances in the field to the present.
Without the electric fields, essential physical quantities such as the Poynting flux could not be determined in the plasmas. Unlike most particle fluxes and magnetic fields, electric fields are generally much more difficult to measure because spacecraft carrying instruments can easily disturb the fields. Early space-age discussions involved the possible feasibility of using electron beams and long antennae of various types. However, double probes proved from the outset to be far superior. In addition to his double-probe innovations, Professor Mozer also was the first to develop and fly (on the International Sun-Earth Explorer 1 (ISEE-1) Earth-orbiting spacecraft) a burst memory device for the capture of waveform bursts (electric and magnetic), which included the first microprocessor flown in space in a science experiment. Such waveform capture, generally triggered by a large-amplitude wave, has become essential in experimental magnetosphere research to return electric (and magnetic) field data that would otherwise be lost and thus not available for complete physical interpretation and application to theory.
Professor Mozer, his students and his colleagues, and, eventually, investigators around the world have employed his electric field and waveform capture inventions and subsequent improvements to make fundamental contributions in many areas of space plasma physics. For example, it was long recognized that electrons and ions produce aurora emissions. Professor Mozer and his students and colleagues, using data from his instruments, discovered that electrostatic shocks (at altitudes of ~1 Earth radius) accelerated the electrons downward into the atmosphere to make discrete auroras. He also discovered double layers and solitary waves in the plasmas in auroral regions and their relevance for acceleration processes.
Without Mozer’s double-probe and waveform burst techniques flown on many spacecraft (including the recent Cluster, Time History of Events and Macroscale Interactions during Substorms (THEMIS), Van Allen Probes, and Magnetospheric Multiscale (MMS) missions), instances of space plasma reconnection and their physical nature would not have been identified or understood. The very first measurements of the Hall electric field at Earth’s magnetopause were possible because of the double-probe technique. More recently, on the MMS spacecraft, he and his colleagues measured the parallel acceleration of electrons by Fermi reflection from time domain structures in reconnection regions.
In addition to his pioneering contributions over more than 5 decades in space plasma physics, Professor Mozer invented and patented in 1974 the first integrated circuit speech synthesizer in a commercial product. This was motivated in part by his mentoring of a sight-challenged physics graduate student. As an entrepreneur he has cofounded two companies to develop and market speech systems. Professor Mozer, a true Renaissance physicist, amply deserves the John Adam Fleming Medal recognition by AGU.
—Louis J. Lanzerotti, New Jersey Institute of Technology, Newark; also at Alcatel-Lucent Bell Laboratories (retired), Murray Hill, N.J.
