2017 Cecelia Payne-Gaposchkin Medal and Prize

Professor Steven J Schwartz of Imperial College London, for his many contributions to shock waves, particle acceleration, and fundamental plasma phenomena in the Sun’s atmosphere, interplanetary medium, near-Earth environment and wider astrophysical contexts.

Professor Steven J Schwartz is a leading authority in space physics. The rarefied, ionised gases that make up the solar atmosphere, interplanetary medium, and environments of the planets and comets are paradigms for the dynamics and acceleration of particles in more distant astrophysical objects and in laboratory plasmas.

Schwartz has pioneered studies of the shockwave formed by the interaction of the Sun’s expanding supersonic corona, the solar wind, with the Earth’s magnetised outer reaches. In the absence of collisions, such shockwaves accelerate some particles to high energies and mediate the solar wind-terrestrial space weather, responsible for dazzling auroral displays and hazards both to space-borne technology and to humans in flight.

Schwartz has discovered violent interactions known as hot flow anomalies, quantified the amount of shock energy made available for electron and ion heating and for energetic particle acceleration, and was a pioneer in the interpretation of certain shockwaves as an inhomogeneous collection of isolated structures, which have a dramatic influence on the energisation of ions to high energies.

He continues to advance this field, playing a leading role in NASA’s Magnetospheric Multiscale (MMS) mission. His recent work includes an investigation into the rippled surface of collisionless shockwaves – such ripples are potential sites for electron acceleration. Their pulsed behaviour also feeds back into the processes that reflect a fraction of incident ions, thereby enhancing the seed particles for further shock acceleration.

Furthermore, Schwartz’s familiarity both with plasma instrumentation and a breadth of fundamental plasma physics has been an active force in MMS’s game-changing studies of magnetic reconnection.

His work has explored the way magnetic fields in real plasmas change their topologies via such reconnection. In rolled up Kelvin-Helmholtz vortices, reconnection gives rise to plasma exchange. At the smallest kinetic electron scales the patchy, rather than laminar, processes drive electric fields parallel to the magnetic field, leading to electron acceleration revealed by Schwartz’s analyses.

Schwartz was awarded the Royal Astronomical Society’s Chapman Medal in 2006.