Thursday, April 11, 2019 at 4:00 PM

JILA Auditorium

David Malaspina, LASP

"Plasma waves: micro-scale physics with macro-scale consequences "

Abstract:

We live in a universe of waves. In astrophysical objects, in the clouds overhead, in the beat of our hearts, the transport of energy is often mediated by waves. In space plasmas, waves occur both on large scales, where magnetohydrodynamics (MHD) can describe their behavior, and on small scales, where kinetic effects must be considered. The combined action of numerous small-scale wave-particle interactions can produce important macro-scale effects that cannot be understood using MHD alone, such as the generation of solar radio bursts and turbulent energy dissipation in collisionless plasmas.

The Heliosphere, the portion of space influenced by the Sun's stellar wind, contains a range of plasma environments that provide amazing natural laboratories for exploring small-scale plasma waves and their macro-scale consequences, including planetary ionospheres, magnetospheres, and the solar wind. This talk describes two of these regions, the Earth's radiation belts and the solar wind, where advances in spacecraft instrumentation have recently revealed dense populations of small-scale plasma waves and solitary structures.

In Earth's radiation belts, copious small-scale nonlinear plasma waves and solitary structures were identified using data from the Van Allen Probes mission. Together, these waves and structures represent a previously unconsidered class of wave-particle interaction in the inner magnetosphere capable of significantly influencing inner magnetospheric plasma dynamics.

In the solar wind, the recently launched Parker Solar Probe mission is providing the first in-situ observations of the near-Sun plasma environment. Preliminary data indicate a host of small-scale plasma waves that may be regulating macro-scale aspects of the solar wind's radial evolution.

In these regions and others, our understanding of the importance of small-scale plasma waves for the macro-scale evolution of plasma populations has only just begun.

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