Ion Energization, Heating and Outflow in Broadband Electromagnetic Waves above the High Latitude Ionosphere

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Earth’s electrically charged upper atmosphere streams outward into near-Earth space at a rate determined by space weather conditions. This outflow has profound effects on the response of the near-Earth space environment to disturbances emanating from the Sun. This response can affect critical infrastructure both on the ground and in space. At high latitudes, the outflow is driven by interactions with fluctuating electromagnetic fields that energize positively charged particles known as ions. This research characterizes how this energization operates. It uses measurements of the energized outflowing ions, the background plasma through which these ions stream, and the electromagnetic fields to characterize the physics of the interactions that drive the outflow. For broader impact, this research advances the understanding of a critical yet largely unresolved component in the sequence of phenomena that characterize the response of Earth’s near-space environment to space weather events. While promoting the progress of science, this research will support the training of a young scientist and student in the field of space physics. This field is an expanding area of increasing importance for the nation's prosperity, welfare, and defense as we become ever more dependent on space-based assets. The outflow of energized ions from the high-latitude ionosphere is one of the defining features of magnetosphere-ionosphere coupling. Global simulations of the near-Earth space environment have, in recent years, demonstrated just how vital this coupling is for defining the response of the magnetosphere to space weather events. While ion outflows are primarily driven by broadband plasma waves, models characterizing the physics of the underlying wave-particle interaction are not well constrained from observations and are often reduced to empirical scaling laws relating wave energy inputs to outflow rates. This research uses observations from the FAST spacecraft through the altitude range where outflows are initiated and energized to resolve the spatio-temporal characteristics of the wavefields and the energization of the outflowing ion populations within them. The goal of the project is to use these observations to create an empirically derived physical model for ion heating in broad-band EM waves defined by the measured spatio-temporal wave spectrum. This effort will provide parameterized, physics based, expressions for ion heating rates that are observationally verified and suitable for use in global simulations of near-Earth space. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.