A New Space Weather Faraday Cup and Large Scale Structures in the Solar Wind

Abstract

At the largest scales, the magnetized plasma of the solar wind is organized into stable streams that evolve and interact as they move out into interplanetary space while retaining signatures of their origins in the solar corona. In-situ ion observations at many scales and encompassing many species are necessary to develop a full picture of these structures' kinetic properties and propagation history. We pursue several avenues of analysis and instrument development to advance the quality and parameter range of these measurements.

We first develop a simple model of expanding spherical shells to characterize the impact of weak stream interactions on long studied linear relationships of bulk speed with density and temperature. Through validation of this model against many years of Wind/SWE FC spectra, we are able not only to report a new driver of variability in the solar wind but also empirically measure the polytropic index at a variety of timescales and extract ``pristine" solar wind conditions.

We then seek to improve the statistics of the HIS time-of-flight mass spectrometer aboard Solar Orbiter through dynamic setting of its proton avoidance threshold. Contributions to validation of its first releases of public data are also presented.

Finally, we present a series of Faraday cup design activities building up to the development and proposal of a novel Space Weather Faraday Cup. Performance of the RPA-style ion optic is demonstrated through an end-to-end model, including detection of bulk speeds up to 2500 km/s. The final design was submitted to NOAA's Space Weather Next L1 Series request for proposals.