The Arecibo NOON (coroNa tO sOlar wiNd) project

Abstract:

The best ground-based technique available to infer the solar wind speeds/density fluctuations from the outer corona to 1AU (and beyond), inside and outside the ecliptic, is the Interplanetary Scintillation (IPS) method. Analogous to the twinkling of visible stars in the night sky due to density variations in the Earth's atmosphere, IPS represents the rapid fluctuations in the phase and amplitude of the observed radio signal caused by the diffraction of its wave front as it propagates through the turbulent interplanetary and coronal plasma. To probe the region where the outer corona becomes solar wind using IPS technique, wavelengths shorter than the traditional few MHz observations becomes necessary. The Arecibo Observatory, an NSF facility located in Puerto Rico, is one of the world's most sensitive radio telescopes available and permits observations between 327 MHz and 10 GHz, with high sensitivity and high spectral/time resolutions, becoming a unique facility to be used for the IPS purpose. Our team is systematically using the IPS multi-frequency Arecibo capability to monitoring the coronal and interplanetary plasma structures since 2018, enabling the combination of this remote sensing data with the new in-situ data from space missions. The compilation of the first results will be presented here and represents the base for an annual Arecibo NOON project, planned to happen between 2021 and 2025, monitoring the space plasma within 20 solar radii every year. The NOON project 5 years results will provide global context and optimization of the interpretation of the solar wind in-situ data from space missions and will be crucial to understand the evolution of the coronal plasma parameters in the Alfvenic region along the solar cycle 25, enabling the better characterization of the background quiescent plasma regime and improving our understanding of the role of turbulence and waves in the solar wind acceleration process as well as heat dissipation and coronal heating.