EGUsphere EGUsphere EGUsphere EGUsphere Copernicus Publications Göttingen, Germany 10.5194/egusphere-2026-2344 The composite radar-GNSS spectrum of auroral plasma turbulence Ivarsen Magnus F. https://orcid.org/0000-0003-3116-6209 1 2 Song Kaili 3 Spogli Luca https://orcid.org/0000-0003-2310-0306 4 St-Maurice Jean-Pierre 1 5 Huyghebaert Devin Ray https://orcid.org/0000-0002-4257-4235 6 1 Pitzel Brian 1 Marei Saif 1 Shen Yangyang https://orcid.org/0000-0003-1969-5597 7 Kasahara Satoshi https://orcid.org/0000-0002-3479-772X 8 Keika Kunihiro 8 Miyoshi Yoshizumi https://orcid.org/0000-0001-7998-1240 9 Hori Tomo 9 Shinbori Atsuki 9 Yamamoto Kazuhiro 9 Themens David Russel 10 Jayachandran P. Thayyil 3 Kazama Yoichi 11 Wang Shiang-Yu 11 Matsuoka Ayako https://orcid.org/0000-0001-5777-9711 12 Shinohara Iku 13 Mitani Takefumi 13 Takashima Takeshi 13 Yokota Shoichiro 14 Kasahara Yoshiya 15 Hussey Glenn 1 Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Canada The European Space Agency Centre for Earth Observation, Frascati, Italy Physics Department, University of New Brunswick, Fredericton, Canada Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy Department of Physics and Astronomy, University of Western Ontario, London, Canada Leibniz Institute of Atmospheric Physics, Kühlungsborn, Germany Department of Physics, University of Alberta, Edmonton, Canada Department of Earth and Planetary Science, University of Tokyo, Tokyo, Japan Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan School of Engineering, University of Birmingham, Birmingham, UK Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan Data Analysis Center for Geomagnetism and Space Magnetism, Kyoto University, Kyoto, Japan Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan Department of Earth and Space Science, Osaka University, Toyonaka, Japan Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan 21 05 2026 2026 1 37 Copyright: © 2026 Magnus F. Ivarsen et al. 2026 This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/ This article is available from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2344/ The full text article is available as a PDF file from https://egusphere.copernicus.org/preprints/2026/egusphere-2026-2344/egusphere-2026-2344.pdf

In the auroral ionosphere, plasma turbulence acts as an important dissipation mechanism for magnetospheric energy and the primary cause of radio wave scintillation. Characterizing auroral plasma turbulence across its full spatial extent has historically been limited by the narrow bandwidths of individual instruments. Our investigation approaches the problem of obtaining accurate, scale-dependent information using the physics of the Farley-Buneman (FB) instability, a modified two-stream plasma instability. In this study, we construct a composite spatial powerspectrum of plasma turbulence in the auroral electrojets spanning roughly four orders of magnitude in scale (from ~100 km down to ~20 m). This is achieved by combining a recent Monte-Carlo-based method of spatial clustering of very-high-frequency (VHF) radar echoes, with phase screen information derived from global navigation satellite system (GNSS) signals, using ground-based instrumentation in Canada. Through multi-instrument conjunctions with the European Swarm and Japanese Arase missions, we observe that the clustering of electrojet turbulence matches the structuring of field-aligned currents, and correlates with magnetospheric electron fluxes. Statistical analysis of the <em>composite</em> spectra, as well as a very large database of radar clustering spectra only, reveals a consistently steep decay of spectral power in the auroral electrojets, with the most probable spectral index being near &minus;8/3. The observations suggest a continuous, scale-invariant cascade that frequently preserves the spatial signature of its magnetospheric drivers, where we outline a way for Alfv&eacute;n waves to structure the turbulent E-region. Furthermore, we demonstrate that the plasma structures guilty of causing GPS scintillations (~270 meters in size) were moving at the ion acoustic speed, implying that those structures were, in fact, FB waves, and we thereby establish an observational basis for low-frequency electrojet turbulence. The method that we present, the composite radar-GNSS spectra, will on both counts offer useful empirical constraints for future efforts seeking to simulate the "sub-grid" turbulence that complicates the magnetosphere-ionosphere coupling around aurorae.

 European Space Agency 1000012348