A citizen-science catalogue of interplanetary Type III solar radio bursts and first statistical results

¹ LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS, 92190 Meudon, France
² Radboud Radio Lab, Department of Astrophysics, Radboud University Nijmegen, Nijmegen, The Netherlands
³ European Space Astronomy Centre, Madrid, Spain
⁴ Johns Hopkins University Applied Physics Laboratory (JHU/APL), North Laurel, Maryland, USA
⁵ NASA Goddard Space Flight Center (GSFC), Greenbelt, Maryland, USA
⁶ University of Maryland, Baltimore County (UMBC), Baltimore, Maryland, USA

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 5 February 2026
Accepted: 1 April 2026

Abstract

Aims. We present the first extensive catalogue of interplanetary Type III solar radio bursts compiled through human participation, and provide a statistical analysis of burst occurrence, peak flux, and frequency drift.

Methods. The catalogue is based on Radio and Plasma Waves (RPW) observations from Solar Orbiter, collected via the citizen science campaign Solar Radio Burst Tracker on Zooniverse.org with contributions from 1952 volunteers between February 2020 and March 2025. A dedicated post-processing pipeline extracted each burst’s time-frequency extent, peak flux, and quantitative uncertainties, enabling statistical analyses.

Results. The catalogue comprises 15 934 bursts. Burst occurrence strongly correlates with sunspot number and shows modulation with Solar Orbiter’s heliocentric distance. Peak flux distributions across 23 frequencies follow power laws with an average slope of –1.56 ± 0.004, steepening at higher frequencies. This is consistent with earlier studies of smaller samples. At still higher frequencies, slopes plateau around –1.7 to –1.8, resembling self-organized criticality behaviour. Burst occurrence peaks at 1-2 MHz, reflecting efficient electron-beam transport and beam-plasma interaction. Frequency drift rates for 13 074 bursts scale as df/dt = –0.001 f^1.37, differing from prior relations over other frequency ranges.

Conclusions. This human-validated, large-scale catalogue provides a robust statistical resource for Type III bursts, capturing solar cycle and observational effects, extending analyses to faint and complex events, and constraining frequency-dependent flux and drift rates. It also offers a benchmark for future automated and machine-learning detection methods.