A Hierarchical Relationship between the Fluence Spectra and CME Kinematics in Large Solar Energetic Particle Events: A Radio Perspective

Abstract

We report on further evidence that solar energetic particles are organized by the kinematic properties of coronal mass ejections (CMEs)[1]. In particular, we focus on the starting frequency of type II bursts, which is related to the distance from the Sun where the radio emission starts. We find that the three groups of solar energetic particle (SEP) events known to have distinct values of CME initial acceleration, also have distinct average starting frequencies of the associated type II bursts. SEP events with ground level enhancement (GLE) have the highest starting frequency (107 MHz), while those associated with filament eruption (FE) in quiescent regions have the lowest starting frequency (22 MHz); regular SEP events have intermediate starting frequency (81 MHz). Taking the onset time of type II bursts as the time of shock formation, we determine the shock formation heights measured from the Sun center. We find that the shocks form on average closest to the Sun (1.51 Rs) in GLE events, farthest from the Sun in FE SEP events (5.38 Rs), and at intermediate distances in regular SEP events (1.72 Rs). Finally, we present the results of a case study of a CME with high initial acceleration (~3 km s^-2) and a type II radio burst with high starting frequency (~200 MHz) but associated with a minor SEP event. We find that the relation between the fluence spectral index and CME initial acceleration continues to hold even for this minor SEP event.

11 pages, 7 figures, 1 table, to appear in Journal of Physics: Conference Series (JPCS), Proceedings of the 16th Annual International Astrophysics Conference held in Santa Fe, NM, 2017

References in corpus (4)

• Major Solar Eruptions and High Energy Particle Events during Solar Cycle 24
• Large Solar Energetic Particle Events Associated with Filament Eruptions Outside of Active Regions
• The 2012 July 23 Backside Eruption: An Extreme Energetic Particle Event?
• A critical Mach number for electron injection in collisionless shocks

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• Comparing Long-Duration Gamma-Ray Flares and High-Energy Solar Energetic Particles
• The Common Origin of High-energy Protons in Solar Energetic Particle Events and Sustained Gamma-ray Emission from the Sun
• Global Energetics of Solar Flares: VII. Aerodynamic Drag in Coronal Mass Ejections
• Forecasting Solar Energetic Proton Integral Fluxes with Bi-Directional Long Short-Term Memory Neural Networks
• Space weather: the solar perspective -- an update to Schwenn (2006)