North/South Hemispheric Periodicities in the >25 MeV Solar Proton Event Rate During the Rising and Peak Phases of Solar Cycle 24

Abstract

We present evidence that $>25$ MeV solar proton events show a clustering in time at intervals of $\approx$ six months that persisted during the rising and peak phases of Solar Cycle 24. This phenomenon is most clearly demonstrated by considering events originating in the northern or southern solar hemispheres separately. We examine how these variations in the solar energetic particle (SEP) event rate are related to other phenomena, such as hemispheric sunspot numbers and areas, rates of coronal mass ejections, and the mean solar magnetic field. Most obviously, the SEP event rate closely follows the sunspot number and area in the same hemisphere. The $\approx$ six-month variations are associated with features in many of the other parameters we examine, indicating that they are just one signature of the episodic development of Cycle 24. They may be related to the "$\approx$150~day" periodicities reported in various solar and interplanetary phenomena during previous solar cycles. The clear presence of $\approx$six-month periodicities in Cycle 24 that evolve independently in each hemisphere conflicts with a scenario suggested by McIntosh et al. (2015, Nature Com. 6, 6491) for the variational time scales of solar magnetism.

References in corpus (5)

• Why Is the Great Solar Active Region 12192 Flare-Rich But CME-Poor?
• The Solar Energetic Particle Event on 2013 April 11: An Investigation of its Solar Origin and Longitudinal Spread
• Confined Flares in Solar Active Region 12192 from 2014 October 18 to 29
• The Properties of Solar Energetic Particle Event-Associated Coronal Mass Ejections Reported in Different CME Catalogs
• Coronal Mass Ejections and the Solar Cycle Variation of the Sun's Open Flux

Cited by in corpus (6)

• Solar-Cycle Characteristics in Kodaikanal Sunspot Area: North--South Asymmetry, Phase Distribution and Gnevyshev Gap
• 25 MeV Solar Proton Events in Cycle 24 and Previous Cycles
• Variation of Coronal Activity from the Minimum to Maximum of Solar Cycle 24 using Three Dimensional Coronal Electron Density Reconstructions from STEREO/COR1
• Temporal evolutions and quasi-periodic variations present in the sunspot number and group sunspot area data measured at Kodaikanal Observatory for solar cycles 14 to 24
• Forecasting Solar Energetic Proton Integral Fluxes with Bi-Directional Long Short-Term Memory Neural Networks
• Solar Energetic Particle-Associated Coronal Mass Ejections Observed by the Mauna Loa Solar Observatory Mk3 and Mk4 Coronameters