Spectral Analysis of the September 2017 Solar Energetic Particle Events
arXiv:1902.03969 · doi:10.1029/2018SW002085
Abstract
An interval of exceptional solar activity was registered in early September 2017, late in the decay phase of solar cycle 24, involving the complex Active Region 12673 as it rotated across the western hemisphere with respect to Earth. A large number of eruptions occurred between 4-10 September, including four associated with X-class flares. The X9.3 flare on 6 September and the X8.2 flare on 10 September are currently the two largest during cycle 24. Both were accompanied by fast coronal mass ejections and gave rise to solar energetic particle (SEP) events measured by near-Earth spacecraft. In particular, the partially-occulted solar event on 10 September triggered a ground level enhancement (GLE), the second GLE of cycle 24. A further, much less energetic SEP event was recorded on 4 September. In this work we analyze observations by the Advanced Composition Explorer (ACE) and the Geostationary Operational Environmental Satellites (GOES), estimating the SEP event-integrated spectra above 300 keV and carrying out a detailed study of the spectral shape temporal evolution. Derived spectra are characterized by a low-energy break at few/tens of MeV; the 10 September event spectrum, extending up to ~1 GeV, exhibits an additional rollover at several hundred MeV. We discuss the spectral interpretation in the scenario of shock acceleration and in terms of other important external influences related to interplanetary transport and magnetic connectivity, taking advantage of multi-point observations from the Solar Terrestrial Relations Observatory (STEREO). Spectral results are also compared with those obtained for the 17 May 2012 GLE event.
arXiv commentAccepted for publication in Space Weather; 24 pages, 10 figures, 1 table
References in corpus (18)
- A Unified Approach to the Classical Statistical Analysis of Small Signals
- Microwave and Hard X-Ray Observations of the 2017 September 10 Solar Limb Flare
- Spectroscopic Observations of Current Sheet Formation and Evolution
- Deriving the properties of coronal pressure fronts in 3-D: application to the 17 May 2012 ground level enhancement
- Observations of the December 13 and 14, 2006, Solar Particle Events in the 80 MeV/n - 3 GeV/n range from space with PAMELA detector
- Observations of an Eruptive Solar Flare in the Extended EUV Solar Corona
- Solar energetic particle events observed by the PAMELA mission
- Modeling the evolution and propagation of the 2017 September 9th and 10th CMEs and SEPs arriving at Mars constrained by remote-sensing and in-situ measurement
- Why the Shock-ICME Complex Structure is Important: Learning From the Early 2017 September CMEs
- Extreme Kinematics of the 2017 September 10 Solar Eruption and the Spectral Characteristics of the Associated Energetic Particles
- Fermi-LAT observations of the 2017 September 10 solar flare
- PAMELA's Measurements of Magnetospheric Effects on High Energy Solar Particles
- The Properties of Solar Energetic Particle Event-Associated Coronal Mass Ejections Reported in Different CME Catalogs
- Calibration of the GOES-13/15 high energy proton detectors based on the PAMELA solar energetic particle observations
- Plasma evolution within an erupting coronal cavity
- Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017
- A Hierarchical Relationship between the Fluence Spectra and CME Kinematics in Large Solar Energetic Particle Events: A Radio Perspective
- Powerful Solar Flares of September 2017: Correspondence Between Parameters of Microwave Bursts and Proton Fluxes near Earth
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- CME-CME Interactions as Sources of CME Geo-effectiveness: The Formation of the Complex Ejecta and Intense Geomagnetic Storm in Early September 2017
- Microwave Spectral Imaging of an Erupting Magnetic Flux Rope: Implications for the Standard Solar Flare Model in Three Dimensions
- Comparing Long-Duration Gamma-Ray Flares and High-Energy Solar Energetic Particles
- Empirical Model of 10-130 MeV Solar Energetic Particle Spectra at 1 AU Based on Coronal Mass Ejection Speed and Direction
- Modeling the 10 September 2017 solar energetic particle event using the iPATH model
- Double-power-law feature of energetic particles accelerated at coronal shocks
- The magnetic field environment of active region 12673 that produced the energetic particle events of September 2017
- Space weather: the solar perspective -- an update to Schwenn (2006)
- Characteristics of SEPs during Solar Cycle 21-24
- Interplanetary Radio Emission: A Summary of Recent Results