Subsecond Spikes in Fermi GBM X-ray Flux as a Probe for Solar Flare Particle Acceleration

Abstract

Solar flares are known to release a large amount of energy into accelerating electrons. Studying small timescale ($\le$ 2s) fluctuations in nonthermal X-ray flux offers the opportunity to probe the nature of those acceleration mechanisms. By comparing the durations, differences in timing between energy bands, and the periodicity of these spikes against the relevant timescales called for by various acceleration mechanisms, a test for each mechanism's validity can be made. This work details the analysis of fast fluctuations in Fermi Gamma-ray Burst Monitor (Fermi GBM) data from 2 M9.3 class solar flares that occurred on SOL2011-07-30 and SOL2011-08-04. This study shows the usefulness of Fermi GBM data as a means of examining these small timescale spikes and presents a rigorous method of identifying, counting, and measuring the temporal properties of these subsecond X-ray spikes. In the 2 flares examined we found spikes to primarily occur in spans of 60-100 seconds in the impulsive phase. The relative spike intensity ranged from 5% to 46% of the total counts, depending on the energy band the spike was measured in. The average spike durations were 0.96 and 0.66 seconds and the median durations were 0.79 and 0.32 seconds for the 2 flares. The spike duration distribution for the SOL2011-08-04 flare was found to follow a power law with a -1.8 $\pm$ 0.5 index. Of the 3 spiking intervals identified, only 1 was found to have a periodicity, showing significant power at the 1.7 $\pm$ 0.1 Hz frequency.

arXiv comment24 pages, 12 figures, 2 tables; Accepted by ApJ

References in corpus (13)

• The Fermi Gamma-Ray Burst Monitor
• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Impulsive phase flare energy transport by large-scale Alfven waves and the electron acceleration problem
• Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
• Fermi acceleration at fast shock in a solar flare and impulsive loop-top hard X-ray source
• Periodic Acceleration of Electrons in the 1998 November 10 Solar Flare
• Oscillatory processes in solar flares
• Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares
• Determination of Stochastic Acceleration Model Characteristics in Solar Flares
• Solar flare hard X-ray spikes observed by RHESSI: a case study
• Electron Acceleration and Jet-Facilitated Escape in an M Class Solar Flare on 2002 August 19
• Solar flare hard X-ray spikes observed by RHESSI: a statistical study
• Rapid Variability in the SOL2011-08-04 Flare: Implications for Electron Acceleration

Cited by in corpus (11)

• The Atmospheric Response to High Nonthermal Electron Beam Fluxes in Solar Flares. II. Hydrogen Broadening Predictions for Solar Flare Observations with the Daniel K. Inouye Solar Telescope
• Modeling Electron Acceleration and Transport in the Early Impulsive Phase of the 2017 September 10 Solar Flare
• Localising pulsations in the hard X-ray and microwave emission of an X-class flare
• Characterising fast-time variations in the hard X-ray time profiles of solar flares using Solar Orbiter's STIX
• Radio and X-ray Observations of Short-lived Episodes of Electron Acceleration in a Solar Microflare
• Localizing short-period pulsations in hard X-rays and Gamma-rays during an X9.0 flare
• Magnetic Energy Powers the Corona: How We Can Understand its 3D Storage & Release
• Geant4 Modeling of a Cerium Bromide Scintillator Detector for the IMPRESS CubeSat Mission
• HEL1OS -- A Hard X-ray Spectrometer on Board Aditya-L1
• Detecting fast-variation pulsations in solar hard X-ray and radio emissions
• Sun CubE OnE: A Multi-wavelength Synoptic Solar Micro Satellite