GLE # 67 Event on 2 November 2003: An Analysis of the Spectral and Anisotropy Characteristics Using Verified Yield Function and Detrended Neutron Monitor Data

During Solar Cycle 23 16 ground-level enhancement events were registered by the global neutron monitor network. In this work we focus on the period with increased solar activity during late October – early November 2003 producing a sequence of three events, specifically on ground-level enhancement GLE 67 on 2 November 2003. On the basis of an analysis of neutron monitor and space-borne data we derived the spectra and pitch-angle distribution of high-energy solar particles with their dynamical evolution throughout the event. According to our analysis, the best fit of the spectral and angular properties of solar particles was obtained by a modified power-law rigidity spectrum and a double Gaussian, respectively. The derived angular distribution is consistent with the observations where an early count rate increase at Oulu neutron monitor with asymptotic viewing direction in the anti-Sun direction was registered. The quality of the fit and model constraints were assessed by a forward modeling. The event integrated particle fluence was derived using two different methods. The derived results are briefly discussed.

Very narrow coronal mass ejections producing solar energetic particles

Aims. Our main aim is to study the relationship between low-energy solar particles (energies below 1 MeV) and very narrow coronal mass ejections (“jets” with angular width ≤ 20°). Methods. For this purpose, we considered 125 very narrow coronal mass ejections (CMEs) from 1999 to 2003 that are potentially associated with low-energy solar particles (LESPs). These events were chosen on the basis of their source location. We studied only very narrow CMEs at the western limb, which are expected to have good magnetic connectivity with Earth. Results. We found 24 very narrow CMEs associated with energetic particles such as ions (protons and 3He), electrons, or both. We show that arrival times at Earth of energetic particles are consistent with onset times of the respective CMEs, and that in the same time intervals, there are no other potential sources of energetic particles. We also demonstrate statistical differences for the angular width distributions using the Kolmogorov–Smirnov test for angular widths for these 24 events. We consider a coherent sample of jets (mostly originating from boundaries of coronal holes) to identify properties of events that produce solar energetic particles (velocities, widths, and position angles). Our study presents a new approach and result: very narrow CMEs can generate low-energy particles in the vicinity of Earth without other activity on the Sun. The results could be very useful for space weather forecasting.