The Longitudinal Properties of a Solar Energetic Particle Event Investigated Using Modern Solar Imaging

Creators: Rouillard, A. P.; Sheeley, N. R., Jr.; Tylka, A.; Vourlidas, A.; Ng, C. K.; Rakowski, C.; Cohen, C. M. S.; Mewaldt, R. A.; Mason, G. M.; Reames, D.; Savani, N. P.; StCyr, O. C.; Szabo, A.

Abstract

We use combined high-cadence, high-resolution, and multi-point imaging by the Solar-Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory to investigate the hour-long eruption of a fast and wide coronal mass ejection (CME) on 2011 March 21 when the twin STEREO spacecraft were located beyond the solar limbs. We analyze the relation between the eruption of the CME, the evolution of an Extreme Ultraviolet (EUV) wave, and the onset of a solar energetic particle (SEP) event measured in situ by the STEREO and near-Earth orbiting spacecraft. Combined ultraviolet and white-light images of the lower corona reveal that in an initial CME lateral "expansion phase," the EUV disturbance tracks the laterally expanding flanks of the CME, both moving parallel to the solar surface with speeds of ~450 km s^(–1). When the lateral expansion of the ejecta ceases, the EUV disturbance carries on propagating parallel to the solar surface but devolves rapidly into a less coherent structure. Multi-point tracking of the CME leading edge and the effects of the launched compression waves (e.g., pushed streamers) give anti-sunward speeds that initially exceed 900 km s^(–1) at all measured position angles. We combine our analysis of ultraviolet and white-light images with a comprehensive study of the velocity dispersion of energetic particles measured in situ by particle detectors located at STEREO-A (STA) and first Lagrange point (L1), to demonstrate that the delayed solar particle release times at STA and L1 are consistent with the time required (30-40 minutes) for the CME to perturb the corona over a wide range of longitudes. This study finds an association between the longitudinal extent of the perturbed corona (in EUV and white light) and the longitudinal extent of the SEP event in the heliosphere.

Additional Information

© 2012 American Astronomical Society. Received 2012 January 6; accepted 2012 March 9; published 2012 May 24. We thank Dennis Haggerty for providing the EPAM ion data plotted in Figure 13. We thank Dr. Valtonen for making the ERNE data available online. The SECCHI images were obtained from the World Data Center, Chilton, UK and the Naval Research Laboratory, Washington, DC, USA. We thank Yi-Ming Wang and Judith Lean for their continual support. We also acknowledge constructive exchanges with Ed Cliver and Raúl Gómez Herrero. The STEREO SECCHI data are produced by a consortium of RAL (UK), NRL (USA), LMSAL (USA), GSFC (USA), MPS (Germany), CSL (Belgium), IOTA (France), and IAS (France). The ACE data were obtained from the ACE science center. The Wind data were obtained from the Space Physics Data Facility. The work of C.M.S.C. and R.A.M. on ACE data was partly funded by the NASA contract NNX08AI11G. The Caltech subcontract SA2715-26309 was funded with NASA contract NAS5-0313 (UC Berkeley). The work of A.P.R. was partly funded by NASA contracts NNX11AD40G-45527 and NNXIOAT06G and that of C.K.N. was partially supported by NASA grant NNX09AU98G. NASA contract SA4889-26309 from University of Berkeley (STEREO SIT) and NASA grant NMX07AN45G permitted the preparation and calibration of the ULEIS and SIT data. A.J.T. was supported in part by NASA grant NNH09AK79I. The NRL employees acknowledge support from the Office of Naval Research and NASA.

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