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Shock Connectivity in the August 2010 and July 2012 Solar Energetic Particle Events Inferred from Observations and ENLIL Modeling  

Hazel Bain   Submitted: 2016-06-28 13:36

During periods of increased solar activity, coronal mass ejections (CMEs) can occur in close succession and proximity to one another. This can lead to the interaction and merger of CME ejecta as they propagate in the heliosphere. The particles accelerated in these shocks can result in complex solar energetic particle (SEP) events, as observing spacecraft form both remote and local shock connections. It can be challenging to understand these complex SEP events from in situ profiles alone. Multipoint observations of CMEs in the near-Sun environment, from the Solar Terrestrial Relations Observatory-Sun Earth Connection Coronal and Heliospheric Investigation and the Solar and Heliospheric Observatory Large Angle and Spectrometric Coronagraph, greatly improve our chances of identifying the origin of these accelerated particles. However, contextual information on conditions in the heliosphere, including the background solar wind conditions and shock structures, is essential for understanding SEP properties well enough to forecast their characteristics. Wang-Sheeley-Arge WSA-ENLIL + Cone modeling provides a tool to interpret major SEP event periods in the context of a realistic heliospheric model and to determine how much of what is observed in large SEP events depends on nonlocal magnetic connections to shock sources. We discuss observations of the SEP-rich periods of 2010 August and 2012 July in conjunction with ENLIL modeling. We find that much SEP activity can only be understood in the light of such models, and in particular from knowing about both remote and local shock source connections. These results must be folded into the investigations of the physics underlying the longitudinal extent of SEP events, and the source connection versus diffusion pictures of interpretations of SEP events.

Authors: H. M. Bain, M. L. Mays, J. G. Luhmann, Y. Li, L. K. Jian, and D. Odstrcil
Projects: ACE,SoHO-LASCO,STEREO

Publication Status: Published
Last Modified: 2016-06-29 13:47
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Radio Imaging of Shock-accelerated Electrons Associated with an Erupting Plasmoid on 2010 November 3  

Hazel Bain   Submitted: 2012-05-03 12:32

We present observations of a metric type II solar radio burst that occurred on the 3rd of November 2010 in association with an erupting plasmoid. The eruption was well observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory and the Reuven Ramaty High Energy Solar Spectroscopic Imager, while the burst occurred in the frequency range of the Nançay Radioheliograph (NRH). Such events, where the type II emission occurs in the NRH frequency range, allowing us to image the burst, are infrequent. Combining these data sets, we find that the type II is located ahead of the hot (~11 MK) core of the plasmoid, which is surrounded by a well-defined envelope of cool (few MK) plasma. Using two methods, we determine the propagation velocity of the shock: (1) fitting the type II emission observed in PHOENIX and HUMAIN radio spectrogram data; (2) direct imaging of the type II source location using NRH observations. We use LASCO C2 polarized brightness images to normalize our coronal density model. However, we find that information from imaging is required in order to fine-tune this normalization. We determine a shock propagation velocity between 1900 km s-1 and 2000 km s-1. This is faster than the plasmoid observed at extreme-ultraviolet wavelengths by AIA (v = 670-1440 km s-1, where the cooler plasma propagates faster than the hot core). The positioning of the type II, ahead of the plasmoid, suggests that the electrons are accelerated in a piston-driven shock.

Authors: Bain, H. M.; Krucker, Säm; Glesener, L.; Lin, R. P.
Projects: Nançay Radioheliograph,RHESSI,SDO-AIA

Publication Status: Accepted
Last Modified: 2012-05-04 15:01
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Shock Connectivity in the August 2010 and July 2012 Solar Energetic Particle Events Inferred from Observations and ENLIL Modeling
Radio Imaging of Shock-accelerated Electrons Associated with an Erupting Plasmoid on 2010 November 3

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