Longitudinal Properties of a Widespread Solar Energetic Particle Event on 2014 February 25: Evolution of the Associated Cme Shock

Abstract

We investigate the solar phenomena associated with the origin of the solar energetic particle (SEP) event observed on 2014 February 25 by a number of spacecraft distributed in the inner heliosphere over a broad range of heliolongitudes. These include spacecraft located near Earth; the twin Solar TErrestrial RElations Observatory spacecraft, STEREO-A and STEREO-B, located at ∼1 au from the Sun 153°west and 160°east of Earth, respectively; the MErcury Surface Space ENvironment GEochemistry and Ranging mission (at 0.40 au and 31°w est of Earth); and the Juno spacecraft (at 2.11 au and 48°east of Earth). Although the footpoints of the field lines nominally connecting the Sun with STEREO-A, STEREO-B and near-Earth spacecraft were quite distant from each other, an intense high-energy SEP event with Fe-rich prompt components was observed at these three locations. The extent of the extreme-ultraviolet wave associated with the solar eruption generating the SEP event was very limited in longitude. However, the white-light shock accompanying the associated coronal mass ejection extended over a broad range of longitudes. As the shock propagated into interplanetary space it extended over at least ∼190°i n longitude. The release of the SEPs observed at different longitudes occurred when the portion of the shock magnetically connected to each spacecraft was already at relatively high altitudes (2 R e above the solar surface). The expansion of the shock in the extended corona, as opposite to near the solar surface, determined the SEP injection and SEP intensity-time profiles at different longitudes.

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

“…However, recent studies have shown that even events on the far side of the Sun can produce particle detections at Earth, with studies by Rouillard et al (2012) and Lario et al (2016) suggesting that the global waves travelled across the Sun and eventually encountered field lines connected to Earth/L1. It has also been shown that particles can be detected despite being produced far from the footpoint of a magnetic field line connected to the spacecraft as a result of either super-radial spreading of field lines throughout the corona (e.g.…”

Solar flares, coronal mass ejections and solar energetic particle event characteristics

“…Thus, by linear fitting of the onset times as a function of the corresponding inverse velocity, estimates for both the solar release time (SRT) and the apparent path length of the particles can be obtained. The validity of the VDA method has been an item of active research by several authors (Lintunen & Vainio 2004;Sáiz et al 2005;Rouillard et al 2012;Vainio et al 2013), with the VDA method typically used to estimate the SRT of SEP events (Lario et al 2014(Lario et al , 2016. For the first time, in our analysis, we have incorporated in the VDA the new and improved E effective for each of the P2-P7 GOES energy channels that have been obtained by the cross-calibration of GOES/SEM with IMP-8/GME data (Sandberg et al 2014, their Tabs.…”

“…Recent observations by several spacecraft widely distributed in heliolongitude have allowed the observation of SEP events filling a broad region around the Sun (Richardson et al 2014;Lario et al 2016). The interpretations offered for such widespread events include: (a) the propagation of CME-driven shocks able to inject SEPs over broad angular regions (Rouillard et al 2012;Lario et al 2016); (b) the effective propagation of particles perpendicular to the direction of the interplanetary magnetic field (IMF), i.e. cross-field diffusion (Dresing et al 2012;Dröge et al 2014); (c) the perpendicular transport of particles through processes other than diffusion (Wiedenbeck et al 2012).…”

The density compression ratio of shock fronts associated with coronal mass ejections

“…There is a growing amount of evidence for the association of CME-driven shocks with SEPs in the corona (see recent papers, e.g., Rouillard et al, 2012Rouillard et al, , 2016Carley et al, 2013;Lario et al, 2014Lario et al, , 2016Salas-Matamoros et al, 2016, and references therein) but it remains unclear whether such shock waves are capable of accelerating particles at the observed energies Mancuso, 2010, 2011). An important shock parameter that could be accessible from coronagraphic observations is the ratio between the downstream and upstream electron densities or density compression ratio, X.…”

“…The upstream density is derived with two methods: using the Leblanc et al (1998) model and via the inversion of a pre-event polarized brightness image. The method is applied to two CMEs, on 2011 March 7 and 2014 February 25, associated with intense SEP events (Park et al, 2013;Lario et al, 2016).…”