The unusual widespread solar energetic particle event on 2013 August 19. Solar origin and particle longitudinal distribution. (arXiv:2107.10257v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_Garcia_L/0/1/0/all/0/1">L. Rodríguez-García</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gomez_Herrero_R/0/1/0/all/0/1">R. Gómez-Herrero</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zouganelis_I/0/1/0/all/0/1">I. Zouganelis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Balmaceda_L/0/1/0/all/0/1">L. Balmaceda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nieves_Chinchilla_T/0/1/0/all/0/1">T. Nieves-Chinchilla</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dresing_N/0/1/0/all/0/1">N. Dresing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dumbovic_M/0/1/0/all/0/1">M. Dumbovic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nitta_N/0/1/0/all/0/1">N. V. Nitta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carcaboso_F/0/1/0/all/0/1">F. Carcaboso</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Santos_L/0/1/0/all/0/1">L.F.G. dos Santos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jian_L/0/1/0/all/0/1">L. K. Jian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mays_L/0/1/0/all/0/1">L. Mays</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Williams_D/0/1/0/all/0/1">D. Williams</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_Pacheco_J/0/1/0/all/0/1">J. Rodríguez-Pacheco</a>
Context: Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey,
and the L1 spacecraft, spanning a longitudinal range of 222{deg} in the
ecliptic plane, observed an energetic particle flux increase. The widespread
solar energetic particle (SEP) event was associated with a coronal mass
ejection (CME) that came from a region located near the far-side central
meridian from Earth’s perspective. The CME erupted in two stages, and was
accompanied by a late M-class flare observed as a post-eruptive arcade,
persisting low-frequency (interplanetary) type II and groups of
shock-accelerated type III radio bursts, all of them making this SEP event
unusual. Aims: There are two main objectives of this study, disentangling the
reasons for the different intensity-time profiles observed by the spacecraft,
especially at MESSENGER and STEREO-A locations, longitudinally separated by
only 15{deg}, and unravelling the single solar source related with the
widespread SEP event. Results: The solar source associated with the widespread
SEP event is the shock driven by the CME, as the flare observed as a
post-eruptive arcade is too late to explain the estimated particle onset. The
different intensity-time profiles observed by STEREO-A, located at 0.97 au, and
MESSENGER, at 0.33 au, can be interpreted as enhanced particle scattering
beyond Mercury’s orbit. The longitudinal extent of the shock does not explain
by itself the wide spread of particles in the heliosphere. The particle
increase observed at L1 may be attributed to cross-field diffusion transport,
and this is also the case for STEREO-B, at least until the spacecraft is
eventually magnetically connected to the shock when it reaches ~0.6 au.
Context: Late on 2013 August 19, STEREO-A, STEREO-B, MESSENGER, Mars Odyssey,
and the L1 spacecraft, spanning a longitudinal range of 222{deg} in the
ecliptic plane, observed an energetic particle flux increase. The widespread
solar energetic particle (SEP) event was associated with a coronal mass
ejection (CME) that came from a region located near the far-side central
meridian from Earth’s perspective. The CME erupted in two stages, and was
accompanied by a late M-class flare observed as a post-eruptive arcade,
persisting low-frequency (interplanetary) type II and groups of
shock-accelerated type III radio bursts, all of them making this SEP event
unusual. Aims: There are two main objectives of this study, disentangling the
reasons for the different intensity-time profiles observed by the spacecraft,
especially at MESSENGER and STEREO-A locations, longitudinally separated by
only 15{deg}, and unravelling the single solar source related with the
widespread SEP event. Results: The solar source associated with the widespread
SEP event is the shock driven by the CME, as the flare observed as a
post-eruptive arcade is too late to explain the estimated particle onset. The
different intensity-time profiles observed by STEREO-A, located at 0.97 au, and
MESSENGER, at 0.33 au, can be interpreted as enhanced particle scattering
beyond Mercury’s orbit. The longitudinal extent of the shock does not explain
by itself the wide spread of particles in the heliosphere. The particle
increase observed at L1 may be attributed to cross-field diffusion transport,
and this is also the case for STEREO-B, at least until the spacecraft is
eventually magnetically connected to the shock when it reaches ~0.6 au.
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