National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

The Role of Solar Activity in the Longitudinal Broadening of SEP Events

ROSES ID: NNH14ZDA001N      Selection Year: 2014      

Program Element: Focused Science Topic

Principal Investigator: David Lario

Affiliation(s): Applied Physics Laboratory

Project Member(s):
Riley, Pete Collaborator Predictive Science, Incorporated
Thernisien, Arnaud Francois Rene Co-I Naval Research Laboratory
Decker, Robert B. Collaborator Johns Hopkins Univ. Applied Physics Lab.
Gomez-Herrero, Raul Collaborator University of Alcalá
Raouafi, Nour Eddine Co-I Johns Hopkins University Apllied Physics Laboratory


Current Understanding: The fleet of spacecraft distributed through the inner heliosphere (R<~1 AU) offers us the unique opportunity to study solar energetic particle (SEP) events from multiple vantage points. Particles from individual SEP events have been observed to extend over broad ranges of longitude, in some cases nearing a 360 span. Hypotheses that invoke particle injection from inherently broad particle sources, multiple particle injections from distant eruptive sources, and/or spatial dispersion driven by transport processes in interplanetary space have been proposed to explain the wide spread of SEP events. We will study the role that solar activity plays in producing the longitudinal spread of SEP events.

Science Questions and Objectives: We propose a well-delimited and very focused research program aimed at testing the hypotheses proposed to explain the wide spread of SEP events. In particular, we will test those related to solar activity processes; namely: (a) CME-driven shocks accelerate and inject particles over a broad longitudinal range as the shocks expand through the inner heliosphere. (b) Sympathetic solar eruptions that occur in temporal association with, but separated from, the main solar event accelerate and inject particles over a range of longitudes that are well separated from the active region identified as the event origin. (c) Magnetic field configurations close to the Sun allow active regions to connect to a broad range of longitudes in such a way that particles injected from a compact source spread to fill a broad volume of the inner heliosphere. The study of these three hypotheses will allow us to answer the following questions: (1) Is the extension of the coronal EUV waves an indication of the longitudinal spreading of the SEP events? (2) Do sympathetic eruptions play a role in SEP injection at different longitudes? (3) Is the magnetic connection between CME-driven shocks and each spacecraft the dominant factor controlling the arrival of particles at each observer?

Methodology: The proposed methodology is very focused and feasible. We will select SEP events observed by one, two or more spacecraft well separated in longitude. We will combine multi-point remote sensing observations from SDO, SOHO and STEREO A/B with multi-point in-situ solar wind, magnetic field and energetic particle data from ACE, MESSENGER, SOHO, GOES and STEREO A/B to (1) identify the environment where SEP events develop, (2) resolve the solar activity associated with the origin of the SEP events, (3) determine the evolution and extent of EUV waves and CME-driven shocks that track the sources of SEPs, (4) estimate the magnetic connection between each spacecraft and the particle sources by using coronal magnetic field models, and (5) evaluate the release time of the first arriving SEPs at each spacecraft.

Relevance and Contributions to the Focus Team Effort: The proposed study is very timely because of the current configuration of spacecraft and very relevant to the Focus Team Effort (FTE). Our work will determine the solar processes responsible for the observation of SEPs at different points in the heliosphere. Collaborative efforts with other members of the FTE dealing with SEP acceleration and transport processes will allow us to constrain the mechanisms responsible for the longitudinal spread of SEP events. Our experience in both multi-spacecraft analysis of SEP events and solar transient events is a crucial asset for the success of the FTE. We will identify the relative roles played by solar transient phenomena on the formation and development of SEP events as a function of longitude and thus establish the physical association between the first particles arriving at observers well separated in longitude and the longitudinal extent of CMEs in the corona. This work targets several Heliophysics and space weather strategic goals as to how and where solar eruptions accelerate particles that reach Earth.


Performance YearReferenceInvestigation TypeActions
4Afanasiev A.; Aran A.; Vainio R.; Rouillard A.; Zucca P.; La...
Data Model Comparison
3Lario D.; Kwon R.-Y.; Riley P.; Raouafi N. E.; (2017). On th...
Data Model Comparison
3Gomez-Herrero R.; Dresing N.; Klassen A.; Heber B.; Temmer M...
Data Analysis
3Lario D.; Kwon R.-Y.; Richardson I. G.; Raouafi N. E.; Thomp...
Data Model Comparison
2Agueda N.; Lario D.; (2016). Release History and Transport P...
Data Model Comparison
2Lario D.; Kwon R.-Y.; Vourlidas A.; Raouafi N. E.; Haggerty ...
Data Model Comparison
2Riley P.; Caplan R. M.; Giacalone J.; Lario D.; Liu Y.; (201...
Data Model Comparison
1Lario D.; Decker R. B.; Roelof E. C.; Vinas A.-F.; (2015). E...
Data Analysis
1Gomez-Herrero R.; Dresing N.; Klassen A.; Heber B.; Lario D....
Data Model Comparison
4Lario D.; Berger L.; Wilson L. B.; Decker R. B.; Haggerty D....
Data Analysis
1Lario D.; Decker R. B.; Roelof E. C.; Vinas A.-F.; (2015). E...
Data Analysis

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