Understanding the Longitudinal Extent and Timing of the SEP Onset

ROSES ID: NNH14ZDA001N      Selection Year: 2014      

Program Element: Focused Science Topic

Principal Investigator: Hong Xie

Affiliation(s): Catholic University of America

Project Member(s):
St. Cyr, O. C. Collaborator NASA

Summary:

This investigation will focus on large SEP events with energies above 25 MeV that have been observed by both STEREO and near-Earth spacecraft. Recently, Richardson et al. (2014) compiled a catalog of 209 individual greater than 25 MeV solar proton events in cycle 24 and found that there were 25 events observed at all three spacecraft [STEREO and a near-Earth platform] from December 2009December 2013 when the STEREO spacecraft were separated by greater than ~60 degrees in heliolongitude from Earth. We will combine remote-sensing multi-point observations with forward-modeling using an oblate spheroid shock model to (1) study the longitudinal extent and angular width of the expanding CME-shock and EUV wave for the 25 three-spacecraft SEP events; (2) study the acceleration profiles of the CME-shock and EUV wave in its early evolution, including both radial expansion and lateral expansion; 3) develop the relations between the shock front speed and the shock leading edge speed and the expansion speeds at semi-major and semi-minor axes. By using a full 3D forward-modeling, we can accurately determine the true speed, heliographic distance, angular width, and the location where the magnetic connectivity occurs. Based on the above results, we will study the correlation between the proton peak intensities, the shock speeds and angular widths and derive a formula predicting the SEP intensity. The main objective of this proposal is to investigate whether the wide spread SEP events are in fact a result of the expanding shock and to gain sufficient scientific understanding that will lead to a predictive capability. This proposal is highly relevant to the scientific objectives of the Focused Topic: 3.1.2 Physics-based methods to predict connectivity of SEP sources to points in the inner heliosphere, tested by location, timing, and longitudinal separation of SEPs since the proposed work will focus on models & observations that provide a better understanding of the initial phases of CMEs and how that couples into longitudinal extent and timing for the SEPs. We will contribute data analysis expertise, as well as modeling capabilities that are directly relevant to team objectives. By the end of Year Four we will also provide a three-spacecraft event list with accurate heliographic distances, space speeds, and angular widths of the CME-shock at SEP onset times at each spacecraft. The extensive list developed as part of the proposed investigation will be made available to the modeling efforts and theoretical studies through the CDAW website.

Publications:

Performance Year	Reference	Investigation Type	Actions
2	Xie H.; Makela P.; Gopalswamy N.; St. Cyr O. C.; (2016). Ene...	Data Analysis
3	Xie H.; Makela P.; St. Cyr O. C.; Gopalswamy N.; (2017). Com...	Data Model Comparison
1	Gopalswamy N.; Xie H.; Akiyama S.; Makela P. A.; Yashiro S.;...	Data Analysis
4	Xie H.; St. Cyr O. C.; Makela P.; Gopalswamy N.; (2018). Rel...	Other Investigations

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