Modeling the 2017 September 10 solar energetic particle event using the iPATH model

Abstract

On 2017 September 10, a fast coronal mass ejection (CME) erupted from the active region (AR) 12673, leading to a ground level enhancement (GLE) event at Earth. Using the 2D improved Particle Acceleration and Transport in the Heliosphere (iPATH) model, we model the large solar energetic particle (SEP) event of 2017 September 10 observed at Earth, Mars and STEREO-A. Based on observational evidence, we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption, which is modeled by a double Gaussian velocity profile in this simulation. We apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model parameters. The modeled time intensity profiles and fluence for energetic protons are then compared with observations. Reasonable agreements with observations at Mars and STEREO-A are found. The simulated results at Earth differ from observations of GOES-15. However, the simulated results at a heliocentric longitude 20° west to Earth fit reasonably well with the GOES observation. This can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker field. Our results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.

Assessing the Influence of Input Magnetic Maps on Global Modeling of the Solar Wind and CME‐Driven Shock in the 2013 April 11 Event

“…For example, based on the DSA theory (Drury, 1983), the instantaneous particle spectral index depends only on the shock compression ratio and the higher shock compression ratio in Case I will lead to a harder SEP spectra. The higher shock compression ratio and quasi‐parallel nature found in the Case I also suggests the shock is a more efficient accelerator than in the Case II (Ding et al., 2020). However, due to the complex physical processes of the particle acceleration and transport involved, to quantitatively link the shock properties near the Sun to the SEP spectra at 1 AU requires advanced coupling between the MHD model and a particle acceleration/transport model (G. Li, Jin, et al., 2021; Young et al., 2021), which is beyond the scope of this work and will be examined in a future study.…”

Extreme energetic particle events by superflare-associated CMEs from solar-like stars

“…Early applications of the 1D PATH code on individual SEP events have been pursued by Verkhoglyadova et al ( 37 , 38 ). Recently, the 2D iPATH code has been successfully used to reproduce the time profiles and event fluences for two large GLE events ( 39 , 40 ). These studies show the applicability of using the iPATH code and its capabilities to model extreme SEP and StEP events as pursued in this work.…”

Modeling the East‐West Asymmetry of Energetic Particle Fluence in Large Solar Energetic Particle Events Using the iPATH Model

“…H is the Heaviside function, and c 1 is a normalization constant given by $$${c}_{1}=1/{\int }_{{p}_{inj,\mathbf{r}}}^{+\infty }{p}^{-\beta }H\left[p-{p}_{inj,\mathbf{r}}\right]\mathrm{exp}\left(-\frac{E}{{E}_{0,\mathbf{r}}}\right){d}^{3}p.$$$ The instantaneous proton flux J ( E ) equals to p 2 f ( p ). Note that the proton intensity at shock front ( I shk ( E )) is the flux of escaped protons at an escape length l = 4 λ esc in front of the shock, where λ esc is the scatter length scale (Ding et al., 2020).…”

“…One advantage of the iPATH model is its capability of modeling a single large SEP event at multiple observer locations (Ding et al, 2020;Hu et al, 2017Hu et al, , 2018Li et al, 2021). For our purpose here, we consider different cases with different CME speeds and different background solar wind speeds.…”