Modelling large solar proton events with the shock-and-particle model

Abstract

We have developed a new version of a model that combines a two-dimensional Sun-to-Earth magnetohydrodynamic (MHD) simulation of the propagation of a CME-driven shock and a simulation of the transport of particles along the interplanetary magnetic field (IMF) line connecting the shock front and the observer. We assume that the shock-accelerated particles are injected at the point along the shock front that intersects this IMF line, i.e. at the cobpoint. Novel features of the model are an improved solar wind model and an enhanced fully automated algorithm to extract the necessary plasma characteristics from the shock simulation. In this work, the new algorithms have been employed to simulate the 2000 April 4 and the 2006 December 13 SEP events. In addition to quantifying the performance of the new model with respect to results obtained using previous versions of the shock-and-particle model, we investigate the semi-empirical relation between the injection rate of shock-accelerated particles, Q, and the jump in speed across the shock, VR, known as the Q(VR) relation. Our results show that while the magnetic field and density compression at the shock front is markedly different than in our previous modeling, the evolution of VR remains largely similar. As a result, we confirm that a simple relation can still be established between Q and VR, which enables the computation of synthetic intensity-time profiles at any location in interplanetary space. Furthermore, the new shock extraction tool is found to yield improved results being in general more robust. These results are important not only with regard to efforts to develop coupled magnetohydrodynamic and particle simulation models, but also to improve space weather related software tools that aim to predict the peak intensities, fluences and proton intensity-time profiles of SEP events (such as the SOLPENCO tool).

Modelling of Shock-Accelerated Gamma-Ray Events

“…Table 9.1 provides values of the input solar wind parameters at 1:03 Rˇ. The input parameters of the shock-driving disturbance are its density cme D 0:3 10 13 kg m 3 , speed v cme D 1000 km s 1 , and the shock-front shape parameter D 0:5a cme determined by the angular extent a cme of the disturbance (see Pomoell et al 2015 for details). One can see that the simulations reproduce quite well the average characteristics of the solar wind at 1 AU prior to the shock arrival (note, however, that the temperature is somewhat underestimated) as well as the shock arrival time.…”

“…In order to derive the proton injection rate from the shock into the magnetic flux tube connecting the observer with the shock front, we fitted the proton (Pomoell et al 2015); and is the adiabatic index. intensity-time profiles provided by the ACE/EPAM instrument (in the energy range 0.59-4.8 MeV), SEPEM reference data (Jiggens et al 2012) (6-166.3 MeV) and GOES/HEPAD detector (330-700 MeV).…”

“…intensity-time profiles provided by the ACE/EPAM instrument (in the energy range 0.59-4.8 MeV), SEPEM reference data (Jiggens et al 2012) (6-166.3 MeV) and GOES/HEPAD detector (330-700 MeV). The fitting was performed using SaP particle transport simulations, following the method described in Pomoell et al (2015). Figure 9.3 shows examples of the fitted intensity-time profiles for several high-energy channels.…”

SEPEM: A tool for statistical modeling the solar energetic particle environment

“…The physical model underlying SOLPENCO2 [e.g., Aran et al ., , ; Jacobs and Poedts , ; Pomoell et al , ] combines 2‐D MHD interplanetary shock propagation simulations developed during the SEPEM project with the particle transport code of Lario et al [] to model proton intensity‐time profiles of gradual SEP events. The new features of this shock‐and‐particle model that follows the same modular structure as previous models applied to single spacecraft and multispacecraft SEP events [e.g., Aran et al , ] are as follows: (i) a solar wind model starting from 1.03 R ⊙ [ Jacobs and Poedts , ], (ii) a simulation of the CME‐driven shock tracked from 4 R ⊙ up to 1.6 AU, (iii) an automated method to detect the location of the shock front where a given observer is magnetically connected during the event, i.e., the observer's cobpoint (“Connecting with the OBserver POINT”) [ Heras et al , ], and to compute the plasma variable ratios at the cobpoint, and (iv) the modeling of the transport of protons up to 200 MeV.…”

Prediction and warning system of SEP events and solar flares for risk estimation in space launch operations

“…Coronal mass ejection (CME)-driven shocks are believed to be the primary drivers of large, gradual SEP events (Reames 2004;Tylka et al 2005); however, SEP-occurrence forecasts from these shocks are currently unreliable for real-time purposes and, consequently, cannot be used in operations mode until a solar proxy that generates the shock is found for the initial conditions, and until a statistical validation to estimate the errors in the prediction of the timing and size of the events is performed (Pomoell et al 2015). A lot of effort is currently being put into achieving a proper determination of the strength of the CME-driven shock from observational data to derive predictions (e.g.…”