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Current efforts in space weather forecasting of CMEs have been focused on predicting their arrival time and magnetic structure. To make these predictions, methods have been developed to derive the true CME speed, size, position, and mass, among others. Difficulties in determining the input parameters for CME forecasting models arise from the lack of direct measurements of the coronal magnetic fields and uncertainties in estimating the CME 3D geometric and kinematic parameters after eruption. White-light coronagraph images are usually employed by a variety of CME reconstruction techniques that assume more or less complex geometries. This is the first study from our International Space Science Institute (ISSI) team "Understanding Our Capabilities in Observing and Modeling Coronal Mass Ejections", in which we explore how subjectivity affects the 3D CME parameters that are obtained from the Graduated Cylindrical Shell (GCS) reconstruction technique, which is widely used in CME research. To be able to quantify such uncertainties, the "true" values that are being fitted should be known, which are impossible to derive from observational data. We have designed two different synthetic scenarios where the "true" geometric parameters are known in order to quantify such uncertainties for the first time. We explore this by using two sets of synthetic data: 1) Using the ray-tracing option from the GCS model software itself, and 2) Using 3D magnetohydrodynamic (MHD) simulation data from the Magnetohydrodynamic Algorithm outside a Sphere code. Our experiment includes different viewing configurations using single and multiple viewpoints. CME reconstructions using a single viewpoint had the largest errors and error ranges overall for both synthetic GCS and simulated MHD white-light data. As the number of viewpoints increased from one to two, the errors decreased by approximately 4 ° in latitude, 22 ° in longitude, 14 ° in tilt, and 10 ° in half-angle. Our results quantitatively show the critical need for at least two viewpoints to be able to reduce the uncertainty in deriving CME parameters. We did not find a significant decrease in errors when going from two to three viewpoints for our specific hypothetical three spacecraft scenario using synthetic GCS white-light data. As we expected, considering all configurations and numbers of viewpoints, the mean absolute errors in the measured CME parameters are generally significantly higher in the case of the simulated MHD white-light data compared to those from the synthetic white-light images generated by the GCS model. We found the following CME parameter error bars as a starting point for quantifying the minimum error in CME parameters from white-light reconstructions: Δ θ (latitude)= 6 ° - 3 ° + 2 ° , Δ ϕ (longitude)= 11 ° - 6 ° + 18 ° , Δ γ (tilt)= 25 ° - 7 ° + 8 ° , Δ α (half-angle)= 10 ° - 6 ° + 12 ° , Δ h (height)= 0.6 - 0.4 + 1.2 R ⊙ , and Δ κ (ratio)= 0.1 - 0.02 + 0.03 . [ABSTRACT FROM AUTHOR]

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth's protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data. [ABSTRACT FROM AUTHOR]

The Effective Acceleration Model (EAM) predicts the Time-of-Arrival (ToA) of the Coronal Mass Ejection (CME) driven shock and the average speed within the sheath at 1 AU. The model is based on the assumption that the ambient solar wind interacts with the interplanetary CME (ICME) resulting in constant acceleration or deceleration. The upgraded version of the model (EAMv3), presented here, incorporates two basic improvements: (i) a new technique for the calculation of the acceleration (or deceleration) of the ICME from the Sun to 1 AU and (ii) a correction for the CME plane-of-sky speed. A validation of the upgraded EAM model is performed via comparisons to predictions from the ensemble version of the Drag-Based model (DBEM) and the WSA-ENLIL+Cone ensemble model. A common sample of 16 CMEs/ICMEs, in 2013 – 2014, is used for the comparison. Basic performance metrics such as the mean absolute error (MAE), mean error (ME) and root mean squared error (RMSE) between observed and predicted values of ToA are presented. MAE for EAM model was 8.7 ± 1.6 hours while for DBEM and ENLIL was 14.3 ± 2.2 and 12.8 ± 1.7 hours, respectively. ME for EAM was − 1.4 ± 2.7 hours in contrast with − 9.7 ± 3.4 and − 6.1 ± 3.3 hours from DBEM and ENLIL. We also study the hypothesis of stronger deceleration in the interplanetary (IP) space utilizing the EAMv3 and DBEM models. In particularly, the DBEM model perform better when a greater value of drag parameter, of order of a factor of 3, is used in contrast to previous studies. EAMv3 model shows a deceleration of ICMEs at greater distances, with a mean value of 0.72 AU. [ABSTRACT FROM AUTHOR]

The deep Solar Cycle (SC) 23 minimum and the modestly active SC 24 maximum have produced generally weaker solar events and heliospheric conditions. Surprisingly, on September 10, 2017 late in the declining phase of SC 24, some of the strongest solar activity erupted from active region (AR) 12673, including an X8.2-class solar flare and a fast coronal mass ejection (CME). Associated with this activity are the solar energetic particles (SEPs), which may be accelerated locally at the flare site or by the moving shock front propagating ahead of the CME. Although AR 12673 was not centrally facing Mars (it was located about 67 degrees east in heliolongitude from the Sun-to-Mars line), the solar events impacted the local space weather environment. To name a few, some of the effects include heating of the upper atmosphere by solar flare emissions, flare-related enhancements of ion and neutral densities, solar energetic particles impacting the atmosphere and surface, bright emissions of a diffuse (global) aurora, deeply penetrating interplanetary magnetic fields over the Martian dayside, and enhanced atmospheric escape rates. In this presentation we will give an overview of the observations at Mars obtained from various Mars missions, including MAVEN, MEX, and MSL. Numerical results from the Wang-Sheeley-Arge (WSA)-Enlil-cone modeling system together with observations at Earth/L1 and STEREO-A will also be presented to provide global heliospheric context of the event period. [ABSTRACT FROM AUTHOR]