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For a three-dimensional magnetohydrodynamics solar wind model, it is necessary to carry out assessment studies to reveal its ability and limitation. In this paper, the ambient solar wind results of year 2008 generated by the CESE-HLLD 3D MHD model are compared with multipoint in-situ measurements during the late declining phase of solar cycle 23. The near-ecliptic results are assessed both quantitatively and qualitatively by comparing with in-situ data obtained at the L1 point and by the twin STEREO spacecraft. The assessment reveals the model’s ability in reproducing the time series and statistical characteristics of solar wind parameters, and in catching the change of interplanetary magnetic field polarity and the occurrence of the stream interaction regions. We find that the two-stream structure observed near the ecliptic plane is reproduced, but the differences among observations at L1 and the twin STEREO spacecraft are not caught by the model. The latitudinal variation of the results is assessed by comparing with the Ulysses observation. The characters of variation in different latitudinal ranges are duplicated by the model, but biases of the results are seen, and the boundary layers between fast and slow solar wind are sometimes thicker than observation.

This paper presents a study of a 2021 October 9 coronal mass ejection (CME) with multipoint imaging and in situ observations. We also simulate this CME from the Sun to Earth with a passive tracer to tag the CME's motion. The coronagraphic images show that the CME is observed as a full halo by SOHO and as a partial halo by STEREO-A. The heliospheric images reveal that the propagation speed of the CME approaches about 1° hr−1, suggesting a slow CME. With simulated results matching these observation results, the simulation discloses that as the CME ejects from the Sun out to interplanetary space, its global morphology is distorted from an ellipsoid to a concave shape owing to interactions with the bimodal solar wind. The cross section of the CME's flux rope structure transforms from a circular shape into a flat one. As a result of the deflection, the propagation direction of the CME is far away from the Sun–Earth line. This means that the CME flank (or the ICME leg) likely arrives at both Solar Orbiter and the L1 point. From the CME's eruption to 1 au, its volume and mass increase by about two orders and one order of magnitude, respectively. Its kinetic energy is about 100 times larger than its magnetic energy at 1 au. These results have important implications for our understanding of CMEs' morphology, as well as their space weather impacts. [ABSTRACT FROM AUTHOR]

Aimed to be ready for the transition from research to operation, we have developed a solar wind model by coupling a data-driven empirical coronal model with a magnetohydrodynamics heliospheric model. We performed a data-driven simulation of the solar wind for a two-year period during the declining and minimum phases of solar cycle 23. Comparisons with OMNI and Ulysses spacecraft data show that the model can reproduce the large-scale variations of the solar wind plasma parameters. The evolution of geocentric solar magnetospheric (GSM) Bx and Bz components are also reasonably duplicated by the model in terms of polarity and strength. Apparent signatures of the Russell–McPherron (R-M) effect are found from both observed data and simulated results, indicating that during the investigated interval the R-M effect is the dominant mechanism that controls the large-scale evolution of the north–south component of the interplanetary magnetic field in the GSM frame. The results demonstrate that the established model can provide valuable space weather information about the solar wind. [ABSTRACT FROM AUTHOR]

In this paper, the CESE‐HLL three‐dimensional magnetohydrodynamic solar wind model is first modified to be able to work in a corona‐heliosphere integrated approach and then used to simulate the evolution of solar wind from the solar surface to the Earth's orbit during year 2008. Here high‐cadence photospheric magnetic field data are used to drive the model at the solar surface via the projected normal characteristic boundary equations. The simulated results are analyzed and quantitatively evaluated by comparing the simulated results with solar and interplanetary observations. The analyses demonstrate that our model reproduces the main pattern and the evolutionary feature of large‐scale coronal structures. The simulated results show that the height of the pseudostreamer X point is positively correlated with the distance of the coronal holes connected by the pseudostreamer. During year 2008, the helmet streamer belt is found to have a net southward displacement from the equator while the pseudostreamer belts are biased to the Northern Hemisphere. Both helmet streamer belt and pseudostreamer belts exhibit a general trend of becoming more concentrated along the equator throughout 2008. The evaluation of the simulated results at the L1 point shows that the general structures can be generated by the model, and that speed is the best among the solar wind parameters reproduced. However, the temperature of the fast solar wind and the magnitude of the interplanetary magnetic field are underestimated. The success rate of prediction and arrival time error are also calculated for magnetic field polarity reversals and stream interaction regions. Key Points: Magnetic field data‐driven simulation of the ambient solar wind is carried out for the whole of year 2008Analysis of the solar wind evolution is focused on helmet streamer and pseudostreamer global structureSimulation results are evaluated quantitatively by comparison with in situ measurements [ABSTRACT FROM AUTHOR]