首页期刊导航|Advances in space research: The official journal of the Committee on Space Research
期刊信息/Journal information
Advances in space research: The official journal of the Committee on Space Research
Pergamon Press
Pergamon Press
0273-1177
Advances in space research: The official journal of the Committee on Space Research/Journal Advances in space research: The official journal of the Committee on Space ResearchSCIEIISTP
查看更多>>摘要：Our planet lies within an active and dynamic interplanetary space environment resulting from the expansion of our Sun's atmosphere, the solar corona, expanding outwards through the inner heliosphere at supersonic speeds. This carries with it vast amounts of plasma along with an embedded interplanetary magnetic field (IMF). This variable, but continuous, outflow is known as the solar wind, but it also includes large structures such as coronal mass ejections (CMEs). CMEs are eruptions of dense, highly-magnetised plasma, launched at high speeds from the Sun out into the heliosphere. These ever-changing conditions drive processes in the Earth's space-environment (the mag-netosphere and ionosphere), as well as at other planetary bodies in the solar system, which can strongly affect satellite/spacecraft communications, Earth's navigation systems and power grids, and other complex technologies and infrastructures upon which modern society relies. Collectively, study of the Sun-Earth-Heliosphere system is known as heliophysics.
Kathryn WhitmanRicky EgelandIan G. RichardsonClayton Allison...
5161-5242页
查看更多>>摘要：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.
查看更多>>摘要：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 magnetohydro-dynamic (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: ∆θ (latitude)=6°_(-3°)~(+2°), ∆ø (longitude)=11°_(-6°)~(+18°), ∆γ (tilt)=25°_(-7°)~(+8°), ∆α(half-angIe)=10°_(-6°)~(+12°), ∆h (height)=0.6_(-0.4)~(+1.2)R_⊙, and ∆κ (ratio)=0.l_(-0.02)~(+0.03).
查看更多>>摘要：The deflection of Solar Coronal Mass Ejections (CMEs) near the Sun may be the consequence of interaction between a CME and a coronal hole or the solar wind (Gopalswamy et al., 2009a, 2009b). In this study, 124 halo-CMEs that originate from 40 active regions are analyzed to deduce whether multiple CMEs from the same active region are deflected in the same direction, as well as to find the accuracy of predicting the deflection direction of a CME according to the ambient large-scale magnetic field configuration. It was found that at least 73% (29 groups) were significantly deflected. Also of the 16 groups with multiple significantly deflected CMEs from the same active regions, the deflection direction for the CMEs in 88% (14 groups) was consistent with each other. The magnetic field configuration was computed from synoptic maps of magnetic field from SOHO/MDI and SDO/HMI using a Potential Field Source Surface (PFSS) model. We have performed the error analysis for the calculation of the ambient magnetic field. After excluding the cases with high error, of the remaining 23 significantly deflected groups, the deflection of 91% (21 groups) was consistent with the ambient magnetic field configuration. Among them, 86% of the groups were deflected toward the Heliospheric Current Sheet (HCS), the boundary between the magnetic field polarities, and 14% toward Pseudo-Streamers (PS), the boundary between the same-polarity magnetic field regions. It was found to be in good agreement with previous studies.
Martin A. ReissKarin MuglachRichard MullinixMaria M. Kuznetsova...
5275-5286页
查看更多>>摘要：Progress in space weather research and awareness needs community-wide strategies and procedures to evaluate our modeling assets. Here we present the activities of the Ambient Solar Wind Validation Team embedded in the COSPAR ISWAT initiative. We aim to bridge the gap between model developers and end-users to provide the community with an assessment of the state-of-the-art in solar wind forecasting. To this end, we develop an open online platform for validating solar wind models by comparing their solutions with in situ spacecraft measurements. The online platform will allow the space weather community to test the quality of state-of-the-art solar wind models with unified metrics providing an unbiased assessment of progress over time. In this study, we propose a metadata architecture and recommend community-wide forecasting goals and validation metrics. We conclude with a status update of the online platform and outline future perspectives.
查看更多>>摘要：Solar-wind 3-D reconstruction tomography based on interplanetary scintillation (IPS) studies provides fundamental information for space-weather forecasting models, and gives the possibility to determine heliospheric column densities. Here we compare the time series of Solar-wind column densities derived from long-term observations of pulsars, and the Solar-wind reconstruction provided by the UCSD IPS tomography. In particular, we analyze the 2016, 2017 and 2018 Solar passages of PSR J0034-0534, and the 2016 and 2018 Solar passages of PSR J1022 + 1001. The results show that, where the UCSD IPS tomography makes use of its most robust settings, the matches between the two techniques are characterized by Pearson's R coefficients ranging from 0.64 to 0.90, indicating a good level of agreement. This unique work represents a completely independent comparison and validation of these techniques to provide such measurements, and it strengthens confidence in the use of both in space-weather analyses applications.
查看更多>>摘要：In space weather studies and forecasting we employ magnetohydrodynamic (MHD) simulations which can provide rather accurate reconstruction of the solar wind dynamics and its evolution. However, all MHD simulations are restricted by the input data and the modelled solar wind characteristics need to be validated with different types of observations. That is very difficult, in particular for the solar wind characteristics close to the Sun, since the majority of in situ observations are taken in the vicinity of the Earth. This is why all alternative methods for estimation of solar wind plasma characteristics are very important. In this study we utilise low radio frequency observations of pulsars to probe the total electron content along the line of sight. For the first time, we compare density estimates from pulsars with predictions from the 3D MHD modelling code; the EUropean Heliospheric FORecasting Information Asset (EUHFORIA). We find a very good correlation for the solar wind density along a given line of sight obtained by EUHFORIA and pulsar observations. We demonstrate that pulsar observations can be very useful not only for the model validation but also for understanding its limitations.
查看更多>>摘要：Observations of interplanetary scintillation (IPS - the scintillation of compact radio sources due to density variations in the solar wind) enable the velocity of the solar wind to be determined, and its bulk density to be estimated, throughout the inner heliosphere. A series of observations using the Low Frequency Array (LOFAR - a radio telescope centred on the Netherlands with stations across Europe) were undertaken using this technique to observe the passage of an ultra-fast CME which launched from the Sun following the X-class flare of 10 September 2017. LOFAR observed the strong radio source 3C147 at an elongation of 82 degrees from the Sun over a period of more than 30 h and observed a strong increase in speed to 900 km s~(-1) followed two hours later by a strong increase in the level of scintillation, interpreted as a strong increase in density. Both speed and density remained enhanced for a period of more than seven hours, to beyond the period of observation. Further analysis of these data demonstrates a view of magnetic-field rotation due to the passage of the CME, using advanced IPS techniques only available to a unique instrument such as LOFAR.
Kazumasa IwaiRichard A. FallowsMario M. BisiDaikou Shiota...
5328-5340页
查看更多>>摘要：Interplanetary scintillation (IPS) is a useful tool for detecting coronal mass ejections (CMEs) throughout interplanetary space. Global magnetohydrodynamic (MHD) simulations of the heliosphere, which are usually used to predict the arrival and geo-effectiveness of CMEs, can be improved using IPS data. In this study, we demonstrate an MHD simulation that includes IPS data from multiple stations to improve CME modelling. The CMEs, which occurred on 09-10 September 2017, were observed over the period 10-12 September 2017 using the Low-Frequency Array (LOFAR) and IPS array of the Institute for Space-Earth Environmental Research (ISEE), Nagoya University, as they tracked through the inner heliosphere. We simulated CME propagation using a global MHD simulation, SUSANOO-CME, in which CMEs were modeled as spheromaks, and the IPS data were synthesised from the simulation results. The MHD simulation suggests that the CMEs merged in interplanetary space, forming complicated IPS g-level distributions in the sky map. We found that the MHD simulation that best fits both LOFAR and ISEE data provided a better reconstruction of the CMEs and a better forecast of their arrival at Earth than from measurements when these simulations were fit from the ISEE site alone. More IPS data observed from multiple stations at different local times in this study can help reconstruct the global structure of the CME, thus improving and evaluating the CME modelling.
查看更多>>摘要：The University of California, San Diego (UCSD) time-dependent three-dimensional (3-D) reconstruction technique provides volumetric maps of density, velocity, and solar surface extrapolated magnetic fields by iteratively fitting our kinematic 3-D model to interplanetary scintillation (IPS) observations. While we currently use data from the Institute for Space-Earth Environmental Research (ISEE), Japan, we have also integrated this system adding data from Worldwide IPS Stations (WIPSS) network groups to increase both spatial and temporal coverage when these data are available. Some of these stations, especially the LOw Frequency ARray (LOFAR), centered in the Netherlands, currently operate in "campaign" mode only during periods of interest when the Parker Solar Probe (PSP) makes close passes to the Sun. The UCSD 3-D iterative reconstruction technique is unique in its ability to yield a low-resolution seamless extension of density and velocity parameters measured in situ, going outward into the surrounding interplanetary medium at the resolution of the volumetric data. We here present analyses using archival data sets from both ISEE, LOFAR, and BSA3 (Pushchino, Russia), mostly during PSP close passes of the Sun. These analyses provide the location of all inner planets from Mercury to Mars, and the spacecraft PSP, BepiColombo, and Solar Orbiter in the 3-D reconstructed volumes and can show the heliospheric structures that reach them as in-situ predictions of the structures present and forecasts of these parameters in near real time compared with near-Earth data sets.
NETL
NSTL
Elsevier