Geomagnetic disturbance forecasting is based on the identification of solar wind structures and accurate determination of their magnetic field orientation. For nowcasting activities, this is currently a tedious and manual process. Focusing on the main driver of geomagnetic disturbances, the twisted internal magnetic field of interplanetary coronal mass ejections (ICMEs), we explore a convolutional neural network's (CNN) ability to predict the embedded magnetic flux rope's orientation once it has been identified from in situ solar wind observations. Our work uses CNNs trained with magnetic field vectors from analytical flux rope data. The simulated flux ropes span many possible spacecraft trajectories and flux rope orientations. We train CNNs first with full duration flux ropes and then again with partial duration flux ropes. The former provides us with a baseline of how well CNNs can predict flux rope orientation while the latter provides insights into real-time forecasting by exploring how accuracy is affected by percentage of flux rope observed. The process of casting the physics problem as a machine learning problem is discussed as well as the impacts of different factors on prediction accuracy such as flux rope fluctuations and different neural network topologies. Finally, results from evaluating the trained network against observed ICMEs from Wind during 1995-2015 are presented.
Interplanetary coronal mass ejections (ICMEs) are a significant feature of the heliospheric environment and the primary cause of adverse space weather at the Earth. ICME propagation, and the evolution of ICME magnetic field structure during propagation, are still not fully understood. We analyze the magnetic field structures of 18 ICME magnetic flux ropes observed by radially aligned spacecraft in the inner heliosphere. Similarity in the underlying flux rope structures is determined through the application of a simple technique that maps the magnetic field profile from one spacecraft to the ot…
Flux ropes (FRs) ejected from the Sun may change their geometrical orientation during their evolution which directly affects their geoeffectiveness. Therefore, it is crucial to understand how solar FRs evolve in the heliosphere to improve our space weather forecasting tools. We analyze 15 coronal mass ejections (CMEs), with clear FR signatures, observed during the decay of Solar Cycle 23 and rise of Solar Cycle 24. We estimate initial orientations of the FRs at the origin using extreme ultraviolet observations of post-eruption arcades and/or eruptive prominences. Then we reconstruct multiviewp…
Studying the evolution of magnetic clouds entrained in coronal mass ejections using in-situ data is a difficult task since only a limited number of observational points is available at large heliocentric distances. Remote sensing observations can, however, provide important information for events close to the Sun. In this work we estimate the flux rope orientation first in the close vicinity of the Sun (2-20 Rs) using forward modeling of STEREO/SECCHI and SOHO/LASCO coronagraph images of coronal mass ejections and then in-situ using Grad-Shafranov reconstruction of the magnetic cloud. Thus, we…
The Parker Solar Probe (PSP) observed an interplanetary coronal mass ejection (ICME) event during its first orbit around the sun, among many other events. This event is analyzed by applying a wavelet analysis technique to obtain the reduced magnetic helicity, cross helicity, and residual energy, the first two of which are magnetohydrodynamics (MHD) invariants. Our results show that the ICME, as a large scale magnetic flux rope, possesses high magnetic helicity, very low cross helicity, and highly negative residual energy, thus pointing to a magnetic fluctuation dominated structure. Using the s…
We present a comprehensive analysis of the three-dimensional magnetic flux rope structure generated during the Lynch et al. (2019) magnetohydrodynamic (MHD) simulation of a global-scale, 360 degree-wide streamer blowout coronal mass ejection (CME) eruption. We create both fixed and moving synthetic spacecraft to generate time series of the MHD variables through different regions of the flux rope CME. Our moving spacecraft trajectories are derived from the spatial coordinates of Parker Solar Probe's past encounters 7 and 9 and future encounter 23. Each synthetic time series through the simulati…
Small-scale magnetic flux ropes (SFRs), in the solar wind, have been studied for decades. Statistical analysis utilizing various in situ spacecraft measurements is the main observational approach which helps investigate the generation and evolution of these small-scale structures. Based on the Grad-Shafranov (GS) reconstruction technique, we use the automated detection algorithm to build the databases of these small-scale structures via various spacecraft measurements at different heliocentric distances. We present the SFR properties including the magnetic field and plasma parameters at differ…
We present observations of the same magnetic cloud made near Earth by the Advance Composition Explorer (ACE), Wind, and the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS) mission comprising the Time History of Events and Macroscale Interactions during Substorms (THEMIS) B and THEMIS C spacecraft, and later by Juno at a distance of 1.2 AU. The spacecraft were close to radial alignment throughout the event, with a longitudinal separation of $3.6^{\circ}$ between Juno and the spacecraft near Earth. The magnetic cloud likely originated f…
We analyze multi-spacecraft observations associated with the 2012 July 12 Coronal Mass Ejection (CME), covering the source region on the Sun from SDO, stereoscopic imaging observations from STEREO, magnetic field characteristics at MESSENGER, and type II radio burst and in situ measurements from Wind. A triangulation method based on STEREO stereoscopic observations is employed to determine the kinematics of the CME, and the outcome is compared with the result derived from the type II radio burst with a solar wind electron density model. A Grad-Shafranov technique is applied to Wind in situ dat…
We identify coronal mass ejections (CMEs) associated with magnetic clouds (MCs) observed near Earth by the Wind spacecraft from 2008 to mid-2012, a time period when the two STEREO spacecraft were well positioned to study Earth-directed CMEs. We find 31 out of 48 Wind MCs during this period can be clearly connected with a CME that is trackable in STEREO imagery all the way from the Sun to near 1 AU. For these events, we perform full 3-D reconstructions of the CME structure and kinematics, assuming a flux rope morphology for the CME shape, considering the full complement of STEREO and SOHO imagi…
Coronal Mass Ejections (CMEs) are major drivers of extreme space weather conditions, this being a matter of serious concern for our modern technologically-dependent society. Development of numerical approaches that would simulate CME generation and propagation through the interplanetary space is an important step towards our capability to predict CME arrival times at Earth and their geo-effectiveness. In this paper, we utilize a data-constrained Gibson--Low (GL) flux rope model to generate CMEs. We derive the geometry of the initial GL flux rope using the Graduated Cylindrical Shell (GCS) meth…
Small-scale magnetic flux ropes (SFRs) are a type of structures in the solar wind that possess helical magnetic field lines. In a recent report (Chen & Hu 2020), we presented the radial variations of the properties of SFR from 0.29 to 8 au using in situ measurements from the Helios, ACE/Wind, Ulysses, and Voyager spacecraft. With the launch of the Parker Solar Probe (PSP), we extend our previous investigation further into the inner heliosphere. We apply a Grad-Shafranov-based algorithm to identify SFRs during the first two PSP encounters. We find that the number of SFRs detected near the Sun i…
We present an analysis of the ionic composition of iron for two interplanetary coronal mass ejections observed in May 21-23 2007 by the ACE and STEREO spacecraft in the context of the magnetic structure of the ejecta flux rope, sheath region, and surrounding solar wind flow. This analysis is made possible due to recent advances in multispacecraft data interpolation, reconstruction, and visualization as well as results from recent modeling of ionic charge states in MHD simulations of magnetic breakout and flux cancellation CME initiation. We use these advances to interpret specific features of …
Interplanetary coronal mass ejections (ICMEs) contain magnetic field and velocity fluctuations across a wide range of scales. These fluctuations may be interpreted as Alfvénic wave packets propagating parallel or anti-parallel to the background magnetic field, with the difference in power between counter-propagating fluxes quantified by the cross helicity. We have determined the cross helicity of inertial range fluctuations at $10^{-3}-10^{-2}$ Hz in 226 ICME flux ropes and 176 ICME sheaths observed by the Wind spacecraft at 1 au during 1995-2015. The flux ropes and sheaths had mean, normalise…
An unexpected strong geomagnetic storm occurred on 2018 August 26, which was caused by a slow coronal mass ejection (CME) from a gradual eruption of a large quiet-region filament. We investigate the eruption and propagation characteristics of this CME in relation to the strong geomagnetic storm with remote sensing and in situ observations. Coronal magnetic fields around the filament are extrapolated and compared with EUV observations. We determine the propagation direction and tilt angle of the CME flux rope near the Sun using a graduated cylindrical shell (GCS) model and the Sun-to-Earth kine…
Using a refined setup process, we simulated the propagation of six observed Coronal Mass Ejections (CMEs) with the 2012 Block-Adaptive-Tree-Solarwind-Roe-Upwind-Scheme (BATS-R-US) code from the Sun to the Earth or STEREO A and compared the outputs with observations. A linear relation between the average CME speed below 6 solar radii and the flux rope current is demonstrated and used to tune the simulations. The simulations correctly predict if and when an observable CME shock reaches one astronomical unit (AU). The arrival time predictions of the CME shocks at 1 AU have an accuracy of 0.9 $\pm…
Magnetic clouds (MCs) are twisted magnetic structures ejected from the Sun and probed by in situ instruments. They are typically modeled as flux ropes (FRs). The determination of the FR global characteristics requires the estimation of the FR axis orientation. Among the developed methods, the minimum variance (MV) is the most flexible, and features only a few assumptions. However, as other methods, MV has biases. We aim to investigate the limits of the method and extend it to a less biased method. We first identified the origin of the biases by testing the MV method on cylindrical and elliptic…
The Grad-Shafranov reconstruction is a method of estimating the orientation (invariant axis) and cross-section of magnetic flux ropes using the data from a single spacecraft. It can be applied to various magnetic structures such as magnetic clouds (MCs) and flux ropes embedded into the magnetopause and in the solar wind. We develop a number of improvements of this technique and show some examples of the reconstruction procedure of interplanetary coronal mass ejections (ICMEs) observed at 1 AU by the STEREO, WIND and ACE spacecraft during the minimum following the solar cycle 23. The analysis i…
Predicting the effects of a coronal mass ejection (CME) impact requires knowing if impact will occur, which part of the CME impacts, and its magnetic properties. We explore the relation between CME deflections and rotations, which change the position and orientation of a CME, and the resulting magnetic profiles at 1 AU. For 45 STEREO-era, Earth-impacting CMEs, we determine the solar source of each CME, reconstruct its coronal position and orientation, and perform a ForeCAT (Kay et al. 2015a) simulation of the coronal deflection and rotation. From the reconstructed and modeled CME deflections a…
Towards a Fully Automated Pipeline for Short-Term Forecasting of In Situ Coronal Mass Ejection Magnetic Field Structure
Austrian Space Weather Office, GeoSphere Austria（奥地利空间天气办公室，GeoSphere奥地利）；Institute of Physics, University of Graz（格拉茨大学物理研究所）；Goddard Planetary Heliophysics Institute, University of Maryland, Baltimore County（马里兰大学巴尔的摩县戈达德行星日球物理学研究所）；Heliophysics Science Division, NASA Goddard Space Flight Center（NASA戈达德太空飞行中心日球物理学部）；Community Coordinated Modeling Center, NASA Goddard Space Flight Center（NASA戈达德太空飞行中心社区协调建模中心）；Universities Space Research Association（大学空间研究协会）；DPHY, ONERA（ONERA DPHY）
The largest geomagnetic storms of solar cycle 24 so far occurred on 2015 March 17 and June 22 with $D_{\rm st}$ minima of $-223$ and $-195$ nT, respectively. Both of the geomagnetic storms show a multi-step development. We examine the plasma and magnetic field characteristics of the driving coronal mass ejections (CMEs) in connection with the development of the geomagnetic storms. A particular effort is to reconstruct the in situ structure using a Grad-Shafranov technique and compare the reconstruction results with solar observations, which gives a larger spatial perspective of the source cond…
