45 research outputs found
Prediction of Shock Arrival Times from CME and Flare Data
This paper presents the Shock ARrival Model (SARM) for predicting shock arrival times for distances from 0.72 AU to 8.7 AU by using coronal mass ejections (CME) and flare data. SARM is an aerodynamic drag model described by a differential equation that has been calibrated with a dataset of 120 shocks observed from 1997 to 2010 by minimizing the mean absolute error (MAE), normalized to 1 AU. SARM should be used with CME data (radial, earthward or plane-of-sky speeds), and flare data (peak flux, duration, and location). In the case of 1 AU, the MAE and the median of absolute errors were 7.0 h and 5.0 h respectively, using the available CMEflare data. The best results for 1 AU (an MAE of 5.8 h) were obtained using both CME data, either radial or cone-model-estimated speeds, and flare data. For the prediction of shock arrivals at distances from 0.72 AU to 8.7 AU, the normalized MAE and the median were 7.1 h and 5.1 h respectively, using the available CMEflare data. SARM was also calibrated to be used with CME data alone or flare data alone, obtaining normalized MAE errors of 8.9 h and 8.6 h respectively for all shock events. The model verification was carried out with an additional dataset of 20 shocks observed from 2010 to 2012 with radial CME speeds to compare SARM with the empirical ESA model [Gopalswamy et al., 2005a] and the numerical MHD-based ENLIL model [Odstrcil et al., 2004]. The results show that the ENLIL's MAE was lower than the SARM's MAE, which was lower than the ESA's MAE. The SARM's best results were obtained when both flare and true CME speeds were used
Distorted-Toroidal Flux Rope model for Heliospheric Flux Ropes
The three-dimensional characterization of magnetic flux-ropes observed in the
heliosphere has been a challenging task for decades. This is mainly due to the
limitation to infer the 3D global topology and the physical properties from the
1D time series from any spacecraft. To advance our understanding of magnetic
flux-ropes whose configuration departs from the typical stiff geometries, here
we present the analytical solution for a 3D flux-rope model with an arbitrary
cross-section and a toroidal global shape. This constitutes the next level of
complexity following the elliptic-cylindrical (EC) geometry. The mathematical
framework was established by Nieves-Chinchilla et al. (2018) ApJ, with the EC
flux-rope model that describes the magnetic topology with elliptical
cross-section as a first approach to changes in the cross-section. In the
distorted-toroidal flux rope model, the cross-section is described by a general
function. The model is completely described by a non-orthogonal geometry and
the Maxwell equations can be consistently solved to obtain the magnetic field
and relevant physical quantities. As a proof of concept, this model is
generalized in terms of the radial dependence of current density components.
The last part of this paper is dedicated to a specific function,
, to illustrate possibilities of the
model. This model paves the way to investigate complex distortions of the
magnetic structures in the solar wind. Future investigations will in-depth
explore these distortions by analyzing specific events, the implications in the
physical quantities, such as magnetic fluxes, heliciy or energy, and evaluating
the force balance with the ambient solar wind that allows such distortions.Comment: 19 pages, 8 figure
Modeling FETCH Observations of 2005 May 13 CME
This paper evaluates the quality of CME analysis that has been undertaken
with the rare Faraday rotation observation of an eruption. Exploring the
capability of the FETCH instrument hosted on the MOST mission, a four-satellite
Faraday rotation radio sounding instrument deployed between the Earth and the
Sun, we discuss the opportunities and challenges to improving the current
analysis approaches.Comment: 33 pages, 24 figure
Evidence of a complex structure within the 2013 August 19 coronal mass ejection: Radial and longitudinal evolution in the inner heliosphere
Context. Late on 2013 August 19, a coronal mass ejection (CME) erupted from an active region located near the far-side central meridian from Earthâs perspective. The event and its accompanying shock were remotely observed by the STEREO-A, STEREO-B, and SOHO spacecraft. The interplanetary counterpart (ICME) was intercepted by MESSENGER near 0.3 au and by both STEREO-A and STEREO-B near 1 au, which were separated from each other by 78° in heliolongitude.
Aims. The main objective of this study is to follow the radial and longitudinal evolution of the ICME throughout the inner heliosphere and to examine possible scenarios for the different magnetic flux-rope configuration observed on the solar disk and measured in situ at the locations of MESSENGER and STEREO-A, separated by 15° in heliolongitude, and at STEREO-B, which detected the ICME flank.
Methods. Solar disk observations are used to estimate the âmagnetic flux-rope typeâ, namely, the magnetic helicity, axis orientation, and axial magnetic field direction of the flux rope. The graduated cylindrical shell model is used to reconstruct the CME in the corona. The analysis of in situ data, specifically the plasma and magnetic field, is used to estimate the global interplanetary shock geometry and to derive the magnetic flux-rope type at different in situ locations, which is compared to the type estimated from solar disk observations. The elliptical cylindrical analytical model is used for the in situ magnetic flux-rope reconstruction.
Results. Based on the CME geometry and on the spacecraft configuration, we find that the magnetic flux-rope structure detected at STEREO-B belongs to the same ICME detected at MESSENGER and STEREO-A. The opposite helicity deduced at STEREO-B might be due to that fact that it intercepted one of the legs of the structure far from the flux-rope axis, in contrast to STEREO-A and MESSENGER, which were crossing through the core of the magnetic flux rope. The different flux-rope orientations measured at MESSENGER and STEREO-A probably arise because the two spacecraft measure a curved, highly distorted, and rather complex magnetic flux-rope topology. The ICME may have suffered additional distortion in its evolution in the inner heliosphere, such as the west flank propagating faster than the east flank when arriving near 1 au.
Conclusions. This work illustrates how a wide, curved, highly distorted, and rather complex CME showed different orientations as observed on the solar disk and measured in situ at 0.3 au and near 1 au. Furthermore, the work shows how the ambient conditions can significantly affect the expansion and propagation of the CME and ICME, introducing additional irregularities to the already asymmetric eruption. The study also manifests how these complex structures cannot be directly reconstructed with the currently available models and that multi-point analysis is of the utmost importance in such complex events.Agencia Estatal de InvestigaciĂł
Deep Learning for Space Weather Prediction: Bridging the Gap between Heliophysics Data and Theory
Traditionally, data analysis and theory have been viewed as separate
disciplines, each feeding into fundamentally different types of models. Modern
deep learning technology is beginning to unify these two disciplines and will
produce a new class of predictively powerful space weather models that combine
the physical insights gained by data and theory. We call on NASA to invest in
the research and infrastructure necessary for the heliophysics' community to
take advantage of these advances.Comment: Heliophysics 2050 White Pape
CME Evolution in the Structured Heliosphere and Effects at Earth and Mars During Solar Minimum
The activity of the Sun alternates between a solar minimum and a solar
maximum, the former corresponding to a period of "quieter" status of the
heliosphere. During solar minimum, it is in principle more straightforward to
follow eruptive events and solar wind structures from their birth at the Sun
throughout their interplanetary journey. In this paper, we report analysis of
the origin, evolution, and heliospheric impact of a series of solar transient
events that took place during the second half of August 2018, i.e. in the midst
of the late declining phase of Solar Cycle 24. In particular, we focus on two
successive coronal mass ejections (CMEs) and a following high-speed stream
(HSS) on their way towards Earth and Mars. We find that the first CME impacted
both planets, whilst the second caused a strong magnetic storm at Earth and
went on to miss Mars, which nevertheless experienced space weather effects from
the stream interacting region (SIR) preceding the HSS. Analysis of
remote-sensing and in-situ data supported by heliospheric modelling suggests
that CME--HSS interaction resulted in the second CME rotating and deflecting in
interplanetary space, highlighting that accurately reproducing the ambient
solar wind is crucial even during "simpler" solar minimum periods. Lastly, we
discuss the upstream solar wind conditions and transient structures responsible
for driving space weather effects at Earth and Mars.Comment: 27 pages, 7 figures, 1 table, accepted for publication in Space
Weathe