CME

Magnetic field and plasma diagnostics for solar coronal mass ejections: A case study using the forward modeling approach

whawkins — Fri, 03 Mar 2023 22:05:34 +0000

Magnetic field and plasma diagnostics for solar coronal mass ejections: A case study using the forward modeling approach whawkins Fri, 03/03/2023 - 15:05

Author:

whawkins

Mar 3, 2023

Synthesized results of the Fe xiii 10747 line, along with several POS cross section quantities in the model during CME eruption (a)-(e): Intensity (Stokes I), linear polarization degree(L/I), line width, Doppler velocity, and azimuth derived from synthesized signals. (f)-(h): Magnetic field, temperature, and density distributions in the POS. The arc-shaped contour in each panel represents ∇ · v = −0.05. Two leading fronts (LF) can be distinguished in panel (a). Each white arrow in panel (g) represents the POS projection of the deduced shock normals. The solar disk is indicated by the yellow curve in each panel. The region below 1.05R⊙ is masked.

Solar Physics: The proposed COronal Solar Magnetism Observatory (COSMO) Large Coronagraph (LC) will provide unique observations to study coronal mass ejections (CMEs) with its ability to diagnose the magnetic field and plasma properties in the solar corona. Here we take a realistic magnetohydrodynamic CME model, and synthesize the signals of several coronal emission lines (CELs) to perform forward modeling of COSMO LC observation of a CME. We use the Stokes parameters of the Fe xiii 10747 Angstrom line to diagnose the magnetic field and plasma properties of the CME flux rope. The results show that COSMO LC can provide magnetic field measurements of CME progenitors with a high spatial resolution (2′′ pixels). By using a worse resolution (6′′ pixels), the COSMO LC observation may also be used to qualitatively study the evolution of magnetic field during the CME eruption. We then use the synthetic signals of several other CELs to diagnose the physical conditions in the CME leading front, including the shock. The COSMO LC observations of the Fe xiii 10798/10747 Angstrom and Ar xiii 8300/10143 Angstrom line pair can provide density diagnostics of the front. By observing several CELs with different formation temperatures, the COSMO LC can be used to diagnose the temperature and ionization states in the front. We suggest that the Fe xiii 10747 Angstrom line should be given the highest priority when observing CMEs, while observations of the Fe xiii 10798 Angstrom, Fe xiv 5303 Angstrom, Fe xv 7062 Angstrom, and Ar xiii 10143 Angstrom lines can also provide valuable information on CMEs.

Predicting the Geoeffectiveness of CMEs Using Machine Learning

whawkins — Tue, 23 Aug 2022 15:59:37 +0000

Predicting the Geoeffectiveness of CMEs Using Machine Learning whawkins Tue, 08/23/2022 - 09:59

Author:

whawkins

Aug 23, 2022

UMAP of the predictions of the ensemble model, applied on the test set (20% of the data), colored by their correctness. Labels: TN - True Negative; FP - False Positive; TP - True Positive; FN - False Negative.

Coronal mass ejections are the most important space weather phenomena, being associated with large geomagnetic storms, and having the potential to cause disturbances to telecommunications, satellite network disruptions, and power grid damage and failures. Thus, considering these storms' potential effects on human activities, accurate forecasts of the geoeffectiveness of CMEs are paramount. This work focuses on experimenting with different machine-learning methods trained on data sets of close-to-Sun CMEs, to estimate whether such a newly erupting ejection has the potential to induce geomagnetic activity. We developed classification models using a variety of machine learning approaches. At this time, we limited our forecast to exclusively use solar onset parameters, to ensure extended warning times. We discuss the main challenges of this task and show that adequate predictions can be achieved with these models.

Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare

kolinski — Thu, 18 Nov 2021 19:02:39 +0000

Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare kolinski Thu, 11/18/2021 - 12:02

Publication Name: ApJL; First HAO Author's Name: Philip Judge

Author:

kolinski

Nov 18, 2021

We examine spectropolarimetric data from the CoMP instrument, acquired during the evolution of the September 10th 2017 X8.2 solar flare on the western solar limb. CoMP captured linearly polarized light from two emission lines of Fe XIII at 1074.7 and 1079.8 nm, from 1.03 to 1.5 solar radii. We focus here on the hot plasma-sheet lying above the bright flare loops and beneath the ejected CME.

Intensity and polarization data surrounding the current sheet formed on Sept 10 2017.

The polarization has a striking and coherent spatial structure, with unexpectedly small polarization aligned with the plasma-sheet. By elimination, we find that small-scale magnetic field structure is needed to cause such significant depolarization, and suggest that plasmoid formation during reconnection (associated with the tearing mode instability) creates magnetic structure on scales below instrument resolution of 6 Mm. We conclude that polarization measurements with new coronagraphs, such as the upcoming DKIST, will further enhance our understanding of magnetic reconnection and development of turbulence in the solar corona.

Convolutional Neural Networks for Predicting the strength of the Near-Earth Magnetic Field Caused by Interplanetary Coronal Mass Ejections

kolinski — Wed, 17 Nov 2021 16:26:43 +0000

Convolutional Neural Networks for Predicting the strength of the Near-Earth Magnetic Field Caused by Interplanetary Coronal Mass Ejections kolinski Wed, 11/17/2021 - 09:26

Publication Name: Frontiers in Astronomy; Authors names as they are listed in article: Anna Malanushenko, Natasha Flyer, Sarah Gibson

Author:

kolinski

Nov 17, 2021

In this paper, regression-based deep convolutional neural networks (CNN), with 12 layers, are developed for predicting the maximal amplitude of the southward component of the near-Earth magnetic field from a passing interplanetary coronal mass ejection (ICME). The input to the CNN is the Gibson and Low (GLOW) flux rope model (Gibson and Low, 1998) that describes the coronal properties of a CME, where its morphology and position is controlled by 5 varying parameters, i.e. input sampling occurs over a 5D parameter space. The ultimate goal is to determine the extent to which coronal spectropolarimetric observations at the Sun encode sufficient information to predict southward magnetic field component at the Earth.

Examples of various initial GLOW configurations. Blue and green lines are magnetic field lines sampling the magnetic structure of the GLOW spheromak, shown here with different combinations of parameters for angular size, topology, orientation. Solar surface is shown in thin black lines for reference.

The GLOW model is used as a first simple test of a self-similarly expanding magnetic flux rope which nevertheless allows consideration of the impact of varying CME location, orientation, size, and morphology. The CNN problem is set up in two experiments: 1) given input data near the Sun, three 2D images in the meridional plane of the components of the magnetic field, predict the maximal southward amplitude of the measured magnetic field at the Earth; 2) given line-of-sight integrated images of the Stokes parameters, corresponding to the physical configurations of the over 30K flux ropes from Part 1, predict the maximal southward amplitude of the measured magnetic field at the Earth.

CME

Magnetic field and plasma diagnostics for solar coronal mass ejections: A case study using the forward modeling approach

Recent News

Predicting the Geoeffectiveness of CMEs Using Machine Learning

Recent News

Spectropolarimetric Insight into Plasma-Sheet Dynamics of a Solar Flare

Recent News

Convolutional Neural Networks for Predicting the strength of the Near-Earth Magnetic Field Caused by Interplanetary Coronal Mass Ejections

Recent News