Measuring the magnetic origins of solar flares, CMEs and Space Weather

Abstract

We take a broad look at the problem of identifying the magnetic solar causes of space weather. With the lackluster performance of extrapolations based upon magnetic field measurements in the photosphere, we identify a region in the near UV part of the spectrum as optimal for studying the development of magnetic free energy over active regions. Using data from SORCE, Hubble Space Telescope, and SKYLAB, along with 1D computations of the near-UV (NUV) spectrum and numerical experiments based on the MURaM radiation-MHD and HanleRT radiative transfer codes, we address multiple challenges. These challenges are best met through a combination of near UV lines of bright \ion{Mg}{2}, and lines of \ion{Fe}{2} and \ion{Fe}{1} (mostly within the $4s-4p$ transition array) which form in the chromosphere up to $2\times 10^4$ K. Both Hanle and Zeeman effects can in principle be used to derive vector magnetic fields. However, for any given spectral line the $\tau =1$ surfaces are generally geometrically corrugated owing to fine structure such as fibrils and spicules. By using multiple spectral lines spanning different optical depths, magnetic fields across nearly-horizontal surfaces can be inferred in regions of low plasma $\beta$, from which free energies, magnetic topology and other quantities can be derived. Based upon the recently-reported successful suborbital space measurements of magnetic fields with the CLASP2 instrument, we argue that a modest space-borne telescope will be able to make significant advances in the attempts to predict solar eruptions. Difficulties associated with blended lines are shown to be minor in an Appendix.

arXiv commentAccepted in ApJ, V2 fixed author spelling error

References in corpus (37)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The stellar atmosphere simulation code Bifrost
• Solar Flare Prediction Using SDO/HMI Vector Magnetic Field Data with a Machine-Learning Algorithm
• A Comparison of Flare Forecasting Methods, I: Results from the "All-Clear" Workshop
• Extension of the MURaM radiative MHD code for coronal simulations
• Deep Flare Net (DeFN) model for solar flare prediction
• Predicting Solar Flares Using a Long Short-Term Memory Network
• The solar chromosphere at high resolution with IBIS. I. New insights from the Ca II 854.2 nm line
• Solar Force-free Magnetic Fields
• A Comparison of Flare Forecasting Methods. II. Benchmarks, Metrics and Performance Results for Operational Solar Flare Forecasting Systems
• Identifying Solar Flare Precursors Using Time Series of SDO/HMI Images and SHARP Parameters
• The Unresolved Fine Structure Resolved - IRIS observations of the Solar Transition Region
• An active region filament studied simultaneously in the chromosphere and photosphere: I - Magnetic structure
• Flare Prediction Using Photospheric and Coronal Image Data
• The Multi-slit Approach to Coronal Spectroscopy with the Multi-slit Solar Explorer (MUSE)
• Magnetic Diagnostics of the Solar Chromosphere with the Mg II h-k Lines
• The polarization of the solar MgII h and k lines
• Discovery of Scattering Polarization in the Hydrogen Lyman-$\alpha$ Line of the Solar Disk Radiation
• Mapping Solar Magnetic Fields from the Photosphere to the Base of the Corona
• Stokes Inversion based on Convolutional Neural Networks
• On the magnetic field of off-limb spicules
• Influence of atomic polarization and horizontal illumination on the Stokes profiles of the He I 10830 multiplet
• The magnetic sensitivity of the Mg ii k line to the joint action of Hanle, Zeeman and magneto-optical effects
• Vector magnetic field measurements along a cooled stereo-imaged coronal loop
• Thermal fine structure and magnetic fields in the solar atmosphere: spicules and fibrils
• The magnetic sensitivity of the resonance and subordinate lines of Mg II in the solar chromosphere
• On the Origin of a Sunquake during the 29 March 2014 X1 Flare
• Real-time flare prediction based on distinctions between flaring and non-flaring active region spectra
• Casting the Coronal Magnetic Field Reconstruction Tools in 3D Using MHD Bifrost Model
• Solar Flare Prediction Using Magnetic Field Diagnostics Above the Photosphere
• From Forbidden Coronal Lines to Meaningful Coronal Magnetic Fields
• Spectropolarimetric analysis of an active region filament. I. Magnetic and dynamical properties from single component inversions
• CLASP Constraints on the Magnetization and Geometrical Complexity of the Chromosphere-Corona Transition Region
• Prospects of solar magnetometry - from ground and in space
• The chromosphere above a $\delta$-sunspot in the presence of fan-shaped jets
• On the Probable Existence of an Abrupt Magnetization in the Upper Chromosphere of the Quiet Sun
• Magnetic connections across the chromosphere-corona transition region

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