Decay of the coronal magnetic field can release sufficient energy to power a solar flare

Magnetic energy release in a solar flare Solar flares are bright flashes and associated eruptions of plasma from the Sun that are thought to be powered by violent rearrangement of the magnetic fields near sunspots. Fleishman et al. observed a bright solar flare with a microwave interferometer, allowing them to map the magnetic field in the solar corona and monitor how it changed during the flare. They found a large drop in the local field strength over 2 minutes, releasing enough magnetic energy to power the entire solar flare. Determining the origin of this energy will help to predict how strong future solar flares may be and their potential space weather impacts on Earth. Science, this issue p. 278 Microwave observations of a solar flare show a drop in the magnetic field, rapid enough to power the flare. Solar flares are powered by a rapid release of energy in the solar corona, thought to be produced by the decay of the coronal magnetic field strength. Direct quantitative measurements of the evolving magnetic field strength are required to test this. We report microwave observations of a solar flare, showing spatial and temporal changes in the coronal magnetic field. The field decays at a rate of ~5 Gauss per second for 2 minutes, as measured within a flare subvolume of ~1028 cubic centimeters. This fast rate of decay implies a sufficiently strong electric field to account for the particle acceleration that produces the microwave emission. The decrease in stored magnetic energy is enough to power the solar flare, including the associated eruption, particle acceleration, and plasma heating.

[1]  G. Fleishman,et al.  Record-breaking Coronal Magnetic Field in Solar Active Region 12673 , 2019, The Astrophysical Journal.

[2]  E. Priest,et al.  Evidence for Downflows in the Narrow Plasma Sheet of 2017 September 10 and Their Significance for Flare Reconnection , 2018, The Astrophysical Journal.

[3]  S. White,et al.  Microwave and Hard X-Ray Observations of the 2017 September 10 Solar Limb Flare , 2018, The Astrophysical Journal.

[4]  S. Krucker,et al.  Fermi-LAT Observations of the 2017 September 10 Solar Flare , 2018, The Astrophysical Journal.

[5]  Y. Uchihori,et al.  The Cosmic Ray Energy Spectrum between 2 PeV and 2 EeV Observed with the TALE Detector in Monocular Mode , 2018, The Astrophysical Journal.

[6]  H. Hara,et al.  Photospheric and Coronal Abundances in an X8.3 Class Limb Flare , 2018 .

[7]  H. Hara,et al.  Plasma Evolution within an Erupting Coronal Cavity , 2018, 1802.01391.

[8]  K. Schawinski,et al.  Optical, Near-IR, and Sub-mm IFU Observations of the Nearby Dual Active Galactic Nuclei MRK 463 , 2018, 1801.06190.

[9]  X. Cheng,et al.  Spectroscopic Observations of a Current Sheet in a Solar Flare , 2018, 1801.03631.

[10]  Mark S. Giampapa,et al.  The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets , 2017, 1711.05691.

[11]  A. Bolton,et al.  The BOSS Emission-line Lens Survey. V. Morphology and Substructure of Lensed Lyα Emitters at Redshift Z ≈ 2.5 in the BELLS GALLERY , 2017, 1708.08854.

[12]  D. Rooks,et al.  SPECTROSCOPIC OBSERVATIONS OF CURRENT SHEET FORMATION AND EVOLUTION , 2018 .

[13]  P. Groot,et al.  Magnetically gated accretion in an accreting ‘non-magnetic’ white dwarf , 2017, Nature.

[14]  H. Warren,et al.  Spectroscopic Observations of Current Sheet Formation and Evolution , 2017, 1711.10826.

[15]  J. Drake,et al.  The role of three-dimensional transport in driving enhanced electron acceleration during magnetic reconnection , 2017, 1706.00481.

[16]  S. Antiochos,et al.  A universal model for solar eruptions , 2017, Nature.

[17]  Dale E. Gary,et al.  EOVSA Implementation of a Spectral Kurtosis Correlator for Transient Detection and Classification , 2016, 1702.05391.

[18]  L. Kashapova,et al.  A COLD FLARE WITH DELAYED HEATING , 2016, 1603.07273.

[19]  D. Gary,et al.  Magnetography of Solar Flaring Loops with Microwave Imaging Spectropolarimetry , 2013, 1303.1573.

[20]  Yang Liu,et al.  EVOLUTION OF MAGNETIC FIELD AND ENERGY IN A MAJOR ERUPTIVE ACTIVE REGION BASED ON SDO/HMI OBSERVATION , 2011, 1201.3404.

[21]  G. Fleishman,et al.  FAST GYROSYNCHROTRON CODES , 2010 .

[22]  D. Gary,et al.  DYNAMIC MAGNETOGRAPHY OF SOLAR FLARING LOOPS , 2009, 0906.0192.

[23]  D. Gary,et al.  Evaluating Mean Magnetic Field in Flare Loops , 2009 .

[24]  Carolus J. Schrijver,et al.  A CRITICAL ASSESSMENT OF NONLINEAR FORCE-FREE FIELD MODELING OF THE SOLAR CORONA FOR ACTIVE REGION 10953 , 2009, 0902.1007.

[25]  Yukio Katsukawa,et al.  Chromospheric Anemone Jets as Evidence of Ubiquitous Reconnection , 2007, Science.

[26]  Torus instability. , 2006, Physical review letters.

[27]  J. Ashby.  References and Notes , 1999 .

[28]  T. Yokoyama,et al.  Magnetic reconnection as the origin of X-ray jets and Hα surges on the Sun , 1995, Nature.

[29]  G. Dulk,et al.  Radio Emission from the Sun and Stars , 1985 .

[30]  R. Kopp,et al.  Magnetic reconnection in the corona and the loop prominence phenomenon , 1976 .

[31]  J. Högbom,et al.  APERTURE SYNTHESIS WITH A NON-REGULAR DISTRIBUTION OF INTERFEROMETER BASELINES. Commentary , 1974 .

[32]  T. Hirayama.  Theoretical model of flares and prominences , 1974 .

[33]  H. Zell.  Solar Flare , 1973, Nature.

[34]  P. Sturrock.  Model of the High-Energy Phase of Solar Flares , 1966, Nature.

[35]  John A. Nelder,et al.  A Simplex Method for Function Minimization , 1965, Comput. J..

[36]  H. Carmichael,et al.  A process for flares , 1964 .

[37]  Wilmot N. Hess,et al.  AAS-NASA Symposium on the physics of Solar Flares : proceedings of a symposium held at the Goddard Space Flight Center, Greenbelt, Maryland, October 28-30, 1963 , 1964 .

[38]  H. Dreicer,et al.  Electron and Ion Runaway in a Fully Ionized Gas. I , 1959 .