Skip to Main content Skip to Navigation
Journal articles

Estimation of a coronal mass ejection magnetic field strength using radio observations of gyrosynchrotron radiation

Abstract : Coronal mass ejections (CMEs) are large eruptions of plasma and magnetic field from the low solar corona into interplanetary space. These eruptions are often associated with the acceleration of energetic electrons which produce various sources of high intensity plasma emission. In relatively rare cases, the energetic electrons may also produce gyrosynchrotron emission from within the CME itself, allowing for a diagnostic of the CME magnetic field strength. Such a magnetic field diagnostic is important for evaluating the total magnetic energy content of the CME, which is ultimately what drives the eruption. Here, we report on an unusually large source of gyrosynchrotron radiation in the form of a type IV radio burst associated with a CME occurring on 2014-September-01, observed using instrumentation from the Nancay Radio Astronomy Facility. A combination of spectral flux density measurements from the Nancay instruments and the Radio Solar Telescope Network (RSTN) from 300 MHz to 5 GHz reveals a gyrosynchrotron spectrum with a peak flux density at similar to 1 GHz. Using this radio analysis, a model for gyrosynchrotron radiation, a non-thermal electron density diagnostic using the Fermi Gamma Ray Burst Monitor (GBM) and images of the eruption from the GOES Soft X-ray Imager (SXI), we were able to calculate both the magnetic field strength and the properties of the X-ray and radio emitting energetic electrons within the CME. We find the radio emission is produced by non-thermal electrons of energies > 1MeV with a spectral index of delta similar to 3 in a CME magnetic field of 4.4G at a height of 1.3 R circle dot, while the X-ray emission is produced from a similar distribution of electrons but with much lower energies on the order of 10 keV. We conclude by comparing the electron distribution characteristics derived from both X-ray and radio and show how such an analysis can be used to define the plasma and bulk properties of a CME.
Document type :
Journal articles
Complete list of metadatas

Cited literature [72 references]  Display  Hide  Download

https://hal-insu.archives-ouvertes.fr/insu-01701187
Contributor : Nathalie Pothier <>
Submitted on : Monday, December 9, 2019 - 1:55:05 PM
Last modification on : Wednesday, September 23, 2020 - 4:39:52 AM
Long-term archiving on: : Tuesday, March 10, 2020 - 5:25:59 PM

File

aa31368-17.pdf
Publisher files allowed on an open archive

Identifiers

Citation

Eoin Carley, Nicole Vilmer, Paulo Simões, Brían Ó Fearraigh. Estimation of a coronal mass ejection magnetic field strength using radio observations of gyrosynchrotron radiation. Astronomy and Astrophysics - A&A, EDP Sciences, 2017, 608 (A137), 14 p. ⟨10.1051/0004-6361/201731368⟩. ⟨insu-01701187⟩

Share

Metrics

Record views

435

Files downloads

637