Constraining ICME Magnetic Field Orientations: Murchison Widefield Array measurements
Abstract
It is possible to remotely sense the orientation of magnetic fields in CME plasma using polarimetric radio imaging. Synchrotron emission from early-stage CMEs will exhibit linear polarization with an E-vector orientation that is intrinsically perpendicular to the sky plane component of the field. Independently, the linear polarization of background radio sources will be Faraday-rotated upon passage through interplanetary CME (ICME) plasma, yielding information on the direction and strength of the line of sight component of the field. Such observations have hitherto been difficult, because they are optimally made at low radio frequencies, must be sensitive, and require high dynamic range. The technology of low frequency imaging arrays has now advanced to the point that it is possible to contemplate an operational capability for such measurements.The Murchison Widefield Array (MWA) in western Australia is optimized for high fidelity imaging within narrow time and frequency slices, coupled with an extraordinarily wide field of view, on the order of 1000 deg2. The MWA features 128 independent phased-array “tiles” operating in the 80-300 MHz range, and completed science commissioning on June 20, 2013. We propose to demonstrate the feasibility of radio polarimetric remote sensing of ICME magnetic field orientations, via MWA imaging both of synchrotron radiation from CME plasma, and Faraday rotation of background emission passing through ICME plasma.We will determine the performance requirements for an operational round-the-clock radio-polarimetric remote sensing system capable of measuring the magnetic field orientation in ICME plasma before the disturbance reaches 0.4 AU. This would provide strong constraints on modeling of ICME events, and allows robust prediction of the field orientation upon arrival at the Earth. This would yield a practical means of predicting ICME geo-effectiveness with dramatically improved lead-time (~1 day instead of ~1 hour).
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 09, 2018
- Source ID
- FA23861714126
Entities
People
- John Morgan
Organizations
- Air Force Office of Scientific Research
- Curtin University
- United States Air Force