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Title: USING COORDINATED OBSERVATIONS IN POLARIZED WHITE LIGHT AND FARADAY ROTATION TO PROBE THE SPATIAL POSITION AND MAGNETIC FIELD OF AN INTERPLANETARY SHEATH

Coronal mass ejections (CMEs) can be continuously tracked through a large portion of the inner heliosphere by direct imaging in visible and radio wavebands. White light (WL) signatures of solar wind transients, such as CMEs, result from Thomson scattering of sunlight by free electrons and therefore depend on both viewing geometry and electron density. The Faraday rotation (FR) of radio waves from extragalactic pulsars and quasars, which arises due to the presence of such solar wind features, depends on the line-of-sight magnetic field component B{sub ∥} and the electron density. To understand coordinated WL and FR observations of CMEs, we perform forward magnetohydrodynamic modeling of an Earth-directed shock and synthesize the signatures that would be remotely sensed at a number of widely distributed vantage points in the inner heliosphere. Removal of the background solar wind contribution reveals the shock-associated enhancements in WL and FR. While the efficiency of Thomson scattering depends on scattering angle, WL radiance I decreases with heliocentric distance r roughly according to the expression I∝r {sup –3}. The sheath region downstream of the Earth-directed shock is well viewed from the L4 and L5 Lagrangian points, demonstrating the benefits of these points in terms of space weather forecasting.more » The spatial position of the main scattering site r{sub sheath} and the mass of plasma at that position M{sub sheath} can be inferred from the polarization of the shock-associated enhancement in WL radiance. From the FR measurements, the local B{sub ∥sheath} at r{sub sheath} can then be estimated. Simultaneous observations in polarized WL and FR can not only be used to detect CMEs, but also to diagnose their plasma and magnetic field properties.« less
Authors:
; ;  [1] ; ;  [2] ; ;  [3]
  1. State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing (China)
  2. Rutherford-Appleton Laboratory (RAL) Space, Harwell Oxford (United Kingdom)
  3. Reading University, Reading (United Kingdom)
Publication Date:
OSTI Identifier:
22270672
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; ELECTRON DENSITY; ELECTRONS; FARADAY EFFECT; HELIOSPHERE; LAGRANGIAN FUNCTION; MAGNETIC FIELDS; PLASMA; POLARIZATION; PULSARS; QUASARS; RADIOWAVE RADIATION; SHOCK WAVES; SOLAR CORONA; SOLAR WIND; SUN; THOMSON SCATTERING