Radio Remote Sensing of Coronal Mass Ejections: Implications for Parker
Solar Probe and Solar Orbiter
Abstract
Coronal mass ejections (CMEs) are fast-moving magnetic field structures
of enhanced plasma density that play an important role in space weather.
The Solar Orbiter and Parker Solar Probe will usher in a new era of in
situ measurements, probing CMEs within distances of 60 and 10 solar
radii, respectively. At the present, only remote-sensing techniques such
as Faraday rotation can probe the plasma structure of CMEs at these
distances. Faraday rotation is the change in polarization position angle
of linearly polarized radiation as it propagates through a magnetized
plasma (e.g. a CME) and is proportional to the path integral of the
electron density and line-of-sight magnetic field. In conjunction with
white-light coronagraph measurements, Faraday rotation observations have
been used in recent years to determine the magnetic field strength of
CMEs. We report recent results from simultaneous white-light and radio
observations made of a CME in July 2015. We made radio observations
using the Karl G. Jansky Very Large Array (VLA) at 1 - 2 GHz frequencies
of a set of radio sources through the solar corona at heliocentric
distances that ranged between 8 - 23 solar radii. These Faraday rotation
observations provide a priori estimates for comparison with future in
situ measurements made by the Solar Orbiter and Parker Solar Probe.
Similar Faraday rotation observations made simultaneously with
observations by the Solar Orbiter and Parker Solar Probe in the future
could provide information about the global structure of CMEs sampled by
these probes and, therefore, aid in understanding the in situ
measurements.