  Observations of interplanetary scintillation (IPS - the scintillation of
compact radio sources due to density variations in the solar wind) enable the
velocity of the solar wind to be determined, and its bulk density to be
estimated, throughout the inner heliosphere. A series of observations using the
Low Frequency Array (LOFAR - a radio telescope centred on the Netherlands with
stations across Europe) were undertaken using this technique to observe the
passage of an ultra-fast CME which launched from the Sun following the X-class
flare of 10 September 2017. LOFAR observed the strong radio source 3C147 at an
elongation of 82 degrees from the Sun over a period of more than 30 hours and
observed a strong increase in speed to 900km/s followed two hours later by a
strong increase in the level of scintillation, interpreted as a strong increase
in density. Both speed and density remained enhanced for a period of more than
seven hours, to beyond the period of observation. Further analysis of these
data demonstrates a view of magnetic-field rotation due to the passage of the
CME, using advanced IPS techniques only available to a unique instrument such
as LOFAR.
