Abstract
We describe a new method to analyze the properties of plasma waves, and
apply it to observations made upstream from Mars by the Mars Atmosphere
and Volatile EvolutioN (MAVEN) mission. The slow measurement cadence of
most charged particle instrumentation has limited the application of
analysis techniques based on correlations between particle and magnetic
field measurements. We show that we can extend the frequency range of
applicability for these techniques, for a subset of waves that remain
coherent over multiple wave periods, by sub-sampling velocity
distribution function measurements and binning them by the wave phase.
This technique enables the computation of correlations and transport
ratios for plasma waves previously inaccessible to this technique at
Mars. By computing the cross helicity, we find that most identified
waves propagate upstream in the plasma frame. This supports the
conclusions of previous studies, but enables a clearer determination of
the intrinsic wave mode and characteristics. The intrinsic properties of
observed waves with frequencies close to the proton cyclotron frequency
have little spatial variability, but do have large temporal variations,
likely due to seasonal changes in the hydrogen exosphere. In contrast,
the predominant characteristics of waves at higher frequencies have less
temporal variability, but more spatial variability. We find several
indications of the presence of multiple wave modes in the lower
frequency wave observations, with unusual wave properties observed for
propagation parallel to the magnetic field and for background magnetic
fields nearly perpendicular to the solar wind flow.