  A variety of kinetic waves develop in the solar wind. The relationship
between these waves and larger-scale structures, such as current sheets and
ongoing turbulence remain a topic of investigation. Similarly, the
instabilities producing ion-acoustic waves in the solar wind remains an open
question. The goals of this paper are to investigate kinetic electrostatic
Langmuir and ion-acoustic waves in the solar wind at 0.5 AU and determine
whether current sheets and associated streaming instabilities can produce the
observed waves. The relationship between these waves and currents is
investigated statistically. Solar Orbiter's Radio and Plasma Waves instrument
suite provides high-resolution snapshots of the fluctuating electric field. The
Low Frequency Receiver resolves the waveforms of ion-acoustic waves and the
Time Domain Sampler resolves the waveforms of both ion-acoustic and Langmuir
waves. Using these waveform data we determine when these waves are observed in
relation to current structures in the solar wind, estimated from the background
magnetic field. Langmuir and ion-acoustic waves are frequently observed in the
solar wind. Ion-acoustic waves are observed about 1% of the time at 0.5 AU. The
waves are more likely to be observed in regions of enhanced currents. However,
the waves typically do not occur at current structures themselves. The observed
currents in the solar wind are too small to drive instability by the relative
drift between single ion and electron populations. When multi-component ion
and/or electron distributions are present the observed currents may be
sufficient for instability. Ion beams are the most plausible source of
ion-acoustic waves. The spacecraft potential is confirmed to be a reliable
probe of the background electron density by comparing the peak frequencies of
Langmuir waves with the plasma frequency calculated from the spacecraft
potential.
