Dust detection by the wave instrument on STEREO: nanoparticles picked up by the solar wind?

TL;DR

The paper proposes that intense voltage pulses detected by STEREO/WAVES are caused by nanoparticles impacting the spacecraft at solar wind speeds, potentially marking the first detection of such fast nanoparticles in interplanetary space.

Contribution

It introduces a novel interpretation that nanoparticle impacts produce the observed voltage pulses, linking dust impact signals to nanometer-sized particles in space.

Findings

Voltage pulses are consistent with impacts by 10-nm nanoparticles.

Flux estimates align with existing interplanetary dust models.

First possible detection of fast-moving nanoparticles near Earth.

Abstract

The STEREO/WAVES instrument has detected a very large number of intense voltage pulses. We suggest that these events are produced by impact ionisation of nanoparticles striking the spacecraft at a velocity of the order of magnitude of the solar wind speed. Nanoparticles, which are half-way between micron-sized dust and atomic ions, have such a large charge-to-mass ratio that the electric field induced by the solar wind magnetic field accelerates them very efficiently. Since the voltage produced by dust impacts increases very fast with speed, such nanoparticles produce signals as high as do much larger grains of smaller speeds. The flux of 10-nm radius grains inferred in this way is compatible with the interplanetary dust flux model. The present results may represent the first detection of fast nanoparticles in interplanetary space near Earth orbit.