Smart dusty plasma liquids on the International Space Station*

This study examines dusty plasma liquids using data from the PK-4 facility on board the ISS. Similar to smart materials which change their properties in response to externally applied stimuli, microgravity dusty plasmas are highly sensitive to changes in the discharge conditions. Here we report the observation of dust acoustic waves at lower pressure and the formation of long dust chains (electrorheology) at higher pressures in a DC neon discharge with polarity switched field. The driving mechanism of the waves is studied by comparison to analytically derived dispersion relations corresponding to different scenarios, including strong coupling effects and fast ion drift speeds. Strong coupling of the dust grains is expected to deviate from the usual Yukawa form due to the formation of dust-ion-wakefield proxy dipoles. The possibility of large ion drift speeds in the bulk plasma can result from high frequency ionization waves due to the polarity switching of the DC field. These phenomena are further compared to data from on-ground experiments performed in the PK-4 analogue facility at Baylor University.