Investigation of charge and ion drag force dynamics in complex plasma experiments with neon and argon under microgravity

Abstract In complex dusty plasmas, micron-sized particles immersed in ionized gas acquire a significant negative charge and experience various forces. One of the primary forces acting on these particles is the ion drag force. The PK-4 facility aboard the International Space Station enables precise studies of such systems under microgravity. During campaigns #17 and #18, we investigated the ion drag force on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mn>3.4</mml:mn> <mml:mstyle scriptlevel="0"/> <mml:mi>μ</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:mrow> </mml:math> melamine-formaldehyde microparticles in argon and neon plasmas across a pressure range of 10–120 Pa. We combined experimental data with advanced machine learning techniques and ion drag force modeling. This allowed us to evaluate and improve theoretical models, including an analytical approach for weak and intermediate ion coupling, as well as a hybrid model that incorporates kinetic simulations. Our results reveal a pronounced enhancement of the ion drag force measured at low pressures (below 30 Pa), especially in neon, where ion collisions and drift velocities significantly affect particle dynamics. These findings emphasize the role of ion-neutral collisions and plasma composition in determining dust-plasma interactions, offering new insight into the limitations of existing theoretical models and the need for gas-specific model refinements.