Ambipolar electrostatic field in dusty plasma

L. Z. Hadid (1) , O. Shebanits (2, 3) , J.-E. Wahlund (3) , M. W. Morooka (3) , A. Nagy (4) , W. M. Farrell (5) , M. K. G. Holmberg (6) , Ronan Modolo (7) , A. M. Persoon (8) , W. L. Tseng (9) , S.-Y. Ye (10)

1 LPP - Laboratoire de Physique des Plasmas
2 Blackett Laboratory
3 IRF - Swedish Institute of Space Physics [Uppsala / Kiruna]
4 CLaSP - Department of Climate and Space Sciences and Engineering
5 GSFC - NASA Goddard Space Flight Center
6 ESTEC - European Space Research and Technology Centre
7 HELIOS - LATMOS
8 Department of Physics and Astronomy [Iowa City]
9 Department of Earth Sciences [NTNU Taipei]
10 SUSTech - Southern University of Science and Technology

We study the effect of negatively charged dust on the magnetic-field-aligned polarisation electrostatic field (E) using Cassini's RPWS/LP in situ measurements during the 'ring-grazing' orbits. We derive a general expression for E and estimate for the first time in situ E (approximately 10 −5 V m −1) near the Janus and Epimetheus rings. We further demonstrate that the presence of the negatively charged dust close to the ring plane (|Z| 0.11 R s) amplifies E by at least one order of magnitude and reverses its direction due to the effect of the charged dust gravitational and inertial forces. Such reversal confines the electrons at the magnetic equator within the dusty region, around 0.047 R s above the ring plane. Furthermore, we discuss the role of the collision terms, in particular the ion-dust drag force, in amplifying E. These results imply that the charged dust, as small as nanometres in size, can have a significant influence on the plasma transport, in particular ambipolar diffusion along the magnetic field lines, and so their presence must be taken into account when studying such dynamical processes.

Mots clés: dusty plasmas; space plasma physics; astrophysical plasmas

Domaines: Planète et Univers [physics]

L. Z. Hadid, O. Shebanits, J.-E. Wahlund, M. W. Morooka, A. Nagy, et al.. Ambipolar electrostatic field in dusty plasma. Journal of Plasma Physics, 2022, 88 (2), pp.555880201. ⟨10.1017/s0022377822000186⟩. ⟨insu-03663734⟩