Rocket spin effects on the current collected by a cylindrical probe in the ionosphere

Abstract

The dc current collected by a rocket‐borne cylindrical probe with various bias potentials has been measured, along with the plasma parameters (by in situ independent measurements on the same payload). Periodic variations synchronous with the rocket spin cycle appear; they are related to wake effects for the ion current and to both wake and V × B effects for the electron current. The ion current modulations are quantitatively explained by a theory on the wake which takes account of the angle between the velocity and the rocket axis; the electron current modulations due to the V × B field are separated from the others and quantitatively explained by simple calculations. As a by‐product the ion current outside the wake gives an unperturbed density measurement in agreement to within 15% with an independent measurement.

Numerical simulations of a sounding rocket in ionospheric plasma: Effects of magnetic field on the wake formation and rocket potential

“…As the angle increases, the magnetic field will have less impact on the floating potential. In contrast to the work by Meyer‐Vernet [], where it was concluded that, for ionospheric conditions, the effect of the magnetic field and its orientation on the current modulations measured by Langmuir probes is negligible, our simulation results clearly demonstrate how the electric potential is changed due to the orientation of the magnetic field.…”

“…These disturbances will have an important impact on the in situ measurements. Such disturbances have been reported in sounding rocket experiments [ Meyer‐Vernet , ; Svenes et al , ]. Thus, to ensure that we have reliable measurements of the ionospheric plasma, it is important to account for the disturbances due to the effects of the rocket wake and also due to the magnetic field.…”

“…While we simplify the shape of the rocket, we also note that exact details of the rocket's shape are of less importance for the problem of plasma‐object interaction and the floating potential [ Miloch et al , ]. The booms of the rocket would certainly modify the results to a certain degree [ Miyake et al , ], but the cylindrical body of the rocket will dominate the plasma disturbances far away from the surface [ Meyer‐Vernet , ] and is used here as a first approximation. Moreover, for computational reasons we scale down the cylinder but maintain the characteristic ratios between the typical lengths in plasma: cylinder radius, Debye length, and electron/ion gyroradius, so as to reflect the conditions in the ionospheric F layer.…”

“…However, because of the complexity of the problem of the plasma‐object interaction, most of the theoretical analysis is limited to simplified and idealized conditions [ Hastings , ]. In addition to the perturbations caused by the rocket or satellite itself, there are perturbations due to the wake formation of the probes [ Meyer‐Vernet , ]. Finally, the presence of a background magnetic field B 0 , and the corresponding convective electric field E 0 =− v D × B 0 ( v D being the drift velocity) can significantly influence the plasma‐particle dynamics [ Miller , ; Whipple , ; Lafon , ].…”

“…Finally, the presence of a background magnetic field B 0 , and the corresponding convective electric field E 0 =− v D × B 0 ( v D being the drift velocity) can significantly influence the plasma‐particle dynamics [ Miller , ; Whipple , ; Lafon , ]. These complex interactions can affect in situ experiments in the ionosphere; it is therefore crucial in analyzing results from such experiments, to have a proper understanding of plasma‐rocket interactions and related phenomena [ Al'pert et al , ; Temerin and Kintner , ; Hasegawa , ; Meyer‐Vernet , ].…”