Modeling of Cluster's electric antennas in space: Application to plasma diagnostics

Abstract

[1] The main characteristics of the long-boom electric antennas installed on board the Cluster satellites are derived from finite element modeling in a kinetic and isotropic space plasma, in the frequency range of about 1-100 kHz. The model is based on the surface charge distribution method in quasi-static conditions. The impedances of both types of antenna, i.e., the double-wire and the double-probe, are computed versus the frequency normalized with respect to the local plasma frequency and for several different Debye lengths. Most of the code outputs are checked using analytic estimations for better understanding of the involved physical mechanisms. As a by-product, the effective length of the double-probe antenna and the mutual impedance between the two antennas are computed by the code. It is shown that if it had been possible to implement such measurements on board, one would have been able not only to determine accurately the electric characteristics of the antennas but also to estimate the local plasma parameters. Nevertheless, an interesting feature predicted by the model has been checked recently in orbit by running a special mode of operation for testing the mutual impedance measurement. The preliminary results are globally consistent with the predictions, except that they suggest that our Maxwellian model for the electron distribution should be revised in order to explain the unexpected low-frequency response. After analysis of the electron flux measurements obtained simultaneously, it appears that a rough adjustment of the electron distribution with a two-component distribution allows us to account for the observations. Citation: Béghin, C., P. M. E. Décréau, J. Pickett, D. Sundkvist, and B. Lefebvre (2005), Modeling of Cluster's electric antennas in space: Application to plasma diagnostics, Radio Sci., 40, RS6008,

Characteristics of Langmuir electric field waveforms and power spectra exhibiting nonlinear behavior in Earth's foreshock

“…Recently, modeling and mutual impedance tests of the Cluster antennas have indicated that under certain conditions, the effective length of the antennas may be shorter than their actual physical length [ Béghin et al , 2005]. The results of these tests indicate that we may still be underestimating the actual waveform amplitudes, even when we correct for spin modulation.…”

Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

“…1b and c display the spectral power density of electric field integrated along the effective length of the antenna, a quantity expressed in units of V 2 rms Hz −1 . The latter quantity, closer to the raw measurement, is directly proportional to the former, according to a coefficient identical on both spacecraft, since their respective receiving antenna have the same physical length and provided that the plasma regime is similar enough on each platform for effective lengths to be equal to each other (Béghin et al, 2005).…”

Development and Application of Geospace Environment Simulator for the Analysis of Spacecraft–Plasma Interactions

“…As examined in many past works (e.g., [28]), it is shown that the resistance, the real part of the impedance, has a peak value, and the reactance, the imaginary part, shows a drastic change both at the plasma frequency. The impedance modification by ES waves depends on the Debye length and its relative ratio to the antenna length, which is discussed in the latest work with the CLUSTER antenna modeling [38]. In the current simulation, the Debye length of the background plasma is 4.5 m, while the entire length of the antenna is 24 m. In this situation, the signature of the resonance around the plasma frequency of the background plasma is rather difficult to be observed because it is generally known that it appears for antenna lengths around 8-10 m Debye lengths.…”

“…In this method, the ion sheath interface is given as a parameter. The antenna analysis with the SCD method has been successfully applied to the interpretation of impedance measurements onboard spacecraft such as the CLUSTER satellite [38].…”