Christian T. Steigies

Development of a fast impedance probe for absolute electron density measurements in the ionosphere

The design of a digitally controlled impedance probe for the fast absolute measurement of the ionospheric plasma density aboard a sounding rocket is described. Instrument performance is tested in a large plasma chamber. The first results from two flights within the DEOS-campaign are reported, and discussed with respect to spatial resolution and wake effects. The resulting density profiles have the same shape as ground-based ionosonde measurements. The in situ impedance probe measurements yield absolute electron densities that are lower by a factor of 1.5-2.

Plasma diagnostics with Langmuir probes in the equatorial ionosphere: I. The influence of surface contamination

The application of spherical Langmuir probes for measuring the electron temperature and density on ionospheric sounding rockets is discussed with respect to the influence of the geomagnetic field effects and probe contamination. The influence of the contamination layer is thoroughly analysed in the frame of a nonlinear equivalent circuit. When operating the probe in ramp mode, it is found that the distortion of the current-voltage characteristic is different for decreasing and increasing probe voltages. The resulting error of the electron temperature is determined for a range of capacitance (C) and resistance (R) values of the contamination layer. A method is described to determine the parameters R and C from the flight data. Further, a correction algorithm is discussed that allows the true probe characteristic to be retrieved from the measured distorted characteristic.

Plasma diagnostics with Langmuir probes in the equatorial ionosphere: II. Evaluation of DEOS flight F06

The flight data of an ionospheric sounding rocket (DEOS campaign flight F06) are evaluated with respect to electron density and temperature profiles. The probe characteristic is analysed in the frame of a model that takes the influence of the geomagnetic field and of a contamination layer into account, as described in part?I (Piel et al 2001 J.?Phys.?D: Appl.?Phys.). The electron temperature of the night-time ionosphere is found to be higher (1300?K) than that predicted by the IRI-95 model (Bilitza?D 1999 J.?Atmos. Terr. Phys. 61 167), but in general agreement with the model of Watanabe et al (Watanabe et al 1995 J.?Geophys. Res. 100 14?581). It is also found that the electron temperature in depleted plasma regions (plasma bubbles) is lower than in the unperturbed plasma. This is a hint at the action of the Rayleigh-Taylor mechanism that convects cold low-density plasma from the bottomside of the F-layer to higher altitudes inside the plasma bubbles. An absolute comparison of the electron density profiles from the analysis of the Langmuir probe and by an independent impedance probe is performed. Excellent agreement of the profile shape and of absolute density values can be achieved over the entire altitude regime. It is demonstrated which steps in the evaluation procedure of the probe characteristic may lead to systematic errors in electron density.

Electron density measurements with impedance and Langmuir probes in the DEOS campaign

Abstract The DEOS campaign comprises three sounding rockets that are launched from southern India to study the diurnal variation of the dynamics of the E- and F-layers at the edge of the equatorial electrojet under equinox conditions. Langmuir and impedance probes are employed for in-situ measurements of plasma densities, temperatures and density fluctuations. The improved impedance probe uses digital frequency synthesis and, due to the fast sweep time of the instrument, allows for a good spatial resolution (130 m) together with high accuracy (1.5%). Of the two Langmuir probes, one is operated in sweep mode for electron temperature measurements, the other in electron saturation mode for density fluctuations (f = 5 Hz − 1.5 kHz). Preliminary results from the first flight (F05) on April 19, 1998 at 19:21 local time are presented.

Electron density and temperature measurements obtained in the DEOS campaign

Abstract In the DEOS campaign (Dynamics of the Equatorial ionosphere Over SHAR) electron densities and temperatures have been measured with impedance and Langmuir probes. Three rocket flights have been performed in the evening equatorial ionosphere, shortly before and during equatorial spread- F (ESF). In the first flight, an undisturbed evening ionosphere was encountered and the resulting density profiles are compared with a profile obtained from ionosonde observations during the flight and with predictions from the IRI-95 model. In the second flight, which was launched under ESF conditions, large plasma bubbles were detected during the upleg. Both instruments resolve the large scale features as well as the intermediate scale fluctuations inside the plasma bubbles and agree well in the absolute densities measured. The temperature profiles show a strong reduction of the electron temperature in the depleted region, as compared with the ambient plasma. A temperature profile taken under unperturbed conditions is presented and compared with current models.

The early phase of spread F development studied in situ with impedance and Langmuir probes

The postsunset equatorial ionosphere is studied with rocket-borne plasma diagnostic instruments within the Dynamics of the Equatorial Ionosphere Over Shriharikota Range (DEOS) campaign. Data from an impedance probe and a Langmuir probe allow for a critical comparison between the instruments, with ionosonde data, and with the International Reference Ionosphere model. During flight F05, which was launched before the onset of equatorial spread F (ESF), a generally smooth density profile was found. Density depletions (bubbles) are only found when the rocket crosses the lower edge of the F layer during the downleg of the trajectory. In flight F06, launched shortly after onset of ESF, a large-scale depletion is found on the upleg of the trajectory below 360-km altitude, where a transition to an unperturbed density profile occurs. Impedance probe and Langmuir probe data show close agreement of the density depletions and their fine structure with a resolution of 100 m. The morphology of the plasma depletion is compared with models and previous investigations. Electron temperature measurements with Langmuir probes show that the temperature in the depleted region is lower than that in the ambient plasma.