Ionosphere plasma electron parameters from radio frequency sweeping impedance probe measurements

Abstract

In this work we will describe the technique of using an RF sweeping impedance probe (SIP) to measure the AC impedance of an electrically short monopole immersed in a plasma. We analyze the SIP measurements which are taken from the payload of the Storms sounding rocket, launched from Wallops Island, Virginia, in 2007. The scientific objective of the Storms mission was to concentrate on whether density irregularities observed in midlatitude spread F could arise from ionospheric coupling to terrestrial weather. As such, independent measurements of the electron density profile are crucial. Since the inherent nature of the SIP technique makes it relatively insensitive to errors introduced through spacecraft charging, probe contamination, and other DC effects, it is an ideal instrument to employ under disturbed plasma conditions. The instrument measures both the magnitude and phase of the AC impedance from 100 kHz to 20 MHz in 128 frequency steps, performing 45,776 sweeps over the entire flight. From these measurements we infer both the absolute electron density n e and the electron neutral collision frequencies en throughout the flight trajectory. The SIP data can be approximately analyzed using a fluid formulation and thin sheath approximation particularly at altitudes below 200 km, which allows us to match the measurements to quasi-static analytical formulas. At about 265 km on the upleg, the magnitude data transitioned to a highly damped response with increasing altitude. The phase data, on the other hand, continued to indicate increased plasma density and reduced collisionality as expected. For a large portion of the flight, the payload of the Storms mission exhibited an uncontrolled coning motion, making the local magnetic field orientation with respect to the dipole difficult to decipher. Despite these difficulties, we were able to obtain robust estimates of the electron density profile, using the phase information from each sweep. In addition, the electron neutral collision frequency obtained from matching to phase data alone was on the correct order of magnitude with respect to Naval Research Laboratory Mass Spectrometer Incoherent Scatter-Extended model values in the ionosphere between 100 km and 150 km.

Spectrum of Langmuir fluctuations trapped in a cavity of a collisional plasma

“…. The Debye length for the ionospheric plasma can be found using the International Reference Ionosphere model [36]. In particular, for the ionospheric F-layer the Debye length is usually of the order of 1cm.…”

“…The equations (A.1)-(A.8) determine in full the function B 1 ( ) which enters into the expression for the electron density fluctuation spectrum (36). Recall that x 1,2 and x 3,4 are the turning points and the generation points, respectively (see figure 1); Γ determines the one-cycle damping of the Langmuir wave (18); w F( ) is the full phase shift of the wave passed one cycle (29); x , y w ( ) is the wavenumber of the Langmuir wave depending on the frequency ω and the coordinate x (11), and T x k , x 3 ( | |)is the phase function given by (14).…”

Electrostatic thermal noise in a weakly ionized collisional plasma

“…On the other hand, laboratory and ionospheric plasmas (especially at lower ionospheric layers) dominantly consist of neutral atoms and molecules, which frequently collide with electron population. The antenna impedance in a collisional plasma has been theoretically treated in the hydrodynamic approximation (which is reliable above the plasma frequency) by Balmain [1964] and measured in various rocket [see, e.g., Hoang, 1972;Spencer and Patra, 2015] and laboratory experiments [see, e.g., Hall and Landauer, 1971;Blackwell et al, 2007aBlackwell et al, , 2007b. This paper uses kinetic approach to examine the influence of collisions.…”

Numerical Study of Non-Linear Effects for a Swept Bias Langmuir Probe

“…The trade-off is a more complicated setup involving more circuitry that needs to be calibrated. In the ionosphere radio frequency (RF) probes like sweeping impedance probes (SIP) and High Frequency Capacitance probes (HFC) are also used [2]- [4]. While Langmuir probes require a low frequency of the sweep, at which the sheath gets time to establish itself, SIP rely on sweeping frequencies so high that the sheath does not get time to form and the effect of the sheath is negligible [5].…”

“…While Langmuir probes require a low frequency of the sweep, at which the sheath gets time to establish itself, SIP rely on sweeping frequencies so high that the sheath does not get time to form and the effect of the sheath is negligible [5]. These probes are normally operated in the range from a few hundred kHz to a few dozen MHz, and the data can be analyzed using a fluid formulation and thin sheath approximation [2], [6], [7].…”