Earth's ambipolar electrostatic field and its role in ion escape to space.

Cold plasma of ionospheric origin has recently been found to be a much larger contributor to the magnetosphere of Earth than expected. Numerous competing mechanisms have been postulated to drive ion escape to space, including heating and acceleration by wave-particle interactions and a global electrostatic field between the ionosphere and space (called the ambipolar or polarization field). Observations of heated O ions in the magnetosphere are consistent with resonant wave-particle interactions.

A gated-time-of-flight top-hat electrostatic analyzer for low energy ion measurements.

When incorporated into a top-hat electrostatic analyzer, a gate electrode enables the separation of ions by their mass-per-charge with modest mass resolution (M/∆M ∼ 10). Gated-time-of-flight (TOF) instruments avoid the energy straggling and angular scattering effects prevalent in foil-based detection systems, providing more pristine measurements of three-dimensional distribution functions of incident ions. Gated-TOF implementations are ideal for measuring the properties of low-energy (i.

Ionospheric ambipolar electric fields of Mars and Venus: Comparisons between theoretical predictions and direct observations of the electric potential drop.

We test the hypothesis that their dominant driver of a planetary ambipolar electric field is the ionospheric electron pressure gradient (∇ ). The ionospheres of Venus and Mars are mapped using Langmuir probe measurements from NASA's and missions. We then determine the component of the ionospheric potential drop that can be explained by the electron pressure gradient drop along a simple draped field line.

Constraining electric fields from electrostatic deflector plates: A brief report and case study from the Fast Plasma Investigation for the Magnetospheric Multiscale Mission.

A common feature of top hat space plasma analyzers are electrostatic "deflector plates" mounted externally to the aperture which steer the incoming particles and permit the sensor to rapidly scan the sky without moving. However, the electric fields generated by these plates can penetrate the mesh or grid on the outside of the sensor, potentially violating spacecraft electromagnetic cleanliness requirements. In this brief report we discuss how this issue was addressed for the Dual Electron Spectrometer for the Magnetospheric Multiscale Mission using a double-grid system and the simple modeling technique employed to assure the safe containment of the stray fields from its deflector plates.