The Solar Probe ANalyzers—Electrons on the Parker Solar Probe

Abstract

Electrostatic analyzers of different designs have been used since the earliest days of the space age, beginning with the very earliest solar wind measurements made by Mariner 2 en route to Venus in 1962. The Parker Solar Probe (PSP) mission, NASA's first dedicated mission to study the innermost reaches of the heliosphere, makes its thermal plasma measurements using a suite of instruments called the Solar Wind Electrons, Alphas, and Protons (SWEAP) investigation. SWEAP's electron Parker Solar Probe Analyzer (SPAN-E) instruments are a pair of top-hat electrostatic analyzers on PSP that are capable of measuring the electron distribution function in the solar wind from 2 eV to 30 keV. For the first time, in-situ measurements of thermal electrons provided by SPAN-E will help reveal the heating and acceleration mechanisms driving the evolution of the solar wind at the points of acceleration and heating, closer than ever before to the Sun. This paper details the design of the SPAN-E sensors and their operation, data formats, and measurement caveats from Parker Solar Probe's first two close encounters with the Sun. lowered from 35 solar radii (R S ) at the start of the mission to 9.86 solar radii at the end of the prime mission. PSP's overarching science questions are: 1) Determine the structure and dynamics of the magnetic fields at the sources of the fast and slow solar wind; 2) Trace the flow of energy that heats the solar corona and accelerates the solar wind; and 3) Explore mechanisms that accelerate and transport energetic particles. PSP uses an encounter-based operations scheme: the science instruments on the spacecraft collect their primary, high cadence data during a solar "encounter" phase that lasts for 10-15 days (when the distance from the Sun is less than 0.25 AU) around perihelion, and occasionally collect lower cadence data during the remaining portion of

Plasma Double Layers at the Boundary Between Venus and the Solar Wind

“…The magnetic field sensors include two fluxgate magnetometers (FGM) and one search coil magnetometer (SCM) mounted to the magnetometer boom. The low-energy particle instrument suite, SWEAP, consists of four detectors: the Solar Probe Cup (SPC), a Faraday cup pointing normal to the heat shield plane (Case et al, 2020), two SPANe electron detectors (Whittlesey et al, 2020), one on either side of the spacecraft but behind the heat shield, and one SPANi ion detector, also behind the heat shield. The SPAN detectors are top hat electrostatic analyzers measuring the distributions of electrons or protons from a few eV to ∼30 keV, at a cadence of ∼13.98 s for the second Venus encounter.…”

Constraining Ion-Scale Heating and Spectral Energy Transfer in Observations of Plasma Turbulence

“…We consider frequencies up to 100 Hz (k ⊥ ρ i ∼ 10), to avoid the SCM noise floor. Average plasma properties are computed for each interval using solar wind electrons alphas and protons (SWEAP) investigation data [62]; n i and T i from the SWEAP-solar probe cup (SPC) [72] and n e , T e from SWEAP-solar probe analyzers PHYSICAL REVIEW LETTERS 125, 025102 (2020) 025102-2 (SPAN) electron fits [73,74]. On average, β i (β e ) is 0.26 (0.74) with a standard deviation of 0.13 (0.25), with…”

Could Switchbacks Originate in the Lower Solar Atmosphere? I. Formation Mechanisms of Switchbacks

“…In fact, the measured distribution of deflections resembles a power law, with most of the deflections at small angles relative to the Parker spiral (Dudok de Wit et al 2020). There is evidence that switchbacks are localized kinks in the magnetic field and not polarity reversals or closed loops (Whittlesey et al 2020;McManus et al 2020). However, switchbacks are not a new finding.…”