DOI: 10.5281/zenodo.8364796
title: Wind spacecraft floating potential measurements

description: <strong>Quick Summary:</strong> The ASCII files herein are a dataset of spacecraft electric potential for the <em>Wind</em> spacecraft between January 1, 2005 and January 1, 2022. The data is thoroughly described in the publication "Spacecraft floating potential measurements for the <em>Wind</em> spacecraft," <em>The Astrophysical Journal Supplement Series</em>. <strong><em>Wind</em> Spacecraft:</strong> The <em>Wind</em> spacecraft (https://wind.nasa.gov and https://doi.org/10.1029/2020RG000714) was launched on November 1, 1994 and currently is in a halo orbit about the first Sun-Earth Lagrange point. It holds a suite of instruments from gamma ray detectors to quasi-static magnetic field instruments, Bo. The instruments used in this study and these datasets are the fluxgate magnetometer (MFI), the radio receivers (WAVES), ion Faraday cups (SWE), and the electron and ion electrostatic analyzers (3DP). The MFI measures 3-vector <strong>B</strong><sub>o</sub> at ~11 samples per second (sps); the SWE measures reduced velocity distribution functions (VDFs) of the thermal proton and alpha-particle populations from which velocity moments are derived and used herein; WAVES observes electromagnetic radiation from ~4 kHz to &gt;12 MHz which provides an observation of the upper hybrid line (also called the plasma line) used to define the total electron density; and 3DP observes full 4π steradian VDFs of electrons and ions from a few eV to ~30 keV which provide both ion velocity moments and the electron VDFs modeled herein. <strong>Brief Method Description:</strong> The spacecraft potential, \(\phi_{sc}\), was found using four methods. Three of these methods return a range of values while the fourth returns a single value. The methods rely on examining the shape of the electron energy distribution function (EDF), f(E) versus energy, E, for three different pitch-angles (parallel, perpendicular, and anti-parallel with respect to the quasi-static magnetic field, <strong>B</strong><sub>o</sub>). The instrument has a physical lower energy threshold, E<sub>min</sub>, below which no data are measured. We impose an upper energy threshold, E<sub>max</sub>, allowed when searching for \(\phi_{sc}\) based on empirical evidence. The methods are as follows: Method 1: find the range of energies where d<sup>2</sup>f/dE<sup>2</sup> &gt; 0, also referred to as the positive curvature region;<br> Method 2: find the range of energies where df/dE transitions from negative to positive, i.e., the local minimum point of f(E);<br> Method 3: find the range of energies bounding the minimum and maximum values of d<sup>2</sup>f/dE<sup>2</sup>, i.e., region of minimum to maximum curvature; and<br> Method 4: find the local minimum between E<sub>min</sub> and E<sub>max</sub> There are some additional constraints imposed in the software, available at https://github.com/lynnbwilsoniii/wind_3dp_pros (https://doi.org/10.5281/zenodo.6141586). We found four basic shapes for the EDFs (see paper for example figures), two (i.e., Types A and B) of which satisfy E<sub>min</sub> &lt; \(\phi_{sc}\) and thus are good. The other two shapes (i.e., Types C1 and C2) satisfy E<sub>min</sub> &gt; \(\phi_{sc}\), and thus we cannot determine \(\phi_{sc}\) from the EDF. We can only know that it has an upper bound of E<sub>min</sub>. All Type A EDFs are given a quality flag (QF) of 4 (i.e., the best), all Type Bs are given a QF of 2 (i.e., still okay and useable), and all Type Cs are given a QF of 0 (i.e., do not use these). <strong>ASCII File Description:</strong> Each ASCII file contains one year of data. There is summary information contained in the header of each file. The first two columns are the start and end times (UTC) of the EDF (format 'YYYY-MM-DD/hh:mm:ss.xxx'). After the times, Methods 1-3 have six columns and Method 4 has three columns. The first(second) three columns for Methods 1-3 correspond to the lower(upper) bound on the range of \(\phi_{sc}\) [eV] solutions. Method 4 only has one set of three-column solutions. Each three-column set corresponds to the parallel, perpendicular, and anti-parallel pitch-angle solutions. All of these in total comprise 21 columns. The \(\phi_{sc}\) solutions are followed by a column for E<sub>min</sub> [eV] and E<sub>max</sub> [eV]. The last two columns are the EDF label or type (i.e., A, B, C1, or C2) and the quality flag (i.e., 4, 2, or 0). Note that NaNs have been replaced with -10<sup>30</sup> fill values
description: {"references": ["10.1029/2020RG000714"]}