Iridium Communications Satellite Constellation Data for Study of Earth's Magnetic Field

Abstract

The magnetic field of the Earth yields clues to the dynamics of the present-day core dynamo and its history through magnetization in the crust (cf. Aubert et al., 2010). The internally generated magnetic field of the Earth arises predominantly from the dynamo in the outer core, and the structure and intensity of the field above the core is given by a potential field extrapolated from the core-mantle boundary ∼3,000 km below the surface (cf. Roberts & King, 2013). The dynamo field typically varies by ∼1% per decade and includes wave-like features at middle-to-low latitudes extending and propagating in longitude (cf. Finlay, Dumberry, et al., 2010). Sub-annual variations have also been observed and identified as geomagnetic jerks that exhibit rapid changes in the first and second time derivatives in the secular variation at a fixed observatory (Brown et al., 2013;Finlay et al., 2016;Mandea et al., 2010). While the mantle is not a dominant source of magnetic field, induction of currents in the mantle on time scales of hours to days in response to correspondingly

Distributions of Birkeland Current Density Observed by AMPERE are Heavy‐Tailed or Long‐Tailed

“…AMPERE is a data set that combines measurements of magnetic perturbations from Iridium satellites with spherical harmonic fitting to estimate the spatial variation of Birkeland current densities. The data processing method was first outlined by Anderson et al (2000); Waters et al (2001) and a more detailed consideration is presented in Anderson et al (2021); Waters et al (2020). This current density j is presented on a grid of 1° latitude by 1 hr of magnetic local time (MLT) in altitude-adjusted corrected geomagnetic coordinates (AACGM), with a convention that upward currents are j > 0 and downward currents are j < 0. j is estimated from measurements in a ten-minute long sliding window, which is evaluated every 2 min.…”

“…Although Chisham et al (2009) demonstrated that ionospheric vorticity could be used as a proxy for Birkeland current, the work done to quantify the vorticity distributions found using SuperDARN data (Chisham & Freeman, 2010 has not been done using Birkeland current data directly, because until now a suitable data set was not available for this type of analysis. We address this by using the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE, Anderson et al, 2000Anderson et al, , 2021Waters et al, 2001Waters et al, , 2020. Furthermore, SuperDARN studies of ionospheric vorticity have been constrained by the geographical locations of the radars, whereas AMPERE is truly global.…”

A Mosaic of the Inner Heliosphere: Three Carrington Rotations During the Whole Heliosphere and Planetary Interactions Interval

“…The AMPERE project (Anderson et al, 2002(Anderson et al, , 2021 consists of 66 satellites distributed in six polar, low-Earth orbit (780 km altitude) planes, yielding global measurements of magnetic perturbations over 10-min accumulation windows shifted in time by 2-min steps. These measurements allow for the study of the large-scale Region-1 and Region-2 field-aligned current systems (see, e.g., Iijima & Potemra, 1976) and ionospheric electrodynamics in both hemispheres.…”

Multi‐Scale Ionospheric Poynting Fluxes Using Ground and Space‐Based Observations

“…AMPERE (Anderson et al, 2014(Anderson et al, , 2021 provides global scale measurements of magnetic fields perturbed (δB) due to FACs. These are obtained from the Iridium Communications Satellite Network constellation after subtracting the background terrestrial magnetic field from onboard magnetometer data using a main field reference model (IGRF or the World Magnetic Model (WMM; Chulliat et al, 2020), the former of which is used in this study), then fitting a spherical harmonic formulation (Waters et al, 2001(Waters et al, , 2020.…”