[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-21] The Electrojet Zeeman Imaging Explorer (EZIE) Mission

*Jeng-Hwa Yee¹、Jesper Gjerloev¹、Nelofar Mosavi¹、Rafael Mesquita¹、Karl Landal²、Patrick Alken³、Viacheslav G. Merkin¹、Kareem A. Sorathia¹、Larry Kepko⁵、Wenbin Wang⁴、Astrid Maute³、Olga K. Verkhoglyadova⁶、Heikki Vanhamaki⁷、Richard Larsson⁹、Patrick Espy¹⁰、Dong L. Wu⁵、Kirsti Kauristie⁸ (1.Johns Hopkins University, Applied Physics Laboratory、2.Unversity of Bergen、3.University of Colorado, CIRES、4.National Center for Atmospheric Research (NCAR)、5.NASA Goddard Space Flight Center、6.Jet Propulsion Laboratory、7.University of Oulu、8.Finnish Meteorological Institute、9.University of Hamburg、10.Norwegian Unversity of Science (NTNU))

キーワード：Electrojets, Currents, Magnetosphere-Ionosphere Coupling

EZIE, the Electrojet Zeeman Imaging Explorer, is a recently selected NASA Heliophysics mission of opportunity to study the electrojets in the ionosphere. It employs four identical miniaturized radiometers on each of the three 6U CubeSat, flying in a pearls-on-a-string managed formation, to measure, for the first time, the two-dimensional structure and the temporal evolution of the electrojets flowing at altitudes of ~100–130 km. It employs the Zeeman sensing technique from low-earth orbiting satellite to remotely obtain the current-induced magnetic field vectors at ~80 km, an altitude region very close to the electrojet. The four cross-track downward-looking antennae on each satellite measure polarimetric radiances of the Zeeman-splitted 118 GHz O₂ thermal emission line and obtain the magnetic signatures of the electrojet based on measured Zeeman splitting spectral properties. This novel measurement technique allows for the remote sensing of the electrojets at four different cross-track locations simultaneously at altitudes notoriously difficult to measure in situ. The compact 118-GHz heterodyne spectro-polarimeters, leveraging technologies demonstrated by TEMPEST-D and CubeRRT; the 6U CubeSat bus heritage includes RAVAN, CAT, TEMPEST-D, and CubeRRT. Differential drag maneuvers are used to manage satellite along-track temporal separation to within 2–10 minutes between adjacent satellite to record the electrojet temporal evolution, eliminating the need for on-board propulsion. The combination of the sensing technique, compact instrument, CubeSat technologies, mission operations, allow EZIE to cost-effectively obtain never-before 'mesoscale' measurements of the electrojets needed to understand how the solar wind energies stored in the magnetosphere are transferred to the thermosphere and ionosphere. In this paper we will present an overview of the EZIE mission, its science objectives, the Zeeman sensing technique employed, and the measurement products to be provided.