Abstract
Abstract. The Earth’s ring current and how it responds to varying interplanetary conditions is described and an account provided of the production of Energetic Neutral Atoms (ENAs) in the geo-corona. Also, the potential to remotely monitor, on a global scale, the temporal and spatial evolution of magnetospheric plasma populations through analysing ENA images recorded during magnetic storms/substorms is indicated. A technical account of the Energetic NeUtral Atom Detector Unit NUADU aboard China’s TC-2 mission (measurement range 45–>158 keV) follows, together with an account of the scientific objectives of NUADU, both in stand-alone mode and in the context of multi-point imaging. Low altitude ENA emissions recorded by NUADU during south polar passages of TC-2 at the time of a moderate magnetic storm in September 2004, as well as bright ring current emissions recorded in November 2004 during a major geomagnetic storm, are presented and discussed in the context of various, accompanying, terrestrial disturbances. Also, ENA observations of the November 2004 ring current imaged simultaneously by TC-2/NUADU and by IMAGE/ HENA (viewing, respectively, from the Northern and Southern Hemispheres), are compared.
Highlights
The Double Star Mission has its origin in an interagency agreement between the Chinese and European Space Agen-cies whereby two spacecraft from China, one flying in a polar and the other in an equatorial orbit, provide scientific support for experiments conducted aboard the four spacecraft of the European Space Agency’s Cluster Mission.Of relevance to the present paper is the polar satellite (TC-2) which was launched at 15:15 UT on 25 July 2004 to monitor physical processes taking place over the terrestrial magnetic poles
Since its power dissipation is rather low (4.7 W), this unit, which is thermally de-coupled from the Sensor Head, “follows” the platform temperature, which is itself controlled by the spacecraft, within a range that ensures a safe operational margin for the electronics under both nominal and eclipse conditions
The history of Energetic Neutral Atoms (ENAs) measurements at the Earth indicates the value of this technique in obtaining insights into the dynamics of the storm-time ring current; see, for example, accounts of ENA data recorded aboard the IMP-7, IMP-8 and ISEE-1 spacecraft (Williams et al, 1978; Roelof et al, 1985; Roelof, 1987); aboard CRRES (Voss et al, 1992, 1993); aboard Geotail (Lui et al, 1996; Wilken et al, 1997a; Orsini et al, 2000); aboard ASTRID (Barabash et al, 1997; Brandt et al, 1999); aboard CLUSTER (Wilken et al, 1997b); aboard POLAR (Blake et al, 1995; Henderson et al, 1997) and, most recently, aboard IMAGE (Burch, 2003)
Summary
Of relevance to the present paper is the polar satellite (TC-2) which was launched at 15:15 UT on 25 July 2004 to monitor physical processes taking place over the terrestrial magnetic poles. Included in the payload is an Energetic NeUtral Atom (ENA) imager NUADU, which is designed to detect ENAs in the energy range 45–>158 keV. 3 the production in the Earth’s magnetosphere of Energetic Neutral Atoms (ENAs) is discussed. 6 ENA images recorded by NUADU during two different episodes of geomagnetic storm activity in September and November 2004 are presented and discussed in the context of contemporaneous, background, solar related terrestrial disturbances. A comparison is made between images of the November ring current recorded simultaneously by NUADU and by the High Energy Neutral Atom (HENA) imager (Mitchell et al, 2000) on board the IMAGE satellite (Burch, 2003).
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