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Nomenclature

The Cluster PEACE experiment is made up of two sensor heads called LEEA and HEEA (Low and High Energy Electrostatic Analysers), mounted on opposite sides of each of the four Cluster spacecraft (Johnstone et al (1997)). Generally LEEA scans the lower energy range and HEEA the upper range, together covering electrons with $0.7$ eV $< E < 26$ keV. Over the duration of a spin ($\sim 4$ s), LEEA and HEEA cover 4$\pi$ steradians of velocity space.

The moment sums can be thought of as combinations of the low energy moments (the B (BOTTOM) moments, $E \sim 10$ eV), the high energy moments (the T (TOP) moments, $E \gtrsim 2$ keV), and the moments from where the energy scan of LEEA and HEEA overlap (which we call L1L2 and H1H2 respectively) as sketched in Figure 3.2. These separate pieces are telemetered to the ground, where we can construct moment sums covering the entire energy range by summing B, L1L2/H1H2 and T moments. The `measured' moments (subscript `m') are the raw sum of, for example B+overlap+T moments, which have not been corrected.

Figure 3.2: Schematic representation of the PEACE sensor coverage. The two sensor heads HEEA and LEEA are split into an energy range which is divided into 88 bins. The sensor coverages can overlap by some amount (left), leaving a low energy portion (BOTTOM) and a high energy portion (TOP). The sensors can be made to overlap completely (right) leaving no BOTTOM or TOP moments.

Image energy_levels


next up previous contents
Next: The algorithm Up: Definitions Previous: Moments of the velocity   Contents
Steve Schwartz 2005-03-26