Articles | Volume 19, issue 10/12
Ann. Geophys., 19, 1355–1366, 2001

Special issue: CLUSTER

Ann. Geophys., 19, 1355–1366, 2001

  30 Sep 2001

30 Sep 2001

First results from the RAPID imaging energetic particle spectrometer on board Cluster

B. Wilken1,*, P. W. Daly1, U. Mall1, K. Aarsnes2, D. N. Baker3, R. D. Belian4, J. B. Blake5, H. Borg6, J. Büchner1, M. Carter7, J. F. Fennell5, R. Friedel4, T. A. Fritz8, F. Gliem9, M. Grande7, K. Kecskemety10, G. Kettmann1, A. Korth1, S. Livi1, S. McKenna-Lawlor11, K. Mursula12, B. Nikutowski1, C. H. Perry7, Z. Y. Pu13, J. Roeder5, G. D. Reeves4, E. T. Sarris14, I. Sandahl15, F. Søraas2, J. Woch1, and Q.-G. Zong1 B. Wilken et al.
  • 1Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, D-37191 Katlenburg Lindau, Germany
  • 2University of Bergen, Allegt. 55, 5007 Bergen-U, Norway
  • 3LASP, Boulder-CO 80309, USA
  • 4LANL, Los Alamos-NM 87545, USA
  • 5Aerospace Corporation, Los Angeles-CA 90009, USA
  • 6IRF, 90187 Umea, Sweden
  • 7RAL, Chilton, Didcot, Oxfordshire OX110QX, UK
  • 8Boston University, Boston-MA 02215, USA
  • 9IDA, D-38106 Braunschweig, Germany
  • 10KFKI, H-1525 Budapest-114, Hungary, USA
  • 11NUI, Maynooth-Co., Kildare, Ireland
  • 12University of Oulu, 90571 Oulu, Finland
  • 13Peking University, Beijing 100871, China
  • 14University of Thrace, Xanthi, Greece
  • 15IRF,S-98128 Kiruna-C, Sweden00871, China
  • *The RAPID team deeply regrets the untimely demise of B. Wilken, PI of the Cluster project. Without him, the RAPID instrument would never have been created

Abstract. The advanced energetic particle spectrometer RAPID on board Cluster can provide a complete description of the relevant particle parameters velocity, V , and atomic mass, A, over an energy range from 30 keV up to 1.5 MeV. We present the first measurements taken by RAPID during the commissioning and the early operating phases. The orbit on 14 January 2001, when Cluster was travelling from a perigee near dawn northward across the pole towards an apogee in the solar wind, is used to demonstrate the capabilities of RAPID in investigating a wide variety of particle populations. RAPID, with its unique capability of measuring the complete angular distribution of energetic particles, allows for the simultaneous measurements of local density gradients, as reflected in the anisotropies of 90° particles and the remote sensing of changes in the distant field line topology, as manifested in the variations of loss cone properties. A detailed discussion of angle-angle plots shows considerable differences in the structure of the boundaries between the open and closed field lines on the nightside fraction of the pass and the magnetopause crossing. The 3 March 2001 encounter of Cluster with an FTE just outside the magnetosphere is used to show the first structural plasma investigations of an FTE by energetic multi-spacecraft observations.

Key words. Magnetospheric physics (energetic particles, trapped; magnetopause, cusp and boundary layers; magnetosheath)

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