CLUSTER & IMAGE: Preliminary comparison between ion distribution - PowerPoint PPT Presentation

CLUSTER & IMAGE: Preliminary comparison between ion distribution functions measured by CLUSTER-CIS in the inner magnetosphere and ion distributions obtained from IMAGE-HENA energetic neutral atom image inversions Iannis Dandouras (1), Claire Vallat (1), Pontus C:son Brandt (2), Donald G. Mitchell (2), Edmond C. Roelof (2), Malcolm Dunlop (3), Henri Rème (1), André Balogh (3) (1) Centre d'Etude Spatiale des Rayonnements, Toulouse, France (2) Applied Physics Laboratory, Johns Hopkins University, Maryland, USA (3) Blackett Laboratory, Imperial College, London, UK Yosemite Magnetospheric Imaging Workshop, Feb. 2002

Regions visited by Cluster Bow shock Plasmasphere Orbit Solar wind Magnetopause • High eccentricity, high inclination orbit : several plasma domains analyzed. • Tetrahedric configuration : temporal and spatial decorrelation. • Adaptive geometry of the tetrahedron : according to the plasma cell scale s.

IMAGE FOV CLUSTER

CIS : The Instrument

CIS Dynamic Range Solar wind Magnetosheath Lobe

CODIF : Ion Composition and Distribution Function Analyser RPA entrance : ≈ 0 eV ≤ E RPA ≤ 25 eV Main entrance E q TOF system L   E ×   2     m q = 2   q L     TOF

Main features and measured parameters of the CIS experiment

CIS – HENA: EVENTS

Dst = 6 nT Dst = -28 nT

Dst = -28 nT

HENA: ring current with some enhancement around dusk CIS: near the inner edge of the ring current

For α ≈ 90° ions (27 keV < E < 39 keV) : From HENA inversions: f i ≈ 6 × 10 5 cm -2 s -1 sr -1 keV -1 Measured in situ by CIS: f i ≈ 8.5 × 10 4 cm -2 s -1 sr -1 keV -1

HENA: recovery ring current CIS: near the outer edge of the ring current; substantial O + content

For α ≈ 90° ions (27 keV < E < 39 keV) : From HENA inversions: f i ≈ 1 × 10 5 cm -2 s -1 sr -1 keV -1 Measured in situ by CIS: f i ≈ 3.5 × 10 4 cm -2 s -1 sr -1 keV -1

HENA: narrow substorm injection on the nightside; low counting statistics elsewhere CIS: low, equatorially gyrating ion fluxes ⇓ Ions not generating ENAs in the HENA FOV

For α ≈ 90° ions (27 keV < E < 39 keV) : From HENA inversions: f i ≈ 2 × 10 4 cm -2 s -1 sr -1 keV -1 Measured in situ by CIS: f i ≈ 4.3 × 10 4 cm -2 s -1 sr -1 keV -1 CAUTION: low counting statistics

CIS – HENA Ion Flux Comparison 1.0E+06 Ion Flux (27 - 39 keV) 1.0E+05 CIS 90° ion flux 1.0E+04 HENA inv. 90° ion flux 1.0E+03 1.0E+02 4/12/01 5/12/01 6/12/01 7/12/01 Event date Note : Preliminary calibration values for CIS and for HENA (each by a factor of 2 – 3)

CONCLUSIONS • First comparisons between ion fluxes obtained by HENA energetic neutral atom image inversions and ion fluxes measured in situ by CIS. • Preliminary results show the obtained and measured ion fluxes being very consistent. • Complementarity of the two approaches: • ENA images allow to put local measurements into a global context. • Local measurements provide the full distribution function and give the “ground truth” for a given pixel of an ENA image. • Ion distribution functions show a variety of structures (equatorially gyrating ions, fine-structured energy bands, etc.) . • Coming soon : • Analysis of ENA image time series: latitude profile and ion dynamics. • ENA image inversions to obtain full pitch-angle distributions. • Comparison with the ring current density obtained with the curlometer technique (FGM ). • Analysis of higher energy ion measurements (RAPID).