1. Locations of boundaries of outer and inner radiation belts as observed by Cluster and Double Star Natalia Ganushkina (1, 2), Iannis Dandouras (3), Yuri Shprits (4) and Jinbin Cao (5) (1) Finnish Meteorological Institute, Helsinki, Finland (2) University of Michigan, Ann Arbor, USA (3) CESR, Toulouse, France (4) UCLA, USA (5) State Key Laboratory of Space Weather, CSSAR, CAS, Beijing, China 2011 Joint CEDAR-GEM Workshop,26 June - 01 July 2011, Santa Fe, NM, USA

2. CLUSTER CIS measurements between April 2007 and June 2009 The Cluster Ion Spectrometry (CIS) experiment on board Cluster: - provides the three-dimensional ion distributions with one spacecraft spin (4 sec) time resolution [Rème et al., 2001]; - consists of two complementary spectrometers HIA and CODIF. Time-of-flight ion COmposition and DIstribution Function (CODIF) sensor: - high-sensitivity mass-resolving spectrometer to measure complete 3D distribution functions; - for major ion species H+, He++, He+ and O+ within one spin period; - covers the energy range between 0.02 and 40 keV/charge. Hot Ion Analyser (HIA) sensor: - Ions in the energy range ~ 5 eV/e – 32 keV/e; - does not provide mass discrimination; - but has a better angular resolution (~ 5.6°).

3. CLUSTER orbit at perigee on June 30, 2008 During the period between April 2007 and June 2009 Cluster was deep in the radiation belts coming to Earth at its perigee as close as L = 2. ORB IRB ORB

4. B1 (a) Outer RB B2B3B4B5B6 Outer RB Inner RB (b) Example of boundaries of outer and inner radiation belts as observed by Cluster CIS

5. B2 (a) Outer RB B1B5B6 Inner RB B3B4 (b) Boundaries of outer and inner radiation belts as observed by Cluster CIS at different orbits ORB IRB

6. protons electrons 48 3 2 Energy Thickness 4 Cluster 8 Double Star 30 40 Energy of penetrating electrons for HIA and CODIF at CLUSTER and Double Star

7. Locations of boundaries for all events, MLT distribution B1 and B6: outer boundary of outer RB B2 and B5: inner boundary of outer RB B3 and B4: outer boundary of inner RB

8. Locations of boundaries for all events with activity indices B1 and B6: outer boundary of outer RB B2 and B5: inner boundary of outer RB B3 and B4: outer boundary of inner RB

9. Zoom 1 Zoom 2 Locations of boundaries for all events with SW parameters Zoom 3 B1 and B6: outer boundary of outer RB B2 and B5: inner boundary of outer RB B3 and B4: outer boundary of inner RB Running Average

10. Zoom 1 Outer boundary of outer RB: - comes closer to Earth L=4 - then moves tailward L=6 Time scale: 50 days Before boundary dip: - Vsw from 430 to 540 km/sec - Kp to 5 - Dst drop to -28 nT - AE to 700 nT - 2 peaks in Psw, 8 and 5 nPa After boundary dip: - Vsw to 650 km/s - Kp to 5 - Dst drop to -50 nT - AE to 800 nT - Psw at 3 nPa

11. Zoom 2 Outer boundary of outer RB: - comes closer to Earth L=4.5 - then moves tailward L=7 Time scale: 40 days Before boundary dip: - Vsw decreased to 300 km/sec - Kp to 2 - Dst at +5 nT - AE to 300 nT - peak in Psw to 5.5 nPa and to 8 nPa at dip After boundary dip: - Vsw to 650 km/s - Kp to 4 - Dst drop to -25 nT - AE to 700 nT - Psw at 1 nPa

12. Zoom 3 Outer boundary of outer RB: - comes closer to Earth L=5 - then moves tailward L=7(7.5) Time scale: 70 days Picture is the same: Before boundaries’ dip: peaks in Psw to 4 and 5.5 nPa After boundaries’ dip: - Vsw jumps to 60 km/s - Kp to 4 and 3 - Dst drops to -20 nT - AE to 600(500) nT

13. Locations and width of slot region Zoom of slot widening

14. Example of boundaries’ locations at Double Star B2B3B0B4B5 Outer RBInner RBOuter RBInner RB

15. Locations of boundaries observed at Double Star

16. Summary - boundaries of radiation belts determined from background measurements on the instruments with energy ranges that do not cover the radiation belts’ energies provide valuable additional information that is useful for radiation belts’ model development and validation; - solar wind pressure increases are important for the Earthward shift of the outer boundary of the outer belt; - during intervals of low activity in the solar wind parameters, the slot region widens, which is consistent with weaker inward radial diffusion and weak local acceleration that can occur only at higher L-shells outside the plasmasphere.

17. Locations of boundaries for all events, MLT distribution