E.E. Grigorenko 1 , R. Koleva 2 , J.-A. Sauvaud 3 , L.M. Zelenyi 1

1. Different types of accelerated ion structures registered in the magnetotail PSBL and their spatial-temporal characteristics. E.E. Grigorenko1, R. Koleva2, J.-A. Sauvaud3, L.M. Zelenyi1 1Space Research Institute of RAS, Moscow, Russia 2Solar-Terrestrial Influences Institute of BAS, Sofia, Bulgary 3CESR, Toulouse, France

2. Cluster advantages in PSBL studies PSBL is an interface between magnetotail lobe and PS so it contains magnetic separatrix between yet open and already closed field lines. PSBL field lines could be mapped to an acceleration region in the magnetotail CS. (e.g. Takahashi and Hones, 1988 and so on) • Multipoint measurements of ion velocity distribution functions at the lobeward edge • of PSBL allow studying: • spatial and temporal characteristics of accelerated ion structures • 2D structure of high-latitude surface of the PSBL

3. “Quiet” PSBL:“Active” PSBL no FAC, quasi-steady field-aligned ions (E<5-10 keV) FAC system: yes; energetic ~isotropic electrons (E<1keV) field-aligned ions (E≥30 keV), anisotropic electrons (E~ a few keV)

4. lobe PS At the lobeward edge of PSBL s/c periodicallyobserve either field-aligned or PS-like ion distribution. No velocity dispersion: Field-aligned ions have V||~1000 km/s during 20 min Interval. Electron E ~ 1 keV Electrons are almost isotropic along the MF.

5. View of the lobeward surface of PSBL (in XY plane) Magnetic flux tubes populated by accelerated field-aligned ions are confined in Y direction: ΔY≤0.5RE

6. 3D cartoon of the PSBL spatial structure during quiet geomagnetic periods. ΔY ~ 0.5 RE In course of global motion of PSBL magnetic flux tubes in (YZ) plane Cluster s/c successively observe either PS-like or beam-like ion velocity distribution functions due to Y-localization of the flux tubes populated by field-aligned ions. This may explain why sometimes during quiet periods the accelerated ion beams are not observed in the PSBL by one-spacecraft missions.

7. CBB x BLC • |AL| ≤ 100 nT • “Quiet” magnetograms • Auroral precipitations are localized in MLT • and in latitudes.

8. Ion beamlet simultaneous acceleration at two resonant sources located at CLOSED MF lines: Cluster observations of double-picked ion velocity distribution functions. Quiet period: |AL|~100 nT Twoenergy collimated(ΔV||/V|| < 0.2)ion beamlets with energiesW1≥ 30 keVand W2 ~ 5 keVare observedsimultaneously during ~ 2.5 min. At higher latitudes than ion beamlet location and also at their high-latitude edge isotropic electron velocity distributions are registered. Te≤ 1 keV and gradually increases towards the PS. 01.09.2003 Ion beamlets were accelerated at two spatially separated resonant sources located in CS at the region with closed MF lines (with finite BZ>0). Duration of acceleration was > 2.5 min. Cluster at [-18,0,-4] RE

9. Ion beam overlapping due to: Velocity filter effect (ExB)+ ”place of birth effect (ion energy depends on the location of acceleration source)

10. Summary for “Quiet” PSBL observations: PSBL without well-define reconnection pattern Kinetic approach predicts that: distant CS is non-uniform in terms of ion orbits: localized (in XY plane) sites of ion “direct” acceleration along magnetic field lines versus the sites of ion enhanced scattering Lobeward surface of PSBL may consist of spatially localized (in YZ plane) magnetic flux tubes populated by energy-collimated field-aligned ions ΔV||/V|| ~0.1.

11. Statistical analysis of characteristics of field-aligned ions non-adiabatically accelerated at CLOSED MF lines(isotropic electron distributions) andNEAR X-line. • at CLOSED MFNear X-line: • are observed during are observed mostly • quiet periods; during active periods; • the majority of them the majority of them are • are moving earthward moving tailward • even at X ~ -110 RE at X > -80 RE • energies < 30 keV ion energies > 30 keV • typical temperatures typical temperatures of • of electrons < 1 keV electrons > 1 keV • observed durations observed durations are • 3 – 25 min 1-6 min. (Grigorenko et al., 2009)