Different types of accelerated ion Different types of accelerated ion structures registered in the structures registered in the magnetotail PSBL and their magnetotail PSBL and their

spatial-temporal characteristics.spatial-temporal characteristics.

E.E. GrigorenkoE.E. Grigorenko11, R. Koleva, R. Koleva22, J.-A. Sauvaud, J.-A. Sauvaud33, L.M. Zelenyi, L.M. Zelenyi11

11Space Research Institute of RAS, Moscow, RussiaSpace Research Institute of RAS, Moscow, Russia22Solar-Terrestrial Influences Institute of BAS, Sofia, BulgarySolar-Terrestrial Influences Institute of BAS, Sofia, Bulgary

33CESR, Toulouse, FranceCESR, Toulouse, France

Cluster advantages in PSBL studiesPSBL 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.

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

(e.g. Takahashi and Hones, 1988 and so on)

“Quiet” PSBL: “Active” PSBLno 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)

At the lobeward edge of PSBLs/c periodically observe eitherfield-aligned or PS-like ion distribution.No velocity dispersion:Field-aligned ions have V||~1000 km/s during 20 minInterval.

Electron E ~ 1 keVElectrons are almost isotropic along the MF.

lobe

PS

View of the lobeward surface of PSBL (in XY plane)

Magnetic flux tubes populated byaccelerated field-aligned ions are confined in Y direction: ΔY≤0.5RE

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.

3D cartoon of the PSBL spatial structure during quiet geomagnetic periods.

This may explain why sometimes during quiet periods the accelerated ion beams are not observed in the PSBL by one-spacecraft missions.

ΔY ~ 0.5 RE

BLC

CBBx

•|AL| ≤ 100 nT

•“Quiet” magnetograms

•Auroral precipitations are localized in MLT and in latitudes.

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

Two energy collimated (ΔV||/V|| < 0.2) ionbeamlets with energies W1≥ 30 keV and W2 ~ 5 keV are observed simultaneously 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.

Ion beamlets were accelerated at two spatially separated resonant sources located in CS at the region withclosed MF lines (with finite BZ>0).Duration of acceleration was > 2.5 min.

Cluster at [-18,0,-4] RE

01.09.2003

Ion beam overlapping due to:

Velocity filter effect (ExB)+ ”place of birth effect (ion energy depends on the location of acceleration source)

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.

at CLOSED MF Near X-line:

• are observed during are observed mostly quiet periods; during active periods;

•the majority of them the majority of them areare moving earthward moving tailward even at X ~ -110 RE at X > -80 RE

•energies < 30 keV ion energies > 30 keV

•typical temperatures typical temperatures ofof electrons < 1 keV electrons > 1 keV

•observed durations observed durations are3 – 25 min 1-6 min.

Statistical analysis of characteristics of field-aligned ions non-adiabatically accelerated at CLOSED MF lines (isotropic electron distributions) and NEAR X-line.

(Grigorenko et al., 2009)