Recent KTH Cluster research T. Karlsson, A. Collier, T. Johansson, S. Liléo (Figueiredo), G. Marklund, m. fl.

Pi2 pulsations within plasmasphere 2003-01-21 Andrew Collier, KTH and Univ. Of KwaZulu-Natal, Durban Pi2 pulsations within plasmasphere 2003-01-21 L = 4.6 MLT = 02:43 C4 m n

CONCLUSIONS C4 Poynting Flux, P m n L = 4.6 MLT = 02:43 C4 m n P CONCLUSIONS 1. Phase shift 90 between E and B, indicative of standing wave in radial direction – cavity resonance 2. Poynting vector indicates energy flow in azimuthal direction, possibly indicating open-ended cavity.

Cluster results j//up event 1 temporal / spatial evolution of discrete auroral arcs Figueiredo et al., AG, 2005 Temporal Evolution Symmetric U-shaped potential 1keV e- ↓ -10 V (kV) 820 E (mV/m) 3 j// (mA/m2) O+ 1-10 keV 10-38 ↑ ↓ ↑O+ 0' 15' 30' 45' V= ∫ E^ · ds j// s/c 1 s/c 2 +16’30’’ s/c 4 + 39’30’’ s/c 3 + 57’ 35' LS Inverted-V LS Inv-V arc arc V= ∫ E^ · ds arc merging together intensifying PSBL CPS PSBL CPS PSBL CPS Cluster s/c 1 obs 030501 Upward 10 keV O+-beam GM050825

Cluster results j//up event 2 temp / spatial evolution of discrete auroral arcs DMSP image DMSP surge surge horn Cluster South Pole ASI images surge horn poleward expansion 0.5 km/s Cluster s/c Cluster observations 030503 s/c 2 — +7’ s/c 4 — +22’ s/c 1 5 kV 10 mA/m2 20' V= ∫ E^ · ds j// surge horn multiple arcs merging together & intensifying PC PS PC PS GM050825

Auroral current circuit Evolution of pos & neg U-shaped potentials in two connected FAC branches Marklund et al, 2006 s/c 1 s/c 2 s/c 3 s/c 4 acc ions 14 FEB 2001 EVENT SUMMARY · bipolar, div E-field » 1.7 V/m · PSBL / CPS boundary & Ne-grad · scale size of 8 km · DF^, increases from » 0.4 to 2.7 kV in 100 s · DF// in jllup » - DF^ in jlldown · Local Ne-min & E-region Ne-hole · downward FAC » 10 µA/m2 DF// decreases from 3 kV to 1 kV acc electrons conv E-field DF^ = ∫ E^ · ds increases from 0.4 kV to 3 kV s/c 1 s/c 3 s/c 2 s/c 4 » div E-field · · aurora Ne-hole black aurora t = 0 s t = 100 s t = 200s t=300s Auroral current circuit GM050825

evolution of div E-field structures Cluster data j//down event 2 evolution of div E-field structures div E ^ Bt EN Bt EN div E ^ = 0.3 V/m -Vs/c V -Vs/c V EFW FGM data PSBL CPS up FAC down FAC PSBL CPS up FAC down FAC div E ^= 1.7 V/m div E ^ Bt EN Bt EN -Vs/c V -Vs/c V PSBL CPS up FAC down FAC PSBL CPS up FAC down FAC Marklund et al, 2006 GM050825

5. Evolution of U+-potential: Simulation of Event 1 Jll ENS equator L= 8.25 L= 7.25 Cut along Cluster track s. iono- sphere Jll ENS Cluster track cross-section Streltsov and Marklund, acc for JGR, 2006

Interpretation Bipolar Where do monopolar and bipolar E-fields occur with respect to boundaries ? Statistical study of bi- & monopolar E-field events Johansson et al, accepted Ann. Geophys. 2006 Equatorward, monopolar E-fields, are found at the PC boundary in the evening LT sector # mono- polar E # bipolar E increase in β (%) PC boundary 10 706 PS 1 16 253 PC PSBL CPS Interpretation (Marklund et al, 2004) Bipolar E-fields are found at particle boundaries within PS Bipolar Monopolar fields, if plasma, dense enough to support connecting FACs, exists on one side of the boundary only Bipolar fields, if plasma, dense enough to support connecting FACs, exists on both sides of the boundary GM050825

beta ┴ potential Eeast Eequator bipolar monopolar Johansson et al., accepted Ann. Geophysicae, 2006

Auroral potential and associated FAC reconfiguration during thinning of the PSBL Marklund et al, subm to JGR, 2006 t = t0 t = t0 + 16 min

Auroral potential reconfiguration: Cluster observations Cluster s/c 1 t= t0 Cluster s/c 2 t = t0 + 16 min PEACE electron data ^ PSBL CPS PSBL CPS F^ EFW & FGM data F^ Potential step -Vs/c -Vs/c Potential well Es Es BT monopolar E-field BT Bipolar E-field FAC FAC

Auroral scale sizes (ongoing) 5 km 5 km # # S(n) S(E) Which are the characteristic scale sizes of E, FAC, Δn and how are they related to mono/conv/div E, ΔV, Kp, ΣP…. ? >1000 events 2 km 4 km # # S(FAC) gyroradius Johansson et al.

High-altitude signatures of ionospheric density depletions T. Karlsson et al. Expected correlation with constant ionospheric conductivity and no E// : En Bt Instead sometimes, correlation [downward j// ] ~ En 2005-05-19, SH, MLT ~ 20 j// (mA/m2) En (mV/m) upward current downward current t (s)

From earlier simulations Model – ionospheric modification by downward FACs From earlier simulations j// Magnetosphere Jn upward j// S downward j// Ionosphere En

2002-04-27 2005-01-11 DBt En SP j// DBt En SP j//

High-altitude signatures of ionospheric density depletions T. Karlsson et al. Expected correlation with constant ionospheric conductivity and no E// : En Bt t (s) Instead sometimes, correlation [downward j// ] ~ En 2005-05-19, SH, MLT ~ 20 j// (mA/m2) En (mV/m) downward current upward current