THEMIS 2010 hjmn 10 02 2010 THEMIS 2010

THEMIS 2010 -… - hjmn - ИКИ, 10. 02. 2010

THEMIS 2010 -… - hjmn - ИКИ, 10. 02. 2010

THEMIS 2010 -… - hjmn - ИКИ, 10. 02. 2010

Среднестатистический BBF Generic BBF in CPS (Ohtani et al, 2004, Geotail 818 CPS events) T 0 Tons Tpost. Dip BBF диполизация plasma bubble Compression / Dipolarization phase ИКИ, 10. 02. 2010

Dipolarization Front at spin resolution Feb. 23, 2008 event f : Sharp Dipolarization Front (SDF) ü Time delay P 3, P 4 P 5 dt=53 sec, Earthward propagation Vx~220 km/s from 11. 3 Re 9. 5 Re ü Prior to SDF Vix~200 km/s at P 3, P 4, Vix~70 km at P 5 , propagtion with plasma, flow braking ü MVA normals SC 2/ 3 N P 3 28. 77 28 P 4 32. 02 16 P 5 7. 49 16 N 3 [0. 95; 0. 04; 0. 30] [0. 93; 0. 09; 0. 34] [0. 94; -0. 21; 0. 24] R [-11. 3; 1. 7; -2. 7] gsm [-11. 1; 2. 6; -2. 8] gsm [ -9. 3 ; 1. 3; -2. 6] gsm ü SDF duration (peak-to-peak Bz increase) ~4 sec at P 4, P 5, ~7 sec at P 3. Front thickness 220 km/s * 4 sec = <880 km Ion gyroradius Wi=7 ke. V in Bz=20 n. T rcp= 600 km ion inertial length for n=0. 3 cm-3 lpi = 420 km üSDF = Thin (gyro-scale) vertical current sheet ! ИКИ, 10. 02. 2010

SDF – particle features Equatorial angles Spacecraft P 5 (9. 3 Re) : Sudden change of particle distributions at Sharp Dipolarization Front (in one spin) ü energization of both p, e ü electrons: field-aligned bi-directional before SDF (at P 3, P 4, P 5) , ü stay bi-directional at P 3, P 4, at P 5 change to pancake (energetic) + bidirectional (low energies) after SDF Pitchangles ИКИ, 10. 02. 2010

Ion (finite gyroradius) pattern at SDF Cold /dense Spacecraft P 5 (9. 3 Re) : Energetic /low-density Equatorial angles üSharp temperature boundary üprotons (looking ~ B) : nice Zigzag pattern with complementary patterns at high/low energies; size ~ Wp 1/2 - finite gyroradius effect of sharp temperature boundary co-located with TCS 2 rci üRemote sensing of Earthward-moving temperature boundary: Vx ~ 2 rci / t ~ 2*760 km/15 s ~100 km/s consistent with ion velocity Vx~80 km/s (measured in front of SDF). TCS E, ke. V ИКИ, 10. 02. 2010

Zoom of TCS and energization boundary (within 1 spin timescale) Energization Substructure of the thin current sheet : Boundary 2 outer Themis spacecraft ü Electrons take ~2 sec for complete replacement cold hot population at P 3, P 4; ü Deep density depletion (from probe 1, 2 potential Vp) colocated with : ü Very intense E-field ~40 -60 m. V/m in the spin plane (Esp) which have the wave/bursts time scale of 100 msec, about Low Hybrid timescale (f. LH~13 Hz) Density Depletion(s) Intense E f LH 2 = fpi 2 fce 2 (fpe 2 + fce 2) -1 TCS one 3 s spin ИКИ, 10. 02. 2010

Example of Dipolarizations at the periphery of dipole-like region – general properties Example of multiple injections: P 3, P 4, P 5 triangle in XY plane near Neutral Sheet Steady Earthward P, B : SC are at the periphery of dipole-like region 5 distinct Dipolarizations (DIP), basic features : ü Plasma (and total) pressure generally increase during DIP events; also pressure dropped (for short time) in many cases (bubbles) ü Generally density & p. V decrease inside DIPs; less pronounced at the inner SC ü HE particle flux increases at DIP fronts (dispersionless) ü Later - zoom in : event f ИКИ, 10. 02. 2010

Zoom of TCS and energization boundary (within 1 spin timescale) Substructure of the thin current sheet : ü Electrons take ~2 sec for complete replacement of population (energization) at P 3, P 4; ü Large density depletion (from probe 1, 2 potential Vp) colocated with : ü Very intense E-field ~40 -60 m. V/m in the spin plane (Esp) which have the wave/bursts time scale of 100 msec, about Low Hybrid timescale (f. LH~13 Hz) ü Nearly same structure in the flow braking region (P 5) but with smaller depletion and longer electron energy change: ü üDensity depletion + intense LH E-field resemble the (weaker!) LH Cavities previously studied in strong B low-altitude region ИКИ, 10. 02. 2010

Individual injection – zoom in. . SDF – a thin spatial structure of ~600 -900 km, here observed near PS equator At the discontinuity : ü strong E up to 60 m. V/m sitting upon Bz peaks ; ü SC potential drops; ü ESA spectra change in <1 spin ; ü MVA gives the Eartward-directed normals SC l 2/l 3 P 3 28. P 4 32. P 5 7. 5 Nmva 28 16 16 N 3 x N 3 y N 3 z [0. 95; 0. 04; 0. 30] [0. 93; 0. 09; 0. 34] [0. 94; -0. 21; 0. 24] x y z [-11. 31; 1. 73; -2. 71] [-11. 13; 2. 63; -2. 75] [ -9. 29; 1. 25; ИКИ, -2. 59] 10. 02. 2010

Auroral signature of Dipolarization Front Break Up at ~2107 UT (Polar UVI, TV Loparskaya): Ø followed by poleward and Equatorward auroral expansion Ø Image of turbulent Dipolarization - enhanced diffuse aurora with considerable structure Ø distinct EQ boundary but not outlined by bright auroral form ; (Sergeev et al. , JGR 2010) ИКИ, 10. 02. 2010

Auroral signatureof Dipolarization –mapping Adapt T 96 model to Themis P 2/P 5 external B-fields, compare to T 96 sw BU arcs EQ edge Ø Importance of accurate mapping, footpoint variations up to ± 3 o. CGLat , even for mapping from 7 Re Ø expected crossing of EQ boundary by P 5 – between 2112 and 2118 UT – dipolarization in progress on P 5, spiky structures overlapped onto Bz increase ØOther comparison (two step Bz increase, two injections, two traces EAB on Dec. 31, 2007) also confirm spatial relationship between SDF and EAB HEe (Sergeev et al. , JGR 2010) ИКИ, 10. 02. 2010