1 GENERATION OF DENSITY IRREGULARITIES IN THE PLASMASPHERE Evgeny Mishin Boston College ISR MURI Workshop 3-6 March 2008

2 2 OUTLINE  Introduction: Inner magnetosphere PS  Sub-Auroral Polarization Streams & Ion Drifts (SAPS & SAID)  SAPS/SAID-related plasmaspheric structures  Shear-flow and gradient-drift instabilities APPROACH Compare plasmaspheric density structures with enhanced subauroral electric field Specify possible instabilities OBJECTIVE : Specify the ducts formation conditions Why should one care? Necessary for VLF triggering

3 3 Inner Magnetosphere Inner magnetosphere: Plasmasphere & Ring Current  Driven by convection electric field  Driven by the magnetospheric convection electric field generated by the solar wind- magnetosphere interaction A schematic diagram of the Earth’s magnetosphere convection and corotation electric fields  Usually described by the cold plasma drift approximation: Balance of the convection and corotation electric fields

4 4 Large-Scale Structures: SAPS During magnetic (sub)storms energetic particles are injected into the plasmasphere forming the “partial” ring current at dusk Plasma sheet boundary Upward (Region 1) & downward (Region 2) FACs enhance. Subauroral poleward electric fields appear  enhanced westward convection (SAPS/SAID). Topside Ionosphere: 850 km ~1 R E

5 Middle-Scale Structure: SAID 08-Apr-2004 SAID event 50 min after onset Puhl-Quinn et al., C1 & F16: Magnetically conjugate within 0.2 o DMSP F16 PPause C1 C4 <1000 km Plasma sheet boundary

6 6 Wave (sub) StructuresWS Middle-Scale SAPS Wave (sub) Structures (SAPSWS) Conjugate DMSP observations show that after subsequent onsets SAPSWS enhance and move equatorward. Short-scale e.m. field oscillations fade away during the substorm recovery. Onsets at 1555 and 1710 UT The outbound portion of CRRES orbit 765: The beginning of the 4-5 June 1991 storm SAPSWS 8 min after the substorm onset

7 7 Middle-Scale Structures: Plumes & Shoulders Volland-Stern IMAGE EUV image : PS equatorial cross-section plume 1-2 R E Including SAPS [Khazanov+]

8 8 SAPSWS and Plasmaspheric Irregularities Plasma Sheet boundary Elect Ions diamagnetic current CRRES orbit 766 during the main phase on 5 June 1991 ion and electron fluxes at pitch angles near 90 o plume

9 SAID & Plasmaspheric trough Adrian et al. [ 2007] Simulated equatorial density distribution containing a SAID generated trough Simulated EUV image

10 SAID & Plasmaspheric Irregularities SAID 08-Apr-2004  Co-located with the SAID E-field variations  Strong shear flow: dV W /dr ~ 0.2 s -1 ~1/20 H + -gyrofrequency Mishin et al., 2008

11 SAID & Plasmapause & Auroral Boundary Mishin and Puhl-Quinn, GRL March min after onset DMSP F14 The outer side of the SAID channel is aligned with the plasmapause and its outer edge marks the electron precipitation (auroral zone) boundary. The overall SAID features agree with a short-circuiting of the substorm-injected plasmoid over the plasmasphere and the formation of a turbulent boundary layer. PPause

12 SAID and Plasmasphere’s Structuring Cluster observations in the SAID system of reference diamagnetic current near the inner edge The short-circuit system in the plasmasphere extends far ahead the SAID channel Mishin and Puhl-Quinn, GRL2007

13 The current-convective instability in the RC- plasmasphere overlap Volkov& Maltsev, 1986 (static approximation) Plasma cloud’s transverse motion favors generation of short-scale modes Rise time a few min Doppler-shifted frequency

14 Density irregularities from Cluster CLUSTER, 11- Apr-2002, 2130 MLT, K p =3 Darrouzet et al., 2004 Cluster electron density profiles in the plasmasphere IN OUT plume

15 Motion of Plumes Darrouzet et al., 2004 The radial boundary velocity V R =(R 1 -R 2 )/(t 1 -t 2 ) The normal boundary velocity Co-rotation speed V cor =0.47· R equat km/s Shear flows near the plume

16 Plasmapause & Electron Injection boundary IMAGE/FUV electron aurora images. The color is proportional to brightness of the detected auroral emissions. The FUV images mapped to the equatorial plane: The EUV determined plasmapause is overlaid on the mapped images. IMAGE/FUV measurements of the substorm of 1900–2038 UT on 17 April Goldstein et al., 2005

17 Motion of Irregularities inside the PS Darrouzet et al., 2004

18 SUMMARY Substorm injections generate highly-structured electromagnetic fields (SAPSWS) in the RC-plasmasphere overlap. SAPSWS generate small-scale density ducts inside the plasmasphere. Plasmaspheric irregularities develop shortly after the substorm injection front arrives at the plasmapause. SAPS/SAID define the outer boundary (plasmapause) of the perturbed plasmasphere and create strong shear flows. Irregularities inside the plasmasphere last for a few hours, virtually co- rotating.

19 Stationary Conditions The subscript S refers to a stagnation point in cold plasma drift. convection corotation L y and  PC are defined by the solar wind pressure and IMF Zero-order, cold plasma drift approximation (Volland-Stern) separatrix

20 SAPSWS- (cont’d) The outbound portions of CRRES orbits 765 (onset), 766 (middle of the 1 st main phase) and 767 (middle of the 2 nd main phase) on 5 June 1991

21 Plasmapause & RB boundary (a) SAMPEX high-energy (2–6 MeV) electrons, vs. L and day of year Four main bursts of enhanced outer belt flux are labeled (‘1’ through ‘4’). (b) Dst index, showing 4 main (‘1’–‘4’) and disturbances. 2–6-MeV, monthly window-averaged electron fluxes from SAMPEX (600 km) The white curve represents every 10- day’s minimum Lpp based on the CRRES empirical model Goldstein et al. [2005] Li et al. [2006]

22 Plasmapause & RB boundary (cont’d) Red (L min ) and blue (L avg ) dots respectively give 3.5-day running average of minimum and mean per- image plasmapause Lp. Blue line (L MAX ): L of peak flux. Red line (L -1 ): 0.1 of peak flux. IMAGE/EUV plasmapause data

23 Structured precipitation from RB at HAARP [Pedersen et al., JGR, 2007] Co-rotating, several-km-scale optical structures (‘angels dancing on the head of a pin’)

24 SAPS & RB boundary at HAARP Substorm onset at 04:50-UT [Pedersen et al., JGR, 2007] Background-subtracted negative all-sky nm images mapped to geographic coordinates and superimposed with tracks for various satellite passes.

25 SAPS & RB boundary at HAARP (cont’d)

26 SAPS/SAID, RB boundary & Plasmapause RB region Similarities between Cluster and DMSP/NOAA observations