SM31B-01
Plume Contribution to the Plasma Sheet and Ring Current
We investigate the fate of plasmaspheric plumes to assess the resultant enhancement of plasma sheet and ring
current pressure and compare with that for steady polar wind outflows. We use test particle motions in LFM global
circulation model fields. The inner magnetosphere is simulated with the CRCM model of Fok and Wolf, including
the Ober plasmasphere model. Global circulation is stimulated by a period of southward IMF embedded in a
longer interval of northward IMF. This leads to the production of a realistic plasmaspheric plume, enhancing the
plasma density on the dayside. Large numbers of test particles are launched with the properties of
plasmaspheric ions on the L=8 shell, and weighted by densities as specified by the Ober model, as it responds
to enhanced convection. Particles are tracked until they are lost from the system downstream or into the
atmosphere, using the full equations of motion as implemented in the Delcourt code. Results are compared with
earlier computations for polar wind outflows from the region above 55 deg. latitude. The plume produces an
enhanced cloud of polar wind like plasma that flows through the polar caps and lobes, entering the plasma sheet
reconnection region and splitting into earthward and tailward flows. We assess the magnitude and duration of
the resultant pressure enhancement.
http:gpl.gsfc.nasa.gov/public/traj/dynamic-fields/SBz/plasmasphere/
SM31B-02
Cross-Tail Electric Field Magnitude Derived From Plasmaspheric Alfven Layer Motions
The plasmasphere is a highly dynamic region of considerable importance as an energy conduit in magnetosphere-ionosphere coupling and for its role in the modulation of the ring current and radiation belts. A complete explanation of the mechanism(s) responsible for the morphology of the plasmasphere, especially the morphology of small scale features, has yet to be found. The macro-dynamics are driven by the convective plasmasphere model, which is based on the superposition of the cross-tail convection electric field and the Earth's corotation electric field. The general plasmasphere shape is formed and modulated through E-cross-B drift of the local plasma. In the convective plasmasphere model, the steady state plasmapause is identified as the location of the last closed streamline, known at the plasmaspheric Alfven layer. Comparisons of the response times of plasmapause motion to response times of changes in the intensity of the cross-tail electric field guarantee that the plasmapause and Alfven layer only coincide during extended quiet periods. Variations in response time allow for observations of the Alfven layer position interior to the plasmapause which provides a means to compute the convection electric field by tracking its location in IMAGE-EUV plasmaspheric images. This study presents the EUV derived convection electric field for two storm-time events, 8 April 2001 and 17 April 2001, over a range of 0.25 to 0.5 mV/m. The fit is excellent between the EUV derived convection field and the convection field as derived from a Weimer model for the polar cap potential based on the IMF magnitude, clock angle, and solar wind velocity.
SM31B-03
Acceleration and particle loss within the Van Allen radiation belts associated with the Halloween storm of 2003
During and following the Halloween Storm period (October-November 2003), the Van Allen belt electron population was powerfully accelerated and redistributed inward. From November 1 to November 10, 2003, the outer belt had its center only at about 2.5 RE geocentric distance. As shown in published papers using IMAGE spacecraft data, the Earth's plasmasphere was displaced inward (to an unprecedented degree) in late October 2003, and concurrently the whole radiation belt structure was transformed. The region between the Van Allen belts, normally devoid of particles, became the location of highest radiation belt particle intensities. After the magnetosphere relaxed to a more normal outer belt configuration, the new belt of electrons decayed over a period of days to years. We have examined quantitatively the loss rates for electrons seen in the region of 1.5 ≤ L ≤ 3.0 using SAMPEX observations. We compare these loss rates to those expected from prior observational and theoretical studies.
SM31B-04
Investigating the Relationship of EMIC Waves and Relativistic Electron Precipitation Events
EMIC waves are generated and driven by anisotropic ring current protons. These unstable protons are injected into the inner magnetosphere by increased earthward convection during periods of elevated geomagnetic activity. A study by Meredith et al. (2003) showed EMIC wave events resonant with radiation belt electrons of energies less then 2MeV were located near the plasmapause in high density regions typical of the plasmaspheric plume. This study seeks to investigate the theory of relativistic electron precipitation (REP) due to wave particle interaction with EMIC waves. REP events were detected by balloon borne instrumentation during the MAXIS and MINIS balloon campaigns conducted in Jan. of 2000 and 2005 respectively. The location of these events with respect to the plasmapause will be explored using a plasmapause test particle simulation code and IMAGE EUV data. Also, data provided by the LANL satellite MPA instrument will be used to investigate the temperature anisotropy of ring current protons that may drive EMIC waves in the region of detected REP.
SM31B-05
EXTREME MAGNETOSPHERE-IONOSPHERE COUPLING AT THE PLASMAPAUSE: A ONCE- IN-A-LIFETIME BRIGHT SAR ARC
Heat conduction from the ring current - plasmapause interaction region generates high electron temperature within the ionosphere that drive stable auroral red (SAR) arc emission at 6300 A. On the night of 29 October 1991, a SAR arc was observed using an all-sky imager and meridional imaging spectrograph at Millstone Hill. At xxxx UT, the SAR arc was south of Millstone at approximate L = 2 and reached emission levels of 13,000 rayleighs (R). Over two solar cycle of imaging observations have been made at Millstone Hill, and SAR arc brightness levels (excluding this event) averaged ~ 500 R. Simultaneous observations using the incoherent scatter radar (ISR), a DMSP satellite pass, the MSIS neutral atmosphere and SAR arc modeling using the Rees and Roble formalism succeeded in simulations of the observed emission. The reason for the unusual brightness was not the extreme temperatures achieved (and therefore heat conduction input), but the fact that the end of the plasmapause field line where the elevated Te values were measured did not occur in the ionospheric trough, but equatorward of it, thereby having far more ambient electrons to heat and subsequently collide with atomic oxygen. This unusual spatial geometry probably resulted from unusual convection patterns early in a superstorm scenario.
SM31B-06
Study of Magnetospheric Convection near a Drainage Plume Using Simultaneous Observations from IMAGE and Three DMSP satellites
We report on equatorial convection associated with a plasmaspheric drainage plume using simultaneous observations from IMAGE and three DMSP satellites. During the early recovery phase of the July 2000 Bastille Day magnetic storm the Extreme Ultraviolet (EUV) sensor on the IMAGE satellite detected the plume near 16:00 - 17:00 MLT extending outward to L = 2.8. The plasmaspheric boundary was near L = 2 at other local times. We mapped simultaneously-measured ionospheric plasma drifts from three DMSP spacecraft along magnetic field lines to infer equatorial convection velocities in the inner magnetosphere. The meridional profile of horizontal velocities deduced from DMSP measurements shows a large, westward-flowing sub-auroral polarization stream (SAPS) located outside the plasmapause. The peak velocity of the SAPS centered at a radial distance of L = 2.8 with a full-width of about 1 RE. In the inertial frame of reference, equatorial plasmas flowed toward the plume from both its day and evening sides, suggesting a negative gradient in the equatorial azimuthal velocity that was largest near plume's outermost boundary. These observations provide new evidence about diversion of SAPS plasma flows and distinctive azimuthal velocity patterns in the vicinity of plasmaspheric plumes.