Pamela Ann Puhl-Quinn

Multispacecraft observations of the electron current sheet, neighboring magnetic islands, and electron acceleration during magnetotail reconnection

Open questions concerning structures and dynamics of diffusion regions and electron acceleration in collisionless magnetic reconnection are addressed based on data from the four-spacecraft mission Cluster and particle-in-cell simulations. Using time series of electron distribution functions measured by the four spacecraft, distinct electron regions around a reconnection layer are mapped out to set the framework for studying diffusion regions. A spatially extended electron current sheet (ecs), a series of magnetic islands, and bursts of energetic electrons within islands are identified during magnetotail reconnection with no appreciable guide field. The ecs is collocated with a layer of electron-scale electric fields normal to the ecs and pointing toward the ecs center plane. Both the observed electron and ion densities vary by more than a factor of 2 within one ion skin depth north and south of the ecs, and from the ecs into magnetic islands. Within each of the identified islands, there is a burst of supr...

Cluster and DMSP observations of SAID electric fields

[1] We report on magnetically conjugate Cluster and the Defense Meteorological Satellite Program (DMSP) satellite observations of subauroral ion drifts (SAID) during moderate geomagnetic activity levels on 8 April 2004. To our knowledge, the field-aligned separation of DMSP and Cluster (%28,000 km) is the largest separation ever analyzed with respect to the SAID phenomenon. Nonetheless, we show coherent, subauroral magnetosphere-ionosphere (MI) coupling along an entire field line in the post-dusk sector. The four Cluster satellites crossed SAID electric field channels with meridional magnitude E M of 25 mV/m in situ and latitudinal extent DL % 0.5° in the southern and northern hemispheres near 07:00 and 07:30 UT, respectively. Cluster was near perigee (R % 4 R E) and within 5° (15°) of the magnetic equator for the southern (northern) crossing. The SAID were located near the plasmapause—within the ring current-plasmasphere overlap region. Downward field-aligned current signatures were observed across both SAID crossings. The most magnetically and temporally conjugate SAID field from DMSP F16A at 07:12 UT was practically identical in latitudinal size to that mapped from Cluster. Since the DMSP ion drift meter saturated at 3000 m/s (or

Generalized Walén tests through Alfvén waves and rotational discontinuities using electron flow velocities

114 mV/m) and the electrostatically mapped value for E M from Cluster exceeded 300 mV/m, a magnitude comparison of E M was not possible. Although the conjugate measurements show similar large-scale SAID features, the differences in substructure highlight the physical and chemical diversity of the conjugate regions.

EDI Data Products in the Cluster Active Archive

A new formulation of the Walen test [Walen, 1944] to locate rotational discontinuities (RD) or Alfven wave trains is constructed that is more appropriate for use within and across the current-carrying layers of these structures. This generalized test is to be distinguished from the traditional rigorous jump condition that is only appropriate for connecting asymptotic, current free states on either side of the discontinuity or wave train. The generalized test is most simply formulated as a vector difference equation relating changes in the electron flow velocity vector and changes of the magnetic field vector, ΔUe(x) = αeΔB(x) with a prescribed scalar constant of proportionality. For an electron proton plasma this paper shows that αe is precisely the same constant of the jump condition that has long been in use. Small corrections to αe are computed for minor helium populations. This new formulation is used with Polar plasma, E, and B measurements to search for rotational discontinuities at the magnetopause. Of the 44 cases where electrons gave acceptable theoretical correlations and coefficients αe predicted by the theory, nearly 95% of the simultaneous ion fits gave corresponding values of at that were smaller in magnitude than implied by simple ideal MHD jump conditions. Possible explanations for this discrepancy are discussed. In addition, these data have been used to provide the first empirical evidence of the importance of the electron pressure gradient in these RD current layers and represent the first direct determination of the sizes EnHT ≃ 0.3−5 mV/m of the deHoffmann-Teller electric field in RD current layers at the magnetopause.

Observation of energetic electrons within magnetic islands

The Electron Drift Instrument (EDI) contribution to the Cluster Active Archive (CAA) is described. Presented are descriptions of the EDI instrument, the various CAA/EDI data products, the CAA ingestion schedule and the current EDI status. An example of a science application is given for one of the main EDI data products available in the CAA.