Cluster and DMSP observations of SAID electric fields

P A Puhl-Quinn (1) , H Matsui (1) , E Mishin (2) , C Mouikis (3) , L Kistler (4) , Y Khotyaintsev (5) , Pierrette Décréau (6) , E Lucek (7)

1 UNH - University of New Hampshire
2 AFRL Space Vehicles Directorate
3 Department of Physics [Durham]
4 SSC - UNH Space Science Center [Durham]
5 IRF - Swedish Institute of Space Physics [Uppsala / Kiruna]
6 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
7 Space and Atmospheric Physics Group [London]

[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 $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.

Domaines: Planète et Univers [physics]

P A Puhl-Quinn, H Matsui, E Mishin, C Mouikis, L Kistler, et al.. Cluster and DMSP observations of SAID electric fields. Journal of Geophysical Research Space Physics, 2007, 112, pp.5219 - 5219. ⟨10.1029/2006JA012065⟩. ⟨insu-01408871⟩