ANGEO Annales Geophysicae ANGEO 1432-0576 Copernicus GmbH Göttingen, Germany 10.5194/angeo-20-391-2002 Polarization Jet: characteristics and a model Galperin Y. I. 1 2 3 Space Research Institute, 84/32 Profsoyuznaya Str., Moscow, 117997, Russia passed away on the 28 December 2001 Correspondence to: L. Zelenyi (lzelenyi@iki.rssi.ru) 30 11 1999 20 3 391 404 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.ann-geophys.net/20/391/2002/angeo-20-391-2002.html The full text article is available as a PDF file from http://www.ann-geophys.net/20/391/2002/angeo-20-391-2002.pdf

Recent analysis of the ground-based observations of the Polarization Jet (PJ) effects in the subauroral ionosphere has shown that PJ can rapidly develop in the near-midnight sector near the Harang Discontinuity (HD). Based on these observations, a simple, semi-quantitative theory of the PJ formation and its main characteristics is constructed. According to the model, PJ starts to develop, as proposed by Southwood and Wolf, 1978, due to the penetration of the injected energetic ions to the deeper L-shells in the presence of the westward component of the electric field. The injection near the tip of the HD is assumed here. The initial development stage of the PJ band, considered only qualitatively, is supposed to lead to its inclination inward toward evening with respect to the lines <i>B</i> = const. Within the model proposed, the PJ band, once formed, will be sustained by the continuous charging at its equatorial side, at first, mainly by the newly injected ring current ions, and later by the plasma sheet ions convected inward through the HD. In addition, an important charging of the PJ band occurs at its polar side by energetic electrons drifting eastward. These electrons were either previously on the trapped orbits or convected inward from the plasma sheet, and encounter the PJ polar border. The model semi-quantitatively describes the main features of the PJ events: the typical cross-PJ voltage drop ( ~ 10 kV), the resulting double-sheet current loop feeding the PJ, the recently observed short PJ formation time near midnight ( ~ 10 min or less) accompanied by a fast westward HD displacement, the nearly steady-state PJ location in the evening to midnight MLT sector and width in the ionospheric frame, the bell-shape of the electric field latitude profile, and the long PJ lifetime (up to several hours) - all are in rough accord with observations. Further developments of the model now in progress are briefly described.<br><br><b>Key words. </b>Magnetospheric physics (electric fields; magnetosphere-ionosphere interactions; storms and sub-storms)