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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 33, issue 3
Ann. Geophys., 33, 371–380, 2015
https://doi.org/10.5194/angeo-33-371-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 33, 371–380, 2015
https://doi.org/10.5194/angeo-33-371-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 20 Mar 2015

Regular paper | 20 Mar 2015

Observation of electron biteout regions below sporadic E layers at polar latitudes

G. A. Lehmacher1, M. F. Larsen1, and C. L. Croskey2 G. A. Lehmacher et al.
  • 1Department of Physics & Astronomy, Clemson University, Clemson, SC, USA
  • 2Department of Electrical Engineering, The Pennsylvania State University, University Park, PA, USA

Abstract. The descent of a narrow sporadic E layer near 95 km altitude over Poker Flat Research Range in Alaska was observed with electron probes on two consecutive sounding rockets and with incoherent scatter radar during a 2 h period near magnetic midnight. A series of four trimethyl aluminum chemical releases demonstrated that the Es layer remained just slightly above the zonal wind node, which was slowly descending due to propagating long-period gravity waves. The location of the layer is consistent with the equilibrium position due to combined action of the wind shear and electric fields. Although the horizontal electric field could not be measured directly, we estimate that it was ~ 2 mV m−1 southward, consistent with modeling the vertical ion drift, and compatible with extremely quiet conditions. Both electron probes observed deep biteout regions just below the Es enhancements, which also descended with the sporadic layers. We discuss several possibilities for the cause of these depletions; one possibility is the presence of negatively charged, nanometer-sized mesospheric smoke particles. Such particles have recently been detected in the upper mesosphere, but not yet in immediate connection with sporadic E. Our observations of electron depletions suggest a new process associated with sporadic E.

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Short summary
The descent of a sporadic E layer near 95km was observed with two rockets during a geomagnetically very quiet period. Four wind profiles showed that the location was surprisingly consistent with the neutral wind shear and a small electric field. Both electron probes found deep depletions just below the layers, which could be due to charged mesospheric smoke particles. Those have recently been detected in the mesosphere, but not yet in immediate connection with sporadic E.
The descent of a sporadic E layer near 95km was observed with two rockets during a...
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