The role of electric field and neutral wind in the generation of polar cap sporadic E

Abstract

Abstract. This paper investigates the roles of electric field and neutral wind in the generation of sporadic-E layers within the polar cap. Two Es layers above Svalbard, observed by the EISCAT Svalbard Radar (ESR), were chosen for investigation. The radar experiment contains four beam directions, and this was used for determining the electric field. The neutral wind was obtained from the HWM93 model. Formation of Es layers was calculated by integrating the continuity equation under the action of driving forces due to neutral wind and electric field. A flat height profile of metal ions was assumed in the beginning. The calculation gives the time variation of the layer, which can be compared with observations. In one case the electric field was shown to be the main driving agent in layer generation. In the other case the electric field was weak and the layer was produced mainly by the neutral wind, but the electric field had influence on the height of the layer. A fairly good agreement between the variations of the observed and calculated layer altitudes was obtained and some agreement between the intensity variations was also found.

The effects of mesoscale regions of precipitation on the ionospheric dynamics, electrodynamics and electron density in the presence of strong ambient electric fields

“…(∂/∂z) (∂/∂x), which is not the case when examining precipitation arcs. Nygrén et al (2008) have noted the importance of horizontal transport in forming sporadic E-layers. For precipitation ionisation, we find that all terms in the vector drift have an important influence on the E-region electron density profile and on the coupling of the ionospheric dynamics with the electrodynamics.…”

Field‐aligned current loop model on formation of sporadic metal layers

“…The formation of the midlatitude E s layer is interpreted by the vertical redistribution and convergence of metal ions arising from wind shear effect [ Whitehead , ]. The high‐latitude E s are investigated at the auroral region and the polar cap region [ Nygren et al ., ], and the importance of the electric fields originating in the magnetosphere is suggested for the vertical redistribution of ions to form the E s layer at high latitudes, where the vertical plasma motion driven by the electric fields is relatively larger than that driven by the winds.…”

Localized mesosphere-stratosphere-troposphere radar echoes from theEregion at 69°N: Properties and physical mechanisms

“…This is also the case for instance at polar latitudes, where it is generally thought that electric fields are mainly responsible for sporadic E generation [e.g., Nygrén et al , 1984; Kirkwood and Nilsson , 2000; Voiculescu et al , 2006; Nygrén et al , 2006]. Using a combination of observations with the EISCAT Svalbard Radar and numerical modeling, Nygrén et al [2008] were able to demonstrate that depending on the specific situation, sporadic E generation in the polar cap can be mainly attributed to the wind shear mechanism, to the electric field mechanism, or to the combined effect of both.…”

“…While this wind shear mechanism was originally proposed to explain the occurrence of sporadic E layers at midlatitudes where the Earth's magnetic field has a large horizontal component [ Whitehead , 1960], it has recently been shown by Nygrén et al [2008] that even a small horizontal component of the magnetic field can be sufficient for the wind shear mechanism to be active. This is also the case for instance at polar latitudes, where it is generally thought that electric fields are mainly responsible for sporadic E generation [e.g., Nygrén et al , 1984; Kirkwood and Nilsson , 2000; Voiculescu et al , 2006; Nygrén et al , 2006].…”