Observing electric field and neutral wind with EISCAT 3D
<p>Measurements of height-dependent electric field (<span class="inline-formula"><strong><em>E</em></strong></span>) and neutral wind (<span class="inline-formula"><strong><em>u</em></strong></span>) ar...
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| Autores principales: | , , |
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| Formato: | article |
| Lenguaje: | EN |
| Publicado: |
Copernicus Publications
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/301bf96ddc7342648992ef9c79bd23eb |
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| Sumario: | <p>Measurements of height-dependent electric field (<span class="inline-formula"><strong><em>E</em></strong></span>) and neutral wind (<span class="inline-formula"><strong><em>u</em></strong></span>) are important governing parameters of the Earth's upper atmosphere, which can be used to study, for example, how auroral currents close or how energy flows between the ionized and neutral constituents. The new EISCAT 3D (E3D) incoherent scatter radar will be able to measure a three-dimensional ion velocity vector (<span class="inline-formula"><strong><em>v</em></strong></span>) at each measurement point, which will allow less stringent prior assumptions about <span class="inline-formula"><strong><em>E</em></strong></span> and <span class="inline-formula"><strong><em>u</em></strong></span> to be made when estimating them from radar measurements. This study investigates the feasibility of estimating the three-dimensional electric field and neutral wind vectors along a magnetic field-aligned profile from E3D measurements, using the ion momentum equation and Maxwell's equations. The uncertainty of ion drift measurements is estimated for a time and height resolution of 5 s and 2 km. With the most favourable ionospheric conditions, the ion wind at E region peak can be measured with an accuracy of less than 1 m/s. In the worst case, during a geomagnetically quiet night, the uncertainty increases by a factor of around 10. The uncertainty of neutral wind and electric field estimates is found to be strongly dependent on the prior constraints imposed on them. In the lower E region, neutral wind estimates have a lower standard deviation than 10 m/s in the most favourable conditions. In such conditions, also the F region electric field can be estimated with uncertainty of about 1 mV/m. Simulated measurements of <span class="inline-formula"><strong><em>v</em></strong></span> are used to demonstrate the ability to resolve the field-aligned profile of <span class="inline-formula"><strong><em>E</em></strong></span> and <span class="inline-formula"><strong><em>u</em></strong></span>. However, they can only be determined well at the heights where they dominate the ion drift, that is above 125 km for <span class="inline-formula"><strong><em>E</em></strong></span> and below 115 km for <span class="inline-formula"><strong><em>u</em></strong></span>. At the other heights, the results are strongly dependent on the prior assumptions of smoothness.</p> |
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