The science case for the EISCAT_3D radar

The EISCAT (European Incoherent SCATer) Scientific Association has provided versatile incoherent scatter (IS) radar facilities on the mainland of northern Scandinavia (the EISCAT UHF and VHF radar systems) and on Svalbard (the electronically scanning radar ESR (EISCAT Svalbard Radar) for studies of the high-latitude ionised upper atmosphere (the ionosphere). The mainland radars were constructed about 30 years ago, based on technological solutions of that time. The science drivers of today, however, require a more flexible instrument, which allows measurements to be made from the troposphere to the topside ionosphere and gives the measured parameters in three dimensions, not just along a single radar beam. The possibility for continuous operation is also an essential feature. To facilitatefuture science work with a world-leading IS radar facility, planning of a new radar system started first with an EU-funded Design Study (2005–2009) and has continued with a follow-up EU FP7 EISCAT_3D Preparatory Phase project (2010–2014). The radar facility will be realised by using phased arrays, and a key aspect is the use of advanced software and data processing techniques. This type of software radar will act as a pathfinder for other facilities worldwide. The new radar facility will enable the EISCAT_3D science community to address new, significant science questions as well as to serve society, which is increasingly dependent on space-based technology and issues related to space weather. The location of the radar within the auroral oval and at the edge of the stratospheric polar vortex is also ideal for studies of the long-term variability in the atmosphere and global change. This paper is a summary of the EISCAT_3D science case, which was prepared as part of the EU-funded Preparatory Phase project for the new facility. Three science working groups, drawn from the EISCAT user community, participated in preparing this document. In addition to these working group members, who are listed as authors, thanks are due to many others in the EISCAT scientific community for useful contributions, discussions, and support

The science case for the EISCAT_3D radar

The EISCAT (European Incoherent SCATer) Scientific Association has provided versatile incoherent scatter (IS) radar facilities on the mainland of northern Scandinavia (the EISCAT UHF and VHF radar systems) and on Svalbard (the electronically scanning radar ESR (EISCAT Svalbard Radar) for studies of the high-latitude ionised upper atmosphere (the ionosphere). The mainland radars were constructed about 30 years ago, based on technological solutions of that time. The science drivers of today, however, require a more flexible instrument, which allows measurements to be made from the troposphere to the topside ionosphere and gives the measured parameters in three dimensions, not just along a single radar beam. The possibility for continuous operation is also an essential feature. To facilitatefuture science work with a world-leading IS radar facility, planning of a new radar system started first with an EU-funded Design Study (2005–2009) and has continued with a follow-up EU FP7 EISCAT_3D Preparatory Phase project (2010–2014). The radar facility will be realised by using phased arrays, and a key aspect is the use of advanced software and data processing techniques. This type of software radar will act as a pathfinder for other facilities worldwide. The new radar facility will enable the EISCAT_3D science community to address new, significant science questions as well as to serve society, which is increasingly dependent on space-based technology and issues related to space weather. The location of the radar within the auroral oval and at the edge of the stratospheric polar vortex is also ideal for studies of the long-term variability in the atmosphere and global change. This paper is a summary of the EISCAT_3D science case, which was prepared as part of the EU-funded Preparatory Phase project for the new facility. Three science working groups, drawn from the EISCAT user community, participated in preparing this document. In addition to these working group members, who are listed as authors, thanks are due to many others in the EISCAT scientific community for useful contributions, discussions, and support

The mid-and high-altitude cusp observed by Cluster

International audienc

On the ionospheric and thermospheric footprint of the polar cusp

International audienceAt the footprint of the polar cusp, the ionosphere and the thermosphere are strongly affected by the combination of intense precipitation of magnetosheath particles and strong convection electric fields. In particular, incoherent radar observations indicate that the electron density may decrease significantly in the cusp ionosphere, despite the intense precipitation of low-energy electrons. In order to understand the physics and the chemistry of these regions, we have modelled the ionospheric footprints of the cusp and mantle regions, and we focus on the two rival processes acting pro and con the electron density build-up. We investigate various combinations of E-field and initial electron densities and their roles on the local ionosphere and thermosphere. Our simulations clearly show that the overall result depends on the origin of the flux tube, which eventually opens in the cusp region. We interpret our results in terms of seasonal effects, IMF-By and MLT dependences

Overlapping cusp ion structures under Northward IMF: signature of re-closed magnetic field lines?

abstract SM22B-04On some occasions, Cluster data in the mid-altitude cusp reveal overlapping ion populations under Northward IMF. While the poleward part of the cusp exhibits the expected reverse dispersion due to lobe reconnection, its equatorward part shows a second high-energy ion population that coexists with the low energy tail of the dispersion. This second populations is either dispersionless or slightly dispersed with energies increasing with increasing latitude, indicative of sunward convection. The analysis of data from Cluster fleet and, for one event, of data from the EISCAT Svalbard Radar in conjunction with Cluster, reveals that the second population comes very likely from the opposite hemisphere and is on closed field lines. We interpret this overlap of closed-LLBL and cusp populations in terms of magnetic field lines being opened in one hemisphere by lobe reconnection and re- closed in the other

Coordinated Cluster and Double Star observations of the dayside magnetopause near magnetic noon

abstract SM24B-0151We present results of a Double Star TC-1/Cluster conjunction where Double Star is at the magnetopause, near the equatorward edge of the Southern hemisphere's polar cusp, while Cluster sits at the poleward edge of the same cusp. This configuration makes it possible to compare observations at different places of the magnetopause, in more or less the same magnetic local time but at different latitudes. In this paper, we report on and discuss three interesting events. First, a FTE is observed at TC-1 and not at Cluster; we discuss the implications this has on the evolution of FTEs. Then, a variation in the solar wind pressure makes the magnetosphere expend slightly and the satellites, then out in the sheath, get near the magnetopause. The delay between Double Star and Cluster suggests that a rarefaction wave propagates along the magnetopause. This rarefaction wave made Cluster move close to the magnetopause, where a rotational discontinuity is observed. At last, a northward turning of the magnetosheath magnetic field is observed at TC-1 and a reverse FTE is subsequently seen at Cluster, suggesting that magnetic reconnection is fast to start at a given location following a change in the IMF orientation. We put our observations in the global context of solar wind /magnetosphere interactions, by means of magnetic reconnection or surface waves along the magnetopause

EISCAT observations and TRANSCAR simulation of the solar eclipse of August 1, 2008

Abstract SA33B-1639On 1 August 2008, the footprint of the solar eclipse passed north east of the Svalbard archipelago, where the EISCAT Svalbard Radars (ESR) are installed. The radars measured a depletion in electron density in the low F-region of a factor ~10 and a decrease in temperature of about 1000K. Also, the VHF dish of the mainland EISCAT system measured a decrease in the same parameters, showing the influence of the penumbra and of a partial eclipse. We have modelled the response of the high-latitude ionosphere to a solar eclipse with the TRANSCAR code and used its new capability to model the response of the conjugated ionosphere in the southern hemisphere