An imaging interferometry capability for the EISCAT Svalbard Radar.

Interferometric imaging (aperture synthesis imaging) is a technique used by radio astronomers to achieve angular resolution that far surpasses what is possible with a single large aperture. A similar technique has been used for radar imaging studies of equatorial ionospheric phenomena at the Jicamarca Radio Observatory. We present plans for adding an interferometric imaging capability to the EISCAT Svalbard Radar (ESR), a capability which will contribute significantly to several areas of active research, including naturally and artificially enhanced ion-acoustic echoes and their detailed relation in space and time to optical phenomena, polar mesospheric summer echoes (PMSE), and meteor studies. Interferometry using the two antennas of the ESR has demonstrated the existence of extremely narrow, fieldaligned scattering structures, but having only a single baseline is a severe limitation for such studies. Building additional IS-class antennas at the ESR is not a trivial task. However, the very high scattering levels in enhanced ion-acoustic echoes and PMSE means that a passive receiver antenna of more modest gain should still be capable of detecting these echoes. In this paper we present simulations of what an imaging interferometer will be capable of observing for different antenna configurations and brightness distributions, under ideal conditions, using two different image inversion algorithms. We also discuss different antenna and receiver technologies

Study of the lower thermospheric wind in the polar region using EISCAT data obtained in 2 solar cycles

第3回極域科学シンポジウム/第36回極域宙空圏シンポジウム 11月26日（月）、27日（火） 国立極地研究所 2階ラウン

Studies of mean winds, tides and quasi-2 day waves using three meteor radars in northern Scandinavia

第2回極域科学シンポジウム/第35回極域宙空圏シンポジウム 11月14日（月） 国立極地研究所 2階大会議

北極域上部中間圏・下部熱圏における鉛直運動

第6回極域科学シンポジウム分野横断型セッション：[IM] 横断　中層大気・熱圏11月17日（火）　統計数理研究所 セミナー室2（D304

A case study on identification of blocking mechanism for upward propagating gravity wave in polar MLT region

第3回極域科学シンポジウム　横断セッション「中層大気・熱圏」 11月26日（月） 国立極地研究所 ２階大会議

Statistical study of sporadic sodium layer (SSL) in the polar lower thermosphere and upper mesosphere by using the Tromsø sodium LIDAR

第7回極域科学シンポジウム/横断セッション:[IM] 中空大気・熱圏11月30日（水）国立極地研究所1階交流アトリウ

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

A Comparison of Height-Integrated Ionospheric Currents and Magnetic Perturbation in the Auroral Zone

Data taken by the Incoherent Scatter Radar facility at Chatanika, Alaska (L=5.6,A=65°) have been used to study E-region height-integrated conductivities and currents. It is found that the radar measurements agree well with the magnetic H-component measured by the nearby magnetometer at college. Fairly large discrepancies occur between the radar data and the D component measured at college, indicating that field aligned currents are present. It is also found that the neutral wind is important, particularly during daytime, in driving a portion of the ionospheric currents

IRS - The Ultimate Istrument for Upper Polar Atmosphere Research

When the incoherent scatter radar (IRS) was installed at Chatanika, Fairbanks, Alaska in the fall of 1971, it opened up a door of magic. As soon as new results from a Chatanika experiment was published, they attracted attention in the science community engaged in the physics of the upper polar atmosphere and the aurora boralis. Time series of altitude profiles of parameters like electric fields and conductivities, electron densities and currents as well as ion composition and neutral winds, had been stronly desired for years by researchers who wanted to test out their models for the very dynamical processes that took place in the auroral ionosphere. We had seen a few rocket experiments presenting snapshots of electron density and ion composition profiles, but time series were outside reach. The observations by Chatanika radar were the first to meet these desires and gave the scientists new inspiration to submerge into the complex field of upper polar atmosphere dynamics where the whirling auroras stood out as evidences of dramatic electrodynamical processes unfolding in near space. Since then IRS\u27s have been introduced to higher latitudes to probe the more central parts of the Polar Cap where the interactions between the solar wind and the upper atmosphere is more direct. In addition to presenting some of the most outstanding findings in the upper polar atmosphere on the basis of IRS observations, a demonstration of some of the most epoch braking signal processing and data handling methods that have evolved throug the last 40 years will be presented; such phased array systems, pulse coding techniques and fast data storage procedures. A presentation of the planned EISCAT_3D in Northern Scandinavia that will offer volumetric images of the polar upper atmosphere with time and spatial resolutions that never have been accomplished before will also be given

Fysikk i den polare atmosfæren og nordlyset

Den polare atmosfæren har fått mer oppmerksomhet i den senere tid enn den vanligvis har vært forunt. Dette henger sammen med tanken om at den er så ren og upåvirket av eventuelle forurensninger som vi pumper ut i atmosfæren i de mer urbane strøk. Dersom atmosfæren tar skade av denne aktiviteten, forventer en å se skadevirkningene først og klarest i den polare atmosfæren. Svekkelsen av ozonlaget over Antarktis kan være et slikt sykdomstegn som har brakt miljøpolitikere verden over til å reagere. Vi ønsker ut fra de fysiske kunnskaper om atmosfæren å kaste lys over denne situasjonen