Description: Highlights • High lithogenic input in surface waters in the Panama Basin results in radiogenic εNd of up to +4.3. • Radiogenic Nd derived from particles can reset the Nd IC of water masses within time scales years. • Lithogenic input of REEs and corresponding Nd IC in surface waters are seasonally influenced. The distribution of dissolved rare earth elements (REEs) and neodymium isotopes (εNd) in the open ocean traces water mass mixing and provides information on lithogenic inputs to the source regions of the water masses. However, the processes influencing the REE budget at the ocean margins, in particular source and sink mechanisms, are not yet well quantified. In this study the first dissolved REE concentrations and Nd isotope compositions of seawater from the Panama Basin (RV Meteor cruise M90) in the Eastern Equatorial Pacific (EEP) are presented. The EEP is characterized by one of the world's largest oxygen minimum zones (OMZs). It is dominated by high particle fluxes that are expected to enhance the removal of REEs from the water column by scavenging. The measured REE concentrations peak at the surface indicating high lithogenic input, which is supported by shale-normalized REE patterns in surface waters and highly radiogenic εNd signatures ranging between +1.4 and +4.3, the latter value constituting the most radiogenic value measured for seawater to date. In contrast, intermediate and deep water REE concentrations are low compared to other Pacific Basins and suggest enhanced removal via scavenging associated with high particle fluxes. The εNd signatures of intermediate and deep waters are less radiogenic than surface waters ranging between −1.4 and +1.3 but significantly more radiogenic than source water masses in the EEP. The εNd signatures consequently do not reflect mixing of intermediate and deep water masses entering the Panama Basin but can only be explained by lithogenic inputs originating from source rocks with highly radiogenic Nd isotope signatures such as the Central American Volcanic Arc (εNd=+3 to +10). Our data demonstrate significant surface input via continental particles, which are partially dissolved in the water column and thereby release REEs and particularly radiogenic Nd isotope signatures to the subsurface ocean. Data obtained from a re-occupied station in the southern Panama Basin for the first time shows that these processes can partially reset water mass Nd isotope and REE signatures of the entire water column proximal to continental sources on time scales of a few years.

Description: Author(s): G. Bossé, L. S. Bilbro, R. Valdés Aguilar, LiDong Pan, Wei Liu, A. V. Stier, Y. Li, L. H. Greene, J. Eckstein, and N. P. Armitage We present time-domain terahertz spectroscopy data of a thin film of the Kondo-lattice antiferromagnet CeCu 2 Ge 2 . The low-frequency complex conductivity has been obtained down to temperatures below the onset of magnetic order. At low temperatures a narrow Drude-like peak forms, which is similar to on... [Phys. Rev. B 85, 155105] Published Wed Apr 04, 2012

Description: Recent observations with spectro-photo-polarimeters have shown that the auroral emissions from oxygen at 577.7 nm (green line), and from the N2+ 1st negative band emissions at 427.8 nm (blue line) and 391.4 nm (purple line) are polarized at a few percent level and that this polarization is linked to geomagnetic activity and cannot be explained by light pollution only. The origin of this polarization is still puzzling and could be related to ionospheric currents, either field-aligned or horizontal Pedersen/Hall currents.In November 2022, we set-up a multi-instrument observing campaign in Norway in order to better understand this situation. At the Skibotn observatory, we used two instruments dedicated to the measurements of auroral light polarization : PLIP, a Polar Lights Imaging Polarimeter, able to measure polarization of the three main auroral emissions (green, red and blue) on a large FOV (~44° × 30°) on the sky, and Corbel Cru, a spectro-photo polarimeter able to measure faint polarized signals in a 2° FOV in the green, blue and purple line. These data were complemented by optical observations from the ALIS_4D network in Sweden in order to obtain 2D precipitating electron fluxes using tomographic-like inversion techniques, and by radar observations with the EISCAT UHF antenna working in scanning mode. In this contribution we will present preliminary results from these instruments for a good case study obtained during this campaign. One goal of the campaign is to check whether the angle of linear polarization can be used as tracers for ionospheric currents.

Description: In the last decade, several instruments have been developped to measure the auroral light polarisation. However, its study has faced the issue of anthropic light pollution and scattering in the lower atmosphere (Bosse et al., 2020). To overcome this challenge the most succesfull method was the use of a polarised radiative transfer model to identify the light pollution contribution (Bosse et al., 2022). This year, a new look at the data revealed that pulsating aurorae are polarised, and that this polarisation carries a lot of information. Searching for polarisation in pulsating aurorae allows us to dismiss any external source of polarisation that is not synched with the pulsation of the aurora. Thus light pollution is not a problem anymore.These polarisation patterns are seen in the green atomic oxygen line at 557.7 nm, the 1st N2+ negative band at 391.4 nm (purple) and 427.8 nm (blue). Today, there are no clear explanations on the origin of this auroral polarisation, or its relation to the local state of the upper atmosphere. An hypothesis is that this polarisation can be either created directly at the radiative de-excitation or may occur when the non-polarised emission crosses the ionospheric currents. We will present how these new findings confirm the ionospheric origin of the polarisation observed from the ground, and discussing about the opportunities these observations and models offer in the frame of space weather, aerosol and light pollution study.