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1. FDTD Simulations Of The Impedance Of A Dipole Antenna in A Plasma

   https://doi.org/10.1109/APUSNCURSINRSM.2019.8888864  

   Spencer, E.; Latif, S. (July 2019, 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting)

   The impedance of a dipole antenna in the earth’s ionospheric plasma is dependent on the ambient plasma properties such as electron density and electron neutral collision frequency. Depending on the length of the dipole, it is possible to not only measure the plasma properties, but in addition, receive plasma waves that are found propagating in the ionosphere. Here we report on some FDTD simulations of a dipole antenna in a cold plasma, and present some approximate expressions that can be used to analyze this behavior. When the dipole antenna resonant wavelength /4 and associated frequency is far from the upper hybrid, cyclotron and plasma frequencies of the local plasma, the expressions work fairly well. However, when the length of the antenna is such that it’s resonant wavelength coincides or is close to the plasma resonances, the expressions fail, and a full-wave FDTD simulation has to be performed to extract meaningful plasma data. 

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2. Observation of long-range dipole-dipole interactions in hyperbolic metamaterials

   https://doi.org/10.1126/sciadv.aar5278  

   Newman, Ward D.; Cortes, Cristian L.; Afshar, Amir; Cadien, Ken; Meldrum, Al; Fedosejevs, Robert; Jacob, Zubin (October 2018, Science Advances)

   Dipole-dipole interactions ( V dd ) between closely spaced atoms and molecules are related to real photon and virtual photon exchange between them and decrease in the near field connected with the characteristic Coulombic dipole field law. The control and modification of this marked scaling with distance have become a long-standing theme in quantum engineering since dipole-dipole interactions govern Van der Waals forces, collective Lamb shifts, atom blockade effects, and Förster resonance energy transfer. We show that metamaterials can fundamentally modify these interactions despite large physical separation between interacting quantum emitters. We demonstrate a two orders of magnitude increase in the near-field resonant dipole-dipole interactions at intermediate field distances (10 times the near field) and observe the distance scaling law consistent with a super-Coulombic interaction theory curtailed only by absorption and finite size effects of the metamaterial constituents. We develop a first-principles numerical approach of many-body dipole-dipole interactions in metamaterials to confirm our theoretical predictions and experimental observations. In marked distinction to existing approaches of engineering radiative interactions, our work paves the way for controlling long-range dipole-dipole interactions using hyperbolic metamaterials and natural hyperbolic two-dimensional materials. 

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3. An “Eddy β-Spiral” mechanism for vertical velocity dipole patterns of isolated oceanic mesoscale eddies

   https://doi.org/10.3389/fmars.2022.1036783  

   Hou, Yinglin; Jin, Fei-Fei; Gao, Shan; Zhao, Jun; Liu, Kai; Qu, Tangdong; Wang, Fan (October 2022, Frontiers in Marine Science)

   Oceanic eddies accompanied by a significant vertical velocity ( w ) are known to be of great importance for the vertical transport of various climatically, biologically or biogeochemically relevant properties. Using quasi-geostrophic w -thinking to extend the classic “ β -spiral” w -theory for gyre circulations to isolated and nearly symmetric oceanic mesoscale eddies, we propose that their w motion will be dominated by a strong east-west dipole pattern with deep ocean penetrations. Contrasting numerical simulations of idealized isolated eddies together with w -equation diagnostics confirm that the w -dipole is indeed dominated by the “eddy β -spiral” mechanism in the β -plane simulation, whereas this w -dipole expectedly disappears in the f -plane simulation. Analyses of relatively isolated warm and cold eddy examples show good agreement with the proposed mechanism. Our studies further clarify eddy vertical motions, have implications for ocean mixing and vertical transport, and inspire further studies. 

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4. Diverse impacts of Indian Ocean Dipole on El Niño-Southern Oscillation

   https://doi.org/10.1175/JCLI-D-21-0085.1  

   Zhang, Lei; Han, Weiqing; Meehl, Gerald A.; Hu, Aixue; Rosenbloom, Nan; Shinoda, Toshiaki; McPhaden, Michael J. (September 2021, Journal of Climate)

   Abstract Understanding the impact of the Indian Ocean Dipole (IOD) on El Niño-Southern Oscillation (ENSO) is important for climate prediction. By analyzing observational data and performing Indian and Pacific Ocean pacemaker experiments using a state-of-the-art climate model, we find that a positive IOD (pIOD) can favor both cold and warm sea surface temperature anomalies (SSTA) in the tropical Pacific, in contrast to the previously identified pIOD-El Niño connection. The diverse impacts of the pIOD on ENSO are related to SSTA in the Seychelles-Chagos thermocline ridge (SCTR; 60°E-85°E and 7°S-15°S) as part of the warm pole of the pIOD. Specifically, a pIOD with SCTR warming can cause warm SSTA in the southeast Indian Ocean, which induces La Niña-like conditions in the tropical Pacific through interbasin interaction processes associated with a recently identified climate phenomenon dubbed the “Warm Pool Dipole”. This study identifies a new pIOD-ENSO relationship and examines the associated mechanisms. 

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5. Fundamental figure of merit for engineering dipole-dipole interactions

   https://doi.org/10.1364/CLEO_QELS.2019.FTu3D.3  

   Cortes, Cristian L.; Newman, Ward; Boddeti, Ashwin K.; Sentz, Tyler; Jacob, Zubin (January 2019, Conference on Lasers and Electro Optics (CLEO))

   Over the last decade there has been a debate regarding the role of the photonic environment in enhancing, inhibiting and imparting coherence to dipole-dipole interactions. We develop a unified figure of merit to conclusively explain multiple recent experiments. 

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