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1. Obtaining High‐Resolution Magnetic Records From Speleothems Using Magnetic Microscopy

   https://doi.org/10.1029/2024GC011594  

   Borlina, Cauê S; Lima, Eduardo A; Feinberg, Joshua M; Jaqueto, Plinio; Lascu, Ioan; Trindade, Ricardo_I F; Font, Eric; Sánchez‐Moreno, Elisa M; Dimuccio, Luca Antonio; Yokoyama, Yusuke; et al (October 2024, Geochemistry, Geophysics, Geosystems)

   Abstract Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high‐resolution paleomagnetic records of short‐term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10⁻¹¹ Am²), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm³, averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm³) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10⁻¹⁵ Am². To determine the application of SQUID microscopy for obtaining robust high‐resolution records from small‐volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five‐fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales. 

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2. Magnetic Phase Imaging Using Interferometric STEM

   https://doi.org/10.1017/S143192762002173X  

   Greenberg, Alice; McMorran, Benjamin; Johnson, Cameron; Yasin, Fehmi (August 2020, Microscopy and Microanalysis)

   null (Ed.)
3. Identification of Active Magnetic Reconnection Using Magnetic Flux Transport in Plasma Turbulence

   https://doi.org/10.3847/2041-8213/abea0b  

   Li, Tak Chu; Liu, Yi-Hsin; Qi, Yi (March 2021, The Astrophysical Journal Letters)

   Abstract Magnetic reconnection has been suggested to play an important role in the dynamics and energetics of plasma turbulence by spacecraft observations, simulations, and theory over the past two decades, and recently, by magnetosheath observations of MMS. A new method based on magnetic flux transport (MFT) has been developed to identify reconnection activity in turbulent plasmas. This method is applied to a gyrokinetic simulation of two-dimensional (2D) plasma turbulence. Results on the identification of three active reconnection X-points are reported. The first two X-points have developed bidirectional electron outflow jets. Beyond the category of electron-only reconnection, the third X-point does not have bidirectional electron outflow jets because the flow is modified by turbulence. In all cases, this method successfully identifies active reconnection through clear inward and outward flux transport around the X-points. This transport pattern defines reconnection and produces a new quadrupolar structure in the divergence of MFT. This method is expected to be applicable to spacecraft missions such as MMS, Parker Solar Probe, and Solar Orbiter. 

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4. Magnetic Nanowire Biolabels Using Ferromagnetic Resonance Identification

   https://doi.org/10.1021/acsanm.1c00086  

   Um, Joseph; Zhang, Yali; Zhou, Wen; Zamani Kouhpanji, Mohammad R.; Radu, Cosmin; Franklin, Rhonda R.; Stadler, Bethanie J. (April 2021, ACS Applied Nano Materials)

   null (Ed.)
5. Downhole wireless communication using magnetic induction technique

   Yan, Li; Wei, Debing; Pan, Miao; Chen, Jiefu (February 2018, 2018 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM))

   This paper presents a novel method utilizing magnetic induction (MI) for wireless data transmission in oilfield borehole systems. Compared with conventional techniques, MI telemetry can achieve massive data transmission with low cost. Three coil configurations in borehole system are investigated, and most effective one is selected out based on numerical simulations. Through equivalent circuit model analysis, path loss and channel capacity are derived. 

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