aeklund

• Clausen, Lasse; Bekkeng, Tore André; Els, Sebastian; Khoory, Mohammed S.; Sharaf, Ahmed A. & Adhikari, Sayan [Vis alle 9 forfattere av denne artikkelen] (2025). The Langmuir Probe Instrument on Board the Rashid-1 Rover of the Emirates Lunar Mission. Space Science Reviews. ISSN 0038-6308. 221, s. 1–17. doi: 10.1007/s11214-025-01159-5. Fulltekst i vitenarkiv Vis sammendrag

  The Rashid-1 rover, which was part of the Emirates Lunar Mission (ELM) program, was a small rover aimed to be operated for one lunar day on the lunar surface. As part of its scientific instrumentation, Rashid-1 carried a Langmuir probe experiment (LNG) in order to provide the first extensive, high-resolution in situ measurements of the bulk parameters of the lunar dayside thermal plasma at different altitudes above the lunar surface. The LNG was comprised of four probes, mounted at different locations and heights above the lunar surface on the Rashid-1 rover. This way, the LNG was intended to derive an altitude profile of the two plasma parameters electron density and electron temperature above the lunar surface. The design of the instrument and a description of the data analysis technique, calibration, and validation are provided in this paper. Due to the short separation between the probes and the rover body (in terms of Debye length), the measurements of the LNG were expected to be influenced by the presence of the rover and its sheath. This was addressed through numerical modeling, which is described and preliminary results are presented. Unfortunately, the landing in the Atlas crater of the lunar lander carrying Rashid-1 to the surface was not successful – however, this description of the instrument design and the data analysis techniques are still useful for future explorations of the lunar plasma environment.

• Mishra, Rinku; Moulick, R.; Adhikari, Sayan; Marholm, Sigvald; Eklund, Anders Johan & Miloch, Wojciech Jacek (2024). Beam–plasma dynamics in finite-length, collisionless inhomogeneous systems. Physics of Plasmas. ISSN 1070-664X. 31(10). doi: 10.1063/5.0218386. Fulltekst i vitenarkiv Vis sammendrag

  This study investigates the streaming instability triggered by ion motion in a plasma system that is finite in length, collisionless, and inhomogeneous. Employing numerical simulations using particle-in-cell techniques and kinetic equations, the study examines how inhomogeneity emerges from integrating a cold ion beam with a background plasma within a confined system. The findings suggest that steady ion flow can modify ion sound waves through acoustic reflections from system boundaries, leading to instability. Such phenomena are known to be a hydrodynamic effect. However, there are also signatures of the beam-driven ion sound instability where kinetic resonances play a pivotal role. The main objective is to understand the impact of a finite-length system on beam–plasma instability and to identify the wave modes supported in such configurations.

• Liu, Guangdong; Marholm, Sigvald; Eklund, Anders Johan; Clausen, Lasse & Marchand, Richard (2023). m-NLP Inference Models Using Simulation and Regression Techniques. Journal of Geophysical Research (JGR): Space Physics. ISSN 2169-9380. 128(2). doi: 10.1029/2022JA030835. Fulltekst i vitenarkiv Vis sammendrag

  Current inference techniques for processing multi-needle Langmuir probe (m-NLP) data are often based on adaptations of the Orbital Motion-Limited (OML) theory which relies on several simplifying assumptions. Some of these assumptions, however, are typically not well satisfied in actual experimental conditions, thus leading to uncontrolled uncertainties in inferred plasma parameters. In order to remedy this difficulty, three-dimensional kinetic particle in cell simulations are used to construct a synthetic data set, which is used to compare and assess different m-NLP inference techniques. Using a synthetic data set, regression-based models capable of inferring electron density and satellite potentials from 4-tuples of currents collected with fixed-bias needle probes similar to those on the NorSat-1 satellite, are trained and validated. The regression techniques presented show promising results for plasma density inferences with RMS relative errors less than 20%, and satellite potential inferences with RMS errors less than 0.2 V for potentials ranging from −6 to −1 V. The new inference approaches presented are applied to NorSat-1 data, and compared with existing state-of-the-art inference techniques.

• Eklund, Anders Johan; Dvornik, Mykola; Qejvanaj, Fatjon; Jiang, Sheng; Chung, Sunjae & Åkerman, Jonas [Vis alle 7 forfattere av denne artikkelen] (2021). Impact of intragrain spin wave reflections on nanocontact spin torque oscillators. Physical review B (PRB). ISSN 2469-9950. 103(21). doi: 10.1103/PhysRevB.103.214433. Fulltekst i vitenarkiv Vis sammendrag

  We investigate the origin of the experimentally observed varying current-frequency nonlinearity of the propagating spin wave mode in nanocontact spin torque oscillators. Nominally identical devices with 100 nm diameter are characterized by electrical microwave measurements and show large variation in the generated frequency as a function of drive current. This quantitative and qualitative device-to-device variation is described in terms of continuous and discontinuous nonlinear transitions between linear current intervals. The thin-film grain microstructure in our samples is determined using atomic force and scanning electron microscopy to be on the scale of 30 nm. Micromagnetic simulations show that the reflection of spin waves against the grain boundaries results in standing wave resonance configurations. For a simulated device with a single artificial grain, the frequency increases linearly with the drive current until the decreased wavelength eventually forces another spin wave antinode to be formed. This transition results in a discontinuous step in the frequency versus current relation. Simulations of complete, randomly generated grain microstructures additionally shows continuous nonlinearity and a resulting device-to-device variation in frequency that is similar to the experimental levels. The impact of temperature from 4 to 300 K on the resonance mode-transition nonlinearity and frequency noise is investigated using simulations and it is found that the peak levels of the spectral linewidth as a function of drive current agree quantitatively with typical levels found in experiments at room temperature. The impact of the grain microstructure on the localized oscillation modes is also investigated.

• Chung, Sunjae; Eklund, Anders Johan; Iacocca, Ezio; Mohseni, Seyed Majid; Sani, Sohrab R. & Bookman, Lake [Vis alle 9 forfattere av denne artikkelen] (2016). Magnetic droplet nucleation boundary in orthogonal spin-torque nano-oscillators. Nature Communications. doi: 10.1038/ncomms11209. Fulltekst i vitenarkiv
• Chen, Tingsu; Eklund, Anders Johan; Sani, Sohrab; Rodriguez, Saul; Malm, B. Gunnar & Åkerman, Johan [Vis alle 7 forfattere av denne artikkelen] (2015). Integration of GMR-based spin torque oscillators and CMOS circuitry. Solid-State Electronics. ISSN 0038-1101. doi: 10.1016/j.sse.2015.05.037. Fulltekst i vitenarkiv
• Bonetti, S.; Kukreja, R.; Chen, Z.; Macià, F.; Hernàndez, J. M. & Eklund, Anders Johan [Vis alle 15 forfattere av denne artikkelen] (2015). Direct observation and imaging of a spin-wave soliton with p-like symmetry. Nature Communications. doi: 10.1038/ncomms9889. Fulltekst i vitenarkiv
• Eklund, Anders Johan; Bonetti, Stefano; Sani, Sohrab R.; Mohseni, S. Majid; Persson, Johan & Chung, Sunjae [Vis alle 11 forfattere av denne artikkelen] (2014). Dependence of the colored frequency noise in spin torque oscillators on current and magnetic field. Applied Physics Letters. ISSN 0003-6951. doi: 10.1063/1.4867257. Fulltekst i vitenarkiv

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• Gouttebroze, Sylvain; Andersen, Casper Welzel; Hagelien, Thomas Fjæstad; Eklund, Anders Johan; Langner, Eric & Makradi, Ahmed [Vis alle 8 forfattere av denne artikkelen] (2024). Towards a Knowledge-based Simulation Platform for the design of SOFC anode material. Fulltekst i vitenarkiv
• Adamovic, Nadja; Bleken, Francesca Lønstad; Calvio, Alessandro; Cantrill, Vikki; Beber, Vinicius Carrillo & Courtney, Seán [Vis alle 22 forfattere av denne artikkelen] (2024). Semantic Knowledge Management for Materials: the benefits of a FAIR data and model-based approach in industrial research and development. zenodo. doi: 10.5281/zenodo.13304677. Fulltekst i vitenarkiv

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