| 1. |
- Li, Yu-Xuan, et al.
(author)
-
Quantification of Cold-Ion Beams in a Magnetic Reconnection Jet
- 2021
-
In: Frontiers in Astronomy and Space Sciences. - : Frontiers Media S.A.. - 2296-987X. ; 8
-
Journal article (peer-reviewed)abstract
- Cold (few eV) ions of ionospheric origin are widely observed in the lobe region of Earth's magnetotail and can enter the ion jet region after magnetic reconnection is triggered in the magnetotail. Here, we investigate a magnetotail crossing with cold ions in one tailward and two earthward ion jets observed by the Magnetospheric Multiscale (MMS) constellation of spacecraft. Cold ions co-existing with hot plasma-sheet ions form types of ion velocity distribution functions (VDFs) in the three jets. In one earthward jet, MMS observe cold-ion beams with large velocities parallel to the magnetic fields, and we perform quantitative analysis on the ion VDFs in this jet. The cold ions, together with the hot ions, are reconnection outflow ions and are a minor population in terms of number density inside this jet. The average bulk speed of the cold-ion beams is approximately 38% larger than that of the hot plasma-sheet ions. The cold-ion beams inside the explored jet are about one order of magnitude colder than the hot plasma-sheet ions. These cold-ion beams could be accelerated by the Hall electric field in the cold ion diffusion region and the shrinking magnetic field lines through the Fermi effect.
|
|
| 2. |
- Toledo-Redondo, S., et al.
(author)
-
Statistical Observations of Proton-Band Electromagnetic Ion Cyclotron Waves in the Outer Magnetosphere: Full Wavevector Determination
- 2024
-
In: Journal of Geophysical Research - Space Physics. - : John Wiley and Sons Inc. - 2169-9380 .- 2169-9402. ; 129:5
-
Journal article (peer-reviewed)abstract
- Electromagnetic Ion Cyclotron (EMIC) waves mediate energy transfer from the solar wind to the magnetosphere, relativistic electron precipitation, or thermalization of the ring current population, to name a few. How these processes take place depends on the wave properties, such as the wavevector and polarization. However, inferring the wavevector from in-situ measurements is problematic since one needs to disentangle spatial and time variations. Using 8 years of Magnetospheric Multiscale (MMS) mission observations in the dayside magnetosphere, we present an algorithm to detect proton-band EMIC waves in the Earth's dayside magnetosphere, and find that they are present roughly 15% of the time. Their normalized frequency presents a dawn-dusk asymmetry, with waves in the dawn flank magnetosphere having larger frequency than in the dusk, subsolar, and dawn near subsolar region. It is shown that the observations are unstable to the ion cyclotron instability. We obtain the wave polarization and wavevector by comparing Single Value Decomposition and Ampere methods. We observe that for most waves the perpendicular wavenumber (k⊥) is larger than the inverse of the proton gyroradius (ρi), that is, k⊥ρi > 1, while the parallel wavenumber is smaller than the inverse of the ion gyroradius, that is, k‖ρi < 1. Left-hand polarized waves are associated with small wave normal angles (θBk < 30°), while linearly polarized waves are associated with large wave normal angles (θBk > 30°). This work constitutes, to our knowledge, the first attempt to statistically infer the full wavevector of proton-band EMIC waves observed in the outer magnetosphere.
|
|
| 3. |
- Toledo-Redondo, S., et al.
(author)
-
Solar Wind-Magnetosphere Coupling During Radial Interplanetary Magnetic Field Conditions : Simultaneous Multi-Point Observations
- 2021
-
In: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 126:11
-
Journal article (peer-reviewed)abstract
- In-situ spacecraft missions are powerful assets to study processes that occur in space plasmas. One of their main limitations, however, is extrapolating such local measurements to the global scales of the system. To overcome this problem at least partially, multi-point measurements can be used. There are several multi-spacecraft missions currently operating in the Earth's magnetosphere, and the simultaneous use of the data collected by them provides new insights into the large-scale properties and evolution of magnetospheric plasma processes. In this work, we focus on studying the Earth's magnetopause (MP) using a conjunction between the Magnetospheric Multiscale and Cluster fleets, when both missions skimmed the MP for several hours at distant locations during radial interplanetary magnetic field (IMF) conditions. The observed MP positions as a function of the evolving solar wind conditions are compared to model predictions of the MP. We observe an inflation of the magnetosphere (similar to 0.7 R-E), consistent with magnetosheath pressure decrease during radial IMF conditions, which is less pronounced on the flank (<0.2 R-E). There is observational evidence of magnetic reconnection in the subsolar region for the whole encounter, and in the dusk flank for the last portion of the encounter, suggesting that reconnection was extending more than 15 R-E. However, reconnection jets were not always observed, suggesting that reconnection was patchy, intermittent or both. Shear flows reduce the reconnection rate up to similar to 30% in the dusk flank according to predictions, and the plasma beta enhancement in the magnetosheath during radial IMF favors reconnection suppression by the diamagnetic drift.
|
|
| 4. |
|
|
| 5. |
- Karlsson, P, et al.
(author)
-
Low-Density Cellulose-Based Foams: Preparation, Characterization and Biodegradation
- 2023
-
In: Book of Abstracts EPNOE 2023. - : Graz University of Technology. ; , s. 345-
-
Conference paper (other academic/artistic)abstract
- The demands for alternatives to fossil-based materials for the packaging and building sector is rapidly increasing as new regulations and laws are set. The usage of such materials in low- density applications is increasingly questioned since only a small amount is recycled and a large part ends up in the environment where it has a very long decomposition time and contributes to the emergence of microplastics in our marine eco systems. Alternatives to fossil- based low-density materials has been demonstrated using e.g., starch [1] and cellulose [2] as raw materials. However, challenges remain regarding the process parameters and properties such as strength and water integrity. To fulfil these properties requested by the specification owners, understanding is needed regarding which tools that are available for incorporating wet-integrity and hydrophobicity without causing the wet foam to collapse during the foaming or drying process. It is also of highest importance to have an early understanding of how such materials can be recycled and/or bio-degraded to fit a circular economy. In this study two different cross-linkers and two different types of hydrophobisers are used to obtain a wet stable and a water repelling low-density material. The wet foams are characterized by measuring the foamability and foam stability and the dry foams are characterized in terms of structure, porosity and degradability. Two demonstrators have been produced based on the most promising material composition and the up-scaling processes of the developed foaming technology to both batch-wise and continuous fabrication of composite foams is underway. Finally, a biodegradation study was conducted and evaluated.[1] S. Chaireh, P. Ngasatool, and K. Kaewtatip, “Novel composite foam made from starch and water hyacinth with beeswax coating for food packaging applications,” Int. J. Biol. Macromol., vol. 165, pp. 1382–1391, 2020[2] C. Qin, M. Yao, Y. Liu, Y. Yang, Y. Zong, and H. Zhao, “MFC/NFC-based foam/aerogel for production of porous materials: Preparation, properties and applications,” Materials (Basel)., vol. 13, no. 23, pp. 1–21, 2020
|
|
| 6. |
- Li, Wenya, et al.
(author)
-
Upper-Hybrid Waves Driven by Meandering Electrons Around Magnetic Reconnection X Line
- 2021
-
In: Geophysical Research Letters. - : American Geophysical Union (AGU). - 0094-8276 .- 1944-8007. ; 48:16
-
Journal article (peer-reviewed)abstract
- Magnetic reconnection is a fundamental process in collisionless space plasma environment, and plasma waves relevant to the kinetic interactions can have a significant impact on the multiscale behavior of reconnection. Here, we present Magnetospheric Multiscale (MMS) observations during an encounter of an X line of symmetric magnetic reconnection in the magnetotail. The X line is characterized by reversals of ion and electron jets and electromagnetic fields, agyrotropic electron velocity distribution functions (VDFs), and an electron-scale current sheet. MMS observe large-amplitude nonlinear upper-hybrid (UH) waves on both sides of the neutral line, and the wave amplitudes have highly localized distribution along the normal direction. The inbound meandering electrons drive the UH waves, releasing the free energy stored from the reconnection electric field along the meandering trajectories. The interaction between the meandering electrons and the UH waves may modify the balance of the reconnection electric field around the X line. Plain Language Summary The electron-scale kinetic physics in the electron diffusion region (EDR) controls how magnetic field lines break and reconnect. Electron crescent, an indicator of EDR, can drive high-frequency electrostatic waves around EDR. For the first time, the upper-hybrid (UH) waves are observed on both sides of the X line and we show the direct association between the UH waves and the reconnection electric field. The strong wave-electron interaction can change the electron-scale dynamics and may modify the reconnection electric field. This study demonstrates that the UH waves may play an important role in controlling the reconnection rate.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Dahlström, Christina, 1977-, et al.
(author)
-
Ion conductivity through TEMPO-mediated oxidated and periodate oxidated cellulose membranes
- 2020
-
In: Carbohydrate Polymers. - : ELSEVIER SCI LTD. - 0144-8617 .- 1879-1344. ; 233
-
Journal article (peer-reviewed)abstract
- Cellulose in different forms is increasingly used due to sustainability aspects. Even though cellulose itself is an isolating material, it might affect ion transport in electronic applications. This effect is important to understand for instance in the design of cellulose-based supercapacitors. To test the ion conductivity through membranes made from cellulose nanofibril (CNF) materials, different electrolytes chosen with respect to the Hofmeister series were studied. The CNF samples were oxidised to three different surface charge levels via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and a second batch was further cross-linked by periodate oxidation to increase wet strength and stability. The outcome showed that the CNF pre-treatment and choice of electrolyte are both crucial to the ion conductivity through the membranes. Significant specific ion effects were observed for the TEMPO-oxidised CNF. Periodate oxidated CNF showed low ion conductivity for all electrolytes tested due to an inhibited swelling caused by the crosslinking reaction.
|
|
| 10. |
- Dahlström, Christina, 1977-, et al.
(author)
-
Stacking self-gluing cellulose II films : A facile strategy for the formation of novel all-cellulose laminates
- 2024
-
In: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 344
-
Journal article (peer-reviewed)abstract
- Cellulose laminates represent a remarkable convergence of natural materials and modern engineering, offering a wide range of versatile applications in sustainable packaging, construction, and advanced materials. In this study, novel all-cellulose laminates are developed using an environmentally friendly approach, where freshly regenerated cellulose II films are stacked without the need for solvents (for impregnation and/or partial dissolution), chemical modifications, or resins. The structural and mechanical properties of these all-cellulose laminates were thoroughly investigated. This simple and scalable procedure results in transparent laminates with exceptional mechanical properties comparable to or even superior to common plastics, with E-modulus higher than 9 GPa for a single layer and 7 GPa for the laminates. These laminates are malleable and can be easily patterned. Depending on the number of layers, they can be thin and flexible (with just one layer) or thick and rigid (with three layers). Laminates were also doped with 10 wt% undissolved fibers without compromising their characteristics. These innovative all-cellulose laminates present a robust, eco-friendly alternative to traditional synthetic materials, thus bridging the gap between environmental responsibility and high-performance functionality.
|
|
