scholarly journals The end of the lunar dynamo

2020 ◽  
Vol 6 (1) ◽  
pp. eaax0883 ◽  
Author(s):  
Saied Mighani ◽  
Huapei Wang ◽  
David L. Shuster ◽  
Cauȇ S. Borlina ◽  
Claire I. O. Nichols ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Measurements ◽  
Zero Magnetic Field ◽  
The Moon ◽  
Lunar Crust ◽  
Lunar Core

Magnetic measurements of the lunar crust and Apollo samples indicate that the Moon generated a dynamo magnetic field lasting from at least 4.2 until <2.5 billion years (Ga) ago. However, it has been unclear when the dynamo ceased. Here, we report paleomagnetic and 40Ar/39Ar studies showing that two lunar breccias cooled in a near-zero magnetic field (<0.1 μT) at 0.44 ± 0.01 and 0.91 ± 0.11 Ga ago, respectively. Combined with previous paleointensity estimates, this indicates that the lunar dynamo likely ceased sometime between ~1.92 and ~0.80 Ga ago. The protracted lifetime of the lunar magnetic field indicates that the late dynamo was likely powered by crystallization of the lunar core.

Newton novel magnetic instrument. Potential application to unveil key questions as the origin of the Moon

2020 ◽  
Author(s):  
José Luis Mesa Uña ◽  
Marina Díaz Michelena ◽  
Francisco Javier de Frutos Hernánsanz ◽  
Claudio Aroca Hernández-Ros ◽  
Marina Pérez Jiménez ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Temporal Variations ◽  
Magnetic Characteristics ◽  
Potential Contribution ◽  
The European Union ◽  
The Moon ◽  
Lunar Crust ◽  
Sensors And Actuators ◽  
Earth Planet

&lt;p&gt;The main objective of this contribution is to present the evolution of NEWTON novel magnetic susceptometer for planetary exploration, a state of the art sensor for the measurement of the complex magnetic susceptibility developed in the frame of an EU H2020 funded project [1].&lt;/p&gt;&lt;p&gt;The magnetic susceptibility is a complex parameter dependent on the external magnetic field amplitude, direction and frequency. NEWTON susceptometer has been developed to determine the magnetic susceptibility of rocks and soils, with the capability to determine not only the real part but also the imaginary part of the susceptibility.&lt;/p&gt;&lt;p&gt;The calibration and validation process for the susceptometer prototype casted very good results in comparison with other commercial and high resolution laboratory devices, reaching a resolution in the order of &amp;#967; = 10&lt;sup&gt;&amp;#8722;4&lt;/sup&gt; (I.S. Vol. Susceptibility), representative of Earth, Moon and Mars rocks. The critical parts of the prototype have been subjected to different tests, i.e. vibration and TVT, to verify the capability to withstand the hard environmental conditions of interplanetary missions.&lt;/p&gt;&lt;p&gt;In this work we discuss the potential contribution of NEWTON instrument on the technical and scientific objectives achievement in future investigations on the Moon, either as payload during in-situ exploration with rovers or in sample return missions, providing a useful tool for fast in place sample analysis.&lt;/p&gt;&lt;p&gt;There are still open questions regarding Moon&amp;#8217;s magnetic field and geological characteristics of the satellite. Most hypotheses to explain the magnetic characteristics and anomalies on the lunar surface invoke a thermally driven core dynamo during its Pre-Nectarian and Nectarian history [2]. However, this theory is problematical given the small size of the core and the required strong magnetic field strength of an ancient dynamo. Further investigations on the lunar samples from missions [3] indicate ancient magnetic fields with intensities of &lt;1 to 120 &amp;#956;T for the period between 4.2 to 4.0 Ga. This huge range of intensities may indicate that the Moon&amp;#8217;s magnetic field experienced extreme high temporal variations [2]. Even if considering large uncertainties, dynamo models should consider paleointensities of at least ~35 &amp;#956;T for this high-field period.&lt;/p&gt;&lt;p&gt;The use of scientific instruments like NEWTON susceptometer in rover exploration missions could shed some light on the ancient dynamo magnetic field, the magnetic and mineral composition of the lunar crust and other unanswered questions from the Moon.&lt;/p&gt;&lt;p&gt;Acknowledgements:&lt;/p&gt;&lt;p&gt;This project has received funding from the European Union&amp;#8217;s Horizon 2020 research and innovation program under grant agreement No 730041 and the Spanish Programme of Research, Development and Innovation oriented to the challenges of the society under grant ESP2017-88930-R.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References:&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1]&amp;#160;M.Diaz Michelena, J.L Mesa U&amp;#241;a, M. Perez Jimenez, M. Maicas Ramos, P. Cobos Arribas, C. Aroca Hernandez-Ros, Sensors and Actuators, A: Physical, volume 263, pages 471-479 (2017)&lt;/p&gt;&lt;p&gt;[2] Tikoo, S.M., Weiss, B.P., Cassata, W.S., Shuser, D.L., Gattacceca, J., Lima, E.A., Suavet, C., Nimmo, F. &amp; Fuller, M.D. Earth Planet. Sci. Lett., 404: 89-97 (2014)&lt;/p&gt;&lt;p&gt;[3] Tsunakawa, H., Takahashi, F., Shimizu, H., Shibuya, H., &amp; Matsushima, M. Icarus 228: 35-53 (2014).&lt;/p&gt;&lt;p&gt;[3] Fuller, M. (1974). Reviews of Geophysics, 12 &amp;#8211; 1, 101-103 (1974)&lt;/p&gt;

Simulations of Magnetic Fields Produced by Asteroid Impact: Possible Implications for Planetary Paleomagnetism

2019 ◽  
Author(s):  
David A. Crawford
Keyword(s):  
Magnetic Field ◽  
Magnetic Measurements ◽  
Magnetic Anomalies ◽  
Iron Core ◽  
The Moon ◽  
Major Question ◽  
Asteroid Impact ◽  
Origin And Evolution ◽  
The Impact ◽  
The Magnetic Field

Abstract The origin and evolution of the Moon's magnetic field has been a major question in lunar science ever since Luna 1 made the first magnetic measurements in the vicinity of the Moon in 1959. Orbital measurements show that the magnetic field at the surface of the Moon has local scale lengths on the order of 1-100 km. While this could suggest a correlation with impact craters, most lunar magnetic anomalies don’t appear to correlate with known geologic structures, including impacts [1]. However, the magnetic field produced by impact events are spatially and temporally complex. Add in the complexity of remanence acquisition (localized regions of heating/cooling and/or shock that can produce remanence in the presence of a magnetic field) and we have the potential for a complex pattern to emerge. Wieczorek et al. [1] showed just how such complexity may play out. In their simulations, some lunar magnetic anomalies may be caused by regions of concentrated magnetic materials associated with fragments of the South Pole-Aitken impactor, especially if the impactor was differentiated with an iron core. More recently, Oliveira et al. [2] showed that magnetic anomalies associated with five large lunar basins may be caused by impact melt sheets that cooled in the presence of an early lunar dynamo. In this paper we will look at an alternative explanation for many lunar anomalies that doesn’t require the presence of a lunar dynamo. At least some lunar anomalies may be associated with a deeper, thicker yet more varied region of magnetization acquired by rocks that became hot and cooled rapidly enough during crater formation to have acquired the transient magnetic field produced by the impact itself.

Numerical and laboratory studies of magnetic enhancements produced by solar wind interaction with Lunar crustal magnetic fields

2021 ◽  
Author(s):  
Andrey Divin ◽  
Ildar Shaikhislamov ◽  
Marina Rumenskikh ◽  
Ivan Zaitsev ◽  
Vladimir Semenov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Laboratory Experiment ◽  
Numerical Study ◽  
The Moon ◽  
Lunar Crust ◽  
Solar Wind Interaction ◽  
Field Source ◽  
Theta Pinch ◽  
Spacecraft Data

&lt;p&gt;In this study, we use a combination of 3D Particle-in-Cell (PIC) simulations and a laboratory experiment to investigate the dynamics of solar wind - Moon interaction. It is known that the Moon has no global magnetic field, but there exist areas of intense remanent magnetization of the lunar crust which are strongly non-dipolar. Performed simulations indicate that the localized crustal fields are capable of scattering solar wind ions, efficiently heat electrons, and produce magnetic field perturbations in the upstream plasma. Numerical study of reflected ion flux compares well to the laboratory experiment performed at induction discharge theta-pinch &quot;KI-1&quot; facility (Novosibirsk). The plasma flow interacts with a magnetic field source (dipolar or quadrupolar), producing a minimagnetosphere with typical scales comparable to (or less than) a few ion inertial lengths. Our numerical and laboratory study concludes that the magnetic field should drop faster than r&lt;sup&gt;-3&lt;/sup&gt; with the distance in order to reproduce the spacecraft observations. In this case, gyroradii of the reflected ions are considerably larger than the scale of the minimagnetosphere density cavity. Reflected ions generate enhancements in the upstream magnetic field, supposedly seen as LEMEs (lunar external magnetic enhancements) in spacecraft data above the Moon crustal fields.&lt;/p&gt;

scholarly journals Experimental signatures of nodeless multiband superconductivity in a $$\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2$$ single crystal

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chanhee Kim ◽  
Dilip Bhoi ◽  
Yeahan Sur ◽  
Byung-Gu Jeon ◽  
Dirk Wulferding ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Single Crystal ◽  
Zero Magnetic Field ◽  
Anisotropy Ratio ◽  
Strong Temperature Dependence ◽  
Critical Fields ◽  
Band Theory ◽  
Plane Field ◽  
Low Field ◽  
Out Of Plane

AbstractIn order to understand the superconducting gap nature of a $$\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2$$ 2H-Pd 0.08 TaSe 2 single crystal with $$T_{c} = 3.13 \text { K}$$ T c = 3.13 K , in-plane thermal conductivity $$\kappa $$ κ , in-plane London penetration depth $$\lambda _{\text {L}}$$ λ L , and the upper critical fields $$H_{c2}$$ H c 2 have been investigated. At zero magnetic field, it is found that no residual linear term $$\kappa _{0}/T$$ κ 0 / T exists and $$\lambda _{\text {L}}$$ λ L follows a power-law $$T^n$$ T n (T: temperature) with n = 2.66 at $$T \le \frac{1}{3}T_c$$ T ≤ 1 3 T c , supporting nodeless superconductivity. Moreover, the magnetic-field dependence of $$\kappa _{0}$$ κ 0 /T clearly shows a shoulder-like feature at a low field region. The temperature dependent $$H_{c2}$$ H c 2 curves for both in-plane and out-of-plane field directions exhibit clear upward curvatures near $$T_c$$ T c , consistent with the shape predicted by the two-band theory and the anisotropy ratio between the $$H_{c2}$$ H c 2 (T) curves exhibits strong temperature-dependence. All these results coherently suggest that $$\hbox {2H-Pd}_{0.08} \hbox {TaSe}_2$$ 2H-Pd 0.08 TaSe 2 is a nodeless, multiband superconductor.

scholarly journals Imaging the formation and surface phase separation of the CE phase

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Haibiao Zhou ◽  
Qiyuan Feng ◽  
Yubin Hou ◽  
Masao Nakamura ◽  
Yoshinori Tokura ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Charge Ordering ◽  
Zero Magnetic Field ◽  
Ferromagnetic Phase ◽  
Emergent Properties ◽  
Orbital Ordering ◽  
Strong Electron ◽  
Antiferromagnetic Correlation ◽  
Ordering Transitions

AbstractThe CE phase is an extraordinary phase exhibiting the simultaneous spin, charge, and orbital ordering due to strong electron correlation. It is an ideal platform to investigate the role of the multiple orderings in the phase transitions and discover emergent properties. Here, we use a cryogenic high-field magnetic force microscope to image the phase transitions and properties of the CE phase in a Pr0.5Ca0.5MnO3 thin film. In a high magnetic field, we observed a clear suppression of magnetic susceptibility at the charge-ordering insulator transition temperature (TCOI), whereas, at the Néel temperature (TN), no significant change is observed. This observation favors the scenario of strong antiferromagnetic correlation developed below TCOI but raises questions about the Zener polaron paramagnetic phase picture. Besides, we discoverd a phase-separated surface state in the CE phase regime. Ferromagnetic phase domains residing at the surface already exist in zero magnetic field and show ultra-high magnetic anisotropy. Our results provide microscopic insights into the unconventional spin- and charge-ordering transitions and revealed essential attributes of the CE phase, highlighting unusual behaviors when multiple electronic orderings are involved.

scholarly journals Colossal anomalous Nernst effect in a correlated noncentrosymmetric kagome ferromagnet

2021 ◽  
Vol 7 (13) ◽  
pp. eabf1467
Author(s):  
T. Asaba ◽  
V. Ivanov ◽  
S. M. Thomas ◽  
S. Y. Savrasov ◽  
J. D. Thompson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electronic Structure ◽  
Theoretical Calculations ◽  
Zero Magnetic Field ◽  
Nernst Effect ◽  
Nodal Lines ◽  
Transverse Response ◽  
Narrow Bands ◽  
Strong Spin ◽  
Anomalous Nernst Effect

The transverse voltage generated by a temperature gradient in a perpendicularly applied magnetic field, termed the Nernst effect, has promise for thermoelectric applications and for probing electronic structure. In magnetic materials, an anomalous Nernst effect (ANE) is possible in a zero magnetic field. We report a colossal ANE in the ferromagnetic metal UCo0.8Ru0.2Al, reaching 23 microvolts per kelvin. Uranium’s 5f electrons provide strong electronic correlations that lead to narrow bands, a known route to producing a large thermoelectric response. In addition, uranium’s strong spin-orbit coupling produces an intrinsic transverse response in this material due to the Berry curvature associated with the relativistic electronic structure. Theoretical calculations show that in UCo0.8Ru0.2Al at least 148 Weyl nodes, and two nodal lines, exist within 60 millielectron volt of the Fermi level. This work demonstrates that magnetic actinide materials can host strong Nernst and Hall responses due to their combined correlated and topological nature.

scholarly journals TRANSPORT PROPERTIES OF 2D ELECTRON GAS IN AN n-InGaAs/GaAs DQW IN A VICINITY OF LOW MAGNETIC-FIELD-INDUCED HALL INSULATOR–QUANTUM HALL LIQUID TRANSITION

2007 ◽  
Vol 06 (03n04) ◽  
pp. 173-177
Author(s):  
YU. G. ARAPOV ◽  
S. V. GUDINA ◽  
G. I. HARUS ◽  
V. N. NEVEROV ◽  
N. G. SHELUSHININA ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Gas ◽  
Quantum Hall ◽  
Zero Magnetic Field ◽  
Double Quantum ◽  
Ballistic Regime ◽  
2D Electron Gas ◽  
Double Quantum Well ◽  
Liquid Transition ◽  
Low Magnetic Field

The resistivity (ρ) of low mobility dilute 2D electron gas in an n- InGaAs / GaAs double quantum well (DQW) exhibits the monotonic "insulating-like" temperature dependence (dρ/dT < 0) at T = 1.8–70 K in zero magnetic field. This temperature interval corresponds to a ballistic regime (kBTτ/ħ > 0.1–3.5) for our samples, and the electron density is on an "insulating" side of the so-called B = 0 2D metal–insulator transition. We show that the observed features of localization and Landau quantization in a vicinity of the low magnetic-field-induced insulator–quantum Hall liquid transition is due to the σxy(T) anomalous T-dependence.

Calculation of the hydrogen dimer spectrum in zero magnetic field

1981 ◽  
Vol 54 (2) ◽  
pp. 189-200 ◽  
Author(s):  
J. Verberne ◽  
J. Reuss
Keyword(s):  
Magnetic Field ◽  
Zero Magnetic Field

scholarly journals Consideration of Magnetic Measurements for Characterisation of Ferrite–Martensite Commercial Dual-Phase (DP) Steel and Basis for Optimisation of the Operating Magnetic Field for Open Loop Deployable Sensors

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 490
Author(s):  
Mohsen Aghadavoudi Jolfaei ◽  
Lei Zhou ◽  
Claire Davis
Keyword(s):  
Magnetic Field ◽  
Applied Magnetic Field ◽  
Magnetic Measurements ◽  
Initial Permeability ◽  
Open Loop ◽  
Dual Phase ◽  
Dp Steel ◽  
Ferrite Fraction ◽  
Lift Off ◽  
Steel Properties

The magnetic properties of commercial dual-phase (DP) steels (DP600, DP800 and DP1000 grades) were evaluated using initial permeability, incremental permeability and coercivity and correlated with the key microstructural differences between the grades. The ferrite grain sizes and ferrite fractions have been compared with the magnetic parameters obtained from minor and major magnetisation loops within each DP grade. It has been revealed that the incremental permeability increases with the applied magnetic field amplitude to reach a peak and then drops at a higher magnetic field, with the values being different for the three DP grades at a lower field and converging to a similar permeability value at the high field. The effects of ferrite grain size and phase fraction on the incremental permeability are considered, and it has been shown that the influence of ferrite grain boundaries on magnetic permeability is more dominant than the effect of ferrite fraction in commercial DP steel samples. An analysis of the correlation between coercivity and initial permeability with tensile strength shows that the initial permeability provides a slightly better prediction of strength for the steels examined, which is believed to be due to the fact that a combination of reversible and irreversible domain components affect the coercivity value, while the initial permeability is predominantly affected by reversible domain movements. Based on the trend between incremental permeability and applied magnetic field and the commercial EM sensor (EMspec) operating parameters, the effect of lift-off and hence magnetic field strength on the sensitivity to DP steel properties can be assessed.

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