The Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) Mission

Space Science Reviews · 2025-06-27 · 24 citations

The overarching science goal of the Tandem Reconnection And Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission is to connect the cusp to the magnetosphere by discovering how spatial or temporal variations in magnetic reconnection drive cusp dynamics. This goal will be achieved with a simple mission design comprising two identical small spacecraft in identical low-Earth orbits in a follow-the-leader configuration. TRACERS will make repeated measurements in the cusp for a twelve-month primary mission using plasma and field instruments. These data will be analyzed using established dual-spacecraft techniques and supported by modeling that ensures science closure on the objectives. The TRACERS team leverages hardware collaborations from the University of Iowa, Southwest Research Institute, University of California Los Angeles, University of California Berkeley, and Millennium Space Systems. The larger science team consists of experts in reconnection, cusp physics, and modeling. TRACERS is dedicated to its proposer, and original Principal Investigator, Professor Craig Kletzing.

 L-MAG: a temperature-stabilized fluxgate magnetometer system for lunar surface observatories 

2025-07-09

Lunar magnetic field investigation connects the interior, the surface, and the space environment of the Moon. Measuring and understanding the lunar magnetic field at different length-scales and time-scales is of critical importance to understand the bulk water content and temperature profile in the lunar mantle, the existence and properties of a partial melt layer above the lunar core, the size of the lunar core, the origin and distribution of volatiles on the lunar surface, and the origin and properties of the past lunar dynamo, all of which are intimately connected to the origin of the Earth-Moon system and the subsequent thermal-chemical-environmental evolution of the Moon. The surface of the Moon, however, is a challenging environment, including contrasting temperatures between lunar day and lunar night, dust, and surface charging.Here we report our progress in the designing, building, and testing of a temperature-stabilized fluxgate magnetometer (FGM) system for long-term operations on the surface of the Moon. The sensor design draws heritage from those onboard the NASA Magnetospheric Multiscale (MMS) mission, InSight Mars Lander, and the Europa Clipper mission. We refer to this FGM system configuration as L-MAG. One of the key improvements is a magnetically clean heater system that is integrated with the FGM sensor. It is designed to yield a temperature stability of 0.2 degrees C around two set-point temperatures with minimal power consumption. The collocation of the heater with the sensor drastically reduces the necessary heater power. This power efficient FGM design will be compatible with installation onto a lunar lander or placed on the surface of the moon by an astronaut. Our L-MAG system will significantly improve measurement capabilities for upcoming lunar science missions including those via the Commercial Lunar Payload Services (CLPS) and via Artemis astronaut deployments.

Time-varying dynamo models consistent with Uranus’ and Neptune’s magnetic fields

2025-07-09

Uranus and Neptune present unique non-dipole-dominated magnetic fields that are also strongly non-axisymmetric (i.e., peak power for m>0). Their distinctly high power in the m = 1 component appears to be a persistent feature and, therefore, a key diagnostic for determining the mechanisms underlying magnetic field generation within these planets. Here, we highlight numerical dynamo models that successfully reproduce the large-scale features of ice giant magnetic fields, with the profile of radially varying electrical conductivity being a critical ingredient. Moreover, the magnetic fields in these dynamo models evolve rapidly with time. We thus hypothesize that Uranus' and Neptune's magnetic fields may have changed in intensity and/or orientation since the Voyager 2 flybys. This secular variation has implications for telescopic observations of auroral features (e.g., via the James Webb Space Telescope) and provides essential groundwork for the Uranus Orbiter and Probe Flagship and Triton Ocean World Surveyor New Frontier mission concepts prioritized in the Origins, Worlds, and Life Decadal Survey.

The TRACERS Fluxgate Magnetometer (MAG)

Space Science Reviews · 2025-09-01

The NASA Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) mission is a two-spacecraft mission designed to explore the temporal and spatial signatures of magnetic reconnection as observed at the low altitude dayside cusp. The instrumentation on each TRACERS spacecraft includes a three-axis vector fluxgate magnetometer (MAG). The MAG sensor design heritage is from Magnetospheric Multiscale (MMS), while the electronics heritage is from the InSight mission to Mars. Testing as part of the MAG instrument delivery verified that the MAG dynamic range exceeded ±60,000 nT with a resolution of ∼9 pT to provide margin. The fluxgate magnetometers have been calibrated on the ground, but as is typical for fluxgates they will be re-calibrated using on-orbit data. The TRACERS spacecraft are spinning spacecraft in an orbit at 590 km altitude. Absolute gains, orientation, and spin-axis offsets will be determined through comparison with the International Geomagnetic Reference Field (IGRF) with an underlying orbit-period cadence. Additionally, spin-tones allow determination of relative angular orientation and gain and spin-plane offsets at spin-period temporal resolution. To meet the TRACERS mission science objectives MAG will measure magnetic field perturbations from large scale field-aligned currents, and shorter scale Alfvén waves. The electromagnetic energy flux associated with these magnetic field perturbations has major impacts on particle acceleration along the flux tube and ionospheric heating through Joule dissipation. This conversion from electromagnetic to particle energy is a primary driver for the escape of ionospheric plasma into the magnetosphere, making this an important secondary science objective for the TRACERS mission.

Giant Planet Interior Dynamics in the Context of Rotating Turbulence Scaling Laws

2025-07-09

All four giant planets in our solar system feature planetary-scale magnetic fields and internal heat fluxes that exceed the adiabat. These observations point towards vigorous convection inside the planets, while some stable stratified internal layers have also been suggested. Rotating convective scaling laws can be employed to infer the bulk characteristics of planetary interior dynamics. A recent theoretical study connected the turbulent convection scaling laws across nonrotating, slowly rotating, and rapidly rotating regimes (Aurnou et al. 2020).Here we apply these scaling laws to the interior dynamics of the four giant planets in the solar system. With the measured heat flow as a critical input parameter, we estimate the characteristic flow speeds and dynamical length-scales within the different giant planet convective zones. These estimations inform us about the importance of rotation on the local dynamics via the local Rossby number. In addition, they can be used to kinematically evaluate the local magnetic field generation efficiency and the importance of Lorentz force via the local magnetic Reynolds number and the local Elsasser number. Our analysis indicates that the local magnetic Reynolds number exhibits a dichotomy between the gas giants and the ice giants. We will discuss how this might contribute to the dipole-multipole dichotomy in their observed magnetic fields.

Damping and Compressive Properties of SLM-Fabricated Rhombic Dodecahedron-Structured Ni–Ti Shape Memory Alloy Foams

Metals · 2025-03-19 · 6 citations

Ni–Ti shape memory alloy (SMA) foams, capable of bringing revolutionary changes to crucial fields such as aerospace, energy engineering, and biomedical applications, are at the forefront of materials science research. With the aim of designing Ni–Ti SMA foams with complex structures, near-equiatomic Ni–Ti SMA foams featuring a rhombic dodecahedron (RD) structure were fabricated using selective laser melting (SLM) technology. Damping, superelasticity, and quasi-static compressive mechanical tests were carried out on the resultant foams. The findings indicated that the smaller the unit structure of the RD or the larger the rod diameter, the higher the damping and compressive strength of the foams would be. Foams with a cell structure of 2 mm × 2 mm × 2 mm and a rod diameter of 0.6 mm exhibited the highest damping, reaching up to 0.049, along with the highest compressive strength, reaching up to 145 MPa. Furthermore, if the specimen underwent solution and aging heat treatments, its strength could be further enhanced. Meanwhile, the specimens also exhibited excellent superelasticity; even when the pre-strain was 6%, the elastic recovery could still reach 97%. Based on microstructure characterization and finite element simulation, the property mechanisms and deformation rules of the foams were revealed.

Mercury’s enigmatic magnetic field: a dynamo case against an extended basal iron-snow layer in the liquid outer core? 

2025-07-09

Mercury, the innermost planet in the solar system, remains an enigma after the wealth of measurements collected by NASA's MESSENGER mission. The state of Mercury's iron-rich core and the dynamo action that generates Mercury’s relatively weak, axially aligned, north-south asymmetric internal magnetic field is not well understood. Here we investigate the dynamo action associated with one unique possibility of Mercury's core: a double-iron-snow (DIS) dynamo with an extended, stably-stratified basal iron snow zone. This DIS structure model is one possible scenario that fits most other geophysical constraints at Mercury, including the Moment of Inertia. Our three-dimensional numerical dynamo survey varying the convective forcing (Rayleigh number), relative electrical conductivity (magnetic Prandtl number), and Brunt-Väisälä frequency revealed that although a relatively weak surface magnetic field can be achieved within this set-up, the external magnetic field remains highly dipolar and north-south symmetric under most scenarios. We hypothesize that this symmetry preference is due to the magnetic anchoring effect of the basal iron snow zone and the electromagnetic screening effect of the top iron snow zone. Our results indicate that while the existence of a top iron-snow zone (or a stably stratified layer) can lead to a weak and more axisymmetric magnetic field, the existence of an extended basal iron-snow zone would prohibit the equatorial symmetry breaking in the magnetic field observed at Mercury. Thus, our dynamo modeling results argue against the existence of an extended basal iron snow zone inside Mercury's core at present.

Low latitude field-aligned currents (FACs) at Jupiter: perspective from Juno MAG 

2025-07-09

Low latitude field-aligned current systems have been well documented at the Earth and reported at Saturn. Here we presented a comprehensive analysis of Juno magnetic field measurements in the low-latitude region within 1 Jovian radii from the surface of Jupiter. After removing the internal magnetic field (and its time variations) as well as the large-scale magnetodisk field, our analysis revealed a “sandwich” structure in the azimuthal component of the Jovian magnetic field, Bphi, with day-night asymmetries: on the dayside, Bphi is positive at mid-to-low latitudes but reverses sign at high latitudes; on the other hand, the pre-dawn side between 3am and 6am features a negative band of Bphi in the low-latitude region.Based on the observed spatial structures, we propose a day-night asymmetric low-latitude field-aligned current (FAC) system at Jupiter: currents flow from the northern to the southern hemisphere along low-latitude magnetic field lines on the dayside, and reverse direction on the pre-dawn side. These FACs are closed via ionospheric Pedersen currents, forming meridional current loops. We will also discuss the Ohmic heating associated with this current system in the Jovian upper atmosphere.

Towards an understanding of the morphology of Jupiter’s magnetic field

2025-03-14

As has been recognized since the completion of Juno’s first nine orbits, Jupiter’s magnetic field is morphologically distinct from that of the other planets. Six years later, with over 50 additional orbits, that picture has not fundamentally changed. While, like Earth, the field has a strong axial dipole component, the most intense field occurs in two distinct regions: the Great Blue Spot (GBS) and the Northern Hemisphere Flux Band (NHFB). Elsewhere, there are large regions of very low flux. What processes drive this field morphology?  While the axial dipole is almost certainly the result of a global dynamo (though of uncertain depth extent), these other features likely result from more localized dynamical processes. We consider various possibilities to explain the GBS, including flux expulsion, but only concentration of flux by a convergent (i.e. downwelling) flow seems plausible. For the NHFB, enhanced convection at the outer edge of the tangent cylinder to a deep stably stratified region is one possibility, though this does not explain the lack of such a feature in the southern hemisphere. Here, too, flux concentration by convergent flow is also a possibility. The regions of low flux may indicate the regions from which flux has been swept by divergent flow towards the regions of convergent flow. We will also discuss whether such processes are consistent with predominantly zonal flow in the presence of possible stable stratification.

Puzzles in Planetary Dynamos: Implications for Planetary Interiors

Annual Review of Earth and Planetary Sciences · 2025-02-14 · 5 citations

Intrinsic magnetic fields were once commonplace across our Solar System, and many planetary bodies have sustained active dynamos to the present day. The nature and behavior of these dynamos vary widely, however, reflecting the diverse internal conditions of planets as summarized in this review. For the terrestrial planets, the existence of active dynamos and/or ancient remanent magnetization recorded in crustal rocks, or lack thereof, lead to questions about their timing and power sources. Paleomagnetic studies reveal that many small bodies in the Solar System exhibit remanent magnetization, often attributed to ancient core dynamos with little known about the fluid dynamics. For the gas giants, their dipole-dominated magnetic fields and internal structures are relatively well-characterized, with dilute cores that are not centrally concentrated and other stable layers that likely affect the dynamo in ways that are not yet understood. For the ice giants, their multipolar magnetic fields and internal structures are unusual yet poorly constrained, to the extent that even the water-to-rock ratio is not well-known. Through adoption of a broader comparative planetology approach, the study of dynamos in exoplanets and cool stars enriches our understanding of dynamo theories. ▪ Planetary dynamos exhibit diverse magnetic fields shaped by their distinct physical and chemical conditions. ▪ The study of planets and stars connects planetary science, geophysics, and astrophysics, revealing shared dynamo processes. ▪ While significant progress has been made in understanding planetary and stellar magnetic fields, many puzzles still persist.