Space Science Reviews最新文献

Since the Voyager mission flybys in 1979, we have known the moon Io to be both volcanically active and the main source of plasma in the vast magnetosphere of Jupiter. Material lost from Io forms neutral clouds, the Io plasma torus and ultimately the extended plasma sheet. This material is supplied from Io's upper atmosphere and atmospheric loss is likely driven by plasma-interaction effects with possible contributions from thermal escape and photochemistry-driven escape. Direct volcanic escape is negligible. The supply of material to maintain the plasma torus has been estimated from various methods at roughly one ton per second. Most of the time the magnetospheric plasma environment of Io is stable on timescales from days to months. Similarly, Io's atmosphere was found to have a stable average density on the dayside, although it exhibits lateral (longitudinal and latitudinal) and temporal (both diurnal and seasonal) variations. There is a potential positive feedback in the Io torus supply: collisions of torus plasma with atmospheric neutrals are probably a significant loss process, which increases with torus density. The stability of the torus environment may be maintained by limiting mechanisms of either torus supply from Io or the loss from the torus by centrifugal interchange in the middle magnetosphere. Various observations suggest that occasionally (roughly 1 to 2 detections per decade) the plasma torus undergoes major transient changes over a period of several weeks, apparently overcoming possible stabilizing mechanisms. Such events (as well as more frequent minor changes) are commonly explained by some kind of change in volcanic activity that triggers a chain of reactions which modify the plasma torus state via a net change in supply of new mass. However, it remains unknown what kind of volcanic event (if any) can trigger events in torus and magnetosphere, whether Io's atmosphere undergoes a general change before or during such events, and what processes could enable such a change in the otherwise stable torus. Alternative explanations, which are not invoking volcanic activity, have not been put forward. We review the current knowledge on Io's volcanic activity, atmosphere, and the magnetospheric neutral and plasma environment and their roles in mass transfer from Io to the plasma torus and magnetosphere. We provide an overview of the recorded events of transient changes in the torus, address several contradictions and inconsistencies, and point out gaps in our current understanding. Lastly, we provide a list of relevant terms and their definitions.

Ultra-low frequency waves, with periods between 1-1000 s, are ubiquitous in the near-Earth plasma environment and play an important role in magnetospheric dynamics and in the transfer of electromagnetic energy from the solar wind to the magnetosphere. A class of those waves, often referred to as Pc3 waves when they are recorded from the ground, with periods between 10 and 45 s, are routinely observed in the dayside magnetosphere. They originate from the ion foreshock, a region of geospace extending upstream of the quasi-parallel portion of Earth's bow shock. There, the interaction between shock-reflected ions and the incoming solar wind gives rise to a variety of waves, and predominantly fast-magnetosonic waves with a period typically around 30 s. The connection between these waves upstream of the shock and their counterparts observed inside the magnetosphere and on the ground was inferred already early on in space observations due to similar properties, thereby implying the transmission of the waves across near-Earth space, through the shock and the magnetopause. This review provides an overview of foreshock 30-second/Pc3 waves research from the early observations in the 1960s to the present day, covering the entire propagation pathway of these waves, from the foreshock to the ground. We describe the processes at play in the different regions of geospace, and review observational, theoretical and numerical works pertaining to the study of these waves. We conclude this review with unresolved questions and upcoming opportunities in both observations and simulations to further our understanding of these waves.

Chondritic meteorites (chondrites) contain evidence for the interaction of liquid water with the interiors of small bodies early in Solar System history. Here we review the processes, products and timings of the low-temperature aqueous alteration reactions in CR, CM, CI and ungrouped carbonaceous chondrites, the asteroids Ryugu and Bennu, and hydrated dark clasts in different types of meteorites. We first consider the nature of chondritic lithologies and the insights that they provide into alteration conditions, subdivided by the mineralogy and petrology of hydrated chondrites, the mineralogy of hydrated dark clasts, the effects of alteration on presolar grains, and the evolution of organic matter. We then describe the properties of the aqueous fluids and how they reacted with accreted material as revealed by physicochemical modelling and hydrothermal experiments, the analysis of fluid inclusions in aqueously formed minerals, and isotope tracers. Lastly, we outline the chronology of aqueous alteration reactions as determined using the ⁵³Mn-⁵³Cr and ¹²⁹I-¹²⁹Xe systems.

Supplementary information: The online version contains supplementary material available at 10.1007/s11214-024-01132-8.

Magnetic reconnection is a ubiquitous plasma process that transforms magnetic energy into particle energy during eruptive events throughout the universe. Reconnection not only converts energy during solar flares and geomagnetic substorms that drive space weather near Earth, but it may also play critical roles in the high energy emissions from the magnetospheres of neutron stars and black holes. In this review article, we focus on collisionless plasmas that are most relevant to reconnection in many space and astrophysical plasmas. Guided by first-principles kinetic simulations and spaceborne in-situ observations, we highlight the most recent progress in understanding this fundamental plasma process. We start by discussing the non-ideal electric field in the generalized Ohm's law that breaks the frozen-in flux condition in ideal magnetohydrodynamics and allows magnetic reconnection to occur. We point out that this same reconnection electric field also plays an important role in sustaining the current and pressure in the current sheet and then discuss the determination of its magnitude (i.e., the reconnection rate), based on force balance and energy conservation. This approach to determining the reconnection rate is applied to kinetic current sheets with a wide variety of magnetic geometries, parameters, and background conditions. We also briefly review the key diagnostics and modeling of energy conversion around the reconnection diffusion region, seeking insights from recently developed theories. Finally, future prospects and open questions are discussed.

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.

Plasma flows with enhanced dynamic pressure, known as magnetosheath jets, are often found downstream of collisionless shocks. As they propagate through the magnetosheath, they interact with the surrounding plasma, shaping its properties, and potentially becoming geoeffective upon reaching the magnetopause. In recent years (since 2016), new research has produced vital results that have significantly enhanced our understanding on many aspects of jets. In this review, we summarise and discuss these findings. Spacecraft and ground-based observations, as well as global and local simulations, have contributed greatly to our understanding of the causes and effects of magnetosheath jets. First, we discuss recent findings on jet occurrence and formation, including in other planetary environments. New insights into jet properties and evolution are then examined using observations and simulations. Finally, we review the impact of jets upon interaction with the magnetopause and subsequent consequences for the magnetosphere-ionosphere system. We conclude with an outlook and assessment on future challenges. This includes an overview on future space missions that may prove crucial in tackling the outstanding open questions on jets in the terrestrial magnetosheath as well as other planetary and shock environments.

The primary purpose of the Tandem Reconnection And Cusp Electrodynamics Reconnaissance Satellites (TRACERS) Science Operations Center (SOC) is to ensure that the data necessary to achieve the TRACERS science goals are acquired, processed, and distributed to the scientific community. The SOC role in data acquisition is to facilitate science instrument planning and operations, through a weekly commanding cycle. Data processing includes generation of Level 0 and Level 1 data products, creation of Spacecraft Planet Instrument Camera-matrix Events (SPICE) kernels to provide spacecraft ephemerides and coordinate transforms for the mission, and ensuring consistency of all Level 2+ products produced by the individual instrument teams. Data distribution is undertaken in two ways. First, by hosting TRACERS data products on a public web portal during the active mission, and second by preparing mission data for transfer to the Space Physics Data Facility (SPDF) for long-term archiving.

Here we consider initial steps of how upcoming data from the SMILE Soft X-ray Imager and Ultraviolet Imager may be combined with additional data sources to provide a more holistic view of the coupled magnetosphere-ionosphere system. The Ground-based and Additional Science Working Group aims to embed SMILE in a multi-scale and holistic view of the Earth's magnetosphere by exploring coordination of ground-based and other spacecraft's data with SMILE. This working group is one of four working groups within the SMILE Science Working Team who are tasked with preparing all aspects of the mission. Adequate preparation is essential to optimise the tools, multiple instrument campaigns and procedures to allow the maximum science return from SMILE in the context of the entire available range of temporal and spatial scales in the terrestrial system. SMILE instruments will not work in isolation from each other, nor from other spacecraft or ground-based experiments. Synergies with other missions and ground-based experimentation will be fundamental for full science exploitation of the data. In this paper, we expand on the previous publications by the Ground-Based and Additional Science working group, by exploring the possibilities of using a two-way approach to deriving scientific results from SMILE, using a small isolated substorm as a case study. We use knowledge of the contemporaneous solar wind conditions during the substorm to simulate SMILE Soft X-ray Imager data. We also use observed ultraviolet auroral emissions and field-aligned current data as measured in the high-latitude polar regions to act as either a proxy for the SMILE Ultraviolet Imager, or an alternative source of information for the open-closed field line boundary. The observational data is used to constrain the minimisation of the two-dimensional X-ray images, leading to an improvement in the derived shape of the flank magnetopause position. We also comment on mission's possibilities to inspire the public through various engagement programmes, and current activities to involve diverse communities in the preparations and science exploitation of SMILE.

The Magnetic Search Coil (MSC) instruments on the TRACERS mission provide the three magnetic components of the waves from ∼1 Hz to 1 kHz from two closely spaced spacecraft in low Earth orbit that pass through the magnetospheric cusp. These measurements of Alfvén and other waves help meet the TRACERS Science Objective 3: "Determine to what extent dynamic structures in the cusp are associated with temporal versus spatial reconnection". The TRACERS MSC uses a three axis, dual sensor coil system and amplifiers with current feedback to provide continuous analog outputs to the Electric Field Instrument (EFI) Electric Signal Processing (ESP) Board. The ESP digitally samples each MSC analog output channel with 16-bit resolution at 2048 samples/second and sends the digitally sampled data to the Central Data Processing Unit (CDPU). The TRACERS MSC design, calibration, and performance is described.