The distinction between plasma properties in different dayside regions in the Earth's magnetosphere is of strong interest as it is often indicative of specific physical processes. This is certainly ...true for the distinction between low latitude boundary layer (LLBL) and cusp plasma, which has been attributed to the effects of plasma diffusion across the magnetopause (LLBL) versus a more direct entry of magnetosheath plasma (cusp). It is also the case, however, that quite different plasma regions can result more simply from a common source plasma, and from different stages of temporal evolution of the plasma associated with magnetospheric convection. In this paper, we show that, for southward interplanetary magnetic field (IMF) conditions, the distinction between the cusp and cleft/LLBL at low altitudes may result from the single process of magnetosheath plasma entry into the magnetosphere on reconnected field lines. The different plasma characteristics of the two regions result from the properties of the source magnetosheath ion distribution and the effects of magnetic reconnection. Using well known properties of the magnetosheath, several predictions concerning the cusp and cleft/LLBL precipitation are readily derived.
We predict the field‐aligned currents around cusp ion steps produced by pulsed reconnection between the geomagnetic field and an interplanetary magnetic field (IMF) with a BY component that is large ...in magnitude. For BY > 0, patches of newly opened flux move westward and eastward in the Northern and Southern Hemispheres, respectively, under the influence of the magnetic curvature force. These flow directions are reversed for BY < 0. The speed of this longitudinal motion initially grows with elapsed time since reconnection, but then decays as the newly opened field lines straighten. We predict sheets of field‐aligned current on the boundaries between the patches produced by successive reconnection pulses, associated with the difference in the speeds of their longitudinal motion. For low elapsed times since reconnection, near the equatorward edge of the cusp region where the field lines are accelerating, the field‐aligned current sheets will be downward or upward in both hemispheres for positive or negative IMF BY, respectively. At larger elapsed times since reconnection, as events slow and evolve from the cusp into the mantle region, these field‐aligned current directions will be reversed. Observations by the Polar spacecraft on August 26, 1998, show the predicted upward current sheets at steps seen in the mantle region for IMF BY > 0. Mapped into the ionosphere, the steps coincide with poleward moving events seen by the CUTLASS HF radar. The mapped location of the largest step also coincides with a poleward moving arc seen by the UVI imager on Polar. We show that the arc is consistent with a region of upward field‐aligned current that has become unstable, such that a potential drop of about 1 kV formed below the spacecraft. The importance of these observations is that they confirm that the poleward moving events, as seen by the HF radar and the UV imager, are due to pulsed magnetopause reconnection. Milan et al. 2000 noted that the great longitudinal extent of these events means that the required reconnection pulses would have contributed almost all the voltage placed across the magnetosphere at this time. The observations also show that auroral arcs can form on open field lines in response to the pulsed application of voltage at the magnetopause.
It is shown that the open magnetosphere model can reproduce both the down‐going and the up‐going magnetosheath ions seen in the cusp and mantle regions by the Polar satellite at middle altitudes. The ...pass studied shows a series of discontinuities in the ion dispersion, most of which are shown to arise from pulses of magnetopause reconnection rate. A total of 9 pulses are detected in an interval estimated to be about 30 min long, giving a mean repetition period of about 3 min: they vary in length between 0.5 min and 3.5 min and are separated by periods of much slower reconnection of duration 1–3 min. One step is not as predicted for reconnection rate pulses but is explained in terms of compressive motions caused by a pulse of solar wind dynamic pressure. The reconnection site is found to be 16 ± 3 RE from the ionosphere along the separatrix field line, placing it at low latitudes on the dayside magnetopause.
Potential industrial routes for production of H
2 via formate intermediates are outlined. Experimental data demonstrate that potassium, rubidium and caesium carbonates react to form their respective ...formate salts at 100 °C under 10 bar atmosphere of CO. The formate production rate is highly dependent upon type of alkali metal, type of solvent and concentration of water. Methanol is demonstrated to be a suitable solvent. It is also suggested that the formate salt intermediate can be made using methyl-formate. The production of H
2 is effectively achieved by a 5–10% Pd on activated carbon catalyst under mild condition (70–140 °C).
The high time resolution observations by the Fast Auroral Snapshot satellite resolve burst‐like electrons and nonmonotonic ion dispersion in the cusp region. Electric field data from a dawn‐dusk cusp ...crossing show that the DC electric field has small‐scale variations superimposed on a large‐scale pattern. The large‐scale DC electric field variations are well correlated with the large‐scale perturbation magnetic field, indicating a field‐aligned current system that reflects a relatively homogenous conductivity. Ion structures best correlate with the perturbed magnetic field and the large‐scale electric field. The burst‐like precipitating electrons are correlated with the small‐scale electric field variations, which are most easily explained as propagating Alfvén waves. We also found that the observed ion structures result from the spacecraft crossing the flow streamlines, each of which has its own individual history of dayside reconnection. The magnetosheath ion structures therefore contain information of both the spatial and temporal variations of dayside reconnection.
A cusp ion injection model incorporating mutually consistent electric and magnetic fields is developed. We have simulated cusp ion energy‐latitude spectrograms for paths similar to certain orbits of ...DE‐1 and Viking. Both the large‐scale energy‐latitude dispersion and the embedded small‐scale energy‐pitch‐angle V signatures are clearly evident in these simulated spectrograms. Our results show that a much narrower V microsignature is obtained when the ion injection source is restricted to a small region. However, the cutoff of the plasma injection at the magnetosheath sonic line alone also yields relatively narrow V‧s, without restricting the injection region. This effect is most noticeable in winter conditions. By introducing a time‐dependent magnetosheath plasma density variation along the magnetopause to our cusp model, we are also able to reproduce a well observed meso‐scale ion injection pattern which can appear to be the overlap of multiple injections, even with assuming steady interconnection.
Electron and ion precipitation data from two co-orbiting Defense Meteorological Satellite Program (DMSP) spacecraft (F6 and F8) are used to investigate the model of pulsed magnetopause reconnection. ...We suggest that the two energy dispersions observed can be explained by two separate injections resulting from two bursts of magnetopause reconnection. However, an observed overlap between the two ion dispersions cannot be explained with the conventional model of bursty magnetopause reconnection. We propose a generalization of the pulsed reconnection model that involves elements of both the bursty single x-line and multiple x-line reconnection models. In the framework of this unified model, the observed electron features can be explained in terms of the “fossil” flux transfer event picture.
The outer radiation belt injection, transport, acceleration and loss satellite (ORBITALS) is a small satellite mission proposed as a Canadian contribution to the satellite infrastructure for the ...International Living With a Star (ILWS) program. The ORBITALS will monitor the energetic electron and ion populations in the inner magnetosphere across a wide range of energies (keV to tens of MeV) as well as the dynamic electric and magnetic fields, waves and cold plasma environment which govern the injection, transport, acceleration and loss of these energetic and space weather critical particle populations. ORBITALS will be launched around 2010–2012 into a low-inclination GTO-like orbit which maximizes the long-lasting apogee-pass conjunctions with both the ground-based instruments of the Canadian Geospace Monitoring (CGSM) array as well as with the GOES East and West and geosynchronous communications satellites in the North American sector. Specifically, the ORBITALS will make the measurements necessary to gain fundamental new understanding of the relative importance of different physical acceleration and loss processes which are hypothesised to shape the energetic particle populations in the inner magnetosphere. The ORBITALS will also provide the raw radiation measurements at MEO altitudes necessary for the development of the next-generation of radiation belt specification models, and on-board experiments will also monitor the dose, single-event upset, and deep-dielectric charging responses of electronic components on-orbit. In this paper we outline the scientific objectives of the ORBITALS mission, discuss how the ORBITALS will lead to solutions to outstanding questions in inner magnetospheric science, and examine how the ORBITALS will complement other proposed inner magnetosphere missions in the ILWS era.
Parks et al. 1998 recently presented observations from the Wind spacecraft in Earth's Plasma Sheet Boundary Layer (PSBL). They argue that these observations are substantially different from previous ...observations. Furthermore, they argue that the interpretation of fast flows and ion beams in terms of a neutral line model needs to be reexamined, despite the fact that this interpretation has successfully described the observed particle properties in numerous studies. We argue in this comment that the Wind observations are readily understood using the established mechanism for PSBL formation. In fact, it is remarkable how well the ion distributions in Parks et al. support the neutral line model.
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