Experimental evidence and properties of EMIC wave driven electron precipitation

One of the key drivers of electron losses from the radiation belts is the interaction between radiation belt electrons and the electromagnetic plasma waves that populate the magnetosphere. In particular, electromagnetic ion cyclotron (EMIC) waves have been touted as a potential sources of significant electron loss from the radiation belts. However, until recently there has been a lack of experimental evidence for this precipitation occurring. Because of this, there is little experimental evidence for the properties of the precipitation, in particular the lower energy limit of EMIC interactions with radiation belt electrons. The main focus of this thesis is investigating a 17 year database of proton precipitation-associated relativistic electron precipitation events detected by the POES satellite constellation, believed to be driven by interactions with EMIC waves. This database represents an unheralded opportunity for in-depth study of EMIC waves and their interactions with energetic electrons. Unfortunately, the utility of this database has been limited due to the lack of accompanying wave observations; without direct evidence of EMIC wave activity, there remains significant doubt as to the true driver of the observed precipitation. In this thesis, we initially present two in-depth case studies of events from the precipitation database, showing clear evidence of concurrent EMIC wave activity and the observed precipitation. We follow up these studies with a broad statistical analysis of the precipitation database, comparing the event locations to ground-based magnetometers. We show a remarkable correlation between the precipitation events and EMIC waves observed on the ground, with as many as 90% of precipitation events occurring during periods of EMIC wave activity. We show that this correlation cannot be due to random chance, establishing a strong link between the precipitation events and EMIC wave activity. Finally, we also show that while our precipitation events imply wave activity, wave activity does not necessarily imply electron precipitation. Given the results of these studies, we have significant confidence that our database represents EMIC-wave scattered electron precipitation. We present two further case studies, investigating in-depth the energy and intensity characteristics of two events from the precipitation database. Through comparison with the DEMETER satellite, we are able derive electron energy spectra for these events

Evidence of sub-MeV EMIC-driven electron precipitation

Electromagnetic ion cyclotron (EMIC) waves are potentially important drivers of the loss of energetic electrons from the radiation belts. Numerous theoretical calculations exist with conflicting predictions of one of the key parameters: the minimum resonance energy of electrons precipitated into the atmosphere by EMIC waves. In this study we initially analyze an EMIC electron precipitation event using data from two different spacecraft instruments to investigate the energies involved. Combining observations from these satellites, we find that the electron precipitation has a peak flux at ∼250 keV. Extending the analysis technique to a previously published database of similar scattering events, we find that the peak electron precipitation flux occurs predominantly around 300 keV, with only ∼11% of events peaking in the 1–4 MeV range. Such a significant population of low-energy EMIC-driven electron precipitation events highlights the possibility for EMIC waves to be significant drivers of radiation belt electron losses

Magnetic local time‐resolved examination of radiation belt dynamics during high speed solar wind speedtTriggered substorm clusters

Particle observations from low Earth orbiting satellites are used to undertake superposed epoch analysis around clusters of substorms, in order to investigate radiation belt dynamical responses to mild geomagnetic disturbances. Medium energy electrons and protons have drift periods long enough to discriminate between processes occurring at different MLT, such as magnetopause shadowing, plasma wave activity, and substorm injections. Analysis shows that magnetopause shadowing produces clear loss in proton and electron populations over a wide range of L‐shells, initially on the dayside, which interact with nightside substorm‐generated flux enhancements following charge‐dependent drift directions. Inner magnetospheric injections recently identified as an important source of 10's to 100's keV electrons at low L (L<3), occurring during similar solar wind‐driving conditions as recurrent substorms, show similar but more enhanced geomagnetic AU‐index signatures. Two‐fold increases in substorm occurrence at the time of the sudden particle enhancements at low L shells (SPELLS), suggests a common linkage

Electron precipitation from EMIC waves: a case study from 31 May 2013

On 31 May 2013 several rising-tone electromagnetic ion-cyclotron (EMIC) waves with intervals of pulsations of diminishing periods (IPDP) were observed in the magnetic local time afternoon and evening sectors during the onset of a moderate/large geomagnetic storm. The waves were sequentially observed in Finland, Antarctica, and western Canada. Co-incident electron precipitation by a network of ground-based Antarctic Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK) and riometer instruments, as well as the Polar-orbiting Operational Environmental Satellite (POES) electron telescopes, was also observed. At the same time POES detected 30-80 keV proton precipitation drifting westwards at locations that were consistent with the ground-based observations, indicating substorm injection. Through detailed modelling of the combination of ground and satellite observations the characteristics of the EMIC-induced electron precipitation were identified as: latitudinal width of 2-3° or ΔL=1 Re, longitudinal width ~50° or 3 hours MLT, lower cut off energy 280 keV, typical flux 1×104 el. cm-2 sr-1 s-1 >300 keV. The lower cutoff energy of the most clearly defined EMIC rising tone in this study confirms the identification of a class of EMIC-induced precipitation events with unexpectedly low energy cutoffs of <400 keV

Generation of EMIC Waves and Effects on Particle Precipitation During a Solar Wind Pressure Intensification With Bz>0.

During geomagnetic storms, some fraction of the solar wind energy is coupled via reconnection at the dayside magnetopause, a process that requires a southward interplanetary magnetic field Bz. Through a complex sequence of events, some of this energy ultimately drives the generation of electromagnetic ion cyclotron (EMIC) waves, which can then scatter energetic electrons and ions from the radiation belts. In the event described in this paper, the interplanetary magnetic field remained northward throughout the event, a condition unfavorable for solar wind energy coupling through low‐latitude reconnection. While this resulted in SYM/H remaining positive throughout the event (so this may not be considered a storm, in spite of the very high solar wind densities), pressure fluctuations were directly transferred into and then propagated throughout the magnetosphere, generating EMIC waves on global scales. The generation mechanism presumably involved the development of temperature anisotropies via perpendicular pressure perturbations, as evidenced by strong correlations between the pressure variations and the intensifications of the waves globally. Electron precipitation was recorded by the Balloon Array for RBSP Relativistic Electron Losses balloons, although it did not have the same widespread signatures as the waves and, in fact, appears to have been quite patchy in character. Observations from Van Allen Probe A satellite (at postmidnight local time) showed clear butterfly distributions, and it may be possible that the EMIC waves contributed to the development of these distribution functions. Ion precipitation was also recorded by the Polar‐orbiting Operational Environmental Satellite satellites, though tended to be confined to the dawn‐dusk meridians

High-resolution in situ observations of electron precipitation-causing EMIC waves

Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic electron losses from the outer radiation belt through precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced electron precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC-induced electron precipitation inferred from coincident precipitation data and relate them to the EMIC wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. These observations will better constrain modeling into the importance of EMIC wave-particle interactions

The effectiveness of intermediate care including transitional care interventions on function, healthcare utilisation and costs: a scoping review.

Background and aim Intermediate care describes services, including transitional care, that support the needs of middle-aged and older adults during care transitions and between different settings. This scoping review aimed to examine the effectiveness of intermediate care including transitional care interventions for middle-aged and older adults on function, healthcare utilisation, and costs. Design A scoping review of the literature was conducted including studies published between 2002 and 2019 with a transitional care and/or intermediate care intervention for adults aged ≥ 50. Searches were performed in CINAHL, Cochrane Library, EMBASE, Open Grey and PubMed databases. Qualitative and quantitative approaches were employed for data synthesis. Results In all, 133 studies were included. Interventions were grouped under four models of care: (a) Hospital-based transitional care (n = 8), (b) Transitional care delivered at discharge and up to 30 days after discharge (n = 70), (c) Intermediate care at home (n = 41), and (d) Intermediate care delivered in a community hospital, care home or post-acute facility (n = 14). While these models were associated with a reduced hospital stay, this was not universal. Intermediate including transitional care services combined with telephone follow-up and coaching support were reported to reduce short and long-term hospital re-admissions. Evidence for improved ADL function was strongest for intermediate care delivered by an interdisciplinary team with rehabilitation at home. Study design and types of interventions were markedly heterogenous, limiting comparability. Conclusions Although many studies report that intermediate care including transitional care models reduce hospital utilisation, results were mixed. There is limited evidence for the effectiveness of these services on function, institutionalisation, emergency department attendances, or on cost-effectiveness. Electronic supplementary material The online version of this article (10.1007/s41999-020-00365-4) contains supplementary material, which is available to authorized users

A diatom extension to the cGEnIE Earth system model – EcoGEnIE 1.1

We extend the ecological component (ECOGEM) of the carbon-centric Grid-Enabled Integrated Earth system model (cGEnIE) to include a diatom functional group. ECOGEM represents plankton community dynamics via a spectrum of ecophysiological traits originally based on size and plankton food web (phyto- and zooplankton; EcoGEnIE 1.0), which we developed here to account for a diatom functional group (EcoGEnIE 1.1). We tuned EcoGEnIE 1.1, exploring a range of ecophysiological parameter values specific to phytoplankton, including diatom growth and survival (18 parameters over 550 runs) to achieve best fits to observations of diatom biogeography and size class distribution as well as to global ocean nutrient and dissolved oxygen distributions. This, in conjunction with a previously developed representation of opal dissolution and an updated representation of the ocean iron cycle in the water column, resulted in an improved distribution of dissolved oxygen in the water column relative to the previous EcoGEnIE 1.0, with global export production (7.4 Gt C yr−1) now closer to previous estimates. Simulated diatom biogeography is characterised by larger size classes dominating at high latitudes, notably in the Southern Ocean, and smaller size classes dominating at lower latitudes. Overall, diatom biological productivity accounts for ∼20 % of global carbon biomass in the model, with diatoms outcompeting other phytoplankton functional groups when dissolved silica is available due to their faster maximum photosynthetic rates and reduced palatability to grazers. Adding a diatom functional group provides the cGEnIE Earth system model with an extended capability to explore ecological dynamics and their influence on ocean biogeochemistry