IMECE2006-15704 THERMO-MECHANICAL BEHAVIOR OF A MICROMIRROR FOR LASER-TO-FIBER ACTIVE ALIGNMENT USING BIMORPHS WITH BREAKABLE TETHERS

ABSTRACT We will present a novel micromirror design in which tethered bimorph strips are used for mirror active alignment including beam steering and position fixing. A micromirror is attached to bimorphs that are pre-stressed at room temperature. A series of tethers link the bimorphs to the substrate to restrain their deformation. Breaking a tether by Joule heating allows the deformation of the bimorph to increase, changing the mirror position and orientation for precision alignment. With a large number of tethers, an optimum alignment can be achieved after breaking a selected group of tethers. We also report the experimental results of devices fabricated

Modelling electrified railway signalling misoperations during extreme space weather events in the UK

Space weather has the potential to impact ground-based technologies on Earth, affecting many systems including railway signalling. This study uses a recently developed model to analyse the impact of geomagnetically induced currents on railway signalling systems in the United Kingdom during the March 1989 and October 2003 geomagnetic storms. The March 1989 storm is also scaled to estimate a 1-in-100 year and a 1-in-200 year extreme storm. Both the Glasgow to Edinburgh line, and the Preston to Lancaster section of the West Coast Main Line are modelled. No “right side” failures (when unoccupied sections appear occupied) are suggested to have occurred during either storm, and the total number of potential “wrong side” failures (when occupied sections appear clear) is low. However, the modelling indicates “right side” and “wrong side” failures are possible on both routes during the 1-in-100 year and 1-in-200 year extreme storms, with the Glasgow to Edinburgh line showing more total misoperations than the Preston to Lancaster section of the West Coast Main Line. A 1-in-100 year or 1-in-200 year extreme storm would result in misoperations over an extended period of time, with most occurring over a duration of 2–3 h either side of the peak of the storm

Nighttime Magnetic Perturbation Events Observed in Arctic Canada: 3. Occurrence and Amplitude as Functions of Magnetic Latitude, Local Time, and Magnetic Disturbance Indices

Rapid changes of magnetic fields associated with nighttime magnetic perturbation events (MPEs) with amplitudes |ΔB| of hundreds of nT and 5–10 min duration can induce geomagnetically induced currents (GICs) that can harm technological systems. This study compares the occurrence and amplitude of nighttime MPEs with |dB/dt| ≥ 6 nT/s observed during 2015 and 2017 at five stations in Arctic Canada ranging from 64.7° to 75.2° in corrected geomagnetic latitude (MLAT) as functions of magnetic local time (MLT), the SME (SuperMAG version of AE) and SYM/H magnetic indices, and time delay after substorm onsets. Although most MPEs occurred within 30 min after a substorm onset, ∼10% of those observed at the four lower latitude stations occurred over two hours after the most recent onset. A broad distribution in local time appeared at all five stations between 1700 and 0100 MLT, and a narrower distribution appeared at the lower latitude stations between 0200 and 0700 MLT. There was little or no correlation between MPE amplitude and the SYM/H index; most MPEs at all stations occurred for SYM/H values between −40 and 0 nT. SME index values for MPEs observed \u3e1 h after the most recent substorm onset fell in the lower half of the range of SME values for events during substorms, and dipolarizations in synchronous orbit at GOES 13 during these events were weaker or more often nonexistent. These observations suggest that substorms are neither necessary nor sufficient to cause MPEs, and hence predictions of GICs cannot focus solely on substorms

A new adaptive marine policy toolbox to support ecosystem-based approach to management

4 p.As a consequence of increasing threats to the marine ecosystems, new decision support tools are necessary to support the implementation of the Ecosystem-Based Approach (EBA) to management in order to ensure their sustainable exploitation whilst ensuring their preservation. *To operationalize Ecosystem-Based Approach (EBA) to management and translate scientific knowledge into decision tools, an innovative Adaptive Marine Policy Toolbox has been created. It provides policymakers with necessary framework and resources to develop adaptive policies according to the EBA. *The Adaptive Marine Policy Toolbox provides a one-stop single location to access all the guidelines and resources necessary to design and implement adaptive marine policies according to the Marine Strategy Framework Directive. *The toolbox presents a high transferability to additional regulations calling for the Ecosystem-Based Approach to management such as the Ecosystem Approach of the Mediterranean Action Plan and the Black Sea´s Strategic Action Plan. *The Resources existing within the toolbox are presented in a user-friendly format. The presence of assessments and models capable to cope with uncertain conditions allows for high flexibility and adaptation in management strategies when future conditions change

A blueprint for integrating scientific approaches and international communities to assess basin-wide ocean ecosystem status

Ocean ecosystems are at the forefront of the climate and biodiversity crises, yet we lack a unified approach to assess their state and inform sustainable policies. This blueprint is designed around research capabilities and cross-sectoral partnerships. We highlight priorities including integrating basin-scale observation, modelling and genomic approaches to understand Atlantic oceanography and ecosystem connectivity; improving ecosystem mapping; identifying potential tipping points in deep and open ocean ecosystems; understanding compound impacts of multiple stressors including warming, acidification and deoxygenation; enhancing spatial and temporal management and protection. We argue that these goals are best achieved through partnerships with policy-makers and community stakeholders, and promoting research groups from the South Atlantic through investment and engagement. Given the high costs of such research (€800k to €1.7M per expedition and €30–40M for a basin-scale programme), international cooperation and funding are integral to supporting science-led policies to conserve ocean ecosystems that transcend jurisdictional borders

Principles Of Heliophysics: a textbook on the universal processes behind planetary habitability

This textbook gives a perspective of heliophysics in a way that emphasizes universal processes from a perspective that draws attention to what provides Earth (and similar (exo-)planets) with a relatively stable setting in which life as we know it can thrive. The book is intended for students in physical sciences in later years of their university training and for beginning graduate students in fields of solar, stellar, (exo-)planetary, and planetary-system sciences.Comment: 419 pages, 119 figures, and 200 "activities" in the form of problems, exercises, explorations, literature readings, and "what if" challenge

An investigation of polar substorms observed at Halley Bay, Antarctica

Ground observations of magnetic and ionospheric substorms are reviewed, and the processes involved are explained. Then magnetic and absorption results from an auroral zone station, Halley Bay, are examined. Positive H bays occur in the evening sector between 16.00 and 22.00 local time while negative H bays occur on the nightside between 22.00 and 06.00 local time. Clockwise and counterclockwise rotating Pi2 pulsations respectively have similar times of occurrence, as do westward and eastward moving radio aurora. Short-period absorption occurs coincident with magnetic bays while longer-period absorption occurs on the dayside (04.00 to 20.00 local time). This information is used to determine the disturbance pattern in local time seen at auroral zone stations. A simple model is presented to illustrate the processes responsible for the effects observed in the 3 different local-time zones. On the nightside there is direct injection of particles from the tail, into the ionosphere, accompanied by short-circuiting of the cross-tail current through the ionosphere to produce the westward electrojet. Protons are injected into the radiation belt on the evening side, and their westward drift constitutes a partial ring current. The plasmasphere bulge modifies the distribution of proton precipitation and influences the location of the ionospheric return current, the eastward electrojet. Trapped electrons drift into the morning and dayside sectors and precipitate steadily into the ionosphere producing periods of slowly-varying absorption, The diurnal and seasonal variations of this absorption at Halley Bay suggests that photodetachment of negative ions in the D region is a significant factor in the production of auroral absorption. It is shown that variations in fxI significantly affect the occurrence of blackout on the ionoscnde, making this an unreliable indicator of absorption. Anomalies in the magnetic bays observed at Halley Bay are shown to be due to the presence of induced currents in the sea flowing parallel to the continental shelf. An analysis of electrical power system disturbances identifies magnetic substorms as the primary cause, and discusses how knowledge about substorms can aid prediction of the power system disturbances.Science, Faculty ofEarth, Ocean and Atmospheric Sciences, Department ofGraduat

Occurrence rate and duration of space weather impacts on high-frequency radio communication used by aviation

High frequency (HF) radio wave propagation is sensitive to space weather-induced ionospheric disturbances that result from enhanced photoionization and energetic particle precipitation. Recognizing the potential risk to HF radio communication systems used by the aviation industry, as well as potential impacts on GNSS navigation and the risk of elevated radiation levels, the International Civil Aviation Organization (ICAO) initiated the development of a space weather advisory service. For HF systems, this service specifically identifies shortwave fadeout, auroral absorption, polar cap absorption, and post-storm maximum useable frequency depression (PSD) as phenomena impacting HF radio communication and specifies moderate and severe event thresholds to describe event severity. This paper examines the occurrence rate and duration of events crossing the moderate and severe thresholds. Shortwave fadeout was evaluated based on thresholds in the solar X-ray flux. Analysis of 40-years of solar X-ray flux data showed that moderate and severe level solar X-ray flares were observed, on average, 123 and 5 times per 11-year solar cycle, respectively. The mean event duration was 68 min for moderate level events and 132 min for severe level events. Auroral absorption events crossed the moderate threshold for 40 events per solar cycle, with a mean event duration of 5.1 h. The severe threshold was crossed for 3 events per solar cycle with a mean event duration of 12 h. Polar cap absorption had the longest mean duration at ~8 h for moderate events and 1.6 days for severe events; on average, 24 moderate and 13 severe events were observed per solar cycle. Moderate and severe thresholds for shortwave fadeout, auroral absorption, and polar cap absorption were used to determine the expected impacts on HF radio communication. Results for polar cap absorption and shortwave fadeout were consistent with each other, but the expected impact for auroral absorption was shown to be 2–3 times higher. Analysis of 22 years of ionosonde data showed moderate, and severe PSD events occurred, on average, 200 and 56 times per 11-year solar cycle, respectively. The mean event duration was 5.5 h for moderate-level events and 8.5 h for severe-level events. During solar cycles 22 and 23, HF radio communication was expected to experience moderate or severe impacts due to the ionospheric disturbances caused by space weather, a maximum of 163 and 78 days per year, respectively, due to the combined effect of absorption and PSD. The distribution of events is highly non-uniform with respect to the solar cycle: 70% of moderate or severe events were observed during solar maximum compared to solar minimum