Empirical modeling of the quiet time nightside magnetosphere

Empirical modeling of plasma pressure and magnetic field for the quiet time nightside magnetosphere is investigated. Two models are constructed for this study. One model, referred to here as T89R, is basically the magnetic field model of Tsyganenko (1989) but is modified by the addition of an inner eastward ring current at a radial distance of ∼3 RE as suggested by observation. The other is a combination of the T89R model and the long version of the magnetic field model of Tsyganenko (1987) such that the former dominates the magnetic field in the inner magnetosphere, whereas the latter prevails in the distant tail. The distribution of plasma pressure, which is required to balance the magnetic force for each of these two field models, is computed along the tail axis in the midnight meridian. The occurrence of pressure anisotropy in the inner magnetospheric region is also taken into account by determining an empirical fit to the observed plasma pressure anisotropy. This effort is the first attempt to obtain the plasma pressure distribution in force equilibrium with magnetic stresses from an empirical field model with the inclusion of pressure anisotropy. The inclusion of pressure anisotropy alters the plasma pressure by as much as a factor of ∼3 in the inner magnetosphere. The deduced plasma pressure profile along the tail axis is found to be in good agreement with the observed quiet time plasma pressure for geocentric distances between ∼2 and ∼35 RE

Cross-border voting chains and the case for improving the quality of shareholder engagement

The purpose of this paper is to explore current difficulties with shareholder engagement in the 21st century in light of complex cross-border voting chains. To improve the quality of shareholder engagement, the study recommends that cooperation between countries needs to be strengthened by improving information flow and transparency. Better disclosure is a fundamental step to improving information flow and cross-border voting. There are a number of legal and practical hurdles in relation to cross-border voting. As it is unlikely that the length of the voting chains will be reduced owing to the inherent structure of the ownership model, a combination of legislative modifications and improved voting facilities with reduced costs are necessary. The initial strong compliance to the concept of 'stewardship' in the UK is difficult to sustain owing to the inherent structure of the complex, equity chain model

Single or twin? the UK financial regulatory landscape after the financial crisis of 2007-2009

The author aims to analyse the weaknesses of the Financial Services Authority (FSA) and the Bank of England during the financial crisis of 2007-2009. She aims to discover whether the coalition government's proposal to a twin-peaks model is a better alternative to the single regulator. The focus of this article is on micro-prudential regulatory failures in the United Kingdom. A comparison will be made with the twin-peaks regulatory model in Australia where there were no bank failures. The article is based on an analysis of recent papers and reports. Descriptive statistics are used to provide an insight into the financial ratios of the top banks in the United Kingdom and Australia. A comparative legal analysis between the United Kingdom and Australia is used to reflect the common law system used by both. The structure of the UK regulator was only a minor contributory factor to the financial crisis. The main regulatory and supervisory failures are due to organisational and management problems. There needs to be better information flow, coordination, cooperation, engagement with banks and stricter internal controls. The new UK regulator also needs to be prepared for the changes on the European dimension, following the de Larosiere report. This article will have policy implications for practitioners and policymakers on national, European and international dimensions. Changes in the European regulatory structure will see an emphasis on vertical regulatory cooperation. By first reviewing the weaknesses of the FSA in the light of Northern Rockand HBOS and then comparing the FSA with the Australian regulatory model, this article provides a new insight into financial regulation

Multiple principal-agent problems in securitisation

Every crisis presents opportunities. The financial crisis of 2007-2009 provides a valuable opportunity to study the corporate governance and regulatory aspects of the banking sector, a hinge point in the development of corporate governance in banks. There is a tremendous amount of academic literature on corporate governance of corporations generally, but not of banks. Banks share many characteristics in common with other corporations but differ in respect of the social costs involved. Banks play a fundamental role in a country’s economy and problems within the banking sector will have an impact on the wider community. The author argues that corporate governance played an important contributing factor to the financial crisis. In particular, the financial crisis has highlighted multiple principal-agent problems within the ‘originate-to-distribute’ model of banking. Multiple principal-agent problems are the direct consequence of financial innovation and regulatory dialectic. The ‘originate-to-distribute’ model relies on securitisation. Academic literature has revealed that securitisation is opaque and complex (Buiter, 2007; Berndt and Gupta, 2008; Fender and Mitchell 2009a). Little research however, has been conducted into why securitisation is opaque and complex from a principal-agent angle. This paper thus provides a new perspective to the literature on principal-agent theory and banking corporate governance

Search and Seizure of Journalistic Material: the Sing Tao Daily Case

AnalysisThe constitutional guarantee of a free press has been almost taken for granted by all in Hong Kong. In safeguarding press freedom, the protection of journalistic sources is of particular importance to ensure that the press can properly perform its role as society's watchdog. However, in So Wing Keung v Sing Tao Limited and Hsu Hiu Yee, the Hong Kong Court of Appeal has taken quite a different view on the matter. This could have a long-term impact on the development of press freedom and the use of journalistic material in Hong Kong. This article seeks to look at the subtle, but significant change in the landscape on press freedom resulting from the Court's decision.published_or_final_versio

Simultaneous structural and control optimization via linear quadratic regulator eigenstructure assignment

A method for simultaneous structural and control design of large flexible space structures (LFSS) to reduce vibration generated by disturbances is presented. Desired natural frequencies and damping ratios for the closed loop system are achieved by using a combination of linear quadratic regulator (LQR) synthesis and numerical optimization techniques. The state and control weighing matrices (Q and R) are expressed in terms of structural parameters such as mass and stiffness. The design parameters are selected by numerical optimization so as to minimize the weight of the structure and to achieve the desired closed-loop eigenvalues. An illustrative example of the design of a two bar truss is presented

A current disruption mechanism in the neutral sheet for triggering substorm expansions

Two main areas were addressed in support of an effort to understand mechanism responsible for the broadband electrostatic noise (BEN) observed in the magnetotail. The first area concerns the generation of BEN in the boundary layer region of the magnetotail whereas the second area concerns the occassional presence of BEN in the neutral sheet region. For the generation of BEN in the boundary layer region, a hybrid simulation code was developed to perform reliable longtime, quiet, highly resolved simulations of field aligned electron and ion beam flow. The result of the simulation shows that broadband emissions cannot be generated by beam-plasma instability if realistic values of the ion beam parameters are used. The waves generated from beam-plasma instability are highly discrete and are of high frequencies. For the plasma sheet boundary layer condition, the wave frequencies are in the kHz range, which is incompatible with the observation that the peak power in BEN occur in the 10's of Hz range. It was found that the BEN characteristics are more consistent with lower hybrid drift instability. For the occasional presence of BEN in the neutral sheet region, a linear analysis of the kinetic cross-field streaming instability appropriate to the neutral sheet condition just prior to onset of substorm expansion was performed. By solving numerically the dispersion relation, it was found that the instability has a growth time comparable to the onset time scale of substorm onset. The excited waves have a mixed polarization in the lower hybrid frequency range. The imposed drift driving the instability corresponds to unmagnetized ions undergoing current sheet acceleration in the presence of a cross-tail electric field. The required electric field strength is in the 10 mV/m range which is well within the observed electric field values detected in the neutral sheet during substorms. This finding can potentially account for the disruption of cross-tail current and its diversion to the ionosphere to form the substorm current wedge. Furthermore, a number of features associated with substorm expansion onset can be understood based on this substorm onset scenario

AMPTE/CCE‐SCATHA simultaneous observations of substorm‐associated magnetic fluctuations

This study examines substorm-associated magnetic field fluctuations observed by the AMPTE/CCE and SCATHA satellites in the near-Earth tail. Three tail reconfiguration events are selected, one event on August 28, 1986, and two consecutive events on August 30, 1986. The fractal analysis was applied to magnetic field measurements of each satellite. The result indicates that (1) the amplitude of the fluctuation of the north-south magnetic component is larger, though not overwhelmingly, than the amplitudes of the other two components and (2) the magnetic fluctuations do have a characteristic timescale, which is several times the proton gyroperiod. In the examined events the satellite separation was less than 10 times the proton gyroradius. Nevertheless, the comparison between the AMPTE/CCE and SCATHA observations indicates that (3) there was a noticeable time delay between the onsets of the magnetic fluctuations at the two satellite positions, which is too long to ascribe to the propagation of a fast magnetosonic wave, and (4) the coherence of the magnetic fluctuations was low in the August 28, 1986, event and the fluctuations had different characteristic timescales in the first event of August 30, 1986, whereas some similarities can be found for the second event of August 30, 1986. Result 1 indicates that perturbation electric currents associated with the magnetic fluctuations tend to flow parallel to the tail current sheet and are presumably related to the reduction of the tail current intensity. Results 2 and 3 suggest that the excitation of the magnetic fluctuations and therefore the trigger of the tail current disruption is a kinetic process in which ions play an important role. It is inferred from results 3 and 4 that the characteristic spatial scale of the associated instability is of the order of the proton gyroradius or even shorter, and therefore the tail current disruption is described as a system of chaotic filamentary electric currents. However, result 4 suggests that the nature of the tail current disruption can vary from event to event

Distinct Scaling Regimes of Energy Release Dynamics in the Nighttime Magnetosphere

Based on a spatiotemporal analysis of POLAR UVI images, we show that the auroral emission events that initiate equatorward of the isotropic boundary (IB) obtained from a time-dependent empirical model, have systematically steeper power-law slopes of energy, power, area and lifetime probability distributions compared to the events that initiate poleward of the IB. The low-latitude group of events contains a distinct subpopulation of substorm-scale disturbances violating the power-law behavior, while the high latitude group is described by nearly perfect power-law statistics over the entire range of scales studied. The results obtained indicate that the inner and outer portions of the plasma sheet are characterized by substantially different scaling regimes of bursty energy dissipation suggestive of different physics in these regions.Comment: 11 pages, 2 figures, 2 table

Evaluation on the analogy between the dynamic magnetosphere and a forced and/or self-organized critical system

International audienceThe dissipation power and size of auroral blobs are investigated in detail to examine the possible analogy between the dynamic magnetosphere and a forced and/or self-organized critical system. The distributions of these auroral parameters are sorted in terms of different levels of activity, namely substorms, pseudo-breakups, and quiet conditions. A power law (scale-free) component is seen in all these distributions. In addition, a peak distribution is found for substorm intervals and a hump for pseudo-breakup intervals. The peak distribution is present prominently during magnetic storms, i.e. when the magnetosphere is strongly driven by the solar wind. It is interpreted that the scale-free component is associated with the activity of the diffuse aurora, corresponding to disturbances at all permissible scales within the plasma sheet. Ionospheric feedback appears to be essential for the presence of two components in the distribution for auroral dissipation power. These results are consistent with the concept that the magnetosphere is in a forced and/or self-organized critical state, although they do not constitute conclusive evidence for the analogy