Evolution of magnetic flux in an isolated reconnection process

A realistic notion of magnetic reconnection is essential to understand the dynamics of magnetic fields in plasmas. Therefore a three-dimensional reconnection process is modeled in a region of nonvanishing magnetic field and is analyzed with respect to the way in which the connection of magnetic flux is changed. The process is localized in space in the sense that the diffusion region is limited to a region of finite radius in an otherwise ideal plasma. A kinematic, stationary model is presented, which allows for analytical solutions. Aside from the well-known flipping of magnetic flux in the reconnection process, the localization requires additional features which were not present in previous two- and 2.5-dimensional models. In particular, rotational plasma flows above and below the diffusion region are found, which substantially modify the process. (C) 2003 American Institute of Physics.</p

Free Magnetic Energy in Solar Active Regions above the Minimum-Energy Relaxed State

To understand the physics of solar flares, including the local reorganization of the magnetic field and the acceleration of energetic particles, we have first to estimate the free magnetic energy available for such phenomena, which can be converted into kinetic and thermal energy. The free magnetic energy is the excess energy of a magnetic configuration compared to the minimum-energy state, which is a linear force-free field if the magnetic helicity of the configuration is conserved. We investigate the values of the free magnetic energy estimated from either the excess energy in extrapolated fields or the magnetic virial theorem. For four different active regions, we have reconstructed the nonlinear force-free field and the linear force-free field corresponding to the minimum-energy state. The free magnetic energies are then computed. From the energy budget and the observed magnetic activity in the active region, we conclude that the free energy above the minimum-energy state gives a better estimate and more insights into the flare process than the free energy above the potential field state

Our dynamic sun : 2017 Hannes Alfvén Medal lecture at the EGU

This lecture summarises how our understanding of many aspects of the Sun has been revolutionised over the past few years by new observations and models. Much of the dynamic behaviour of the Sun is driven by the magnetic field since, in the outer atmosphere, it represents the largest source of energy by far. The interior of the Sun possesses a strong shear layer at the base of the convection zone, where sunspot magnetic fields are generated. A small-scale dynamo may also be operating near the surface of the Sun, generating magnetic fields that thread the lowest layer of the solar atmosphere, the turbulent photosphere. Above the photosphere lies the highly dynamic fine-scale chromosphere, and beyond that is the rare corona at high temperatures exceeding 1 million degrees K. Possible magnetic mechanisms for heating the corona and driving the solar wind (two intriguing and unsolved puzzles) are described. Other puzzles include the structure of giant flux ropes, known as prominences, which have complex fine structure. Occasionally, they erupt and produce huge ejections of mass and magnetic fields (coronal mass ejections), which can disrupt the space environment of the Earth. When such eruptions originate in active regions around sunspots, they are also associated with solar flares, in which magnetic energy is converted to kinetic energy, heat and fast-particle energy. A new theory will be presented for the origin of the twist that is observed in erupting prominences and for the nature of reconnection in the rise phase of an eruptive flare or coronal mass ejection.Publisher PDFPeer reviewe

Are tornado-like magnetic structures able to support solar prominence plasma?

Recent high-resolution and high-cadence observations have surprisingly suggested that prominence barbs exhibit apparent rotating motions suggestive of a tornado-like structure. Additional evidence has been provided by Doppler measurements. The observations reveal opposite velocities for both hot and cool plasma on the two sides of a prominence barb. This motion is persistent for several hours and has been interpreted in terms of rotational motion of prominence feet. Several authors suggest that such barb motions are rotating helical structures around a vertical axis similar to tornadoes on Earth. One of the difficulties of such a proposal is how to support cool prominence plasma in almost-vertical structures against gravity. In this work we model analytically a tornado-like structure and try to determine possible mechanisms to support the prominence plasma. We have found that the Lorentz force can indeed support the barb plasma provided the magnetic structure is sufficiently twisted and/or significant poloidal flows are present.Comment: Accepted for publication in ApJ

Copyright and the Harvard Open Access Mandate

Open access proponents argue that scholars are far more likely to make their articles freely available online if they are required to do so by their university or funding institution. Therefore, if the open access movement is to achieve anything close to its goal of seeing all scholarly articles freely available online, mandates will likely play a significant role. In 2008, the Harvard University Faculty of Arts and Sciences adopted a policy that purports not only to require scholars to deposit their works in open access repositories, but also to grant the university nonexclusive copyright licenses to archive and publicly distribute all faculty-produced scholarly articles. A number of other American universities have since adopted similar policies. The principal aim of this Article is to analyze the legal effect of these Harvard-style open access “permission” mandates. By invoking copyright law terminology in permission mandates, schools might intend that they have the legal effect of transferring nonexclusive rights to the school, thereby clarifying and fortifying the school’s rights to reproduce and publicly disseminate faculty works. However, the legal effect of these mandates is uncertain for several reasons. First, it is unsettled whether scholars or their university employers are the authors and initial owners of scholarly articles under U.S. copyright law’s work-made-for-hire rules, which vest authorship and copyright ownership in the employer for works created by employees within the scope of employment. Second, the mandates are broad university policies that purport to grant the university nonexclusive copyright licenses in every scholarly article unless a faculty member affirmatively opts out on a per-article basis. Are the policies specific enough to provide the essential terms of the grant? Furthermore, can the mere adoption of a school policy, without some additional affirmative act by the author, effectuate such a grant without unduly encroaching upon the author’s autonomy interests? Lastly, even if the policies effectuate nonexclusive license grants, will the licenses survive after the author transfers copyright ownership to a journal publisher as per common practice? Section 205(e) of the Copyright Act provides that a prior nonexclusive license evidenced in a writing signed by the right holder prevails over a subsequent conflicting transfer of copyright ownership, so the answer appears to turn on whether permission mandates satisfy the requirements of § 205(e). This Article argues that permission mandates can create legally enforceable, durable nonexclusive licenses. First, it argues that although there are important justifications, including academic freedom concerns, for recognizing the controversial “teacher exception” to the work for hire rules for scholarly articles, such an exception may be unnecessary because a strong argument also exists that much scholarship is produced outside the scope of employment for work for hire purposes. Second, it argues that permission mandates provide sufficient evidence of the grantor’s intent and the rights granted to create effective nonexclusive licenses. Third, permission mandates satisfy the requirements of § 205(e) and establish the license’s priority over the subsequent transfer of copyright ownership largely because they fulfill the underlying purposes of § 205(e) by providing sufficient evidence and notice of the license to potential copyright transferees (typically academic publishers). In reaching these conclusions, this Article emphasizes that Courts should consider the uniformity costs (social costs resulting from applying uniform rules and granting uniform entitlements across diverse conditions) that arise from applying to scholarly articles copyright rules developed to address proprietary models of information production. Applying the relevant copyright rules in a manner sensitive to the nonmarket nature of scholarly production is the most effective way to reduce these social costs, and reinforces the conclusion that mandate licenses are enforceable. Lastly, the Article considers whether the opt-out nature of permission mandates offends notions of authorial autonomy in copyright. It compares permission mandates with another high profile opt-out licensing regime: the proposed Google Books settlement agreement, which the court rejected partly because of authorial autonomy concerns. However, authorial autonomy is far less of a concern for scholarly articles than for the books at issue in the Google Books case, due to the nonmarket nature of scholarly article production coupled with academic community norms. Accordingly, it does not substantially interfere with authors’ autonomy interests to find that the opt-out structure of permission mandates creates valid nonexclusive licenses in universities

WHY EMERGING BUSINESS MODELS AND NOT COPYRIGHT LAW ARE THE KEY TO MONETISING CONTENT ONLINE

The multimedia Internet is here to stay. Rich media – including videos, music, podcasts, and flash animation – is already a key feature of the Internet experience, and will only grow in diversity and importance. As Internet users increasingly crave – and technology increasingly enables – multimedia content delivered on demand over broadband connections, the number of songs, videos, and other media online will increase exponentially to feed the demand. As online media consumption increases, so will expectations for its capacity to generate revenue for content owners and creators. Analysts boldly predict a bright future for the entertainment industries, especially in Asia, with broadband Internet cited as a key growth driver.1 The main point of contention in the 2007 Hollywood writers’ strike was compensation for media streamed or downloaded over the Internet.2 Yet, to date, the vast majority of music and video acquired or consumed online is free and uncompensated. Despite the rising expectations for monetising content on the Web, no clear sustainable, scalable model for monetising content has emerged that compare to the level of revenues copyright owners have enjoyed in the “physical” (as opposed to online) market. This chapter considers the primary strategies that the international music and film industries have employed to date, namely lawsuits and technological protections, and why these strategies have failed to produce a viable path to long-term revenue generation. I argue that content owners should not hold out hope that using law (in the form of copyright infringement lawsuits against individuals) or technology (in the form of digital rights management encryption software) will unlock the Web’s potential for monetising their content. Instead, successful monetisation of content online will come through business models that can harness and monetise the current behaviour of Internet users. There are three emerging such models, each of which has significant potential and challenges: retail online content subscriptions, ad-supported content, and voluntary blanket licensing. The following discussion is mostly broad, outlining circumstances facing copyright owners globally, and some emerging potential solutions. Nevertheless, I make a point throughout to highlight the situation in China in particular. Why? China is a challenging but dynamic Internet and digital media market, and is in fact the first market in the world where all three of the emerging models discussed in this chapter are actually being deployed in an effort to jumpstart the digital creative economy. China is an important market for the rest of the world to watch regarding emerging monetisation models. Lastly this chapter is not meant to be a comprehensive overview of the many innovative ways that musicians, filmmakers, and other creators and companies are using the Web to make money from their content. Undoubtedly the Web has empowered many small and medium-sized content owners to distribute their works and connect with their fans in exciting and unprecedented ways. The purpose of this chapter is to explore the Web’s potential for generating wide-scale, significant, and sustainable content revenues for the entertainment industry, including minor and major content owners

The influence of a mean magnetic field on three-dimensional magnetohydrodynamic turbulence

Building on results from two-dimensional magnetohydrodynamic (MHD) turbulence (Shebalin, Matthaeus & Montgomery 1983), the development of anisotropic states from initially isotropic ones is investigated numerically for fully three-dimensional incompressible MHD turbulence. It is found that when an external d.c. magnetic field (B₀) is imposed on viscous and resistive MHD systems, excitations are preferentially transferred to modes with wavevectors perpendicular to B₀). The anisotropy increases with increasing mechanical and magnetic Reynolds numbers, and also with increasing wavenumber. The tendency of B₀ to inhibit development of turbulence is also examined

Human uniqueness : debates in science and theology

In both science and theology, there has been a revolution in our understanding of the nature of human uniqueness. As a background to this Symposium on the subject, a summary is here given of the history of Homo sapiens that is being revealed by fossil, archaeological, and genetic evidence. This is followed by a description of some of the distinctive characteristics of humans that have been proposed in the past, such as language, tool use, self-consciousness, art, and culture. Ideas from theology and philosophy that are salient for the dialogue with science are then mentioned, together with a summary of the scientific and theological insights on uniqueness from contributors to this Symposium in Zygon: Journal of Religion and Science.Publisher PDFPeer reviewe

The Chinese Copyright Dream

Chinese President Xi Jinping's vision of the "Chinese Dream" has captured the popular imagination. As a slogan, the Chinese Dream is intentionally broad. Intended to inspire rather than prescribe, it captures diverse aspirations including dreams of material prosperity, environmental sustainability, national rejuvenation, and global leadership. The Dream's ramifications continue to ricochet through state policy echelons and lend themselves to competing interpretations. In that spirit, we advance a modest suggestion: that the Chinese Dream should be, at least in part, a dream about copyright law. A more effective copyright system would bolster China's creative industries, generating a diverse supply of high-quality expressive works whose realization would advance many plausible goals of the Chinese Dream. Yet, copyright has a more fundamental role to play. Xi himself has emphasized that "[t]he Chinese dream, after all, is the dream of the people." Now that dreaming broadly and boldly is state policy, China's people need the space to dream. Copyright provides a mechanism to harness the collective imagination of China's authors and artists. Decentralized investments in diverse, high-quality media will stimulate the robust popular discourse that China needs to articulate and actualize its Dream. In short, copyright can help China dream its own dream

Redeeming Globalization through Unfair Competition Law

Globalization's seamless integration of manufacturing across extended supply chains has brought unprecedented efficiency to global economic production. The results often seem magical. Components sourced from dispersed suppliers in multiple countries are assembled into finished goods that arrive miraculously on our doorsteps at the click of a mouse.I Globalization's magic has a less savory side, however. Outsourcing production to overseas suppliers allows manufacturers to save money while rendering the human and environmental costs invisible. Not only do such externalities magically disappear with distance, but a sophisticated corporate shell game ensures that legal accountability for such harms vanishes as well.