Ion-scale kinetic Alfvén turbulence: MMS measurements of the Alfvén ratio in the magnetosheath

Turbulence in the Earth's magnetosheath at ion kinetic scales is investigated with the magnetospheric multiscale spacecraft. Several possibilities in the wave paradigm have been invoked to explain plasma turbulence at ion kinetic scales such as kinetic Alfvén, slow, or magnetosonic waves. To differentiate between these different plasma waves is a challenging task, especially since some waves, in particular, kinetic slow waves and kinetic Alfvén waves, share some properties making the possibility to distinguishing between them very difficult. Using the excellent time resolution data set provided from both the fluxgate magnetometer and the Fast Plasma Instrument, the ratio of trace velocity fluctuations to the magnetic fluctuations (in Alfvén units), which is termed the Alfvén ratio, can be calculated down to ion kinetic scales. Comparison of the measured Alfvén ratio is performed with respect to the expectation from two‐fluid magnetohydrodynamic theory for the kinetic slow wave and kinetic Alfvén wave. Moreover, the plasma data also allow normalized fluctuation amplitudes of density and magnetic field to be compared differentiating between magnetosonic‐like and kinetic Alfvén‐like turbulence. Using these two different ratios, we can rule out that the fluctuations at ion scales are dominated by magnetosonic‐like fluctuations or kinetic slow‐like fluctuations and show that they are consistent with kinetic Alfvén‐like fluctuations. This suggests that in the wave paradigm, heating in the direction of the parallel magnetic field is predominantly by the Landau damping of the kinetic Alfvén wave

Genealogies and generations: the politics and praxis of third wave feminism

This article interrogates the ways in which post-feminism and third wave feminism are used interchangeably, both within the academy and in the media. As it identifies the ways in which third wave feminism seeks to define itself as a non-academic discourse, it points up the tensions implicit in the contemporary feminist project. It outlines such popular components of third wave feminism as girl culture, the grrrl movement and BUST magazine, before addressing the arguments concerning agency in such icons as Courtney Love, Madonna and the Spice Girls. Positing that the metonymic gap between the personal and the political allows post-feminism to be a viable alternative to feminism, it argues that the wave paradigm paralyses feminism, pitting generations against one another. PD

Finding Common Feminist Ground: The Role of the Next Generation in Shaping Feminist Legal Theory

This article explores the ways in which current feminist frameworks are dividing the women’s movement along generational lines, thereby inhibiting progress in the struggle for gender equality. Third-wave feminists, or the generation of feminists that came of age in the 1990s and continues today, have been criticized for focusing on personal stories of oppression and failing to influence feminist legal theory. Yet this critique presupposes that third-wave feminism is fundamentally different from the feminism of past generations. In contrast, this article argues that third-wave feminism is rooted in the feminist legal theory developed in the prior generation. This article demonstrates that the third-wave appears to be failing to influence feminist legal theory not because it is theoretically different, but because third-wave feminists approach activism in such a different way. For example, third-wavers envision “women’s issues” broadly, and rely on new tactics such as online organizing. Using the case study of Spark, a nonprofit organization employing third-wave activism to support global grassroots women’s organizations, this article provides a model of this new brand of feminism in practice. This article proposes the adoption of social justice feminism, which advocates casting a broader feminist net to capture those who have been traditionally neglected by the women’s movement, such as low-income women and women of color. Social justice feminism is a way to broaden the focus from a rights-based approach to an examination of the dynamics of power and privilege that continue to shape women’s lives even when legal rights to equality have been won. Adopting social justice feminism can be a way to bridge second- and third-wave feminism and create a more robust and unified feminist movement, thereby mending the divisions that currently prevent unification in the women’s movement

A Wave-centric View of Special Relativity

An approach to special relativity is outlined which emphasizes the wave and field mechanisms which physically produce the relativistic effects, with the goal of making them seem more natural to students by connecting more explicitly with prior studies of waves and oscillators

2-Testability and Relabelings Produce Everything

AbstractWe show that grammar systems with communication by command and with extremely simple rewriting rules (in fact, only relabelings are needed) are able to generate all recursively enumerable languages. The result settles several open problems in the area of grammar systems. We also present the result in a general framework, without referring to grammar systems, obtaining a characterization of recursively enumerable languages from a new point of view

Observation of an MHD Alfvén vortex in the slow solar wind

In the solar wind, magnetic field power spectra usually show several power-laws. In this paper, magnetic field data from the Cluster mission during an undisturbed interval of slow solar wind is analyzed at 0.28Hz, near the spectral break point between the ion inertial and dissipation/dispersion ranges. Assuming Taylor's frozen-in condition, it corresponds to a proton kinetic scale of $kv_A/\Omega_p \sim 0.38$, where $v_A$ and $\Omega_p$ are the Alfv\'en speed and proton angular gyrofrequency, respectively. Data show that the Cluster spacecraft passed through a series of wavepackets. A strong isolated wavepacket is found to be in accordance with the four Cluster satellites crossing an Alfv\'en vortex, a nonlinear solution to the incompressible MHD equations. A strong agreement is seen between the data from four satellites and a model vortex with a radius of the order of $40$ times the local proton gyro-radii. The polarization at different spacecraft is compared and is found to agree with the vortex model, whereas it cannot be explained solely by the linear plane wave approach.Comment: Submitte

Mosaic Warfare: from philosophy to model to solutions

The paper relates to advanced management of large distributed dynamic systems in unpredictable and crisis situations. It briefs the newest DARPA Mosaic Warfare concept oriented on rapidly composable networks of low-cost sensors, multi-domain command and control nodes, and cooperative manned and unmanned systems, with runtime integration of scattered resources which should operate together as one holistic system. It may have the highest value for solving complex national and international defense and security problems for which scattered throughout the world mosaic resources should be quickly integrated to collectively fight disaster and crisis situations, with separate nations unable of doing this individually. The paper shows how distributed mosaic systems can be modeled under the developed Spatial Grasp Technology (SGT) using active distributed knowledge networks, with solving such exemplary problems on them as runtime collection of scattered resources into integral forces operating under unified control, and grouping of certain distributed resources for the surrounding and collective elimination of unwanted phenomena.Стаття присвячена розширеному управлінню великими розподіленими динамічними системами в непередбачуваних і кризових ситуаціях. Викладено новітню концепцію Агентства оборонних проектів (DARPA) Мозаїчні війни, орієнтовану на швидко компоновану мережу сенсорів, багатодоменних вузлів управління, а також спільні пілотовані і безпілотні системи з інтеграцією розкиданих ресурсів, які повинні працювати разом як єдина система. Це може мати особливе значення для вирішення складних національних і міжнародних проблем оборони і безпеки, де розкидані по всьому світу мозаїчні ресурси повинні швидко об’єднуватися для колективної боротьби з лихами і кризами, оскільки окремі країни не в змозі здійснювати це самостійно. Показано, як розподілені мозаїчні системи можна моделювати за допомогою розробленої Технології просторового захоплення (ТПЗ), яка використовує активні розподілені мережі знань, вирішуючи такі проблеми, як збір і інтеграція в реальному часі поширених ресурсів під єдиним управлінням і групування таких ресурсів для колективної ліквідації небажаних явищ.Статья посвящена расширенному управлению большими распределенными динамическими системами в непредсказуемых и кризисных ситуациях. Изложена новейшая концепция Агентства оборонных проектов (DARPA) Мозаичные войны, ориентированная на быстро компонуемые сети сенсоров, многодоменных узлов управления, а также совместные пилотируемые и беспилотные системы с интеграцией разбросанных ресурсов, которые должны работать вместе как единая система. Это может иметь особое значение для решения сложных национальных и международных проблем обороны и безопасности, где разбросанные по всему миру мозаичные ресурсы должны быстро объединяться для коллективной борьбы с бедствиями и кризисами, поскольку отдельные страны не в состоянии осуществлять это самостоятельно. Показано, как распределенные мозаичные системы можно моделировать с помощью разработанной Технологии пространственного захвата (ТПЗ), использующей активные распределенные сети знаний, решая такие проблемы, как сбор и интеграция в реальном времени распространенных ресурсов под единым управлением и группирование таких ресурсов для коллективной ликвидации нежелательных явлений