From Solar and Stellar Flares to Coronal Heating: Theory and Observations of How Magnetic Reconnection Regulates Coronal Conditions

There is currently no explanation of why the corona has the temperature and density it has. We present a model which explains how the dynamics of magnetic reconnection regulates the conditions in the corona. A bifurcation in magnetic reconnection at a critical state enforces an upper bound on the coronal temperature for a given density. We present observational evidence from 107 flares in 37 sun-like stars that stellar coronae are near this critical state. The model may be important to self-organized criticality models of the solar corona.Comment: 13 pages, 2 figures, accepted to Ap. J. Lett., February 200

Alone with the other : paradoxes of shame and recognition in psychoanalytic theory, case material and Home alone

Shame and recognition co-occur in the human psyche. Phenomenologically, shame is relational: experienced in the world with the Other. Psychoanalytically, the shame affect is treated as one of the ego\u27s defenses, for example, as a protection from exposure. Shame seems to either promote or prevent the subject\u27s capacity to recognize otherness and difference. In this paper, I attempt to re-read these respective theories on shame and recognition, eventually placing shame in, among other places, Lacan\u27s (1988) mirror stage and relational perspectives of human development. I turn to two cases, one clinical, one from popular culture, to elaborate on the paradoxical experience of shame and recognition

Are Coronae of Magnetically Active Stars Heated by Flares? III. Analytical Distribution of Superimposed Flares

(abridged) We study the hypothesis that observed X-ray/extreme ultraviolet emission from coronae of magnetically active stars is entirely (or to a large part) due to the superposition of flares, using an analytic approach to determine the amplitude distribution of flares in light curves. The flare-heating hypothesis is motivated by time series that show continuous variability suggesting the presence of a large number of superimposed flares with similar rise and decay time scales. We rigorously relate the amplitude distribution of stellar flares to the observed histograms of binned counts and photon waiting times, under the assumption that the flares occur at random and have similar shapes. Applying these results to EUVE/DS observations of the flaring star AD Leo, we find that the flare amplitude distribution can be represented by a truncated power law with a power law index of 2.3 +/- 0.1. Our analytical results agree with existing Monte Carlo results of Kashyap et al. (2002) and Guedel et al. (2003). The method is applicable to a wide range of further stochastically bursting astrophysical sources such as cataclysmic variables, Gamma Ray Burst substructures, X-ray binaries, and spatially resolved observations of solar flares.Comment: accepted for publication in Ap

An X-ray and Optical Investigation of the Starburst-driven Superwind in the Galaxy Merger Arp 299

We present a detailed investigation of the X-ray and optical properties of the starburst-merger system Arp299 (NGC 3690, Mrk 171), with an emphasis on its spectacular gaseous nebula. We analyse \rosat and \asca X-ray data and optical spectra and narrow-band images. We suggest that the on-going galaxy collision has tidally-redistributed the ISM of the merging galaxies. The optical emission-line nebula results as this gas is photoionized by radiation that escapes from the starburst, and is shock-heated, accelerated, and pressurized by a `superwind' driven by the collective effect of the starburst supernovae and stellar winds. The X-ray nebula in Arp 299 is is plausibly a mass-loaded flow of adiabatically-cooling gas that carries out a substantial fraction of the energy and metals injected by the starburst at close to the escape velocity from Arp 299. The mass outflow rate likely exceeds the star-formation rate in this system. We conclude that powerful starbursts are able to heat (and possibly eject) a significant fraction of the ISM in merging galaxies.Comment: 54 pages, 17 postscript figures, AAS late

Preliminary Assessment of and Lessons Learned in PITCH: an Integrated Approach to Developing Technical Communication Skills in Engineers

The Project to Integrate Technical Communication Habits (PITCH) has been implemented across seven engineering and computer science undergraduate programs starting in fall 2012. The overarching goal of PITCH is to develop written, oral and visual communication skills and professional habits in engineering students. PITCH activities begin in the very first semester and are reinforced and extended through all four years of each program. After three years of progressively more extensive development and deployment, a preliminary assessment of student writing over their first three years in programs was performed. In May 2016 the first cohort of students will have completed the entire sequence of PITCH courses, including senior design. PITCH was designed to include technical memoranda, poster presentations, oral presentations, laboratory reports, proposals, and senior design reports. In addition to text elements, the use of tables and graphics also were addressed. These technical communication products are integrated into specific foundational courses common to several programs, as well as higher-level courses unique to each program. Engineering faculty teaching these courses were progressively trained through workshops conducted over three summers, so in the early years not all instructors teaching these courses had been fully trained. A random sample of students from four programs was selected for the assessment. These students had taken freshman through junior courses with trained instructors, and the assessment was performed based on the PITCH writing assignments they submitted in four courses. Four faculty members and an external consultant involved in the development and deployment of PITCH performed the assessment. Each writing assignment was evaluated through use of a common rubric to see how well students achieved the overall PITCH learning outcomes. The evaluations were done in a series of collective settings with all five evaluators present and each writing assignment was assessed. Student progress through the four courses spanning the first three years of PITCH is quantified and the results are discussed. Also discussed are pedagogical and administrative lessons learned during development and implementation of PITCH to date. PITCH is supported by a grant from the Davis Educational Foundation

An Integrated Approach to Developing Technical Communication Skills in Engineering Students

The Project to Integrate Technical Communication Habits (PITCH) is being implemented across seven engineering and computer science undergraduate programs. The overarching goal of PITCH is to develop written, oral and visual communication skills and professional habits in engineering students. PITCH activities begin in the very first semester and are reinforced and extended through all four years of each program. Senior design becomes the culminating experience in which students demonstrate the skills and habits acquired through PITCH courses. Student outcomes for the project were established based on an extensive survey of employers, alumni and faculty. Communication instruments include technical memoranda, poster presentations, oral presentations, laboratory reports, proposals, and senior design reports. In addition to text elements, the use of tables and graphics also are addressed. Advice tables, annotated sample assignments and grading rubrics are being developed for each instrument to assist students in their work and facilitate consistency in instruction and assessment across multiple instructors teaching different course sections. Within each of the seven programs, specific courses within all four years are targeted for implementation and assessment of technical communication skills. Roadmaps showing the target courses, and the instruments deployed and outcomes to be learned in each course are made available to students in each program. The different communication products are distributed across courses as appropriate, and the skills are developed at deeper and deeper levels as students progress through the years. Two critical and distinctive features of the project are that technical communication skills are fully integrated into the content of regular engineering courses and are taught by regular engineering faculty. These features will make PITCH sustainable over the longer term. In the first year of the project, 16 engineering and computer science faculty were trained by an external consultant through summer workshops to deliver and assess the technical communication instruments in their courses. All PITCH assignments submitted by students are being archived and will be used in a longitudinal assessment of the effectiveness of the project as the first cohort of students who started in fall 2012 near graduation. PITCH is funded by the Davis Educational Foundation and is designed to be self-sustaining after the three-year period of grant support. This paper describes the approach used, lists the PITCH student outcomes, and provides examples of the PITCH roadmaps, as well as the resources provided to students and faculty

Critical dynamics in trapped particle systems

We discuss the effects of a trapping space-dependent potential on the critical dynamics of lattice gas models. Scaling arguments provide a dynamic trap-size scaling framework to describe how critical dynamics develops in the large trap-size limit. We present numerical results for the relaxational dynamics of a two-dimensional lattice gas (Ising) model in the presence of a harmonic trap, which support the dynamic trap-size scaling scenario.Comment: 7 page

Adiabatic dynamics of an inhomogeneous quantum phase transition: the case of z > 1 dynamical exponent

We consider an inhomogeneous quantum phase transition across a multicritical point of the XY quantum spin chain. This is an example of a Lifshitz transition with a dynamical exponent z = 2. Just like in the case z = 1 considered in New J. Phys. 12, 055007 (2010) when a critical front propagates much faster than the maximal group velocity of quasiparticles vq, then the transition is effectively homogeneous: density of excitations obeys a generalized Kibble-Zurek mechanism and scales with the sixth root of the transition rate. However, unlike for z = 1, the inhomogeneous transition becomes adiabatic not below vq but a lower threshold velocity v', proportional to inhomogeneity of the transition, where the excitations are suppressed exponentially. Interestingly, the adiabatic threshold v' is nonzero despite vanishing minimal group velocity of low energy quasiparticles. In the adiabatic regime below v' the inhomogeneous transition can be used for efficient adiabatic quantum state preparation in a quantum simulator: the time required for the critical front to sweep across a chain of N spins adiabatically is merely linear in N, while the corresponding time for a homogeneous transition across the multicritical point scales with the sixth power of N. What is more, excitations after the adiabatic inhomogeneous transition, if any, are brushed away by the critical front to the end of the spin chain.Comment: 10 pages, 6 figures, improved version accepted in NJ

X-raying hot plasma in solar active regions with the SphinX spectrometer

The detection of very hot plasma in the quiescent corona is important for diagnosing heating mechanisms. The presence and the amount of such hot plasma is currently debated. The SphinX instrument on-board CORONAS-PHOTON mission is sensitive to X-ray emission well above 1 keV and provides the opportunity to detect the hot plasma component. We analyzed the X-ray spectra of the solar corona collected by the SphinX spectrometer in May 2009 (when two active regions were present). We modelled the spectrum extracted from the whole Sun over a time window of 17 days in the 1.34-7 keV energy band by adopting the latest release of the APED database. The SphinX broadband spectrum cannot be modelled by a single isothermal component of optically thin plasma and two components are necessary. In particular, the high statistics and the accurate calibration of the spectrometer allowed us to detect a very hot component at ~7 million K with an emission measure of ~2.7 x 10^44 cm^-3. The X-ray emission from the hot plasma dominates the solar X-ray spectrum above 4 keV. We checked that this hot component is invariably present both at high and low emission regimes, i.e. even excluding resolvable microflares. We also present and discuss a possible non-thermal origin (compatible with a weak contribution from thick-target bremsstrahlung) for this hard emission component. Our results support the nanoflare scenario and might confirm that a minor flaring activity is ever-present in the quiescent corona, as also inferred for the coronae of other stars.Comment: 6 pages, 5 figures. Accepted for publication in A&

Lobster eye optics for nano-satellite x-ray monitor

The Lobster eye design for a grazing incidence X-ray optics provides wide field of view of the order of many degrees, for this reason it would be a convenient approach for the construction of space X-ray monitors. In this paper, we compare previously reported measurements of prototype lobster eye X-ray optics called P-25 with computer simulations and discuss differences between the theoretical end experimentally obtained results. Usability of this prototype lobster eye and manufacturing technology for the nano-satellite mission is assessed. The specific scientific goals are proposed