Right-Hand Polarized 4\u3ci\u3ef\u3c/i\u3e\u3csub\u3ece\u3c/sub\u3e Auroral Roar Emissions: 2. Nonlinear Generation Theory

Auroral roar emissions are commonly interpreted as Z (or upper hybrid) mode naturally excited by precipitating auroral electrons. Subsequent conversion to escaping radiation makes it possible for these emissions to be detected on the ground. Most emissions are detected as having left-hand (L) circular (or ordinary O) polarization, but the companion paper presents a systematic experimental study on the rare occurrence of the right-hand polarized, or equivalently, extraordinary (X) mode 4fce emission. A similar observation was reported earlier by Sato et al. (2015). The suggested emission mechanism is the nonlinear coalescence of two upper hybrid roars at 2fce. The present paper formulates a detailed theory for such an emission mechanism

Access to Investigational Drugs: FDA Expanded Access Programs or “Right‐to‐Try” Legislation?

PurposeThe Food and Drug Administration Expanded Access (EA) program and “Right‐to‐Try” legislation aim to provide seriously ill patients who have no other comparable treatment options to gain access to investigational drugs and biological agents. Physicians and institutions need to understand these programs to respond to questions and requests for access.MethodsFDA EA programs and state and federal legislative efforts to provide investigational products to patients by circumventing FDA regulations were summarized and compared.ResultsThe FDA EA program includes Single Patient‐Investigational New Drug (SP‐IND), Emergency SP‐IND, Intermediate Sized Population IND, and Treatment IND. Approval rates for all categories exceed 99%. Approval requires FDA and Institutional Review Board (IRB) approval, and cooperation of the pharmaceutical partner is essential. “Right‐to‐Try” legislation bypasses some of these steps, but provides no regulatory or safety oversight.ConclusionThe FDA EA program is a reasonable option for patients for whom all other therapeutic interventions have failed. The SP‐IND not only provides patient access to new drugs, but also maintains a balance between immediacy and necessary patient protection. Rather than circumventing existing FDA regulations through proposed legislation, it seems more judicious to provide the knowledge and means to meet the EA requirements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115991/1/cts12255.pd

GPS phase scintillation at high latitudes during geomagnetic storms of 7-17 March 2012, part 2: interhemispheric comparison

During the ascending phase of solar cycle 24, a series of interplanetary coronal mass ejections (ICMEs) in the period 7–17 March 2012 caused geomagnetic storms that strongly affected high-latitude ionosphere in the Northern and Southern Hemisphere. GPS phase scintillation was observed at northern and southern high latitudes by arrays of GPS ionospheric scintillation and TEC monitors (GISTMs) and geodetic-quality GPS receivers sampling at 1 Hz. Mapped as a function of magnetic latitude and magnetic local time (MLT), the scintillation was observed in the ionospheric cusp, the tongue of ionization fragmented into patches, sun-aligned arcs in the polar cap, and nightside auroral oval and subauroral latitudes. Complementing a companion paper (Prikryl et al., 2015a) that focuses on the high latitude ionospheric response to variable solar wind in the North American sector, interhemispheric comparison reveals commonalities as well as differences and asymmetries between the northern and southern high latitudes, as a consequence of the coupling between the solar wind and magnetosphere. The interhemispheric asymmetries are caused by the dawn–dusk component of the interplanetary magnetic field controlling the MLT of the cusp entry of the storm enhanced density plasma into the polar cap and the orientation relative to the noon–midnight meridian of the tongue of ionization

Interhemispheric comparison of GPS phase scintillation at high latitudes during the magnetic-cloud-induced geomagnetic storm of 5–7 April 2010

Arrays of GPS Ionospheric Scintillation and TEC Monitors (GISTMs) are used in a comparative scintillation study focusing on quasi-conjugate pairs of GPS receivers in the Arctic and Antarctic. Intense GPS phase scintillation and rapid variations in ionospheric total electron content (TEC) that can result in cycle slips were observed at high latitudes with dual-frequency GPS receivers during the first significant geomagnetic storm of solar cycle 24 on 5–7 April 2010. The impact of a bipolar magnetic cloud of north-south (NS) type embedded in high speed solar wind from a coronal hole caused a geomagnetic storm with maximum 3-hourly Kp = 8- and hourly ring current Dst =−73 nT. The interhemispheric comparison of phase scintillation reveals similarities but also asymmetries of the ionospheric response in the northern and southern auroral zones, cusps and polar caps. In the nightside auroral oval and in the cusp/cleft sectors the phase scintillation was observed in both hemispheres at about the same times and was correlated with geomagnetic activity. The scintillation level was very similar in approximately conjugate locations in Qiqiktarjuaq (75.4° N; 23.4° E CGM lat. and lon.) and South Pole (74.1° S; 18.9° E), in Longyearbyen (75.3° N; 111.2° E) and Zhongshan (74.7° S; 96.7° E), while it was significantly higher in Cambridge Bay (77.0° N; 310.1° E) than at Mario Zucchelli (80.0° S; 307.7° E). In the polar cap, when the interplanetary magnetic field (IMF) was strongly northward, the ionization due to energetic particle precipitation was a likely cause of scintillation that was stronger at Concordia (88.8° S; 54.4° E) in the dark ionosphere than in the sunlit ionosphere over Eureka (88.1° N; 333.4° E), due to a difference in ionospheric conductivity. When the IMF tilted southward, weak or no significant scintillation was detected in the northern polar cap, while in the southern polar cap rapidly varying TEC and strong phase scintillation persisted for many hours. This interhemispheric asymmetry is explained by the difference in the location of solar terminator relative to the cusps in the Northern and Southern Hemisphere. Solar terminator was in the immediate proximity of the cusp in the Southern Hemisphere where sunlit ionospheric plasma was readily convected into the central polar cap and a long series of patches was observed. In contrast, solar terminator was far poleward of the northern cusp thus reducing the entry of sunlit plasma and formation of dense patches. This is consistent with the observed and modeled seasonal variation in occurrence of polar cap patches. The GPS scintillation and TEC data analysis is supported by data from ground-based networks of magnetometers, riometers, ionosondes, HF radars and all-sky imagers, as well as particle flux measurements by DMSP satellites

IMF clock angle control of multifractality in ionospheric velocity fluctuations

We present an analysis of 8 years of meridional line-of-sight ionospheric plasma velocity measurements from the Halley SuperDARN radar which investigates the effect of the interplanetary magnetic field (IMF) clock angle on the scaling exponents of the first three order velocity structure functions. We only use velocity measurements made poleward of the open/closed magnetic field line boundary in the nightside ionosphere. The measured scaling exponents are consistent with multifractal Kraichnan-Iroshnikov turbulence for all clock angles but with varying intermittency that decreases to zero during purely northward IMF conditions. We thus propose that intermittency is inherited from the solar wind but also discuss other possible reasons for this relationship. Citation: Abel, G. A., M. P. Freeman, and G. Chisham (2009), IMF clock angle control of multifractality in ionospheric velocity fluctuations, Geophys. Res. Lett., 36, L19102, doi:10.1029/2009GL040336

An interhemispheric comparison of GPS phase scintillation with auroral emission observed at the South Pole and from the DMSP satellite

The global positioning system (GPS) phase scintillation caused by highlatitude ionospheric irregularities during an intense high-speed stream (HSS) of the solar wind from April 29 to May 5, 2011, was observed using arrays of GPS ionospheric scintillation and total electron content monitors in the Arctic and Antarctica. The one-minute phase-scintillation index derived from the data sampled at 50 Hz was complemented by a proxy index (delta phase rate) obtained from 1-Hz GPS data. The scintillation occurrence coincided with the aurora borealis and aurora australis observed by an all-sky imager at the South Pole, and by special sensor ultraviolet scanning imagers on board satellites of the Defense Meteorological Satellites Program. The South Pole (SP) station is approximately conjugate with two Canadian High Arctic Ionospheric Network stations on Baffin Island, Canada, which provided the opportunity to study magnetic conjugacy of scintillation with support of riometers and magnetometers. The GPS ionospheric pierce points were mapped at their actual or conjugate locations, along with the auroral emission over the South Pole, assuming an altitude of 120 km. As the aurora brightened and/or drifted across the field of view of the all-sky imager, sequences of scintillation events were observed that indicated conjugate auroras as a locator of simultaneous or delayed bipolar scintillation events. In spite of the greater scintillation intensity in the auroral oval, where phase scintillation sometimes exceeded 1 radian during the auroral break-up and substorms, the percentage occurrence of moderate scintillation was highest in the cusp. Interhemispheric comparisons of bipolar scintillation maps show that the scintillation occurrence is significantly higher in the southern cusp and polar cap

Modeling Ionospheric Absorption Modified by Anomalous Heating During Substorms

Abstract. Riometers monitor the changes in ionospheric conductivity by measuring the absorption of very high frequency radio noise of galactic origin passing through the ionosphere. In this Letter the absorption of radio signals by a thin layer of ionospheric plasma, produced by ionization due to energetic precipitating electrons, is modeled by taking into account strong turbulent heating caused by instabilities. The precipitating electron population is obtained from a global MHD simulation of the magnetosphere, along with the electric fields which excite the Farley-Buneman instability and lead to turbulent electron heating. A comparison, the first of its kind, of the data from polar and sub-auroral riometers for the magnetic cloud event of January 10, 1997 shows good agreement. The ionospheric conductance modified by turbulent electron heating can be used to improve the magnetosphereionosphere coupling in the current global MHD models

25 Years of Self-organized Criticality: Concepts and Controversies

Introduced by the late Per Bak and his colleagues, self-organized criticality (SOC) has been one of the most stimulating concepts to come out of statistical mechanics and condensed matter theory in the last few decades, and has played a significant role in the development of complexity science. SOC, and more generally fractals and power laws, have attracted much comment, ranging from the very positive to the polemical. The other papers (Aschwanden et al. in Space Sci. Rev., 2014, this issue; McAteer et al. in Space Sci. Rev., 2015, this issue; Sharma et al. in Space Sci. Rev. 2015, in preparation) in this special issue showcase the considerable body of observations in solar, magnetospheric and fusion plasma inspired by the SOC idea, and expose the fertile role the new paradigm has played in approaches to modeling and understanding multiscale plasma instabilities. This very broad impact, and the necessary process of adapting a scientific hypothesis to the conditions of a given physical system, has meant that SOC as studied in these fields has sometimes differed significantly from the definition originally given by its creators. In Bak’s own field of theoretical physics there are significant observational and theoretical open questions, even 25 years on (Pruessner 2012). One aim of the present review is to address the dichotomy between the great reception SOC has received in some areas, and its shortcomings, as they became manifest in the controversies it triggered. Our article tries to clear up what we think are misunderstandings of SOC in fields more remote from its origins in statistical mechanics, condensed matter and dynamical systems by revisiting Bak, Tang and Wiesenfeld’s original papers

CAD-based computer vision: the automatic generation of recognition stragtegies

Journal ArticleThree-dimensional model-based computer vision uses geometric models of objects and sensed data to recognize objects in a scene. Likewise, Computer Aided Design (CAD) systems are used to interactively generate three-dimensional models during these fields. Recently, the unification of CAD and vision systems has become the focus of research in the context of manufacturing automation. This paper explores the connection between CAD and computer vision. A method for the automatic generation of recognition strategies based on the geometric properties of shape has been devised and implemented. This uses a novel technique developed for quantifying the following properties of features which compose models used in computer vision: robustness, completeness, consistency, cost, and uniqueness. By utilizing this information, the automatic synthesis of a specialized recognition scheme, called a Strategy Tree, is accomplished. Strategy Trees describe, in a systematic and robust manner. the search process used for recognition and localization of particular objects in the given scene. They consist of selected features which satisfy system constraints and Corroborating Evidence Subtrees which are used in the formation of hypotheses. Verification techniques, used to substantiate or refute these hypotheses, are explored. Experiments utilizing 3-D data are presented

Sustained Antarctic Research: A 21st Century Imperative

The view from the south is, more than ever, dominated by ominous signs of change. Antarctica and the Southern Ocean are intrinsic to the Earth system, and their evolution is intertwined with and influences the course of the Anthropocene. In turn, changes in the Antarctic affect and presage humanity's future. Growing understanding is countering popular beliefs that Antarctica is pristine, stable, isolated, and reliably frozen. An aspirational roadmap for Antarctic science has facilitated research since 2014. A renewed commitment to gathering further knowledge will quicken the pace of understanding of Earth systems and beyond. Progress is already evident, such as addressing uncertainties in the causes and pace of ice loss and global sea-level rise. However, much remains to be learned. As an iconic global “commons,” the rapidity of Antarctic change will provoke further political action. Antarctic research is more vital than ever to a sustainable future for this One Earth