Aurorasaurus and the St Patrick’s Day storm

The recent St. Patrick's Day geomagnetic storm provided a rare chance for the public to witness a dazzling auroral display, even from mid-latitudes. An unprecedented number of citizen scientists reported their sightings to Aurorasaurus, offering an exciting opportunity for future scientific study

A comparison of modeled auroral boundaries with observations from citizen scientists

Over the past year, the citizen science project Aurorasaurus has collected new, globally-distributed, ground-based observations of the aurora and has integrated them with space-based estimates of auroral activity. A case study of these observations were compared to the OVATION Prime model of aurora, run by the NOAA Space Weather Prediction Center (SWPC). The observations were comprised of positive and negative sightings directly reported to Aurorasaurus, along with verified tweets, which are positive sightings reported on Twitter and verified by Aurorasaurus users. The observations were collected during March and April 2015, a period spanning three large geomagnetic storms, and covered a wide range of latitudes. The observations demonstrated that, during these events, over 60% of the positive aurora observations (which includes those reported directly to Aurorasaurus and the verified tweets) occurred at latitudes equatorward of the SWPC predicted "view line". New scaling parameters were determined from the relationship of the differences in latitude between the positive observations and the view line, and the maximum probability of visible aurora. Future work testing these scaling parameters and using them in the Aurorasaurus real-time alert system will be presented

Using citizen science reports to define the equatorial extent of auroral visibility

An aurora may often be viewed hundreds of kilometers equatorward of the auroral oval owing to its altitude. As such, the NOAA Space Weather Prediction Center (SWPC) Aurora Forecast product provides a “view line” to demonstrate the equatorial extent of auroral visibility, assuming that it is sufficiently bright and high in altitude. The view line in the SWPC product is based upon the latitude of the brightest aurora, for each hemisphere, as specified by the real-time oval variation, assessment, tracking, intensity, and online nowcasting (OVATION) Prime (2010) aurora precipitation model. In this study, we utilize nearly 500 citizen science auroral reports to compare with the view line provided by an updated SWPC aurora forecast product using auroral precipitation data from OVATION Prime (2013). The citizen science observations were recorded during March and April 2015 using the Aurorasaurus platform and cover one large geomagnetic storm and several smaller events. We find that this updated SWPC view line is conservative in its estimate and that the aurora is often viewable further equatorward than is indicated by the forecast. By using the citizen reports to modify the scaling parameters used to link the OVATION Prime (2013) model to the view line, we produce a new view line estimate that more accurately represents the equatorial extent of visible aurora. An OVATION Prime (2013) energy flux-based equatorial boundary view line is also developed and is found to provide the best overall agreement with the citizen science reports, with an accuracy of 91%

A real-time hybrid aurora alert system:combining citizen science reports with an auroral oval model

Accurately predicting when, and from where, an aurora will be visible is particularly difficult, yet it is a service much desired by the general public. Several aurora alert services exist that attempt to provide such predictions but are, generally, based upon fairly coarse estimates of auroral activity (e.g. Kp or Dst). Additionally, these services are not able to account for a potential observer's local conditions (such as cloud cover or level of darkness). Aurorasaurus, however, combines data from the well-used, solar wind driven, OVATION Prime auroral oval model with real-time observational data provided by a global network of citizen scientists. This system is designed to provide more accurate and localized alerts for auroral visibility than currently available. Early results are promising and show that over 100,000 auroral visibility alerts have been issued, including nearly 200 highly localized alerts, to over 2,000 users located right across the globe

Determining the accuracy of crowdsourced tweet verification for auroral research

The Aurorasaurus citizen science project harnesses volunteer crowdsourcing to identify sightings of an aurora (or the "northern/southern lights") posted by citizen scientists on Twitter. Previous studies have demonstrated that aurora sightings can be mined from Twitter but with the caveat that there is a high level of accompanying non-sighting tweets, especially during periods of low auroral activity. Aurorasaurus attempts to mitigate this, and thus increase the quality of its Twitter sighting data, by utilizing volunteers to sift through a pre-filtered list of geo-located tweets to verify real-time aurora sightings. In this study, the current implementation of this crowdsourced verification system, including the process of geo-locating tweets, is described and its accuracy (which, overall, is found to be 68.4%) is determined. The findings suggest that citizen science volunteers are able to accurately filter out unrelated, spam-like, Twitter data but struggle when filtering out somewhat related, yet undesired, data. The citizen scientists particularly struggle with determining the real-time nature of the sightings and care must therefore be taken when relying on crowdsourced identification

One God or one Lord?: deuteronomy and the meaning of'monotheism'

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Numerical models of collisions between core-collapse supernovae and circumstellar shells

Recent observations of luminous Type IIn supernovae (SNe) provide compelling evidence that massive circumstellar shells surround their progenitors. In this paper we investigate how the properties of such shells influence the SN lightcurve by conducting numerical simulations of the interaction between an expanding SN and a circumstellar shell ejected a few years prior to core collapse. Our parameter study explores how the emergent luminosity depends on a range of circumstellar shell masses, velocities, geometries, and wind mass-loss rates, as well as variations in the SN mass and energy. We find that the shell mass is the most important parameter, in the sense that higher shell masses (or higher ratios of M_shell/M_SN) lead to higher peak luminosities and higher efficiencies in converting shock energy into visual light. Lower mass shells can also cause high peak luminosities if the shell is slow or if the SN ejecta are very fast, but only for a short time. Sustaining a high luminosity for durations of more than 100 days requires massive circumstellar shells of order 10 M_sun or more. This reaffirms previous comparisons between pre-SN shells and shells produced by giant eruptions of luminous blue variables (LBVs), although the physical mechanism responsible for these outbursts remains uncertain. The lightcurve shape and observed shell velocity can help diagnose the approximate size and density of the circumstellar shell, and it may be possible to distinguish between spherical and bipolar shells with multi-wavelength lightcurves. These models are merely illustrative. One can, of course, achieve even higher luminosities and longer duration light curves from interaction by increasing the explosion energy and shell mass beyond values adopted here.Comment: Accepted for publication in MNRAS. Tables of numerical results (SN lightcurves and velocities) to be published online. (Updated to fix figures

Potential Cislunar and Interplanetary Proving Ground Excursion Trajectory Concepts

NASA has been investigating potential translunar excursion concepts to take place in the 2020s that would be used to test and demonstrate long duration life support and other systems needed for eventual Mars missions in the 2030s. These potential trajectory concepts could be conducted in the proving ground, a region of cislunar and near-Earth interplanetary space where international space agencies could cooperate to develop the technologies needed for interplanetary spaceflight. Enabled by high power Solar Electric Propulsion (SEP) technologies, the excursion trajectory concepts studied are grouped into three classes of increasing distance from the Earth and increasing technical difficulty: the first class of excursion trajectory concepts would represent a 90-120 day round trip trajectory with abort to Earth options throughout the entire length, the second class would be a 180-210 day round trip trajectory with periods in which aborts would not be available, and the third would be a 300-400 day round trip trajectory without aborts for most of the length of the trip. This paper provides a top-level summary of the trajectory and mission design of representative example missions of these three classes of excursion trajectory concepts

Chiral Rings and Phases of Supersymmetric Gauge Theories

We solve for the expectation values of chiral operators in supersymmetric U(N) gauge theories with matter in the adjoint, fundamental and anti-fundamental representations. A simple geometric picture emerges involving a description by a meromorphic one-form on a Riemann surface. The equations of motion are equivalent to a condition on the integrality of periods of this form. The solution indicates that all semiclassical phases with the same number of U(1) factors are continuously connected.Comment: 55 page

Scribalism and Ritual Innovation

In Wellhausen’s judgement, it was with the prophet Ezekiel that “the sacred praxis […] became a matter of theory and writing,” rather than a matter of the correct performance of rituals that had been handed down through the generations. With the Jerusalem temple in ruins, the path of transmission came under threat. In the face of the potential loss of priestly lore, “it is easy to understand […] how an exiled priest should have begun to paint the picture of it as he carried it in his memory, and to publish it as a programme for the future restoration of the theocracy.” This pithy account of how ritual came to be first written down amongst the ancient Judahites glosses over a number of complexities. On most assessments, Ezekiel’s programme of the restored theocracy did not correspond to the cultic practice of pre-destruction Judah. Was this the result of Ezekiel’s faulty memory, the programmatic and prophetic nature of the envisaged future cult, the transformation of sacred praxis into theory, or a combination of all three