Whistler Waves in the Radiation Belt

The Van Allen Radiation Belt is a region in space populated with high-energy, electrically-charged particles trapped in earth’s magnetic field. These particles constitute a danger to spacecraft in low-earth orbit, including the ISS and its crew. Solar storms and high-altitude nuclear explosions can increase the number of particles in the radiation belt by a factor of 100, rendering many important defense and communications satellites inoperable. It is of national security interest to develop a physical understanding of remediation of energetic particles from space. One possible method to achieve this is to use electromagnetic whistler-mode waves. Using data from the Van Allen Probes, we have conducted a preliminary analysis to validate simulations developed by Dr. Anatoly Streltsov which describe the propagation of whistler waves in space. Over the next year, we plan to further validate the models. This poster will present advances in whistler-wave physics which have important applications to future projects of launching whistlers into the radiation belt

Observations and Simulations of Whistler Waves in the Van Allen Radiation Belts

When the first American satellite, Explorer I, was launched into space in 1958 it inadvertently discovered one the most significant features of our local space environment: the Van Allen Radiation Belts. This region contains highly energetic protons and electrons from the sun which become trapped in the Earth’s magnetic field. These particles are extremely hazardous for spacecraft, causing damage to electronics and endangering astronauts on the International Space Station. Certain natural or artificial events, such as solar coronal mass ejections or high-altitude nuclear explosions, can enhance the radiation belts and decrease satellite lifetimes by orders of magnitude. Therefore, there is a strong motivation to develop a means by which to deplete the radiation and protect our assets in space from this threat. We present one promising remediation mechanism based on the interactions between these particles and very-low-frequency electromagnetic waves known as whistlers. One important property of whistler waves is that they can be guided along narrow inhomogeneities of plasma density called ducts. We have analyzed several events of ducted whistlers observed by the Van Allen Probes satellites and reproduce them with numerical simulations based on whistler theory. We demonstrate quantitative agreement between our simulations and the observations, indicating that our model successfully explains the existing satellite observations and can be used to predict the results from future experiments of launching whistler waves into the radiation belts from ground stations and space-based transmitters

Ducting of Whistler Waves in the Van Allen Radiation Belts

Whistler waves are electromagnetic waves in the very-low-frequency range which propagate in the near-earth space plasma environment, specifically within a region called the Van Allen Radiation Belts. This region contains many highly energetic particles which pose a significant threat to spacecraft in Earth orbit, including the International Space Station. Whistler waves are particularly interesting because they can interact with the energetic particles and precipitate them out of the Van Allen Radiation Belts. One important characteristic of whistlers is that they can become trapped inside enhancements or depletions of the ambient plasma density. We compare wave and particle observations from the Van Allen Probes spacecraft to results from a numerical simulation developed to model the wave propagation physics. By using the observed conditions as inputs to the simulation, we can reproduce the ducted waves with good, quantitative agreement. The results from this study will be important for future experiments of launching whistler waves into the Van Allen Radiation Belts from ground antennae or space vehicles

Velocity-Resolved Reverberation Mapping of NGC 3227

We describe the results of a new reverberation mapping program focused on the nearby Seyfert galaxy NGC 3227. Photometric and spectroscopic monitoring were carried out from 2022 December to 2023 June with the Las Cumbres Observatory network of telescopes. We detected time delays in several optical broad emission lines, with H$\beta$ having the longest delay at $\tau_{\rm cent}=4.0^{+0.9}_{-0.9}$ days and He II having the shortest delay with $\tau_{\rm cent}=0.9^{+1.1}_{-0.8}$ days. We also detect velocity-resolved behavior of the H$\beta$ emission line, with different line-of-sight velocities corresponding to different observed time delays. Combining the integrated H$\beta$ time delay with the width of the variable component of the emission line and a standard scale factor suggests a black hole mass of $M_{\rm BH}=1.1^{+0.2}_{-0.3} \times 10^7 M_{\odot}$. Modeling of the full velocity-resolved response of the H$\beta$ emission line with the phenomenological code CARAMEL finds a similar mass of $M_{\rm BH}=1.2^{+1.5}_{-0.7} \times 10^7 M_{\odot}$, and suggests that the H$\beta$-emitting broad line region (BLR) may be represented by a biconical or flared disk structure that we are viewing at an inclination angle of $\theta_i \approx 33^{\circ}$ and with gas motions that are dominated by rotation. The new photoionization-based BLR modeling tool BELMAC finds general agreement with the observations when assuming the best-fit CARAMEL results, however BELMAC prefers a thick disk geometry and kinematics that are equally comprised of rotation and inflow. Both codes infer a radially extended and flattened BLR that is not outflowing.Comment: 16 pages, 9 figures, 4 tables; submitted to Ap

A Modern Copyright Framework for the Internet of Things (IoT): Intellectual Property Scholars\u27 Joint Submission to the Canadian Government Consultation

In response to the Canadian government consultation process on the modernization of the copyright framework launched in the summer 2021, we hereby present our analysis and recommendations concerning the interaction between copyright and the Internet of Things (IoT). The recommendations herein reflect the shared opinion of the intellectual property scholars who are signatories to this brief. They are informed by many combined decades of study, teaching, and practice in Canadian, US, and international intellectual property law.In what follows, we explain:•The importance of approaching the questions raised in the consultation with a firm commitment to maintaining the appropriate balance of rights and interests in Canada’s copyright system, within the broader framework of the Constitution;•That the modernization of the Copyright Act requires a careful examination of the copyright framework within larger observable trends of dominant positions in the marketplace and anti-competitive practices, of the extraction of big (personal) data, and of market and legal infrastructures’ heavy reliance on non-negotiated standard form contracts;-That the growing prevalence of the IoT shows more clearly than ever before why Technological Protection Measures (TPMs) need to be recalibrated in keeping with the objectives of copyright, the Constitution, property rights, and of promoting competitive markets.As such, we recommend:-To narrow the scope of the TPM prohibitions under the Copyright Act, whereby the circumvention of access controls or copy controls for non-copyright-infringing purposes would be lawful, with a non-exhaustive list of such purposes to provide greater legal certainty. The same treatment would apply to the dealing in TPM circumvention technology enabling the exercise of non-copyright-infringing purposes.In the alternative, the Copyright Act should be amended to:-Introduce a new exception that would confirm that the TPM provisions (and other relevant exclusive rights in the Copyright Act) do not apply to the right to repair, including for maintenance and diagnostics purposes.-Introduce a new exception to encourage follow-on innovation.-Additionally, just as copyright holders should not be allowed to contract out of exceptions to copyright infringement through non-negotiated standard form agreements, neither should they be allowed to opt out of exceptions to TPM prohibitions by contract

A Modern Copyright Framework for Artificial Intelligence: IP Scholars\u27 Joint Submission to the Canadian Government Consultation

In response to the Canadian government consultation process on the modernization of the copyright framework launched in the summer 2021, we hereby present our analysis and recommendations concerning the interaction between copyright and artificial intelligence (AI). The recommendations herein reflect the shared opinion of the intellectual property scholars who are signatories to this brief. They are informed by many combined decades of study, teaching, and practice in Canadian and international intellectual property law.In what follows, we explain:- The importance of approaching the questions raised in the consultation with a firm commitment to maintaining the appropriate balance of rights and interests in Canada’s copyright system, consistent with a robust principle of technological neutrality.- The importance of ensuring that text and data mining (TDM) activity can be undertaken in Canada without the threat of potential copyright liability. We therefore propose both an opening up of Canada’s fair dealing doctrine to better accommodate TDM activities, and the enactment of a specific statutory provision to confirm that uses of copyright works and other subject matter for TDM (whether commercial or non-commercial) do not infringe copyright.- The importance of resisting calls to extend copyright protection to AI-generated outputs. We therefore propose maintaining and confirming the existing principled requirements of human authorship and original expression as preconditions of copyright protection, and we caution against any move to establish new neighbouring or sui generis rights in respect of AI outputs. Works generated by AI should remain in the public domain.As such, we recommend:- Enacting a broad statutory provision confirming that use of a work or other subject matter for TDM does not infringe copyright. This specific exception should be available to all users, apply to commercial and noncommercial uses, permit the retention and sharing of copies, and be protected from contractual override.- Amending section 29 of the Copyright Act to make the list of purposes an illustrative list (“for purposes such as”) and adding TDM or data/informational analysis as an enumerated purpose therein.- Confirming in section 2 of the Copyright Act that “author” means a human being/natural person; and confirming in section 5 of the Copyright Act that copyright shall not subsist in a work created without a human author

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Modeling the Reverberation Response of the Broad Line Region in Active Galactic Nuclei

The supermassive black holes (SMBHs) that reside at the centers of massive galaxies are observed as active galactic nuclei (AGN) when they are rapidly consuming matter from a surrounding accretion disk, which releases large amounts of electromagnetic radiation. Closely surrounding this engine are the dense gas clouds of the broad line region (BLR), which are photoionized by the continuum radiation emitted by the accretion disk. As these clouds are deep within the potential well of the SMBH, the gas emission lines (the broad emission lines; BELs) are Doppler-broadened by several 1,000 km/s. Measuring the size and velocity dispersion of the BLR provides a way to infer the mass of the SMBH. However, the distances to most active galactic nuclei (AGN) make spatially resolving the BLR very challenging, and much of its structure and dynamics are uncertain. The variable continuum emission of an AGN produces corresponding responses in the broad lines that are modulated by light travel-time delays. The response is described by the transfer function, which contains information on the physical properties, structure, and kinematics of the BLR. The reverberation mapping technique, a time-series analysis of the driving light continuum curve and time-delayed response of the BELs, can recover some of this information. We have developed a new forward-modeling tool, the Broad Emission Line MApping Code (BELMAC), to simulate the velocity-resolved reverberation response of the BLR to an observed input light curve, given the bolometric luminosity and spectral energy distribution of the AGN. It is the first reverberation mapping code to incorporate photoionization models to enable modeling of multi-BEL. We present numerical approximations to the transfer function by simulating the velocity-resolved responses to a single continuum pulse for sets of models representing a spherical BLR with a radiatively driven outflow and a disk-like BLR with Keplerian rotation, as well as biconical winds. We explore how the structure, velocity field, and other BLR properties affect the transfer function. We calculate the response-weighted time delay, which is considered to be a proxy for the luminosity-weighted radius of the BLR. We find in certain BLR environments, the line response is inversely correlated to changes in the continuum. In such cases, the response-weighted delay can overestimate the luminosity-weighted radius by a factor of 2 or more. We used BELMAC to model the broad H response of Markarian 142 and found a delay of 12 days, which is consistent with previous results. We also infer an SMBH mass of 5 x 10⁷ M⊙, which is about an order of magnitude greater than in previous studies. BELMAC has a fast and flexible design that allows other geometries and velocity fields to be easily added as modules. Therefore, BELMAC is a unique tool for interpreting the wealth of BLR reverberation and spectroscopy data that will come from near-future, large-scale time-domain surveys

Modeling the Reverberation Response of the Broad-line Region in Active Galactic Nuclei

The variable continuum emission of an active galactic nucleus (AGN) produces corresponding responses in the broad emission lines, which are modulated by light travel delays, and contain information on the physical properties, structure, and kinematics of the emitting gas region. The reverberation mapping technique, a time series analysis of the driving light curve and response, can recover some of this information, including the size and velocity field of the broad-line region (BLR). Here we introduce a new forward-modeling tool, the Broad Emission Line MApping Code, which simulates the velocity-resolved reverberation response of the BLR to any given input light curve by setting up a 3D ensemble of gas clouds for various specified geometries, velocity fields, and cloud properties. In this work, we present numerical approximations to the transfer function by simulating the velocity-resolved responses to a single continuum pulse for sets of models representing a spherical BLR with a radiatively driven outflow and a disklike BLR with Keplerian rotation. We explore how the structure, velocity field, and other BLR properties affect the transfer function. We calculate the response-weighted time delay (reverberation “lag”), which is considered to be a proxy for the luminosity-weighted radius of the BLR. We investigate the effects of anisotropic cloud emission and matter-bounded (completely ionized) clouds and find the response-weighted delay is only equivalent to the luminosity-weighted radius when clouds emit isotropically and are radiation-bounded (partially ionized). Otherwise, the luminosity-weighted radius can be overestimated by up to a factor of 2