Cosmic-ray transport in the galactic magnetosphere

It is advantageous to regard cosmic rays as the constitutent particles of the Galactic radiation belts and cosmic ray energization as a consequence of inward radial diffusion in the quasi-dipolar Galactic magnetosphere. This process occurs in addition to Fermi acceleration. The purpose of this work is to explore a magnetospheric explanation for the elevation of Galactic charged particles to cosmic ray energies. The magnetosphere that is of interest in this context is not a planetary magnetosphere but a galactic magnetosphere entirely analogous to those inferred from radio observations of distant galaxies. It is the magnetosphere of the Milky Way. Cosmic rays are (by this interpretation) the charged particles that constitute the radiation belts of the Galactic magnetosphere. Thus, the mechanism by which charged particles attain cosmic-ray energies is presumable the mechanism by which radiation-belt particles attain high energies in more familiar magnetosphere, i.e., the radial diffusion associated with magnetic disturbances that contain spectral power resonant with the azimuthal drift of the particles

Workshop on the evolution of the Martian atmosphere

Thirty-three papers based on the state of our knowledge prior to the anticipated new results from Mars Observer were presented at the workshop. Because of the nature of the subject, the scope of the papers covered a broad disciplinary range encompassing astronomy and solar physics, geology and geophysics, climatology, atmospheric science, aeronomy, and space physics. The 42 participants heard about topics from the evolution of solar-type stars to candidate instrumentation for measuring escape to space on yet-unscheduled future missions

Propagation of the 2012 March Coronal Mass Ejections from the Sun to Heliopause

In 2012 March the Sun exhibited extraordinary activities. In particular, the active region NOAA AR 11429 emitted a series of large coronal mass ejections (CMEs) which were imaged by STEREO as it rotated with the Sun from the east to west. These sustained eruptions are expected to generate a global shell of disturbed material sweeping through the heliosphere. A cluster of shocks and interplanetary CMEs (ICMEs) were observed near the Earth, and are propagated outward from 1 AU using an MHD model. The transient streams interact with each other, which erases memory of the source and results in a large merged interaction region (MIR) with a preceding shock. The MHD model predicts that the shock and MIR would reach 120 AU around 2013 April 22, which agrees well with the period of radio emissions and the time of a transient disturbance in galactic cosmic rays detected by Voyager 1. These results are important for understanding the "fate" of CMEs in the outer heliosphere and provide confidence that the heliopause is located around 120 AU from the Sun.Comment: 13 pages, 5 figures, accepted for publication in ApJ Letter

Trust, regulatory processes and NICE decision-making: Appraising cost-effectiveness models through appraising people and systems.

This article presents an ethnographic study of regulatory decision-making regarding the cost-effectiveness of expensive medicines at the National Institute for Health and Care Excellence (NICE) in England. We explored trust as one important mechanism by which problems of complexity and uncertainty were resolved. Existing studies note the salience of trust for regulatory decisions, by which the appraisal of people becomes a proxy for appraising technologies themselves. Although such (dis)trust in manufacturers was one important influence, we describe a more intricate web of (dis)trust relations also involving various expert advisors, fellow committee members and committee Chairs. Within these complex chains of relations, we found examples of both more blind-acquiescent and more critical-investigative forms of trust as well as, at times, pronounced distrust. Difficulties in overcoming uncertainty through other means obliged trust in some contexts, although not in others. (Dis)trust was constructed through inferences involving abstract systems alongside actors’ oral and written presentations-of-self. Systemic features and ‘forced options’ to trust indicate potential insidious processes of regulatory capture

An investigation of solar wind effects on the evolution of the Martian atmosphere

This investigation concentrated on the question of how atmosphere escape, related to both photochemistry and the Mars solar wind interaction, may have affected the evolution of Mars' atmosphere over time. The principal investigator and postdoctoral researcher adopted the premise that contemporary escape processes have dominated the losses to space over the past 3.5 billion years, but that the associated loss rates have been modified by solar evolution. A model was constructed for the contemporary escape scenario based on knowledge gained from both Venus in-situ measurements from Pioneer Venus Orbiter and Mars measurements from Phobos-2. Venus provided a valuable second example of a weakly magnetized planet having a similar solar wind interaction where we have more knowledge from observations. The model included photochemical losses from recombining ionospheric molecular ions, scavenging Martian upper atmosphere ('pickup') ions by the solar wind, and sputtering of the atmosphere by reentering pickup ions. The existence of the latter mechanism was realized during the course of the supported investigation, and is now thought by Jakosky and Pepin to explain some of the Martian noble gas isotope ratios

Solar Wind Effects on Atmospheres of the Weakly Magnetized Bodies: Mars, Titan and the Moon

The atmospheres of planetary bodies without significant intrinsic magnetic fields exhibit unique features because they interact with the external plasma flows in their space environment. The plasma interactions also have the potential of altering the evolutionary paths of these atmospheres since the processes (such as ion pickup and sputtering) that lead to loss of constituents have effects unlike those of other escape mechanisms. This ongoing investigation has been concentrating on the characterization of the plasma interactions and the associated plasma physical escape processes at Mars and Titan. The results are relevant to both mission planning and interpretation of data from past and future Mars and Lunar missions, and to tour and mission operations planning for the Cassini Orbiter. The also contribute to our general understanding, from a comparative planetology standpoint, of the role that planetary magnetic field play in determining the state and fate of a planetary atmosphere

Co-Investigator Participation in the Mars-94 Mission Studies of the Mars-Solar Wind Interaction: Topside Sounder and Magnetometer

The purpose of this investigation has been to provide United States co-investigator support toward the preparation of the Topside Ionospheric Sounder and Magnetometer experiments on the Russian Mars-96 (previously Mars-94) mission. The main role has been to assist in the preparation of software tools for the optimum design of the investigation and the evaluation of mission operational plans and orbits

Sun-to-Earth Characteristics of Two Coronal Mass Ejections Interacting near 1 AU: Formation of a Complex Ejecta and Generation of a Two-Step Geomagnetic Storm

On 2012 September 30 - October 1 the Earth underwent a two-step geomagnetic storm. We examine the Sun-to-Earth characteristics of the coronal mass ejections (CMEs) responsible for the geomagnetic storm with combined heliospheric imaging and in situ observations. The first CME, which occurred on 2012 September 25, is a slow event and shows an acceleration followed by a nearly invariant speed in the whole Sun-Earth space. The second event, launched from the Sun on 2012 September 27, exhibits a quick acceleration, then a rapid deceleration and finally a nearly constant speed, a typical Sun-to-Earth propagation profile for fast CMEs \citep{liu13}. These two CMEs interacted near 1 AU as predicted by the heliospheric imaging observations and formed a complex ejecta observed at Wind, with a shock inside that enhanced the pre-existing southward magnetic field. Reconstruction of the complex ejecta with the in situ data indicates an overall left-handed flux rope-like configuration, with an embedded concave-outward shock front, a maximum magnetic field strength deviating from the flux rope axis and convex-outward field lines ahead of the shock. While the reconstruction results are consistent with the picture of CME-CME interactions, a magnetic cloud-like structure without clear signs of CME interactions \citep{lugaz14} is anticipated when the merging process is finished.Comment: 15 pages, 5 figures. Accepted for publication in ApJ Letter

Thermal radiation dominated heat transfer in nanomechanical silicon nitride drum resonators

Nanomechanical silicon nitride (SiN) drum resonators are currently employed in various fields of applications that arise from their unprecedented frequency response to physical quantities. In the present study, we investigate the thermal transport in nanomechanical SiN drum resonators by analytical modelling, computational simulations, and experiments for a better understanding of the underlying heat transfer mechanism causing the thermal frequency response. Our analysis indicates that radiative heat loss is a non-negligible heat transfer mechanism in nanomechanical SiN resonators limiting their thermal responsivity and response time. This finding is important for optimal resonator designs for thermal sensing applications as well as cavity optomechanics.Comment: 8 pages, 4 figures in main text, 3 figures in supplementar