1,617 research outputs found
Can Streamer Blobs prevent the Buildup of the Interplanetetary Magnetic Field?
Coronal Mass Ejections continuously drag closed magnetic field lines away
from the Sun, adding new flux to the interplanetary magnetic field (IMF). We
propose that the outward-moving blobs that have been observed in helmet
streamers are evidence of ongoing, small-scale reconnection in streamer current
sheets, which may play an important role in the prevention of an indefinite
buildup of the IMF. Reconnection between two open field lines from both sides
of a streamer current sheet creates a new closed field line, which becomes part
of the helmet, and a disconnected field line, which moves outward. The blobs
are formed by plasma from the streamer that is swept up in the trough of the
outward moving field line. We show that this mechanism is supported by
observations from SOHO/LASCO. Additionally, we propose a thorough statistical
study to quantify the contribution of blob formation to the reduction of the
IMF, and indicate how this mechanism may be verified by observations with
SOHO/UVCS and the proposed NASA STEREO and ESA Polar Orbiter missions.Comment: 7 pages, 2 figures; accepted by The Astrophysical Journal Letters;
uses AASTe
An improved expected temperature formula for identifying interplanetary coronal mass ejections
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95056/1/jgra17698.pd
Sensing directional forces in levitated optomechanics
Optomechanical devices are being harnessed as sensors of ultraweak forces for
applications ranging from inertial sensing to the search for the elusive dark
matter; For the latter, the focus is on detection of either higher energy
single recoils or ultralight, narrowband sources; a directional signal is
expected. However, the possibility of searching for a directional broadband
signal need not be excluded; with this and other applications in mind, we apply
a stochastic signal with a well defined direction, , to a trapped and
cooled levitated nanosphere. We find that cross-correlation power spectra offer
a calibration-free distinctive signature of the presence of a directional
force, and its orientation quadrant, unlike normal power spectral densities
(PSDs). With calibration we are able to accurately measure the angle ,
akin to a force compass in a plane
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First imaging of corotating interaction regions using the STEREO spacecraft
Plasma parcels are observed propagating from the Sun out to the large coronal heights monitored by the Heliospheric Imagers (HI) instruments onboard the NASA STEREO spacecraft during September 2007. The source region of these out-flowing parcels is found to corotate with the Sun and to be rooted near the western boundary of an equatorial coronal hole. These plasma enhancements evolve during their propagation through the HI camerasâ fields of view and only becoming fully developed in the outer camera field of view. We provide evidence that HI is observing the formation of a Corotating Interaction Region(CIR) where fast solar wind from the equatorial coronal hole is interacting with the slow solar wind of the streamer belt located on the western edge of that coronal hole. A dense plasma parcel is also observed near the footpoint of the observed CIR at a distance less than 0.1AU from the Sun where fast wind would have not had time to catch up slow wind. We suggest that this low-lying plasma enhancement is a plasma parcel which has been disconnected from a helmet streamer and subsequently becomes embedded inside the corotating interaction region
A programming and a modelling perspective on the evaluation of Java card implementations
Java Card Technology has provided a huge step forward in programming smart cards: from assembler to using a high level Object Oriented language. However, the authors have found some differences between the current Java Card version (2.1) and main stream Java that may restrict the benefits of using Java achievable in smartcard programming. In particular, efforts towards evaluating Java Card implementations at a high level of assurance may be hampered by the presence of these differences as well as by the complexity of the Java Card VM and API. The goal of the present paper is to detail the differences from a programming and a modelling point of view
Simulations of Electron Acceleration at Collisionless Shocks: The Effects of Surface Fluctuations
Energetic electrons are a common feature of interplanetary shocks and
planetary bow shocks, and they are invoked as a key component of models of
nonthermal radio emission, such as solar radio bursts. A simulation study is
carried out of electron acceleration for high Mach number, quasi-perpendicular
shocks, typical of the shocks in the solar wind. Two dimensional
self-consistent hybrid shock simulations provide the electric and magnetic
fields in which test particle electrons are followed. A range of different
shock types, shock normal angles, and injection energies are studied. When the
Mach number is low, or the simulation configuration suppresses fluctuations
along the magnetic field direction, the results agree with theory assuming
magnetic moment conserving reflection (or Fast Fermi acceleration), with
electron energy gains of a factor only 2 - 3. For high Mach number, with a
realistic simulation configuration, the shock front has a dynamic rippled
character. The corresponding electron energization is radically different:
Energy spectra display: (1) considerably higher maximum energies than Fast
Fermi acceleration; (2) a plateau, or shallow sloped region, at intermediate
energies 2 - 5 times the injection energy; (3) power law fall off with
increasing energy, for both upstream and downstream particles, with a slope
decreasing as the shock normal angle approaches perpendicular; (4) sustained
flux levels over a broader region of shock normal angle than for adiabatic
reflection. All these features are in good qualitative agreement with
observations, and show that dynamic structure in the shock surface at ion
scales produces effective scattering and can be responsible for making high
Mach number shocks effective sites for electron acceleration.Comment: 26 pages, 12 figure
The future of enterprise groupware applications
This paper provides a review of groupware technology and products. The purpose of this review is to investigate the appropriateness of current groupware technology as the basis for future enterprise systems and evaluate its role in realising, the currently emerging, Virtual Enterprise model for business organisation. It also identifies in which way current technological phenomena will transform groupware technology and will drive the development of the enterprise systems of the future
Ion heating resulting from pickup in magnetic reconnection exhausts
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95415/1/jgra19672.pd
Influences on academics' approaches to development: voices from below
The purpose of this qualitative case study research was to explore faculty-based academicsâ views on what influences their behaviours and attitudes towards their development. Informed by critical realist ontology, the data collection was carried out through narrative interviews with academics in two contrasting English Universities. Findings, or areas for reflection, have emerged about the constraints and enablements academics perceive in respect of their professional development. In particular, themes such as the significance of professional status; misaligned initiatives and priorities; the influence of supportive networks; and emergent personal, individual concerns have surfaced. The conclusion is drawn that the significance of agency raises the importance of responding to the âvoices from belowâ
Scaling up malaria elimination management and leadership: a pilot in three provinces in Zimbabwe, 2016-2018
BACKGROUND: Focus for improved malaria programme performance is often placed on the technical challenges, while operational issues are neglected. Many of the operational challenges that inhibit malaria programme effectiveness can be addressed by improving communication and coordination, increasing accountability, maintaining motivation, providing adequate training and supervision, and removing bureaucratic silos. METHODS: A programme of work was piloted in Zimbabwe with one malaria eliminating province, Matabeleland South in 2016-2017, and scaled up to include two other provinces, Matabeleland North and Midlands, in 2017-2018. The intervention included participatory, organization development and quality improvement methods. RESULTS: Workshop participants in Matabeleland South reported an improvement in data management. In Matabeleland North, motivation among nurses improved as they gained confidence in case management from training, and overall staff morale improved. There was also an improvement in data quality and data sharing. In Midlands, the poorly performing district was motivated to improve, and both participating districts became more goal-oriented. They also became more focused on monitoring their data regularly. Participants from all provinces reported having gained skills in listening, communicating, facilitating discussions, and making presentations. Participation in the intervention changed the mindset of malaria programme staff, increasing ownership and accountability, and empowering them to identify and solve problems, make decisions, and act within their sphere of influence, elevating challenges when appropriate. CONCLUSIONS: This pilot demonstrates that a participatory, organization development and quality improvement approach has broad ranging effects, including improving local delivery of interventions, tailoring strategies to target specific populations, finding efficiencies in the system that could not be found using the traditional top-down approach, and improving motivation and communication between different cadres of health workers. Scale-up of this simple model can be achieved and benefits sustained over time if the process is imbedded into the programme with the training of health staff who can serve as management improvement coaches. Methods to improve operational performance that are scalable at the district level are urgently needed: this approach is a possible tactic that can significantly contribute to the achievement of global malaria eradication goals
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