Subpacket structure in strong VLF chorus rising tones: characteristics and consequences for relativistic electron acceleration

Van Allen Probes in situ observations are used to examine detailed subpacket structure observed in strong VLF (very low frequency) rising-tone chorus elements observed at the time of a rapid MeV electron energization in the inner magnetosphere. Analysis of the frequency gap between lower and upper chorus-band waves identifies fceEQ, the electron gyrofrequency in the equatorial wave generation region. Initial subpackets in these strong chorus rising-tone elements begin at a frequency near 1/4 fceEQ and exhibit smooth gradual frequency increase across their > 10 ms temporal duration. A second much stronger subpacket is seen at frequencies around the local value of 1/4 fce with small wave normal angle (< 10°) and steeply rising df/dt. Smooth frequency and phase variation across and between the initial subpackets support continuous phase trapping of resonant electrons and increased potential for MeV electron acceleration. The total energy gain for individual seed electrons with energies between 100 keV and 3 MeV ranges between 2 and 15%, in their nonlinear interaction with a single chorus element.

Quasiperiodic emissions and related particle precipitation bursts observed by the DEMETER spacecraft

&lt;p&gt;Electromagnetic waves observed in the inner magnetosphere at frequencies between about 0.5 and 4 kHz sometimes exhibit a quasiperiodic (QP) time modulation of the wave intensity with modulation periods from tens of seconds up to a few minutes. Such waves are typically termed &amp;#8220;QP emissions&amp;#8221; and their origin is still not fully understood. We use a large set of more than 2,000 of these events identified in the low-altitude DEMETER spacecraft data to analyze how the wave properties (modulation period, intensity) depend on relevant controlling factors. Moreover, in-situ measurements of energetic electron precipitation are used to check for precipitation peaks matching the individual QP elements. We successfully identified several such events and we perform their detailed analysis. Most importantly, while the waves may propagate unducted across L-shells, the precipitating particles follow magnetic field lines from the interaction region down to the observation point. They can thus be used to deduce important information about the location and spatial extent of the anticipated generation region of the emissions.&lt;/p&gt;

Subpacket Structure in Strong VLF Chorus Rising Tones: Characteristics and Consequences for Radiation Belt Acceleration

Van Allen Probes in situ observations are used to examine detailed subpacket structure observed in strong VLF (very low frequency) rising tone chorus elements observed at the time of a rapid MeV electron energization in the inner magnetosphere. Analysis of the frequency gap between lower and upper chorus-band waves identifies fceEQ, the electron gyrofrequency in the equatorial wave generation region. Initial subpackets in these strong chorus rising-tone elements begin at a frequency near 1/4 fceEQ, exhibit smooth gradual frequency increase across their > 10 ms temporal duration. A second much stronger subpacket is seen at frequencies around the local value of 1/4 fce with small wave normal angle (< 10 deg) and steeply rising df/dt. Smooth frequency and phase variation across and between the initial subpackets supports continuous phase trapping of resonant electrons and increased potential for MeV electron acceleration. The total energy gain for seed electrons with energies between 100 keV and 3 MeV ranges between 2 % and 15 %, in their nonlinear interaction with a single chorus element.

Tourism Theories, Concepts and Models

Tourism Theories, Concepts and Models: Explains why we think about tourism the way we do; Explores key theories, concepts and models that explain how tourism works; Is a comprehensive and cohesive text that develops a series of key ideas that deepens understanding and encourages critical thinking. This important text provides a critical overview of the core theories, concepts and ideas that have shaped the way we think about tourism. Divided into six parts, it takes the reader through the following areas to ensure thorough and coherent knowledge, looking at the important key theories, models and concepts, ensuring clear understanding and the ability for critical thinking: Setting the stage: looking at the interdisciplinary nature of tourism and its’ structure (5 core aspects of generation region, industry, destination region, transit route and tourist) How tourism works: explores the three core dimensions of tourism factors, attractions, access and government policy The evolution of tourism: examines the main models that have depicted the evolution of tourism destinations, economies and geographies. The tourist: motivations and influences of the tourist as an individual, covering typology, social demographic factors and constraints. Planning models: destination planning, scenarios and forecasting, including responses to current challenges Current issues: examines the theoretical and conceptual foundations for a range of contemporary issues that will affect tourism well into the future, including climate change, overtourism, crisis management and political change. Additional resources consist of web links, online videos and teaching reference materials. These can be found at www.goodfellowpublishers.com/TTCM from Academy fellows and other academic links explaining the ideas in the book. A must-have text for post graduate tourism and hospitality studies, as well as a key resource text for those teaching and studying tourism subjects at the later stages of undergraduate level.

15% enhancement of the photocurrent at the maximum power point of a thin film solar cell

A modulation doped region placed away from the charge generation region reduces recombination loss by enhancing the charge extraction.

Spiciness Anomalies in the Upper South Indian Ocean

This study investigates an isopycnal temperature/salinity T/S, or spiciness, anomaly in the upper south Indian Ocean for the period from 2004 to 2015 using observations and reanalyses. Spiciness anomalies at about 15°S on 24–26σθ are focused on, whose standard deviation is about 0.1 psu in salinity and 0.25°C in temperature, and they have a contribution to isobaric temperature variability comparable to thermocline heave. A plausible generation region of these anomalies is the southeastern Indian Ocean, where the 25σθ surface outcrops in southern winter, and the anticyclonic subtropical gyre advects subducted water equatorward. Unlike the Pacific and Atlantic, spiciness anomalies in the upper south Indian Ocean are not T/S changes in mode water, and meridional variations in SST and sea surface salinity in their generation region are not density compensating. It is possible that this peculiarity is owing to freshwater originating from the Indonesian Seas. The production of spiciness anomalies is estimated from surface heat and freshwater fluxes and the surface T/S relationship in the outcrop region, based on several assumptions including the dominance of surface fluxes in the surface T/S budget and effective mixed layer depth proposed by Deser et al. The result agrees well with isopycnal salinity anomalies at the outcrop line, which indicates that spiciness anomalies are generated by local surface fluxes. It is suggested that the Ningaloo Niño and El Niño–Southern Oscillation lead to interannual variability in surface heat flux in the southeastern Indian Ocean and contribute to the generation of spiciness anomalies.