Evidence for duskside relativistic electron precipitation (DREP) within the Earth's outer radiation belt has historically been seen in a few sets of high altitude balloon data (MAXIS, MINIS, ...INTERBOA), and in satellite data. We present statistical evidence that the relativistic electron precipitation events from the outer radiation belt with e‐folding energies > 0.5 MeV are concentrated in the dusk‐to‐midnight sector, based on a survey of data collected by the SAMPEX satellite from 1992 to 2004. A correlation between spectral hardness and duskside MLT is observed in our sample, the largest studied to date. Out of 9380 precipitation events within the bounce loss cone, 1048 are observed to have exponentially falling spectra with e‐folding energies above 0.5 MeV (“hard events”) and 1648 events below 0.2 MeV. Of the hard events, 81% occur within 12 h to 24 h MLT, compared to only 37% of events having e‐folding energies below 0.2 MeV. With microbursts removed from this softer population the percentage of duskside events rises to 46%. The hard events occur at slightly elevated levels of geomagnetic activity (Ap and Dst) relative to softer nonmicroburst events, but these correlations are much weaker than for microbursts. The hard events are observed to peak in occurrence at L ~ 5.5, significantly higher than nonmicroburst softer events, even though the opposite might be expected from compression of the magnetosphere due to the more negative average Dst of the hard events. The hard events are most prevalent during the declining phase of the 11 year solar cycle.
Key Points
The most relativistic precipitation events are in the dusk to midnight sector.
They are only slightly correlated with geomagnetic activity, unlike microbursts.
They peak at higher L than other events, and in the decline of the solar cycle.
We present the first evidence of electron microbursts observed near the equatorial plane in Earth's outer radiation belt. We observed the microbursts on 31 March 2017 with the Magnetic Electron Ion ...Spectrometer and Radiation Belt Storm Probes Ion Composition Experiment on the Van Allen Probes. Microburst electrons with kinetic energies of 29–92 keV were scattered over a substantial range of pitch angles, and over time intervals of 150–500 ms. Furthermore, the microbursts arrived without dispersion in energy, indicating that they were recently scattered near the spacecraft. We have applied the relativistic theory of wave‐particle resonant diffusion to the calculated phase space density, revealing that the observed transport of microburst electrons is not consistent with the hypothesized quasi‐linear approximation.
Plain Language Summary
Microbursts are a subsecond impulsive increase of electron precipitation from the outer Van Allen radiation belt into the atmosphere, believed to be an important loss process of radiation belt electrons. One possible source of microbursts is scattering of trapped radiation belt electrons by a plasma wave called chorus. Diffusion models show that chorus can both accelerate and scatter electrons into the atmosphere. Since microbursts have been previously observed by high‐altitude balloons and low Earth orbiting spacecraft, there has been little evidence that directly link the chorus wave and the microburst that it generated. We show evidence of microbursts and their progenitor waves observed deep inside the outer radiation belt by the Van Allen Probes spacecraft. The Van Allen Probes are configured to extensively study the wave and particle environment in the magnetosphere, which allows us to understand the microbursts' energy dependence, angular extent, and the scattering mechanism. This unique perspective enables us to understand how these electrons were transported by the chorus wave, and compare it to a hypothesized quasi‐linear diffusion model. Our results indicate that the observed transport of microburst electrons was not consistent with the hypothesized diffusion model.
Key Points
The first report of direct observation of microbursts at high altitude, near the equatorial plane
Microbursts' duration, flux enhancement, and energy spectra are similar to prior observations in LEO
Microburst generation is not consistent with a single quasi‐linear gyroresonant interaction with chorus waves
We studied the geomagnetic, plasmaspheric, and solar wind context of relativistic electron precipitation (REP) events seen with the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), ...Proton Electron Telescope (PET) to derive an exponential folding energy E0 for each event. Events with E0< 400 keV peak near midnight, and with increasing E0, the peak magnetic local time (MLT) moves earlier but never peaks as early as the MLT distribution of electromagnetic ion cyclotron (EMIC) waves in the outer belt, and a distinct component near midnight remains. Events with E0>750 keV near dusk (1400 < MLT < 2000) show correlations with solar wind dynamic pressure and proton density, AE index, negative Dst index, and an extended plasmasphere, all supporting an EMIC wave interpretation. Events with 500 keV <E0< 600 keV near midnight (MLT 2200–0200) do not show these correlations. Comparing these two samples to all events with E0>500 keV (“hard REP”), we estimate that roughly 45% of the whole population has the distributions of geomagnetic and solar wind parameters associated with EMIC waves, while 55% does not. We hypothesize that the latter events may be caused by current sheet scattering (CSS), which can be mistaken for EMIC wave scattering in that both simultaneously precipitate MeV electrons and keV protons. Since a large number of MeV electrons are lost in the near‐midnight hard REP events, and in the large number of E0< 400 keV events that show no dusk‐like peak at all, we conclude that CSS should be studied further as a possibly important loss channel for MeV electrons.
Key Points
Hard e‐ precipitation (folding energy >500 keV) has two populations: nearer dusk, with harder spectra, and nearer midnight, with softer spectra
The harder population shows evidence of being due to EMIC wave scattering, while the softer may be due to current sheet scattering
Concurrent proton precipitation does not necessarily help distinguish the two mechanisms
Tile-based online mapping systems have replaced traditional Web GIS systems, because of their improved speed and usability. The trend towards tile-base systems was started by Internet services ...companies, such as Google, Yahoo, and Microsoft. They have been followed by the traditional GIS community, government organizations and open source development communities, because tile based systems yield faster and work stronger with 3-D mapping tools. Tile-Based Geospatial Information Systems: Principles and Practice presents a detailed examination of the principles of tile-based systems. Topics include discussions of projections, coordinate systems, image processing, data basing and indexing requirements and web access. Attention is devoted to understanding and development of algorithms needed to make tile-based systems functional and efficient. In addition to the theoretical examination of the topic, this book includes detailed practical content helpful to those charged with implementation of tile-based systems. Case studies are provided in the last 2 chapters of this book. Tile-Based Geospatial Information Systems: Principles and Practice is designed for a professional audience composed of researchers, practitioners and government workers, focusing on geographic information systems and internet technologies and image processing techniques related to GIS. This book is also suitable for advanced-level students in computer science and geography as a secondary text or reference book.
Precipitation of relativistic electrons into the atmosphere has been suggested as the primary loss mechanism for radiation belt electrons during large geomagnetic storms. Here we investigate the ...geographical spread of precipitation as a result of the arrival of a coronal mass ejection (CME) on 21 January 2005. In contrast to previous statistical studies we provide one of the first attempts to describe the geographic and temporal variability of energetic particle precipitation on a global scale using an array of instruments. We combine data from subionospheric VLF radio wave receivers, the high‐altitude Miniature Spectrometer (MINIS) balloons, riometers, and pulsation magnetometers during the first hour of the event. There were three distinct types of energetic electron precipitation observed, one globally, one on the dayside, and one on the nightside. The most extensively observed form of precipitation was a large burst starting when the CME arrived at the Earth, where electrons from the outer radiation belt were lost to the atmosphere over a large region of the Earth. On the dayside of the Earth (10–15 MLT) the CME produced a further series of precipitation bursts, while on the nightside dusk sector (∼20 MLT) a continuous precipitation event lasting ∼50 min was observed at 2.5 < L < 3.7 along with Pc 1–2 pulsations observed with a ground‐based magnetometer. These observations suggest that the generation of energetic electron precipitation at the inner edge of the outer radiation belt from electromagnetic ion cyclotron (EMIC) wave scattering into the loss cone is the most direct evidence to date connecting EMIC activity and energetic precipitation.
Properties of Relativistic Bouncing Microbursts Wetzel, Wyatt; Sample, John; Engel, Eric ...
Journal of geophysical research. Space physics,
June 2024, 2024-06-00, 20240601, Letnik:
129, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Microbursts are short duration intensifications in precipitating electron flux that are believed to be a significant contributor to electron losses in the magnetosphere. Microbursts have been ...observed in the form of bouncing electron packets, which offer a unique opportunity to study their properties and importance as a loss process. We present a collection of bouncing microbursts observed by the HILT instrument on SAMPEX from 1994 to 2004. We analyze the locations of the bouncing microbursts in L and MLT and find they align well with the properties of relativistic microbursts as a whole. We find that the majority of bouncing microbursts observed by SAMPEX have scale sizes of ∼30 km at the point of observation, or ∼300 km when mapped to the magnetic equator. The time separation between the peaks of these bouncing microbursts is usually either half a bounce period or a whole bounce period.
Key Points
A large collection of bouncing microbursts from SAMPEX are found
A distribution of scale sizes for bouncing microbursts shows that most are a few tens of kilometers in size
There are roughly equal numbers of one way and two way bouncing microbursts observed in this study
The Myers-Briggs Type Indicator (MBTI) is a trusted and widely used personality assessment, having extensive applications in curriculum development and research in the organizational sciences, ...including public affairs education. The MBTI is a reliable and valid assessment of personality that identifies four cognitive processes, eight dichotomous preferences, and 16 distinct personality types and may be applied to a variety of topics of interest in public affairs education, including curriculum development and classroom instruction, student career and occupational counseling, and for researching of issues and problems in public agencies and nonprofit organizations. This article reviews the author's experience using the MBTI in a graduate course in human resource management for students enrolled in a Master of Public Administration program at large public university in the southeast United States. Those who consider using the MBTI are cautioned to become knowledgeable, qualified, and certified in the ethical use of this personality assessment.
Accurate knowledge of the full, three-dimensional electric field vector is of fundamental importance in understanding electrodynamics of a vast variety of space plasmas. However, heliophysics ...research still lacks access to the reliable parallel electric field measurements required to close many significant science questions. This uncertainty represents a significant barrier to progress in the field. The only way to close this major observational gap is a profound change in electric field instrument design. A new electric field instrument called Grotifer is now being designed to address the need for highly accurate three-dimensional electric field measurements while enabling lower cost missions and constellation missions in deep space. Grotifer (Giant rotifer) is a reference to the rotifer, also known as the “wheel animalcule.” Similarly, Grotifer consists of mounting detectors on two rotating plates, orthogonal to each other, on a non-rotating central body. The two rotating plates provide continuous high-accuracy three-dimensional measurements of both electric fields and magnetic fields. The Grotifer design leverages more than 50 years of expertise in delivering highly accurate spin plane electric field measurements, while overcoming inaccuracies generated by spin axis electric field measurements. Our current efforts focus on designing Grotifer as a SmallSat (27U CubeSat). That said, Grotifer could also become part of the payload on a much larger platform. In the future, one could imagine fleets of Grotifers studying electrodynamics at many points, facilitating differentiation between spatial and temporal dynamics. Plasma detectors could also be added to the rotating plates to cover the full phase space better than is done on spinning spacecraft, leading to more complete correlation studies of the fields and plasmas.
Who has not heard of the federal copyright law and been confused by the many interpretations of what a correctional educator can and cannot copy and distribute in the classroom? The author reviews ...the basic copyright law that includes examples and a summary of “fair use” principles applicable to correctional educators. The author also explains the impact of the TEACH Act of 2002 on correctional programs that use online and distance learning programs to educate employees and inmates. Failure to heed both of these federal laws could result in embarrassing litigation for a correctional institution.
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