Spatial Distribution of Particle Precipitation in Terms of Energy Channels under Different Geomagnetic Conditions

2020 ◽  
Author(s):  
Han-Wen Shen ◽  
Jih-Hong Shue ◽  
John Dombeck ◽  
Hsien-Ming Li
Keyword(s):  
Spatial Distribution ◽  
Wave Scattering ◽  
High Energy ◽  
Low Energy ◽  
Electron Precipitation ◽  
Spatial Distributions ◽  
Static Potential ◽  
Physical Processes ◽  
High Energy Electrons ◽  
Energy Channels

<p>The geomagnetic activity can modulate the number and energy fluxes of precipitation and their spatial distributions. Most previous studies examined precipitation in terms of energy spectrum types associated with quasi-static potential structures (QSPS) acceleration, Alfvénic acceleration, and wave scattering under various geomagnetic conditions. In this study, we instead categorize precipitation according to energy channels of particles. The spatial distribution of the precipitation for various energy channels is also derived under different geomagnetic conditions. Our results indicate that regardless of active and quiet times, low-energy (high-energy) precipitation is mostly distributed on the dayside (nightside). By comparing with past results, we infer that electron precipitation is mainly caused by QSPS and Alfvénic acceleration for most cases; however, the high-energy electrons during quiet times are predominantly created by wave scattering. For high-energy precipitation, the dawn-dusk asymmetry of the spatial distribution during active times is found to be opposite of that during quiet times. Based on their spatial distributions, we suggest that the high-energy precipitation during quiet times is dominated by the curvature and gradient drifts, while that during active times is mainly affected by physical processes related to substorms in the magnetotail.</p>

scholarly journals Symmetric and triangle-shaped variability of blazars

2014 ◽  
Vol 10 (S313) ◽  
pp. 97-98
Author(s):  
Kenji Yoshida
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Low Energy ◽  
Light Curves ◽  
X Ray ◽  
High Energy Electrons ◽  
Flux Variability ◽  
Low Energy Electrons ◽  
Flux Increase ◽  
Rise Phase

AbstractSymmetric and triangle-shaped flux variability in X-ray and gamma-ray light curves is observed from many blazars. We derived the X-ray spectrum changing in time by using a kinetic equation of high energy electrons. Giving linearly changing the injection of low energy electrons into accelerating and emitting region, we obtained the preliminary results that represent the characteristic X-ray variability of the linear flux increase with hardening in the rise phase and the linear decrease with softening in the decay phase.

On Lensless Imaging of Organics with Neutrons, X-Rays, Helium Atoms and Low Energy Electrons: Damage and Iterative Phase Retrieval

2001 ◽  
Vol 7 (S2) ◽  
pp. 268-269
Author(s):  
J.C.H. Spence ◽  
U. Weierstall ◽  
J. Fries
Keyword(s):  
Phase Retrieval ◽  
Iterative Algorithms ◽  
High Energy ◽  
Low Energy ◽  
X Rays ◽  
Noise Sources ◽  
Helium Atoms ◽  
High Energy Electrons ◽  
Elastic Event ◽  
Low Energy Electrons

Recent experiments with X-rays and high energy electrons have shown that image recovery from diffracted intensities is possible for non-periodic objects using iterative algorithms. Application of these methods to biological molecules raises the crucial problem of radiation damage, which may be quantified by Q = ΔE σi/σe, the amount of energy deposited by inelastic events per elastic event. Neutrons, helium atoms and low energy electrons below most ionization thresholds produce the smallest values of Q (see for TMV imaged at 60 eV). For neutrons (λ = 10-2Å, and deuterated, 15N-abelled molecules) Q is ∼3000 times smaller (∼50 times for λ = 1.8Å) than for electrons (80- 500keV) and about 4x 106 times smaller than for soft X-rays (1.5Å). Since σe for neutrons is about 105 times smaller than for electrons (and about 10 times smaller than for soft X-rays), a 105 times higher neutron dose is required to obtain the same S/N in a phase contrast image compared with electrons, if other noise sources are absent.

scholarly journals Substorm correlated absorption on a 3200 km trans-auroral HF propagation path

1996 ◽  
Vol 14 (2) ◽  
pp. 182-190 ◽  
Author(s):  
S. E. Milan ◽  
T. B. Jones ◽  
M. Lester ◽  
E. M. Warrington ◽  
G. D. Reeves
Keyword(s):  
High Energy ◽  
Electron Precipitation ◽  
Propagation Path ◽  
Expansion Phase ◽  
Experimental Campaign ◽  
High Energy Electrons ◽  
Hf Propagation ◽  
Median Level ◽  
D Region ◽  
Asymmetric Behaviour

Abstract. A high-frequency transmitter located at Clyde River, NWT, Canada, and a receiver located near Boston, USA, provide a 3200 km trans-auroral, near-meridional propagation path over which the propagation characteristics have been measured. Out of the fourteen frequencies in the HF band sampled every hour for the duration of the experimental campaign (16 January–8 February 1989), the signal level measurements of 6.800 MHz transmissions were selected in order to determine the extent and occurrence of auroral absorption. The median level of auroral absorption along the path is found to increase with geomagnetic activity, quantified by the index Kp, with the increase being greater in the post-midnight sector than in the pre-midnight sector. This asymmetric behaviour is attributed to the precipitation of high energy electrons into the midnight and morning sector auroral D region. The measured diurnal variation in the median level of absorption is consistent with previous models describing the extent and magnitude of auroral absorption and electron precipitation. Individual substorms, identified from geosynchronous satellite data, are found to cause short-lived absorption events in the HF signal level of ~30 dB at 6.800 MHz. The occurrence of substorm correlated auroral absorption events is confined to the midnight and morning sectors, consistent with the location of the electron precipitation. The magnitude of absorption is related to the magnetotail stress during the substorm growth phase and the magnetotail relaxation during the substorm expansion phase onset. The absorption magnitude and the occurrence of substorms during the period of the campaign increase at times of high Kp , leading to an increase in median auroral absorption during disturbed periods.

scholarly journals Longitudinal hotspots in the mesospheric OH variations due to energetic electron precipitation

2014 ◽  
Vol 14 (2) ◽  
pp. 1095-1105 ◽  
Author(s):  
M. E. Andersson ◽  
P. T. Verronen ◽  
C. J. Rodger ◽  
M. A. Clilverd ◽  
S. Wang
Keyword(s):  
Geomagnetic Activity ◽  
Function Analysis ◽  
Energetic Electron ◽  
High Energy ◽  
Electron Precipitation ◽  
Data Sets ◽  
Activity Levels ◽  
Atmospheric Conditions ◽  
Longitudinal Response ◽  
High Energy Electrons

Abstract. Using Microwave Limb Sounder (MLS/Aura) and Medium Energy Proton and Electron Detector (MEPED/POES) observations between 2005–2009, we study the longitudinal response of nighttime mesospheric OH to radiation belt electron precipitation. Our analysis concentrates on geomagnetic latitudes from 55–72° N/S and altitudes between 70 and 78 km. The aim of this study is to better assess the spatial distribution of electron forcing, which is important for more accurate modelling of its atmospheric and climate effects. In the Southern Hemisphere, OH data show a hotspot, i.e. area of higher values, at longitudes between 150° W–30° E, i.e. poleward of the Southern Atlantic Magnetic Anomaly (SAMA) region. In the Northern Hemisphere, energetic electron precipitation-induced OH variations are more equally distributed with longitude. This longitudinal behaviour of OH can also be identified using Empirical Orthogonal Function analysis, and is found to be similar to that of MEPED-measured electron fluxes. The main difference is in the SAMA region, where MEPED appears to measure very large electron fluxes while MLS observations show no enhancement of OH. This indicates that in the SAMA region the MEPED observations are not related to precipitating electrons, at least not at energies >100 keV, but rather to instrument contamination. Analysis of selected OH data sets for periods of different geomagnetic activity levels shows that the longitudinal OH hotspot south of the SAMA (the Antarctic Peninsula region) is partly caused by strong, regional electron forcing, although atmospheric conditions also seem to play a role. Also, a weak signature of this OH hotspot is seen during periods of generally low geomagnetic activity, which suggests that there is a steady drizzle of high-energy electrons affecting the atmosphere, due to the Earth's magnetic field being weaker in this region.

scholarly journals Quantum Mechanisms of Electron and Positron Acceleration through Nonlinear Compton Scatterings and Nonlinear Breit-Wheeler Processes in Coherent Photon Dominated Regime

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Bo Zhang ◽  
Zhimeng Zhang ◽  
Zhi-gang Deng ◽  
Jian Teng ◽  
Shu-kai He ◽  
...  
Keyword(s):  
Charged Particles ◽  
High Energy ◽  
Low Energy ◽  
Electric Force ◽  
Quantum Processes ◽  
High Energies ◽  
Large Numbers ◽  
High Energy Electrons ◽  
Electrons And Positrons ◽  
Proof Of Principle

AbstractElectric force is presently the only means in laboratory to accelerate charged particles to high energies, corresponding acceleration processes are classical and continuous. Here we report on how to accelerate electrons and positrons to high energies using ultra intense lasers (UIL) through two quantum processes, nonlinear Compton scattering and nonlinear Breit-Wheeler process. In the coherent photon dominated regime of these two processes, the former can effectively boost electrons/positrons and the latter can produce high energy electrons and positrons with low energy γ photons. The energy needed for such quantum acceleration (QA) is transferred from large numbers of coherent laser photons through the two quantum processes. QA also collimate the generated high energy electrons and positrons along the laser axis and the effective acceleration distance is of microscopic dimensions. Proof of principle QA experiment can be performed on 100 petawatt (PW) scale lasers which are in building or planning.

scholarly journals The Role of Low Energy Electrons in Radiobiology and Cancer Treatment

2021 ◽  
Author(s):  
Sasan Esmaili ◽  
Farzaneh Allaveisi
Keyword(s):  
Cancer Treatment ◽  
Anticancer Agents ◽  
High Energy ◽  
Low Energy ◽  
New Drugs ◽  
Particle Radiation ◽  
Energy Radiation ◽  
Regulatory Pathways ◽  
High Energy Electrons ◽  
Low Energy Electrons

Low energy radiation can be produced by all types of high energy radiation. Studies of low energy particle radiation help us to understand the chemistry induced by high energy radiations. Low energy electrons are capable of chemical selectivity in contrast to high energy electrons due to the large number of open dissociative channels in the former case and their resonant nature. Among different types of radiation, low energy electrons have a higher cross-section to DNA damage and they have an important role in the synergistic effect between radiation and chemotherapy anticancer agents in cancer treatment. Analysis of these combined records helps assign function of cells, identify metabolic and regulatory pathways and suggest targets for diagnostics and therapeutics identify animal models to develop new drugs, among other goals of biomedical interest.

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