scholarly journals Mapping travelling convection vortex events with respect to energetic particle boundaries

1998 ◽  
Vol 16 (8) ◽  
pp. 891-899 ◽  
Author(s):  
T. Moretto ◽  
A. Yahnin
Keyword(s):  
Electric Fields ◽  
Energetic Particle ◽  
Energetic Electron ◽  
High Energy ◽  
Electron Trapping ◽  
Particle Measurements ◽  
High Energy Electrons ◽  
Precipitation Boundary ◽  
Magnetometer Data ◽  
Electric Fields And Currents

Abstract. Thirteen events of high-latitude ionospheric travelling convection vortices during very quiet conditions were identified in the Greenland magnetometer data during 1990 and 1991. The latitudes of the vortex centres for these events are compared to the energetic electron trapping boundaries as identified by the particle measurements of the NOAA 10 satellite. In addition, for all events at least one close DMSP overpass was available. All but one of the 13 cases agree to an exceptional degree that: the TCV centres are located within the region of trapped, high energy electrons close to the trapping boundary for the population of electrons with energy greater than >100 keV. Correspondingly, from the DMSP data they are located within the region of plasmasheet-type precipitation close to the CPS/BPS precipitation boundary. That is, the TCV centres map to deep inside the magnetosphere and not to the magnetopause.Key Words. Ionosphere (Electric fields and currents; Particle precipitation) · Magnetospheric physics (Magnetosphere-ionosphere interaction)

scholarly journals Astrid-2 and ground-based observations of the auroral bulge in the middle of the nightside convection throat

2001 ◽  
Vol 19 (6) ◽  
pp. 633-641 ◽  
Author(s):  
G. T. Marklund ◽  
T. Karlsson ◽  
P. Eglitis ◽  
H. Opgenoorth
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Large Scale ◽  
Current Model ◽  
Energetic Electron ◽  
Auroral Oval ◽  
Plasma Convection ◽  
Magnetometer Data ◽  
Electric Fields And Currents ◽  
Good Agreement

Abstract. Results concerning the electrodynamics of the nightside auroral bulge are presented based on simultaneous satellite and ground-based observations. The satellite data include Astrid-2 measurements of electric fields, currents and particles from a midnight auroral oval crossing and Polar UVI images of the large-scale auroral distribution. The ground-based observations include STARE and SuperDARN electric fields and magnetic records from the Greenland and MIRACLE magnetometer network, the latter including stations from northern Scandinavia north to Svalbard. At the time of the Astrid-2 crossing the ground-based data reveal intense electrojet activity, both to the east and west of the Astrid-2 trajectory, related to the Polar observations of the auroral bulge but not necessarily to a typical substorm. The energetic electron fluxes measured by Astrid-2 across the auroral oval were generally weak being consistent with a gap observed in the auroral luminosity distribution. The electric field across the oval was directed westward, intensifying close to the poleward boundary followed by a decrease in the polar cap. The combined observations suggests that Astrid-2 was moving close to the separatrix between the dusk and dawn convection cells in a region of low conductivity. The constant westward direction of the electric field across the oval indicates that current continuity was maintained, not by polarisation electric fields (as in a Cowling channel), but solely by localized up- and downward field-aligned currents in good agreement with the Astrid-2 magnetometer data. The absence of a polarisation electric field and thus of an intense westward closure current between the dawn and dusk convection cells is consistent with the relatively weak precipitation and low conductivity in the convection throat. Thus, the Cowling current model is not adequate for describing the electrodynamics of the nightside auroral bulge treated here.Key words. Ionosphere (auroral ionosphere; electric fields and currents; plasma convection)

scholarly journals Estimates of the field-aligned current density in current-carrying filaments using auroral zone ground-based observations

2001 ◽  
Vol 19 (7) ◽  
pp. 699-706 ◽  
Author(s):  
M. A. Danielides ◽  
S. Shalimov ◽  
J. Kangas
Keyword(s):  
Electric Fields ◽  
Low Frequency ◽  
Threshold Value ◽  
Auroral Zone ◽  
Local Current ◽  
Magnetometer Data ◽  
Late Evening ◽  
Field Lines ◽  
Electric Fields And Currents ◽  
Upper Ionosphere

Abstract. We described the ground signatures of dynamic substorm features as observed by the imaging riometer, magnetometers and all-sky camera (ASC) at Kilpisjärvi, Finland on 5 and 25 October 1999 during the late evening hours. The magnetometer data was consistent with the motion of up-ward field-aligned currents (FACs) associated with absorption patches moving within the field of view of the riometer. We used riometer data in order to estimate the intensity of FACs associated with these local current-carrying filaments. It is shown that during these events, the estimated FAC intensity exceeds a threshold value that corresponds to the excitation of the low-frequency turbulence in the upper ionosphere. As a result, a quasi-oscillating regime of anomalous resistivity on the auroral field lines can give rise to the burst-like electron acceleration responsible for simultaneously observed auroral forms and bursts of Pi1B pulsations.Key words. Ionosphere (active experiments; auroral ionosphere; electric fields and currents)

scholarly journals A superconducting switch actuated by injection of high-energy electrons

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M. F. Ritter ◽  
A. Fuhrer ◽  
D. Z. Haxell ◽  
S. Hart ◽  
P. Gumann ◽  
...  
Keyword(s):  
Critical Current ◽  
Electric Fields ◽  
Physical Mechanism ◽  
High Energy ◽  
Critical Currents ◽  
Metal Nanowires ◽  
Resistive State ◽  
Gate Electrodes ◽  
High Energy Electrons ◽  
The Impact

AbstractRecent experiments with metallic nanowires devices seem to indicate that superconductivity can be controlled by the application of electric fields. In such experiments, critical currents are tuned and eventually suppressed by relatively small voltages applied to nearby gate electrodes, at odds with current understanding of electrostatic screening in metals. We investigate the impact of gate voltages on superconductivity in similar metal nanowires. Varying materials and device geometries, we study the physical mechanism behind the quench of superconductivity. We demonstrate that the transition from superconducting to resistive state can be understood in detail by tunneling of high-energy electrons from the gate contact to the nanowire, resulting in quasiparticle generation and, at sufficiently large currents, heating. Onset of critical current suppression occurs below gate currents of 100fA, which are challenging to detect in typical experiments.

Low-altitude magnetic reconnection events as possible drivers of Jupiter’s polar auroras

2021 ◽  
Author(s):  
Adam Masters ◽  
William Dunn ◽  
Tom Stallard ◽  
Harry Manners ◽  
Julia Stawarz
Keyword(s):  
Magnetic Reconnection ◽  
Electric Fields ◽  
High Energy ◽  
Space Environment ◽  
Polar Regions ◽  
Particle Interactions ◽  
High Energy Electrons ◽  
Surrounding Space ◽  
Auroral Emissions ◽  
Static Electric Fields

<p>Charged particles impacting Jupiter’s atmosphere represent a major energy input, generating the most powerful auroral emissions in the Solar System. Most auroral features have now been explained as the result of impacting particles accelerated by quasi-static electric fields and/or wave-particle interactions in the surrounding space environment. However, the reason for Jupiter’s bright and dynamic polar regions remains a long-standing mystery. Recent spacecraft observations above these regions of “swirl” auroras have shown that high-energy electrons are regularly beamed away from the planet, which is inconsistent with traditional auroral drivers. The unknown downward-electron-acceleration mechanism operating close to Jupiter represents a gap in our fundamental understanding of planetary auroras. Here we propose a possible explanation for both the swirl auroras and the upward electron beams. We show that the perturbations of Jupiter’s strong magnetic field above the swirl regions that are driven by dynamics of the distant space environment can cause magnetic reconnection events at altitudes as low as ~0.2 Jupiter radii, rapidly releasing energy and potentially producing both the required downward and observed upward beams of electrons. Such an auroral driver has never before been postulated, resembling physics at work in the solar corona.</p>

scholarly journals All-optical quasi-monoenergetic GeV positron bunch generation by twisted laser fields

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Jie Zhao ◽  
Yan-Ting Hu ◽  
Yu Lu ◽  
Hao Zhang ◽  
Li-Xiang Hu ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Electric Fields ◽  
High Energy Physics ◽  
Energetic Electron ◽  
Three Dimensional ◽  
High Energy ◽  
Electron Positron ◽  
All Optical ◽  
Positron Bunch ◽  
Energy Physics

AbstractGeneration of energetic electron-positron pairs using multi-petawatt (PW) lasers has recently attracted increasing interest. However, some previous laser-driven positron beams have severe limitations in terms of energy spread, beam duration, density, and collimation. Here we propose a scheme for the generation of dense ultra-short quasi-monoenergetic positron bunches by colliding a twisted laser pulse with a Gaussian laser pulse. In this scheme, abundant γ-photons are first generated via nonlinear Compton scattering and positrons are subsequently generated during the head-on collision of γ-photons with the Gaussian laser pulse. Due to the unique structure of the twisted laser pulse, the positrons are confined by the radial electric fields and experience phase-locked-acceleration by the longitudinal electric field. Three-dimensional simulations demonstrate the generation of dense sub-femtosecond quasi-monoenergetic GeV positron bunches with tens of picocoulomb (pC) charge and extremely high brilliance above 1014 s−1 mm−2 mrad−2 eV−1, making them promising for applications in laboratory physics and high energy physics.

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 ULYSSES observations of energetic particle acceleration and the superposed CME and CIR events of November 1992

1996 ◽  
Vol 14 (4) ◽  
pp. 400-410 ◽  
Author(s):  
T. L. Lim ◽  
J. J. Quenby ◽  
M. K. Reuss ◽  
E. Keppler ◽  
H. Kunow ◽  
...  
Keyword(s):  
Energetic Particle ◽  
High Energy ◽  
Alpha Particles ◽  
Alternative Possibilities ◽  
Shock Acceleration ◽  
Diffusive Shock Acceleration ◽  
Magnetometer Data ◽  
Proton Data ◽  
Mass Ejection ◽  
Unique Study

Abstract. During November 1992, a series of forward and reverse shocks passed the ULYSSES spacecraft. Spectral and anisotropy measurements are reported for protons and alpha particles between 0.28 and 6 MeV observed by the Energetic Particle Composition Experiment, data recorded by the Magnetometer Experiment and the high-energy (2.7–300 MeV) proton data from the Kiel Electron Telescope. An analysis of energetic particle, plasma and magnetometer data from ULYSSES has allowed a unique study of the corresponding arrival of fare particles, particles within a corotating interaction region and particles transported with a coronal mass ejection. We present an analysis of these data in terms of possible diffusive shock acceleration but conclude that this is likely to be incompatible with the short transit time of the particles. Shock drift acceleration of particles with energies 0.3 MeV/nucleon or solar acceleration followed by particle trapping behind the shock front are alternative possibilities.

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