Suprathermal Electron Acceleration Perpendicular to the Magnetic Field in the Topside Ionosphere

2020 ◽  
Vol 125 (2) ◽  
Author(s):  
Yangyang Shen ◽  
David J. Knudsen
Keyword(s):  
Magnetic Field ◽  
Electron Acceleration ◽  
Topside Ionosphere ◽  
Suprathermal Electron ◽  
The Magnetic Field

scholarly journals The expected imprint of flux rope geometry on suprathermal electrons in magnetic clouds

2009 ◽  
Vol 27 (10) ◽  
pp. 4057-4067 ◽  
Author(s):  
M. J. Owens ◽  
N. U. Crooker ◽  
T. S. Horbury
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Pitch Angle ◽  
Flux Rope ◽  
Magnetic Clouds ◽  
Magnetic Field Direction ◽  
Magnetic Flux Rope ◽  
Suprathermal Electron ◽  
Angle Scattering ◽  
The Magnetic Field

Abstract. Magnetic clouds are a subset of interplanetary coronal mass ejections characterized by a smooth rotation in the magnetic field direction, which is interpreted as a signature of a magnetic flux rope. Suprathermal electron observations indicate that one or both ends of a magnetic cloud typically remain connected to the Sun as it moves out through the heliosphere. With distance from the axis of the flux rope, out toward its edge, the magnetic field winds more tightly about the axis and electrons must traverse longer magnetic field lines to reach the same heliocentric distance. This increased time of flight allows greater pitch-angle scattering to occur, meaning suprathermal electron pitch-angle distributions should be systematically broader at the edges of the flux rope than at the axis. We model this effect with an analytical magnetic flux rope model and a numerical scheme for suprathermal electron pitch-angle scattering and find that the signature of a magnetic flux rope should be observable with the typical pitch-angle resolution of suprathermal electron data provided ACE's SWEPAM instrument. Evidence of this signature in the observations, however, is weak, possibly because reconnection of magnetic fields within the flux rope acts to intermix flux tubes.

scholarly journals Bi-layer structure of counterstreaming energetic electron fluxes: a diagnostic tool of the acceleration mechanism in the Earth's magnetotail

2010 ◽  
Vol 28 (2) ◽  
pp. 455-477 ◽  
Author(s):  
D. V. Sarafopoulos
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Layer Structure ◽  
Energetic Electron ◽  
Electron Acceleration ◽  
Recovery Phase ◽  
Curvature Radius ◽  
Distinct Region ◽  
Acceleration Mechanism ◽  
The Magnetic Field

Abstract. For the first time we identify a bi-layer structure of energetic electron fluxes in the Earth's magnetotail and establish (using datasets mainly obtained by the Geotail Energetic Particles and Ion Composition (EPIC/ICS) instrument) that it actually provides strong evidence for a purely spatial structure. Each bi-layer event is composed of two distinct layers with counterstreaming energetic electron fluxes, parallel and antiparallel to the local ambient magnetic field lines; in particular, the tailward directed fluxes always occur in a region adjacent to the lobes. Adopting the X-line as a standard reconnection model, we determine the occurrence of bi-layer events relatively to the neutral point, in the substorm frame; four (out of the shown seven) events are observed earthward and three tailward, a result implying that four events probably occurred with the substorm's local recovery phase. We discuss the bi-layer events in terms of the X-line model; they add more constraints for any candidate electron acceleration mechanism. It should be stressed that until this time, none proposed electron acceleration mechanism has discussed or predicted these layered structures with all their properties. Then we discuss the bi-layer events in terms of the much promising "akis model", as introduced by Sarafopoulos (2008). The akis magnetic field topology is embedded in a thinned plasma sheet and is potentially causing charge separation. We assume that as the Rc curvature radius of the magnetic field line tends to become equal to the ion gyroradius rg, then the ions become non-adiabatic. At the limit Rc=rg the demagnetization process is also under way and the frozen-in magnetic field condition is violated by strong wave turbulence; hence, the ion particles in this geometry are stochastically scattered. In addition, ion diffusion probably takes place across the magnetic field, since an intense pressure gradient is directed earthward; hence, ions are ejected tailward of akis. This way, in front of akis an "ion capsule region" is formed with net positive charge. In between them a distinct region with an electric field E⊥ orthogonal to the magnetic field is emerged; E⊥ in front of akis is directed earthward. The field-aligned and highly anisotropic energetic electron populations have probably resulted via spatially separated antiparallel and field-aligned electric fields being the very heart of the acceleration source. We assume that the ultimate cause for the field-aligned electric fields are the net positive capsule charge and the net negative charge trapped at the tip of akis; both charges will be eventually neutralized through field aligned currents, but they remain unshielded for sufficient time to produce the observed events.

scholarly journals Lower Hybrid Drive in Solar Magnetic Reconnection Regions: Implications for Electron Acceleration and Solar Heating

2001 ◽  
Vol 18 (4) ◽  
pp. 336-344 ◽  
Author(s):  
Iver H. Cairns
Keyword(s):  
Magnetic Field ◽  
Magnetic Reconnection ◽  
Charge Exchange ◽  
Electron Acceleration ◽  
Solar Radio Emission ◽  
Lower Hybrid ◽  
Neutral Atmosphere ◽  
Ion Heating ◽  
Lower Corona ◽  
The Magnetic Field

AbstractLower hybrid (LH) drive involves the resonant acceleration of electrons parallel to the magnetic field by lower hybrid waves, often driven by ions with ring or ring-beam distributions. Charge-exchange between hydrogen atoms and protons with relative motions perpendicular to the magnetic field leads to ring distributions of pickup ions, with concomitant perpedicular ion ‘heating’. This paper considers the combination of LH drive and charge-exchange in the outflow regions of magnetic reconnection sites in the solar chromosphere and lower corona, showing that the combined mechanism naturally predicts major perpendicular ion heating and parallel electron acceleration, and exploring the mechanism’s relevance to specific solar reconnection phenomena, heating of the solar atmosphere, and production of energetic electrons that generate solar radio emission. Although primarily qualitative, analysis shows that the mechanism has numerous attractive aspects, including perpendicular ion heating that increases linearly with ion mass, parallel electron acceleration, predicted ion and electron temperatures that span those of the chromosphere and lower corona, and parallel electron speeds spanning those for type III bursts. Applications to chromospheric explosive events and low-lying active regions, and to heating the chromosphere, appear particularly suitable. Sweeping of plasma frozen-in to chromospheric and coronal magnetic field lines across the neutral atmosphere due to motions of sub-photospheric fields represents an obvious and important generalisation of the mechanism away from reconnection sites. The requirements that the neutrals not be strongly collisionally coupled to the plasma and that sufficient neutrals are available for charge-exchange restricts the LH drive mechanism to above the photosphere but below where the corona is essentially fully ionised. LH drive may thus be important in heating the chromosphere and low corona while other heating mechanisms dominate at higher altitudes. Although attractive thus far, quantitative analyses of LH drive in these contexts are necessary before definitive conclusions are reached.

Recent scientific findings based on high-resolution core plasma imaging of the ionosphere with Swarm and ePOP

2020 ◽  
Author(s):  
David Knudsen
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Electron Acceleration ◽  
Alfven Waves ◽  
Distribution Functions ◽  
Alfvén Waves ◽  
Topside Ionosphere ◽  
High Time Resolution ◽  
Ion Heating ◽  
Suprathermal Electron

<p>The Thermal Ion Imagers on Swarm A-C, and the Suprathermal Electron/Ion Imager on ePOP (now “Swarm-E”) provide a unique view of charged particle distribution functions in the ionosphere at high time resolution (up to 100 images/s). Through high resolution, CCD-based imaging (~3000 pixels/image), ion drift velocity is derived from these images at a resolution of 20 m/s or better, and in general agreement with velocities derived from ground based radars [1] and an empirical convection model [2]. This talk reviews recent scientific applications of this technique, which are wide-ranging and include mechanisms of ion heating and upflow [3,4], M-I coupling via Alfven waves [5,6], electron acceleration and heating by Alfven waves [7,8, 9], intense plasma flows associated with “Steve” [10,11], and electrodynamics of large-scale FAC systems[ 12], among others. In addition, future opportunities made possible by these data will be discussed.</p><p>[1] Koustov et al. (2019), JGR, https://doi.org/10.1029/2018JA026245</p><p>[2] Lomidze et al. (2019), ESS, https://doi.org/10.1029/2018EA000546</p><p>[3] Shen and Knudsen (2020a), On O+ ion heating by BBELF waves at low altitude, JGR, in revision.</p><p>[4] van Irsel et al. (2020), Highly correlated ion upflow and electron temperature variations in the high latitude topside ionosphere, submitted to JGR.</p><p>[5] Pakhotin et al. (2020), JGR, https://doi.org/10.1029/2019JA027277</p><p>[6] Wu et al. (2020a), Swarm survey of Alfvenic fluctuations and their relation to nightside field-aligned current and auroral arcs systems, JGR, in revision.</p><p>[7] Liang et al. (2019), JGR, https://doi.org/10.1029/2019JA026679</p><p>[8] Wu et al. (2020b), e-POP observations of suprathermal electron bursts in the ionospheric Alfven resonator, GRL, submitted.  </p><p>[9] Shen and Knudsen (2020b), Suprathermal electron acceleration perpendicular to the magnetic field in the topside ionosphere, JGR, in press.</p><p>[10] Archer et al. (2019), JGR, https://doi.org/10.1029/2019GL082687</p><p>[11] Nishimura et al. (2019), JGR, https://doi.org/10.1029/2019GL082460</p><p>[12] Olifer et al (2020), Swarm observations of dawn/dusk asymmetries between Pedersen conductance in upward and downward FAC regions, submitted to JGR.</p><p> </p>

scholarly journals Electron Acceleration by Strong DC Electric Fields in Extragalactic Jets

2000 ◽  
Vol 195 ◽  
pp. 311-312
Author(s):  
Y. E. Litvinenko
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Current Sheet ◽  
Electric Fields ◽  
Electron Acceleration ◽  
Acceleration Time ◽  
Extragalactic Jets ◽  
Dc Electric Field ◽  
The Magnetic Field

Fast magnetic reconnection in extragalactic jets leads to electron acceleration by the DC electric field in the reconnecting current sheet. The maximum electron energy (γ > 106) and the acceleration time (< 106 s) are determined by the magnetic field dynamics in the sheet.

scholarly journals The Effect of the Ionosphere on the Controlled-Source Field in the Frequency Range between 0.4 and 95 Hz

2021 ◽  
Author(s):  
Pavel Tereshchenko
Keyword(s):  
Magnetic Field ◽  
Kola Peninsula ◽  
Geomagnetic Activity ◽  
The State ◽  
Topside Ionosphere ◽  
Frequency Range ◽  
Controlled Source ◽  
The Earth ◽  
Source Field ◽  
The Magnetic Field

The paper addresses the effect of the ionosphere on the ELF and lower frequency waves excited in the Earth-ionosphere waveguide by a controlled source. The experiment carried out on the Kola Peninsula is described and the results of measurements in the frequency range 0.4–95 Hz are presented. Non-monotonic behavior of the magnetic field with time is revealed. It is shown that variations in the magnetic field are related to the state of the ionosphere and depend on the geomagnetic activity. The importance of the effect of the topside ionosphere on the structure of the studied field is discussed.

scholarly journals Cyclotron resonance effects on electron acceleration by two lasers of different wavelengths

2012 ◽  
Vol 30 (2) ◽  
pp. 275-280 ◽  
Author(s):  
D.N. Gupta ◽  
K.P. Singh ◽  
H. Suk
Keyword(s):  
Magnetic Field ◽  
Cyclotron Resonance ◽  
Larmor Frequency ◽  
Electron Acceleration ◽  
Laser Frequency ◽  
Energy Gain ◽  
Additional Energy ◽  
Resonance Effects ◽  
Experimental Parameters ◽  
The Magnetic Field

AbstractCyclotron resonance effects on electron acceleration by two lasers of different wavelengths in the presence of a magnetic field have been investigated. Beating of two high-intensity lasers of different wavelengths, propagating in opposite direction to each other, can produce a high accelerating field gradient. An electron can be accelerated by such accelerating field to a sufficiently higher energy level. Additional energy gain has been observed due to the applied magnetic field. The magnetic field turns down the electrons to the acceleration region to extract more energy from the accelerating field produced by the beating of the lasers. At resonance, when the Larmor frequency is comparable to the laser frequency, this effect becomes more pronounced. Using some reasonable experimental parameters, we estimate the electron energy gain for this mechanism.

scholarly journals Double power-law spectra of energetic electrons in the Earth magnetotail

2013 ◽  
Vol 31 (1) ◽  
pp. 91-106 ◽  
Author(s):  
A. V. Artemyev ◽  
M. Hoshino ◽  
V. N. Lutsenko ◽  
A. A. Petrukovich ◽  
S. Imada ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Power Law ◽  
Relativistic Effects ◽  
Electron Acceleration ◽  
Relativistic Electrons ◽  
The Earth ◽  
Field Fluctuations ◽  
The Magnetic Field ◽  
Theoretical Results

Abstract. In this paper, we consider electron acceleration in the vicinity of X-line and corresponding formation of energy spectra. We develop an analytical model including the effect of the electron trapping by electrostatic fields and surfing acceleration. Speiser, Fermi and betatron mechanisms of acceleration are also taken into account. Analytical estimates are verified by the numerical integration of electron trajectories. The surfing mechanism and adiabatic heating are responsible for the formation of the double power-law spectrum in agreement with the previous studies. The energy of the spectrum knee is about ~150 keV for typical conditions of the Earth magnetotail. We compare theoretical results with the spacecraft observations of electron double power-law spectra in the magnetotail and demonstrate that the theory is able to describe typical energy of the spectra knee. We also estimate the role of relativistic effects and magnetic field fluctuations on the electron acceleration: the acceleration is more stable for relativistic electrons, while fluctuations of the magnetic field cannot significantly decrease the gained energy for typical magnetospheric conditions.

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