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I G Richardson - One of the best experts on this subject based on the ideXlab platform.
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voyager observations in the distant heliosheath an analogy with isee 3 observations in the deep Geomagnetic Tail
Advances in Space Research, 2017Co-Authors: I G RichardsonAbstract:Abstract We suggest an analogy between energetic particle and magnetic field observations made by the Voyager 1 spacecraft in the distant heliosheath at 122 AU in August 2012, and those made in the distant Geomagnetic Tail by the ISEE 3 spacecraft in 1982–1983, despite large differences in the time and distance scales. The analogy suggests that in August, 2012, Voyager 1 may not have moved from the anomalous cosmic ray (ACR)-dominated heliosheath into the interstellar medium but into a region equivalent to the “lobes” of the Geomagnetic Tail, composed of heliospheric field lines which have reconnected with the interstellar medium beyond the spacecraft and so are open to the entry of cosmic rays, while heliospheric particles (e.g., ACRs) are free to escape, and which maintain a ∼Parker spiral configuration. The heliopause, analogous to the magnetopause forming the outer boundary of the lobes, may then lie beyond this so-called “heliocliff”. Even if this analogy is incorrect, the remarkable similarities between the energetic particle and magnetic field observations in these very different regions are worth noting.
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effects on the distant Geomagnetic Tail of a fivefold density drop in the inner sheath region of a magnetic cloud a joint wind ace study
Advances in Space Research, 2009Co-Authors: C J Farrugia, I G Richardson, N V Erkaev, N C Maynard, P E Sandholt, D Langmayr, K W Ogilvie, A Szabo, U TaubenschussAbstract:Abstract Using a serendipitous configuration of the ACE and Wind spacecraft, we monitor the response of the distant Geomagnetic Tail (∼ −220 R E ) to an abrupt, approx. fivefold pressure drop (from ∼19.0 to ∼3.5 nPa) at the front boundary of a magnetic cloud (MC) on November 20, 2003. The interplanetary data are from ACE in orbit around the L1 point. The far-Tail observations are from Wind, which was nominally in the magnetosheath, separated from the Sun–Earth line by ∼ 40 R E . The magnetic field in the innermost sheath region of the MC had a large B y ( ∼ 30 nT ) and substantial and variable flows lateral to the Sun–Earth line. There was also a significant northward field (∼35 nT), unique in the vicinity of this MC. These extreme values are reached in a filament forming the earliest relic of material accreted by the MC en route to Earth. The effects resulting from these on the far Geomagnetic Tail are: (1) expansion, (2) Tail twisting, and (3) Tail tilting. These extreme conditions were in part responsible for a crossing by Wind of a neutral sheet which is tilted by ∼85° to the ecliptic. Further, Wind made two successive excursions deep into the Geomagnetic Tail, in the first of which a Tailward flow burst of ∼1200 km/s was observed. The dayside part of the interaction of the sudden and large dynamic pressure drop with the bow shock is studied with a local 3D MHD simulation. This work is a contribution to the area ICME/MC-sheaths–magnetosheath interactions.
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energetic 0 2 mev electron bursts observed by isee 3 in the deep 240 re Geomagnetic Tail
Journal of Geophysical Research, 1993Co-Authors: I G Richardson, J A Slavin, C J Owen, T T Von RosenvingeAbstract:The Goddard Space Flight Center medium-energy cosmic ray experiment on ISEE 3 made as yet unreported observations of 0.2-2 MeV electrons and >1 MeV/amu ions in the deep Geomagnetic Tail out to ∼240 RE from the Earth during the geoTail mission in 1982-1983. The most notable feature of these data is the presence of brief (<1-hour duration) electron bursts which exceed the instrument background of ∼0.02 (s cm2; sr MeV)−1. These occur most frequently and have the highest intensities, within ∼80 RE of the Earth and are relatively absent at greater distances downTail. Approximately 60% of these bursts are observed in the plasma sheet. These occur most frequently on closed field lines connected to the Earth, based on their association with slow earthward or mixed plasma sheet flows and northward directed magnetic fields. The near-absence of such events beyond ∼80 RE downTail provides evidence for predominantly open rather than closed magnetic field structures in the plasma sheet beyond this distance downTail. The observations are consistent with the presence of a distant neutral line in the Tail plasma sheet at an average distance of ∼80 RE from the Earth. Approximately 30% of plasma sheet electron bursts are associated with north then south turning magnetic field deviations and fast Tailward plasma flows, which may be related to the expulsion of plasmoids following substorm onsets. Approximately 20% of all the electron bursts are seen in the Tail lobes, probably associated with encounters with the plasma sheet boundary (separatrix) layer. The lobe events show no clear trend in intensity with downTail distance. We show examples of plasma sheet and lobe electron bursts that are clearly associated with substorms, indicating that temporal as well as spatial variations in the energetic electron intensity do indeed occur in the Geomagnetic Tail. Finally, ∼20% of the electron bursts are observed in the magnetosheath. The intensity of magnetosheath bursts also falls off with downTail distance such that they are nearly absent beyond ∼100 RE from the Earth.
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theory and observation of energetic ions in the lobes of the Geomagnetic Tail
Planetary and Space Science, 1991Co-Authors: C J Owen, S W H Cowley, I G Richardson, A Balogh, B T TsurutaniAbstract:Abstract In a recent paper, Owen et al. (1990, Planet. Space Sci.38, 851) presented a model which attempts to explain the nature of the pitch angle distributions of energetic ions within the lobes of the distant Geomagnetic Tail. There has, however, been little discussion of the relevant observations in the literature, and the motivation for the above mentioned work was largely based on unpublished observations plus a few examples presented in the paper itself. In this paper we aim to rectify this situation. After briefly reviewing the model and its results, we present energetic (E ⩾ 35 keV>) ion data from the ISEE-3 spacecraft obtained during early 1983, when the spacecraft made several traversals of the distant Geomagnetic Tail (xGSE = − 230 RE). The data demonstrate that during quiet periods in which the spacecraft is continuously located in the Tail lobes, the pitch angle distribution is observed to be highly anisotropic, being peaked closely perpendicular to the magnetic field direction, but with a small net flow in the antisunward direction, in agreement with the model results. Further predictions of the model, concerning the variation of the lobe energetic ion distributions with position in the lobes, are compared to observations made as the spacecraft performed a traversal of the lobe. Finally, since the model indicates that a more isotropic distribution should exist in the Tail lobe during solar particle events, we present data from such a period for further comparison. In all the above cases, good agreement is demonstrated between the data and the expectations of the model.
D J Williams - One of the best experts on this subject based on the ideXlab platform.
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considerations of source transport acceleration heating and loss processes responsible for Geomagnetic Tail particle populations
Space Science Reviews, 1997Co-Authors: D J WilliamsAbstract:The relative importance of the two known substantive sources of magnetospheric particles, the solar wind and the ionosphere, remains largely undetermined throughout much of the magnetosphere. For the specific case of the Geomagnetic Tail however, the development of a remarkable family of models incorporating the kinetics of charged particle motion, has opened the possibility of determining relative strengths and geometries of the solar wind and ionospheric sources that are responsible for observed Tail particle populations. Once source strengths and geometries are determined, transport paths and mechanisms can be identified, in turn leading to a determination of acceleration/heating mechanisms and locations. Loss processes then determine the quasi-equilibrium particle distributions in the Tail. A quantitative understanding of the Tail and its dynamics requires extensive, deTailed comparisons of data and model results. Data obtained over the past two decades have led to the result that for energies at least above ~ 1 eV, both sources are well mixed throughout the Tail and that the solar wind is the dominant source. New, unique data sets have provided the initial data comparisons with the models and show great promise in deconvolving source strengths and geometries and ultimately understanding the formation and behavior of the Tail.
T Tajima - One of the best experts on this subject based on the ideXlab platform.
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collisionless conductivity and stochastic heating of the plasma sheet in the Geomagnetic Tail
Journal of Geophysical Research, 1991Co-Authors: W Horton, T TajimaAbstract:The chaotic single particle orbits in the Geomagnetic Tail are used to calculate the collisionless conductivity. It is shown that the stochasticity from inhomogeneous magnetic fields leads to a power law decay of the single particle correlation function similar to an elastic collisional process. The height-integrated dissipative part of the collisionless conductivity governs the irreversible stochastic heating of the plasma sheet. Both exponentially growing reconnection type magnetic perturbations and a sinusoidal pulse with a half period up to 1 hour in duration are used to analyze the plasma sheet heating.
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transport from chaotic orbits in the Geomagnetic Tail
Geophysical Research Letters, 1991Co-Authors: W Horton, T TajimaAbstract:The rapid change in direction and magnitude of the magnetic field vector in crossing the quasineutral sheet in the Geomagnetic Tail leads to deterministic Hamiltonian chaos. The finite correlation times in the single particle orbits due to the continuum of orbital frequencies leads to well-defined collisionless transport coefficients. The transport coefficients are derived for plasma trapped in the quasineutral sheet.
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decay of correlations and the collisionless conductivity in the Geomagnetic Tail
Geophysical Research Letters, 1990Co-Authors: W Horton, T TajimaAbstract:The collisionless electrical conductivity is calculated for the Geomagnetic Tail from the stochastic orbits in the plasma sheet. The new conductivity formula is important for the stochastic heating of the plasma sheet and modifies the Galeev-Zelenyi formulas for the collisionless reconnection growth rate for Geomagnetic substorms.
Patrick Canu - One of the best experts on this subject based on the ideXlab platform.
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solitary electromagnetic pulses detected with super alfvenic flows in earth s Geomagnetic Tail
Physical Review Letters, 2007Co-Authors: G K Parks, F S Mozer, M Wilber, I Dandouras, H Reme, E Lucek, A N Fazakerley, M L Goldstein, C Gurgiolo, Patrick CanuAbstract:: Solitary nonlinear (deltaB/B>>1) electromagnetic pulses have been detected in Earth's Geomagnetic Tail accompanying plasmas flowing at super-Alfvenic speeds. The pulses in the current sheet had durations of approximately 5 s, were left-hand circularly polarized, and had phase speeds of approximately the Alfven speed in the plasma frame. These pulses were associated with a field-aligned current J(parallel) and observed in low density (approximately 0.3 cm(-3)), high temperature (T(e) approximately T(i) approximately 3x10(7) K), and beta approximately 10 plasma that included electron and ion beams streaming along B. The wave activity was enhanced from below the ion cyclotron frequency to electron cyclotron and upper hybrid frequencies. The deTailed properties suggest the pulses are nonlinearly steepened ion cyclotron or Alfven waves.
G K Parks - One of the best experts on this subject based on the ideXlab platform.
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electron flat top distributions and cross scale wave modulations observed in the current sheet of Geomagnetic Tail
Physics of Plasmas, 2017Co-Authors: G K Parks, Duo Zhao, Suiyan Fu, Qiugang Zong, Tong WuAbstract:We present new observations of electron distributions and the accompanying waves during the current sheet activities at ∼60 RE in the Geomagnetic Tail detected by the ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun) spacecraft. We find that electron flat-top distribution is a common feature near the neutral sheet of the Tailward flowing plasmas, consistent with the electron distributions that are shaped in the reconnection region. Whistler mode waves are generated by the anisotropic electron temperature associated with the electron flat-top distributions. These whistler mode waves are modulated by low frequency ion scale waves that are possibly excited by the high-energy ions injected during the current sheet instability. The magnetic and electric fields of the ion scale waves are in phase with electron density variations, indicating that they are compressional ion cyclotron waves. Our observations present examples of the dynamical processes occu...
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solitary electromagnetic pulses detected with super alfvenic flows in earth s Geomagnetic Tail
Physical Review Letters, 2007Co-Authors: G K Parks, F S Mozer, M Wilber, I Dandouras, H Reme, E Lucek, A N Fazakerley, M L Goldstein, C Gurgiolo, Patrick CanuAbstract:: Solitary nonlinear (deltaB/B>>1) electromagnetic pulses have been detected in Earth's Geomagnetic Tail accompanying plasmas flowing at super-Alfvenic speeds. The pulses in the current sheet had durations of approximately 5 s, were left-hand circularly polarized, and had phase speeds of approximately the Alfven speed in the plasma frame. These pulses were associated with a field-aligned current J(parallel) and observed in low density (approximately 0.3 cm(-3)), high temperature (T(e) approximately T(i) approximately 3x10(7) K), and beta approximately 10 plasma that included electron and ion beams streaming along B. The wave activity was enhanced from below the ion cyclotron frequency to electron cyclotron and upper hybrid frequencies. The deTailed properties suggest the pulses are nonlinearly steepened ion cyclotron or Alfven waves.
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relativistic electron dropouts by pitch angle scattering in the Geomagnetic Tail
Annales Geophysicae, 2006Co-Authors: G K Parks, M Mccarthy, J H Park, Junga HwangAbstract:Relativistic electron dropout (RED) events are characterized by fast electron flux decrease at the geostationary orbit. It is known that the main loss process is non adiabatic and more effective for the high energy particles. RED events generally start to occur at midnight sector and propagate to noon sector and are correlated with magnetic field stretching. In this paper, we discuss this kind of event can be caused from pitch angle diffusion induced when the gyro radius of the electrons is comparable to the radius of curvature of the magnetic field and the magnetic moment is not conserved any more. While this process has been studied theoretically, the question is whether electron precipitation could be explained with this process for the real field configuration. This paper will show that this process can successfully explain the precipitation that occurred on 14 June 2004 observed by the low-altitude (680 km) polar orbiting Korean satellite, STSAT-1. In this precipitation event, the energy dispersion showed higher energy electron precipitation occurred at lower L values. This feature is a good indicator that precipitation was caused by the magnetic moment scattering in the Geomagnetic Tail. This interpretation is supported by the geosynchronous satellite GOES observations that showed significant magnetic field distortion occurred on the night side accompanying the electron flux depletion. Tsyganenko-01 model also shows the magnetic moment scattering could occur under the Geomagnetic conditions existing at that time. We suggest the pitch angle scattering by field curvature violating the first adiabatic invariant as a possible candidate for loss mechanism of relativistic electrons in radiation belt.