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Title: Modeling of traveling compression regions in the Earth's magnetotail by the spontaneous fast reconnection model

Abstract

The spontaneous fast reconnection model is applied to the traveling compression regions (TCRs) observed in the Earth's magnetotail lobe region in association with substorms. For this purpose, virtual satellites are located at spatial points in the (low-{beta}) magnetic field region in the three-dimenisonal simulation domain, so that each satellite directly observes the temporal variations of magnetic fields, obtained from simulations, in accordance with the growth and proceeding of the fast reconnection mechanism. If the virtual satellite is located ahead of the initial plasmoid formation, it observes a pulse-like field compression with the compression rate of more than 10% as well as the bipolar structure of the magnetic field component from northward to southward tilting, when the plasmoid center passes through the satellite location. On the other hand, if it is located behind the plasmoid formation, it observes the unipolar structure of the southward field component. The simulation results are shown to be, both quantitatively and qualitatively, in good agreement with the actual satellite observations. It is demonstrated that the TCR event is the fast reconnection mechanism itself that is seen in the ambient (low-{beta}) magnetic field (magnetotail lobe) region.

Authors:
;  [1]
  1. Department of Computer Science, Faculty of Engineering, Ehime University, Matsuyama 790-8577 (Japan)
Publication Date:
OSTI Identifier:
20782564
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 3; Other Information: DOI: 10.1063/1.2168408; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COMPRESSION; MAGNETIC FIELDS; MAGNETIC STORMS; MAGNETOHYDRODYNAMICS; MAGNETOTAIL; PLASMA; PLASMA SIMULATION; PULSES; VARIATIONS

Citation Formats

Ugai, M., and Zheng, L. Modeling of traveling compression regions in the Earth's magnetotail by the spontaneous fast reconnection model. United States: N. p., 2006. Web. doi:10.1063/1.2168408.
Ugai, M., & Zheng, L. Modeling of traveling compression regions in the Earth's magnetotail by the spontaneous fast reconnection model. United States. doi:10.1063/1.2168408.
Ugai, M., and Zheng, L. Wed . "Modeling of traveling compression regions in the Earth's magnetotail by the spontaneous fast reconnection model". United States. doi:10.1063/1.2168408.
@article{osti_20782564,
title = {Modeling of traveling compression regions in the Earth's magnetotail by the spontaneous fast reconnection model},
author = {Ugai, M. and Zheng, L.},
abstractNote = {The spontaneous fast reconnection model is applied to the traveling compression regions (TCRs) observed in the Earth's magnetotail lobe region in association with substorms. For this purpose, virtual satellites are located at spatial points in the (low-{beta}) magnetic field region in the three-dimenisonal simulation domain, so that each satellite directly observes the temporal variations of magnetic fields, obtained from simulations, in accordance with the growth and proceeding of the fast reconnection mechanism. If the virtual satellite is located ahead of the initial plasmoid formation, it observes a pulse-like field compression with the compression rate of more than 10% as well as the bipolar structure of the magnetic field component from northward to southward tilting, when the plasmoid center passes through the satellite location. On the other hand, if it is located behind the plasmoid formation, it observes the unipolar structure of the southward field component. The simulation results are shown to be, both quantitatively and qualitatively, in good agreement with the actual satellite observations. It is demonstrated that the TCR event is the fast reconnection mechanism itself that is seen in the ambient (low-{beta}) magnetic field (magnetotail lobe) region.},
doi = {10.1063/1.2168408},
journal = {Physics of Plasmas},
number = 3,
volume = 13,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • On the basis of the spontaneous fast reconnection model, the traveling compression region (TCR) is studied by magnetohydrodynamic simulations for various plasma parameters. Once the fast reconnection mechanism involving slow shocks builds up, the general features of TCR, observed by virtual satellites located in the simulation box, are in good agreement with actual satellite observations. Quantitatively, the TCR signature is not significantly influenced by plasma {beta}, whereas its duration time is proportional to V{sub Ae}{sup -1}, where V{sub Ae} is the Alfven velocity in the magnetic field region; also, the compression ratio of TCR is larger for the smaller plasmamore » density {rho}{sub e} in the magnetic field region because of larger compressibility. In the diffusion region, resistive tearing is likely to occur, giving rise to multiple small-scale TCRs following the major TCR. For the uniform resistivity model, where the fast reconnection mechanism is not realized, any TCR signature cannot be observed. Hence, the TCR signature, observed in association with substorms, provides a definite evidence such that the fast reconnection mechanism is realized in the Earth's magnetotail.« less
  • A traveling compression region (TCR) is a several-minute long compression of the lobe magnetic field produced by a plasmoid as it moves down the tail. They are generally followed by a longer interval of southward tilting magnetic fields. This study reports the first comprehensive survey of TCRs in the distant magnetotail. A total of 116 TCRs were observed to be separated by 30 min or more from any other TCR and are termed {open_quotes}isolated{close_quotes} events. {open_quotes}Paired{close_quotes} events are defined as two TCRs separated by less than 30 min. There were 36 such TCRs corresponding to 18 paired events. {open_quotes}Multiple{close_quotes} eventsmore » were also observed in which more than two TCRs occurred in a series without a gap between TCRs of more than 30 min. The 11 multiple events identified in this study had an average of about four traveling compression regions each for a total of 43 TCRs. The mean amplitude, {Delta}B/B, and duration, {Delta}T, for all TCRs were found to be 7.6% and 158 s, respectively. TCR amplitude and duration were found to be independent of location within the tail lobes suggesting that the plasmoids which cause the TCRs maintain approximately constant volume and shape as they move down the tail. Mean plasmoid dimensions estimated from TCR duration and amplitude under the assumption of a quasi-rigid magnetopause are 35 R{sub E} (length) x 15 R{sub E} (width) x 15 R{sub E} (height). Utilizing auroral kilometric radiation, the AL index, Pi 2 pulsations at two ground stations, and energetic particle data from three geosynchronous spacecraft, it is found that over 91% of the TCR events identified in this study followed substorm onsets or intensifications. The results of this study strongly suggest that the release of plasmoids down the tail near the time of expansion phase onset is an integral step in the substorm process and an important element in the substorm energy budget. 51 refs., 23 figs.« less
  • The process of driven magnetic reconnection induced by perturbing the magnetopause boundary of the Earth's magnetotail is analytically studied in the framework of kinetic theory. An explicit expression for the reconnection flux is obtained. The driven reconnection can either be exponential or bursty (i.e., short lived) type. The exponential type reconnection can occur only when the trapped electron population is less than 30%. The reconnection rates for the exponential type reconnection are either smaller than or at the most equal to the ion tearing mode instability growth rates. On the other hand, the bursty type reconnection generally occurs at ratesmore » much faster than the growth rates of the ion tearing instability. The bursty type reconnection, however, lasts typically for a period equal to the inverse of its reconnection rate. The size of the magnetic islands formed, and the magnitude and duration of the plasma flows induced along the tail axis are much larger during the exponential type than during the bursty type reconnection. Under certain conditions the bursty type reconnection is expected to be important for the onset of magnetospheric substorms and their energization.« less
  • This letter reports the results of a systematic study of streaming >200 keV electrons observed in the magnetotail with the Caltech Electron/Isotope Spectrometers aboard IMP-7 and IMP-8. A clear statistical association of streaming events with southward magnetic fields, often of steep inclination, and with substorms as evidenced by the AE index is demonstrated. These results support the interpretation that streaming energetic electrons are indicative of substorm-associated magnetic reconnection in the near-earth plasma sheet.
  • Magnetic reconnection (MR) in Earth's magnetotail is usually followed by a systemwide redistribution of explosively released kinetic and thermal energy. Recently, multispacecraft observations from the THEMIS mission were used to study localized explosions associated with MR in the magnetotail so as to understand subsequent Earthward propagation of MR outbursts during substorms. Here we investigate plasma and magnetic field fluctuations/structures associated with MR exhaust and ion-ion kink mode instability during a well-documented THEMIS MR event. Generation, evolution, and fading of kinklike oscillations are followed over a distance of approx70 000 km from the reconnection site in the midmagnetotail to the moremore » dipolar region near the Earth. We have found that the kink oscillations driven by different ion populations within the outflow region can be at least 25 000 km from the reconnection site.« less