ISSI Team 91

Transient Processes and Localized Structures in the Magnetotail:
Analysis, Modeling and Theory

ISSI, Bern, 2006



Recent data taken by Cluster in the magnetotail have stimulated the study of transient, meso-scale processes such as bursty bulk flows, beamlets, energy dispersed ion beams, flux ropes, travelling compression regions, night-side flux transfer events, and "rapid" flappings of the current sheets. Each of these phenomena have similar characteristic temporal scale of several minutes. Although some of these may be causally related, or may have the same source, most have been studied independently based on different models or theories and using different analysis techniques. An example of such observation is the magnetic field disturbances in the plasma sheet boundary layer which have been alternately interpreted as due either to changes in the reconnection rate, or to spatially localized multiple reconnection, or to crossings of filamentary currents not directly relevant to reconnection. We propose a new task to revisit these different phenomena in a coordinated effort to review the observational characteristics, to compare the different analysis techniques, and their underlying assumptions, and to examine the associated theories. The primary objective of the task is to achieve a better understanding of these meso-scale processes, which play fundamental roles in the energy conversion in the Earth's magnetotail.



Transients in the plasma sheet

Bursty bulk flows/flow bursts
A number of studies have shown that flows in the near-Earth and mid-tail plasma sheet tend to occur in 10-min timescale flow enhancements, called bursty bulk flow (BBF) events, which contain embedded velocity peaks of 1-min duration, called flow bursts. BBFs are thought to play a key role in magnetotail flux transport processes and are most likely the result of acceleration in the reconnection region. Multipoint observations by Cluster have allowed the determination of the spatial structure of these fast flows, together with the motion of the dipolarization front, which is a sudden increase in the magnetic field inclination leading the plasma flows (Nakamura et al., 2002; 2004).

Flux ropes
Magnetic flux ropes, originally observed at distant tail, have also been reported in the nearer Earth plasma sheet including Cluster (Slavin et al. 2003a). These show south-north (north-south) BZ deflections when they are embedded in Earthward (tailward) flows and have been interpreted as evidence of magnetic reconnection occurring near-simultaneously at several X-lines.

Rapid current sheet flappings
The oscillation of the tail current sheet, known as current sheet flapping motion, has been frequently identified both by Cluster and previous missions. With the four point measurements, Cluster enables the study of the internal structure of the current sheet (Runov et al., 2004) and the characteristics of these flappings (Sergeev et al., 2004). Although many of these rapid flappings take place during quiet periods (Runov et al., 2005; Petrokovich et al., 2005), some are associated with strong dipolarization of the magnetic field similar to the BBFs. Furthermore, the dawn-dusk propagation direction of the current sheet flappings suggests a source region close to midnight, the location where most active substorms and BBFs are observed (Angelopoulos et al., 1994).

Transients near the lobe/plasma sheet boundary

Beamlets are bursty (1-2 min), mostly dispersionless, Earthward streaming high-velocity field-aligned ion beams which are associated with energetic processes occurring in the distant magnetotail (Grigorenko et al., 2005). The underlying driving process is the non-adiabatic acceleration of plasma in the distant current sheet (Zelenyi et al. 1990). The multipoint observations by Cluster provide a unique opportunity to investigate the spatial structure of beamlets in the Y-Z plane of the tail and to distinguish between temporal and spatial variations in these structures.

Velocity dispersed ion structures
Previous studies of spatial structures in the magnetotail due to convective filtering was recently re-examined by including energy-dispersed structures of transient origin (Sauvaud et al., 1999). This led to the possibility of estimating the distance to the acceleration region and the time of acceleration. Earlier, the energy dispersed ion beams were mostly investigated from low- and mid-altitudes, but recently similar structures were also identified with Geotail in the near-equatorial region (Kazama and Mukai, 2003). A study of this phenomenon with Cluster in the tail with the view to establish its relationship with other transient structures is a one of the tasks of the team.

Traveling compression region
The passage of the flux ropes creates a localized bulge in the plasma sheet, which in turn gives a transient increase of magnetic field in the lobe. These have been called the traveling compression regions (TCRs). Recent multipoint observations by Cluster have enabled the study of the detailed spatial structures and dynamics of these flux ropes and TCRs. TCRs have been found by Cluster in the same region possessing similar propagation speeds and spatial scales to the small flux ropes and strong substorm associations. (Slavin et al., 2003b; Owen et al., 2005).

Nightside flux transfer events
Asymmetric BZ deflections similar to the flux rope/TCR disturbances have alternatively been interpreted as due to the temporal change in the reconnection rate (Semenov et al., 1992), and have been called nightside flux transfer events (Sergeev et al., 1992) as this mechanism has also been proposed as the cause of flux transfer events on the magnetopause. Recent global multi-point observations of substorm onset showed that such events observed by Cluster could play an important role in the substorm dynamics (Sergeev et al., 2005).

Field aligned current filaments
Some of transient plasma sheet entries with particle and magnetic field disturbances observed by Geotail have been interpreted as field-aligned current filaments in association with substorm plasma sheet expansions. Cluster multi-point data enabled to obtain the spatial scale of these filaments. Whereas some of these transient field-aligned currents can be interpreted as due to the closure of the Hall-current through the reconnection site (Nakamura et al., 2004), similar currents associated with bursty bulk flows have also been identified (Sergeev et al., 2005).


Summary of the proposed tasks

Multi-point Cluster observations with spatial separation up to several thousands km have provided new information on the characteristics of the transient processes in the magnetotail. We propose a new task to revisit these different phenomena in a coordinated effort to review the observational characteristics, different analysis techniques, and their underlying assumptions, and by comparing with the predictions of theories. Such efforts can be only performed in an environment where experts can meet and spend time in detailed discussions and collaborations, as in the ISSI team activity. The proposed team consists of members who are already engaged in study of these transients with Cluster data, or who have developed the essential models and theories relevant to these transient processes. The objective of the task is to achieve a better understanding of these meso-scale processes, which play fundamental roles in the energy conversion in the Earth's magnetotail.



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  • Grigorenko, E. E., L. M. Zelenyi, A. O. Fedorov, Plasma Phys. Report, 321, 3, 212-228, 2005.
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  • Kazama,Y, T. Mukai, Geophys. Res. Lett., 30, 1384, doi:10.1029/2002GL016637, 2003.
  • Louarn, P., G. Fruit, E. Budnik, et al., J. Geophys. Res., 109, No. A3, A0321610.1029/2003JA010228, 2004.
  • Nakamura, R., W. Baumjohann, B. Klecker, et al., Geophys. Res. Lett., 29, 1942, doi:10.1029/2002GL015763, 2002
  • Nakamura, R., W. Baumjohann, T. Nagai, et al., J. Geophys. Res., 109, A05204, doi:10.1029/2003JA010174, 2004a.
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  • Owen C. J., J. A. Slavin, A. N. Fazakerley, et al., Geophys. Res. Lett., 32, L03104, doi:10.1029/2004GL021767. 2005.
  • Petrukovich, A. A., W. Baumjohann, R. Nakamura, et al., J. Geophys. Res., submitted, 2005.
  • Runov, A., V. Sergeev, R. Nakamura, et al., Ann. Geophys., 22, 2535-2540, 2004.
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  • Sharma, A. S., A. Y. Ukhorskiy and M. I. Sitnov, in Nonequilibrium Phenomena in Plasmas, edited by A. S. Sharma and P. K. Kaw, Springer, 2005
  • Slavin, J. A., R. P. Lepping, J. Gjerloev, et al., Geophys. Res. Lett., 30, 7, 1362, doi:10.1029/2002GL016411, 2003a.
  • Slavin, J. A., C. J. Owen, M. W. Dunlop, et al., Geophys. Res. Lett., 30, 23, 2208, doi:10.1029/2003GL018438, 2003b.
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Team Address List

Elena E. Grigorenko
Skobeltsyn Institute of Nuclear Physics, Moscow State University, Vorob'evygory, Moscow, 119899 Russia
Tel: (7) 095-3331467 Fax: (7)095-3335178
Email: grig at

Hiroshi Hasegawa
Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan
Email: hase at

Masahiro Hoshino
University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
Tel:(81) 3-5841-4584 Fax: (81) 3-5841-8321
Email: hoshino at

Phillippe Louarn
CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346, F-31028 Toulouse, France
Tel: (33) 05-61-55- 81-01 Fax: (33) 05-61-55-67-01
Email: Philippe.Louarn at

Rumi Nakamura
Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, A-8042 Graz, Austria
Tel: +43-316-4120-573 Fax: +43-316-4120-590
Email: rumi.nakamura at

Chris J. Owen
Dept. of Physics, Mullard Space Science Laboratory, Univ. College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, United Kingdom
Tel: 44-1483-274111 Fax: 44-1483-278312
Email: cjo at

Anatoli Petrukovich
Space Research Institute, Russian Academy of Sciences, Profsouiznaia 84/32 Moscow, GSP-7, 117997, Russia
Tel; (7) 095-333-3267 Fax:(7) 095-3331248
Email: aperuko at

Andrei Runov
Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, A-8042 Graz, Austria
Tel: +43-316-4120-572 Fax: +43-316-4120-590
Email: Andrei.Runov at

Jean-Andre Sauvaud
CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346, F-31028 Toulouse Cedex 4, France
Tel: +33-561556676 Fax: +33-561556701
Email: jean-andre.sauvaud at

Vladimir S. Semenov
Institute of Physics, St.-Petersburg State University, 198504 St. Petergof, Russia
Tel: (7) 812-428 46 27 Fax: (7) 812-428 72 40
Email: sem at

Victor Sergeev
Institute of Physics and Physics Faculty, St.Petersburg State University, Petrodvoretz, St.Petersburg 198504, Russia
Tel: (7) 812-428 46 33 Fax: (7) 812-428 7240
Email: victor at

Surja Sharma
Dept. Astronomy, University of Maryland, College Park, MD 20742, U.S.A.
Tel: (1) 301 405 1528 Fax: (1) 301-3149067

Jim A. Slavin
Laboratory for Extraterrestrial Physics, NASA GSFC, Greenbelt, MD 20771, USA.
Tel: (1)301-2865839 Fax: (1)301-2861648
Email: james.a.slavin at

Bengt U. Ö. Sonnerup
Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 0375-8000, U. S. A
Tel: (1) 603-6462883 Fax: (1)603-6463856
Email: bengt.u.o.sonnerup at

Lev Zelenyi
Space Research Ins titute, Russian Academy of Sciences, Profsouiznaia 84/32 Moscow, GSP-7, 117997, Russia
Tel; (7) 095-333-5122 Fax:(7) 095-3333311


Stein Haaland
MPE, Garching, Germany
Email: stein.haaland at

Kristian Snekvik
University of Bergen, Bergen, Norway
Email: snekvik at


Report of 1st Meeting
February 6 - 10, 2006


The primary objective of this team is to achieve a better understanding of the transient, meso-scale processes, which play fundamental roles in the energy conversion in the Earth's magnetotail. Recent data taken by Cluster in the magnetotail have stimulated the study of these transients such as bursty bulk flows, TCR/flux ropes, NFTE, beamlets etc. The taks of this team are (1) to review observational characteristics, particularly new knowledge from Cluster, (2) to examine different analysis techniques and their underlying assumptions, and (3) to compare with the relevant theories. Our primary goal is to write a review paper based on the discussions. As a secondary goal we perform coordinated analysis of selected events. During the first meeting, we first surveyed all components of the transients: theories on reconnection, particle accelerations, and waves, observations of transients in the fields and particles and relevant analysis techniques based on presentations and discussions spending about two days (see below "Presentation"). On Wednesday, we spent most of the day discussing on the structure/outline of the paper and writing assignments. Starting at the late afternoon on Wednesday and throughout Thursday, we discussed the proposed events which consist of Cluster observations of the transients. Here we also did subgroup discussions on different event studies and analysis methods application. On Friday morning, we summarized all the performed/proposed activities related to event studies, which turned out to become several papers. Furthermore, comparison between analysis methods will be also planned using test data from simulation and observation.


  • Vladimir S. Semenov: Reconnection rate calculation from flow/field reconnection MHD effects on transients
  • Victor Sergeev: Bursty bulk flows; Nightside flux transfer events
  • Rumi Nakamura: Field aligned current filaments; Bursty bulk flows
  • Chris J. Owen: Travelling Compression Regions (TCR's) and Plasma Sheet Flux Ropes
  • Bengt U. Ö. Sonnerup: Reconnection process; Grad-Shafranov reconstructions on plasmoid/flux ropes in the tail
  • Hiroshi Hasegawa: Plasma sheet structures recovered by Grad-Shafranov reconstruction; Reproducing the bi-polar magnetic structure at the jet leading-edge by 3-D reconnection with non-zero guide field
  • Phillippe Louarn: Propagation of L.F. fluctuations in the plasmasheet
  • Andrei Runov: Rapid current sheet flapping
  • Surja Sharma: Multiscale properties of the plasma sheet and transients; Multi-dimensional thin current sheet equilibria
  • Masahiro Hoshino: Behavior of Energetic and Thermal Electrons near the Magnetic Reconnection; Surfing Acceleration during Magnetic Reconnection
  • Lev Zelenyi: Beamlets in the Earth's magnetotail, Resonance formation, effects of nonlinearity and dispersion.
  • Elena E. Grigorenko: Multiplet structure and spatial-temporal characteristics of acceleration processes in the magnetotail. Beamlets and related phenomenas
  • Jean-Andre Sauvaud: Current sheet disruption and TCR; Time of flight analysis

2nd Meeting

Nov. 28 -Dec.2, 2006
ISSI, Bern

(ISSI supported)
Elena E. Grigorenko, Hiroshi Hasegawa, Masahiro Hoshino, Phillippe Louarn, Rumi Nakamura (Lead), Chris J. Owen, Anatoli Petrukovich, Andrei Runov, Vladimir S. Semenov, Victor Sergeev, Surja Sharma (Lead editor), Bengt U. Ö. Sonnerup, Lev Zelenyi
(Self supported)
Stein Haaland, Kristian Snekvik

Main Task of the 2nd-Meeting:

  1. (Nearly) complete the review paper
  2. Discuss and report on the coordinated studies


  • Tuesday PM: Warm-up discussions. Status of the paper.
    Starting discussion from Section 1
  • Wednesday AM: Sec. 2. discussions.
    PM: Sec. 2.-3. discussions
    17:45 ISSI wine party
  • Thursday AM: Sec. 2-3. completion
    PM: Sec. 4 discussion
    Dinner (20:00 Casino)
  • Friday AM: Sec. 4 completion
    PM: Other sections, summary, Work assignment
  • Saturday AM(PM): Coordinated studies

Workshop summary

  • Review paper activity
    During the meeting the main body of the paper, Section 2 "Observations" and Section 3 "Theory", have been re-organized and rewritten and cross- referenced. Draft of the other sections have been prepared and discussed. Further missing subsection will be added to complete the next version by the end of January 2007. By that time we are going to make decision whether another editorial meeting with small number of people will be necessary.
  • Even studies and their topics
    • 20010915: Substorm associated recurrent flux rope type structures.
    • 20020813 G-S reconstruction analysis of a flux rope type structure; comparison of observation and models.
    • 20020825 Flux rope type signatures observed as field-aligned current flowing toward the ionosphere during BBF.
    • 20050926 Near-Earth reconnection during substorm reconstructed using transient reconnection model.


  • Review paper:
    • A. S. Sharma, R. Nakamura, A. Runov, E. E. Grigorenko, H. Hasegawa, M. Hoshino, P. Louarn, C. J. Owen, A. Petrukovich, J.-A. Sauvaud, V. S. Semenov, V. A. Sergeev, J. A. Slavin, B. U. Ö. Sonnerup, L. M. Zelenyi, G. Fruit, S. Haaland, H. Malova, and K. Snekvik Transient and Localized Processes in the Magnetotail: A Review, Ann. Geophys. 2007 submitted
  • Individual papers from the members on event studies (with ISSI Acknowledgements)
    • H. Hasegawa, R. Nakamura, M. Fujimoto, V. Sergeev, E. Lucek, H. Reme, and Y. Khotyaintsev, Reconstruction of a bipolar magnetic signature in an earthward jet in the tail: Flux rope or 3D guide-field reconnection? J. Geophys. Res., 2007, accepted
    • A. Runov, I. O. Voronkov, Y. Asano, R. Nakamura, W. Baumjohann, M. Volwerk, T. Takada, Z. Voros, T. L. Zhang, A. Vaivads, S. Haaland, H. Reme, and A. Balogh, Cluster observations during pseudo-breakups and substorms, Proc. Int. Conf. Substorms-8, pp 269-274, 2006
    • A. Runov, I. Voronkov, Y. Asano, W. Baumjohann, M. Fujimoto, R. Nakamura, T. Takada, M. Volwerk, Z. Voros, M. Meurant, A. Fazakerley, H. Reme, and A. Balogh, Structure of the near-Earth plasma sheet during tailward flows, Ann. Geophys., 2007, submitted
    • V. A. Sergeev, V. Semenov, M. Kubyshkina, V. Ivanova, W. Baumjohann, R. Nakamura, T. Penz, A. Runov, T. L. Zhang, K.-H. Glassmeier, V. Angelopoulos, H. Frey, J.-A. Sauvaud, P. Daly, J. B. Cao, H. Singer, and E. Lucek, Observation of repeated intense near-Earth reconnection on closed field lines with Cluster, Double Star and other spacecraft, Geophys. Res. Lett., 34, L02103, doi:10.1029/2006GL028452, 2007.
    • K. Snekvik, S. Haaland, N. Ostgaard, H. Hasegawa, R. Nakamura, T. Takada, L. Juusola, O. Amm, F. Pitout, H. Reme, B. Klecker, and E. A. Lucek, Cluster observations of a field aligned current at the dawn flank of a bursty bulk flow, Ann. Geophys. 2007, accepted.


Last update 05.22.2006