Ion dynamics in magnetic reconnection: Comparison between numerical simulation and Geotail observations

Hoshino, Masahiro; Mukai, T.; Yamamoto, T.; Kokubun, S.

doi:10.1029/97ja01785

Cited by 146 publications

(159 citation statements)

References 36 publications

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“…Imada et al (2007) showed how the supra-thermal electrons appeared associated with another B z transient around 09:48:50 UT, which could well be explained by acceleration of bounced population at the front of the outward flow region as predicted by Hoshino et al (1998) in PIC simulations. Large-amplitude (up to 50 mV/m) solitary waves, identified as electron holes, were seen near the outer edge of the plasma sheet, within and on the edge of a density cavity, at distances on the order of a few ion inertial lengths from the center of the current sheet between 09:47 and 09:51 UT .…”

Section: Event 2: Interpretation With Nenl Modelmentioning

confidence: 95%

Dynamics of thin current sheets: Cluster observations

et al. 2007

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Abstract. The paper tries to sort out the specific signatures of the Near Earth Neutral Line (NENL) and the Current Disruption (CD) models, and looks for these signatures in Cluster data from two events. For both events transient magnetic signatures are observed, together with fast ion flows. In the simplest form of NENL scenario, with a large-scale two-dimensional reconnection site, quasi-invariance along Y is expected. Thus the magnetic signatures in the S/C frame are interpreted as relative motions, along the X or Z direction, of a quasi-steady X-line, with respect to the S/C. In the simplest form of CD scenario an azimuthal modulation is expected. Hence the signatures in the S/C frame are interpreted as signatures of azimuthally (along Y) moving current system associated with low frequency fluctuations of J y and the corresponding field-aligned currents (J x ). Event 1 covers a pseudo-breakup, developing only at high latitudes. First, a thin (H ≈2000 km≈2ρ i , with ρ i the ion gyroradius) Current Sheet (CS) is found to be quiet. A slightly thinner CS (H ≈1000-2000 km≈1-2ρ i ), crossed about 30 min later, is found to be active, with fast earthward ion flow bursts (300-600 km/s) and simultaneous large amplitude fluctuations (δB/B∼1). In the quiet CS the current density J y is carried by ions. Conversely, in the active CS ions are moving eastward; the westward current is carried by electrons that move eastward, faster than ions. Similarly, the velocity of earthward flows (300-600 km/s), observed during the active period, maximizes near or at the CS center. During the active phase of Event 1 no signature of the crossing of an X-line is identified, but an X-line located beyond Cluster could account for the observed ion flows, provided that it is active for at least 20 min. Ion flow bursts can also be Correspondence to: W. Baumjohann (baumjohann@oeaw.ac.at) due to CD and to the corresponding dipolarizations which are associated with changes in the current density. Yet their durations are shorter than the duration of the active period. While the overall ∂B z /∂t is too weak to accelerate ions up to the observed velocities, short duration ∂B z /∂t can produce the azimuthal electric field requested to account for the observed ion flow bursts. The corresponding large amplitude perturbations are shown to move eastward, which suggests that the reduction in the tail current could be achieved via a series of eastward traveling partial dipolarisations/CD. The second event is much more active than the first one. The observed flapping of the CS corresponds to an azimuthally propagating wave. A reversal in the proton flow velocity, from −1000 to +1000 km/s, is measured by CODIF. The overall flow reversal, the associated change in the sign of B z and the relationship between B x and B y suggest that the spacecraft are moving with respect to an X-line and its associated Hall-structure. Yet, a simple tailward retreat of a largescale X-line cannot account for all the observations, since several flow reversals are observed. These ...

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Section: Event 2: Interpretation With Nenl Modelmentioning

confidence: 95%

Dynamics of thin current sheets: Cluster observations

et al. 2007

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“…Meanwhile, the particle gains energy from its motion along the electric field E y . However, the acceleration process cannot go infinitely, because the particle will finally become magnetized and be guided by the B z component to be ejected out in the x direction with fast speed [Speiser, 1967;Hoshino et al, 1998]. The net motion of ions in the dawn-dusk direction then carries the current.…”

Section: 1002/2014gl060440mentioning

confidence: 99%

The scale of the magnetotail reconnecting current sheet in the presence of O⁺

Liu

Kistler

Mouikis

et al. 2014

Geophysical Research Letters

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The reconnection current layer thickness is expected to scale with either the ion inertial length or the ion gyroradius. Both of these quantities scale with the mass of the ions present. During geomagnetically disturbed times, the reconnection layer in the magnetotail can contain a significant amount of O + . UsingCluster multi-spacecraft measurements, we have studied nine reconnection events in the magnetotail plasmasheet, to determine whether the reconnecting current sheet thickness scales with the ion gyroradius or the ion inertial length, and whether the amount of O + in the plasma sheet has an effect on the current layer thickness. We find that the thickness is equal to the H + gyroradius, even when the plasma sheet has a high O + content. This result is in contrast to Hall MHD expectations and likely results from the multiscale nature of the current sheet.

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“…Since we found that some of the non-gyrotropic ions observed by Geotail can be understood as the behavior of magnetic reconnection region, we think that the above non-Maxwellian electrons are observed in the thin plasma sheet during magnetic reconnection. It is also known that the thickness of the plasma sheet becomes of the order of ion skin depth during magnetic reconnection from the kinetic simulation study (e.g., Hoshino et al, 1998;Hesse et al, 1999;Shay et al, 1999).…”

Section: Geotail Observationmentioning

confidence: 99%

“…Based on the recent satellite observations and the kinetic simulation studies of reconnection, it is revealed that the thickness of the plasma sheet near the X-type region becomes of the order of ion skin depth (e.g., Hoshino et al, 1998;Hesse et al, 1999;Shay et al, 1999). Since the kinetic features beyond the MHD description appears in the macroscopic scale length, the self-consistent understanding of both the macroscopic evolution of reconnection and the microscopic behavior of plasma dynamics becomes important.…”

Section: Introductionmentioning

confidence: 99%

Strong electron heating and non-Maxwellian behavior in magnetic reconnection

2014

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We discuss the electron heating in the course of magnetic reconnection by using both the Geotail observation and the particle-in-cell simulation. Geotail observes several unique non-Maxwellian velocity distribution functions during the plasma sheet crossing in association with a fast plasma flow. We find that the observed distributions can be classified into four different types depending on the position in the plasma sheet. In the boundary between the lobe and the plasma sheet, the distribution consists of the cold plasma flowing toward the X-type region and the hot plasma escaping from the X-type region along the magnetic field. In the plasma sheet side of the boundary, the distribution becomes bi-Maxwellian distribution with T > T ⊥ . Inside the plasma sheet, the distribution is deformed into a hot and isotropic distribution. We discuss the physical mechanism responsible for those electron heating in a thin plasma sheet by using the kinetic reconnection simulation. We find that the dawn-dusk reconnection electric field as well as the turbulent waves excited by the strong Hall electric currents play an important role on the strong electron heating and acceleration.

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Ion dynamics in magnetic reconnection: Comparison between numerical simulation and Geotail observations

Cited by 146 publications

References 36 publications

Dynamics of thin current sheets: Cluster observations

Dynamics of thin current sheets: Cluster observations

The scale of the magnetotail reconnecting current sheet in the presence of O⁺

Strong electron heating and non-Maxwellian behavior in magnetic reconnection

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Ion dynamics in magnetic reconnection: Comparison between numerical simulation and Geotail observations

Cited by 146 publications

References 36 publications

Dynamics of thin current sheets: Cluster observations

Dynamics of thin current sheets: Cluster observations

The scale of the magnetotail reconnecting current sheet in the presence of O+

Strong electron heating and non-Maxwellian behavior in magnetic reconnection

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The scale of the magnetotail reconnecting current sheet in the presence of O⁺