Dual spacecraft observations of lobe magnetic field perturbations before, during and after plasmoid release

Slavin, J. A.; Hesse, M.; Owen, C. J.; Taguchi, S.; Fairfield, D. H.; Lepping, R. P.; Kokubun, S.; Mukai, T.; Lui, A. T. Y.; Anderson, R. R.; Matsumoto, Hiroshi; Sutcliffe, P.

doi:10.1029/1999gl003606

Cited by 26 publications

(21 citation statements)

References 2 publications

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“…Flux ropes have been directly observed and reported by a number of authors (e.g. Slavin et al, 1999Slavin et al, , 2003aWalsh et al, 2007;Imber et al, 2011), they are 2-5 R E in lateral extent and likely to be consistent with the B/B ∼1-10 % values reported in the literature. Non-force-free magnetic structures have also been observed (e.g.…”

Section: Multiple X-line Reconnection (Mxr)supporting

confidence: 57%

Cluster observations of a transient signature in the magnetotail: implications for the mode of reconnection

et al. 2011

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Abstract. Travelling compression regions (TCRs) are perturbations in the magnetotail lobe magnetic field caused by structures moving Earthward or tailward within the plasma sheet. Previous works have suggested that these structures are created by either time-dependant reconnection occurring at a single X-line, forming a flux-bulge-type structure, or space-variant reconnection at multiple X-lines, forming fluxrope-type structures. In this study we examine an event in which Cluster 2 observed a TCR while the 3 remaining Cluster spacecraft observed the underlying magnetic structure at a range of distances from the neutral sheet. The magnetic structure has a velocity of (99, 154, −31) km s −1 in GSM (|V | = 186 km s −1 ), an estimated size of 1.19 R E along the direction of travel and a size between 1.94 and 2.86 R E in the direction perpendicular to the current sheet. As the structure passes the spacecraft, Cluster 1 and Cluster 4 observed a bipolar signature in B Z , plasma-sheet-like plasma and fieldaligned electron flows. Cluster 3 passed closest to the centre of the structure and observed two separate reductions in the plasma density (with field-aligned electron flows); these drop-outs in the plasma sheet were possibly created by the actions of X-lines. The second drop-out in the plasma sheet also includes a reversal of the ion flow, a signature consistent with the passage of a reconnecting X-line past the spacecraft. Between the X-lines, the plasma outflow from the X-lines caused an increase in pressure which led to a localised expansion of the plasma and also the observations at Cluster 1Correspondence to: S. Beyene (sb2@mssl.ucl.ac.uk) and Cluster 4 and the TCR. Our observations do not uniquely match either of the flux rope or the flux bulge predictions although the observation of two plasma sheet drop-outs (interpreted as X-lines, one active, one dormant) with plasmasheet-like between them and only one TCR is a situation expected in multiple X-line reconnection.

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Section: Multiple X-line Reconnection (Mxr)supporting

confidence: 57%

Cluster observations of a transient signature in the magnetotail: implications for the mode of reconnection

et al. 2011

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“…Haaland et al (2012) estimated that 90 % of the ions flowing into the lobes are convected into the plasma sheet. There they can be recirculated into the inner magnetosphere and finally return to the atmosphere (Dungey, 1961;Seki et al, 2001) or ultimately be lost to interplanetary space (Slavin et al, 1989(Slavin et al, , 1999. This is also true for the ions flowing out from the cusp.…”

Section: Introductionmentioning

confidence: 97%

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016

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Abstract. The cold ions (energy less than several tens of electronvolts) flowing out from the polar ionosphere, called the polar wind, are an important source of plasma for the magnetosphere. The main source of energy driving the polar wind is solar illumination, which therefore has a large influence on the outflow. Observations have shown that solar illumination creates roughly two distinct regimes where the outflow from a sunlit ionosphere is higher than that from a dark one. The transition between both regimes is at a solar zenith angle larger than 90 • . The rotation of the Earth and its orbit around the Sun causes the magnetic polar cap to move into and out of the sunlight. In this paper we use a simple set-up to study qualitatively the effects of these variations in solar illumination of the polar cap on the ion flux from the whole polar cap. We find that this flux exhibits diurnal and seasonal variations even when combining the flux from both hemispheres. In addition there are asymmetries between the outflows from the Northern Hemisphere and the Southern Hemisphere.

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“…[8] Because of the limitations of single-spacecraft observations, there are few direct observations of plasmoid growth or expulsion. In a two-point case study of a TCR event using IMP 8 and GEOTAIL observations, Slavin et al [1999] suggested that the expansion rate of a "young" plasmoid located between X GSM = À26 R E and X GSM = À44 R E was 1.3 R E /min in the X GSM direction. In that study, the two spacecraft were separated by more than 7 R E in all three directions.…”

Section: Introductionmentioning

confidence: 99%

Plasmoid growth and expulsion revealed by two‐point ARTEMIS observations

Angelopoulos

Kiehas

et al. 2013

JGR Space Physics

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[1] On 12 October 2011, two ARTEMIS probes, in lunar orbit~9 R E north of the neutral sheet, sequentially observed a tailward-moving, expanding plasmoid. Their observations revealed a multilayered plasma sheet composed of tailward-flowing hot plasma within the plasmoid surrounded by earthward-flowing, less energetic plasma. Prior observations of similar earthward flows ahead of or behind plasmoids have been interpreted as earthward outflow from a continuously active distant-tail neutral line opposite an approaching plasmoid. No evidence of active distant neutral line reconnection was observed by the probes, however, as they traversed the plasmoid's leading and trailing edges, penetrating above its core. We suggest an alternate interpretation: compression of ambient plasma by the tailward-moving plasmoid proper propels the plasma lobeward and earthward, i.e., above and below the plasmoid proper. Using the propagation velocity obtained from timing analysis, we estimate the average plasmoid proper size in its propagation direction to be 9 R E and its expansion rate to be~7 R E /min at the observation locations. This observation of plasmoid expansion made at the plasmoid boundary is interpreted as plasmoid growth in both the X GSM and the Z GSM directions due to near-Earth-neutral-line reconnection on closed plasma sheet field lines. The velocity inside the plasmoid proper was found to be nonuniform; the core likely moves as fast as 500 km/s, yet the outer layers move more slowly (and in the reverse direction). The absence of lobe reconnection, in particular on the earthward side, suggests that plasmoid formation and expulsion both result from closed plasma sheet field-line reconnection.

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Dual spacecraft observations of lobe magnetic field perturbations before, during and after plasmoid release

Cited by 26 publications

References 2 publications

Cluster observations of a transient signature in the magnetotail: implications for the mode of reconnection

Cluster observations of a transient signature in the magnetotail: implications for the mode of reconnection

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

Plasmoid growth and expulsion revealed by two‐point ARTEMIS observations

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