Reconnection at the high‐latitude magnetopause during northward interplanetary magnetic field conditions

Onsager, T. G.; Scudder, J. D.; Lockwood, Mike; Russell, C. T.

doi:10.1029/2000ja000444

Cited by 164 publications

(236 citation statements)

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“…Although previous studies have demonstrated that enhanced amounts of plasma enter to form a relatively thick, lowlatitude boundary layer 2,12,13 and a denser plasma sheet 13,14 when the IMF is northward even during quiet times, the dominant mechanism of solar wind entry into the magnetosphere (and entry location on the magnetopause) under these conditions is less clear and still controversial. It is still not very clearly understood whether the entering plasma is a result of the highlatitude MR 12,[15][16][17][18][19][20][21][22] , impulsive penetration 23,24 , or from the low latitudes through instabilities 25,26 or gradient drift 27 .…”

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confidence: 99%

Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

et al. 2013

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An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times.

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confidence: 99%

Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

et al. 2013

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“…While single-spacecraft measurements have provided ample in-situ evidence for the occurrence of reconnection at the MP (e.g. Paschmann et al, 1979Paschmann et al, , 1986Sonnerup et al, 1981;Gosling et al, 1991;Smith and Rodgers, 1991;Fuselier et al, 1991;Onsager et al, 2001;Avanov et al, 2001;Mozer et al, 2002), little is known about the large-scale spatial and temporal nature of reconnection from single-point in-situ observations. For example, it is not known whether reconnection at the MP is intrinsically intermittent or continuous.…”

Section: Introductionmentioning

confidence: 99%

Cluster observations of continuous reconnection at the magnetopause under steady interplanetary magnetic field conditions

et al. 2004

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Abstract. On 26 January 2001, the Cluster spacecraft detected high-speed plasma jets at multiple crossings of the high-latitude duskside magnetopause (MP) and boundary layer (BL) over a period of more than 2 h. The 4 spacecraft combined spent more than half of this time in the MP/BL and jets were observed whenever a spacecraft was in the MP. These observations were made under steady southward and dawnward interplanetary magnetic field (IMF) conditions. The magnetic shear across the local MP was ∼100 • and β∼1 in the adjacent magnetosheath. The jet velocity is in remarkable agreement with reconnection prediction throughout the entire interval, except for one crossing that had no ion measurements inside the current layer. The flow speed measured in the deHoffmann Teller frame is 90% of the Alfvén speed on average for the 10 complete MP current layer crossings that are resolved by the ion measurements. These findings strongly suggest that reconnection was continuously active for more than two hours. The jets were directed persistently in the same northward and anti-sunward direction, implying that the X-line was always below the spacecraft. This feature is inconsistent with patchy and random reconnection or convecting multiple X-lines. The majority of MP/BL crossings in this two-hour interval were partial crossings, implying that they are caused by bulges sliding along the MP, not by inward-outward motion of a uniformly thin MP/BL. The presence of the bulges suggests that, although reconnection is continuously active under steady IMF conditions, its rate may be modulated. The present investigation also reveals that (1) the predicted ion D-shaped distributions are absent in all reconnection jets on this day, (2) the electric field fluctuations are larger in the reconnecting MP than in the magnetosheath proper, but their amplitudes never exceed 20 mV/m, (3) the ion-electron differential motion is ∼20 km/s for the Correspondence to: T. D. Phan (phan@ssl.berkeley.edu) observed MP current density of ∼50 nA/m 2 (deduced from ∇×B), thus inconsequential for the deHoffmann-Teller and Walén analyses, (4) flows in an isolated flux transfer event (FTE) are directed in the same direction as the MP jets and satisfy the Walén relation, suggesting that this FTE is also generated by reconnection. Finally, the present event cannot be used to evaluate the validity of component or anti-parallel merging models because, although the magnetic shear at the local MP was ∼100 • ( 180 • ), the X-line may be located more than 9 R E away (in the opposite hemisphere), where the shear could be substantially different.

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“…These observations often show a "reverse" cusp ion dispersion signature under northward IMF conditions, whereby the observed energy of precipitating magnetosheath-like ions in the cusp decreases with decreasing invariant latitude (Burch et al, 1980;Woch and Lundin, 1992;Matsuoka et al, 1996), in the opposite sense to that observed in the cusp during southward IMF conditions. This is a direct result of the energy dispersion of the particles during their time-of-flight, otherwise known as the velocity filter effect, resulting in particles precipitating at different latitudes as the newly-reconnected field lines convect sunward following reconnection (Onsager et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field

et al. 2004

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Abstract. This study presents, for the first time, detailed spatiotemporal measurements of the reconnection electric field in the Northern Hemisphere ionosphere during an extended interval of northward interplanetary magnetic field. Global convection mapping using the SuperDARN HF radar network provides global estimates of the convection electric field in the northern polar ionosphere. These are combined with measurements of the ionospheric footprint of the reconnection X-line to determine the spatiotemporal variation of the reconnection electric field along the whole X-line. The shape of the spatial variation is stable throughout the interval, although its magnitude does change with time. Consequently, the total reconnection potential along the X-line is temporally variable but its typical magnitude is consistent with the cross-polar cap potential measured by low-altitude satellite overpasses. The reconnection measurements are mapped out from the ionosphere along Tsyganenko model magnetic field lines to determine the most likely reconnection location on the lobe magnetopause. The X-line length on the lobe magnetopause is estimated to be ∼6-11 R E in extent, depending on the assumptions made when determining the length of the ionospheric X-line. The reconnection electric field on the lobe magnetopause is estimated to be ∼0.2 mV/m in the peak reconnection region.

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Reconnection at the high‐latitude magnetopause during northward interplanetary magnetic field conditions

Cited by 164 publications

References 39 publications

Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

Cluster observations of continuous reconnection at the magnetopause under steady interplanetary magnetic field conditions

Measuring the dayside reconnection rate during an interval of due northward interplanetary magnetic field

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