X lines in the magnetotail for southward and northward IMF conditions

Zhang, Lingqian; Wang, J. Y.; Baumjohann, W.; Rème, H.; Dai, Lei; Dunlop, Malcolm; Chen, Ti; Huang, Ya

doi:10.1002/2015ja021503

Cited by 13 publications

(28 citation statements)

References 76 publications

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“…Signals of the X lines are identified by the tailward fast flows (TFFs) with negative B z (refer to Zhang et al . []). The selection criterion of the X lines (GSM coordinates) is that the duration of V x < −300 km/s exceeds 35 s and B z < 0.…”

Section: Data Descriptionsmentioning

confidence: 99%

“…This selection criterion is the same as the one used in Zhang et al . []. There are 374 X line events selected inside the region of −30 R E < X < −15 R E , −10 R E < Y < 10 R E , and −5 R E < Z < 5 R E .…”

Section: Data Descriptionsmentioning

confidence: 99%

“…However, direct observational evidence of X lines during NW‐IMF has not been found till the recent study of Zhang et al . [].…”

Section: Introductionmentioning

confidence: 99%

“…According to Zhang et al . [], X lines in the tail can occur for SW‐IMF as well as NW‐IMF but more frequently for SW‐IMF. In particular, typical a case presented in Zhang et al .…”

Section: Introductionmentioning

confidence: 99%

“…In particular, typical a case presented in Zhang et al . [] clearly showed that a near‐Earth X line for NW‐IMF occurs while the geomagnetic activity is particularly quiet ( AE index is about 60 nT). This is quite different from the situation of SW‐IMF in which X lines are always present during enhanced geomagnetic activities [ Nagai et al ., ; Nakamura et al ., , ; Lyons et al ., ; Zhang et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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Temporal evolutions of the solar wind conditions at 1 AU prior to the near‐Earth X lines in the tail: Superposed epoch analysis

et al. 2016

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Utilizing conjunction observations of the Geotail and ACE satellites from 1998 to 2005, we investigated the temporal evolutions of the solar wind conditions prior to the formation of X lines in the near‐Earth magnetotail. We first show the statistical properties of Bz, By, density, and velocity of the solar wind related to the 374 tail X line events. A superposed epoch analysis is performed to study the temporal evolutions of the solar wind conditions 5 h prior to the tail X lines. The solar wind conditions for tail X lines during southward interplanetary magnetic field (IMF) (SW‐IMF) and northward IMF (NW‐IMF) are analyzed. The main results are as follows: (1) For events classified as SW‐IMF, near‐Earth X line observations in the magnetosphere are preceded by ~2 h intervals of southward IMF; (2) for events classified as NW‐IMF, the northward IMF orientation preceding near‐Earth X line observations lasts ~ 40 min.

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Section: Data Descriptionsmentioning

confidence: 99%

Section: Data Descriptionsmentioning

confidence: 99%

“…However, direct observational evidence of X lines during NW‐IMF has not been found till the recent study of Zhang et al . [].…”

Section: Introductionmentioning

confidence: 99%

“…According to Zhang et al . [], X lines in the tail can occur for SW‐IMF as well as NW‐IMF but more frequently for SW‐IMF. In particular, typical a case presented in Zhang et al .…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Temporal evolutions of the solar wind conditions at 1 AU prior to the near‐Earth X lines in the tail: Superposed epoch analysis

et al. 2016

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Bursty bulk flows at different magnetospheric activity levels: Dependence on IMF conditions

et al. 2016

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Based on concurrent observations of the ACE and Geotail satellites from 1998 to 2005, we statistically analyzed and compared the earthward bursty bulk flows (BBFs) with local positive Bz under different interplanetary magnetic field (IMF) conditions. Four different magnetospheric activity levels (MALs), including quiet times and substorm growth/expansion/recovery phases, are considered. The properties of the BBFs, including their ion temperature (T), Vx component, x component of the energy flux density (Qx), and the solar wind dawn‐dusk electric field Ey (observed at ~1 AU), are analyzed. Main observations include the following: (1) BBF tends to have less penetration distance for northward IMF (NW‐IMF) than for southward IMF (SW‐IMF). Inward of 15 RE the BBFs for SW‐IMF are dominant. Few BBFs for NW‐IMF occur within 15 RE. (2) The occurrence probabilities of the BBFs at each MAL depend highly on the orientations of the IMF. During quiet times, the BBFs for NW‐IMF are dominant. Reversely, during the growth and expansion phases of a substorm, the BBFs for SW‐IMF are dominant. (3) The strengths of the BBF have significant evolution with substorm development. For SW‐IMF condition, the strengths of the BBFs are the lowest for quiet times. The strength of the BBFs tends to increase during the growth phase and reaches to the strongest value during the expansion phase, then, decays during the recovery phase. For NW‐IMF condition, the strengths of the BBFs evolve with the substorm development in a similar way as for SW‐IMF condition. (4) For SW‐IMF, the solar wind Ey evolves with the substorm development in a similar way to the strength of the BBFs. However, no clear evolution is found for NW‐IMF. (5) The strengths of the BBF Qx and solar wind Ey are closely related. Both tend to be stronger for growth phase than for quite time, reach the strongest for expansion phase, then decay for recovery phase. It appears that to trigger a substorm, the strength of the BBFs should achieve energy thresholds with values different for NW‐IMF and SW‐IMF.

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The formation of superdense plasma sheet in association with the IMF turning from northward to southward

Raeder

Thomsen

et al. 2017

JGR Space Physics

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We have studied two events in which relatively superdense plasma appeared near geosynchronous orbit after the interplanetary magnetic field (IMF) changed from a long period of northward condition to southward condition. We used the magnetosphere MHD model Open Geospace General Circulation Model to simulate these two events and compared the simulation results with observations. The observations and the simulation results show that an extended period of northward IMF caused a cold dense plasma sheet (CDPS) to form in the near tail, and a subsequent southward IMF caused a highly stretched near‐tail dipole field, which enhanced the earthward convection and eventually set off reconnection. Some of the cold dense plasma was thus consequently transported to geosynchronous orbit and formed a superdense plasma sheet (SDPS). CDPS is the main source of SDPS in its early stage after the IMF southward turning.

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X lines in the magnetotail for southward and northward IMF conditions

Cited by 13 publications

References 76 publications

Temporal evolutions of the solar wind conditions at 1 AU prior to the near‐Earth X lines in the tail: Superposed epoch analysis

Temporal evolutions of the solar wind conditions at 1 AU prior to the near‐Earth X lines in the tail: Superposed epoch analysis

Bursty bulk flows at different magnetospheric activity levels: Dependence on IMF conditions

The formation of superdense plasma sheet in association with the IMF turning from northward to southward

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