The Effect of Solar Wind Mach Numbers on the Occurrence Rate of Flux Transfer Events at the Dayside Magnetopause

2019 ◽  
Vol 46 (8) ◽  
pp. 4106-4113 ◽  
Author(s):  
C. Chen ◽  
T. R. Sun ◽  
C. Wang ◽  
Z. H. Huang ◽  
B. B. Tang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Occurrence Rate ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Mach Numbers ◽  
Flux Transfer

scholarly journals Evidence for transient, local ion foreshocks caused by dayside magnetopause reconnection

2016 ◽  
Vol 34 (11) ◽  
pp. 943-959 ◽  
Author(s):  
Yann Pfau-Kempf ◽  
Heli Hietala ◽  
Steve E. Milan ◽  
Liisa Juusola ◽  
Sanni Hoilijoki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Ion Beams ◽  
Bow Shock ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Flux Transfer ◽  
Push Out ◽  
Magnetopause Reconnection

Abstract. We present a scenario resulting in time-dependent behaviour of the bow shock and transient, local ion reflection under unchanging solar wind conditions. Dayside magnetopause reconnection produces flux transfer events driving fast-mode wave fronts in the magnetosheath. These fronts push out the bow shock surface due to their increased downstream pressure. The resulting bow shock deformations lead to a configuration favourable to localized ion reflection and thus the formation of transient, travelling foreshock-like field-aligned ion beams. This is identified in two-dimensional global magnetospheric hybrid-Vlasov simulations of the Earth's magnetosphere performed using the Vlasiator model (http://vlasiator.fmi.fi). We also present observational data showing the occurrence of dayside reconnection and flux transfer events at the same time as Geotail observations of transient foreshock-like field-aligned ion beams. The spacecraft is located well upstream of the foreshock edge and the bow shock, during a steady southward interplanetary magnetic field and in the absence of any solar wind or interplanetary magnetic field perturbations. This indicates the formation of such localized ion foreshocks.

scholarly journals Concerning the occurrence pattern of flux transfer events on the dayside magnetopause

2009 ◽  
Vol 27 (2) ◽  
pp. 895-903 ◽  
Author(s):  
D. G. Sibeck
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Reconnection ◽  
Interplanetary Magnetic Field ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Two Factors ◽  
Flux Transfer ◽  
Occurrence Pattern ◽  
The Magnetic Field

Abstract. We present an analytical model for the magnetic field perturbations associated with flux transfer events (FTEs) on the dayside magnetopause as a function of the shear between the magnetosheath and magnetospheric magnetic fields and the ratio of their strengths. We assume that the events are produced by component reconnection along subsolar reconnection lines with tilts that depend upon the orientation of the interplanetary magnetic field (IMF), and show that the amplitudes of the perturbations generated during southward IMF greatly exceed those during northward IMF. As a result, even if the distributions of magnetic reconnection burst durations/event dimensions are identical during periods of northward and southward IMF orientation, events occurring for southward IMF orientations must predominate in surveys of dayside events. Two factors may restore the balance between events occurring for northward and southward IMF orientations on the flanks of the magnetosphere. Events generated on the dayside magnetopause during periods of southward IMF move poleward, while those generated during periods of northward IMF slip dawnward or duskward towards the flanks. Due to differing event and magnetospheric magnetic field orientations, events that produce weak signatures on the dayside magnetopause during intervals of northward IMF orientation may produce strong signatures on the flanks.

Dependence of flux transfer events on solar wind conditions from 3 years of Cluster observations

2006 ◽  
Vol 111 (A4) ◽  
Author(s):  
Y. L. Wang ◽  
R. C. Elphic ◽  
B. Lavraud ◽  
M. G. G. T. Taylor ◽  
J. Birn ◽  
...  
Keyword(s):  
Solar Wind ◽  
Flux Transfer Events ◽  
Flux Transfer

scholarly journals Coordinated polar spacecraft, geosynchronous spacecraft, and ground-based observations of magnetopause processes and their coupling to the ionosphere

2004 ◽  
Vol 22 (12) ◽  
pp. 4329-4350 ◽  
Author(s):  
G. Le ◽  
S.-H. Chen ◽  
Y. Zheng ◽  
C. T. Russell ◽  
J. A. Slavin ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Speed ◽  
Reconnection Rate ◽  
Flux Transfer Events ◽  
Speed Solar Wind ◽  
Flux Transfer ◽  
Field Lines ◽  
Magnetopause Oscillations ◽  
High Speed Solar Wind

Abstract. In this paper, we present in-situ observations of processes occurring at the magnetopause and vicinity, including surface waves, oscillatory magnetospheric field lines, and flux transfer events, and coordinated observations at geosynchronous orbit by the GOES spacecraft, and on the ground by CANOPUS and 210° Magnetic Meridian (210MM) magnetometer arrays. On 7 February 2002, during a high-speed solar wind stream, the Polar spacecraft was skimming the magnetopause in a post-noon meridian plane for ~3h. During this interval, it made two short excursions and a few partial crossings into the magnetosheath and observed quasi-periodic cold ion bursts in the region adjacent to the magnetopause current layer. The multiple magnetopause crossings, as well as the velocity of the cold ion bursts, indicate that the magnetopause was oscillating with an ~6-min period. Simultaneous observations of Pc5 waves at geosynchronous orbit by the GOES spacecraft and on the ground by the CANOPUS magnetometer array reveal that these magnetospheric pulsations were forced oscillations of magnetic field lines directly driven by the magnetopause oscillations. The magnetospheric pulsations occurred only in a limited longitudinal region in the post-noon dayside sector, and were not a global phenomenon, as one would expect for global field line resonance. Thus, the magnetopause oscillations at the source were also limited to a localized region spanning ~4h in local time. These observations suggest that it is unlikely that the Kelvin-Helmholz instability and/or fluctuations in the solar wind dynamic pressure were the direct driving mechanisms for the observed boundary oscillations. Instead, the likely mechanism for the localized boundary oscillations was pulsed reconnection at the magnetopause occurring along the X-line extending over the same 4-h region. The Pc5 band pressure fluctuations commonly seen in high-speed solar wind streams may modulate the reconnection rate as an indirect cause of the observed Pc5 pulsations. During the same interval, two flux transfer events were also observed in the magnetosphere near the oscillating magnetopause. Their ground signatures were identified in the CANOPUS data. The time delays of the FTE signatures from the Polar spacecraft to the ground stations enable us to estimate that the longitudinal extent of the reconnection X-line at the magnetopause was ~43° or ~5.2 RE. The coordinated in-situ and ground-based observations suggest that FTEs are produced by transient reconnection taking place along a single extended X-line at the magnetopause, as suggested in the models by Scholer (1988) and Southwood et al. (1988). The observations from this study suggest that the reconnection occurred in two different forms simultaneously in the same general region at the dayside magnetopause: 1) continuous reconnection with a pulsed reconnection rate, and 2) transient reconnection as flux transfer events. Key words. Magnetospheric physics (Magnetopause, cusp and boundary layers; Magnetosphere-ionosphere interactions; MHD waves and instabilities)

scholarly journals Flux Transfer Events: 1. generation mechanism for strong southward IMF

2006 ◽  
Vol 24 (1) ◽  
pp. 381-392 ◽  
Author(s):  
J. Raeder
Keyword(s):  
Magnetic Field ◽  
Generation Process ◽  
Numerical Resolution ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Semiannual Variation ◽  
Flux Transfer ◽  
Sequential Generation ◽  
The Magnetic Field ◽  
Dipole Tilt

Abstract. We use a global numerical model of the interaction of the solar wind and the interplanetary magnetic field with Earth's magnetosphere to study the formation process of Flux Transfer Events (FTEs) during strong southward IMF. We find that: (i) The model produces essentially all observational features expected for FTEs, in particular the bipolar signature of the magnetic field BN component, the correct polarity, duration, and intermittency of that bipolar signature, strong core fields and enhanced core pressure, and flow enhancements; (ii) FTEs only develop for large dipole tilt whereas in the case of no dipole tilt steady magnetic reconnection occurs at the dayside magnetopause; (iii) the basic process by which FTEs are produced is the sequential generation of new X-lines which makes dayside reconnection inherently time dependent and leads to a modified form of dual or multiple X-line reconnection; (iv) the FTE generation process in this model is not dependent on specific assumptions about microscopic processes; (v) the average period of FTEs can be explained by simple geometric arguments involving magnetosheath convection; (vi) FTEs do not develop in the model if the numerical resolution is too coarse leading to too much numerical diffusion; and (vii) FTEs for nearly southward IMF and large dipole tilt, i.e., near solstice, should only develop in the winter hemisphere, which provides a testable prediction of seasonal modulation. The semiannual modulation of intermittent FTE reconnection versus steady reconnection is also expected to modulate magnetospheric and ionospheric convection and may thus contribute to the semiannual variation of geomagnetic activity.

scholarly journals Ionospheric ion upwelling in the wake of flux transfer events at the dayside magnetopause

1988 ◽  
Vol 93 (A6) ◽  
pp. 5641 ◽  
Author(s):  
M. Lockwood ◽  
M. F. Smith ◽  
C. J. Farrugia ◽  
G. L. Siscoe
Keyword(s):  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Flux Transfer ◽  
Ion Upwelling

scholarly journals Dayside magnetopause transients correlated with changes of the magnetosheath magnetic field orientation

2011 ◽  
Vol 29 (4) ◽  
pp. 687-699 ◽  
Author(s):  
O. Tkachenko ◽  
J. Šafránková ◽  
Z. Němeček ◽  
D. G. Sibeck
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Surface Deformation ◽  
Low Latitude ◽  
Field Orientation ◽  
Magnetic Field Orientation ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
Transient Events ◽  
The Magnetic Field

Abstract. The paper analyses one long-term pass (26 August 2007) of the THEMIS spacecraft across the dayside low-latitude magnetopause. THEMIS B, serving partly as a magnetosheath monitor, observed several changes of the magnetic field that were accompanied by dynamic changes of the magnetopause location and/or the structure of magnetopause layers observed by THEMIS C, D, and E, whereas THEMIS A scanned the inner magnetosphere. We discuss the plasma and the magnetic field data with motivation to identify sources of observed quasiperiodic plasma transients. Such events at the magnetopause are usually attributed to pressure pulses coming from the solar wind, foreshock fluctuations, flux transfer events or surface waves. The presented transient events differ in nature (the magnetopause surface deformation, the low-latitude boundary layer thickening, the crossing of the reconnection site), but we found that all of them are associated with changes of the magnetosheath magnetic field orientation and with enhancements or depressions of the plasma density. Since these features are not observed in the data of upstream monitors, the study emphasizes the role of magnetosheath fluctuations in the solar wind-magnetosphere coupling.

scholarly journals The azimuthal extent of three flux transfer events

2008 ◽  
Vol 26 (8) ◽  
pp. 2353-2369 ◽  
Author(s):  
R. C. Fear ◽  
S. E. Milan ◽  
A. N. Fazakerley ◽  
E. A. Lucek ◽  
S. W. H. Cowley ◽  
...  
Keyword(s):  
Flux Tube ◽  
Time Varying ◽  
Magnetic Shear ◽  
Simple Interpretation ◽  
Flux Transfer Events ◽  
Dayside Magnetopause ◽  
In Situ Observations ◽  
Flux Transfer ◽  
Separation Size

Abstract. In early 2006, the Cluster spacecraft crossed the dayside magnetopause twice each orbit with the spacecraft at their largest separation of the entire mission (~10 000 km). In this paper, we present in situ observations at this separation size of flux transfer events (FTEs), which are a signature of transient or time-varying magnetopause reconnection. We study a magnetopause crossing on 27 January 2006; for half an hour, the tetrahedron of Cluster spacecraft straddled the magnetopause and during this time a large number of flux transfer events were observed. Three particular FTEs were observed by all four spacecraft, enabling it to be shown that individual FTEs at the magnetopause can extend azimuthally for at least 10 000 km. By combining the Cluster tetrahedron geometry with the observed velocity of the FTEs, it can be shown that the poleward extent of one FTE is significantly smaller than its azimuthal extent. The location of the Cluster spacecraft when they observed this FTE suggests that it is inconsistent with the simple interpretation of an "elbow-shaped" flux tube. The FTE's azimuthal extent suggests that it was more likely generated at a comparatively long reconnection line or lines, although the magnetic shear across the magnetopause is not high enough to exclude the "elbow-shaped" model entirely.

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