scholarly journals Solar-wind-driven pulsed magnetic reconnection at the dayside magnetopause, Pc5 compressional oscillations, and field line resonances

1998 ◽  
Vol 103 (A8) ◽  
pp. 17307-17322 ◽  
Author(s):  
P. Prikryl ◽  
R. A. Greenwald ◽  
G. J. Sofko ◽  
J. P. Villain ◽  
C. W. S. Ziesolleck ◽  
...  
Keyword(s):  
Solar Wind ◽  
Magnetic Reconnection ◽  
Field Line ◽  
Field Line Resonances ◽  
Dayside Magnetopause

scholarly journals Interplanetary magnetic field control of Saturn's polar cusp aurora

2005 ◽  
Vol 23 (4) ◽  
pp. 1405-1431 ◽  
Author(s):  
E. J. Bunce ◽  
S. W. H. Cowley ◽  
S. E. Milan
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Field Line ◽  
High Latitude ◽  
Closed Field ◽  
Vortical Flows ◽  
Dayside Magnetopause ◽  
Closed Field Line ◽  
Lobe Reconnection

Abstract. Dayside UV emissions in Saturn's polar ionosphere have been suggested to be the first observational evidence of the kronian "cusp" (Gérard et al., 2004). The emission has two distinct states. The first is a bright arc-like feature located in the pre-noon sector, and the second is a more diffuse "spot" of aurora which lies poleward of the general location of the main auroral oval, which may be related to different upstream interplanetary magnetic field (IMF) orientations. Here we take up the suggestion that these emissions correspond to the cusp. However, direct precipitation of electrons in the cusp regions is not capable of producing significant UV aurora. We have therefore investigated the possibility that the observed UV emissions are associated with reconnection occurring at the dayside magnetopause, possibly pulsed, akin to flux transfer events seen at the Earth. We devise a conceptual model of pulsed reconnection at the low-latitude dayside magnetopause for the case of northwards IMF which will give rise to pulsed twin-vortical flows in the magnetosphere and ionosphere in the vicinity of the open-closed field-line boundary, and hence to bi-polar field-aligned currents centred in the vortical flows. During intervals of high-latitude lobe reconnection for southward IMF, we also expect to have pulsed twin-vortical flows and corresponding bi-polar field-aligned currents. The vortical flows in this case, however, are displaced poleward of the open-closed field line boundary, and are reversed in sense, such that the field-aligned currents are also reversed. For both cases of northward and southward IMF we have also for the first time included the effects associated with the IMF By effect. We also include the modulation introduced by the structured nature of the solar wind and IMF at Saturn's orbit by developing "slow" and "fast" flow models corresponding to intermediate and high strength IMF respectively. We then consider the conditions under which the plasma populations appropriate to either sub-solar reconnection or high-latitude lobe reconnection can carry the currents indicated. We have estimated the field-aligned voltages required, the resulting precipitating particle energy fluxes, and the consequent auroral output. Overall our model of pulsed reconnection under conditions of northwards and southwards IMF, and for varying orientations of IMF By, is found to produce a range of UV emission intensities and geometries which is in good agreement with the data presented by Gérard et al. (2004). The recent HST-Cassini solar wind campaign provides a unique opportunity to test the theoretical ideas presented here.

scholarly journals A case study of dayside reconnection under extremely low solar wind density conditions

2008 ◽  
Vol 26 (11) ◽  
pp. 3571-3583
Author(s):  
R. Maggiolo ◽  
J. A. Sauvaud ◽  
I. Dandouras ◽  
E. Luceck ◽  
H. Rème
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
High Speed ◽  
Radial Distance ◽  
Plasma Jets ◽  
Solar Wind Density ◽  
Ion Distribution ◽  
Dayside Magnetopause ◽  
Field Lines

Abstract. From 15 February 2004, 20:00 UT to 18 February 2004, 01:00 UT, the solar wind density dropped to extremely low values (about 0.35 cm−3). On 17 February, between 17:45 UT and 18:10 UT, the CLUSTER spacecraft cross the dayside magnetopause several times at a large radial distance of about 16 RE. During each of these crossings, the spacecraft detect high speed plasma jets in the dayside magnetopause and boundary layer. These observations are made during a period of southward and dawnward Interplanetary Magnetic Field (IMF). The magnetic shear across the local magnetopause is ~90° and the magnetosheath beta is very low (~0.15). We evidence the presence of a magnetic field of a few nT along the magnetopause normal. We also show that the plasma jets, accelerated up to 600 km/s, satisfy the tangential stress balance. These findings strongly suggest that the accelerated jets are due to magnetic reconnection between interplanetary and terrestrial magnetic field lines northward of the satellites. This is confirmed by the analysis of the ion distribution function that exhibits the presence of D shaped distributions and of a reflected ion population as predicted by theory. A quantitative analysis of the reflected ion population reveals that the reconnection process lasts about 30 min in a reconnection site located at a very large distance of several tens RE from the Cluster spacecraft. We also estimate the magnetopause motion and thickness during this event. This paper gives the first experimental study of magnetic reconnection during such rare periods of very low solar wind density. The results are discussed in the frame of magnetospheric response to extremely low solar wind density conditions.

Dependence of magnetopause reconnection events on interplanetary parameters

2020 ◽  
Author(s):  
Walter Gonzalez ◽  
Daiki Koga
Keyword(s):  
Solar Wind ◽  
Mach Number ◽  
Electric Field ◽  
Magnetic Reconnection ◽  
Flow Direction ◽  
Time History ◽  
Normal Vector ◽  
Dayside Magnetopause ◽  
Energy And Momentum ◽  
Magnetopause Reconnection

<p>Magnetic reconnection permits topological rearrangements of the interplanetary and magnetospheric magnetic fields and the entry of solar wind mass, energy, and momentum into the magnetosphere. Thus, magnetic reconnection is a key issue to understand space weather. However, it hasnot been fully understood yet under which interplanetary/magnetosheath conditions magnetic reconnection takes place more effectively at the dayside magnetopause. For this purpose,  in the present study 25 dayside magnetopause reconnection events are investigated using the Time History of Events and Macroscale Interactions during Substorms ( THEMIS ) spacecraft  observations. It was found, (1) that the reconnection electric field is proportional to the interplanetary electric field, (2) that the reconnection electric field is inversely proportional to the solar wind-Alfvén Mach number,  (3) that thereconnection outflow speed is proportional to the solar wind Alfvén speed, and (4) that the reconnection outflow speed is  inversely proportional to the magnetosheath plasma beta. Finally, it is shown that the range of magnetic shear angles for which magnetic reconnection should occur is restricted to large shears as the magnetosheath flow direction becomes more perpendicular to the direction of the local magnetopause normal vector. Since these results refer to fairly typical solar wind-Alfvén Mach number condition, they may not apply to more extreme cases.</p>

scholarly journals On the location of dayside magnetic reconnection during an interval of duskward oriented IMF

2007 ◽  
Vol 25 (1) ◽  
pp. 219-238 ◽  
Author(s):  
J. A. Wild ◽  
S. E. Milan ◽  
J. A. Davies ◽  
M. W. Dunlop ◽  
D. M. Wright ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Local Magnetic Field ◽  
High Latitudes ◽  
Reconnection Rate ◽  
Flux Tubes ◽  
Dayside Magnetopause ◽  
Line Passing ◽  
Open Flux

Abstract. We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs), namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs) and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection) may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field. While no one-to-one correspondence with the pulsed reconnection rate suggested by the ground-based observation of pulsed ionospheric flow has been demonstrated, we note that similar periodicity oscillations were observed throughout the solar wind-magnetosphere-ionosphere system. These findings are consistent with previously proposed mechanisms of solar wind modulation of the dayside reconnection rate.

scholarly journals Solar wind driving of magnetospheric ULF waves: Field line resonances driven by dynamic pressure fluctuations

2010 ◽  
Vol 115 (A11) ◽  
pp. n/a-n/a ◽  
Author(s):  
S. G. Claudepierre ◽  
M. K. Hudson ◽  
W. Lotko ◽  
J. G. Lyon ◽  
R. E. Denton
Keyword(s):  
Solar Wind ◽  
Field Line ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
Ulf Waves ◽  
Field Line Resonances

scholarly journals MMS Observations of Field Line Resonances Under Disturbed Solar Wind Conditions

2021 ◽  
Author(s):  
G. Le ◽  
P. J. Chi ◽  
R. J. Strangeway ◽  
C. T. Russell ◽  
J. A. Slavin ◽  
...  
Keyword(s):  
Solar Wind ◽  
Field Line ◽  
Field Line Resonances

scholarly journals Coherence between radar observations of magnetospheric field line resonances and discrete oscillations in the solar wind

2010 ◽  
Vol 28 (1) ◽  
pp. 47-59 ◽  
Author(s):  
J. A. E. Stephenson ◽  
A. D. M. Walker
Keyword(s):  
Solar Wind ◽  
Field Line ◽  
Sampling Rate ◽  
Driving Mechanism ◽  
Data Sets ◽  
Spectrum Estimation ◽  
Field Line Resonances ◽  
Entire Duration ◽  
High Degree

Abstract. Field line resonances have been observed for decades by ground-based and in situ instruments. The driving mechanism(s) are still unclear, although previous work has provided strong grounds that coherent waves in the solar wind may be a source. Here we present further evidence, with the use of multitaper analysis, a sophisticated spectrum estimation technique. A set of windows (dpss tapers) is chosen with characteristics that best suit the width of the narrowband peaks to be identified. The orthogonality of the windows allows for a confidence level (of say 95%) against a null hypothesis of a noisy spectrum, so that significant peaks can be identified. Employing multitaper analysis we can determine the phase and amplitude coherence at the sampling rate of the data sets and, over their entire duration. These characteristics make this technique superior to single windowing or wavelet analysis. A high degree of phase and amplitude (greater then 95%) coherence is demonstrated between a 2.1 mHz field line resonance observed by the SHARE radar at Sanae, Antarctica and the solar wind oscillation detected by WIND and ACE satellites.

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