scholarly journals Excitation of field line resonances by MHD waves originating in the solar wind

2002 ◽  
Vol 107 (A12) ◽  
pp. SMP 38-1-SMP 38-14 ◽  
Author(s):  
A. D. M. Walker
Keyword(s):  
Solar Wind ◽  
Field Line ◽  
Mhd Waves ◽  
Field Line Resonances

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 Upstream waves and field line resonances: simultaneous presence and alternation in Pc3 pulsation events

1998 ◽  
Vol 16 (1) ◽  
pp. 34-48 ◽  
Author(s):  
J. Verõ ◽  
H. Lühr ◽  
M. Vellante ◽  
I. Best ◽  
J. Střeštik ◽  
...  
Keyword(s):  
Field Line ◽  
Geomagnetic Field ◽  
Interplanetary Medium ◽  
Mhd Waves ◽  
Field Line Resonance ◽  
Field Line Resonances ◽  
Line Resonance ◽  
Mhd Waves And Instabilities ◽  
Field Lines ◽  
Upstream Waves

Abstract. Based on a detailed study of Pc3 events at an array between L = 1.5 and 3 in Central Europe, the authors found quick changes between upstream waves (UW, i.e. pulsation directly driven by UW) and field line resonance (FLR, i.e. azimuthal oscillations of geomagnetic field lines). The alternation of the two types is especially characteristic (and the UW part stronger) if the interplanetary magnetic field (IMF) is highly variable. Events due to field line resonance may have a structure consisting of multiple lines with frequencies differing by about 10%, corresponding to neighbouring shells of field lines separated by about 100 km at the surface. This coincides with previous findings (about 10% at a meridional distance of 80 km). The frequency of the UW type is well correlated with the frequency of waves in the interplanetary medium. Additionally, there are signals of unidentified origin which also seem to be influenced by IMF.>Key words. Magnetosphere Physics · MHD waves and instabilities · Plasmasphere · Solar wind/magnetosphere interactions

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 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 High-latitude HF Doppler observations of ULF waves. 1. Waves with large spatial scale sizes

1997 ◽  
Vol 15 (12) ◽  
pp. 1548-1556 ◽  
Author(s):  
D. M. Wright ◽  
T. K. Yeoman ◽  
P. J. Chapman
Keyword(s):  
Field Line ◽  
High Latitude ◽  
Vertical Component ◽  
Low Frequency ◽  
Mhd Waves ◽  
Ulf Waves ◽  
Large Spatial Scale ◽  
Field Line Resonances ◽  
Doppler Data ◽  
Magnetometer Data

Abstract. A quantitative study of observations of the ionospheric signatures of magnetospheric ultra low frequency (ULF) waves by a high-latitude (geographic: 69.6°N 19.2°E) high-frequency Doppler sounder has been undertaken. The signatures, which are clearly correlated with pulsations in ground magnetometer data, exhibit periods in the range 100–400 s and have azimuthal wave numbers in the range 3–8. They are interpreted here as local field line resonances. Phase information provided by O- and X-mode Doppler data support the view that these are associated with field line resonances having large azimuthal scale sizes. The relative phases and amplitudes of the signatures in the Doppler and ground magnetometer data are compared with a model for the generation of Doppler signatures from incident ULF waves. The outcome suggests that the dominant mechanism involved in producing the Doppler signature is the vertical component of an E × B bulk motion of the local plasma caused by the electric field perturbation of the ULF wave.Key words. Auroral ionosphere · Magnetosphere-ionosphere interactions · MHD waves and instabilities HF Doppler · ULF Waves

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.

scholarly journals 3-D global hybrid simulations of magnetospheric response to foreshock processes

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Feng Shi ◽  
Yu Lin ◽  
Xueyi Wang ◽  
Boyi Wang ◽  
Yukitoshi Nishimura
Keyword(s):  
Solar Wind ◽  
Field Line ◽  
Mode Conversion ◽  
Wave Spectrum ◽  
Alfven Waves ◽  
Wide Frequency Range ◽  
Alfvén Waves ◽  
Wave Power ◽  
Field Line Resonances ◽  
Field Aligned Current

AbstractIt has been suggested that ion foreshock waves originating in the solar wind upstream of the quasi-parallel (Q-||) shock can impact the planetary magnetosphere leading to standing shear Alfvén waves, i.e., the field line resonances (FLRs). In this paper, we carry out simulations of interaction between the solar wind and terrestrial magnetosphere under radial interplanetary magnetic field conditions by using a 3-D global hybrid model, and show the properties of self-consistently generated field line resonances through direct mode conversion in magnetospheric response to the foreshock disturbances for the first time. The simulation results show that the foreshock disturbances from the Q-|| shock can excite magnetospheric ultralow-frequency waves, among which the toroidal Alfvén waves are examined. It is found that the foreshock wave spectrum covers a wide frequency range and matches the band of FLR harmonics after excluding the Doppler shift effects. The fundamental harmonic of field line resonances dominates and has the strongest wave power, and the higher the harmonic order, the weaker the corresponding wave power. The nodes and anti-nodes of the odd and even harmonics in the equatorial plane are also presented. In addition, as the local Alfvén speed increases earthward, the corresponding frequency of each harmonic increases. The field-aligned current in the cusp region indicative of the possibly observable aurora is found to be a result of magnetopause perturbation which is caused by the foreshock disturbances, and a global view substantiating this scenario is given. Finally, it is found that when the solar wind Mach number decreases, the strength of both field line resonance and field-aligned current decreases accordingly.

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.

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