scholarly journals The structure of low-latitude Pc3 pulsations observed by CHAMP and on the ground

2009 ◽  
Vol 27 (3) ◽  
pp. 1267-1277 ◽  
Author(s):  
D. C. Ndiitwani ◽  
P. R. Sutcliffe
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Field Measurements ◽  
Doppler Frequency ◽  
Resonance Region ◽  
Compressional Wave ◽  
Mhd Waves ◽  
Low Latitude ◽  
Field Line Resonance ◽  
Line Resonance

Abstract. The structure of low-latitude continuous pulsations termed Pc3, which are naturally occurring MHD waves in the Earth's magnetosphere, were studied by comparing ground and satellite magnetic field measurements. Data from two induction magnetometers, located at Hermanus and Sutherland in South Africa were used in conjunction with Challenging Minisatellite Payload (CHAMP) satellite observations to study a Pc3 event observed on 15 February 2003, at a time when CHAMP was passing over the ground stations. We observed a number of discrete frequency oscillations for the fast mode wave, one of which drives a field line resonance (FLR) at characteristic latitude as detected by both ground and satellite measurements. Consequently, our observations confirmed the compressional wave as being the driver of the field line resonance. The toroidal mode frequency observed on CHAMP experienced a Doppler frequency shift due to the rapid motion across the resonance region. Polarization hodograms in the resonance region clearly showed the expected 90° rotation of the field line resonant magnetic field components.

scholarly journals Magnetosonic resonance in a dipole-like magnetosphere

2006 ◽  
Vol 24 (8) ◽  
pp. 2277-2289 ◽  
Author(s):  
A. S. Leonovich ◽  
D. A. Kozlov ◽  
V. A. Pilipenko
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Ring Current ◽  
Effective Interaction ◽  
Field Line Resonance ◽  
Line Resonance ◽  
Field Lines

Abstract. A theory of resonant conversion of fast magnetosonic (FMS) waves into slow magnetosonic (SMS) oscillations in a magnetosphere with dipole-like magnetic field has been constructed. Monochromatic FMS waves are shown to drive standing (along magnetic field lines) SMS oscillations, narrowly localized across magnetic shells. The longitudinal and transverse structures, as well as spectrum of resonant SMS waves are determined. Frequencies of fundamental harmonics of standing SMS waves lie in the range of 0.1–1 mHz, and are about two orders of magnitude lower than frequencies of similar Alfvén field line resonance harmonics. This difference makes an effective interaction between these MHD modes impossible. The amplitude of SMS oscillations rapidly decreases along the field lines from the magnetospheric equator towards the ionosphere. In this context, magnetospheric SMS oscillations cannot be observed on the ground, and the ionosphere does not play any role either in their generation or dissipation. The theory developed can be used to interpret the occurrence of compressional Pc5 waves in a quiet magnetosphere with a weak ring current.

scholarly journals High-latitude dayside ionosphere response to Pc5 field line resonance

2003 ◽  
Vol 21 (7) ◽  
pp. 1509-1520 ◽  
Author(s):  
F. Pitout ◽  
P. Eglitis ◽  
P.-L. Blelly
Keyword(s):  
Electric Field ◽  
Field Line ◽  
High Latitude ◽  
Mhd Waves ◽  
Ion Temperature ◽  
Field Line Resonance ◽  
Temperature Oscillations ◽  
Dayside Magnetopause ◽  
Line Resonance ◽  
Ground Magnetic

Abstract. We report observations of pulsations due to Field Line Resonance (FLR) in the morning sector of the high-latitude dayside ionosphere on 1 February 1998. The Geotail spacecraft, ideally skimming the dayside magnetopause, monitored the magnetopause motion, which is seen to induce a modulated response of the ionosphere by means of ULF waves. Pulsations in the Pc5 frequency range were observed in the ground magnetic field measured by the IMAGE array, as well as in the electron and ion temperatures measured by the EISCAT Svalbard Radar. The ion temperature oscillations are an indicator of a modulated convection electric field while field-aligned currents (FAC) associated with the FLR control the electron temperature. We have performed a simulation of the ionosphere experiencing sinusoidal FAC and electric field in order to confirm our hypothesis. In addition to the ionospheric response, the possible cause of the FLR and processes involved are also discussed.Key words. Magnetospheric physics (MHD waves and instabilities; magnetosphere-ionosphere interactions) – Ionosphere (polar ionosphere)

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 Cluster spacecraft observations of a ULF wave enhanced by Space Plasma Exploration by Active Radar (SPEAR)

2009 ◽  
Vol 27 (9) ◽  
pp. 3591-3599 ◽  
Author(s):  
S. V. Badman ◽  
D. M. Wright ◽  
L. B. N. Clausen ◽  
R. C. Fear ◽  
T. R. Robinson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Space Plasma ◽  
Local Magnetic Field ◽  
Field Line Resonance ◽  
Ionospheric Heating ◽  
Ulf Wave ◽  
Line Resonance ◽  
Magnetometer Data ◽  
Field Lines

Abstract. Space Plasma Exploration by Active Radar (SPEAR) is a high-latitude ionospheric heating facility capable of exciting ULF waves on local magnetic field lines. We examine an interval from 1 February 2006 when SPEAR was transmitting a 1 Hz modulation signal with a 10 min on-off cycle. Ground magnetometer data indicated that SPEAR modulated currents in the local ionosphere at 1 Hz, and enhanced a natural field line resonance with a 10 min period. During this interval the Cluster spacecraft passed over the heater site. Signatures of the SPEAR-enhanced field line resonance were present in the magnetic field data measured by the magnetometer on-board Cluster-2. These are the first joint ground- and space-based detections of field line tagging by SPEAR.

scholarly journals Coordinated observation of field line resonance in the mid-tail

2006 ◽  
Vol 24 (2) ◽  
pp. 707-723 ◽  
Author(s):  
Y. Zheng ◽  
A. T. Y. Lui ◽  
I. R. Mann ◽  
K. Takahashi ◽  
J. Watermann ◽  
...  
Keyword(s):  
Field Line ◽  
Low Frequency ◽  
Field Measurements ◽  
Early Morning ◽  
Field Line Resonance ◽  
Cluster Data ◽  
Line Resonance ◽  
Field Lines ◽  
First Time

Abstract. Standing Alfvén waves of 1.1 mHz (~15 min in period) were observed by the Cluster satellites in the mid-tail during 06:00-07:00 UT on 8 August 2003. Pulsations with the same frequency were also observed at several ground stations near Cluster's footpoint. The standing wave properties were determined from the electric and magnetic field measurements of Cluster. Data from the ground magnetometers indicated a latitudinal amplitude and phase structure consistent with the driven field line resonance (FLR) at 1.1 mHz. Simultaneously, quasi-periodic oscillations at different frequencies were observed in the post-midnight/early morning sector by GOES 12 (l0≈8.7), Polar (l0≈11-14) and Geotail (l0≈9.8). The 8 August 2003 event yields rare and interesting datasets. It provides, for the first time, coordinated in situ and ground-based observations of a very low frequency FLR in the mid-tail on stretched field lines.

scholarly journals Statistical analysis of ground based magnetic field measurements with the field line resonance detector

2008 ◽  
Vol 26 (11) ◽  
pp. 3477-3489 ◽  
Author(s):  
F. Plaschke ◽  
K.-H. Glassmeier ◽  
O. D. Constantinescu ◽  
I. R. Mann ◽  
D. K. Milling ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Wave Field ◽  
Field Line ◽  
Field Measurements ◽  
Dispersion Analysis ◽  
Spectral Energy ◽  
Field Line Resonance ◽  
Resonance Detector ◽  
Line Resonance ◽  
One Year

Abstract. In this paper we introduce the field line resonance detector (FLRD), a wave telescope technique which has been specially adapted to estimate the spectral energy density of field line resonance (FLR) phase structures in a superposed wave field. The field line resonance detector is able to detect and correctly characterize several superposed FLR structures of a wave field and therefore constitutes a new and powerful tool in ULF pulsation studies. In our work we derive the technique from the classical wave telescope beamformer and present a statistical analysis of one year of ground based magnetometer data from the Canadian magnetometer network CANOPUS, now known as CARISMA. The statistical analysis shows that the FLRD is capable of detecting and characterizing superposed or hidden FLR structures in most of the detected ULF pulsation events; the one year statistical database is therefore extraordinarily comprehensive. The results of this analysis confirm the results of previous FLR characterizations and furthermore allow a detailed generalized dispersion analysis of FLRs.

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