High-latitude observations of impulse-driven ULF pulsations in the ionosphere and on the ground

Abstract. We report the simultaneous observation of 1.6–1.7 mHz pulsations in the ionospheric F-region with the CUTLASS bistatic HF radar and an HF Doppler sounder, on the ground with the IMAGE and SAMNET magnetometer arrays, and in the upstream solar wind. CUTLASS was at the time being operated in a special mode optimized for high resolution studies of ULF waves. A novel use is made of the ground returns to detect the ionospheric signature of ULF waves. The pulsations were initiated by a strong, sharp decrease in solar wind dynamic pressure near 09:28 UT on 23 February 1996, and persisted for some hours. They were observed with the magnetometers over 20° in latitude, coupling to a field line resonance near 72° magnetic latitude. The magnetic pulsations had azimuthal m numbers ~ -2, consistent with propagation away from the noon sector. The radars show transient high velocity flows in the cusp and auroral zones, poleward of the field line resonance, and small amplitude 1.6–1.7 mHz F-region oscillations across widely spaced regions at lower latitudes. The latter were detected in the radar ground scatter returns and also with the vertical incidence Doppler sounder. Their amplitude is of the order of ± 10 ms-1. A similar perturbation frequency was present in the solar wind pressure recorded by the WIND spacecraft. The initial solar wind pressure decrease was also associated with a decrease in cosmic noise absorption on an imaging riometer near 66° magnetic latitude. The observations suggest that perturbations in the solar wind pressure or IMF result in fast compressional mode waves that propagate through the magnetosphere and drive forced and resonant oscillations of geomagnetic field lines. The compressional wave field may also stimulate ionospheric perturbations. The observations demonstrate that HF radar ground scatter may contain important information on small-amplitude features, extending the scope and capability of these radars to track features in the ionosphere.Key words. Ionosphere (Ionosphere-magnetosphere interactions; ionospheric disturbances) – Magnetospheric physics (MHD waves and instabilities)

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Pseudo-field line resonances in ground Pc5 pulsation events

Annales Geophysicae ◽

10.5194/angeo-23-593-2005 ◽

2005 ◽

Vol 23 (2) ◽

pp. 593-608 ◽

Cited By ~ 7

Author(s):

D. V. Sarafopoulos

Keyword(s):

Solar Wind ◽

Field Line ◽

Large Scale ◽

Research Effort ◽

Current System ◽

Oscillation Mode ◽

Wind Pressure ◽

Single Vortex ◽

Solar Wind Pressure ◽

Current Systems

Abstract. In this work we study four representative cases of Pc5 ground pulsation events with discrete and remarkably stable frequencies extended at least in a high-latitude range of ~20°; a feature that erroneously gives the impression for an oscillation mode with "one resonant field line". Additionally, the presented events show characteristic changes in polarization sense, for a meridian chain of stations from the IMAGE array, and maximize their amplitude at or close to the supposed resonant magnetic field shell, much like the typical FLR. Nevertheless, they are not authentic FLRs, but pseudo-FLRs, as they are called. These structures are produced by repetitive and tilted twin-vortex structures caused by magnetopause surface waves, which are probably imposed by solar wind pressure waves. The latter is confirmed with in-situ measurements obtained by the Cluster satellites, as well as the Geotail, Wind, ACE, and LANL 1994-084 satellites. This research effort is largely based on two recent works: first, Sarafopoulos (2004a) has observationally established that a solar wind pressure pulse (stepwise pressure variation) produces a twin-vortex (single vortex) current system over the ionosphere; second, Sarafopoulos (2004b) has studied ground events with characteristic dispersive latitude-dependent structures and showed that these are associated with twin-vortex ionosphere current systems. In this work, we show that each pseudo-FLR event is associated with successive and tilted large-scale twin-vortex current systems corresponding to a magnetopause surface wave with wavelength 10-20RE. We infer that between an authentic FLR, which is a spatially localized structure with an extent 0.5RE in the magnetospheric equatorial plane, and the magnetopause surface wavelength, there is a scale factor of 20-40. A chief observational finding, in this work, is that there are Pc5 ground pulsation events showing two gradual and latitude dependent phase-shifts of 180°, at the same time.

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Multi-satellite study of the excitation of Pc3 and Pc4-5 ULF waves and their penetration across the plasmapause during the 2003 Halloween superstorm

Annales Geophysicae ◽

10.5194/angeo-33-1237-2015 ◽

2015 ◽

Vol 33 (10) ◽

pp. 1237-1252 ◽

Cited By ~ 9

Author(s):

G. Balasis ◽

I. A. Daglis ◽

I. R. Mann ◽

C. Papadimitriou ◽

E. Zesta ◽

...

Keyword(s):

Solar Wind ◽

Field Line ◽

Magnetic Data ◽

Topside Ionosphere ◽

Ulf Waves ◽

Inhomogeneous Field ◽

Range Analysis ◽

Field Line Resonance ◽

Time Frequency ◽

Line Resonance

Abstract. We use multi-satellite and ground-based magnetic data to investigate the concurrent characteristics of Pc3 (22–100 mHz) and Pc4-5 (1–22 mHz) ultra-low-frequency (ULF) waves on the 31 October 2003 during the Halloween magnetic superstorm. ULF waves are seen in the Earth's magnetosphere, topside ionosphere, and Earth's surface, enabling an examination of their propagation characteristics. We employ a time–frequency analysis technique and examine data from when the Cluster and CHAMP spacecraft were in good local time (LT) conjunction near the dayside noon–midnight meridian. We find clear evidence of the excitation of both Pc3 and Pc4-5 waves, but more significantly we find a clear separation in the L shell of occurrence of the Pc4-5 and Pc3 waves in the equatorial inner magnetosphere, separated by the density gradients at the plasmapause boundary layer. A key finding of the wavelet spectral analysis of data collected from the Geotail, Cluster, and CHAMP spacecraft and the CARISMA and GIMA magnetometer networks was a remarkably clear transition of the waves' frequency into dominance in a higher-frequency regime within the Pc3 range. Analysis of the local field line resonance frequency suggests that the separation of the Pc4-5 and Pc3 emissions across the plasmapause is consistent with the structure of the inhomogeneous field line resonance Alfvén continuum. The Pc4-5 waves are consistent with direct excitation by the solar wind in the plasma trough, as well as Pc3 wave absorption in the plasmasphere following excitation by upstream waves originating at the bow shock in the local noon sector. However, despite good solar wind coverage, our study was not able to unambiguously identify a clear explanation for the sharp universal time (UT) onset of the discrete frequency and large-amplitude Pc3 wave power.

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Systematical Analyses of Global Ionospheric Disturbance Current Systems Caused by Multiple Processes: Penetration Electric Fields, Solar Wind Pressure Impulses, Magnetospheric Substorms, and ULF Waves

Journal of Geophysical Research Space Physics ◽

10.1029/2020ja027942 ◽

2020 ◽

Vol 125 (9) ◽

Author(s):

Chao‐Song Huang

Keyword(s):

Solar Wind ◽

Electric Fields ◽

Ionospheric Disturbance ◽

Wind Pressure ◽

Ulf Waves ◽

Magnetospheric Substorms ◽

Multiple Processes ◽

Solar Wind Pressure ◽

Current Systems

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Observational features of field line resonances excited by solar wind pressure variations on 4 September 1984

Planetary and Space Science ◽

10.1016/0032-0633(90)90157-l ◽

1990 ◽

Vol 38 (12) ◽

pp. 1517-1531 ◽

Cited By ~ 6

Author(s):

J. Warnecke ◽

H. Lühr ◽

K. Takahashi

Keyword(s):

Solar Wind ◽

Field Line ◽

Wind Pressure ◽

Field Line Resonances ◽

Solar Wind Pressure

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Solar wind and substorm excitation of the wavy current sheet

Annales Geophysicae ◽

10.5194/angeo-27-2457-2009 ◽

2009 ◽

Vol 27 (6) ◽

pp. 2457-2474 ◽

Cited By ~ 25

Author(s):

C. Forsyth ◽

M. Lester ◽

R. C. Fear ◽

E. Lucek ◽

I. Dandouras ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Current Sheet ◽

Pressure Pulse ◽

Wind Pressure ◽

Expansion Velocity ◽

Solar Wind Pressure ◽

Wave Models ◽

Best Fit ◽

The Magnetic Field

Abstract. Following a solar wind pressure pulse on 3 August 2001, GOES 8, GOES 10, Cluster and Polar observed dipolarizations of the magnetic field, accompanied by an eastward expansion of the aurora observed by IMAGE, indicating the occurrence of two substorms. Prior to the first substorm, the motion of the plasma sheet with respect to Cluster was in the ZGSM direction. Observations following the substorms show the occurrence of current sheet waves moving predominantly in the −YGSM direction. Following the second substorm, the current sheet waves caused multiple current sheet crossings of the Cluster spacecraft, previously studied by Zhang et al. (2002). We further this study to show that the velocity of the current sheet waves was similar to the expansion velocity of the substorm aurora and the expansion of the dipolarization regions in the magnetotail. Furthermore, we compare these results with the current sheet wave models of Golovchanskaya and Maltsev (2005) and Erkaev et al. (2008). We find that the Erkaev et al. (2008) model gives the best fit to the observations.

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Global MHD modeling of the impact of a solar wind pressure change

Journal of Geophysical Research Atmospheres ◽

10.1029/2001ja000060 ◽

2002 ◽

Vol 107 (A7) ◽

Cited By ~ 30

Author(s):

Kristi A. Keller

Keyword(s):

Solar Wind ◽

Pressure Change ◽

Wind Pressure ◽

Solar Wind Pressure ◽

Mhd Modeling ◽

The Impact

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Induced and Permanent Magnetism on the Moon: Structural and Evolutionary Implications

Highlights of Astronomy ◽

10.1017/s1539299600000113 ◽

1971 ◽

Vol 2 ◽

pp. 173-188

Author(s):

C. P. Sonett ◽

P. Dyal ◽

D. S. Colburn ◽

B. F. Smith ◽

G. Schubert ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Dynamic Pressure ◽

Wind Pressure ◽

Dark Side ◽

The Moon ◽

Permanent Magnetic Field ◽

Crustal Layer ◽

Induced Field ◽

Solar Wind Pressure

AbstractIt is shown that the Moon possesses an extraordinary response to induction from the solar wind due to a combination of a high interior electrical conductivity together with a relatively resistive crustal layer into which the solar wind dynamic pressure forces back the induced field. The dark side response, devoid of solar wind pressure, is approximately that expected for the vacuum case. These data permit an assessment of the interior conductivity and an estimate of the thermal gradient in the crustal region. The discovery of a large permanent magnetic field at the Apollo 12 site corresponds approximately to the paleomagnetic residues discovered in both Apollo 11 and 12 rock samples The implications regarding an early lunar magnetic field are discussed and it is shown that among the various conjectures regarding the early field the most prominent are either an interior dynamo or an early approach to the Earth though no extant model is free of difficulties.

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