Hydromagnetic waves excited during an ssc

Kaufmann, Richard L.; Walker, D. N.

doi:10.1029/ja079i034p05187

Cited by 40 publications

(24 citation statements)

References 20 publications

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“…A series of Psc oscillations follows, at all stations. Such waves have been shown to be associated with sudden commencements and sudden impulses (Voelker, 1966;Saito and Matsushita, 1967;Kaufman and Walker, 1974). For at least three complete periods, the oscillations in the H-component at the higher two stations are approximately 180° out of phase with the oscillations observed at the lower latitude stations.…”

Section: Response Amplitude Resonance and Phase Reversalsmentioning

confidence: 84%

The CME Event of February 21, 1994: Response of the Magnetic Field at the Earth's Surface.

Petrinec

Yumoto

Lühr

et al. 1996

J. geomagn. geoelec

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On February 21, 1994, a large coronal mass ejection (CME) passed by the Earth. In the solar wind, the CME front was noted by very large changes in the solar wind dynamic pressure, flow direction, and magnetic field, as measured by several spacecraft. At the Earth's surface, many ground stations also recorded the passage of this CME, as a storm sudden commencement onset. We examine here several interesting features of the surface magnetic field response to this sudden commencement onset. In particular, we use the magnetometer records to examine the propagation time of the initial impulse along the Earth's surface. We also study in detail the initial amplitude change at several stations, and note the variation in the response as a function of magnetic latitude. In addition, we crudely estimate the relative contributions of the Chapman-Ferraro and the ionospheric current system to the surface response. Also of interest is the polarization and period of Psc oscillations superposed on the main impulse at several stations, including polarization reversals as a function of magnetic latitude. Corresponding ionospheric currents at stations along the 210° MM chain are also computed, and very large and sudden changes in the ionospheric current flow patterns are reported during the initial minutes of the sudden commencement onset. These and other results are interpreted in terms of previous models, paradigms, and statistical results.

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Section: Response Amplitude Resonance and Phase Reversalsmentioning

confidence: 84%

The CME Event of February 21, 1994: Response of the Magnetic Field at the Earth's Surface.

Petrinec

Yumoto

Lühr

et al. 1996

J. geomagn. geoelec

View full text Add to dashboard Cite

show abstract

“…If sudden and/or step‐like increases in the solar wind dynamic pressure hit the magnetopause, the magnetosphere is compressed and broadband fast mode waves may be launched because of the impulsive nature of the source. Observations suggest that such fast mode waves couple to local standing Alfvén waves [ Kaufmann and Walker , 1974; Baumjohann et al , 1984; Laakso and Schmidt , 1989], which are characterized by an azimuthal magnetic field oscillation and a radial electric field oscillation, through the field line resonance process. The theoretical description of the coupling process is well established for a monochromatic source [ Chen and Hasegawa , 1974; Southwood , 1974] and for an impulsive (i.e., broadband) source [ Hasegawa et al , 1983; Kivelson and Southwood , 1985].…”

Section: Introductionmentioning

confidence: 99%

Magnetospheric responses to sudden and quasiperiodic solar wind variations

Kim¹

2002

J.‐Geophys.‐Res.

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On April 13 (day 103), 2001, 0700–1400 UT, the Polar satellite experienced different plasma regimes (i.e., magnetosphere, magnetosheath, and solar wind) because of the solar wind dynamic pressure variations and its high orbital inclination near the subsolar magnetopause meridian. When Polar was in the magnetosheath, quasiperiodic spacecraft potential (SP) variations, corresponding to density variations, with a recurrence time of ∼3–10 min were observed. Using simultaneous solar wind observations, it was confirmed that the magnetosheath SP variations were inherent in the solar wind. We observed an almost one‐to‐one correspondence between the SP variations and the geomagnetic field perturbations at lower latitudes (L = 1.1–2.8) on the nightside. At higher latitudes (L = 2.9–6.1) on the dayside, however, the field perturbations are more complicated than the magnetosheath SP variations. This suggests that if the magnetospheric perturbations produced by the external source (solar wind/magnetosheath pressure variations) deeply penetrate into the magnetosphere, the lower‐latitude data on the nightside are important to monitor the external source variations. In addition, we observed the radial electric field oscillations excited nearly simultaneously with the magnetic field enhancement, associated with a sudden increase in the solar wind dynamic pressure, when Polar was in the magnetosphere. These oscillations may be considered as transient standing Alfvén waves excited by externally applied pressure changes as reported by previous studies.

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“…Whereas these studies suggest that nightside toroidal oscillations are associated with the onset of a substorm, the substorm onset may not be the only source mechanism. In fact, changes in the solar wind dynamic pressure that produce storm sudden commencement (ssc) signatures on the ground are known to excite toroidal waves at various local times [Kaufmann and Walker, 1974;Baumjohann et al, 1984;Kuwashima and Fukunishi, 1985]. With single-spacecraft observations it is difficult to determine the location of TTW sources.…”

Section: Introductionmentioning

confidence: 99%

Multisatellite study of nightside transient toroidal waves

Takahashi¹,

Anderson²,

Ohtani³

1996

J. Geophys. Res.

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Transverse magnetic pulsations polarized in the east‐west direction (toroidal waves) are a common feature in the dayside magnetosphere, but they are also observed in the nightside magnetosphere in the form of transient oscillations typically lasting 10–20 min. Until now, little attention has been paid to these transient toroidal waves (TTWs). To get insight into the propagation mode and generation mechanism of TTWs, we have examined magnetic field records from the elliptically orbiting AMPTE CCE, geostationary GOES 5 (located at a geographic longitude of ∼75° W), and GOES 6 (∼ 100°W) satellites. We find that TTW onset times are often simultaneous among the satellites within an accuracy of 1–2 min, but that the wave periods differ from one satellite to another. The latter feature is evidence that TTWs are due to standing Alfvén waves on individual magnetic field lines. Additional evidence of the standing waves is provided from the phase relationship between oscillations in magnetic field and ion flux anisotropy. We show by a numerical calculation of the ionospheric damping rate that toroidal mode standing waves can last for a few wave periods once they are excited. Thus, the general lack of continuous toroidal waves on the nightside can be attributed to the absence of sources rather than to strong ionospheric damping. Using CCE data and ground magnetic field data, we confirm that TTWs can be observed immediately following ∼30% (∼2%) of substorm onsets when the satellite is on the nightside (dayside) at 4 < L < 7. Substorms and pseudo substorm onsets produce magnetohydrodynamic disturbances in the near‐Earth magnetotail, and these disturbances appear to be a major source of TTWs.

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Hydromagnetic waves excited during an ssc

Cited by 40 publications

References 20 publications

The CME Event of February 21, 1994: Response of the Magnetic Field at the Earth's Surface.

The CME Event of February 21, 1994: Response of the Magnetic Field at the Earth's Surface.

Magnetospheric responses to sudden and quasiperiodic solar wind variations

Multisatellite study of nightside transient toroidal waves

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