The Foreshock

Eastwood, J. P.; Lucek, E.; Mazelle, C.; Meziane, K.; Narita, Yasuhito; Pickett, J. S.; Treumann, R. A.

doi:10.1007/1-4020-4582-4_3

Cited by 26 publications

(35 citation statements)

References 111 publications

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“…Stronger toroidal mode wave power in the Northern Hemisphere can be explained by this IMF orientation. Namely, the radially IMF dominant configuration favors formation of an ion foreshock upstream of the magnetopause (Eastwood et al., 2005). When both B x and B z are positive, a quasi‐parallel foreshock favors the Northern Hemisphere, leading to a more turbulent magnetosheath and elevated ULF disturbances in the Northern Hemisphere (Guglielmi et al., 2017; Hwang & Sibeck, 2016).…”

Section: Discussionmentioning

confidence: 99%

Multipoint Conjugate Observations of Dayside ULF Waves During an Extended Period of Radial IMF

et al. 2020

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Long-lasting Pc5 ultralow frequency (ULF) waves spanning the dayside and extending from L ∼ 5.5 into the polar cap region were observed by conjugate ground magnetometers. Observations from MMS satellites in the magnetosphere and magnetometers on the ground confirmed that the ULF waves on closed field lines were due to fundamental toroidal standing Alfvén waves. Monochromatic waves at lower latitudes tended to maximize their power away from noon in both the morning and afternoon sectors, while more broadband waves at higher latitudes tended to have a wave power maximum near noon. The wave power distribution and MMS satellite observations during the magnetopause crossing indicate surface waves on a Kelvin-Helmholtz (KH) unstable magnetopause coupled with standing Alfvén waves. The more turbulent ion foreshock during an extended period of radial interplanetary magnetic field (IMF) likely plays an important role in providing seed perturbations for the growth of the KH waves. These results indicate that the Pc5 waves observed on closed field lines and on the open field lines of the polar cap were from the same source. Plain Language Summary The Earth's magnetic field lines can oscillate at ultralow frequencies (ULF: 1 mHz to 5 Hz). These natural oscillations of closed magnetic field lines, analogous to vibrations on a stretched string, are also called geomagnetic pulsations or ULF waves. ULF waves play a key role in the transfer of energy from terrestrial space to Earth's upper atmosphere. In this study, we report a long-lasting large spatial scale ULF wave event observed by ground observatories from both hemispheres. Together with satellite measurements in space, we are able to confirm that these waves were driven by upstream turbulent structures due to the interaction between matter and electromagnetic fields emitted from the Sun and the Earth's outer atmosphere and magnetic field.

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Section: Discussionmentioning

confidence: 99%

Multipoint Conjugate Observations of Dayside ULF Waves During an Extended Period of Radial IMF

et al. 2020

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“…To summarize the observations, both MMS events show isolated SLAMS developed from ULF waves that are (1) right‐hand polarized and propagate earthward in the plasma frame and (2) gyro‐resonant with a significant subset of the solar wind ions. The presented SLAMS properties (characteristic time scales and waveforms) differ from the structures known as shocklets (e.g., Le & Russell, 1994) which are in part associated with 30 s ULF waves (e.g., Hoppe & Russell, 1983) that gyro‐resonate with backstreaming ions (Eastwood et al., 2005b).…”

Section: Spacecraft Measurementsmentioning

confidence: 94%

Solitary Magnetic Structures at Quasi‐Parallel Collisionless Shocks: Formation

Chen

Wang

et al. 2021

Geophysical Research Letters

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“…[3] Observations of the terrestrial foreshock have shown an abundance of ULF plasma wave activity. These waves have been investigated by many authors [e.g., Hoppe et al, 1981;Kennel et al, 1985;Greenstadt et al, 1995;Le and Russell, 1994;Burgess, 1997;Eastwood et al, 2005b] and their basic properties have been determined. Three different types of ULF waves have been identified, namely a 30 s period wave, a 3 s wave, and shocklets.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of terrestrial foreshock ULF waves: Cluster observations

et al. 2007

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[1] ULF waves in the terrestrial foreshock observed simultaneously by the four Cluster satellites were analyzed to identify the plasma wave modes and to study the effect of plasma beta on the intrinsic wave properties. The wave properties in the spacecraft and solar wind frames, such as the wave frequency, total wave number, phase speed, and wave polarization, are experimentally derived using the minimum variance analysis (MVA) for the case study and the phase differencing (MVA-free) technique for the statistical study. Both studies indicate that the waves with a 30 s period propagate in the upstream direction at a finite angle with respect to the background magnetic field in the plasma rest frame but are then convected downstream in the spacecraft frame. It is shown that these waves propagate in the fast magnetosonic mode. A similar analysis of the 3 s period waves shows them to be propagating in the upstream direction in the Alfvén/ion cyclotron mode. The measured wave properties in the plasma rest frame are in good agreement with theoretical kinetic dispersion relation with a different plasma beta, which has rather significant deviation from fluid model especially for the high plasma beta. In conclusion it is found that the experimentally derived foreshock ULF wave properties are basically in good agreement with previous results but the effect of plasma beta is indispensable to choose the correct wave mode branch especially for the high plasma beta condition.

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The Foreshock

Cited by 26 publications

References 111 publications

Multipoint Conjugate Observations of Dayside ULF Waves During an Extended Period of Radial IMF

Multipoint Conjugate Observations of Dayside ULF Waves During an Extended Period of Radial IMF

Solitary Magnetic Structures at Quasi‐Parallel Collisionless Shocks: Formation

Characteristics of terrestrial foreshock ULF waves: Cluster observations

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