An initial response of magnetic fields at geosynchronous orbit to Pi 2 onset as observed from the dip-equator

Abstract. Fluxgate magnetometer data recorded at the dip-equator (Huancayo, Peru; 1.44°N, 355.9° in geomagnetic coordinates; 12.1°S, 75.2°W in geographic coordinates; L = 1.00) with higher accuracy of timing (0.1 s) and amplitude resolution (0.01 nT) were utilized to survey an onset of Pi 2 pulsations in the midnight sector (2100–0100 LT) during PROMIS (Polar Region and Outer Magnetosphere International Study) periods (1 March–20 June, 1986). It is found that changing field line magnitude and vector as observed by magnetometer on board the synchronous satellites in the midnight sector often takes place simultaneously with the onset of Pi 2 pulsations at the dip-equator. The field disturbances that follow thereafter tend to last for some time both at the geosynchronous altitudes and the dip-equator. In this report, we examine the initial response of the field lines in space, and attempt to classify how the field line vector changed in the meridional plane. Key words. Magnetospheric physics · Magnetospheric configuration and dynamics · MHD waves and instabilities · Plasmasphere

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A slow mode wave as a possible source of Pi 2 and associated particle precipitation: a case study

Annales Geophysicae ◽

10.1007/s00585-999-0674-4 ◽

1999 ◽

Vol 17 (5) ◽

pp. 674-681 ◽

Cited By ~ 7

Author(s):

O. Saka ◽

O. Watanabe ◽

K. Okada ◽

D. N. Baker

Keyword(s):

Mhd Waves ◽

Wave Form ◽

Fluxgate Magnetometer ◽

Syowa Station ◽

Low Energy Electrons ◽

Dip Equator ◽

Substorm Activity ◽

Mhd Waves And Instabilities ◽

Break Up ◽

Auroral Phenomena

Abstract. An intensification of auroral luminosity referred to as an auroral break-up often accompanies the onset of geomagnetic pulsation (Pi 2) at the dip-equator. One such auroral break-up occurred at 2239 UT on 16 June, 1986, being accompanied by weak substorm activity (AE~50 nT) which was recorded in all-sky image of Syowa Station, Antarctica (66.2°S, 71.8°E in geomagnetic coordinates). The associated Pi 2 magnetic pulsation was detected by a fluxgate magnetometer in the afternoon sector at the dip-equator (Huancayo, Peru; 1.44°N, 355.9° in geomagnetic coordinates; 12.1°S, 75.2°W in geographic coordinates; L=1.00). In spite of the large separation of the two stations in longitude and latitude, the auroral break-up and subsequent luminosity modulation were seen to be correlated with the wave form of the ground Pi 2 pulsation. This occurred in such a way that the luminosity maximum was seen to occur at the phase of maximum amplitudes of Pi 2 wave form. We argue that the observed correlation could be interpreted as indicating a Pi 2-modulation of a field-aligned acceleration of the low energy electrons that may occur near the equator of the midnight magnetosphere.Key words. Magnetospheric physics (auroral phenomena; energetic particles · precipitating; MHD waves and instabilities)

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

Annales Geophysicae ◽

10.1007/s00585-997-0034-1 ◽

1998 ◽

Vol 16 (1) ◽

pp. 34-48 ◽

Cited By ~ 13

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

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

Annales Geophysicae ◽

10.5194/angeo-27-3591-2009 ◽

2009 ◽

Vol 27 (9) ◽

pp. 3591-3599 ◽

Cited By ~ 1

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.

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

Annales Geophysicae ◽

10.1007/s00585-997-1548-2 ◽

1997 ◽

Vol 15 (12) ◽

pp. 1548-1556 ◽

Cited By ~ 10

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

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SPATIAL STRUCTURE OF AZIMUTHALLY SMALL-SCALE MHD WAVES IN ONE-DIMENSIONALLY INHOMOGENEOUS FINITE PRESSURE PLASMA WITH CURVED FIELD LINES

Solnechno-Zemnaya Fizika ◽

10.12737/szf-61202006 ◽

2020 ◽

Vol 6 (1) ◽

pp. 63-74

Author(s):

Aleksandr Petrashchuk ◽

Dmitriy Klimushkin

Keyword(s):

Spatial Structure ◽

Field Line ◽

Wave Structure ◽

Plasma Pressure ◽

Mhd Waves ◽

Small Scale ◽

Radial Coordinate ◽

Pressure Plasma ◽

Transparent Region ◽

Field Lines

We have studied propagation of hydromagnetic (MHD) waves in one-dimensionally inhomogeneous finite pressure plasma with curved field lines. Magnetic surfaces are considered to be concentric cylinders, where the cylinder’s radius models the radial coordinate in Earth’s magnetosphere. The waves are supposed to be azimuthally small-scale. In this approximation there are only two MHD modes — Alfvén and slow magnetosonic (SMS). We have derived an ordinary differential equation for the spatial structure of the wave field in this model. We have examined the character of the singularity on the surface of Alfvén and SMS resonances and the influence of field line curvature on them. We have determined wave transparent regions. The SMS transparent region was found to essentially broaden as compared to the straight field line case. The very existence of the Alfvén transparent region is caused by the field line curvature and finite plasma pressure; otherwise, the wave structure is represented by a localized resonance.

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Cluster observations of surface waves on the dawn flank magnetopause

Annales Geophysicae ◽

10.5194/angeo-22-971-2004 ◽

2004 ◽

Vol 22 (3) ◽

pp. 971-983 ◽

Cited By ~ 39

Author(s):

C. J. Owen ◽

M. G. G. T. Taylor ◽

I. C. Krauklis ◽

A. N. Fazakerley ◽

M. W. Dunlop ◽

...

Keyword(s):

Mhd Waves ◽

Driving Mechanism ◽

Magnetic Field Direction ◽

Wave Propagation Direction ◽

Magnetospheric Configuration And Dynamics ◽

Trailing Edges ◽

Field Lines ◽

The Waves ◽

Two Populations ◽

Spacecraft Location

Abstract. On 14 June 2001 the four Cluster spacecraft recorded multiple encounters of the dawn-side flank magnetopause. The characteristics of the observed electron populations varied between a cold, dense magnetosheath population and warmer, more rarified boundary layer population on a quasi-periodic basis. The demarcation between these two populations can be readily identified by gradients in the scalar temperature of the electrons. An analysis of the differences in the observed timings of the boundary at each spacecraft indicates that these magnetopause crossings are consistent with a surface wave moving across the flank magnetopause. When compared to the orientation of the magnetopause expected from models, we find that the leading edges of these waves are approximately 45° steeper than the trailing edges, consistent with the Kelvin-Helmholtz (KH) driving mechanism. A stability analysis of this interval suggests that the magnetopause is marginally stable to this mechanism during this event. Periods in which the analysis predicts that the magnetopause is unstable correspond to observations of greater wave steepening. Analysis of the pulses suggests that the waves have an average wavelength of approximately 3.4 RE and move at an average speed of ~65km s-1 in an anti-sunward and northward direction, despite the spacecraft location somewhat south of the GSE Z=0 plane. This wave propagation direction lies close to perpendicular to the average magnetic field direction in the external magnetosheath, suggesting that these waves may preferentially propagate in the direction that requires no bending of these external field lines Key words. Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and unstabilities; solar wind-magnetosphere interactions)

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SPATIAL STRUCTURE OF AZIMUTHALLY SMALL-SCALE MHD WAVES IN ONE-DIMENSIONALLY INHOMOGENEOUS FINITE PRESSURE PLASMA WITH CURVED FIELD LINES

Solar-Terrestrial Physics ◽

10.12737/stp-61202006 ◽

2020 ◽

Vol 6 (1) ◽

pp. 50-59

Author(s):

Aleksandr Petrashchuk ◽

Dmitriy Klimushkin

Keyword(s):

Spatial Structure ◽

Field Line ◽

Wave Structure ◽

Plasma Pressure ◽

Mhd Waves ◽

Small Scale ◽

Radial Coordinate ◽

Pressure Plasma ◽

Transparent Region ◽

Field Lines

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High resolution observations of spectral width features associatedwith ULF wave signatures in artificial HF radar backscatter

Annales Geophysicae ◽

10.5194/angeo-22-169-2004 ◽

2004 ◽

Vol 22 (1) ◽

pp. 169-182 ◽

Cited By ~ 4

Author(s):

D. M. Wright ◽

T. K. Yeoman ◽

L. J. Baddeley ◽

J. A. Davies ◽

R. S. Dhillon ◽

...

Keyword(s):

High Resolution ◽

Plasma Source ◽

Spectral Width ◽

Hf Radar ◽

Mhd Waves ◽

Small Scale ◽

Ulf Waves ◽

Source Population ◽

Radar Backscatter ◽

Field Lines

Abstract. The EISCAT high power heating facility at Tromsø, northern Norway, has been utilised to generate artificial radar backscatter in the fields of view of the CUTLASS HF radars. It has been demonstrated that this technique offers a means of making very accurate and high resolution observations of naturally occurring ULF waves. During such experiments, the usually narrow radar spectral widths associated with artificial irregularities increase at times when small scale-sized (high m-number) ULF waves are observed. Possible mechanisms by which these particle-driven high-m waves may modify the observed spectral widths have been investigated. The results are found to be consistent with Pc1 (ion-cyclotron) wave activity, causing aliasing of the radar spectra, in agreement with previous modelling work. The observations also support recent suggestions that Pc1 waves may be modulated by the action of longer period ULF standing waves, which are simultaneously detected on the magnetospheric field lines. Drifting ring current protons with energies of ∼ 10keV are indicated as a common plasma source population for both wave types. Key words. Magnetospheric physics (MHD waves and instabilities) – Space plasma physics (wave-particle interactions) – Ionosphere (active experiments)

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The development of magnetic field line wander by plasma turbulence

Journal of Plasma Physics ◽

10.1017/s0022377817000617 ◽

2017 ◽

Vol 83 (4) ◽

Cited By ~ 5

Author(s):

Gregory G. Howes ◽

Sofiane Bourouaine

Keyword(s):

Magnetic Field ◽

Field Line ◽

Magnetic Field Line ◽

Large Scale ◽

Magnetic Energy ◽

Plasma Turbulence ◽

Alfven Wave ◽

Astrophysical Plasmas ◽

Field Lines ◽

The Magnetic Field

Plasma turbulence occurs ubiquitously in space and astrophysical plasmas, mediating the nonlinear transfer of energy from large-scale electromagnetic fields and plasma flows to small scales at which the energy may be ultimately converted to plasma heat. But plasma turbulence also generically leads to a tangling of the magnetic field that threads through the plasma. The resulting wander of the magnetic field lines may significantly impact a number of important physical processes, including the propagation of cosmic rays and energetic particles, confinement in magnetic fusion devices and the fundamental processes of turbulence, magnetic reconnection and particle acceleration. The various potential impacts of magnetic field line wander are reviewed in detail, and a number of important theoretical considerations are identified that may influence the development and saturation of magnetic field line wander in astrophysical plasma turbulence. The results of nonlinear gyrokinetic simulations of kinetic Alfvén wave turbulence of sub-ion length scales are evaluated to understand the development and saturation of the turbulent magnetic energy spectrum and of the magnetic field line wander. It is found that turbulent space and astrophysical plasmas are generally expected to contain a stochastic magnetic field due to the tangling of the field by strong plasma turbulence. Future work will explore how the saturated magnetic field line wander varies as a function of the amplitude of the plasma turbulence and the ratio of the thermal to magnetic pressure, known as the plasma beta.

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A study of Pc-5 ULF oscillations

Annales Geophysicae ◽

10.5194/angeo-22-289-2004 ◽

2004 ◽

Vol 22 (1) ◽

pp. 289-302 ◽

Cited By ~ 48

Author(s):

M. K. Hudson ◽

R. E. Denton ◽

M. R. Lessard ◽

E. G. Miftakhova ◽

R. R. Anderson

Keyword(s):

Radiation Effects ◽

Dominant Mode ◽

Mhd Waves ◽

Azimuthal Mode ◽

Magnetospheric Configuration And Dynamics ◽

Sudden Commencements ◽

Magnetic Pulsations ◽

Pulsation Activity ◽

Using Data ◽

Three Components

Abstract. A study of Pc-5 magnetic pulsations using data from the Combined Release and Radiation Effects Satellite (CRRES) was carried out. Three-component dynamic magnetic field spectrograms have been used to survey ULF pulsation activity for the approximate fourteen month lifetime of CRRES. Two-hour panels of dynamic spectra were examined to find events which fall into two basic categories: 1) toroidal modes (fundamental and harmonic resonances) and 2) poloidal modes, which include compressional oscillations. The occurence rates were determined as a function of L value and local time. The main result is a comparable probability of occurence of toroidal mode oscillations on the dawn and dusk sides of the magnetosphere inside geosynchronous orbit, while poloidal mode oscillations occur predominantly along the dusk side, consistent with high azimuthal mode number excitation by ring current ions. Pc-5 pulsations following Storm Sudden Commencements (SSCs) were examined separately. The spatial distribution of modes for the SSC events was consistent with the statistical study for the lifetime of CRRES. The toroidal fundamental (and harmonic) resonances are the dominant mode seen on the dawn-side of the magnetosphere following SSCs. Power is mixed in all three components. In the 21 dusk side SSC events there were only a few examples of purely compressional (two) or radial (one) power in the CRRES study, a few more examples of purely toroidal modes (six), with all three components predominant in about half (ten) of the events. Key words. Magnetospheric physics (MHD waves and instabilities; magnetospheric configuration and dynamics) – Space plasma physics (waves and instabilities)

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