scholarly journals Interaction of Pc4 ULF waves with solar wind velocity and its dependence on Kp values

2021 ◽  
Vol 14 (12) ◽  
pp. 1013-1020
Author(s):  
M T Khan ◽  
◽  
K A Nafees ◽  
A K Singh
Keyword(s):  
Solar Wind ◽  
Solar Wind Speed ◽  
Mhd Waves ◽  
Ulf Waves ◽  
Ulf Wave ◽  
Magnetic Pulsations ◽  
Recorded Data ◽  
Mhd Waves And Instabilities ◽  
Field Lines ◽  
East West

Background/Objectives: Magnetic Pulsations recorded on the ground in the earth are produced by processes inside the magnetosphere and solar wind. These processes produce a wide variety of ULF hydromagnetic wave type which can be categorized on the ground as either Pi or Pc pulsations (irregular or continuous). Methods: Distinctive regions of the magnetosphere originate different frequencies of waves. Digital Dynamic Spectra (DDS) for the northsouth (X), east-west (Y) and vertical (Z) components of the recorded data were constructed for every day for 365 days (January 1 to December 31, 2005) in the station order PON, HAN and NAG respectively. Pc4 geomagnetic pulsations are quasi-sinusoidal fluctuations in the earth’s magnetic field in the length range 45-150 seconds. The magnitude of these pulsations ranges from fraction of a Nano Tesla (nT) to several nT. The monthly variation of Pc4 occurrence has a Kp dependence range of 0 to 9-. However, Pc4 occurrence was reported for Kp values, yet the major Pc4 events occurred for rage 5+ <Kp< 8+. The magnitudes of intervals of Pc4 occurrence decreased in the station order PON, HAN and NAG respectively. Analysis of the data for the whole year 2005 provided similar patterns of Pc4 occurrence for Vsw at all the three stations. Although Pc4 ULF wave occurrence become reported for Vsw ranging from 250 to 1000 Km/s, yet the major Pc4 event recorded for a Vsw range of 300-700 Km/sec. Findings: The current study is undertaken for describing the interaction of Pc4 ULF waves with solar wind speed and its dependence on Kp values. The results suggest that the solar wind control Pc4 occurrence through a mechanism in which Pc4 wave energy is convected through the magnetosheath and coupled to the standing oscillations of the magnetospheric field lines. PACS Nos: 94.30.cq; 96.50.Tf Keywords: Geomagnetic micropulsations; MHD waves and instabilities; Solar wind-control of Pc4 pulsation

scholarly journals Coordinated ground-based and Cluster observations of large amplitude global magnetospheric oscillations during a fast solar wind speed interval

2002 ◽  
Vol 20 (4) ◽  
pp. 405-426 ◽  
Author(s):  
I. R. Mann ◽  
I. Voronkov ◽  
M. Dunlop ◽  
E. Donovan ◽  
T. K. Yeoman ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Large Amplitude ◽  
Solar Wind Speed ◽  
Mhd Waves ◽  
Ulf Waves ◽  
Fast Solar Wind ◽  
Discrete Frequency ◽  
Waveguide Modes

Abstract. We present magnetospheric observations of very large amplitude global scale ULF waves, from 9 and 10 December 2000 when the upstream solar wind speed exceeded 600 km/s. We characterise these ULF waves using ground-based magnetometer, radar and optical instrumentation on both the dawn and dusk flanks; we find evidence to support the hypothesis that discrete frequency field line resonances (FLRs) were being driven by magnetospheric waveguide modes. During the early part of this interval, Cluster was on an outbound pass from the northern dusk side magnetospheric lobe into the magnetosheath, local-time conjugate to the Canadian sector. In situ magnetic fluctuations, observed by Cluster FGM, show evidence of quasi-periodic motion of the magnetosheath boundary layer with the same period as the ULF waves seen on the ground. Our observations represent the first simultaneous magnetometer, radar and optical observations of the characteristics of FLRs, and confirm the potential importance of ULF waves for magnetosphere-ionosphere coupling, particularly via the generation and modulation of electron precipitation into the ionosphere. The in situ Cluster measurements support the hypothesis that, during intervals of fast solar wind speed, the Kelvin-Helmholtz instability (KHI) can excite magnetospheric waveguide modes which bathe the flank magnetosphere with discrete frequency ULF wave power and drive large amplitude FLRs.  Paper submitted to the special issue devoted to "Cluster: First scientific results", Ann. Geophysicae, 19, 10/11/12, 2001.Key words. Magnetospheric physics (magnetopause, cusp and boundary layers; MHD waves and instabilities; solar wind-magnetosphere interactions)

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

2004 ◽  
Vol 22 (1) ◽  
pp. 169-182 ◽  
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)

scholarly journals The Pulsating Magnetosphere at Jupiter

2020 ◽  
Author(s):  
Harry Manners ◽  
Adam Masters
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Global Scale ◽  
Wave Activity ◽  
Ulf Waves ◽  
Ulf Wave ◽  
Wide Range

&lt;p&gt;The magnetosphere of Jupiter is the largest planetary magnetosphere in the solar system, and plays host to internal dynamics that remain, in many ways, mysterious. Prominent among these mysteries are the ultra-low-frequency (&lt;strong&gt;ULF&lt;/strong&gt;) pulses ubiquitous in this system. Pulsations in the electromagnetic emissions, magnetic field and flux of energetic particles have been observed for decades, with little to indicate the source mechanism. While ULF waves have been observed in the magnetospheres of all the magnetized planets, the magnetospheric environment at Jupiter seems particularly conducive to the emergence of ULF waves over a wide range of periods (1-100+ minutes). This is mainly due to the high variability of the system on a global scale: internal plasma sources and a powerful intrinsic magnetic field produce a highly-compressible magnetospheric cavity, which can be reduced to a size significantly smaller than its nominal expanded state by variations in the dynamic pressure of the solar wind. Compressive fronts in the solar wind, turbulent surface interactions on the magnetopause and internal plasma processes can also all lead to ULF wave activity inside the magnetosphere.&lt;/p&gt;&lt;p&gt;To gain the first comprehensive view of ULF waves in the Jovian system, we have performed a heritage survey of magnetic field data measured by six spacecraft that visited the magnetosphere (Galileo, Ulysses, Voyager 1 &amp; 2 and Pioneer 10 &amp; 11). We found several-hundred wave events consisting of wave packets parallel or transverse to the mean magnetic field, interpreted as fast-mode or Alfv&amp;#233;nic MHD wave activity, respectively. Parallel and transverse events were often coincident in space and time, which may be evidence of global Alfv&amp;#233;nic resonances of the magnetic field known as field-line-resonances. We found that 15-, 30- and 40-minute periods dominate the Jovian ULF wave spectrum, in agreement with the dominant &amp;#8220;magic frequencies&amp;#8221; often reported in existing literature.&lt;/p&gt;&lt;p&gt;We will discuss potential driving mechanisms as informed by the results of the heritage survey, how this in turn affects our understanding of energy transfer in the magnetosphere, and potential investigations to be made using data from the JUNO spacecraft. We will also discuss the potential for multiple resonant cavities, and how the resonance modes of the Jovian magnetosphere may differ from those of the other magnetized planets.&lt;/p&gt;

scholarly journals Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1683-1696 ◽  
Author(s):  
K. Kauristie ◽  
T. I. Pulkkinen ◽  
O. Amm ◽  
A. Viljanen ◽  
M. Syrjäsuo ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Auroral Oval ◽  
Outer Edge ◽  
Satellite Observations ◽  
Mhd Waves ◽  
Clear Correlation ◽  
Close Relationship ◽  
Magnetic Pulsations ◽  
Dusk Sector

Abstract. On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76) simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT). The location of the auroras (near the ionospheric convection reversal boundary) and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cluster spacecraft were making observations in the magnetospheric region associated with the auroras, although exact magnetic conjugacy between the ground-based and satellite observations did not exist. The solar wind variations appeared to control both the behaviour of the auroras and the magnetopause dynamics. Auroral structures were observed at Ny Ålesund especially during periods of negative IMF BZ. In addition, the Cluster spacecraft experienced periodic (T ~ 4 - 6 min) encounters between magnetospheric and magnetosheath plasmas. These undulations of the boundary can be interpreted as a consequence of tailward propagating magnetopause surface waves. Simultaneous dusk sector ground-based observations show weak, but discernible magnetic pulsations (Pc 5) and occasionally periodic variations (T ~ 2 - 3 min) in the high-latitude auroras. In the dusk sector, Pc 5 activity was stronger and had characteristics that were consistent with a field line resonance type of activity. When IMF BZ stayed positive for a longer period, the auroras were dimmer and the spacecraft stayed at the outer edge of the magnetopause where they observed electromagnetic pulsations with T ~ 1 min. We find these observations interesting especially from the viewpoint of previously presented studies relating poleward-moving high-latitude auroras with pulsation activity and MHD waves propagating at the magnetospheric boundary layers.Key words. Ionosphere (ionosphere-magnetosphere interaction) – Magnetospheric physics (auroral phenomena; solar wind – magnetosphere interactions)

scholarly journals Statistical study of ULF waves in the magnetotail by THEMIS observations

2018 ◽  
Vol 36 (5) ◽  
pp. 1335-1346 ◽  
Author(s):  
Shuai Zhang ◽  
Anmin Tian ◽  
Quanqi Shi ◽  
Hanlin Li ◽  
Alexander W. Degeling ◽  
...  
Keyword(s):  
Standing Waves ◽  
Low Frequency ◽  
Radial Distance ◽  
Time History ◽  
Flank Region ◽  
Wave Frequency ◽  
Ulf Waves ◽  
Tail Region ◽  
Ulf Wave ◽  
Field Lines

Abstract. Ultra-low-frequency (ULF) waves are ubiquitous in the magnetosphere. Previous studies mostly focused on ULF waves in the dayside or near-Earth region (with radial distance R<12 RE). In this study, using the data of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission during the period from 2008 to 2015, the Pc5–6 ULF waves in the tail region with XGSM∗<0, 8 RE<R<32 RE (mostly on the stretched magnetic field lines) are studied statistically. A total of 1089 azimuthal oscillating events and 566 radial oscillating events were found. The statistical results show that both the azimuthal and radial oscillating events in the magnetotail region (12 RE<R<32 RE) are more frequently observed in the post-midnight region. The frequency decreases with increasing radial distance from Earth for both azimuthal oscillating events (8 RE<R<16 RE) and radial oscillating events (8 RE<R<14 RE), which is consistent with the field line resonances theory. About 52 % of events (including the azimuthal and radial oscillating events) are standing waves in the region of 8–16 RE, while only 2 % are standing waves in the region of 16–32 RE. There is no obvious dawn–dusk asymmetry of ULF wave frequency for events in 8 RE<R<32 RE, which contrasts with the obvious dawn–dusk asymmetry found by previous studies in the inner magnetosphere (4 RE<R<9 RE). An examination for possible statistical relationships between the ULF wave parameters and substorm occurrences is carried out. We find that the wave frequency is higher after the substorm onset than before it, and the frequency differences are more obvious in the midnight region than in the flank region.

Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach

2021 ◽  
Author(s):  
Elena Kronberg ◽  
Fabio Gastaldello ◽  
Stein Haaland ◽  
Artem Smirnov ◽  
Max Berrendorf ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Machine Learning ◽  
Solar Wind ◽  
Southern Hemisphere ◽  
Solar Wind Speed ◽  
Flank Region ◽  
Learning Approach ◽  
X Ray ◽  
Machine Learning Approach ◽  
Field Lines

&lt;p&gt;One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes flying mainly in the magnetosphere are soft protons with few tens to hundreds of keV concentrated. One such telescope is the X-ray Multi-Mirror Mission (XMM-Newton) by ESA. Its observing time lost due to the contamination is &amp;#160;about 40%. This affects all the major broad science goals of XMM, ranging from cosmology to astrophysics of neutron stars and black holes. The soft proton background could dramatically impact future X-ray missions such Athena and SMILE missions. Magnetopsheric processes that trigger this background are still poorly understood. We use a machine learning approach to delineate related important parameters and to develop a model to predict the background contamination using 12 years of XMM observations. As predictors we use the location of XMM, solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in southern direction, ZGSE, (XMM observations were in the southern hemisphere), the solar wind velocity and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the best two individual predictors and a machine learning model which utilizes an ensemble of the predictors (Extra Trees Regressor) and gives better performance. Based on our analysis, future X-Ray missions in the magnetosphere should minimize observations during &amp;#160;times &amp;#160;associated with high solar wind speed &amp;#160;and avoid closed magnetic field lines, especially at the dusk flank region at least in the southern hemisphere.&amp;#160;&lt;/p&gt;

scholarly journals ULF wave occurrence statistics in a high-latitude HF Doppler sounder

1999 ◽  
Vol 17 (6) ◽  
pp. 749-758 ◽  
Author(s):  
D. M. Wright ◽  
T. K. Yeoman ◽  
T. B. Jones
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
High Latitude ◽  
Statistical Study ◽  
Low Frequency ◽  
Occurrence Rate ◽  
Mhd Waves ◽  
Ulf Wave ◽  
High Latitude Ionosphere ◽  
Mhd Waves And Instabilities

Abstract. Ultra low frequency (ULF) wave activity in the high-latitude ionosphere has been observed by a high frequency (HF) Doppler sounder located at Tromsø, Norway (69.7°N, 19.2°E geographic coordinates). A statistical study of the occurrence of these waves has been undertaken from data collected between 1979 and 1984. The diurnal, seasonal, solar cycle and geomagnetic activity variations in occurrence have been investigated. The findings demonstrate that the ability of the sounder to detect ULF wave signatures maximises at the equinoxes and that there is a peak in occurrence in the morning sector. The occurrence rate is fairly insensitive to changes associated with the solar cycle but increases with the level of geomagnetic activity. As a result, it has been possible to characterise the way in which prevailing ionospheric and magnetospheric conditions affect such observations of ULF waves.Key words. Ionosphere (auroral ionosphere; ionosphere -magnetosphere interactions) · Magnetospheric physics (MHD waves and instabilities)

scholarly journals Penetration of magnetosonic waves into the magnetosphere: influence of a transition layer

2003 ◽  
Vol 21 (5) ◽  
pp. 1083-1093 ◽  
Author(s):  
A. S. Leonovich ◽  
V. V. Mishin ◽  
J. B. Cao
Keyword(s):  
Solar Wind ◽  
Energy Flux ◽  
Transition Layer ◽  
External Source ◽  
Mhd Waves ◽  
Time Interval ◽  
Total Energy Input ◽  
Mhd Waves And Instabilities ◽  
The Waves ◽  
Stratified Model

Abstract. We have constructed a theory for the penetration of magnetosonic waves from the solar wind into the magnetosphere through a transition layer in a plane-stratified model for the medium. In this model the boundary layer is treated as a region, inside of which the parameters of the medium vary from values characteristic for the magnetosphere, to values typical of the solar wind. It is shown that if such a layer has sufficiently sharp boundaries, then magnetosonic eigen-oscillations can be excited inside of it. The boundaries of such a layer are partially permeable for magnetosonic waves. Therefore, if the eigen-oscillations are not sustained by an external source, they will be attenuated, because some of the energy is carried away by the oscillations that penetrate the solar wind and the magnetosphere. It is shown that about 40% of the energy flux of the waves incident on the transition layer in the magnetotail region penetrate to the magnetosphere’s interior. This energy flux suffices to sustain the stationary convection of magnetospheric plasma. The total energy input to the magnetosphere during a time interval of the order of the substorm growth phase time is comparable with the energetics of an average substorm.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind–magnetosphere interactions) – Space plasma physics (kinetic and MHD theory)

scholarly journals Pc5 geomagnetic field fluctuations at discrete frequencies at a low latitude station

2001 ◽  
Vol 19 (3) ◽  
pp. 321-325 ◽  
Author(s):  
U. Villante ◽  
P. Francia ◽  
S. Lepidi
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Wind Pressure ◽  
Mhd Waves ◽  
Low Latitude ◽  
Time Intervals ◽  
Latitude Station ◽  
Field Fluctuations ◽  
Mhd Waves And Instabilities ◽  
Solar Wind Pressure

Abstract. A statistical analysis of the geomagnetic field fluctuations in the Pc5 frequency range (1–5 mHz) at a low latitude station (L = 1.6) provides further evidence for daytime power peaks at discrete frequencies. The power enhancements, which become more pronounced during high solar wind pressure conditions, may be interpreted in terms of ground signatures of magnetospheric cavity/waveguide compressional modes driven by solar wind pressure pulses. In this sense, the much clearer statistical evidence for afternoon events can be related to corotating structures mainly impinging the postnoon magnetopause. A comparison with results obtained for the same time intervals from previous investigations at higher latitudes and in the Earth’s magnetosphere confirms the global character of the observed modes.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind-magnetospheric interactions)

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