scholarly journals On the Origin of ULF Magnetic Waves Before the Taiwan Chi-Chi 1999 Earthquake

2021 ◽  
Vol 9 ◽  
Author(s):  
Georgios Anagnostopoulos
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Space ◽  
Solar Rotation ◽  
Rotation Period ◽  
Wave Activity ◽  
Alfven Wave ◽  
Ulf Waves ◽  
Storm Activity ◽  
Data Set

The ultra low frequency (ULF) electromagnetic (EM) wave activity usually recorded on Earth’s ground has been found to depend on various types of space weather. In addition ULF waves observed before an earthquake have been hypothesized to be a result of geotectonic processes. In this study we elaborate for the first time the origin of sub-ULF (<1 msec) magnetic field waves before an earthquake (Chi-Chi/Taiwan, 20.9.1999) by comparing simultaneously obtained measurements in the interplanetary space (ACE satellite) and on the Earth’s ground (Taiwan). The most striking result of our data analysis, during a period of 7 weeks, is that the detection of four groups of sub-ULF waves in Taiwan coincide in time with the quasi-periodic detection of two solar wind streams by the satellite ACE with approximately the solar rotation period (∼28 days). The high speed solar wind streams (HSSs) in the interplanetary space were accompanied by sub-ULF Alfvén wave activity, quasi-periodic southward IMF and solar wind density perturbations, which are known as triggering agents of magnetic storm activity. The four HSSs were followed by long lasting decreases in the magnetic field in Taiwan. The whole data set examined in this study strongly suggest that the subULF magnetic field waves observed in Taiwan before the Chi-Chi 1999 earthquake is a normal consequence of the incident of HSSs to the magnetosphere. We provide some observational evidence that the sub-ULF electromagnetic radiation on the Earth was most probably a partner to (not a result of) geotectonic processes preparing the Taiwan 1999 earthquake.

Formation of current sheets and plasmoids within corotating/stream interaction regions

2020 ◽  
Author(s):  
Timofey Sagitov ◽  
Roman Kislov
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coronal Hole ◽  
High Speed ◽  
Solar Rotation ◽  
Coronal Holes ◽  
Rotation Period ◽  
The Sun ◽  
Current Sheets ◽  
Interaction Regions

<p>High speed streams originating from coronal holes are long-lived plasma structures that form corotating interaction regions (CIRs) or stream interface regions (SIRs) in the solar wind. The term CIR is used for streams existing for at least one solar rotation period, and the SIR stands for streams with a shorter lifetime. Since the plasma flows from coronal holes quasi-continuously, CIRs/SIRs simultaneously expand and rotate around the Sun, approximately following the Parker spiral shape up to the Earth’s orbit.</p><p>Coronal hole streams rotate not only around the Sun but also around their own axis of simmetry, resembling a screw. This effect may occur because of the following mechanisms: (1) the existence of a difference between the solar wind speed at different sides of the stream, (2) twisting of the magnetic field frozen into the plasma, and  (3) a vortex-like motion of the edge of the mothering coronal hole at the Sun. The screw type of the rotation of a CIR/SIR can lead to centrifugal instability if CIR/SIR inner layers have a larger angular velocity than the outer. Furthermore, the rotational plasma movement and the stream distortion can twist magnetic field lines. The latter contributes to the pinch effect in accordance with a well-known criterion of Suydam instability (Newcomb, 1960, doi: 10.1016/0003-4916(60)90023-3). Owing to the presence of a cylindrical current sheet at the boundary of a coronal hole, conditions for tearing instability can also appear at the CIR/SIR boundary. Regardless of their geometry, large scale current sheets are subject to various instabilities generating plasmoids. Altogether, these effects can lead to the formation of a turbulent region within CIRs/SIRs, making them filled with current sheets and plasmoids. </p><p>We study a substructure of CIRs/SIRs, characteristics of their rotation in the solar wind, and give qualitative estimations of possible mechanisms which lead to splitting of the leading edge a coronal hole flow and consequent formation of current sheets within CIRs/SIRs.</p>

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

<p>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 (<strong>ULF</strong>) 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.</p><p>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 & 2 and Pioneer 10 & 11). We found several-hundred wave events consisting of wave packets parallel or transverse to the mean magnetic field, interpreted as fast-mode or Alfvénic MHD wave activity, respectively. Parallel and transverse events were often coincident in space and time, which may be evidence of global Alfvénic 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 “magic frequencies” often reported in existing literature.</p><p>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.</p>

scholarly journals Cusp-like plasma in high altitudes: a statistical study of the width and location of the cusp from Magion-4

2002 ◽  
Vol 20 (3) ◽  
pp. 311-320 ◽  
Author(s):  
J. Mĕrka ◽  
J. Šafránková ◽  
Z. Nĕmeček
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
High Altitudes ◽  
Data Set ◽  
Latitudinal Dependence ◽  
Merging Process ◽  
Low Altitude ◽  
Field Lines ◽  
The Magnetic Field ◽  
Dipole Tilt

Abstract. The width of the cusp region is an indicator of the strength of the merging process and the degree of opening of the magnetosphere. During three years, the Magion-4 satellite, as part of the Interball project, has collected a unique data set of cusp-like plasma observations in middle and high altitudes. For a comparison of high- and low-altitude cusp determination, we map our observations of cusp-like plasma along the magnetic field lines down to the Earth’s surface. We use the Tsyganenko and Stern 1996 model of the magnetospheric magnetic field for the mapping, taking actual solar wind and IMF parameters from the Wind observations. The footprint positions show substantial latitudinal dependence on the dipole tilt angle. We fit this dependence with a linear function and subtract this function from observed cusp position. This process allows us to study both statistical width and location of the inspected region as a function of the solar wind and IMF parameters. Our processing of the Magion-4 measurements shows that high-altitude regions occupied by the cusp-like plasma (cusp and cleft) are projected onto a much broader area (in magnetic local time as well as in a latitude) than that determined in low altitudes. The trends of the shift of the cusp position with changes in the IMF direction established by low-altitude observations have been confirmed.Key words. Magnetospheric physics (magnetopause, cusp and boundary layer; solar wind – magnetosphere interactions)

scholarly journals Foreshock cavitons and spontaneous hot flow anomalies: A statistical study with a global hybrid-Vlasov simulation

2021 ◽  
Author(s):  
Vertti Tarvus ◽  
Lucile Turc ◽  
Markus Battarbee ◽  
Jonas Suni ◽  
Xóchitl Blanco-Cano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Rest Frame ◽  
Statistical Study ◽  
Plasma Temperature ◽  
Propagation Speed ◽  
Bow Shock ◽  
Ulf Waves ◽  
Subsequent Formation ◽  
Comparable Amount

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs), which evolve from cavitons as they accumulate suprathermal ions while being carried to the bow shock by the solar wind. Using the global hybrid-Vlasov simulation model Vlasiator, we have conducted a statistical study in which we track the motion of individual cavitons and SHFAs in order to examine their properties and evolution. In our simulation run where the interplanetary magnetic field (IMF) is directed at a sunward-southward angle of 45 degrees, continuous formation of cavitons is found up to ~ 11 Earth radii (RE) from the bow shock (along the IMF direction), and caviton-to-SHFA evolution takes place within ~ 2 RE from the shock. A third of the cavitons in our run evolve into SHFAs, and we find a comparable amount of SHFAs forming independently near the bow shock. We compare the properties of cavitons and SHFAs to prior spacecraft observations and simulations, finding good agreement. We also investigate the variation of the properties as a function of position in the foreshock, showing that the transients close to the bow shock are associated with larger depletions in the plasma density and magnetic field magnitude, along with larger increases in the plasma temperature and the level of bulk flow deflection. Our measurements of the propagation velocities of cavitons and SHFAs agree with earlier studies, showing that the transients propagate sunward in the solar wind rest frame. We show that SHFAs have a greater solar wind rest frame propagation speed than cavitons, which is related to an increase in the magnetosonic speed near the bow shock.

scholarly journals Foreshock cavitons and spontaneous hot flow anomalies: a statistical study with a global hybrid-Vlasov simulation

2021 ◽  
Vol 39 (5) ◽  
pp. 911-928
Author(s):  
Vertti Tarvus ◽  
Lucile Turc ◽  
Markus Battarbee ◽  
Jonas Suni ◽  
Xóchitl Blanco-Cano ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Rest Frame ◽  
Statistical Study ◽  
Plasma Temperature ◽  
Propagation Speed ◽  
Bow Shock ◽  
Ulf Waves ◽  
Subsequent Formation ◽  
Comparable Amount

Abstract. The foreshock located upstream of Earth's bow shock hosts a wide variety of phenomena related to the reflection of solar wind particles from the bow shock and the subsequent formation of ultra-low-frequency (ULF) waves. In this work, we investigate foreshock cavitons, which are transient structures resulting from the non-linear evolution of ULF waves, and spontaneous hot flow anomalies (SHFAs), which are thought to evolve from cavitons as they accumulate suprathermal ions while being carried to the bow shock by the solar wind. Using the global hybrid-Vlasov simulation model Vlasiator, we have conducted a statistical study in which we track the motion of individual cavitons and SHFAs in order to examine their properties and evolution. In our simulation run where the interplanetary magnetic field (IMF) is directed at a sunward–southward angle of 45∘, continuous formation of cavitons is found up to ∼11 Earth radii (RE) from the bow shock (along the IMF direction), and caviton-to-SHFA evolution takes place within ∼2 RE from the shock. A third of the cavitons in our run evolve into SHFAs, and we find a comparable amount of SHFAs forming independently near the bow shock. We compare the properties of cavitons and SHFAs to prior spacecraft observations and simulations, finding good agreement. We also investigate the variation of the properties as a function of position in the foreshock, showing that transients close to the bow shock are associated with larger depletions in the plasma density and magnetic field magnitude, along with larger increases in the plasma temperature and the level of bulk flow deflection. Our measurements of the propagation velocities of cavitons and SHFAs agree with earlier studies, showing that the transients propagate sunward in the solar wind rest frame. We show that SHFAs have a greater solar wind rest frame propagation speed than cavitons, which is related to an increase in the magnetosonic speed near the bow shock.

scholarly journals Compressional wave events in the dawn plasma sheet observed by Interball-1

1999 ◽  
Vol 17 (9) ◽  
pp. 1145-1154 ◽  
Author(s):  
O. Verkhoglyadova ◽  
A. Agapitov ◽  
A. Andrushchenko ◽  
V. Ivchenko ◽  
S. Romanov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Field Line ◽  
Plasma Sheet ◽  
Inhomogeneous Plasma ◽  
Partial Solution ◽  
Alfven Wave ◽  
Data Set ◽  
Background Magnetic Field ◽  
Phase Variations

Abstract. Compressional waves with periods greater than 2 min (about 10-30 min) at low geomagnetic latitudes, namely compressional Pc5 waves, are studied. The data set obtained with magnetometer MIF-M and plasma analyzer instrument CORALL on board the Interball-1 are analyzed. Measurements performed in October 1995 and October 1996 in the dawn plasma sheet at -30 RE ≤ XGSM and |ZGSM| ≤ 10 RE are considered. Anti-phase variations of magnetic field and ion plasma pressures are analyzed by searching for morphological similarities in the two time series. It is found that longitudinal and transverse magnetic field variations with respect to the background magnetic field are of the same order of magnitude. Plasma velocities are processed for each time period of the local dissimilarity in the pressure time series. Velocity disturbances occur mainly transversely to the local field line. The data reveal the rotation of the velocity vector. Because of the field line curvature, there is no fixed position of the rotational plane in the space. These vortices are localized in the regions of anti-phase variations of the magnetic field and plasma pressures, and the vortical flows are associated with the compressional Pc5 wave process. A theoretical model is proposed to explain the main features of the nonlinear wave processes. Our main goal is to study coupling of drift Alfven wave and magnetosonic wave in a warm inhomogeneous plasma. A vortex is the partial solution of the set of the equations when the compression is neglected. A compression effect gives rise to a nonlinear soliton-like solution.Key words. Magnetosphere physics (magnetotail) · Space plasma physics (kinetic and MHD theory; non-linear phenomena)

scholarly journals Instabilities of Magnetic Fields in Stars

1974 ◽  
Vol 59 ◽  
pp. 177-177
Author(s):  
R. J. Tayler
Keyword(s):  
Magnetic Field ◽  
Gravitational Potential ◽  
Rotation Period ◽  
Region Of Interest ◽  
Alfven Wave ◽  
Closed Field ◽  
Toroidal Plasma ◽  
Wide Range ◽  
Field Lines ◽  
Rotating Star

It has been shown (Markey and Tayler, 1973; Tayler, 1973; Wright, 1973) that a wide range of simple magnetic field configurations in stars are unstable. Although the ultimate effect of the instabilities is unclear, it seems likely that they would lead to enhanced destruction of magnetic flux, so that magnetic field decay would be much more rapid than previously supposed. Instability is almost certain in a non-rotating star containing either a purely toroidal field or a purely poloidal field, which has closed field lines inside the star. In both cases the instability resembles the well known instabilities of cylindrical and toroidal current channels, modified by the constraint that motion must be almost entirely along surfaces of constant gravitational potential.If both toroidal and poloidal fields are present, the problem is more complicated. In a toroidal plasma with a helical field, the worst instabilities are also helical but it is impossible for a helical disturbance to be parallel to a surface of constant gravitational potential everywhere. As a result, the admixture of toroidal and poloidal fields has a stabilizing influence, but it is not at present clear whether the majority of such configurations are completely stable.The effect of rotation has not yet been studied but it will certainly be important if the rotation period is less than the time taken for an Alfvén wave to cross the region of interest. This is true in most stars unless the internal magnetic field is very much stronger than any observed field.

scholarly journals On the probability distribution function of small-scale interplanetary magnetic field fluctuations

2004 ◽  
Vol 22 (10) ◽  
pp. 3751-3769 ◽  
Author(s):  
R. Bruno ◽  
V. Carbone ◽  
L. Primavera ◽  
F. Malara ◽  
L. Sorriso-Valvo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Robust Statistics ◽  
Interplanetary Space ◽  
Parametric Instability ◽  
Field Vector ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
The One

Abstract. In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as: a) Do we really know how the magnetic field vector orientation fluctuates in space? b) What are the statistics followed by the orientation of the vector itself? c) Do the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence. In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

Solar Wind and Terrestrial Planets

2020 ◽  
Author(s):  
Edik Dubinin ◽  
Janet G. Luhmann ◽  
James A. Slavin
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Fields ◽  
Interplanetary Space ◽  
Upper Atmosphere ◽  
Dipole Field ◽  
Terrestrial Planets ◽  
Solar Wind Interaction ◽  
Additional Energy ◽  
First Case

Knowledge about the solar wind interactions of Venus, Mars, and Mercury is rapidly expanding. While the Earth is also a terrestrial planet, it has been studied much more extensively and in far greater detail than its companions. As a result we direct the reader to specific references on that subject for obtaining an accurate comparative picture. Due to the strength of the Earth’s intrinsic dipole field, a relatively large volume is carved out in interplanetary space around the planet and its atmosphere. This “magnetosphere” is regarded as a shield from external effects, but in actuality much energy and momentum are channeled into it, especially at high latitudes, where the frequent interconnection between the Earth’s magnetic field and the interplanetary field allows some access by solar wind particles and electric fields to the upper atmosphere and ionosphere. Moreover, reconnection between oppositely directed magnetic fields occurs in Earth’s extended magnetotail—producing a host of other phenomena including injection of a ring current of energized internal plasma from the magnetotail into the inner magnetosphere—creating magnetic storms and enhancements in auroral activity and related ionospheric outflows. There are also permanent, though variable, trapped radiation belts that strengthen and decay with the rest of magnetospheric activity—depositing additional energy into the upper atmosphere over a wider latitude range. Virtually every aspect of the Earth’s solar wind interaction, highly tied to its strong intrinsic dipole field, has its own dedicated textbook chapters and review papers. Although Mercury, Venus, Earth, and Mars belong to the same class of rocky terrestrial planets, their interaction with solar wind is very different. Earth and Mercury have the intrinsic, mainly dipole magnetic field, which protects them from direct exposure by solar wind. In contrast, Venus and Mars have no such shield and solar wind directly impacts their atmospheres/ionospheres. In the first case, intrinsic magnetospheric cavities with a long tail are found. In the second case, magnetospheres are also formed but are generated by the electric currents induced in the conductive ionospheres. The interaction of solar wind with terrestrial planets also varies due to changes caused by different distances to the Sun and large variations in solar irradiance and solar wind parameters. Other important planetary differences like local strong crustal magnetization on Mars and almost total absence of the ionosphere on Mercury create new essential features to the interaction pattern. Solar wind might be also a feasible driver for planetary atmospheric losses of volatiles, which could historically affect the habitability of the terrestrial planets.

scholarly journals Rosetta and Mars Express observations of the influence of high solar wind pressure on the Martian plasma environment

2009 ◽  
Vol 27 (12) ◽  
pp. 4533-4545 ◽  
Author(s):  
N. J. T. Edberg ◽  
U. Auster ◽  
S. Barabash ◽  
A. Bößwetter ◽  
D. A. Brain ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Pressure ◽  
Solar Wind ◽  
Pressure Pulse ◽  
Wind Pressure ◽  
Data Set ◽  
Mars Express ◽  
Boundary Crossings ◽  
Plasma Environment ◽  
Solar Wind Pressure

Abstract. We report on new simultaneous in-situ observations at Mars from Rosetta and Mars Express (MEX) on how the Martian plasma environment is affected by high pressure solar wind. A significant sharp increase in solar wind density, magnetic field strength and turbulence followed by a gradual increase in solar wind velocity is observed during ~24 h in the combined data set from both spacecraft after Rosetta's closest approach to Mars on 25 February 2007. The bow shock and magnetic pileup boundary are coincidently observed by MEX to become asymmetric in their shapes. The fortunate orbit of MEX at this time allows a study of the inbound boundary crossings on one side of the planet and the outbound crossings on almost the opposite side, both very close to the terminator plane. The solar wind and interplanetary magnetic field (IMF) downstream of Mars are monitored through simultaneous measurements provided by Rosetta. Possible explanations for the asymmetries are discussed, such as crustal magnetic fields and IMF direction. In the same interval, during the high solar wind pressure pulse, MEX observations show an increased amount of escaping planetary ions from the polar region of Mars. We link the high pressure solar wind with the observed simultaneous ion outflow and discuss how the pressure pulse could also be associated with the observed boundary shape asymmetry.

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