Statistical Differences of Magnetic Field Kinks Observed by PSP and WIND

2021 ◽  
Author(s):  
Chuanpeng Hou ◽  
Xingyu Zhu ◽  
Rui Zhuo ◽  
Jiansen He
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Velocity ◽  
Slow Solar Wind ◽  
Number Density ◽  
Ion Temperature ◽  
Group I ◽  
Rotational Discontinuity ◽  
Background Magnetic Field ◽  
The Magnetic Field

<p>Parker Solar Probe’s (PSP) observations near the sun show the extensive presence of magnetic field kinks (switchback for large kinks) in the slow solar wind. These kinks are usually accompanied by the enhancement of radial solar wind velocity and ion temperature, increasing or decreasing of number density. The magnetic field kinks have also been observed by WIND and Ulysses to exist near and beyond 1 AU, respectively. In this study, we statistically analyze the property difference of magnetic field kinks observed by PSP and WIND. We obtain the following four points of results. (1) Inside the PSP-kinks, the radial velocity and protons’ temperature increase while density shows enhancement or descent. However, inside the WIND-kinks, besides the slight enhancement of radial velocity, the density and temperature show no obvious change compared with the outside plasma. (2) By employing the Walen-test of kinks, we find that, R components of some PSP-kinks but not all satisfy the rotational discontinuity (RD) features, while the three components of most WIND-kinks well match the RD features. (3) The correlation between magnetic field and velocity inside the PSP-kinks and WIND-kinks does not show significant differences. (4) Both the PSP-kinks and WIND-kinks can be divided into two groups based on the histograms of θ<sub>Bn</sub>, where B is the background magnetic field, and n is the normal direction of kink. The first group (group-I) has θ<sub>Bn</sub> concentrating around 20° for PSP-kinks and 30° for WIND-kinks, indicating that the satellites were crossing the same kinked interplanetary magnetic field (IMF) from the upstream to the downstream. The second group (group-II) has θ<sub>Bn</sub> concentrating around 90° for PSP-kinks and WIND-kinks, suggesting that the satellites were crossing an interface between the unkinked and kinked IMF regions. Our findings help better understanding the nature of kinks and provide the observational basis for testifying models about radial propagation and evolution of magnetic field kinks.</p>

scholarly journals The evolution of inverted magnetic fields through the inner heliosphere

2020 ◽  
Vol 494 (3) ◽  
pp. 3642-3655 ◽  
Author(s):  
Allan R Macneil ◽  
Mathew J Owens ◽  
Robert T Wicks ◽  
Mike Lockwood ◽  
Sarah N Bentley ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Radial Distance ◽  
Occurrence Rate ◽  
Slow Solar Wind ◽  
The Sun ◽  
Radial Evolution ◽  
In Transit ◽  
The Magnetic Field ◽  
Inner Heliosphere

ABSTRACT Local inversions are often observed in the heliospheric magnetic field (HMF), but their origins and evolution are not yet fully understood. Parker Solar Probe has recently observed rapid, Alfvénic, HMF inversions in the inner heliosphere, known as ‘switchbacks’, which have been interpreted as the possible remnants of coronal jets. It has also been suggested that inverted HMF may be produced by near-Sun interchange reconnection; a key process in mechanisms proposed for slow solar wind release. These cases suggest that the source of inverted HMF is near the Sun, and it follows that these inversions would gradually decay and straighten as they propagate out through the heliosphere. Alternatively, HMF inversions could form during solar wind transit, through phenomena such velocity shears, draping over ejecta, or waves and turbulence. Such processes are expected to lead to a qualitatively radial evolution of inverted HMF structures. Using Helios measurements spanning 0.3–1 au, we examine the occurrence rate of inverted HMF, as well as other magnetic field morphologies, as a function of radial distance r, and find that it continually increases. This trend may be explained by inverted HMF observed between 0.3 and 1 au being primarily driven by one or more of the above in-transit processes, rather than created at the Sun. We make suggestions as to the relative importance of these different processes based on the evolution of the magnetic field properties associated with inverted HMF. We also explore alternative explanations outside of our suggested driving processes which may lead to the observed trend.

Cassini observations of magnetic holes in the solar wind and Saturn magnetosheath

2020 ◽  
Author(s):  
Tomas Karlsson ◽  
Lina Hadid ◽  
Michiko Morooka ◽  
Jan-Erik Wahlund
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
High Time Resolution ◽  
Magnetic Field Direction ◽  
Scale Size ◽  
Background Magnetic Field ◽  
Cycle Dependence ◽  
The Magnetic Field

<p>We present the first Cassini observations of magnetic holes on the near-Saturn solar wind and magnetosheath, based on data from the MAG magnetometer. We conclude that magnetic holes (defined as isolated decreases of at least 50% compared to the background magnetic field strength) are common in both regions. We present statistical properties of the magnetic holes, including scale size, depth of the magnetic field reduction, orientation, change in magnetic field direction over the holes, and solar cycle dependence. For magnetosheath magnetic holes, also high-time resolution density measurements from the LP Langmuir probe are available, allowing us to study the anti-correlation of density and magnetic field strength in the magnetic holes. We compare to recent results from MESSENGER observations from Mercury orbit, and finally discuss the possible importance of magnetic holes in solar wind-magnetosphere interaction at Saturn.</p>

scholarly journals Exploring the Properties of the Electron Strahl at 1 AU as an Indicator of the Quality of the Magnetic Connection Between the Earth and the Sun

2021 ◽  
Vol 8 ◽  
Author(s):  
Joseph E. Borovsky
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Coulomb Scattering ◽  
Magnetic Field Direction ◽  
The Sun ◽  
Number Density ◽  
Intensity Changes ◽  
The Magnetic Field ◽  
Region Plasma

In this report some properties of the electron strahl at 1 AU are examined to assess the strahl at 272 eV as an indicator of the quality of the magnetic connection of the near-Earth solar wind to the Sun. The absence of a strahl has been taken to represent either a lack of magnetic connection to the corona or the strahl not surviving to 1 AU owing to scattering. Solar-energetic-electron (SEE) events can be used as indicators of good magnetic connection: examination of 216 impulsive SEE events finds that they are all characterized by strong strahls. The strahl intensity at 1 AU is statistically examined for various types of solar-wind plasma: it is found that the strahl is characteristically weak in sector-reversal-region plasma. In sector-reversal-region plasma and other slow wind, temporal changes in the strahl intensity at 1 AU are examined with 64 s resolution measurements and the statistical relationships of strahl changes to simultaneous plasma-property changes are established. The strahl-intensity changes are co-located with current sheets (directional discontinuities) with strong changes in the magnetic-field direction. The strahl-intensity changes at 1 AU are positively correlated with changes in the proton specific entropy, the proton temperature, and the magnetic-field strength; the strahl-intensity changes are anti-correlated with changes in the proton number density, the angle of the magnetic field with respect to the Parker-spiral direction, and the alpha-to-proton number-density ratio. Reductions in the strahl intensity are not consistent with expectations for a simple model of whistler-turbulence scattering. Reductions in the strahl intensity are mildly consistent with expectations for Coulomb scattering, however the strongest-observed plasma-change correlations are unrelated to Coulomb scattering and whistler scattering. The implications of the strahl-intensity-change analysis are that the change in the magnetic-field direction at a strahl change represents a change in the magnetic connection to the corona, resulting in a different strahl intensity and different plasma properties. An outstanding question is: Does an absence of an electron strahl represent a magnetic disconnection from the Sun or a poor strahl source in some region of the corona?

Characteristics and variability of Titan's magnetic environment

2008 ◽  
Vol 367 (1889) ◽  
pp. 789-798 ◽  
Author(s):  
César L Bertucci
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Current Sheet ◽  
Radial Component ◽  
Wind Pressure ◽  
Rotation Direction ◽  
Background Magnetic Field ◽  
Solar Wind Pressure ◽  
Field Lines ◽  
The Magnetic Field

The structure and variability of Saturn's magnetic field in the vicinity of Titan's orbit is studied. In the dawn magnetosphere, the magnetic field presents a significant radial component directed towards Saturn, suggesting that Titan is usually located below the planet's warped and dynamic magnetodisc. Also, a non-negligible component along the co-rotation direction suggests that Saturn's magnetic field lines close to the magnetodisc are being swept back from their respective magnetic meridians. In the noon sector, Titan seems to be closer to the magnetodisc central current sheet, as the field lines in this region seem to be more dipolar. The distance between the central current sheet and Titan depends mainly on the solar wind pressure. Also, δ | B |/| B |∼0.5 amplitude waveforms at periods close to Saturn's kilometric radiation period are present in the background magnetic field. This modulation in the field is ubiquitous in Saturn's magnetosphere and associated with the presence of a rotating asymmetry in the planet's magnetic field.

scholarly journals Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov–Gerasimenko

2021 ◽  
Vol 39 (4) ◽  
pp. 721-742
Author(s):  
Katharina Ostaszewski ◽  
Karl-Heinz Glassmeier ◽  
Charlotte Goetz ◽  
Philip Heinisch ◽  
Pierre Henri ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interaction Region ◽  
Occurrence Rate ◽  
Solar Wind Interaction ◽  
Background Magnetic Field ◽  
The Waves ◽  
Comet 67P ◽  
The Magnetic Field ◽  
Field Enhancements

Abstract. We present a statistical survey of large-amplitude, asymmetric plasma and magnetic field enhancements detected outside the diamagnetic cavity at comet 67P/Churyumov–Gerasimenko from December 2014 to June 2016. Based on the concurrent observations of plasma and magnetic field enhancements, we interpret them to be magnetosonic waves. The aim is to provide a general overview of these waves' properties over the mission duration. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of these waves and their characteristics. In total, we identified ∼ 70 000 steepened waves in the magnetic field data by means of machine learning. We observe that the occurrence of these steepened waves is linked to the activity of the comet, where steepened waves are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressional nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual steepened waves. With increasing mass loading, the average amplitude of the waves decreases, while the skewness increases. Using a modified 1D magnetohydrodynamic (MHD) model, we investigated if the waves can be described by the combination of nonlinear and dissipative effects. By combining the model with observations of amplitude, width and skewness, we obtain an estimate of the effective plasma diffusivity in the comet–solar wind interaction region and compare it with suitable reference values as a consistency check. At 67P/Churyumov–Gerasimenko, these steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

Using Compressibility and Electric Field to Characterize Circularly-Polarized Waves Near the Proton Cyclotron Frequency Observed by Solar Orbiter

2021 ◽  
Author(s):  
Yuri Khotyaintsev ◽  
Daniel B Graham ◽  
Konrad Steinvall ◽  
Andris Vaivads ◽  
Milan Maksimovic ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electric Field ◽  
Electromagnetic Waves ◽  
Cyclotron Frequency ◽  
Density Fluctuations ◽  
Background Magnetic Field ◽  
The Waves ◽  
The Magnetic Field ◽  
Proton Cyclotron

<p>We report Solar Orbiter observations of electromagnetic waves near the proton cyclotron frequency during the first perihelion. The waves have polarization close to circular and have wave vectors closely aligned with the background magnetic field. Such waves are potentially important for heating of the solar wind as their frequency and polarization allows effective energy exchange with solar wind protons. The Radio and Plasma Waves (RPW) instrument provides a high-cadence measurement of plasma density and electric field which we use together with the magnetic field measured by MAG to characterize these waves. In particular we compute the compressibility and the phase between the density fluctuations and the parallel component of the magnetic field, and show that these have a distinct behavior for the waves compared to the Alfvénic turbulence. We compare the observations to multi-fluid plasma dispersion and identify the waves modes corresponding to the observed waves. We discuss the importance of the waves for solar wind heating.</p>

Analysis of the Internal structure of the Streamer Blow Out Observed by the Parker Solar Probe during the First Solar Encounter

2020 ◽  
Author(s):  
Teresa Nieves-Chinchilla ◽  
Adam Szabo ◽  
Kelly E. Korreck ◽  
Nathalia Alzate ◽  
Laura A. Balmaceda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Internal Structure ◽  
Flux Rope ◽  
Internal Force ◽  
Slow Solar Wind ◽  
Angle Distribution ◽  
The Hours ◽  
The Magnetic Field

<p>We present an analysis of the internal structure of a coronal mass ejection (CME) detected by in situ<span> </span>instruments onboard the Parker Solar Probe (PSP) spacecraft during its first solar encounter. On 2018 November 11 at 23:53 UT, the FIELDS magnetometer measured an increase in strength of the magnetic field as well as a coherent change in the field direction. The SWEAP instrument simultaneously detected the low proton temperature and signatures of bi-directionality in the electron pitch angle distribution (PAD). These signatures are indicative of a CME embedded in the slow solar wind. In conjunction with PSP was the STEREO A spacecraft, which enabled the remote observation of a streamer blow-out by the SECCHI suite of instruments. The source at the Sun of the slow and well-structured<span> fl</span>ux-rope was identified in an overlying streamer.</p><p>Our detailed inspection of the internal transient structure magnetic properties suggests high complexity in deviations from an ideal<span> </span>flux rope 3D topology. Reconstructions of the magnetic field conguration reveal a highly distorted structure consistent with the highly elongated `bubble' observed remotely. A double-ring substructure observed in the SECCHI-COR2 eld of view (FOV) is suggestive of a double internal<span> </span>flux rope. Furthermore, we describe a scenario in which mixed topology of a closed<span> </span>flux rope is combined with the magnetically open structure, which helps explain the<span> </span>flux dropout observed in the measurements of the electron PAD. Our justication for this is the plethora of structures observed by the EUV imager (SECCHI-EUVI) in the hours preceding the streamer blowout evacuation. Finally, taking advantage of the unique observations from PSP, we explore the first stages of the effects of coupling with the solar wind and the evolutionary processes in the magnetic structure. We found evidence of bifurcated current sheets in the structure boundaries suggestive of magnetic reconnection. Our analysis of the internal force imbalance indicates that internal Lorentz forces continue to dominate the evolution of the structure in the COR2 FOV and serves as the main driver of the internal<span> fl</span>ux rope distortion as detected in situ at PSP solar distance.</p>

scholarly journals Steepening of magnetosonic waves in the inner coma of comet 67P/Churyumov-Gerasimenko

2020 ◽  
Author(s):  
Katharina Ostaszewski ◽  
Karl-Heinz Glassmeier ◽  
Charlotte Goetz ◽  
Philip Heinisch ◽  
Pierre Henri ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interaction Region ◽  
Occurrence Rate ◽  
Solar Wind Interaction ◽  
Plasma Properties ◽  
Background Magnetic Field ◽  
The Waves ◽  
Comet 67P ◽  
The Magnetic Field

Abstract. We present a statistical survey of large amplitude, asymmetric plasma, and magnetic field enhancements at comet 67P/Churyumov-Gerasimenko from December 2014 to June 2016. The aim is to provide a general overview of these structures' properties over the mission duration. At comets, nonlinear wave evolution plays an integral part in the development of turbulence and in particular facilitates the transfer of energy and momentum. As the first mission of its kind, the ESA Rosetta mission was able to study the plasma properties of the inner coma for a prolonged time and during different stages of activity. This enables us to study the temporal evolution of steepened waves and their characteristics. In total, we identified ~70000 events in the magnetic field data by means of machine learning. We observe that the occurrence of wave events is linked to the activity of the comet, where events are primarily observed at high outgassing rates. No clear indications of a relationship between the occurrence rate and solar wind conditions were found. The waves are found to propagate predominantly perpendicular to the background magnetic field, which indicates their compressive nature. Characteristics like amplitude, skewness, and width of the waves were extracted by fitting a skew normal distribution to the magnetic field magnitude of individual events. With increasing massloading the average amplitude of steepened waves decreases while the skewness increases. Using a modified 1D MHD model it was possible to show that such solitary structures can be described by the combination of nonlinear, dispersive, and dissipative effects. By combining the model with observations of amplitude, width, and skewness we obtain an estimate of the effective plasma viscosity in the comet-solar wind interaction region. At 67P/Churyumov-Gerasimenko steepened waves are of particular importance as they dominate the innermost interaction region for intermediate to high activity.

scholarly journals Automatic parameterization for magnetometer zero offset determination

2012 ◽  
Vol 1 (2) ◽  
pp. 103-109 ◽  
Author(s):  
M. A. Pudney ◽  
C. M. Carr ◽  
S. J. Schwartz ◽  
S. I. Howarth
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Slow Solar Wind ◽  
Fixed Parameter ◽  
Zero Offset ◽  
Parameter Approach ◽  
The Magnetic Field ◽  
Key Parameter

Abstract. In-situ magnetic field measurements are of critical importance in understanding how the Sun creates and controls the heliosphere. To ensure the measurements are accurate, it is necessary to track the combined slowly varying spacecraft magnetic field and magnetometer zero offset – the systematic error in the sensor measurements. For a 3-axis stabilised spacecraft, in-flight correction of zero offsets primarily relies on the use of Alfvénic rotations in the magnetic field. We present a method to automatically determine a key parameter related to the ambient compressional variance of the signal (which determines the selection criteria for identifying clear Alfvénic rotations). We apply our method to different solar wind conditions, performing a statistical analysis of the data periods required to achieve a 70% chance of calculating an offset using Helios datasets. We find that 70% of 40 min data periods in regions of fast solar wind possess sufficient rotational content to calculate an offset. To achieve the same 70% calculation probability in regions of slow solar wind requires data periods of 2 h duration. We also find that 40 min data periods at perihelion compared to 1 h and 40 min data periods at aphelion are required to achieve the same 70% calculation probability. We compare our method with previous work that uses a fixed parameter approach and demonstrate an improvement in the calculation probability of up to 10% at aphelion and 5% at perihelion.

scholarly journals Automatic parameterization for magnetometer zero offset determination

2012 ◽  
Vol 2 (1) ◽  
pp. 245-266
Author(s):  
M. A. Pudney ◽  
C. M. Carr ◽  
S. J. Schwartz ◽  
S. I. Howarth
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Slow Solar Wind ◽  
Fixed Parameter ◽  
Zero Offset ◽  
Parameter Approach ◽  
The Magnetic Field ◽  
Key Parameter

Abstract. In-situ magnetic field measurements are of critical importance in understanding how the Sun creates and controls the heliosphere. To ensure the measurements are accurate, it is necessary to track the combined slowly-varying spacecraft magnetic field and magnetometer zero offset – the systematic error in the sensor measurements. For a 3-axis stabilised spacecraft, in-flight correction of zero offsets primarily relies on the use of Alfvénic rotations in the magnetic field. We present a method to automatically determine a key parameter related to the ambient compressional variance of the signal (which determines the selection criteria for identifying clear Alfvénic rotations). We apply our method to different solar wind conditions, performing a statistical analysis of the data periods required to achieve a 70% chance of calculating an offset using Helios datasets. We find that 70% of 40 min data periods in regions of fast solar wind possess sufficient rotational content to calculate an offset. To achieve the same 70% calculation probability in regions of slow solar wind requires data periods of 2 h duration. We also find that 40 min data periods at perihelion compared to 1 h and 40 min data periods at aphelion are required to achieve the same 70% calculation probability. We compare our method with previous work that uses a fixed parameter approach and demonstrate an improvement in the calculation probability of up to 10% at aphelion and 5% at perihelion.

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