scholarly journals Are there current-sheet-like structures in the Earth's magnetotail as in the solar wind – results and implications from high time resolution magnetic field measurements by Cluster

2008 ◽  
Vol 26 (7) ◽  
pp. 1889-1895 ◽  
Author(s):  
G. Li ◽  
E. Lee ◽  
G. Parks
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Current Sheet ◽  
Time Resolution ◽  
Field Measurements ◽  
Solar Wind Plasma ◽  
High Time ◽  
High Time Resolution ◽  
Mhd Turbulence ◽  
Flux Tubes

Abstract. Recent studies of solar wind MHD turbulence show that current-sheet-like structures are common in the solar wind and they are a significant source of solar wind MHD turbulence intermittency. While numerical simulations have suggested that such structures can arise from non-linear interactions of MHD turbulence, a recent study by Borovsky (2006), upon analyzing one year worth of ACE data, suggests that these structures may represent the magnetic walls of flux tubes that separate solar wind plasma into distinct bundles and these flux tubes are relic structures originating from boundaries of supergranules on the surface of the Sun. In this work, we examine whether there are such structures in the Earth's magnetotail, an environment vastly different from the solar wind. We use high time resolution magnetic field data of the FGM instrument onboard Cluster C1 spacecraft. The orbits of Cluster traverse through both the solar wind and the Earth's magnetosheath and magnetotail. This makes its dataset ideal for studying differences between solar wind MHD turbulence and that inside the Earth's magnetosphere. For comparison, we also perform the same analysis when Cluster C1 is in the solar wind. Using a data analysis procedure first introduced in Li (2007, 2008), we find that current-sheet-like structures can be clearly identified in the solar wind. However, similar structures do not exist inside the Earth's magnetotail. This result can be naturally explained if these structures have a solar origin as proposed by Borovsky (2006). With such a scenario, current analysis of solar wind MHD turbulence needs to be improved to include the effects due to these curent-sheet-like structures.

scholarly journals Current sheets from Ulysses observation

2011 ◽  
Vol 29 (2) ◽  
pp. 237-249 ◽  
Author(s):  
B. Miao ◽  
B. Peng ◽  
G. Li
Keyword(s):  
Solar Wind ◽  
Current Sheet ◽  
Solar Wind Plasma ◽  
Mhd Turbulence ◽  
Automatic Data ◽  
Flux Tubes ◽  
Current Sheets ◽  
Solar Origin ◽  
Turbulence Intermittency ◽  
Solar Wind Magnetic Field

Abstract. Current sheet is a significant source of solar wind MHD turbulence intermittency. It has long been recognized that these structures can arise from non-linear interactions of MHD turbulence. Alternatively, they may also be relic structures in the solar wind that have a solar origin, e.g., magnetic walls of flux tubes that separate solar wind plasma into distinct parcels. Identifying these structures in the solar wind is crucial to understanding the properties of the solar wind MHD turbulence. Using Ulysses observations we examine 3-year worth of solar wind magnetic field data when the Ulysses is at low latitude during solar minimum. Extending the previous work of Li (2007, 2008), we develop an automatic data analysis method of current sheet identification. Using this method, we identify more than 28000 current sheets. Various properties of the current sheet are obtained. These include the distributions of the deflection angle across the current sheet, the thickness of the current sheet and the waiting time statistics between current sheets.

scholarly journals Higher-Order Statistics in Compressive Solar Wind Plasma Turbulence: High-Resolution Density Observations From the Magnetospheric MultiScale Mission

2021 ◽  
Author(s):  
Owen Roberts ◽  
Jessica Thwaites ◽  
Luca Sorriso-Valvo ◽  
Rumi Nakamura ◽  
Zoltan Voros
Keyword(s):  
Solar Wind ◽  
Time Resolution ◽  
Measurement Techniques ◽  
Time Lag ◽  
Solar Wind Plasma ◽  
Density Fluctuations ◽  
High Time ◽  
High Time Resolution ◽  
Time Lags ◽  
Spacecraft Potential

<p>Turbulent density fluctuations are investigated in the solar wind at sub-ion scales using calibrated spacecraft potential. The measurement technique using the spacecraft potential allows for a much higher time resolution and sensitivity when compared to direct measurements using plasma instruments. Using this novel method, density fluctuations can be measured with unprecedentedly high time resolutions for in situ measurements of solar wind plasma at 1 a.u. By investigating 1 h of high-time resolution data, the scale dependant kurtosis is calculated by varying the time lag τ to calculate increments between observations. The scale-dependent kurtosis is found to increase towards ion scales but then plateaus and remains fairly constant through the sub-ion range in a similar fashion to magnetic field measurements. The sub-ion range is also found to exhibit self-similar monofractal behavior contrasting sharply with the multi-fractal behavior at large scales. The scale-dependent kurtosis is also calculated using increments between two different spacecraft. When the time lags are converted using the ion bulk velocity to a comparable spatial lag, a discrepancy is observed between the two measurement techniques. Several different possibilities are discussed including a breakdown of Taylor’s hypothesis, high-frequency plasma waves, or intrinsic differences between sampling directions.</p>

Statistical relations between in-situ measured Bz component and thermospheric density variations

2021 ◽  
Author(s):  
Sofia Kroisz ◽  
Lukas Drescher ◽  
Manuela Temmer ◽  
Sandro Krauss ◽  
Barbara Süsser-Rechberger ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Field Measurements ◽  
Satellite Orbit ◽  
Solar Wind Plasma ◽  
Statistical Investigation ◽  
Neutral Density ◽  
Special Focus ◽  
Short Term

<p>Through advanced statistical investigation and evaluation of solar wind plasma and magnetic field data, we investigate the statistical relation between the magnetic field B<sub>z</sub> component, measured at L1, and Earth’s thermospheric neutral density. We will present preliminary results of the time series analyzes using in-situ plasma and magnetic field measurements from different spacecraft in near Earth space (e.g., ACE, Wind, DSCOVR) and relate those to derived thermospheric densities from various satellites (e.g., GRACE, CHAMP). The long and short term variations and dependencies in the solar wind data are related to variations in the neutral density of the thermosphere and geomagnetic indices. Special focus is put on the specific signatures that stem from coronal mass ejections and stream or corotating interaction regions.  The results are used to develop a novel short-term forecasting model called SODA (Satellite Orbit DecAy). This is a joint study between TU Graz and University of Graz funded by the FFG Austria (project “SWEETS”).</p>

scholarly journals Evolution of the Magnetic Field Configuration in an Active Region

1971 ◽  
Vol 43 ◽  
pp. 243-248 ◽  
Author(s):  
Dennis L. Schatz
Keyword(s):  
Magnetic Field ◽  
Active Region ◽  
Time Resolution ◽  
Field Configuration ◽  
High Time ◽  
High Time Resolution ◽  
Magnetic Field Configuration ◽  
The Magnetic Field

Described and discussed is the evolution of the magnetic field configuration in an Active Region from observations made with high time resolution.

scholarly journals Design and Optimization of a High-Time-Resolution Magnetic Plasma Analyzer (MPA)

2020 ◽  
Vol 10 (23) ◽  
pp. 8483
Author(s):  
Benjamin Criton ◽  
Georgios Nicolaou ◽  
Daniel Verscharen
Keyword(s):  
Magnetic Field ◽  
Time Resolution ◽  
Permanent Magnets ◽  
Instrument Design ◽  
High Time ◽  
Acquisition Time ◽  
High Time Resolution ◽  
Design And Optimization ◽  
New Instrument ◽  
Α Particles

In-situ measurements of space plasma throughout the solar system require high time resolution to understand the plasma’s kinetic fine structure and evolution. In this context, research is conducted to design instruments with the capability to acquire the plasma velocity distribution and its moments with high cadence. We study a new instrument design, using a constant magnetic field generated by two permanent magnets, to analyze solar wind protons and α-particles with high time resolution. We determine the optimal configuration of the instrument in terms of aperture size, sensor position, pixel size and magnetic field strength. We conduct this analysis based on analytical calculations and SIMION simulations of the particle trajectories in our instrument. We evaluate the velocity resolution of the instrument as well as Poisson errors associated with finite counting statistics. Our instrument is able to resolve Maxwellian and κ-distributions for both protons and α-particles. This method retrieves measurements of the moments (density, bulk speed and temperature) with a relative error below 1%. Our instrument design achieves these results with an acquisition time of only 5 ms, significantly faster than state-of-the-art electrostatic analyzers. Although the instrument only acquires one-dimensional cuts of the distribution function in velocity space, the simplicity and reliability of the presented instrument concept are two key advantages of our new design.

A Survey of Interplanetary Small Flux Ropes at Mercury

2020 ◽  
Author(s):  
Réka Winslow ◽  
Amy Murphy ◽  
Nathan Schwadron ◽  
Noé Lugaz ◽  
Wenyuan Yu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Current Sheet ◽  
Heliocentric Distance ◽  
Free Field ◽  
Flux Rope ◽  
Solar Wind Plasma ◽  
The Sun ◽  
Superposed Epoch Analysis ◽  
Flux Ropes

<p>Small flux ropes (SFRs) are interplanetary magnetic flux ropes with durations from a few minutes to a few hours. We have built a comprehensive catalog of SFRs at Mercury using magnetometer data from the orbital phase of the MESSENGER mission (2011-2015). In the absence of solar wind plasma measurements, we developed strict identification criteria for SFRs in the magnetometer observations, including conducting force-free field fits for each flux rope. We identified a total of 48 events that met our strict criteria, with events ranging in duration from 2.5 minutes to 4 hours. Using superposed epoch analysis, we obtained the generic SFR magnetic field profile at Mercury. Due to the large variation in Mercury's heliocentric distance (0.31-0.47 AU), we split the data into two distance bins. We found that the average SFR profile is more symmetric "farther from the Sun", in line with the idea that SFRs form closer to the Sun and undergo a relaxation process in the solar wind. Based on this result, as well as the SFR durations and the magnetic field strength fall-off with heliocentric distance, we infer that the SFRs observed at Mercury are expanding as they propagate with the solar wind. We also determined that the SFR occurrence frequency is nearly four times as high at Mercury as for similarly detected events at 1 AU. Most interestingly, we found two SFR populations in our dataset, one likely generated in a quasi-periodic formation process near the heliospheric current sheet, and the other formed away from the current sheet in isolated events.</p>

Fine structure of the interplanetary shock front according to measurements of the ion flux of the solar wind with high time resolution

2017 ◽  
Vol 55 (1) ◽  
pp. 30-45 ◽  
Author(s):  
V. G. Eselevich ◽  
N. L. Borodkova ◽  
M. V. Eselevich ◽  
G. N. Zastenker ◽  
Y. Šafránkova ◽  
...  
Keyword(s):  
Solar Wind ◽  
Fine Structure ◽  
Shock Front ◽  
Time Resolution ◽  
Interplanetary Shock ◽  
Ion Flux ◽  
High Time ◽  
High Time Resolution

scholarly journals The Vector Electric Field Investigation (VEFI) on the C/NOFS Satellite

2021 ◽  
Vol 217 (8) ◽  
Author(s):  
R. Pfaff ◽  
P. Uribe ◽  
R. Fourre ◽  
J. Kujawski ◽  
N. Maynard ◽  
...  
Keyword(s):  
Electric Field ◽  
Time Resolution ◽  
Langmuir Probe ◽  
Field Measurements ◽  
Field Investigation ◽  
High Time ◽  
High Time Resolution ◽  
Sphere Diameter ◽  
Nasa Goddard Space ◽  
Ac Electric Field

AbstractThe Vector Electric Field Investigation (VEFI) on the C/NOFS satellite comprises a suite of sensors controlled by one central electronics box. The primary measurement consists of a vector DC and AC electric field detector which extends spherical sensors with embedded pre-amps at the ends of six, 9.5-m booms forming three orthogonal detectors with baselines of 20 m tip-to-tip each. The primary VEFI measurement is the DC electric field at 16 vectors/sec with an accuracy of 0.5 mV/m. The electric field receiver also measures the broad spectra of irregularities associated with equatorial spread-F and related ionospheric processes that create the scintillations responsible for the communication and navigation outages for which the C/NOFS mission is designed to understand and predict. The AC electric field measurements range from ELF to HF frequencies.VEFI includes a flux-gate magnetometer providing DC measurements at 1 vector/sec and AC-coupled measurements at 16 vector/sec, as well as a fast, fixed-bias Langmuir probe that serves as the input signal to trigger the VEFI burst memory collection of high time resolution wave data when plasma density depletions are encountered in the low latitude nighttime ionosphere. A bi-directional optical lightning detector designed by the University of Washington (UW) provides continuous average lightning counts at different irradiance levels as well as high time resolution optical lightning emissions captured in the burst memory. The VEFI central electronics box receives inputs from all of the sensors and includes a configurable burst memory with 1–8 channels at sample rates as high as 32 ks/s per channel. The VEFI instrument is thus one experiment with many sensors. All of the instruments were designed, built, and tested at the NASA/Goddard Space Flight Center with the exception of the lightning detector which was designed at UW. The entire VEFI instrument was delivered on budget in less than 2 years.VEFI included a number of technical advances and innovative features described in this article. These include: (1) Two independent sets of 3-axis, orthogonal electric field double probes; (2) Motor-driven, pre-formed cylinder booms housing signal wires that feed pre-amps within tip-mounted spherical sensors; (3) Extended shadow equalizers (2.5 times the sphere diameter) to mitigate photoelectron shadow mismatch for sun angles along the boom directions, particularly important at sunrise/sunset for a low inclination satellite; (4) DC-coupled electric field channels with “boosted” or pre-emphasized amplitude response at ELF frequencies; (5) Miniature multi-channel spectrum analyzers using hybrid technology; (6) Dual-channel optical lightning detector with on-board comparators and counters for 7 irradiance levels with high-time-resolution data capture; (7) Spherical Langmuir probe with Titanium Nitride-coated sensor element and guard; (8) Selectable data rates including 200 kbps (fast), 20 kbps (nominal), and 2 kbps (low for real-time TDRSS communication); and (9) Highly configurable burst memory with selectable channels, sample rates and number, duration, and precursor length of bursts, chosen based on best triggering algorithm “score”.This paper describes the various sensors that constitute the VEFI experiment suite and discusses their operation during the C/NOFS mission. Examples of data are included to illustrate the performance of the different sensors in space.

scholarly journals Eclipsing AM Herculis Binaries

1997 ◽  
Vol 163 ◽  
pp. 391-395
Author(s):  
Jeremy Bailey
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Time Resolution ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
High Time ◽  
High Time Resolution ◽  
Companion Star ◽  
Fundamental Properties ◽  
Cyclotron Radiation

AbstractAM Herculis Binaries (or Polars) are a subclass of the Cataclysmic Variables in which the accreting white dwarf has a strong magnetic field giving rise to highly polarized cyclotron radiation from the shock heated accretion region. A number of AM Herculis binaries are now known in which the white dwarf is eclipsed by the companion star. High time resolution observations of these eclipses allow a particularly detailed study of the process of accretion onto the magnetic white dwarf. Results on a number of systems will be presented and used to derive information on the accretion structure as well as on the fundamental properties of the binaries.

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