Magnetic helicity of a flux rope in the magnetotail: THEMIS results

Abstract. The magnetic field in many regions of magnetosphere has a complex topological structure. As a parameter to measure the topological complexity, the concept of magnetic helicity is a useful tool in magnetospheric physics. Here we present a case study of magnetic helicity in the flux rope (FR) in the near-Earth plasma sheet (PS) based on the in-situ observation from THEMIS for the first time. With the help of the Grad-Shafranov reconstruction technique, we determine the spatial distribution of magnetic field and evaluate the magnetic helicity in the flux rope. The conservation of magnetic helicity during multiple X-line reconnections and the transport of magnetic helicity between different magnetic field configurations are also discussed. The further application of helicity in magnetosphere will provide us more knowledge about the topologic property of the magnetic fields there and more attention should be paid to that.

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Principal Component Gradiometer technique for removal of spacecraft-generated disturbances from magnetic field data

10.5194/gi-2020-10 ◽

2020 ◽

Cited By ~ 1

Author(s):

Ovidiu Dragoş Constantinescu ◽

Hans-Ulrich Auster ◽

Magda Delva ◽

Olaf Hillenmaier ◽

Werner Magnes ◽

...

Keyword(s):

Magnetic Field ◽

Principal Component ◽

Field Measurements ◽

Magnetic Field Data ◽

Service Oriented ◽

Sensor Configuration ◽

Time Required ◽

First Time ◽

The Magnetic Field

Abstract. In situ measurement of the magnetic field using space borne instruments requires either a magnetically clean platform and/or a very long boom for accommodating magnetometer sensors at a large distance from the spacecraft body. This significantly drives up the costs and time required to build a spacecraft. Here we present an alternative sensor configuration and an algorithm allowing for ulterior removal of the spacecraft generated disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness program and allowing for shorter boom length. The proposed algorithm is applied to the Service Oriented Spacecraft Magnetometer (SOSMAG) onboard the Korean geostationary satellite GeoKompsat-2A (GK2A) which uses for the first time a multi-sensor configuration for onboard data cleaning. The successful elimination of disturbances originating from several sources validates the proposed cleaning technique.

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Cleaning magnetometer data using multi sensor configuration

10.5194/egusphere-egu2020-17741 ◽

2020 ◽

Author(s):

Dragos Constantinescu ◽

Hans-Ulrich Auster ◽

Magda Delva ◽

Olaf Hillenmaier ◽

Werner Magnes ◽

...

Keyword(s):

Magnetic Field ◽

Field Measurements ◽

Sensor Arrangement ◽

Magnetometer Data ◽

Service Oriented ◽

Sensor Configuration ◽

First Time ◽

The Magnetic Field ◽

Magnetic Cleanliness

Measuring the in situ magnetic field using space borne instruments requires either a magnetically clean platform and/or a very long boom for accommodating magnetometers sensors at a large distance from the spacecraft body. This significantly drives up the costs and time for building the spacecraft. Here we present an alternative sensor configuration and an algorithm allowing for ulterior removing of the spacecraft generated disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness program.The Service Oriented Spacecraft Magnetometer (SOSMAG) onboard the Korean Geostationary Satellite GEO-KOMPSAT-2A (GK-2A) uses for the first time a multi-sensor configuration for onboard data cleaning. To remove the AC disturbances, a combination of the measurements from sensors placed at different positions from the disturbance sources is processed onboard. Sensor biases due to daily temperature variations are also removed using the specific SOSMAG sensor arrangement.&#160;&#160;

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A New Model to Describe the Magnetic Structure of CMEs

10.5194/egusphere-egu2020-3172 ◽

2020 ◽

Author(s):

Nada Al-Haddad ◽

Noé Lugaz

Keyword(s):

Magnetic Field ◽

Flux Rope ◽

Challenging Problem ◽

New Paradigm ◽

Field Orientation ◽

Magnetic Field Orientation ◽

The Past ◽

Current Paradigm ◽

The Magnetic Field

The structure of coronal mass ejections (CMEs) has been the center of numerous studies over the past few decades. Defining the magnetic field orientation locally and globally has proven to be a challenging problem, due to the limited nature of observations that we have, as well as our reliance on the current paradigm of highly-twisted flux ropes. Studies suggest that not all CMEs measured in situ fit within the simple twisted and well-organized flux rope topology. Additionally, many of the events that can be well fitted by existing static flux rope models, do not have as simple a structure as that assumed by the models. This is clear from remote observations and multi-spacecraft measurements. With the wealth of data that we have today, as well as the affluence of research and analysis performed over the last 40 years, it is dues time to present an alternative paradigm, that better represents those data. In this work, we discuss this new paradigm and the literature leading to it.&#160;

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

10.5194/egusphere-egu2020-22182 ◽

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

We present an analysis of the internal structure of a coronal mass ejection (CME)&#160;detected by in situ&#160;instruments onboard the Parker Solar Probe (PSP) spacecraft during its first solar&#160;encounter. On 2018 November 11 at 23:53 UT, the FIELDS magnetometer measured an increase&#160;in strength of the magnetic field as well as a coherent change in the field direction. The SWEAP&#160;instrument simultaneously detected the low proton temperature and signatures of bi-directionality in&#160;the electron pitch angle distribution (PAD). These signatures are indicative of a CME embedded in the&#160;slow solar wind. In conjunction with PSP was the STEREO A spacecraft, which enabled the remote&#160;observation of a streamer blow-out by the SECCHI suite of instruments. The source at the Sun of&#160;the slow and well-structured&#160;flux-rope was identified in an overlying streamer.Our detailed inspection of the internal transient structure magnetic properties suggests high complexity&#160;in deviations from an ideal&#160;flux rope 3D topology. Reconstructions of the magnetic field&#160;conguration reveal a highly distorted structure consistent with the highly elongated `bubble' observed&#160;remotely. A double-ring substructure observed in the SECCHI-COR2 eld of view (FOV) is&#160;suggestive of a double internal&#160;flux rope. Furthermore, we describe a scenario in which mixed topology&#160;of a closed&#160;flux rope is combined with the magnetically open structure, which helps explain the&#160;flux&#160;dropout observed in the measurements of the electron PAD. Our justication for this is the plethora&#160;of structures observed by the EUV imager (SECCHI-EUVI) in the hours preceding the streamer blowout&#160;evacuation. Finally, taking advantage of the unique observations from PSP, we explore the first&#160;stages of the effects of coupling with the solar wind and the evolutionary processes in the magnetic&#160;structure. We found evidence of bifurcated current sheets in the structure boundaries suggestive of&#160;magnetic reconnection. Our analysis of the internal force imbalance indicates that internal Lorentz&#160;forces continue to dominate the evolution of the structure in the COR2 FOV and serves as the main&#160;driver of the internal&#160;flux rope distortion as detected in situ at PSP solar distance.

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Connecting a Star’s Convection Zone with its Corona

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000020245 ◽

1995 ◽

Vol 12 (2) ◽

pp. 180-185 ◽

Cited By ~ 2

Author(s):

D. J. Galloway ◽

C. A. Jones

Keyword(s):

Magnetic Field ◽

Convection Zone ◽

Flux Rope ◽

Field System ◽

Stellar Convection ◽

Coronal Activity ◽

Flux Concentration ◽

Global Understanding ◽

The Magnetic Field

AbstractThis paper discusses problems which have as their uniting theme the need to understand the coupling between a stellar convection zone and a magnetically dominated corona above it. Interest is concentrated on how the convection drives the atmosphere above, loading it with the currents that give rise to flares and other forms of coronal activity. The role of boundary conditions appears to be crucial, suggesting that a global understanding of the magnetic field system is necessary to explain what is observed in the corona. Calculations are presented which suggest that currents flowing up a flux rope return not in the immediate vicinity of the rope but rather in an alternative flux concentration located some distance away.

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Non-damping oscillations at flaring loops

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832991 ◽

2018 ◽

Vol 617 ◽

pp. A86 ◽

Cited By ~ 11

Author(s):

D. Li ◽

D. Yuan ◽

Y. N. Su ◽

Q. M. Zhang ◽

W. Su ◽

...

Keyword(s):

Magnetic Field ◽

Line Width ◽

Line Emission ◽

Flux Rope ◽

Doppler Velocity ◽

Narrow Slit ◽

Plasma Properties ◽

Spectral Window ◽

Peak Intensity ◽

The Magnetic Field

Context. Quasi-periodic oscillations are usually detected as spatial displacements of coronal loops in imaging observations or as periodic shifts of line properties (i.e., Doppler velocity, line width and intensity) in spectroscopic observations. They are often applied for remote diagnostics of magnetic fields and plasma properties on the Sun. Aims. We combine the imaging and spectroscopic measurements of available space missions, and investigate the properties of non-damping oscillations at flaring loops. Methods. We used the Interface Region Imaging Spectrograph (IRIS) to measure the spectrum over a narrow slit. The double-component Gaussian fitting method was used to extract the line profile of Fe XXI 1354.08 Å at the “O I” spectral window. The quasi-periodicity of loop oscillations were identified in the Fourier and wavelet spectra. Results. A periodicity at about 40 s is detected in the line properties of Fe XXI 1354.08 Å, hard X-ray emissions in GOES 1−8 Å derivative, and Fermi 26−50 keV. The Doppler velocity and line width oscillate in phase, while a phase shift of about π/2 is detected between the Doppler velocity and peak intensity. The amplitudes of Doppler velocity and line width oscillation are about 2.2 km s−1 and 1.9 km s−1, respectively, while peak intensity oscillates with amplitude at about 3.6% of the background emission. Meanwhile, a quasi-period of about 155 s is identified in the Doppler velocity and peak intensity of the Fe XXI 1354.08 Å line emission, and AIA 131 Å intensity. Conclusions. The oscillations at about 40 s are not damped significantly during the observation; this might be linked to the global kink modes of flaring loops. The periodicity at about 155 s is most likely a signature of recurring downflows after chromospheric evaporation along flaring loops. The magnetic field strengths of the flaring loops are estimated to be about 120−170 G using the magnetohydrodynamic seismology diagnostics, which are consistent with the magnetic field modeling results using the flux rope insertion method.

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A case study of the plasma in the magneto-sheath using the numerical magnetosheath-magnetosphere model and THEMIS measure-ments

MATEC Web of Conferences ◽

10.1051/matecconf/201814503004 ◽

2018 ◽

Vol 145 ◽

pp. 03004

Author(s):

Polya Dobreva ◽

Olga Nitcheva ◽

Monio Kartalev

Keyword(s):

Magnetic Field ◽

Field Model ◽

Specific Aspect ◽

Plasma Parameters ◽

Ion Density ◽

Magnetic Field Model ◽

Wind Spacecraft ◽

The Mean ◽

The Magnetic Field

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

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Scattering of field-aligned beam ions upstream of Earth's bow shock

Annales Geophysicae ◽

10.5194/angeo-25-785-2007 ◽

2007 ◽

Vol 25 (3) ◽

pp. 785-799 ◽

Cited By ~ 24

Author(s):

A. Kis ◽

M. Scholer ◽

B. Klecker ◽

H. Kucharek ◽

E. A. Lucek ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Field Measurements ◽

Bow Shock ◽

Ion Distribution ◽

Parallel Side ◽

Earth’S Bow Shock ◽

High Mach ◽

The Magnetic Field

Abstract. Field-aligned beams are known to originate from the quasi-perpendicular side of the Earth's bow shock, while the diffuse ion population consists of accelerated ions at the quasi-parallel side of the bow shock. The two distinct ion populations show typical characteristics in their velocity space distributions. By using particle and magnetic field measurements from one Cluster spacecraft we present a case study when the two ion populations are observed simultaneously in the foreshock region during a high Mach number, high solar wind velocity event. We present the spatial-temporal evolution of the field-aligned beam ion distribution in front of the Earth's bow shock, focusing on the processes in the deep foreshock region, i.e. on the quasi-parallel side. Our analysis demonstrates that the scattering of field-aligned beam (FAB) ions combined with convection by the solar wind results in the presence of lower-energy, toroidal gyrating ions at positions deeper in the foreshock region which are magnetically connected to the quasi-parallel bow shock. The gyrating ions are superposed onto a higher energy diffuse ion population. It is suggested that the toroidal gyrating ion population observed deep in the foreshock region has its origins in the FAB and that its characteristics are correlated with its distance from the FAB, but is independent on distance to the bow shock along the magnetic field.

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The UVMag space project: UV and visible spectropolarimetry of massive stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314007212 ◽

2014 ◽

Vol 9 (S307) ◽

pp. 389-390

Author(s):

Coralie Neiner ◽

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Massive Stars ◽

Spectral Energy Distribution ◽

Spectral Energy ◽

Medium Size ◽

Space Project ◽

First Time ◽

The Magnetic Field ◽

Circumstellar Environment

AbstractUVMag is a medium-size space telescope equipped with a high-resolution spectropolarimetrer working in the UV and visible domains. It will be proposed to ESA for a future M mission. It will allow scientists to study all types of stars as well as e.g. exoplanets and the interstellar medium. It will be particularly useful for massive stars, since their spectral energy distribution peaks in the UV. UVMag will allow us to study massive stars and their circumstellar environment (in particular the stellar wind) spectroscopically in great details. Moreover, with UVMag's polarimetric capabilities we will be able, for the first time, to measure the magnetic field of massive stars simultaneously at the stellar surface and in the wind lines, i.e. to completely map their magnetosphere.

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Transport of energetic particles from reconnecting current sheets in flaring corona to the heliosphere

10.5194/egusphere-egu21-15163 ◽

2021 ◽

Author(s):

Philippa Browning ◽

Mykola Gordovskyy ◽

Satashi Inoue ◽

Eduard Kontar ◽

Kanya Kusano ◽

...

Keyword(s):

Magnetic Field ◽

Energetic Particles ◽

Transport Processes ◽

Data Driven ◽

Current Sheets ◽

Electrons And Ions ◽

Data Driven Approach ◽

Particle Simulations ◽

The Magnetic Field

In this study, we inverstigate the acceleration of electrons and ions at current sheets in the flaring solar corona, and their transport into the heliosphere. We consider both generic solar flare models and specific flaring events with a data-driven approach. The aim is to answer two questions: (a) what fraction of particles accelerated in different flares can escape into the heliosphere?; and (b) what are the characteristics of the particle populations propagating towards the chromosphere and into the heliosphere?We use a combination of data-driven 3D magnetohydrodynamics simulations with drift-kinetic particle simulations to model the evolution of the magnetic field and both thermal and non-thermal plasma and to forward-model observable characteristics. Particles are accelerated in current sheets associated with flaring reconnection. When applied to a specific flare, the model successfully predicts observed features such as the location and relative intensity of hard X-ray sources and helioseismic source locations. This confirms the viability of the approach.Using these MHD-particle models, we will show how the magnetic field evolution and particle transport processes affect the characteristics of both energetic electrons and ions in the the inner corona and the heliosphere. The implications for interpretation of in situ measurements of energetic particles by Solar Orbiter and Parker Solar Probe will be discussed.&#160;&#160;

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