A Solar Source of Alfvénic Magnetic Field Switchbacks: In Situ Remnants of Magnetic Funnels on Supergranulation Scales

Abstract One of the striking observations from the Parker Solar Probe (PSP) spacecraft is the prevalence in the inner heliosphere of large amplitude, Alfvénic magnetic field reversals termed switchbacks. These δ B R / B ∼  ( 1 ) fluctuations occur over a range of timescales and in patches separated by intervals of quiet, radial magnetic field. We use measurements from PSP to demonstrate that patches of switchbacks are localized within the extensions of plasma structures originating at the base of the corona. These structures are characterized by an increase in alpha particle abundance, Mach number, plasma β and pressure, and by depletions in the magnetic field magnitude and electron temperature. These intervals are in pressure balance, implying stationary spatial structure, and the field depressions are consistent with overexpanded flux tubes. The structures are asymmetric in Carrington longitude with a steeper leading edge and a small (∼1°) edge of hotter plasma and enhanced magnetic field fluctuations. Some structures contain suprathermal ions to ∼85 keV that we argue are the energetic tail of the solar wind alpha population. The structures are separated in longitude by angular scales associated with supergranulation. This suggests that these switchbacks originate near the leading edge of the diverging magnetic field funnels associated with the network magnetic field—the primary wind sources. We propose an origin of the magnetic field switchbacks, hot plasma and suprathermals, alpha particles in interchange reconnection events just above the solar transition region and our measurements represent the extended regions of a turbulent outflow exhaust.

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Disentangling flows in the solar transition region

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732055 ◽

2018 ◽

Vol 614 ◽

pp. A110 ◽

Cited By ~ 1

Author(s):

P. Zacharias ◽

V. H. Hansteen ◽

J. Leenaarts ◽

M. Carlsson ◽

B. V. Gudiksen

Keyword(s):

Magnetic Field ◽

Field Line ◽

Transition Region ◽

Magnetic Field Line ◽

Spectral Lines ◽

Continuous Heating ◽

Solar Transition Region ◽

Solar Transition ◽

Energy Flows ◽

The Magnetic Field

Context. The measured average velocities in solar and stellar spectral lines formed at transition region temperatures have been difficult to interpret. The dominant redshifts observed in the lower transition region naturally leads to the question of how the upper layers of the solar (and stellar) atmosphere can be maintained. Likewise, no ready explanation has been made for the average blueshifts often found in upper transition region lines. However, realistic three-dimensional radiation magnetohydrodynamics (3D rMHD) models of the solar atmosphere are able to reproduce the observed dominant line shifts and may thus hold the key to resolve these issues. Aims. These new 3D rMHD simulations aim to shed light on how mass flows between the chromosphere and corona and on how the coronal mass is maintained. These simulations give new insights into the coupling of various atmospheric layers and the origin of Doppler shifts in the solar transition region and corona. Methods. The passive tracer particles, so-called corks, allow the tracking of parcels of plasma over time and thus the study of changes in plasma temperature and velocity not only locally, but also in a co-moving frame. By following the trajectories of the corks, we can investigate mass and energy flows and understand the composition of the observed velocities. Results. Our findings show that most of the transition region mass is cooling. The preponderance of transition region redshifts in the model can be explained by the higher percentage of downflowing mass in the lower and middle transition region. The average upflows in the upper transition region can be explained by a combination of both stronger upflows than downflows and a higher percentage of upflowing mass. The most common combination at lower and middle transition region temperatures are corks that are cooling and traveling downward. For these corks, a strong correlation between the pressure gradient along the magnetic field line and the velocity along the magnetic field line has been observed, indicating a formation mechanism that is related to downward propagating pressure disturbances. Corks at upper transition region temperatures are subject to a rather slow and highly variable but continuous heating process. Conclusions. Corks are shown to be an essential tool in 3D rMHD models in order to study mass and energy flows. We have shown that most transition region plasma is cooling after having been heated slowly to upper transition region temperatures several minutes before. Downward propagating pressure disturbances are identified as one of the main mechanisms responsible for the observed redshifts at transition region temperatures.

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3D Magneto-Buoyancy-Thermocapillary Convection of CNT-Water Nanofluid in the Presence of a Magnetic Field

Processes ◽

10.3390/pr8030258 ◽

2020 ◽

Vol 8 (3) ◽

pp. 258 ◽

Cited By ~ 6

Author(s):

Lioua Kolsi ◽

Salem Algarni ◽

Hussein A. Mohammed ◽

Walid Hassen ◽

Emtinene Lajnef ◽

...

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Heat Transfer Rate ◽

Flow Structure ◽

Transfer Rate ◽

Volume Fraction ◽

Numerical Study ◽

Flow Stabilization ◽

Magnetic Field Magnitude ◽

The Magnetic Field

A numerical study is performed to investigate the effects of adding Carbon Nano Tube (CNT) and applying a magnetic field in two directions (vertical and horizontal) on the 3D-thermo-capillary natural convection. The cavity is differentially heated with a free upper surface. Governing equations are solved using the finite volume method. Results are presented in term of flow structure, temperature field and rate of heat transfer. In fact, results revealed that the flow structure and heat transfer rate are considerably affected by the magnitude and the direction of the magnetic field, the presence of thermocapillary forces and by increasing nanoparticles volume fraction. In opposition, the increase of the magnetic field magnitude leads to the control the flow causing flow stabilization by merging vortexes and reducing heat transfer rate.

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Magnetic field disturbances in the sheath region of a super-sonic interplanetary magnetic cloud

Annales Geophysicae ◽

10.5194/angeo-26-3153-2008 ◽

2008 ◽

Vol 26 (10) ◽

pp. 3153-3158 ◽

Cited By ~ 2

Author(s):

E. Romashets ◽

M. Vandas ◽

S. Poedts

Keyword(s):

Magnetic Field ◽

Geomagnetic Storms ◽

Magnetic Cloud ◽

The Body ◽

Magnetic Clouds ◽

Shock Surface ◽

Sheath Region ◽

Magnetic Field Magnitude ◽

The Magnetic Field ◽

Magnetic Disturbances

Abstract. It is well-known that interplanetary magnetic clouds can cause strong geomagnetic storms due to the high magnetic field magnitude in their interior, especially if there is a large negative Bz component present. In addition, the magnetic disturbances around such objects can play an important role in their "geo-effectiveness". On the other hand, the magnetic and flow fields in the CME sheath region in front of the body and in the rear of the cloud are important for understanding both the dynamics and the evolution of the interplanetary cloud. The "eventual" aim of this work is to calculate the magnetic field in this CME sheath region in order to evaluate the possible geo-efficiency of the cloud in terms of the maximum |Bz|-component in this region. In this paper we assess the potential of this approach by introducing a model with a simplified geometry. We describe the magnetic field between the CME shock surface and the cloud's boundary by means of a vector potential. We also apply our model and present the magnetic field distribution in the CME sheath region in front of the body and in the rear of the cloud formed after the event of 20 November 2003.

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Planar magnetic structures in coronal mass ejection-driven sheath regions

Annales Geophysicae ◽

10.5194/angeo-34-313-2016 ◽

2016 ◽

Vol 34 (2) ◽

pp. 313-322 ◽

Cited By ~ 27

Author(s):

Erika Palmerio ◽

Emilia K. J. Kilpua ◽

Neel P. Savani

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Coronal Mass Ejection ◽

Leading Edge ◽

Formation Mechanisms ◽

Single Plane ◽

Magnetic Structures ◽

Automated Method ◽

Mass Ejection ◽

The Magnetic Field

Abstract. Planar magnetic structures (PMSs) are periods in the solar wind during which interplanetary magnetic field vectors are nearly parallel to a single plane. One of the specific regions where PMSs have been reported are coronal mass ejection (CME)-driven sheaths. We use here an automated method to identify PMSs in 95 CME sheath regions observed in situ by the Wind and ACE spacecraft between 1997 and 2015. The occurrence and location of the PMSs are related to various shock, sheath, and CME properties. We find that PMSs are ubiquitous in CME sheaths; 85 % of the studied sheath regions had PMSs with the mean duration of 6 h. In about one-third of the cases the magnetic field vectors followed a single PMS plane that covered a significant part (at least 67 %) of the sheath region. Our analysis gives strong support for two suggested PMS formation mechanisms: the amplification and alignment of solar wind discontinuities near the CME-driven shock and the draping of the magnetic field lines around the CME ejecta. For example, we found that the shock and PMS plane normals generally coincided for the events where the PMSs occurred near the shock (68 % of the PMS plane normals near the shock were separated by less than 20° from the shock normal), while deviations were clearly larger when PMSs occurred close to the ejecta leading edge. In addition, PMSs near the shock were generally associated with lower upstream plasma beta than the cases where PMSs occurred near the leading edge of the CME. We also demonstrate that the planar parts of the sheath contain a higher amount of strong southward magnetic field than the non-planar parts, suggesting that planar sheaths are more likely to drive magnetospheric activity.

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Cluster-C1 observations on the geometrical structure of linear magnetic holes in the solar wind at 1 AU

Annales Geophysicae ◽

10.5194/angeo-28-1695-2010 ◽

2010 ◽

Vol 28 (9) ◽

pp. 1695-1702 ◽

Cited By ~ 27

Author(s):

T. Xiao ◽

Q. Q. Shi ◽

T. L. Zhang ◽

S. Y. Fu ◽

L. Li ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Geometrical Structure ◽

Occurrence Rate ◽

Geometrical Shape ◽

Magnetic Field Data ◽

Magnetic Field Magnitude ◽

The Relationship ◽

Plasma Measurements ◽

The Magnetic Field

Abstract. Interplanetary linear magnetic holes (LMHs) are structures in which the magnetic field magnitude decreases with little change in the field direction. They are a 10–30% subset of all interplanetary magnetic holes (MHs). Using magnetic field and plasma measurements obtained by Cluster-C1, we surveyed the LMHs in the solar wind at 1 AU. In total 567 interplanetary LMHs are identified from the magnetic field data when Cluster-C1 was in the solar wind from 2001 to 2004. We studied the relationship between the durations and the magnetic field orientations, as well as that of the scales and the field orientations of LMHs in the solar wind. It is found that the geometrical structure of the LMHs in the solar wind at 1 AU is consistent with rotational ellipsoid and the ratio of scales along and across the magnetic field is about 1.93:1. In other words, the structure is elongated along the magnetic field at 1 AU. The occurrence rate of LMHs in the solar wind at 1 AU is about 3.7 per day. It is shown that not only the occurrence rate but also the geometrical shape of interplanetary LMHs has no significant change from 0.72 AU to 1 AU in comparison with previous studies. It is thus inferred that most of interplanetary LMHs observed at 1 AU are formed and fully developed before 0.72 AU. The present results help us to study the formation mechanism of the LMHs in the solar wind.

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First measurements of the Mesospheric Magnetic Field in the Auroral Zone by means of laser

10.5194/egusphere-egu2020-7839 ◽

2020 ◽

Author(s):

Magnar G. Johnsen ◽

Njål Gulbrandsen ◽

Paul Hillman ◽

Craig Denman ◽

Jürgen Matzka ◽

...

Keyword(s):

Magnetic Field ◽

Time Scales ◽

Optical Pumping ◽

Sodium Atom ◽

Auroral Zone ◽

Geomagnetic Variations ◽

Sum Frequency ◽

Sodium Layer ◽

Magnetic Field Magnitude ◽

The Magnetic Field

In December 2019, for the first time, we were able to remotely measure the magnetic field in the mesospheric sodium layer, in the auroral zone.By means of laser optical pumping and Larmor-resonance detection, it is possible to use the naturally occurring sodium layer in the mesosphere to measure Earth&#8217;s magnetic field magnitude at 90 km above ground. This is an altitude otherwise only accessible by rockets, which only will provide point measurements of very short time scales.During the winter of 2019-20 we have applied a cw sum-frequency fasor/laser for probing the sodium-atom Larmor resonance at the Artic Lidar Observatory for Mesospheric Research (ALOMAR) at And&#248;ya in northern Norway in order to measure and monitor the magnetic field in situ in the high latitude mesosphere over longer time scales.The technique, which has been proved earlier at mid-latitudes, has now been confirmed and applied to high latitudes in the auroral zone during disturbed auroral and geomagnetic conditions. The magnetic field in the auroral zone is close to vertical making our measurements a notable achievement since the beam is closer to parallel with the magnetic field, contary to earlier measurements being closer to perpendicular as shown as best by theory.This opens up for a completely new domain of measurements of externally generated geomagnetic variations related to currents in the magnetosphere-ionosphere system.Here we report on the instrumental setup, and discuss our measurements of the mesospheric magnetic field.

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Development of a database of Jovian magnetodisc crossings by Galileo and Juno spacecraft from magnetometer data

10.5194/epsc2020-615 ◽

2020 ◽

Author(s):

Igor Alekseev ◽

Elena Belenkaya ◽

Alexander Lavrukhin ◽

David Parunakian ◽

Ivan Pensionerov

Keyword(s):

Magnetic Field ◽

Current Sheet ◽

Polar Axis ◽

Dipole Axis ◽

Radial Magnetic Field ◽

Jovian Magnetosphere ◽

Central Surface ◽

Magnetometer Data ◽

Plasma Measurements ◽

The Magnetic Field

Jovian magnetosphere has &#160;&#160;a huge equatorial plasma disk, which is also known as the current sheet or magnetodisk. This current sheet enlarges the subsolar magnetosphere size more than twice compare to purely planetary dipole magnetosphere. Near to the planet &#160;&#160;the magnetodisk is aligned with the magnetic equatorial plane. As consequence of the dipole axis tilted to the polar axis about 10, each of Juno orbits crossed the central surface of the disk current two times during one jovian day (9, 92 hours). Finally, we have &#160;about 1725 current sheet crossings to study the plasma sheet and current sheets structure. In our work we have developed a database of Jovian current sheet crossings, performed by Galileo and Juno spacecraft, which includes magnetic field and plasma measurements. Current sheet crossings were determined using magnetometer data in distant magnetosphere as a region with the magnetic field strength less than the dipole value at the same point and central current sheet position have been marked by boundary between the region with opposite signum of the radial magnetic field component.

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Threshold speed for two-dimensional confinement of charged particles in certain axisymmetric magnetic fields

Canadian Journal of Physics ◽

10.1139/cjp-2017-0415 ◽

2018 ◽

Vol 96 (5) ◽

pp. 519-523 ◽

Cited By ~ 1

Author(s):

K. Kabin ◽

G. Kalugin ◽

E. Spanswick ◽

E. Donovan

Keyword(s):

Magnetic Field ◽

Power Law ◽

Critical Speed ◽

Longitudinal Magnetic Field ◽

Strong Dependence ◽

Charged Particles ◽

Transcendental Equation ◽

Power Exponent ◽

Magnetic Field Magnitude ◽

The Magnetic Field

In this paper we discuss conditions under which charged particles are confined by an axisymmetric longitudinal magnetic field with power law dependence on the radius. We derive a transcendental equation for the critical speed corresponding to the threshold between bounded and unbounded trajectories of the particles. This threshold speed shows strong dependence on the direction, and this dependence becomes more prominent as the exponent of the power law increases. The equation for threshold speed can be solved exactly for several specific values of the power exponent, but in general it requires a numerical treatment. Remarkably, if the magnetic field magnitude decreases more slowly than the inverse of the radius, charged particles remain confined no matter how large their energies may be.

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Investigation of DC Vacuum Arc Interruption Ability with Combined Axial and Radial Magnetic Field

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.516-517.1791 ◽

2012 ◽

Vol 516-517 ◽

pp. 1791-1797 ◽

Cited By ~ 2

Author(s):

Mohmmad Al Dweikat ◽

Yu Long Huang ◽

Xiao Lin Shen ◽

Wei Dong Liu

Keyword(s):

Magnetic Field ◽

Axial Magnetic Field ◽

Vacuum Arc ◽

Axial Component ◽

Circuit Breakers ◽

Radial Magnetic Field ◽

Vacuum Interrupter ◽

Magnetic Field Simulation ◽

The Magnetic Field ◽

Field Influence

DC Vacuum Circuit Breakers based arc control has been a major topic in the last few decades. Understanding vacuum arc (VA) gives the ability to improve vacuum circuit breakers capacity. In this paper, the interaction of a DC vacuum arc with a combined Axial-Radial magnetic field was investigated. The proposed system contains an external coil to produce axial magnetic field (AMF) across the vacuum chamber. The vacuum interrupter (VI) contacts were assumed to be untreated radial magnetic field (RMF) contacts. For this purpose, Finite Element Method (FEM) based Multiphysics simulation of the immerging magnetic field influence on the VA is presented. The simulation shown the ability of the presented system to deflect high DC vacuum arc, also reveals that the vacuum arc interruption capability increases with the rise of the axial component of the magnetic field. Simulation results shown that this method can be applied to improve the interruption capability of the VI.

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High-resolution spectropolarimetry of κ Cet: A proxy for the young Sun

Proceedings of the International Astronomical Union ◽

10.1017/s1743921314001902 ◽

2013 ◽

Vol 9 (S302) ◽

pp. 142-143

Author(s):

J. D. do Nascimento ◽

P. Petit ◽

M. Castro ◽

G. F. Porto de Mello ◽

S. V. Jeffers ◽

...

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Atmospheric Model ◽

Longitudinal Component ◽

Least Square ◽

Doppler Imaging ◽

Inversion Method ◽

Radial Magnetic Field ◽

Field Geometry ◽

The Magnetic Field

Abstractκ1 Cet (HD 20630, HIP 15457, d = 9.16 pc, V = 4.84) is a dwarf star approximately 30 light-years away in the equatorial constellation of Cetus. Among the solar proxies studied in the Sun in Time, κ1 Cet stands out as potentially having a mass very close to solar and a young age. On this study, we monitored the magnetic field and the chromospheric activity from the Ca II H & K lines of κ1 Cet. We used the technique of Least-Square-Deconvolution (LSD, Donati et al. 1997) by simultaneously extracting the information contained in all 8,000 photospheric lines of the echelogram (for a linelist matching an atmospheric model of spectral type K1). To reconstruct a reliable magnetic map and characterize the surface differential rotation of κ1 Cet we used 14 exposures spread over 2 months, in order to cover at least two rotational cycles (Prot ~9.2 days). The Least Square deconvolution (LSD) technique was applied to detect the Zeeman signature of the magnetic field in each of our 14 observations and to measure its longitudinal component. In order to reconstruct the magnetic field geometry of κ1 Cet, we applied the Zeeman Doppler Imaging (ZDI) inversion method. ZDI revealed a structure in the radial magnetic field consisting of a polar magnetic spot. On this study, we present the fisrt look results of a high-resolution spectropolarimetric campaign to characterize the activity and the magnetic fields of this young solar proxy.

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