Evaluating the Reliability of a Simple Method to Map the Magnetic Field Azimuth in the Solar Chromosphere

This study aims to evaluate the efficiency of a novel in vitro technique in clot capturing and dissolving them by applying magnetic force on magnetic nanoparticles (MNP) carrying thrombolytic agents. It is a quick and simple method to protect patients from a life-threatening pulmonary embolism in an emergency to provide time for the medical team. To analyze the in vitro efficiency of nano-magnetic capturing and dissolving of clots (NCDC), different levels of process parameter including strength magnetic field (0.1, 0.2 and 0.3 T) and fluid flow rate (2.5, 5 and 7 l/min) are exposed to different blood clots sizes from 5 × 10 to 20 × 10 mm2 (length × diameter), in an in vitro flow model. The results show that by increasing the parameters to their maximum values, it is possible to immobilize 100% of the clots and dissolve around 61.4% of clots weight. In addition, the clot-dissolving is directly proportional to the magnetic field strength. NCDC is an efficient technique in immobilizing and dissolving the clots and its efficiency depends on process parameters especially the magnetic field.

Download Full-text

THE INFLUENCE OF THE MAGNETIC FIELD ON RUNNING PENUMBRAL WAVES IN THE SOLAR CHROMOSPHERE

The Astrophysical Journal ◽

10.1088/0004-637x/779/2/168 ◽

2013 ◽

Vol 779 (2) ◽

pp. 168 ◽

Cited By ~ 57

Author(s):

D. B. Jess ◽

V. E. Reznikova ◽

T. Van Doorsselaere ◽

P. H. Keys ◽

D. H. Mackay

Keyword(s):

Magnetic Field ◽

Solar Chromosphere ◽

The Magnetic Field

Download Full-text

Joint Discussion 3 Solar active regions and 3D magnetic structure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307010071 ◽

2006 ◽

Vol 2 (14) ◽

pp. 139-168

Author(s):

Debi Prasad Choudhary ◽

Michal Sobotka

Keyword(s):

Magnetic Field ◽

Active Region ◽

Large Scale ◽

Focal Point ◽

Active Regions ◽

Theoretical Modelling ◽

Solar Chromosphere ◽

Origin And Evolution ◽

Solar Active Regions ◽

The Magnetic Field

AbstractKeeping in view of the modern powerful observing tools, among othersHinode(formerlySOLAR-B),STEREOand Frequency-Agile Solar Radiotelescope, and sophisticated modelling techniques, Joint Discussion 3 during the IAU General Assembly 2006 focused on the properties of magnetic field of solar active regions starting in deep interior of the Sun, from where they buoyantly rise to the coronal heights where the site of most explosive events are located. Intimately related with the active regions, the origin and evolution of the magnetic field of quiet Sun, the large scale chromospheric structures were also the focal point of the Joint Discussion. The theoretical modelling of the generation and dynamics of magnetic field in solar convective zone show that the interaction of the magnetic field with the Coriolis force and helical turbulent convection results in the tilts and twists in the emerging flux. In the photosphere, some of these fluxes appear in sunspots with field strengths up to about 6100 G. Spectro-polarimetric measurements reveal that the line of sight velocities and magnetic field of these locations are found to be uncombed and depend on depth in the atmosphere and exhibit gradients or discontinuities. The inclined magnetic fields beyond penumbra appear as moving magnetic features that do not rise above upper photospheric heights. As the flux rises, the solar chromosphere is the most immediate and intermediary layer where competitive magnetic forces begin to dominate their thermodynamic counterparts. The magnetic field at these heights is now measured using several diagnostic lines such as CaII854.2 nm, HI656.3 nm, and HeI1083.0 nm. The radio observations show that the coronal magnetic field of post flare loops are of the order of 30 G, which might represent the force-free magnetic state of active region in the corona. The temperatures at these coronal heights, derived from the line widths, are in the range from 2.4 to 3.7 million degree. The same line profile measurements indicate the existence of asymmetric flows in the corona. The theoretical extrapolation of photospheric field into coronal heights and their comparison with the observations show that there exists a complex topology with separatrices associated to coronal null points. The interaction of these structures often lead to flares and coronal mass ejections. The current MHD modelling of active region field shows that for coronal mass ejection both local active region magnetic field and global magnetic field due to the surrounding magnetic flux are important. Here, we present an extended summary of the papers presented in Joint Discussion 03 and open questions related to the solar magnetic field that are likely to be the prime issue with the modern observing facilities such asHinodeandSTEREOmissions.

Download Full-text

Numerical modelling of MHD waves in the solar chromosphere

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2005.1705 ◽

2005 ◽

Vol 364 (1839) ◽

pp. 395-404 ◽

Cited By ~ 22

Author(s):

Mats Carlsson ◽

Thomas J Bogdan

Keyword(s):

Magnetic Field ◽

Acoustic Waves ◽

Mode Conversion ◽

Three Dimensions ◽

Mhd Waves ◽

Solar Chromosphere ◽

Fast Mode ◽

Reflected Waves ◽

The Waves ◽

The Magnetic Field

Acoustic waves are generated by the convective motions in the solar convection zone. When propagating upwards into the chromosphere they reach the height where the sound speed equals the Alfvén speed and they undergo mode conversion, refraction and reflection. We use numerical simulations to study these processes in realistic configurations where the wavelength of the waves is similar to the length scales of the magnetic field. Even though this regime is outside the validity of previous analytic studies or studies using ray-tracing theory, we show that some of their basic results remain valid: the critical quantity for mode conversion is the angle between the magnetic field and the k-vector: the attack angle. At angles smaller than 30° much of the acoustic, fast mode from the photosphere is transmitted as an acoustic, slow mode propagating along the field lines. At larger angles, most of the energy is refracted/reflected and returns as a fast mode creating an interference pattern between the upward and downward propagating waves. In three-dimensions, this interference between waves at small angles creates patterns with large horizontal phase speeds, especially close to magnetic field concentrations. When damping from shock dissipation and radiation is taken into account, the waves in the low–mid chromosphere have mostly the character of upward propagating acoustic waves and it is only close to the reflecting layer we get similar amplitudes for the upward propagating and refracted/reflected waves. The oscillatory power is suppressed in magnetic field concentrations and enhanced in ring-formed patterns around them. The complex interference patterns caused by mode-conversion, refraction and reflection, even with simple incident waves and in simple magnetic field geometries, make direct inversion of observables exceedingly difficult. In a dynamic chromosphere it is doubtful if the determination of mean quantities is even meaningful.

Download Full-text

Solar image denoising with convolutional neural networks

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936069 ◽

2019 ◽

Vol 629 ◽

pp. A99 ◽

Cited By ~ 3

Author(s):

C. J. Díaz Baso ◽

J. de la Cruz Rodríguez ◽

S. Danilovic

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Spatial Coherence ◽

Principal Component ◽

Real Data ◽

Spectral Lines ◽

Solar Chromosphere ◽

Weak Signals ◽

Statistical Characterization ◽

The Magnetic Field

The topology and dynamics of the solar chromosphere are greatly affected by the presence of magnetic fields. The magnetic field can be inferred by analyzing polarimetric observations of spectral lines. Polarimetric signals induced by chromospheric magnetic fields are, however, particularly weak, and in most cases very close to the detection limit of current instrumentation. Because of this, there are only few observational studies that have successfully reconstructed the three components of the magnetic field vector in the chromosphere. Traditionally, the signal-to-noise ratio of observations has been improved by performing time-averages or spatial averages, but in both cases, some information is lost. More advanced techniques, like principal-component analysis, have also been employed to take advantage of the sparsity of the observations in the spectral direction. In the present study, we use the spatial coherence of the observations to reduce the noise using deep-learning techniques. We designed a neural network that is capable of recovering weak signals under a complex noise corruption (including instrumental artifacts and non-linear post-processing). The training of the network is carried out without a priori knowledge of the clean signals, or an explicit statistical characterization of the noise or other corruption. We only use the same observations as our generative model. The performance of this method is demonstrated on both synthetic experiments and real data. We show examples of the improvement in typical signals obtained in current telescopes such as the Swedish 1 m Solar Telescope. The presented method can recover weak signals equally well no matter what spectral line or spectral sampling is used. It is especially suitable for cases when the wavelength sampling is scarce.

Download Full-text

Microdrop Manipulation and Mixing Using Dynamic Ferrofluid Cage Array

Fluids Engineering ◽

10.1115/imece2006-14827 ◽

2006 ◽

Author(s):

Woo-Bin Song ◽

Zhenwen Ding ◽

Chulwoo Son ◽

Babak Ziaie

Keyword(s):

Magnetic Field ◽

Finite Element Method ◽

Finite Element ◽

Water Droplet ◽

Dynamic Change ◽

Simple Method ◽

Mixing Effect ◽

Array Pattern ◽

Simulation Results ◽

The Magnetic Field

In this paper, we present a simple method to manipulate free microdroplets using ferrofluid dynamics. First, we use two strip magnets (20 Gauss) to generate a ferrofluid cage-array pattern. Then, a magnetic stirrer (200 Gauss) is placed and rotated underneath them to induce a dynamic change in the pattern. The generated ferrofluid pattern and its dynamics are compared with the simulation results of the magnetic field distribution under various static/dynamic configurations using finite element method (FEM). The mixing effect in individual cells is investigated using silica beads (0.2 μm in size) and a water droplet (40 microliter in volume) first. In order to demonstrate free droplet mixing, two colored water microdroplets (10 microliter in volume) are placed in two separate wells and are driven to move and mix without sample evaporation.

Download Full-text

Approximation of Hysteresis Changes in Electrical Steel Sheets

Energies ◽

10.3390/en14144110 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4110

Author(s):

Witold Mazgaj ◽

Michal Sierzega ◽

Zbigniew Szular

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Hysteresis Loop ◽

Flux Density ◽

Electrical Steel ◽

Transformer Steel ◽

Simple Method ◽

Steel Sheets ◽

Electrical Steel Sheets ◽

The Magnetic Field

This paper describes a simple method of approximating hysteresis changes in electrical steel sheets. This method is based on assumptions that flux density or field strength changes are a sum or a difference of functions that describe one curve of the limiting hysteresis loop and a certain ‘transient’ component. Appropriate formulas that present the flux density as functions of the field strength and those that present inverse dependencies are proposed. An application of this approximation requires knowledge of the measured limiting hysteresis loop and a few minor loops. Algorithms for determining changes in the flux density or field strength are proposed and discussed. The correctness of the proposed approximation of hysteresis changes was verified through a comparison of measured hysteresis loops with the loops calculated for several different excitations of the magnetic field occurring in dynamo and transformer steel sheets. Additionally, an example of the application of the proposed approximation of hysteresis changes is discussed in the paper. The proposed approximation of hysteresis changes is recommended for numerical calculations of the magnetic field distribution in dynamo and transformer steel sheets.

Download Full-text

The presence of a systematic error in SDO/HMI data

Solnechno-Zemnaya Fizika ◽

10.12737/szf-42201801 ◽

2018 ◽

Vol 4 (2) ◽

pp. 3-10

Author(s):

Георгий Руденко ◽

Georgiy Rudenko ◽

Ирина Дмитриенко ◽

Irina Dmitrienko

Keyword(s):

Magnetic Field ◽

Systematic Error ◽

Radial Direction ◽

Disk Center ◽

Magnetic Data ◽

Solar Dynamics Observatory ◽

Simple Method ◽

Small Grains ◽

Solar Dynamics ◽

The Magnetic Field

In this paper, we came to the conclusion that there is a systematic error in SDO/HMI (Helioseismic and Magnetic Imager aboard the Solar Dynamics Observatory) vector magnetic data, which reveals itself in a deviation from the radial direction of the knot mag-netic fields manifesting themselves on magnetograms in the form of small grains in a strong magnetic field. This deviation demonstrates a dependence on the distance to the disk center, which cannot be a property of the magnetic field – it can only be artificially introduced into the data. We suggest a simple method for correcting vector magnetograms, which eliminates the detected systematic error.

Download Full-text

Intermediate shock sub-structures within a slow-mode shock occurring in partially ionised plasma

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935326 ◽

2019 ◽

Vol 626 ◽

pp. A46 ◽

Cited By ~ 6

Author(s):

B. Snow ◽

A. Hillier

Keyword(s):

Magnetic Field ◽

Initial Conditions ◽

Frictional Heating ◽

Physical Parameters ◽

Solar Chromosphere ◽

Finite Width ◽

Slow Mode ◽

Wide Range ◽

Intermediate Shock ◽

The Magnetic Field

Context. Slow-mode shocks are important in understanding fast magnetic reconnection, jet formation and heating in the solar atmosphere, and other astrophysical systems. The atmospheric conditions in the solar chromosphere allow both ionised and neutral particles to exist and interact. Under such conditions, fine sub-structures exist within slow-mode shocks due to the decoupling and recoupling of the plasma and neutral species. Aims. We study numerically the fine sub-structure within slow-mode shocks in a partially ionised plasma, in particular, analysing the formation of an intermediate transition within the slow-mode shock. Methods. High-resolution 1D numerical simulations were performed using the (PIP) code using a two-fluid approach. Results. We discover that long-lived intermediate (Alfvén) shocks can form within the slow-mode shock, where there is a shock transition from above to below the Alfvén speed and a reversal of the magnetic field across the shock front. The collisional coupling provides frictional heating to the neutral fluid, resulting in a Sedov-Taylor-like expansion with overshoots in the neutral velocity and neutral density. The increase in density results in a decrease of the Alfvén speed and with this the plasma inflow is accelerated to above the Alfvén speed within the finite width of the shock leading to the intermediate transition. This process occurs for a wide range of physical parameters and an intermediate shock is present for all investigated values of plasma-β, neutral fraction, and magnetic angle. As time advances the magnitude of the magnetic field reversal decreases since the neutral pressure cannot balance the Lorentz force. The intermediate shock is long-lived enough to be considered a physical structure, independent of the initial conditions. Conclusions. Intermediate shocks are a physical feature that can exist as shock sub-structure for long periods of time in partially ionised plasma due to collisional coupling between species.

Download Full-text