Magnetohydrodynamic Simulations for Solar Active Regions using Time-series Data of Surface Plasma Flow and Electric Field Inferred from Helioseismic Magnetic Imager Vector Magnetic Field Measurements

2019 ◽  
Vol 871 (2) ◽  
pp. L28 ◽  
Author(s):  
Keiji Hayashi ◽  
Xueshang Feng ◽  
Ming Xiong ◽  
Chaowei Jiang
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Time Series Data ◽  
Active Regions ◽  
Field Measurements ◽  
Series Data ◽  
Surface Plasma ◽  
Vector Magnetic Field ◽  
Magnetic Field Measurements ◽  
Magnetohydrodynamic Simulations

scholarly journals Driving Layer of Solar Activity

2002 ◽  
Vol 12 ◽  
pp. 371-377
Author(s):  
Jingxiu Wang
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Magnetic Energy ◽  
Field Measurements ◽  
Basic Structure ◽  
The Sun ◽  
Flux Emergence ◽  
Vector Magnetic Field ◽  
Elementary Processes ◽  
Magnetic Field Measurements

AbstractThere should be a driving layer on the Sun, in which the interaction between magnetic field and plasma motion would provide enough magnetic energy and necessary topology for the explosion of solar activity in the corona.Although the exact location of the driving layer is not known, phenomenologically, the photosphere is acting, in many aspects, as the driving layer. Vector magnetic field measurements on the photosphere are greatly needed in clarifying the nature of the driving.Two elementary processes, flux emergence and cancellation, andone basic structure, magnetic interface between topology-independent magnetic loops, are key elements in the driving.

scholarly journals Correcting for chromatic stellar activity effects in transits with multiband photometric monitoring: application to WASP-52

2020 ◽  
Vol 641 ◽  
pp. A82 ◽  
Author(s):  
A. Rosich ◽  
E. Herrero ◽  
M. Mallonn ◽  
I. Ribas ◽  
J. C. Morales ◽  
...  
Keyword(s):  
Time Series ◽  
Time Series Data ◽  
Giant Planet ◽  
Active Regions ◽  
Residual Effects ◽  
Series Data ◽  
Test Case ◽  
Surface Phenomena ◽  
Surface Distribution ◽  
Order Of Magnitude

Context. The properties, distribution, and evolution of inhomogeneities on the surface of active stars, such as dark spots and bright faculae, significantly influence the determination of the parameters of an orbiting exoplanet. The chromatic effect they have on transmission spectroscopy, for example, could affect the analysis of data from future space missions such as James Webb Space Telescope and Ariel. Aims. To quantify and mitigate the effects of those surface phenomena, we developed a modelling approach to derive the surface distribution and properties of active regions by modelling simultaneous multi-wavelength time-series observables. Methods. We present an upgraded version of the StarSim code, now featuring the capability to solve the inverse problem and derive the properties of the stars and their active regions by modelling time-series data. As a test case, we analyse ~600 days of BV RI multiband photometry from the 0.8-m Joan Oró (TJO) and 1.2-m STELLA telescopes of the K2 V exoplanet host star WASP-52. From the results, we further simulated the chromatic contribution of surface phenomena on the observables of its transiting planet. Results. Using StarSim we are able to determine the relevant activity parameters of WASP-52 and reconstruct the time-evolving longitudinal map of active regions. The star shows a heterogeneous surface composed of dark spots with a mean temperature of 575 ± 150 K lower than the photospheric value, with filling factors ranging from 3 to 14%. We used the results to study the chromatic effects on the depths of exoplanet transits obtained at different epochs and corresponding to different stellar spot distributions. In the case of WASP-52, which has peak-to-peak photometric variations of ~7% in the visible, the residual effects of dark spots on the measured transit depth of its giant planet, after applying the calculated corrections, are about 10−4 at 550 nm and 3 × 10−5 at 6 μm. Conclusions. We demonstrate that by using contemporaneous ground-based multiband photometry of an active star, it is possible to reconstruct the parameters and distribution of active regions over time, thus making it feasible to quantify the chromatic effects on the planetary radii measured with transit spectroscopy and mitigate them by about an order of magnitude.

scholarly journals Deterministic dynamics of the magnetosphere: results of the 0–1 test

2013 ◽  
Vol 20 (1) ◽  
pp. 11-18 ◽  
Author(s):  
S. Prabin Devi ◽  
S. B. Singh ◽  
A. Surjalal Sharma
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Solar Wind ◽  
Time Series Data ◽  
Nonlinear Dynamical System ◽  
Series Data ◽  
Nonlinear Dynamical ◽  
Deterministic Dynamics ◽  
Time Period ◽  
Solar Wind Magnetic Field

Abstract. A test for deterministic dynamics in a time series data, namely the 0–1 test (Gottawald and Melbourne, 2004, 2005), is used to study the magnetospheric dynamics. The data, corresponding to the same time period, of the auroral electrojet index AL and the magnetic field component Bz of the solar wind magnetic field measured at 1 AU are used to compute the parameter K, which is zero for non-chaotic and unity for chaotic systems. For the magnetosphere and also for the turbulent solar wind, K has values corresponding to a nonlinear dynamical system with chaotic behaviour. This result is consistent with the Lyapunov exponents computed from the same time series data.

scholarly journals Improved Current Density and Magnetization Reconstruction Through Vector Magnetic Field Measurements

2020 ◽  
Vol 14 (2) ◽  
Author(s):  
D.A. Broadway ◽  
S.E. Lillie ◽  
S.C. Scholten ◽  
D. Rohner ◽  
N. Dontschuk ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Field Measurements ◽  
Vector Magnetic Field ◽  
Magnetic Field Measurements

Observing the Sun with the Atacama Large Millimeter/submillimeter Array – from continuum to magnetic fields

2019 ◽  
Vol 15 (S354) ◽  
pp. 24-37
Author(s):  
Sven Wedemeyer ◽  
Mikolaj Szydlarski ◽  
Jaime de la Cruz Rodriguez ◽  
Shahin Jafarzadeh
Keyword(s):  
Magnetic Field ◽  
Time Series ◽  
Solar Magnetic Field ◽  
Extended Period ◽  
Field Measurements ◽  
The Sun ◽  
Post Processing ◽  
Magnetic Field Measurements ◽  
Scientific Results ◽  
Temperature Maps

AbstractThe Atacama Large Millimeter/submillimeter Array offers regular observations of our Sun since 2016. After an extended period of further developing and optimizing the post-processing procedures, first scientific results are now produced. While the first observing cycles mostly provided mosaics and time series of continuum brightness temperature maps with a cadence of 1-2s, additional receiver bands and polarization capabilities will be offered in the future. Currently, polarization capabilities are offered for selected receiver bands but not yet for solar observing. An overview of the recent development, first scientific results and potential of solar magnetic field measurements with ALMA will be presented.

scholarly journals Two Kinds of Activity in Late-type Stars

1991 ◽  
Vol 130 ◽  
pp. 440-442
Author(s):  
M.M. Katsova
Keyword(s):  
Magnetic Field ◽  
Active Regions ◽  
Field Measurements ◽  
Spherically Symmetric ◽  
The Sun ◽  
Late Type ◽  
X Ray ◽  
Magnetic Field Measurements ◽  
Local Magnetic Fields ◽  
Uniform Manner

Several years ago we proposed a method for the analysis of X-ray observations of late-type stars. It allowed the determination in a uniform manner of coronal base electron densities for more than 40 late-type stars, in terms of a one-temperature consideration of homogeneous spherically symmetric coronae (Katsova et al., 1987). Fig. 1 shows the results as a function of spectral type. Comparison of our results with values for different kinds of solar regions shows that physical characteristics of F and G star coronae correspond to densities less than those in active regions on the Sun. Values for the active K-M0 stars are comparable with those of dense steady condensations found directly above large sunspots.On this basis, activity can be explained as an increase in that part of the stellar surface that is occupied by strong local magnetic fields. This is illustrated in the table where we compare magnetic field measurements by Saar and Linsky (1988) with our calculations.

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