scholarly journals Starspots Magnetic field by transit mapping

2013 ◽  
Vol 9 (S302) ◽  
pp. 220-221
Author(s):  
Adriana Válio ◽  
Eduardo Spagiari
Keyword(s):  
Magnetic Field ◽  
Light Curve ◽  
Field Component ◽  
Solar Magnetic Field ◽  
Line Of Sight ◽  
The Sun ◽  
Using Data ◽  
The Magnetic Field ◽  
Spot Temperature

AbstractSunspots are important signatures of the global solar magnetic field cycle. It is believed that other stars also present these same phenomena. However, today it is not possible to observe directly star spots due to their very small sizes. The method applied here studies star spots by detecting small variations in the stellar light curve during a planetary transit. When the planet passes in front of its host star, there is a chance of it occulting, at least partially, a spot. This allows the determination of the spots physical characteristics, such as size, temperature, and location on the stellar surface. In the case of the Sun, there exists a relation between the magnetic field and the spot temperature. We estimate the magnetic field component along the line-of-sight and the intensity of sunspots using data from the MDI instrument on board of the SOHO satellite. Assuming that the same relation applies to other stars, we estimate spots magnetic fields of CoRoT-2 and Kepler-17 stars.

scholarly journals A new weak-field magnetic DA white dwarf in the local 20 pc volume

2019 ◽  
Vol 628 ◽  
pp. A1 ◽  
Author(s):  
J. D. Landstreet ◽  
S. Bagnulo
Keyword(s):  
Magnetic Field ◽  
White Dwarf ◽  
Field Component ◽  
Main Sequence ◽  
Mean Field ◽  
Weak Field ◽  
Line Of Sight ◽  
Limited Sample ◽  
Field Decay ◽  
The Magnetic Field

We report the discovery of a new magnetic DA white dwarf (WD), WD 0011 − 721, which is located within the very important 20 pc volume-limited sample of the closest WDs to the Sun. This star has a mean field modulus ⟨|B|⟩ of 343 kG, and from the polarisation signal we deduce a line-of-sight field component of 75 kG. The magnetic field is sufficiently weak to have escaped detection in classification spectra. We then present a preliminary exploration of the data concerning the frequency of such fields among WDs with hydrogen-rich atmospheres (DA stars). We find that 20 ± 5% of the DA WDs in this volume have magnetic fields, mostly weaker than 1 MG. Unlike the slow field decay found among the magnetic Bp stars of the upper main sequence, the WDs in this sample show no evidence of magnetic field or flux changes over several Gyr.

scholarly journals Analog Video Magnetograms in Real Time

1971 ◽  
Vol 43 ◽  
pp. 76-83 ◽  
Author(s):  
R. C. Smithson ◽  
R. B. Leighton
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Magnetic Field ◽  
Solar Spectrum ◽  
Zeeman Splitting ◽  
The Other ◽  
Line Of Sight ◽  
Zero Field ◽  
The Sun ◽  
Solar Magnetic Fields

For many years solar magnetic fields have been measured by a variety of techniques, all of which exploit the Zeeman splitting of lines in the solar spectrum. One of these techniques (Leighton, 1959) involves a photographic subtraction of two monochromatic images to produce a picture of the Sun in which the line-of-sight component of the solar magnetic field appears as various shades of gray. In a magnetogram made by this method, zero field strength appears as neutral gray, while magnetic fields of one polarity or the other appear as lighter or darker areas, respectively. Figure 1 shows such a magnetogram.

Determination of Solar Energetic Particle anisotropies based on four-sector measurements - Study based on STEREO/SEPT in preperation of SolO/EPT

2020 ◽  
Author(s):  
Maximilian Bruedern ◽  
Nina Dresing ◽  
Bernd Heber ◽  
Lars Berger ◽  
Alexander Kollhoff ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Radial Distance ◽  
Solar Energetic Particle ◽  
The Sun ◽  
Angle Scattering ◽  
Bootstrap Approach ◽  
The Magnetic Field ◽  
The Imf

<p>With the launch of Solar Orbiter (SolO) Solar Energetic Particles (SEPs) can be observed at a radial distance of 0.284 to 0.9 AU and an inclination out of the ecliptic up to 34 degree. The properties of SEP observations carry information about their source at the Sun as well as their transport through the interplanetary medium. Their energy is mostly determined close to the Sun. As SEPs propagate outward along the Interplanetary Magnetic Field (IMF) the pitch-angle with respect to the local field is systematically focused due to the radially decreasing IMF. However, stochastic changes are induced by scattering at fluctuations of the IMF. Often the first order anisotropy of SEPs is calculated to disentangle imprints of source and transport. Strong anisotropies indicate periods of weak pitch-angle scattering. Although many modeling and observational studies are based on the anisotropy, its uncertainty is often neglected which could result in inaccurate conclusions. Therefore, we propose a new method based on a bootstrap approach where we consider (1) directional instrument responses, (2) the variation of the magnetic field, and (3) the stochastic nature of detection. Here, we present our procedure and final results for different SEP events using measured data of the IMF and particle fluxes by the Solar Electron and Proton Telescope (SEPT) on board of each STEREO spacecraft. The SEPT provides four viewing directions with a view cone of 0.66 sr each on a three axis stabilized spacecraft. In contrast the Electron and Proton Telescope (EPT) on board SolO also consists of four viewing directions but each telescope has a much smaller view cone of 0.21 sr. Due to the very similar instrument setup we can apply our method both to the SEPT and EPT.</p>

scholarly journals The magnetic field strength in the Large Magellanic Cloud

1991 ◽  
Vol 148 ◽  
pp. 101-102
Author(s):  
M.E. Costa ◽  
P. M. McCulloch ◽  
P. A. Hamilton
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Large Magellanic Cloud ◽  
Radio Pulsar ◽  
Line Of Sight ◽  
The Sun ◽  
A Value ◽  
Rotation Measure ◽  
The Magnetic Field

We have measured a value of 4±5m--2rad for the rotation measure of the radio pulsar PSR0529-66 in the LMC and, after allowing for the dispersion and rotation measures of our Galaxy on the pulsar's line of sight, we deduce that the magnetic field strength in the LMC is in the range 0 to 5μGauss oriented away from the Sun.

scholarly journals Magnetic field structure of the Galactic plane from differential analysis of interstellar polarization

2020 ◽  
Vol 72 (2) ◽  
Author(s):  
Tetsuya Zenko ◽  
Tetsuya Nagata ◽  
Mikio Kurita ◽  
Masaru Kino ◽  
Shogo Nishiyama ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Galactic Plane ◽  
Color Change ◽  
Field Structure ◽  
Line Of Sight ◽  
The Sun ◽  
Differential Analysis ◽  
Field Orientation ◽  
Magnetic Field Structure ◽  
The Magnetic Field

Abstract A new method for measuring the global magnetic field structure of the Galactic plane is presented. We have determined the near-infrared polarization of field stars around 52 Cepheids found in recent surveys toward the Galactic plane. The Cepheids are located at the galactic longitudes $-10^{\circ} \le l \le +10.^{\!\!\!\circ }5$ and latitudes $-0.^{\!\!\!\circ }22\le b \le +0.^{\!\!\!\circ }45$, and their distances are mainly in the range of 10 to 15 kpc from the Sun. Simple classification of the sightlines is made with the polarization behavior vs. $H-K_{\mathrm{S}}$ color of field stars, and typical examples of three types are presented. Then, division of the field stars in each line of sight into (a) foreground, (b) bulge, and (c) background is made with the Gaia DR2 catalog, the peak of the $H-K_{\mathrm{S}}$ color histogram, and $H-K_{\mathrm{S}}$ colors consistent with the distance of the Cepheid in the center, respectively. Differential analysis between them enables us to examine the magnetic field structure more definitely than just relying on the $H-K_{\mathrm{S}}$ color difference. In one line of sight, the magnetic field is nearly parallel to the Galactic plane and well aligned all the way from the Sun to the Cepheid position on the other side of the Galactic center. Contrary to our preconceived ideas, however, sightlines having such well-aligned magnetic fields in the Galactic plane are rather small in number. At least 36 Cepheid fields indicate random magnetic field components are significant. Two Cepheid fields indicate that the magnetic field orientation changes more than $45^{\circ }$ in the line of sight. The polarization increase per color change $\Delta P/\Delta (H-K_{\mathrm{S}})$ varies from region to region, reflecting the change in the ratio of the magnetic field strength and the turbulence strength.

RSFP PREDICTIONS FOR TRANSVERSE SOLAR MAGNETIC FIELD DISTRIBUTION FROM SOLAR NEUTRINO DATA

1998 ◽  
Vol 13 (15) ◽  
pp. 1163-1170 ◽  
Author(s):  
B. C. CHAUHAN ◽  
U. C. PANDEY ◽  
S. DEV
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Distribution ◽  
Magnetic Moment ◽  
Solar Neutrino ◽  
Solar Magnetic Field ◽  
Magnetic Field Distribution ◽  
The Sun ◽  
Solar Magnetic Fields ◽  
The Magnetic Field

Even though the standard solar model (SSM) has been very successful in predicting the thermal and nuclear evolution of the Sun, it does not throw enough light on solar magnetic activity. In the absence of a generally accepted theory of solar dynamo, various general arguments have been put forth to constrain solar magnetic fields. In the absence of reliable knowledge of solar magnetic fields from available astrophysical data, it may be worthwhile to constrain the solar magnetic fields from solar neutrino observations assuming Resonant Spin-Flavor Precession (RSFP) to be responsible for the solar neutrino deficit. The configuration of solar magnetic field derived in this work is in reasonably good agreement with the magnetic field distribution proposed by Akhmedov et al. (Sov. Phys. JETP68, 250 (1989)). However, the magnetic field distribution in the radiation zone used by Pulido (Phys. Rep.211, 167 (1992)) is ruled out. The magnitude of the magnetic field in the radiation and convective zones of the Sun are very sensitive to the value chosen for the neutrino magnetic moment. However, any change in the value of neutrino magnetic moment does not affect the magnetic field distribution as it only scales the magnetic field strength at different points by the same amount.

scholarly journals About long term modulation of cosmic rays in the 23-24 solar activity cycles

2021 ◽  
pp. 23-29
Author(s):  
Anatoly V. Belov ◽  
Raisa T. Gushchina ◽  
Victor Yanke
Keyword(s):  
Magnetic Field ◽  
Solar Activity ◽  
Cosmic Rays ◽  
Solar Magnetic Field ◽  
The Sun ◽  
Model Calculations ◽  
Activity Cycles ◽  
The Magnetic Field ◽  
Solar Activity Cycles

Recently, there has been a significant trend in magnetic fields on the Sun. The total magnetic field of the Sun from the end of the 22nd cycle of solar activity (SA) has more than halved and this decrease continues. Chan- ges in the magnetic field are the key to all the active phenomena occurring on the Sun and in the heliosphere and, accordingly, to processes in cosmic rays. In long-term CR variations in 23-24 cycles of SA the attenuation of the solar magnetic field is displayed and these variations turned out to be the smallest for the entire time of CR observations. Model calculations of CR modulation for 21-22 and 23-24 cycles of SA showed: with a slight difference in the regression characteristics obtained, the distribution of contributions to the generated CR modulation from the effects of various SA indices is strongly varies in the analyzed periods. Possible reasons for the features of the last two CA cycles are discussed.

scholarly journals The Integrated Magnetic Field of the Sun Seen by the Golf Experiment

1998 ◽  
Vol 185 ◽  
pp. 225-226
Author(s):  
R.A. García ◽  
T. Roca Cortés ◽  
Keyword(s):  
Magnetic Field ◽  
Resonant Scattering ◽  
Space Mission ◽  
Quarter Wave Plate ◽  
Line Of Sight ◽  
The Sun ◽  
Quarter Wave ◽  
Secondary Objective ◽  
The Magnetic Field ◽  
Selection Of

The secondary objective of the GOLF experiment on-board the SOHO space mission is to measure the line-of-sight component of the disk averaged magnetic field of the Sun. GOLF is an improved disk-integrated sunlight resonant scattering spectrophotometer. Using an extra fixed quarter wave plate placed at the entrance of the instrument, enables a selection of the circularly polarized solar light and therefore, the disk averaged solar line-of-sight component of the magnetic field can be obtained. Unfortunately, due to occasional malfunction of the rotating mechanisms, only a series of 26 continuous days are available. Here, the analysis of this series is presented including the value of the averaged magnetic field.

scholarly journals Digital Videomagnetograms in Real Time

1971 ◽  
Vol 43 ◽  
pp. 44-50 ◽  
Author(s):  
Thomas J. Janssens ◽  
Neal K. Baker
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Magnetic Fields ◽  
Real Time ◽  
Temporal Resolution ◽  
Optical Filter ◽  
Line Of Sight ◽  
The Sun ◽  
The Magnetic Field

The Aerospace – NASA Videomagnetograph began operation one month ago, two years after components were ordered and construction began. The design grew out of a desire to obtain magnetic fields in real time using an optical filter. The aim was to study and analyze magnetic configurations and changes, quantitatively if possible, with high spatial and temporal resolution and as much sensitivity as possible. This instrument is restricted to the line-of-sight component of the magnetic field and is primarily intended for high resolution studies of selected regions of the sun. The rationale behind our approach is shown in the next section and the design details in the following.

Energetic particles and the solar cycle: Impact of solar magnetic field amplitude and geometry on SEPs and GCRs diffusion coefficients

2021 ◽  
Author(s):  
Barbara Perri ◽  
Allan Sacha Brun ◽  
Antoine Strugarek ◽  
Victor Réville
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Cycle ◽  
Diffusion Coefficients ◽  
Solar Magnetic Field ◽  
Energetic Particles ◽  
Field Amplitude ◽  
The Sun ◽  
Magnetic Field Amplitude ◽  
The Magnetic Field

<p>SEPs are correlated with the 11-year solar cycle due to their production by flares and interaction with the inner heliosphere, while GCRs are anti-correlated with it due to the modulation of the heliospheric magnetic field. The solar magnetic field along the cycle varies in amplitude but also in geometry, causing diffusion of the particles along and across the field lines; the solar wind distribution also evolves, and its turbulence affects particle trajectories.</p><p>We combine 3D MHD compressible numerical simulations to compute the configuration of the magnetic field and the associated polytropic solar wind up to 1 AU, with analytical prescriptions of the corresponding parallel and perpendicular diffusion coefficients for SEPs and GCRs. First, we analyze separately the impact of the magnetic field amplitude and geometry for a 100 MeV proton. By varying the amplitude, we change the amplitude of the diffusion by the same factor, and the radial gradients by changing the spread of the current sheet. By varying the geometry, we change the latitudinal gradients of diffusion by changing the position of the current sheets. We also vary the energy, and show that the statistical distribution of parallel diffusion is different for SEPs and GCRs. Then, we use realistic solar configurations, showing that diffusion is highly non-axisymmetric due to the configuration of the current sheets, and that the distribution varies a lot with the distance to the Sun, especially at minimum of activity. With this model, we are thus able to study the direct influence of the Sun on Earth spatial environment in terms of energetic particles. </p>

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