scholarly journals High frequency oscillations in the solar chromosphere and their connection with heating

2007 ◽  
Vol 3 (S247) ◽  
pp. 312-315 ◽  
Author(s):  
Aleksandra Andic ◽  
M. Mathioudakis ◽  
F. P. Keenan ◽  
D. B. Jess ◽  
D. S. Bloomfield
Keyword(s):  
Magnetic Fields ◽  
Acoustic Waves ◽  
High Frequency ◽  
Solar Observatory ◽  
Solar Chromosphere ◽  
Frequency Interval ◽  
Solar Telescope ◽  
National Solar Observatory ◽  
High Frequency Oscillations ◽  
Using Data

AbstractHigh frequency acoustic waves have been suggested as a source of mechanical heating in the quiet solar chromosphere. To investigate this, we have observed intensity oscillations of several lines in the frequency interval 1.64-70mHz using data from the VTT Tenerife and the Dunn Solar Telescope at the National Solar Observatory. Our analysis of Fe i 543.45 nm, Fe i 543.29 nm and the G-band, indicate that the majority of oscillations are connected with the magnetic fields and do not provide sufficient mechanical flux for the heating of the chromosphere. This correlation is also observed in quiet Sun areas.

scholarly journals Mutual relationship of oscillations in the frequency range 3.6 mHz to 22 mHz in the solar chromosphere

2006 ◽  
pp. 27-40 ◽  
Author(s):  
A. Andjic
Keyword(s):  
High Frequency ◽  
Spatial Scales ◽  
Low Frequency ◽  
Radial Component ◽  
Solar Chromosphere ◽  
Frequency Interval ◽  
Acoustic Oscillations ◽  
High Frequency Oscillations ◽  
Relationship Of ◽  
Different Sources

High frequency acoustic oscillations were suggested as the source of mechanical heating in the chromosphere. In this work the radial component of the oscillations in the frequency interval 3 mHz to 22 mHz are investigated. The observations were performed using "D spectrometry on the Fe I neutral spectral line at 543:45 nm. The high frequency oscillations of different frequencies appear to be associated with different spatial scales. It seems that different sources produce high and low frequency acoustic oscillations.

High-frequency acoustic waves are not sufficient to heat the solar chromosphere

Nature ◽  
2005 ◽  
Vol 435 (7044) ◽  
pp. 919-921 ◽  
Author(s):  
Astrid Fossum ◽  
Mats Carlsson
Keyword(s):  
Acoustic Waves ◽  
High Frequency ◽  
Solar Chromosphere

Synoptic Magnetic Fields Measurements of the Solar Chromosphere from SOLIS/VSM at NSO

2018 ◽  
Vol 13 (S340) ◽  
pp. 91-92
Author(s):  
Sanjay Gosain ◽  
Keyword(s):  
Magnetic Field ◽  
Solar Wind Speed ◽  
Active Regions ◽  
Field Measurements ◽  
Solar Observatory ◽  
Solar Chromosphere ◽  
Polar Regions ◽  
National Solar Observatory ◽  
Perspective Effect ◽  
Stokes Polarimetry

AbstractFull disk magnetic field measurements of the photosphere and chromosphere have been performed at National Solar Observatory (NSO), USA for many decades. Here we briefly describe recent upgrades made to this synoptic observing program. In particular, we present the full Stokes polarimetry observations made using the chromospheric Ca II 854.2 nm spectral line. These new observations have the potential to probe vector nature of magnetic field in the chromosphere above the active regions and provide improved estimates of magnetic free-energy, which is released during flares and coronal mass ejections (CMEs). We emphasize that these observations could improve estimates of polar fields, as compared to photospheric observations, due to magnetic field expansion in higher layers and perspective effect near the polar regions. The global coronal potential field models and solar wind speed estimates depend critically on polar field measurements.

Two-telescope-based solar seeing profile measurement simulation

2022 ◽  
Vol 21 (12) ◽  
pp. 298
Author(s):  
Zi-Yue Wang ◽  
De-Qing Ren ◽  
Raffi Saadetian
Keyword(s):  
Numerical Simulations ◽  
Atmospheric Turbulence ◽  
Adaptive Optics ◽  
Solar Observatory ◽  
Performance Estimation ◽  
Image Motion ◽  
Profile Measurement ◽  
Solar Telescope ◽  
National Solar Observatory ◽  
Bear Lake

Abstract Measurements of the daytime seeing profile of the atmospheric turbulence are crucial for evaluating a solar astronomical site so that research on the profile of the atmospheric turbulence as a function of altitude C n 2 ( h n ) becomes more and more critical for performance estimation and optimization of future adaptive optics (AO) including the multi-conjugate adaptive optics (MCAO) systems. Recently, the S-DIMM+ method has been successfully used to measure daytime turbulence profiles above the New Solar Telescope (NST) on Big Bear Lake. However, such techniques are limited by the requirement of using a large solar telescope which is not realistic for a new potential astronomical site. Meanwhile, the A-MASP (advanced multiple-aperture seeing profiler) method is more portable and has been proved that can reliably retrieve the seeing profile up to 16 km with the Dunn Solar Telescope (DST) on the National Solar Observatory (Townson, Kellerer et al.). But the turbulence of the ground layer is calculated by combining A-MASP and S-DIMM+ (Solar Differential Image Motion Monitor+) due to the limitation of the two-individual-telescopes structure. To solve these problems, we introduce the two-telescope seeing profiler (TTSP) which consists of two portable individual telescopes. Numerical simulations have been conducted to evaluate the performance of TTSP. We find our TTSP can effectively retrieve seeing profiles of four turbulence layers with a relative error of less than 4% and is dependable for actual seeing measurement.

scholarly journals High frequency generation in the corona: Resonant cavities

2018 ◽  
Vol 611 ◽  
pp. A10 ◽  
Author(s):  
I. C. Santamaria ◽  
T. Van Doorsselaere
Keyword(s):  
Magnetic Field ◽  
Shock Wave ◽  
Acoustic Waves ◽  
High Frequency ◽  
Spatial Scales ◽  
Wave Train ◽  
Null Point ◽  
Solar Chromosphere ◽  
High Frequency Region ◽  
Frequency Wave

Aims. Null points are prominent magnetic field singularities in which the magnetic field strength strongly decreases in very small spatial scales. Around null points, predicted to be ubiquitous in the solar chromosphere and corona, the wave behavior changes considerably. Null points are also responsible for driving very energetic phenomena, and for contributing to chromospheric and coronal heating. In previous works we demonstrated that slow magneto-acoustic shock waves were generated in the chromosphere propagate through the null point, thereby producing a train of secondary shocks escaping along the field lines. A particular combination of the shock wave speeds generates waves at a frequency of 80 MHz. The present work aims to investigate this high frequency region around a coronal null point to give a plausible explanation to its generation at that particular frequency. Methods. We carried out a set of two-dimensional numerical simulations of wave propagation in the neighborhood of a null point located in the corona. We varied both the amplitude of the driver and the atmospheric properties to investigate the sensitivity of the high frequency waves to these parameters. Results. We demonstrate that the wave frequency is sensitive to the atmospheric parameters in the corona, but it is independent of the strength of the driver. Thus, the null point behaves as a resonant cavity generating waves at specific frequencies that depend on the background equilibrium model. Moreover, we conclude that the high frequency wave train generated at the null point is not necessarily a result of the interaction between the null point and a shock wave. This wave train can be also developed by the interaction between the null point and fast acoustic-like magneto-acoustic waves, that is, this interaction within the linear regime.

Surges of the weak magnetic field in the photosphere of the Sun

2021 ◽  
Author(s):  
Dmitrii Baranov ◽  
Elena Vernova ◽  
Marta Tyasto
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Summation Method ◽  
Solar Observatory ◽  
Primary Data ◽  
Solar Photosphere ◽  
The Sun ◽  
National Solar Observatory ◽  
Weak Magnetic Fields ◽  
One Year

<p>The properties of the magnetic fields of the solar photosphere are investigated, in particular, the distribution of fields of different polarity over the solar surface. As primary data, synoptic maps of the photospheric magnetic field of the Kitt Peak National Solar Observatory for 1978-2016 were used. Using the vector summation method, the non-axisymmetric component of the magnetic field is determined. It was found that the nonaxisymmetric component of weak magnetic fields B < 5 G changes in antiphase with the flux of these fields. Magnetic fields of B < 5 G constitute a significant part of the total magnetic field of the Sun, since they occupy more than 60% of the area of the photosphere. The fine structure of the distribution of weak fields can  be observed by setting the upper limit to the strength of the  fields  included in the time–latitude diagram. This allows to eliminate the contribution of the strong fields of sunspots.</p><p>On the time-latitude diagram for weak magnetic fields (B < 5 G), bands of differing colors correspond to the streams of the magnetic fields moving in the direction to the Sun’s poles.. These streams or surges show the alternation of the dominant polarity - positive or negative - which is clearly seen in all four cycles. The slopes of the bands indicate the velocity of the fields movement towards the poles. The surges can be divided into two groups. The surges of the first group belong to the so-called Rush-to-the-Poles. These are bands with the width of about three years, which begin at approximately 40° of latitude and have the same polarity as the trailing sunspots. They reach high latitudes and cause the polarity reversal of the polar field. However, in addition to these surges, for most of the solar  cycle (the descending phase, the minimum and the ascending phase), there are narrower surges of both polarities (with the width less than one year), which extend from the equator almost to the poles. These surges are most clearly visible in the southern hemisphere when the southern pole is positive. Consideration of the latitude-time diagrams separately for positive and negative polarities showed that the alternating dominance of one of the polarities is associated with the antiphase development  of the positive and negative fields of the surges. The widths of surges and the periodicity of their appearance vary significantly for the two hemispheres and from one solar cycle to the other. The mean period of the polarity alternation is about 1.5 years.</p>

scholarly journals Twisting flux tubes as a cause of micro-flaring activity

2007 ◽  
Vol 3 (S247) ◽  
pp. 360-363
Author(s):  
D. B. Jess ◽  
R. T. J. McAteer ◽  
M. Mathioudakis ◽  
F. P. Keenan ◽  
A. Andic ◽  
...  
Keyword(s):  
Solar Observatory ◽  
Optical Observations ◽  
Bright Point ◽  
Solar Telescope ◽  
Camera System ◽  
Flux Tubes ◽  
National Solar Observatory ◽  
Blue Wing ◽  
Significance Levels ◽  
High Cadence

AbstractHigh-cadence optical observations of an H-α blue-wing bright point near solar AR NOAA 10794 are presented. The data were obtained with the Dunn Solar Telescope at the National Solar Observatory/Sacramento Peak using a newly developed camera system, the rapid dual imager. Wavelet analysis is undertaken to search for intensity-related oscillatory signatures, and periodicities ranging from 15 to 370 s are found with significance levels exceeding 95%. During two separate microflaring events, oscillation sites surrounding the bright point are observed to twist. We relate the twisting of the oscillation sites to the twisting of physical flux tubes, thus giving rise to reconnection phenomena. We derive an average twist velocity of 8.1 km/s and detect a peak in the emitted flux between twist angles of 180° and 230°.

scholarly journals Infrared heterodyne spectroscopy: a tool for helioseismology

1988 ◽  
Vol 123 ◽  
pp. 481-484
Author(s):  
D.A. Glenar ◽  
H.U. Käufl ◽  
D. Deming ◽  
T. Kostiuk ◽  
M.J. Mumma
Keyword(s):  
Doppler Shift ◽  
Single Point ◽  
Solar Observatory ◽  
Solar Telescope ◽  
Solar Oscillation ◽  
Velocity Measurements ◽  
National Solar Observatory ◽  
Heterodyne Spectroscopy ◽  
Heterodyne Spectrometer ◽  
Absorption Features

Heterodyne spectroscopy at infrared (IR) wavelengths is a technique well suited for measuring small velocities in the solar atmosphere. An IR heterodyne spectrometer for solar oscillation measurements has been located at the McMath Solar Telescope of the Kitt Peak National Solar Observatory. It is now being used for single point Doppler shift measurements of 11 micron OH absorption features formed in the upper photosphere, with sampling rates as high as 33 mHz. The instrument employs a stabilized CO2. laser permitting absolute velocity measurements with an uncertainty of < 10 ms−1.

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