Here, we report on the unique observation of flaring coronal loops at the solar limb using high-resolution imaging spectropolarimetry from the Swedish 1 m Solar Telescope. The vantage position, ...orientation, and nature of the chromospheric material that filled the flare loops allowed us to determine their magnetic field with unprecedented accuracy using the weak-field approximation method. Our analysis reveals coronal magnetic field strengths as high as 350 G at heights up to 25 Mm above the solar limb. These measurements are substantially higher than a number of previous estimates and may have considerable implications for our current understanding of the extended solar atmosphere.
Aims.
Our aim is to investigate the role of acoustic and magneto-acoustic waves in heating the solar chromosphere. Observations in strong chromospheric lines are analyzed by comparing the deposited ...acoustic-energy flux with the total integrated radiative losses.
Methods.
Quiet-Sun and weak-plage regions were observed in the Ca
II
854.2 nm and H
α
lines with the Fast Imaging Solar Spectrograph (FISS) at the 1.6-m Goode Solar Telescope on 2019 October 3 and in the H
α
and H
β
lines with the echelle spectrograph attached to the Vacuum Tower Telescope on 2018 December 11 and 2019 June 6. The deposited acoustic energy flux at frequencies up to 20 mHz was derived from Doppler velocities observed in line centers and wings. Radiative losses were computed by means of a set of scaled non-local thermodynamic equilibrium 1D hydrostatic semi-empirical models obtained by fitting synthetic to observed line profiles.
Results.
In the middle chromosphere (
h
= 1000–1400 km), the radiative losses can be fully balanced by the deposited acoustic energy flux in a quiet-Sun region. In the upper chromosphere (
h
> 1400 km), the deposited acoustic flux is small compared to the radiative losses in quiet as well as in plage regions. The crucial parameter determining the amount of deposited acoustic flux is the gas density at a given height.
Conclusions.
The acoustic energy flux is efficiently deposited in the middle chromosphere, where the density of gas is sufficiently high. About 90% of the available acoustic energy flux in the quiet-Sun region is deposited in these layers, and thus it is a major contributor to the radiative losses of the middle chromosphere. In the upper chromosphere, the deposited acoustic flux is too low, so that other heating mechanisms have to act to balance the radiative cooling.
Context.
The solar radiation in the Lyman-
α
spectral line of hydrogen plays a significant role in the illumination of chromospheric and coronal structures, such as prominences, spicules, ...chromospheric fibrils, cores of coronal mass ejections, and solar wind. Moreover, it is important for the investigation of the heliosphere, Earth’s ionosphere, and the atmospheres of planets, moons, and comets.
Aims.
We derive a reference quiet-Sun Lyman-
α
spectral profile that is representative of the Lyman-
α
radiation from the solar disk during a minimum of solar activity. This profile can serve as an incident radiation boundary condition for the radiative transfer modelling of chromospheric and coronal structures. Because the solar radiation in the Lyman lines is not constant over time but varies significantly with the solar cycle, we provide a method for the adaptation of the incident radiation Lyman line profiles (Lyman-
α
and higher lines) to a specific date. Moreover, we analyse how the change in the incident radiation influences the synthetic spectra produced by the radiative transfer modelling.
Methods.
We used SOHO/SUMER Lyman-
α
raster scans obtained without the use of the attenuator in various quiet-Sun regions on the solar disk. The observations were performed on three consecutive days (June 24, 25, and 26, 2008) during a period of minimum solar activity. The reference Lyman-
α
profile was obtained as a spatial average over eight available raster scans. To take into account the Lyman-
α
variation with the solar cycle, we used the LISIRD composite Lyman-
α
index. To estimate the influence of the change in the incident radiation in the Lyman lines on the results of radiative transfer models, we used a 2D prominence fine structure model.
Results.
We present the reference quiet-Sun Lyman-
α
profile and a table of coefficients describing the variation of the Lyman lines with the solar cycle throughout the lifetime of SOHO. The analysis of the influence of the change in the incident radiation shows that the synthetic spectra are strongly affected by the modification of the incident radiation boundary condition. The most pronounced impact is on the central and integrated intensities of the Lyman lines. There, the change in the synthetic spectra can often have the same amplitude as the change in the incident radiation itself. The impact on the specific intensities in the peaks of reversed Lyman-line profiles is smaller but still significant. The hydrogen H
α
line can also be considerably affected, despite the fact that the H
α
radiation from the solar disk does not vary with the solar cycle.
We study the C8.4-class solar flare SOL2016-05-14T11:34 UT using high-resolution spectral imaging in the Ca ii 8542 line obtained with the CRISP imaging spectropolarimeter on the Swedish 1 m Solar ...Telescope. Spectroscopic inversions of the Ca ii 8542 line using the non-LTE code NICOLE are used to investigate the evolution of the temperature and velocity structure in the flaring chromosphere. A comparison of the temperature stratification in flaring and non-flaring areas reveals strong footpoint heating during the flare peak in the lower atmosphere. The temperature of the flaring footpoints between log τ 500 − 2.5 and − 3.5 , where τ500 is the continuum optical depth at 500 nm, is ∼ 5 - 6.5 kK close to the flare peak, reducing gradually to ∼ 5 kK . The temperature in the middle and upper chromosphere, between log τ 500 − 3.5 and −5.5, is estimated to be ∼6.5-20 kK, decreasing to preflare temperatures, ∼5-10 kK, after approximately 15 minutes. However, the temperature stratification of the non-flaring areas is unchanged. The inverted velocity fields show that the flaring chromosphere is dominated by weak downflowing condensations at the formation height of Ca ii 8542 .
Context.
On 2021 February 12, two subsequent eruptions occurred above the western limb of the Sun, as seen along the Sun-Earth line. The first event was a typical slow coronal mass ejection (CME), ...followed ∼7 h later by a smaller and collimated prominence eruption, originating south of the CME, followed by a plasma blob. These events were observed not only by the SOHO and STEREO-A missions, but also by the suite of remote-sensing instruments on board Solar Orbiter.
Aims.
We show how data acquired by the Full Sun Imager (FSI), the Metis coronagraph, and the Heliospheric Imager (HI) from the Solar Orbiter perspective can be combined to study the eruptions and different source regions. Moreover, we show how Metis data can be analyzed to provide new information about solar eruptions.
Methods.
Different 3D reconstruction methods were applied to the data acquired by different spacecraft, including remote-sensing instruments on board Solar Orbiter. Images acquired by the two Metis channels in the visible light (VL) and H
I
Ly-
α
line (UV) were combined to derive physical information about the expanding plasma. The polarization ratio technique was also applied for the first time to Metis images acquired in the VL channel.
Results.
The two eruptions were followed in 3D from their source region to their expansion in the intermediate corona. By combining VL and UV Metis data, the formation of a post-CME current sheet (CS) was followed for the first time in the intermediate corona. The plasma temperature gradient across a post-CME blob propagating along the CS was also measured for the first time. Application of the polarization ratio technique to Metis data shows that by combining four different polarization measurements, the errors are reduced by ∼5 − 7%. This constrains the 3D plasma distribution better.
The magnetization of a ferromagnetic electrode in an external homogeneous magnetic field leads to a stray field in front of the electrode. This stray and its gradients can alter the anodic behaviour ...of the electrode significantly. Potentiodynamic polarisation measurements of an iron wire in a 0.5
M sulfuric acid solution (pH 0.25) and in a 0.5
M phthalate buffer solution (pH 5) without and with applied magnetic fields up to 0.6
T in different orientations to the electrode surface were performed. In sulfuric acid solution an increase of the diffusion-limited dissolution current density and a shift of the active–passive transition potential to more noble potentials was observed when the magnetic field was applied parallel to the electrode surface. In contrast, in perpendicular field configuration the diffusion-limited current density is lowered and the active–passive transition potential is shifted to less noble values. In phthalate buffer no significant influence of the magnetic field on the current density was observed in the active region, but a shift of the active–passive transition to less noble potentials occurred irrespective of the magnetic field configuration.
The observed effects of a superimposed magnetic field on the anodic behaviour of iron are discussed with respect to an increase of the mass transport due to the Lorentz-force-driven magnetohydrodynamic (MHD) effect, the magnetic field gradient force and its interaction with the paramagnetic iron ions. The results of this paper show that the effect of the field gradient force can become very important due to the high magnetic field gradient at ferromagnetic electrodes.
Psoriasis vulgaris is a common and often chronic inflammatory skin disease. The incidence of psoriasis in Western industrialized countries ranges from 1.5 to 2%. Patients afflicted with severe ...psoriasis vulgaris may experience a significant reduction in quality of life. Despite the large variety of treatment options available, patient surveys have revealed insufficient satisfaction with the efficacy of available treatments and a high rate of medication non-compliance (Richards et al. in J Am Acad Dermatol 41(4):581–583,
1999
). To optimize the treatment of psoriasis in Germany, the Deutsche Dermatologische Gesellschaft (DDG) and the Berufsverband Deutscher Dermatologen (BVDD) have initiated a project to develop evidence-based guidelines for the management of psoriasis first published in 2006 and now updated in 2011. The Guidelines focus on induction therapy in cases of mild, moderate, and severe plaque-type psoriasis in adults. This short version of the guidelines presents the resulting series of therapeutic recommendations, which were based on a systematic literature search and discussed and approved by a team of dermatology experts. In addition to the therapeutic recommendations provided in this short version, the full version of the guidelines includes information on contraindications, adverse events, drug interactions, practicality, and costs, as well as detailed information on how best to apply the treatments described (for full version please see Nast et al. in JDDG Suppl 2:S1–S104,
2011
or
http://www.psoriasis-leitlinie.de
).
Aims. Changes of the magnetic field and the line-of-sight velocities in the photosphere are being reported for an M-class flare that originated at a δ-spot belonging to active region NOAA 11865. ...Methods. High-resolution ground-based near-infrared spectropolarimetric observations were acquired simultaneously in two photospheric spectral lines, Fe i 10783 Å and Si i 10786 Å, with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope (VTT) in Tenerife on 2013 October 15. The observations covered several stages of the M-class flare. Inversions of the full-Stokes vector of both lines were carried out and the results were put into context using (extreme)-ultraviolet filtergrams from the Solar Dynamics Observatory (SDO). Results. The active region showed high flaring activity during the whole observing period. After the M-class flare, the longitudinal magnetic field did not show significant changes along the polarity inversion line (PIL). However, an enhancement of the transverse magnetic field of approximately 550 G was found that bridges the PIL and connects umbrae of opposite polarities in the δ-spot. At the same time, a newly formed system of loops appeared co-spatially in the corona as seen in 171 Å filtergrams of the Atmospheric Imaging Assembly (AIA) on board SDO. However, we cannot exclude that the magnetic connection between the umbrae already existed in the upper atmosphere before the M-class flare and became visible only later when it was filled with hot plasma. The photospheric Doppler velocities show a persistent upflow pattern along the PIL without significant changes due to the flare. Conclusions. The increase of the transverse component of the magnetic field after the flare together with the newly formed loop system in the corona support recent predictions of flare models and flare observations.
Aims. We investigate the temporal evolution of magnetic flux emerging within a granule in the quiet-Sun internetwork at disk center. Methods. We combined IR spectropolarimetry of high angular ...resolution performed in two Fe i lines at 1565 nm with speckle-reconstructed G-band imaging. We determined the magnetic field parameters by a LTE inversion of the full Stokes vector using the SIR code, and followed their evolution in time. To interpret the observations, we created a geometrical model of a rising loop in 3D. The relevant parameters of the loop were matched to the observations where possible. We then synthesized spectra from the 3D model for a comparison to the observations. Results. We found signatures of magnetic flux emergence within a growing granule. In the early phases, a horizontal magnetic field with a distinct linear polarization signal dominated the emerging flux. Later on, two patches of opposite circular polarization signal appeared symmetrically on either side of the linear polarization patch, indicating a small loop-like structure. The mean magnetic flux density of this loop was roughly 450 G, with a total magnetic flux of around 3 $\times$ 1017 Mx. During the ~12 min episode of loop occurrence, the spatial extent of the loop increased from about 1 to 2 arcsec. The middle part of the appearing feature was blueshifted during its occurrence, supporting the scenario of an emerging loop. There is also clear evidence for the interaction of one loop footpoint with a preexisting magnetic structure of opposite polarity. The temporal evolution of the observed spectra is reproduced to first order by the spectra derived from the geometrical model. During the phase of clearest visibility of the loop in the observations, the observed and synthetic spectra match quantitatively. Conclusions. The observed event can be explained as a case of flux emergence in the shape of a small-scale loop. The fast disappearance of the loop at the end could possibly be due to magnetic reconnection.
The effect of color on orthonasal and retronasal odor intensities was investigated. When odorants were smelled orthonasally (i.e., through the nostrils), color enhanced odor intensity ratings, ...consistent with previous reports. However, when odorants were smelled retronasally (i.e., the odorous solution was put in the mouth), color reduced odor intensity ratings. These different effects of color on odor intensity (i.e., enhancement orthonasally and suppression retronasally) appear to be the result of route of olfactory stimulation rather than of any procedural artifact. This supports previous reports that retronasal and orthonasal odors are perceived differently.
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