18 research outputs found
Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
How and where are coronal loops rooted in the solar lower atmosphere? The
details of the magnetic environment and its evolution at the footpoints of
coronal loops are crucial to understanding the processes of mass and energy
supply to the solar corona. To address the above question, we use
high-resolution line-of-sight magnetic field data from the Imaging Magnetograph
eXperiment instrument on the SUNRISE balloon-borne observatory and coronal
observations from the Atmospheric Imaging Assembly onboard the Solar Dynamics
Observatory of an emerging active region. We find that the coronal loops are
often rooted at the locations with minor small-scale but persistent
opposite-polarity magnetic elements very close to the larger dominant polarity.
These opposite-polarity small-scale elements continually interact with the
dominant polarity underlying the coronal loop through flux cancellation. At
these locations we detect small inverse Y-shaped jets in chromospheric Ca II H
images obtained from the SUNRISE Filter Imager during the flux cancellation.
Our results indicate that magnetic flux cancellation and reconnection at the
base of coronal loops due to mixed polarity fields might be a crucial feature
for the supply of mass and energy into the corona.Comment: Published in the Astrophysical Journal Supplement Serie
Kinematics of Magnetic Bright Features in the Solar Photosphere
Convective flows are known as the prime means of transporting magnetic fields
on the solar surface. Thus, small magnetic structures are good tracers of the
turbulent flows. We study the migration and dispersal of magnetic bright
features (MBFs) in intergranular areas observed at high spatial resolution with
Sunrise/IMaX. We describe the flux dispersal of individual MBFs as a diffusion
process whose parameters are computed for various areas in the quiet Sun and
the vicinity of active regions from seeing-free data. We find that magnetic
concentrations are best described as random walkers close to network areas
(diffusion index, gamma=1.0), travelers with constant speeds over a
supergranule (gamma=1.9-2.0), and decelerating movers in the vicinity of flux
emergence and/or within active regions (gamma=1.4-1.5). The three types of
regions host MBFs with mean diffusion coefficients of 130 km^2/s, 80-90 km^2/s,
and 25-70 km^2/s, respectively. The MBFs in these three types of regions are
found to display a distinct kinematic behavior at a confidence level in excess
of 95%.Comment: 8 pages, 4 figure
Bright points in the quiet Sun as observed in the visible and near-UV by the balloon-borne observatory Sunrise
Bright points (BPs) are manifestations of small magnetic elements in the
solar photosphere. Their brightness contrast not only gives insight into the
thermal state of the photosphere (and chromosphere) in magnetic elements, but
also plays an important role in modulating the solar total and spectral
irradiance. Here we report on simultaneous high-resolution imaging and
spectropolarimetric observations of BPs using Sunrise balloon-borne observatory
data of the quiet Sun at disk center. BP contrasts have been measured between
214 nm and 525 nm, including the first measurements at wavelengths below 388
nm. The histograms of the BP peak brightness show a clear trend toward broader
contrast distributions and higher mean contrasts at shorter wavelengths. At 214
nm we observe a peak brightness of up to five times the mean quiet-Sun value,
the highest BP contrast so far observed. All BPs are associated with a magnetic
signal, although in a number of cases it is surprisingly weak. Most of the BPs
show only weak downflows, the mean value being 240 m/s, but some display strong
down- or upflows reaching a few km/s.Comment: Accepted for publication in The Astrophysical Journal Letters on
September 08 201
Fully resolved quiet-Sun magnetic flux tube observed with the Sunrise IMaX instrument
Until today, the small size of magnetic elements in quiet Sun areas has
required the application of indirect methods, such as the line-ratio technique
or multi-component inversions, to infer their physical properties. A consistent
match to the observed Stokes profiles could only be obtained by introducing a
magnetic filling factor that specifies the fraction of the observed pixel
filled with magnetic field. Here, we investigate the properties of a small
magnetic patch in the quiet Sun observed with the IMaX magnetograph on board
the balloon-borne telescope Sunrise with unprecedented spatial resolution and
low instrumental stray light. We apply an inversion technique based on the
numerical solution of the radiative transfer equation to retrieve the
temperature stratification and the field strength in the magnetic patch. The
observations can be well reproduced with a one-component, fully magnetized
atmosphere with a field strength exceeding 1 kG and a significantly enhanced
temperature in the mid- to upper photosphere with respect to its surroundings,
consistent with semi-empirical flux tube models for plage regions. We therefore
conclude that, within the framework of a simple atmospheric model, the IMaX
measurements resolve the observed quiet-Sun flux tube.Comment: Accepted for publication in The Astrophysical Journal Letters on Aug
11 201
Sunrise: instrument, mission, data and first results
The Sunrise balloon-borne solar observatory consists of a 1m aperture Gregory
telescope, a UV filter imager, an imaging vector polarimeter, an image
stabilization system and further infrastructure. The first science flight of
Sunrise yielded high-quality data that reveal the structure, dynamics and
evolution of solar convection, oscillations and magnetic fields at a resolution
of around 100 km in the quiet Sun. After a brief description of instruments and
data, first qualitative results are presented. In contrast to earlier
observations, we clearly see granulation at 214 nm. Images in Ca II H display
narrow, short-lived dark intergranular lanes between the bright edges of
granules. The very small-scale, mixed-polarity internetwork fields are found to
be highly dynamic. A significant increase in detectable magnetic flux is found
after phase-diversity-related reconstruction of polarization maps, indicating
that the polarities are mixed right down to the spatial resolution limit, and
probably beyond.Comment: accepted by ApJ
Models and data analysis tools for the Solar Orbiter mission
Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk.Aims. The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency's Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies.Methods. Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter.Results. This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission.Conclusions. The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission.Peer reviewe
Expression and regulation of interferon-related development regulator-1 in cystic fibrosis neutrophils.
A genome-wide association study identified interferon-related development regulator-1 (IFRD1), a protein expressed by neutrophils, as a key modifier gene in cystic fibrosis (CF) lung disease. Here, we investigated the expression and regulation of IFRD1 in CF neutrophils. IFRD1 expression was quantified in peripheral blood and airway neutrophils from patients with CF, patients with non-CF lung disease, and healthy control subjects. The regulation of IFRD1 expression was analyzed using isolated neutrophils and ex vivo stimulation assays with CF airway fluids. IFRD1 single-nucleotide polymorphisms (SNPs) were analyzed in a CF cohort (n = 572) and correlated with longitudinal lung function and IFRD1 expression. Patients with CF expressed higher protein levels of IFRD1 in peripheral blood neutrophils compared with healthy or non-CF disease control subjects. Within patients with CF, IFRD1 protein expression levels in neutrophils were lower in airway fluids compared with peripheral blood. High IFRD1 expression was positively associated with the production of reactive oxygen species (ROS) in CF neutrophils. In vitro regulation studies showed that CF airway fluid and the CF-characteristic chemokines CXCL8 and CXCL2 down-regulated IFRD1 expression in neutrophils, an effect that was mediated through CXCR2. Genetic analyses showed that three IFRD1 SNPs were associated with longitudinal declines in lung function, and modulated IFRD1 expression. These studies demonstrate that IFRD1 expression is systemically up-regulated in human CF neutrophils, is linked to the production of ROS, and is modulated by chemokines in CF airway fluids, depending on the IFRD1 genotype. Understanding the regulation of IFRD1 may pave the way for novel therapeutic approaches to target neutrophilic inflammation in CF