282 research outputs found
Nonlinear Force-Free Field Modeling of the Solar Magnetic Carpet and Comparison with SDO/HMI and Sunrise/IMaX Observations
In the quiet solar photosphere, the mixed polarity fields form a magnetic
carpet, which continuously evolves due to dynamical interaction between the
convective motions and magnetic field. This interplay is a viable source to
heat the solar atmosphere. In this work, we used the line-of-sight (LOS)
magnetograms obtained from the Helioseismic and Magnetic Imager (HMI) on the
\textit{Solar Dynamics Observatory} (\textit{SDO}), and the Imaging
Magnetograph eXperiment (IMaX) instrument on the \textit{Sunrise} balloon-borne
observatory, as time dependent lower boundary conditions, to study the
evolution of the coronal magnetic field. We use a magneto-frictional relaxation
method, including hyperdiffusion, to produce time series of three-dimensional
(3D) nonlinear force-free fields from a sequence of photospheric LOS
magnetograms. Vertical flows are added up to a height of 0.7 Mm in the modeling
to simulate the non-force-freeness at the photosphere-chromosphere layers.
Among the derived quantities, we study the spatial and temporal variations of
the energy dissipation rate, and energy flux. Our results show that the energy
deposited in the solar atmosphere is concentrated within 2 Mm of the
photosphere and there is not sufficient energy flux at the base of the corona
to cover radiative and conductive losses. Possible reasons and implications are
discussed. Better observational constraints of the magnetic field in the
chromosphere are crucial to understand the role of the magnetic carpet in
coronal heating.Comment: Accepted for publication in The Astrophysical Journal (13 pages, 10
figures
Nature of the energy source powering solar coronal loops driven by nanoflares
Magnetic energy is required to heat the corona, the outer atmosphere of the
Sun, to millions of degrees. We study the nature of the magnetic energy source
that is probably responsible for the brightening of coronal loops driven by
nanoflares in the cores of solar active regions. We consider observations of
two active regions (ARs), 11890 and 12234, in which nanoflares have been
detected. To this end, we use ultraviolet (UV) and extreme ultraviolet (EUV)
images from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory (SDO) for coronal loop diagnostics. These images are combined with
the co-temporal line-of-sight magnetic field maps from the Helioseismic and
Magnetic Imager (HMI) onboard SDO to investigate the connection between coronal
loops and their magnetic roots in the photosphere. The core of these ARs
exhibit loop brightening in multiple EUV channels of AIA, particularly in its
9.4 nm filter. The HMI magnetic field maps reveal the presence of a complex
mixed polarity magnetic field distribution at the base of these loops. We
detect the cancellation of photospheric magnetic flux at these locations at a
rate of about Mx s. The associated compact coronal
brightenings directly above the cancelling magnetic features are indicative of
plasma heating due to chromospheric magnetic reconnection. We suggest that the
complex magnetic topology and the evolution of magnetic field, such as flux
cancellation in the photosphere and the resulting chromospheric reconnection,
can play an important role in energizing active region coronal loops driven by
nanoflares. Our estimate of magnetic energy release during flux cancellation in
the quiet Sun suggests that chromospheric reconnection can also power the quiet
corona.Comment: A&A Letters (in press
Observations of solar chromospheric heating at sub-arcsec spatial resolution
A wide variety of phenomena such as gentle but persistent brightening,
dynamic slender features (~100 km), and compact (~1'') ultraviolet (UV) bursts
are associated with the heating of the solar chromosphere. High spatio-temporal
resolution is required to capture the finer details of the likely magnetic
reconnection-driven, rapidly evolving bursts. Such observations are also needed
to reveal their similarities to large-scale flares, which are also thought to
be reconnection driven, and more generally their role in chromospheric heating.
Here we report observations of chromospheric heating in the form of a UV burst
obtained with the balloon-borne observatory, SUNRISE. The observed burst
displayed a spatial morphology similar to that of a large-scale solar flare
with circular ribbon. While the co-temporal UV observations at 1.5'' spatial
resolution and 24s cadence from the Solar Dynamics Observatory showed a compact
brightening, the SUNRISE observations at diffraction-limited spatial resolution
of 0.1'' at 7s cadence revealed a dynamic sub-structure of the burst that it is
composed of extended ribbon-like features and a rapidly evolving arcade of thin
(~0.1'' wide) magnetic loop-like features, similar to post-flare loops. Such a
dynamic sub-structure reveals the small-scale nature of chromospheric heating
in these bursts. Furthermore, based on magnetic field extrapolations, this
heating event is associated with a complex fan-spine magnetic topology. Our
observations strongly hint at a unified picture of magnetic heating in the
solar atmosphere from some large-scale flares to small-scale bursts, all being
associated with such a magnetic topology.Comment: Accepted for publication in A&A, online movie of the observations is
available at https://goo.gl/RRDuX
Study of Dengue virus E proteingene of clinical isolates of Andhra Pradesh: in the contest to Epidemiological features
In this current article, we showed the dengue virus serotype 2 protein E gene from the clinical samples of Andhra Pradesh in an acute phase infection. The models showed positive for the protein E gene with RT-PCR techniques and cellular isolates. Two unique sequences are identified with new substrains, which are similar to the hermits of the earlier reports. This study provided the epidemiology insight of the isolated strain through the phylogenetic analyses
Targeted treatment for chronic lymphocytic leukemia
The treatment of chronic lymphocytic leukemia (CLL) has evolved over the last few decades. Recognition has increased of several key components of CLL biology currently manipulated for therapeutics. A milestone in the treatment of CLL was reached with the incorporation of immunotherapy with conventional chemotherapy. The fludarabine/cyclophosphamide/rituximab combination has demonstrated survival advantage for the first time in the treatment of CLL. Several other biological compounds are being explored with the hope of improving responses, impacting survival, and ultimately curing CLL. Important agents being tested are targeted on CLL surface molecules and their ligands, signal transduction protein and oncogenes. This review provides a brief summary of the recent advances made in preclinical and clinical investigation of selected promising therapeutic agents, which lead the target-directed therapeutic approach
Clinical isolates of Anantapuramu for the protein E isolation of the dengue virus
In theclinical samples from the state of Anantapuramu, the dengue virus serotype 2 protein E gene was found. It was established that the protein E gene was present in the models by using RT-PCR and cellular isolates. There has been one new sub strain discovered that are akin to the hermits described in previous investigations. An investigation of the epidemiology of the isolated strain was conducted using a phylogenetic analysis of the strain
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
Preliminary Results on Irradiance Measurements from Lyra and Swap
International audienceThe first and preliminary results of the photometry of Large Yield Radiometer (LYRA) and Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard PROBA2 are presented in this paper. To study the day-to-day variations of LYRA irradiance, we have compared the LYRA irradiance values (observed Sun as a star) measured in Aluminum filter channel (171 Å-500 Å) with spatially resolved full-disk integrated intensity values measured with SWAP (174 Å) and Ca II K 1 Å index values (ground-based observations from NSO/Sac Peak) for the period from 01 April 2010 to 15 Mar 2011. We found that there is a good correlation between these parameters. This indicates that the spatial resolution of SWAP complements the high temporal resolution of LYRA. Hence SWAP can be considered as an additional radiometric channel. Also the K emission index is the integrated intensity (or flux) over a 1 Å band centered on the K line and is proportional to the total emission from the chromosphere; this comparison clearly explains that the LYRA irradiance variations are due to the various magnetic features, which are contributing significantly. In addition to this we have made an attempt to segregate coronal features from full-disk SWAP images. This will help to understand and determine the actual contribution of the individual coronal feature to LYRA irradiance variations
- …