59 research outputs found
Digitization of sunspot drawings by Sp\"orer made in 1861-1894
Most of our knowledge about the Sun's activity cycle arises from sunspot
observations over the last centuries since telescopes have been used for
astronomy. The German astronomer Gustav Sp\"orer observed almost daily the Sun
from 1861 until the beginning of 1894 and assembled a 33-year collection of
sunspot data covering a total of 445 solar rotation periods. These sunspot
drawings were carefully placed on an equidistant grid of heliographic longitude
and latitude for each rotation period, which were then copied to copper plates
for a lithographic reproduction of the drawings in astronomical journals. In
this article, we describe in detail the process of capturing these data as
digital images, correcting for various effects of the aging print materials,
and preparing the data for contemporary scientific analysis based on advanced
image processing techniques. With the processed data we create a butterfly
diagram aggregating sunspot areas, and we present methods to measure the size
of sunspots (umbra and penumbra) and to determine tilt angles of active
regions. A probability density function of the sunspot area is computed, which
conforms to contemporary data after rescaling.Comment: 10 pages, 8 figures, accepted for publication in Astronomische
Nachrichten/Astronomical Note
Dynamics and connectivity of an extended arch filament system
In this study, we analyzed a filament system, which expanded between moving
magnetic features (MMFs) of a decaying sunspot and opposite flux outside of the
active region from the nearby quiet-Sun network. This configuration deviated
from a classical arch filament system (AFS), which typically connects two pores
in an emerging flux region. Thus, we called this system an extended AFS. We
contrasted classical and extended AFSs with an emphasis on the complex magnetic
structure of the latter. Furthermore, we examined the physical properties of
the extended AFS and described its dynamics and connectivity. At the southern
footpoint, we measured that the flux decreases over time. We find strong
downflow velocities at the footpoints of the extended AFS, which increase in a
time period of 30 minutes. The velocities are asymmetric at both footpoints
with higher velocities at the southern footpoint.
The extended AFS was observed with two instruments at the Dunn Solar
Telescope (DST). The Rapid Oscillations in the Solar Atmosphere (ROSA) imager
provided images in three different wavelength regions. The Interferometric
Bidimensional Spectropolarimeter (IBIS) provided spectroscopic H data
and spectropolarimetric data that was obtained in the near-infrared Ca II 8542
\AA\ line. We used He II 304 \AA\ extreme ultraviolet images of the Atmospheric
Imaging Assembly (AIA) and LOS magnetograms of the Helioseismic and Magnetic
Imager (HMI) on board the Solar Dynamics Observatory (SDO) as context data.Comment: 14 pages, 12 figure
Proton Radiation Hardness of Perovskite Tandem Photovoltaics.
Monolithic [Cs0.05(MA0. 17FA0. 83)0.95]Pb(I0.83Br0.17)3/Cu(In,Ga)Se2 (perovskite/CIGS) tandem solar cells promise high performance and can be processed on flexible substrates, enabling cost-efficient and ultra-lightweight space photovoltaics with power-to-weight and power-to-cost ratios surpassing those of state-of-the-art III-V semiconductor-based multijunctions. However, to become a viable space technology, the full tandem stack must withstand the harsh radiation environments in space. Here, we design tailored operando and ex situ measurements to show that perovskite/CIGS cells retain over 85% of their initial efficiency even after 68 MeV proton irradiation at a dose of 2 × 1012 p+/cm2. We use photoluminescence microscopy to show that the local quasi-Fermi-level splitting of the perovskite top cell is unaffected. We identify that the efficiency losses arise primarily from increased recombination in the CIGS bottom cell and the nickel-oxide-based recombination contact. These results are corroborated by measurements of monolithic perovskite/silicon-heterojunction cells, which severely degrade to 1% of their initial efficiency due to radiation-induced recombination centers in silicon.F.L. acknowledges financial support from the Alexander von Humboldt Foundation via the Feodor Lynen program and thanks Prof. Sir R. Friend for supporting his Fellowship at the Cavendish Laboratory. This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (HYPERION, grant agreement number 756962). M.J, A.A.A., E.K., and S.A. acknowledge financial support from the German Federal Ministry of Education and Research (BMBF) via program “Materialforschung für die Energiewende” (grant no. 03SF0540), by the German Federal Ministry for Economic Affairs and Energy (BMWi) through the ‘PersiST’ project (Grant No. 0324037C). T.B. C.A.K. and R.S. acknowledge funding by BMWi through the speedCIGS (grant no. 0324095E) and EFFCIS project (grant no. 0324076D). D.K. and M.C. acknowledge financial support from the Dutch Ministry of Economic Affairs, via The Top-consortia Knowledge and Innovation (TKI) Program ‘‘Photovoltaic modules based on a p-i-n stack, manufactured on a roll-to-roll line featuring high efficiency, stability and strong market perspective’’ (PVPRESS) (TEUE118010) and “Bridging the voltage gap” (BRIGHT) (1721101). K. F. acknowledges the George and Lilian Schiff Fund, the Engineering and Physical Sciences Research Council (EPSRC), the Winton Sustainability Fellowship, and the Cambridge Trust for funding. S.D.S. acknowledges the Royal Society and Tata Group (UF150033). The authors acknowledge the EPSRC for funding (EP/R023980/1). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 841265. A.R.B. acknowledges funding from a Winton Studentship, Oppenheimer Studentship, and funding from the Engineering and Physical Sciences Research Council (EPSRC) Doctoral Training Centre in Photovoltaics (CDT-PV). K.G. acknowledges the Polish Ministry of Science and Higher Education within the Mobilnosc Plus program (Grant No. 1603/MOB/V/2017/0)
- …