This article discusses the colors of the aurora borealis and the physical processes that cause the different colors. It begins with a brief history of observations and understanding of the aurora. It then explains that the colors are caused by atoms and molecules in the upper atmosphere emitting light as they are struck by energetic particles from space. Specifically, green light is emitted by oxygen atoms, while red and purple colors come from higher altitude emissions. By analyzing the color balance and structure of the aurora, scientists can learn about the atmospheric composition and electric currents in near-Earth space that generate the colorful northern lights.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Gliese 12 b: A Temperate Earth-sized Planet at 12 pc Ideal for Atmospheric Tr...Sérgio Sacani
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the
atmospheres of terrestrial planets via follow-up spectroscopic observations. However, the number of such planets
receiving low insolation is still small, limiting our ability to understand the diversity of the atmospheric
composition and climates of temperate terrestrial planets. We report the discovery of an Earth-sized planet
transiting the nearby (12 pc) inactive M3.0 dwarf Gliese 12 (TOI-6251) with an orbital period (Porb) of 12.76 days.
The planet, Gliese 12 b, was initially identified as a candidate with an ambiguous Porb from TESS data. We
confirmed the transit signal and Porb using ground-based photometry with MuSCAT2 and MuSCAT3, and
validated the planetary nature of the signal using high-resolution images from Gemini/NIRI and Keck/NIRC2 as
well as radial velocity (RV) measurements from the InfraRed Doppler instrument on the Subaru 8.2 m telescope
and from CARMENES on the CAHA 3.5 m telescope. X-ray observations with XMM-Newton showed the host
star is inactive, with an X-ray-to-bolometric luminosity ratio of log 5.7 L L X bol » - . Joint analysis of the light
curves and RV measurements revealed that Gliese 12 b has a radius of 0.96 ± 0.05 R⊕,a3σ mass upper limit of
3.9 M⊕, and an equilibrium temperature of 315 ± 6 K assuming zero albedo. The transmission spectroscopy metric
(TSM) value of Gliese 12 b is close to the TSM values of the TRAPPIST-1 planets, adding Gliese 12 b to the small
list of potentially terrestrial, temperate planets amenable to atmospheric characterization with JWST.
Gliese 12 b, a temperate Earth-sized planet at 12 parsecs discovered with TES...Sérgio Sacani
We report on the discovery of Gliese 12 b, the nearest transiting temperate, Earth-sized planet found to date. Gliese 12 is a
bright (V = 12.6 mag, K = 7.8 mag) metal-poor M4V star only 12.162 ± 0.005 pc away from the Solar system with one of the
lowest stellar activity levels known for M-dwarfs. A planet candidate was detected by TESS based on only 3 transits in sectors
42, 43, and 57, with an ambiguity in the orbital period due to observational gaps. We performed follow-up transit observations
with CHEOPS and ground-based photometry with MINERVA-Australis, SPECULOOS, and Purple Mountain Observatory,
as well as further TESS observations in sector 70. We statistically validate Gliese 12 b as a planet with an orbital period of
12.76144 ± 0.00006 d and a radius of 1.0 ± 0.1 R⊕, resulting in an equilibrium temperature of ∼315 K. Gliese 12 b has excellent
future prospects for precise mass measurement, which may inform how planetary internal structure is affected by the stellar
compositional environment. Gliese 12 b also represents one of the best targets to study whether Earth-like planets orbiting cool
stars can retain their atmospheres, a crucial step to advance our understanding of habitability on Earth and across the galaxy.
The importance of continents, oceans and plate tectonics for the evolution of...Sérgio Sacani
Within the uncertainties of involved astronomical and biological parameters, the Drake Equation
typically predicts that there should be many exoplanets in our galaxy hosting active, communicative
civilizations (ACCs). These optimistic calculations are however not supported by evidence, which is
often referred to as the Fermi Paradox. Here, we elaborate on this long-standing enigma by showing
the importance of planetary tectonic style for biological evolution. We summarize growing evidence
that a prolonged transition from Mesoproterozoic active single lid tectonics (1.6 to 1.0 Ga) to modern
plate tectonics occurred in the Neoproterozoic Era (1.0 to 0.541 Ga), which dramatically accelerated
emergence and evolution of complex species. We further suggest that both continents and oceans
are required for ACCs because early evolution of simple life must happen in water but late evolution
of advanced life capable of creating technology must happen on land. We resolve the Fermi Paradox
(1) by adding two additional terms to the Drake Equation: foc
(the fraction of habitable exoplanets
with significant continents and oceans) and fpt
(the fraction of habitable exoplanets with significant
continents and oceans that have had plate tectonics operating for at least 0.5 Ga); and (2) by
demonstrating that the product of foc
and fpt
is very small (< 0.00003–0.002). We propose that the lack
of evidence for ACCs reflects the scarcity of long-lived plate tectonics and/or continents and oceans on
exoplanets with primitive life.
A Giant Impact Origin for the First Subduction on EarthSérgio Sacani
Hadean zircons provide a potential record of Earth's earliest subduction 4.3 billion years ago. Itremains enigmatic how subduction could be initiated so soon after the presumably Moon‐forming giant impact(MGI). Earlier studies found an increase in Earth's core‐mantle boundary (CMB) temperature due to theaccumulation of the impactor's core, and our recent work shows Earth's lower mantle remains largely solid, withsome of the impactor's mantle potentially surviving as the large low‐shear velocity provinces (LLSVPs). Here,we show that a hot post‐impact CMB drives the initiation of strong mantle plumes that can induce subductioninitiation ∼200 Myr after the MGI. 2D and 3D thermomechanical computations show that a high CMBtemperature is the primary factor triggering early subduction, with enrichment of heat‐producing elements inLLSVPs as another potential factor. The models link the earliest subduction to the MGI with implications forunderstanding the diverse tectonic regimes of rocky planets.
Climate extremes likely to drive land mammal extinction during next supercont...Sérgio Sacani
Mammals have dominated Earth for approximately 55 Myr thanks to their
adaptations and resilience to warming and cooling during the Cenozoic. All
life will eventually perish in a runaway greenhouse once absorbed solar
radiation exceeds the emission of thermal radiation in several billions of
years. However, conditions rendering the Earth naturally inhospitable to
mammals may develop sooner because of long-term processes linked to
plate tectonics (short-term perturbations are not considered here). In
~250 Myr, all continents will converge to form Earth’s next supercontinent,
Pangea Ultima. A natural consequence of the creation and decay of Pangea
Ultima will be extremes in pCO2 due to changes in volcanic rifting and
outgassing. Here we show that increased pCO2, solar energy (F⨀;
approximately +2.5% W m−2 greater than today) and continentality (larger
range in temperatures away from the ocean) lead to increasing warming
hostile to mammalian life. We assess their impact on mammalian
physiological limits (dry bulb, wet bulb and Humidex heat stress indicators)
as well as a planetary habitability index. Given mammals’ continued survival,
predicted background pCO2 levels of 410–816 ppm combined with increased
F⨀ will probably lead to a climate tipping point and their mass extinction.
The results also highlight how global landmass configuration, pCO2 and F⨀
play a critical role in planetary habitability.
Constraints on Neutrino Natal Kicks from Black-Hole Binary VFTS 243Sérgio Sacani
The recently reported observation of VFTS 243 is the first example of a massive black-hole binary
system with negligible binary interaction following black-hole formation. The black-hole mass (≈10M⊙)
and near-circular orbit (e ≈ 0.02) of VFTS 243 suggest that the progenitor star experienced complete
collapse, with energy-momentum being lost predominantly through neutrinos. VFTS 243 enables us to
constrain the natal kick and neutrino-emission asymmetry during black-hole formation. At 68% confidence
level, the natal kick velocity (mass decrement) is ≲10 km=s (≲1.0M⊙), with a full probability distribution
that peaks when ≈0.3M⊙ were ejected, presumably in neutrinos, and the black hole experienced a natal
kick of 4 km=s. The neutrino-emission asymmetry is ≲4%, with best fit values of ∼0–0.2%. Such a small
neutrino natal kick accompanying black-hole formation is in agreement with theoretical predictions.
Detectability of Solar Panels as a TechnosignatureSérgio Sacani
In this work, we assess the potential detectability of solar panels made of silicon on an Earth-like
exoplanet as a potential technosignature. Silicon-based photovoltaic cells have high reflectance in the
UV-VIS and in the near-IR, within the wavelength range of a space-based flagship mission concept
like the Habitable Worlds Observatory (HWO). Assuming that only solar energy is used to provide
the 2022 human energy needs with a land cover of ∼ 2.4%, and projecting the future energy demand
assuming various growth-rate scenarios, we assess the detectability with an 8 m HWO-like telescope.
Assuming the most favorable viewing orientation, and focusing on the strong absorption edge in the
ultraviolet-to-visible (0.34 − 0.52 µm), we find that several 100s of hours of observation time is needed
to reach a SNR of 5 for an Earth-like planet around a Sun-like star at 10pc, even with a solar panel
coverage of ∼ 23% land coverage of a future Earth. We discuss the necessity of concepts like Kardeshev
Type I/II civilizations and Dyson spheres, which would aim to harness vast amounts of energy. Even
with much larger populations than today, the total energy use of human civilization would be orders of
magnitude below the threshold for causing direct thermal heating or reaching the scale of a Kardashev
Type I civilization. Any extraterrrestrial civilization that likewise achieves sustainable population
levels may also find a limit on its need to expand, which suggests that a galaxy-spanning civilization
as imagined in the Fermi paradox may not exist.
Jet reorientation in central galaxies of clusters and groups: insights from V...Sérgio Sacani
Recent observations of galaxy clusters and groups with misalignments between their central AGN jets
and X-ray cavities, or with multiple misaligned cavities, have raised concerns about the jet – bubble
connection in cooling cores, and the processes responsible for jet realignment. To investigate the
frequency and causes of such misalignments, we construct a sample of 16 cool core galaxy clusters and
groups. Using VLBA radio data we measure the parsec-scale position angle of the jets, and compare
it with the position angle of the X-ray cavities detected in Chandra data. Using the overall sample
and selected subsets, we consistently find that there is a 30% – 38% chance to find a misalignment
larger than ∆Ψ = 45◦ when observing a cluster/group with a detected jet and at least one cavity. We
determine that projection may account for an apparently large ∆Ψ only in a fraction of objects (∼35%),
and given that gas dynamical disturbances (as sloshing) are found in both aligned and misaligned
systems, we exclude environmental perturbation as the main driver of cavity – jet misalignment.
Moreover, we find that large misalignments (up to ∼ 90◦
) are favored over smaller ones (45◦ ≤ ∆Ψ ≤
70◦
), and that the change in jet direction can occur on timescales between one and a few tens of Myr.
We conclude that misalignments are more likely related to actual reorientation of the jet axis, and we
discuss several engine-based mechanisms that may cause these dramatic changes.
The solar dynamo begins near the surfaceSérgio Sacani
The magnetic dynamo cycle of the Sun features a distinct pattern: a propagating
region of sunspot emergence appears around 30° latitude and vanishes near the
equator every 11 years (ref. 1). Moreover, longitudinal flows called torsional oscillations
closely shadow sunspot migration, undoubtedly sharing a common cause2. Contrary
to theories suggesting deep origins of these phenomena, helioseismology pinpoints
low-latitude torsional oscillations to the outer 5–10% of the Sun, the near-surface
shear layer3,4. Within this zone, inwardly increasing differential rotation coupled with
a poloidal magnetic field strongly implicates the magneto-rotational instability5,6,
prominent in accretion-disk theory and observed in laboratory experiments7.
Together, these two facts prompt the general question: whether the solar dynamo is
possibly a near-surface instability. Here we report strong affirmative evidence in stark
contrast to traditional models8 focusing on the deeper tachocline. Simple analytic
estimates show that the near-surface magneto-rotational instability better explains
the spatiotemporal scales of the torsional oscillations and inferred subsurface
magnetic field amplitudes9. State-of-the-art numerical simulations corroborate these
estimates and reproduce hemispherical magnetic current helicity laws10. The dynamo
resulting from a well-understood near-surface phenomenon improves prospects
for accurate predictions of full magnetic cycles and space weather, affecting the
electromagnetic infrastructure of Earth.
Extensive Pollution of Uranus and Neptune’s Atmospheres by Upsweep of Icy Mat...Sérgio Sacani
In the Nice model of solar system formation, Uranus and Neptune undergo an orbital upheaval,
sweeping through a planetesimal disk. The region of the disk from which material is accreted by
the ice giants during this phase of their evolution has not previously been identified. We perform
direct N-body orbital simulations of the four giant planets to determine the amount and origin of solid
accretion during this orbital upheaval. We find that the ice giants undergo an extreme bombardment
event, with collision rates as much as ∼3 per hour assuming km-sized planetesimals, increasing the
total planet mass by up to ∼0.35%. In all cases, the initially outermost ice giant experiences the
largest total enhancement. We determine that for some plausible planetesimal properties, the resulting
atmospheric enrichment could potentially produce sufficient latent heat to alter the planetary cooling
timescale according to existing models. Our findings suggest that substantial accretion during this
phase of planetary evolution may have been sufficient to impact the atmospheric composition and
thermal evolution of the ice giants, motivating future work on the fate of deposited solid material.
Exomoons & Exorings with the Habitable Worlds Observatory I: On the Detection...Sérgio Sacani
The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy
was the construction of an observatory capable of characterizing habitable worlds. In this paper series
we explore the detectability of and interference from exomoons and exorings serendipitously observed
with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting
in this manuscript with Earth-Moon analog mutual events. Unlike transits, which only occur in systems
viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every
star-planet-moon system. The cadence of these events can vary widely from ∼yearly to multiple events
per day, as was the case in our younger Earth-Moon system. Leveraging previous space-based (EPOXI)
lightcurves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive
the detectability of Moon analogs with HWO. We determine that Earth-Moon analogs are detectable
with observation of ∼2-20 mutual events for systems within 10 pc, and larger moons should remain
detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet
features and weather. We find that HWO wavelength coverage in the near-IR, specifically in the 1.4 µm
water band where large moons can outshine their host planet, will aid in differentiating exomoon signals
from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin
to our Moon are more likely to be detected in younger systems, where shorter orbital periods and
favorable geometry enhance the probability and frequency of mutual events.
Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for...Sérgio Sacani
Mars is a particularly attractive candidate among known astronomical objects
to potentially host life. Results from space exploration missions have provided
insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to
its toxicity. However, it can also provide potential benefits, such as producing
brines by deliquescence, like those thought to exist on present-day Mars. Here
we show perchlorate brines support folding and catalysis of functional RNAs,
while inactivating representative protein enzymes. Additionally, we show
perchlorate and other oxychlorine species enable ribozyme functions,
including homeostasis-like regulatory behavior and ribozyme-catalyzed
chlorination of organic molecules. We suggest nucleic acids are uniquely wellsuited to hypersaline Martian environments. Furthermore, Martian near- or
subsurface oxychlorine brines, and brines found in potential lifeforms, could
provide a unique niche for biomolecular evolution.
Continuum emission from within the plunging region of black hole discsSérgio Sacani
The thermal continuum emission observed from accreting black holes across X-ray bands has the potential to be leveraged as a
powerful probe of the mass and spin of the central black hole. The vast majority of existing ‘continuum fitting’ models neglect
emission sourced at and within the innermost stable circular orbit (ISCO) of the black hole. Numerical simulations, however,
find non-zero emission sourced from these regions. In this work, we extend existing techniques by including the emission
sourced from within the plunging region, utilizing new analytical models that reproduce the properties of numerical accretion
simulations. We show that in general the neglected intra-ISCO emission produces a hot-and-small quasi-blackbody component,
but can also produce a weak power-law tail for more extreme parameter regions. A similar hot-and-small blackbody component
has been added in by hand in an ad hoc manner to previous analyses of X-ray binary spectra. We show that the X-ray spectrum
of MAXI J1820+070 in a soft-state outburst is extremely well described by a full Kerr black hole disc, while conventional
models that neglect intra-ISCO emission are unable to reproduce the data. We believe this represents the first robust detection of
intra-ISCO emission in the literature, and allows additional constraints to be placed on the MAXI J1820 + 070 black hole spin
which must be low a• < 0.5 to allow a detectable intra-ISCO region. Emission from within the ISCO is the dominant emission
component in the MAXI J1820 + 070 spectrum between 6 and 10 keV, highlighting the necessity of including this region. Our
continuum fitting model is made publicly available.
WASP-69b’s Escaping Envelope Is Confined to a Tail Extending at Least 7 RpSérgio Sacani
Studying the escaping atmospheres of highly irradiated exoplanets is critical for understanding the physical
mechanisms that shape the demographics of close-in planets. A number of planetary outflows have been observed
as excess H/He absorption during/after transit. Such an outflow has been observed for WASP-69b by multiple
groups that disagree on the geometry and velocity structure of the outflow. Here, we report the detection of this
planet’s outflow using Keck/NIRSPEC for the first time. We observed the outflow 1.28 hr after egress until the
target set, demonstrating the outflow extends at least 5.8 × 105 km or 7.5 Rp This detection is significantly longer
than previous observations, which report an outflow extending ∼2.2 planet radii just 1 yr prior. The outflow is
blueshifted by −23 km s−1 in the planetary rest frame. We estimate a current mass-loss rate of 1 M⊕ Gyr−1
. Our
observations are most consistent with an outflow that is strongly sculpted by ram pressure from the stellar wind.
However, potential variability in the outflow could be due to time-varying interactions with the stellar wind or
differences in instrumental precision.
X-rays from a Central “Exhaust Vent” of the Galactic Center ChimneySérgio Sacani
Using deep archival observations from the Chandra X-ray Observatory, we present an analysis of
linear X-ray-emitting features located within the southern portion of the Galactic center chimney,
and oriented orthogonal to the Galactic plane, centered at coordinates l = 0.08◦
, b = −1.42◦
. The
surface brightness and hardness ratio patterns are suggestive of a cylindrical morphology which may
have been produced by a plasma outflow channel extending from the Galactic center. Our fits of the
feature’s spectra favor a complex two-component model consisting of thermal and recombining plasma
components, possibly a sign of shock compression or heating of the interstellar medium by outflowing
material. Assuming a recombining plasma scenario, we further estimate the cooling timescale of this
plasma to be on the order of a few hundred to thousands of years, leading us to speculate that a
sequence of accretion events onto the Galactic Black Hole may be a plausible quasi-continuous energy
source to sustain the observed morphology
Enhancing Performance with Globus and the Science DMZGlobus
ESnet has led the way in helping national facilities—and many other institutions in the research community—configure Science DMZs and troubleshoot network issues to maximize data transfer performance. In this talk we will present a summary of approaches and tips for getting the most out of your network infrastructure using Globus Connect Server.
Le nuove frontiere dell'AI nell'RPA con UiPath Autopilot™UiPathCommunity
In questo evento online gratuito, organizzato dalla Community Italiana di UiPath, potrai esplorare le nuove funzionalità di Autopilot, il tool che integra l'Intelligenza Artificiale nei processi di sviluppo e utilizzo delle Automazioni.
📕 Vedremo insieme alcuni esempi dell'utilizzo di Autopilot in diversi tool della Suite UiPath:
Autopilot per Studio Web
Autopilot per Studio
Autopilot per Apps
Clipboard AI
GenAI applicata alla Document Understanding
👨🏫👨💻 Speakers:
Stefano Negro, UiPath MVPx3, RPA Tech Lead @ BSP Consultant
Flavio Martinelli, UiPath MVP 2023, Technical Account Manager @UiPath
Andrei Tasca, RPA Solutions Team Lead @NTT Data
Elevating Tactical DDD Patterns Through Object CalisthenicsDorra BARTAGUIZ
After immersing yourself in the blue book and its red counterpart, attending DDD-focused conferences, and applying tactical patterns, you're left with a crucial question: How do I ensure my design is effective? Tactical patterns within Domain-Driven Design (DDD) serve as guiding principles for creating clear and manageable domain models. However, achieving success with these patterns requires additional guidance. Interestingly, we've observed that a set of constraints initially designed for training purposes remarkably aligns with effective pattern implementation, offering a more ‘mechanical’ approach. Let's explore together how Object Calisthenics can elevate the design of your tactical DDD patterns, offering concrete help for those venturing into DDD for the first time!
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
SAP Sapphire 2024 - ASUG301 building better apps with SAP Fiori.pdfPeter Spielvogel
Building better applications for business users with SAP Fiori.
• What is SAP Fiori and why it matters to you
• How a better user experience drives measurable business benefits
• How to get started with SAP Fiori today
• How SAP Fiori elements accelerates application development
• How SAP Build Code includes SAP Fiori tools and other generative artificial intelligence capabilities
• How SAP Fiori paves the way for using AI in SAP apps
zkStudyClub - Reef: Fast Succinct Non-Interactive Zero-Knowledge Regex ProofsAlex Pruden
This paper presents Reef, a system for generating publicly verifiable succinct non-interactive zero-knowledge proofs that a committed document matches or does not match a regular expression. We describe applications such as proving the strength of passwords, the provenance of email despite redactions, the validity of oblivious DNS queries, and the existence of mutations in DNA. Reef supports the Perl Compatible Regular Expression syntax, including wildcards, alternation, ranges, capture groups, Kleene star, negations, and lookarounds. Reef introduces a new type of automata, Skipping Alternating Finite Automata (SAFA), that skips irrelevant parts of a document when producing proofs without undermining soundness, and instantiates SAFA with a lookup argument. Our experimental evaluation confirms that Reef can generate proofs for documents with 32M characters; the proofs are small and cheap to verify (under a second).
Paper: https://eprint.iacr.org/2023/1886
In his public lecture, Christian Timmerer provides insights into the fascinating history of video streaming, starting from its humble beginnings before YouTube to the groundbreaking technologies that now dominate platforms like Netflix and ORF ON. Timmerer also presents provocative contributions of his own that have significantly influenced the industry. He concludes by looking at future challenges and invites the audience to join in a discussion.
Climate Impact of Software Testing at Nordic Testing DaysKari Kakkonen
My slides at Nordic Testing Days 6.6.2024
Climate impact / sustainability of software testing discussed on the talk. ICT and testing must carry their part of global responsibility to help with the climat warming. We can minimize the carbon footprint but we can also have a carbon handprint, a positive impact on the climate. Quality characteristics can be added with sustainability, and then measured continuously. Test environments can be used less, and in smaller scale and on demand. Test techniques can be used in optimizing or minimizing number of tests. Test automation can be used to speed up testing.
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
2. Alaska Park Science, Volume 8, Issue 1
The Colors of the Aurora
By Dirk Lummerzheim for his duties as a ruler. reflected by ice crystals in the air, the glow
The term aurora borealis originated of glacier ice near the pole, or a light
Abstract in the 1600s, when Galileo combined the emanating from the edge of Earth. In the
The aurora has fascinated observers word “aurora,” the Latin word for “dawn,” eighteenth century, scientists discovered
at high latitudes for centuries, but only with the term “boreal,” the Greek word a connection between the aurora and
recently have we begun to understand the for “north.” Aurora also appears in the disturbances in Earth’s magnetic field
processes that cause it. This article discuss- southern hemisphere, where it is called and associated aurora with sunspots.
es the mechanisms that are responsible for the “aurora australis.” Since there is very But it took until the end of the twentieth
the colors of the aurora. Observations of little populated landmass at high southern century before a satisfactory explanation of
color balance in aurora can provide us with latitudes, there are no known historical and the aurora, its colors, and the mechanisms
information about the physical processes mythological references to the southern behind it emerged.
in the near Earth space that cause aurora. aurora. Although the native people from
High-resolution spectral observations let New Zealand must have seen aurora on The Processes that Cause Aurora
us understand how the upper atmosphere occasion, Captain Cook is considered the The light of the aurora is generated by
is affected by aurora. discoverer of the aurora australis; he saw it atoms and molecules of the air when they
in 1773 on his voyage around the southern are struck with energetic particles from
A Brief History of Understanding tip of South America. space. These energetic particles come from
the Aurora At mid-latitudes, people rarely see the the volume of space just above the aurora,
Descriptions of aurora, or the northern lights. Aurora is visible at mid- and are accelerated by plasma physics
northern lights, go as far back as latitudes during the largest magnet- processes that are still under investi-
written history. 2,300 years ago, Aristotle ic storms, but it is dominated by red gation. But we do have a fairly good
saw curtains of light in the sky and called colors. In ancient times when the understanding of the general processes
the phenomena “chasmata” to indicate that aurora appeared overhead, people often and the flow of energy that feeds these
the cause was cracks in the sky, allowing associated the aurora with good or bad processes. We can model the aurora and
in light from beyond the heavenly sphere. omens and sometimes considered it a are now gaining the understanding to
In his book Majestic Lights, Eather (1980) manifestation of activities of heavenly forecast its appearance (Lummerzheim
presents several quotes from the Bible that spirits or gods. The peoples who lived at 2007).
most likely refer to aurora. high latitude and who had a regular display Charged particles, like those that cause
The first recorded use of the words of the aurora held similar beliefs. the aurora, can generally only travel along
“northern lights” to describe the aurora In the Middle Ages, scientists came the direction of the magnetic field. This
Figure 1. Multi-colored aurora over Klondike
Gold Rush National Historical Park near
was in 1230, in a book titled The King’s up with other guesses as to what was shapes the aurora into curtain and ray-
White Pass in Southeast Alaska. Mirror. The author wrote the book to pre- behind the northern lights: they suggested like structures (Figure 2). Following the
Photograph courtesy of Michael Klensch pare Norwegian King Magnus Lagabøte that the light of the aurora was sunlight magnetic field up from the aurora, we
37
3. The Colors of the Aurora
get to the auroral acceleration region,
Photograph courtesy of D. Lummerzheim
Photograph courtesy of Michael Klensch
about 620-6,200 miles (1,000-10,000
km) above the earth. The smaller scale
structures like rays, small curls, and thin
curtains shown in Figure 3 represent
structures in the acceleration processes.
This region is connected to the outer
magnetosphere by electric currents. Large-
scale structures, like multiple parallel arcs
Figure 2. Green curtains and rays above (Figures 4-5) and spirals that fill almost
the Brooks Range and Gates of the Arctic
National Park.
the entire sky (Figure 6) show the spatial
pattern of these currents. The magneto-
sphere is the region of space around Earth
Photograph courtesy of Poul Jensen
that is controlled by Earth’s magnetic field.
Its diameter is about 30 Earth radii, and out-
side of the magnetosphere is the solar wind.
The magnetosphere forms an obstacle for
the solar wind, which has to flow around it.
This interaction of the solar wind with the
magnetosphere provides the energy that
eventually accelerates the auroral electrons
Figure 3. Small-scale structure in aurora in the inner magnetosphere. Strong solar
shows as thin curtains and small rays and activity causes strong variations in the solar
curls over Fairbanks, Alaska. This structure wind; byproducts of this space weather are
is related to the auroral acceleration process
directly above the atmosphere. therefore geomagnetic storms and aurora.
Light Emission in Aurora
Photograph courtesy of Carl Johnson
When energetic electrons strike an
atom or molecule, they slow down and
transfer some of their energy to that atom
or molecule. The molecules can store this
energy only for a very short time, and then
radiate the energy away as light. Some
molecules get dissociated into atoms in
this process, and some molecules and
Figure 4. Large-scale structure in aurora atoms get ionized. At the altitude where
shows as large folds and parallel curtains aurora occurs, above about 62 miles (100
over Gates of the Arctic National Park and
Preserve. This structure reflects the pro-
km), the air is thin enough that oxygen can
cesses in the magnetosphere where large exist in atomic form, while the air that we
currents transport energy into the auroral Figure 5. Several parallel curtains above Rock Creek in Denali National Park and Preserve. breathe contains only molecular oxygen.
region. Note comet Hale-Bopp in the lower right hand corner.
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4. Alaska Park Science, Volume 8, Issue 1
During the day, the ultraviolet sunlight 0.7-second lifetime allows radiation. This auroral brightness depends on the rate of
Photograph courtesy of Poul Jensen
splits the molecular oxygen into atoms, determines the bottom edge of the green incoming auroral electrons. In analogy to
while at night the aurora continues this emission in aurora. electric currents we can say that the color
process. However, the auroral electrons some- tells us the voltage, the brightness tells us
When an atom or molecule emits times have enough energy to give them the the current.
light as a photon, to rid itself of its excess punch to penetrate deeper than that into During very large magnetic storms
energy, that photon has a wavelength the atmosphere. When that happens, only the aurora is visible from mid and low
that is characteristic for that atom. We emissions with a much shorter lifetime latitudes. It is common to have very bright
perceive wavelength as color. Laboratory are possible. The most abundant gas is red auroral displays during such large
experiments can reproduce these light- molecular nitrogen, and it radiates storms. Notable were the magnetic storms Figure 6. A large spiral that fills a large por-
tion of the sky in this extreme wide-angle
emitting processes by forcing a current promptly in deep blue and red colors. on Halloween and late November in 2003, photo from Ester Dome near Fairbanks,
through an evacuated glass tube that Mixing these together gives purple. The when red aurora was seen above the Medi- Alaska.
contains a small amount of a selected gas. bottom edge of a green auroral curtain terranean, Florida, and the entire U.S. The
Photograph courtesy of Poul Jensen
The study of these light-emitting processes gets this purple color when auroral elec- outstanding brightness and dominance of
led to the understanding of atoms early in trons are accelerated to very high energy high altitude red oxygen emissions indi-
the twentieth century, and to the discovery (Figures 7-8). cate that during such storms the magne-
of quantum mechanics. Because each type On occasion the aurora gets a deep red tosphere has very large currents flowing,
of atom or molecule emits colors unique color. This comes from higher altitudes, while the auroral acceleration only pro-
to it, we can use the colors of the aurora to around 120-180 miles (200-300 km). It is duces low energy electrons.
determine the atmospheric composition at again the oxygen atom that is responsible In addition to looking at the color
the auroral altitude. for this color. The oxygen atom has an balance and brightness, we can measure
The time that a molecule or atom can excited state for this red line emission the wavelength of individual emission lines
Figure 7. Intense aurora develops a purple
store the energy that it gained in a colli- with a mean lifetime of 100 seconds, and in the aurora with very high accuracy. This border below the green curtains in this fish
sion is very short, typically between 1/1000 only at very high altitudes are collisions allows us to determine the Doppler shift eye view of almost the entire sky above
and less than 1/1,000,000 of a second. infrequent enough to allow this radiation of emission lines. The Doppler effect for Fairbanks, Alaska. Note the Big Dipper near
the zenith.
Atomic oxygen is one notable exception, to be emitted (Figure 9). Since the long life- light emission causes a shortening of the
and the excited state that causes the most time of the oxygen red line also allows the wavelength of the emission if the emitting
Photograph courtesy of Poul Jensen
common auroral emission, the green line, aurora to move before it radiates, the de- atom or molecule is moving toward the
has a lifetime of 0.7 seconds. When an tailed structure in auroral curtains is also observer, and a lengthening of the wave-
excited atom takes that long to radiate washed out in these emissions (Figure 10). length if it is moving away. A shorter wave-
away the internally stored energy, other length means a color closer to the blue
processes, chemical reactions or collisions, Relating the Color to Physical end of the spectrum; longer wavelength
compete with the radiation process for Processes means a shift to red. In aurora, these shifts
that energy. The denser the air is, the more The energy of auroral electrons are miniscule, but can be observed with
frequent are the collisions between the determines how deep into the atmosphere high spectral resolution instruments, in
atoms and molecules. Below the altitude these particles penetrate. Since auroral particular Fabry-Perot interferometers Figure 8. High-energy auroral electrons
of about 59 miles (95 km), collisions are so emissions are characteristic of the altitude (FPI). Because the red and green line above Fairbanks, Alaska penetrate deep
enough to cause the purple lower border of
frequent that the green oxygen line has no where they originate, we can use the color emissions from atomic oxygen are so long the green curtains. High-energy aurora also
chance to be emitted. All the energy that is balance of the aurora to determine the lived, they are good candidates for FPI produces highly structured and very thin
put into the oxygen atom is lost before the energy of the auroral electrons. The observations. The long lifetime ensures curtains that move fast. Short exposure times
are necessary to resolve these structures.
39
5. The Colors of the Aurora
Photograph courtesy of Michael Klensch
Photograph courtesy of Michael Klensch
Figure 10. The diffuse looking red aurora
above Klondike Gold Rush National Historical
Park near White Pass comes from long-lived
oxygen atoms at high altitudes. The structure
of the curtain below is lost in the red aurora
because the excited atoms can move with
the wind before emitting light.
Image from Conde et al. 2008
Figure 9. Red aurora above the Sawtooth Mountains near Klondike Gold Rush National Historical Park and Skagway, Alaska Figure 11. The wind vectors at 150 miles (240
km) altitude drawn over a composite all-sky
image of the green and red oxygen emission.
Through its interaction with the atmosphere,
the aurora modifies the wind direction and
speed in the upper atmosphere.
40
6. Alaska Park Science, Volume 8, Issue 1
us much about the physical processes that
Photograph courtesy of Michael Klensch
Photograph courtesy of Jan Curtis
cause aurora and the effects that aurora
has on the upper atmosphere. The color
balance tells us the altitude of aurora.
We can relate that to the processes that
accelerate auroral electrons in the
near earth space, and we can see the
evolution of electric currents that flow
in the magnetosphere. High-resolution
spectroscopy lets us see the wind in the
upper atmosphere and how it is changed
by the aurora. High altitude blue aurora
tells us that ions that are generated in the
aurora are pulled out of the atmosphere
into space. And the colors themselves tell
us the composition of the atmospheric gas
at the altitude of the aurora.
Figure 12. Aurora over Klondike Gold Rush National Historical Park as seen from Yukon,
Canada.
Acknowledgements
that the atoms are drifting with the wind, The top end of the auroral curtains Figure 13. This photo is taken shortly after
I would like to thank Mark Conde sunset, when the sun illuminates the upper
and their velocity is not affected by the and rays sometimes show a deep blue
for suggestions and comments, and the part of the aurora. Ions that are produced
collision with the auroral electron that color. This is indicative of still another light by the aurora at these altitudes scatter the
people who have provided the photo-
caused the excitation in the first place. The emission process. The auroral electrons blue part of the sunlight, causing the upper
graphs of the aurora for this article: Poul edge of the aurora to look blue.
small shift in wavelength can thus be used not only produce light emitting excited
Jensen at the Geophysical Institute at
to measure the ambient wind at the alti- atoms and molecules, they also ionize
the University of Alaska Fairbanks; Mi-
tude of the aurora. some molecules. These ions can then be
chael Klensch from Skagway, Alaska; Carl
These FPI wind observations only give pulled upward by electric fields in the REFERENCES
Johnson from Anchorage, Alaska; and
the component of the wind velocity along aurora and reach altitudes high enough that
Jan Curtis from Oregon. More aurora Conde, M.G., C. Anderson, and C. Ander-
the line of sight, the component toward under some conditions they will be son. 2008.
photos by these photographers can be
or away from the observing station. By exposed to sunlight. This sunlight then New results from the Poker Flat all-sky
found at their websites:
using model constraints or by placing scatters off these ions. There exists a blue imaging Fabry-Perot spectrometer.
three such instruments in separate loca- emission of the molecular nitrogen ion that www.gfy.ku.dk/~flyvholm (P. Jensen) CEDAR workshop, Zermatt, UT.
tions we can reconstruct the actual wind is particularly strong in scattering sunlight, www.muk.uni-hannover.de/~theusner/
Eather, R.H. 1980.
vector by measuring three components of it. which is why we see a blue upper end of polarlicht/ (M. Theusner) Majestic Lights: The Aurora in Science,
Figure 11 shows a composite of the auroral the auroral curtains (Figure 13). www.alpenglowphoto.net (M. Klensch) History, and the Arts. American Geo-
brightness with the deduced wind physical Union. Washington DC.
climate.gi.alaska.edu/Curtis/aurora/
vectors at 150 miles (240 km) altitude Putting it all Together
aurora.html (J. Curtis) Lummerzheim, D. 2007.
superimposed. This example (Conde et al. The observations of the colors of
www.carljohnsonphoto.com (C. Johnson) Modeling and forecasting aurora.
2008) shows that the wind is affected by the the aurora, either in a broader sense by
Computing in Science and Engineering
aurora as the direction and speed changes looking at the overall color balance, or by
9(5):53-61.
right at the position of the auroral curtain. detailed spectroscopic methods, can teach
41