Author name code: delzanna
ADS astronomy entries on 2022-09-14
author:Del Zanna, Giulio
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Title: Defining the Middle Corona
Authors: West, Matthew J.; Seaton, Daniel B.; Wexler, David B.;
Raymond, John C.; Del Zanna, Giulio; Rivera, Yeimy J.; Kobelski,
Adam R.; DeForest, Craig; Golub, Leon; Caspi, Amir; Gilly, Chris R.;
Kooi, Jason E.; Alterman, Benjamin L.; Alzate, Nathalia; Banerjee,
Dipankar; Berghmans, David; Chen, Bin; Chitta, Lakshmi Pradeep; Downs,
Cooper; Giordano, Silvio; Higginson, Aleida; Howard, Russel A.; Mason,
Emily; Mason, James P.; Meyer, Karen A.; Nykyri, Katariina; Rachmeler,
Laurel; Reardon, Kevin P.; Reeves, Katharine K.; Savage, Sabrina;
Thompson, Barbara J.; Van Kooten, Samuel J.; Viall, Nicholeen M.;
Vourlidas, Angelos
Bibcode: 2022arXiv220804485W
Altcode:
The middle corona, the region roughly spanning heliocentric altitudes
from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential
physical transitions and processes that govern the behavior of
coronal outflow into the heliosphere. Eruptions that could disrupt
the near-Earth environment propagate through it. Importantly, it
modulates inflow from above that can drive dynamic changes at lower
heights in the inner corona. Consequently, this region is essential
for comprehensively connecting the corona to the heliosphere and for
developing corresponding global models. Nonetheless, because it is
challenging to observe, the middle corona has been poorly studied by
major solar remote sensing missions and instruments, extending back to
the Solar and Heliospheric Observatory (SoHO) era. Thanks to recent
advances in instrumentation, observational processing techniques,
and a realization of the importance of the region, interest in the
middle corona has increased. Although the region cannot be intrinsically
separated from other regions of the solar atmosphere, there has emerged
a need to define the region in terms of its location and extension
in the solar atmosphere, its composition, the physical transitions
it covers, and the underlying physics believed to be encapsulated by
the region. This paper aims to define the middle corona and give an
overview of the processes that occur there.
Title: Multiwavelength Observations by XSM, Hinode, and SDO of an
Active Region. Chemical Abundances and Temperatures
Authors: Del Zanna, G.; Mondal, B.; Rao, Y. K.; Mithun, N. P. S.;
Vadawale, S. V.; Reeves, K. K.; Mason, H. E.; Sarkar, A.; Janardhan,
P.; Bhardwaj, A.
Bibcode: 2022ApJ...934..159D
Altcode: 2022ApJ...934..159Z; 2022arXiv220706879D
We have reviewed the first year of observations of the Solar X-ray
Monitor (XSM) on board Chandrayaan-2 and the available multiwavelength
observations to complement the XSM data, focusing on the Solar
Dynamics Observatory AIA and Hinode XRT and EIS observations. XSM has
provided disk-integrated solar spectra in the 1-15 keV energy range,
observing a large number of microflares. We present an analysis of
multiwavelength observations of AR 12759 during its disk crossing. We
use a new radiometric calibration of EIS to find that the quiescent
active region (AR) core emission during its disk crossing has a
distribution of temperatures and chemical abundances that does
not change significantly over time. An analysis of the XSM spectra
confirms the EIS results and shows that the low first ionization
potential (FIP) elements are enhanced compared to their photospheric
values. The frequent microflares produced by the AR did not affect the
abundances of the quiescent AR core. We also present an analysis of
one of the flares it produced, SOL2020-04-09T09:32. The XSM analysis
indicates isothermal temperatures reaching 6 MK. The lack of very
high-T emission is confirmed by AIA. We find excellent agreement
between the observed XSM spectrum and the one predicted using an AIA
DEM analysis. In contrast, the XRT Al-poly/Be-thin filter ratio gives
lower temperatures for the quiescent and flaring phases. We show that
this is due to the sensitivity of this ratio to low temperatures,
as the XRT filter ratios predicted with a DEM analysis based on EIS
and AIA give values in good agreement with the observed ones.
Title: Magnetoseismology for the solar corona: from 10 Gauss to
coronal magnetograms
Authors: Yang, Zihao; Gibson, Sarah; He, Jiansen; Del Zanna, Giulio;
Tomczyk, Steven; Morton, Richard; McIntosh, Scott; Wang, Linghua;
Karak, Bidya Binay; Samanta, Tanmoy; Tian, Hui; Chen, Yajie; Bethge,
Christian; Bai, Xianyong
Bibcode: 2022cosp...44.2490Y
Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Title: Diagnostics of non-Maxwellian electron distributions in solar
active regions from Fe XII lines observed by Hinode/EIS and IRIS
Authors: Del Zanna, G.; Polito, V.; Dudík, J.; Testa, P.; Mason,
H. E.; Dzifčáková, E.
Bibcode: 2022arXiv220707026D
Altcode:
We present joint Hinode/EIS and IRIS observations of Fe XII lines
in active regions, both on-disk and off-limb. We use an improved
calibration for the EIS data, and find that the 192.4 A / 1349 A
observed ratio is consistent with the values predicted by CHIANTI and
the coronal approximation in quiescent areas, but not in all active
region observations, where the ratio is often lower than expected
by up to a factor of about two. We investigate a number of physical
mechanisms that could affect this ratio, such as opacity and absorption
from cooler material. We find significant opacity in the EIS Fe XII
193 and 195 A lines, but not in the 192.4 A line, in agreement with
previous findings. As we cannot rule out possible EUV absorption by
H, He and He II in the on-disk observations, we focus on an off-limb
observation where such absorption is minimal. After considering these,
as well as possible non-equilibrium effects, we suggest that the most
likely explanation for the observed low Fe XII 192.4 A / 1349 A ratio
is the presence of non-Maxwellian electron distributions in the active
regions. This is in agreement with previous findings based on EIS and
IRIS observations independently.
Title: Large-scale Multiconfiguration Dirac-Hartree-Fock Calculations
for Astrophysics: C-like Ions from O III to Mg VII
Authors: Li, J. Q.; Zhang, C. Y.; Del Zanna, G.; Jönsson, P.;
Godefroid, M.; Gaigalas, G.; Rynkun, P.; Radžiūtė, L.; Wang, K.;
Si, R.; Chen, C. Y.
Bibcode: 2022ApJS..260...50L
Altcode:
Large-scale multiconfiguration Dirac-Hartree-Fock calculations
are provided for the n ≤ 5 states in C-like ions from O III to
Mg VII. Electron correlation effects are accounted for by using
large configuration state function expansions, built from sets of
orbitals with principal quantum numbers n ≤ 10. An accurate and
complete data set of excitation energies, wavelengths, radiative
transition parameters, and lifetimes is offered for the 156 (196, 215,
272, 318) lowest states of the 2s 22p 2, 2s2p
3, 2p 4, 2s 22p3s, 2s 22p3p,
2s 22p3d, 2s2p 23s, 2s2p 23p, 2s2p
23d, 2p 33s, 2p 33p, 2p 33d,
2s 22p4s, 2s 22p4p, 2s 22p4d,
2s 22p4f, 2s2p 24s, 2s2p 24p,
2s2p 24d, 2s2p 24f, 2s 22p5s,
2s 22p5p, 2s 22p5d, 2s 22p5f,
and 2s 22p5g configurations in O III (F IV, Ne V, Na VI,
Mg VII). By comparing available experimental wavelengths with the
MCDHF results, the previous line identifications for the n = 5, 4, 3
→ n = 2 transitions of Na VI in the X-ray and EUV wavelength range
are revised. For several previous identifications discrepancies are
found, and tentative new (or revised) identifications are proposed. A
consistent atomic data set including both energy and transition data
with spectroscopic accuracy is provided for the lowest hundreds of
states for C-like ions from O III to Mg VII.
Title: Helium line emissivities for nebular astrophysics
Authors: Del Zanna, G.; Storey, P. J.
Bibcode: 2022MNRAS.513.1198D
Altcode: 2022MNRAS.tmp..905D; 2022arXiv220401537D
We present the results of several collisional-radiative models
describing optically thin emissivities of the main lines in neutral
helium formed by recombination, for a grid of electron temperatures
and densities, typical of H II regions and planetary nebulae. Accurate
emissivities are required for example to measure the helium abundance
in nebulae and as a consequence its primordial value. We compare our
results with those obtained by previous models, finding significant
differences, well above the target accuracy of 1 per cent. We discuss
in some detail our chosen set of atomic rates and the differences
with those adopted by previous models. The main differences lie in
the treatment of electron and proton collision rates and we discuss
which transitions are least sensitive to the choice of these rates and
therefore best suited to high-precision abundance determinations. We
have focused our comparisons on the case B approximation where only
He and He+ are considered, but also present results of full
models including the bare nuclei, photoexcitation, and photoionization,
and either black-body or observed illuminating spectrum in the case
of the Orion nebula, to indicate which spectral lines are affected
by opacity. For those transitions, accurate radiative transfer
calculations should be performed. We provide tables of emissivities for
all transitions within n ≤ 5 and all those between the n ≤ 5 and n'
≤ 25 states, in the log Te (K) = 103.0(0.1)4.6
and log Ne (cm-3) = 102(0.5)6 ranges,
and a FORTRAN code to interpolate to any Te, Ne
within these ranges.
Title: Diagnostics of Non-Maxwellian Electron Distributions in
Solar Active Regions from Fe XII Lines Observed by the Hinode
Extreme Ultraviolet Imaging Spectrometer and Interface Region
Imaging Spectrograph
Authors: Del Zanna, G.; Polito, V.; Dudík, J.; Testa, P.; Mason,
H. E.; Dzifčáková, E.
Bibcode: 2022ApJ...930...61D
Altcode:
We present joint Hinode Extreme Ultraviolet Imaging Spectrometer
(EIS) and Interface Region Imaging Spectrograph (IRIS) observations
of Fe XII lines in active regions, both on-disk and off-limb. We use
an improved calibration for the EIS data, and find that the 192.4
Å/1349 Å observed ratio is consistent with the values predicted by
CHIANTI and the coronal approximation in quiescent areas, but not in
all active-region observations, where the ratio is often lower than
expected by up to a factor of about two. We investigate a number of
physical mechanisms that could affect this ratio, such as opacity and
absorption from cooler material. We find significant opacity in the EIS
Fe XII 193 and 195 Å lines, but not in the 192.4 Å line, in agreement
with previous findings. As we cannot rule out possible EUV absorption by
H, He, and He II in the on-disk observations, we focus on an off-limb
observation where such absorption is minimal. After considering these,
as well as possible nonequilibrium effects, we suggest that the most
likely explanation for the observed low Fe XII 192.4 Å/1349 Å ratio
is the presence of non-Maxwellian electron distributions in the active
regions. This is in agreement with previous findings based on EIS and
IRIS observations independently.
Title: The centre-to-limb variation of non-thermal velocities using
IRIS Si IV
Authors: Rao, Yamini K.; Del Zanna, Giulio; Mason, Helen E.
Bibcode: 2022MNRAS.511.1383R
Altcode: 2022arXiv220107290R; 2022MNRAS.tmp..149R
We study the non-thermal velocities in the quiet Sun using various
high spatial, temporal, and spectral resolution observations from the
Interface Region Imaging Spectrograph (IRIS). We focus our analysis on
the transition region using the optically thin line (Si IV 1393.7 Å),
and select line profiles that are nearly Gaussian. We find evidence
of a centre-to-limb variation using different observations having
different exposure times, ranging from 5 to 30 s. The distribution of
non-thermal velocities close to the limb is observed to peak around
20 km s-1 while the disc observations show a peak around
15 km s-1. The distributions are also different. The
overall variation in the non-thermal velocities are correlated with
the intensity of the line, as found previously. The on-disc velocities
are smaller than most previous observations. In general, we find that
the non-thermal velocities are independent of the selected exposure
times. The Si IV lines did not seem to exhibit any significant opacity
effects. We conclude that these Doppler motions are mostly transverse
to the radial direction. The possibility of swaying/torsional motions
leading to such variations are validated from these IRIS observations.
Title: Magnetoseismology for the solar corona: from 10 Gauss to
coronal magnetograms
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Bai,
Xianyong; Wang, Linghua
Bibcode: 2021AGUFMSH12C..07Y
Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Title: Benchmarking Multiconfiguration Dirac-Hartree-Fock Calculations
for Astrophysics: Si-like Ions from Cr XI to Zn XVII
Authors: Zhang, X. H.; Del Zanna, G.; Wang, K.; Rynkun, P.; Jönsson,
P.; Godefroid, M.; Gaigalas, G.; Radžiūtė, L.; Ma, L. H.; Si, R.;
Xiao, J.; Chen, Z. B.; Yan, J.; Wu, Y.; Chen, C. Y.
Bibcode: 2021ApJS..257...56Z
Altcode:
The multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic
configuration interaction methods are used to provide excitation
energies, lifetimes, and radiative transition data for the 604 (699,
702, 704, 704, 704, and 699) lowest levels of the 3s 23p
2, 3s3p 3, 3s 23p3d, 3p 4,
3s3p 23d, 3s 23d 2, 3p 33d,
3s3p3d 2, 3s3d 3, 3p3d 3, 3p
23d 2, 3s 23p4s, 3s 23p4p,
3s 23p4d, 3s 23p4f, 3s3p 24s,
3s3p 24p, 3s3p 24d, 3s3p 24f,
3s 23d4s, 3s 23d4p, 3p 34s, 3p
34p, 3s3p3d4s, 3s 23p5s, and 3s 23p5p
configurations in Cr XI, (Mn XII, Fe XIII, Co XIV, Ni XV, Cu XVI, and
Zn XVII). Previous line identifications of Fe XIII and Ni XV in the EUV
and X-ray wavelength ranges are reviewed by comprehensively comparing
the MCDHF theoretical results with available experimental data. Many
recent identifications of Fe XIII and Ni XV lines are confirmed,
and several new identifications for these two ions are proposed. A
consistent atomic data set with spectroscopic accuracy is provided for
the lowest hundreds of levels for Si-like ions of iron-group elements of
astrophysical interest, for which experimental values are scarce. The
uncertainty estimation method suggested by Kramida, applied to the
comparison of the length and velocity line strength values, is used
for ranking the transition data. The correlation of the latter with
the gauge dependency patterns of the line strengths is investigated.
Title: Modeling Inner Proton Belt Variability at Energies 1 to 10
MeV Using BAS-PRO
Authors: Lozinski, Alexander R.; Horne, Richard B.; Glauert, Sarah A.;
Del Zanna, Giulio; Claudepierre, Seth G.
Bibcode: 2021JGRA..12629777L
Altcode:
Geomagnetically trapped protons forming Earth's proton radiation
belt pose a hazard to orbiting spacecraft. In particular, solar
cell degradation is caused by non-ionising collisions with protons at
energies of several megaelectron volts (MeV), which can shorten mission
lifespan. Dynamic enhancements in trapped proton flux following solar
energetic particle events have been observed to last several months,
and there is a strong need for physics-based modeling to predict the
impact on spacecraft. However, modeling proton belt variability at
this energy is challenging because radial diffusion coefficients are
not well constrained. We address this by using the British Antarctic
Survey proton belt model BAS-PRO to perform 3D simulations of the
proton belt in the region 1.15 ≤ L ≤ 2 from 2014 to 2018. The
model is driven by measurements from the Radiation Belt Storm Probes
Ion Composition Experiment and Magnetic Electron Ion Spectrometer
instruments carried by the Van Allen Probe satellites. To investigate
sensitivity, simulations are repeated for three different sets of
proton radial diffusion coefficients DLL taken from previous
literature. Comparing the time evolution of each result, we find that
solar cycle variability can drive up to a ∼75% increase in 7.5 MeV
flux at L = 1.3 over four years due to the increased importance of
collisional loss at low energies. We also show how the anisotropy of
proton pitch angle distributions varies with L and energy, depending
on DLL. However we find that phase space density can
vary by three orders of magnitude at L = 1.4 and μ = 20 MeV/G due
to uncertainty in DLL, highlighting the need to better
constrain proton DLL at low energy.
Title: Modelling Inner Proton Belt Variability at Energies 1 to
10MeV using BAS-PRO
Authors: Lozinski, Alexander; Horne, Richard; Glauert, Sarah; Del
Zanna, Giulio; Claudepierre, Seth
Bibcode: 2021AGUFMSM12A..06L
Altcode:
Geomagnetically trapped protons forming Earth's proton radiation
belt pose a hazard to orbiting spacecraft. In particular, solar
cells are prone to degradation caused by non-ionising collisions with
protons in the energy range of several megaelectron volts, which can
ultimately shorten the lifespan of a mission. Dynamic enhancements
in trapped proton flux following solar energetic particle events have
been observed to last several months, and there is a strong need for
physicsbased modelling in order to predict the impact such changes may
have on orbiting spacecraft. To address this, we perform 3D dynamic
simulations of the proton radiation belt over four years from 2014 to
2018 in the region L = 1.15 to 2. Simulations are performed using the
British Antarctic Survery proton belt model BAS-PRO, which is driven at
the outer boundary using measurements of protons from sub-MeV to 20MeV
taken by the RBSPICE and MagEIS instruments on the now retired Van
Allen Probe satellites. We investigate the sensitivity of modelling
results to the selection of proton radial diffusion coefficients
by repeating a simulation for three sets of DLL values taken from
previous literature. We demonstrate how higher DLL allows radial
diffusion to control variability at lower L. On the other hand we show
that changes in coulomb collisional loss rates, driven by solar cycle,
cause higher variability in lower energy proton flux, resulting in solar
cycle variations of equatorially mirroring MeV protons at L=1.3. We
discuss the implications of these results on solar cell degradation
for spacecraft in LEO orbits, which will experience variations in the
rate of non-ionising dose driven partly by the solar cycle variability.
Title: Preliminary Results from the Marshall Grazing Incidence X-ray
Spectrometer (MaGIXS)
Authors: Winebarger, Amy; Savage, Sabrina; Kobayashi, Ken; Champey,
Patrick; Golub, Leon; Walsh, Robert; Athiray, P. S.; Bradshaw, Stephen;
Cheimets, Peter; Cirtain, Jonathan; DeLuca, Edward; Del Zanna, Giulio;
Mason, Helen; McKenzie, David; Ramsey, Brian; Reeves, Katharine;
Testa, Paola; Vigil, Genevieve; Warren, Harry
Bibcode: 2021AGUFMSH51A..06W
Altcode:
Coronal heating mechanisms are notoriously difficult to constrain with
current observations. We present new observations from an instrument
designed to measure a critical diagnostic of the frequency heating
events in active regions. The Marshall Grazing Incidence X-ray
Spectrometer (MaGIXS) is a sounding rocket mission that aims to
observe the soft x-ray solar spectrum (0.6 2.5 nm) with both spatial
and spectral resolution. This wavelength range has several high
temperature and abundance diagnostics that can be used to infer the
coronal heating frequency. MaGIXS will observe the Sun through a 12
x 33 slot, producing ``overlappograms, where the spatial and spectral
information are overlapped and must be unfolded. In this presentation,
I will report on the MaGIXS launch and data collection and provide
preliminary analysis of MaGIXS observations.
Title: Exploring the middle corona: new instrumentation to address
science questions critical to understanding the thermal structure
and dynamic evolution of the middle corona
Authors: DeLuca, Edward; Winebarger, Amy; Reeves, Katharine; Golub,
Leon; Samra, Jenna; Madsen, Chad; Rivera, Yeimy; Karna, Nishu;
Savage, Sabrina; Seaton, Daniel; West, Matthew; Downs, Cooper; Del
Zanna, Giulio
Bibcode: 2021AGUFMSH25F2150D
Altcode:
The global structure of the largely unexplored middle corona determines
the physical properties of the inner heliosphere, affects the formation
and acceleration of the solar wind, and controls the dynamics of
eruptive events. Tracing the short and long term global evolution
of the extended corona, identifying changes in corona/heliosphere
connectivity and following the dynamic evolution of eruptive events
in this unexplored region will provide observational data that will
clarify how the corona transitions from closed to open, illuminate the
genesis of coronal mass ejections, and provide input for the design
of the next generation of physics based space weather forecasts. This
poster outlines several critical science questions and identifies the
measurements that are required to make substantial progress towards
addressing the questions. We review and discuss the instrumentation
necessary to capture the observations needed for meaningful progress
in this area as well as the role of simulations in the interpretation
of the observations.
Title: Linking the Sun to the Heliosphere Using Composition Data
and Modelling
Authors: Parenti, Susanna; Chifu, Iulia; Del Zanna, Giulio; Edmondson,
Justin; Giunta, Alessandra; Hansteen, Viggo H.; Higginson, Aleida;
Laming, J. Martin; Lepri, Susan T.; Lynch, Benjamin J.; Rivera, Yeimy
J.; von Steiger, Rudolf; Wiegelmann, Thomas; Wimmer-Schweingruber,
Robert F.; Zambrana Prado, Natalia; Pelouze, Gabriel
Bibcode: 2021SSRv..217...78P
Altcode: 2021arXiv211006111P
Our understanding of the formation and evolution of the corona and
the heliosphere is linked to our capability of properly interpret the
data from remote sensing and in-situ observations. In this respect,
being able to correctly connect in-situ observations with their source
regions on the Sun is the key for solving this problem. In this work
we aim at testing a diagnostics method for this connectivity.
Title: The high-energy Sun - probing the origins of particle
acceleration on our nearest star
Authors: Matthews, S. A.; Reid, H. A. S.; Baker, D.; Bloomfield, D. S.;
Browning, P. K.; Calcines, A.; Del Zanna, G.; Erdelyi, R.; Fletcher,
L.; Hannah, I. G.; Jeffrey, N.; Klein, L.; Krucker, S.; Kontar, E.;
Long, D. M.; MacKinnon, A.; Mann, G.; Mathioudakis, M.; Milligan,
R.; Nakariakov, V. M.; Pesce-Rollins, M.; Shih, A. Y.; Smith, D.;
Veronig, A.; Vilmer, N.
Bibcode: 2021ExA...tmp..135M
Altcode:
As a frequent and energetic particle accelerator, our Sun provides
us with an excellent astrophysical laboratory for understanding
the fundamental process of particle acceleration. The exploitation
of radiative diagnostics from electrons has shown that acceleration
operates on sub-second time scales in a complex magnetic environment,
where direct electric fields, wave turbulence, and shock waves all
must contribute, although precise details are severely lacking. Ions
were assumed to be accelerated in a similar manner to electrons, but
γ-ray imaging confirmed that emission sources are spatially separated
from X-ray sources, suggesting distinctly different acceleration
mechanisms. Current X-ray and γ-ray spectroscopy provides only a basic
understanding of accelerated particle spectra and the total energy
budgets are therefore poorly constrained. Additionally, the recent
detection of relativistic ion signatures lasting many hours, without
an electron counterpart, is an enigma. We propose a single platform
to directly measure the physical conditions present in the energy
release sites and the environment in which the particles propagate and
deposit their energy. To address this fundamental issue, we set out
a suite of dedicated instruments that will probe both electrons and
ions simultaneously to observe; high (seconds) temporal resolution
photon spectra (4 keV - 150 MeV) with simultaneous imaging (1 keV -
30 MeV), polarization measurements (5-1000 keV) and high spatial and
temporal resolution imaging spectroscopy in the UV/EUV/SXR (soft X-ray)
regimes. These instruments will observe the broad range of radiative
signatures produced in the solar atmosphere by accelerated particles.
Title: Evolution of Elemental Abundances during B-Class Solar Flares:
Soft X-Ray Spectral Measurements with Chandrayaan-2 XSM
Authors: Mondal, Biswajit; Sarkar, Aveek; Vadawale, Santosh V.;
Mithun, N. P. S.; Janardhan, P.; Del Zanna, Giulio; Mason, Helen E.;
Mitra-Kraev, Urmila; Narendranath, S.
Bibcode: 2021ApJ...920....4M
Altcode: 2021arXiv210707825M
The Solar X-ray Monitor (XSM) payload on board Chandrayaan-2 provides
disk-integrated solar spectra in the 1-15 keV energy range with an
energy resolution of 180 eV (at 5.9 keV) and a cadence of 1 s. During
the period from 2019 September to 2020 May, covering the minimum of
Solar Cycle 24, it observed nine B-class flares ranging from B1.3 to
B4.5. Using time-resolved spectroscopic analysis during these flares,
we examined the evolution of temperature, emission measure, and absolute
elemental abundances of four elements-Mg, Al, Si, and S. These are
the first measurements of absolute abundances during such small flares
and this study offers a unique insight into the evolution of absolute
abundances as the flares evolve. Our results demonstrate that the
abundances of these four elements decrease toward their photospheric
values during the peak phase of the flares. During the decay phase,
the abundances are observed to quickly return to their preflare coronal
values. The depletion of elemental abundances during the flares is
consistent with the standard flare model, suggesting the injection
of fresh material into coronal loops as a result of chromospheric
evaporation. To explain the quick recovery of the so-called coronal
"First Ionization Potential bias" we propose two scenarios based on
the Ponderomotive force model.
Title: R-matrix electron-impact excitation data for the O-like
iso-electronic sequence
Authors: Mao, Junjie; Badnell, N. R.; Del Zanna, G.
Bibcode: 2021A&A...653A..81M
Altcode: 2021arXiv210706975M
Context. Astrophysical plasma codes are built on atomic databases. In
the current atomic databases, R-matrix electron-impact excitation
data of O-like ions are limited. The accuracy of plasma diagnostics
with O-like ions depends on the availability and accuracy of the
atomic data. This is particularly relevant in the context of future
observatories equipped with the next generation of high-resolution
spectrometers.
Aims: We aim to obtain level-resolved
effective collision strengths of O-like ions from Ne III to Zn XXIII
(i.e. Ne2+ to Zn22+) over a wide range of
temperatures. This includes transitions up to nl = 5d for each ion. We
also aim to assess the accuracy of the new data, as well as their impact
on solar atmosphere plasma diagnostics, compared to those available
within the CHIANTI database.
Methods: Large-scale R-matrix
intermediate coupling frame transformation calculations were performed
systematically for the O-like iso-electronic sequence. For each ion,
630 fine-structure levels were included in both the configuration
interaction target and close-coupling collision expansions.
Results: Our results (energy levels, oscillator strengths, and effective
collision strengths) of selected ions across the iso-electronic sequence
are compared with those in archival databases and the literature. For
the selected ions throughout the iso-electronic sequence, we find
general agreement with the few previous R-matrix calculations of
collision strengths. We illustrate the improvements for a few solar
plasma diagnostics over existing CHIANTI atomic models based on
distorted wave (DW) data. The electron-impact excitation data are
archived according to the Atomic Data and Analysis Structure (ADAS)
data class adf04 and will be available in OPEN-ADAS.
Title: Small-scale Turbulent Motion of the Plasma in a Solar Filament
as the Precursor of Eruption
Authors: Seki, Daikichi; Otsuji, Kenichi; Isobe, Hiroaki; Del Zanna,
Giulio; Ishii, Takako T.; Sakaue, Takahito; Ichimoto, Kiyoshi;
Shibata, Kazunari
Bibcode: 2021ApJ...918...38S
Altcode: 2021arXiv210611875S
A filament, a dense cool plasma supported by the magnetic fields in
the solar corona, often becomes unstable and erupts. It is empirically
known that the filament often demonstrates some activations such
as a turbulent motion prior to eruption. In our previous study, we
analyzed the Doppler velocity of an Hα filament and found that the
standard deviation of the line-of-sight velocity distribution in a
filament, which indicates the increasing amplitude of the small-scale
motions, increased prior to the onset of the eruption. Here, we
present a further analysis on this filament eruption, which initiated
approximately at 03:40 UT on 2016 November 5 in the vicinity of NOAA
Active Region 12605. It includes a coronal line observation and the
extrapolation of the surrounding magnetic fields. We found that both
the spatially averaged microturbulence inside the filament and the
nearby coronal line emission increased 6 and 10 hr prior to eruption,
respectively. In this event, we did not find any significant changes
in the global potential field configuration preceding the eruption for
the past 2 days, which indicates that there is a case in which it is
difficult to predict the eruption only by tracking the extrapolated
global magnetic fields. In terms of space weather prediction, our
result on the turbulent motions in a filament could be used as the
useful precursor of a filament eruption.
Title: Modelling low charge ions in the solar atmosphere
Authors: Dufresne, R. P.; Del Zanna, G.; Storey, P. J.
Bibcode: 2021MNRAS.505.3968D
Altcode: 2021arXiv210512517D
Extensions have been made recently to the coronal approximation for the
purpose of modelling line emission from carbon and oxygen in the lower
solar atmosphere. The same modelling is used here for other elements
routinely observed in the solar transition region: N, Ne, Mg, Si, and
S. The modelling includes the effects of higher densities suppressing
dielectronic recombination and populating long lived, metastable levels;
the presence of metastable levels typically causes effective ionization
rates to increase and recombination rates to decrease. Processes induced
by the radiation field, namely photoionization and photoexcitation,
have been included, along with charge transfer, which occurs when
electrons are exchanged during atom-ion and ion-ion collisions. The
resulting ion balances are shown, and indicate significant changes
compared to the frequently employed coronal approximation. The effect
on level populations within ions caused by photoexcitation is also
assessed. To give an illustration of how line emission could be altered
by these processes, selected line contribution functions are presented
at the end.
Title: The influence of photo-induced processes and charge transfer
on carbon and oxygen in the lower solar atmosphere
Authors: Dufresne, R. P.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2021MNRAS.503.1976D
Altcode: 2021arXiv210209278D; 2021MNRAS.tmp..536D
To predict line emission in the solar atmosphere requires models that
are fundamentally different depending on whether the emission is from
the chromosphere or the corona. At some point between the two regions,
there must be a change between the two modelling regimes. Recent
extensions to the coronal modelling for carbon and oxygen lines in
the solar transition region have shown improvements in the emission
of singly and doubly charged ions, along with Li-like ions. However,
discrepancies still remain, particularly for singly charged ions and
intercombination lines. The aim of this work is to explore additional
atomic processes that could further alter the charge-state distribution
and the level populations within ions, in order to resolve some of the
discrepancies. To this end, excitation and ionization caused by both
the radiation field and by atom-ion collisions have been included, along
with recombination through charge transfer. The modelling is carried out
using conditions which would be present in the quiet Sun. This allows
an assessment of the part atomic processes play in changing coronal
modelling, separately from dynamic and transient events taking place
in the plasma. The effect the processes have on the fractional ion
populations are presented, as well as the change in level populations
brought about by the new excitation mechanisms. Contribution functions
of selected lines from low-charge states are also shown, to demonstrate
the extent to which line emission in the lower atmosphere could be
affected by the new modelling.
Title: Future perspectives in solar hot plasma observations in the
soft X-rays
Authors: Corso, Alain Jody; Del Zanna, Giulio; Polito, Vanessa
Bibcode: 2021ExA...tmp...49C
Altcode: 2021arXiv210505549C
The soft X-rays (SXRs: 90-150 Å) are among the most interesting
spectral ranges to be investigated in the next generation of solar
missions due to their unique capability of diagnosing phenomena
involving hot plasma with temperatures up to 15 MK. Multilayer
(ML) coatings are crucial for developing SXR instrumentation, as
so far they represent the only viable option for the development
of high-efficiency mirrors in the this spectral range. However, the
current standard MLs are characterized by a very narrow spectral band
which is incompatible with the science requirements expected for a SXR
spectrometer. Nevertheless, recent advancement in the ML technology has
made the development of non-periodic stacks repeatable and reliable,
enabling the manufacturing of SXR mirrors with a valuable efficiency
over a large range of wavelengths. In this work, after reviewing the
state-of-the-art ML coatings for the SXR range, we investigate the
possibility of using M-fold and aperiodic stacks for the development
of multiband SXR spectrometers. After selecting a possible choice
of key spectral lines, some trade-off studies for an eight-bands
spectrometer are also presented and discussed, giving an evaluation
of their feasibility and potential performance.
Title: Mapping the global magnetic field in the solar corona through
magnetoseismology
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
Wang, Linghua; Bai, Xianyong
Bibcode: 2021EGUGA..23..642Y
Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
Title: VizieR Online Data Catalog: Rate coefficients and ion
populations (Dufresne+, 2021)
Authors: Dufresne, R. P.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2021yCat..75031976D
Altcode:
The file ct_temps.dat gives the temperatures at which charge transfer
rate coefficients have been calculated. The file ct_rates.dat gives the
rate coefficients for charge transfer and charge transfer ionisation
resolved by initial and final levels where possible, otherwise resolved
by initial level only. Rate coefficients are only given here for those
transitions where rate coefficients were not provided in the original
sources. They were produced for this work from the published cross
sections given by those sources. Zero values for rate coefficients
mean the published cross sections were not given at energies which are
suitable to provide rate coefficients at those temperatures. The file
co_pict.dat gives the ion fractional populations for each ion of carbon
and oxygen at the temperatures given in file tempions.dat, derived from
the ionisation equilibrium at a constant pressure of 3.0e+14 K/cm+3. The
co_pict.dat file is in the Chianti .ioneq file format. Details of
methods for calculations are given in the paper. (4 data files).
Title: High resolution soft X-ray spectroscopy and the quest for
the hot (5-10 MK) plasma in solar active regions
Authors: Del Zanna, Giulio; Andretta, Vincenzo; Cargill, Peter J.;
Corso, Alain J.; Daw, Adrian N.; Golub, Leon; Klimchuk, James A.;
Mason, Helen E.
Bibcode: 2021FrASS...8...33D
Altcode: 2021arXiv210306156D
We discuss the diagnostics available to study the 5--10 MK plasma in
the solar corona, which is key to understanding the heating in the
cores of solar active regions. We present several simulated spectra,
and show that excellent diagnostics are available in the soft X-rays,
around 100 Angstroms, as six ionisation stages of Fe can simultaneously
be observed, and electron densities derived, within a narrow spectral
region. As this spectral range is almost unexplored, we present an
analysis of available and simulated spectra, to compare the hot emission
with the cooler component. We adopt recently designed multilayers to
present estimates of count rates in the hot lines, with a baseline
spectrometer design. Excellent count rates are found, opening up
the exciting opportunity to obtain high-resolution spectroscopy of
hot plasma.
Title: Optimization of Radial Diffusion Coefficients for the Proton
Radiation Belt During the CRRES Era
Authors: Lozinski, Alexander R.; Horne, Richard B.; Glauert, Sarah A.;
Del Zanna, Giulio; Albert, Jay M.
Bibcode: 2021JGRA..12628486L
Altcode:
Proton flux measurements from the Proton Telescope instrument aboard the
CRRES satellite are revisited, and used to drive a radial diffusion
model of the inner proton belt at 1.1 ≤ L ≤ 1.65. Our model
utilizes a physics based evaluation of the cosmic ray albedo neutron
decay (CRAND) source, and coulomb collisional loss is driven by a
drift averaged density model combining results from the International
Reference Ionosphere, NRLMSIS 00 atmosphere and Radio Plasma Imager
plasmasphere models, parameterized by solar activity and season. We
drive our model using time averaged data at L = 1.65 to calculate
steady state profiles of equatorial phase space density, and optimize
our choice of radial diffusion coefficients based on four defining
parameters to minimize the difference between model and data. This is
first performed for a quiet period when the belt can be assumed to
represent steady state. Additionally, we investigate fitting steady
state solutions to time averages taken during active periods where the
data exhibits limited deviation from steady state, demonstrated by CRRES
measurements following the March 24, 1991 storm. We also discuss a way
to make the optimization process more reliable by excluding periods of
variability in plasmaspheric density from any time average. Lastly,
we compare our resultant diffusion coefficients to those derived via
a similar process in previous work, and diffusion coefficients derived
for electrons from ground and in situ observations. We find that higher
diffusion coefficients are derived compared with previous work, and
suggest more work is required to derive proton diffusion coefficients
for different geomagnetic activity levels.
Title: CHIANTI—An Atomic Database for Emission Lines. XVI. Version
10, Further Extensions
Authors: Del Zanna, G.; Dere, K. P.; Young, P. R.; Landi, E.
Bibcode: 2021ApJ...909...38D
Altcode: 2020arXiv201105211D
We present version 10 of the CHIANTI package. In this release, we
provide updated atomic models for several helium-like ions and for
all the ions of the beryllium, carbon, and magnesium isoelectronic
sequences that are abundant in astrophysical plasmas. We include rates
from large-scale atomic structure and scattering calculations that
are in many cases a significant improvement over the previous version,
especially for the Be-like sequence, which has useful line diagnostics
to measure the electron density and temperature. We have also added
new ions and updated several of them with new atomic rates and line
identifications. Also, we have added several improvements to the IDL
software, to speed up the calculations and to estimate the suppression
of dielectronic recombination.
Title: Electron Densities in the Solar Corona Measured Simultaneously
in the Extreme Ultraviolet and Infrared
Authors: Dudík, Jaroslav; Del Zanna, Giulio; Rybák, Ján;
Lörinčík, Juraj; Dzifčáková, Elena; Mason, Helen E.; Tomczyk,
Steven; Galloy, Michael
Bibcode: 2021ApJ...906..118D
Altcode: 2020arXiv201109175D
Accurate measurements of electron density are critical for
determination of the plasma properties in the solar corona. We compare
the electron densities diagnosed from Fe XIII lines observed by the
Extreme-Ultraviolet Imaging Spectrometer (EIS) onboard the Hinode
mission with the near-infrared (NIR) measurements provided by the
ground-based Coronal Multichannel Polarimeter (CoMP). To do that, the
emissivity-ratio method based on all available observed lines of Fe
XIII is used for both EIS and CoMP. The EIS diagnostics is further
supplemented by the results from Fe XII lines. We find excellent
agreement, within 10%, between the electron densities measured from both
extreme-ultraviolet and NIR lines. In the five regions selected for
detailed analysis, we obtain electron densities of log(Ne
[cm-3]) = 8.2-8.6. Where available, the background
subtraction has a significant impact on the diagnostics, especially on
the NIR lines, where the loop contributes less than a quarter of the
intensity measured along the line of sight. For the NIR lines, we find
that the line center intensities are not affected by stray light within
the instrument, and recommend using these for density diagnostics. The
measurements of the Fe XIII NIR lines represent a viable method for
density diagnostics using ground-based instrumentation.
Title: Optimisation of a Steady State Radial Diffusion Model to
Derive Diffusion Coefficients for the Proton Radiation Belt
Authors: Lozinski, A. R.; Horne, R. B.; Glauert, S. A.; Del Zanna,
G.; Albert, J.
Bibcode: 2020AGUFMSM0310013L
Altcode:
Proton flux measurements from the Proton Telescope instrument aboard
the CRRES satellite are revisited, and used to drive a radial diffusion
model of the inner proton belt at 1.1≤L≤1.7. Our model utilises
a physics-based evaluation of the cosmic ray albedo neutron decay
(CRAND) source, and coulomb collisional loss is driven by plasmaspheric
electron density according to the Global Core Plasma Model. We drive
our model using time-averaged data at L=1.7 to calculate steady
state profiles of phase space density, and optimise our choice of
radial diffusion coefficients based on four defining parameters, so
as to minimise the difference between model and data. This is first
performed for a quiet period when the belt can be assumed to represent
steady state. Additionally, we investigate the viability of fitting
steady state solutions to time averages taken during active periods
that exhibit limited deviation from steady state, demonstrated by
CRRES measurements following the 24th March 1991 storm. We discuss
a way to make the optimisation process more reliable by excluding
periods of variability in plasmaspheric density from any time average,
applicable to other empirically modelled factors. Lastly, we compare
our resultant diffusion coefficients to those derived via a similar
process in previous work, as well as diffusion coefficients derived
for electrons from ground and in situ observations. We find that
higher diffusion coefficients are derived compared with previous work,
but that our estimates may be increased by uncertainty in inner zone
plasmaspheric density, which we identify as an important potential
caveat for modelling.
Title: R-matrix electron-impact excitation data for the N-like
iso-electronic sequence
Authors: Mao, Junjie; Badnell, N. R.; Del Zanna, G.
Bibcode: 2020A&A...643A..95M
Altcode: 2020arXiv200909506M
Context. Spectral lines from N-like ions can be used to measure the
temperature and density of various types of astrophysical plasmas. The
atomic databases of astrophysical plasma modelling codes still have
room for improvement in their electron-impact excitation data sets for
N-like ions, especially for R-matrix data. This is particularly relevant
for future observatories (e.g. Arcus), which will host high-resolution
spectrometers.
Aims: We aim to obtain level-resolved effective
collision strengths for all transitions up to nl = 5d over a wide range
of temperatures for N-like ions from O II to Zn XXIV (i.e. O+
to Zn23+) and to assess the accuracy of the present
work. We also examine the impact of our new data on plasma diagnostics
by modelling solar observations with CHIANTI.
Methods: We
carried out systematic R-matrix calculations for N-like ions, which
included 725 fine-structure target levels in both the configuration
interaction target and close-coupling collision expansions. The
R-matrix intermediate coupling frame transformation method was used
to calculate the collision strengths, while the AUTOSTRUCTURE code
was used for the atomic structures.
Results: We compare the
present results for selected ions with those in archival databases
and the literature. The comparison covers energy levels, oscillator
strengths, and effective collision strengths. We show examples of
improved plasma diagnostics when compared to CHIANTI models, which
use only distorted wave data as well as some using previous R-matrix
data. The electron-impact excitation data are archived according to
the Atomic Data and Analysis Structure (ADAS) data class adf04 and
will be available in OPEN-ADAS. The data can be used to improve the
atomic databases for astrophysical plasma diagnostics.
Title: Introduction of Zeeman splitting in CHIANTI
Authors: Giarrusso, M.; Landi, E.; Del Zanna, G.; Leone, F.
Bibcode: 2020JPlPh..86e8402G
Altcode:
High-resolution spectra emitted by laboratory plasmas provide invaluable
diagnostic tools for the measurement of plasma properties. To be
implemented, they require a large amount of atomic data and transition
rates, which are available in several spectral codes. In this paper we
present a new feature added to the CHIANTI code, which allows us to
calculate the Zeeman splitting of spectral lines in the presence of
a magnetic field with known intensity and orientation. When combined
with the CHIANTI database and software to calculate level populations
and line emissivities, this new feature returns the emissivities in
all four Stokes parameters, that can be utilized for the measurement of
the magnetic field inside laboratory plasma chambers, along with other
plasma parameters. This new feature can be applied to the analysis of
the emission of laboratory plasmas created in different devices.
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
Bibcode: 2020A&A...642A..14S
Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal.
Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing.
Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
Title: The Solar Orbiter EUI instrument: The Extreme Ultraviolet
Imager
Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz,
W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado,
R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.;
Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel,
V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau,
M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar,
S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.;
Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.;
Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.;
Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud,
A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.;
Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.;
Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan,
K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.;
Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.;
Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq,
S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.;
Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining,
S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort,
F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.;
Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.;
Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.;
Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.;
Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane,
K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit,
S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen,
K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.;
Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.;
Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.;
Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N.
Bibcode: 2020A&A...642A...8R
Altcode:
Context. The Extreme Ultraviolet Imager (EUI) is part of the remote
sensing instrument package of the ESA/NASA Solar Orbiter mission
that will explore the inner heliosphere and observe the Sun from
vantage points close to the Sun and out of the ecliptic. Solar Orbiter
will advance the "connection science" between solar activity and the
heliosphere.
Aims: With EUI we aim to improve our understanding
of the structure and dynamics of the solar atmosphere, globally as well
as at high resolution, and from high solar latitude perspectives.
Methods: The EUI consists of three telescopes, the Full Sun Imager and
two High Resolution Imagers, which are optimised to image in Lyman-α
and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere
up to corona. The EUI is designed to cope with the strong constraints
imposed by the Solar Orbiter mission characteristics. Limited telemetry
availability is compensated by state-of-the-art image compression,
onboard image processing, and event selection. The imposed power
limitations and potentially harsh radiation environment necessitate
the use of novel CMOS sensors. As the unobstructed field of view of
the telescopes needs to protrude through the spacecraft's heat shield,
the apertures have been kept as small as possible, without compromising
optical performance. This led to a systematic effort to optimise the
throughput of every optical element and the reduction of noise levels
in the sensor.
Results: In this paper we review the design
of the two elements of the EUI instrument: the Optical Bench System
and the Common Electronic Box. Particular attention is also given to
the onboard software, the intended operations, the ground software,
and the foreseen data products.
Conclusions: The EUI will
bring unique science opportunities thanks to its specific design,
its viewpoint, and to the planned synergies with the other Solar
Orbiter instruments. In particular, we highlight science opportunities
brought by the out-of-ecliptic vantage point of the solar poles,
the high-resolution imaging of the high chromosphere and corona,
and the connection to the outer corona as observed by coronagraphs.
Title: Effects of density on the oxygen ionization equilibrium in
collisional plasmas
Authors: Dufresne, R. P.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2020MNRAS.497.1443D
Altcode: 2020arXiv200700465D; 2020MNRAS.tmp.2122D
The ion populations most frequently adopted for diagnostics in
collisional plasmas are derived from the density independent coronal
approximation. In higher density, lower temperature conditions,
ionization rates are enhanced once metastable levels become populated,
and recombination rates are suppressed if ions recombine into Rydberg
levels. As a result, the formation temperatures of ions shift, altering
the diagnostics of the plasma. To accurately model the effect of
ionization from metastable levels, new electron impact ionization
cross-sections have been calculated for oxygen, both for direct
ionization and excitation-auto-ionization of the ground and metastable
levels. The results have been incorporated into collisional radiative
modelling to show how the ionization equilibrium of oxygen changes
once metastable levels become populated. Suppression of dielectronic
recombination has been estimated and also included in the modelling,
demonstrating the shifts with density in comparison to the coronal
approximation. The final results for the ionization equilibrium are
used in differential emission measure modelling to predict line
intensities for many lines emitted by O II-O VI> in the solar
transition region. The predictions show improved agreement by 15-40 per
cent for O II, O VI>, and the intercombination lines of O III-O V,
when compared to results from coronal approximation modelling. While
there are still discrepancies with observations of these lines, this
could, to a large part, be explained by variability in the observations.
Title: Study of the spatial association between an active region
jet and a nonthermal type~${\rm III}$ radio burst
Authors: Mulay, Sargam M.; Sharma, Rohit; Valori, Gherardo; Vásquez,
Alberto M.; Del Zanna, Giulio; Mason, Helen; Oberoi, Divya
Bibcode: 2020arXiv200914581M
Altcode:
We aim to investigate the spatial location of the source of an active
region (AR) jet and its relation with associated nonthermal type~III
radio emission. An emission measure (EM) method was used to study
the thermodynamic nature of the AR jet. The nonthermal type~{\rm III}
radio burst observed at meterwavelength was studied using the Murchison
Widefield Array (MWA) radio imaging and spectroscopic data. The local
configuration of the magnetic field and the connectivity of the source
region of the jet with open magnetic field structures was studied using
a nonlinear force-free field (NLFFF) extrapolation and potential field
source surface (PFSS) extrapolation respectively. The plane-of-sky
velocity of the AR jet was found to be $\sim$136~km/s. The EM analysis
confirmed the presence of low temperature 2~MK plasma for the spire,
whereas hot plasma, between 5-8 MK, was present at the footpoint region
which also showed the presence of Fe~{\sc xviii} emission. A lower limit
on the electron number density was found to be 1.4$\times$10$^{8}$
cm$^{-3}$ for the spire and 2.2$\times$10$^{8}$~cm$^{-3}$ for
the footpoint. A temporal and spatial correlation between the AR
jet and nonthermal type III burst confirmed the presence of open
magnetic fields. An NLFFF extrapolation showed that the photospheric
footpoints of the null point were anchored at the location of the
source brightening of the jet. The spatial location of the radio
sources suggests an association with the extrapolated closed and
open magnetic fields although strong propagation effects are also
present. The multi-scale analysis of the field at local, AR, and solar
scales confirms the interlink between different flux bundles involved
in the generation of the type III radio signal with flux transferred
from a small coronal hole to the periphery of the sunspot via null
point reconnection with an emerging structure.
Title: Global maps of the magnetic field in the solar corona
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott W.; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
Wang, Linghua
Bibcode: 2020Sci...369..694Y
Altcode: 2020arXiv200803136Y
Understanding many physical processes in the solar atmosphere requires
determination of the magnetic field in each atmospheric layer. However,
direct measurements of the magnetic field in the Sun’s corona are
difficult to obtain. Using observations with the Coronal Multi-channel
Polarimeter, we have determined the spatial distribution of the
plasma density in the corona and the phase speed of the prevailing
transverse magnetohydrodynamic waves within the plasma. We combined
these measurements to map the plane-of-sky component of the global
coronal magnetic field. The derived field strengths in the corona,
from 1.05 to 1.35 solar radii, are mostly 1 to 4 gauss. Our results
demonstrate the capability of imaging spectroscopy in coronal magnetic
field diagnostics.
Title: Fe III emission in quasars: evidence for a dense turbulent
medium
Authors: Temple, Matthew J.; Ferland, Gary J.; Rankine, Amy L.;
Hewett, Paul C.; Badnell, N. R.; Ballance, Connor P.; Del Zanna,
Giulio; Dufresne, Roger P.
Bibcode: 2020MNRAS.496.2565T
Altcode: 2020MNRAS.tmp.1846T; 2020arXiv200608617T
Recent improvements to atomic energy-level data allow, for the
first time, accurate predictions to be made for the Fe III line
emission strengths in the spectra of luminous, $L_\text{bol}\simeq
10^{46}\!-\!10^{48}\mbox{${\rm \, erg}{\rm \, s}^{-1}\, $}$ , active
galactic nuclei. The Fe III emitting gas must be primarily photoionized,
consistent with observations of line reverberation. We use CLOUDY
models exploring a wide range of parameter space, together with ≃26
000 rest-frame ultraviolet spectra from the Sloan Digital Sky Survey,
to constrain the physical conditions of the line emitting gas. The
observed Fe III emission is best accounted for by dense (nH
≃ 1014 cm-3) gas which is microturbulent,
leading to smaller line optical depths and fluorescent excitation. Such
high density gas appears to be present in the central regions of the
majority of luminous quasars. Using our favoured model, we present
theoretical predictions for the relative strengths of the Fe III UV34
λλ1895, 1914, 1926 multiplet. This multiplet is blended with the Si
III] λ1892 and C III] λ1909 emission lines and an accurate subtraction
of UV34 is essential when using these lines to infer information about
the physics of the broad line region in quasars.
Title: Helium Line Emissivities in the Solar Corona
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Andretta, V.
Bibcode: 2020ApJ...898...72D
Altcode: 2020arXiv200608971D
We present new collisional-radiative models (CRMs) for helium in
the quiescent solar corona and predict the emissivities of the He
and He+ lines to be observed by DKIST, Solar Orbiter, and
Proba-3. We discuss in detail the rates we selected for these models,
highlighting several shortcomings we have found in previous work. As no
previous complete and self-consistent coronal CRM for helium existed,
we have benchmarked our largest model at a density of 106
cm-3 and temperature of 20,000 K against recent CRMs
developed for photoionized nebulae. We then present results for the
outer solar corona, using new dielectronic recombination rates we have
calculated, which increase the abundance of neutral helium by about
a factor of 2. We also find that all optical triplet He I lines,
and in particular the well-known He I 10830 and 5876 Å lines, are
strongly affected by both photoexcitation and photoionization from the
disk radiation and that extensive CRMs are required to obtain correct
estimates. Close to the Sun, at an electron density of 108
cm-3 and temperature of 1 MK, we predict the emissivity of
He I 10830 Å to be comparable to that of the strong Fe XIII coronal
line at 10798 Å. However, we expect the He I emissivity to sharply
fall in the outer corona, with respect to Fe XIII. We confirm that
the He+ Lyα at 304 Å is also significantly affected by
photoexcitation and is expected to be detectable as a strong coronal
line up to several solar radii.
Title: VizieR Online Data Catalog: Ionisation and ion fraction data
(Dufresne+, 2020)
Authors: Dufresne, R. P.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2020yCat..74971443D
Altcode:
The file levels.dat gives indices for energy levels of ions for which
data has been given. The file temprate.dat gives the temperatures at
which the rate coefficients have been calculated for each ion. The
file di_lr.dat gives the rate coefficients for direct ionisation
(DI) by electron impact resolved by initial and final levels,
and the file di_total.dat gives total DI rate coefficients from
each initial level. The file ea_lr.dat gives the rate coefficients
for excitation-auto-ionisation (EA) by electron impact resolved by
initial and final levels, and the file ea_total.dat gives total EA
rate coefficients from each initial level. Files oioneqXX.dat give the
ion populations for each ion of oxygen for temperatures given in file
tempions.dat, derived from the ionisation equilibrium at log electron
density XX (cm-3). The files are in the Chianti .ioneq file
format. Details of methods for calculations are given in the paper. (14 data files).
Title: Roadmap on cosmic EUV and x-ray spectroscopy
Authors: Smith, Randall; Hahn, Michael; Raymond, John; Kallman, T.;
Ballance, C. P.; Polito, Vanessa; Del Zanna, Giulio; Gu, Liyi; Hell,
Natalie; Cumbee, Renata; Betancourt-Martinez, Gabriele; Costantini,
Elisa; Corrales, Lia
Bibcode: 2020JPhB...53i2001S
Altcode:
Cosmic EUV/x-ray spectroscopists, including both solar and astrophysical
analysts, have a wide range of high-resolution and high-sensitivity
tools in use and a number of new facilities in development for
launch. As this bandpass requires placing the spectrometer beyond
the Earth's atmosphere, each mission represents a major investment
by a national space agency such as NASA, ESA, or JAXA, and more
typically a collaboration between two or three. In general justifying
new mission requires an improvement in capabilities of at least an
order of magnitude, but the sensitivity of these existing missions
are already taxing existing atomic data quantity and accuracy. This
roadmap reviews the existing missions, showing how in a number of areas
atomic data limits the science that can be performed. The missions that
will be launched in the coming Decade will without doubt require both
more and improved measurements of wavelengths and rates, along with
theoretical calculations of collisional and radiative cross sections
for a wide range of processes.
Title: Plasma Diagnostics from Active Region and Quiet-Sun Spectra
Observed by Hinode/EIS: Quantifying the Departures from a Maxwellian
Distribution
Authors: Lörinčík, Juraj; Dudík, Jaroslav; del Zanna, Giulio;
Dzifčáková, Elena; Mason, Helen E.
Bibcode: 2020ApJ...893...34L
Altcode: 2020arXiv200307091L
We perform plasma diagnostics, including that of the non-Maxwellian
κ-distributions, in several structures observed in the solar corona
by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on board the
Hinode spacecraft. To prevent uncertainties due to the in-flight
calibration of EIS, we selected spectral atlases observed shortly
after the launch of the mission. One spectral atlas contains an
observation of an active region, while the other is an off-limb
quiet-Sun region. To minimize the uncertainties of the diagnostics,
we rely only on strong lines and average the signal over a spatial
area within selected structures. Multiple plasma parameters are
diagnosed, such as the electron density, the differential emission
measure, and the non-Maxwellian parameter κ. To do that, we use
a simple, well-converging iterative scheme based on refining the
initial density estimates via the differential emission measure
(DEM) and κ. We find that while the quiet-Sun spectra are consistent
with a Maxwellian distribution, the coronal loops and moss observed
within the active region are strongly non-Maxwellian with κ ⪅
3. These results were checked by calculating synthetic ratios using
DEMs obtained as a function of κ. Ratios predicted using the DEMs
assuming κ-distributions converged to the ratios observed in the
quiet Sun and coronal loops. To our knowledge, this work presents a
strong evidence of the presence of different electron distributions
between two physically distinct parts of the solar corona.
Title: Large-scale Multiconfiguration Dirac-Hartree-Fock Calculations
for Astrophysics: n = 4 Levels in P-like Ions from Mn XI to Ni XIV
Authors: Song, C. X.; Wang, K.; Del Zanna, G.; Jönsson, P.; Si, R.;
Godefroid, M.; Gaigalas, G.; Radži; ūtė, L.; Rynkun, P.; Zhao,
X. H.; Yan, J.; Chen, C. Y.
Bibcode: 2020ApJS..247...70S
Altcode: 2020arXiv200300121S
Using the multiconfiguration Dirac-Hartree-Fock and the relativistic
configuration interaction methods, a consistent set of transition
energies and radiative transition data for the lowest 546 (623, 701,
and 745) states of the 3p43d, 3s3p23d2,
3s3p34p, 3s3p4, 3s23d3,
3s23p23d, 3s23p24d,
3s23p24s, 3p33d2,
3p5, 3s3p3d3, 3s3p33d,
3s3p34s, 3s23p3d2,
3s23p24p, and 3s23p3
configurations in Mn XI (Fe XII, Co XIII, and Ni XIV) is provided. The
comparison between calculated excitation energies for the n = 4
states and available experimental values for Fe XII indicate that
the calculations are highly accurate, with uncertainties of only a
few hundred cm-1. Lines from these states are prominent
in the soft X-rays. With the present calculations, several recent
new identifications are confirmed. Other identifications involving
3p24d levels in Fe XII that were found to be questionable
are discussed and a few new assignments are recommended. As some
n = 4 states of the other ions also show large discrepancies
between experimental and calculated energies, we reassess their
identification. The present study provides highly accurate atomic
data for the n = 4 states of P-like ions of astrophysical interest,
for which experimental data are scarce.
Title: R-matrix electron-impact excitation data for the C-like
iso-electronic sequence
Authors: Mao, J.; Badnell, N. R.; Del Zanna, G.
Bibcode: 2020A&A...634A...7M
Altcode: 2019arXiv191208466M
Context. Emission and absorption features from C-like ions
serve as temperature and density diagnostics of astrophysical
plasmas. R-matrix electron-impact excitation data sets for C-like
ions in the literature merely cover a few ions, and often only for the
ground configuration.
Aims: Our goal is to obtain level-resolved
effective collision strength over a wide temperature range for C-like
ions from N II to Kr XXXI (i.e., N+ to Kr30+)
with a systematic set of R-matrix calculations. We also aim to assess
their accuracy.
Methods: For each ion, we included a total
of 590 fine-structure levels in both the configuration interaction
target and close-coupling collision expansion. These levels arise
from 24 configurations 2l3nl' with n = 2-4, l = 0-1,
and l' = 0-3 plus the three configurations 2s22p5l with
l = 0-2. The AUTOSTRUCTURE code was used to calculate the target
structure. Additionally, the R-matrix intermediate coupling frame
transformation method was used to calculate the collision strengths.
Results: We compare the present results of selected ions with
archival databases and results in the literature. The comparison covers
energy levels, transition rates, and effective collision strengths. We
illustrate the impact of using the present results on an Ar XIII
density diagnostic for the solar corona. The electron-impact excitation
data is archived according to the Atomic Data and Analysis Structure
(ADAS) data class adf04 and will be available in OPEN-ADAS. The data
will be incorporated into spectral codes, such as CHIANTI and SPEX,
for plasma diagnostics.
Title: Large-scale Multiconfiguration Dirac-Hartree-Fock Calculations
for Astrophysics: Cl-like Ions from Cr VIII to Zn XIV
Authors: Wang, K.; Jönsson, P.; Del Zanna, G.; Godefroid, M.; Chen,
Z. B.; Chen, C. Y.; Yan, J.
Bibcode: 2020ApJS..246....1W
Altcode: 2019arXiv191103815W
We use the multiconfiguration Dirac-Hartree-Fock (MCDHF) method
combined with the relativistic configuration interaction approach
(GRASP2K) to provide a consistent set of transition energies and
radiative transition data for the lower n = 3 states in all Cl-like
ions of astrophysical importance, from Cr VIII to Zn XIV. We also
provide excitation energies calculated for Fe X using the many-body
perturbation theory (MBPT, implemented within FAC). The comparison
of the present MCDHF results with MBPT and with the available
experimental energies indicates that the theoretical excitation
energies are highly accurate, with uncertainties of only a few
hundred cm-1. Detailed comparisons for Fe X and Ni XII
highlight discrepancies in the experimental energies found in the
literature. Several new identifications are proposed.
Title: Benchmarked atomic data for astrophysics
Authors: Del Zanna, Giulio
Bibcode: 2020IAUS..350..341D
Altcode:
The recent calculations of atomic data for ions of astrophysical
interest are reviewed with a focus on work performed in Cambridge. The
calculations have been benchmarked against high-resolution laboratory
and astrophysical spectra. A framework for assessing uncertainties
in atomic data has also been developed. Long-standing discrepancies
in predicted spectral line intensities have been resolved, and a
significant number of levels in coronal ions have finally been
identified, improving the modelling of the extreme-ultraviolet
and soft X-ray spectral regions. Recent improvements based on
collisional-radiative modelling are presented. They are relevant
for the modelling of satellite lines in the X-rays and for solving
the long-standing problems in the chromosphere-corona transition in
stellar atmospheres.
Title: Study of the spatial association between an active region
jet and a nonthermal type III radio burst
Authors: Mulay, Sargam M.; Sharma, Rohit; Valori, Gherardo; Vásquez,
Alberto M.; Del Zanna, Giulio; Mason, Helen; Oberoi, Divya
Bibcode: 2019A&A...632A.108M
Altcode:
Aims: We aim to investigate the spatial location of the source
of an active region (AR) jet and its relation with associated nonthermal
type III radio emission.
Methods: An emission measure (EM) method
was used to study the thermodynamic nature of the AR jet. The nonthermal
type III radio burst observed at meterwavelength was studied using
the Murchison Widefield Array (MWA) radio imaging and spectroscopic
data. The local configuration of the magnetic field and the connectivity
of the source region of the jet with open magnetic field structures was
studied using a nonlinear force-free field (NLFFF) extrapolation and
potential field source surface (PFSS) extrapolation respectively.
Results: The plane-of-sky velocity of the AR jet was found to be
∼136 km s-1. The EM analysis confirmed the presence of
low temperature 2 MK plasma for the spire, whereas hot plasma, between
5 and 8 MK, was present at the footpoint region which also showed the
presence of Fe XVIII emission. A lower limit on the electron number
density was found to be 1.4 × 108 cm-3 for the
spire and 2.2 × 108 cm-3 for the footpoint. A
temporal and spatial correlation between the AR jet and nonthermal
type III burst confirmed the presence of open magnetic fields. An NLFFF
extrapolation showed that the photospheric footpoints of the null point
were anchored at the location of the source brightening of the jet. The
spatial location of the radio sources suggests an association with the
extrapolated closed and open magnetic fields although strong propagation
effects are also present.
Conclusions: The multi-scale analysis
of the field at local, AR, and solar scales confirms the interlink
between different flux bundles involved in the generation of the type
III radio signal with flux transferred from a small coronal hole to the
periphery of the sunspot via null point reconnection with an emerging
structure. The movie associated to Fig. 4 is available at https://www.aanda.org
Title: Exploring the Occurrence of MeV Electron Flux Enhancements
in the Radiation Belt Region
Authors: Allison, H. J.; Horne, R. B.; Glauert, S. A.; Shprits, Y.;
Del Zanna, G.
Bibcode: 2019AGUFMSM51I3279A
Altcode:
The Earth's electron radiation belts are a dynamic environment and
can change dramatically on short timescales. From Van Allen Probes
observations, we see storm time drop-out events followed by a rapid
recovery of the electron flux over a broad range of energies. However,
how the electron flux is replenished across energy space, and the
sequence of events leading to flux enhancements, remains an open
question. Satellite measurements have shown links between increases
in the low energy seed population and enhancements in the >1-MeV
flux. Here, the impact of variations in the seed population on the
1-MeV flux level are explored using a 3-D Radiation Belt Model. We find
that, for a period from the 21 April to 9 May 2013, the increase d seed
population was vital to recreate the observed 1-MeV flux enhancement
on the 1 May but was less important for the 1-MeV enhancement on the
27 April 2013. To better understand the relationships between the
different energy populations, a series of idealized experiments with
the 2-D British Antarctic Survey Radiation Belt Model were performed,
which highlight a careful balance between losses and acceleration
from chorus waves. Seed population enhancements alter this balance
by increasing the phase space density gradient, and consequently,
the rate of energy diffusion, allowing acceleration to surpass
loss. Additionally, we demonstrate that even with the same chorus
diffusion coefficients and the same low-energy boundary condition,
the flux of ∼500-keV to 1-MeV electrons increased when starting
with a hard spectrum but decreased for a soft initial spectrum. This
suggests that initial energy gradients in the phase space density were
important to determine whether >500-keV electrons were enhanced due
to chorus wave acceleration. Finally, we explore how the accelerated
1-MeV population influences electrons at multi-MeV energies.
Title: Hinode EIS line widths in the quiet corona up to 1.5
R⊙
Authors: Del Zanna, G.; Gupta, G. R.; Mason, H. E.
Bibcode: 2019A&A...631A.163D
Altcode: 2019arXiv190509783D
We present an analysis of several Hinode Extreme-ultraviolet Imaging
Spectrometer (EIS) observations of coronal line widths in the quiet Sun,
up to 1.5 R⊙ radial distances. Significant variations are
found, which indicates no damping of Alfvén waves in the quiescent
corona. However, the uncertainties in estimating the instrumental
width mean that a firm conclusion cannot be reached. We present a
discussion of various EIS instrumental issues and suggest that the
strongest lines, from Fe XII at 193.5 Å and 195.1 Å, have anomalous
instrumental widths. We also show how line widths in EIS are uncertain
when the signal is low, and that the instrumental variation along
the slit is also uncertain. We also find an anomalous decrease (up
to 40%) in the intensities of these lines in many off-limb and active
region observations, and provide evidence that this is due to opacity
effects. We find that the most reliable measurements are obtained from
the weaker lines.
Title: Closing gaps to our origins. The UV window into the Universe
Authors: Gomez de Castro, Ana I.; Barstow, Martin A.; Baudin,
Fréderic; Benetti, Stefano; Bouret, Jean Claude; Brosch, Noah; de
Martino, Domitilla; del Zanna, Giulio; Evans, Chris; García, Miriam;
Gaensicke, Boris; Kehrig, Carolina; Lapington, Jon; Lecavelier des
Etangs, Alain; Naletto, Giampiero; Nazé, Yael; Neiner, Coralie;
Nichols, Jonathan; Orio, Marina; Pagano, Isabella; Rauw, Gregor;
Shore, Steven; Tovmasian, Gagik; ud-Doula, Asif; France, Kevin;
Hillenbrand, Lynne
Bibcode: 2019arXiv191100769G
Altcode:
The investigation of the emergence of life is a major endeavour
of science. Astronomy is contributing to it in three fundamental
manners: (1) by measuring the chemical enrichment of the Universe,
(2) by investigating planet formation and searching for exoplanets
with signatures of life and, (3) by determining the abundance of
aminoacids and the chemical routes to aminoacid and protein growth in
astronomical bodies. This proposal deals with the first two. In the
Voyage to 2050, the world-wide scientific community is getting equipped
with large facilities for the investigation of the emergence of life in
the Universe (i.e. VLT, JWST, ELT, GMT, TMT, ALMA, FAST, VLA, ATHENA,
SKA) including the ESA's CHEOPS, PLATO and ARIEL missions. This white
paper is a community effort to call for the development of a large
ultraviolet optical observatory to gather fundamental data for this
investigation that will not be accessible through other ranges of
the electromagnetic spectrum. A versatile space observatory with UV
sensitivity a factor of 50-100 greater than existing facilities will
revolutionize our understanding of the pathway to life in the Universe.
Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
Peter R.
Bibcode: 2019PASJ...71R...1H
Altcode:
Hinode is Japan's third solar mission following Hinotori (1981-1982)
and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
operation currently. Hinode carries three instruments: the Solar Optical
Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
instruments were built under international collaboration with the
National Aeronautics and Space Administration and the UK Science and
Technology Facilities Council, and its operation has been contributed
to by the European Space Agency and the Norwegian Space Center. After
describing the satellite operations and giving a performance evaluation
of the three instruments, reviews are presented on major scientific
discoveries by Hinode in the first eleven years (one solar cycle long)
of its operation. This review article concludes with future prospects
for solar physics research based on the achievements of Hinode.
Title: Unfolding Overlapped Slitless Imaging Spectrometer Data for
Extended Sources
Authors: Winebarger, Amy R.; Weber, Mark; Bethge, Christian; Downs,
Cooper; Golub, Leon; DeLuca, Edward; Savage, Sabrina; del Zanna,
Giulio; Samra, Jenna; Madsen, Chad; Ashraf, Afra; Carter, Courtney
Bibcode: 2019ApJ...882...12W
Altcode: 2018arXiv181108329W
Slitless spectrometers can provide simultaneous imaging and spectral
data over an extended field of view, thereby allowing rapid data
acquisition for extended sources. In some instances, when the object
is greatly extended or the spectral dispersion is too small, there
may be locations in the focal plane where emission lines at different
wavelengths contribute. It is then desirable to unfold the overlapped
regions in order to isolate the contributions from the individual
wavelengths. In this paper, we describe a method for such an unfolding,
using an inversion technique developed for an extreme ultraviolet
imaging spectrometer and coronagraph named the COronal Spectroscopic
Imager in the EUV (COSIE). The COSIE spectrometer wavelength range
(18.6-20.5 nm) contains a number of strong coronal emission lines and
several density sensitive lines. We focus on optimizing the unfolding
process to retrieve emission measure maps at constant temperature,
maps of spectrally pure intensity in the Fe XII and Fe XIII lines,
and density maps based on both Fe XII and Fe XIII diagnostics.
Title: Solar microflares: a case study on temperatures and the Fe
XVIII emission
Authors: Mitra-Kraev, U.; Del Zanna, G.
Bibcode: 2019A&A...628A.134M
Altcode: 2019arXiv190508579M
In this paper, we discuss the temperature distribution and evolution
of a microflare, simultaneously observed by Hinode's X-Ray Telescope
(XRT), its Extreme Ultraviolet Imaging Spectrometer (EIS), as well
as the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics
Observatory (SDO). Using EIS lines, we find that during peak emission
the distribution is nearly isothermal and peaked around 4.5 MK. This
temperature is in good agreement with that obtained from the XRT filter
ratio, validating the use of XRT to study these small events, invisible
to full-Sun X-ray monitors such as the Geostationary Operational
Environmental Satellite (GOES). The increase in the estimated Fe XVIII
emission in the AIA 94 Å band can mostly be explained with the small
temperature increase from the background temperatures. The presence
of Fe XVIII emission does not guarantee that temperatures of 7 MK
are reached, as is often assumed. With the help of new atomic data,
we also revisit the temperatures measured by a Solar and Heliospheric
Observatory (SoHO) Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) observation of an active region that produced microflares,
also finding low temperatures (3-4 MK) from an Fe XVIII/Ca XIV ratio.
Title: Coronal Plasma Characterization via Coordinated Infrared and
Extreme Ultraviolet Observations of a Total Solar Eclipse
Authors: Madsen, Chad A.; Samra, Jenna E.; Del Zanna, Giulio; DeLuca,
Edward E.
Bibcode: 2019ApJ...880..102M
Altcode: 2019arXiv190110425M
We present coordinated coronal observations of the 2017 August 21 total
solar eclipse with the Extreme-ultraviolet Imaging Spectrometer (EIS)
and the Airborne Infrared Spectrometer (AIR-Spec). These instruments
provide an unprecedented view of the solar corona in two disparate
wavelength regimes, the extreme ultraviolet (EUV) and the near- to
mid-infrared (IR), opening new pathways for characterizing the complex
coronal plasma environment. During totality, AIR-Spec sampled coronal
IR spectra near the equatorial west limb, detecting strong sources
of Mg VIII, S XI, Si IX, and Si X in two passbands encompassing 1.4-4
μm. We apply an intensity-ratio diagnostic to a strong resonant Fe XII
line pair arising from the coordinated EIS observations. This results
in a high-resolution map of electron density throughout the shared
EIS/AIR-Spec field of view. Electron density measurements allow us to
produce a similar map of plasma temperature using emission measure
(EM) loci analysis as applied to 27 EIS emission lines, providing
temperatures of 106.12 ± 103.5 K along the
limb and 106.19 ± 103.5 K at about 100″
outward. Applying EM loci analysis to AIR-Spec IR spectra coadded
over two 31″ wide ranges centered at two locations, 30″ and
100″ from the limb, produces temperatures consistent with the EIS
data, albeit suffering from moderate uncertainties. Regardless, we
demonstrate that EUV spectral data are valuable constraints to coronal
IR emission models, and will be powerful supplements for future IR
solar observatories, particularly DKIST.
Title: Exploring the damping of Alfvén waves along a long off-limb
coronal loop, up to 1.4 R⊙
Authors: Gupta, G. R.; Del Zanna, G.; Mason, H. E.
Bibcode: 2019A&A...627A..62G
Altcode: 2019arXiv190508194G
The Alfvén wave energy flux in the corona can be explored using the
electron density and velocity amplitude of the waves. The velocity
amplitude of Alfvén waves can be obtained from the non-thermal velocity
of spectral line profiles. Previous calculations of the Alfvén wave
energy flux with height in active regions and polar coronal holes have
provided evidence for the damping of Alfvén waves with height. We
present off-limb Hinode Extreme-ultraviolet Imaging Spectrometer (EIS)
observations of a long coronal loop up to 1.4 R⊙. We
obtained the electron density along the loop and found the loop to be
almost in hydrostatic equilibrium. We obtained the temperature using
the emission measure-loci (EM-loci) method and found the loop to be
isothermal across, as well as along, the loop with a temperature of
about 1.37 MK. We significantly improve the estimate of non-thermal
velocities over previous studies by using the estimated ion (equal to
electron) temperature. Estimates of electron densities are improved
using the significant updates of the CHIANTI v.8 atomic data. More
accurate measurements of propagating Alfvén wave energy along the
coronal loop and its damping are presented up to distances of 1.4
R⊙, further than have been previously explored. The
Alfvén wave energy flux obtained could contribute to a significant
part of the coronal losses due to radiation along the loop.
Title: Latest updates to the CHIANTI atomic database
Authors: Young, Peter R.; Dere, Kenneth P.; Del Zanna, Giulio; Landi,
Enrico; Sutherland, Ralph
Bibcode: 2019AAS...23431402Y
Altcode:
CHIANTI is a database of atomic data parameters and a software
package for computing the radiative emissions from optically-thin
astrophysical plasmas. CHIANTI is freely available to the community
(http://chiantidatabase.org),
and is very widely used in the Heliophysics and Astrophysics
communities. The papers describing CHIANTI have been cited over
3500 times in the 22-year lifetime of the project. Version 9 of
CHIANTI was released in March 2019, and this presentation summarizes
the new updates and highlights important applications. The key change
for CHIANTI 9 was the implementation of a new method to account for
recombination and dielectronic capture in the level balance equations
through new, two-ion models that fully capture the state-to-state
transitions between ions. The models are needed for the calculation
of X-ray satellite lines and, for the first time, enable density
sensitivity to be modeled. A number of the standard atomic
data-sets have been updated, including recombination rates for several
important coronal iron ions. New software routines have been written
for computing the differential emission measure of a plasma, and for
computing the response functions of the Atmospheric Imaging Assembly
on board NASA's Solar Dynamics Observatory .
Title: Modelling ion populations in astrophysical plasmas: carbon
in the solar transition region
Authors: Dufresne, R. P.; Del Zanna, G.
Bibcode: 2019A&A...626A.123D
Altcode: 2019arXiv190108992D
The aim of this work is to improve the modelling of ion populations in
higher density, lower temperature astrophysical plasmas, of the type
commonly found in lower solar and stellar atmospheres. Ion population
models for these regions frequently employ the coronal approximation,
which assumes conditions more suitable to the upper solar atmosphere,
where high temperatures and lower densities prevail. The assumed
conditions include all ions being in the ground state and steady-state
equilibrium, where there is sufficient time for ionisation and
recombination to take place. Using the coronal approximation
for modelling the solar transition region gives theoretical lines
intensities for the Li-like and Na-like isoelectronic sequences which
are often factors of two to five times lower than observed. The works
of Burgess & Summers (1969, ApJ, 157, 1007) and Nussbaumer &
Storey (1975, A&A, 44, 321) show the important part ions in excited
levels play when included in the modelling. As density increases
metastable levels become populated and ionisation rates increase,
whereas dielectronic recombination through highly excited levels
is suppressed. Photo-ionisation is also shown by Nussbaumer &
Storey to have an effect on the charge-state distribution of carbon
in these regions. Their models, however, use approximations for the
atomic rates to determine the ion balance. Presented here is the
first stage in updating these earlier models of carbon by using rates
from up-to-date atomic calculations and more recent photo-ionising
radiances. Where atomic rates were not readily available, in the case
of electron impact direct ionisation and excitation-auto-ionisation, new
calculations were made using the Flexible Atomic Code and Autostructure,
and compared to theoretical and experimental studies. The effects
each atomic process has on the ion populations as density changes is
illustrated, and final results from the modelling are compared to the
earlier works. Lastly, the new results for ion populations were used to
predict line intensities for the solar transition region in the quiet
Sun. In comparison to coronal approximation modelling the new results
show significantly improved agreement with observations. Rate
coefficients for direct ionisation and excitation-auto-ionisation by
electron impact are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/626/A123
Title: VizieR Online Data Catalog: Electron impact ionisation data
(Dufresne+, 2019)
Authors: Dufresne, R. P.; Del Zanna, G.
Bibcode: 2019yCat..36260123D
Altcode:
The file levels.dat gives indices for energy levels of ions for which
data has been given. The file temps.dat gives the temperatures at
which the rate coefficients have been calculated for each ion. The
file di_rates.dat gives the rate coefficients for direct ionisation
(DI) by electron impact and the file ea_rates.dat gives the rate
coefficients for excitation--auto-ionisation (EA) by electron
impact. Details of methods for calculations given in the paper and at
https://arxiv.org/abs/1901.08992. (4 data files).
Title: Signatures of the non-Maxwellian κ-distributions in optically
thin line spectra. II. Synthetic Fe XVII-XVIII X-ray coronal spectra
and predictions for the Marshall Grazing-Incidence X-ray Spectrometer
(MaGIXS)
Authors: Dudík, Jaroslav; Dzifčáková, Elena; Del Zanna, Giulio;
Mason, Helen E.; Golub, Leon L.; Winebarger, Amy R.; Savage, Sabrina L.
Bibcode: 2019A&A...626A..88D
Altcode: 2019arXiv190510356D
Aims: We investigated the possibility of diagnosing the degree of
departure from the Maxwellian distribution using the Fe XVII-Fe XVIII
spectra originating in plasmas in collisional ionization equilibrium,
such as in the cores of solar active regions or microflares.
Methods: The original collision strengths for excitation are integrated
over the non-Maxwellian electron κ-distributions characterized by a
high-energy tail. Synthetic X-ray emission line spectra were calculated
for a range of temperatures and κ. We focus on the 6-24 Å spectral
range to be observed by the upcoming Marshall Grazing-Incidence X-ray
Spectrometer MaGIXS.
Results: We find that many line intensity
ratios are sensitive to both T and κ. Best diagnostic options are
provided if a ratio involving both Fe XVII and Fe XVIII is combined
with another ratio involving lines formed within a single ion. The
sensitivity of such diagnostics to κ is typically a few tens of per
cent. Much larger sensitivity, of about a factor of two to three, can
be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used
in conjuction with the X-ray lines.
Conclusions: We conclude
that the MaGIXS instrument is well-suited for detection of departures
from the Maxwellian distribution, especially in active region cores.
Title: Linking the Sun to the heliosphere using composition data
and modelling: coronal jets as a test case
Authors: Wimmer-Schweingruber, Robert F.; Parenti, Susanna; Del Zanna,
G.; Edmondson, J.; Giunta, A.; Hansteen, V. H.; Higginson, A.; Lepri,
S.; Laming, M.; Lynch, B. J.; von Steiger, R. E.; Wiegelmann, T.;
Zambrana Prado, N.
Bibcode: 2019shin.confE.231W
Altcode:
Understanding the formation and evolution of the solar wind is still
a priority in the Solar and Heliospheric communities. We expect
a significant progress in terms of observations with the upcoming
Solar Orbiter mission (launch in 2020), which will provide detailed
in-situ measurements of the solar wind and several remote-sensing
observations. However, real progress will only be possible if we
improve our understanding of the physical link between what measured
in-situ and its source regions on the Sun. In this respect, the plasma
chemical and charge-state compositions are considered good diagnostic
tools. In this paper we present results obtained from an extensive team
work aiming at providing solid diagnostics for linking the in-situ and
the remote sensing measurements. For our test cases, we selected two
periods when a single active region produced, close to its sunspot,
jets which had a counterpart signature in the Heliosphere in the form
of type-III radio bursts. These jets therefore marked magnetically
open regions expanding in the heliosphere. Firstly, we looked for
signatures of the open field associated with the active regions in
in-situ data from ACE and WIND, finding potential tracers. Secondly,
we studied the magnetic topology of the full Sun and Heliosphere with
extrapolations of photospheric data and MHD modeling. We found that
the open field area is consistent with the source and evolution of the
jets, as observed with EUV imagers (SDO/AIA, STEREO/EUVI). Thirdly, we
analysed remote sensing EUV spectroscopic observations to measure the
plasma conditions (densities, temperatures and chemical composition)
whenever available. We then modeled the solar wind and charge
state evolution with the solar distance along the open fields to
establish a link between the in-situ signatures and the remote sensing
observations. We discuss the various difficulties associated with such
studies, and highlight how Solar Orbiter measurements can improve them.
Title: Elemental composition in quiescent prominences
Authors: Parenti, S.; Del Zanna, G.; Vial, J. -C.
Bibcode: 2019A&A...625A..52P
Altcode: 2019arXiv190500871P
Context. The first ionization potential (FIP) bias is currently used
to trace the propagation of solar features ejected by the wind and
solar eruptions (coronal mass ejections). The FIP bias also helps us to
understand the formation of prominences, as it is a tracer for the solar
origin of prominence plasma.
Aims: This work aims to provide
elemental composition and FIP bias in quiescent solar prominences. This
is key information to link these features to remnants of solar eruptions
measured in-situ within the heliosphere and to constrain the coronal or
photospheric origin of prominence plasma.
Methods: We used the
differential emission measure technique to derive the FIP bias of two
prominences. Quiet Sun chromospheric and transition region data were
used to test the atomic data and lines formation processes. We used
lines from low stage of ionization of Si, S, Fe, C, N, O, Ni, Mg, and
Ne, constraining the FIP bias in the range 4.2 ≤ log T ≤ 5.8. We
adopted a density-dependent ionization equilibrium.
Results:
We showed that the two prominences have photospheric composition. We
confirmed a photospheric composition in the quiet Sun. We also
identified opacity and/or radiative excitation contributions to the
line formation of a few lines regularly observed in prominences.
Conclusions: With our results we thus provide important elements for
correctly interpreting the upcoming Solar Orbiter/SPICE spectroscopic
data and to constrain prominence formation.
Title: Elemental composition in quiescent prominences
Authors: Parenti, Susanna; Del Zanna, Giulio; Vial, Jean-Claude
Bibcode: 2019shin.confE.182P
Altcode:
The first ionization potential (FIP) bias is currently used to trace the
propagation of solar features ejected by the wind and solar eruptions
(coronal mass ejections). The FIP bias also helps us to understand
the formation of prominences, as it is a tracer for the solar origin
of prominence plasma. This work aims to provide elemental composition
and FIP bias in quiescent solar prominences. This is key information
to link these features to remnants of solar eruptions measured in-situ
within the heliosphere and to constrain the coronal or photospheric
origin of prominence plasma. We used the differential emission measure
technique to derive the FIP bias of two prominences observed with
SOHO/SUMER. Quiet Sun chromospheric and transition region data were
used to test the atomic data and lines formation processes. We used
lines from low stage of ionization of Si, S, Fe, C, N, O, Ni, Mg, and
Ne, constraining the FIP bias in the range 4.2 < log T< 5.8. We
adopted a density-dependent ionization equilibrium. We showed that
the two prominences have photospheric composition. We also identified
opacity and/or radiative excitation contributions to the line formation
of a few lines regularly observed in prominences. With our results
we thus provide important elements for correctly interpreting the
upcoming Solar Orbiter/SPICE spectroscopic data and to constrain
prominence formation.
Title: On the Importance of Gradients in the Low-Energy Electron
Phase Space Density for Relativistic Electron Acceleration
Authors: Allison, Hayley J.; Horne, Richard B.; Glauert, Sarah A.;
Del Zanna, Giulio
Bibcode: 2019JGRA..124.2628A
Altcode:
Observations of the electron radiation belts have shown links between
increases in the low-energy seed population and enhancements in
the >1-MeV flux. During active times, low-energy electrons are
introduced to the radiation belt region before being accelerated to
higher energies via a range of mechanisms. The impact of variations
in the seed population on the 1-MeV flux level were explored using
the British Antarctic Survey Radiation Belt Model. We find that, for a
period from the 21 April to 9 May 2013, the increase in the low-energy
electron flux was vital to recreate the observed 1-MeV flux enhancement
on the 1 May but was less important for the 1-MeV enhancement on the 27
April 2013. To better understand the relationships between the different
energy populations, a series of idealized experiments with the 2-D
British Antarctic Survey Radiation Belt Model were performed, which
highlight a careful balance between losses and acceleration from chorus
waves. Seed population enhancements alter this balance by increasing
the phase space density gradient, and consequently, the rate of energy
diffusion, allowing acceleration to surpass loss. Additionally, we
demonstrate that even with the same chorus diffusion coefficients and
the same low-energy boundary condition, the flux of ∼500-keV to 1-MeV
electrons increased when starting with a hard spectrum but decreased for
a soft initial spectrum. This suggests that initial energy gradients in
the phase space density were important to determine whether >500-keV
electrons were enhanced due to chorus wave acceleration.
Title: CHIANTI—An Atomic Database for Emission Lines. XV. Version 9,
Improvements for the X-Ray Satellite Lines
Authors: Dere, K. P.; Del Zanna, G.; Young, P. R.; Landi, E.;
Sutherland, R. S.
Bibcode: 2019ApJS..241...22D
Altcode: 2019arXiv190205019D
CHIANTI contains a large quantity of atomic data for the analysis
of astrophysical spectra. Programs are available in IDL and
Python to perform calculation of the expected emergent spectrum
from these sources. The database includes atomic energy levels,
wavelengths, radiative transition probabilities, rate coefficients
for collisional excitation, ionization, and recombination, as well
as data to calculate free-free, free-bound, and two-photon continuum
emission. In Version 9, we improve the modeling of the satellite
lines at X-ray wavelengths by explicitly including autoionization
and dielectronic recombination processes in the calculation of level
populations for select members of the lithium isoelectronic sequence
and Fe XVIII-XXIII. In addition, existing data sets are updated,
new ions are added, and new total recombination rates for several Fe
ions are included. All data and IDL programs are freely available at http://www.chiantidatabase.org
or through SolarSoft, and the Python code
ChiantiPy is also freely available at https://github.com/chianti-atomic/ChiantiPy.
Title: Uncertainties on atomic data. A case study: N IV
Authors: Del Zanna, G.; Fernández-Menchero, L.; Badnell, N. R.
Bibcode: 2019MNRAS.484.4754D
Altcode: 2019MNRAS.tmp..393D; 2019arXiv190108450D
We consider three recent large-scale calculations for the radiative
and electron-impact excitation data of N IV, carried out with
different methods and codes. The scattering calculations employed the
relativistic Dirac R-matrix (DARC) method, the intermediate coupling
frame transformation (ICFT) R-matrix method, and the B-spline R-matrix
(BSR) method. These are all large-scale scattering calculations with
well-tested and sophisticated codes, which use the same set of target
states. One concern raised in previous literature is related to the
increasingly large discrepancies in the effective collision strengths
between the three sets of calculations for increasingly weak and/or
high-lying transitions. We have built three model ions and calculated
the intensities of all the main spectral lines in this ion. We have
found that, despite such large differences, excellent agreement (to
within ±20 per cent) exists between all the spectroscopically relevant
line intensities. This provides confidence in the reliability of the
calculations for plasma diagnostics. We have used the differences in the
radiative and excitation rates amongst the three sets of calculations
to obtain a measure of the uncertainty in each rate. Using a Monte
Carlo approach, we have shown how these uncertainties affect the
main theoretical ratios that are used to measure electron densities
and temperatures.
Title: VizieR Online Data Catalog: EUV irradiances of the quiet Sun
(Del Zanna, 2019)
Authors: Del Zanna, G.
Bibcode: 2019yCat..36240036D
Altcode:
Within the UK APAP network (www.apap-network.org), we have carried out
several large-scale structure and scattering R-matrix calculations
over the past few years to produce atomic data for dozens of ions
(see the review in Badnell et al., 2016JPhB...49i4001B). For the
assessment here, we use CHIANTI v.8 as a baseline, together with a few
minor changes that are being released within CHIANTI v.9 (Dere et al.,
2019, ApJ, submitted) and a large set of new atomic data that have
been prepared for CHIANTI v.10 (Del Zanna et al., in preparation). (1 data file).
Title: The EUV spectrum of the Sun: Quiet- and active-Sun irradiances
and chemical composition
Authors: Del Zanna, G.
Bibcode: 2019A&A...624A..36D
Altcode: 2019arXiv190108841D
We benchmark new atomic data against a selection of irradiances
obtained from medium-resolution quiet-Sun spectra in the extreme
ultraviolet (EUV), from 60 to 1040 Å. We used as a baseline the
irradiances measured during solar minimum on 2008 April 14 by the
prototype (PEVE) of the Solar Dynamics Observatory Extreme ultraviolet
Variability Experiment (EVE). We took into account some inconsistencies
in the PEVE data, using flight EVE data and irradiances we obtained
from Solar and Heliospheric Observatory (SoHO) Coronal Diagnostics
Spectrometer (CDS) data. We performed a differential emission measure
and find overall excellent agreement (to within the accuracy of the
observations, about 20%) between predicted and measured irradiances
in most cases, although we point out several problems with the
currently available ion charge-state distributions. We used the
photospheric chemical abundances of Asplund et al. (2009, ARA&A,
47, 481). The new atomic data are nearly complete in this spectral
range for medium-resolution irradiance spectra. Finally, we used
observations of the active Sun in 1969 to show that the composition
of the solar corona up to 1 MK is nearly photospheric in this case as
well. Variations of a factor of 2 are present for higher-temperature
plasma, which is emitted within active regions. These results are
in excellent agreement with our previous findings. The full
Table A.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/624/A36
Title: VizieR Online Data Catalog: S-like ions from Cr IX to Cu XIV
transitions (Wang+, 2018)
Authors: Wang, K.; Song, C. X.; Jonsson, P.; Del Zanna, G.; Schiffmann,
S.; Godefroid, M.; Gaigalas, G.; Zhao, X. H.; Si, R.; Chen, C. Y.;
Yan, J.
Bibcode: 2019yCat..22390030W
Altcode:
We present a consistent set of calculated energies and E1, M1,
E2, M2 radiative transition data for the main n=3 levels from the
3s23p4, 3p6, 3s3p43d,
3s23p23d2, 3s3p5,
3s23p33d, and 3s3p33d2
configurations for S-like ions from CrIX to CuXIV. The fully
relativistic multiconfiguration Dirac-Hartree-Fock method implemented in
the GRASP2K code (Jonsson+ 2007CoPhC.177..597J ; 2013CoPhC.184.2197J)
is used to perform the present calculations. The excitation energies
of the lowest 47 levels from the 3s23p4,
3s3p5, and 3s23p33d configurations,
producing the strongest lines, are found to be in good agreement,
reaching spectroscopic accuracy, with the latest experimental
values for FeXI evaluated by Del Zanna. Our energies can reliably
be used to identify in astrophysical and laboratory spectra the
3s23p33d levels in other S-like ions, which are
mostly unknown. On the contrary, significant discrepancies with the
3s3p43d levels were found, emphasizing the need for more
detailed experimental studies. A few new tentative identifications
are suggested. The benchmarks we present indicate that our consistent
set of radiative data is accurate and can be used for spectral line
modeling. (2 data files).
Title: Flare-related Recurring Active Region Jets: Evidence for Very
Hot Plasma
Authors: Mulay, Sargam M.; Matthews, Sarah; Hasegawa, Takahiro;
Del Zanna, Giulio; Mason, Helen; Shimizu, Toshifumi
Bibcode: 2018SoPh..293..160M
Altcode:
We present a study of two active region jets (AR jets) that are
associated with two C-class X-ray flares. The recurrent, homologous
jets originated from the northern periphery of a sunspot. We
confirm flare-like temperatures at the footpoints of these jets using
spectroscopic observations of Fe XXIII (263.76 Å) and Fe XXIV (255.11
Å) emission lines. The emission measure loci method was used to obtain
an isothermal temperature, and the results show a decrease (17.7 to 13.6
MK) in the temperature during the decay phase of the C 3.0 flare. The
electron number densities at the footpoints were found to range from
1.7 ×1010 to 2.0 ×1011cm−3 using
the Fe XIV line pair ratio. Nonthermal velocities were found to range
from 34 - 100 km/s for Fe XXIV and 51 - 89 km/s for Fe XXIII. The
plane-of-sky velocities were calculated to be 462 ±21 and 228 ±23
km/s for the two jets using the Atmospheric Imaging Assembly (AIA)
171 Å channel. The AIA light curves of the jet footpoint regions
confirmed the temporal and spatial correlation between the two X-ray
flares and the jet footpoint emission. The Gamma-ray Burst Monitor (GBM)
also confirmed superhot plasma of 27 (25) MK with a nonthermal energy
of 2.38 ×1026 (2.87 ×1027) ergs−1
in the jet footpoint region during the rise (peak) phase of one of the
flares. The temperatures of the jet footpoint regions obtained from
EIS agree very well (within an uncertainty of 20%) with temperatures
obtained from the Geostationary Environmental Operational Satellite
(GOES) flux ratios. These results provide clear evidence for very hot
plasma (>10 MK) at the footpoints of the flare-related jets, and
they confirm the heating and cooling of the plasma during the flares.
Title: Benchmarking Atomic Data from Large-scale Multiconfiguration
Dirac-Hartree-Fock Calculations for Astrophysics: S-like Ions from
Cr IX to Cu XIV
Authors: Wang, K.; Song, C. X.; Jönsson, P.; Del Zanna, G.;
Schiffmann, S.; Godefroid, M.; Gaigalas, G.; Zhao, X. H.; Si, R.;
Chen, C. Y.; Yan, J.
Bibcode: 2018ApJS..239...30W
Altcode:
We present a consistent set of calculated energies and E1,
M1, E2, M2 radiative transition data for the main n = 3
levels from the 3s 23p 4, 3p 6,
3s3{p}43d, 3{s}23{p}23{d}2,
3s3{p}5, 3{s}23{p}33d, and
3s3{p}33{d}2 configurations for S-like ions
from Cr IX to Cu XIV. The fully relativistic multiconfiguration
Dirac-Hartree-Fock method implemented in the GRASP2K code is used
to perform the present calculations. The excitation energies of
the lowest 47 levels from the 3{s}23{p}4,
3s3{p}5, and 3{s}23{p}33d
configurations, producing the strongest lines, are found to be in
good agreement, reaching spectroscopic accuracy, with the latest
experimental values for Fe XI evaluated by Del Zanna. Our energies can
reliably be used to identify in astrophysical and laboratory spectra the
3{s}23{p}33d levels in other S-like ions, which
are mostly unknown. On the contrary, significant discrepancies with the
3s3p 43d levels were found, emphasizing the need for more
detailed experimental studies. A few new tentative identifications are
suggested. The benchmarks we present indicate that our consistent set of
radiative data is accurate and can be used for spectral line modeling.
Title: Determination of the Equatorial Electron Differential Flux
From Observations at Low Earth Orbit
Authors: Allison, Hayley J.; Horne, Richard B.; Glauert, Sarah A.;
Del Zanna, Giulio
Bibcode: 2018JGRA..123.9574A
Altcode:
Variations in the high-energy relativistic electron flux of the
radiation belts depend on transport, acceleration, and loss processes,
and importantly on the lower-energy seed population. However, data
on the seed population is limited to a few satellite missions. Here
we present a new method that utilizes data from the Medium Energy
Proton/Electron Detector on board the low-altitude Polar Operational
Environmental Satellites to retrieve the seed population at a pitch
angle of 90°. The integral flux values measured by Medium Energy
Proton/Electron Detector relate to a low equatorial pitch angle and were
converted to omnidirectional flux using parameters obtained from fitting
one or two sinNα functions to pitch angle distributions given by three
and a half years of Van Allen Probes data. Two methods to convert from
integral to differential flux are explored. One utilizes integral and
differential flux energy distributions from the AE9 model, the second
employs an iterative fitting approach based on a Reverse Monte Carlo
(RMC) method. The omnidirectional differential flux was converted to
an equatorial pitch angle of 90°, again using statistical pitch angle
distributions from Van Allen Probe data. We validate the resulting
90° flux for 100- to 600-keV electrons against measurements from the
Van Allen Probes and show an average agreement within a factor of 4
for L* > 3.7. The resulting data set offers a high time resolution,
across multiple magnetic local time planes, and may be used to formulate
event-specific low-energy boundary conditions for radiation belt models.
Title: Predicting the COSIE-C Signal from the Outer Corona up to 3
Solar Radii
Authors: Del Zanna, Giulio; Raymond, John; Andretta, Vincenzo; Telloni,
Daniele; Golub, Leon
Bibcode: 2018ApJ...865..132D
Altcode: 2018arXiv180807951D
We present estimates of the signal to be expected in quiescent solar
conditions, as would be obtained with the COronal Spectrographic
Imager in the EUV in its coronagraphic mode (COSIE-C). COSIE-C has been
proposed to routinely observe the relatively unexplored outer corona,
where we know that many fundamental processes affecting both the lower
corona and the solar wind are taking place. The COSIE-C spectral band,
186-205 Å, is well-known as it has been observed with Hinode EIS. We
present Hinode EIS observations that we obtained in 2007 out to 1.5 R
⊙, to show that this spectral band in quiescent streamers
is dominated by Fe XII and Fe XI and that the ionization temperature
is nearly constant. To estimate the COSIE-C signal in the 1.5-3.1
R ⊙ region we use a model based on CHIANTI atomic data
and SoHO UVCS observations in the Si XII and Mg X coronal lines of
two quiescent 1996 streamers. We reproduce the observed EUV radiances
with a simple density model, photospheric abundances, and a constant
temperature of 1.4 MK. We show that other theoretical or semi-empirical
models fail to reproduce the observations. We find that the coronal
COSIE-C signal at 3 R ⊙ should be about 5 counts/s per
3.″1 pixel in quiescent streamers. This is unprecedented and opens
up a significant discovery space. We also briefly discuss stray light
and the visibility of other solar features. In particular, we present
UVCS observations of an active region streamer, indicating increased
signal compared to the quiet Sun cases.
Title: Incorporating Uncertainties in Atomic Data into the Analysis
of Solar and Stellar Observations: A Case Study in Fe XIII
Authors: Yu, Xixi; Del Zanna, Giulio; Stenning, David C.;
Cisewski-Kehe, Jessi; Kashyap, Vinay L.; Stein, Nathan; van Dyk,
David A.; Warren, Harry P.; Weber, Mark A.
Bibcode: 2018ApJ...866..146Y
Altcode: 2018arXiv180906173Y
Information about the physical properties of astrophysical objects
cannot be measured directly but is inferred by interpreting
spectroscopic observations in the context of atomic physics
calculations. Ratios of emission lines, for example, can be used
to infer the electron density of the emitting plasma. Similarly,
the relative intensities of emission lines formed over a wide range
of temperatures yield information on the temperature structure. A
critical component of this analysis is understanding how uncertainties
in the underlying atomic physics propagate to the uncertainties in
the inferred plasma parameters. At present, however, atomic physics
databases do not include uncertainties on the atomic parameters and
there is no established methodology for using them even if they
did. In this paper we develop simple models for uncertainties in
the collision strengths and decay rates for Fe XIII and apply them
to the interpretation of density-sensitive lines observed with the
EUV (extreme ultraviolet) Imagining spectrometer (EIS) on Hinode. We
incorporate these uncertainties in a Bayesian framework. We consider
both a pragmatic Bayesian method where the atomic physics information is
unaffected by the observed data, and a fully Bayesian method where the
data can be used to probe the physics. The former generally increases
the uncertainty in the inferred density by about a factor of 5 compared
with models that incorporate only statistical uncertainties. The latter
reduces the uncertainties on the inferred densities, but identifies
areas of possible systematic problems with either the atomic physics
or the observed intensities.
Title: VizieR Online Data Catalog: Energy levels & transition
rates for P-like ions (Wang+, 2018)
Authors: Wang, K.; Jonsson, P.; Gaigalas, G.; Radziute, L.; Rynkun,
P.; Del Zanna, G.; Chen, C. Y.
Bibcode: 2018yCat..22350027W
Altcode:
The fully relativistic multiconfiguration Dirac-Hartree-Fock method
is used to compute excitation energies and lifetimes for the 143
lowest states of the 3s23p3, 3s3p4,
3s23p23d, 3s3p33d, 3p5,
3s23p3d2 configurations in P-like ions from Cr X
to Zn XVI. Multipole (E1, M1, E2, M2) transition rates, line strengths,
oscillator strengths, and branching fractions among these states are
also given. Valence-valence and core-valence electron correlation
effects are systematically accounted for using large basis function
expansions. Computed excitation energies are compared with the NIST ASD
and CHIANTI compiled values and previous calculations. The mean average
absolute difference, removing obvious outliers, between computed and
observed energies for the 41 lowest identified levels in Fe XII, is
only 0.057%, implying that the computed energies are accurate enough
to aid identification of new emission lines from the Sun and other
astrophysical sources. The amount of energy and transition data of
high accuracy are significantly increased for several P-like ions of
astrophysics interest, where experimental data are still very scarce. (2 data files).
Title: Solar UV and X-ray spectral diagnostics
Authors: Del Zanna, Giulio; Mason, Helen E.
Bibcode: 2018LRSP...15....5D
Altcode: 2018arXiv180901618D
X-ray and ultraviolet (UV) observations of the outer solar atmosphere
have been used for many decades to measure the fundamental parameters
of the solar plasma. This review focuses on the optically thin
emission from the solar atmosphere, mostly found at UV and X-ray (XUV)
wavelengths, and discusses some of the diagnostic methods that have
been used to measure electron densities, electron temperatures,
differential emission measure (DEM), and relative chemical
abundances. We mainly focus on methods and results obtained from
high-resolution spectroscopy, rather than broad-band imaging. However,
we note that the best results are often obtained by combining imaging
and spectroscopic observations. We also mainly focus the review on
measurements of electron densities and temperatures obtained from single
ion diagnostics, to avoid issues related to the ionisation state of
the plasma. We start the review with a short historical introduction
on the main XUV high-resolution spectrometers, then review the basics
of optically thin emission and the main processes that affect the
formation of a spectral line. We mainly discuss plasma in equilibrium,
but briefly mention non-equilibrium ionisation and non-thermal electron
distributions. We also summarise the status of atomic data, which
are an essential part of the diagnostic process. We then review the
methods used to measure electron densities, electron temperatures,
the DEM, and relative chemical abundances, and the results obtained
for the lower solar atmosphere (within a fraction of the solar radii),
for coronal holes, the quiet Sun, active regions and flares.
Title: Chemical fractionation in solar prominences
Authors: Parenti, Susanna; Vial, Jean-Claude; Del Zanna, Giulio
Bibcode: 2018cosp...42E2585P
Altcode:
The First Ionization Potential (FIP) fractionation of elemental
abundances in the solar atmosphere and solar wind is a known process
which appears to vary depending on the magnetic field property and
the dynamic nature of the environment. It is generally identified
by an increase of the low FIP elements (with FIP energy below 10 eV)
compared to the high FIP elements (with respect to the photospheric
values). For instance, the low FIP element abundance is enhanced
within active regions by about a factor of 3-4, with respect to
photospheric values. A similar property is measured in the slow
solar wind. This is one of the reasons why the FIP fractionation is
used as a proxy for identifying the solar wind source regions on the
Sun, a topic of particular relevance for the upcoming Solar Orbiter
mission.Cool, low-state ionized plasma and its composition have been
measured in-situ within interplanetary Coronal Mass Ejections (ICMEs)
in only a few cases. This cool plasma has been associated to remnants
of erupting prominences. However, this association is not confirmed,
because the measurement of the composition within prominence plasma is
very difficult and poorly known. The scope of this paper is to provide
a reliable measurement of elements composition and FIP fractionation in
a prominence using the available SOHO/SUMER dataset of the prominence
atlas presented in Parenti et. al 2005. Our investigation will consider
ions formed in the prominence-corona transition region, taking into
account possible density and opacity effects in the formation of the
spectral lines.
Title: Energy Levels, Lifetimes, and Transition Rates for P-like Ions
from Cr X to Zn XVI from Large-scale Relativistic Multiconfiguration
Calculations
Authors: Wang, K.; Jönsson, P.; Gaigalas, G.; Radžiūtė, L.;
Rynkun, P.; Del Zanna, G.; Chen, C. Y.
Bibcode: 2018ApJS..235...27W
Altcode: 2018arXiv180209671W
The fully relativistic multiconfiguration Dirac-Hartree-Fock
method is used to compute excitation energies and lifetimes for
the 143 lowest states of the 3{s}23{p}3, 3s3p
4, 3{s}23{p}23d, 3s3p 33d,
3p 5, 3{s}23p3{d}2 configurations in
P-like ions from Cr X to Zn XVI. Multipole (E1, M1, E2, M2) transition
rates, line strengths, oscillator strengths, and branching fractions
among these states are also given. Valence-valence and core-valence
electron correlation effects are systematically accounted for using
large basis function expansions. Computed excitation energies are
compared with the NIST ASD and CHIANTI compiled values and previous
calculations. The mean average absolute difference, removing obvious
outliers, between computed and observed energies for the 41 lowest
identified levels in Fe XII, is only 0.057%, implying that the computed
energies are accurate enough to aid identification of new emission lines
from the Sun and other astrophysical sources. The amount of energy
and transition data of high accuracy are significantly increased for
several P-like ions of astrophysics interest, where experimental data
are still very scarce.
Title: Solar Coronal Lines in the Visible and Infrared: A Rough Guide
Authors: Del Zanna, Giulio; DeLuca, Edward E.
Bibcode: 2018ApJ...852...52D
Altcode: 2017arXiv170803626D
We review the coronal visible and infrared lines, collecting previous
observations and comparing, whenever available, observed radiances to
those predicted by various models: the quiet Sun (QS), a moderately
active Sun, and an active region as observed near the limb, around
1.1 R ⊙. We also model the off-limb radiances for the QS
case. We used the most up-to-date atomic data in CHIANTI version 8. The
comparison is satisfactory, in that all of the strong visible lines now
have a firm identification. We revise several previous identifications
and suggest some new ones. We also list the large number of observed
lines for which we do not currently have atomic data, and therefore
still await firm identifications. We also show that a significant number
of coronal lines should be observable in the near-infrared region of
the spectrum by the upcoming Daniel K. Inouye Solar Telescope (DKIST)
and the AIR-Spec instrument, which observed the corona during the 2017
August 21 solar eclipse. We also briefly discuss the many potential
spectroscopic diagnostics available to the visible and infrared, with
particular emphasis on measurements of electron densities and chemical
abundances. We briefly point out some of the potential diagnostics
that could be available with the future infrared instrumentation that
is being built for DKIST and planned for the Coronal Solar Magnetism
Observatory. Finally, we highlight the need for further improvements
in the atomic data.
Title: The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS)
Authors: Winebarger, A. R.; Savage, S. L.; Kobayashi, K.; Champey,
P. R.; McKenzie, D. E.; Golub, L.; Testa, P.; Reeves, K.; Cheimets,
P.; Cirtain, J. W.; Walsh, R. W.; Bradshaw, S. J.; Warren, H.; Mason,
H. E.; Del Zanna, G.
Bibcode: 2017AGUFMSH44A..06W
Altcode:
For over four decades, X-ray, EUV, and UV spectral observations have
been used to measure physical properties of the solar atmosphere. At
wavelengths below 10 nm, however, observations of the solar corona
with simultaneous spatial and spectral resolution are limited,
and not since the late 1970's have spatially resolved solar X-ray
spectra been measured. Because the soft X-ray regime is dominated
by emission lines formed at high temperatures, X-ray spectroscopic
techniques yield insights to fundamental physical processes that are
not accessible by any other means. Using a novel implementation of
corrective optics, the Marshall Grazing Incidence X-ray Spectrometer
(MaGIXS) will measure, for the first time, the solar spectrum from 0.6-
2.4 nm with a 6 arcsec resolution over an 8 arcmin slit. The MaGIXS
mission will address on of the fundamental problems of coronal physics:
the nature of coronal heating. There are several observables in the
MaGIXS wavelength range that will constrain the heating frequency and
hence discriminate between competing coronal heating theories. In this
presentation, we will present the MaGIXS scientific motivation and
provide an update on instrument development. MaGIXS will be launched
from White Sands Missile Range in the summer of 2019.
Title: Cool and hot emission in a recurring active region jet
Authors: Mulay, Sargam M.; Del Zanna, Giulio; Mason, Helen
Bibcode: 2017A&A...606A...4M
Altcode:
Aims: We present a thorough investigation of the cool and hot
temperature components in four recurring active region jets observed
on July 10, 2015 using the Atmospheric Imaging Assembly (AIA),
X-ray Telescope (XRT), and Interface Region Imaging Spectrograph
(IRIS) instruments.
Methods: A differential emission measure
(DEM) analysis was performed on areas in the jet spire and footpoint
regions by combining the IRIS spectra and the AIA observations. This
procedure better constrains the low temperature DEM values by adding
IRIS spectral lines. Plasma parameters, such as Doppler velocities,
electron densities, nonthermal velocities and a filling factor
were also derived from the IRIS spectra.
Results: In the
DEM analysis, significant cool emission was found in the spire and
the footpoint regions. The hot emission was peaked at log T [K] =
5.6-5.9 and 6.5 respectively. The DEM curves show the presence of
hot plasma (T = 3 MK) in the footpoint region. We confirmed this
result by estimating the Fe XVIII emission from the AIA 94 Å channel
which was formed at an effective temperature of log T [K] = 6.5. The
average XRT temperatures were also found to be in agreement with log
T [K] = 6.5. The emission measure (EM) was found to be three orders
of magnitude higher in the AIA-IRIS DEM compared with that obtained
using only AIA. The O IV (1399/1401 Å) electron densities were found
to be 2.0×1010 cm-3 in the spire and 7.6 ×
1010 cm-3 in the footpoint. Different threads
along the spire show different plane-of-sky velocities both in the
lower corona and transition region. Doppler velocities of 32 km
s-1 (blueshifted) and 13 km s-1 (redshifted)
were obtained in the spire and footpoint, respectively from the
Si IV 1402.77 Å spectral line. Nonthermal velocities of 69 and 53
km s-1 were recorded in the spire and footpoint region,
respectively. We obtained a filling factor of 0.1 in the spire at
log T [K] = 5.
Conclusions: The recurrent jet observations
confirmed the presence of significant cool emission co-spatial with the
coronal emission. The movie attached to Fig. 3 is available at http://www.aanda.org
Title: Spectroscopy of Very Hot Plasma in Non-flaring Parts of a
Solar Limb Active Region: Spatial and Temporal Properties
Authors: Parenti, Susanna; del Zanna, Giulio; Petralia, Antonino;
Reale, Fabio; Teriaca, Luca; Testa, Paola; Mason, Helen E.
Bibcode: 2017ApJ...846...25P
Altcode: 2017arXiv170708445P
In this work we investigate the thermal structure of an off-limb
active region (AR) in various non-flaring areas, as it provides key
information on the way these structures are heated. In particular,
we concentrate on the very hot component (> 3 {MK}) as it is a
crucial element to distinguish between different heating mechanisms. We
present an analysis using Fe and Ca emission lines from both the
Solar Ultraviolet Measurement of Emitted Radiation (SUMER) on board
the Solar and Heliospheric Observatory (SOHO) and the EUV Imaging
Spectrometer (EIS) on board Hinode. A data set covering all ionization
stages from Fe x to Fe xix has been used for the thermal analysis
(both differential emission measure and emission measure, EM). Ca
xiv is used for the SUMER-EIS radiometric cross calibration. We show
that the very hot plasma is present and persistent almost everywhere
in the core of the limb AR. The off-limb AR is clearly structured in
Fe xviii. Almost everywhere, the EM analysis reveals plasma at 10 MK
(visible in Fe xix emission), which is down to 0.1% of EM of the main
3 {MK} plasma. We estimate the power-law index of the hot tail of
the EM to be between -8.5 and -4.4. However, the question about the
possible existence of a small minor peak at around 10 {MK} remains
open. The absence in some part of the AR of the Fe xix and Fe xxiii
lines (which fall into our spectral range) enables us to determine
an upper limit on the EM at these temperatures. Our results include
a new Ca xiv 943.59 Å atomic model.
Title: Nonequilibrium Processes in the Solar Corona, Transition
Region, Flares, and Solar Wind (Invited Review)
Authors: Dudík, Jaroslav; Dzifčáková, Elena; Meyer-Vernet, Nicole;
Del Zanna, Giulio; Young, Peter R.; Giunta, Alessandra; Sylwester,
Barbara; Sylwester, Janusz; Oka, Mitsuo; Mason, Helen E.; Vocks,
Christian; Matteini, Lorenzo; Krucker, Säm; Williams, David R.;
Mackovjak, Šimon
Bibcode: 2017SoPh..292..100D
Altcode: 2017arXiv170603396D
We review the presence and signatures of the non-equilibrium processes,
both non-Maxwellian distributions and non-equilibrium ionization, in
the solar transition region, corona, solar wind, and flares. Basic
properties of the non-Maxwellian distributions are described
together with their influence on the heat flux as well as on the
rates of individual collisional processes and the resulting optically
thin synthetic spectra. Constraints on the presence of high-energy
electrons from observations are reviewed, including positive detection
of non-Maxwellian distributions in the solar corona, transition
region, flares, and wind. Occurrence of non-equilibrium ionization
is reviewed as well, especially in connection to hydrodynamic and
generalized collisional-radiative modeling. Predicted spectroscopic
signatures of non-equilibrium ionization depending on the assumed
plasma conditions are summarized. Finally, we discuss the future
remote-sensing instrumentation that can be used for the detection of
these non-equilibrium phenomena in various spectral ranges.
Title: Non-Maxwellian Analysis of the Transition-region Line Profiles
Observed by the Interface Region Imaging Spectrograph
Authors: Dudík, Jaroslav; Polito, Vanessa; Dzifčáková, Elena;
Del Zanna, Giulio; Testa, Paola
Bibcode: 2017ApJ...842...19D
Altcode: 2017arXiv170502104D
We investigate the nature of the spectral line profiles for
transition-region (TR) ions observed with the Interface Region Imaging
Spectrograph (IRIS). In this context, we analyzed an active-region
observation performed by IRIS in its 1400 Å spectral window. The TR
lines are found to exhibit significant wings in their spectral profiles,
which can be well fitted with a non-Maxwellian κ distribution. The fit
with a κ distribution can perform better than a double-Gaussian fit,
especially for the strongest line, Si IV 1402.8 Å. Typical values of κ
found are about 2, occurring in a majority of spatial pixels where the
TR lines are symmetric, I.e., the fit can be performed. Furthermore,
all five spectral lines studied (from Si IV, O IV, and S IV) appear
to have the same full-width at half-maximum irrespective of whether
the line is an allowed or an intercombination transition. A similar
value of κ is obtained for the electron distribution by the fitting
of the line intensities relative to Si IV 1402.8 Å, if photospheric
abundances are assumed. The κ distributions, however, do not remove
the presence of non-thermal broadening. Instead, they actually increase
the non-thermal width. This is because, for κ distributions, TR ions
are formed at lower temperatures. The large observed non-thermal width
lowers the opacity of the Si IV line sufficiently enough for this line
to become optically thin.
Title: Analysis and modelling of recurrent solar flares observed
with Hinode/EIS on March 9, 2012
Authors: Polito, V.; Del Zanna, G.; Valori, G.; Pariat, E.; Mason,
H. E.; Dudík, J.; Janvier, M.
Bibcode: 2017A&A...601A..39P
Altcode: 2016arXiv161203504P
Three homologous C-class flares and one last M-class flare were observed
by both the Solar Dynamics Observatory (SDO) and the Hinode EUV Imaging
Spectrometer (EIS) in the AR 11429 on March 9, 2012. All the recurrent
flares occurred within a short interval of time (less than 4 h),
showed very similar plasma morphology and were all confined, until the
last one when a large-scale eruption occurred. The C-class flares are
characterized by the appearance, at approximatively the same locations,
of two bright and compact footpoint sources of ≈3-10 MK evaporating
plasma, and a semi-circular ribbon. During all the flares, the
continuous brightening of a spine-like hot plasma (≈10 MK) structure
is also observed. Spectroscopic observations with Hinode/EIS are used to
measure and compare the blueshift velocities in the Fe xxiii emission
line and the electron number density at the flare footpoints for each
flare. Similar velocities, of the order of 150-200 km s-1,
are observed during the C2.0 and C4.7 confined flares, in agreement
with the values reported by other authors in the study of the last M1.8
class flare. On the other hand, lower electron number densities and
temperatures tend to be observed in flares with lower peak soft X-ray
flux. In order to investigate the homologous nature of the flares, we
performed a non-linear force-free field (NLFFF) extrapolation of the 3D
magnetic field configuration in the corona. The NLFFF extrapolation and
the Quasi-Separatrix Layers (QSLs) provide the magnetic field context
which explains the location of the kernels, spine-like hot plasma and
semi-circular brightenings observed in the (non-eruptive) flares. Given
the absence of a coronal null point, we argue that the homologous
flares were all generated by the continuous recurrence of bald patch
reconnection. The movie associated to Fig. 2 is available at http://www.aanda.org
Title: Multi-instrument observations of a failed flare eruption
associated with MHD waves in a loop bundle
Authors: Nisticò, G.; Polito, V.; Nakariakov, V. M.; Del Zanna, G.
Bibcode: 2017A&A...600A..37N
Altcode: 2016arXiv161202077N
Context. We present observations of a B7.9-class flare that occurred on
the 24th January, 2015, using the Atmospheric Imaging Assembly (AIA)
of the Solar Dynamics Observatory (SDO), the EUV Imaging Spectrometer
(EIS) and the X-Ray Telescope of Hinode. The flare triggers the eruption
of a dense cool plasma blob as seen in AIA 171 Å, which is unable
to completely break out and remains confined within a local bundle
of active region loops. During this process, transverse oscillations
of the threads are observed. The cool plasma is then observed to
descend back to the chromosphere along each loop strand. At the same
time, a larger diffuse co-spatial loop observed in the hot wavebands
of SDO/AIA and Hinode/XRT is formed, exhibiting periodic intensity
variations along its length.
Aims: The formation and evolution
of magnetohydrodynamic (MHD) waves depend upon the values of the local
plasma parameters (e.g. density, temperature and magnetic field),
which can hence be inferred by coronal seismology. In this study we
aim to assess how the observed MHD modes are affected by the variation
of density and temperature.
Methods: We combined analysis
of EUV/X-ray imaging and spectroscopy using SDO/AIA, Hinode/EIS
and XRT.
Results: The transverse oscillations of the cool
loop threads are interpreted in terms of vertically polarised kink
oscillations. The fitting procedure applied to the loop displacement
time series gives a period of 3.5 to 4 min, and an amplitude of 5
Mm. The oscillations are strongly damped showing very low quality
factor (1.5-2), which is defined as the ratio of the damping time and
the oscillation period. The weak variation of the period of the kink
wave, which is estimated from the fitting analysis, is in agreement
with the density variations due to the presence of the plasma blob
inferred from the intensity light curve at 171 Å. The coexisting
intensity oscillations along the hot loop are interpreted as a slow
MHD wave with a period of 10 min and phase speed of approximately 436
km s-1. Comparison between the fast and slow modes allows
for the determination of the Alfvén speed, and consequently magnetic
field values. The plasma-β inferred from the analysis is estimated to
be approximately 0.1-0.3.
Conclusions: We show that the evolution
of the detected waves is determined by the temporal variations of the
local plasma parameters, caused by the flare heating and the consequent
cooling. We apply coronal seismology to both waves obtaining estimates
of the background plasma parameters. Movies are available at http://www.aanda.org
Title: Temperature and density structure of a recurring active
region jet
Authors: Mulay, Sargam M.; Del Zanna, Giulio; Mason, Helen
Bibcode: 2017A&A...598A..11M
Altcode: 2016arXiv160908472M
Aims: We present a study of a recurring jet observed on
October 31, 2011 by the Atmosphereic Imaging Assembly (AIA) on
board the Solar Dynamic Observatory, the X-ray Telescope (XRT)
and EUV Imaging Spectrometer (EIS) on board Hinode. We discuss the
physical parameters of the jet that are obtained using imaging and
spectroscopic observations, such as density, differential emission
measure, peak temperature, velocity, and filling factor.
Methods:
A differential emission measure (DEM) analysis was performed at the
region of the jet spire and the footpoint using EIS observations
and also by combining AIA and XRT observations. The resulting
EIS DEM curves were compared to those obtained with AIA-XRT. The
DEM curves were used to create synthetic spectra with the CHIANTI
atomic database. The predicted total count rates for each AIA channel
were compared with the observed count rates. The effects of varying
elemental abundances and the temperature range for the DEM inversion
were investigated. Spectroscopic diagnostics were used to obtain
an electron number density distribution for the jet spire and the
jet footpoint.
Results: The plasma along the line of sight
in the jet spire and jet footpoint was found to be peak at 2.0 MK
(log T [K] = 6.3). We calculated electron densities using the Fe XII
(λ186/λ195) line ratio in the region of the spire (Ne
= 7.6 × 1010 cm-3) and the footpoint (1.1
× 1011 cm-3). The plane-of-sky velocity of
the jet is found to be 524 km s-1. The resulting EIS DEM
values are in good agreement with those obtained from AIA-XRT. The
synthetic spectra contributing to each AIA channel confirms the
multi-thermal nature of the AIA channels in both regions. There is
no indication of high temperatures, such as emission from Fe XVII
(λ254.87) (log T [K] = 6.75) seen in the jet spire. In the case of
the jet footpoint, synthetic spectra predict weak contributions from
Ca XVII (λ192.85) and Fe XVII (λ254.87). With further investigation,
we confirmed emission from the Fe XVIII (93.932 Å) line in the AIA
94 Å channel in the region of the footpoint. We also found good
agreement between the estimated and predicted Fe XVIII count rates. A
study of the temporal evolution of the jet footpoint and the presence
of high-temperature emission from the Fe XVIII (λ93.932) (log T [K]
= 6.85) line leads us to conclude that the hot component in the jet
footpoint was present initially and that the jet had cooled down by the
time EIS observed it. Two movies attached to Fig. 2 are available
at http://www.aanda.org
Title: Can the non-Maxwellian kappa-distributions be diagnosed in
the solar corona?
Authors: Dudík, J.; Dzifcakova, E.; Del Zanna, G.; Mackovjak, Š.;
Mason, H. E.
Bibcode: 2016AGUFMSH21D2555D
Altcode:
We report on the search of signatures of the non-Maxwellian
kappa-distributions in the emission line spectra of the solar
corona. A survey of coronal lines is performed for single-ion and
multi-ion diagnostics using ions spanning the temperature range of
0.5 - 6 MK. State-of-art excitation cross-sections are integrated
directly to obtain the corresponding non-Maxwellian excitation and
deexcitation rates. Ionization and recombination rates are obtained by
approximative methods. We find that there are only a few good diagnostic
options. This is due to majority of lines being formed from similar
energy levels. The best diagnostic options rely on lines formed at
different excitation tresholds, i.e., at different wavelengths. This
highlights the importance of absolute intensity calibration of
space-borne spectrometers. The applicability of these methods is
demonstrated on analysis of a dedicated extreme-ultraviolet observations
made in the Fe XI-XIII lines by the Hinode/EIS satellite during HOP
226. The observations are performed in an active region containing a
filament and several coronal loops. A transient coronal loop appears
at the foot of a filament and is preceded by activity within this
filament. EIS spectra are used to diagnose the electron density,
but also reveal that the transient loop is highly non-Maxwellian,
characterized by a kappa=2 distribution. We discuss the methods for
separation the non-Maxwellian effects from the effects of plasma
multi-thermality arising due to finite spatial resolution, as well
as the effect of kappa-distributions on the degree of multithermality
diagnosed in various observed coronal features.
Title: Density diagnostics derived from the O iv and S iv
intercombination lines observed by IRIS
Authors: Polito, V.; Del Zanna, G.; Dudík, J.; Mason, H. E.; Giunta,
A.; Reeves, K. K.
Bibcode: 2016A&A...594A..64P
Altcode: 2016arXiv160705072P
The intensity of the O iv 2s2 2p
2P-2s2p24P and S iv 3 s2
3p 2P-3s 3p24 P intercombination lines
around 1400 Å observed with the Interface Region Imaging Spectrograph
(IRIS) provide a useful tool to diagnose the electron number density
(Ne) in the solar transition region plasma. We measure the
electron number density in a variety of solar features observed by
IRIS, including an active region (AR) loop, plage and brightening,
and the ribbon of the 22-June-2015 M 6.5 class flare. By using the
emissivity ratios of O iv and S iv lines, we find that our observations
are consistent with the emitting plasma being near isothermal
(logT[K] ≈ 5) and iso-density (Ne ≈ 1010.6
cm-3) in the AR loop. Moreover, high electron number
densities (Ne ≈ 1013 cm-3) are
obtained during the impulsive phase of the flare by using the S iv line
ratio. We note that the S iv lines provide a higher range of density
sensitivity than the O iv lines. Finally, we investigate the effects
of high densities (Ne ≳ 1011 cm-3)
on the ionization balance. In particular, the fractional ion
abundances are found to be shifted towards lower temperatures for
high densities compared to the low density case. We also explored the
effects of a non-Maxwellian electron distribution on our diagnostic
method. The movie associated to Fig. 3 is available at http://www.aanda.org
Title: Scaling of collision strengths for highly-excited states of
ions of the H- and He-like sequences
Authors: Fernández-Menchero, L.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2016A&A...592A.135F
Altcode: 2016arXiv160702487F
Emission lines from highly-excited states (n ≥ 5) of H- and He-like
ions have been detected in astrophysical sources and fusion plasmas. For
such excited states, R-matrix or distorted wave calculations for
electron-impact excitation are very limited, due to the large size
of the atomic basis set needed to describe them. Calculations for n
≥ 6 are also not generally available. We study the behaviour of
the electron-impact excitation collision strengths and effective
collision strengths for the most important transitions used to
model electron collision dominated astrophysical plasmas, solar, for
example. We investigate the dependence on the relevant parameters: the
principal quantum number n or the nuclear charge Z. We also estimate
the importance of coupling to highly-excited states and the continuum
by comparing the results of different sized calculations. We provide
analytic formulae to calculate the electron-impact excitation collision
strengths and effective collision strengths to highly-excited states (n
≥ 8) of H- and He-like ions. These extrapolated effective collision
strengths can be used to interpret astrophysical and fusion plasma
via collisional-radiative modelling. Tables of atomic data for
Si xiii and S xv are only available at the CDS via anonymous ftp to
http://cdsarc.u-strasbg.fr
(http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A135
Title: VizieR Online Data Catalog: SiXIII and SXV collision strengths
(Fernandez-Menchero+, 2016)
Authors: Fernandez-Menchero, L.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2016yCat..35920135F
Altcode:
In present online material we provide in CDS format the extrapolated
values of energies, radiative parameters (gf), and electron-impact
excitation effective collision strengths (Upsilon) obtained with the
extrapolation rules described in the manuscript for the two test ions:
He-like Si XIII and S XV. (6 data files).
Title: Multiwavelength study of 20 jets that emanate from the
periphery of active regions
Authors: Mulay, Sargam M.; Tripathi, Durgesh; Del Zanna, Giulio;
Mason, Helen
Bibcode: 2016A&A...589A..79M
Altcode: 2016arXiv160200151M
Aims: We present a multiwavelength analysis of 20 EUV jets which
occurred at the periphery of active regions close to sunspots. We
discuss the physical parameters of the jets and their relation
with other phenomena such as Hα surges, nonthermal type-III radio
bursts and hard X-ray (HXR) emission.
Methods: These jets
were observed between August 2010 and June 2013 by the Atmospheric
Imaging Assembly (AIA) instrument that is onboard the Solar Dynamic
Observatory (SDO). We selected events that were observed on the solar
disk within +/-60° latitude. Using AIA wavelength channels that
are sensitive to coronal temperatures, we studied the temperature
distribution in the jets using the line of sight (LOS) differential
emission measure (DEM) technique. We also investigated the role of the
photospheric magnetic field using the LOS magnetogram data from the
Helioseismic and Magnetic Imager (HMI) onboard SDO.
Results:
It has been observed that most of the jets originated from the western
periphery of active regions. Their lifetimes range from 5 to 39 min
with an average of 18 min and their velocities range from 87 to 532
km s-1 with an average of 271 km s-1. All the
jets are co-temporally associated with Hα surges. Most of the jets
are co-temporal with nonthermal type-III radio bursts observed by the
Wind/WAVES spacecraft in the frequency range from 20 kHz to 13 MHz. We
confirm the source region of these bursts using the potential field
source surface (PFSS) technique. Using Reuven Ramaty High Energy Solar
Spectroscopic Imager (RHESSI) observations, we found that half of the
jets produced HXR emission and they often shared the same source region
as the HXR emission (6-12 keV). Ten out of 20 events showed that the
jets originated in a region of flux cancellation and six jets in a
region of flux emergence. Four events showed flux emergence and then
cancellation during the jet evolution. DEM analyses showed that for
most of the spires of the jets, the DEM peaked at around log T [K] =
6.2/6.3 (~2 MK). In addition, we derived an emission measure and a lower
limit of electron density at the location of the spire (jet 1: log EM =
28.6, Ne = 1.3 × 1010 cm-3; jet 2:
log EM = 28.0, Ne = 8.6 × 109 cm-3)
and the footpoint (jet 1 - log EM = 28.6, Ne = 1.1 ×
1010 cm-3; jet 2: log EM = 28.1, Ne =
8.4 × 109 cm-3). These results are in agreement
with those obtained earlier by studying individual active region
jets.
Conclusions: The observation of flux cancellation, the
association with HXR emission and emission of nonthermal type-III
radio bursts, suggest that the initiation and therefore, heating
is taking place at the base of the jet. This is also supported by
the high temperature plasma revealed by the DEM analysis in the jet
footpoint (peak in the DEM at log T [K] = 6.5). Our results provide
substantial constraints for theoretical modeling of the jets and their
thermodynamic nature. Movies are available in electronic form at http://www.aanda.org
Title: Slipping Magnetic Reconnection, Chromospheric Evaporation,
Implosion, and Precursors in the 2014 September 10 X1.6-Class
Solar Flare
Authors: Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay,
Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio;
Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte
Bibcode: 2016ApJ...823...41D
Altcode: 2016arXiv160306092D
We investigate the occurrence of slipping magnetic reconnection,
chromospheric evaporation, and coronal loop dynamics in the 2014
September 10 X-class flare. Slipping reconnection is found to be present
throughout the flare from its early phase. Flare loops are seen to slip
in opposite directions toward both ends of the ribbons. Velocities
of 20-40 km s-1 are found within time windows where the
slipping is well resolved. The warm coronal loops exhibit expanding and
contracting motions that are interpreted as displacements due to the
growing flux rope that subsequently erupts. This flux rope existed and
erupted before the onset of apparent coronal implosion. This indicates
that the energy release proceeds by slipping reconnection and not via
coronal implosion. The slipping reconnection leads to changes in the
geometry of the observed structures at the Interface Region Imaging
Spectrograph slit position, from flare loop top to the footpoints in
the ribbons. This results in variations of the observed velocities of
chromospheric evaporation in the early flare phase. Finally, it is found
that the precursor signatures, including localized EUV brightenings as
well as nonthermal X-ray emission, are signatures of the flare itself,
progressing from the early phase toward the impulsive phase, with
the tether-cutting being provided by the slipping reconnection. The
dynamics of both the flare and outlying coronal loops is found to be
consistent with the predictions of the standard solar flare model in
three dimensions.
Title: The CHIANTI atomic database
Authors: Young, P. R.; Dere, K. P.; Landi, E.; Del Zanna, G.; Mason,
H. E.
Bibcode: 2016JPhB...49g4009Y
Altcode: 2015arXiv151205620Y
The freely available CHIANTI atomic database was first released
in 1996 and has had a huge impact on the analysis and modeling of
emissions from astrophysical plasmas. It contains data and software
for modeling optically thin atom and positive ion emission from low
density (≲1013 cm-3) plasmas from x-ray to
infrared wavelengths. A key feature is that the data are assessed
and regularly updated, with version 8 released in 2015. Atomic data
for modeling the emissivities of 246 ions and neutrals are contained
in CHIANTI, together with data for deriving the ionization fractions
of all elements up to zinc. The different types of atomic data are
summarized here and their formats discussed. Statistics on the impact
of CHIANTI to the astrophysical community are given and examples of
the diverse range of applications are presented.
Title: Importance of the completeness of the configuration interaction
and close coupling expansions in R-matrix calculations for highly
charged ions: electron-impact excitation of Fe20+
Authors: Fernández-Menchero, L.; Giunta, A. S.; Del Zanna, G.;
Badnell, N. R.
Bibcode: 2016JPhB...49h5203F
Altcode: 2015arXiv151105776F
We have carried out two intermediate coupling frame transformation
(ICFT) R-matrix calculations for the electron-impact excitation
of {{C}}-like {{Fe}}20+, both of which use the
same expansions for their configuration interaction (CI) and
close-coupling (CC) representations. The first expansion arises from
the configurations 2{{{s}}}2 2{{{p}}}2,2{{s}}
2{{{p}}}3,2{{{p}}}4, \{2{{{s}}}2
2{{p}},2{{s}} 2{{{p}}}2,2{{{p}}}3\} {nl}, with
n = 3, 4, for l=0-3, which give rise to 564 CI/CC levels. The second
adds configurations 2{{{s}}}2 2{{p}} 5{{l}}, for l=0-2,
which give rise to 590 CI/CC levels in total. Comparison of oscillator
strengths and effective collision strengths from these two calculations
demonstrates the lack of convergence in data for n = 4 from the smaller
one. Comparison of results for the 564 CI/CC level calculation with
an earlier ICFT R-matrix calculation which used the exact same CI
expansion but truncated the CC expansion to only 200 levels demonstrates
the lack of convergence of the earlier data, particularly for n =
3 levels. Also, we find that the results of our 590 CC R-matrix
calculation are significantly and systematically larger than those
of an earlier comparable DW-plus-resonances calculation. Thus, it is
important still to take note of the (lack of) convergence in both atomic
structural and collisional data, even in such a highly charged ion
as Fe20+, and to treat resonances non-perturbatively. This
is of particular importance for Fe ions given their importance in the
spectroscopic diagnostic modelling of astrophysical plasmas.
Title: Atomic data and density diagnostics for S IV
Authors: Del Zanna, G.; Badnell, N. R.
Bibcode: 2016MNRAS.456.3720D
Altcode:
We present a new large-scale R-matrix scattering calculation for S
IV. We used the intermediate-coupling frame transformation method and
applied term energy corrections. Our calculation has a much larger
configuration-interaction and close-coupling expansion than previous
calculations. Despite that, we find good agreement in the predicted
intensities of the decays from the three 3s 3p2 4P
levels around 1400 Å, important for density diagnostics. A discrepancy
between the observed and predicted intensity of the 1404.8 Å line,
which is known to be blended at least with an O IV transition, is still
present. Significant differences compared to previous models are found
instead for the 1062.7 and 1073.0 Å lines, useful for diagnostics
in low-density plasma such as in nebulae. Several other significant
differences were also found, concerning the population of the 3s 3p
3d 4F9/2 metastable level, and the intensities
of several transitions.
Title: Atomic data for astrophysics: Ni XII
Authors: Del Zanna, G.; Badnell, N. R.
Bibcode: 2016A&A...585A.118D
Altcode:
We present new large-scale R-matrix (up to n = 4) scattering
calculations for the electron collisional excitation of Cl-like
Ni xii. We used the intermediate-coupling frame transformation
method. We compare predicted and observed line intensities using
laboratory and solar spectra, finding good agreement for all the
main soft X-ray lines. With the exception of the three strongest
transitions, large discrepancies with previous estimates are found,
especially for the decays from the lowest 3s2 3p4
3d levels. This includes the forbidden UV lines. The atomic data for
the n = 4 levels are the first to be calculated. We revise previous
experimental energies, and suggest several new identifications. We
point out the uncertainty in the wavelength of the 3s2
3p52P1/2-3s2
3p4 3d 2D3/2 transition,
which is important for density diagnostics. The full dataset is available at our APAP website (http://www.apapnetwork.org)
and at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A118
Title: Simultaneous IRIS and Hinode/EIS Observations and Modelling
of the 2014 October 27 X2.0 Class Flare
Authors: Polito, V.; Reep, J. W.; Reeves, K. K.; Simões, P. J. A.;
Dudík, J.; Del Zanna, G.; Mason, H. E.; Golub, L.
Bibcode: 2016ApJ...816...89P
Altcode: 2015arXiv151206378P
We present a study of the X2-class flare which occurred on 2014 October
27 and was observed with the Interface Region Imaging Spectrograph
(IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode
satellite. Thanks to the high cadence and spatial resolution of the IRIS
and EIS instruments, we are able to compare simultaneous observations
of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature
emission (≳10 MK) in the flare ribbon during the chromospheric
evaporation phase. We find that IRIS observes completely blueshifted
Fe xxi line profiles, up to 200 km s-1 during the rise
phase of the flare, indicating that the site of the plasma upflows is
resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric,
which we interpret as being due to the lower spatial resolution of
EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot
emission (log(T[K]) > 7.2) is first concentrated at the footpoints
before filling the loops. Density-sensitive lines from IRIS and
EIS give estimates of electron number density of ≳1012
cm-3 in the transition region lines and 1010
cm-3 in the coronal lines during the impulsive phase. In
order to compare the observational results against theoretical
predictions, we have run a simulation of a flare loop undergoing
heating using the HYDRAD 1D hydro code. We find that the simulated
plasma parameters are close to the observed values that are obtained
with IRIS, Hinode, and AIA. These results support an electron beam
heating model rather than a purely thermal conduction model as the
driving mechanism for this flare.
Title: The making of a new solar spectral irradiance composite -
overview of the results from the SOLID Project
Authors: Haberreiter, M.; Dudok de Wit, T.; Kretzschmar, M.; Schöll,
M.; Del Zanna, G.; Ermolli, I.
Bibcode: 2015AGUFMSH32A..04H
Altcode:
Solar spectral irradiance (SSI) is a key driver for the Earth's climate
system. To understand in detail the processes at play a consistent SSI
time series with realistic uncertainty estimates is needed as input
for climate models. However, irradiance observations exist only as
numerous and disperse data sets. Also, different SSI instruments show
varying instrumental noise and degradation. Due to these effects it
is a challenge to build a consistent SSI data set. Within the European
Project SOLID we developed tools to derive an objective SSI time series
based on existing SSI measurements, complemented with reconstruction
models. We present the SOLID SSI composite with a focus on the UV
spectral range and compare it with other available SSI reconstructions.
Title: The EUV spectrum of the Sun: Irradiances during 1998-2014
Authors: Del Zanna, G.; Andretta, V.
Bibcode: 2015A&A...584A..29D
Altcode:
We present calibrated EUV spectral irradiances obtained from
observations with the Solar and Heliospheric Observatory (SOHO) Coronal
Diagnostics Spectrometer (CDS) Normal Incidence Spectrometer (NIS)
during the 1998-2014 period, which spans the cycle 23 maximum and
minimum and the cycle 24 maximum. We revise the corrections for the
burn-in of the strong lines and our previous long-term calibration of
the NIS. We find no indications of further overall degradation of the
instrument responsivities after 2010. We compare the CDS irradiances
with those obtained by the prototype and flight instruments aboard
the Solar Dynamics Observatory (SDO) Extreme ultraviolet Variability
Experiment (EVE) and the Thermosphere Ionosphere Mesosphere
Energetics Dynamics (TIMED) Solar EUV Experiment (SEE) EUV Grating
Spectrograph (EGS). We find overall excellent agreement (to within
a relative 10-20%) with the EVE data (especially during 2010-2012),
but point out inconsistencies in some of the prototype and flight
EVE irradiances. There is overall agreement with some of the TIMED
SEE EGS data. We confirm the small variations in the irradiances of
low-temperature lines (except the helium lines) and show that the
irradiances in the hot (2-3 MK) lines are significantly lower for the
cycle 24 maximum compared to the previous one.
Title: On the validity of the ICFT R-matrix method: Fe XIV
Authors: Del Zanna, G.; Badnell, N. R.; Fernández-Menchero, L.;
Liang, G. Y.; Mason, H. E.; Storey, P. J.
Bibcode: 2015MNRAS.454.2909D
Altcode:
Recently, Aggarwal & Keenan published a Dirac R-matrix (DARC)
calculation for the electron-impact excitation of Fe XIV. A 136-level
configuration-interaction/close-coupling (CI/CC) expansion was
adopted. Comparisons with earlier calculations, obtained by Liang
et al. with the intermediate coupling frame transformation (ICFT)
R-matrix method, showed significant discrepancies. One of the main
differences was that the Liang et al. effective collision strengths
were consistently larger. Aggarwal & Keenan suggested various
possible causes for the differences. We discuss them in detail here. We
have carried out an ICFT R-matrix calculation with the same 136-level
CI/CC expansion adopted by Aggarwal & Keenan, and compared the
results with theirs and with those of Liang et al., which employed a
much larger CI/CC expansion. We find that the main differences arise
because of the different CC and CI expansions, and not because of the
use of the ICFT method, as suggested by Aggarwal & Keenan. The
significant increase in the effective collision strengths obtained by
Liang et al. is mainly due to the extra resonances that are present
because of the larger target expansion.
Title: CHIANTI - An atomic database for emission lines. Version 8
Authors: Del Zanna, G.; Dere, K. P.; Young, P. R.; Landi, E.; Mason,
H. E.
Bibcode: 2015A&A...582A..56D
Altcode: 2015arXiv150807631D
We present version 8 of the CHIANTI database. This version includes
a large amount of new data and ions, which represent a significant
improvement in the soft X-ray, extreme UV (EUV) and UV spectral
regions, which several space missions currently cover. New data for
neutrals and low charge states are also added. The data are assessed,
but to improve the modelling of low-temperature plasma the effective
collision strengths for most of the new datasets are not spline-fitted
as previously, but are retained as calculated. This required a change
of the format of the CHIANTI electron excitation files. The format
of the energy files has also been changed. Excitation rates between
all the levels are retained for most of the new datasets, so the data
can in principle be used to model high-density plasma. In addition,
the method for computing the differential emission measure used in
the CHIANTI software has been changed.
Title: The EUV spectrum of the Sun: SOHO, SEM, and CDS irradiances
Authors: Del Zanna, G.; Wieman, S. R.; Andretta, V.; Didkovsky, L.
Bibcode: 2015A&A...581A..25D
Altcode:
We use calibrated extreme-UV (EUV) spectral irradiances obtained from
observations with the Solar & Heliospheric Observatory (SOHO)
Coronal Diagnostics Spectrometer Normal Incidence Spectrometer (NIS) to
estimate the signal measured by the Solar EUV Monitor (SEM) first-order
band, 260 to 340 Å (SEM 1). The NIS observes the resonance lines He
ii 304 Å and Si xi 303 Å directly in second order. The irradiances of
the other lines in the band are estimated with a differential emission
measure (DEM) modelling, using updated atomic data. The observations
analysed here were obtained during 1998-2011, which means that they span
the maximum and minimum of Cycle 23. The current knowledge of the SEM 1
degradation is used to find effective areas during the dates of the NIS
observations and to predict the SEM 1 count rates across the band. The
total count rates, estimated by folding the NIS-based spectra with the
SEM 1 effective areas, agree very well (within 10-20%) with the observed
ones during solar minimum conditions, when the He ii 304 Å is the
dominant contribution to the band. Excellent agreement with the Solar
Dynamics Observatory (SDO) Extreme ultraviolet Variability Experiment
(EVE) observations is also found. On the other hand, the predicted
SEM 1 count rates during the Cycle-23 maximum are significantly (by
about 30%) lower than the observed ones. The solar spectrum in the
SEM 1 band changes significantly during maximum conditions, with the
He ii 304 Å only contributing about 40%. A significant fraction of
the observed count rates comes from coronal emission in an off-band
spectral region that has recently been discovered. An explanation for
the discrepancy needs further investigation.
Title: Slipping reconnection and chromospheric evaporation in the
10 September 2014 flare
Authors: Dudík, Jaroslav; Janvier, Miho; Polito, Vanessa; Mulay,
Sargam; Del Zanna, Giulio; Mason, Helen; Aulanier, Guillaume
Bibcode: 2015IAUGA..2252237D
Altcode:
We study the occurrence of slipping reconnection in the long-duration
X-class flare of 2014 September 10. From the start, the flare shows
apparent slippage of hot Fe XXI flare loops observed in the 131A
channel of SDO/AIA. Using the time-distance plots, we show that the
slipping motion of the flare loops proceeds in counter directions in
both flare ribbons. Simultaneous IRIS Fe XXI observations show the
occurrence of chromospheric evaporation at brightening kernels that are
involved in the slipping reconnection of AIA loops. This happens also
during a flux-rope breakout accompanied by a faint 'magnetic implosion'
of a coronal loop. Based on the 3D MHD flare model, we argue that the
'implosion' is caused by the erupting flux rope pushing the neighbouring
loops aside, with the low-lying loops being squeezed.
Title: Imaging and Spectroscopic Observations of a Transient Coronal
Loop: Evidence for the Non-Maxwellian K Distributions
Authors: Dudík, Jaroslav; Mackovjak, Šimon; Dzifčáková, Elena;
Del Zanna, Giulio; Williams, David R.; Karlický, Marian; Mason,
Helen E.; Lörinčík, Juraj; Kotrč, Pavel; Fárník, František;
Zemanová, Alena
Bibcode: 2015ApJ...807..123D
Altcode: 2015arXiv150504333D
We report on the Solar Dynamics Observatory/Atmospheric Imaging Assembly
(AIA) and Hinode/EUV Imaging Spectrograph (EIS) observations of a
transient coronal loop. The loop brightens up in the same location after
the disappearance of an arcade formed during a B8.9-class microflare
3 hr earlier. EIS captures this loop during its brightening phase,
as observed in most of the AIA filters. We use the AIA data to study
the evolution of the loop, as well as to perform the differential
emission measure (DEM) diagnostics as a function of κ. The Fe xi-Fe
xiii lines observed by EIS are used to perform the diagnostics of
electron density and subsequently the diagnostics of κ. Using ratios
involving the Fe xi 257.772 Å self-blend, we diagnose κ ≲ 2,
i.e., an extremely non-Maxwellian distribution. Using the predicted
Fe line intensities derived from the DEMs as a function of κ, we
show that, with decreasing κ, all combinations of ratios of line
intensities converge to the observed values, confirming the diagnosed
κ ≲ 2. These results represent the first positive diagnostics of
κ-distributions in the solar corona despite the limitations imposed
by calibration uncertainties.
Title: Validity of the ICFT R-matrix method: Be-like Al 9+
a case study
Authors: Fernández-Menchero, L.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2015MNRAS.450.4174F
Altcode:
We have carried out 98-level configuration-interaction/close-coupling
(CI/CC) intermediate coupling frame transformation (ICFT) and
Breit-Pauli R-matrix calculations for the electron-impact excitation
of Be-like Al 9+. The close agreement that we find
between the two sets of effective collision strengths demonstrates
the continued robustness of the ICFT method. On the other hand, a
comparison of this data with previous 238-level CI/CC ICFT effective
collision strengths shows that the results for excitation up to n =
4 levels are systematically and increasingly underestimated over a
wide range of temperatures by R-matrix calculations whose CC expansion
extends only to n = 4 (98-levels). Thus, we find to be false a recent
conjecture that the ICFT approach may not be completely robust. The
conjecture was based upon a comparison of 98-level CI/CC Dirac R-matrix
effective collision strengths for Al 9+ with those from the
238-level CI/CC ICFT R-matrix calculations. The disagreement found
recently is due to a lack of convergence of the CC expansion in the
98-level CI/CC Dirac work. The earlier 238-level CI/CC ICFT work has
a superior target to the 98-level CI/CC Dirac one and provides more
accurate atomic data. Similar considerations need to be made for other
Be-like ions and for other sequences.
Title: Resolution of the forbidden (J = 0 → 0) excitation puzzle
in Mg-like ions
Authors: Fernández-Menchero, L.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2015A&A...577A..95F
Altcode: 2015arXiv150304980F
We investigate the source of the discrepancy between
R-matrix and distorted-wave (DW) collision strengths
for J - J' = 0-0 transitions in Mg-like ions, for example
3s21S0-3p21S0,
as reported previously. We find it to be due to the neglect of coupling,
for example via 3s3p 1P1, as done by most DW
codes. We have implemented an option to account for such coupling
as a perturbation within the autostructure DW code. This removes the
discrepancy of a factor ~10 and ~100 for Fe14 + and S4
+, respectively, for such transitions. The neglect of coupling
would have affected (to some degree) the atomic data for a few weak
optically forbidden transitions in other isoelectronic sequences if
they were calculated with DW codes such as FAC and HULLAC. In addition,
we compare the Fe14 + line intensities predicted with the
R-matrix collision strengths against observations of solar active
regions and flares; they agree well. For Fe14 +, we suggest
that the best density diagnostic ratio is 327.0/321.8 Å.
Title: Joint High Temperature Observation of a Small C6.5 Solar
Flare With Iris/Eis/Aia
Authors: Polito, V.; Reeves, K. K.; Del Zanna, G.; Golub, L.; Mason,
H. E.
Bibcode: 2015ApJ...803...84P
Altcode:
We present the observation of a C6.5 class flare on 2014 February 3,
obtained with the Interface Region Imaging Spectrograph (IRIS) and
the EUV Imaging Spectrometer (EIS) on board HINODE. We follow the
details of the impulsive phase with IRIS and the gradual decay phase
with both IRIS and EIS. The IRIS Slit-Jaw Imager and Atmospheric
Imaging Assembly (AIA) are used to precisely co-align the two sets
of spectroscopic observations. Of particular interest is the Fe xxi
1354.08 Å spectral line, which is the highest temperature emission
(∼10 MK) observed in the IRIS wavelength range. We show the evolution
of the Fe xxi profiles during the impulsive phase of the flare at the
same ribbon location with a 75 s temporal cadence. Totally blueshifted
(∼82 km {{s}-1}) profiles are found at the very early
phase of the flare and gradually decrease in about 6 minutes. This
result is consistent with 1D model predictions during chromospheric
evaporation in flares. The blueshifted components also exhibit large
non-thermal broadening, which decreases simultaneously with the
blueshifted velocity. After the evaporation first occurs, the Fe xxi
intensity progressively moves from the footpoints to the top of the
hot flare loops seen in the AIA 131 Å images, where the emission is
observed to be at rest and thermal. Emission measure estimates from
IRIS/EIS/AIA observations during the gradual phase show isothermal loop
top structures cooling from about 13.5 to 12 MK with electron densities
of the order of ∼ 5-6× {{10}10} c{{m}-3}.
Title: Benchmarking atomic data for astrophysics: Si iii
Authors: Del Zanna, G.; Fernández-Menchero, L.; Badnell, N. R.
Bibcode: 2015A&A...574A..99D
Altcode:
We investigate the main spectral diagnostics for Si iii UV lines, which
have been previously used to measure electron densities, temperatures,
and to suggest that non-Maxwellian electron distributions might be
present in the low transition region of the solar atmosphere. Previous
atomic calculations and observations are reviewed. We benchmark
the observations using a new large-scale R-matrix scattering
calculation for electron collisional excitation of Si iii,
carried out with the intermediate-coupling frame transformation
(ICFT) method. We find generally good agreement between predicted
and observed line intensities, if one takes into account the
different temperature sensitivity of the lines, and the structure
of the solar transition region. We find no conclusive evidence
for the presence of non-Maxwellian electron distributions. The full dataset (energies, transition probabilities and
rates) are available in electronic form at our APAP website (http://www.apap-network.org)
Title: The evolution of the emission measure distribution in the
core of an active region
Authors: Del Zanna, Giulio; Tripathi, Durgesh; Mason, Helen;
Subramanian, Srividya; O'Dwyer, Brendan
Bibcode: 2015A&A...573A.104D
Altcode: 2014arXiv1411.0128D
We study the spatial distribution and evolution of the slope of the
emission measure (EM) between 1 MK and 3 MK in the core of the active
region (AR) NOAA 11193, first when it appeared near the central meridian
and then again when it reappeared after a solar rotation. We use
observations recorded by the Extreme-ultraviolet Imaging Spectrometer
(EIS) aboard Hinode, with a new radiometric calibration. We also use
observations from the Atmospheric Imaging Assembly (AIA) aboard the
Solar Dynamics Observatory (SDO). We present the first spatially
resolved maps of the EM slope in the 1-3 MK range within the core
of the AR using several methods, either from approximations or from
the differential emission measure (DEM). A significant variation of
the slope is found at different spatial locations within the active
region. We selected two regions that were not greatly affected by lower
temperature emission along the line of sight. We found that the EM
had a power law of the form EM ∝ Tb, with b = 4.4 ± 0.4,
and 4.6 ± 0.4, during the first and second appearance of the active
region, respectively. During the second rotation, line-of-sight effects
become more important, although difficult to estimate. We found that
the use of the ground calibration for Hinode/EIS and the approximate
method to derive the EM, used in previous publications, produce an
underestimation of the slopes. The EM distribution in active region
cores is generally found to be consistent with high frequency heating,
and does not change much during the evolution of the active region.
Title: R-matrix electron-impact excitation data for the Mg-like
iso-electronic sequence
Authors: Fernández-Menchero, L.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2014A&A...572A.115F
Altcode:
Aims: Emission lines from ions in the Mg-like iso-electronic
sequence can be used as reliable diagnostics of temperature and
density of astrophysical and fusion plasmas over a wide range of
parameters. Data in the literature are quite lacking, there are no
calculations for many of the ions in the sequence.
Methods: We
have carried-out intermediate coupling frame transformation R-matrix
calculations which include a total of 283 fine-structure levels in both
the configuration interaction target and close-coupling collision
expansions. These arise from the configurations 1s2
2s2 2p6 3 {s,p,d} nl with n = 4,5, and for
l = 0-4.
Results: We obtain ordinary collision strengths and
Maxwell-averaged effective collision strengths for the electron-impact
excitation of all the ions of the Mg-like sequence, from Al+
to Zn18 +. We compare our results with those from previous
R-matrix and distorted waves calculations, where available, for
some benchmark ions. We find good agreement with the results of
previous calculations for the transitions n = 3-3. We also find good
agreement for the most intense transitions n = 3-4. These transitions
are important for populating the upper levels of the main diagnostic
lines. These data are made available in the APAP archive via http://www.apap-network.org,
CHIANTI via http://www.chiantidatabase.org
and open-ADAS via http://open.adas.ac.uk
Title: Reconstruction of the solar EUV irradiance from 1996 to 2010
based on SOHO/EIT images
Authors: Haberreiter, Margit; Delouille, Véronique; Mampaey, Benjamin;
Verbeeck, Cis; Del Zanna, Giulio; Wieman, Seth
Bibcode: 2014JSWSC...4A..30H
Altcode:
The solar Extreme UltraViolet (EUV) spectrum has important effects on
the Earth's upper atmosphere. For a detailed investigation of these
effects it is important to have a consistent data series of the EUV
spectral irradiance available. We present a reconstruction of the
solar EUV irradiance based on SOHO/EIT images, along with synthetic
spectra calculated using different coronal features which represent
the brightness variation of the solar atmosphere. The EIT images are
segmented with the SPoCA2 tool which separates the features based on
a fixed brightness classification scheme. With the SOLMOD code we then
calculate intensity spectra for the 10-100 nm wavelength range and each
of the coronal features. Weighting the intensity spectra with the area
covered by each of the features yields the temporal variation of the
EUV spectrum. The reconstructed spectrum is then validated against the
spectral irradiance as observed with SOHO/SEM. Our approach leads to
good agreement between the reconstructed and the observed spectral
irradiance. This study is an important step toward understanding
variations in the solar EUV spectrum and ultimately its effect on the
Earth's upper atmosphere.
Title: Signatures of the non-Maxwellian κ-distributions in optically
thin line spectra. I. Theory and synthetic Fe IX-XIII spectra
Authors: Dudík, J.; Del Zanna, G.; Mason, H. E.; Dzifčáková, E.
Bibcode: 2014A&A...570A.124D
Altcode: 2014arXiv1408.0950D
Aims: We investigate the possibility of diagnosing the degree of
departure from the Maxwellian distribution using single-ion spectra
originating in astrophysical plasmas in collisional ionization
equilibrium.
Methods: New atomic data for excitation of Fe ix
- Fe xiii are integrated under the assumption of a κ-distribution
of electron energies. Diagnostic methods using lines of a single
ion formed at any wavelength are explored. Such methods minimize
uncertainties from the ionization and recombination rates, as well as
the possible presence of non-equilibrium ionization. Approximations
to the collision strengths are also investigated.
Results: The
calculated intensities of most of the Fe ix - Fe xiii EUV lines show
consistent behaviour with κ at constant temperature. Intensities
of these lines decrease with κ, with the vast majority of ratios
of strong lines showing little or no sensitivity to κ. Several of
the line ratios, especially involving temperature-sensitive lines,
show a sensitivity to κ that is of the order of several tens of per
cent, or, in the case of Fe ix, up to a factor of two. Forbidden
lines in the near-ultraviolet, visible, or infrared parts of the
spectrum are an exception, with smaller intensity changes or even
a reverse behaviour with κ. The most conspicuous example is the Fe
x 6378.26 Å red line, whose intensity incerases with κ. This line
is a potentially strong indicator of departures from the Maxwellian
distribution. We find that it is possible to perform density diagnostics
independently of κ, with many Fe xi, Fe xii, and Fe xiii line ratios
showing strong density-sensitivity and negligible sensitivity to κ
and temperature. We also tested different averaging of the collision
strengths. It is found that averaging over 0.01 interval in log(E [ Ryd
]) is sufficient to produce accurate distribution-averaged collision
strengths Υ(T,κ) at temperatures of the ion formation in ionization
equilibrium. Appendices are available in electronic form at http://www.aanda.org
Title: Atomic data for astrophysics: improved collision strengths
for Fe viii
Authors: Del Zanna, G.; Badnell, N. R.
Bibcode: 2014A&A...570A..56D
Altcode:
We describe, and present the results of, a new large-scale R-matrix
scattering calculation for the electron collisional excitation of Fe
viii. We first discuss the limitations of the previous calculations,
in particular concerning some strong EUV lines observed in the solar
corona by the Hinode EUV Imaging Spectrometer. We then present a new
target which represents an improvement over the previous ones for
this particularly complex ion. We developed a new method, based on
the use of term energy corrections within the intermediate coupling
frame transformation method, to calculate the collision strengths. We
compare predicted and observed line intensities using laboratory and
solar spectra, finding excellent agreement for all the main soft X-ray
and extreme ultraviolet (EUV) transitions, using the present atomic
data. In particular, we show that Fe viii EUV lines observed by Hinode
EIS can now be used to provide reliable electron temperatures for the
solar corona. The full dataset (energies, transition probabilities
and rates) is only available in electronic form at our APAP website (http://www.apap-network.org)
as well as at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A56
Title: Atomic data for astrophysics: Ni XV
Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E.
Bibcode: 2014A&A...567A..18D
Altcode:
We present the first R-matrix scattering calculation for electron
collisional excitation of Ni xv. The large-scale target includes
configurations up to n = 4. The calculations were carried out using
the intermediate-coupling frame transformation method. Significant
enhancements in the collision strengths, compared to previous
distorted-wave (DW) calculations, are found for several cases,
in particular the forbidden lines within the ground configuration
and the 3s2 3p 4s levels. We provide a complete set
of rates and a list of strongest lines that are observable in
astrophysical plasmas. Previous identifications are reviewed, and
a few new ones suggested. The new data can be used to accurately
measure electron densities for high-temperature (3 MK) plasmas, and
the nickel abundance. The full dataset (energies, transition
probabilities and rates) is available from our APAP website http://www.apap-network.org,
and also at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/567/A18
Title: R-matrix electron-impact excitation data for the Be-like
iso-electronic sequence
Authors: Fernández-Menchero, L.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2014A&A...566A.104F
Altcode:
Aims: Emission lines from ions in the Be-like isoelectronic
sequence can be used for reliable diagnostics of temperature and
density of astrophysical and fusion plasmas over a wide range of
temperatures. Surprisingly, interpolated data is all that is available
for a number of astrophysically important ions.
Methods: We
have carried out intermediate coupling frame transformation R-matrix
calculations which include a total of 238 fine-structure levels in both
the configuration interaction target and close-coupling collision
expansions. These arise from the configurations 1s2
2 {s, p} nl with n = 3-7, and l = 0-4 for n ≤ 5 and l = 0-2 for
n = 6,7.
Results: We obtain ordinary collision strengths and
Maxwell-averaged effective collision strengths for the electron-impact
excitation of all the ions of the Be-like sequence, from B+
to Zn26+. We compare with previous R-matrix calculations and
interpolated values for some benchmark ions. We find good agreement
for transitions n = 2-2 with previous R-matrix calculations but
some disagreements with interpolated values. We also find good
agreement for the most intense transitions n = 2-3 which contribute
via cascade to the (n = 2) diagnostic radiating levels. These data are made available in the archives of APAP via http://www.apap-network.org
and OPEN-ADAS via http://open.adas.ac.uk
Title: Atomic data for astrophysics: Ni XI
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.
Bibcode: 2014A&A...566A.123D
Altcode:
We present a new large-scale R-matrix scattering calculation for
electron collisional excitation of Ni xi, carried out with the
intermediate-coupling frame transformation method. The target
includes all the main configurations up to n = 4, and is a
significant improvement over earlier R-matrix (only three n =
3 configurations) and distorted-wave (DW) calculations. We find
significant enhancements in the collision strengths of many of the
strong transitions to the n = 3,4 levels. They are due to the resonances
that arise within the present large-scale target. This results in
significant increases in the predicted intensities of the UV and
visible forbidden lines within the 3s23p53d
configuration, the strong EUV lines that result from the decays
of the 3s23p53d levels to the ground state,
and the decays from the n = 4 levels, which are visible in the soft
X-rays. We find good agreement between predicted and observed line
intensities in the EUV. With the present atomic data, lines from Ni
xi can reliably be used for plasma diagnostics. We also revise some
level energies and suggest a few new possible identifications. The full dataset (energies, transition probabilities and rates)
are only available in electronic form at our APAP website (http://www.apap-network.org)
as well as at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/566/A123
Title: VizieR Online Data Catalog: Ni XV electron collisional
excitation (Del Zanna+, 2014)
Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E.
Bibcode: 2014yCat..35670018D
Altcode: 2014yCat..35679018D
We present the first R-matrix scattering calculation for electron
collisional excitation of NiXV. The large-scale target includes
configurations up to n=4. The calculations were carried out using the
intermediate-coupling frame transformation method (ICFT). Significant
enhancements in the collision strengths, compared to previous
distorted wave (DW) calculations, are found for several cases, in
particular the forbidden lines within the ground configuration and
the 3s2 3p 4s levels. We provide a complete set of rates
and a list of strongest lines that are observable in astrophysical
plasmas. Previous identifications are reviewed, and a few new ones
suggested. The new data can be used to accurately measure electron
densities for high-temperature (3MK) plasmas, and the nickel
abundance. (2 data files).
Title: Reconstruction of the solar EUV irradiance as observed with
PROBA2/LYRA
Authors: Haberreiter, Margit; Delouille, Veronique; Del Zanna, Giulio;
Ermolli, Ilaria; Kretzschmar, Matthieu; Mampeay, Benjamin; Dominique,
Marie; Schmutz, Werner
Bibcode: 2014EGUGA..1614449H
Altcode:
The solar EUV spectrum has important effects on the upper atmosphere
of the Earth and any planet. For a detailed investigation of these
effects it is important to have a constistent data series of the EUV
spectral irradiance available. Here, we present the reconstruction of
the solar EUV irradiance based on PSPT and SOHO/EIT images and along
with synthetic spectra calculated for six different coronal features
representing the brightness variation of the solar atmosphere. The
EIT images are segmented with the SPoCA tool which allows to identify
the features based on a consistent brightness classification for each
feature. With the SOLMOD code we then calculate intensity spectra
for 10 nm to 100 nm for each of the coronal feature. Weighting the
intensity spectra with the area covered by each of the features yields
the temporal variation of the EUV spectrum. The reconstructed time
series is then validated against the spectral irradiance as observed
with PROBA2/LYRA. This is an important step towards the understanding
of the variations of the solar EUV spectrum and ultimately its detailed
effect on the Earth's upper atmosphere.
Title: VizieR Online Data Catalog: NiXI electron collisional
excitation (Del Zanna+, 2014)
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.
Bibcode: 2014yCat..35660123D
Altcode: 2014yCat..35669123D
We present a new large-scale R-matrix scattering calculation for
electron collisional excitation of Ni XI, carried out with the
intermediate-coupling frame transformation method (ICFT). The target
includes all the main configurations up to n=4, and is a significant
improvement over earlier R-matrix (only three n=3 configurations) and
distorted-wave (DW) calculations. We find significant enhancements
in the collision strengths of many of the strong transitions to
the n=3,4 levels. They are due to the resonances that arise within
the present large-scale target. This results in significant
increases in the predicted intensities of the UV and visible forbidden
lines within the 3s2 3p5 3d configuration, the
strong EUV lines that result from the decays of the 3s2
3p5 3d levels to the ground state, and the decays from the
n=4 levels, which are visible in the soft X-rays. We find good agreement
between predicted and observed line intensities in the EUV. With the
present atomic data, lines from Ni XI can reliably be used for plasma
diagnostics. We also revise some level energies and suggest a few new
possible identifications. (2 data files).
Title: Atomic data for astrophysics: Fe IX
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E.
Bibcode: 2014A&A...565A..77D
Altcode:
We present the results of a new large-scale intermediate-coupling frame
transformation R-matrix scattering calculation for electron collisional
excitation of Fe ix. The target includes all the main configurations
up to n = 5, to improve our earlier R-matrix and distorted-wave (DW)
calculations for the n = 3,4 levels. Unlike similar calculations
which we carried out for the other coronal iron ions, in this case the
larger target does not significantly affect the collision strengths
of the strongest transitions to the n = 3,4 levels. Some differences
are however present for a few transitions, in particular for the 3d-4p
line at 197.86 Å. For the weaker transitions, significant enhancements
due to extra resonances resulting from this much bigger target are
found. Several new line identifications are suggested. We find excellent
agreement between predicted and observed line intensities in the EUV
(Hinode EIS) showing that Fe ix lines provide a reliable temperature
diagnostic. We also show that the visible forbidden lines are a good
diagnostic to measure electron densities. The full dataset
(energies, transition probabilities and rates) are also available
in electronic form at the APAP website (www.apap-network.org)
and are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/565/A77
Title: Elemental abundances and temperatures of quiescent solar
active region cores from X-ray observations
Authors: Del Zanna, G.; Mason, H. E.
Bibcode: 2014A&A...565A..14D
Altcode:
A brief review of studies of elemental abundances and emission measures
in quiescent solar active region cores is presented. Hinode EUV Imaging
Spectrometer (EIS) observations of strong iron spectral lines have
shown sharply peaked distributions around 3 MK. EIS observations of
lines emitted by a range of elements have allowed good estimates of
abundances relative to iron. However, X-ray observations are required
to measure the plasma emission above 3 MK and the abundances of
oxygen and neon. We revisit, using up-to-date atomic data, older
X-ray observations obtained by a sounding rocket and by the Solar
Maximum Mission (SMM) Flat Crystal Spectrometer (FCS). We find that
the Fe/O and Fe/Ne ratios are normally increased by a factor of 3.2,
compared to the photospheric values. Similar results are obtained
from FCS observations of six quiescent active region cores. The FCS
observations also indicate that the emission measure above 3 MK has
a very steep negative slope, with very little plasma observed at 5
MK or above. Appendix A is available in electronic form at http://www.aanda.org
Title: Slipping Magnetic Reconnection during an X-class Solar Flare
Observed by SDO/AIA
Authors: Dudík, J.; Janvier, M.; Aulanier, G.; Del Zanna, G.;
Karlický, M.; Mason, H. E.; Schmieder, B.
Bibcode: 2014ApJ...784..144D
Altcode: 2014arXiv1401.7529D
We present SDO/AIA observations of an eruptive X-class flare of
2012 July 12, and compare its evolution with the predictions of a
three-dimensional (3D) numerical simulation. We focus on the dynamics of
flare loops that are seen to undergo slipping reconnection during the
flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations,
lower parts of 10 MK flare loops exhibit an apparent motion with
velocities of several tens of km s-1 along the developing
flare ribbons. In the early stages of the flare, flare ribbons consist
of compact, localized bright transition-region emission from the
footpoints of the flare loops. A differential emission measure analysis
shows that the flare loops have temperatures up to the formation of
Fe XXIV. A series of very long, S-shaped loops erupt, leading to a
coronal mass ejection observed by STEREO. The observed dynamics are
compared with the evolution of magnetic structures in the "standard
solar flare model in 3D." This model matches the observations well,
reproducing the apparently slipping flare loops, S-shaped erupting
loops, and the evolution of flare ribbons. All of these processes are
explained via 3D reconnection mechanisms resulting from the expansion
of a torus-unstable flux rope. The AIA observations and the numerical
model are complemented by radio observations showing a noise storm
in the metric range. Dm-drifting pulsation structures occurring
during the eruption indicate plasmoid ejection and enhancement of the
reconnection rate. The bursty nature of radio emission shows that the
slipping reconnection is still intermittent, although it is observed
to persist for more than an hour.
Title: Thermal structure of a hot non-flaring corona from Hinode/EIS
Authors: Petralia, A.; Reale, F.; Testa, P.; Del Zanna, G.
Bibcode: 2014A&A...564A...3P
Altcode: 2014arXiv1402.6554P
Aims: In previous studies, a very hot plasma component has
been diagnosed in solar active regions through the images in three
different narrow-band channels of Atmospheric Imaging Assembly (AIA)
on board the Solar Dynamics Observatory (SDO). This diagnostic from
extreme ultraviolet (EUV) imaging data has also been supported
by the matching morphology of emission in the hot Ca XVII line,
as observed with Extreme-Ultraviolet Imaging Spectrometer (EIS)
on board Hinode. This evidence is debated because of the unknown
distribution of the emission measure along the line of sight. Here
we investigate in detail the thermal distribution of one such region
using EUV spectroscopic data.
Methods: In an active region
observed with SDO/AIA, Hinode/EIS, and X-ray telescope (XRT), we
select a sub-region with a very hot plasma component and another cooler
sub-region for comparison. The average spectrum is extracted for both,
and 14 intense lines are selected for analysis that probe the 5.5 <
log T < 7 temperature range uniformly. From these lines, the emission
measure distributions are reconstructed with the Markov-chain Monte
Carlo method. Results are cross-checked in comparison with the two
sub-regions, with a different inversion method, with the morphology
of the images, and with the addition of fluxes measured with narrow,
and broadband imagers.
Results: We find that, whereas the
cool region has a flat and featureless distribution that drops at
temperature log T ≥ 6.3, the distribution of the hot region shows
a well-defined peak at log T = 6.6 and gradually decreasing trends on
both sides, thus supporting the very hot nature of the hot component
diagnosed with imagers. The other cross-checks are consistent with
this result.
Conclusions: This study provides a completion of
the analysis of active region components, and the resulting scenario
supports the presence of a minor very hot plasma component in the core,
with temperatures log T > 6.6.
Title: VizieR Online Data Catalog: Atomic data for FeIX (Del Zanna+,
2014)
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E.
Bibcode: 2014yCat..35650077D
Altcode: 2014yCat..35659077D
We present the results of a new large-scale intermediate-coupling frame
transformation R-matrix scattering calculation for electron collisional
excitation of Fe IX. The target includes all the main configurations
up to n=5, to improve our earlier R-matrix and distorted-wave (DW)
calculations for the n=3,4 levels. Unlike similar calculations which
we carried out for the other coronal iron ions, in this case the
larger target does not significantly affect the collision strengths
of the strongest transitions to the n=3,4 levels. Some differences
are however present for a few transitions, in particular for the 3d-4p
line at 197.86Å. For the weaker transitions, significant enhancements
due to extra resonances resulting from this much bigger target are
found. Several new line identifications are suggested. We find excellent
agreement between predicted and observed line intensities in the EUV
(Hinode EIS) showing that Fe IX lines provide a reliable temperature
diagnostic. We also show that the visible forbidden lines are a good
diagnostic to measure electron densities. (2 data files).
Title: The EUV spectrum of the Sun: SOHO CDS NIS radiances during
solar cycle 23
Authors: Andretta, V.; Del Zanna, G.
Bibcode: 2014A&A...563A..26A
Altcode: 2014arXiv1401.7570A
For the first time, we present and discuss EUV radiances of the solar
transition region (TR) and corona obtained during a solar cycle. The
measurements were obtained with the SOHO/coronal diagnostic spectrometer
(CDS) during the period from 1996 to 2010. We find that limb-brightening
significantly affects any characterisation of the solar radiances. We
present the limb-brightening function for the main lines and find that
it does not change measurably during the cycle. We confirm earlier
findings that the radiance histogram of the cooler lines have a well
defined, log-normal quiet-Sun component, although our results differ
from previous ones. The width of the lowest-radiance log-normal
distribution is constant along the cycle. Both the analysis of the
centre-to-limb variation and of the radiance statistical distribution
point to a constant quiet Sun emission along solar cycle 23. Lines
formed above 1 MK are dramatically affected by the presence of active
regions, and indeed, no "quiet Sun" region can be defined during
periods of maximum activity. Much of the irradiance variability in lines
formed below 1.5 MK is due to a change in the emitting area. For hotter
lines, the emitting area saturates to almost 100% of full solar disk
at the maximum of activity, while simultaneously the emission due to
active regions increases by more than an order of magnitude. We show
that structures around active regions, sometimes referred to as dark
halos or dark canopies, are common and discuss their similarities and
differences with coronal holes. In particular, we show how they are
well visible in TR lines, contrary to coronal holes.
Title: Diagnostics for the O IV and Si IV lines observed by IRIS
Authors: Dudik, Jaroslav; Mason, Helen; Del Zanna, Giulio; Golub,
Leon; Dzifcakova, Elena
Bibcode: 2014cosp...40E.754D
Altcode:
We investigate the formation of the IRIS O IV and Si IV lines under
non-Maxwellian conditions characterized by kappa-distributions. It is
found that the Si IV lines are always formed at lower temperatures
than the O IV lines. However, as the departure from the Maxwellian
increases, the peak formation temperatures are shifted progressively to
lower and lower temperatures. Coupled with the slope of the differential
emission measure (DEM), it is possible for the Si IV lines to be formed
very close to the solar chromosphere, with the majority of the O IV
intensities coming from a different, higher part of the transition
region. The predicted spectra for kappa-distributions exhibit very low O
IV intensities compared to Si IV, analogously to what is observed by the
IRIS spacecraft. Potential density diagnostics are discussed, as well
as the contribution of photoexcitation to the formation of these lines.
Title: Spectral diagnostics with the Solar Orbiter SPICE spectrometer.
Authors: Del Zanna, Giulio
Bibcode: 2014cosp...40E.671D
Altcode:
Some of the spectral diagnostics available to the SPICE spectrometer
are presented, with emphasis on those useful to measure electron
temperatures, chemical abundances, and Doppler motions. We explore
the possibility to link these remote-sensing observations with the
local in-situ measurements of the solar wind plasma parameters. In
particular, we discuss the solar wind source regions in coronal holes
and active regions.
Title: Chromospheric evaporation in recurrent flares
Authors: Polito, V.; Mason, Helen; Del Zanna, Giulio; Dudik, Jaroslav
Bibcode: 2014cosp...40E2581P
Altcode:
We present high-cadence (3 minutes) Hinode/EIS observations of small
recurrent flares and provide densities and velocities of the upflowing
plasma in the locations of the chromospheric evaporation. Lines formed
in the 2-10 MK range have significant blueshifts, of the order of
50 km/s or more. This upflowing plasma is the source of the 10 MK
plasma that emits strongly in EUV and X-ray lines after the impulsive
phases. We use the high-cadence and high-resolution SDO/AIA images
to describe the locations of the upflows, and magnetograms to locate
the ribbons. One interesting feature is that the recurrent flares are
confined, until the last one when a large-scale eruption occurs.
Title: Multithermal emission in active regions
Authors: Del Zanna, Giulio
Bibcode: 2014cosp...40E.670D
Altcode:
High-resolution EUV observations from SDO/AIA, Hi-C and Hinode/EIS are
used, together with updated new atomic data, to study the multi-thermal
emission in active region structures. Previous observations are largely
confirmed, with most structures being not co-spatial and having nearly
isothermal cross-sections. Those at temperatures below 1 MK appear as
nearly resolved but those at 1-3 MK are still largely unresolved even
at the Hi-C resolution. Very little emission above 3 MK is present
in quiescent active regions. Elemental abundances vary in different
structures. The active region cores show FIP enhancements of about a
factor of three. X-ray spectroscopy confirms the results of the EUV
observations for the hot cores.
Title: Response of Hinode XRT to quiet Sun, active region and
flare plasma
Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E.
Bibcode: 2014A&A...561A..20O
Altcode:
Aims: We examine the response of the Hinode X-Ray
Telescope (XRT), using simultaneous observations with the Hinode
Extreme-ultraviolet Imaging Spectrometer (EIS), for a flare, an active
region and a quiet Sun region. We also examine the relative intensity
calibration of EIS and XRT.
Methods: EIS differential emission
measure distribution (DEM) curves were used to create synthetic spectra
with the CHIANTI atomic database. The contribution of spectral lines
and continuum emission to each of the XRT channels was determined from
the synthetic spectra, which were then convolved with the effective
area of each XRT channel. The predicted total count rates for each
channel were compared with the observed count rates. The effects
of varying elemental abundances and the temperature range for the
inversion were investigated. DEMs obtained from the XRT bands were
also computed and compared to those obtained with EIS.
Results:
For the active region observations, the observed XRT count rates for
most of the channels are in reasonable agreement with those predicted
using EIS observations, but are dependent on the elemental abundances
chosen. Significant discrepancies between predicted and observed count
rates were found and are discussed for the adjacent quiet Sun region
and also for the flare. Synthetic spectra and continuum emission
contributing to the XRT channels are presented and discussed for the
active region, quiet Sun and flare observations.
Title: Solar Transition Region Lines Observed by the Interface Region
Imaging Spectrograph: Diagnostics for the O IV and Si IV Lines
Authors: Dudík, J.; Del Zanna, G.; Dzifčáková, E.; Mason, H. E.;
Golub, L.
Bibcode: 2014ApJ...780L..12D
Altcode: 2013arXiv1311.6978D
The formation of the transition region O IV and Si IV lines observable
by the Interface Region Imaging Spectrograph (IRIS) is investigated
for both Maxwellian and non-Maxwellian conditions characterized by
a κ-distribution exhibiting a high-energy tail. The Si IV lines
are formed at lower temperatures than the O IV lines for all κ. In
non-Maxwellian situations with lower κ, the contribution functions
are shifted to lower temperatures. Combined with the slope of the
differential emission measure, it is possible for the Si IV lines to be
formed at very different regions of the solar transition region than the
O IV lines; possibly close to the solar chromosphere. Such situations
might be discernible by IRIS. It is found that photoexcitation can be
important for the Si IV lines, but is negligible for the O IV lines. The
usefulness of the O IV ratios for density diagnostics independently of
κ is investigated and it is found that the O IV 1404.78 Å/1399.77
Å ratio provides a good density diagnostics except for very low T
combined with extreme non-Maxwellian situations.
Title: On-Orbit Degradation of Solar Instruments
Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.;
Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.;
Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah,
M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley,
L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.;
Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo,
B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge,
D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.;
Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N.
Bibcode: 2013SoPh..288..389B
Altcode: 2013arXiv1304.5488B
We present the lessons learned about the degradation observed in
several space solar missions, based on contributions at the Workshop
about On-Orbit Degradation of Solar and Space Weather Instruments
that took place at the Solar Terrestrial Centre of Excellence (Royal
Observatory of Belgium) in Brussels on 3 May 2012. The aim of this
workshop was to open discussions related to the degradation observed
in Sun-observing instruments exposed to the effects of the space
environment. This article summarizes the various lessons learned
and offers recommendations to reduce or correct expected degradation
with the goal of increasing the useful lifespan of future and ongoing
space missions.
Title: The multi-thermal emission in solar active regions
Authors: Del Zanna, G.
Bibcode: 2013A&A...558A..73D
Altcode:
We present simultaneous SDO AIA and Hinode EIS observations of the hot
cores of active regions (ARs) and assess the dominant contributions
to the AIA EUV bands. This is an extension of our previous work. We
find good agreement between SDO AIA, EVE and EIS observations, using
our new EIS calibration and the latest EVE v.3 data. We find that all
the AIA bands are multi-thermal, with the exception of the 171 and
335 Å, and provide ways to roughly estimate the main contributions
directly from the AIA data. We present and discuss new atomic data
for the AIA bands, showing that they are now sufficiently complete to
obtain temperature information in the cores of ARs, with the exception
of the 211 Å band. We found that the newly identified Fe xiv 93.61
Å line is the dominant contribution to the 94 Å band, whenever Fe
xviii is not present. Three methods to estimate the Fe xviii emission
in this band are presented, two using EIS and one directly from the
AIA data. Fe xviii emission is often present in the cores of ARs,
but we found cases where it is formed at 3 MK and not 7 MK, the
temperature of peak ion abundance in equilibrium. The best EIS lines
for elemental abundance determination and differential emission measure
(DEM) analysis are discussed. A new set of abundances for many elements
are obtained from EIS observations of hot 3 MK loops. The abundances
of the elements with low first ionisation potential (FIP), relative
to those of the high-FIP elements, are found to be enhanced by about
a factor of three, compared to the photospheric values. A measurement
of the path length implies that the absolute abundances of the low-FIP
elements are higher than the photospheric values by at least a factor
of three. We present a new DEM method customised for the AIA bands, to
study the thermal structure of ARs at 1'' resolution. This was tested
on a few ARs, including one observed during the Hi-C rocket flight. We
found excellent agreement between predicted and observed AIA count
rates and EIS radiances. Overall we found few differences between the
AIA and Hi-C 193 Å images of coronal structures, despite the higher
Hi-C resolution (0.25''). The Hi-C images and the AIA DEM modelling
suggest that some of the cooler loops (below 1 MK) are already resolved
by AIA, while the hotter (1.5-2.5 MK) "background" emission is in most
places still unresolved even at the Hi-C resolution. This unresolved
emission is significantly lower than previously observed with TRACE,
the SOHO CDS, and Hinode EIS spectrometers. Its enhancement appears
to be mostly due to increased iron abundance. We find an ubiquitous
presence of emission at different temperatures that is not co-spatial,
and suggest that future high-resolution imaging is carried out with
isothermal bands.
Title: A revised radiometric calibration for the Hinode/EIS instrument
Authors: Del Zanna, G.
Bibcode: 2013A&A...555A..47D
Altcode: 2012arXiv1211.6771D
An assessment of the in-flight radiometric calibration of the Hinode
EUV Imaging Spectrometer (EIS) is presented. This is done with the
line ratio technique applied to a wide range of observations of the
quiet Sun, active regions, and flares from 2006 until 2012. The
best diagnostic lines and the relevant atomic data are discussed
in detail. Radiances over the quiet Sun are also considered, with
comparisons with previous measurements. Some departures in the shapes
of the ground calibration responsivities are found at the start of the
mission. These shapes do not change significantly over time, with the
exception of the shorter wavelengths of the EIS short-wavelength (SW)
channel, which shows some degradation. The sensitivity of the SW channel
at longer wavelengths does not show significant degradation, while that
of the long-wavelength (LW) channel shows a significant degradation
with time. By the beginning of 2010 the responsivity of the LW channel
was already lower than the values measured on the ground by a factor of
two or more. A first-order correction is proposed. With this correction,
the main ratios of lines in the two channels become constant to within
a relative 20%, and the He ii 256 Å radiances over the quiet Sun
also become constant over time. This correction removes long-standing
discrepancies for a number of lines and ions, in particular those
involving the strongest Fe x, Fe xiii, Fe xiv, Fe xvii, and Fe xxiv
lines, where discrepancies of factors of more than two were found. These
results have important implications for various EIS science analyses,
in particular for measurements of temperatures, emission measures and
elemental abundances. Appendices are available in electronic form
at http://www.aanda.org
Title: Spectral diagnostics with the SDO EVE flare lines
Authors: Del Zanna, G.; Woods, T. N.
Bibcode: 2013A&A...555A..59D
Altcode:
The diagnostic use of the soft X-ray and EUV lines observed with
the Solar Dynamics Observatory (SDO) Extreme ultraviolet Variability
Experiment (EVE) is discussed. We focus on all the flare lines observed
in the 80-640 Å range (mainly due to Fe xviii - Fe xxiv), showing
their use to measure temperatures, emission measures, densities,
and chemical abundances. We discuss their identification at the
EVE resolution, by using the latest atomic data, and by assessing
possible sources of blending, taking into account higher-resolution
solar spectra. We present observations of four flares, and study
in more detail the gradual phase peak of the 7 March 2012 X5.6
flare. Good agreement between observations and theory is found in
most cases, and the best lines for diagnostics are recommended. We
found reasonable densities (1011.2 cm-3 from
Fe xxi lines), but isothermal temperatures (12 MK) lower than those
estimated with GOES. We show that EVE can be used to measure relative
elemental abundance, and find photospheric argon/iron and calcium/iron
abundances. We also show that lines normally formed in the quiet Sun
in the low transition region such as O III are the best to study the
impulsive phase. Appendix A is available in electronic form at
http://www.aanda.org
Title: A Collaborative FP7 Effort towards the First European
Comprehensive SOLar Irradiance Data Exploitation (SOLID)
Authors: Haberreiter, Margit; Dasi, Maria; Delouille, Veronique; Del
Zanna, Giulio; Dudok de Wit, Thierry; Ermolli, Ilaria; Kretzschmar,
Matthieu; Krivova, Natalie; Mason, Helen; Qahwaji, Rami; Schmutz,
Werner; Solanki, Sami; Thuillier, Gerard; Tourpali, Kleareti; Unruh,
Yvonne; Verbeeck, Cis; Weber, Mark; Woods, Tom
Bibcode: 2013EGUGA..1513079H
Altcode:
Variations of solar irradiance are the most important natural factor
in the terrestrial climate and as such, the time dependent spectral
solar irradiance is a crucial input to any climate modelling. There
have been previous efforts to compile solar irradiance but it is
still uncertain by how much the spectral and total solar irradiance
changed on yearly, decadal and longer time scales. Observations of
irradiance data exist in numerous disperse data sets. Therefore, it
is important to bring together the European expertise in the field
to analyse and merge the complete set of European irradiance data,
complemented by archive data that include data from non-European
missions. We report on the initiation of a collaborative effort to unify
representatives from all European solar space experiments and European
teams specialized in multi-wavelength solar image processing. It is
intended to include the European groups involved in irradiance modelling
and reconstruction. They will work with two different state of the art
approaches to produce reconstructed spectral and total solar irradiance
data as a function of time. These results will be used to bridge
gaps in time and wavelength coverage of the observational data. This
will allow the proposing SOLID team to reduce the uncertainties in
the irradiance time series - an important requirement by the climate
community - and to provide uniform data sets of modelled and observed
solar irradiance data from the beginning of the space era to the
present including proper error and uncertainty estimates. Climate
research needs these data sets and therefore, the primary benefit
is for the climate community, but the stellar community, planetary,
lunar, and ionospheric researchers are also interested in having at
their disposition incident radiation of the Sun. The proposing team
plans to realize a wide international synergy in solar physics from
7 European countries, and collaborators from the US, complemented by
representatives from the climate community, who will accompany their
research work with wide dissemination activities.
Title: Doppler Shifts in Active Region Moss Using SOHO/SUMER
Authors: Winebarger, Amy; Tripathi, Durgesh; Mason, Helen E.; Del
Zanna, Giulio
Bibcode: 2013ApJ...767..107W
Altcode:
The velocity of the plasma at the footpoint of hot loops in active
region cores can be used to discriminate between different heating
frequencies. Velocities on the order of a few kilometers per second
would indicate low-frequency heating on sub-resolution strands,
while velocities close to zero would indicate high-frequency (steady)
heating. To discriminate between these two values requires accurate
velocity measurements; previous velocity measurements suffer from
large uncertainties, mainly due to the lack of an absolute wavelength
reference scale. In this paper, we determine the velocity in the loop
footpoints using observations from Solar Ultraviolet Measurements of
Emitted Radiation (SUMER) on Solar and Heliospheric Observatory. We
use neutral spectral lines to determine the wavelength scale of the
observations with an uncertainty in the absolute velocity of <3.5 km
s-1 and co-aligned Transition Region and Coronal Explorer
(TRACE) images to identify footpoint regions. We studied three
different active regions and found average redshifts in the Ne VIII
770 Å emission line (formed at 6 × 105 K) of 5.17 ± 5.37
km s-1 and average redshifts in the C IV 1548 and 1550 Å
emission lines (formed at 1 × 105 K) of 13.94 ± 4.93 km
s-1 and 14.91 ± 6.09 km s-1, respectively. We
find no correlation between the brightness in the spectral line and
the measured velocity, nor do we find correlation between the Ne VIII
and C IV velocities measured co-spatially and co-temporally. SUMER
scanned two of the active regions twice; in those active regions we
find positive correlation between the co-spatial velocities measured
during the first and second scans. These results provide definitive
and quantitative measurements for comparisons with simulations of
different coronal heating mechanisms.
Title: CHIANTI 7.1: a new database release for SDO data analysis
Authors: Young, P. R.; Landi, E.; Del Zanna, G.; Dere, K. P.; Mason,
H. E.
Bibcode: 2013enss.confE..58Y
Altcode:
Version 7.1 of the CHIANTI atomic database was released in October 2012
and contains a number of improvements to better model data returned by
the AIA and EVE instruments on board SDO. Specifically the models for
the important iron ions Fe VIII to Fe XIV have been greatly expanded,
yielding many thousands of new transitions in the 50-170 angstrom
range that enable the irradiance spectra obtained by EVE to be modeled
more accurately. A lack of available atomic data meant that the AIA 94
angstrom channel was not well modeled at low temperatures in earlier
versions of CHIANTI. New data for Fe VIII, Fe X and Fe XIV added to
CHIANTI 7.1 give important contributions to the channel and greatly
improve comparisons with theory.
Title: CHIANTI—An Atomic Database for Emission Lines. XIII. Soft
X-Ray Improvements and Other Changes
Authors: Landi, E.; Young, P. R.; Dere, K. P.; Del Zanna, G.; Mason,
H. E.
Bibcode: 2013ApJ...763...86L
Altcode:
The CHIANTI spectral code consists of two parts: an atomic database
and a suite of computer programs in Python and IDL. Together, they
allow the calculation of the optically thin spectrum of astrophysical
objects and provide spectroscopic plasma diagnostics for the analysis
of astrophysical spectra. The database includes atomic energy levels,
wavelengths, radiative transition probabilities, collision excitation
rate coefficients, ionization, and recombination rate coefficients,
as well as data to calculate free-free, free-bound, and two-photon
continuum emission. Version 7.1 has been released, which includes
improved data for several ions, recombination rates, and element
abundances. In particular, it provides a large expansion of the
CHIANTI models for key Fe ions from Fe VIII to Fe XIV to improve the
predicted emission in the 50-170 Å wavelength range. All data and
programs are freely available at http://www.chiantidatabase.org and
in SolarSoft, while the Python interface to CHIANTI can be found at
http://chiantipy.sourceforge.net.
Title: Atomic data for astrophysics: Fe xi soft X-ray lines
Authors: Del Zanna, G.; Storey, P. J.
Bibcode: 2013A&A...549A..42D
Altcode:
We present new large-scale R-matrix (up to n = 4) and distorted
wave (up to n = 6) scattering calculations for electron collisional
excitation of Fe xi. These data are needed for the analysis of soft
X-ray spectra of astrophysical plasmas, where strong n = 4 → n =
3 transitions are present. As found in previous work on Fe x, Fe xii,
and Fe xiii, resonances from within the n = 4 levels and cascading
from higher levels significantly increase the intensities of these
lines. We provide a list of the strongest lines, many of which are
unidentified. The present larger model produces intensities for decays
from n = 3 levels mostly consistent with our previous work, however
significant enhancements for some lower levels are found, in particular
for the 3s2 3p3 3d 5D which can be
used to measure electron temperatures in the solar corona with the
Hinode/EIS spectrometer. The full dataset is only available at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/549/A42
Title: The Sun as a Star
Authors: Del Zanna, Giulio; Mason, Helen
Bibcode: 2013pss4.book...87D
Altcode:
In this chapter we provide an overview of various observational and
theoreticalaspects about the Sun, paying more attention to global ones,
i.e., to thosewhere the Sun is considered as a star, so they can be
more or less directlyrelated to those studied for other stars. The
emphasis is on the processes bywhich energy is transferred to the
solar atmosphere and then flows fromthe Sun in the form of radiation
and particles. The chapter starts withan historical introduction,
and then discusses various subjects, startingwith a brief description
of the photosphere, the chromosphere, and thetransition region of
the Sun. The interior of the Sun is then introduced,with the standard
model and solar neutrinos, and with the observationsand theory of solar
oscillations. We present some important results fromhelioseismology,
and briefly discuss the problematics involved with theproduction and
regeneration of the solar magnetic fields during a solarcycle.
Title: SDO AIA and EVE observations and modelling of solar flare loops
Authors: Petkaki, P.; Del Zanna, G.; Mason, H. E.; Bradshaw, S. J.
Bibcode: 2012A&A...547A..25P
Altcode:
We present imaging and spectroscopic observations of an isolated
C1-class solar flare, obtained with the Atmospheric Imaging Assembly
(AIA) and Extreme ultraviolet Variability Experiment (EVE) on the Solar
Dynamics Observatory (SDO). We obtain excellent agreement between the
peak flare temperatures estimated using the EVE spectra with those
obtained from GOES and, most importantly, from the ratio of the 94
Å and 131 Å AIA channels, which are found to be dominated by Fe
xviii and Fe xxi. These results confirm that these two AIA bands can
be reliably used to provide temperature diagnostics for the peak and
gradual phases of solar flares. The flare kernels, probable sources
of chromospheric evaporation, are seen as strong localised emission
in the AIA bands at the footpoints of flare loops. The flare loops
are close to isothermal during the gradual phase. We have run several
hydrodynamic simulations (using the HYDRAD code) to study the cooling
of the flare loops. We find good overall agreement between observed and
predicted electron temperatures and densities when a gradual increase
and decrease of the heating is assumed.
Title: VizieR Online Data Catalog: FeXI soft X-ray lines (Del
Zanna+, 2013)
Authors: Del Zanna, G.; Storey, P. J.
Bibcode: 2012yCat..35490042D
Altcode: 2012yCat..35499042D
We present new large-scale R-matrix (up to n=4) and distorted
wave (up to n=6) scattering calculations for electron collisional
excitation of Fe XI. These data are needed for the analysis of soft
X-ray spectra of astrophysical plasmas, where strong n=4-->n=3
transitions are present. As found in previous work on Fe X, Fe XII,
and Fe XIII, resonances from within the n=4 levels and cascading
from higher levels significantly increase the intensities of these
lines. We provide a list of the strongest lines, many of which are
unidentified. The present larger model produces intensities for
decays from n=3 levels mostly consistent with our previous work,
however significant enhancements for some lower levels are found, in
particular for the 3s23p33d5D which
can be used to measure electron temperatures in the solar corona with
the Hinode/EIS spectrometer. (5 data files).
Title: LEMUR: Large European module for solar Ultraviolet
Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
Thomas; Winter, Berend; Young, Peter
Bibcode: 2012ExA....34..273T
Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
The solar outer atmosphere is an extremely dynamic environment
characterized by the continuous interplay between the plasma and the
magnetic field that generates and permeates it. Such interactions play a
fundamental role in hugely diverse astrophysical systems, but occur at
scales that cannot be studied outside the solar system. Understanding
this complex system requires concerted, simultaneous solar observations
from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
high spatial resolution (between 0.1'' and 0.3''), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
from the chromosphere to the flaring corona), and the capability of
measuring magnetic fields through spectropolarimetry at visible and
near-infrared wavelengths. Simultaneous spectroscopic measurements
sampling the entire temperature range are particularly important. These
requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload
providing a significant improvement of imaging and spectropolarimetric
capabilities in the UV, visible, and near-infrared with respect to
what is available today and foreseen in the near future. The Large
European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload
of high-resolution imaging spectrographs and cameras. LEMUR consists
of two major components: a VUV solar telescope with a 30 cm diameter
mirror and a focal length of 3.6 m, and a focal-plane package composed
of VUV spectrometers covering six carefully chosen wavelength ranges
between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with
0.14'' per pixel sampling. In addition, LEMUR is capable of measuring
mass flows velocities (line shifts) down to 2 km s - 1 or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.
Title: Benchmarking atomic data for astrophysics: a first look at
the soft X-ray lines
Authors: Del Zanna, G.
Bibcode: 2012A&A...546A..97D
Altcode: 2012arXiv1208.2142D
A collection of the best solar and laboratory spectra in the soft X-rays
is used to perform a preliminary benchmark in this wavelength region,
by comparing observed with predicted wavelengths and calibrated solar
irradiances. The benchmark focuses on the Fe ix - Fe xiv ions, for
which we have recently calculated the relevant atomic data; however,
a few other ions have also been benchmarked. The iron ions dominate the
soft X-rays, however a large fraction of the strongest soft X-ray lines
due to n = 4 → n = 3 transitions were previously unidentified. The
strongest transitions are all identified here, in particular the decays
from the core-excited levels (3s 3pl 4s, l = 5,4,3,2,1
for Fe x, Fe xi, Fe xii, Fe xiii, and Fe xiv, respectively), which
are the strongest soft X-ray transitions from these ions. Many new
identifications are proposed, some only tentatively. Good agreement
in terms of solar irradiances between the soft-Xray and EUV (n =
3 → n = 3) transitions is found, confirming the reliability of
the new large-scale calculations. Some of the new atomic data and
identifications are particularly important for the Solar Dynamic
Observatory (SDO) Atmospheric Imaging Assembly (AIA) 94 Å band.
Title: Propagating Disturbances in Coronal Loops: A Detailed Analysis
of Propagation Speeds
Authors: Kiddie, G.; De Moortel, I.; Del Zanna, G.; McIntosh, S. W.;
Whittaker, I.
Bibcode: 2012SoPh..279..427K
Altcode: 2012arXiv1205.0891K
Quasi-periodic disturbances have been observed in the outer solar
atmosphere for many years. Although first interpreted as upflows
(Schrijver et al., Solar Phys.187, 261, 1999), they have been widely
regarded as slow magneto-acoustic waves, due to their observed
velocities and periods. However, recent observations have questioned
this interpretation, as periodic disturbances in Doppler velocity,
line width, and profile asymmetry were found to be in phase with the
intensity oscillations (De Pontieu and McIntosh, Astrophys. J.722,
1013, 2010; Tian, McIntosh, and De Pontieu, Astrophys. J. Lett.727,
L37, 2011), suggesting that the disturbances could be quasi-periodic
upflows. Here we conduct a detailed analysis of the velocities of
these disturbances across several wavelengths using the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). We
analysed 41 examples, including both sunspot and non-sunspot regions
of the Sun. We found that the velocities of propagating disturbances
(PDs) located at sunspots are more likely to be temperature dependent,
whereas the velocities of PDs at non-sunspot locations do not show a
clear temperature dependence. This suggests an interpretation in terms
of slow magneto-acoustic waves in sunspots but the nature of PDs in
non-sunspot (plage) regions remains unclear. We also considered on
what scale the underlying driver is affecting the properties of the
PDs. Finally, we found that removing the contribution due to the cooler
ions in the 193 Å wavelength suggests that a substantial part of the
193 Å emission of sunspot PDs can be attributed to the cool component
of 193 Å.
Title: Coronal Diagnostics from Narrowband Images Around 30.4 nm
Authors: Andretta, V.; Telloni, D.; Del Zanna, G.
Bibcode: 2012SoPh..279...53A
Altcode: 2012SoPh..tmp...73A; 2012arXiv1203.4091A
Images taken in the band centered at 30.4 nm are routinely used to map
the radiance of the He II Ly α line on the solar disk. That line is
one of the strongest, if not the strongest, line in the EUV observed in
the solar spectrum, and one of the few lines in that wavelength range
providing information on the upper chromosphere or lower transition
region. However, when observing the off-limb corona, the contribution
from the nearby Si XI 30.3 nm line can become significant. In this
work we aim at estimating the relative contribution of those two
lines in the solar corona around the minimum of solar activity. We
combine measurements from CDS taken in August 2008 with temperature
and density profiles from semiempirical models of the corona to
compute the radiances of the two lines, and of other representative
coronal lines (e.g. Mg X 62.5 nm, Si XII 52.1 nm). Considering both
diagnosed quantities from line ratios (temperatures and densities)
and line radiances in absolute units, we obtain a good overall match
between observations and models. We find that the Si XI line dominates
the He II line from just above the limb up to ≈ 2 R⊙
in streamers, while its contribution to narrowband imaging in the 30.4
nm band is expected to become smaller, even negligible in the corona
beyond ≈ 2 - 3 R⊙, the precise value being strongly
dependent on the coronal temperature profile.
Title: Atomic data for astrophysics: Fe xii soft X-ray lines
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E.
Bibcode: 2012A&A...543A.139D
Altcode:
We present new large-scale R-matrix (up to n = 4) and distorted-wave
(DW, up to n = 6) scattering calculations for electron collisional
excitation of Fe xii. The first aim is to provide accurate atomic data
for the soft X-rays, where strong decays from the n = 4 levels are
present. As found in previous work on Fe x, resonances attached to n =
4 levels increase the cross-sections for excitations from the ground
state to some n = 4 levels, when compared to DW calculations. Cascading
from higher levels is also important. We provide a number of models and
line intensities, and list a number of strong unidentified lines. The
second aim is to assess the effects of the large R-matrix calculation
on the n = 3 transitions. Compared to our previous (n = 3) R-matrix
calculation, we find overall excellent agreement to within a few
percent, however a few key density diagnostic EUV intensities differ
by about 60% at coronal densities. The new atomic data result in
lower electron densities, resolving previous discrepancies with solar
observations. The full dataset (energies, transition probabilities
and rates) are available in electronic form at our APAP website (http://www.apap-network.org)
as well as at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A139
Title: VizieR Online Data Catalog: Fe XIII soft X-ray lines (Del
Zanna+, 2012)
Authors: Del Zanna, G.; Storey, P. J.
Bibcode: 2012yCat..35430144D
Altcode: 2012yCat..35439144D
We present new large-scale R-matrix (up to n=4) and distorted wave (up
to n=6) scattering calculations for electron collisional excitation
of Fe XIII. We aim to provide accurate atomic data for the soft
X-rays, where strong n=4-n=3 transitions are present. As found
in previous work on Fe X, resonances from within the n=4 levels and
cascading from higher levels significantly increase the intensities
of these lines. We provide a number of models and line intensities,
and list a number of strong unidentified lines. (5 data files).
Title: Atomic data for astrophysics: Fe xiii soft X-ray lines
Authors: Del Zanna, G.; Storey, P. J.
Bibcode: 2012A&A...543A.144D
Altcode:
We present new large-scale R-matrix (up to n = 4) and distorted wave
(up to n = 6) scattering calculations for electron collisional
excitation of Fe xiii. We aim to provide accurate atomic data
for the soft X-rays, where strong n = 4 → n = 3 transitions are
present. As found in previous work on Fe x, resonances from within
the n = 4 levels and cascading from higher levels significantly
increase the intensities of these lines. We provide a number of
models and line intensities, and list a number of strong unidentified
lines. The full dataset (energies, transition probabilities
and rates) are available in electronic form at our APAP website (http://www.apap-network.org)
as well as at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A144
Title: VizieR Online Data Catalog: Fe XII soft X-ray lines (Del
Zanna+, 2012)
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E.
Bibcode: 2012yCat..35430139D
Altcode: 2012yCat..35439139D
We present new large-scale R-matrix (up to n=4) and distorted-wave (DW,
up to n=6) scattering calculations for electron collisional excitation
of Fe XII. The first aim is to provide accurate atomic data for the soft
X-rays, where strong decays from the n=4 levels are present. As found
in previous work on Fe X, resonances attached to n=4 levels increase the
cross-sections for excitations from the ground state to some n=4 levels,
when compared to DW calculations. Cascading from higher levels is also
important. We provide a number of models and line intensities,
and list a number of strong unidentified lines. The second aim
is to assess the effects of the large R-matrix calculation on the n=3
transitions. Compared to our previous (n=3) R-matrix calculation, we
find overall excellent agreement to within a few percent, however a few
key density diagnostic EUV intensities differ by about 60% at coronal
densities. The new atomic data result in lower electron densities,
resolving previous discrepancies with solar observations. (5
data files).
Title: Observations of Plasma Upflow in a Warm Loop with Hinode/EIS
Authors: Tripathi, Durgesh; Mason, Helen E.; Del Zanna, Giulio;
Bradshaw, Steven
Bibcode: 2012ApJ...754L...4T
Altcode: 2012arXiv1206.3367T
A complete understanding of Doppler shift in active region loops can
help probe the basic physical mechanism involved into the heating
of those loops. Here, we present observations of upflows in coronal
loops detected in a range of temperatures (log T = 5.8-6.2). The loop
was not discernible above these temperatures. The speed of upflow
was strongest at the footpoint and decreased with height. The upflow
speed at the footpoint was about 20 km s-1 in Fe VIII, which
decreased with temperature, being about 13 km s-1 in Fe X,
about 8 km s-1 in Fe XII, and about 4 km s-1 in
Fe XIII. To the best of our knowledge, this is the first observation
providing evidence of upflow of plasma in coronal loop structures at
these temperatures. We interpret these observations as evidence of
chromospheric evaporation in quasi-static coronal loops.
Title: Moving towards a comprehensive model for active region outflows
Authors: Aulanier, Guillaume; Del Zanna, Giulio; Bradshaw, Stephen
Bibcode: 2012cosp...39...72A
Altcode: 2012cosp.meet...72A
Coronal outflows located at the edges of strong magnetic flux
concentrations seem to be a common and persistent property of solar
active regions. They have been reported and discussed using both direct
imaging in EUV and SXR, as well as using Doppler measurements from
EUV spectroscopy. Due to their potential role in feeding the solar
wind with extra mass and momentum, which is one of the primary goal of
the upcoming Solar Orbiter mission, coronal outflows have received a
broad attention since more than a decade. But for the genuine reader,
the nature of the observed motions, as well as their physical origins,
still look to be very unclear. I will review some of the most debated
interpretations for these features, such as : Do the `warm' outflows,
reported in imagery, which are in fact associated with redshifts seen in
spectroscopy, correspond to upward-traveling waves ? Do the redshifts
indicate a global mass circulation along the chromosphere-coronal axis
? Do the non-steady, quasi-periodic, and relatively faster disturbances,
that are superposed on quasi-steady and relatively-slower upflows,
correspond to magnetoacoustic waves, to spicule transient jets, or to
some other bulk flows ? More generally, do the assymetric `hot' line
profiles reported in several observations really highlight different
plasmas along the LOS, and thus require the development of specific
models ? Do the increasing Dopplershifts with line temperature formation
indicate accelerating upflows, or do they simply show different flows
along different flux tubes ? Do all the observed outflows feed the
solar wind, or do some of them end up as downflows ? In the latter
case, does the mass fall back at remote coronal locations, or right
towards the underlying chromosphere ? Is the continuing growth of
active regions responsible for the flows, and if yes are the flows
induced by high-altitude reconnection or by low altitude squashing of
the plasma ? Owing to the intrinsic limitations of the EUV spectroscopic
observations, new studies have investigated this intriguing phenomenon,
using others methods of investigation : magnetic field extrapolations,
topological analyses, radiative hydrodynamic simulations, calculation of
synthetic line profiles, and last but not least, radio observations as
well as in-situ solar wind plasma measurements. I will argue that these
studies, when reviewed alltogether, appear to provide an important
step towards an integrated model for coronal outflows, even though
they do not solve all the aforementioned issues.
Title: VizieR Online Data Catalog: FeX soft X-ray lines (Del Zanna+,
2012)
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E.
Bibcode: 2012yCat..35410090D
Altcode: 2012yCat..35419090D
New atomic calculations for Fe X are presented. They focus on the need
to model the soft X-ray spectrum and in particular the line at 94.0Å
which is the dominant contribution to the Solar Dynamics Observatory
(SDO) Atmospheric Imaging Assembly (AIA) 94Å band in quiet Sun
conditions. This line, and others in the band, are due to strong
decays from n=4 levels. We present new large-scale R-matrix (up to
n=4) and distorted-wave (DW, up to n=6) scattering calculations for
electron collisional excitation and compare them to earlier work. We
find significant discrepancies with previous calculations. We show that
resonances significantly increase the cross-sections for excitations
from the ground state to some n=4 levels, in particular to those in
the 3s2 3p4 4s configuration. Cascading from
higher levels is also important. We suggest a new identification for
the 3s 3p6 2S1/2 - 3s 3p5
4s 2P3/2 transition, that has a predicted
intensity larger than the decays from the 3s2 3p4
4s levels which were identified by Edlen in 1936. The results presented
here are relevant to our understanding of transitions from n=4 levels
in a wide range of other ions. (5 data files).
Title: Atomic data for astrophysics: Fe x soft X-ray lines
Authors: Del Zanna, G.; Storey, P. J.; Badnell, N. R.; Mason, H. E.
Bibcode: 2012A&A...541A..90D
Altcode:
New atomic calculations for Fe x are presented. They focus on the need
to model the soft X-ray spectrum and in particular the line at 94.0 Å
which is the dominant contribution to the Solar Dynamics Observatory
(SDO) Atmospheric Imaging Assembly (AIA) 94 Å band in quiet Sun
conditions. This line, and others in the band, are due to strong decays
from n = 4 levels. We present new large-scale R-matrix (up to n =
4) and distorted-wave (DW, up to n = 6) scattering calculations for
electron collisional excitation and compare them to earlier work. We
find significant discrepancies with previous calculations. We show that
resonances significantly increase the cross-sections for excitations
from the ground state to some n = 4 levels, in particular to those
in the 3s2 3p4 4s configuration. Cascading from
higher levels is also important. We suggest a new identification for
the 3s 3p62S1/2-3s 3p5 4s
2P3/2 transition, that has a predicted intensity
larger than the decays from the 3s2 3p4 4s levels
which were identified by Edlén in 1936. The results presented here
are relevant to our understanding of transitions from n = 4 levels in a
wide range of other ions. The full dataset (energies, transition
probabilities and rates) are available in electronic form at our APAP
website (www.apap-network.org)
as well as at the CDS via anonymous ftp to
cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/541/A90
Title: VizieR Online Data Catalog: Atomic data for X-ray lines of
FeVIII and FeIX (O'Dwyer+, 2012)
Authors: O'Dwyer, B.; Del Zanna, G.; Badnell, N. R.; Mason, H. E.;
Storey, P. J.
Bibcode: 2012yCat..35370022O
Altcode: 2012yCat..35379022O
The distorted wave extension of the autostructure code has been used
to calculate energy levels, radiative transition probabilities and
collisional excitation rates of Fe VIII and Fe IX up to n=6 for Fe IX
and n=7 for Fe VIII. We have compared some of the data with previous
calculations, finding overall agreement for radiative transition
rates, but interesting differences for some collisional data. **************************************************************************
* * * Sorry, but the author(s) never supplied the
tabular material * * announced in the paper * * *
**************************************************************************
Title: Spectroscopic Diagnostics with IRIS
Authors: Mason, H. E.; Del Zanna, G.
Bibcode: 2012decs.confE..47M
Altcode:
This talk will review the spectroscopic diagnostics available in the
IRIS wavelength bands, built on the previous heritage of observations
in the 1330-1410A wavelength band. Consideration will be given to the
accuracy of available atomic data in CHIANTI and the relevant atomic
processes. Ways in which the IRIS data could be used to complement
observations from other observatories (SDO and Hinode) will be explored
with a view to probing the energy transport and dissipation in the
solar atmosphere.
Title: CHIANTI—An Atomic Database for Emission Lines. XII. Version
7 of the Database
Authors: Landi, E.; Del Zanna, G.; Young, P. R.; Dere, K. P.; Mason,
H. E.
Bibcode: 2012ApJ...744...99L
Altcode:
The CHIANTI spectral code consists of an atomic database and
a suite of computer programs to calculate the optically thin
spectrum of astrophysical objects and carry out spectroscopic plasma
diagnostics. The database includes atomic energy levels, wavelengths,
radiative transition probabilities, collision excitation rate
coefficients, and ionization and recombination rate coefficients,
as well as data to calculate free-free, free-bound, and two-photon
continuum emission. Version 7 has been released, which includes
several new ions, significant updates to existing ions, as well as
Chianti-Py, the implementation of CHIANTI software in the Python
programming language. All data and programs are freely available at
http://www.chiantidatabase.org, while the Python interface to CHIANTI
can be found at http://chiantipy.sourceforge.net.
Title: Atomic data for the X-ray lines of Fe viii and Fe ix
Authors: O'Dwyer, B.; Del Zanna, G.; Badnell, N. R.; Mason, H. E.;
Storey, P. J.
Bibcode: 2012A&A...537A..22O
Altcode:
The distorted wave extension of the autostructure code has been used
to calculate energy levels, radiative transition probabilities and
collisional excitation rates of Fe viii and Fe ix up to n = 6 for Fe ix
and n = 7 for Fe viii. We have compared some of the data with previous
calculations, finding overall agreement for radiative transition
rates, but interesting differences for some collisional data. We have
merged our data for the higher energy levels with published R-matrix
collisional excitation rates for the lower ones to calculate spectral
line intensities and compare them with observations. In particular,
we have focused on the transitions from high energy levels of Fe
viii & Fe ix which are present in the 93-95 Å region. A few new
identifications are tentatively provided. We find that Fe ix 5f-3d
and Fe viii 7f-3d transitions only comprise a small fraction of
the observed lines in the 93-95 Å region for quiet Sun conditions,
and thus their contribution to the Solar Dynamics Observatory (SDO)
Atmospheric Imaging Assembly (AIA) 94 Å band is expected to be
small. A complete list of calculated energies, radiative data
and thermally averaged collision strengths is only available at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A22
Title: Benchmarking atomic data for the CHIANTI atomic database:
coronal lines observed by Hinode EIS
Authors: Del Zanna, G.
Bibcode: 2012A&A...537A..38D
Altcode:
The coronal lines that are observable in the Hinode EUV Imaging
Spectrometer (EIS) wavelengths are assessed with new atomic data that
have recently become available for a range of important ions. EIS
spectral lines are identified based on their spatial variation across
different solar regions, their wavelengths, and their intensities. Two
off-limb observations are presented, one above an active region, and one
in the quiet Sun. The spectra are relatively free of low-temperature
lines. Accurate wavelengths and intensities are provided. The
observed and predicted line intensities generally agree excellently,
once blending is taken into account. The main diagnostics available
for measuring the electron density of the solar corona using EIS are
highlighted with the use of the emissivity ratio technique. Densities
obtained from different ions agree excellently. Most of the previous
identifications are confirmed. A considerable number of weaker
lines still await identification, however. The approximate formation
temperature of the main unidentified lines is provided to aid the
identification process. The EIS radiometric calibration appears to be
in need of revision. A new quiet-Sun argon/iron relative abundance of
0.16, in line with Galactic measurements, is found. The abundances
of sulphur and argon in the "background" unresolved active region
emission are found to be lower by a factor of about two at 1.5 MK,
and even lower at 3 MK.
Title: Benchmarking atomic data for astrophysics: Fe XVII X-ray lines
Authors: Del Zanna, G.
Bibcode: 2011A&A...536A..59D
Altcode:
Recent R-matrix scattering calculations for electron impact
excitation of Fe xvii are benchmarked against various X-ray solar
observations. Quiescent active region observations are considered,
together with a few SMM/FCS observations of active regions and
flares analysed here. Extremely good agreement (within 10%) between
expected and measured line intensities is found, with the exception
of a few weaker lines that appear to be blended, and without the need
to invoke opacity effects in the stronger line. The long-standing
discrepancies that have been present when distorted wave (DW)
calculations are adopted are now finally resolved. As was shown in
the Fe xviii case, the differences with the DW calculations are caused
by resonances that significantly increase the collision strengths of
the 2p-3s transitions. The strong Fe xvii lines can now be reliably
used to measure electron temperatures in the solar corona and other
astrophysical sources. Emission measure modelling with the most recent
atomic data of quiescent active region cores indicates O/Fe and Ne/Fe
abundances reduced by factors of two to four compared to the latest
compilation of "photospheric" abundances.
Title: Underflight Calibration of SOHO/CDS and Hinode/EIS with
EUNIS-07
Authors: Wang, Tongjiang; Thomas, Roger J.; Brosius, Jeffrey W.; Young,
Peter R.; Rabin, Douglas M.; Davila, Joseph M.; Del Zanna, Giulio
Bibcode: 2011ApJS..197...32W
Altcode: 2011arXiv1109.6598W
Flights of Goddard Space Flight Center's Extreme Ultraviolet
Normal Incidence Spectrograph (EUNIS) sounding rocket in 2006
and 2007 provided updated radiometric calibrations for Solar and
Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS)
and Hinode/Extreme Ultraviolet Imaging Spectrometer (Hinode/EIS). EUNIS
carried two independent imaging spectrographs covering wavebands of
300-370 Å in first order and 170-205 Å in second order. After each
flight, end-to-end radiometric calibrations of the rocket payload were
carried out in the same facility used for pre-launch calibrations of
CDS and EIS. During the 2007 flight, EUNIS, SOHO/CDS, and Hinode/EIS
observed the same solar locations, allowing the EUNIS calibrations to
be directly applied to both CDS and EIS. The measured CDS NIS 1 line
intensities calibrated with the standard (version 4) responsivities with
the standard long-term corrections are found to be too low by a factor
of 1.5 due to the decrease in responsivity. The EIS calibration update
is performed in two ways. One uses the direct calibration transfer of
the calibrated EUNIS-07 short wavelength (SW) channel. The other uses
the insensitive line pairs, in which one member was observed by the
EUNIS-07 long wavelength (LW) channel and the other by EIS in either the
LW or SW waveband. Measurements from both methods are in good agreement,
and confirm (within the measurement uncertainties) the EIS responsivity
measured directly before the instrument's launch. The measurements also
suggest that the EIS responsivity decreased by a factor of about 1.2
after the first year of operation (although the size of the measurement
uncertainties is comparable to this decrease). The shape of the EIS SW
response curve obtained by EUNIS-07 is consistent with the one measured
in laboratory prior to launch. The absolute value of the quiet-Sun
He II 304 Å intensity measured by EUNIS-07 is consistent with the
radiance measured by CDS NIS in quiet regions near the disk center
and the solar minimum irradiance recently obtained by CDS NIS and the
Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment.
Title: A Reconnection-driven Rarefaction Wave Model for Coronal
Outflows
Authors: Bradshaw, S. J.; Aulanier, G.; Del Zanna, G.
Bibcode: 2011ApJ...743...66B
Altcode:
We conduct numerical experiments to determine whether interchange
reconnection at high altitude coronal null points can explain the
outflows observed as blueshifts in coronal emission lines at the
boundaries between open and closed magnetic field regions. In this
scenario, a strong, post-reconnection pressure gradient forms in the
field-aligned direction when dense and hot, active region core loops
reconnect with neighboring tenuous and cool, open field lines. We
find that the pressure gradient drives a supersonic outflow and a
rarefaction wave develops in both the open and closed post-reconnection
magnetic field regions. We forward-model the spectral line profiles
for a selection of coronal emission lines to predict the spectral
signatures of the rarefaction wave. We find that the properties of
the rarefaction wave are consistent with the observed velocity versus
temperature structure of the corona in the outflow regions, where
the velocity increases with the formation temperature of the emission
lines. In particular, we find excellent agreement between the predicted
and observed Fe XII 195.119 Å spectral line profiles in terms of the
blueshift (10 km s-1), full width at half-maximum (83 mÅ)
and symmetry. Finally, we find that Ti < Te in
the open field region, which indicates that the interchange reconnection
scenario may provide a viable mechanism and source region for the slow
solar wind.
Title: SDO AIA and Hinode EIS observations of "warm" loops
Authors: Del Zanna, G.; O'Dwyer, B.; Mason, H. E.
Bibcode: 2011A&A...535A..46D
Altcode:
We present simultaneous observations of active region "warm" (1 MK)
loops using the Solar Dynamics Observatory (SDO) Atmospheric Imaging
Assembly (AIA) and Hinode EUV Imaging Spectrometer (EIS). Sample EIS
spectra for a loop footpoint and a lop leg region are presented, and are
used to describe the spectral lines which contribute to the six AIA EUV
channels, both directly and predicted with DEM modeling. We find good
overall agreement between observed and predicted count rates for the 131
Å, 193 Å, and 335 Å bands, but highlight a number of problems, partly
to be ascribed to inter-calibration issues, partly due to the fact that
a large number of lines remain unidentified for the 94 Å, 171 Å, and
211 Å bands. We also found that the 335 Å band is severely affected by
cross-talk with the 131 Å band and by second order contributions. We
extend our previous work where we highlighted the multi-thermal nature
of the SDO AIA bands to show that emission from lines formed at typical
transition region temperatures (log T[K] = 5.0-5.8) can be significant
for all the EUV channels, and even dominant in some cases. We also
assess the possibility of deriving accurate emission measures from the
AIA observations. We have found that the inversion of the AIA data to
obtain a description of the thermal characteristics of warm loops is
unreliable. We highlight the need for further work on the relevant
atomic data before the AIA data can be reliably used for plasma
diagnostic purposes. Appendices A-C are available in electronic
form at http://www.aanda.org
Title: The EVE Doppler Sensitivity and Flare Observations
Authors: Hudson, H. S.; Woods, T. N.; Chamberlin, P. C.; Fletcher,
L.; Del Zanna, G.; Didkovsky, L.; Labrosse, N.; Graham, D.
Bibcode: 2011SoPh..273...69H
Altcode: 2011SoPh..tmp..362H
The Extreme-ultraviolet Variability Experiment (EVE; see Woods et al.,
2009) obtains continuous EUV spectra of the Sun viewed as a star. Its
primary objective is the characterization of solar spectral irradiance,
but its sensitivity and stability make it extremely interesting for
observations of variability on time scales down to the limit imposed
by its basic 10 s sample interval. In this paper we characterize the
Doppler sensitivity of the EVE data. We find that the 30.4 nm line of
He II has a random Doppler error below 0.001 nm (1 pm, better than 10
km s−1 as a redshift), with ample stability to detect
the orbital motion of its satellite, the Solar Dynamics Observatory
(SDO). Solar flares also displace the spectrum, both because of Doppler
shifts and because of EVE's optical layout, which (as with a slitless
spectrograph) confuses position and wavelength. As a flare develops,
the centroid of the line displays variations that reflect Doppler shifts
and therefore flare dynamics. For the impulsive phase of the flare
SOL2010-06-12, we find the line centroid to have a redshift of 16.8 ±
5.9 km s−1 relative to that of the flare gradual phase
(statistical errors only). We find also that high-temperature lines,
such as Fe XXIV 19.2 nm, have well-determined Doppler components for
major flares, with decreasing apparent blueshifts as expected from
chromospheric evaporation flows.
Title: How to Make an Atomic Blog in Your Own Kitchen. Summary of
the Workshop: Uncertainties in Atomic Data and How They Propagate
in Chemical Abundances
Authors: Luridiana, Valentina; García-Rojas, Jorge; Aggarwal,
Kanti; Bautista, Manuel; Bergemann, Maria; Delahaye, Franck; del
Zanna, Giulio; Ferland, Gary; Lind, Karin; Manchado, Arturo; Mendoza,
Claudio; Mesa Delgado, Adal; Núñez Díaz, Manuel; Shaw, Richard A.;
Wesson, Roger
Bibcode: 2011arXiv1110.1873L
Altcode:
This workshop brought together scientists (including atomic
physicists, theoretical astrophysicists and astronomers) concerned
with the completeness and accuracy of atomic data for astrophysical
applications. The topics covered in the workshop included the evaluation
of uncertainties in atomic data, the propagation of such uncertainties
in chemical abundances, and the feedback between observations and
calculations. On a different level, we also discussed communication
issues such as how to ensure that atomic data are correctly understood
and used, and which forum is the best one for a fluid interaction
between all communities involved in the production and use of atomic
data. This paper reports on the discussions held during the workshop
and introduces AstroAtom, a blog created as a platform for timely
and open discussions on the needs and concerns over atomic data, and
their effects on astronomical research. The complete proceedings will
be published on http://astroatom.wordpress.com/.
Title: Benchmarking atomic data for astrophysics: Fe xiii EUV lines
Authors: Del Zanna, G.
Bibcode: 2011A&A...533A..12D
Altcode:
Recent atomic data for Fe xiii are benchmarked against high-resolution
spectroscopic observations of the solar corona. All the identifications
of the EUV lines are reviewed by also taking into account laboratory
measurements. A few new identifications are proposed, and many
wavelengths are revised. All the strongest EUV lines are now
identified. Very good agreement between predicted and observed line
intensities is generally found using the latest atomic calculations. We
clearly indicate which EUV lines are blended, and which are best for
electron-density measurements in different regimes.
Title: The 3s23p3d3Foterm in the Si-like spectrum of Fe (Fe XIII)
Authors: Träbert, Elmar; Ishikawa, Yasuyuki; Santana, Juan A.;
Del Zanna, Giulio
Bibcode: 2011CaJPh..89..403T
Altcode:
No abstract at ADS
Title: Solar plasma spectroscopy: achievements and future challenges
Authors: Del Zanna, Giulio; Tripathi, Durgesh; Young, Peter
Bibcode: 2011A&G....52b..17D
Altcode:
MEETING REPORT Giulio Del Zanna, Durgesh Tripathi and Peter Young
report on a meeting to celebrate the career of Helen Mason - and the
development of an important field in solar physics.
Title: The EUV spectrum of the Sun: SOHO CDS NIS irradiances from
1998 until 2010
Authors: Del Zanna, G.; Andretta, V.
Bibcode: 2011A&A...528A.139D
Altcode:
We present extreme-ultraviolet (EUV) irradiances of the Sun taken during
the 1998-2010 period from the Solar and Heliospheric Observatory (SoHO)
Coronal Diagnostic Spectrometer (CDS) Normal Incidence Spectrograph
(NIS). They were obtained from NIS full-Sun radiance observations, and
represent the first set of EUV spectral observations spanning a solar
cycle. We compare the CDS line irradiances with those obtained from
rocket measurements, one that flew in May 1997 and one in April 2008,
together with the Thermosphere Ionosphere Mesosphere Energetics Dynamics
(TIMED) Solar EUV Experiment (SEE) EUV Grating Spectrograph (EGS) and
various historical records. Excellent agreement (to within a relative
20%) is found in most cases, with a few notable exceptions. Lines formed
in the transition region show very small changes with the solar cycle,
with the exception of the helium lines. The irradiances of lines formed
around 1 MK already change during the cycle by a factor ~5; for hotter
lines (2.5 MK) the variability reaches factors of the order of 40. For
lines formed around 1-3 MK, and to a less extent, the helium lines,
we find a good linear correlation between CDS irradiances and the 10.7
cm radio flux, although each line has a different coefficient. No
correlation is found for the transition-region lines. Significant
discrepancies between the observed irradiances and those modelled
is found. This confirms the importance in obtaining EUV spectral
measurements of the solar irradiance.
Title: A single picture for solar coronal outflows and radio noise
storms
Authors: Del Zanna, G.; Aulanier, G.; Klein, K. -L.; Török, T.
Bibcode: 2011A&A...526A.137D
Altcode:
We propose a unified interpretation for persistent coronal outflows
and metric radio noise storms, two phenomena typically observed in
association with quiescent solar active regions. Our interpretation
is based on multi-wavelength observations of two such regions as
they crossed the meridian in May and July 2007. For both regions,
we observe a persistent pattern of blue-shifted coronal emission in
high-temperature lines with Hinode/EIS, and a radio noise storm with the
Nançay Radioheliograph. The observations are supplemented by potential
and linear force-free extrapolations of the photospheric magnetic
field over large computational boxes, and by a detailed analysis of
the coronal magnetic field topology. We find true separatrices in the
coronal field and null points high in the corona, which are preferential
locations for magnetic reconnection and electron acceleration. We
suggest that the continuous growth of active regions maintains a steady
reconnection across the separatrices at the null point. This interchange
reconnection occurs between closed, high-density loops in the core of
the active region and neighbouring open, low-density flux tubes. Thus,
the reconnection creates strong pressure imbalances which are the main
drivers of plasma upflows. Furthermore, the acceleration of low-energy
electrons in the interchange reconnection region sustains the radio
noise storm in the closed loop areas, as well as weak type III emission
along the open field lines. For both active regions studied, we find a
remarkable agreement between the observed places of persistent coronal
outflows and radio noise storms with their locations as predicted by
our interpretation.
Title: Hinode observations and 3D magnetic structure of an X-ray
bright point
Authors: Alexander, C. E.; Del Zanna, G.; Maclean, R. C.
Bibcode: 2011A&A...526A.134A
Altcode:
Aims: We present complete Hinode Solar Optical Telescope (SOT),
X-Ray Telescope (XRT)and EUV Imaging Spectrometer (EIS) observations
of an X-ray bright point (XBP) observed on the 10, 11 of October 2007
over its entire lifetime (~12 h). We aim to show how the measured
plasma parameters of the XBP change over time and also what kind of
similarities the X-ray emission has to a potential magnetic field
model.
Methods: Information from all three instruments on-board
Hinode was used to study its entire evolution. XRT data was used
to investigate the structure of the bright point and to measure the
X-ray emission. The EIS instrument was used to measure various plasma
parameters over the entire lifetime of the XBP. Lastly, the SOT was used
to measure the magnetic field strength and provide a basis for potential
field extrapolations of the photospheric fields to be made. These were
performed and then compared to the observed coronal features.
Results: The XBP measured ~15´´ in size and was found to be formed
directly above an area of merging and cancelling magnetic flux on the
photosphere. A good correlation between the rate of X-ray emission
and decrease in total magnetic flux was found. The magnetic fragments
of the XBP were found to vary on very short timescales (minutes),
however the global quasi-bipolar structure remained throughout the
lifetime of the XBP. The potential field extrapolations were a good
visual fit to the observed coronal loops in most cases, meaning that
the magnetic field was not too far from a potential state. Electron
density measurements were obtained using a line ratio of Fe XII and the
average density was found to be 4.95 × 109 cm-3
with the volumetric plasma filling factor calculated to have an average
value of 0.04. Emission measure loci plots were then used to infer a
steady temperature of log Te [ K] ~ 6.1. The calculated Fe
XII Doppler shifts show velocity changes in and around the bright point
of ±15 km s-1 which are observed to change on a timescale
of less than 30 min.
Title: The 22 May 2007 B-class flare: new insights from Hinode
observations
Authors: Del Zanna, G.; Mitra-Kraev, U.; Bradshaw, S. J.; Mason,
H. E.; Asai, A.
Bibcode: 2011A&A...526A...1D
Altcode:
We present multi-wavelength observations of a small B-class flare
which occurred on the Sun on 2007 May 22. The observations include
data from Hinode, GOES, TRACE and the Nobeyama Radioheliograph. We
obtained spatially and spectrally-resolved information from the Hinode
EUV Imaging Spectrometer (EIS) during this event. The temporal and
temperature coverage of the EIS observations provides new insights into
our understanding of chromospheric evaporation and cooling. The flare
showed many “typical” features, such as brightenings in the ribbons,
hot (10 MK) loop emission and subsequent cooling. We also observed
a new feature, strong (up to 170 km s-1) blue-shifted
emission in lines formed around 2-3 MK, located at the footpoints of
the 10 MK coronal emission and within the ribbons. Electron densities
at 2 MK in the kernels are high, of the order of 1011
cm-3, suggesting a very narrow layer where the chromospheric
evaporation occurs. We have run a non-equilibrium hydrodynamic numerical
simulation using the HYDRAD code to study the cooling of the 10 MK
plasma, finding good agreement between the predicted and observed
temperatures, densities and ion populations. Line blending for some
potentially useful diagnostic lines for flares, which are observed
with Hinode/EIS, is also discussed.
Title: The First Measurement of the Adiabatic Index in the Solar
Corona Using Time-dependent Spectroscopy of Hinode/EIS Observations
Authors: Van Doorsselaere, Tom; Wardle, Nick; Del Zanna, Giulio;
Jansari, Kishan; Verwichte, Erwin; Nakariakov, Valery M.
Bibcode: 2011ApJ...727L..32V
Altcode:
We use observations of a slow magnetohydrodynamic wave in the corona
to determine for the first time the value of the effective adiabatic
index, using data from the Extreme-ultraviolet Imaging Spectrometer
on board Hinode. We detect oscillations in the electron density,
using the CHIANTI atomic database to perform spectroscopy. From
the time-dependent wave signals from multiple spectral lines the
relationship between relative density and temperature perturbations is
determined, which allows in turn to measure the effective adiabatic
index to be γeff = 1.10 ± 0.02. This confirms that the
thermal conduction along the magnetic field is very efficient in the
solar corona. The thermal conduction coefficient is measured from
the phase lag between the temperature and density, and is shown to be
compatible with Spitzer conductivity.
Title: Hinode extreme-ultraviolet imaging spectrometer observations
of a limb active region
Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E.; Sterling, A. C.;
Tripathi, D.; Young, P. R.
Bibcode: 2011A&A...525A.137O
Altcode:
Aims: We investigate the electron density and temperature
structure of a limb active region.
Methods: We have carried out
a study of an active region close to the solar limb using observations
from the Extreme-ultraviolet Imaging Spectrometer (EIS) and the X-ray
telescope (XRT) on board Hinode. The electron density and temperature
distributions of the coronal emission have been determined using
emission line intensity ratios. Differential emission measure (DEM)
analysis and the emission measure (EM) loci technique were used to
examine the thermal structure of the emitting plasma as a function
of distance from the limb.
Results: The highest temperature
and electron density values are found to be located in the core of
the active region, with a peak electron number density value of 1.9
× 1010 cm-3 measured using the Fe XII 186.887
Å to 192.394 Å line intensity ratio. The plasma along the line of
sight in the active region was found to be multi-thermal at different
distances from the limb. The EIS and XRT DEM analyses appear to be
in agreement in the temperature interval from log T = 6.5-6.7.
Conclusions: Our results provide new constraints for models of coronal
heating in active regions.
Title: Science Objectives for an X-Ray Microcalorimeter Observing
the Sun
Authors: Laming, J. Martin; Adams, J.; Alexander, D.; Aschwanden, M;
Bailey, C.; Bandler, S.; Bookbinder, J.; Bradshaw, S.; Brickhouse,
N.; Chervenak, J.; Christe, S.; Cirtain, J.; Cranmer, S.; Deiker, S.;
DeLuca, E.; Del Zanna, G.; Dennis, B.; Doschek, G.; Eckart, M.; Fludra,
A.; Finkbeiner, F.; Grigis, P.; Harrison, R.; Ji, L.; Kankelborg,
C.; Kashyap, V.; Kelly, D.; Kelley, R.; Kilbourne, C.; Klimchuk, J.;
Ko, Y. -K.; Landi, E.; Linton, M.; Longcope, D.; Lukin, V.; Mariska,
J.; Martinez-Galarce, D.; Mason, H.; McKenzie, D.; Osten, R.; Peres,
G.; Pevtsov, A.; Porter, K. Phillips F. S.; Rabin, D.; Rakowski, C.;
Raymond, J.; Reale, F.; Reeves, K.; Sadleir, J.; Savin, D.; Schmelz,
J.; Smith, R. K.; Smith, S.; Stern, R.; Sylwester, J.; Tripathi, D.;
Ugarte-Urra, I.; Young, P.; Warren, H.; Wood, B.
Bibcode: 2010arXiv1011.4052L
Altcode:
We present the science case for a broadband X-ray imager with
high-resolution spectroscopy, including simulations of X-ray spectral
diagnostics of both active regions and solar flares. This is part of
a trilogy of white papers discussing science, instrument (Bandler et
al. 2010), and missions (Bookbinder et al. 2010) to exploit major
advances recently made in transition-edge sensor (TES) detector
technology that enable resolution better than 2 eV in an array that
can handle high count rates. Combined with a modest X-ray mirror, this
instrument would combine arcsecondscale imaging with high-resolution
spectra over a field of view sufficiently large for the study of
active regions and flares, enabling a wide range of studies such as
the detection of microheating in active regions, ion-resolved velocity
flows, and the presence of non-thermal electrons in hot plasmas. It
would also enable more direct comparisons between solar and stellar
soft X-ray spectra, a waveband in which (unusually) we currently have
much better stellar data than we do of the Sun.
Title: SDO/AIA response to coronal hole, quiet Sun, active region,
and flare plasma
Authors: O'Dwyer, B.; Del Zanna, G.; Mason, H. E.; Weber, M. A.;
Tripathi, D.
Bibcode: 2010A&A...521A..21O
Altcode:
Aims: We examine the contribution of spectral lines and continuum
emission to the EUV channels of the Atmospheric Imaging Assembly (AIA)
on the Solar Dynamics Observatory (SDO) in different regions of the
solar atmosphere.
Methods: Synthetic spectra were obtained using
the CHIANTI atomic database and sample differential emission measures
for coronal hole, quiet Sun, active region and flare plasma. These
synthetic spectra were convolved with the effective area of each
channel, in order to determine the dominant contribution in different
regions of the solar atmosphere.
Results: We highlight the
contribution of particular spectral lines which under certain conditions
can affect the interpretation of SDO/AIA data.
Title: R-matrix Electron-impact Excitation of Fe13+ and
its Application to the Soft X-ray and Extreme-ultraviolet Spectroscopy
of Corona-like Plasmas
Authors: Liang, G. Y.; Badnell, N. R.; Crespo López-Urrutia, J. R.;
Baumann, T. M.; Del Zanna, G.; Storey, P. J.; Tawara, H.; Ullrich, J.
Bibcode: 2010ApJS..190..322L
Altcode:
Accurate excitation parameters are required to interpret the
ultraviolet and X-ray spectra of Fe13+. In this work,
we use the AUTOSTRUCTURE code to describe the atomic structure of
Fe13+. The 197 lowest-lying fine-structure levels of
the 3sx 3py 3dz (x + y + z = 3),
3s 24l, and 3s3p4{s, p, and d} configurations are included
along with further correlation configurations: 3s3p4f, 3px
3dy 4l (x + y = 2), 3l4l'4l'', and 3l3l'5l''. The resultant
level energies, lifetimes of excited states, and oscillator strengths
of transitions between these levels are assessed by comparison with
available experimental data and previous calculations. Electron-impact
excitation data among these lowest-lying levels are generated using
the intermediate-coupling frame transformation R-matrix method. We
assess the present results by comparisons with laboratory measurement
for the excitation to the metastable level 3s 23p
2 P o 3/2 and with available
close-coupling calculations for other excitations. Using these data
and a collisional-radiative model, we have analyzed soft X-ray and
extreme-ultraviolet spectra from space satellite observations of a
stellar corona and of solar flares, as well as measurements from an
electron beam ion trap. We assess the contribution from Fe13+
emission lines in the solar and Procyon corona observations, and find
and identify new lines in the X-ray region observed in the solar and
Procyon coronae. The laboratory measurements also confirm that weak
lines (218.177 Å and 224.354 Å) of Fe13+ contribute to the
observed intensities in solar observations. The polarization effect
due to the directional monoenergetic distribution of the electron
energy has been taken into account in comparison with the laboratory
measurements. Electron density diagnostics for the astrophysical plasma
sources have been performed using the updated data so as to investigate
their sensitivity to the atomic data source.
Title: VizieR Online Data Catalog: R-matrix electron-impact excitation
of Fe13+^ (Liang+, 2010)
Authors: Liang, G. Y.; Badnell, N. R.; Crespo Lopez-Urrutia, J. R.;
Baumann, T. M.; Del Zanna, G.; Storey, P. J.; Tawara, H.; Ullrich, J.
Bibcode: 2010yCat..21900322L
Altcode:
Accurate excitation parameters are required to interpret the
ultraviolet and X-ray spectra of Fe13+^. In this work, we
use the autostructure code to describe the atomic structure
of Fe13+^. The 197 lowest-lying fine-structure levels of the
3sx3py3dz(x+y+z=3), 3s2^4l, and
3s3p4{s,p, and d} configurations are included along with further
correlation configurations: 3s3p4f, 3px3dy4l
(x+y=2), 3l4l'4l", and 3l3l'5l". The resultant level energies, lifetimes
of excited states, and oscillator strengths of transitions between
these levels are assessed by comparison with available experimental
data and previous calculations. Electron-impact excitation data among
these lowest-lying levels are generated using the intermediate-coupling
frame transformation R-matrix method. We assess the present results
by comparisons with laboratory measurement for the excitation to the
metastable level 3s23p2Po3/2 and with
available close-coupling calculations for other excitations. Using these
data and a collisional-radiative model, we have analyzed soft X-ray
and extreme-ultraviolet spectra from space satellite observations
of a stellar corona and of solar flares, as well as measurements
from an electron beam ion trap. We assess the contribution from
Fe13+^ emission lines in the solar and Procyon corona observations,
and find and identify new lines in the X-ray region observed in the
solar and Procyon coronae. The laboratory measurements also confirm
that weak lines (218.177Å and 224.354Å) of Fe13+^ contribute to the
observed intensities in solar observations. The polarization effect
due to the directional monoenergetic distribution of the electron
energy has been taken into account in comparison with the laboratory
measurements. Electron density diagnostics for the astrophysical plasma
sources have been performed using the updated data so as to investigate
their sensitivity to the atomic data source. (1 data file).
Title: Active region moss. Basic physical parameters and their
temporal variation
Authors: Tripathi, D.; Mason, H. E.; Del Zanna, G.; Young, P. R.
Bibcode: 2010A&A...518A..42T
Altcode: 2010arXiv1005.2220T
Context. Active region moss are transition region phenomena, first noted
in the images recorded by the Transition Region and Coronal Explorer
(TRACE) in λ171. Moss regions are thought to be the footpoints of
hot loops (3-5 MK) seen in the core of active regions. These hot
loops appear “fuzzy” (unresolved). Therefore, it is difficult to
study the physical plasma parameters in individual hot core loops and
hence their heating mechanisms. Moss regions provide an excellent
opportunity to study the physics of hot loops. In addition, they
allow us to study the transition region dynamics in the footpoint
regions.
Aims: To derive the physical plasma parameters such as
temperature, electron density, and filling factors in moss regions and
to study their variation over a short (an hour) and a long time period
(5 consecutive days).
Methods: Primarily, we have analyzed
spectroscopic observations recorded by the Extreme-ultraviolet Imaging
Spectrometer (EIS) aboard Hinode. In addition we have used supplementary
observations taken from TRACE and the X-Ray Telescope (XRT) aboard
Hinode.
Results: The moss emission is strongest in the Fe XII
and Fe XIII lines. Based on analyses using line ratios and emission
measure we found that moss regions have a characteristic temperature
of log T[K] = 6.2. The temperature structure in moss region remains
almost identical from one region to another and it does not change
with time. The electron densities measured at different locations in
the moss regions using Fe XII ratios are about 1-3 × 1010
cm-3 and about 2-4 × 109 cm-3 using
Fe XIII and Fe XIV. The densities in the moss regions are similar in
different places and show very little variation over short and long
time scales. The derived electron density substantially increased (by
a factor of about 3-4 or even more in some cases) when a background
subtraction was performed. The filling factor of the moss plasma
can vary between 0.1-1 and the path length along which the emission
originates is from a few 100 to a few 1000 kms long. By combining the
observations recorded by TRACE, EIS and XRT, we find that the moss
regions correspond to the footpoints of both hot and warm loops.
Title: VizieR Online Data Catalog: IRON project. LXVIII (Del Zanna+,
2010)
Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E.
Bibcode: 2010yCat..35140040D
Altcode: 2010yCat..35149040D
**************************************************************************
* * * Sorry, but the author(s) never supplied the tabular
material * * (detailed tables) as announced in the paper. *
**************************************************************************
Title: The EUV spectrum of the Sun: long-term variations in the SOHO
CDS NIS spectral responsivities
Authors: Del Zanna, G.; Andretta, V.; Chamberlin, P. C.; Woods, T. N.;
Thompson, W. T.
Bibcode: 2010A&A...518A..49D
Altcode:
We present SOHO Coronal Diagnostic Spectrometer (CDS) normal incidence,
extreme-ultraviolet spectra of the Sun taken from the beginning of
the mission in 1996 until now. We use various methods to study the
performance of the instrument during such a long time span. Assuming
that the basal chromospheric-transition region emission in the quiet
parts of the Sun does not vary over the cycle, we find a slow decrease
in the instrument sensitivity over time. We applied a correction to the
NIS (Normal Incidence Spectrograph) data, using as a starting reference
the NIS absolute calibration obtained from a comparison with a rocket
flight in May 1997. We then obtained NIS full-Sun spectral irradiances
from observations in 2008 and compared them with the EUV irradiances
obtained from the rocket that flew on April 14, 2008 a prototype of
the Solar Dynamics Observatory EVE instrument. Excellent agreement is
found between the EUV irradiances from NIS and from the EVE-prototype,
confirming the NIS radiometric calibration. The NIS instrument over
13 years has performed exceptionally well, with only a factor of about
2 decrease in responsivity for most wavelengths.
Title: Benchmarking atomic data for astrophysics: Fe xi
Authors: Del Zanna, G.
Bibcode: 2010A&A...514A..41D
Altcode:
High-resolution spectroscopic observations of the solar corona and
laboratory measurements are used to review all the line identifications
for Fe xi, from the EUV to the visible. The results of the atomic
structure and scattering calculations are presented elsewhere, while
detailed comparisons between observed and predicted wavelengths
and intensities are discussed here. All the brightest EUV lines
in the solar corona are now finally firmly identified. Several
new identifications are proposed, in particular, coronal forbidden
lines. The previously-known density-diagnostics are confirmed. New and
important temperature diagnostics are presented, and the presence of
blends highlighted.
Title: Atomic data from the IRON project. LXVIII. Electron impact
excitation of Fe xi
Authors: Del Zanna, G.; Storey, P. J.; Mason, H. E.
Bibcode: 2010A&A...514A..40D
Altcode:
A new R-matrix scattering calculation for electron collisional
excitation of Fe xi is presented and compared to earlier
calculations. The calculation includes 145 LS terms and 465
fine-structure levels and uses the intermediate-coupling frame
transformation method (ICFT). We discuss the strong interactions that
exist between three J = 1 levels in the 3s2 3p3
3d electron configuration. These levels give rise to strong lines
in the EUV spectrum and their energies and identifications have
been the source of much confusion in the literature. We show that
the oscillator and collision strengths linking these levels to
the ground levels of the ion are very sensitive to the choice of
configuration basis and argue that most earlier calculations have
failed to represent these levels adequately. Detailed tables
of the present data are available in electronic form at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/514/A40
Title: Anatomy of a Slow Wave in a Coronal Loop
Authors: Van Doorsselaere, Tom; Wardle, N.; Del Zanna, G.; Jansari, K.
Bibcode: 2010AAS...21640708V
Altcode: 2010BAAS...41..860V
We analyse an observation of a 5 minute quasi-periodic oscillation
detected in the coronal line FeXII at 195A, near the footpoint of a
coronal loop in Hinode/EIS data on 08 Feb 2007. The same oscillation
is detected simultaneously in two other coronal lines, FeXIII at 204A
and FeXI at 192A. The oscillation is observed for a full 2 periods in
both Doppler shift and intensity. We use Fourier and wavelet analysis
to determine the period of the oscillation to be P = 314 ± 83s in the
Doppler shift and P = 344 ± 61s in the intensity. We observe negligible
phase shift between Doppler and intensity time series. This is strong
evidence for the interpretation of the observed phenomenon in terms
of a propagating slow magneto-acoustic MHD mode. For the first time,
we use spectroscopy to detect oscillations in the electron density,
using the CHIANTI atomic database. Comparing the density variations and
the Doppler shifts allows us to derive the line-of-sight component of
the phase speed. The comparison of the temperature and the density
allows to estimate the coronal value of the ratio of specific
heats. A comparative study of Hinode/EIS and multi-temperature
high cadence SDO/AIA observations of this phenomenon is discussed. The research leading to these results has received funding from
the European community's seventh framework programme (FP7/2007-2013)
under grant agreement number 220555.
Title: VizieR Online Data Catalog: IRON Project. LVIII. (Storey+,
2005)
Authors: Storey, P. J.; Del Zanna, G.; Mason, H. E.; Zeippen, C. J.
Bibcode: 2010yCat..34330717S
Altcode:
A new calculation of rate coefficients for electron collisional
excitation of Fe XII is presented and compared to earlier
calculations. Significant differences are found with all earlier work
due to the inclusion of resonance processes that have not previously
been considered and to the use of the intermediate coupling frame
transformation method. The resulting dataset of collision strengths
is shown to resolve many of the outstanding discrepancies between
theory and solar observations. In particular, density sensitive
line ratios in Fe XII now indicate electron densities close to
those derived from other ions of comparable ionization potential. **************************************************************************
* * * Sorry, but the author(s) never supplied the
tabular material * * announced in the paper * * *
**************************************************************************
Title: The EUV spectral irradiance of the Sun from 1997 to date
Authors: Del Zanna, Giulio; Andretta, Vincenzo
Bibcode: 2010IAUS..264...78D
Altcode:
We present measurements of the EUV spectral irradiance we have
obtained from radiance measurements with the SOHO Coronal Diagnostic
Spectrometer, from 1997 to date. We discuss the contribution of
the various regions of the Sun to the total EUV irradiance, and how
they varied dramatically between the last two solar minima. These
observations allow us to interpret spectral irradiance measurements in
the EUV which have been available since 2002 with the TIMED mission. We
also briefly discuss how changes in various activity indices compare
with the EUV spectral variability, and the limitations of spectral
modelling.
Title: Flows in active region loops
Authors: Del Zanna, Giulio
Bibcode: 2010cosp...38.2956D
Altcode: 2010cosp.meet.2956D
Hinode EIS spectroscopic observations of active regions are
presented. They show a persistent pattern of Dopplershifts. These
observations are complemented with EUV imaging and obser-vations of
the photospheric magnetic field. It is clear that these flows play
an important part in the formation and evolution of loops. A detailed
physical picture is presented, to clarify some of the puzzling features,
together with a discussion of possible interpretations for both the
downflows and the upflows.
Title: An Erupting Filament and Associated CME Observed by Hinode,
STEREO and SOHO
Authors: Bemporad, A.; Del Zanna, G.; Andretta, V.; Magrí, M.;
Poletto, G.; Ko, Y. -K.
Bibcode: 2009ASPC..415..385B
Altcode:
A multi-spacecraft campaign was set up in May 2007 to observe the
off-limb corona with Hinode, STEREO and SOHO instruments (Hinode
HOP 7). During this campaign, a filament eruption and a coronal
mass ejection (CME) occurred on May 9 from NOAA 10953 at the West
limb. The filament eruption starts around 13:40 UT and results in a
CME at 4°SW latitude. Remarkably, the event was observed by STEREO
(EUVI and COR1) and by the Hinode/EIS and SOHO/UVCS spectrometers. We
present results from all these instruments. High-cadence data from
Stereo/EUVI A and B in the He II λ304 line were used to study the
3-D expansion of the filament. A slow rising phase, during which the
filament moved southward, was followed by an impulsive phase during
which the filament appeared to change direction and then contribute
to the westward-expanding CME as seen in STEREO/COR 1. Hinode/EIS was
scanning with the 2'' slit the region where the filament erupted. The
EIS spectra show remarkable non-thermal broadening in lines emitted at
different temperatures at the location of the filament eruption. The
CME was also observed by the SOHO/UVCS instrument: the spectrograph
slit was centered at 1.7 solar radii, at a latitude of 5°SW and
recorded a sudden increase in the O VI λλ 1032-1037 and Si XI λ520
spectral line intensities. We discuss the overall morphology of this
interesting eruptive event, and provide a preliminary assessment of
its temperature and density structure.
Title: Benchmarking atomic data for astrophysics: Fe XVII EUV lines
Authors: Del Zanna, G.; Ishikawa, Y.
Bibcode: 2009A&A...508.1517D
Altcode:
In the light of accurate structure and scattering calculations for
Fe XVII, we review the status of identifications in the EUV spectrum
of this ion using various experimental data, from the X-rays to the
UV. Most previous identifications are confirmed, although a critical
revision leads to changes in many wavelength values, in particular
for the 2p5 3s-2p5 3p and 2p5
3p-2p5 3d transitions, which we observed with the Hinode EUV
Imaging Spectrometer (EIS). Several lines are identified here for the
first time. We find good agreement between expected and measured line
intensities, with a few notable exceptions. In particular, the strong
line in the EIS spectra, observed at 254.88 Å, has a consistently
low observed intensity. We present two Hinode/EIS observations and
discuss which lines are clearly blended in these datasets, and which
are reliable for diagnostic purposes.
Title: Diagnostics of Active Region Loops Observed with Hinode/EIS
Authors: Tripathi, D.; Mason, H. E.; Dwivedi, B. N.; Del Zanna, G.
Bibcode: 2009ASPC..415..260T
Altcode:
The Extreme Ultraviolet Imaging Spectrometer (EIS) on board Hinode
provides us with an excellent opportunity to study the physical
parameters in spatially resolved coronal structures. In this paper
we have carried out a study of active region loops using observations
from the EIS. The active region was observed on 2007 Ma 19 using the
1 arcsec slit of EIS. At coronal temperatures, we find that electron
densities measured from Fe XII and Si X line ratios decrease along
the loop length, being ≈10100 cm-3 at foot
point and ≈108.5 cm-3 at a height of about 75
Mm. However, the electron densities measured from the Mg VII line ratios
(at a transition region temperature) show significantly lower values
at the foot point. The electron temperature along the loop increases
with height from ≈0.8 MK (at foot point) to ≈1.5 MK (at a height
of 75 Mm). The temperature diagnostics using EM-loci at different
locations along the loop show that the loop is ``nearly isothermal''
or ``mildly multi-thermal'' along the LOS. These measurements provide
important constraints on the theoretical modelling of coronal loops.
Title: Benchmarking atomic data for astrophysics: Fe VIII EUV lines
Authors: Del Zanna, G.
Bibcode: 2009A&A...508..513D
Altcode:
The EUV spectrum of ion{Fe}{viii} is reviewed, using new solar
observations from the Hinode EUV Imaging Spectrometer (EIS), together
with older solar and laboratory data. The most up-to-date scattering
calculations are benchmarked against these experimental data, with the
use of a large atomic structure calculation. Once adjustments are made
to the excitation rates, good agreement is found between calculated
and observed line intensities. All previous line identifications have
been re-assessed. Several lines are identified here for the first time,
most notably the strong decays from the 3s2 3p5
3d2 ^4Dj levels. It is shown that they provide a new,
important diagnostic of electron temperature for the upper transition
region. The temperatures obtained at the base of solar coronal loops
are lower (log T [K] = 5.5) than those predicted by assuming ionization
equilibrium (log T [K] = 5.6), however firm measurements will only be
possible once better scattering calculations are available, and the
EIS radiometric calibration is properly assessed.
Title: Multi-Instrument Campaigns to Observe the Off-Limb Corona
Authors: Del Zanna, G.; Andretta, V.; Poletto, G.; Teriaca, L.; Ko,
Y. -K.; Mason, H. E.; Vourdilas, A.; Bemporad, A.; Magri, M.
Bibcode: 2009ASPC..415..315D
Altcode:
We briefly describe two multi-instrument campaigns we coordinated to
observe the off-limb corona in 2007, with some preliminary results. The
first one (Hinode HOP 7) was a SOHO/Hinode/TRACE/STEREO/Ulysses
week-long campaign during the SOHO-Ulysses quadrature in 2007 May. We
could not achieve all of our goals, however we were very fortunate in
that the ``Del Zanna'' active region appeared on the Sun at the right
longitude, and that a filament eruption and a CME were observed. Of
particular significance is the finding of large (100 km s-1)
non-thermal broadenings in all coronal lines observed by Hinode/EIS
in the region where the filament was erupting. The second campaign
(Hinode HOP 44) involved SOHO (CDS, SUMER, UVCS), Hinode, and TRACE to
measure the physical parameters of plume/interplume regions in the polar
coronal holes from the low corona to 1.7 solar radii, on 30/10-4/11. We
obtained a good set of observations, however various instrumental
constraints and the lack of fully developed plumes limited our goals.
Title: Benchmarking atomic data for astrophysics: Fe VII and other
cool lines observed by Hinode EIS
Authors: Del Zanna, G.
Bibcode: 2009A&A...508..501D
Altcode:
The EUV spectrum of ion{Fe}{vii} is reviewed, using new rates
for electron impact excitation, atomic structure calculations, and
experimental data. In particular, solar observations of a sunspot loop
spectrum obtained from the Hinode EUV Imaging Spectrometer (EIS) are
used. Previous line identifications, mostly based on laboratory data,
have been assessed. Large discrepancies between observed and predicted
line intensities and wavelengths are found for the decays from the
3s2 3p5 3d3 configuration, which are
strong EUV lines. We ascribe these discrepancies to incorrect line
identifications. A number of new identifications are proposed. With
these, very good agreement between theory and experimental data
is found. A few transitions, in particular from the 3s2
3p6 3d 4s configuration, are observed for the first time,
and are shown to provide a new important diagnostic for measuring the
electron temperature in the solar transition region. The temperatures
obtained at the base of solar coronal loops are found to be close
to the temperature of maximum abundance in ionization equilibrium
(log T [K]= 5.4). The assessment of the ion{Fe}{vii} lines was done in
conjunction with an assessment of all the strongest cool lines observed
with EIS. This spectrum is rich in transition region lines. Some new
identifications are presented, in particular for ion{Fe}{ix}. Most of
the strongest transitions are identified, however a large number of
lines still awaits firm identification.
Title: Coronal Loops: New Insights from EIS Observations
Authors: Del Zanna, G.; Bradshaw, S. J.
Bibcode: 2009ASPC..415..264D
Altcode:
Multi-instrument observations of coronal loops of different active
regions have been studied. The general features discussed in Del
Zanna (2003) and Del Zanna and Mason (2003) based on SOHO/CDS are
confirmed. Hinode/EIS high-cadence observations clearly show how
dynamic loops are at all temperatures. This clearly reflects the fast
changes in the photospheric magnetic fields measured by SOT over a
minute timescale. Despite that, persistent patterns are present. In
particular, the pattern of Doppler shifts and non-thermal widths,
found for the first time in NOAA 10926 (cf. Del Zanna 2007, 2008),
is actually a common feature in all active regions. It is likely
that the majority of cool (0.5--1 MK) loops are observed during their
radiatively cooling phase.
Title: Multispacecraft observations of a prominence eruption
Authors: Bemporad, A.; Del Zanna, G.; Andretta, V.; Poletto, G.;
Magrí, M.
Bibcode: 2009AnGeo..27.3841B
Altcode:
On 9 May 2007 a prominence eruption occurred at the West
limb. Remarkably, the event was observed by the STEREO/EUVI telescopes
and by the HINODE/EIS and SOHO/UVCS spectrometers. We present results
from all these instruments. High-cadence (~37 s) data from STEREO/EUVI
A and B in the He II λ304 line were used to study the 3-D shape and
expansion of the prominence. The high spatial resolution EUVI images
(~1.5"/pixel) have been used to infer via triangulation the 3-D shape
and orientation of the prominence 12 min after the eruption onset. At
this time the prominence has mainly the shape of a "hook" highly
inclined southward, has an average thickness of 0.068 R⊙,
a length of 0.43 R⊙ and lies, in first approximation,
on a plane. Hence, the prominence is mainly a 2-D structure and there
is no evidence for a twisted flux rope configuration. HINODE/EIS was
scanning with the 2" slit the region where the filament erupted. The
EIS spectra show during the eruption remarkable non-thermal broadening
(up to ~100 km s-1) in the region crossed by the filament
in spectral lines emitted at different temperatures, possibly with
differences among lines from higher Fe ionization stages. The CME was
also observed by the SOHO/UVCS instrument: the spectrograph slit was
centered at 1.7 R⊙, at a latitude of 5° SW and recorded
a sudden increase in the O VI λλ1032-1037 and Si XII λ520 spectral
line intensities, representative of the CME front transit.
Title: Atomic data for the X-ray plasma modelling - recent advances
Authors: Del Zanna, G.
Bibcode: 2009hrxs.confE..11D
Altcode:
The status of atomic data important for the analysis of high-resolution
X-ray spectra is briefly described. New calculations of ionization
and recombination rates have become available, as well as many
new scattering calculations. Atomic data have been made easily
accessible but a large amount of work is still needed, in particular
in benchmarking the theoretical data, and identify transitions. The
latest R-matrix calculations provide for a range of important ions
excellent agreement with experimental data, and a range of new density
and temperature diagnostics have been found.
Title: CHIANTI - an atomic database for emission lines. IX. Ionization
rates, recombination rates, ionization equilibria for the elements
hydrogen through zinc and updated atomic data
Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G.; Landini,
M.; Mason, H. E.
Bibcode: 2009A&A...498..915D
Altcode:
Aims: The goal of the CHIANTI atomic database is to provide a set of
atomic data for the interpretation of astrophysical spectra emitted by
collisionally dominated, high temperature, optically thin sources.
Methods: A complete set of ground level ionization and recombination
rate coefficients has been assembled for all atoms and ions of the
elements of H through Zn and inserted into the latest version of the
CHIANTI database, CHIANTI 6. Ionization rate coefficients are taken from
the recent work of Dere (2007, A&A, 466, 771) and recombination
rates from a variety of sources in the literature. These new rate
coefficients have allowed the calculation of a new set of ionization
equilibria and radiative loss rate coefficients. For some ions, such
as Fe VIII and Fe IX, there are significant differences from previous
calculations. In addition, existing atomic parameters have been revised
and new atomic parameters inserted into the database.
Results:
For each ion in the CHIANTI database, elemental abundances, ionization
potentials, atomic energy levels, radiative rates, electron and proton
collisional rate coefficients, ionization and recombination rate
coefficients, and collisional ionization equilibrium populations are
provided. In addition, parameters for the calculation of the continuum
due to bremsstrahlung, radiative recombination and two-photon decay are
provided. A suite of programs written in the Interactive Data Language
(IDL) are available to calculate line and continuum emissivities
and other properties. All data and programs are freely available at
http://wwwsolar.nrl.navy.mil/chianti
Title: CHIANTI Version 6.0 - Inclusion of Ionization and Recombination
Rates
Authors: Dere, Kenneth P.; Landi, E.; Young, P.; Del Zanna, G.; Mason,
H.; Landini, M.
Bibcode: 2009SPD....40.1504D
Altcode:
A new version of the CHIANTI atomic database for astrophysical
spectroscopy is being prepared for imminent release. This will
constitute Version 6.0. The main focus of this release is the inclusion
of ionization cross-sections and rate coefficients from Dere (2007)
and recombination rate coefficients from the literature, in particular,
the calculations of Badnell and colleagues. A new set of ionization
equilibria have been calculated from these rate coefficients. These
show some significant differences from previous calculations. Atomic
data for many ions have been revised and new calculations are included
that enable the calculation of spectra of ions new to the CHIANTI
database. The radiative loss function has been calculated based on
the CHIANTI Version 6 database for both coronal and photospheric
abundances. A paper describing CHIANTI Version 6.0 in detail has
been accepted for publication in Astronomy and Astrophysics.
Title: Stellar and galactic environment survey (SAGE)
Authors: Barstow, M. A.; Burleigh, M. R.; Bannister, N. J.; Lapington,
J. S.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.; Auchere,
F.; Bode, M. F.; Bromage, G. E.; Gibson, B.; Collier Cameron, A.;
Cassatella, A.; Delmotte, F.; Ravet, M. -F.; Doyle, J. G.; Jeffery,
C. S.; Gaensicke, B.; Jordan, C.; Kappelmann, N.; Werner, K.;
Lallement, R.; de Martino, D.; Matthews, S. A.; Phillips, K. J. H.;
Del Zanna, G.; Orio, M.; Pace, E.; Pagano, I.; Schmitt, J. H. M. M.;
Welsh, B. Y.
Bibcode: 2009Ap&SS.320..231B
Altcode: 2008Ap&SS.tmp..161B
This paper describes a proposed high resolution soft X-ray and
Extreme Ultraviolet (EUV) spectroscopy mission to carry out a survey
of Stellar and Galactic Environments (SAGE). The payload is based on
novel diffraction grating technology which has already been proven in
a sub-orbital space mission and which is ready to fly on a satellite
platform with minimal development. Much of the technical detail of
the instrumentation has been reported elsewhere and we concentrate
our discussion here on the scientific goals of a SAGE base-line
mission, demonstrating the scientific importance of high resolution
spectroscopy in the Extreme Ultraviolet for the study of stars and
the local interstellar medium.
Title: VizieR Online Data Catalog: Electron-impact excitation of
Be-like Mg (Del Zanna+, 2008)
Authors: Del Zanna, G.; Rozum, I.; Badnell, N. R.
Bibcode: 2009yCat..34871203D
Altcode:
We present an R-matrix calculation of electron-impact excitation
of Be-like Mg. The calculation is similar to that one presented
for Be-like Fe by Chidichimo et al. (2005A&A...430..331C),
and was done with the intermediate-coupling frame transformation
method and including a total of 98 fine-structure levels, up to n=4. **************************************************************************
* * * Sorry, but the author(s) never supplied the
tabular material * * announced in the paper * * *
**************************************************************************
Title: Active Region Loops: Hinode/Extreme-Ultraviolet Imaging
Spectrometer Observations
Authors: Tripathi, Durgesh; Mason, Helen E.; Dwivedi, Bhola N.;
del Zanna, Giulio; Young, Peter R.
Bibcode: 2009ApJ...694.1256T
Altcode: 2009arXiv0901.0095T
We have carried out a study of active region loops using observations
from the Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode
using 1'' raster data for an active region observed on 2007 May 19. We
find that active region structures which are clearly discernible in
cooler lines (≈1 MK) become "fuzzy" at higher temperatures (≈2
MK). The active region was comprised of redshifted emissions (downflows)
in the core and blueshifted emissions (upflows) at the boundary. The
flow velocities estimated in the two regions located near the footpoints
of coronal loop showed redshifted emission at transition region
temperature and blueshifted emission at coronal temperature. The upflow
speed in these regions increased with temperature. For more detailed
study we selected one particular well-defined loop. Downward flows are
detected along the coronal loop, being stronger in lower-temperature
lines (rising up to 60 km s-1 near the footpoint). The
downflow was localized toward the footpoint in transition region lines
(Si VII) and toward the loop top in high-temperature line (Fe XV). By
carefully accounting for the background emission we found that the
loop structure was close to isothermal for each position along the
loop, with the temperature rising from around 0.8 MK to 1.5 MK from
the close to the base to higher up toward the apex (≈75 Mm). We
derived electron density using well-established line ratio diagnostic
techniques. Electron densities along the active region loop were found
to vary from 1010 cm-3 close to the footpoint to
108.5 cm-3 higher up. A lower electron density,
varying from 109 cm-3 close to the footpoint to
108.5 cm-3 higher up, was found for the lower
temperature density diagnostic. Using these densities we derived filling
factors in along the coronal loop which can be as low as 0.02 near the
base of the loop. The filling factor increased with projected height
of the loop. These results provide important constraints on coronal
loop modeling.
Title: Changes in the solar corona during the last cycle
Authors: Del Zanna, G.
Bibcode: 2009JBAA..119...98D
Altcode:
No abstract at ADS
Title: Stellar And Galactic Environment survey (SAGE)
Authors: Barstow, M. A.; Kowalski, M. P.; Cruddace, R. G.; Wood, K. S.;
Auchere, F.; Bannister, N. J.; Bode, M. F.; Bromage, G. E.; Burleigh,
M. R.; Collier Cameron, A.; Cassatella, A.; Delmotte, F.; Doyle, J. G.;
Gaensicke, B.; Gibson, B.; Jeffery, C. S.; Jordan, C.; Kappelmann,
N.; Lallement, R.; Lapington, J. S.; de Martino, D.; Matthews, S. A.;
Orio, M.; Pace, E.; Pagano, I.; Phillips, K. J. H.; Ravet, M. -F.;
Schmitt, J. H. M. M.; Welsh, B. Y.; Werner, K.; Del Zanna, G.
Bibcode: 2009ExA....23..169B
Altcode: 2008ExA...tmp...25B
This paper describes a proposed high resolution soft X-ray and Extreme
Ultraviolet spectroscopy mission to carry out a survey of Stellar
and Galactic Environments (SAGE). The payload is based on novel
diffraction grating technology which has already been proven in a
sub-orbital space mission and which is ready to fly on a satellite
platform with minimal development. We discuss the goals of a SAGE
base-line mission and demonstrate the scientific importance of high
resolution spectroscopy in the Extreme Ultraviolet for the study of
stars and the local interstellar medium.
Title: Are Coronal Loops Isothermal or Multithermal?
Authors: Schmelz, J. T.; Nasraoui, K.; Rightmire, L. A.; Kimble,
J. A.; del Zanna, G.; Cirtain, J. W.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2009ApJ...691..503S
Altcode: 2009arXiv0901.3281S
Surprisingly few solar coronal loops have been observed simultaneously
with TRACE and SOHO/Coronal Diagnostics Spectrometer (CDS), and even
fewer analyses of these loops have been conducted and published. The
SOHO Joint Observing Program 146 was designed in part to provide the
simultaneous observations required for in-depth temperature analysis of
active region loops and determine whether these loops are isothermal
or multithermal. The data analyzed in this paper were taken on 2003
January 17 of AR 10250. We used TRACE filter ratios, emission measure
loci, and two methods of differential emission measure analysis to
examine the temperature structure of three different loops. TRACE and
CDS observations agree that Loop 1 is isothermal with log T = 5.85,
both along the line of sight as well as along the length of the loop
leg that is visible in the CDS field of view. Loop 2 is hotter than
Loop 1. It is multithermal along the line of sight, with significant
emission between 6.2 < log T< 6.4, but the loop apex region
is out of the CDS field of view so it is not possible to determine
the temperature distribution as a function of the loop height. Loop
3 also appears to be multithermal, but a blended loop that is just
barely resolved with CDS may be adding cool emission to the Loop
3 intensities and complicating our results. So, are coronal loops
isothermal or multithermal? The answer appears to be yes.
Title: Magnetic flux cancellation associated with a recurring solar
jet observed with Hinode, RHESSI, and STEREO/EUVI
Authors: Chifor, C.; Isobe, H.; Mason, H. E.; Hannah, I. G.; Young,
P. R.; Del Zanna, G.; Krucker, S.; Ichimoto, K.; Katsukawa, Y.;
Yokoyama, T.
Bibcode: 2008A&A...491..279C
Altcode:
Aims: We study the physical properties of a recurring solar active
region jet observed in X-rays and extreme-ultraviolet (EUV).
Methods: Multi-wavelength data from all three instruments on
board Hinode were analysed. X-ray imaging and spectroscopy of the
microflaring emission associated with the jets was performed with the
Reuven Ramaty High Energy Spectroscopic Imager (RHESSI). Associated
EUV jets were observed with the Sun Earth Connection Coronal and
Heliospheric Investigation (SECCHI)/Extreme Ultraviolet Imager
(EUVI) on board STEREO.
Results: We found a correlation between
recurring magnetic flux cancellation close to a pore, the X-ray jet
emission, and associated Ca II H ribbon brightenings. We estimated the
lower limit for the decrease in magnetic energy associated with the
X-ray jet emission at 3 × 1029 erg. The recurring plasma
ejection was observed simultaneously at EUV and X-ray temperatures,
associated with type III radio bursts and microflaring activity at the
jet footpoint.
Conclusions: The recurring jet (EUV and X-ray)
emissions can be attributed to chromospheric evaporation flows due to
recurring coronal magnetic reconnection. In this process, the estimated
minimum loss in the magnetic energy is sufficient to account for the
total energy required to launch the jet. Movie of Fig. 3 is only
available in electronic form via http://www.aanda.org
Title: VOTADA - VO Tools and Atomic Data for Astrophysics
Authors: Del Zanna, G.
Bibcode: 2008asvo.proc..199D
Altcode:
An overview of the VOTADA project is presented, with highlights of
progress made and various issues related to the provision of atomic
data to the astrophysical community.
Title: Active Region 1 MK Loops: EIS vs. SOHO/CDS Observations
Authors: Del Zanna, G.
Bibcode: 2008ASPC..397...87D
Altcode:
I briefly discuss some of the capabilities of the EIS spectrometer
(compared to those of SOHO/CDS), the status of atomic calculations,
and some characteristics of quiescent active regions as observed in
the corona, with emphasis on loop structures. Previous CDS measurements
are confirmed by EIS. However, the high spectral resolution of EIS is
providing us with a new, dynamic view of active region loops. One active
region showed ubiquitous downflows in loops at all temperatures. Upflows
are instead found in small dark areas outside the loop system, where
high non-thermal broadening is present. Loops seem to be cooling
structures, perhaps the result of slow flux emergence and reconnection.
Title: Density Structure in Active Regions from Hinode/EIS
Authors: Tripathi, D.; Mason, H. E.; Young, P. R.; Chifor, C.; Del
Zanna, G.
Bibcode: 2008ASPC..397...45T
Altcode:
The Extreme-ultraviolet Imaging Spectrometer (EIS) on board Hinode
provides an excellent opportunity to study the physical plasma
parameters in spatially resolved coronal features. In this paper we
present the density structure in an active region at many different
temperatures. The active region was rastered on May 01, 2007 with the
2^{''} slit. We find that the electron density is highest in the core
of the active region where it exceeds log_{10} N_e = 10.5.
Title: Electron-impact excitation of Be-like Mg
Authors: Del Zanna, G.; Rozum, I.; Badnell, N. R.
Bibcode: 2008A&A...487.1203D
Altcode:
We present an R-matrix calculation of electron-impact excitation
of Be-like Mg. The calculation is similar to that one presented for
Be-like Fe by Chidichimo et al. (2005, A&A, 430, 331), and was
done with the intermediate-coupling frame transformation method
and including a total of 98 fine-structure levels, up to n=4. We
find significant differences with the widely used n=2 excitation
rates of Keenan et al. (1986, Phys. Scr., 34, 216), calculated by
interpolating R-matrix calculations along the Be-like sequence. We
present a list of the most important transitions and a few comparisons
with SOHO SUMER and CDS/GIS spectra of the solar corona. We show that
previous long-standing discrepancies between observed and predicted line
intensities are now resolved. We also show how temperatures of the solar
corona were significantly underestimated. For example, a coronal hole
inter-plume temperature of 850 000 K found by Wilhelm et al. (1998,
ApJ, 500, 1023) is now revised to 1 160 000 K. Full dataset of
excitation and radiative data are only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/487/1203
Title: Nonthermal and thermal diagnostics of a solar flare observed
with RESIK and RHESSI
Authors: Dzifčáková, E.; Kulinová, A.; Chifor, C.; Mason, H. E.;
Del Zanna, G.; Sylwester, J.; Sylwester, B.
Bibcode: 2008A&A...488..311D
Altcode:
Aims: We aim to prove and diagnose the occurrence of nonthermal
electron distributions in solar flare plasma using X-ray spectral
observations.
Methods: An M4.9 flare on 2003 January 7/8 was
observed with the RESIK instrument in the 3-6 Å wavelength range (2-4
keV) and with RHESSI at energies above 6 keV. The temporal behavior
of RESIK flare spectra has been analyzed for two different types of
velocity distributions - a thermal (Maxwellian) distribution and a
nonthermal plasma distribution of free electrons. The Si XIV, Si XIII,
and Si XIId satellite lines observed with RESIK in the 5-6 Å range
were used to determine the degree of deviation from Maxwellian, and
the equivalent non-Maxwellian pseudo-temperature, τ. The diagnostics
presented are sensitive to the shape of the distribution in the energy
range where the maximum of the electron distribution occurs (where
the bulk of electrons reside) and does not include the influence
of the shape of the high-energy tail of the distribution. Under
the assumption of a Maxwellian distribution of electron velocities,
the plasma temperature was determined from an emission measure (EM)
loci analysis and a differential emission measure (DEM) analysis of
RESIK spectra. The high-energy end of the flare radiative emission
was investigated through RHESSI spectral analysis.
Results:
The nonthermal analysis of RESIK spectra has shown that the largest
deviations of the plasma electron distribution from Maxwellian appeared
during the impulsive phase of the flare. The decay phase spectra had
an almost isothermal character. The pseudo-temperature, τ, reached
its maximum around the peak time of the soft and hard X-ray fluxes. The
temporal behavior of the temperatures derived from the thermal analysis
was similar to the behavior of the nonthermal pseudo-temperature. The
values of the pseudo-temperature were consistent with the temperatures
obtained in both thermal analyses, but lower than the temperatures
derived from the slope of the RHESSI continua. In comparison with the
synthetic isothermal or multithermal spectra, the nonthermal synthetic
spectra fitted the observed Si XIId satellite lines much more closely
(the error is less than 10%). The fluxes in the Si XIId satellite lines
in isothermal or multithermal spectra have been underestimated by a
factor of three or more in comparison to the observed fluxes. The
value of this factor varies with time and it is different for the
different satellite lines.
Conclusions: Evidence was found for
considerable deviations of the distribution of free electrons from
Maxwellian in the plasma during a solar flare. These occurred mainly
during the flare impulsive phase and can be diagnosed using existing
X-ray spectral observations.
Title: Flows in active region loops observed by Hinode EIS
Authors: Del Zanna, G.
Bibcode: 2008A&A...481L..49D
Altcode:
We aim to investigate the overall characteristics of coronal active
region loops and their evolution. The Hinode database was searched for
observations of active regions as they crossed the Sun centre. NOAA
10926 was selected. The morphology of this young active region did
not significantly change over the course of a few days. Persistent
redshifts, stronger in cooler lines (about 5-10 km s-1 in Fe
XII and 20-30 km s-1 in Fe VIII), were observed in most loop
structures with the EUV Imaging Spectrometer. Persistent blueshifts,
stronger in the hotter lines (typically 5-20 km s-1 in Fe
XII and 10-30 km s-1 in Fe XV), were present in areas of
weak emission, in a sharp boundary between the low-lying “hot” 3
MK loops and the higher “cooler” 1 MK loops.
Title: Density structure of an active region and associated moss
using Hinode/EIS
Authors: Tripathi, D.; Mason, H. E.; Young, P. R.; Del Zanna, G.
Bibcode: 2008A&A...481L..53T
Altcode: 2008arXiv0802.3311T
Context: Studying the problem of active region heating requires precise
measurements of physical plasma parameters such as electron density,
temperature, etc. It is also important to understand the relationship
of coronal structures with the magnetic field. The Extreme-ultraviolet
Imaging Spectrometer (EIS) aboard Hinode provides a rare opportunity to
derive electron density simultaneously at different temperatures.
Aims: We study the density structure and characterise plasma in
active regions and associated moss regions. In addition, we study its
relationship to the photospheric magnetic field.
Methods: We used
data recorded by the EIS, together with magnetic field measurements
from the Michelson Doppler Imager (MDI) aboard SoHO and images recorded
with the Transition Region And Coronal Explorer (TRACE) and X-Ray
Telescope (XRT/Hinode).
Results: We find that the hot core of
the active region is densest with values as high as 1010.5
cm-3. The electron density estimated in specific regions
in the active region moss decreases with increasing temperature. The
moss areas were located primarily on one side of the active region,
and they map the positive polarity regions almost exactly. The density
within the moss region was highest at log T=5.8{-}6.1, with a value
around 1010.0{-10.5} cm-3. The moss densities
were highest in the strong positive magnetic field region. However,
there was no such correlation for the negative polarity areas, where
there was a large sunspot.
Title: Flare lines in Hinode EIS spectra
Authors: Del Zanna, G.
Bibcode: 2008A&A...481L..69D
Altcode:
We aim to identify the brightest hot emission lines in Hinode EIS
spectra, and suggest the best ones to be used in flare observations. The
EIS database was searched in order to find suitable datasets to identify
the prominent lines. A B2-class flare spectrum was found. Most previous
identifications are confirmed, however some are revised by noting
the presence of blending. A new Fe XVII self-blend is identified. A
recommended list of emission lines formed at high temperatures is
provided. The brightest lines are the Ca XVII 192.85 Å and the Fe
XXIV 192 Å, however they are blended. The best unblended lines are
the Ca XV 200.99 Å, Fe XVII 269.42 Å and Fe XXIII 263.76 Å lines.
Title: Solar Transition Region Features Observed with Hinode/EIS
Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Doschek,
George A.; Culhane, Len; Hara, Hirohisa
Bibcode: 2007PASJ...59S.727Y
Altcode: 2007arXiv0706.1856Y
Two types of solar active region feature prominent at transition region
temperatures are identified in Hinode/EIS data of AR 10938 taken on
2007 January 20. The footpoints of 1 MK TRACE loops are shown to emit
strongly in emission lines formed at log T = 5.4-5.8, allowing the
temperature increase along the footpoints to be clearly seen. A density
diagnostic of Mg VII yields the density in the footpoints, with one
loop showing a decrease from 3 × 109 cm-3 at the
base to 1.5 × 109 cm-3 at a projected height
of 20 Mm. The second feature is a compact active region transition
region brightening which is particularly intense in O V emission
(log T = 5.4) but also has a signature at temperatures up to log T =
6.3. The Mg VII diagnostic gives a density of 4 × 1010
cm-3, and emission lines of Mg VI and Mg VII show line
profiles broadened by 50kms-1 and wings extending beyond
± 200kms-1. Continuum emission in the short wavelength
band is also found to be enhanced, and is suggested to be free-bound
emission from recombination onto He+.
Title: EUV Emission Lines and Diagnostics Observed with Hinode/EIS
Authors: Young, Peter R.; Del Zanna, Giulio; Mason, Helen E.; Dere,
Ken P.; Landi, Enrico; Landini, Massimo; Doschek, George A.; Brown,
Charles M.; Culhane, Len; Harra, Louise K.; Watanabe, Tetsuya; Hara,
Hirohisa
Bibcode: 2007PASJ...59S.857Y
Altcode: 2007arXiv0706.1857Y
Quiet Sun and active region spectra from the Hinode/EIS instrument are
presented, and the strongest lines from different temperature regions
discussed. A list of emission lines recommended to be included in EIS
observation studies is presented based on analysis of blending and
diagnostic potential using the CHIANTI atomic database. In addition
we identify the most useful density diagnostics from the ions covered
by EIS.
Title: Application of CHIANTI to Solar-B
Authors: Dere, K.; Landi, E.; Del Zanna, G.; Young, P.; Mason, H.;
Landini, M.
Bibcode: 2007ASPC..369...35D
Altcode:
CHIANTI (http://wwwsolar.nrl.navy.mil/chianti.html) has been developed
to support the interpretation of solar and astrophysical spectroscopic
measurements. The most recent release, version 5.0 (Landi et al. 2005)
presents an improvement over previous versions by including new
large scale datasets for Fe ions from Fe XVII to Fe XXIV for X-ray
emission and improved atomic data for EUV line emission. We will
demonstrate how this can be applied to the analysis of XRT and EIS
data, in particular. For example, new excitation rates for Fe XII have
resolved a long standing problem in the use of Fe XII line ratios as
accurate density diagnostics. Current work involves improvements to
ionization and recombination rates which will also be useful in the
interpretation of Solar-B data
Title: The In-Flight Performance of the SOHO/CDS Grazing Incidence
Spectrometer
Authors: Kuin, N. P. M.; Del Zanna, G.
Bibcode: 2007SoPh..242..187K
Altcode:
We present the characteristics, operations history, performance,
and calibration of the Grazing Incidence Spectrometer (GIS) of the
Coronal Diagnostic Spectrometer onboard SOHO. The GIS sensitivity has
been monitored in a direct manner by examining the quiet Sun count rates
during 1996 - 2006, nearly a whole solar cycle of observations. Overall,
the instrument, with its grazing-incidence optics and microchannel
plates, has performed exceptionally well. For most spectral regions,
changes in the instrument sensitivity have been very small over a
10-year period. The trends in sensitivities support the use of the
radiometric calibration of Del Zanna et al. (Astron. Astrophys.379,
708, 2001) throughout the mission. The verification of the detector
performance over such a long period allows us to point out the spectral
lines that can reliably be used for scientific analysis.
Title: Atomic data from the IRON project. LXIII. Electron-impact
excitation of Fe19+ up to n = 4
Authors: Witthoeft, M. C.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2007A&A...466..763W
Altcode:
We present results for the electron-impact excitation of N-like Fe as
part of the RmaX network. R-matrix theory using an intermediate-coupling
frame transformation method is used to obtain level-resolved collision
strengths. Separate calculations are performed using different target
expansions. The first is a 215 level close-coupling calculation
which has the 2s2 2p^3, 2s 2p^4, 2p^5, 2s2
2p2 3l, and 2s 2p3 3l configurations while the
second calculation also includes the levels from the 2s2
2p2 4l configurations for a total of 302 close-coupling
levels. The effect of the additional resonant enhancement of the
larger calculation is explored and compared with a previous IRON
Project report and other, more recent, calculations. As a final
comparison, we model an astrophysical plasma using the results
of the present calculations and previous work. The full list
of energy levels (Table 2) is available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/466/763
Title: Coronal Loops: Isothermal or Multithermal?
Authors: Kimble, Jason; Schmelz, J. T.; Nasraoui, K.; Cirtain, J. W.;
Del Zanna, G.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2007AAS...210.9120K
Altcode: 2007BAAS...39..207K
The coronal loop data used for this analysis were taken on 2003 January
17 at 14:24:45 UT by the Coronal Diagnostic Spectrometer (CDS) aboard
the Solar and Heliospheric Observatory. We use the Chianti atomic
physics data base and the hybrid coronal abundances to determine
temperatures and densities for positions along several loops. The
traditional method used to create our differential emission measure
(DEM) curves has been forward folding, but we are now using both
emission measure loci plots and DEM automatic inversion to support
and confirm the original conclusions. In this poster, we will look
specifically at the emission measure loci analysis of three loops
visible in the CDS data set. We find different results for each of
these loops. One of the loops seems to be composed of isothermal
plasma with Log T = 5.8 MK. The temperature does not appear to change
with position, from the footpoint to the loop leg. Unfortunately,
the loop top is outside the CDS field of view. Each pixel examined in
the second loop seems to require a multithermal DEM distribution. For
the third loop, the temperature increases and the density appears
to decrease with loop height, reminiscent of traditional hydrostatic
loop models. Solar physics research at the University of Memphis is
supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: SOHO-CDS: Thermal and Density Analysis of Coronal Loops
Authors: Rightmire, Lisa; Schmelz, J. T.; Cirtain, J. W.; Del Zanna,
G.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2007AAS...210.9121R
Altcode: 2007BAAS...39..207R
Data was obtained using the Coronal Diagnostic Spectrometer (CDS)
instrument on the Solar and Heliospheric Observatory (SOHO). The goal
of this project is to analyze the data obtained by the CDS instrument
in order to determine the behavior of temperature and density of the
coronal loop progressing from the foot point and moving up the loop. The
loop being analyzed was observed by CDS on 2003 January 17 and the foot
point was located at solar coordinates (585,-472) arcsecs. A background
pixel and several pixels on the loop were selected. The background pixel
intensity was then subtracted from each loop pixel intensity in order to
isolate the emission from each loop pixel. The spectral line intensities
of each loop pixel were analyzed to determine which spectral lines
had any significant contribution to the loop intensity. The predicted
and observed intensities of these significant lines were then used to
create a differential emission measure (DEM) curve to best fit each
loop pixel emission. Comparison of the DEM curves for each loop pixel
indicates that the temperature increases and the density decreases,
while progressing up the loop. Solar physics research at the University
of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: VizieR Online Data Catalog: Fe XVIII Benchmarking atomic data
(Del Zanna+, 2006)
Authors: Del Zanna, G.
Bibcode: 2007yCat..34590307D
Altcode:
**************************************************************************
* * * Sorry, but the author(s) never supplied the tabular material
* * (full table 2 and table A1) announced in the paper * * *
**************************************************************************
(3 data files).
Title: Are Coronal Loops Isothermal Or Multithermal? Yes!
Authors: Schmelz, Joan T.; Nasraoui, K.; Rightmire, L.; Garst, J.;
Kimble, J.; Cirtain, J.; DeLuca, E. E.; Del Zanna, G.; Mason, H.
Bibcode: 2007AAS...210.9431S
Altcode: 2007BAAS...39..222S
Analysis of loops observed with the Coronal Diagnostics Spectrometer
(CDS) and the Transition Region and Coronal Explorer (TRACE) reveal
examples of both isothermal and multithermal plasma. These data
were taken on 2003 January 17, and since the loops are on the disk,
a lot of work was done on the details of background subtraction. The
background-subtracted CDS intensities were analyzed using three
methods: (1) Emission Measure Loci, (2) Forward-Folding DEM, and (3)
Automatic-Inversion DEM. The first loop appears to be isothermal,
with Log T = 5.8 MK. The forward-folding DEM shows a spike at this
temperature and the EM Loci curves all intersect at this point. The
automatic-inversion DEM results are broadened, however, as a result
of the smoothing required for this method. This loop has a uniform
temperature along the segment visible in the CDS field of view,
and this result is confirmed using the TRACE data. The pixels along
the second loop do not appear to be isothermal. The EM Loci curves
do not intersect at a single point and both DEM methods show a broad
curve. Other loops in this data set as well as loop evolution will be
investigated if time permits. Solar physics research at the University
of Memphis is supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: Differential Emission Measurements on Sparse Raster Data
from SOHO-CDS
Authors: Garst, Jennifer W.; Schmelz, J. T.; Nasraoui, K.; Cirtain,
J. W.; DeLuca, E. E.; Del Zanna, G.; Mason, H. E.
Bibcode: 2007AAS...210.2517G
Altcode: 2007BAAS...39..133G
Two types of rasters were taken on 2003 January 17 with the Solar and
Heliospheric Observatory’s Coronal Diagnostic Spectrometer. The
first type contains a continuous image of coronal loops under
investigation while the second, the ‘sparse raster,’ was taken at
spatial intervals in order to simulate enhanced time resolution. With
this technique, intensities in 14 passbands were collected at fixed
positions on the solar disk every 7 minutes. The start time for the
CDS observations was 06:51:27 UT and the observing sequences ran for
7 hours. The continuous rasters were interspersed with the sparse
rasters. All the rasters were then co-aligned and a loop pixel and a
background pixel were selected for detailed analysis. Differential
emission measure was performed on the background-subtracted CDS
intensities to determine the temporal evolution of the loop pixel
plasma. Solar physics research at the University of Memphis is supported
by NSF ATM-0402729 and NASA NNG05GE68G.
Title: Coronal Diagnostics Spectrometer Observations of Coronal Loops
Authors: Nasraoui, Kaouther; Schmelz, J. T.; Cirtain, J. W.; Del Zanna,
G.; DeLuca, E. E.; Mason, H. E.
Bibcode: 2007AAS...210.9122N
Altcode: 2007BAAS...39..207N
Two side by side loops from the solar disk were analyzed. These two
loops were observed with the Coronal Diagnostics Spectrometer on
SOHO on 2003 January 17. The first loop was best seen in Mg IX at
a wavelength of 368 angstroms and a peak formation temperature of
Log T = 6.0. Seven pixels on the loop and one background pixel were
chosen. The intensity of the background pixel was subtracted from each
of the loop pixels. Only the lines that had a significant intensity
after background subtraction were considered. A differential emission
measure (DEM) curve was constructed for the background subtracted data
using the forward folding technique. The DEM for most of these pixels
had a spike shape at Log T equal to 5.85. This result shows that the
loop is isothermal at most of these pixels. The second loop was best
seen in Si XII at a wavelength of 520 angstroms and a peak formation
temperature of Log T = 6.3. The same procedure was followed for the
data analysis. After background subtraction only some hot lines had a
significant intensity and a DEM curve was constructed for each loop
pixel. This time the DEM is broader with a shape that shows that
the loop plasma is multithermal with a log temperature range of 6.1
to 6.5. Solar physics research at the University of Memphis is
supported by NSF ATM-0402729 and NASA NNG05GE68G.
Title: Coronal Diagnostic Spectrometer Observations of Isothermal
and Multithermal Coronal Loops
Authors: Schmelz, J. T.; Nasraoui, K.; Del Zanna, G.; Cirtain, J. W.;
DeLuca, E. E.; Mason, H. E.
Bibcode: 2007ApJ...658L.119S
Altcode:
A data set obtained on 2003 January 17 with the Coronal Diagnostic
Spectrometer (CDS) shows two loops sitting side by side on the solar
disk. These loops are oriented along the CDS slit, so all pixels in
each loop were observed simultaneously. So, although the instrument
has a relatively slow time cadence, changes as a function of time
that may occur during the CDS raster buildup will not affect the loop
temperature results. Differential emission measure (DEM) analysis
using a forward-folding technique shows different results for the
two loops. For the first loop, the intensities of the lines that
remain after background subtraction are well fit with a DEM curve that
collapses to a single spike. In other words, the loop plasma at this
location is isothermal. This analysis is confirmed with an emission
measure loci method and agrees with the results obtained recently
by other authors that show that the moderate spatial resolution
of CDS can detect isothermal structures. For the second loop, the
background-subtracted line intensities require a broad DEM, not
consistent with isothermal plasma. This conclusion is confirmed with
an automatic-inversion DEM method. In this Letter, we specifically
address some of the concerns raised about CDS temperature analysis:
the slow CDS temporal resolution, the moderate CDS spatial resolution,
the inherent smoothing associated with DEM inversion, and line-of-sight
effects on the DEM distribution.
Title: VizieR Online Data Catalog: Electron-impact excitation of
Fe19+ (Witthoeft+,
Authors: Witthoeft, M. C.; Del Zanna, G.; Badnell, N. R.
Bibcode: 2007yCat..34660763W
Altcode:
An extension of Table 2 in the paper, this data file contains a full
listing of the energy levels from the n=4 calculations described in
the text. The energy-ordered index, energy in Ry, configuration index,
2J, and parity are listed in the file. (1 data file).
Title: Active Region Loops: Temperature Measurements as a Function
of Time from Joint TRACE and SOHO CDS Observations
Authors: Cirtain, J. W.; Del Zanna, G.; DeLuca, E. E.; Mason, H. E.;
Martens, P. C. H.; Schmelz, J. T.
Bibcode: 2007ApJ...655..598C
Altcode:
In this paper, we aim to quantitatively investigate the structure
and time variation of quiescent active region loop structures. We
coordinated a joint program of observations (JOP 146) using TRACE, to
obtain high-cadence EUV images, and SOHO CDS, to obtain spectroscopic
data. Loop intensities are used to determine temperature as a function
of time for a single loop, taking full account of the background
emission. In many locations, the emission measure loci are consistent
with an isothermal structure. However, the results indicate significant
changes in the loop temperature (between 1 and 2 MK) over the 6 hr
observing period. It is possible that the loop structures are composed
of multiple, independently heated strands with sizes less than the
resolution of the imager and spectrometer.
Title: A benchmark study for CHIANTI based on RESIK solar flare
spectra
Authors: Chifor, C.; Del Zanna, G.; Mason, H. E.; Sylwester, J.;
Sylwester, B.; Phillips, K. J. H.
Bibcode: 2007A&A...462..323C
Altcode:
Aims:To perform a benchmark analysis for the recent version of the
CHIANTI atomic database (v. 5.2) based on high-resolution solar
flare X-ray spectra in the range 3.4-6.1 Å from the RESIK crystal
spectrometer on the CORONAS-F spacecraft.
Methods: A C5.8 flare
occurring on 2003 February 22 was chosen for analysis. RESIK spectra
of this flare include emission lines of He-like and H-like K, Ar,
S, and Si, with some dielectronic lines. Initially, two independent
plasma diagnostic techniques are employed: an emission measure
(EM) loci analysis using the line flux and the line contribution
function G(T_e, N_e), and a new method based on continuum fluxes and
contribution functions. We further apply a differential emission measure
(DEM) analysis, from which CHIANTI synthetic spectra are derived. The
continuum from RESIK spectra is checked against simultaneous RHESSI and
GOES observations. Comparisons of CHIANTI synthetic spectra with those
from the MEKAL code in the 3.4-6.1 Å range are also presented.
Results: The emitting plasma appears multi-thermal, having one
dominant temperature component determined independently from the line
and continuum EM loci and DEM analyses. Consistency between line
and continuum emissions requires photospheric elemental abundances
(Asplund et al. 2005), with a depleted sulphur abundance. With the
exception of RESIK channel 4 (5.0-6.1 Å), we find overall very
good agreement between the calculated and observed intensities. From
comparisons with other instruments, RESIK's precision in the continuum
level is confirmed to be within the estimated 20% uncertainties in the
intensity calibration. We find general agreement between CHIANTI and
MEKAL isothermal spectra, but we note that the atomic data for the
Si xii and Si xiii ions contained in CHIANTI are more complete.
Conclusions: .RESIK observations of both lines and continua are
suitable for characterising the properties of the flaring plasma such
as temperature, emission measure and elemental abundance. These spectra
can be used to evaluate any atomic database.
Title: EIT and TRACE responses to flare plasma
Authors: Tripathi, D.; Del Zanna, G.; Mason, H. E.; Chifor, C.
Bibcode: 2006A&A...460L..53T
Altcode: 2008arXiv0802.3852T
Aims.To understand the contribution of active region and flare
plasmas to the λ195 channels of SOHO/EIT (Extreme-ultraviolet Imaging
Telescope) and TRACE (Transition Region and Coronal Explorer).
Methods: .We have analysed an M8 flare simultaneously observed by
the Coronal Diagnostic Spectrometer (CDS), EIT, TRACE and RHESSI. We
obtained synthetic spectra for the flaring region and an outer region
using the differential emission measures (DEM) of emitting plasma based
on CDS and RHESSI observations and the CHIANTI atomic database. We
then predicted the EIT and TRACE count rates.
Results: .For the
flaring region, both EIT and TRACE images taken through the λ195
filter are dominated by Fe XXIV (formed at about 20 MK). However,
in the outer region, the emission was primarily due to the Fe XII,
with substantial contributions from other lines. The average count
rate for the outer region was within 25% the observed value for EIT,
while for TRACE it was a factor of two higher. For the flare region,
the predicted count rate was a factor of two (in case of EIT) and
a factor of three (in case of TRACE) higher than the actual count
rate.
Conclusions: .During a solar flare, both TRACE and EIT
λ195 channels are found to be dominated by Fe XXIV emission. Reasonable
agreement between predictions and observations is found, however some
discrepancies need to be further investigated.
Title: The Gradual Phase of the X17 Flare on October 28, 2003
Authors: del Zanna, G.; Schmieder, B.; Mason, H.; Berlicki, A.;
Bradshaw, S.
Bibcode: 2006SoPh..239..173D
Altcode: 2006SoPh..239..173Z; 2006SoPh..tmp...74Z
We present SOHO/CDS observations taken during the gradual phase of
the X17 flare that occurred on October 28, 2003. The CDS data are
supplemented with TRACE and ground-based observations. The spectral
observations allow us to determine velocities from the Doppler
shifts measured in the flare loops and in the two ribbon kernels,
one hour and a half after the flare peak. Strong downflows (>70 km
s-1) are observed along the loop legs at transition-region
temperatures. The velocities are close to those expected for free
fall. Observations and results from a hydrodynamic simulation are
consistent with the heating taking place for a short time near the
top of the arcade. Slight upflows are observed in the outer edges of
the ribbons (<60 km s-1) in the EUV lines formed at log
T < 6.3. These flows could correspond to the so-called “gentle
evaporation.” At “flare” temperatures (Fe xix, log T = 6.9),
no appreciable flows are observed. The observations are consistent
with the general standard reconnection models for two-ribbons flares.
Title: Benchmarking atomic data for astrophysics: Fe xviii
Authors: Del Zanna, G.
Bibcode: 2006A&A...459..307D
Altcode:
Fe xviii produces, in the X-ray and extreme ultraviolet, L-shell
(n=2,3,4 to 2) spectral lines which are among the brightest ones
in e.g. solar flares and in Chandra, XMM-Newton spectra of active
stars. Recent R-matrix scattering calculations of Witthoeft et
al. (2006, A&A, 446, 361) produce theoretical intensities for some
of the brightest transitions increased by large factors (2-3), so it is
timely to use these calculations to review and assess all previous line
identifications on a quantitative basis. This paper discusses only the
most important lines for laboratory and astrophysical applications. Many
previous identifications are revised and some tentative ones finally
confirmed. Many lines are found to be significantly blended. A
considerable number of new identifications are proposed. Excellent
agreeement between observed and predicted intensities is found in the
majority of cases for the first time. It is therefore now possible to
use Fe xviii L-shell lines to measure electron densities in laboratory
plasmas and temperatures for a wide range of astrophysical sources.
Title: The EUV Spectral Irradiance and the Physical Characteristics
of the Solar Corona During the 10 Years of SOHO Measurements
Authors: Del Zanna, G.; Andretta, V.
Bibcode: 2006ESASP.617E.124D
Altcode: 2006soho...17E.124D
No abstract at ADS
Title: SOHO/CDS Observations of Quiescent Active Region Loops
Authors: Del Zanna, G.; Mason, H. E.; Cirtain, J.
Bibcode: 2006ESASP.617E..86D
Altcode: 2006soho...17E..86D
No abstract at ADS
Title: How to See Northern Lights Through the Clouds in England
Authors: Del Zanna, G.
Bibcode: 2006ESASP.617E..32D
Altcode: 2006soho...17E..32D
No abstract at ADS
Title: RESIK Flare X-ray Spectra: Benchmark Analysis And Plasma
Diagnostics Based On CHIANTI
Authors: Chifor, Cristina; Del Zanna, G.; Sylwester, J.; Sylwester,
B.; Phillips, K. J. H.
Bibcode: 2006SPD....37.1314C
Altcode: 2006BAAS...38..243C
We perform a benchmark analysis between the recent version 5.2 of the
CHIANTI atomic database and high-resolution solar flare X-ray spectra
obtained with the RESIK instrument in the wavelength range 3.4-6.1
Angstrom. The physical properties of emitting plasmas during a C-class
solar flare on 2003 February 22 are determined through two independent
plasma diagnostic techniques: an emission measure analysis applied to
strong, unblended atomic lines and a new method analyzing continuum
contributions. From these parameters, synthetic spectra are derived
using the CHIANTI database and software. The predicted spectra are then
benchmarked against observed RESIK lines and continuum. Comparisons
between CHIANTI and the MEKAL spectral code are also presented. In
order to evaluate the level of confidence in RESIK's calibration, RESIK
continuum levels are checked against simultaneous RHESSI observations
as well as GOES continua obtained from parameters derived from GOES
channel ratios.
Title: The Coronal Loop Controversy: Resolved!
Authors: Schmelz, Joan T.; Nasraoui, K.; Cirtain, J.; DeLuca, E.;
Del Zanna, G.; Mason, H.
Bibcode: 2006SPD....37.1701S
Altcode: 2006BAAS...38..245S
Critics have pointed out the shortcomings of CDS coronal loop
temperature analysis - the large pixel size and the slow time
cadence. It is these limitations, some say, that have produced
multithermal results for the loop observed with CDS on 1998 April
20, both along the line of sight and along the loop length. Analysis
of the CDS observations of AR 10250 from 2003 January 17, however,
seem to contradict these critics. Two loops sit side-by-side right
along the slit in this raster, so all pixels in each loop were
observed at the same time. As a result changes as a function of time
will not affect the temperature results. The first loop is observed
primarily in Mg IX (Log T = 6.0) and the second in Si XII (Log T =
6.3). Differential Emission Measure (DEM) analysis of background
subtracted line intensities of pixels in each loop show distinctly
different results. For the first loop, the intensities of the lines
that remain after background subtraction are well fit with a DEM that
collapses to a single spike. In other words, the loop plasma at this
location is isothermal. This proves that it is neither the DEM method
nor the CDS pixel size that produced the multithermal distributions
for the 1998 April 20 loop plasma. In addition the DEM distribution for
the second loop is similar to those produced for the 1998 April 20 loop
and is clearly inconsistent with isothermal plasma. Both distributions
change as a function of position along the loop, with the temperatures
increasing with loop height. Solar physics research at the University
of Memphis is supported by grants from NSF and NASA.
Title: A Multi-Wavelength Study of the Compact M1 Flare on October
22, 2002
Authors: del Zanna, G.; Berlicki, A.; Schmieder, B.; Mason, H. E.
Bibcode: 2006SoPh..234...95D
Altcode: 2006SoPh..234...95Z
In this paper we present a further study of the Ml class
flare observed on October 22, 2002. We focus on the SOHO Coronal
Diagnostic Spectrometer (CDS) spectral observations performed during a
multi-wavelength campaign with TRACE and ground-based instruments (VTT,
THEMIS). Strong blue-shifts are observed in the CDS coronal lines in
flare kernels during the impulsive phase of this flare. From a careful
wavelength calibration we deduce upflows of 140 km/s for the Fe XIX
flare emission, with a pattern of progressively smaller flows at lower
temperatures. Large line-widths were observed, especially for the Fe
XIX line, which indicate the existence of turbulent velocities. The
strong upflows correspond to full shifts of the line profiles. These
flows are observed at the initial phase of the flare, and correspond
to the “explosive evaporation”. The regions of the blueshifted
kernels, a few arc seconds away from the flare onset location, could be
explained by the chain reaction of successive magnetic reconnections of
growing emerging field line with higher and higher overlying field. This
interpretation is evidenced by the analysis of the magnetic topology
of the active region using a linear force-free-field extrapolation of
THEMIS magnetograms.
Title: Pointing and Alignment of the CDS Grazing Incidence
Spectrometer on SOHO
Authors: Kuin, N. P. M.; Del Zanna, G.
Bibcode: 2006CDSsw..57.....K
Altcode:
The pointing of the Grazing Incidence Spectrometer (GIS) on the SOHO CDS
instrument has been determined by study of the limb data, and has been
compared to the pointing of the Normal Incidence Spectrometer (NIS), The
results show that the size of the solar image seen by both instruments
is the same, but since the SOHO attitude loss incident in June 1998
the GIS observes the sun at a different position, shifted 20.2 arcsec
to the south, for zero roll angle, compared to the NIS. No evidence
for a distortion of the rastered image of the sun in GIS data was found.
Title: Benchmarking atomic data for astrophysics: Fe XXIV
Authors: Del Zanna, G.
Bibcode: 2006A&A...447..761D
Altcode:
Fe XXIV produces strong L-shell (n=3, 4, 5 to 2) spectral lines in the
X-rays. These lines have been observed in solar flares, in laboratory
spectra, and in a variety of astrophysical sources with e.g. the Chandra
and XMM-Newton satellites. In this paper atomic data for Fe XXIV L-shell
emission are benchmarked against experimental data. The work focuses on
reviewing and assessing previous line identifications on a quantitative
basis, paying particular attention to the most important lines for
laboratory and astrophysical applications. Previous identifications
are confirmed, but many lines turn out to be significantly blended. The
agreement between theoretical and observed data in terms of wavelengths,
line intensities and level lifetimes is good, within the experimental
uncertainties. Fe XXIV L-shell lines can be used to measure electron
densities in laboratory plasmas and temperatures for a wide range of
astrophysical sources.
Title: X-ray emission from PTT stars
Authors: Del Zanna, G.; Worters, H. L.; Bromage, G. E.; Foley, C. A.;
Mason, H. E.; Landini, M.; Whiting, A.
Bibcode: 2006AdSpR..38.1475D
Altcode:
We present preliminary results on an XMM-Newton observation dedicated to
Post-T-Tauri (PTT) stars. We observed the visual binary 2RE J0241-53 of
the Horologium association of nearby PTT stars. The XMM observations
have been complemented with ground-based optical spectroscopy and
photometry. Several flares have been observed. The X-ray spectrum of
the brightest star during quiescence indicates a rather cool corona
(with no emission at temperatures ⩾10 MK) more similar to that of the
Classical T-Tauri star TW Hya (observed with Chandra and XMM-Newton)
and at variance with that of another PTT Star (PZ Tel) observed with
Chandra. Approximate analysis shows large Ne/Fe, N/Fe, C/Fe abundances
(compared to solar photospheric values).
Title: Atomic data from the IRON project. LX. Electron-impact
excitation of n = 3, 4 levels of Fe17+
Authors: Witthoeft, M. C.; Badnell, N. R.; del Zanna, G.; Berrington,
K. A.; Pelan, J. C.
Bibcode: 2006A&A...446..361W
Altcode:
We present results for electron-impact excitation of F-like Fe
calculated using R-matrix theory where an intermediate-coupling
frame transformation (ICFT) is used to obtain level-resolved
collision strengths. Two such calculations are performed, the
first expands the target using 2s2 2p5, 2s
2p6, 2s2 2p4 3l, 2s 2p5
3l, and 2p6 3l configurations while the second calculation
includes the 2s2 2p4 4l, 2s 2p5
4l, and 2p6 4l configurations as well. The effect of the
additional structure in the latter calculation on the n=3 resonances
is explored and compared with previous calculations. We find strong
resonant enhancement of the effective collision strengths to the
2s2 2p4 3s levels. A comparison with a Chandra
X-ray observation of Capella shows that the n=4 R-matrix calculation
leads to good agreement with observation.
Title: CHIANTI-An Atomic Database for Emission Lines. VII. New Data
for X-Rays and Other Improvements
Authors: Landi, E.; Del Zanna, G.; Young, P. R.; Dere, K. P.; Mason,
H. E.; Landini, M.
Bibcode: 2006ApJS..162..261L
Altcode:
The CHIANTI atomic database contains atomic energy levels, wavelengths,
radiative transition probabilities, and collisional excitation data for
a large number of ions of astrophysical interest. CHIANTI also includes
a suite of IDL routines to calculate synthetic spectra and carry out
plasma diagnostics. Version 5 has been released, which includes several
new features, as well as new data for many ions. The new features in
CHIANTI are as follows: the inclusion of ionization and recombination
rates to individual excited levels as a means to populate atomic
levels; data for Kα and Kβ emission from Fe II to Fe XXIV; new data
for high-energy configurations in Fe XVII to Fe XXIII; and a complete
reassessment of level energies and line identifications in the X-ray
range, multitemperature particle distributions, and photoexcitation
from any user-defined radiation field. New data for ions already in
the database, as well as data for ions not present in earlier versions
of the database, are also included. Version 5 of CHIANTI represents a
major improvement in the calculation of line emissivities and synthetic
spectra in the X-ray range and expands and improves theoretical spectra
calculations in all other wavelength ranges.
Title: Multi-Wavelength Analysis of Plasma Flows during Solar Flares
Authors: Berlicki, A.; Schmieder, B.; Heinzel, P.; Li, H.; Del Zanna,
G.; Rudawy, P.
Bibcode: 2005ESASP.600E..58B
Altcode: 2005dysu.confE..58B; 2005ESPM...11...58B
No abstract at ADS
Title: Dynamics of Active Region Loops: Temperature Measurements as
a function of Time
Authors: Cirtain, J. J.; del Zanna, G.; Mason, H.; Deluca, E.;
Martens, P.
Bibcode: 2005AGUFMSH44A..03C
Altcode:
The combination of moderate resolution EUV spectroscopy and high
resolution narrow band filter images provides the most accurate
measure of temperature and density for coronal loops to date. We will
demonstrate our technique for combining the data sets from the Coronal
Diagnostic Spectrometer on SoHO and the Transition Region and Coronal
Explorer. Background subtracted spectral intensities are used to
determine the temperature of coronal loops and the TRACE images help
determine the loop cross-section, temporal variability, and filling
factor. The resulting temperature profiles for multiple positions along
a loop leg are determined using the EM LOCI method, and a technique for
determining whether a single temperature can characterize the plasma is
also presented. We compare the results of our study to current models.
Title: Flows and Heating of the Solar Atmosphere during Solar Flares
Authors: Schmieder, B.; Berlicki, A.; Li, H.; Del Zanna, G.; Mason, H.
Bibcode: 2005ESASP.592..543S
Altcode: 2005soho...16E.102S; 2005ESASP.592E.102S
No abstract at ADS
Title: Electron densities in EUV coronal bright points
Authors: Ugarte-Urra, I.; Doyle, J. G.; Del Zanna, G.
Bibcode: 2005A&A...435.1169U
Altcode:
Electron density measurements of six coronal bright points have been
obtained using line ratio diagnostics of four ions in the temperature
range 1.3-2.0 × 106 K. The results suggest that BP plasma
has more similarities to active region plasma than to quiet Sun
plasma. Nevertheless, they do not show the exact same behaviour: the
increase of electron density at temperatures over log~Te ~
6.2, observed in the core of active regions, has not been detected. The
Fe XII results based on new atomic data, although in better agreement
decreasing more than a factor of two the densities obtained with older
calculations, are still in some instances higher than those from Si
X. This could be a consequence of the inhomogeneity of the plasma in
the observed volume. New measurements with a better constriction of
the volumetric properties seem necessary to rule out the influence of
other factors and confirm whether there is an inconsistency between
the ions, perhaps due to line blending problems in the Fe XII lines.
Title: Recent developments of the CHIANTI database in the X-ray
wavelength range
Authors: Landi, E.; Dere, K. P.; Young, P. R.; del Zanna, G.; Mason,
H. E.; Landini, M.
Bibcode: 2005AIPC..774..409L
Altcode:
CHIANTI is a database of atomic data and transition probabilities that
allows the calculation of synthetic spectra and plasma diagnostics of
optically thin plasmas. It is primarily suited for wavelengths shorter
than 2000 Å but in principle can also be used at longer wavelengths. In
the present paper we illustrate the latest development of the CHIANTI
database, that include a huge expansion of the database in the X-ray
wavelength range, the renewal of several data in the EUV range, and
the inclusion of ionization and recombination in the level population
calculation. This enhanced database will constitute the Version 5
of CHIANTI.
Title: EUV Observations of Active Region Dynamics
Authors: Deluca, E. E.; Cirtain, J. W.; del Zanna, G.; Mason, H. E.;
Martens, P. C.; Schmelz, J.; Golub, L.
Bibcode: 2005AGUSMSP33A..03D
Altcode:
Data collected during SoHO JOP 146, in collaboration with TRACE, is
used to investigate the physical characteristics of coronal active
region loops as a function of time and position along and across
loop structures. These data include TRACE images in all three EUV
passbands, and simultaneous CDS spectroscopic observations. Preliminary
measurements of the loop temperature both along the loop half-length
and loop cross-section are presented as a function of time. We will
show the temperature and density profiles of several structures as a
function of position, show changes in temperature and density with time
and characterize the coronal background emission. Questions raised
by these results will be greatly advanced with the high resolution
spectra available from the EIS on Solar-B.
Title: Benchmarking atomic data for astrophysics: Fe XII
Authors: Del Zanna, G.; Mason, H. E.
Bibcode: 2005A&A...433..731D
Altcode:
We use recently calculated electron collisional data by [CITE] for
ion{Fe}{xii} (n=3 configurations) to build a model ion to compare
to spectroscopic observations of the solar corona and laboratory
measurements. We review all the line identifications of the brightest
lines, by comparing both wavelengths and line intensities. The
presence of blends in different plasma conditions is highlighted. A
large number of new energy levels and line identifications are
proposed. In particular, we identify the electric quadrupole
^4P{5/2}^e-^4F{9/2}e transition with the bright coronal
line observed at 592.6 Å, previously unidentified. This line, when
observed with the 1242.0, 1349.5 UV forbidden lines, is a good density
diagnostic over a large range of electron densities. We also indicate
the best spectral lines to be used for density diagnostics or instrument
calibration. From various combinations of lines we obtain electron
densities that are significantly different from those published in the
previous literature. Some examples are provided. The agreement between
theory and experimental data in terms of wavelengths, line intensities
and level lifetimes is excellent. The full datasets of energies
(Table 2) and radiative data (Table 3) are only available in electronic
form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/731
Title: Atomic data from the IRON Project
Authors: Storey, P. J.; Del Zanna, G.; Mason, H. E.; Zeippen, C. J.
Bibcode: 2005A&A...433..717S
Altcode:
A new calculation of rate coefficients for electron collisional
excitation of ion{Fe}{xii} is presented and compared to earlier
calculations. Significant differences are found with all earlier work
due to the inclusion of resonance processes that have not previously
been considered and to the use of the intermediate coupling frame
transformation method. The resulting dataset of collision strengths
is shown to resolve many of the outstanding discrepancies between
theory and solar observations. In particular, density sensitive
line ratios in ion{Fe}{xii} now indicate electron densities
close to those derived from other ions of comparable ionization
potential. Table 10 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/433/717
Title: Correlation between coronal hole and quiet Sun intensities:
Evidence for continuous reconnection
Authors: Raju, K. P.; Bromage, B. J. I.; Chapman, S. A.; Del Zanna, G.
Bibcode: 2005A&A...432..341R
Altcode:
Intensities of 12 strong EUV emission lines in a coronal hole and
the neighbouring quiet Sun region have been obtained from SOHO/CDS
observations made in August and September 1996. The field of view
is 1 arcmin wide by 4 arcmin, with a series of observations made at
different spatial locations on the boundary of the north polar hole
and its large equatorial extension, the “Elephant's Trunk”. The
formation temperatures of the observed lines vary from 0.083 MK to
1.10 MK and hence they represent increasing heights in the solar
atmosphere from the upper chromosphere and transition region to the
low corona. Line intensities in the vicinity of the coronal hole
boundary were examined. For lines formed in the transition region, a
correlation was found between intensities in the coronal hole and those
in the adjacent quiet Sun region. However, for lines formed higher up
in the low corona, the correlation gradually disappears. Moreover,
it is found that in the lower transition region the coronal hole
emission is brighter than that in the quiet Sun. We conclude that
the correlation observed in the transition region implies that flux
transport is not impeded by the presence of the coronal hole boundary,
suggesting that reconnection is taking place which changes the status
of the footpoints from closed to open and vice versa, maintaining the
location of the boundary against the movement of the flux. The magnetic
reconnection events provide energy in the corona which conducts down
the field lines until it is absorbed in the transition region. The
brightness of the coronal hole in the lower transition region lines
can be explained if the energy conducted down the open field lines
is able to penetrate to lower temperature levels than it does on the
closed field of the quiet Sun region. This is possible because, for
any given temperature in this range, the density in the coronal hole
is lower than it is in the quiet Sun.
Title: Benchmarking atomic data for astrophysics: Fe XXIII
Authors: Del Zanna, G.; Chidichimo, M. C.; Mason, H. E.
Bibcode: 2005A&A...432.1137D
Altcode:
Recent scattering calculations for Fe XXIII are benchmarked against
laboratory and astrophysical observations. The collisional data are
supplemented by radiative data obtained with empirical adjustments
that take into account observed wavelengths. All previous line
identifications and energy levels are reviewed and assessed in light
of these new calculations. Most of the previous identifications,
in particular of the astrophysically-important spectral lines are
confirmed. However, some identification are rejected or questioned, and
new ones proposed. The agreement between theoretical and experimental
data in terms of wavelengths, line intensities and level lifetimes is
very good. Observations of Fe XXIII L-shell emission lines provide
a great opportunity to directly measure electron temperatures for
a wide range of astrophysical sources. Examples from solar (SMM,
SOLEX) and stellar (Chandra, EUVE) observations are provided. The full set of energies (cf. Table 2), wavelengths and A-values
(cf. Table 3) are available in electronic form at the CDS via
anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/432/1137 .
Title: VizieR Online Data Catalog: Fe XXIII Benchmarking (Del
Zanna+, 2005)
Authors: Del Zanna, G.; Chidichimo, M. C.; Mason, H. E.
Bibcode: 2005yCat..34321137D
Altcode:
Recent scattering calculations for Fe XXIII are benchmarked against
laboratory and astrophysical observations. The collisional data are
supplemented by radiative data obtained with empirical adjustments
that take into account observed wavelengths. All previous line
identifications and energy levels are reviewed and assessed in light
of these new calculations. Most of the previous identifications,
in particular of the astrophysically-important spectral lines are
confirmed. However, some identification are rejected or questioned, and
new ones proposed. The agreement between theoretical and experimental
data in terms of wavelengths, line intensities and level lifetimes is
very good. Observations of Fe XXIII L-shell emission lines provide
a great opportunity to directly measure electron temperatures for
a wide range of astrophysical sources. Examples from solar (SMM,
SOLEX) and stellar (Chandra, EUVE) observations are provided. **************************************************************************
* * * Sorry, but the author(s) never supplied
the tabular material * * announced in the paper * * *
**************************************************************************
(1 data file).
Title: VizieR Online Data Catalog: Atomic data from the IRON
Project. LVI. (Chidichimo+, 2005)
Authors: Chidichimo, M. C.; Del Zanna, G.; Mason, H. E.; Badnell,
N. R.; Tully, J. A.; Berrington, K. A.
Bibcode: 2005yCat..34300331C
Altcode:
Collision strengths for electron induced transitions in
the beryllium-like ion Fe+22 are calculated
using the intermediate coupling frame transformation
(ICFT) version of the R-matrix programs. Our target
has 98 fine structure states ls2 nl n'l'SLJ
corresponding to n=2 and n'=2, 3, 4. The present calculation
is for electron impact energies in the range 3.15 to 380Ry. **************************************************************************
* * * Sorry, but the author(s) never supplied
the tabular material * * announced in the paper * * *
**************************************************************************
(1 data file).
Title: VizieR Online Data Catalog: Fe X Benchmarking atomic data
(Del Zanna+, 2004)
Authors: Del Zanna, G.; Berrington, K. A.; Mason, H. E.
Bibcode: 2005yCat..34220731D
Altcode:
This is the first in a series of papers in which we benchmark recent
atomic data available for astrophysical applications. We review various
issues related to the completeness and accuracy of both theoretical and
experimental data. In this paper, the available experimental and atomic
data for Fe X (n=3 configurations) are reviewed and assessed. New
collisional and radiative data are calculated to supplement
published data. The radiative calculations are done with empirical
adjustements that take into account observed wavelengths. Previous
line identifications are also reviewed and assessed. Our approach
focuses on the brightest spectral lines, and uses both wavelengths and
line intensities to assess the line identifications on a quantitative
basis. Although many previous line identifications are confirmed, some
are rejected (e.g. the coronal line observed at 1582.35{AA}). We confirm
previously suggested identifications (e.g. 257.262{AA},1028.02{AA}),
and we present new ones, (e.g. the lines of the 3s2
3p4 3d-3s 3p5 3d transition array). In addition,
we highlight the presence of blends and we review which spectral lines
are best for density diagnostics or for instrument calibration. The
theoretical data (line intensities and level lifetimes) are benchmarked
against well-calibrated spectroscopic observations of the solar corona
and laboratory measurements. The agreement between theoretical and
experimental data which we achieve with our new model ion is very
good. (3 data files).
Title: The CHIANTI database
Authors: Landi, E.; Dere, K. P.; Young, P. R.; Landini, M.; Mason,
H. E.; Del Zanna, G.
Bibcode: 2005HiA....13..653L
Altcode:
CHIANTI is a database of atomic data and transition rates necessary for
calculating synthetic spectra and carrying out plasma diagnostics of
astrophysical sources in the X-ray EUV and UV wavelength ranges. CHIANTI
includes both line and continuum emission from all astrophysically
abundant elements in the universe. All data are taken from refereed
literature and are critically assessed. CHIANTI also includes a suite
of IDL programs that allow spectroscopic analysis to be carried
out. CHIANTI data and software are freely distributed over the
internet. In the present talk I will describe the contents of
the CHIANTI database its current status and the areas where CHIANTI
is being developed and I will also present a comparison of CHIANTI
predictions with the X-ray emission from astrophysical sources.
Title: Atomic data from the IRON Project = 2, 3, 4 configurations.
LVI. Electron excitation of Be-like Fe XXIII for the n = 2,3,4
configurations
Authors: Chidichimo, M. C.; Del Zanna, G.; Mason, H. E.; Badnell,
N. R.; Tully, J. A.; Berrington, K. A.
Bibcode: 2005A&A...430..331C
Altcode:
Collision strengths for electron induced transitions in the
beryllium-like ion Fe+22 are calculated using the
intermediate coupling frame transformation (ICFT) version of
the R-matrix programs. Our target has 98 fine structure states
1s2 nl n'l' SLJ corresponding to n = 2 and n' = 2, 3,
4 . The present calculation is for electron impact energies in the
range 3.15 to 380 Ry. When T exceeds about ten million degrees one
needs to take account of contributions to the thermally averaged
collision strength Υ coming from electrons with energies in excess of
380 Ry. We discuss a way of allowing for these contributions. Values
of Υ for all the transitions between the ground state and the
excited states 1s2 2l n l n'l' S'L'J', with n'=2,3,4 are
tabulated as a function of log T. The temperature range 6.3 ≤log
T ≤8.1 is centred on log T = 7.1 which is approximately where
Fe+22 has maximum abundance in ionization equilibrium. To
the best of our knowledge these are the first R-matrix calculations
for Fe+22 for excitations to the n = 3,4 levels. Good
agreement with previous distored-wave calculations is found. However,
the resonance contributions have an important effect on the effective
collision strengths and in turn on the level populations. Full Tables 2, 4 and 6 are only available in electronic form at
the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/430/331. The
full datasets of wavelengths and gf values (Table 4) and of
effective collision strengths (Table 7) are only available at
the same address. The same data are also available at the TIPbase
(http://vizier.u-strasbg.fr/tipbase/home.html) database and as an
`adf04' file at the Oak Ridge National Laboratory's database via
http://www-cfadc.phy.ornl.gov/
Title: The EUV spectral irradiance from 1996 to 2003 as obtained
from SOHO
Authors: Del Zanna, G.; Andretta, V.; Beaussier, A.
Bibcode: 2005MmSAI..76..953D
Altcode:
We present EUV (150-800 Å) radiance measurements obtained with the
SOHO/Coronal Diagnostic Spectrometer (CDS) during the period from
1996 to 2003. We complement the CDS measurements with simultaneous
SOHO/EIT EUV images. We use the EIT center-to-limb variations to
obtain an estimate of the EUV spectral irradiance of the 'quiet Sun'
during 1996-2003. We discuss the evolution of the characteristics
of the solar corona from minimum to maximum, and show how it becomes
progressively hotter.
Title: VizieR Online Data Catalog: Fe XII Benchmarking atomic data
(Del Zanna+, 2005)
Authors: Del Zanna, G.; Mason, H. E.
Bibcode: 2005yCat..34330731D
Altcode:
We use recently calculated electron collisional data by Storey
et al. (2005A&A...433..717S) for Fe XII (n=3 configurations)
to build a model ion to compare to spectroscopic observations of
the solar corona and laboratory measurements. We review all the line
identifications of the brightest lines, by comparing both wavelengths
and line intensities. The presence of blends in different plasma
conditions is highlighted. A large number of new energy levels and
line identifications are proposed. In particular, we identify the
electric quadrupole 4P5/2-4^F9/2
transition with the bright coronal line observed at 592.6{AA},
previously unidentified. This line, when observed with the 1242.0,
1349.5 UV forbidden lines, is a good density diagnostic over a large
range of electron densities. We also indicate the best spectral lines
to be used for density diagnostics or instrument calibration. From
various combinations of lines we obtain electron densities that
are significantly different from those published in the previous
literature. Some examples are provided. The agreement between theory
and experimental data in terms of wavelengths, line intensities and
level lifetimes is excellent. (2 data files).
Title: Remote Sensing of Plasma Diagnostics Relating to Coronal
Heating
Authors: Mason, H. E.; Del Zanna, G.; Bradshaw, S.
Bibcode: 2004ESASP.575..312M
Altcode: 2004soho...15..312M
No abstract at ADS
Title: Synthesised Radiative Emission from a Nanoflare Heated
Elemental Solar Loop
Authors: Bradshaw, S. J.; Del Zanna, G.; Mason, H. E.; Cargill, P. J.
Bibcode: 2004ESASP.575..539B
Altcode: 2004soho...15..539B
No abstract at ADS
Title: On the consequences of a non-equilibrium ionisation balance
for compact flare emission and dynamics
Authors: Bradshaw, S. J.; Del Zanna, G.; Mason, H. E.
Bibcode: 2004A&A...425..287B
Altcode:
We carry out a hydrodynamic simulation of a compact flare and find
significant non-equilibrium distributions for the ionisation balance
during the impulsive and gradual phases, which can strongly alter the
radiative emission. This has major implications for attempts to derive
the theoretical intensities of emission lines used for spectroscopic
diagnostic analyses of the plasma properties. During the
impulsive phase we find that the emissivities of He I, He II and C IV
in the transition region can be strongly enhanced above their expected
equilibrium values, followed by a significant reduction which increases
the amount of chromospheric plasma ablated into the corona. Furthermore,
during the flare heating the overall charge state of the coronal
ions can be significantly lower than is suggested by an equilibrium
ionisation balance and, therefore, line ratio measurements will yield
plasma temperatures that are much greater than the formation temperature
of the emitting ion. During the gradual phase the emissivity at
transition region temperatures remains suppressed, compared with its
equilibrium value, with correspondingly reduced downflow velocities and
increased radiative cooling time-scales. Finally, we synthesise
the emission as it would be detected by TRACE in its 171 Å and 195 Å
wavelength bands, and find that the filter ratio technique can give
reasonably good estimates of the plasma temperature in quiescence,
though when the populations of Fe VIII, Fe IX, Fe X and Fe XII exhibit
departures from equilibrium the temperatures derived from filter ratio
measurements become unreliable. Figures \ref{fig4}-\ref{fig39}
are only available in electronic form at http://www.edpsciences.org
Title: Evolution and magnetic topology of the M 1.0 flare of October
22, 2002
Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Aulanier, G.;
Del Zanna, G.
Bibcode: 2004A&A...423.1119B
Altcode:
In this paper we analyse an M 1.0 confined flare observed mainly
during its gradual phase. We use the data taken during a coordinated
observational campaign between ground based instruments (THEMIS and
VTT) and space observatories (SoHO/CDS and MDI, TRACE and RHESSI). We
use these multi-wavelength observations to study the morphology
and evolution of the flare, to analyse its gradual phase and to
understand the role of various heating mechanisms. During the flare,
RHESSI observed emission only within the 3-25 keV spectral range. The
RHESSI spectra indicate that the emission of the flare was mainly of
thermal origin with a small non-thermal component observed between
10 and 20 keV. Nevertheless, the energy contained in the non-thermal
electrons is negligible compared to the thermal energy of the flaring
plasma. The temperature of plasma obtained from the fitting of the
RHESSI X-ray spectra was between 8.5 and 14 MK. The lower temperature
limit is typical for a plasma contained in post flare loops observed
in X-rays. Higher temperatures were observed during a secondary peak
of emission corresponding to a small impulsive event. The SoHO/CDS
observations performed in EUV Fe XIX line also confirm the presence
of a hot plasma at temperatures similar to those obtained from RHESSI
spectra. The EUV structures were located at the same place as RHESSI
X-ray emission. The magnetic topology analysis of the AR coming from a
linear force-free field extrapolation explains the observed features
of the gradual phase of the flare i.e. the asymmetry of the ribbons
and their fast propagation. The combination of the multi-wavelength
observations with the magnetic model further suggests that the onset
of the flare would be due to the reconnection of an emerging flux in
a sheared magnetic configuration.
Title: Benchmarking atomic data for astrophysics: Fe X
Authors: Del Zanna, G.; Berrington, K. A.; Mason, H. E.
Bibcode: 2004A&A...422..731D
Altcode:
This is the first in a series of papers in which we benchmark
recent atomic data available for astrophysical applications. We
review various issues related to the completeness and accuracy
of both theoretical and experimental data. In this paper, the
available experimental and atomic data for Fe X (n=3 configurations)
are reviewed and assessed. New collisional and radiative data are
calculated to supplement published data. The radiative calculations
are done with empirical adjustements that take into account observed
wavelengths. Previous line identifications are also reviewed and
assessed. Our approach focuses on the brightest spectral lines,
and uses both wavelengths and line intensities to assess the line
identifications on a quantitative basis. Although many previous line
identifications are confirmed, some are rejected (e.g. the coronal line
observed at 1582.35 Å). We confirm previously suggested identifications
(e.g. 257.262 Å, 1028.02 Å), and we present new ones, (e.g. the
lines of the 3s23p43d-3s 3p53d
transition array). In addition, we highlight the presence of blends
and we review which spectral lines are best for density diagnostics or
for instrument calibration. The theoretical data (line intensities and
level lifetimes) are benchmarked against well-calibrated spectroscopic
observations of the solar corona and laboratory measurements. The
agreement between theoretical and experimental data which we achieve
with our new model ion is very good. Table 1 and full Tables
3 and \ref{tab:lines} are only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/422/731 Appendix
is only available in electronic form at http://www.edpsciences.org
Title: SOHO CDS and SUMER observations of quiescent filaments and
their interpretation
Authors: Del Zanna, G.; Chiuderi Drago, F.; Parenti, S.
Bibcode: 2004A&A...420..307D
Altcode:
Three quiescent filaments located at different positions on the solar
disk were selected from the SOHO CDS data archive: one of them was also
observed by SUMER in the raster mode. We investigate the filament-corona
transition region (PCTR) emission, to determine whether it is indeed
negligible, as found in one previously-analysed case. The observations
are interpreted on the basis of two different models: an isothermal
(cool) prominence located above the quiet sun transition region (TR)
with a portion of the corona below it, and a model composed of several
cool threads embedded in the hot coronal plasma without any quiet
sun TR below it. The first model indicates that, for all filaments,
the PCTR emission at the top of the filament is indeed negligible, and
that the chromosphere-corona TR emission under the filament is lower
than the average. All filaments have similar column densities, ranging
from ∼2 to 7× 1017 cm-2 according to model A,
and from 5 to 17×1017 cm-2 according to Model
B. It is not possible to determine which model better accounts for the
observations, on the basis of the two prominences observed above and
below the Lyman continuum limit. Model B predicts absorptions that are
generally less consistent with the observations, and produces higher
column densities. The comparison between the line intensities observed
above and below the He I ionization limit provides an estimate of the
relative neutral helium abundance N(He I)/N(H I) in the prominences.
Title: Recent development of the CHIANTI database in the X-ray
wavelength range
Authors: Landi, E.; Dere, K. P.; Mason, H. E.; Del Zanna, G.; Landini,
M.; Young, P. R.
Bibcode: 2004AAS...204.7310L
Altcode: 2004BAAS...36R.801L
CHIANTI consists of a database of critically assessed atomic data
and transition rates to calculate line and continuum emission
from astrophysical plasmas. During the last year the CHIANTI
database has been substantially expanded in the X-ray wavelength
region by including a large number of new configurations and lines,
and by including ionization and recombination processes in the level
population calculations. We will describe these improvements,
the data we used, and illustrate examples of 1) their effects on
predicted emissivities and on plasma diagnostics 2) applications to
the study of flares in solar active regions
Title: The Differential Emission Measure Distribution of EQ Pegasi
Observed by BeppoSAX
Authors: Landini, M.; Landi, E.; Del Zanna, G.; Risaliti, G.
Bibcode: 2004IAUS..219..893L
Altcode: 2003IAUS..219E.126L
Broad band BeppoSAX observation of EQ Pegasi is analyzed using the
CHIANTI spectral database and a differential emission measure versus
temperature distribution of coronal matter. Comparison is performed
with the two temperature modelling usually performed in the data
reduction of broad band observations of active stars.
Title: Spectral diagnostic capabilities of Solar-B EIS
Authors: del Zanna, G.; Mason, H. E.
Bibcode: 2004cosp...35.3002D
Altcode: 2004cosp.meet.3002D
We briefly review the main spectral diagnostics that will be available
with Solar-B EIS, and what kind of scientific questions could be best
addressed, based on our experience with SOHO/CDS observations. We then
report on our progress in reviewing and benchmarking atomic data for
the Fe coronal ions, that are of particular importance for spectral
and instrument calibration purposes.
Title: X-ray emission from PTT stars
Authors: del Zanna, G.; Bromage, G.; Foley, C.; Worters, H.; Mason,
H.; Landini, M.
Bibcode: 2004cosp...35.2995D
Altcode: 2004cosp.meet.2995D
We present preliminary results on new X-ray spectroscopic XMM/RGS
observations of the visual binary nicknamed `Horace Horologii' (2RE
J0241-53). The two stars are strong and very active X-ray emitters, and
are members of an association of Post-T-Tauri stars. A detailed study
(in particular in terms of chemical composition) is important for our
understanding of the evolution from the T-Tauri phase, and to explain
the origin of the X-ray emission in very young stars. The physical
characteristics of the quiescent X-ray emission are described, and
related to other stellar parameters such as photospheric abundances and
the rotational period. Simultaneous ground-based optical spectroscopy
and U-band photometric monitoring observations were obtained at the
South African Astronomical Observatory.
Title: Spectroscopic observations of compact solar flares
Authors: del Zanna, G.; Mason, H. E.
Bibcode: 2004cosp...35.2998D
Altcode: 2004cosp.meet.2998D
We present SOHO/Coronal Diagnostic Spectrometer observations of
solar flares, complemented with data from other instruments (such
as high-resolution images from TRACE, magnetograms from SOHO/MDI,
and Yohkoh SXT). We show that CDS provides essential spectroscopic
information which adds complexity into our understanding of the dynamics
of solar flares. We give a description of the main observational
features, and what types of measurements (densities, temperatures,
flows) are obtained. These observations provide constraints for flare
modeling, and indications on what types of spectroscopic observations
future instruments should provide.
Title: CHIANTI -- An Atomic Database for UV and X-ray Cool star
spectroscopy
Authors: Young, P. R.; Landi, E.; Bromage, G. E.; del Zanna, G.;
Dere, K. P.; Landini, M.; Mason, H. E.
Bibcode: 2003csss...12.1119Y
Altcode:
The CHIANTI atomic database was first released in 1996 and has since
become the standard resource for the interpretation of UV spectra
from the transition regions and coronae of the Sun and other cool
stars. We describe the contents of the most recent release (v.3)
and some of the uses that have been found for the database.
Title: Solar active regions: SOHO/CDS and TRACE observations of
quiescent coronal loops
Authors: Del Zanna, G.; Mason, H. E.
Bibcode: 2003A&A...406.1089D
Altcode:
This study focuses on the diagnostic capabilities of the TRACE and
SOHO-CDS instruments to describe the physical characteristics of
quiescent solar active regions. In particular we concentrate on
the 1 MK loops, best seen in the TRACE EUV 173 Å passband. These
are high-lying structures which can remain stable over timescales
of hours to days. We present simultaneous observations of off-limb
active region 1 MK loops performed with TRACE (173 Å and 195 Å
bands) and the SOHO-CDS. The CDS spectral capabilities complement
the TRACE observations well and allow an in-depth study of the plasma
properties. Some important new results are presented here. In terms of
cross-field characteristics, we find that these loops are isothermal
and much cooler (T =~ 0.7-1.1 x 106 K) than the surrounding
diffuse high-lying active region emission (T =~ 2 x 106
K). We show that the diffuse background-foreground constitutes the
bulk of the high-lying quiescent active region emission. We explain
some of the discrepancies found by various authors (based on SOHO
and TRACE observations) with an overestimation of loop temperatures
and densities. This was caused by inaccurate or neglected background
subtraction in the data analysis. We studied the leg of a 1 MK loop and
found that along its length temperatures and densities have steeper
profiles compared to those derived from previous studies based on
TRACE observations. The observations are consistent with an element
abundance FIP effect of about 4, filling factors close to unity, and
a constant density across the loop. We find a remarkable consistency
between the CDS and TRACE observations, although we also find severe
limitations to the use of TRACE diagnostic techniques.
Title: Solar active regions: The footpoints of 1 MK loops
Authors: Del Zanna, G.
Bibcode: 2003A&A...406L...5D
Altcode:
On-disc SOHO and TRACE observations of the footpoints of 1 MK quiescent
loops in a solar active region are presented. These types of loops are
long-lived and high-lying features that are best seen in the TRACE 173
Å passband, sensitive to 1 MK temperatures. SOHO/CDS data are used
to show the clear association between the high-lying 1 MK coronal
emission and emission formed at lower heights and temperatures, in
the transition region. The 1 MK loops are rooted in strong unipolar
regions located at the supergranular network boundaries. These loops
have near-isothermal distributions at each location along their length,
with peak emission measures at T=0.7 MK, where electron densities are
~ 2 x 109 cm-3. The loops showed photospheric
abundances, at odds with previous results based on Skylab data.
Title: XMM-Newton Proposal 02072101
Authors: Del Zanna, Giulio
Bibcode: 2003xmm..prop..366D
Altcode:
Our main scientific goal is to use the capabilities of XMM/RGS to
determine the physical characteristics of the X-ray emission (during
quiescent and flaring state) of the visual binary 2RE J0241-53. This
binary is a strong and very active X-ray emitter, classified as a member
of an association of Post-T-Tauri stars. Its study (in particular in
terms of chemical coposition) is important for our understanding of
the evolution from the T-Tauri phase, and to explain the origin of the
X-ray emission in young stars. A detailed study of any FIP effect can
be perfomed since the photospheric composition of the stars is known.
Title: The EUV helium spectrum in the quiet Sun: A by-product of
coronal emission?
Authors: Andretta, V.; Del Zanna, G.; Jordan, S. D.
Bibcode: 2003A&A...400..737A
Altcode:
In this paper we test one of the mechanisms proposed to explain the
intensities and other observed properties of the solar helium spectrum,
and in particular of its Extreme-Ultraviolet (EUV) resonance lines. The
so-called Photoionisation-Recombination (P-R) mechanism involves
photoionisation of helium atoms and ions by EUV coronal radiation,
followed by recombination cascades. We present calibrated measurements
of EUV flux obtained with the two CDS spectrometers on board SOHO,
in quiescent solar regions. We were able to obtain an essentially
complete estimate of the total photoionising flux in the wavelength
range below 504 Å (the photoionisation threshold for He I), as well as
simultaneous measurements with the same instruments of the intensities
of the strongest EUV He I and He Ii lines: \specline{He}i{584},
\specline{He}i{537}, and \specline{He}{ii}{304}. We find that there
are not enough EUV ionising photons to account for the observed helium
line intensities. More specifically, we conclude that He Ii intensities
cannot be explained by the P-R mechanism alone. Our results, however,
leave open the possibility that the He I spectrum could be formed by
the P-R mechanism, with the \specline{He}{ii}{304} line as a significant
photoionisating source.
Title: Spectroscopic characteristics of polar plumes
Authors: Del Zanna, G.; Bromage, B. J. I.; Mason, H. E.
Bibcode: 2003A&A...398..743D
Altcode:
Extreme ultraviolet observations of plumes in polar coronal holes are
presented and their spectroscopic signatures discussed. The study
focuses on the base of plumes seen on the disk of the Sun with the
Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric
Observatory (SOHO) satellite. Spectroscopic diagnostic techniques are
applied to characterise the plumes in terms of density, temperature,
emission measure and element abundance. Attention is drawn to the
particular limitations of some of the techniques when applied to plume
structures. In particular, we revisit the Widing & Feldman (1992)
findings of a plume having a large first ionization potential (FIP)
effect of 10, showing that instead the Skylab data are consistent
with no FIP effect. We present for the first time CDS-GIS (grazing
incidence spectrometer) observations of a plume. These observations
have been used to confirm the results obtained from normal incidence
(NIS) observations. We find that polar plumes exhibit the same
characteristics as the Elephant's Trunk equatorial plume. The
most striking characteristic of the plume bases is that they are
near-isothermal with a peak emission measure at transition region
temperatures =~ 8 x 105 K. At these temperatures, plumes have
averaged densities Nlo {e} =~ 1.2 x 109 cm-3,
about twice the value of the surrounding coronal hole region. Element
abundances in the plumes are found to be close to photospheric, with the
exception of neon which appears to be depleted by 0.2 dex relative to
oxygen. The absence of a significant FIP effect in plumes is consistent
with fast solar wind plasma, although it is not sufficient to prove
a link between the two. Finally, we present a comparison between GIS
spectra and the SOHO EIT (EUV Imaging Telescope) broad-band images,
showing that temperatures derived from the EIT ratio technique are
largely overestimated, for plumes and coronal holes. This is partly
due to the fact that the so called ``Fe XII 195 Å'' and ``Fe XV
284 Å'' filters are not isothermal, and in coronal holes and plumes
lower-temperature lines dominate the EIT signal.
Title: SOHO CDS observations of coronal hole plumes
Authors: Del Zanna, G.
Bibcode: 2003MmSAI..74..741D
Altcode:
Coronal Diagnostic Spectrometer (CDS) observations of a polar coronal
hole plume are presented. Spectroscopic diagnostic techniques are
applied to characterise the plume in terms of density, temperature,
emission measure and elemental abundance. It is found that polar
plume bases exhibit the same characteristics as the Elephant's Trunk
equatorial plume, i.e. are nearly isothermal with temperatures =~
8 x 105 K, have densities Nlo {e} =~ 1.2 x 109
cm-3, and do not have a significant FIP effect, contrary
to what has long been thought.
Title: CHIANTI-An Atomic Database for Emission Lines. VI. Proton
Rates and Other Improvements
Authors: Young, P. R.; Del Zanna, G.; Landi, E.; Dere, K. P.; Mason,
H. E.; Landini, M.
Bibcode: 2003ApJS..144..135Y
Altcode: 2002astro.ph..9493Y
The CHIANTI atomic database contains atomic energy levels, wavelengths,
radiative transition probabilities, and electron excitation data for
a large number of ions of astrophysical interest. Version 4 has been
released, and proton excitation data are now included, principally
for ground configuration levels that are close in energy. The fitting
procedure for excitation data, both electrons and protons, has been
extended to allow nine-point spline fits in addition to the previous
five-point spline fits. This allows higher quality fits to data from
close-coupling calculations where resonances can lead to significant
structure in the Maxwellian-averaged collision strengths. The effects
of photoexcitation and stimulated emission by a blackbody radiation
field in a spherical geometry on the level balance equations of
the CHIANTI ions can now be studied following modifications to the
CHIANTI software. With the addition of H I, He I, and N I, the first
neutral species have been added to CHIANTI. Many updates to existing
ion data sets are described, while several new ions have been added
to the database, including Ar IV, Fe VI, and Ni XXI. The two-photon
continuum is now included in the spectral synthesis routines, and a
new code for calculating the relativistic free-free continuum has been
added. The treatment of the free-bound continuum has also been updated.
Title: CHIANTI - An Atomic Database for XUV Emission Lines
Authors: Landi, Enrico; Dere, Ken P.; Landini, Massimo; Young, Peter
R.; Mason, Helen E.; del Zanna, Giulio
Bibcode: 2003IAUJD..17E..10L
Altcode:
CHIANTI is a database of atomic data and transition rates necessary for
calculating synthetic spectra and carrying out plasma diagnostics of
astrophysical sources in the X-ray EUV and UV wavelength ranges. CHIANTI
includes both line and continuum emission from all astrophysically
abundant elements in the universe. All data are taken from refereed
literature and are critically assessed. CHIANTI also includes a suite
of IDL programs that allow spectroscopic analysis to be carried
out. CHIANTI data and software are freely distributed over the
internet. In the present talk I will describe the contents of
the CHIANTI database its current status and the areas where CHIANTI
is being developed and I will also present a comparison of CHIANTI
predictions with the X-ray emission from astrophysical sources.
Title: Active Region Studies with SOHO-CDS
Authors: Mason, H. E.; Del Zanna, G.
Bibcode: 2002ASPC..277...37M
Altcode: 2002sccx.conf...37M
No abstract at ADS
Title: CHIANTI: Application to X-ray High Resolution Spectroscopy
Authors: del Zanna, G.
Bibcode: 2002hrxs.confE..12D
Altcode:
The new Version 4 (released in 2002) of the CHIANTI atomic database
and software is briefly described. New atomic calculations for ions
important in the X-rays are included, together with proton rates,
new relativistic continuum calculations and photoexcitation. The
application of CHIANTI atomic data to Chandra stellar X-ray spectra
is presented, together with comparisons with other spectral codes such
as APED and SPEX.
Title: EUV spectral observations of active region flares
Authors: Del Zanna, G.; Mason, H. E.; Foley, C.
Bibcode: 2002ESASP.506..585D
Altcode: 2002svco.conf..585D; 2002ESPM...10..585D
We present EUV spectral observations of C-M class flares performed
with the Coronal Diagnostic Spectrometer (CDS) onboard SOHO during the
Cambridge active region (AR) campaigns in 1999 and 2001. With the CDS
spectral data, complemented by other space observations (mainly TRACE,
YOHKOH SXT), we investigate the physical properties of ARs, and study
the development of small-scale flares. We discuss the importance of
spectral observations in relation to the correct interpretation of
broad band images. In particular, we present co-spatial simultaneous
YOHKOH SXT and CDS flare observations and discuss the validity of the
temperatures derived from the SXT filter ratios. In addition, we present
sample results that can only be obtained with spectral data, such as
measurements of densities, elemental abundances and post-flare flows,
associated with slow chromospheric evaporation. All these results are
important observational constraints for flare modeling.
Title: Solar and stellar high-resolution X-ray spectra: plasma
diagnostics with the CHIANTI atomic database
Authors: Del Zanna, G.; Mason, H. E.
Bibcode: 2002ASPC..277..333D
Altcode: 2002sccx.conf..333D
No abstract at ADS
Title: The Structure and Evolution of a Sigmoidal Active Region
Authors: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.;
Mason, H. E.; Mandrini, C. H.; Démoulin, P.; Gilbert, H.; Burkepile,
J.; Holzer, T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder,
B.; Thompson, B. J.
Bibcode: 2002ApJ...574.1021G
Altcode:
Solar coronal sigmoidal active regions have been shown to be precursors
to some coronal mass ejections. Sigmoids, or S-shaped structures,
may be indicators of twisted or helical magnetic structures, having
an increased likelihood of eruption. We present here an analysis of a
sigmoidal region's three-dimensional structure and how it evolves in
relation to its eruptive dynamics. We use data taken during a recent
study of a sigmoidal active region passing across the solar disk
(an element of the third Whole Sun Month campaign). While S-shaped
structures are generally observed in soft X-ray (SXR) emission, the
observations that we present demonstrate their visibility at a range of
wavelengths including those showing an associated sigmoidal filament. We
examine the relationship between the S-shaped structures seen in SXR
and those seen in cooler lines in order to probe the sigmoidal region's
three-dimensional density and temperature structure. We also consider
magnetic field observations and extrapolations in relation to these
coronal structures. We present an interpretation of the disk passage
of the sigmoidal region, in terms of a twisted magnetic flux rope
that emerges into and equilibrates with overlying coronal magnetic
field structures, which explains many of the key observed aspects of
the region's structure and evolution. In particular, the evolving flux
rope interpretation provides insight into why and how the region moves
between active and quiescent phases, how the region's sigmoidicity is
maintained during its evolution, and under what circumstances sigmoidal
structures are apparent at a range of wavelengths.
Title: Spectroscopic diagnostics of stellar transition regions and
coronae in the XUV: AU Mic in quiescence
Authors: Del Zanna, G.; Landini, M.; Mason, H. E.
Bibcode: 2002A&A...385..968D
Altcode:
In this paper we review the spectroscopic diagnostic techniques that
can be applied to XUV observations of active stars. In particular, we
discuss methods for the determination of electron densities, emission
measures and the chemical composition of the stellar transition regions
and coronae. We pay particular attention to the atomic data used and
we revise several previous analyses with the most recent atomic data
(from CHIANTI). We find severe limitations to some of the commonly used
methods and atomic data and we obtain results which are significantly
different from other authors. We illustrate this with a number of
examples. We analyse a combined set of multi-wavelength observations
(EUVE, HST/STIS, FUSE) for the quiescent phase of the dMe star AU Mic. A
major conclusion of this paper is that the use of spectral lines from
the Li and Na isoelectronic sequences, common in previous literature,
produces erroneous results in the determination of emission measures,
elemental abundances and transition region densities.
Title: The Use of Atomic Data for the In-flight Calibration of the
CDS Spectrometers
Authors: Del Zanna, G.
Bibcode: 2002ISSIR...2..283D
Altcode: 2002rcs..conf..283D; 2002ESASR...2..283D
I describe a general method that has been used for the in-flight
cross-calibration of the CDS spectrometers. This method relies
on accurate atomic data and uses the Sun as a "calibration'
source. It was successfully applied in the past to calibrate other
EUV spectrometers. The results show significant differences from the
laboratory calibration, good agreement with the calibrations based on
two rocket-flights flown in 1997 and excellent stability of the CDS
instrument during the same year. It is suggested that this method be
used to monitor the in-flight calibration of future EUV spectrometers.
Title: Sigmoidal diagnostics with SOHO/CDS
Authors: Del Zanna, G.; Gibson, S. E.; Mason, H. E.; Pike, C. D.;
Mandrini, C. H.
Bibcode: 2002AdSpR..30..551D
Altcode:
During the third Whole Sun Month Campaign (August 18 - September 14,
1999), the evolution of the active region NOAA 8668 was followed
during its meridian passage and at the limb (Sigmoid JOP 106),
with simultaneous observations with the Solar and Heliospheric
Observatory (SOHO), and with other instruments, both satellite
and ground-based. On August 21st, a small flare, associated with
a brightening of the sigmoidal structure, occurred. SOHO Coronal
Diagnostic Spectrometer (CDS) observations of this small flare are
presented. Coronal temperatures and densities of the sigmoid are
estimated. High transition region densities (in the range 2.5-7 × 10
11 cm -3), obtained using O IV, are present in
the brightenings associated with the flare. At coronal level, high
temperatures of at least 8 MK were reached, as shown by strong Fe
XIX emission. After this small flare, relatively strong blue-shifts
(⋍ 30 km/s) are observed in coronal lines, located at the two ends
of a small loop system associated with the sigmoid.
Title: The solar corona in cycle 23
Authors: Fludra, A.; Ireland, J.; Del Zanna, G.; Thompson, W. T.
Bibcode: 2002AdSpR..29..361F
Altcode:
The Coronal Diagnostic Spectrometer (CDS) on SOHO has been recording
EUV spectra and monitoring time variability of EUV line intensities,
electron temperature and density in the low solar corona during the
rising part of Cycle 23. The four-year data set includes daily synoptic
observations in four EUV lines along the central meridian since April
1996 and weekly diagnostic observations above the polar coronal holes
since July 1997. The history of line intensities along the central
meridian, and radial profiles of electron temperature and density above
the polar regions at heights up to 1.15 R⊙ are derived. EUV
line intensities and photospheric magnetic flux are also calculated
for 50 active regions observed from 1996 to June 1998. Variability of
temperature, density, and EUV spectral line intensities in the polar
coronal holes, quiet sun and active regions with the solar cycle is
discussed. Power-law relationships among the EUV line intensities from
the CDS synoptic data, and also between the EUV line intensities and
magnetic field flux in active regions are presented.
Title: The CHIANTI Atomic Database and Instrument Calibration:
a Symbiosis
Authors: Mason, H. E.; Del Zanna, G.; Dere, K. P.; Landi, E.; Landini,
M.; Young, P. R.
Bibcode: 2002ISSIR...2..271M
Altcode: 2002ESASR...2..271M; 2002rcs..conf..271M
The CHIANTI atomic database comprises a comprehensive, accurate and
up-to-date database of atomic parameters, necessary for emission-line
spectroscopy. The suite of user-friendly software allows plasma
diagnostics to be carried out. Since its release in 1996, CHIANTI has
become a standard resource for the analysis of solar spectra. Accurate
atomic data can provide the foundation for in-flight instrument
calibrations. Conversely, an accurate instrument calibration can provide
a check on atomic parameters. The internal consistency of spectral-line
intensities can be used to highlight specific anomalies. In this paper,
we illustrate how CHIANTI has been used to validate the calibration of
solar EUV instruments: SOHO-CDS, -SUMER, -EIT and SERTS. In addition,
we show how anomalous spectral-line intensities indicate the need for
more accurate atomic calculations.
Title: Coronal and solar wind elemental abundances
Authors: Raymond, J. C.; Mazur, J. E.; Allegrini, F.; Antonucci, E.;
Del Zanna, G.; Giordano, S.; Ho, G.; Ko, Y. -K.; Landi, E.; Lazarus,
A.; Parenti, S.; Poletto, G.; Reinard, A.; Rodriguez-Pacheco, J.;
Teriaca, L.; Wurz, P.; Zangrilli, L.
Bibcode: 2001AIPC..598...49R
Altcode: 2001sgc..conf...49R
Coronal elemental abundances, as compared with abundances in the solar
wind and solar energetic particles, provide the means for connecting
solar wind gas with its coronal source. Comparison of coronal abundances
with photospheric values shows fractionation with the ionization
potential of the atom, providing important, though not yet fully
understood, information about the exchange of material between corona
and chromosphere. Fractionation due to gravitational settling provides
clues about flows within the corona. In this paper, we discuss the
uncertainties of abundance determinations with spectroscopic techniques
and in situ measurements, we survey the ranges of abundance variations
in both the corona and solar wind, and we discuss the progress in
correlating solar wind features with their coronal sources. .
Title: Solar EUV spectroscopic observations with SOHO/CDS. I. An
in-flight calibration study
Authors: Del Zanna, G.; Bromage, B. J. I.; Landi, E.; Landini, M.
Bibcode: 2001A&A...379..708D
Altcode:
An in-flight calibration study of the Coronal Diagnostic Spectrometer
(CDS) instrument on board SOHO (Solar and Heliospheric Observatory) is
presented. The relative intensity calibration of CDS is a fundamental
requirement for deriving important physical parameters of the solar
transition region and corona from the observations. This comprehensive
study provides the first complete in-flight relative calibration
of all nine CDS channels, first and second order. This has been
achieved with the use of a spectroscopic calibration method, mainly
based on the comparison between observed line ratios and theoretical
predictions provided by the CHIANTI atomic database. The calibration
method has been applied to a large number of observations (on-disc,
off-limb, quiet sun, active region), to enable the use of a wide
range of spectral lines from low to high temperatures of formation. The
results are compared to the pre-launch calibration and other post-launch
studies. Significant differences with the ground calibration results are
found, while there is good agreement with the post-launch studies, based
on rocket flights. It is also shown that the relative calibration has
not significantly changed over a long period of time, thus confirming
the excellent stability of the CDS instrument.
Title: Elemental abundances of the low corona as derived from
SOHO/CDS observations
Authors: Del Zanna, G.; Bromage, B. J. I.; Mason, H. E.
Bibcode: 2001AIPC..598...59D
Altcode: 2001sgc..conf...59D
No abstract at ADS
Title: CHIANTI-An Atomic Database for Emission Lines. IV. Extension
to X-Ray Wavelengths
Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G.
Bibcode: 2001ApJS..134..331D
Altcode:
CHIANTI provides a database of atomic energy levels, wavelengths,
radiative transition probabilities, and electron excitation data for
a large number of ions of astrophysical interest. It also includes a
suite of Interactive Data Language programs to calculate optically
thin synthetic spectra and to perform spectral analysis and plasma
diagnostics. This database allows the calculation of theoretical line
emissivities necessary for the analysis of optically thin emission-line
spectra. The first version (1.01) of the CHIANTI database was released
in 1996 and published by Dere et al. in 1997 as Paper I in this
series. The second version, released in 1999 by Landi et al., included
continuum emission and data for additional ions. Both versions of the
CHIANTI database have been used extensively by the astrophysical and
solar communities to analyze emission-line spectra from astrophysical
sources. Now the CHIANTI database has been extended to wavelengths
shorter than 50 Å by including atomic data for the hydrogen and helium
isoelectronic sequences, inner-shell transitions and satellite lines,
and several other ions. In addition, some of the ions already present
in the database have been updated and extended with new atomic data
from published calculations.
Title: CHIANTI - an atomic database for emission lines, Paper 4:
Extension to X-ray Wavelengths
Authors: Dere, K. P.; Landi, E.; Young, P. R.; Del Zanna, G.
Bibcode: 2001AGUSM..SP21B08D
Altcode:
CHIANTI provides a database of atomic energy levels, wavelengths,
radiative transition probabilities and electron excitation data for
a large number of ions of astrophysical interest. It also includes
a suite of Interactive Data Language (IDL) programs to calculate
optically thin synthetic spectra and to perform spectral analysis and
plasma diagnostics. This database allows the calculation of theoretical
line emissivities necessary for the analysis of optically thin emission
line spectra. The first version of the CHIANTI database was released
in 1996 (Dere et al., 1996). The second version, released in 1999,
included continuum emission and data for additional ions (Landi
et al. 1999). Both versions of the CHIANTI database have been used
extensively by the astrophysical and solar communities to analyze
emission line spectra from astrophysical sources. Now the CHIANTI
database has been extended to wavelengths shorter than 50Å by including
atomic data for the hydrogen and helium isoelectronic sequences,
inner-shell transitions and satellite lines and several other ions. In
addition, some of the ions already present in the database have been
updated and extended with new atomic data from published calculations.
Title: EUV Macrospicule in an Off-Limb Observation of the Solar
South Coronal Hole (CD-ROM Directory: contribs/parenti)
Authors: Parenti, S.; Bromage, G. E.; Del Zanna, G.; Bromage, B. J. I.
Bibcode: 2001ASPC..223..715P
Altcode: 2001csss...11..715P
No abstract at ADS
Title: Extreme ultraviolet spectroscopy of the solar corona
Authors: del Zanna, G.
Bibcode: 2000Obs...120..291D
Altcode:
No abstract at ADS
Title: Structure of a Large low-Latitude Coronal Hole
Authors: Bromage, B. J. J.; Alexander, D.; Breen, A.; Clegg, J. R.;
Del Zanna, G.; DeForest, C.; Dobrzycka, D.; Gopalswamy, N.; Thompson,
B.; Browning, P. K.
Bibcode: 2000SoPh..193..181B
Altcode:
Coronal holes on the Sun are the source of high-speed solar wind
streams that produce magnetic disturbances at the Earth. A series
of multi-wavelength, multi-instrument observations obtained during
the 1996 `Whole Sun Month' campaign examined a large coronal hole in
greater detail than ever before. It appeared on the Sun in August, and
extended from the north pole to a large active region in the southern
hemisphere. Its physical and magnetic structure and subsequent evolution
are described.
Title: The CHIANTI atomic database: extension to the X-rays
Authors: del Zanna, G.; et al.
Bibcode: 2000IAUJD...1E..37D
Altcode:
The CHIANTI atomic database consists of a critically evaluated set of
atomic data (energy levels, radiative data, wavelengths, and electron
collisional excitation rates) necessary to calculate the emission line
spectrum of astrophysical optically-thin plasmas. IN the past few
years, CHIANTI has been extensively used in the EUV for calibration
and plasma diagnostics. This database has now been extended in the 1 -
50 Å wavelength region, to include all the significant emission lines
(Dere et al., 2000). Comparisons of CHIANTI predicted line intensities
with high-resolution X-ray solar (SMM/FCS, SOLEX) and stellar (Chandra
HETG) spectra are presented here, to provide an assessment of the
completeness and reliability of the most recent atomic data.
Title: A SOHO/CDS Observation of a Macrospicule in the South
Coronal Hole
Authors: Parenti, S.; Del Zanna, G.; Bromage, B. J. I.
Bibcode: 1999ESASP.448..623P
Altcode: 1999mfsp.conf..623P; 1999ESPM....9..623P
No abstract at ADS
Title: Asymmetries Across a Coronal Hole Extension
Authors: Clegg, J. R.; Browning, P. K.; del Zanna, G.; Bromage,
B. J. I.
Bibcode: 1999ESASP.448.1159C
Altcode: 1999ESPM....9.1159C; 1999mfsp.conf.1159C
No abstract at ADS
Title: SOHO/CDS Observations of Plumes in Coronal Holes
Authors: Del Zanna, G.; Bromage, B. J. I.
Bibcode: 1999ESASP.448.1171D
Altcode: 1999ESPM....9.1171D; 1999mfsp.conf.1171D
No abstract at ADS
Title: CHIANTI: A database for astrophysical emission line
spectroscopy
Authors: Del-Zanna, Giulio; Young, Peter; Dere, Ken; Landini, Massimo;
Landi, Enrico; Mason, Helen
Bibcode: 1999ascl.soft11004D
Altcode:
CHIANTI consists of a critically evaluated set of atomic data necessary
to calculate the emission line spectrum of astrophysical plasmas. The
data consists of atomic energy levels, atomic radiative data such as
wavelengths, weighted oscillator strengths and A values, and electron
collisional excitation rates. A set of programs that use these data to
calculate the spectrum in a desired wavelength range as a function of
temperature and density are also provided. These programs have been
written in Interactive Data Language (IDL) and descriptions of these
various programs are provided on the website.
Title: A Direct Comparison Between EUV Coronal Flux And He Resonance
Line Photon Flux From SOHO/CDS Data
Authors: Andretta, V.; Landi, Enrico; Del Zanna, Giulio; Jordan,
Stuart D.
Bibcode: 1999ESASP.446..123A
Altcode: 1999soho....8..123A
In the wealth of EUV spectroscopic and imaging data gathered by the
SOHO and TRACE missions, a prominent role is played by the helium
resonance emission. For example, He I lines are among the most intense
features in CDS/NIS spectra, while the EIT 304 waveband (dominated by
He II emission) is routinely employed to map the structure of the solar
chromosphere and transition region. However, no 'standard' model has
emerged so far that is able to interpret observed He spectra/images
to a satisfactory degree of self-consistency. Recent research on
the problem of the formation of the solar helium spectrum tends to
rule out a dominant role of coronal radiation in exciting He resonance
lines. However, while evidence for this result is strong, it is based on
indirect tests. Here we present a more direct assessment of this issue
by directly measuring the photon photoionizing EUV flux measured with
CDS/GIS-NIS1. This measure can be directly compared with the observed
flux in the main He I and He II resonance lines observed with CDS/NIS2.
Title: Transition Region Densities And Abundances As Derived From
SOHO/CDS Observations.
Authors: Del Zanna, G.; Bromage, B. J. I.
Bibcode: 1999ESASP.446..269D
Altcode: 1999soho....8..269D
On-disc EUV observations of the solar corona and transition region
with the Coronal Diagnostic Spectrometer (CDS) on SOHO are presented
and discussed. Spectroscopic diagnostic techniques using the CHIANTI
atomic database are applied to give an estimate of plasma parameters
such as electron density (from density-sensitive line ratios) and
relative element abundances in the transition region. Transition
region densities present consistently higher values in the network,
compared to the cell-centre areas. Various methods for deriving
element abundances (when studying the FIP effect) from EUV spectra
are compared and their limitations presented. Elemental abundances
are derived from transition region emission lines and discussed in
relation to the magnetic structure of the observed features (quiet sun,
coronal holes and plumes).
Title: Solar minimum streamer densities and temperatures using Whole
Sun Month coordinated data sets
Authors: Gibson, S. E.; Fludra, A.; Bagenal, F.; Biesecker, D.;
del Zanna, G.; Bromage, B.
Bibcode: 1999JGR...104.9691G
Altcode:
We model electron densities of the simplest, most symmetric solar
minimum streamer structure observed during the Whole Sun Month (WSM)
campaign, using coronal observations of both visible white light and
extreme ultraviolet (EUV) emission. Using white light data from the
SOHO/LASCO/C2 and HAO/Mauna Loa Mark 3 coronagraphs, we determine
electron densities by way of a Van de Hulst inversion. We compare the
white light densities to those determined from the density sensitive
EUV line ratios of Si IX 350/342 Å observed by the SOHO/coronal
diagnostic spectrometer (CDS). Moreover, from the white light density
profiles we calculate hydrostatic temperature profiles and compare
to temperatures derived from the Si XII/Mg X line ratio. We find
the white light and spectral analysis produce consistent density and
temperature information.
Title: The Elephant's Trunk: Spectroscopic diagnostics applied to
SOHO/CDS observations of the August 1996 equatorial coronal hole
Authors: Del Zanna, G.; Bromage, B. J. I.
Bibcode: 1999JGR...104.9753D
Altcode:
A large equatorial coronal hole, named the ``Elephant's Trunk,''
was observed by the coronal diagnostic spectrometer (CDS) on board
the Solar and Heliospheric Observatory (SOHO) during the last
week of August 1996. Spatially averaged spectra within the hole
and in neighboring quiet sun regions are analyzed and calibrated
in intensity. Spectroscopic diagnostic techniques that make
use of the CHIANTI atomic database are applied in an attempt to
characterize such large-scale features. Line intensity ratios are
used to obtain information on the electron density, temperature,
and element abundances inside and outside the coronal hole. The
transequatorial coronal hole showed, on average, coronal electron
densities Ne~=2-3×108cm-3, a factor of
2 higher than the quiet sun areas near the hole. A differential emission
measure analysis shows that emission measures in the coronal hole were
much lower at temperatures above a million degrees than in the quiet sun
regions. In the Elephant's Trunk, the temperature of peak emission is
found to be ~=8×105K, compared to about 9.7×105K
in the quiet sun. Indications of a first ionization potential (FIP)
effect differentiating between cell centers and the network are found,
both in coronal hole and quiet sun regions. A small plume was detected
inside the Elephant's Trunk coronal hole at low latitude, on the disc.
Title: Electron density and temperature of the lower solar corona
Authors: Fludra, A.; Del Zanna, G.; Alexander, D.; Bromage, B. J. I.
Bibcode: 1999JGR...104.9709F
Altcode:
Off limb observations of the quiet Sun corona were made with the
Coronal Diagnostic Spectrometer (CDS) on SOHO during the Whole Sun
Month campaign in August 1996. Selected spectral lines in the Normal
Incidence range were recorded up to 1.2 solar radii above the east
and west limb and above the polar coronal holes. Intensities of the
coronal lines covering the temperature range from 9×105
to 2×106K have been measured and used to derive
electron temperature and electron density as a function of the
radial distance above the solar limb. Results from the east and
west equatorial regions and polar coronal holes are compared. The
temperature and density in the coronal holes is found to be lower
than in the closed field regions. A density-sensitive line ratio
of Si IX 350/342 Å is used to derive an average electron density
which is found to decrease from 5×108cm-3 near
the limb to 1×108cm-3 at 1.15RS,
in the equatorial region. Over the polar coronal holes, where
polar plumes dominate the emission close to the limb, the density
varies from 2×108cm-3 at the limb to
6×107cm-3 at 1.1RS. The
lowest density found inside the coronal hole on the disk is
9.9×107cm-3. An increase in the quiet Sun
temperature with the radial distance is found from the Si XII/Mg
X and Si XII/Mg IX line ratios, and an increase in the coronal
hole temperature is seen from the Mg X/Mg IX ratio. The Si XII/Mg
X temperature varies from 1.1×106K at r=RS
to 1.4×106K at r=1.2RS in the equatorial
regions. The EUV emission is compared with that of the soft X rays as
measured by the Yohkoh SXT. The densities and temperatures determined
from the SXT show a similar behavior to that determined from the
CDS. Density and temperature, averaged over a position angle range of
20-54°, show very little variation over a period of 20 days.
Title: Relative intensity calibration of CDS-GIS detectors on SOHO
using a plasma diagnostic technique
Authors: Landi, E.; Del Zanna, G.; Breeveld, E. R.; Landini, M.;
Bromage, B. J. I.; Pike, C. D.
Bibcode: 1999A&AS..135..171L
Altcode:
The internal intensity calibration of the Coronal Diagnostic
Spectrometer (CDS) - Grazing Incidence Spectrometer (GIS) is studied
using the Arcetri diagnostic method. A large number of spectral lines
observed by the four GIS detectors in solar active and quiet regions is
analysed in order to determine the relative intensity calibration curve
of the instrument. The plasma diagnostic method developed in Arcetri
allows the measurement of the correction factors to the pre-flight
CDS - GIS internal intensity calibration curves and of the relative
calibration between different detectors. No gross deviations from the
pre-flight calibration are found. Also the GIS 3 and GIS 4 second order
sensitivites are measured. The problems of fixed patterning, ghosting,
anomalous line profiles and widths are also discussed, and a list of
lines suitable for further diagnostic studies with GIS is presented.