harrison

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Author name code: harrison
ADS astronomy entries on 2022-09-14
author:"Harrison, Richard A."

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Title: Micromagnetic Modes of Anisotropy of Magnetic Susceptibility
in Natural Magnetite Particles
Authors: Nikolaisen, Even S.; Fabian, Karl; Harrison, Richard; McEnroe,
Suzanne A.
2022GeoRL..4999758N Altcode:
Anisotropy of magnetic susceptibility (AMS) is commonly used
to assess sedimentation, deformation, tectonics, rock fabric,
and texture. Using focused-ion beam nanotomography, we develop a
micromagnetic method to investigate the AMS of individual magnetite
inclusions in silicates across the transition between single-domain
(SD) to multidomain behavior. We calculate individual AMS tensors
by modeling the magnetization response of a particle to weak applied
fields in three orthogonal directions. The main AMS mode of elongated
SD particles is not a homogeneous magnetization rotation, but focused
alignment of spins at their edges and tips. In single-vortex particles,
vortex displacement is the dominant AMS mode, which focuses the largest
magnetization changes in a planar region containing the vortex core,
and perpendicular to the direction of vortex motion. In multi-vortex
structures a combined motion of all vortex centers can lead to high
degrees of anisotropy when some motion patterns are energetically much
easier to achieve than others.

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Title: Calcium-Aluminum-Rich Inclusion Paleomagnetism: A Theoretical
Perspective
Authors: Bai, X. -N.; Borlina, C. S.; Weiss, B. P.; Mansbach, E. N.;
Chatterjee, N.; Tung, P.; Harrison, R.; Lima, E. A.; Tissot, F. L. H.;
McKeegan, K. D.
2022LPICo2678.2000B Altcode:
We theoretically estimate the paleomagnetic field recorded by the
CAIs following FUor-like outbursts to be 30-300 µT, well agreeing
with recent measurements.

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Title: Paleomagnetism of Calcium-Aluminum-Rich Inclusions
Authors: Borlina, C. S.; Weiss, B. P.; Bai, X.; Mansbach, E. N.;
Chatterjee, N.; Tung, P.; Harrison, R.; Lima, E. A.; Tissot, F. L. H.;
McKeegan, K. D.
2022LPICo2678.1913B Altcode:
The paleomagnetism of calcium-aluminum-rich inclusions suggest they
acquired their magnetization beyond 8 AU due to magnetized disk winds
or stellar outbursts.

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Title: Comparing the Heliospheric Cataloging, Analysis, and Techniques
Service (HELCATS) Manual and Automatic Catalogues of Coronal Mass
Ejections Using Solar Terrestrial Relations Observatory/Heliospheric
Imager (STEREO/HI) Data
Authors: Rodriguez, L.; Barnes, D.; Hosteaux, S.; Davies, J. A.;
Willems, S.; Pant, V.; Harrison, R. A.; Berghmans, D.; Bothmer, V.;
Eastwood, J. P.; Gallagher, P. T.; Kilpua, E. K. J.; Magdalenic, J.;
Mierla, M.; Möstl, C.; Rouillard, A. P.; Odstrčil, D.; Poedts, S.
2022SoPh..297...23R Altcode:
We present the results of a comparative study between automatic
and manually compiled coronal mass ejection (CME) catalogues based
on observations from the Heliospheric Imagers (HIs) onboard NASA's
Solar Terrestrial Relations Observatory (STEREO) spacecraft. Using
the Computer Aided CME Tracking software(CACTus), CMEs are identified
in HI data using an automatic feature-detection algorithm, while
the Heliospheric Imagers Catalogue(HICAT) includes CMEs that are
detected by visual inspection of HI images. Both catalogues were
compiled as part of the EU FP7 Heliospheric Cataloguing, Analysis and
Techniques Service (HELCATS) project (www.helcats-fp7.eu). We compare
observational parameters of the CMEs from CACTus to those listed in
HICAT, such as CME frequency, position angle (PA), and PA-width. We
also compare CACTus-derived speeds to speeds derived from applying
geometric modelling to the majority of the HICAT CMEs, the results
of which are listed in the HELCATS Heliospheric Imagers Geometric
Catalogue(HIGeoCAT). We find that both CACTus and HICAT catalogues
contain a similar number of events when we exclude events narrower than
20∘, which are not included in the HICAT catalogue but are
found to be identified by CACTus. PA-distributions are strongly peaked
around 90∘ and 270∘, with a slightly larger
CME frequency northwards of the equatorial plane (particularly for the
STEREO-A versions of both catalogues). The CME PA-widths in both HICAT
and CACTus catalogues peak at approximately 60∘. Manually
derived speeds from HIGeoCAT and automatically derived speeds by
CACTus correlate well for values lower than 1000 km s−1,
in particular when CMEs are propagating close to the plane of the sky.

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Title: Multipoint Interplanetary Coronal Mass Ejections Observed with
Solar Orbiter, BepiColombo, Parker Solar Probe, Wind, and STEREO-A
Authors: Möstl, Christian; Weiss, Andreas J.; Reiss, Martin A.;
Amerstorfer, Tanja; Bailey, Rachel L.; Hinterreiter, Jürgen; Bauer,
Maike; Barnes, David; Davies, Jackie A.; Harrison, Richard A.;
Freiherr von Forstner, Johan L.; Davies, Emma E.; Heyner, Daniel;
Horbury, Tim; Bale, Stuart D.
2022ApJ...924L...6M Altcode: 2021arXiv210907200M
We report the result of the first search for multipoint in situ
and imaging observations of interplanetary coronal mass ejections
(ICMEs) starting with the first Solar Orbiter (SolO) data in 2020
April-2021 April. A data exploration analysis is performed including
visualizations of the magnetic-field and plasma observations made
by the five spacecraft SolO, BepiColombo, Parker Solar Probe (PSP),
Wind, and STEREO-A, in connection with coronagraph and heliospheric
imaging observations from STEREO-A/SECCHI and SOHO/LASCO. We identify
ICME events that could be unambiguously followed with the STEREO-A
heliospheric imagers during their interplanetary propagation to
their impact at the aforementioned spacecraft and look for events
where the same ICME is seen in situ by widely separated spacecraft. We
highlight two events: (1) a small streamer blowout CME on 2020 June 23
observed with a triple lineup by PSP, BepiColombo and Wind, guided by
imaging with STEREO-A, and (2) the first fast CME of solar cycle 25
(≍1600 km s-1) on 2020 November 29 observed in situ by
PSP and STEREO-A. These results are useful for modeling the magnetic
structure of ICMEs and the interplanetary evolution and global shape
of their flux ropes and shocks, and for studying the propagation of
solar energetic particles. The combined data from these missions are
already turning out to be a treasure trove for space-weather research
and are expected to become even more valuable with an increasing number
of ICME events expected during the rise and maximum of solar cycle 25.

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Title: Exploring the dynamics of inward core solidification using
analogue tank experiments.
Authors: Dodds, Kathryn; Bryson, James; Neufeld, Jerome; Harrison,
Richard
2021AGUFMDI34B..05D Altcode:
Given their small sizes and low central pressures, the cores of
asteroids are expected to have started crystallizing at the core
mantle boundary (CMB) instead of at their centre like the Earth. This
behaviour is also predicted for Ganymede and has prompted the
development of the iron snow model to explain its observed dynamo
field, in which iron crystals that grow at the CMB in a snow zone
and subsequently sink into the hotter interior and melt, releasing
dense fluid that drives convection. However, whether this process
could have occurred in asteroidal cores is uncertain due to the small
adiabatic temperature difference between the CMB and the centre of
their cores. Instead, the power for this compositional dynamo may
have come from an increase in convective velocities caused by the
addition of dense crystals at the CMB or turbulence caused by the
settling of the crystals themselves. In this study we use analogue tank
experiments to explore the possible dynamo driving mechanisms during
inward asteroid core crystallisation. Ammonium chloride solution is
cooled from above with a layer of buoyant propanol separating the
solution from the cold plate to prevent the growth of crystals on
this boundary. For a given temperature difference across this layer,
we compare the convective velocities with and without crystallization
to quantify the effect of the additional buoyancy flux on the fluid
flow and to develop a scaling law that we implement in our thermal
models of asteroid evolution. Previous models have suggested that the
CMB heat flux could be sub- or super-adiabatic at the start of core
crystallization, depending on the core size and its sulfur content,
which we account for by varying the driving temperature difference in
the tank. A complete upcoming dataset will allow us to quantify the
mechanisms by which inward core solidification could generate a dynamo
field. We also record the temperature and composition as a function of
depth in the tank, enabling us to determine whether thermal equilibrium
is maintained. This allows us to assess whether thermal equilibrium
can be assumed when modelling snow zones in cores, a problem that is
also relevant to larger planetary bodies cores (e.g. Ganymede, Mars,
the Moon, the early Earth). Initial results suggest that thermal
equilibrium is maintained, validating this key assumption.

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Title: In situ multi-spacecraft and remote imaging observations of
the first CME detected by Solar Orbiter and BepiColombo
Authors: Davies, E. E.; Möstl, C.; Owens, M. J.; Weiss, A. J.;
Amerstorfer, T.; Hinterreiter, J.; Bauer, M.; Bailey, R. L.; Reiss,
M. A.; Forsyth, R. J.; Horbury, T. S.; O'Brien, H.; Evans, V.;
Angelini, V.; Heyner, D.; Richter, I.; Auster, H. -U.; Magnes, W.;
Baumjohann, W.; Fischer, D.; Barnes, D.; Davies, J. A.; Harrison, R. A.
2021A&A...656A...2D Altcode: 2020arXiv201207456D
Context. On 2020 April 19 a coronal mass ejection (CME) was detected in
situ by Solar Orbiter at a heliocentric distance of about 0.8 AU. The
CME was later observed in situ on April 20 by the Wind and BepiColombo
spacecraft whilst BepiColombo was located very close to Earth. This
CME presents a good opportunity for a triple radial alignment study,
as the spacecraft were separated by less than 5° in longitude. The
source of the CME, which was launched on April 15, was an almost
entirely isolated streamer blowout. The Solar Terrestrial Relations
Observatory (STEREO)-A spacecraft observed the event remotely from
−75.1° longitude, which is an exceptionally well suited viewpoint
for heliospheric imaging of an Earth directed CME. Aims: The
configuration of the four spacecraft has provided an exceptionally clean
link between remote imaging and in situ observations of the CME. We
have used the in situ observations of the CME at Solar Orbiter, Wind,
and BepiColombo and the remote observations of the CME at STEREO-A to
determine the global shape of the CME and its evolution as it propagated
through the inner heliosphere. Methods: We used three magnetic
flux rope models that are based on different assumptions about the
flux rope morphology to interpret the large-scale structure of the
interplanetary CME (ICME). The 3DCORE model assumes an elliptical
cross-section with a fixed aspect-ratio calculated by using the STEREO
Heliospheric Imager (HI) observations as a constraint. The other two
models are variants of the kinematically-distorted flux rope (KFR)
technique, where two flux rope cross-sections are considered: one in a
uniform solar wind and another in a solar-minimum-like structured solar
wind. Analysis of CME evolution has been complemented by the use of (1)
the ELEvoHI model to compare predicted CME arrival times and confirm
the connection between the imaging and in situ observations, and (2)
the PREDSTORM model, which provides an estimate of the Dst index at
Earth using Solar Orbiter magnetometer data as if it were a real-time
upstream solar wind monitor. Results: A clear flattening of the
CME cross-section has been observed by STEREO-A, and further confirmed
by comparing profiles of the flux rope models to the in situ data, where
the distorted flux rope cross-section qualitatively agrees most with in
situ observations of the magnetic field at Solar Orbiter. Comparing in
situ observations of the magnetic field between spacecraft, we find
that the dependence of the maximum (mean) magnetic field strength
decreases with heliocentric distance as r−1.24 ± 0.50
(r−1.12 ± 0.14), which is in disagreement with previous
studies. Further assessment of the axial and poloidal magnetic field
strength dependencies suggests that the expansion of the CME is likely
neither self-similar nor cylindrically symmetric.

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Title: Multipoint ICME events during the first 1.5 years of combined
Solar Orbiter, BepiColombo, Parker Solar Probe, Wind and STEREO-A
observations
Authors: Moestl, Christian; Weiss, Andreas; Reiss, Martin; Bailey,
Rachel; Amerstorfer, Tanja; Hinterreiter, Jurgen; Bauer, Maike;
Barnes, David; Harrison, Richard; Davies, Jackie; Heyner, Daniel
2021AGUFMSH15A2027M Altcode:
We show in multipoint situ observations of interplanetary coronal
mass ejections (ICMEs) starting with Solar Orbiter operations
in April 2020. We demonstrate visualizations of the magnetic
field and plasma observations by the 5 spacecraft Solar Orbiter,
BepiColombo, Parker Solar Probe, Wind and STEREO-A, in connection
with heliospheric imager observations from STEREO-A. We identify ICME
events that (1) could be unambiguously followed from their inception
on the Sun to their impact at the aforementioned spacecraft, and (2)
highlight much sought-after lineup events, which are useful for many
different research efforts, e.g. the modeling of ICME flux ropes,
their interplanetary evolution and the studies of solar energetic
particle events. We catalog all these ICME events for the community at
https://www.helioforecast.space/icmecat. The combined data of these
missions is already turning out to be a treasure trove for space
weather research and is expected to become even more valuable with a
increasing number of events expected during the rise of solar cycle 25.

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Title: Predicting CMEs Using ELEvoHI With STEREO-HI Beacon Data
Authors: Bauer, Maike; Amerstorfer, Tanja; Hinterreiter, Jürgen;
Weiss, Andreas J.; Davies, Jackie A.; Möstl, Christian; Amerstorfer,
Ute V.; Reiss, Martin A.; Harrison, Richard A.
2021SpWea..1902873B Altcode: 2021arXiv210808072B
Being able to accurately predict the arrival of coronal mass ejections
(CMEs) at Earth has been a long-standing problem in space weather
research and operations. In this study, we use the ELlipse Evolution
model based on Heliospheric Imager (ELEvoHI) to predict the arrival time
and speed of 10 CME events that were observed by HI on the STEREO-A
spacecraft between 2010 and 2020. Additionally, we introduce a Python
tool for downloading and preparing STEREO-HI data, as well as tracking
CMEs. In contrast to most previous studies, we use not only science
data, which have a relatively high spatial and temporal resolution,
but also lower-quality beacon data, which are—in contrast to science
data—provided in real-time by the STEREO-A spacecraft. We do not use
data from the STEREO-B spacecraft. We get a mean absolute error of 8.81
± 3.18 hr/59 ± 31 km s-1 for arrival time/speed predictions
using science data and 11.36 ± 8.69 hr/106 ± 61 km s-1
for beacon data. We find that using science data generally leads to
more accurate predictions, but using beacon data with the ELEvoHI
model is certainly a viable choice in the absence of higher resolution
real-time data. We propose that these differences could be minimized
if not eliminated altogether if higher quality real-time data were
available, either by enhancing the quality of the already available
data or coming from a new mission carrying a HI instrument on-board.

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Title: The early phase lunar magnetic field as recorded by Apollo
17 mare basalts
Authors: Vervelidou, Foteini; Weiss, Benjamin; Nichols, Claire; Murray,
Mary; Shah, Jay; Sheikh, Hassan; Harrison, Richard; Lagroix, France
2021AGUFMGP44A..05V Altcode:
Lunar rocks provide evidence that the Moon once sustained a lunar
core dynamo. Several studies have provided evidence that the lunar
magnetic field during the period 4.25 to 3.56 Ga had a strength
similar to that of the Earth nowadays. However, dynamo scaling laws
suggest that the Moon lacks the energy budget required to sustain a
convective dynamo that could generate such a strong magnetic field
continuously throughout this period. This possible discrepancy
has motivated the hypothesis that the lunar dynamo field was only
intermittently strong during this time. To test this hypothesis, we
have been conducting paleomagnetic, rock magnetic, and petrologic
measurements on four 3.7 billion years old Apollo 17 mare basalts
with textures ranging from coarse- to fine-grained. Using alternating
field demagnetization and remagnetization experiments, we show that
the recording properties of these samples exhibit a large variability,
even on the millimeter-scale. In particular, we find that using the
anhysteretic remanent magnetization paleointensity method, we can
accurately retrieve paleointensities from thermoremanence acquired in
minimum fields ranging from 7 to 75 T over the coercivity range 3-70
mT. According to our results thus far, all 10 subsamples that can
record fields at least as low as 20 T have recorded magnetizations
which correspond to paleointensities of several tens of T. Therefore,
we have yet to confidently identify samples dating from the early
phase of the lunar dynamo that recorded a low lunar paleofield.

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Title: Venus's induced magnetosphere during active solar wind
conditions at BepiColombo's Venus 1 flyby
Authors: Volwerk, Martin; Sánchez-Cano, Beatriz; Heyner, Daniel;
Aizawa, Sae; André, Nicolas; Varsani, Ali; Mieth, Johannes; Orsini,
Stefano; Baumjohann, Wolfgang; Fischer, David; Futaana, Yoshifumi;
Harrison, Richard; Jeszenszky, Harald; Kazumasa, Iwai; Laky, Gunter;
Lichtenegger, Herbert; Milillo, Anna; Miyoshi, Yoshizumi; Nakamura,
Rumi; Plaschke, Ferdinand; Richter, Ingo; Rojas Mata, Sebastián;
Saito, Yoshifumi; Schmid, Daniel; Shiota, Daikou; Wedlund, Cyril Simon
2021AnGeo..39..811V Altcode:
Out of the two Venus flybys that BepiColombo uses as a gravity assist
manoeuvre to finally arrive at Mercury, the first took place on 15
October 2020. After passing the bow shock, the spacecraft travelled
along the induced magnetotail, crossing it mainly in the YVSO
direction. In this paper, the BepiColombo Mercury Planetary Orbiter
Magnetometer (MPO-MAG) data are discussed, with support from three
other plasma instruments: the Planetary Ion Camera (SERENA-PICAM)
of the SERENA suite, the Mercury Electron Analyser (MEA), and the
BepiColombo Radiation Monitor (BERM). Behind the bow shock crossing,
the magnetic field showed a draping pattern consistent with field
lines connected to the interplanetary magnetic field wrapping around
the planet. This flyby showed a highly active magnetotail, with
e.g. strong flapping motions at a period of ∼7 min. This activity
was driven by solar wind conditions. Just before this flyby, Venus's
induced magnetosphere was impacted by a stealth coronal mass ejection,
of which the trailing side was still interacting with it during the
flyby. This flyby is a unique opportunity to study the full length
and structure of the induced magnetotail of Venus, indicating that
the tail was most likely still present at about 48 Venus radii.

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Title: Magnetic imaging of the outer solar atmosphere (MImOSA)
Authors: Peter, H.; Ballester, E. Alsina; Andretta, V.; Auchère, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; Alemán, T. del Pino; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Štěpán, J.; Teriaca, L.; Bueno, J. Trujillo
2021ExA...tmp...95P Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability of
planets orbiting these host stars. Although the magnetic field at the
surface of the Sun is reasonably well characterised by observations,
the information on the magnetic field in the higher atmospheric layers
is mainly indirect. This lack of information hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution
and high sensitivity. (b) An extreme-UV-to-IR coronagraph that is
designed to measure the large-scale magnetic field in the corona with
an aperture of about 40 cm. (c) An extreme-UV imaging polarimeter
based on a 30 cm telescope that combines high throughput in the
extreme UV with polarimetry to connect the magnetic measurements
of the other two instruments. Placed in a near-Earth orbit, the data
downlink would be maximised, while a location at L4 or L5 would provide
stereoscopic observations of the Sun in combination with Earth-based
observatories. This mission to measure the magnetic field will finally
unlock the driver of the dynamics in the outer solar atmosphere and
thereby will greatly advance our understanding of the Sun and the
heliosphere.

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Title: A journey of exploration to the polar regions of a star:
probing the solar poles and the heliosphere from high helio-latitude
Authors: Harra, Louise; Andretta, Vincenzo; Appourchaux, Thierry;
Baudin, Frédéric; Bellot-Rubio, Luis; Birch, Aaron C.; Boumier,
Patrick; Cameron, Robert H.; Carlsson, Matts; Corbard, Thierry;
Davies, Jackie; Fazakerley, Andrew; Fineschi, Silvano; Finsterle,
Wolfgang; Gizon, Laurent; Harrison, Richard; Hassler, Donald M.;
Leibacher, John; Liewer, Paulett; Macdonald, Malcolm; Maksimovic,
Milan; Murphy, Neil; Naletto, Giampiero; Nigro, Giuseppina; Owen,
Christopher; Martínez-Pillet, Valentín; Rochus, Pierre; Romoli,
Marco; Sekii, Takashi; Spadaro, Daniele; Veronig, Astrid; Schmutz, W.
2021ExA...tmp...93H Altcode: 2021arXiv210410876H
A mission to view the solar poles from high helio-latitudes (above 60°)
will build on the experience of Solar Orbiter as well as a long heritage
of successful solar missions and instrumentation (e.g. SOHO Domingo et
al. (Solar Phys. 162(1-2), 1-37 1995), STEREO Howard et al. (Space
Sci. Rev. 136(1-4), 67-115 2008), Hinode Kosugi et al. (Solar
Phys. 243(1), 3-17 2007), Pesnell et al. Solar Phys. 275(1-2),
3-15 2012), but will focus for the first time on the solar poles,
enabling scientific investigations that cannot be done by any other
mission. One of the major mysteries of the Sun is the solar cycle. The
activity cycle of the Sun drives the structure and behaviour of the
heliosphere and of course, the driver of space weather. In addition,
solar activity and variability provides fluctuating input into the
Earth climate models, and these same physical processes are applicable
to stellar systems hosting exoplanets. One of the main obstructions
to understanding the solar cycle, and hence all solar activity,
is our current lack of understanding of the polar regions. In this
White Paper, submitted to the European Space Agency in response to the
Voyage 2050 call, we describe a mission concept that aims to address
this fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.

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Title: IPSCAT: A Catalogue of Solar Transients Identified through
Interplanetary Scintillation Analysis
Authors: Barnes, David; Bisi, Mario; Davies, Jackie; Harrison, Richard
2021EGUGA..23.2667B Altcode:
We present a catalogue, IPSCAT, of the results of Interplanetary
Scintillation (IPS) analysis applied to observations that are compiled
using data from three European radio networks, EISCAT, MERLIN and
LOFAR, during the early science phase of the STEREO mission, from 2007
to 2012. These analyses provide a means to study the solar wind and
interplanetary transients, which we complement with observations from
the Heliospheric Imagers on-board STEREO. Within the IPS data set we
identify transient phenomena, specifically Coronal Mass Ejections (CMEs)
and Stream Interaction Regions (SIRs), via both visual inspection and
an automatic feature-finding algorithm. We study the effectiveness
of the automated detection algorithm and find it to be successful at
classifying CMEs, whilst the identification of SIRs is less easily
established. A discussion of the statistical properties of IPSCAT
is presented, together with a comparison between the IPS and HI
results. Finally, we present a case study of successive CMEs within
the IPSCAT data set, which were also observed by the HIs on both STEREO
spacecraft and analysed using the Stereoscopic Self-Similar Expansion
(SSSE) method. This work was carried out as part of the EU FP7 HELCATS
(Heliospheric Cataloguing, Analysis and Techniques Service) project
(http://www.helcats-fp7.eu/).

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Title: Effect of the ambient solar wind speed on drag-based CME
prediction accuracy
Authors: Amerstorfer, Tanja; Hinterreiter, Jürgen; Reiss, Martin A.;
Davies, Jackie A.; Möstl, Christian; Weiss, Andreas J.; Bauer, Maike;
Amerstorfer, Ute V.; Bailey, Rachel L.; Harrison, Richard A.
2021EGUGA..23.8932A Altcode:
In the last years, many kinds of CME models, based on a drag-based
evolution through interplanetary space, have been developed and are now
widely used by the community. The unbeatable advantage of those methods
is that they are computationally cheap and are therefore suitable to
be used as ensemble models. Additionally, their prediction accuracy
is absolutely comparable to more sophisticated models.The ELlipse
Evolution model based on heliospheric imager (HI) observations
(ELEvoHI) assumes an elliptic frontal shape within the ecliptic
plane and allows the CME to adjust to the ambient solar wind speed,
i.e. it is drag-based. ELEvoHI is used as an ensemble simulation
by varying the CME frontal shape within given boundary values. The
results include a frequency distribution of predicted arrival time
and arrival speed and an estimation of the arrival probability.In
this study, we investigate the possibility of not only varying the
parameters related to the CME's ecliptic extent but also the ambient
solar wind speed for each CME ensemle member. Although we have used a
range of +/-100 km/s for possible values of the solar wind speed in
the past, only the best candidate was in the end used to contribute
to the prediction. We present the results of this approach by applying
it to a CME propagating in a highly structured solar wind and compare
the frequency distribution of the arrival time and speed predictions
to those of the usual ELEvoHI approach.

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Title: Overview of interplanetary coronal mass ejections observed
by Solar Orbiter, Parker Solar Probe, Bepi Colombo, Wind and STEREO-A
Authors: Möstl, Christian; Weiss, Andreas J.; Bailey, Rachel L.;
Reiss, Martin A.; Amerstorfer, Tanja; Hinterreiter, Jürgen; Bauer,
Maike; Amerstorfer, Ute V.; Davies, Emma E.; Horbury, Tim; Barnes,
David; Davies, Jackie A.; Harrison, Richard A.; Heyner, Daniel;
Richter, Ingo; Auster, Hans-Ulrich; Magnes, Werner; Baumjohann,
Wolfgang
2021EGUGA..23..592M Altcode:
We show in situ observations of ICMEs during the first year of
Solar Orbiter observations based on magnetic field data from the MAG
instrument in conjunction with in situ and imaging observations from
the Heliospheric System Observatory. The in situ magnetic field data
from four other currently active spacecraft - Parker Solar Probe,
BepiColombo, STEREO-Ahead and Wind - are also searched for ICME
signatures, and all clear ICME events that could be identified by
classic signatures such as elevated and rotating magnetic fields
of sufficiently long durations are included in a living online
catalog. Furthermore, we provide a visualization of the in situ magnetic
field data alongside spacecraft positions and propagating CME fronts,
which are based on modeling of STEREO-A heliospheric imager data. This
allows us to identify ICME events that could be unambiguously followed
from their inception on the Sun to their impact at the aforementioned
spacecraft, and highlights sought-after lineup events, in which the same
ICME is observed at multiple points in space, such as the well-studied
2020 April 15-20 ICME. We discuss the ICME rate observed so far, and
provide an outlook on the expected ICME rate in solar cycle 25 based
on different forecasts for the cycle amplitude (see Möstl et al. 2020,
https://doi.org/10.3847/1538-4357/abb9a1).

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Title: Space Weather Awareness, Engagement, and Outreach Activities
at UKRI STFC RAL Space
Authors: Bisi, Mario M.; Hapgood, Mike; Harrison, Richard
2021cosp...43E2432B Altcode:
Space weather is a natural hazard posing a threat to critical
infrastructures worldwide with varying global and regional
impacts. Phenomena such as geomagnetic storms and atmospheric
disturbances can impact power grids, communications, and various
other satellite signals. The risk has increased in prominence as
society has become more dependent on space-based technologies and on
more-modern infrastructures susceptible to space-weather impacts. Space
weather originates at the Sun, and so it is important to understand the
Sun-Earth chain of events to be able to forecast and mitigate for such
space-weather phenomena and to predict their effects and resulting
impacts on human society. Following the inclusion of severe space
weather in the National Risk Register of Civil Emergencies in 2011,
STFC led a Public Dialogue exercise on space weather which brought
experts and the general public together to discuss the space weather and
establish the general awareness of space weather from across different
locations in the UK. The report of this project provided insights on how
best to establish policies that will engage the general public in the
mitigation of problems caused by space weather. In the same timeframe,
STFC also led a three-year academic networking activity (named SEREN)
that funded activities to give scientists better insight into the
types of information that industry and policy-makers need in order
to address the problems caused by space weather. More widely, the UK
has undertaken a series of wide-ranging investigations to mitigate
space-weather impacts at the national level including the ongoing
development of a national Space Weather Strategy - where the UK looks to
experts across all sectors to feed into its development. This has also
previously included the setting up of a UK staffed 24/7 space-weather
forecasting centre at the Met Office alongside the formation of the
Space Environment Impacts Expert Group (SEIEG) of space-weather experts
to provide the necessary advice to government; this latter group is
currently Chaired from RAL Space. In this presentation, we will provide
an overview of the above with an emphasis on the key activities past,
present, and planned, at RAL Space around space weather awareness,
engagement, and outreach.

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Title: Magnetic Imaging of the Outer Solar Atmosphere (MImOSA):
Unlocking the driver of the dynamics in the upper solar atmosphere
Authors: Peter, H.; Alsina Ballester, E.; Andretta, V.; Auchere, F.;
Belluzzi, L.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Calcines, A.;
Chitta, L. P.; Dalmasse, K.; del Pino Aleman, T.; Feller, A.; Froment,
C.; Harrison, R.; Janvier, M.; Matthews, S.; Parenti, S.; Przybylski,
D.; Solanki, S. K.; Stepan, J.; Teriaca, L.; Trujillo Bueno, J.
2021arXiv210101566P Altcode:
The magnetic activity of the Sun directly impacts the Earth and human
life. Likewise, other stars will have an impact on the habitability
of planets orbiting these host stars. The lack of information on the
magnetic field in the higher atmospheric layers hampers our progress in
understanding solar magnetic activity. Overcoming this limitation would
allow us to address four paramount long-standing questions: (1) How
does the magnetic field couple the different layers of the atmosphere,
and how does it transport energy? (2) How does the magnetic field
structure, drive and interact with the plasma in the chromosphere and
upper atmosphere? (3) How does the magnetic field destabilise the outer
solar atmosphere and thus affect the interplanetary environment? (4)
How do magnetic processes accelerate particles to high energies? New
ground-breaking observations are needed to address these science
questions. We suggest a suite of three instruments that far exceed
current capabilities in terms of spatial resolution, light-gathering
power, and polarimetric performance: (a) A large-aperture UV-to-IR
telescope of the 1-3 m class aimed mainly to measure the magnetic
field in the chromosphere by combining high spatial resolution and high
sensitivity. (b) An extreme-UV-to-IR coronagraph that is designed to
measure the large-scale magnetic field in the corona with an aperture
of about 40 cm. (c) An extreme-UV imaging polarimeter based on a 30
cm telescope that combines high throughput in the extreme UV with
polarimetry to connect the magnetic measurements of the other two
instruments. This mission to measure the magnetic field will unlock
the driver of the dynamics in the outer solar atmosphere and thereby
greatly advance our understanding of the Sun and the heliosphere.

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Title: Evaluation of CME Arrival Prediction Using Ensemble Modeling
Based on Heliospheric Imaging Observations
Authors: Amerstorfer, Tanja; Hinterreiter, Jürgen; Reiss, Martin
A.; Möstl, Christian; Davies, Jackie A.; Bailey, Rachel L.; Weiss,
Andreas J.; Dumbović, Mateja; Bauer, Maike; Amerstorfer, Ute V.;
Harrison, Richard A.
2021SpWea..1902553A Altcode: 2020arXiv200802576A
In this study, we evaluate a coronal mass ejection (CME) arrival
prediction tool that utilizes the wide-angle observations made by
STEREO's heliospheric imagers (HI). The unsurpassable advantage of these
imagers is the possibility to observe the evolution and propagation
of a CME from close to the Sun out to 1 AU and beyond. We believe
that by exploiting this capability, instead of relying on coronagraph
observations only, it is possible to improve today's CME arrival time
predictions. The ELlipse Evolution model based on HI observations
(ELEvoHI) assumes that the CME frontal shape within the ecliptic plane
is an ellipse and allows the CME to adjust to the ambient solar wind
speed; that is, it is drag based. ELEvoHI is used to perform ensemble
simulations by varying the CME frontal shape within given boundary
conditions that are consistent with the observations made by HI. In
this work, we evaluate different setups of the model by performing
hindcasts for 15 well-defined isolated CMEs that occurred when STEREO
was near L4/5, between the end of 2008 and the beginning of 2011. In
this way, we find a mean absolute error of between 6.2 ± 7.9 and 9.9
± 13 hr depending on the model setup used. ELEvoHI is specified for
using data from future space weather missions carrying HIs located at
L5 or L1. It can also be used with near-real-time STEREO-A HI beacon
data to provide CME arrival predictions during the next ∼7 years
when STEREO-A is observing the Sun-Earth space.

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Title: A Journey of Exploration to the Polar Regions of a Star:
Probing the Solar Poles and the Heliosphere from High Helio-Latitude
Authors: Finsterle, W.; Harra, L.; Andretta, V.; Appourchaux, T.;
Baudin, F.; Bellot Rubio, L.; Birch, A.; Boumier, P.; Cameron, R. H.;
Carlsson, M.; Corbard, T.; Davies, J. A.; Fazakerley, A. N.; Fineschi,
S.; Gizon, L. C.; Harrison, R. A.; Hassler, D.; Leibacher, J. W.;
Liewer, P. C.; Macdonald, M.; Maksimovic, M.; Murphy, N.; Naletto, G.;
Nigro, G.; Owen, C. J.; Martinez-Pillet, V.; Rochus, P. L.; Romoli,
M.; Sekii, T.; Spadaro, D.; Veronig, A.
2020AGUFMSH0110005F Altcode:
A mission to view the solar poles from high helio-latitudes (above
60°) will build on the experience of Solar Orbiter as well as a long
heritage of successful solar missions and instrumentation (e.g. SOHO,
STEREO, Hinode, SDO), but will focus for the first time on the solar
poles, enabling scientific investigations that cannot be done by
any other mission. One of the major mysteries of the Sun is the solar
cycle. The activity cycle of the Sun drives the structure and behaviour
of the heliosphere and is, of course, the driver of space weather. In
addition, solar activity and variability provides fluctuating input
into the Earth climate models, and these same physical processes
are applicable to stellar systems hosting exoplanets. One of the
main obstructions to understanding the solar cycle, and hence all
solar activity, is our current lack of understanding of the polar
regions. We describe a mission concept that aims to address this
fundamental issue. In parallel, we recognise that viewing the Sun
from above the polar regions enables further scientific advantages,
beyond those related to the solar cycle, such as unique and powerful
studies of coronal mass ejection processes, from a global perspective,
and studies of coronal structure and activity in polar regions. Not
only will these provide important scientific advances for fundamental
stellar physics research, they will feed into our understanding of
impacts on the Earth and other planets' space environment.

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Title: IPSCAT: A Catalogue of Solar Transients Identified through
Interplanetary Scintillation Analysis
Authors: Barnes, D.; Bisi, M. M.; Davies, J. A.; Harrison, R. A.
2020AGUFMSH0440024B Altcode:
We present a catalogue, IPSCAT, of the results of Interplanetary
Scintillation (IPS) analysis applied to observations that are compiled
using data from three European radio networks, EISCAT, MERLIN and
LOFAR, during the early science phase of the STEREO mission, from 2007
to 2012. These analyses provide a means to study the solar wind and
interplanetary transients, which we complement with observations from
the Heliospheric Imagers on-board STEREO. Within the IPS data set we
identify transient phenomena, specifically Coronal Mass Ejections (CMEs)
and Stream Interaction Regions (SIRs), via both visual inspection and
an automatic feature-finding algorithm. We study the effectiveness
of the automated detection algorithm and find it to be successful at
classifying CMEs, whilst the identification of SIRs is less easily
established. A discussion of the statistical properties of IPSCAT
is presented, together with a comparison between the IPS and HI
results. Finally, we present a case study of successive CMEs within
the IPSCAT data set, which were also observed by the HIs on both STEREO
spacecraft and analysed using the Stereoscopic Self-Similar Expansion
(SSSE) method.

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Title: CMEs in the Heliosphere: III. A Statistical Analysis of the
Kinematic Properties Derived from Stereoscopic Geometrical Modelling
Techniques Applied to CMEs Detected in the Heliosphere from 2008 to
2014 by STEREO/HI-1
Authors: Barnes, D.; Davies, J. A.; Harrison, R. A.; Byrne, J. P.;
Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua,
E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D.
2020SoPh..295..150B Altcode: 2020arXiv200614879B
We present an analysis of coronal mass ejections (CMEs) observed
by the Heliospheric Imagers (HIs) onboard NASA's Solar Terrestrial
Relations Observatory (STEREO) spacecraft. Between August 2008 and
April 2014 we identify 273 CMEs that are observed simultaneously,
by the HIs on both spacecraft. For each CME, we track the observed
leading edge, as a function of time, from both vantage points,
and apply the Stereoscopic Self-Similar Expansion (SSSE) technique
to infer their propagation throughout the inner heliosphere. The
technique is unable to accurately locate CMEs when their observed
leading edge passes between the spacecraft; however, we are able to
successfully apply the technique to 151, most of which occur once the
spacecraft-separation angle exceeds 180∘, during solar
maximum. We find that using a small half-width to fit the CME can
result in inferred acceleration to unphysically high velocities and that
using a larger half-width can fail to accurately locate the CMEs close
to the Sun because the method does not account for CME over-expansion
in this region. Observed velocities from SSSE are found to agree well
with single-spacecraft (SSEF) analysis techniques applied to the same
events. CME propagation directions derived from SSSE and SSEF analysis
agree poorly because of known limitations present in the latter.

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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.
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.

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Title: The Solar Orbiter Heliospheric Imager (SoloHI)
Authors: Howard, R. A.; Vourlidas, A.; Colaninno, R. C.; Korendyke,
C. M.; Plunkett, S. P.; Carter, M. T.; Wang, D.; Rich, N.; Lynch,
S.; Thurn, A.; Socker, D. G.; Thernisien, A. F.; Chua, D.; Linton,
M. G.; Koss, S.; Tun-Beltran, S.; Dennison, H.; Stenborg, G.; McMullin,
D. R.; Hunt, T.; Baugh, R.; Clifford, G.; Keller, D.; Janesick, J. R.;
Tower, J.; Grygon, M.; Farkas, R.; Hagood, R.; Eisenhauer, K.; Uhl,
A.; Yerushalmi, S.; Smith, L.; Liewer, P. C.; Velli, M. C.; Linker,
J.; Bothmer, V.; Rochus, P.; Halain, J. -P.; Lamy, P. L.; Auchère,
F.; Harrison, R. A.; Rouillard, A.; Patsourakos, S.; St. Cyr, O. C.;
Gilbert, H.; Maldonado, H.; Mariano, C.; Cerullo, J.
2020A&A...642A..13H Altcode:
 Aims: We present the design and pre-launch performance of
the Solar Orbiter Heliospheric Imager (SoloHI) which is an instrument
prepared for inclusion in the ESA/NASA Solar Orbiter mission, currently
scheduled for launch in 2020. Methods: The goal of this paper
is to provide details of the SoloHI instrument concept, design, and
pre-flight performance to give the potential user of the data a better
understanding of how the observations are collected and the sources
that contribute to the signal. Results: The paper discusses
the science objectives, including the SoloHI-specific aspects, before
presenting the design concepts, which include the optics, mechanical,
thermal, electrical, and ground processing. Finally, a list of planned
data products is also presented. Conclusions: The performance
measurements of the various instrument parameters meet or exceed the
requirements derived from the mission science objectives. SoloHI is
poised to take its place as a vital contributor to the science success
of the Solar Orbiter mission.

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Title: The High Helium Abundance and Charge States of the
Interplanetary CME and Its Material Source on the Sun
Authors: Fu, Hui; Harrison, R. A.; Davies, J. A.; Xia, LiDong; Zhu,
XiaoShuai; Li, Bo; Huang, ZhengHua; Barnes, D.
2020ApJ...900L..18F Altcode: 2020arXiv200808816F
Identifying the source of the material within coronal mass ejections
(CMEs) and understanding CME onset mechanisms are fundamental issues in
solar and space physics. Parameters relating to plasma composition,
such as charge states and He abundance (AHe), may be
different for plasmas originating from differing processes or regions
on the Sun. Thus, it is crucial to examine the relationship between
in situ measurements of CME composition and activity on the Sun. We
study the CME that erupted on 2014 September 10, in association with
an X1.6 flare, by analyzing Atmospheric Imaging Assembly imaging and
Interface Region Imaging Spectrograph (IRIS) spectroscopic observations
and its in situ signatures detected by Wind and Advanced Composition
Explorer. We find that during the slow expansion and intensity increase
of the sigmoid, plasma temperatures of 9 MK, and higher, first appear
at the footpoints of the sigmoid, associated with chromospheric
brightening. Then the high-temperature region extends along the
sigmoid. IRIS observations confirm that this extension is caused by
transportation of hot plasma upflow. Our results show that chromospheric
material can be heated to 9 MK, and above, by chromospheric evaporation
at the sigmoid footpoints before flare onset. The heated chromospheric
material can transport into the sigmoidal structure and supply mass
to the CME. The aforementioned CME mass supply scenario provides a
reasonable explanation for the detection of high charge states and
elevated AHe in the associated interplanetary CME. The
observations also demonstrate that the quasi-steady evolution in the
precursor phase is dominated by magnetic reconnection between the
rising flux rope and the overlying magnetic field structure.

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Title: A comprehensive catalogue of solar wind properties and events
in the inner heliosphere
Authors: Bailey, Rachel; Reiss, Martin; Möstl, Christian; Amerstorfer,
Ute; Wedlund, Cyril Simon; Amerstorfer, Tanja; Weiss, Andreas;
Hinterreiter, Jürgen; Guo, Jingnan; von Forstner, Johan; Barnes,
David; Davies, Jackie; Harrison, Richard
2020EPSC...14..562B Altcode:
The evolving ambient solar wind is one of the key links between
the Sun and planetary bodies in our solar system. Here we present a
comprehensive catalogue of solar wind properties, stream interaction
regions, and coronal mass ejections at different locations in the inner
heliosphere. Our database incorporates observational data products
and also solar wind modelling results. The solar wind modelling is
based on two different approaches for modelling the conditions in
the ambient solar wind. While the WSA/THUX model combination solves
the viscous form of the underlying Burgers equation to compute
the two-dimensional solar wind conditions in our solar system, the
second approach is a computationally fast machine learning method for
predicting the ambient solar wind flows at Earth. Statistics of the
ambient solar wind model results for more than 15 years in combination
with a catalogue of coronal mass ejections observed at the Earth, Mars
and STEREO satellites along with stream interaction regions provide
a comprehensive overview of the past and present solar wind behaviour
for shaping planetary space weather.

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Title: A Catalogue of Coronal Mass Ejections Observed by the
Heliospheric Imagers throughout the STEREO Mission
Authors: Barnes, David; Davies, Jackie; Harrison, Richard
2020EGUGA..2216546B Altcode:
Understanding the evolution of the solar wind is fundamental to
advancing our knowledge of energy and mass transport in the solar
system, rendering it crucial to space weather and its prediction. The
advent of truly wide-angle heliospheric imaging has revolutionised the
study of Coronal Mass Ejections (CMEs) by enabling their direct and
continuous observation out to 1 AU and beyond. A catalogue of CMEs
has been compiled using data from the Heliospheric Imagers (HIs) on
board the two STEREO spacecraft, which began as part of the FP7 HELCATS
project. The mission was launched in 2006 and continues to provide data,
therefore spanning 13 years, over which more than two-thousand CMEs
have been observed using HI. To these CMEs, we apply geometric models
that make use of both single-spacecraft and stereoscopic observations in
order to determine their kinematic properties. These include CME speed,
acceleration, propagation direction and launch time. The resulting
kinematic properties and their statistics are discussed in the context
of existing CME catalogues produced from coronagraph observations. This
is done with emphasis on how the different models we apply influence
our results and how these differences evolve over the solar cycle and
as the angular separation of the STEREO spacecraft increases throughout
the mission.

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Title: CME arrival prediction and its dependency on input data and
model parameters
Authors: Amerstorfer, Tanja; Hinterreiter, Jürgen; Reiss, Martin A.;
Bauer, Maike; Möstl, Christian; Bailey, Rachel L.; Weiss, Andreas J.;
Amerstorfer, Ute V.; Davies, Jackie A.; Harrison, Richard
2020EGUGA..22.4703A Altcode:
During the last years, we focused on developing a prediction tool
that utilizes the wide-angle observations of STEREO's heliospheric
imagers. The unsurpassable advantage of these imagers is the possibility
to observe the evolution and propagation of a coronal mass ejection
(CME) from close to the Sun up to 1 AU and beyond. We believe that
using this advantage instead of relying on coronagraph observations
that are limited to observe only 14% of the Sun-Earth line, it is
possible to improve today's CME arrival time predictions.The ELlipse
Evolution model based on HI observations (ELEvoHI) assumes an elliptic
frontal shape within the ecliptic plane and allows the CME to adjust
to the ambient solar wind speed, i.e. it is drag-based. ELEvoHI is
used as an ensemble simulation by varying the CME frontal shape within
given boundary values. The results include a frequency distrubution
of predicted arrival time and arrival speed and an estimation of the
arrival probability. ELEvoHI can be operated using several kinds of
inputs. In this study we investigate 15 well-defined single CMEs when
STEREO was around L4/5 between the end of 2009 and the beginning of
2011. Three different sources of input propagation directions (and
shapes) are used together with three different sources of ambient solar
wind speed and two different ways of defining the most appropriate
fit to the HI data. The combination of these different approaches and
inputs leads to 18 different model set-ups used to predict each of
the 15 events in our list leading to 270 ELEvoHI ensemble predictions
and all in all to almost 60000 runs. To identify the most suitable and
most accurate model set-up to run ELEvoHI, we compare the predictions
to the actual in situ arrival of the CMEs.This model is specified for
using data from future space weather missions carrying HIs located
at L5 or L1 and can also directly be used together with STEREO-A near
real-time HI beacon data to provide real-time CME arrival predictions
during the next 7 years when STEREO-A is observing the Sun-Earth space.

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Title: From heliophysics to space weather forecasts
Authors: Harrison, Richard; Davies, Jackie; Rae, Jonny
2019A&G....60e5.26H Altcode:
Richard Harrison, Jackie Davies and Jonny Rae summarize progress in
capitalizing on UK expertise in research and instrumentation for new
space weather forecasting - the subject of an RAS Discussion Meeting
in March.

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Title: CMEs in the Heliosphere: II. A Statistical Analysis of the
Kinematic Properties Derived from Single-Spacecraft Geometrical
Modelling Techniques Applied to CMEs Detected in the Heliosphere
from 2007 to 2017 by STEREO/HI-1
Authors: Barnes, D.; Davies, J. A.; Harrison, R. A.; Byrne, J. P.;
Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua,
E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D.
2019SoPh..294...57B Altcode:
Recent observations with the Heliospheric Imagers (HIs) onboard the twin
NASA Solar Terrestrial Relations Observatory (STEREO) spacecraft have
provided unprecedented observations of a large number of coronal mass
ejections (CMEs) in the inner heliosphere. In this article we discuss
the generation of the HIGeoCAT CME catalogue and perform a statistical
analysis of its events. The catalogue was generated as part of the
EU FP7 HELCATS (Heliospheric Cataloguing, Analysis and Techniques
Service) project (www.helcats-fp7.eu/). It is created by generating
time/elongation maps for CMEs using observations from the inner (HI-1)
and outer (HI-2) cameras along a position angle close to the CME
apex. Next, we apply single-spacecraft geometric-fitting techniques
to determine the kinematic properties of these CMEs, including their
speeds, propagation directions, and launch times. The catalogue contains
a total of 1455 events (801 from STEREO-A and 654 from STEREO-B)
from April 2007 to the end of August 2017. We perform a statistical
analysis of the properties of CMEs in HIGeoCAT and compare the results
with those from the Large Angle Spectrometric Coronagraph (LASCO) CDAW
catalogues (Yashiro et al.J. Geophys. Res. Space Phys.109, A07105,
2004) and the COR-2 catalogue of Vourlidas et al. (Astrophys. J.838,
141, 2004) during the same period. We find that the distributions of
both speeds and latitudes for the HIGeoCAT CMEs correlate with the
sunspot number over the solar cycle. We also find that the HI-derived
CME speed distributions are generally consistent with coronagraph
catalogues over the solar cycle, albeit with greater absolute speeds
due to the differing methods with which each is derived.

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Title: Nanopaleomagnetism: How to extract and understand ancient
extraterrestrial magnetic signals from meteorites using synchrotron
X-rays
Authors: Nichols, Claire; Bryson, James; Herrero-Albillos, Julia;
Kronast, Florian; Im, Mi-Young; Harrison, Richard
2019EGUGA..21.3685N Altcode:
Magnetic signals recorded by meteorites provide invaluable information
about the formation and evolution of our solar system. Before
interpreting these signals, it is essential to understand how these
signals are being recorded, and whether they are likely to be stable
for billions of years. Over the last five years significant progress
has been made in understanding the magnetic information recorded
by iron-bearing meteorites. The bulk of meteoritic metal is kamacite
(Fe0.95Ni0.05) which forms large mm-scale lamellae in the Widmanstätten
pattern, a characteristic feature of slow-cooled iron meteorites. These
kamacite lamellae are magnetically soft; they are multidomain and
any magnetic information recorded is easily overwritten. Between the
large-scale kamacite lamellae however, a range of microstructures form,
including the cloudy zone. The cloudy zone consists of nanoscale
islands of tetrataenite (Fe0.5Ni0.5) in an Fe-rich matrix. These
tetrataenite islands are exceptional paleomagnetic recorders
but their small size makes extracting paleomagnetic information
experimentally challenging. X-ray photoemission electron microscopy
(X-PEEM) allows the distribution of magnetization within the cloudy
zone to be imaged with nanoscale resolution. This technique has been
used to characterize the magnetic behavior of numerous meteoritic FeNi
microstructures and has also been used to calculate paleointensities
generated by planetesimal dynamos within the first 200 million years
of solar system formation. Examples of studies on the IAB iron
meteorites, the Main Group pallasites and the mesosiderites will
be discussed. Paleomagnetic signals have also been extracted from
chondritic meteorites, which contain the first solids to have formed
in our solar system. Paleomagnetic signals recorded by nanoscale Fe
particles in dusty olivine grains in the Semarkona LL3.0 chondrite
are interpreted as evidence for the strength of the solar nebula
magnetic field. This record has significant implications for the
evolution of the protoplanetary disk. Numerous microscopy studies have
been conducted to verify the ability of these Fe particles to record
stable paleomagnetic records from the earliest history of the solar
system. Magnetic transmission X-ray microscopy (MTXM) has been used to
image the nanoscale magnetic structure within individual Fe-particles
from the Semarkona LL3.0 chondrite under applied laboratory fields and
they are found to be stable in magnetic fields of at least 200 mT. MTXM
has a significant advantage over electron microscopy techniques since
imaging can be conducted under applied magnetic fields. This is very
difficult to achieve using techniques such as Lorentz microscopy or
electron holography as the applied magnetic field causes the electron
beam to be deflected, defocusing the image.

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Title: Importance of heliospheric imager track quality for CME
arrival prediction accuracy
Authors: Amerstorfer, Tanja; Hinterreiter, Jürgen; Möstl, Christian;
Davies, Jackie A.; Amerstorfer, Ute V.; Reiss, Martin A.; Temmer,
Manuela; Bailey, Rachel L.; Harrison, Richard A.
2019EGUGA..21.7373A Altcode:
Operational CME arrival prediction is mainly conducted using
magnetohydrodynamic models based on coronagraph observations and
magnetograms. Although the Solar TErrestrial RElations Observatory with
its heliospheric imagers (HI) provides the possibility to trace a CME's
propagation along its path from the Sun to 1 AU, these data can hardly
be used to predict CME arrivals in real time (except for a few events
in an early phase of the mission). One of the main reasons for that
is a large number of data gaps in beacon data, which is available in
near real time (in contrast to the complete science data), impeding a
proper measurement of the CME front. With regard to a possible future L5
mission carrying HIs we investigate the most suitable way of extracting
the time-elongation track of CMEs from HI observations leading to
a prediction with the highest possible accuracy. As a first step to
reach this goal, we use time-elongation tracks measured from STEREO/HI
science data and provided by the FP7 HELCATS team as well as tracks
derived using time-elongation maps and tracks measured directly in an
HI image time series. These time-elongation tracks are further used as
input to our CME ensemble prediction tool ELEvoHI (ELlipse Evolution
model based on HI data), which assumes a drag-based interplanetary
CME propagation and an elliptical CME frontal shape. ELEvoHI produces
post-event predictions of arrival times and speeds at 1 AU for all
tracks of each CME under study. By comparing the prediction results from
several ways of tracking we attempt to deduce a preferable approach
for future studies, e.g. when using data from Parker Solar Probe's
Wide-Field Imager for Solar Probe (WISPR), and maybe for future real
time predictions when STEREO-A approaches the L5 point.

---------------------------------------------------------
Title: Prospective White-light Imaging and In Situ Measurements of
Quiescent Large-scale Solar-wind Streams from the Parker Solar Probe
and Solar Orbiter
Authors: Xiong, Ming; Davies, Jackie A.; Feng, Xueshang; Li, Bo;
Yang, Liping; Xia, Lidong; Harrison, Richard A.; Hayashi, Keiji; Li,
Huichao; Zhou, Yufen
2018ApJ...868..137X Altcode:
Deep-space exploration of the inner heliosphere is in an unprecedented
golden age, with the recent and forthcoming launches of the Parker
Solar Probe (PSP) and Solar Orbiter (SolO) missions, respectively. In
order to both predict and understand the prospective observations
by PSP and SolO, we perform forward MHD modeling of the 3D inner
heliosphere at solar minimum, and synthesize the white-light (WL)
emission that would result from Thomson scattering of sunlight
from the coronal and heliospheric plasmas. Both solar rotation and
spacecraft trajectory should be considered when reconstructing quiescent
large-scale solar-wind streams from PSP and SolO WL observations. When
transformed from a static coordinate system into a corotating one, the
elliptical orbit of PSP becomes a multiwinding spiral. The innermost
spiral winding of this corotating PSP orbit takes the form of a closed
“heart shape” within around 80 R ⊙ of the Sun. PSP,
when traveling along this “heart-shaped” trajectory, can cross
a single corotating interaction region (CIR) twice. This enables in
situ measurements of the same CIR to be made in both the corona and
heliosphere. As PSP approaches perihelion, the WL radiance from the
corona increases. Polarization can be used to localize the main WL
scattering region in the corona. Large-scale structures around PSP can
be further resolved in the longitudinal dimension, using additional
WL imagery from the out-of-ecliptic perspective of SolO. Coordinated
observations between PSP and SolO are very promising in the quest to
differentiate background CIRs from transient ejecta.

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Title: Space weather in the UK
Authors: Bisi, Mario; Hapgood, Mike; Bisi, Mario M.; Harrison, Richard
2018cosp...42E.357B Altcode:
The UK Government's inclusion of severe space weather on the National
Risk Register (NRR) of Civil Emergencies in recent years has led to
a somewhat co-ordinated, yet wide-ranging set of activities that is
attempting to tackle space weather threats at the national level,
but incorporating active engagement on the international scene. Two
immediate responses to the Government's decision in managing the space
weather risk are: (a) the setting up of a UK space weather forecasting
centre at the Met Office, in Exeter (UK) - which is only one of two
civil forecasting centres world-wide that are manned 24 hours a day,
7 days a week; and (b) the formation of the Space Environment Impacts
Expert Group (SEIEG), chaired by Prof. Mike Hapgood from STFC RAL Space,
that advises the UK Cabinet Office and the Government Department of
Business, Energy and Industrial Strategy. These activities have come
about from active partnerships between agencies, industrial groups,
and the science community to ensure that the wide range of issues
involved are fully covered. In parallel, the UK Space Agency (UKSA),
in responding to these activities and engaging with key institutes such
as the STFC Rutherford Appleton Laboratory (RAL) and the Met Office,
has become a major supporter of the emerging ESA Space Situational
Awareness (SSA) space weather programme, which ultimately ensured
that the UK has taken leadership roles in the instrument development
activities for the planned Lagrange L5 space weather mission as well
as in service activities such as the Heliospheric Expert Service
Centre. All of these activities, and more, have come about because
of extensive dialogue between the academic community, the industrial
community, the relevant agencies, and Government in the UK, as well as
with international groups such as ESA and NOAA. The strategic approach
in the UK has been particularly successful and continues to evolve. Of
particular interest in the coming years is the development of the role
of the UN COPUOS and COSPAR, with which the UK will be fully engaged.

---------------------------------------------------------
Title: Numerically calibrated model for propagation of a relativistic
unmagnetized jet in dense media
Authors: Harrison, Richard; Gottlieb, Ore; Nakar, Ehud
2018MNRAS.477.2128H Altcode: 2017arXiv170706234H; 2018MNRAS.tmp..736H
Relativistic jets reside in high-energy astrophysical systems of all
scales. Their interaction with the surrounding media is critical as
it determines the jet evolution, observable signature, and feedback
on the environment. During its motion, the interaction of the jet
with the ambient media inflates a highly pressurized cocoon, which
under certain conditions collimates the jet and strongly affects its
propagation. Recently, Bromberg et al. derived a general simplified
(semi-)analytic solution for the evolution of the jet and the cocoon
in case of an unmagnetized jet that propagates in a medium with a
range of density profiles. In this work we use a large suite of 2D
and 3D relativistic hydrodynamic simulations in order to test the
validity and accuracy of this model. We discuss the similarities and
differences between the analytic model and numerical simulations
and also, to some extent, between 2D and 3D simulations. Our main
finding is that although the analytic model is highly simplified,
it properly predicts the evolution of the main ingredients of the
jet-cocoon system, including its temporal evolution and the transition
between various regimes (e.g. collimated to uncollimated). The analytic
solution predicts a jet head velocity that is faster by a factor of
about 3 compared to the simulations, as long as the head velocity
is Newtonian. We use the results of the simulations to calibrate
the analytic model which significantly increases its accuracy. We
provide an applet that calculates semi-analytically the propagation
of a jet in an arbitrary density profile defined by the user at
http://www.astro.tau.ac.il/∼ore/propagation.html.

---------------------------------------------------------
Title: Coronal Magnetic Structure of Earthbound CMEs and In Situ
Comparison
Authors: Palmerio, E.; Kilpua, E. K. J.; Möstl, C.; Bothmer, V.;
James, A. W.; Green, L. M.; Isavnin, A.; Davies, J. A.; Harrison, R. A.
2018SpWea..16..442P Altcode: 2018arXiv180304769P
Predicting the magnetic field within an Earth-directed coronal
mass ejection (CME) well before its arrival at Earth is one of the
most important issues in space weather research. In this article,
we compare the intrinsic flux rope type, that is, the CME orientation
and handedness during eruption, with the in situ flux rope type for 20
CME events that have been uniquely linked from Sun to Earth through
heliospheric imaging. Our study shows that the intrinsic flux rope
type can be estimated for CMEs originating from different source
regions using a combination of indirect proxies. We find that only
20% of the events studied match strictly between the intrinsic and in
situ flux rope types. The percentage rises to 55% when intermediate
cases (where the orientation at the Sun and/or in situ is close to
45°) are considered as a match. We also determine the change in the
flux rope tilt angle between the Sun and Earth. For the majority of
the cases, the rotation is several tens of degrees, while 35% of the
events change by more than 90°. While occasionally the intrinsic flux
rope type is a good proxy for the magnetic structure impacting Earth,
our study highlights the importance of capturing the CME evolution
for space weather forecasting purposes. Moreover, we emphasize that
determination of the intrinsic flux rope type is a crucial input for
CME forecasting models.

---------------------------------------------------------
Title: CMEs in the Heliosphere: I. A Statistical Analysis of the
Observational Properties of CMEs Detected in the Heliosphere from
2007 to 2017 by STEREO/HI-1
Authors: Harrison, R. A.; Davies, J. A.; Barnes, D.; Byrne, J. P.;
Perry, C. H.; Bothmer, V.; Eastwood, J. P.; Gallagher, P. T.; Kilpua,
E. K. J.; Möstl, C.; Rodriguez, L.; Rouillard, A. P.; Odstrčil, D.
2018SoPh..293...77H Altcode: 2018arXiv180402320H
We present a statistical analysis of coronal mass ejections (CMEs)
imaged by the Heliospheric Imager (HI) instruments on board NASA's
twin-spacecraft STEREO mission between April 2007 and August 2017 for
STEREO-A and between April 2007 and September 2014 for STEREO-B. The
analysis exploits a catalogue that was generated within the FP7
HELCATS project. Here, we focus on the observational characteristics
of CMEs imaged in the heliosphere by the inner (HI-1) cameras, while
following papers will present analyses of CME propagation through
the entire HI fields of view. More specifically, in this paper we
present distributions of the basic observational parameters - namely
occurrence frequency, central position angle (PA) and PA span - derived
from nearly 2000 detections of CMEs in the heliosphere by HI-1 on
STEREO-A or STEREO-B from the minimum between Solar Cycles 23 and 24
to the maximum of Cycle 24; STEREO-A analysis includes a further 158
CME detections from the descending phase of Cycle 24, by which time
communication with STEREO-B had been lost. We compare heliospheric CME
characteristics with properties of CMEs observed at coronal altitudes,
and with sunspot number. As expected, heliospheric CME rates correlate
with sunspot number, and are not inconsistent with coronal rates
once instrumental factors/differences in cataloguing philosophy are
considered. As well as being more abundant, heliospheric CMEs, like
their coronal counterparts, tend to be wider during solar maximum. Our
results confirm previous coronagraph analyses suggesting that CME launch
sites do not simply migrate to higher latitudes with increasing solar
activity. At solar minimum, CMEs tend to be launched from equatorial
latitudes, while at maximum, CMEs appear to be launched over a much
wider latitude range; this has implications for understanding the
CME/solar source association. Our analysis provides some supporting
evidence for the systematic dragging of CMEs to lower latitude as they
propagate outwards.

---------------------------------------------------------
Title: Prospective Out-of-ecliptic White-light Imaging of CIRs and
CMEs through the Corona and Heliosphere
Authors: Xiong, Ming; Davies, Jackie; Feng, Xueshang; Harrison,
Richard; Xia, Lidong; Yang, Liping; Zhou, Yufen; Liu, Ying; Li, Bo
2018EGUGA..20.3905X Altcode:
Interplanetary corotating interaction regions (CIRs) and coronal
mass ejections (CMEs) can be remotely imaged in white light (WL),
as demonstrated by the in-flight performance of the Coriolis/SMEI and
STEREO/HI instruments. Because of the in-ecliptic locations of both
the STEREO and Coriolis spacecraft, the longitudinal dimension of
interplanetary CIRs and CMEs has, up to now, always been integrated
in WL imagery. To synthesize the WL radiance patterns of CIRs and
CMEs from an out-of-ecliptic (OOE) vantage point, we perform forward
magnetohydrodynamic (MHD) modeling of the background solar wind flow
at solar maximum and a halo CME at solar minimum. We assert that a
panoramic OOE view in WL would be highly beneficially in revealing the
morphology and kinematics of CIRs and CMEs in the hitherto unresolved
longitudinal dimension, and hence for monitoring the propagation and
evolution of inecliptic CMEs for space weather operations.

---------------------------------------------------------
Title: Key results and services of HELCATS
Authors: Bothmer, Volker; Harrison, Richard; Davies, Jackie; Rouillard,
Alexis
2018EGUGA..20.7441B Altcode:
The EU FP7 project HELCATS (HELIOSPHERIC CATALOGUING, ANALYSIS &amp;
TECHNIQUES SERVICE) has provided new insights into solar wind structure
through combining the comprehensive analysis of heliospheric imaging
observations from the NASA STEREO spacecraft, in concert with associated
remote-sensing and in-situ measurements, with a thorough assessment
of appropriate techniques and models. The project recognised that the
advent of wide-angle imaging of the inner heliosphere has revolutionised
the study of transient and quasi-stationary structures in the solar
wind, in particular Coronal Mass Ejections (CMEs) and Co-rotating
Interaction Regions (CIRs). Prior to the development of wide-angle
imaging of the inner heliosphere, signatures of such solar wind
features could only be observed within a few solar radii of the Sun,
and in the vicinity of a few near-Earth and interplanetary probes making
in-situ measurements of the solar wind. Heliospheric imaging has, for
the first time, filled that vast and crucial observational gap. This
presentation summarises the key results and services established by
the HELCATS project.

---------------------------------------------------------
Title: Prospective Out-of-ecliptic White-light Imaging of Coronal
Mass Ejections Traveling through the Corona and Heliosphere
Authors: Xiong, Ming; Davies, Jackie A.; Harrison, Richard A.; Zhou,
Yufen; Feng, Xueshang; Xia, Lidong; Li, Bo; Liu, Ying D.; Hayashi,
Keiji; Li, Huichao; Yang, Liping
2018ApJ...852..111X Altcode:
The in-flight performance of the Coriolis/SMEI and STEREO/HI instruments
substantiates the high-technology readiness level of white-light (WL)
imaging of coronal mass ejections (CMEs) in the inner heliosphere. The
WL intensity of a propagating CME is jointly determined by its evolving
mass distribution and the fixed Thomson-scattering geometry. From their
in-ecliptic viewpoints, SMEI and HI, the only heliospheric imagers
that have been flown to date, integrate the longitudinal dimension of
CMEs. In this paper, using forward magnetohydrodynamic modeling, we
synthesize the WL radiance pattern of a typical halo CME viewed from an
out-of-ecliptic (OOE) vantage point. The major anatomical elements of
the CME identified in WL imagery are a leading sheath and a trailing
ejecta; the ejecta-driven sheath is the brightest feature of the
CME. The sheath, a three-dimensional (3D) dome-like density structure,
occupies a wide angular extent ahead of the ejecta itself. The 2D
radiance pattern of the sheath depends critically on viewpoint. For
a CME modeled under solar minimum conditions, the WL radiance pattern
of the sheath is generally a quasi-straight band when viewed from an
in-ecliptic viewpoint and a semicircular arc from an OOE viewpoint. The
dependence of the radiance pattern of the ejecta-driven sheath on
viewpoint is attributed to the bimodal nature of the 3D background
solar wind flow. Our forward-modeling results suggest that OOE imaging
in WL radiance can enable (1) a near-ecliptic CME to be continuously
tracked from its coronal initiation, (2) the longitudinal span of the
CME to be readily charted, and (3) the transporting speed of the CME
to be reliably determined. Additional WL polarization measurements can
significantly limit the ambiguity of localizing CMEs. We assert that
a panoramic OOE view in WL would be highly beneficial in revealing
CME morphology and kinematics in the hitherto-unresolved longitudinal
dimension and hence for monitoring the propagation and evolution of
near-ecliptic CMEs for space weather operations.

---------------------------------------------------------
Title: The Heliospheric Cataloguing, Analysis and Techniques Service
(HELCATS) project
Authors: Barnes, D.; Harrison, R. A.; Davies, J. A.; Perry, C. H.;
Moestl, C.; Rouillard, A.; Bothmer, V.; Rodriguez, L.; Eastwood,
J. P.; Kilpua, E.; Gallagher, P.; Odstrcil, D.
2017AGUFMSH31A2713B Altcode:
Understanding solar wind evolution is fundamental to advancing our
knowledge of energy and mass transport in the solar system, whilst
also being crucial to space weather and its prediction. The advent of
truly wide-angle heliospheric imaging has revolutionised the study of
solar wind evolution, by enabling direct and continuous observation
of both transient and background components of the solar wind as they
propagate from the Sun to 1 AU and beyond. The recently completed,
EU-funded FP7 Heliospheric Cataloguing, Analysis and Techniques
Service (HELCATS) project (1st May 2014 - 30th April 2017) combined
European expertise in heliospheric imaging, built up over the last
decade in particular through leadership of the Heliospheric Imager
(HI) instruments aboard NASA's STEREO mission, with expertise in
solar and coronal imaging as well as the interpretation of in-situ
and radio diagnostic measurements of solar wind phenomena. HELCATS
involved: (1) the cataloguing of transient (coronal mass ejections)
and background (stream/corotating interaction regions) solar wind
structures observed by the STEREO/HI instruments, including estimates of
their kinematic properties based on a variety of modelling techniques;
(2) the verification of these kinematic properties through comparison
with solar source observations and in-situ measurements at multiple
points throughout the heliosphere; (3) the assessment of the potential
for initialising numerical models based on the derived kinematic
properties of transient and background solar wind components; and (4)
the assessment of the complementarity of radio observations (Type II
radio bursts and interplanetary scintillation) in the detection and
analysis of heliospheric structure in combination with heliospheric
imaging observations. In this presentation, we provide an overview
of the HELCATS project emphasising, in particular, the principal
achievements and legacy of this unprecedented project.

---------------------------------------------------------
Title: Modeling observations of solar coronal mass ejections with
heliospheric imagers verified with the Heliophysics System Observatory
Authors: Möstl, C.; Isavnin, A.; Boakes, P. D.; Kilpua, E. K. J.;
Davies, J. A.; Harrison, R. A.; Barnes, D.; Krupar, V.; Eastwood,
J. P.; Good, S. W.; Forsyth, R. J.; Bothmer, V.; Reiss, M. A.;
Amerstorfer, T.; Winslow, R. M.; Anderson, B. J.; Philpott, L. C.;
Rodriguez, L.; Rouillard, A. P.; Gallagher, P.; Nieves-Chinchilla,
T.; Zhang, T. L.
2017SpWea..15..955M Altcode: 2017arXiv170300705M
We present an advance toward accurately predicting the arrivals of
coronal mass ejections (CMEs) at the terrestrial planets, including
Earth. For the first time, we are able to assess a CME prediction model
using data over two thirds of a solar cycle of observations with the
Heliophysics System Observatory. We validate modeling results of 1337
CMEs observed with the Solar Terrestrial Relations Observatory (STEREO)
heliospheric imagers (HI) (science data) from 8 years of observations
by five in situ observing spacecraft. We use the self-similar expansion
model for CME fronts assuming 60° longitudinal width, constant speed,
and constant propagation direction. With these assumptions we find that
23%-35% of all CMEs that were predicted to hit a certain spacecraft
lead to clear in situ signatures, so that for one correct prediction,
two to three false alarms would have been issued. In addition, we find
that the prediction accuracy does not degrade with the HI longitudinal
separation from Earth. Predicted arrival times are on average within 2.6
± 16.6 h difference of the in situ arrival time, similar to analytical
and numerical modeling, and a true skill statistic of 0.21. We also
discuss various factors that may improve the accuracy of space weather
forecasting using wide-angle heliospheric imager observations. These
results form a first-order approximated baseline of the prediction
accuracy that is possible with HI and other methods used for data by
an operational space weather mission at the Sun-Earth L5 point.

---------------------------------------------------------
Title: Prospective Out-of-ecliptic White-light Imaging of
Interplanetary Corotating Interaction Regions at Solar Maximum
Authors: Xiong, Ming; Davies, Jackie A.; Li, Bo; Yang, Liping; Liu,
Ying D.; Xia, Lidong; Harrison, Richard A.; Keiji, Hayashi; Li, Huichao
2017ApJ...844...76X Altcode:
Interplanetary corotating interaction regions (CIRs) can be remotely
imaged in white light (WL), as demonstrated by the Solar Mass Ejection
Imager (SMEI) on board the Coriolis spacecraft and Heliospheric Imagers
(HIs) on board the twin Solar TErrestrial RElations Observatory (STEREO)
spacecraft. The interplanetary WL intensity, due to Thomson scattering
of incident sunlight by free electrons, is jointly determined by the
3D distribution of electron number density and line-of-sight (LOS)
weighting factors of the Thomson-scattering geometry. The 2D radiance
patterns of CIRs in WL sky maps look very different from different 3D
viewpoints. Because of the in-ecliptic locations of both the STEREO and
Coriolis spacecraft, the longitudinal dimension of interplanetary CIRs
has, up to now, always been integrated in WL imagery. To synthesize
the WL radiance patterns of CIRs from an out-of-ecliptic (OOE) vantage
point, we perform forward magnetohydrodynamic modeling of the 3D inner
heliosphere during Carrington Rotation CR1967 at solar maximum. The
mixing effects associated with viewing 3D CIRs are significantly
minimized from an OOE viewpoint. Our forward modeling results
demonstrate that OOE WL imaging from a latitude greater than 60° can
(1) enable the garden-hose spiral morphology of CIRs to be readily
resolved, (2) enable multiple coexisting CIRs to be differentiated,
and (3) enable the continuous tracing of any interplanetary CIR back
toward its coronal source. In particular, an OOE view in WL can reveal
where nascent CIRs are formed in the extended corona and how these
CIRs develop in interplanetary space. Therefore, a panoramic view
from a suite of wide-field WL imagers in a solar polar orbit would
be invaluable in unambiguously resolving the large-scale longitudinal
structure of CIRs in the 3D inner heliosphere.

---------------------------------------------------------
Title: Cataloguing radio emission associated with coronal mass
ejections: results from the HELCATS project
Authors: Eastwood, Jonathan; Krupar, Vratislav; Magdalenic, Jasmina;
Bisi, Mario; Gopalswamy, Nat; Davies, Jackie; Harrison, Richard;
Barnes, David
2017EGUGA..19.5249E Altcode:
The goal of the Heliospheric Cataloguing, Analysis and Techniques
Service (HELCATS) is to add value to the STEREO dataset by cataloguing
the properties of coronal mass ejections and corotating interaction
regions observed by STEREO. As part of this work, the complementary
nature of radio measurements and white light observations has been
assessed. Here we report on the cataloguing of slowly-drifting radio
emission observed by STEREO WAVES in conjunction with events identified
in the HELCATS manually-generated coronal mass ejection catalogue. We
present preliminary statistical results derived from the catalogue,
in particular the extent to which radio emission is more likely to
occur in conjunction with fast coronal mass ejections. We further use
the catalogue to make an initial assessment of the angular deviation
between radio emission and coronal mass ejection motion, in order to
determine which part of the coronal mass ejection contributes most to
the radio emission. HELCATS is project 606692 of the European Union's
Seventh Framework Programme.

---------------------------------------------------------
Title: CME properties and solar source region characteristics -
HELCATS results
Authors: Bothmer, Volker; Mrotzek, Niclas; Murray, Sophie; Gallagher,
Peter; Barnes, David; Davies, Jackie; Harrison, Richard
2017EGUGA..19.5107B Altcode:
One objective of the EU FP7 project HELCATS is to derive and
catalogue the characteristics of CMEs observed with the STEREO/COR2
&amp; HI imagers based on geometrical and forward modelling. Here
we present the results of the analysis of a subset of the 122 CME
events that have been dynamically modelled with the GCS-method in
the COR2 field of view and which are compiled in the KINCAT database
at http://www.affects-fp7.eu/helcats-database/database.php. The
CME properties, such as speeds, masses, angular widths, as derived
from modelling, are compared with magnetic field properties of the
corresponding solar source active region, such as magnetic flux,
area, and polarity line characteristics. The results show which solar
parameters define the structure of CMEs at distances around 12 solar
radii and how they can be used for space weather forecast services.

---------------------------------------------------------
Title: Using helispheric imager observations in predicting the impact
of coronal mass ejections (CMEs) at planets
Authors: Kilpua, Emilia; Möstl, Christian; Bothmer, Volker; Isavnin,
Alexey; Harrison, Richard; Davies, Jackie; Palmerio, Erika; Boakes,
Peter; Mrotzek, Niclas
2017EGUGA..19.9051K Altcode:
Connecting coronal mass ejections (CMEs) in remote-sensing and in-situ
observations can be surprisingly difficult. Coronagraphs can detect
CMEs only about 10% of their journey from Sun to 1 AU. One viable
way to track CMEs through the inner heliosphere is using heliospheric
imaging. HELCATS (Heliospheric Cataloguing, Analysis And Techniques
Service) LINKCAT catalogue is the first concerted effort to establish
such linkage automatically by the systematic use of STEREO Heliospheric
Imager (HI) observations and related modelling. This presentation gives
and overview of how the LINKCAT catalogue is generated and evaluates
the potential of HI-based imagining in connecting CMEs near the Sun
and in-situ. We will also discuss the possible problems in our approach
and the key future improvements.

---------------------------------------------------------
Title: EU HELCATS Project WP7: Combining Observations of
Interplanetary Scintillation (IPS) and Heliospheric Visible-Light
Imaging of CMEs and SIRs for Space-Weather Purposes
Authors: Bisi, Mario Mark; Barnes, David; Eastwood, Jonathan; Krupar,
Vratislav; Magdalenic, Jasmina; Harrison, Richard; Davies, Jackie;
Fallows, Richard
2017EGUGA..1912991B Altcode:
The Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS)
project is one of the European Union's Seventh Framework Programme (EU
FP7) projects. The project is primarily targeted to the cataloguing
of transient and background structures observed in the heliosphere
by the visible-light Heliospheric Imagers (HIs) on board the twin
spacecraft STEREO mission, including identification of their source
regions and in-situ signatures. The current version of the HELCATS
manually-generated Coronal Mass Ejection (CME) Catalogue contains more
than 1,000 CMEs observed between 2007 and 2016, and the current HELCATS
Stream Interaction Region (SIR) Catalogue contains signatures of nearly
200 co-rotating density structures in the ecliptic plane. HELCATS also
includes an assessment of the complementary nature of ground-based
radio observations of interplanetary scintillation (IPS), which is
yielding catalogues of IPS features (from EISCAT/MERLIN/ESR and/or
LOFAR data, where available) that are being compared to the STEREO HI
catalogues. Here we discuss the near-final status of this aspects of
HELCATS and provide any insights that have been gleaned from initial
analyses of this joint cataloguing exercise. Such insights relate, in
particular, to the space-weather exploitation of these two complementary
observational techniques. For example, there are cases where a CME is
imaged by the STEREO HI instruments but then not detected using IPS, and
vice versa, and preliminary investigations of these will be discussed.

---------------------------------------------------------
Title: A Catalogue of Coronal Mass Ejections Observed by the STEREO
Heliospheric Imagers: Results from HELCATS
Authors: Barnes, David; Davies, Jackie; Harrison, Richard; Perry,
Chris; Möstl, Christian; Rouillard, Alexis; Bothmer, Volker;
Rodriguez, Luciano; Eastwood, Jonathan; Kilpua, Emilia; Gallagher,
Peter
2017EGUGA..19.8160B Altcode:
The wide fields of view provided by the STEREO Heliospheric Imagers
(HIs) allow far greater coverage of Coronal Mass Ejections (CMEs) than
are typically available from coronagraph observations. As part of the EU
FP7 HELCATS (Heliospheric Cataloguing, Analysis and Techniques Service)
project we present a comprehensive catalogue of CMEs that are observed
in HI data, throughout the lifetime of the instruments. This spans
the period from April 2007 to September 2014 for both STEREO-A and -B,
with additional STEREO-A observations continuing from October 2015 to
present, covering the majority of solar cycle 24. A subset of these
CMEs are tracked through the HI fields of view, to which we apply both
single-spacecraft and stereoscopic models to determine CME kinematic
properties such as propagation directions, speeds and accelerations. The
statistical properties of these results are discussed and they are
compared with coronagraph observations during the same period.

---------------------------------------------------------
Title: A Multi-Model Approach to the Analysis of the Kinematics of
CMEs Based on Multi-point Space Observations
Authors: Mrotzek, Niclas; Bothmer, Volker; Davies, Jackie; Harrison,
Richard
2017EGUGA..19.3532M Altcode:
The interaction between Coronal Mass Ejections (CMEs) and the
ambient solar wind is a crucial factor affecting their interplanetary
evolution. It is believed that acceleration due to the Lorenz force
dominates CME evolution near the Sun and that the aerodynamic drag force
becomes dominant further away. In this study, we present results of a
distance-dependent aerodynamic drag force model taking into account
solar wind measurements from the Helios spacecraft over the spatial
range 0.3 to 0.9 AU. We undertake GCS modelling of the investigated CMEs
based on observations from the coronagraphs on SOHO and STEREO as well
as observations from the STEREO heliospheric imagers (HIs). Application
of the CGS modelling to the HI data enables the height-time profiles of
the CMEs to be extended further from the Sun. To derive transit times
to 1 AU, the height-time profiles are then fitted using a kinematic
drag model and compared with in-situ solar wind measurements. The
study is carried out in the framework of the EU FP7 project HELCATS
(Heliospheric Cataloguing, Analysis and Techniques Service).

---------------------------------------------------------
Title: Modeling of coronal mass ejections with the STEREO heliospheric
imagers verified with in situ observations by the Heliophysics
System Observatory
Authors: Möstl, Christian; Isavnin, Alexey; Kilpua, Emilia; Bothmer,
Volker; Mrotzek, Nicolas; Boakes, Peter; Rodriguez, Luciano; Krupar,
Vratislav; Eastwood, Jonathan; Davies, Jackie; Harrison, Richard;
Barnes, David; Winslow, Reka; Helcats Team
2017EGUGA..19.4536M Altcode:
We present the first study to verify modeling of CMEs as observed by
the heliospheric imagers on the two STEREO spacecraft with a large
scale dataset of in situ plasma and magnetic field observations from
the Heliophysics System Observatory, including MESSENGER, VEX, Wind,
and the in situ measurements on the two STEREO spacecraft. To this end,
we have established a new interplanetary CME catalog (ICMECAT) for these
spacecraft by gathering and updating individual ICME lists. In addition,
we have re-calculated the in situ parameters in a consistent way,
resulting in 668 events observed between 2007-2015. We then calculated
the efficacy of the STEREO/HI instruments for predicting (in hindsight)
with the SSEF30 model the arrival time and speed of CMEs as well as
hit/miss ratios. We also show how ICMECAT gives decent statistics
concerning CME impacts on all of the terrestrial planets, including
Mars. The results show some major implications for future heliospheric
imagers which may be used for space weather forecasting. Our effort
should also serve as a baseline for the upcoming new era in heliospheric
science with Solar Orbiter, Solar Probe Plus, BepiColombo returning
partly comparable observations in the next decade. The presented work
has received funding from the European Union Seventh Framework Programme
(FP7/ 2007-2013) under grant agreement No. 606692 [HELCATS].

---------------------------------------------------------
Title: Long-Term Tracking of Corotating Density Structures Using
Heliospheric Imaging (catalogue of CIRs during 2007-2014)
Authors: Plotnikov, Illya; Rouillard, Alexis P.; Davies, Jackie;
Botmer, Volker; Eastwood, Jonathan; Gallagher, Peter; Harrison,
Richard; Kilpua, Emilia; Möstl, Christian C.; Perry, Chris; Rodriguez,
Luciano; Lavraud, Benoit; Genot, Vincent; Pinto, Rui; Sanchez-Diaz,
Eduardo
2017EGUGA..19.4486P Altcode:
The systematic monitoring of the solar wind in high-cadence and
high-resolution heliospheric images taken by the Solar-Terrestrial
Relation Observatory (STEREO) spacecraft permits the study of the
spatial and temporal evolution of variable solar wind flows from
the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7)
Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS)
project, we have generated a catalogue listing the properties of more
than 190 corotating structures well-observed in images taken by the
Heliospheric Imager (HI) instruments on-board STEREO-A (ST-A). Based
on this catalogue, we present here one of very few long-term analyses
of solar wind structures advected by the background solar wind. We
concentrate on the subset of plasma density structures clearly
identified inside corotating structures. This analysis confirms that
most of the corotating density structures detected by the heliospheric
imagers comprises a series of density inhomogeneities advected by the
slow solar wind that eventually become entrained by stream interaction
regions. We have derived the spatial-temporal evolution of each
of these corotating density structures by using a well-established
fitting technique. The mean radial propagation speed of the corotating
structures is found to be 311 ± 31 km s-1. We show that the speeds of
the corotating density structures derived using our fitting technique
track well the long-term variation of the radial speed of the slow
solar wind during solar minimum years (2007-2008). Furthermore, we
demonstrate that these features originate near the coronal neutral
line that eventually becomes the heliospheric current sheet.

---------------------------------------------------------
Title: Overview of the HELCATS project
Authors: Harrison, Richard; Davies, Jackie; Perry, Chris; Moestl,
Christian; Rouillard, Alexis; Bothmer, Volker; Rodriguez, Luciano;
Eastwood, Jonathan; Kilpua, Emilia; Gallagher, Peter; Odstrcil, Dusan
2017EGUGA..19.5296H Altcode:
Understanding solar wind evolution is fundamental to advancing our
knowledge of energy and mass transport in the solar system, whilst
also being crucial to space weather and its prediction. The advent of
truly wide-angle heliospheric imaging has revolutionised the study of
solar wind evolution, by enabling direct and continuous observation
of both transient and background components of the solar wind as
they propagate from the Sun to 1 AU and beyond. The EU-funded FP7
Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS)
project combines European expertise in heliospheric imaging, built up
over the last decade in particular through lead involvement in NASA's
STEREO mission, with expertise in solar and coronal imaging as well
as the interpretation of in-situ and radio diagnostic measurements of
solar wind phenomena. HELCATS involves: (1) cataloguing of transient
(coronal mass ejections) and background (stream/corotating interaction
regions) solar wind structures observed by the STEREO/Heliospheric
Imagers, including estimates of their kinematic properties based on
a variety of modelling techniques; (2) verifying these kinematic
properties through comparison with solar source observations and
in-situ measurements at multiple points throughout the heliosphere;
(3) assessing the potential for initialising numerical models based
on the derived kinematic properties of transient and background
solar wind components; (4) assessing the complementarity of radio
observations (Type II radio bursts and interplanetary scintillation)
in the detection and analysis of heliospheric structure in combination
with heliospheric imaging observations. We provide an overview of the
achievements of the HELCATS project, as it reaches its conclusion, and
present selected results that seek to illustrate the value and legacy of
this unprecedented, coordinated study of structures in the heliosphere.

---------------------------------------------------------
Title: Magnetic structure of Earth-directed events in the HELCATS
LINKCAT catalog during 2011-2013
Authors: Palmerio, Erika; Kilpua, Emilia; Bothmer, Volker; Isavnin,
Alexey; Möstl, Christian; Green, Lucie; James, Alexander; Davies,
Jackie; Harrison, Richard
2017EGUGA..19.3874P Altcode:
Coronal mass ejections (CMEs) are the main drivers of intense magnetic
storms and various subsequent space weather phenomena at Earth. The
parameter that defines the ability of a CME to drive geomagnetic
storms is the north-south magnetic field component. One of the most
significant problems in current long-term space weather forecasts is
that there is no practical method to measure the magnetic structure
of CMEs routinely in the outer corona. The magnetic structure of CME
flux ropes can however be inferred based on the properties of the
CME's source region characteristics, such as filament details, coronal
EUV arcades, X-ray sigmoids, taking into account nearby coronal and
photospheric features. The linked catalogue (LINKCAT) of solar CMEs
during the STEREO era is part of the HELCATS project. It aims at
connecting CME observations at the Sun and in interplanetary space,
using heliospheric imager observations from the HI1 cameras onboard the
two STEREO spacecraft to connect the different datasets. The HELCATS
LINKCAT catalogue contains 45 Earth-directed events in the period
2011-2013 (https://www.helcats-fp7.eu/catalogues/wp4_cat.html). Here we
present a statistical study based on the LINKCAT Earth-directed events
during 2011-2013 in which we determine the magnetic properties of
the erupting CMEs, i.e. their magnetic helicity sign, flux rope tilt,
and flux rope axial field direction, by using a synthesis of indirect
proxies based on multi-wavelength remote sensing observations from the
STEREO, SOHO, Hinode, and SDO satellites. These parameters define the
“intrinsic” flux rope configuration at the time of the eruption which
is compared with the magnetic structures detected in situ near Earth.

---------------------------------------------------------
Title: HELCATS: Statistical results on interplanetary type II bursts
observed by STEREO/Waves
Authors: Krupar, V.; Eastwood, J. P.; Magdalenic, J.; Gopalswamy,
N.; Bisi, M. M.; Davies, J. A.; Harrison, R. A.; Barnes, D.
2016AGUFMSH11C2246K Altcode:
Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS)
is a project of the European Union's Seventh Framework Programme. The
current version of the HELCATS manually-generated Coronal Mass Ejection
(CME) catalogue contains more than 1,300 CMEs observed between 2007
and 2014. CMEs are sometimes associated with the so called type II
bursts which are considered to be radio signatures of fast electrons
accelerated at the CME-driven shock front. We present statistical
results on 153 type II bursts associated with manually-identified
CMEs in the HELCATS catalogue. We found that faster CMEs are more
likely to produce radio emissions. By comparing frequency drifts with
white-light observations we calculated angular deviations of type II
burst propagation directions from radial. Our results confirm that
type II bursts statistically arise from CME flanks. We also discuss
the use of interplanetary radio emission in the context of space
weather forecasting.

---------------------------------------------------------
Title: A Catalogue of Geometrically-Modelled Coronal Mass Ejections
Observed by the STEREO Heliospheric Imagers
Authors: Barnes, D.; Davies, J. A.; Harrison, R. A.; Perry, C. H.;
Moestl, C.; Rouillard, A.; Bothmer, V.; Rodriguez, L.; Eastwood,
J. P.; Kilpua, E.; Gallagher, P.
2016AGUFMSH31B2588B Altcode:
We present a catalogue of Coronal Mass Ejections (CMEs) observed by the
Heliospheric Imagers (HIs) onboard the two NASA STEREO spacecraft. This
catalogue contains all CMEs observed during the operational phase of the
STEREO mission, April 2007 to September 2014, for both spacecraft and
resumes from November 2015 for STEREO-A. These CMEs are tracked using
time-elongation plots through the HI-1 and HI-2 fields of view and to
them we apply geometric models to determine their kinematic properties,
such as speed, propagation direction and launch time. A subset of
these CMEs, which are observed simultaneously by both spacecraft,
are identified and to which stereoscopic modelling techniques are
applied. The statistical properties of these catalogues are discussed
as are their results compared to existing CME catalogues covering the
same periods. This work is carried out as part of the EU FP7 HELCATS
(Heliospheric Cataloguing, Analysis and Techniques Service) project.

---------------------------------------------------------
Title: Erratum: “ElEvoHI: A Novel CME Prediction
Tool for Heliospheric Imaging Combining an
Elliptical Front with Drag-based Model Fitting” (<A
href="http://dx.doi.org/10.3847/0004-637x/824/2/131">ApJ, 824,
2, 131</A>)
Authors: Amerstorfer, T.; Möstl, C.; Isavnin, A.; Davies, J. A.;
Kubicka, M.; Amerstorfer, U. V.; Harrison, R. A.
2016ApJ...831..210A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A small mission concept to the Sun-Earth Lagrangian L5 point
for innovative solar, heliospheric and space weather science
Authors: Lavraud, B.; Liu, Y.; Segura, K.; He, J.; Qin, G.; Temmer,
M.; Vial, J. -C.; Xiong, M.; Davies, J. A.; Rouillard, A. P.; Pinto,
R.; Auchère, F.; Harrison, R. A.; Eyles, C.; Gan, W.; Lamy, P.;
Xia, L.; Eastwood, J. P.; Kong, L.; Wang, J.; Wimmer-Schweingruber,
R. F.; Zhang, S.; Zong, Q.; Soucek, J.; An, J.; Prech, L.; Zhang,
A.; Rochus, P.; Bothmer, V.; Janvier, M.; Maksimovic, M.; Escoubet,
C. P.; Kilpua, E. K. J.; Tappin, J.; Vainio, R.; Poedts, S.; Dunlop,
M. W.; Savani, N.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard, T.;
DeForest, C.; Webb, D.; Lugaz, N.; Fuselier, S. A.; Dalmasse, K.;
Tallineau, J.; Vranken, D.; Fernández, J. G.
2016JASTP.146..171L Altcode:
We present a concept for a small mission to the Sun-Earth Lagrangian L5
point for innovative solar, heliospheric and space weather science. The
proposed INvestigation of Solar-Terrestrial Activity aNd Transients
(INSTANT) mission is designed to identify how solar coronal magnetic
fields drive eruptions, mass transport and particle acceleration that
impact the Earth and the heliosphere. INSTANT is the first mission
designed to (1) obtain measurements of coronal magnetic fields from
space and (2) determine coronal mass ejection (CME) kinematics with
unparalleled accuracy. Thanks to innovative instrumentation at a vantage
point that provides the most suitable perspective view of the Sun-Earth
system, INSTANT would uniquely track the whole chain of fundamental
processes driving space weather at Earth. We present the science
requirements, payload and mission profile that fulfill ambitious science
objectives within small mission programmatic boundary conditions.

---------------------------------------------------------
Title: Long-Term Tracking of Corotating Density Structures Using
Heliospheric Imaging
Authors: Plotnikov, I.; Rouillard, A. P.; Davies, J. A.; Bothmer,
V.; Eastwood, J. P.; Gallagher, P.; Harrison, R. A.; Kilpua, E.;
Möstl, C.; Perry, C. H.; Rodriguez, L.; Lavraud, B.; Génot, V.;
Pinto, R. F.; Sanchez-Diaz, E.
2016SoPh..291.1853P Altcode: 2016SoPh..tmp..118P; 2016arXiv160601127P
The systematic monitoring of the solar wind in high-cadence and
high-resolution heliospheric images taken by the Solar-Terrestrial
Relation Observatory (STEREO) spacecraft permits the study of the
spatial and temporal evolution of variable solar wind flows from
the Sun out to 1 AU, and beyond. As part of the EU Framework 7 (FP7)
Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS)
project, we have generated a catalog listing the properties of 190
corotating structures well-observed in images taken by the Heliospheric
Imager (HI) instruments onboard STEREO-A (ST-A). Based on this catalog,
we present here one of very few long-term analyses of solar wind
structures advected by the background solar wind. We concentrate on the
subset of plasma density structures clearly identified inside corotating
structures. This analysis confirms that most of the corotating density
structures detected by the heliospheric imagers comprises a series
of density inhomogeneities advected by the slow solar wind that
eventually become entrained by stream interaction regions. We have
derived the spatial-temporal evolution of each of these corotating
density structures by using a well-established fitting technique. The
mean radial propagation speed of the corotating structures is found
to be 311 ±31 kms−1. Such a low mean value corresponds
to the terminal speed of the slow solar wind rather than the speed of
stream interfaces, which is typically intermediate between the slow and
fast solar wind speeds (∼400 kms−1). Using our fitting
technique, we predicted the arrival time of each corotating density
structure at different probes in the inner heliosphere. We find that our
derived speeds are systematically lower by ∼100 kms−1
than those measured in situ at the predicted impact times. Moreover,
for cases when a stream interaction region is clearly detected in situ
at the estimated impact time, we find that our derived speeds are lower
than the speed of the stream interface measured in situ by an average
of 55 kms−1 at ST-A and 84 kms−1 at STEREO-B
(ST-B). We show that the speeds of the corotating density structures
derived using our fitting technique track well the long-term variation
of the radial speed of the slow solar wind during solar minimum years
(2007 - 2008). Furthermore, we demonstrate that these features originate
near the coronal neutral line that eventually becomes the heliospheric
current sheet.

---------------------------------------------------------
Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
2016cosp...41E.607F Altcode:
The SPICE (Spectral Imaging of the Coronal Environment) instrument is
one of the key remote sensing instruments onboard the upcoming Solar
Orbiter Mission. SPICE has been designed to contribute to the science
goals of the mission by investigating the source regions of outflows
and ejection processes which link the solar surface and corona to the
heliosphere. In particular, SPICE will provide quantitative information
on the physical state and composition of the solar atmosphere
plasma. For example, SPICE will access relative abundances of ions to
study the origin and the spatial/temporal variations of the 'First
Ionization Potential effect', which are key signatures to trace the
solar wind and plasma ejections paths within the heliosphere. Here we
will present the instrument and its performance capability to attain the
scientific requirements. We will also discuss how different observation
modes can be chosen to obtain the best science results during the
different orbits of the mission. To maximize the scientific return of
the instrument, the SPICE team is working to optimize the instrument
operations, and to facilitate the data access and their exploitation.

---------------------------------------------------------
Title: Solar abundances with the SPICE spectral imager on Solar
Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
2016cosp...41E.681G Altcode:
Elemental composition of the solar atmosphere and in particular
abundance bias of low and high First Ionization Potential (FIP)
elements are a key tracer of the source regions of the solar wind. These
abundances and their spatio-temporal variations, as well as the other
plasma parameters , will be derived by the SPICE (Spectral Imaging
of the Coronal Environment) EUV spectral imager on the upcoming
Solar Orbiter mission. SPICE is designed to provide spectroheliograms
(spectral images) using a core set of emission lines arising from ions
of both low-FIP and high-FIP elements. These lines are formed over
a wide range of temperatures, enabling the analysis of the different
layers of the solar atmosphere. SPICE will use these spectroheliograms
to produce dynamic composition maps of the solar atmosphere to be
compared to in-situ measurements of the solar wind composition of
the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
study the connectivity between the spacecraft (the Heliosphere) and
the Sun. We will discuss the SPICE capabilities for such composition
measurements.

---------------------------------------------------------
Title: ElEvoHI: A Novel CME Prediction Tool for Heliospheric Imaging
Combining an Elliptical Front with Drag-based Model Fitting
Authors: Rollett, T.; Möstl, C.; Isavnin, A.; Davies, J. A.; Kubicka,
M.; Amerstorfer, U. V.; Harrison, R. A.
2016ApJ...824..131R Altcode: 2016arXiv160500510R
In this study, we present a new method for forecasting arrival times
and speeds of coronal mass ejections (CMEs) at any location in the inner
heliosphere. This new approach enables the adoption of a highly flexible
geometrical shape for the CME front with an adjustable CME angular
width and an adjustable radius of curvature of its leading edge, I.e.,
the assumed geometry is elliptical. Using, as input, Solar TErrestrial
RElations Observatory (STEREO) heliospheric imager (HI) observations,
a new elliptic conversion (ElCon) method is introduced and combined with
the use of drag-based model (DBM) fitting to quantify the deceleration
or acceleration experienced by CMEs during propagation. The result is
then used as input for the Ellipse Evolution Model (ElEvo). Together,
ElCon, DBM fitting, and ElEvo form the novel ElEvoHI forecasting
utility. To demonstrate the applicability of ElEvoHI, we forecast the
arrival times and speeds of 21 CMEs remotely observed from STEREO/HI
and compare them to in situ arrival times and speeds at 1 AU. Compared
to the commonly used STEREO/HI fitting techniques (Fixed-ϕ, Harmonic
Mean, and Self-similar Expansion fitting), ElEvoHI improves the arrival
time forecast by about 2 to ±6.5 hr and the arrival speed forecast
by ≈ 250 to ±53 km s-1, depending on the ellipse aspect
ratio assumed. In particular, the remarkable improvement of the arrival
speed prediction is potentially beneficial for predicting geomagnetic
storm strength at Earth.

---------------------------------------------------------
Title: Deriving CME kinematics from multipoint space observations
Authors: Mrotzek, Niclas; Pluta, Adam; Bothmer, Volker; Davies,
Jackie; Harrison, Richard
2016EGUGA..18.8058M Altcode:
It is commonly believed that the kinematics of CMEs consist of an early
Lorentz acceleration phase near the Sun followed by a decelerating
drag-force phase at distances further out. To better understand
the physical processes of CME evolution, and also to predict more
accurately their arrival times at other heliospheric locations,
we have analysed CMEs using multipoint coronagraph observations
from STEREO and SOHO. The CME speed evolution is analysed by applying
time-series GCS-modelling. The analysis is extended to distances further
away from the Sun through analysis of observations from the STEREO
heliospheric imagers. The results are compared to those obtained from
the geometrical modelling of time-elongation profiles of CMEs extracted
from J-maps. We discuss the implications of our results in the context
of state-of-the-art space weather predictions. The studies are carried
out in the EU FP7 project HELCATS (Heliospheric Cataloguing, Analysis
and Techniques Service).

---------------------------------------------------------
Title: ElEvoHI - Improving CME arrival predictions using heliospheric
imaging
Authors: Rollett, Tanja; Möstl, Christian; Isavnin, Alexey; Kubicka,
Manuel; Amerstorfer, Ute; Davies, Jackie; Harrison, Richard
2016EGUGA..18.7309R Altcode:
The STEREO mission has sampled a tremendous amount of data, which
have served as a basis to develop a lot of new methods to analyze the
dynamics of coronal mass ejections (CMEs) during their journey through
interplanetary space. The STEREO heliospheric imagers (HI) in particular
are unsurpassed in their contribution to a deeper understanding of
how CMEs are influenced by interaction with the solar wind and other
CMEs and how they evolve in the inner heliosphere. Although STEREO is
currently not well observing the space between the Sun and Earth, the
large data repository of HI observations enables us to further improve
the prediction of CME arrival times and speeds using HI observations -
particularly with regard to a potential future L5 mission. We present
a new method for predicting arrival times and speeds of CMEs at any
location in the inner heliosphere: ElEvoHI. This new approach uses
HI observations as input and assumes an elliptic CME front shape. The
solar wind influence is taken into account by fitting the observations
using the drag-based model. In this way, it is possible to gain all
parameters needed as input for the Ellipse Evolution model (ElEvo),
which is then used to predict the CME arrival. To demonstrate the
applicability of ElEvoHI we present the forecasts for 20 CMEs remotely
observed by STEREO/HI and compare the forecasts to their in situ arrival
times and speeds at 1 AU. Compared to the widely used Fixed-φ fitting
method, ElEvoHI improves the arrival time forecast by 2.2 hours to ±6.5
hours and the arrival speed forecast by 260 km s-1 to ±55 km s-1. In
particular, the remarkable improvement of the arrival speed prediction
is crucial for predicting geomagnetic storm strength on Earth.

---------------------------------------------------------
Title: HELCATS - Heliospheric Cataloguing, Analysis and Techniques
Service
Authors: Harrison, Richard; Davies, Jackie; Perry, Chris; Moestl,
Christian; Rouillard, Alexis; Bothmer, Volker; Rodriguez, Luciano;
Eastwood, Jonathan; Kilpua, Emilia; Gallagher, Peter
2016EGUGA..1810220H Altcode:
Understanding the evolution of the solar wind is fundamental to
advancing our knowledge of energy and mass transport in the solar
system, rendering it crucial to space weather and its prediction. The
advent of truly wide-angle heliospheric imaging has revolutionised the
study of both transient (CMEs) and background (SIRs/CIRs) solar wind
plasma structures, by enabling their direct and continuous observation
out to 1 AU and beyond. The EU-funded FP7 HELCATS project combines
European expertise in heliospheric imaging, built up in particular
through lead involvement in NASA's STEREO mission, with expertise in
solar and coronal imaging as well as in-situ and radio measurements
of solar wind phenomena, in a programme of work that will enable a
much wider exploitation and understanding of heliospheric imaging
observations. With HELCATS, we are (1.) cataloguing transient and
background solar wind structures imaged in the heliosphere by STEREO/HI,
since launch in late October 2006 to date, including estimates of their
kinematic properties based on a variety of established techniques
and more speculative, approaches; (2.) evaluating these kinematic
properties, and thereby the validity of these techniques, through
comparison with solar source observations and in-situ measurements
made at multiple points throughout the heliosphere; (3.) appraising
the potential for initialising advanced numerical models based on
these kinematic properties; (4.) assessing the complementarity of radio
observations (in particular of Type II radio bursts and interplanetary
scintillation) in combination with heliospheric imagery. We will,
in this presentation, provide an overview of progress from the first
18 months of the HELCATS project.

---------------------------------------------------------
Title: First Results on Visualization and Verification of the
STEREO Heliospheric Imager CME Catalogue with In Situ Data from the
Heliophysics System Observatory
Authors: Rollett, T.; Moestl, C.; Boakes, P. D.; Isavnin, A.; Davies,
J. A.; Byrne, J.; Barnes, D.; Good, S. W.; Perry, C. H.; Kubicka,
M.; Harrison, R. A.; Kilpua, E.; Forsyth, R. J.; Bothmer, V.
2015AGUFMSH53A2466R Altcode:
The space weather community has recently seen major advances in the
prediction of the speed and arrival time of solar coronal mass ejections
at Earth and other planets. Since the start of the STEREO mission
in 2006, each of the heliospheric imagers (HIs) onboard the Ahead
and Behind spacecraft has successfully tracked hundreds of CMEs. The
advantage of HI is that CMEs can be followed for a significant part of
the inner heliosphere, and the CME evolution in direction and speed
is better constrained than by coronagraphs alone. By tracking and
cataloguing each of those CMEs in the EU HELCATS project, we can apply
geometrical modeling (FPF, HMF, SSEF) techniques on single-spacecraft
HI observations to extract the expected planetary impacts of each
CME. These arrivals are then verified or refuted by in situ solar wind
plasma and magnetic field observations provided by the spacecraft
forming the Heliophysics System Observatory (HSO), such as Wind,
ACE, Venus Express, MESSENGER, and STEREO-A/B, for which various ICME
catalogues are gathered and updated in the course of HELCATS.A first
assessment on the relationship between CME HI and in situ observations
is discussed, such as occurrence rates, speeds and arrival times and
magnetic field strength. We also present visualizations of the HI CME
catalogue and the corresponding in situ observations. The presented
work has received funding from the European Union Seventh Framework
Programme (FP7/ 2007-2013) under grant agreement No. 606692 [HELCATS].

---------------------------------------------------------
Title: HELCATS - Heliospheric Cataloguing, Analysis and Techniques
Service
Authors: Barnes, D.; Harrison, R. A.; Davies, J. A.; Byrne, J.;
Perry, C. H.; Moestl, C.; Rouillard, A. P.; Bothmer, V.; Rodriguez,
L.; Eastwood, J. P.; Kilpua, E.; Odstrcil, D.; Gallagher, P.
2015AGUFMSH21B2410B Altcode:
Understanding the evolution of the solar wind is fundamental to
advancing our knowledge of energy and mass transport in the Solar
System, making it crucial to space weather and its prediction. The
advent of truly wide-angle heliospheric imaging has revolutionised
the study of both transient (CMEs) and background (IRs) solar wind
plasma structures, by enabling their direct and continuous observation
out to 1 AU and beyond. The EU-funded FP7 HELCATS project combines
European expertise in heliospheric imaging, built up in particular
through lead involvement in NASA's STEREO mission, with expertise in
solar and coronal imaging as well as in-situ and radio measurements
of solar wind phenomena, in a programme of work that will enable
a much wider exploitation and understanding of heliospheric imaging
observations. The HELCATS project endeavors to catalogue transient and
background solar wind structures imaged by STEREO/HI throughout the
duration of the mission. This catalogue will include estimates of their
kinematic properties using a variety of established and more speculative
approaches, which are to be evaluated through comparisons with solar
source and in-situ measurements. The potential for driving numerical
models from these kinematic properties is to be assessed, as is their
complementarity to radio observations, specifically Type II bursts and
interplanetary scintillation. This presentation provides an overview of
the HELCATS project and its progress in first 18 months of operations.

---------------------------------------------------------
Title: Requirements for an Operational Coronagraph
Authors: Howard, R.; Vourlidas, A.; Harrison, R. A.; Bisi, M. M.;
Plunkett, S. P.; Socker, D. G.; Eyles, C. J.; Webb, D. F.; DeForest,
C. E.; Davies, J. A.; Howard, T. A.; de Koning, C. A.; Gopalswamy,
N.; Davila, J. M.; Tappin, J.; Jackson, B. V.
2015AGUFMSH14A..02H Altcode:
Coronal mass ejections (CMEs) have been shown to be the major driver
of the non-recurrent space weather events and geomagnetic storms. The
utility of continuously monitoring such events has been very effectively
demonstrated by the LASCO experiment on the SOHO mission. However SOHO
is aging, having been launched 20 years ago on Dec 2, 1995. The STEREO
mission, in which two spacecraft in orbits about the sun are drifting
away from earth, has shown the utility of multiple viewpoints off the
sun-earth line. Up to now the monitoring of CMES has been performed
by scientific instruments such as LASCO and SECCHI with capabilities
beyond those required to record the parameters that are needed to
forecast the impact at earth. However, there is great interest within
the US NOAA and the UK Met Office to launch operational coronagraphs
to L1 and L5. An ad-hoc group was formed to define the requirements
of the L5 coronagraph. In this paper we present some requirements that
must be met by operational coronagraphs. The Office of Naval Research
is gratefully acknowledged.

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Title: Coronal and heliospheric imagers for solar wind phenomena
Authors: Middleton, Kevin F.; Bourdelle, Anthony; Davies, Jackie A.;
Eyles, Chris J.; Griffin, Doug K.; Harrison, Richard A.; Richards,
Tony R.; Rogers, J. Kevin; Tappin, S. James; Tosh, Ian A. J.; Waltham,
Nick R.
2015SPIE.9604E..0RM Altcode:
RAL Space is enhancing its program to lead the development of European
capabilities in space-based visible-light coronal and heliospheric
imaging instrumentation in the light of emerging opportunities
such as the European Space Agency's Space Situational Awareness
program and recent S2 small-mission call. Visible-light coronal and
heliospheric imaging of solar wind phenomena, such as coronal mass
ejections and interaction regions, is of critical importance to
space weather studies, both operationally and in terms of enabling
the underpinning science. This work draws on heritage from scientific
instruments such as LASCO (Large Angle and Spectrometric Coronagraph)
on the SOHO spacecraft, SMEI (Solar Mass Ejection Imager) on the
Coriolis spacecraft and the HI (Heliospheric Imager) instruments
on STEREO. Such visible-light observation of solar wind structures
relies on the detection of sunlight that has been Thomson-scattered by
electrons (the so-called K-corona). The Thomson-scattered signal must
be extracted from other signals that can be many orders of magnitude
greater (such as that from the F-corona and the solar disc itself)
and this places stringent constraints on stray-light rejection, as
well as pointing stability and accuracy. We discuss the determination
of instrument requirements, key design trade-offs and the evolution of
base-line designs for the coronal and heliospheric regimes. We explain
how the next generation of instruments will build on this heritage while
also, in some cases, meeting the challenges on resources imposed on
operational space weather imagers. In particular, we discuss the optical
engineering challenges involved in the design of these instruments.

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Title: Carrington-L5: The UK/US Operational Space Weather Monitoring
Mission
Authors: Trichas, Markos; Gibbs, Mark; Harrison, Richard; Green,
Lucie; Eastwood, Jonathan; Bentley, Bob; Bisi, Mario; Bogdanova,
Yulia; Davies, Jackie; D'Arrigo, Paolo; Eyles, Chris; Fazakerley,
Andrew; Hapgood, Mike; Jackson, David; Kataria, Dhiren; Monchieri,
Emanuele; Windred, Phil
2015Hipp....2l..25T Altcode: 2015Hipp....2...25T
Airbus Defence and Space (UK) has carried out a study to investigate
the possibilities for an operational space weather mission, in
collaboration with the Met Office, RAL, MSSL and Imperial College
London. The study looked at the user requirements for an operational
mission, a model instrument payload, and a mission/spacecraft concept. A
particular focus is cost effectiveness and timelineness of the data,
suitable for 24/7 operational forecasting needs. We have focussed
on a mission at L5 assuming that a mission to L1 will already occur,
on the basis that L5 (Earth trailing) offers the greatest benefit for
the earliest possible warning on hazardous SWE events and the most
accurate SWE predictions. The baseline payload has been selected to
cover all UK Met Office/NOAA's users priorities for L5 using instruments
with extensive UK/US heritage, consisting of: heliospheric imager,
coronograph, magnetograph, magnetometer, solar wind analyser and
radiation monitor. The platform and subsystems are based on extensive
re-use from past Airbus Defence and Space spacecraft to minimize the
development cost and a Falcon-9 launcher has been selected on the same
basis. A schedule analysis shows that the earliest launch could be
achieved by 2020, assuming Phase A kick-off in 2015-2016. The study
team have selected the name "Carrington" for the mission, reflecting
the UK's proud history in this domain.

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Title: Radio Flares from Gamma-ray Bursts
Authors: Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.;
Harrison, R.; Japelj, J.; Guidorzi, C.; Melandri, A.; Gomboc, A.
2015ApJ...806..179K Altcode: 2015arXiv150308428K
We present predictions of centimeter and millimeter radio emission
from reverse shocks (RSs) in the early afterglows of gamma-ray bursts
(GRBs) with the goal of determining their detectability with current and
future radio facilities. Using a range of GRB properties, such as peak
optical brightness and time, isotropic equivalent gamma-ray energy, and
redshift, we simulate radio light curves in a framework generalized for
any circumburst medium structure and including a parameterization of the
shell thickness regime that is more realistic than the simple assumption
of thick- or thin-shell approximations. Building on earlier work by
Mundell et al. and Melandri et al. in which the typical frequency of
the RS was suggested to lie at radio rather than optical wavelengths
at early times, we show that the brightest and most distinct RS radio
signatures are detectable up to 0.1-1 day after the burst, emphasizing
the need for rapid radio follow-up. Detection is easier for bursts
with later optical peaks, high isotropic energies, lower circumburst
medium densities, and at observing frequencies that are less prone to
synchrotron self-absorption effects—typically above a few GHz. Given
recent detections of polarized prompt gamma-ray and optical RS emission,
we suggest that detection of polarized radio/millimeter emission will
unambiguously confirm the presence of low-frequency RSs at early time.

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Title: Long-lived magnetism from inner core solidification on small
planetary bodies
Authors: Bryson, James; Nichols, Claire; Herrero Albillos, Julia;
Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan,
Gerrit; Nimmo, Francis; Harrison, Richard
2015EGUGA..17.3756B Altcode:
Paleomagnetic measurements of meteorites suggest that many asteroids
generated their own magnetic activity during the early solar system,
with the majority of measured meteorite classes appearing to have
recorded dynamo fields. Despite this apparent near ubiquity of
magnetic activity among small planetary bodies, many of the most
fundamental aspects of this activity remain enigmatic. Crucially,
both the temporal evolution and the processes capable of generating
small body magnetic activity are yet to be gleaned from paleomagnetic
measurements. This information has been central in understanding the
dynamic and thermochemical evolution of our planet, and equivalent
information from asteroids could help illuminate the evolution of
matter in our solar system. Here, we present time-resolved records of
the magnetic activity generated on the main-group pallasite parent
body inferred from X-ray photoemission electron microscopy (XPEEM)
images of the metal matrix within the Imilac, Esquel, Brenham and
Marjalahti pallasite meteorites. This metal cooled at &lt;10 K/Myr,
which permitted a unique nanostructure known as the cloudy zone (CZ)
to form. The CZ is an excellent paleomagnetic recorder, and formed over
a distance of ~10 µm over tens of millions of years. By spatially
resolving the magnetism of this nanostructure using XPEEM, we infer
both the direction and intensity of the field experienced by the CZ
of these meteorites. All four meteorites recorded unidirectional
fields. The Brenham and Marjalahti meteorites recorded relatively
weak fields with intensities of &gt;20 µT over a period of ~4 -
10 Myr. The Imilac meteorite recorded a stronger field between 120 -
130 µT over a period of &lt;10 Myr. The Esquel meteorite initially
recorded a field of ~80 µT, which then weakened over time down to
a plateau at ~30 µT, before decreasing further down to ~0 µT. By
comparing experimental cooling rates to those predicted from planetary
cooling models, the Brenham and Marjalahti meteorites are expected to
have recorded the magnetic activity shortly before core solidification,
and the Imilac and Esquel meteorites are expected to have recorded the
magnetic activity associated with the early and later stages of this
process, respectively. Dynamo field intensities predicted from empirical
scaling relationships suggest that the Imilac meteorite experienced a
dipolar dynamo field generated by compositional convection associated
with the early stages of bottom-up core solidification. The Esquel
meteorite appears to have experienced a dipolar-multipolar transition
(intensity decrease), multipolar regime (plateau at ~30 µT), and the
cessation of dynamo activity associated with the near-completion of core
solidification (decrease down to ~0 µT). The weak fields experienced
by the Brenham and Marjalahti are consistent with a period of dynamo
activity quiescence prior to inner core growth. Solidification-driven
convection is yet to be associated with small bodies, but given its
efficiency, likely lead to convection across the majority of bottom-up
solidifying cores in these bodies, implying a widespread, intense and
long-lived epoch of magnetic activity among small bodies during the
early solar system.

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Title: HELCATS Prediction of Planetary CME arrival times
Authors: Boakes, Peter; Moestl, Christian; Davies, Jackie; Harrison,
Richard; Byrne, Jason; Barnes, David; Isavnin, Alexey; Kilpua, Emilia;
Rollett, Tanja
2015EGUGA..17.3601B Altcode:
We present the first results of CME arrival time prediction at
different planetary locations and their comparison to the in situ
data within the HELCATS project. The EU FP7 HELCATS (Heliospheric
Cataloguing, Analysis &amp; Techniques Service) is a European
effort to consolidate the exploitation of the maturing field of
heliospheric imaging. HELCATS aims to catalogue solar wind transients,
observed by the NASA STEREO Heliospheric Imager (HI) instruments, and
validate different methods for the determination of their kinematic
properties. This validation includes comparison with arrivals at
Earth, and elsewhere in the heliosphere, as well as onsets at the Sun
(http://www.helcats-fp7.eu/). A preliminary catalogue of manually
identified CMEs, with over 1000 separate events, has been created
from observations made by the STEREO/HI instruments covering the
years 2007-2013. Initial speeds and directions of each CME have been
derived through fitting the time elongation profile to the state of
the art Self-Similar Expansion Fitting (SSEF) geometric technique
(Davies et al., 2012). The technique assumes that, in the plane
corresponding to the position angle of interest, CMEs can be modelled as
circles subtending a fixed angular width to Sun-center and propagating
anti-sunward in a fixed direction at a constant speed (we use an angular
width of 30 degrees in our initial results). The model has advantages
over previous geometric models (e.g. harmonic mean or fixed phi) as it
allows one to predict whether a CME will 'hit' a specific heliospheric
location, as well as to what degree (e.g. direct assault or glancing
blow). We use correction formulae (Möstl and Davies, 2013) to convert
CME speeds, direction and launch time to speed and arrival time at any
in situ location. From the preliminary CME dataset, we derive arrival
times for over 400 Earth-directed CMEs, and for over 100 Mercury-,
Venus-, Mars- and Saturn-directed CMEs predicted to impact each
planet. We present statistics of predicted CME arrival properties. In
addition, we independently identify CME arrival at in situ locations
using magnetic field data from the Venus Express, Messenger, and Ulysses
spacecraft and show first comparisons to predicted arrival times. The
results hold important implications for space weather prediction at
Earth and other locations, allowing model and predicted CME parameters
to be compared to their in situ counterparts.

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Title: Instant: An Innovative L5 Small Mission Concept for Coordinated
Science with Solar Orbiter and Solar Probe Plus
Authors: Lavraud, B.; Liu, Y. D.; Harrison, R. A.; Liu, W.;
Auchere, F.; Gan, W.; Lamy, P. L.; Xia, L.; Eastwood, J. P.;
Wimmer-Schweingruber, R. F.; Zong, Q.; Rochus, P.; Maksimovic, M.;
Temmer, M.; Escoubet, C. P.; Kilpua, E.; Rouillard, A. P.; Davies,
J. A.; Vial, J. C.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard,
T. A.; DeForest, C. E.
2014AGUFMSH21B4109L Altcode:
We will present both the science objectives and related instrumentation
of a small solar and heliospheric mission concept, INSTANT:
INvestigation of Solar-Terrestrial Activity aNd Transients. It will be
submitted as an opportunity to the upcoming ESA-China S-class mission
call later this year. This concept was conceived to allow innovative
measurements and unprecedented, early determination of key properties
of Earthbound CMEs from the L5 vantage point. Innovative measurements
will include magnetic field determination in the corona thanks to
Hanle measurement in Lyman-α and polarized heliospheric imaging
for accurate determination of CME trajectories. With complementary
in situ measurements, it will uniquely permit solar storm science,
solar storm surveillance, and synergy with Solar Orbiter and Solar
Probe Plus (the ESA-China S2 mission launch is planned in 2021).

---------------------------------------------------------
Title: The HELCATS Project: Characterising the Evolution of Coronal
Mass Ejections Observed During Solar Cycle 24
Authors: Bisi, M. M.; Harrison, R. A.; Davies, J. A.; Perry, C. H.;
Moestl, C.; Rouillard, A. P.; Bothmer, V.; Rodriguez, L.; Eastwood,
J. P.; Kilpua, E.; Gallagher, P.; Odstrcil, D.
2014AGUFMSH43B4214B Altcode:
Understanding the evolution of coronal mass ejections (CMEs) is
fundamental to advancing our knowledge of energy and mass transport in
the solar system, thus also rendering it crucial to space weather and
its prediction. The advent of truly wide-angle heliospheric imaging
has revolutionised the study of CMEs, by enabling their direct and
continuous observation as they propagate from the Sun out to 1 AU and
beyond. The recently initiated EU-funded FP7 Heliospheric Cataloguing,
Analysis and Technique Service (HELCATS) project combines European
expertise in the field of heliospheric imaging, built up over the last
decade in particular through lead involvement in NASA's STEREO mission,
with expertise in such areas as solar and coronal imaging as well as
the interpretation of in-situ and radio diagnostic measurements of
solar wind phenomena. The goals of HELCATS include the cataloguing
of CMEs observed in the heliosphere by the Heliospheric Imager
(HI) instruments on the STEREO spacecraft, since their launch in
late October 2006 to date, an interval that covers much of the
historically weak solar cycle 24. Included in the catalogue will be
estimates of the kinematic properties of the imaged CMEs, based on a
variety of established, and some more speculative, modelling approaches
(geometrical, forward, inverse, magneto-hydrodynamic); these kinematic
properties will be verified through comparison with solar disc and
coronal imaging observations, as well as through comparison with radio
diagnostic and in-situ measurements made at multiple points throughout
the heliosphere. We will provide an overview of the HELCATS project,
and present initial results that will seek to illuminate the unusual
nature of solar cycle 24.

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Title: Connecting Speeds, Directions and Arrival Times of 22 Coronal
Mass Ejections from the Sun to 1 AU
Authors: Möstl, C.; Amla, K.; Hall, J. R.; Liewer, P. C.; De Jong,
E. M.; Colaninno, R. C.; Veronig, A. M.; Rollett, T.; Temmer, M.;
Peinhart, V.; Davies, J. A.; Lugaz, N.; Liu, Y. D.; Farrugia, C. J.;
Luhmann, J. G.; Vršnak, B.; Harrison, R. A.; Galvin, A. B.
2014ApJ...787..119M Altcode: 2014arXiv1404.3579M
Forecasting the in situ properties of coronal mass ejections (CMEs)
from remote images is expected to strongly enhance predictions of
space weather and is of general interest for studying the interaction
of CMEs with planetary environments. We study the feasibility of using
a single heliospheric imager (HI) instrument, imaging the solar wind
density from the Sun to 1 AU, for connecting remote images to in situ
observations of CMEs. We compare the predictions of speed and arrival
time for 22 CMEs (in 2008-2012) to the corresponding interplanetary
coronal mass ejection (ICME) parameters at in situ observatories
(STEREO PLASTIC/IMPACT, Wind SWE/MFI). The list consists of front-
and backsided, slow and fast CMEs (up to 2700 km s-1). We
track the CMEs to 34.9 ± 7.1 deg elongation from the Sun with J maps
constructed using the SATPLOT tool, resulting in prediction lead times
of -26.4 ± 15.3 hr. The geometrical models we use assume different
CME front shapes (fixed-Φ, harmonic mean, self-similar expansion) and
constant CME speed and direction. We find no significant superiority
in the predictive capability of any of the three methods. The absolute
difference between predicted and observed ICME arrival times is 8.1 ±
6.3 hr (rms value of 10.9 hr). Speeds are consistent to within 284 ±
288 km s-1. Empirical corrections to the predictions enhance
their performance for the arrival times to 6.1 ± 5.0 hr (rms value
of 7.9 hr), and for the speeds to 53 ± 50 km s-1. These
results are important for Solar Orbiter and a space weather mission
positioned away from the Sun-Earth line.

---------------------------------------------------------
Title: Connecting speeds, directions and arrival times of 22 coronal
mass ejections from the Sun to 1 AU
Authors: Möstl, Christian; Amla, Keshav; Hall, Jeff R.; Liewer,
Paulett C.; DeJong, Eric M.; Colaninno, Robin C.; Veronig, Astrid M.;
Rollett, Tanja; Temmer, Manuela; Peinhart, Vanessa; Davies, Jackie
A.; Lugaz, Noé; Liu, Ying; Farrugia, Charles J.; Luhmann, Janet G.;
Vrsnak, Bojan; Harrison, Richard A.; Galvin, Antoinette B.
2014EGUGA..16.1755M Altcode:
Forecasting in situ properties of coronal mass ejections (CMEs) from
remote images is expected to strongly enhance predictions of space
weather, and is of general interest for studying the interaction of
the solar wind with planetary environments. We study the feasibility of
using a heliospheric imager (HI) instrument, which is able to image the
solar wind density along the full Sun to 1 AU distance, for connecting
remote images to in situ observations of CMEs. Such an instrument
is currently in operation on each of the two STEREO spacecraft. We
compare the predictions for speed and arrival time for 22 different
CME events (between 2008-2012), each observed remotely by one STEREO
spacecraft, to the interplanetary coronal mass ejection (ICME) speed and
arrival time observed at in situ observatories (STEREO PLASTIC/IMPACT,
Wind SWE/MFI). We use croissant modeling for STEREO/COR2, and with a
single-spacecraft STEREO/HI instrument, we track each CME to 34.9 ± 7.1
degree elongation from the Sun with J-maps constructed with the SATPLOT
tool. We then fit geometrical models to each track, assuming different
CME front shapes (Fixed-Φ, Harmonic Mean, Self-Similar Expansion),
and constant CME speed and direction. We find no significant preference
in the predictive capability for any of the three geometrical modeling
methods used on the full event list, consisting of front- and backsided,
slow and fast CMEs (up to 2700 km s-1). The absolute difference between
predicted and observed ICME arrival times is 8.1 ± 6.4 hours (rms
value of 10.9h), and speeds are consistent within 284 ± 291 km s-1,
including the geometric effects of CME apex or flank encounters. We
derive new empirical corrections to the imaging results, enhancing
the performance of the arrival time predictions to 6.1 ± 5.0 hours
(rms value of 7.9h), and the speed predictions to 53 ± 50 km s-1,
for this particular set of events. The prediction lead time is around
1 day (-26.4 ± 15.3h). CME directions given by the HI methods differ
considerably, and biases are found on the order of 30-50 degree in
heliospheric longitude, consistent with theoretical expectations. These
results are of interest concerning future missions such as Solar Orbiter
or a dedicated space weather mission positioned remotely from the Earth.

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Title: Phenomenology of Reverse-shock Emission in the Optical
Afterglows of Gamma-Ray Bursts
Authors: Japelj, J.; Kopač, D.; Kobayashi, S.; Harrison, R.; Guidorzi,
C.; Virgili, F. J.; Mundell, C. G.; Melandri, A.; Gomboc, A.
2014ApJ...785...84J Altcode: 2014arXiv1402.3701J
We use a parent sample of 118 gamma-ray burst (GRB) afterglows, with
known redshift and host galaxy extinction, to separate afterglows with
and without signatures of dominant reverse-shock (RS) emission and to
determine which physical conditions lead to a prominent reverse-shock
emission. We identify 10 GRBs with reverse-shock signatures: 990123,
021004, 021211, 060908, 061126, 080319B, 081007, 090102, 090424,
and 130427A. By modeling their optical afterglows with reverse- and
forward-shock analytic light curves and using Monte Carlo simulations,
we estimate the parameter space of the physical quantities describing
the ejecta and circumburst medium. We find that physical properties
cover a wide parameter space and do not seem to cluster around any
preferential values. Comparing the rest-frame optical, X-ray, and
high-energy properties of the larger sample of non-RS-dominated GRBs, we
show that the early-time (&lt;1 ks) optical spectral luminosity, X-ray
afterglow luminosity, and γ-ray energy output of our reverse-shock
dominated sample do not differ significantly from the general population
at early times. However, the GRBs with dominant reverse-shock emission
have fainter than average optical forward-shock emission at late times
(&gt;10 ks). We find that GRBs with an identifiable reverse-shock
component show a high magnetization parameter R B =
ɛB, r/ɛB, f ~ 2-104. Our results
are in agreement with the mildly magnetized baryonic jet model of GRBs.

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Title: New constraints on gamma-ray burst jet geometry and
relativistic shock physics
Authors: Guidorzi, C.; Mundell, C. G.; Harrison, R.; Margutti,
R.; Sudilovsky, V.; Zauderer, B. A.; Kobayashi, S.; Cucchiara, A.;
Melandri, A.; Pandey, S. B.; Berger, E.; Bersier, D.; D'Elia, V.;
Gomboc, A.; Greiner, J.; Japelj, J.; Kopač, D.; Kumar, B.; Malesani,
D.; Mottram, C. J.; O'Brien, P. T.; Rau, A.; Smith, R. J.; Steele,
I. A.; Tanvir, N. R.; Virgili, F.
2014MNRAS.438..752G Altcode: 2013arXiv1311.4340G; 2013MNRAS.tmp.2902G
We use high-quality, multiband observations of Swift GRB 120404A,
from γ-ray to radio frequencies, together with the new hydrodynamics
code of van Eerten et al. to test the standard synchrotron shock
model. The evolution of the radio and optical afterglow, with its
prominent optical rebrightening at trest ∼ 260-2600 s,
is remarkably well modelled by a decelerating jet viewed close to the
jet edge, combined with some early re-energization of the shock. We
thus constrain the geometry of the jet with half-opening and viewing
angles of 23° and 21°, respectively, and suggest that wide jets
viewed off-axis are more common in GRBs than previously thought. We
also derive the fireball microphysics parameters ɛB =
2.4 × 10-4 and ɛe = 9.3 × 10-2
and a circumburst density of n = 240 cm-3. The ability to
self-consistently model the microphysics parameters and jet geometry
in this way offers an alternative to trying to identify elusive
canonical jet breaks at late times. The mismatch between the observed
and model-predicted X-ray fluxes is explained by the local rather than
the global cooling approximation in the synchrotron radiation model,
constraining the microphysics of particle acceleration taking place
in a relativistic shock and, in turn, emphasizing the need for a more
realistic treatment of cooling in future developments of theoretical
models. Finally, our interpretation of the optical peak as due to
the passage of the forward shock synchrotron frequency highlights the
importance of high-quality multiband data to prevent some optical peaks
from being erroneously attributed to the onset of fireball deceleration.

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Title: INSTANT: INvestigation of Solar-Terrestrial Associated
Natural Threats
Authors: Lavraud, Benoit; Vial, Jean-Claude; Harrison, Richard; Davies,
Jackie; Escoubet, C. Philippe; Zong, Qiugang; Auchere, Frederic; Liu,
Ying; Bale, Stuart; Gopalswamy, Nat; Li, Gang; Maksimovic, Milan;
Liu, William; Rouillard, Alexis
2014cosp...40E1758L Altcode:
The INSTANT mission will tackle both compelling solar and heliospheric
science objectives and novel space weather capabilities. This is
allowed by combining innovative and state-of-the-art instrumentation
at an appropriate off-Sun-Earth line location on an orbit lagging
the Earth around the Sun, near the L5 Lagrangian point. It is an
affordable mission that tackles major objectives of the European and
Chinese communities in terms of space physics and space weather. The
science objectives are: 1. What is the magnetic field magnitude and
topology in the corona? 2. How does the magnetic field reconfigure
itself during CME eruptions? 3. What are the sources and links between
the slow and fast winds? 4. How do CMEs accelerate and interact in the
interplanetary medium? The mission will further allow the following
crucial space weather capabilities: 5. Three-days advance knowledge
of CIR properties that reach Earth. 6. Twelve hours to 2 days advance
warning of Earth-directed CMEs. 7. Thanks to Lyman-α observations,
first-ever capability of determining the magnetic field magnitude and
orientation of Earth-directed CMEs. The mission will be proposed in
the context of the upcoming ESA-China S-class call for mission.

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Title: GRB 130427A: A Nearby Ordinary Monster
Authors: Maselli, A.; Melandri, A.; Nava, L.; Mundell, C. G.; Kawai,
N.; Campana, S.; Covino, S.; Cummings, J. R.; Cusumano, G.; Evans,
P. A.; Ghirlanda, G.; Ghisellini, G.; Guidorzi, C.; Kobayashi,
S.; Kuin, P.; La Parola, V.; Mangano, V.; Oates, S.; Sakamoto, T.;
Serino, M.; Virgili, F.; Zhang, B. -B.; Barthelmy, S.; Beardmore, A.;
Bernardini, M. G.; Bersier, D.; Burrows, D.; Calderone, G.; Capalbi,
M.; Chiang, J.; D'Avanzo, P.; D'Elia, V.; De Pasquale, M.; Fugazza,
D.; Gehrels, N.; Gomboc, A.; Harrison, R.; Hanayama, H.; Japelj,
J.; Kennea, J.; Kopac, D.; Kouveliotou, C.; Kuroda, D.; Levan, A.;
Malesani, D.; Marshall, F.; Nousek, J.; O'Brien, P.; Osborne, J. P.;
Pagani, C.; Page, K. L.; Page, M.; Perri, M.; Pritchard, T.; Romano,
P.; Saito, Y.; Sbarufatti, B.; Salvaterra, R.; Steele, I.; Tanvir,
N.; Vianello, G.; Weigand, B.; Wiersema, K.; Yatsu, Y.; Yoshii, T.;
Tagliaferri, G.
2014Sci...343...48M Altcode: 2013arXiv1311.5254M
Long-duration gamma-ray bursts (GRBs) are an extremely rare outcome
of the collapse of massive stars and are typically found in the
distant universe. Because of its intrinsic luminosity (L ∼ 3 ×
1053 ergs per second) and its relative proximity (z =
0.34), GRB 130427A reached the highest fluence observed in the γ-ray
band. Here, we present a comprehensive multiwavelength view of GRB
130427A with Swift, the 2-meter Liverpool and Faulkes telescopes, and by
other ground-based facilities, highlighting the evolution of the burst
emission from the prompt to the afterglow phase. The properties of GRB
130427A are similar to those of the most luminous, high-redshift GRBs,
suggesting that a common central engine is responsible for producing
GRBs in both the contemporary and the early universe and over the full
range of GRB isotropic energies.

---------------------------------------------------------
Title: Magnetic Field Structure in Relativistic Jets
Authors: Jermak, Helen; Mundell, Carole; Steele, Iain; Harrison,
Richard; Kobayashi, Shiho; Lindfors, Elina; Nilsson, Kari; Barres de
Almeida, Ulisses
2013EPJWC..6103005J Altcode:
Relativistic jets are ubiquitous when considering an accreting black
hole. Two of the most extreme examples of these systems are blazars and
gamma-ray bursts (GRBs), the jets of which are thought to be threaded
with a magnetic field of unknown structure. The systems are made up of
a black hole accreting matter and producing, as a result, relativistic
jets of plasma from the poles of the black hole. Both systems are
viewed as point sources from Earth, making it impossible to spatially
resolve the jet. In order to explore the structure of the magnetic
field within the jet we take polarisation measurements with the RINGO
polarimeters on the world's largest fully autonomous, robotic optical
telescope: The Liverpool Telescope. Using the polarisation degree and
angle measured by the RINGO polarimeters it is possible to distinguish
between global magnetic fields created in the central engine and random
tangled magnetic fields produced locally in shocks. We also monitor
blazar sources regularly during quiescence with periods of flaring
monitored more intensively. Reported here are the early polarisation
results for GRBs 060418 and 090102, along with future prospects for
the Liverpool Telescope and the RINGO polarimeters.

---------------------------------------------------------
Title: GRB 091024A and the Nature of Ultra-long Gamma-Ray Bursts
Authors: Virgili, F. J.; Mundell, C. G.; Pal'shin, V.; Guidorzi, C.;
Margutti, R.; Melandri, A.; Harrison, R.; Kobayashi, S.; Chornock,
R.; Henden, A.; Updike, A. C.; Cenko, S. B.; Tanvir, N. R.; Steele,
I. A.; Cucchiara, A.; Gomboc, A.; Levan, A.; Cano, Z.; Mottram, C. J.;
Clay, N. R.; Bersier, D.; Kopač, D.; Japelj, J.; Filippenko, A. V.;
Li, W.; Svinkin, D.; Golenetskii, S.; Hartmann, D. H.; Milne, P. A.;
Williams, G.; O'Brien, P. T.; Fox, D. B.; Berger, E.
2013ApJ...778...54V Altcode: 2013arXiv1310.0313V
We present a broadband study of gamma-ray burst (GRB) 091024A within
the context of other ultra-long-duration GRBs. An unusually long
burst detected by Konus-Wind (KW), Swift, and Fermi, GRB 091024A
has prompt emission episodes covering ~1300 s, accompanied by
bright and highly structured optical emission captured by various
rapid-response facilities, including the 2 m autonomous robotic
Faulkes North and Liverpool Telescopes, KAIT, S-LOTIS, and the
Sonoita Research Observatory. We also observed the burst with 8 and
10 m class telescopes and determine the redshift to be z = 1.0924 ±
0.0004. We find no correlation between the optical and γ-ray peaks
and interpret the optical light curve as being of external origin,
caused by the reverse and forward shock of a highly magnetized jet
(RB ≈ 100-200). Low-level emission is detected throughout
the near-background quiescent period between the first two emission
episodes of the KW data, suggesting continued central-engine activity;
we discuss the implications of this ongoing emission and its impact on
the afterglow evolution and predictions. We summarize the varied sample
of historical GRBs with exceptionally long durations in gamma-rays
(gsim1000 s) and discuss the likelihood of these events being from a
separate population; we suggest ultra-long GRBs represent the tail of
the duration distribution of the long GRB population.

---------------------------------------------------------
Title: Establishing a Stereoscopic Technique for Determining the
Kinematic Properties of Solar Wind Transients based on a Generalized
Self-similarly Expanding Circular Geometry
Authors: Davies, J. A.; Perry, C. H.; Trines, R. M. G. M.; Harrison,
R. A.; Lugaz, N.; Möstl, C.; Liu, Y. D.; Steed, K.
2013ApJ...777..167D Altcode:
The twin-spacecraft STEREO mission has enabled simultaneous white-light
imaging of the solar corona and inner heliosphere from multiple
vantage points. This has led to the development of numerous stereoscopic
techniques to investigate the three-dimensional structure and kinematics
of solar wind transients such as coronal mass ejections (CMEs). Two such
methods—triangulation and the tangent to a sphere—can be used to
determine time profiles of the propagation direction and radial distance
(and thereby radial speed) of a solar wind transient as it travels
through the inner heliosphere, based on its time-elongation profile
viewed by two observers. These techniques are founded on the assumption
that the transient can be characterized as a point source (fixed phi,
FP, approximation) or a circle attached to Sun-center (harmonic mean,
HM, approximation), respectively. These geometries constitute extreme
descriptions of solar wind transients, in terms of their cross-sectional
extent. Here, we present the stereoscopic expressions necessary to
derive propagation direction and radial distance/speed profiles of such
transients based on the more generalized self-similar expansion (SSE)
geometry, for which the FP and HM geometries form the limiting cases;
our implementation of these equations is termed the stereoscopic
SSE method. We apply the technique to two Earth-directed CMEs from
different phases of the STEREO mission, the well-studied event of
2008 December and a more recent event from 2012 March. The latter
CME was fast, with an initial speed exceeding 2000 km s-1,
and highly geoeffective, in stark contrast to the slow and ineffectual
2008 December CME.

---------------------------------------------------------
Title: Using Coordinated Observations in Polarized White Light and
Faraday Rotation to Probe the Spatial Position and Magnetic Field
of an Interplanetary Sheath
Authors: Xiong, Ming; Davies, Jackie A.; Feng, Xueshang; Owens,
Mathew J.; Harrison, Richard A.; Davis, Chris J.; Liu, Ying D.
2013ApJ...777...32X Altcode: 2013arXiv1308.3376X
Coronal mass ejections (CMEs) can be continuously tracked through a
large portion of the inner heliosphere by direct imaging in visible and
radio wavebands. White light (WL) signatures of solar wind transients,
such as CMEs, result from Thomson scattering of sunlight by free
electrons and therefore depend on both viewing geometry and electron
density. The Faraday rotation (FR) of radio waves from extragalactic
pulsars and quasars, which arises due to the presence of such solar
wind features, depends on the line-of-sight magnetic field component
B ∥ and the electron density. To understand coordinated
WL and FR observations of CMEs, we perform forward magnetohydrodynamic
modeling of an Earth-directed shock and synthesize the signatures that
would be remotely sensed at a number of widely distributed vantage
points in the inner heliosphere. Removal of the background solar
wind contribution reveals the shock-associated enhancements in WL and
FR. While the efficiency of Thomson scattering depends on scattering
angle, WL radiance I decreases with heliocentric distance r roughly
according to the expression Ivpropr -3. The sheath region
downstream of the Earth-directed shock is well viewed from the L4 and
L5 Lagrangian points, demonstrating the benefits of these points in
terms of space weather forecasting. The spatial position of the main
scattering site r sheath and the mass of plasma at that
position M sheath can be inferred from the polarization
of the shock-associated enhancement in WL radiance. From the FR
measurements, the local B ∥sheath at r sheath
can then be estimated. Simultaneous observations in polarized WL and
FR can not only be used to detect CMEs, but also to diagnose their
plasma and magnetic field properties.

---------------------------------------------------------
Title: Magnetization Degree of Gamma-Ray Burst Fireballs: Numerical
Study
Authors: Harrison, Richard; Kobayashi, Shiho
2013ApJ...772..101H Altcode: 2012arXiv1211.1032H
The relative strength between forward and reverse shock emission in
early gamma-ray burst (GRB) afterglow reflects that of magnetic energy
densities in the two shock regions. We numerically show that with the
current standard treatment, the fireball magnetization is underestimated
by up to two orders of magnitude. This discrepancy is especially large
in the sub-relativistic reverse shock regime (i.e., the thin shell
and intermediate regime), where most optical flashes were detected. We
provide new analytic estimates of the reverse shock emission based on
a better shock approximation, which well describe numerical results
in the intermediate regime. We show that the reverse shock temperature
at the onset of afterglow is constant, (\bar{\Gamma }_d-1)\sim 8\times
10^{-2}, when the dimensionless parameter ξ0 is more than
several. Our approach is applied to case studies of GRB 990123 and
090102, and we find that magnetic fields in the fireballs are even
stronger than previously believed. However, these events are still
likely to be due to a baryonic jet with σ ~ 10-3 for GRB
990123 and ~3 × 10-4 to 3 for GRB 090102.

---------------------------------------------------------
Title: Observations and Modelling of the Inner Heliosphere: Preface
and Tribute to the Late Dr. Andy Breen
Authors: Bisi, M. M.; Harrison, R. A.; Lugaz, N.; van Driel-Gesztelyi,
L.; Mandrini, C. H.
2013SoPh..285....1B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observations of Rapid Velocity Variations in the Slow
Solar Wind
Authors: Hardwick, S. A.; Bisi, M. M.; Davies, J. A.; Breen, A. R.;
Fallows, R. A.; Harrison, R. A.; Davis, C. J.
2013SoPh..285..111H Altcode:
The technique of interplanetary scintillation (IPS) is the observation
of rapid fluctuations of the radio signal from an astronomical compact
source as the signal passes through the ever-changing density of the
solar wind. Cross-correlation of simultaneous observations of IPS
from a single radio source, received at multiple sites of the European
Incoherent SCATter (EISCAT) radio antenna network, is used to determine
the velocity of the solar wind material passing over the lines of sight
of the antennas. Calculated velocities reveal the slow solar wind to
contain rapid velocity variations when viewed on a time-scale of several
minutes. Solar TErrestrial RElations Observatory (STEREO) Heliospheric
Imager (HI) observations of white-light intensity have been compared
with EISCAT observations of IPS to identify common density structures
that may relate to the rapid velocity variations in the slow solar wind.

---------------------------------------------------------
Title: Heliospheric Imaging of 3D Density Structures During the
Multiple Coronal Mass Ejections of Late July to Early August 2010
Authors: Webb, D. F.; Möstl, C.; Jackson, B. V.; Bisi, M. M.; Howard,
T. A.; Mulligan, T.; Jensen, E. A.; Jian, L. K.; Davies, J. A.; de
Koning, C. A.; Liu, Y.; Temmer, M.; Clover, J. M.; Farrugia, C. J.;
Harrison, R. A.; Nitta, N.; Odstrcil, D.; Tappin, S. J.; Yu, H. -S.
2013SoPh..285..317W Altcode:
It is usually difficult to gain a consistent global understanding
of a coronal mass ejection (CME) eruption and its propagation
when only near-Sun imagery and the local measurements derived from
single-spacecraft observations are available. Three-dimensional (3D)
density reconstructions based on heliospheric imaging allow us to
"fill in" the temporal and spatial gaps between the near-Sun and in
situ data to provide a truly global picture of the propagation and
interactions of the CME as it moves through the inner heliosphere. In
recent years the heliospheric propagation of dense structures has been
observed and measured by the heliospheric imagers of the Solar Mass
Ejection Imager (SMEI) and on the twin Solar TErrestrial RElations
Observatory (STEREO) spacecraft. We describe the use of several 3D
reconstruction techniques based on these heliospheric imaging data sets
to distinguish and track the propagation of multiple CMEs in the inner
heliosphere during the very active period of solar activity in late July
- early August 2010. We employ 3D reconstruction techniques used at the
University of California, San Diego (UCSD) based on a kinematic solar
wind model, and also the empirical Tappin-Howard model. We compare
our results with those from other studies of this active period,
in particular the heliospheric simulations made with the ENLIL model
by Odstrcil et al. (J. Geophys. Res., 2013) and the in situ results
from multiple spacecraft provided by Möstl et al. (Astrophys. J.758,
10 - 28, 2012). We find that the SMEI results in particular provide
an overall context for the multiple-density flows associated with
these CMEs. For the first time we are able to intercompare the 3D
reconstructed densities with the timing and magnitude of in situ
density structures at five spacecraft spread over 150° in ecliptic
longitude and from 0.4 to 1 AU in radial distance. We also model the
magnetic flux-rope structures at three spacecraft using both force-free
and non-force-free modelling, and compare their timing and spatial
structure with the reconstructed density flows.

---------------------------------------------------------
Title: Stealth Coronal Mass Ejections: A Perspective
Authors: Howard, Timothy A.; Harrison, Richard A.
2013SoPh..285..269H Altcode:
"Stealth CME" has become a commonly used term in recent studies of solar
activity. It refers to a coronal mass ejection (CME) with no apparent
solar surface association, and therefore has no easily identifiable
signature to locate the region on the Sun from which the CME erupted. We
review the literature and express caution in categorising CMEs in
this way. CMEs were discovered some 40 years ago and there have been
numerous statistical studies of associations with phenomena in the
solar atmosphere which clearly identify a range of associations, from
bright flares and large prominence eruptions to small flares, and even
a lack of flares or any identifiable surface activity at all. In this
sense the stealth CME concept is not new. One major question relates
to whether the range of associations reveal different CME classes,
i.e. different CME launch processes, or are indicative of a spectrum
of coronal responses to one common process. We favour the latter and
stress that this spectrum must be considered in the description of the
CME launch, meaning that the physics of a so-called stealth CME must
not be fundamentally different from a CME associated with major surface
events. On the other hand we also stress that the use of a stealth CME
category implies that all surface activity could indeed be detected
using modern instrumentation. We argue that this may not be the case,
and that even in the SDO era of full-Sun, high resolution imaging, we
are restricted by instrument sensitivity and bandwidth issues. Thus,
having reviewed the case for stealth CMEs as a distinct category,
we stress the need to keep the concept in perspective.

---------------------------------------------------------
Title: A Critical Examination of the Fundamental Assumptions of
Solar Flare and Coronal Mass Ejection Models
Authors: Spicer, D. S.; Bingham, R.; Harrison, R.
2013ApJ...768....8S Altcode:
The fundamental assumptions of conventional solar flare and coronal
mass ejection (CME) theory are re-examined. In particular, the common
theoretical assumption that magnetic energy that drives flares and
CMEs can be stored in situ in the corona with sufficient energy
density is found wanting. In addition, the observational constraint
that flares and CMEs produce non-thermal electrons with fluxes of
order 1034-1036 electrons s-1, with
energies of order 10-20 keV, must also be explained. This constraint
when imposed on the "standard model" for flares and CMEs is found to
miss the mark by many orders of magnitude. We suggest, in conclusion,
there are really only two possible ways to explain the requirements
of observations and theory: flares and CMEs are caused by mass-loaded
prominences or driven directly by emerging magnetized flux.

---------------------------------------------------------
Title: Multi-Technique Remote-Sensing Observations and Modelling of
a Coronal Mass Ejection
Authors: Hardwick, S. A.; Bisi, M. M.; Davies, J.; Morgan, H.; Fallows,
R.; Harrison, R. A.; Xiong, M.; Jensen, E. A.
2012AGUFMSH41C2123H Altcode:
On 14 November 2011, SDO|AIA observed a filament eruption located
around S25 to S30 and extended between W20 and W40 of disc centre. The
resulting coronal mass ejection (CME) is studied in detail using radio,
white-light, and EUV remote-sensing observations from STEREO, SOHO, SDO,
and the new next-generation LOFAR radio telescope system. We present
a detailed story of the CME as it travels through the heliosphere with
its northern flank travelling in the ecliptic out towards Mars. Various
models are fitted to the heliospheric white-light data and different
portions of the CME are investigated as they propagate through the inner
heliosphere. The validity of each model is discussed. This combination
of remote-sensing observational and modelling techniques displays a
valid framework for further detailed investigations of CMEs.

---------------------------------------------------------
Title: Highlights in Remote-Sensing Observations of the Inner
Heliosphere During 2011 and 2012 Focussing on the EISCAT and LOFAR
Radio-Telescope Systems
Authors: Bisi, M. M.; Fallows, R.; Hardwick, S. A.; Jensen, E. A.;
Davies, J.; Harrison, R. A.; Xiong, M.; Wu, C.
2012AGUFMSH43A2138B Altcode:
Significant progress has been made over the last two years on the
implementation of, and science resulting from, radio remote-sensing
observations of the inner heliosphere using the European Incoherent
SCATter (EISCAT) radar and the LOw Frequency ARray (LOFAR)
radio-telescope systems. LOFAR is a precursor to the Square Kilometre
Array (SKA), the world's largest ever radio telescope system. Here, we
highlight some of these advances in radio remote-sensing heliospheric
science, and where appropriate, we show examples of comparative and
joint studies with data from other remote-sensing observations as well
as with modelling of the inner heliosphere. Data from 2011 and 2012
will provide the foci of this work, although historical comparisons
may be necessary. EISCAT has been used for relatively-high-frequency
observations of IPS since the early 1990s, and LOFAR successfully
since 2011. The lower observing frequency of LOFAR allows us to probe
further from the Sun in IPS that using EISCAT; however, two of the
three mainland EISCAT telescopes are due to undergo a conversion to VHF
frequencies (224 MHz) through late summer of 2012. This will result
in a direct-observational overlap towards the high-frequency end of
the observing capabilities using LOFAR (maximum observing frequency of
250 MHz) for IPS studies. Tests, where possible, will be explored with
this new receiver system along with tests of the new EISCAT_3D test-bed,
the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA). This work
comes one year following the death of Dr. Andy Breen who was one of
the early pioneers of the IPS experiment on the early EISCAT system.

---------------------------------------------------------
Title: Multi-point Shock and Flux Rope Analysis of Multiple
Interplanetary Coronal Mass Ejections around 2010 August 1 in the
Inner Heliosphere
Authors: Möstl, C.; Farrugia, C. J.; Kilpua, E. K. J.; Jian, L. K.;
Liu, Y.; Eastwood, J. P.; Harrison, R. A.; Webb, D. F.; Temmer, M.;
Odstrcil, D.; Davies, J. A.; Rollett, T.; Luhmann, J. G.; Nitta, N.;
Mulligan, T.; Jensen, E. A.; Forsyth, R.; Lavraud, B.; de Koning,
C. A.; Veronig, A. M.; Galvin, A. B.; Zhang, T. L.; Anderson, B. J.
2012ApJ...758...10M Altcode: 2012arXiv1209.2866M
We present multi-point in situ observations of a complex
sequence of coronal mass ejections (CMEs) which may serve as
a benchmark event for numerical and empirical space weather
prediction models. On 2010 August 1, instruments on various
space missions, Solar Dynamics Observatory/Solar and Heliospheric
Observatory/Solar-TErrestrial-RElations-Observatory (SDO/SOHO/STEREO),
monitored several CMEs originating within tens of degrees from the
solar disk center. We compare their imprints on four widely separated
locations, spanning 120° in heliospheric longitude, with radial
distances from the Sun ranging from MESSENGER (0.38 AU) to Venus
Express (VEX, at 0.72 AU) to Wind, ACE, and ARTEMIS near Earth and
STEREO-B close to 1 AU. Calculating shock and flux rope parameters at
each location points to a non-spherical shape of the shock, and shows
the global configuration of the interplanetary coronal mass ejections
(ICMEs), which have interacted, but do not seem to have merged. VEX
and STEREO-B observed similar magnetic flux ropes (MFRs), in contrast
to structures at Wind. The geomagnetic storm was intense, reaching
two minima in the Dst index (≈ - 100 nT), and was caused by the
sheath region behind the shock and one of two observed MFRs. MESSENGER
received a glancing blow of the ICMEs, and the events missed STEREO-A
entirely. The observations demonstrate how sympathetic solar eruptions
may immerse at least 1/3 of the heliosphere in the ecliptic with their
distinct plasma and magnetic field signatures. We also emphasize the
difficulties in linking the local views derived from single-spacecraft
observations to a consistent global picture, pointing to possible
alterations from the classical picture of ICMEs.

---------------------------------------------------------
Title: Multi-point shock and flux rope analysis of multiple ICMEs
around 2010 August 1 in the inner heliosphere
Authors: Moestl, Christian; Farrugia, C. J.; Kilpua, E. K. J.; Jian,
L.; Liu, Y.; Jensen, L.; Mulligan, T.; Eastwood, J.; Rollett, T.;
Temmer, M.; Luhmann, J. G.; Harrison, R.; Davies, J. A.; Webb, D.;
Forsyth, R.; Lavraud, B.; Odstrcil, D.; de Koning, C. A.; Nitta, N.;
Veronig, A. M.; Galvin, A. B.; Zhang, T. L.
2012shin.confE..77M Altcode:
We present multi-point in situ observations of a complex sequence
of coronal mass ejections which may serve as a benchmark event for
numerical and empirical space weather prediction models. On 2010 August
1, instruments on various space missions (SDO/SOHO/STEREO) monitored
repeated coronal mass ejections originating within tens of degrees from
solar disk center. We compare their imprints on four widely separated
locations, covering 120 degree in heliospheric longitude, with radial
distances from the Sun ranging from MESSENGER (0.38 AU) to Venus Express
(VEX, at 0.72 AU) to Wind, ACE and ARTEMIS near Earth and STEREO-B close
to 1 AU. Calculating shock and flux rope parameters at each location
points to a non-spherical shape of the shock, and shows the global
configuration of the interplanetary coronal mass ejections (ICMEs),
which have interacted but not merged, making individual identifications
still possible. VEX and STEREO-B observed similar magnetic flux ropes,
in contrast to the structures at Wind. The geomagnetic storm was
moderate to major, reaching two minima in the Dst index, caused by the
sheath region behind the shock and one of two observed magnetic flux
ropes. MESSENGER received a glancing blow of the ICMEs, and the events
missed STEREO-A entirely. The observations demonstrate how sympathetic
solar eruptions may immerse at least 1/3 of the heliosphere in the
ecliptic with their distinct plasma and magnetic field signatures
and emphasize the difficulties in linking the local views derived
from single-spacecraft observations to a consistent global picture,
pointing to possible alterations from the classical picture of ICMEs.

---------------------------------------------------------
Title: An Analysis of the Origin and Propagation of the Multiple
Coronal Mass Ejections of 2010 August 1
Authors: Harrison, R. A.; Davies, J. A.; Möstl, C.; Liu, Y.; Temmer,
M.; Bisi, M. M.; Eastwood, J. P.; de Koning, C. A.; Nitta, N.; Rollett,
T.; Farrugia, C. J.; Forsyth, R. J.; Jackson, B. V.; Jensen, E. A.;
Kilpua, E. K. J.; Odstrcil, D.; Webb, D. F.
2012ApJ...750...45H Altcode:
On 2010 August 1, the northern solar hemisphere underwent significant
activity that involved a complex set of active regions near central
meridian with, nearby, two large prominences and other more distant
active regions. This activity culminated in the eruption of four major
coronal mass ejections (CMEs), effects of which were detected at Earth
and other solar system bodies. Recognizing the unprecedented wealth of
data from the wide range of spacecraft that were available—providing
the potential for us to explore methods for CME identification and
tracking, and to assess issues regarding onset and planetary impact—we
present a comprehensive analysis of this sequence of CMEs. We show that,
for three of the four major CMEs, onset is associated with prominence
eruption, while the remaining CME appears to be closely associated
with a flare. Using instrumentation on board the Solar Terrestrial
Relations Observatory spacecraft, three of the CMEs could be tracked
out to elongations beyond 50° their directions and speeds have been
determined by various methods, not least to assess their potential for
Earth impact. The analysis techniques that can be applied to the other
CME, the first to erupt, are more limited since that CME was obscured
by the subsequent, much faster event before it had propagated far from
the Sun; we discuss the speculation that these two CMEs interact. The
consistency of the results, derived from the wide variety of methods
applied to such an extraordinarily complete data set, has allowed
us to converge on robust interpretations of the CME onsets and their
arrivals at 1 AU.

---------------------------------------------------------
Title: A Self-similar Expansion Model for Use in Solar Wind Transient
Propagation Studies
Authors: Davies, J. A.; Harrison, R. A.; Perry, C. H.; Möstl, C.;
Lugaz, N.; Rollett, T.; Davis, C. J.; Crothers, S. R.; Temmer, M.;
Eyles, C. J.; Savani, N. P.
2012ApJ...750...23D Altcode:
Since the advent of wide-angle imaging of the inner heliosphere,
a plethora of techniques have been developed to investigate the
three-dimensional structure and kinematics of solar wind transients,
such as coronal mass ejections, from their signatures in single-
and multi-spacecraft imaging observations. These techniques, which
range from the highly complex and computationally intensive to methods
based on simple curve fitting, all have their inherent advantages and
limitations. In the analysis of single-spacecraft imaging observations,
much use has been made of the fixed phi fitting (FPF) and harmonic
mean fitting (HMF) techniques, in which the solar wind transient is
considered to be a radially propagating point source (fixed phi,
FP, model) and a radially expanding circle anchored at Sun centre
(harmonic mean, HM, model), respectively. Initially, we compare the
radial speeds and propagation directions derived from application of
the FPF and HMF techniques to a large set of STEREO/Heliospheric Imager
(HI) observations. As the geometries on which these two techniques
are founded constitute extreme descriptions of solar wind transients
in terms of their extent along the line of sight, we describe a
single-spacecraft fitting technique based on a more generalized model
for which the FP and HM geometries form the limiting cases. In addition
to providing estimates of a transient's speed and propagation direction,
the self-similar expansion fitting (SSEF) technique provides, in theory,
the capability to estimate the transient's angular extent in the plane
orthogonal to the field of view. Using the HI observations, and also
by performing a Monte Carlo simulation, we assess the potential of
the SSEF technique.

---------------------------------------------------------
Title: The first STEREO multi-event: Numerical simulation of coronal
mass ejections (CMEs) launched on August 1, 2010
Authors: Odstrcil, D.; de Koning, C. A.; Xie, H.; Moestl, C.;
Temmer, M.; Jian, L.; Rouillard, A. P.; Davies, J. A.; Davis, C. J.;
Harrison, R.
2012EGUGA..1414429O Altcode:
On 2010-08-01 at least four coronal mass ejections (CMEs) were observed
by the Heliospheric Imagers (HIs) onboard STEREO spacecraft. These
events originated at different parts of the solar corona and generated
complex scenario of four mutually interacting CMEs. Real-time
prediction of the arrival times to Earth failed and it is difficult
to associate features observed by HIs with their solar sources and
impacts at spacecraft. We use the heliospheric code ENLIL to show the
global solution for various scenarios using fitted CME parameters
from coronagraph observations by different techniques. We present
the temporal profiles and synthetic white-light images that enables
direct comparison with in-situ and remote observations. These results
show that in addition to multi-perspective coronagraph observations,
heliospheric imagers and numerical simulations are needed to understand
and predict the impact of complex heliospheric disturbances.

---------------------------------------------------------
Title: CME-CME interaction during the 2010 August 1 events
Authors: Temmer, M.; Vrsnak, B.; Rollett, T.; Bein, B.; deKoning,
C. A.; Liu, Y.; Bosman, E.; Davies, J. A.; Möstl, C.; Zic, T.;
Veronig, A. M.; Bothmer, V.; Harrison, R.; Nitta, N.; Bisi, M.; Flor,
O.; Eastwood, J.; Odstrcil, D.; Forsyth, R.
2012EGUGA..14.1677T Altcode:
We study a CME-CME interaction that occurred during the 2010 August 1
events using STEREO/SECCHI data (COR and HI). The CMEs were Earth
directed where clear signatures of magnetic flux ropes could be
measured from in situ Wind data. To give evidence of the actual
interaction we derive the direction of motion for both CMEs applying
several independent methods. From this we obtain that both CMEs head
into similar directions enabling us to actually observe the merging
in the HI1 field-of-view (and rule out the possibility that this is
just a line of sight effect). The full de-projected kinematics of the
faster CME from Sun to Earth is derived when combining data points from
remote observations with in situ parameters of the ICME measured at
1 AU. We study the evolution of the kinematical profile of the faster
CME by applying a drag based model.

---------------------------------------------------------
Title: Characteristics of Kinematics of a Coronal Mass Ejection
during the 2010 August 1 CME-CME Interaction Event
Authors: Temmer, Manuela; Vršnak, Bojan; Rollett, Tanja; Bein, Bianca;
de Koning, Curt A.; Liu, Ying; Bosman, Eckhard; Davies, Jackie A.;
Möstl, Christian; Žic, Tomislav; Veronig, Astrid M.; Bothmer, Volker;
Harrison, Richard; Nitta, Nariaki; Bisi, Mario; Flor, Olga; Eastwood,
Jonathan; Odstrcil, Dusan; Forsyth, Robert
2012ApJ...749...57T Altcode: 2012arXiv1202.0629T
We study the interaction of two successive coronal mass ejections (CMEs)
during the 2010 August 1 events using STEREO/SECCHI COR and heliospheric
imager (HI) data. We obtain the direction of motion for both CMEs by
applying several independent reconstruction methods and find that the
CMEs head in similar directions. This provides evidence that a full
interaction takes place between the two CMEs that can be observed in the
HI1 field of view. The full de-projected kinematics of the faster CME
from Sun to Earth is derived by combining remote observations with in
situ measurements of the CME at 1 AU. The speed profile of the faster
CME (CME2; ~1200 km s-1) shows a strong deceleration over
the distance range at which it reaches the slower, preceding CME (CME1;
~700 km s-1). By applying a drag-based model we are able
to reproduce the kinematical profile of CME2, suggesting that CME1
represents a magnetohydrodynamic obstacle for CME2 and that, after
the interaction, the merged entity propagates as a single structure
in an ambient flow of speed and density typical for quiet solar wind
conditions. Observational facts show that magnetic forces may contribute
to the enhanced deceleration of CME2. We speculate that the increase
in magnetic tension and pressure, when CME2 bends and compresses the
magnetic field lines of CME1, increases the efficiency of drag.

---------------------------------------------------------
Title: Interactions between Coronal Mass Ejections Viewed in
Coordinated Imaging and in situ Observations
Authors: Liu, Ying D.; Luhmann, Janet G.; Möstl, Christian;
Martinez-Oliveros, Juan C.; Bale, Stuart D.; Lin, Robert P.; Harrison,
Richard A.; Temmer, Manuela; Webb, David F.; Odstrcil, Dusan
2012ApJ...746L..15L Altcode: 2012arXiv1201.2968L
The successive coronal mass ejections (CMEs) from 2010 July 30 to
August 1 present us the first opportunity to study CME-CME interactions
with unprecedented heliospheric imaging and in situ observations from
multiple vantage points. We describe two cases of CME interactions:
merging of two CMEs launched close in time and overtaking of a preceding
CME by a shock wave. The first two CMEs on August 1 interact close to
the Sun and form a merged front, which then overtakes the July 30 CME
near 1 AU, as revealed by wide-angle imaging observations. Connections
between imaging observations and in situ signatures at 1 AU suggest
that the merged front is a shock wave, followed by two ejecta observed
at Wind which seem to have already merged. In situ measurements show
that the CME from July 30 is being overtaken by the shock at 1 AU and
is significantly compressed, accelerated, and heated. The interaction
between the preceding ejecta and shock also results in variations
in the shock strength and structure on a global scale, as shown by
widely separated in situ measurements from Wind and STEREO B. These
results indicate important implications of CME-CME interactions for
shock propagation, particle acceleration, and space weather forecasting.

---------------------------------------------------------
Title: Transient Structure in the Slow Solar Wind
Authors: Hardwick, S. A.; Breen, A.; Bisi, M. M.; Fallows, R. A.;
Davies, J. A.; Harrison, R.; Davis, C. J.
2011AGUFMSH22A..07H Altcode:
Solar TErrestrial RElations Observatory (STEREO) Heliospheric Imager
(HI) observations of the slow solar wind commonly show a high degree
of small-scale structure. High-cadence analyses of two-station radio
scintillation observations (IPS) from the EISCAT facility also show
evidence of rapid variation in outflow speed, scintillation level, and
magnetic-field orientation in the slow wind. These are on spatial scales
smaller than the structures seen by the HIs. We compare observations
of IPS of solar-wind outflow speed and field orientation made at times
of good HI coverage with HI white-light intensity levels in order
to determine whether the IPS variations are embedded within larger
transients observed by the HIs.

---------------------------------------------------------
Title: Interaction between Coronal Mass Ejections Viewed in
Coordinated Imaging and In Situ Observations
Authors: Liu, Y.; Luhmann, J. G.; Moestl, C.; Martinez Oliveros,
J. C.; Harrison, R.; Temmer, M.; Bale, S.; Lin, R. P.
2011AGUFMSH23C1973L Altcode:
Interaction between coronal mass ejections (CMEs), which is expected
to be a frequent phenomenon, has important implications for both
space weather and basic plasma physics. First, the interaction alters
the global heliospheric configuration, which may lead to favorable
conditions for geomagnetic storm generation. Second, the interaction
implies significant energy and momentum transfer between the interacting
CMEs where magnetic reconnection may take place. Third, in case a
shock is driven by the trailing CME, interesting physical processes
may occur when the shock is propagating through the preceding one,
such as modifications in the shock strength, particle intensity and
transport. There are successive CMEs on July 30 - August 1, 2011,
which presents us the first opportunity to study CME-CME interaction
with unprecedented heliospheric imaging and in situ observations from
a fleet of spacecraft. The first two CMEs on August 1 interact close
to the Sun and form a merged front, which then overtakes the July
30 CME near 1 AU, as revealed by wide-angle imaging observations. In
situ measurements indicate that the first two CMEs on August 1 seem
to have already merged at 0.7 and 1 AU, and at 1 AU their shock is
propagating into the CME from July 30. We will report and discuss the
CME-CME interaction signatures from the coordinated imaging and in
situ observations in this presentation.

---------------------------------------------------------
Title: The first STEREO multi-event: Numerical simulation of coronal
mass ejections (CMEs) launched on August 1, 2010
Authors: Odstrcil, D.; de Koning, C. A.; Xie, H.; Moestl, C.;
Temmer, M.; Jian, L.; Rouillard, A. P.; Davies, J. A.; Davis, C. J.;
Harrison, R.
2011AGUFMSH32A..03O Altcode:
On 2010-08-01 at least four coronal mass ejections (CMEs) were observed
by the Heliospheric Imagers (HIs) onboard STEREO spacecraft. These
events originated at different parts of the solar corona and generated
complex scenario of four mutually interacting CMEs. Real-time
prediction of the arrival times to Earth failed and it is difficult
to associate features observed by HIs with their solar sources and
impacts at spacecraft. We use the heliospheric code ENLIL to show
the global solution for two scenarios using fitted CME parameters
from coronagraph observations by two different techniques. We present
the temporal profiles and synthetic white-light images that enables
direct comparison with in-situ and remote observations. These results
show that in addition to multi-perspective coronagraph observations,
heliospheric imagers and numerical simulations are needed to understand
and predict the impact of complex heliospheric disturbances.

---------------------------------------------------------
Title: Arrival Time Calculation for Interplanetary Coronal Mass
Ejections with Circular Fronts and Application to STEREO Observations
of the 2009 February 13 Eruption
Authors: Möstl, C.; Rollett, T.; Lugaz, N.; Farrugia, C. J.; Davies,
J. A.; Temmer, M.; Veronig, A. M.; Harrison, R. A.; Crothers, S.;
Luhmann, J. G.; Galvin, A. B.; Zhang, T. L.; Baumjohann, W.; Biernat,
H. K.
2011ApJ...741...34M Altcode: 2011arXiv1108.0515M
One of the goals of the NASA Solar TErestrial RElations Observatory
(STEREO) mission is to study the feasibility of forecasting the
direction, arrival time, and internal structure of solar coronal
mass ejections (CMEs) from a vantage point outside the Sun-Earth
line. Through a case study, we discuss the arrival time calculation
of interplanetary CMEs (ICMEs) in the ecliptic plane using data from
STEREO/SECCHI at large elongations from the Sun in combination with
different geometric assumptions about the ICME front shape [fixed-Φ
(FP): a point and harmonic mean (HM): a circle]. These forecasting
techniques use single-spacecraft imaging data and are based on the
assumption of constant velocity and direction. We show that for the
slow (350 km s-1) ICME on 2009 February 13-18, observed at
quadrature by the two STEREO spacecraft, the results for the arrival
time given by the HM approximation are more accurate by 12 hr than
those for FP in comparison to in situ observations of solar wind
plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by
6 hr for the arrival time at Venus Express (MAG). We propose that the
improvement is directly related to the ICME front shape being more
accurately described by HM for an ICME with a low inclination of its
symmetry axis to the ecliptic. In this case, the ICME has to be tracked
to &gt;30° elongation to obtain arrival time errors &lt; ± 5 hr. A
newly derived formula for calculating arrival times with the HM method
is also useful for a triangulation technique assuming the same geometry.

---------------------------------------------------------
Title: Propagation and impact of multiple coronal mass ejections
events on August 1 2010 in the heliosphere
Authors: Möstl, Christian; Farrugia, Charles J.; Harrison, Richard
A.; Davies, J. A.; Kilpua, Emilia K. J.; Odstrcil, Dusan; Rollett,
Tanja; Temmer, Manuela; Veronig, Astrid; Jian, Lan; Liu, Ying;
Eastwood, Jonathan; Forsyth, Robert; Webb, David; Bisi, Mario M.;
Jackson, Bernard V.; Mulligan, Tamitha; Jensen, Liz; Lavraud, Benoit;
de Koning, Curt A.; Nitta, Nariaki; Luhmann, Janet; Galvin, Antoinette
B.; Zhang, Tielong
2011sdmi.confE..69M Altcode:
On August 1 2010 a large region of the solar northern hemisphere
displayed major activity involving a complex set of central meridian and
remote active regions, and two large prominence channels (Schrijver
and Title, JGR, 2011). We witnessed the eruption of four coronal
mass ejections (CMEs) which partly impacted Earth and lead to one
of the first geomagnetic storms of the new solar cycle. We present an
overview of the results of several analyses exploiting the extraordinary
completeness of the imaging data (SDO/STEREO/SOHO) in combination with
numerical simulations (ENLIL) and in situ observations. The imprints of
the CMEs, including a prior event on July 30, were observed in situ in
an almost laboratory-like configuration at 4 widely separated locations
spanning over 120 degrees of heliospheric longitude (STEREO-B, Venus
Express, ACE/Wind, ARTEMIS, and MESSENGER). The CME density enhancements
could be followed with the STEREO-A/HI and Coriolis/SMEI instruments
continuously from the Sun to 1 AU. Evidences of CME-CME interactions
and resulting overlapping tracks in Jmaps make the analysis complex,
but nevertheless we find robust interpretations for linking two magnetic
flux ropes at Earth, one of them geo-effective and including elevated
alpha particles related to possible filament material, to their solar
counterparts. Additionally, we discuss the relationship between the
in situ observations and the global picture given by the ENLIL model.

---------------------------------------------------------
Title: Straylight-Rejection Performance of the STEREO HI Instruments
Authors: Halain, J. -P.; Eyles, C. J.; Mazzoli, A.; Bewsher, D.;
Davies, J. A.; Mazy, E.; Rochus, P.; Defise, J. M.; Davis, C. J.;
Harrison, R. A.; Crothers, S. R.; Brown, D. S.; Korendyke, C.; Moses,
J. D.; Socker, D. G.; Howard, R. A.; Newmark, J. S.
2011SoPh..271..197H Altcode: 2011SoPh..tmp..189H; 2011SoPh..tmp..132H; 2011SoPh..tmp..258H
The SECCHI Heliospheric Imager (HI) instruments on-board the STEREO
spacecraft have been collecting images of solar wind transients,
including coronal mass ejections, as they propagate through the inner
heliosphere since the beginning of 2007.

---------------------------------------------------------
Title: A unique view of the inner heliosphere from the STEREO
Heliospheric Imagers (Invited)
Authors: Davis, C. J.; Harrison, R. A.; Davies, J. A.; Crothers,
S. R.; Eyles, C. J.
2010AGUFMSH52B..01D Altcode:
Launched in 2006, the twin spacecraft of the STEREO mission have
provided unique views of the Sun and the inner heliosphere in three
dimensions. One pair of instruments in particular, the Heliospheric
Imagers, have revolutionised the way that solar transients, in
particular Earth-directed coronal mass ejections, can be viewed. This
talk will summarise the observations so far, review the techniques
developed to interpret the data and discuss how these techniques will
help to inform future space-weather missions. A CME (right) passes in
front of the Milky Way (left) and Jupiter (left center) observed with
STEREO HI, November 2007.

---------------------------------------------------------
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.
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: Transient Structures and Stream Interaction Regions in the
Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO
HI and Venus Express ASPERA-4 Measurements
Authors: Dorrian, G. D.; Breen, A. R.; Davies, J. A.; Rouillard,
A. P.; Fallows, R. A.; Whittaker, I. C.; Brown, D. S.; Harrison,
R. A.; Davis, C. J.; Grande, M.
2010SoPh..265..207D Altcode: 2010SoPh..tmp..134D; 2012arXiv1207.3968D
We discuss the detection and evolution of a complex series of transient
and quasi-static solar-wind structures in the days following the
well-known comet 2P/Encke tail disconnection event in April 2007. The
evolution of transient solar-wind structures ranging in size from
&lt;105 km to &gt;106 km was characterised
using one-minute time resolution observation of Interplanetary
Scintillation (IPS) made using the European Incoherent SCATter (EISCAT)
radar system. Simultaneously, the global structure and evolution of
these features was characterised by the Heliospheric Imagers (HI)
on the Solar TERrestrial RElations Observatory (STEREO) spacecraft,
placing the IPS observations in context. Of particular interest was
the observation of one transient in the slow wind, apparently being
swept up and entrained by a Stream Interaction Region (SIR). The SIR
itself was later detected in-situ at Venus by the Analyser of Space
Plasma and Energetic Atoms (ASPERA-4) instrument on the Venus Express
(VEX) spacecraft. The availability of such diverse data sources over
a range of different time resolutions enables us to develop a global
picture of these complex events that would not have been possible if
these instruments were used in isolation. We suggest that the range
of solar-wind transients discussed here may be the interplanetary
counterparts of transient structures previously reported from
coronagraph observations and are likely to correspond to transient
magnetic structures reported in in-situ measurements in interplanetary
space. The results reported here also provide the first indication of
heliocentric distances at which transients become entrained.

---------------------------------------------------------
Title: Intermittent release of transients in the slow solar wind:
2. In situ evidence
Authors: Rouillard, A. P.; Lavraud, B.; Davies, J. A.; Savani, N. P.;
Burlaga, L. F.; Forsyth, R. J.; Sauvaud, J. -A.; Opitz, A.; Lockwood,
M.; Luhmann, J. G.; Simunac, K. D. C.; Galvin, A. B.; Davis, C. J.;
Harrison, R. A.
2010JGRA..115.4104R Altcode: 2010JGRA..11504104R
In paper 1, we showed that the Heliospheric Imager (HI) instruments on
the pair of NASA STEREO spacecraft can be used to image the streamer
belt and, in particular, the variability of the slow solar wind
which originates near helmet streamers. The observation of intense
intermittent transient outflow by HI implies that the corresponding in
situ observations of the slow solar wind and corotating interaction
regions (CIRs) should contain many signatures of transients. In the
present paper, we compare the HI observations with in situ measurements
from the STEREO and ACE spacecraft. Analysis of the solar wind ion,
magnetic field, and suprathermal electron flux measurements from the
STEREO spacecraft reveals the presence of both closed and partially
disconnected interplanetary magnetic field lines permeating the slow
solar wind. We predict that one of the transients embedded within
the second CIR (CIR-D in paper 1) should impact the near-Earth ACE
spacecraft. ACE measurements confirm the presence of a transient at the
time of CIR passage; the transient signature includes helical magnetic
fields and bidirectional suprathermal electrons. On the same day, a
strahl electron dropout is observed at STEREO-B, correlated with the
passage of a high-plasma beta structure. Unlike ACE, STEREO-B observes
the transient a few hours ahead of the CIR. STEREO-A, STEREO-B, and
ACE spacecraft observe very different slow solar wind properties ahead
of and during the CIR analyzed in this paper, which we associate with
the intermittent release of transients.

---------------------------------------------------------
Title: Intermittent release of transients in the slow solar wind:
1. Remote sensing observations
Authors: Rouillard, A. P.; Davies, J. A.; Lavraud, B.; Forsyth, R. J.;
Savani, N. P.; Bewsher, D.; Brown, D. S.; Sheeley, N. R.; Davis,
C. J.; Harrison, R. A.; Howard, R. A.; Vourlidas, A.; Lockwood, M.;
Crothers, S. R.; Eyles, C. J.
2010JGRA..115.4103R Altcode: 2010JGRA..11504103R
The Heliospheric Imager (HI) instruments on board the STEREO spacecraft
are used to analyze the solar wind during August and September 2007. We
show how HI can be used to image the streamer belt and, in particular,
the variability of the slow solar wind which originates inside and
in the vicinity of the streamer belt. Intermittent mass flows are
observed in HI difference images, streaming out along the extension of
helmet streamers. These flows can appear very differently in images:
plasma distributed on twisted flux ropes, V-shaped structures, or
“blobs.” The variety of these transient features may highlight the
richness of phenomena that could occur near helmet streamers: emergence
of flux ropes, reconnection of magnetic field lines at the tip of
helmet streamers, or disconnection of open magnetic field lines. The
plasma released with these transient events forms part of the solar
wind in the higher corona; HI observations show that these transients
are frequently entrained by corotating interaction regions (CIRs),
leading to the formation of larger, brighter plasma structures in HI
images. This entrainment is used to estimate the trajectory of these
plasma ejecta. In doing so, we demonstrate that successive transients
can be entrained by the same CIR in the high corona if they emanate
from the same corotating source. Some parts of the streamers are more
effective sources of transients than others. Surprisingly, evidence
is given for the outflow of a recurring twisted magnetic structure,
suggesting that the emergence of flux ropes can be recurrent.

---------------------------------------------------------
Title: Coronal mass ejections in the heliosphere
Authors: Harrison, R. A.; Davis, C. J.; Bewsher, D.; Davies, J. A.;
Eyles, C. J.; Crothers, S. R.
2010AdSpR..45....1H Altcode:
With the advent of the NASA STEREO mission, we are in a position
to perform unique investigations of the evolution of coronal mass
ejections (CMEs) as they propagate through the heliosphere, and thus
can investigate the relationship between CMEs and their interplanetary
counterparts, so-called interplanetary CMEs (ICMEs). ICME studies
have been principally limited to single-point, in-situ observations;
interpretation of the in-situ characteristics of ICMEs has been
used to derive a range of ICME properties which we can now confirm
or refute using the STEREO imaging data. This paper is a review of
early STEREO CME observations and how they relate to our currently
understanding of ICMEs based on in-situ observations. In that sense,
it is a first glance at the applications of the new data-sets to
this topic and provides pointers to more detailed analyses. We find
good agreement with in-situ-based interpretations, but this in turn
leads to an anomaly regarding the final stages of a CME event that we
investigate briefly to identify directions for future study.

---------------------------------------------------------
Title: The radial width of a Coronal Mass Ejection between 0.1 and
0.4 AU estimated from the Heliospheric Imager on STEREO
Authors: Savani, N. P.; Rouillard, A. P.; Davies, J. A.; Owens, M. J.;
Forsyth, R. J.; Davis, C. J.; Harrison, R. A.
2009AnGeo..27.4349S Altcode:
On 15-17 February 2008, a CME with an approximately circular
cross section was tracked through successive images obtained
by the Heliospheric Imager (HI) instrument onboard the STEREO-A
spacecraft. Reasoning that an idealised flux rope is cylindrical
in shape with a circular cross-section, best fit circles are used
to determine the radial width of the CME. As part of the process the
radial velocity and longitude of propagation are determined by fits to
elongation-time maps as 252±5 km/s and 70±5° respectively. With the
longitude known, the radial size is calculated from the images, taking
projection effects into account. The radial width of the CME, S (AU),
obeys a power law with heliocentric distance, R, as the CME travels
between 0.1 and 0.4 AU, such that S=0.26 R0.6±0.1. The
exponent value obtained is compared to published studies based on
statistical surveys of in situ spacecraft observations of ICMEs between
0.3 and 1.0 AU, and general agreement is found. This paper demonstrates
the new opportunities provided by HI to track the radial width of CMEs
through the previously unobservable zone between the LASCO field of
view and Helios in situ measurements.

---------------------------------------------------------
Title: Pre-CME Onset Fuses - Do the STEREO Heliospheric Imagers Hold
the Clues to the CME Onset Process?
Authors: Harrison, Richard A.; Davis, Christopher J.; Davies, Jackie A.
2009SoPh..259..277H Altcode:
Understanding the onset of coronal mass ejections (CMEs) is surely
one of the holy grails of solar physics today. Inspection of data
from the Heliospheric Imagers (HI), which are part of the SECCHI
instrument suite aboard the two NASA STEREO spacecraft, appears to
have revealed pre-eruption signatures which may provide valuable
evidence for identifying the CME onset mechanism. Specifically, an
examination of the HI images has revealed narrow rays comprised of a
series of outward-propagating plasma blobs apparently forming near
the edge of the streamer belt prior to many CME eruptions. In this
pilot study, we inspect a limited dataset to explore the significance
of this phenomenon, which we have termed a pre-CME `fuse'. Although,
the enhanced expulsion of blobs may be consistent with an increase in
the release of outward-propagating blobs from the streamers themselves,
it could also be interpreted as evidence for interchange reconnection
in the period leading to a CME onset. Indeed, it is argued that the
latter could even have implications for the end-of-life of CMEs. Thus,
the presence of these pre-CME fuses provides evidence that the CME
onset mechanism is either related to streamer reconnection processes or
the reconnection between closed field lines in the streamer belt and
adjacent, open field lines. We investigate the nature of these fuses,
including their timing and location with respect to CME launch sites,
as well as their speed and topology.

---------------------------------------------------------
Title: Virtual Observatory studies of Planetary Nebulae
Authors: Mignani, R. P.; Kerber, F.; Smart, R. L.; Vande Putte, D.;
Wicenec, A.; Rauch, T.; Adorf, H. M.; Harrison, R.
2009mavo.proc..173M Altcode: 2009arXiv0902.0960M
Starting from the Strasbourg ESO Catalogue (SEC) of Planetary Nebulae
(PNe), the largest PNe compilation available with ~ 1500 objects,
we undertook a comprehensive study of the whole PN population, never
carried out so far, only using on-line catalogues and data from
public imaging surveys. The study includes the PN dynamics through
their measured proper motions (PMs), the study of their galactocentric
orbits, the study of their interactions with the interstellar medium
(ISM), and the study of their UV-to-IR spectral energy distribution
(SED). As a preliminary step required to perform cross-correlations
with on-line catalogues, we first went through a systematic reassessment
of the PN coordinates (Kerber et al. 2003a).

---------------------------------------------------------
Title: A solar storm observed from the Sun to Venus using the STEREO,
Venus Express, and MESSENGER spacecraft
Authors: Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Savani,
N. P.; Sheeley, N. R.; Thernisien, A.; Zhang, T. -L.; Howard, R. A.;
Anderson, B.; Carr, C. M.; Tsang, S.; Lockwood, M.; Davis, C. J.;
Harrison, R. A.; Bewsher, D.; Fränz, M.; Crothers, S. R.; Eyles,
C. J.; Brown, D. S.; Whittaker, I.; Hapgood, M.; Coates, A. J.; Jones,
G. H.; Grande, M.; Frahm, R. A.; Winningham, J. D.
2009JGRA..114.7106R Altcode: 2009JGRA..11407106R
The suite of SECCHI optical imaging instruments on the STEREO-A
spacecraft is used to track a solar storm, consisting of several coronal
mass ejections (CMEs) and other coronal loops, as it propagates from
the Sun into the heliosphere during May 2007. The 3-D propagation
path of the largest interplanetary CME (ICME) is determined from the
observations made by the SECCHI Heliospheric Imager (HI) on STEREO-A
(HI-1/2A). Two parts of the CME are tracked through the SECCHI images, a
bright loop and a V-shaped feature located at the rear of the event. We
show that these two structures could be the result of line-of-sight
integration of the light scattered by electrons located on a single
flux rope. In addition to being imaged by HI, the CME is observed
simultaneously by the plasma and magnetic field experiments on the Venus
Express and MESSENGER spacecraft. The imaged loop and V-shaped structure
bound, as expected, the flux rope observed in situ. The SECCHI images
reveal that the leading loop-like structure propagated faster than
the V-shaped structure, and a decrease in in situ CME speed occurred
during the passage of the flux rope. We interpret this as the result
of the continuous radial expansion of the flux rope as it progressed
outward through the interplanetary medium. An expansion speed in the
radial direction of ∼30 km s-1 is obtained directly from
the SECCHI-HI images and is in agreement with the difference in speed
of the two structures observed in situ. This paper shows that the flux
rope location can be determined from white light images, which could
have important space weather applications.

---------------------------------------------------------
Title: A Multispacecraft Analysis of a Small-Scale Transient Entrained
by Solar Wind Streams
Authors: Rouillard, A. P.; Savani, N. P.; Davies, J. A.; Lavraud, B.;
Forsyth, R. J.; Morley, S. K.; Opitz, A.; Sheeley, N. R.; Burlaga,
L. F.; Sauvaud, J. -A.; Simunac, K. D. C.; Luhmann, J. G.; Galvin,
A. B.; Crothers, S. R.; Davis, C. J.; Harrison, R. A.; Lockwood, M.;
Eyles, C. J.; Bewsher, D.; Brown, D. S.
2009SoPh..256..307R Altcode:
The images taken by the Heliospheric Imagers (HIs), part of the
SECCHI imaging package onboard the pair of STEREO spacecraft,
provide information on the radial and latitudinal evolution of the
plasma compressed inside corotating interaction regions (CIRs). A
plasma density wave imaged by the HI instrument onboard STEREO-B was
found to propagate towards STEREO-A, enabling a comparison between
simultaneous remote-sensing and in situ observations of its structure to
be performed. In situ measurements made by STEREO-A show that the plasma
density wave is associated with the passage of a CIR. The magnetic
field compressed after the CIR stream interface (SI) is found to have
a planar distribution. Minimum variance analysis of the magnetic field
vectors shows that the SI is inclined at 54° to the orbital plane of
the STEREO-A spacecraft. This inclination of the CIR SI is comparable
to the inclination of the associated plasma density wave observed by
HI. A small-scale magnetic cloud with a flux rope topology and radial
extent of 0.08 AU is also embedded prior to the SI. The pitch-angle
distribution of suprathermal electrons measured by the STEREO-A SWEA
instrument shows that an open magnetic field topology in the cloud
replaced the heliospheric current sheet locally. These observations
confirm that HI observes CIRs in difference images when a small-scale
transient is caught up in the compression region.

---------------------------------------------------------
Title: Study of CME Propagation in the Inner Heliosphere: SOHO LASCO,
SMEI and STEREO HI Observations of the January 2007 Events
Authors: Webb, D. F.; Howard, T. A.; Fry, C. D.; Kuchar, T. A.;
Odstrcil, D.; Jackson, B. V.; Bisi, M. M.; Harrison, R. A.; Morrill,
J. S.; Howard, R. A.; Johnston, J. C.
2009SoPh..256..239W Altcode:
We are investigating the geometric and kinematic characteristics of
interplanetary coronal mass ejections (ICMEs) using data obtained by
the LASCO coronagraphs, the Solar Mass Ejection Imager (SMEI), and the
SECCHI imaging experiments on the STEREO spacecraft. The early evolution
of CMEs can be tracked by the LASCO C2 and C3 and SECCHI COR1 and COR2
coronagraphs, and the HI and SMEI instruments can track their ICME
counterparts through the inner heliosphere. The HI fields of view (4 -
90°) overlap with the SMEI field of view (&gt; 20° to all sky) and,
thus, both instrument sets can observe the same ICME. In this paper
we present results for ICMEs observed on 24 - 29 January 2007, when
the STEREO spacecraft were still near Earth so that both the SMEI and
STEREO views of large ICMEs in the inner heliosphere coincided. These
results include measurements of the structural and kinematic evolution
of two ICMEs and comparisons with drive/drag kinematic, 3D tomographic
reconstruction, the HAFv2 kinematic, and the ENLIL MHD models. We find
it encouraging that the four model runs generally were in agreement
on both the kinematic evolution and appearance of the events. Because
it is essential to understand the effects of projection across large
distances, that are not generally crucial for events observed closer
to the Sun, we discuss our analysis procedure in some detail.

---------------------------------------------------------
Title: Two Years of the STEREO Heliospheric Imagers. Invited Review
Authors: Harrison, Richard A.; Davies, Jackie A.; Rouillard, Alexis
P.; Davis, Christopher J.; Eyles, Christopher J.; Bewsher, Danielle;
Crothers, Steve R.; Howard, Russell A.; Sheeley, Neil R.; Vourlidas,
Angelos; Webb, David F.; Brown, Daniel S.; Dorrian, Gareth D.
2009SoPh..256..219H Altcode:
Imaging of the heliosphere is a burgeoning area of research. As
a result, it is awash with new results, using novel applications,
and is demonstrating great potential for future research in a wide
range of topical areas. The STEREO (Solar TErrestrial RElations
Observatory) Heliospheric Imager (HI) instruments are at the heart
of this new development, building on the pioneering observations of
the SMEI (Solar Mass Ejection Imager) instrument aboard the Coriolis
spacecraft. Other earlier heliospheric imaging systems have included
ground-based interplanetary scintillation (IPS) facilities and the
photometers on the Helios spacecraft. With the HI instruments, we now
have routine wide-angle imaging of the inner heliosphere, from vantage
points outside the Sun-Earth line. HI has been used to investigate the
development of coronal mass ejections (CMEs) as they pass through the
heliosphere to 1 AU and beyond. Synoptic mapping has also allowed us to
see graphic illustrations of the nature of mass outflow as a function
of distance from the Sun - in particular, stressing the complexity of
the near-Sun solar wind. The instruments have also been used to image
co-rotating interaction regions (CIRs), to study the interaction of
comets with the solar wind and CMEs, and to witness the impact of CMEs
and CIRs on planets. The very nature of this area of research - which
brings together aspects of solar physics, space-environment physics,
and solar-terrestrial physics - means that the research papers are
spread among a wide range of journals from different disciplines. Thus,
in this special issue, it is timely and appropriate to provide a review
of the results of the first two years of the HI investigations.

---------------------------------------------------------
Title: STEREO SECCHI and S/WAVES Observations of Spacecraft Debris
Caused by Micron-Size Interplanetary Dust Impacts
Authors: St. Cyr, O. C.; Kaiser, M. L.; Meyer-Vernet, N.; Howard,
R. A.; Harrison, R. A.; Bale, S. D.; Thompson, W. T.; Goetz, K.;
Maksimovic, M.; Bougeret, J. -L.; Wang, D.; Crothers, S.
2009SoPh..256..475S Altcode:
Early in the STEREO mission observers noted that the white-light
instruments of the SECCHI suite were detecting significantly more
spacecraft-related "debris" than any previously flown coronagraphic
instruments. Comparison of SECCHI "debris storms" with S/WAVES indicates
that almost all are coincident with the most intense transient emissions
observed by the radio and plasma waves instrument. We believe the debris
is endogenous (i.e., from the spacecraft thermal blanketing), and the
storms appear to be caused by impacts of large interplanetary dust
grains that are detected by S/WAVES. Here we report the observations,
compare them to interplanetary dust distributions, and document a
reminder for future spacebased coronagraphic instrument builders.

---------------------------------------------------------
Title: Stereoscopic imaging of an Earth-impacting solar coronal mass
ejection: A major milestone for the STEREO mission
Authors: Davis, C. J.; Davies, J. A.; Lockwood, M.; Rouillard, A. P.;
Eyles, C. J.; Harrison, R. A.
2009GeoRL..36.8102D Altcode: 2009GeoRL..3608102D
We present stereoscopic images of an Earth-impacting Coronal Mass
Ejection (CME). The CME was imaged by the Heliospheric Imagers
onboard the twin STEREO spacecraft during December 2008. The apparent
acceleration of the CME is used to provide independent estimates of its
speed and direction from the two spacecraft. Three distinct signatures
within the CME were all found to be closely Earth-directed. At the
time that the CME was predicted to pass the ACE spacecraft, in-situ
observations contained a typical CME signature. At Earth, ground-based
magnetometer observations showed a small but widespread sudden response
to the compression of the geomagnetic cavity at CME impact. In this
case, STEREO could have given warning of CME impact at least 24 hours
in advance. These stereoscopic observations represent a significant
milestone for the STEREO mission and have significant potential for
improving operational space weather forecasting.

---------------------------------------------------------
Title: Coronal mass ejection: key issues
Authors: Harrison, Richard
2009IAUS..257..191H Altcode:
Coronal Mass Ejections (CMEs) have been addressed by a particularly
active research community in recent years. With the advent of the
International Heliophysical Year and the new STEREO and Hinode missions,
in addition to the on-going SOHO mission, CME research has taken centre
stage in a renewed international effort. This review aims to touch
on some key observational areas, and their interpretation. First,
we consider coronal dimming, which has become synonymous with CME
onsets, and stress that recent advances have heralded a move from a
perceived association between the two phenomena to a firm, well-defined
physical link. What this means for our understanding of CME modeling
is discussed. Second, with the new STEREO observations, and noting the
on-going SMEI observations, it is important to review the opening field
of CME studies in the heliosphere. Finally, we discuss some specific
points with regard to EIT-waves and the flare-CME relationship. In
the opinion of the author, these issues cover key hot topics which
need consideration for significant progress in the field.

---------------------------------------------------------
Title: The Heliospheric Imagers Onboard the STEREO Mission
Authors: Eyles, C. J.; Harrison, R. A.; Davis, C. J.; Waltham, N. R.;
Shaughnessy, B. M.; Mapson-Menard, H. C. A.; Bewsher, D.; Crothers,
S. R.; Davies, J. A.; Simnett, G. M.; Howard, R. A.; Moses, J. D.;
Newmark, J. S.; Socker, D. G.; Halain, J. -P.; Defise, J. -M.; Mazy,
E.; Rochus, P.
2009SoPh..254..387E Altcode: 2008SoPh..tmp..193E
Mounted on the sides of two widely separated spacecraft, the two
Heliospheric Imager (HI) instruments onboard NASA's STEREO mission
view, for the first time, the space between the Sun and Earth. These
instruments are wide-angle visible-light imagers that incorporate
sufficient baffling to eliminate scattered light to the extent that the
passage of solar coronal mass ejections (CMEs) through the heliosphere
can be detected. Each HI instrument comprises two cameras, HI-1 and
HI-2, which have 20° and 70° fields of view and are off-pointed
from the Sun direction by 14.0° and 53.7°, respectively, with their
optical axes aligned in the ecliptic plane. This arrangement provides
coverage over solar elongation angles from 4.0° to 88.7° at the
viewpoints of the two spacecraft, thereby allowing the observation
of Earth-directed CMEs along the Sun - Earth line to the vicinity of
the Earth and beyond. Given the two separated platforms, this also
presents the first opportunity to view the structure and evolution
of CMEs in three dimensions. The STEREO spacecraft were launched
from Cape Canaveral Air Force Base in late October 2006, and the HI
instruments have been performing scientific observations since early
2007. The design, development, manufacture, and calibration of these
unique instruments are reviewed in this paper. Mission operations,
including the initial commissioning phase and the science operations
phase, are described. Data processing and analysis procedures are
briefly discussed, and ground-test results and in-orbit observations
are used to demonstrate that the performance of the instruments meets
the original scientific requirements.

---------------------------------------------------------
Title: Commission 10: Solar Activity
Authors: Klimchuk, James A.; van Driel-Gesztelyi, Lidia; Schrijver,
Carolus J.; Melrose, Donald B.; Fletcher, Lyndsay; Gopalswamy,
Natchimuthuk; Harrison, Richard A.; Mandrini, Cristina H.; Peter,
Hardi; Tsuneta, Saku; Vršnak, Bojan; Wang, Jing-Xiu
2009IAUTA..27...79K Altcode: 2008arXiv0809.1444K
Commission 10 deals with solar activity in all of its forms,
ranging from the smallest nanoflares to the largest coronal mass
ejections. This report reviews scientific progress over the roughly
two-year period ending in the middle of 2008. This has been an exciting
time in solar physics, highlighted by the launches of the Hinode and
STEREO missions late in 2006. The report is reasonably comprehensive,
though it is far from exhaustive. Limited space prevents the inclusion
of many significant results. The report is divided into the following
sections: Photosphere and chromosphere; Transition region; Corona and
coronal heating; Coronal jets; flares; Coronal mass ejection initiation;
Global coronal waves and shocks; Coronal dimming; The link between low
coronal CME signatures and magnetic clouds; Coronal mass ejections in
the heliosphere; and Coronal mass ejections and space weather. Primary
authorship is indicated at the beginning of each section.

---------------------------------------------------------
Title: A synoptic view of solar transient evolution in the inner
heliosphere using the Heliospheric Imagers on STEREO
Authors: Davies, J. A.; Harrison, R. A.; Rouillard, A. P.; Sheeley,
N. R.; Perry, C. H.; Bewsher, D.; Davis, C. J.; Eyles, C. J.; Crothers,
S. R.; Brown, D. S.
2009GeoRL..36.2102D Altcode:
By exploiting data from the STEREO/heliospheric imagers (HI) we extend
a well-established technique developed for coronal analysis by producing
time-elongation plots that reveal the nature of solar transient activity
over a far more extensive region of the heliosphere than previously
possible from coronagraph images. Despite the simplicity of these plots,
their power in demonstrating how the plethora of ascending coronal
features observed near the Sun evolve as they move antisunward is
obvious. The time-elongation profile of a transient tracked by HI can,
moreover, be used to establish its angle out of the plane-of-the-sky an
illustration of such analysis reveals coronal mass ejection material
that can be clearly observed propagating out to distances beyond
1AU. This work confirms the value of the time-elongation format in
identifying/characterising transient activity in the inner heliosphere,
whilst also validating the ability of HI to continuously monitor solar
ejecta out to and beyond 1AU.

---------------------------------------------------------
Title: Predicting CME activity, do the Heliospheric Imagers hold
any clues?
Authors: Davis, C. J.; Harrison, R. A.
2008AGUFMSH11A..06D Altcode:
Inspection of images from the STEREO Heliospheric Imagers shows a
remarkable amount of structure in the solar wind and streamer belt, even
at times of little or no solar activity. A subset of these images were
scrutinised for changes in this solar wind structure ahead of coronal
mass ejections in an attempt to verify if these changes were associated
with ensuing mass ejections and whether these changes could be used
to identify the processes by which these mass ejections were triggered.

---------------------------------------------------------
Title: Meeting contribution: The STEREO solar mission
Authors: Harrison, R.
2008JBAA..118..347H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: First imaging of corotating interaction regions using the
STEREO spacecraft
Authors: Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Rees, A.;
Davis, C. J.; Harrison, R. A.; Lockwood, M.; Bewsher, D.; Crothers,
S. R.; Eyles, C. J.; Hapgood, M.; Perry, C. H.
2008GeoRL..3510110R Altcode:
Plasma parcels are observed propagating from the Sun out to the large
coronal heights monitored by the Heliospheric Imagers (HI) instruments
onboard the NASA STEREO spacecraft during September 2007. The source
region of these out-flowing parcels is found to corotate with the Sun
and to be rooted near the western boundary of an equatorial coronal
hole. These plasma enhancements evolve during their propagation through
the HI cameras' fields of view and only becoming fully developed in the
outer camera field of view. We provide evidence that HI is observing
the formation of a Corotating Interaction Region (CIR) where fast
solar wind from the equatorial coronal hole is interacting with the
slow solar wind of the streamer belt located on the western edge of
that coronal hole. A dense plasma parcel is also observed near the
footpoint of the observed CIR at a distance less than 0.1AU from the
Sun where fast wind would have not had time to catch up slow wind. We
suggest that this low-lying plasma enhancement is a plasma parcel
which has been disconnected from a helmet streamer and subsequently
becomes embedded inside the corotating interaction region.

---------------------------------------------------------
Title: Observations of Dust Impacts from STEREO
Authors: Howard, R. A.; St Cyr, C.; Kaiser, M.; Goetz, K.; Harrison,
R. A.
2008AGUSM.P34A..07H Altcode:
The NASA STEREO mission was launched in October, 2006. The two STEREO
spacecraft are in heliospheric orbit about 1 AU from the Sun, one
drifting ahead of Earth and one drifting behind. In order to achieve
the drift the Ahead spacecraft is slightly closer to the Sun than Earth
and the Behind spacecraft is slightly further from the Sun. Since soon
after launch, the optical (STEREO/SECCHI) and radio (STEREO/SWAVES)
remote sensing instruments began observing transients which are being
interpreted as impacts of dust particles. There are three different
types of observations: (1) transients in the potential measured by
the SWAVES radio experiment, (2) optical tracks in the SECCHI (COR1,
COR2 and HI-1) images and (3) results from the on-board image scrubbing
algorithm in HI-1. There is some agreement in the onset times between
the three detection methods, but not always. The frequency of events
detected by STEREO-A and STEREO-B, which are now about 45 degrees
apart, is quite different. We will present the observations and our
preliminary interpretation.

---------------------------------------------------------
Title: Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI)
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Cook, J. W.; Hurley,
A.; Davila, J. M.; Thompson, W. T.; St Cyr, O. C.; Mentzell, E.;
Mehalick, K.; Lemen, J. R.; Wuelser, J. P.; Duncan, D. W.; Tarbell,
T. D.; Wolfson, C. J.; Moore, A.; Harrison, R. A.; Waltham, N. R.;
Lang, J.; Davis, C. J.; Eyles, C. J.; Mapson-Menard, H.; Simnett,
G. M.; Halain, J. P.; Defise, J. M.; Mazy, E.; Rochus, P.; Mercier,
R.; Ravet, M. F.; Delmotte, F.; Auchere, F.; Delaboudiniere, J. P.;
Bothmer, V.; Deutsch, W.; Wang, D.; Rich, N.; Cooper, S.; Stephens,
V.; Maahs, G.; Baugh, R.; McMullin, D.; Carter, T.
2008SSRv..136...67H Altcode: 2008SSRv..tmp...64H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) is a five telescope package, which has been developed for
the Solar Terrestrial Relation Observatory (STEREO) mission by the
Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics
Laboratory (USA), the Goddard Space Flight Center (USA), the University
of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the
Max Planck Institute for Solar System Research (Germany), the Centre
Spatiale de Leige (Belgium), the Institut d’Optique (France) and the
Institut d’Astrophysique Spatiale (France). SECCHI comprises five
telescopes, which together image the solar corona from the solar disk to
beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI:
1 1.7 R⊙), two traditional Lyot coronagraphs (COR1: 1.5 4
R⊙ and COR2: 2.5 15 R⊙) and two new designs
of heliospheric imagers (HI-1: 15 84 R⊙ and HI-2: 66 318
R⊙). All the instruments use 2048×2048 pixel CCD arrays
in a backside-in mode. The EUVI backside surface has been specially
processed for EUV sensitivity, while the others have an anti-reflection
coating applied. A multi-tasking operating system, running on a PowerPC
CPU, receives commands from the spacecraft, controls the instrument
operations, acquires the images and compresses them for downlink
through the main science channel (at compression factors typically
up to 20×) and also through a low bandwidth channel to be used for
space weather forecasting (at compression factors up to 200×). An
image compression factor of about 10× enable the collection of images
at the rate of about one every 2 3 minutes. Identical instruments,
except for different sizes of occulters, are included on the STEREO-A
and STEREO-B spacecraft.

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Title: Heliospheric Images of the Solar Wind at Earth
Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang,
Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.;
Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.;
Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.;
Battams, K.; Esfandiari, E.; Stenborg, G.
2008ApJ...675..853S Altcode:
During relatively quiet solar conditions throughout the spring and
summer of 2007, the SECCHI HI2 white-light telescope on the STEREO
B solar-orbiting spacecraft observed a succession of wave fronts
sweeping past Earth. We have compared these heliospheric images with
in situ plasma and magnetic field measurements obtained by near-Earth
spacecraft, and we have found a near perfect association between the
occurrence of these waves and the arrival of density enhancements
at the leading edges of high-speed solar wind streams. Virtually
all of the strong corotating interaction regions are accompanied by
large-scale waves, and the low-density regions between them lack such
waves. Because the Sun was dominated by long-lived coronal holes and
recurrent solar wind streams during this interval, there is little
doubt that we have been observing the compression regions that are
formed at low latitude as solar rotation causes the high-speed wind
from coronal holes to run into lower speed wind ahead of it.

---------------------------------------------------------
Title: SECCHI Observations of the Sun's Garden-Hose Density Spiral
Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang,
Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.;
Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.;
Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.;
Battams, K.; Esfandiari, E.; Stenborg, G.
2008ApJ...674L.109S Altcode:
The SECCHI HI2 white-light imagers on the STEREO A and B spacecraft
show systematically different proper motions of material moving outward
from the Sun in front of high-speed solar wind streams from coronal
holes. As a group of ejections enters the eastern (A) field of view,
the elements at the rear of the group appear to overrun the elements
at the front. (This is a projection effect and does not mean that the
different elements actually merge.) The opposite is true in the western
(B) field; the elements at the front of the group appear to run away
from the elements at the rear. Elongation/time maps show this effect
as a characteristic grouping of the tracks of motion into convergent
patterns in the east and divergent patterns in the west, consistent
with ejections from a single longitude on the rotating Sun. Evidently,
we are observing segments of the "garden-hose" spiral made visible
when fast wind from a low-latitude coronal hole compresses blobs of
streamer material being shed at the leading edge of the hole.

---------------------------------------------------------
Title: The relationship between EUV dimming and coronal mass
ejections. I. Statistical study and probability model
Authors: Bewsher, D.; Harrison, R. A.; Brown, D. S.
2008A&A...478..897B Altcode:
Aims:There have been many studies of extreme-ultraviolet (EUV) dimming
in association with coronal mass ejection (CME) onsets. However,
there has never been a thorough statistical study of this association,
covering appropriate temperature ranges. Thus, we make use of a large
campaign database utilising the Coronal Diagnostic Spectrometer (CDS)
and the Large Angle and Spectrometric COronagraph (LASCO) both on the
SOlar and Heliospheric Observatory (SOHO) to associate dimming events
detected at 1 and 2 million K with CME activity. The aim is to confirm
whether the dimming-CME association is real or not. This in turn will
confirm whether special attention should be paid to the EUV dimming in
the pre-eruption and eruption periods to study the CME onset process
itself. Methods: The CDS CME onset campaign data for Mg IX and FE
XVI observations on the solar limb are used to compare to LASCO event
lists over a period from 1998 to 2005. Dimming events are identified and
the physical extent explored, whilst comparing the events to overlying
CME activity. Results: For the identified dimming regions we
have shown strong associations with CME onsets, with up to 55% of the
dimming events being associated with CME activity. This is compared
to the random case where up to 47% of the dimming regions are expected
to be associated with CMEs. We have also shown that up to 84% of CMEs
associated with our data can be tracked back to dimming regions. This
compares to a random case of up to 58%. Conclusions: These results
confirm the CME-EUV dimming association, using a statistical analysis
for the first time. We discuss the repercussions for the study of CME
onsets, i.e. analysis of the dimming regions and the periods up to
such dimming may be key to understanding the pre-CME onset plasma
processes. The results stress that one emission line may not be
sufficient for associating dimming regions with CMEs. Appendix
A is only available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: First Imaging of Coronal Mass Ejections in the Heliosphere
Viewed from Outside the Sun Earth Line
Authors: Harrison, Richard A.; Davis, Christopher J.; Eyles,
Christopher J.; Bewsher, Danielle; Crothers, Steve R.; Davies, Jackie
A.; Howard, Russell A.; Moses, Daniel J.; Socker, Dennis G.; Newmark,
Jeffrey S.; Halain, Jean-Philippe; Defise, Jean-Marc; Mazy, Emmanuel;
Rochus, Pierre; Webb, David F.; Simnett, George M.
2008SoPh..247..171H Altcode:
We show for the first time images of solar coronal mass ejections
(CMEs) viewed using the Heliospheric Imager (HI) instrument aboard
the NASA STEREO spacecraft. The HI instruments are wide-angle imaging
systems designed to detect CMEs in the heliosphere, in particular,
for the first time, observing the propagation of such events along the
Sun - Earth line, that is, those directed towards Earth. At the time
of writing the STEREO spacecraft are still close to the Earth and the
full advantage of the HI dual-imaging has yet to be realised. However,
even these early results show that despite severe technical challenges
in their design and implementation, the HI instruments can successfully
detect CMEs in the heliosphere, and this is an extremely important
milestone for CME research. For the principal event being analysed
here we demonstrate an ability to track a CME from the corona to
over 40 degrees. The time - altitude history shows a constant speed
of ascent over at least the first 50 solar radii and some evidence
for deceleration at distances of over 20 degrees. Comparisons of
associated coronagraph data and the HI images show that the basic
structure of the CME remains clearly intact as it propagates from
the corona into the heliosphere. Extracting the CME signal requires
a consideration of the F-coronal intensity distribution, which can be
identified from the HI data. Thus we present the preliminary results
on this measured F-coronal intensity and compare these to the modelled
F-corona of Koutchmy and Lamy (IAU Colloq.85, 63, 1985). This analysis
demonstrates that CME material some two orders of magnitude weaker
than the F-corona can be detected; a specific example at 40 solar
radii revealed CME intensities as low as 1.7×10−14
of the solar brightness. These observations herald a new era in CME
research as we extend our capability for tracking, in particular,
Earth-directed CMEs into the heliosphere.

---------------------------------------------------------
Title: Solar Mass Ejection Studies - Coordinated Investigation
Programme 1
Authors: Harrison, Richard; Bewsher, Danielle; Davis, Chris; Breen,
Andy; Webb, David
2008cosp...37.1181H Altcode: 2008cosp.meet.1181H
IHY Coordinated Investigation Programme number 1 is concerned with
solar coronal mass ejections (CMEs). It has two parts, specifically,
(i) studies of the onset of CMEs through multispacecraft observations
of the source regions of CMEs, in particular including the development
of spectroscopic observations in the extreme-ultraviolet, and (ii)
studies of interplanetary CMEs, especially those directed towards Earth
utilising multiple spacecraft including the new STEREO mission. The
effort has been done in hindsight, i.e. ‘post-event' campaigns are
defined based on particular observation scenarios or on the acquisition
of good quality data-sets and a range of research topics have been
addressed. Here, we summarise the sub-campaigns and their results - but
we also ask how these efforts have been enhanced by the IHY activities.

---------------------------------------------------------
Title: Interplanetary Coronal Mass Ejections
Authors: Harrison, Richard; Davis, Chris; Davies, Jackie; Eyles,
Chris; Crothers, Steve; Bewsher, Danielle
2008cosp...37.1182H Altcode: 2008cosp.meet.1182H
With the new STEREO spacecraft and the Heliospheric Imager instruments
we are now able to make the most basic observations of ICMEs, in
particular those directed towards Earth and to make comparisons to
the interpretations of in-situ data which have been used over the
years to investigate the structure and evolution of ICMEs and of their
connectivity to the Sun. Thus, we present evidence which confirms the
magnetic structure of ICMEs as they propagate to Earth-like distances,
and discuss how that structure evolves with time. We also consider how
ICMEs are connected to the Sun and in particular investigate the view
that interchange reconnection represents the ‘end game' of a CME.

---------------------------------------------------------
Title: Discovery of Accelerating Plasmoids in the Tail of Comet Encke
Authors: Kellett, B.; Bingham, R.; Davies, J. A.; Bewsher, D.;
Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Crothers, S. R.
2007AGUFMSH33A1087K Altcode:
Comet 2P/Encke was the second comet to have its return correctly
predicted (in 1819). Encke is a Jupiter-family comet with a period
of 3.30 years and a perihelion distance of 0.338 AU. The interaction
between cometary plasma and the solar wind plasma provides the potential
for remote monitoring of the solar wind. In this regard comet Encke is
potentially a very useful probe of the solar wind because of its very
short orbital period and therefore large number of close approaches
to the Sun. However, for this reason it is likely to have exhausted
most of its reserves of ice and therefore possess a less dense plasma
tail. The comet could therefore respond faster and more dynamically
to solar wind variations than the tail of a more active or higher gas
production comet. The Heliospheric Imager (HI) of STEREO-A (HI-1A),
observed comet 2P/Encke during April, 2007. The comet was predicted
to have reached perihelion on April 19th 0 UT. This paper will only
consider the observations obtained by HI-1A on April 25th to 27th,
2007. At this time the comet was around 0.63 AU from Earth and 0.39 AU
from the Sun. The comet was seen to exhibit a distinct "flick" of its
plasma tail on April 26th and a series of "whiplash" events. However,
the most interest phenomena seen was a whole series of "plasmoids"
that were observed to break off from the brighter part of the tail near
the nucleus and accelerate along the tail for 4-5 million kilometres
down-wind of the nucleus.

---------------------------------------------------------
Title: Imaging Coronal Mass Ejections in the Heliosphere using the
STEREO Heliospheric Imagers
Authors: Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Bewsher, D.;
Crothers, S.; Davies, J. A.; Howard, R. A.; Moses, D. J.; Halain, J.
2007AGUFMSH42A..05H Altcode:
We present images of Coronal Mass Ejections in the heliosphere, tracked
from the outer corona to Earth-like distances, from the first months
of the scientific operation of the Heliospheric Imagers (HI) aboard
the NASA STEREO spacecraft. The HI instruments are wide-angle imaging
systems designed to detect CMEs in the heliosphere, in particular,
for the first time, observing the propagation of such events along the
Sun-Earth line. These early results show that despite severe technical
challenges in their design and implementation, the HI instruments can
successfully detect CMEs in the heliosphere and this is an extremely
important milestone for CME research. Among the early results, we
show a number of CME events, demonstrating the ability to extract the
F-coronal intensity distribution, and to track a CME from the corona
to the Earth. Early investigations of the velocity profiles of CMEs
as they propagate through the heliosphere and of their basic structure
will be presented.

---------------------------------------------------------
Title: Solar effects at Earth as observed by the STEREO Heliospheric
Imagers
Authors: Rouillard, A.; Davis, C. J.; Harrison, R. A.; Davies, J. A.;
Bewsher, D.; Crothers, S. R.; Eyles, C. J.
2007AGUFMSH51B..05R Altcode:
The twin STEREO spacecraft each carry a Heliospheric Imager. These
wide angle cameras have provided the first ever observations of Earth
directed events from a position outside the Sun-Earth line. We present
combined observations taken with the instruments onboard STEREO, SOHO
and ACE spacecraft as we track the progress of material through the
heliosphere. At Earth, the impact of the solar wind on the Earth's
atmosphere is tracked by the Cluster satellites and EISCAT radars.

---------------------------------------------------------
Title: STEREO SECCHI Observations of Space Debris: Are They Associated
with S/WAVES Dust Detections?
Authors: St. Cyr, O. C.; Howard, R. A.; Wang, D.; Thompson, W. T.;
Harrison, R. A.; Kaiser, M. L.
2007AGUFMSH33A1092S Altcode:
White-light coronagraphs are optimized to reject stray light in order
to accomplish their primary science objective - - the observation
of coronal mass ejections (CMEs) and the corona. Because they were
designed to detect these faint signals while pointing at the Sun,
many spacebased coronagraphs in the past (Skylab, SMM, SOHO) have
detected "debris" apparently associated with the vehicle. These appear
to be sunlit particles very near the front of the telescope aperture
(~meters). In at least one case, these earlier debris sightings were
interpreted as deteriorating insulation from the thermal blankets on
the spacecraft (St. Cyr and Warner, 1991ASPC...17..126S); and for
the earlier Sklyab observations, the sightings were believed to be
associated with water droplets (Eddy, "A New Sun: The Solar Results
from Skylab", NASA SP-402, p119, 1979.) The STEREO SECCHI suite of
white-light coronagraphs represents the most recent instantations of
these specialized instruments, and for the first time we are able
to track CMEs from their initiation at the Sun out to 1 A.U. Since
observations commenced, the SECCHI white-light telescopes have been
sporadically detecting debris particles. Most of the detections
are individual or small numbers of bright objects in the field which
therefore do not affect the primary science goals of the mission. But on
several occasions in the eight months' of observation there have been
"swarms" of these bright objects which completely obscure the field
of view of one or more instrument for a brief period of time. Here we
report on the intriguing possibility that the SECCHI debris sightings
represent particles of thermal insulation, ejected from the spacecraft
by interplanetary dust impacts. Because of the large field of view and
high duty cycle of the Heliospheric Imagers on STEREO, we may be able
to demonstrate that some of these have also been detected by STEREO
S/WAVES as sporadic plasma emissions.

---------------------------------------------------------
Title: A 3D view of coronal mass ejections in interplanetary space
Authors: Breen, A. R.; Dorrian, G. D.; Bisi, M. M.; Davis, C. J.;
Fallows, R. A.; Morgan, H.; Harrison, R. A.
2007AGUFMSH33A1081B Altcode:
Ground-based measurements of interplanetary scintillation (IPS) have
been used to study the solar wind for many years, but interpretation of
the results has always been rendered more difficult by uncertainty about
the electron density distribution along the extended line-of-sight
from radio source to antenna. This has been particularly marked
in the case of Earth-directed coronal mass ejections (CMEs). The
launch of the STEREO spacecraft, with its Heliospheric Imager (HI)
instruments, provides us with the first detailed view of structures
in the Sun-Earth line, revealing the motion of large-scale density
structures, and greatly reducing the uncertainties in interpreting
IPS observations of the speeds of small-scale irregularities embedded
within the larger structures. In this poster we present results from
a co-ordinated programme of measurements which brings together STEREO
HI and two different IPS experiments. We consider two events, one from
2005 in which we use a combination of long-baseline IPS measurements
from EISCAT and MERLIN, tomographically-reconstructed 3D density
distributions from STELab IPS observations, and SOHO EIT and LASCO
images to track the development of an Earth-directed CME. We discuss
the remaining uncertainties in this approach and the ways in which
STEREO HI images would have assisted with the analysis. In the second
event we combine STEREO HI observations of structures in the solar wind
with IPS measurements of solar wind speed from EISCAT and MERLIN and
tomographic reconstructions of 3D structure. We discuss the results
and present suggestions for future co-ordinated campaigns.

---------------------------------------------------------
Title: First Direct Observation of the Interaction between a Comet
and a Coronal Mass Ejection Leading to a Complete Plasma Tail
Disconnection
Authors: Vourlidas, Angelos; Davis, Chris J.; Eyles, Chris J.;
Crothers, Steve R.; Harrison, Richard A.; Howard, Russell A.; Moses,
J. Daniel; Socker, Dennis G.
2007ApJ...668L..79V Altcode:
This a discovery report of the first direct imaging of the interaction a
comet with a coronal mass ejection (CME) in the inner heliosphere with
high temporal and spatial resolution. The observations were obtained
by the Sun-Earth Connection Coronal and Heliospheric Investigation
(SECCHI) Heliospheric Imager-1 (HI-1) aboard the STEREO mission. They
reveal the extent of the plasma tail of comet 2P/Encke to unprecedented
lengths and allow us to examine the mechanism behind a spectacular
tail disconnection event. Our preliminary analysis suggests that the
disconnection is driven by magnetic reconnection between the magnetic
field entrained in the CME and the interplanetary field draped around
the comet and not by pressure effects. Further analysis is required
before we can conclude whether the reconnection occurs on the day side
or on the tail side of the comet. However, the observations offer
strong support to the idea that large-scale tail disconnections are
magnetic in origin. The online movie reveals a wealth of interactions
between solar wind structures and the plasma tail beyond the collision
with the CME. Future analyses of this data set should provide critical
insights on the structure of the inner heliosphere.

---------------------------------------------------------
Title: In-orbit verification, calibration, and performance of the
Heliospheric Imager on the STEREO mission
Authors: Eyles, Chris; Davis, Chris; Harrison, Richard; Waltham,
Nick; Halain, Jean-Philippe; Mazy, Emmanuel; Defise, Jean-Marc;
Howard, Russ; Moses, Dan; Newmark, Jeff; Plunkett, Simon
2007SPIE.6689E..07E Altcode: 2007SPIE.6689E...5E
The Heliospheric Imager (HI) forms part of the SECCHI suite
of instruments aboard the two NASA STEREO spacecraft which were
launched successfully from Cape Canaveral AFB on 25 Oct 2006 (26 Oct
UTC). Following lunar swingby's on 15 Dec and 21 Jan respectively, the
two spacecraft were placed in heliocentric orbits at approximately 1 AU
- one leading and one lagging the Earth, with each spacecraft separating
from the Earth by 22.5° per year. Each HI instrument comprises
two wide-angle optical cameras - HI-1 and HI-2 have 20° and 70°
fields-of-view which are off-pointed from the Sun direction by 14.0°
and 53.7° respectively, with the optical axes pointed towards the
ecliptic plane. In this way the cameras will for the first time provide
stereographic images of the solar corona, and in particular of Coronal
Mass Ejections (CMEs) as they propagate outwards through interplanetary
space towards the Earth and beyond. The wide-field coverage of HI
enables imaging of solar ejecta from 15 to about 330 solar radii
whilst the other SECCHI instruments (2 coronagraphs and an EUV imager)
provide coverage from the lower corona out to 15 solar radii. This
paper briefly reviews the design and performance requirements for the
instrument. The various activation, checkout and calibration activities
before and after opening the instrument's protective cover or door
(instrument 'first-light') are then described and it is shown that
the instrument has met the design requirements, including CCD and
camera imaging performance, correction for shutterless operation of
the cameras, straylight rejection and thermal requirements. It is
demonstrated from observations of a CME event on 24-25 Jan 2007 that
the instrument is capable of detecting CMEs at an intensity of 1% of
the coronal background. Lessons learnt during the design, development
and in-orbit operation of the instrument are discussed.

---------------------------------------------------------
Title: First Combined Observations Of Cmes By The Lasco Coronagraphs,
Smei And The Stereo Secchi Heliospherical Imagers
Authors: Webb, David F.; Howard, R. A.; Morrill, J. S.; Harrison,
R. A.; Eyles, C. J.; Howard, T. A.; Kuchar, T. A.; Johnston, J. C.
2007AAS...21011906W Altcode: 2007BAAS...39..244W
We report on the first combined observations of coronal mass ejections
(CMEs) observed by the SOHO LASCO and STEREO SECCHI COR-2 coronagraphs,
the Coriolis Solar Mass Ejection Imager (SMEI), and the SECCHI
Heliospheric Imagers (HIs) on each STEREO spacecraft. STEREO was
launched on 25 October 2006 and these observations were obtained during
the commissioning phase. All three instruments observe density in the
heliosphere via the Thomson scattering process. The LASCO and COR-2
coronagraphs observe the early development of CMEs out to 30 Rs, or
about 8o. There are two HI systems on each STEREO spacecraft,
HI-1 and HI-2, each with a circular field of view (fov) centered on
the ecliptic plane. The HI-1 fov is 10o in radius, begins at
4o elongation, and, thus, overlaps with the LASCO fov. The
HI-2 fov is 35o in radius, begins at 18.7o, and
overlaps with the HI-1 fov. SMEI is an all-sky imager that detects and
tracks CMEs from near the Sun at elongations &gt; 20o to
beyond 90o. Thus, the SMEI fov overlaps the outer portion
of the HI-1 fov but includes nearly all of the HI-2 fov. The first
HI CME observations were made by the HI-1A on 23- 28 Dec. 2006 and
showed continued outflows from a limb region. One or more CMEs were
observed from the east limb on 24- 25 Jan. 2007 by LASCO and HI-1A,
with HI-2A and SMEI observing the outer loops into 26 Jan. We discuss
the preliminary analyses of these events, including their kinematic
and structural evolution through the fields of these instruments.

---------------------------------------------------------
Title: The Impact of Geometry on CME Observations Made by SEECHI
Authors: Morrill, J.; Kunkel, V.; Halain, J. P.; Harrison, R. A.;
Howard, R. A.; Moses, J. D.; Newmark, J.; Plunkett, S.; Socker, D.;
Wang, D.; Vourlidas, A.
2007AGUSMSH41A..11M Altcode:
Optical observations of Coronal Mass Ejections (CME's) during the past
several decades have generally been confined to events observed near
the sun. Although events originating from most regions of the sun can
be observed, the assumption has often made that the CME is propagating
in the plane-of-the-sky. This assumption is generally adequate to give
lower limits of CME mass and speed. However, continuous observations
of CME's are now being made from very near the solar surface to
large distances from the sun by the SECCHI instrument on STEREO. When
CME's are observed at great distances from the sun, plane-of-the-sky
assumptions are not adequate for analysis of these events. In this
presentation we will discuss some recent observations made by the
SEECHI instruments and the impact of geometry on our interpretation
of these events.

---------------------------------------------------------
Title: The Sun To The Earth, A Panoramic View From SECCHI: Overview
Authors: Moses, John Daniel; Newmark, J.; Howard, R. A.; Plunkett,
S.; Socker, D.; Wang, D.; Vourlidas, A.; Halain, J.; Harrison, R. A.;
Eyles, C. J.; Davila, J.; Lemen, J.; Wuelser, J.
2007AAS...21011904M Altcode: 2007BAAS...39..244M
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) is the remote sensing component of the STEREO mission
to explore the source, initiation, and propagation through the
heliosphere of Coronal Mass Ejections (CMEs). To achieve this goal,
SECCHI must continuously observe CMEs from two different perspectives
beginning with the pre-event coronal configuration and ending with the
propagation of the event out of the inner heliosphere. Thus, each of
the two STEREO observatories carries a suite of SECCHI telescopes with
5 different fields of view providing an uninterrupted view of coronal
and Heliospheric phenomena from the solar chromosphere to 1 AU. This
is the first panoramic view of the inner heliosphere dedicated to
observing the spatial and temporal scales characteristic of CMEs at
elongation angles from 0 to almost 90 degrees. We present first
results from the SECCHI imaging suite with emphasis on the unprecedented
panoramic views of the heliosphere. We show direct observations of
CMEs and the solar wind from initiation on the Sun throughout the inner
heliosphere to 1 AU. The SECCHI suite performance exceeds that necessary
to achieve the Level 1 STEREO science objectives. Thus, as the STEREO
spacecraft separate to provide views from different directions we can
anticipate breakthrough observations for issues currently unresolved
by plane-of-sky projections through optically thin structures. The most current information on SECCHI can be obtained from the
STEREO mission website at http://stereo.gsfc.nasa.gov and the SECCHI
website at http://secchi.nrl.navy.mil. The NRL participation in the
STEREO mission is supported by NASA under S-13631-Y, and by the Office
of Naval Research.

---------------------------------------------------------
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Wang, D.; Plunkett, S. P.; Baugh, R.; McMullin, D. R.;
Davila, J. M.; Thompson, W. T.; Lemen, J. R.; Wuelser, J.; Harrison,
R. A.; Waltham, N. R.; Davis, C. J.; Eyles, C. J.; Defise, J.; Halain,
J.; Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet,
M. F.
2007AGUSMSH33A..01H Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs, and
two telescopes that comprise the heliospheric imager. SECCHI will
observe coronal mass ejections (CMEs) from their birth at the sun,
through the corona and into the heliosphere. A complete instrument
suite is being carried on each of the two STEREO spacecraft, which
will provide the first sampling of a CME from two vantage points. The
spacecraft, launched 25 October 2006, are orbiting the Sun, one Ahead
of the Earth and the other Behind, each separating from Earth at about
22 degrees per year. The varying separation means that we will have
different observational capabilities as the spacecraft separate and
therefore differing science goals. The primary science objectives
all are focused on understanding the physics of the CME process
their initiation, 3D morphology, propagation, interaction with the
interplanetary medium and space weather effects. By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time, answers to some
of the outstanding questions will be obtained. We will show some of
the initial results.

---------------------------------------------------------
Title: Discovery of the Atomic Iron Tail of Comet MCNaught Using
the Heliospheric Imager on STEREO
Authors: Fulle, M.; Leblanc, F.; Harrison, R. A.; Davis, C. J.; Eyles,
C. J.; Halain, J. P.; Howard, R. A.; Bockelée-Morvan, D.; Cremonese,
G.; Scarmato, T.
2007ApJ...661L..93F Altcode:
In 2007 January, at the heliocentric distance r&lt;0.3 AU, comet
McNaught 2006P1 became the brightest comet since C/Ikeya-Seki 1965S1
and was continuously monitored by space-based solar observatories. We
provide strong evidence that an archlike tail observed by the
Heliospheric Imager aboard the STEREO spacecraft is the first ever
detected tail composed of neutral Fe atoms. We obtain an Fe lifetime
τ=(4.1+/-0.4)×104 s at r=0.25 AU, in agreement with
theoretical predictions of the photoionization lifetime. The expected
dust temperature is inconsistent with iron sublimation, suggesting
that Fe atoms are coming from troilite evaporation.

---------------------------------------------------------
Title: Stereo Observations Of The Solar Corona Using The Secchi
Experiment
Authors: Plunkett, Simon P.; Howard, R. A.; Moses, J. D.; Vourlidas,
A.; Socker, D.; Newmark, J.; Wang, D.; Baugh, R.; Davila, J.;
Thompson, W.; St. Cyr, O. C.; Lemen, J.; Wuelser, J. P.; Harrison,
R. A.; Waltham, N.; Davis, C. J.; Eyles, C. J.; Defise, J. M.; Halain,
J. P.; Bothmer, V.; Delaboudiniere, J. P.; Auchere, F.; Mercier, R.;
Ravet, M. F.
2007AAS...21011901P Altcode: 2007BAAS...39..243P
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs,
and two telescopes that comprise the heliospheric imager. The main
objective of SECCHI is to observe coronal mass ejections (CMEs) from
their birth at the sun, through the corona and into the heliosphere. A
complete instrument suite is being carried on each of the two STEREO
spacecraft, which will provide the first sampling of a CME from two
vantage points as the spacecraft separate from each other at the rate
of about 45 degrees per year. We will show examples of some of the
data and some of the initial stereo results.

---------------------------------------------------------
Title: The Sun To The Earth, A Panoramic View From SECCHI: CME
Observations Through The Inner Heliosphere
Authors: Newmark, Jeffrey; Moses, J. D.; Howard, R. A.; Plunkett, S.;
Socker, D.; Wang, D.; Vourlidas, A.; Halain, J. P.; Harrison, R. A.;
Eyles, C. J.; Davila, J.; Lemen, J.; Wuelser, J. P.
2007AAS...21011905N Altcode: 2007BAAS...39..244N
The STEREO SECCHI telescope suite is returning unprecedented viewsvof
the Sun and inner heliosphere. The SECCHI instruments on each of the two
STEREO spacecraft are observing Coronal Mass Ejections (CMEs) from their
initiation, through the corona, and into interplanetary space beyond the
Earth's orbit. We present a first analysis of a CME throughout the inner
heliosphere. We focus on the propagation characteristics of the CME
and the morphological properties of the CME as viewed from STEREO. This first glimpse of a CME in the heliosphere clearly demonstrates
the anticipated scientific returns that future STEREO observations
(at larger angular separations) of CMEs in interplanetary space will
provide. The most current information can be obtained on the STEREO
mission website at http://stereo.gsfc.nasa.gov and the SECCHI website
at http://secchi.nrl.navy.mil. The NRL participation on SECCHI is
supported by NASA under S-13631-Y, and by the Office of Naval Research.

---------------------------------------------------------
Title: Commission 10: Solar Activity
Authors: Melrose, Donald B.; Klimchuk, James A.; Benz, A. O.; Craig,
I. J. D.; Gopalswamy, N.; Harrison, R. A.; Kozlovsky, B. Z.; Poletto,
G.; Schrijver, K. J.; van Driel-Gesztelyi, L.; Wang, J. -X.
2007IAUTA..26...75M Altcode:
Commission 10 aims at the study of various forms of solar activity,
including networks, plages, pores, spots, fibrils, surges, jets,
filaments/prominences, coronal loops, flares, coronal mass ejections
(CMEs), solar cycle, microflares, nanoflares, coronal heating etc.,
which are all manifestation of the interplay of magnetic fields and
solar plasma. Increasingly important is the study of solar activities
as sources of various disturbances in the interplanetary space
and near-Earth "space weather".Over the past three years a major
component of research on the active Sun has involved data from the
RHESSI spacecraft. This review starts with an update on current and
planned solar observations from spacecraft. The discussion of solar
flares gives emphasis to new results from RHESSI, along with updates on
other aspects of flares. Recent progress on two theoretical concepts,
magnetic reconnection and magnetic helicity is then summarized, followed
by discussions of coronal loops and heating, the magnetic carpet
and filaments. The final topic discussed is coronal mass ejections
and space weather.The discussions on each topic is relatively brief,
and intended as an outline to put the extensive list of references
in context.The review was prepared jointly by the members of the
Organizing Committee, and the names of the primary contributors to
the various sections are indicated in parentheses.

---------------------------------------------------------
Title: Searching for solar clouds in interplanetary space
Authors: Harrison, Richard; Davis, Chris; Eyles, Chris; Halain,
Jean-Philippe; Howard, Russ
2007SpReT.168...25H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: T he Solar Orbiter Payload Working Group: Remote Sensing
Authors: Harrison, R.
2007ESASP.641E...2H Altcode:
The activities of the Solar Orbiter Payload Working Group, covering
remote sensing issues are outlined in this report. Solar Orbiter
faces many challenges mainly due to its unusual orbit, encountering
extreme thermal and particle environments, and demanding low mass
and autonomous operation whilst providing major advances in solar
observation. Procedures for the assessment of challenges and subsequent
recommendations to ESA are outlined, as well as the activities relating
to the Payload Definition Document.

---------------------------------------------------------
Title: A benchmark event sequence for mass ejection onset studies. A
flare associated CME with coronal dimming, ascending pre-flare loops
and a transient cool loop
Authors: Harrison, R. A.; Bewsher, D.
2007A&A...461.1155H Altcode:
Aims:In this study, we report on the spectroscopic observations
of a particularly well-observed flare and coronal mass ejection
(CME) event sequence which we feel can be used as a benchmark study
for CME onsets. Methods: Specifically, we report on a set
of extreme-ultraviolet (EUV) spectroscopic observations using the
Solar and Heliospheric Observatory (SOHO) to determine features of
the CME onset process revealed through the analysis of plasma at
different temperatures. Results: The flare which occurred on
the north-western limb was associated with a large CME. The event in
question showed evidence for pre-flare ascending loops containing 1-2
million K plasma, which disappeared just prior to the flare. This
disappearance is interpreted as coronal dimming, and it appears to
coincide with the projected mass ejection onset time. In addition,
a discrete, short-lived coronal loop containing plasma at transition
region temperatures was detected just prior to this eruption. This
loop displayed mass motion, along flux tubes, with oppositely directed
flows. The nature and timing of this transient loop suggest a close
relationship between it and the eruption process. Examinations of the
timing and topology, which extend previous studies considerably, are
found to be consistent with the mass ejection onset interpretation of
Zhang and co-workers. Conclusions: .The clarity of this event
sequence suggests that we should regard it as a benchmark in studies
of the mass ejection onset process.

---------------------------------------------------------
Title: Extreme-Ultraviolet Spectrometer For Solar Orbiter
Authors: Harrison, R.; Sawyer, E.
2007ESASP.641E..35H Altcode:
An Exteme-Ultraviolet Spectrometer (EUS) instrument has always been a
key component of the Solar Orbiter strawman payload. Such an instrument
is required to provide plasma diagnostic capabilities in support of
the goals of Orbiter. We describe the instrument concept for an EUS
instrument on behalf of an established consortium. We outline the
basic optical design approach and the strategy for catering for the
extreme thermal, particle environment and mechanical issues. Reference
is made to a number of papers in this issue and elsewhere which provide
the details of the proposed instrument and we concentrate here on the
instrument strategy.

---------------------------------------------------------
Title: Book Review: Book review
Authors: Harrison, Richard
2007SpReT.170...61H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R. A.; Moses, D.; Vourlidas, A.; Newmark, J.; Socker,
D. G.; Plunkett, S.; Wang, D.; Baugh, R.; McMullin, D.; Davila, J.;
St. Cyr, C.; Thompson, W. T.; Lemen, J.; Wuelser, J.; Harrison, R. A.;
Waltham, N. R.; Davis, C.; Eyles, C. J.; Defise, J.; Halain, J.;
Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet, M.
2006AGUFMSM12A..02H Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs, and
two telescopes that comprise the heliospheric imager. SECCHI will
observe coronal mass ejections (CMEs) from their birth at the sun,
through the corona and into the heliosphere. A complete instrument
suite is being carried on each of the two STEREO spacecraft, which
will provide the first sampling of a CME from two vantage points. The
spacecraft will orbit the Sun, one Ahead of the Earth and the other
Behind, each separating from Earth at about 22 degrees per year. The
varying separation means that we will have different observational
capabilities as the spacecraft separate and therefore differing science
goals. The primary science objectives all are focused on understanding
the physics of the CME process their initiation, 3D morphology,
propagation, interaction with the interplanetary medium and space
weather effects. By observing the CME from multiple viewpoints with UV
and coronagraphic telescopes and by combining these observations with
radio and in-situ observations from the other instruments on STEREO as
well as from other satellites and ground based observatories operating
at the same time, answers to some of the outstanding questions will
be obtained. STEREO follows the very successful SOHO mission. SOHO's
success was primarily due to the highly complementary nature of the
instruments, but it was partly due to the very stable platform. The
L1 orbit enables an extremely stable thermal environment and thus
very stable pointing, as well as uninterrupted solar viewing. The
STEREO will have both of these characteristics, but in addition will
have multi-viewpoint viewing of CMEs, which will greatly enhance the
many discoveries that SOHO data have produced. We have been developing
techniques to interpret the observations from multiple viewpoints and
to perform 3-dimensional deconvolution of the CME observations using
forward modeling and inversion techniques. A continuous downlink of
STEREO data will provide a low-resolution, real- time view from all
of the instruments. The full data are downlinked once a day and will
be available about 24 hours later. We will present some preliminary
results from the instrument, which is expected to be launched in
October/November, 2006

---------------------------------------------------------
Title: Bursting the Solar Bubble: The Flare-Coronal Mass Ejection
Relationship
Authors: Harrison, Richard
2006GMS...165...73H Altcode:
One of the fundamental problems in solar physics research today is our
understanding of the flare-coronal mass ejection (CME) relationship. On
the face of it, a basic investigation of the association between the
two most energetic transient phenomena in the solar system would
appear to be a relatively simple prospect. However, observational
limitations in particular have served to limit our understanding of
the flare-CME phenomenon, and thus our understanding of the CME onset
mechanisms. Here, we review briefly flare-CME research prior to the
Solar and Heliospheric Observatory (SOHO) era, and, through a series
of illustrations of recent observations, and reference to several new
directions of investigation, summarise our current thinking regarding
the flare-CME scenario and the CME onset.

---------------------------------------------------------
Title: 10 Years of CME Onset Studies with SOHO/CDS
Authors: Bewsher, D.; Harrison, R. A.
2006ESASP.617E..21B Altcode: 2006soho...17E..21B
No abstract at ADS

---------------------------------------------------------
Title: Science Plans for the International Heliophysical Year
Authors: Davila, J. M.; Gopalswamy, N.; Harrison, R. A.; Stamper,
R.; Briand, C.; Potgieter, M. S.
2006AGUSM.U34A..04D Altcode:
On October 4, 1957, only 53 years after the beginning of flight in Kitty
Hawk, the launch of Sputnik 1 marked the beginning of the space age;
as mankind took the first steps to leaving the protected environment of
Earth's atmosphere. Discovery of the radiation belts, the solar wind,
and the structure of Earth's magnetosphere prepared the way for the
inevitable human exploration to follow. Soon, Cosmonauts and Astronauts
orbited Earth, and then in 1969, Astronauts landed on the Moon. Today
a similar story is unfolding, the spacecraft Voyager has crossed the
termination shock, and will soon leave the heliosphere. For the first
time, man will begin to explore the local interstellar medium. It is
inevitable that, during the next 50 years, exploration of the solar
system including the Moon, Mars and the outer planets will be the
focus of the space program, and like 50 years ago, unmanned probes
will lead the way, followed by human exploration. The International
Geophysical Year (IGY) of 1957, a broad-based and all-encompassing
effort to push the frontiers of geophysics, resulted in a tremendous
increase of knowledge in space physics, Sun-Earth Connection, planetary
science and the heliosphere in general. Now, 50 years later, we have
the unique opportunity to further advance our knowledge of the global
heliosphere and its interaction with the interstellar medium through
the International Heliophysical Year (IHY) in 2007, and to raise
public awareness of space physics. This presentation will focus on
global science planning efforts and campaigns for all participating
IHY nations.

---------------------------------------------------------
Title: IHY Science and Organization in Europe
Authors: Bougeret, J. -L.; Briand, C.; Bonet Navaro, J. A.; Breen,
A.; Candidi, M.; Georgevia, K.; Harrison, R.; Marsden, R.; Schmieder,
B.; von Steiger, R.
2006cosp...36.3226B Altcode: 2006cosp.meet.3226B
We present the scientific and organizational approach to the
International Heliophysical Year in Europe A summary is given of the
First European General Assembly of the IHY that was held in Paris in
January 2006 Initiatives and expected returns are described

---------------------------------------------------------
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R.; Moses, D.; Vourlidas, A.; Davila, J.; Lemen, J.;
Harrison, R.; Eyles, C.; Defise, J. -M.; Bothmer, V.; Ravet, M. -F.;
Secchi Team
2006cosp...36..870H Altcode: 2006cosp.meet..870H
The Sun Earth Connection Coronal and Heliospheric Investigation SECCHI
on the NASA Solar Terrestrial Relations Observatory STEREO mission
is a suite of remote sensing instruments consisting of an extreme
ultraviolet EUV imager two white light coronagraphs and two telescopes
that comprise the heliospheric imager SECCHI will observe coronal mass
ejections CMEs from their birth at the sun through the corona and into
the heliosphere A complete instrument suite is being carried on each
of the two STEREO spacecraft which will provide the first sampling of
a CME from two vantage points The spacecraft will orbit the Sun one
Ahead of the Earth and the other Behind each separating from Earth at
about 22 degrees per year The varying separation means that we will
have different observational capabilities as the spacecraft separate
and therefore differing science goals The primary science objectives
all are focused on understanding the physics of the CME process -
their initiation 3D morphology propagation interaction with the
interplanetary medium and space weather effects By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time answers to some
of the outstanding questions will be obtained STEREO follows the very
successful SOHO mission SOHO s success was primarily due to the highly
complementary nature of the instruments but it was

---------------------------------------------------------
Title: EUV and UV imaging and spectroscopy from space
Authors: Harrison, Richard A.
2005pmds.book..125H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 2007: International Heliophysical Year
Authors: Harrison, Richard; Breen, Andy; Bromage, Barbara; Davila, Joe
2005A&G....46c..27H Altcode:
In 1957 a programme of international research was organized as the
International Geophysical Year (IGY) to study global phenomena of the
Earth and geospace. This programme was a follow-on to the International
Polar Years in 1882-83 and 1932-33. The IGY involved about 60 000
scientists from 66 nations, working at thousands of stations, from
pole to pole. There had never been anything like it before. The 50th
anniversary of IGY will occur in 2007. Plans are well under way to
organize an international programme of scientific collaboration for
this time period to focus not just on the Earth but extending our
horizons to the heliosphere, including the Sun, and thus including
the drivers of geophysical processes, and making use of the fleet of
spacecraft and numerous ground-based systems in place. This programme
is called the International Heliophysical Year.

---------------------------------------------------------
Title: The widths of vacuum-ultraviolet spectral lines in the
equatorial solar corona observed with CDS and SUMER
Authors: Wilhelm, K.; Fludra, A.; Teriaca, L.; Harrison, R. A.;
Dwivedi, B. N.; Pike, C. D.
2005A&A...435..733W Altcode:
Observations of the solar equatorial corona between heights of 36 Mm and
184 Mm above the limb obtained by the SOHO spectrometers CDS and SUMER
in December 2003 are presented and discussed with special emphasis on
the widths of the spectral lines Mg x at 62.50 nm, Al xi at 55.00 nm
and 56.82 nm, Ca x at 55.78 nm, and Si xi at 58.09 nm. SUMER observed,
in addition, the lines Mg x 60.98 nm, Ca x 57.40 nm, Fe xii 124.20 nm,
Fe xvii 115.31 nm, and Ca xiii 113.37 nm. The Si xii 52.11 nm line
was only observed by CDS. A different behaviour of the line width
of Mg x 62.50 nm as a function of height above the limb had been
found in studies carried out independently with both instruments at
different times. It is the aim of this joint investigation to (a)
study instrumental effects on line-width results; and (b) provide a
thorough analysis of line profiles with altitude for the new campaign.

---------------------------------------------------------
Title: Coronal and Heliospheric Science Opportunities with the SECCHI
Heliospheric Imager
Authors: Moses, J.; Socker, D.; Eyles, C.; Harrison, R.; Defise,
J.; Howard, R.; Rochus, P.; Waltham, N.; Simnett, G.; Newmark, J.;
Halain, J.; Mapson-Menard, H.; Mazy, E.; Davis, C.
2005AGUSMSH51D..02M Altcode:
The Heliospheric Imager (HI) is part of the SECCHI suite of instruments
on-board the two STEREO spacecrafts. The two HI instruments will
provide stereographic image pairs of solar coronal plasma and coronal
mass ejections (CME) over a wide field of view (85 degrees), with an
inner field limit of approximately 13 solar radii. These observations
compliment the 15 solar radii field of view of the solar corona obtained
by the other SECCHI instruments to provide unbroken coverage of the
solar corona and heliosphere from the Sun to the Earth. The as-built
characteristics of the HI will be presented along with the current data
reduction and analysis approach. The constraints that HI observations
place on models of CME propagation in the interplanetary medium will
be discussed.

---------------------------------------------------------
Title: Planning for SECCHI Observations of the Solar Corona and
Heliosphere
Authors: Plunkett, S. P.; Howard, R. A.; Rich, N. B.; Wang, D.;
Harrison, R. A.; Thompson, W. T.; Wuelser, J.
2005AGUSMSH53A..01P Altcode:
The Sun-Earth Connections Coronal and Heliospheric Investigation
(SECCHI) instrument suite consists of five almost identical telescopes
on each of the STEREO spacecraft. Each instrument suite includes
an extreme ultraviolet disk imager (EUVI), two coronagraphs (COR1
and COR2) and two heliospheric imagers (HI1 and HI2) that will
image the corona and heliosphere to distances beyond the Earth's
orbit. SECCHI observations will consist of a synoptic program optimized
to provide simultaneous identical images for stereoscopic viewing of
coronal and heliospheric structures from both STEREO spacecraft, and
special observations that can be tailored to meet specific science
objectives. This paper will describe the observational capabilities
of the SECCHI instruments, and will discuss the operational resources
available and constraints on observations at various stages of the
mission.

---------------------------------------------------------
Title: EUV spectroscopy for Solar Orbiter
Authors: Harrison, R. A.
2005AdSpR..36.1415H Altcode:
Building on the success of EUV/UV spectroscopic studies from the SOHO
mission in particular, a next generation spectroscopic study of the Sun
is included in plans for Solar Orbiter. The combination of close-up and
out of ecliptic observation provides unique possibilities for solar
plasma diagnostics and these are outlined here. Technical challenges
and the instrumental requirements for such an instrument aboard Orbiter
are described in detail.

---------------------------------------------------------
Title: Natural disasters — Are we doing enough?
Authors: Harrison, Richard
2005CIBu..162...47H Altcode: 2005SpReT.162...47H
No abstract at ADS

---------------------------------------------------------
Title: STEREO/HI from near-Earth objects to 3D comets
Authors: Davis, C. J.; Harrison, R. A.
2005AdSpR..36.1524D Altcode:
Scientific objectives are being compared with hardware capabilities
in order to fully exploit the capabilities of the STEREO heliospheric
imager (HI). This has involved detailed image simulation work and
efforts to produce a set of observational plans to tackle specific
scientific questions. While the primary mission for this instrument is
to study the development and propagation of coronal mass ejections,
several additional novel science studies have been proposed. These
include; the detection and study of near-Earth objects and the imaging
of comets in three dimensions. Identifying all potential new uses of
HI before launch will enable us to anticipate user requirements and
provide the necessary data products and operations tools. We report on
the progress of the observational schemes suggested so far and invite
further suggestions in order to maximize the unique capabilities of
the HI.

---------------------------------------------------------
Title: Solar Orbiter—mission profile, main goals and present status
Authors: Marsch, Eckart; Marsden, Richard; Harrison, Richard;
Wimmer-Schweingruber, Robert; Fleck, Bernhard
2005AdSpR..36.1360M Altcode:
The main goals and present status of the Solar Orbiter mission are
briefly described. solar orbiter will determine in situ the properties
of fields and particles in the unexplored near-Sun heliosphere in
three dimensions, investigate remotely the fine-scale structures and
events in the magnetically coupled layers of the Sun’s atmosphere,
identify through near corotation the links between activity on the
solar surface and the resulting evolution of the inner heliosphere, and
observe from relatively high latitudes the polar regions and equatorial
corona. Some results from recent activities, such as industrial studies,
payload working group meetings, science definition team meetings and
ESA internal studies are briefly reviewed. Solar Orbiter is currently
planned for launch in October 2013.

---------------------------------------------------------
Title: Preface
Authors: Culhane, Len; Harrison, Richard
2005AdSpR..36.1477C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A new start
Authors: Harrison, Richard; Fellous, Jean-Louis; Argent, Chris;
Mendez, Mariano
2005CIBu..162....2H Altcode: 2005SpReT.162....2H
No abstract at ADS

---------------------------------------------------------
Title: The STEREO heliospheric imager: how to detect CMEs in the
heliosphere
Authors: Harrison, R. A.; Davis, C. J.; Eyles, C. J.
2005AdSpR..36.1512H Altcode:
The STEREO Heliospheric Imager is a wide-angle imaging system that
will enable, for the first time, a view of Earth-directed coronal
mass ejections (CMEs) in a field of view which also encompasses the
Earth. Twin views from widely spaced platforms, combined with the out
of Sun-Earth line perspective allow a unique and powerful tool for
the study of CMEs and, particularly, Earth-directed CMEs. We outline
the instrumental characteristics and image simulation studies which
reveal the nature of the images we anticipate.

---------------------------------------------------------
Title: Future Solar Missions
Authors: Harrison, R. A.
2004ESASP.575...13H Altcode: 2004soho...15...13H
No abstract at ADS

---------------------------------------------------------
Title: STEREO HI - From CMEs to Near Earth Objects: a Unique View
of the Heliosphere
Authors: Davis, C. J.; Harrison, R. A.
2004AGUFMSH22A..06D Altcode:
The two STEREO Heliospheric Imagers (HI) will have a unique view
of the Heliosphere, with a field of view encompassing the entire
Sun-Earth line. While the primary objective for HI is to detect and
obtain information about the size, velocity and direction of Coronal
Mass Ejections (CMEs), the sensitivity and field of view of these
instruments can be exploited to extend the scientific scope of the
mission. For the first time it will be possible to observe objects in
this region of space in three dimensions. Simulated images are being
used to determine the problems associated with observing objects from
comets and asteroids through to the distribution of interplanetary dust.

---------------------------------------------------------
Title: Summary of the Solar Orbiter payload working group activities
Authors: Fleck, Bernhard; Harrison, Richard A.; Marsden, Richard G.;
Wimmer-Schweingruber, Robert
2004SPIE.5171..123F Altcode:
Approved in October 2000 by ESA's Science Programme Committee as a
flexi-mission, the Solar Orbiter will study the Sun and unexplored
regions of the inner heliosphere from a unique orbit that brings the
probe to within 45 solar radii (0.21 AU) of our star, and to solar
latitudes as high as 38°. The scientific payload to be carried by
the Orbiter will include a sophisticated remote-sensing package, as
well as state-of-the-art in-situ instruments. Given the technical and
financial constraints associated with this mission, it is essential
that key technologies requiring significant development be identified
as early as possible. ESA has therefore set up a Payload Working Group
(PWG), made up of members of the scientific community with expertise
in instrumentation of the kind envisaged for the Solar Orbiter. The
tasks of the PWGs included: 1) a realistic assessment of the strawman
payload, including definition of mass, size, power requirements; 2)
identification of key problem areas arising as a result of the extreme
thermal and radiation environments; 3) identification of necessary
technological developments; and 4) provision of detailed input to a
Solar Orbiter Payload Definition Document (PDD). This contribution
summarizes the activities and findings by the Solar Orbiter Payload
Working Group.

---------------------------------------------------------
Title: On the Coronal Mass Ejection onset and Coronal Dimming
Authors: Howard, Timothy A.; Harrison, Richard A.
2004SoPh..219..315H Altcode:
A comprehensive case and statistical study of CME onsets has been
conducted on the solar limb using the CDS, LASCO and EIT instruments
aboard the SOHO spacecraft. This is the first dedicated campaign to
establish firmly the EUV signatures of CME onsets and is based on
a series of low-corona observing campaigns made in 2002. The event
database consisted of 36 multiple emission line sequences observed
with CDS and the study builds, in particular, on studies of EUV coronal
dimming which have been associated with CME onsets. We witness a range
of dimming events in EUV coronal emission line data. Shorter events,
commonly of duration &lt; 4 hours, we find are indirectly associated
with CME onsets whereas longer-duration dimmings (&gt; 4 hours) appear
to be either due to coronal evolution or rotational effects. However,
for some CME onsets, where the CDS pointing was appropriate, no dimming
was observed. Dimming observed in EIT typically occurred immediately
after the launch of a loop or prominence, and in 5 out of 9 events
there is evidence of a matter buildup within the loop before launch. A
total of 10 events occurred where CDS was used to directly observe the
CME footprint, but no relationship between these events was found. The
results suggest that the response of the corona to a CME launch differs
between the low (1.0 R⊙≤R≤1.2 R⊙) and
middle (1.2 R⊙&lt;R≤2.0 R⊙) corona regions,
hence implying a difference between dimming observations conducted
with different instruments.

---------------------------------------------------------
Title: Dynamics of Transition Region Blinkers
Authors: Bewsher, D.; Parnell, C.; Pike, D.; Harrison, R.
2004ESASP.547..267B Altcode: 2004soho...13..267B
Analysis of CDS data has shown that transition region blinkers and the
chromosphere directly below, are preferentially more redshifted and
have larger non-thermal velocities than the normal transition region
and chromospheric plasma. The ranges of these enhanced velocities,
however, are no larger than the typical spread of Doppler and
non-thermal velocities in these regions. An overview of the Doppler
and non-thermal velocities of blinkers found with CDS in the quiet
Sun and active region are presented. The anticipated range of Doppler
velocities of blinkers are 10 - 15 km s-1 in the quiet-Sun (10 - 20 km
s-1 in active-regions) in the chromosphere (He I) and 25 - 30 km s-1
in the quiet-Sun (20 - 40 km s-1 in activeregions) in the transition
region (O V). The range of non-thermal velocities of blinkers in both
the quiet- Sun and active-regions are estimated to be 15 - 25 km s-1
in He I and 30 - 45 km s-1 in O V. There are more blinkers with larger
Doppler and non-thermal velocities than would be expected in the whole
of the chromosphere and transition region.

---------------------------------------------------------
Title: STEREO/HI: From Near-Earth Objects to 3-D Comets
Authors: Davis, C.; Harrison, R.
2004cosp...35.2121D Altcode: 2004cosp.meet.2121D
Observational methods and campaigns for using the STEREO Heliospheric
Imager are being investigated. This has involved detailed image
simulation work and efforts to produce a set of observational plans
to tackle specific scientific questions. Most plans involve the study
of the development and propagation of coronal mass ejections. However,
several novel schemes are under study, for example, for the detection
and study of Near-Earth Objects (NEOs) and the 3-dimensional study
of comets. We report on progress in these observational schemes which
serve to stress the unique capabilities of the Heliospheric Imager.

---------------------------------------------------------
Title: 1.2 Questionnaire — Summer 2004
Authors: Harrison, Richard
2004CIBu..160....8H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: EUV Spectroscopy from Solar Orbiter
Authors: Harrison, R.
2004cosp...35..453H Altcode: 2004cosp.meet..453H
Building on the success of EUV/UV spectroscopic studies from the
SOHO mission in particular, a next generation spectroscopic study of
the Sun is included in plans for Solar Orbiter. The combination of
close-up and out of ecliptic observation provide unique possibilities
for solar plasma diagnostics and these are outlined here. Technical
challenges and the instrumental requirements for such an instrument
aboard orbiter are described in detail.

---------------------------------------------------------
Title: Evidence for Wave Dissipation through EUV Emission Line
Narrowing
Authors: Harrison, R. A.; Hood, A. W.; Pike, C. D.
2004ESASP.547..229H Altcode: 2004soho...13..229H
Using long-duration observations over closed-field, quiet Sun regions
above the solar equator, evidence has been found for the narrowing of
coronal emission lines with increasing altitude. This is interpreted
as evidence for wave dissipation in the quiet Sun corona.

---------------------------------------------------------
Title: International heliophysical year: a program of global research
continuing the tradition of previous international years
Authors: Davila, Joseph M.; Poland, Arthur I.; Harrison, Richard A.
2004AdSpR..34.2453D Altcode:
In 1957 a program of international research, inspired by the
International Polar Years of 1882-1883 and 1932-1933, was organized
as the International Geophysical Year (IGY) to study global phenomena
of the Earth and geospace. The IGY involved about 60,000 scientists
from 66 nations, working at thousands of stations from pole to pole,
in an effort to obtain simultaneous, global observations on Earth
and in space. There had never been anything like it before. The 50th
anniversary of the International Geophysical Year will occur in 2007. We
propose to organize an international program of scientific collaboration
for this time period called the International Heliophysical Year
(IHY). Like its predecessors, the IHY will focus on fundamental global
questions of Earth science.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard A.; Argent, Chris
2004CIBu..160....4H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Secchi Experiment on the Stereo Mission
Authors: Howard, R.; Moses, D.; Socker, D.; Cook, J.; Davila, J.;
Lemen, J.; Harrison, R.; Eyles, C.; Waltham, N.; Defise, J. -M.
2004cosp...35.3893H Altcode: 2004cosp.meet.3893H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of two
white light coronagraphs, an extreme ultraviolet (EUV) imager, and
a heliospheric imager. SECCHI will observe coronal mass ejections
(CMEs) from their birth at the sun, through the corona and into the
heliosphere. A complete instrument suite is being carried on each
of the two STEREO spacecraft, which will provide the first sampling
of a CME from two vantage points. The spacecraft will orbit the Sun,
one ahead of the Earth and the other behind, separating from Earth at
about 22 degrees per year. The varying separation means that we will
have different observational capabilities as the spacecraft separate
and therefore differing science goals. The primary science objectives
all are focused on understanding the physics of the CME process -
their initiation, 3D morphology, propagation, interaction with the
interplanetary medium and space weather effects. By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time, answers to some
of the outstanding questions will be obtained.

---------------------------------------------------------
Title: The STEREO Heliospheric Imager: How to detect CMEs in the
heliosphere
Authors: Harrison, R.; Davis, C.; Eyles, C.
2004cosp...35..450H Altcode: 2004cosp.meet..450H
The STEREO Heliospheric Imager is a wide-angle imaging system that
will enable for the first time, a view of Earth-directed coronal mass
ejections in a field of view which also encompasses the Earth. Twin
views from widely spaced platforms, combined with the out of Sun-Earth
line perspective allow a unique and powerful tool for the study of CMEs
and, particularly, Earth-directed CMEs. We will outline the instrumental
characteristics and image simulation studies which reveal the nature
of the images we anticipate.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard; Argent, Chris
2004CIBu..161....6H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A study of the unification of quiet-Sun transient-event
phenomena
Authors: Harrison, R. A.; Harra, L. K.; Brković, A.; Parnell, C. E.
2003A&A...409..755H Altcode:
A number of small-scale, globally distributed solar transient
event-types have been reported in the literature. Their potential
role in fundamental processes in the solar atmosphere, such as coronal
heating and wind acceleration, is under active investigation. However,
the event-types, such as those known as blinkers, explosive events,
EUV (extreme-UV) network and cell brightenings, network flares, heating
events, nanoflares and EUV brightenings are basically classifications
which are driven to a large extent by different observational techniques
and different instruments rather than the identification of a clear
differing physical phenomenon. We investigate the different instrumental
and technique limitations and attempt to identify any unification
of the reported quiet-Sun transient, small-scale phenomena. We find
that once observational techniques have been considered, a number of
the different classifications appear to be the same. This suggests
that events known as blinkers, network and cell brightenings and EUV
brightenings are the same event-type. We suggest that the term blinker
be used as a generic term to describe these events. However, there
appears to be little evidence that blinkers and explosive events are
directly related. Furthermore, although a small percentage of blinkers
and nanoflares/heating events appear to be related to one another,
these events pose a number of important questions suggesting that either
(i) blinkers and nanoflare/heating events are all created by the same
mechanism, i.e. for some blinker events, the conditions are such that
higher temperatures are found, or (ii) there are two types of event,
including the “traditional” blinker which is effectively a transition
region brightening driven by a density or filling factor enhancement,
and a mini-flare-like event which reaches higher temperatures,
presumably driven by reconnection.

---------------------------------------------------------
Title: Dynamics of Blinkers
Authors: Bewsher, D.; Parnell, C. E.; Pike, C. D.; Harrison, R. A.
2003SoPh..215..217B Altcode:
The relative Doppler and non-thermal velocities of quiet-Sun
and active-region blinkers identified in O v with CDS are
calculated. Relative velocities for the corresponding chromospheric
plasma below are also determined using the He i line. O v blinkers
and the chromosphere directly below, have a preference to be more
red-shifted than the normal transition region and chromospheric
plasma. The ranges of these enhanced velocities, however, are no larger
than the typical spread of Doppler velocities in these regions. The
anticipated ranges of Doppler velocities of blinkers are 10-15 km
s−1 in the quiet Sun (10-20 km s−1 in active
regions) for He i and 25-30 km s−1 in the quiet Sun
(20-40 km s−1 in active regions) for O v. Blinkers and
the chromosphere below also have preferentially larger non-thermal
velocities than the typical background chromosphere and transition
region. Again the increase in magnitude of these non-thermal velocities
is no greater than the typical ranges of non-thermal velocities. The
ranges of non-thermal velocities of blinkers in both the quiet Sun
and active regions are estimated to be 15-25 km s−1 in
He i and 30-45 km s−1 in O v. There are more blinkers
with larger Doppler and non-thermal velocities than would be expected
in the whole of the chromosphere and transition region. The recently
suggested mechanisms for blinkers are revisited and discussed further
in light of the new results.

---------------------------------------------------------
Title: Coronal dimming and the coronal mass ejection onset
Authors: Harrison, R. A.; Bryans, P.; Simnett, G. M.; Lyons, M.
2003A&A...400.1071H Altcode:
A set of five observations of extreme-ultraviolet (EUV) coronal dimming
associated with coronal mass ejection (CME) activity is examined. Using
spectroscopic data, plasma characteristics across a broad range of
temperatures from 20 000 K to 2 million K are determined. The dimming
events are found to coincide in time, and to coincide spatially, with
the projected onset times and locations of the associated CMEs. The
spectral data confirm that the dimming is due to mass-loss, and not
temperature variations. The actual mass-loss calculated from the degree
of dimming, using two different methods, shows that the extracted
mass in each case, is of the same order as the mass of the associated
CME. In some cases, the EUV observations are limited to relatively small
regions under the CME events and it is expected that we do not witness
the mass-loss associated with the entire event, for these. However,
we believe that this analysis has provided a method for locating the
source region of the trigger for a CME eruption, and that the dimming
characteristics can be used to distinguish between onset processes of
the CME. In particular, the gradual nature of the dimming process,
which takes place over several hours, suggests that either the CME
has a continuous driver rather than a sudden impulsive onset, or the
low coronal response to a CME extends over a long period.

---------------------------------------------------------
Title: Design and tests for the heliospheric imager of the STEREO
mission
Authors: Defise, Jean-Marc; Halain, Jean-Philippe; Mazy, Emmanuel;
Rochus, Pierre P.; Howard, Russell A.; Moses, J. Daniel; Socker,
Dennis G.; Harrison, Richard A.; Simnett, George M.
2003SPIE.4853...12D Altcode:
The Heliospheric Imager (HI) is part of the SECCHI suite of instruments
on-board the two STEREO spacecrafts to be launched in 2005. The two HI
instruments will provide stereographic image pairs of solar coronal
plasma and coronal mass ejections (CME) over a wide field of view
(~90°), ranging from 13 to 330 R0. These observations
compliment the 15 R0 field of view of the solar corona
obtained by the other SECCHI instruments (2 coronagraphs and an EUV
imager). The key challenge of the instrument design is the rejection of
the solar disk light, with total straylight attenuation of the order of
10-13 to 10-15. A multi-vane diffractive baffle
system has been theoretically optimized to achieve the lower requirement
(10-13 for HI-1) and is combined with a secondary baffling
system to reach the 10-15 rejection performance in the
second camera system (HI-2). This paper presents the last updates
of the SECCHI/HI design concept, with the expected performance. A
verification program is currently in progress. The on-going stray-light
verification tests are discussed. A set of tests has been conducted
in air, and under vacuum. The results are presented and compared with
the expected theoretical data.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard A.
2003CIBu..158....3H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Preface — The Columbia accident
Authors: Harrison, Richard
2003CIBu..156....1H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Soho observations relating to the association between flares
and coronal mass ejections
Authors: Harrison, R. A.
2003AdSpR..32.2425H Altcode:
Campaigns to investigate the solar coronal mass ejection (CME) onset
have been run using the Solar andHeliospheric Observatory (SOHO)
since 1996. These have included coronagraph and extreme-ultraviolet
(EUV) disc imaging, along with magnetic mapping of the photosphere,
in concert with EUV and UV spectroscopic observations. These campaigns
have included co-ordination with ground-based observatories, and
with other spacecraft, especially Yohkoh and the Transition Region
and Corona Explorer (TRACE). This multi-instrument, multi-spacecraft
effort has provided many rewards, with some spectacular observations
of countless eruptions. It has included the discovery of unexpected
phenomena such as EUV waves and groundbreaking work on coronal dimming,
and the development of sigmoidal shaped structures. Much has been learnt
about the CME onset yet the most basic questions still remain. We have
an unprecedented view of CME eruptions, yet we are still unable to
identify clearly the onset process and we do not fully understand the
CME-flare relationship. With all of the campaigns producing excellent
multi-wavelength observations of CMEs, how far have we progressed in
the understanding of the CME onset and, in particular, the CME-flare
relationship? Can we identify lines of research using the SOHO data,
which will provide the answers we seek — or do we need fundamentally
different observation scenarios? It is the author's opinion that we
actually have the observational tools required to understand much about
the onset process and the CME/flare links, and the emphasis should be
on understanding the limitations of our instrumentation and on removing
any preconceived ideas from our interpretations.

---------------------------------------------------------
Title: Short-term solar effects
Authors: Harrison, Richard A.
2003RSPTA.361...79H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: MAGRITTE / SPECTRE : the Solar Atmospheric Imaging Assembly
(AIA) aboard the Solar Dynamics Observatory
Authors: Rochus, P.; Defise, J. M.; Halain, J. P.; Mazy, E.; Jamar, C.;
Clette, F.; Cugnon, P.; Berghmans, D.; Hochedez, J. F.; Delaboudiniere,
J. P.; Artzner, G.; Auchere, F.; Mercier, R.; Ravet, M. F.; Delmotte,
M.; Idir, M.; Fineschi, S.; Antonucci, E.; Harrison, R. A.; Howard,
R. A.; Moses, J. D.; Newmark, J. S.
2002AGUFMSH21C..05R Altcode:
The Solar Atmospheric Imaging Assembly (AIA) aboard the Solar
Dynamics Observatory will characterize the dynamical evolution of
the solar plasma from the chromosphere to the corona, and will follow
the connection of plasma dynamics with magnetic activity throughout
the solar atmosphere. The AIA consists of 7 high resolution imaging
telescopes in the following spectral bandpasses: 1215 \x8F Ly-a, 304
\x8F He II, 629 \x8F OV, 465 \x8F Ne VII, 195 \x8F Fe XII (includes Fe
XXIV), 284 \x8F Fe XV, and 335 \x8F Fe XVI. The telescopes are grouped
by instrumental approach: the Magritte Filtergraphs (R. Magritte,
famous 20th Century Belgian Surrealistic Artist), five multilayer EUV
channels with bandpasses ranging from 195 to 1216 \x8F, and the SPECTRE
Spectroheliograph with one soft-EUV channel at OV 629 \x8F. They will
be simultaneously operated with a 10-second imaging cadence. These two
instruments, the electronic boxes and two redundant Guide Telescopes
(GT) constitute the AIA suite. They will be mounted and coaligned on a
dedicated common optical bench. The GTs will provide pointing jitter
information to the whole SHARPP assembly. This poster presents the
selected technologies, the different challenges, the trade-offs to be
made in phase A, and the model philosophy. From a scientific viewpoint,
the unique combination high temporal and spatial resolutions with the
simultaneous multi-channel capability will allow Magritte/SPECTRE
to explore new domains in the dynamics of the solar atmosphere, in
particular the fast small-scale phenomena. We show how the spectral
channels of the different instruments were derived to fulfill the
AIA scientific objectives, and we outline how this imager array will
address key science issues, like the transition region and coronal waves
or flare precursors, in coordination with other SDO experiments. We
finally describe the real-time solar monitoring products that will be
made available for space-weather forecasting applications.

---------------------------------------------------------
Title: The STate of the ARt Telescope Educational Collaboration
(STARTEC)
Authors: Finley, D. G.; Alonso, J. L.; Altschuler, D.; Cianciolo, F.;
Cuesta, L.; Harrison, R.; Hemenway, M. K.; Michaud, P.; Morison, I.;
Preston, S.; Rijsdjk, C.; Teays, T.; West, R. M.; Wetzel, M.
2002AAS...201.1006F Altcode: 2002BAAS...34.1108F
The State of the Art Telescope Educational Collaboration (STARTEC) was
founded in February 2001 at a meeting in Cape Town, South Africa. The
meeting was attended by educational representatives of some of the
largest and most advanced astronomical facilities in the world. The
attending representatives agreed that astronomy, a basic science with
roots in every human culture, possesses an exceptional potential
to attract public interest and elevate science literacy around
the world. In addition, they agreed that large, state-of-the-art
astronomical facilities, as public icons of science and technology,
have a responsibility to assume a leading role in astronomy education
and public outreach. Accordingly, STARTEC was formed to establish a
forum for exchanging resources and expertise in education and public
outreach. Goals of the collaboration include: inspiring the general
public to appreciate and support astronomy; inspiring and preparing
future generations of scientists, engineers and technicians; using
the collective visibility of STARTEC institutions to improve science
literacy through the news media and to improve public awareness of the
threats of light pollution, radio interference and space debris to the
world's astronomical environment; leveraging resources and fostering
collaborations among STARTEC members for educational programs; and
improving members' education and public outreach efforts as well
as encouraging other institutions and other scientific disciplines
to collaborate on educational and outreach programs. The current
members of STARTEC are: Arecibo Observatory, the European Southern
Observatory, Gemini Observatory, the Hubble Space Telescope, the
Instituto de Astrofisica de Canarias and Gran Telescopio Canarias,
Jodrell Bank Observatory/PPARC, McDonald Observatory and the
Hobby-Eberly Telescope, the National Radio Astronomy Observatory,
and the South African Astronomical Observatory/Southern Africa
Large Telescope. Subsequent meetings of STARTEC were held at Arecibo
Observatory in 2001 and at McDonald Observatory in 2002, and plans for
cooperative educational efforts are underway. A STARTEC Web site will
serve as a resource for those engaged in astronomical education and
public outreach efforts. This work was supported by NSF Grant 0084618,
"U.S.-South Africa Workshop: Educational Outreach for Observatories
with State-of-the-Art Telescopes, Cape Town, South Africa, Feb. 2-6,
2001." The National Radio Astronomy Observatory is a facility of the
National Science Foundation, operated under cooperative agreement by
Associated Universities, Inc.

---------------------------------------------------------
Title: Coronal Dimming and the Relationship to Coronal Mass Ejections
Authors: Harrison, R. A.; Howard, T. A.; Simnett, G. M.
2002AGUFMSH52A0485H Altcode:
Around the onset time of coronal mass ejections (CME) it is frequently
observed by the LASCO coronagraphs on SOHO that the mass content of
the low corona is depleted. Spectral observations by the coronal
diagnostic spectrometer (CDS) (also on SOHO) are able to confirm
that this “coronal dimming” is in fact due to mass loss rather than
temperature variations. An important question is whether the observed
mass loss represents the actual mass ejected in the CME, or the mass
required to replenish the coronal mass ejected in the CME. Clearly the
timing of the mass loss observed in the low corona to the timing of the
CME is critical in answering this question. We present recent results
of dedicated campaigns using CDS to investigate this phenomenon; and
we also examine the LASCO-C1 data from 1996--1998 (June) for additional
information on the relationship between CME onsets and coronal dimming.

---------------------------------------------------------
Title: The International Heliophysical Year (IHY)
Authors: Davila, J. M.; Harrison, R.; Poland, A.; Thompson, B.;
Gopalswamy, N.
2002AGUFMSH21A0518D Altcode:
In 1957 a program of international research, inspired by the
International Polar Years of 1882-83 and 1932-33, was organized as
the International Geophysical Year (IGY) to study global phenomena of
the Earth and geospace. The IGY involved about 60,000 scientists from
66 nations, working at thousands of stations, from pole to pole to
obtain simultaneous, global observations on Earth and in space. There
had never been anything like it before. The fiftieth anniversary of
the International Geophysical Year will occur in 2007. We propose to
organize an international program of scientific collaboration for this
time period called the International Heliophysical Year (IHY). Like
it predecessors, the IHY will focus on fundamental global questions
of Earth science.

---------------------------------------------------------
Title: Off-limb EUV line profiles and the search for wave activity
in the low corona
Authors: Harrison, R. A.; Hood, A. W.; Pike, C. D.
2002A&A...392..319H Altcode:
Two extreme-ultraviolet (EUV) observations are used to examine the
off-limb characteristics of emission line widths of the million K Mg X
625 Å line. To obtain sufficient statistical accuracy, the observations
were made over long periods of time and a pixel summing technique is
used. The observations are made above the western limb, for quiet
corona. The most significant result is the discovery of emission
line narrowing as a function of altitude and intensity at altitudes
above 50 000 km. The results are compared to past observations, which
suggest that emission line broadening, at lower altitudes, is due
to the outward propagation of undamped Alfvén waves, in open field
regions with decreasing density with altitude. The narrowing at higher
altitudes, determined by the current study is interpreted as further
evidence for coronal wave activity, but in closed field regions, and
most likely the first evidence of the dissipation of Alfvén waves in
the corona. An additional result of this work is the identification
of a significant line broadening across a narrow region on the limb,
which may be due to flows in low-lying loop systems.

---------------------------------------------------------
Title: Transition-Region Blinkers - II. Active-Region Properties
Authors: Parnell, C. E.; Bewsher, D.; Harrison, R. A.
2002SoPh..206..249P Altcode:
The distribution and general properties of events identified in an
active region that have the same characteristics as quiet-Sun blinkers
are discussed and named `active-region blinkers'. The events are
identified using an automated scheme `BLinker Identification Program'
(BLIP) which was designed for and tested on quiet-Sun blinkers. Like
quiet-Sun blinkers, the active-region events are most easily identified
in the 629 Å emission line from O v although evidence for them is
also found in other extreme UV lines emitted from He i, O iii and O
iv. Unlike quiet-Sun blinkers, however, they may also have coronal
signatures in the lines Mg ix and Mg x. Their properties are very
similar to those of quiet-Sun blinkers with mean lifetimes of 16-19
min, mean areas of 2.4-4.3×107 km2 and mean
intensity enhancements factors of 1.8-3.3. Their global frequency of
7-28 s−1 is about 42%-700% higher than that for quiet-Sun
blinkers. The blinkers discussed here are found above both active-region
(plage) magnetic fields, as well as above the umbra and penumbra of
a sunspot.

---------------------------------------------------------
Title: Transition Region Blinkers I. Quiet-Sun Properties
Authors: Bewsher, D.; Parnell, C. E.; Harrison, R. A.
2002SoPh..206...21B Altcode:
An automated method of identifying transition region blinkers is
presented. The distribution and general properties of blinkers
identified in the quiet Sun are discussed. The blinkers are seen
most clearly in the O v (629 Å) transition region emission line,
but they also have strong signatures in O iv (554 Å), and the
chromospheric line, He i (584 Å). The strongest O v blinkers can
also be identified in O iii (599 Å). No significant signatures are
found for blinkers in the Mg ix (368 Å) and Mg x (624 Å) coronal
lines. A few hundred O v blinkers are analyzed. Their global frequency
is between 1 and 20 s−1 depending on how significant the
peaks of the blinkers are. They have a typical area of 3×107
km2, a typical lifetime of 16 min and a typical intensity
enhancement factor of 1.8. We find the ratios of the oxygen lines
to be flat confirming the result that blinkers are not temperature
events, but are density enhancements or due to increases in filling
factor. Blinkers are found to occur preferentially over regions of
enhanced chromospheric or transition region emission such as network
boundaries, however, it is not so clear that they appear below the
brightest coronal regions. A rough analysis of the magnetic fragments
show that blinkers preferentially occur above regions where there are
large or strong magnetic fragments with 75% occurring in regions where
one polarity dominates.

---------------------------------------------------------
Title: International Solar Cycle Studies [ISCS] Working Group 2:
solar magnetic field variability - from the lower atmosphere through
the inner corona
Authors: Harrison, Richard A.; Michels, Donald
2002AdSpR..29.1583H Altcode:
This report is a summary of activities and plans relating to the
International Solar Cycle Studies (ISCS) Working Group 2, which
is concerned with solar magnetic field variability, from the lower
atmosphere through the inner corona. Whilst the Working Group carries
a rather general title, the activities are focusing on several well
defined topics - in particular the onset of coronal mass ejection
events. Recognising the large number of scientific meetings worldwide,
the working style of this group is aimed at improving communication,
information exchange and collaboration making use of existing meetings
and with a minimum of red tape. The core of the activity is through
the use of the World Wide Web and e-mail. In this way, this Working
Group does not introduce extra effort, but provides a better focus
for on-going projects.

---------------------------------------------------------
Title: A discussion on the practical aspects of running the IHY
project
Authors: Harrison, R.
2002cosp...34E1040H Altcode: 2002cosp.meetE1040H
The International Heliophysical Year (IHY) is not simply a celebration
of the 50th anniversary of the International Geophysical Year (IGY). It
is designed to have a major scientific impact through the efficient
co-ordination of many observations from space-based and ground-based
instrumentation. The best approach may be through the development of
Joint Observing Programmes (JOPs) in a style adopted so successfully
for the co-ordination of the solar missions SOHO, Yohkoh and TRACE, but
on a grander scale. The full IHY programme could consist of numerous
JOPs each co-ordinated by an individual in pursuit of a particular
scientific objective, using a set of well-defined instruments. The
overall management of the programme would be performed by an
international committee, ensuring efficient communication, exchange
of information and overseeing the JOP activities. This 'grass roots'
approach ensures that individual scientists can participate and gain
from the IHY experience. The aim here is to discuss the approach and to
give the community a chance to shape the IHY effort in the way it sees
fit. This will be the first open discussion on IHY and will be used
to lay the foundation for the practical application of the IHY concept.

---------------------------------------------------------
Title: SOHO observations relating to the association between flares
and CMEs
Authors: Harrison, R.
2002cosp...34E1034H Altcode: 2002cosp.meetE1034H
Campaigns to investigate the onset of solar coronal mass ejection (CME)
activity have been run using SOHO instrumentation since 1996. These
have included coronagraph and extreme-ultraviolet (EUV) disc imaging,
along with magnetic mapping of the photosphere, in concert with
off-limb and near-limb EUV and UV spectroscopic observations. It has
included coordination with other spacecraft, providing X-ray and high
resolution EUV/UV imaging, as well as ground-based systems. This effort
has provided many rewards, with spectacular observations of countless
eruptions. It has included the discovery of unexpected phenomena such
as coronal waves, the dimming of EUV coronal emission lines under
CMEs and the observation of sigmoidal shaped structures associated
with CMEs. Much has been learned about the CME onset process yet the
most basic questions still remain. We have an unprecedented view of
CME eruptions, yet we are still unable to identify clearly the onset
process and we do not fully understand the relationship between flares
and CMEs. With all of the campaigns producing excellent multi-wavelength
observations of CMEs, how far have we progressed in the understanding
of the CME onset and, in particular the relationship to the flare? Can
we identify lines of research, using the SOHO data, which will provide
the answers we seek. It is the author's opinion that we actually have
the observational tools required to allow an understanding of the
onset process and the CME/flare links, and the emphasis should be on
understanding the limitations of our instrumentation and on removing
any preconceived ideas from our interpretations.

---------------------------------------------------------
Title: The International Heliophysical Year Concept
Authors: Davila, J.; Harrison, R.; Poland, A.; St-Cyr, O.; Thompson, B.
2002cosp...34E.529D Altcode: 2002cosp.meetE.529D
In 1957 a program of international research, inspired by the
International Polar Years of 1882-83 and 1932-33, was organized as
the International Geophysical Year (IGY) to study global phenomena of
the Earth and geospace. The IGY involved about 60,000 scientists from
66 nations, working at thousands of stations, from pole to pole to
obtain simultaneous, global observations on Earth and in space. There
had never been anything like it before. The fiftieth anniversary of
the International Geophysical Year will occur in 2007. We propose to
organize an international program of scientific collaboration for this
time period called the International Heliophysical Year (IHY). Like
its predecessors, the IHY will focus on fundamental global questions
of Earth science.

---------------------------------------------------------
Title: Solar orbiter, a high-resolution mission to the sun and
inner heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Langevin, Y.; Marsden, R.; Pace, O.; Schwenn,
R.; Vial, J. -C.
2002AdSpR..29.2027M Altcode:
The scientific rationale of the Solar Orbiter is to provide, at high
spatial (35 km pixel size) and temporal resolution, observations of the
solar atmosphere and unexplored inner heliosphere. Novel observations
will be made in the almost heliosynchronous segments of the orbits at
heliocentric distances near 45 R⊙ and out of the ecliptic plane at
the highest heliographic latitudes of 30° - 38°. The Solar Orbiter
will achieve its wide-ranging aims with a suite of sophisticated
instruments through an innovative design of the orbit. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. Over extended periods
the Solar Orbiter will deliver the first images of the polar regions
and the side of the Sun invisible from the Earth.

---------------------------------------------------------
Title: Solar Orbiter: a high-resolution mission to the sun and
inner heliosphere
Authors: Fleck, Bernhard; Marsch, E.; Antonucci, Ester; Bochsler,
Peter A.; Bougeret, J. L.; Harrison, R.; Marsden, R. P.; Coradini,
M.; Pace, Oscar; Schwenn, Rainer; Vial, Jean-Claude
2001SPIE.4498....1F Altcode:
The key mission objective of the Solar Orbiter is to study the Sun
from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar
rotation in order to examine the solar surface and the space above from
a co-rotating vantage point at high spatial resolution. Solar Orbiter
will also provide images of the Sun's polar regions from heliographic
latitudes as high as 38 degrees. The strawman payload encompasses
two instrument packages: Solar remote-sensing instruments: EUV
full-sun and high resolution imager, high-resolution EUV spectrometer,
high-resolution and full-sun visible light telescope and magnetograph,
EUV and visible-light coronagraphs, radiometers. Heliospheric
instruments: solar wind analyzer, radio and plasma wave analyzer,
magnetometer, energetic particle detectors, interplanetary dust
detector, neutral particle detector, solar neutron detector. To
reach its novel orbit, Solar Orbiter will make use of low-thrust
solar electric propulsion (SEP) interleaved by Earth and Venus gravity
assists. Solar Orbiter was selected by ESA's Science Programme Committee
(SPC) in October 2000 as a Flexi-mission, to be implemented after the
BepiColombo cornerstone mission to Mercury before 2013. This paper
summarizes the science to be addressed with the Solar Orbiter, followed
by brief descriptions of the strawman payload, the mission profile,
and the spacecraft and ground segment designs.

---------------------------------------------------------
Title: EUV Sprays: Jet-like eruptive activity on the solar limb
Authors: Harrison, R. A.; Bryans, P.; Bingham, R.
2001A&A...379..324H Altcode:
Jet-like eruptive events have been detected in the extreme ultraviolet
(EUV) observations from the Solar and Heliospheric Observatory
(SOHO) spacecraft. Some jet-like events are shown and for one event,
that of January 22 2000, we provide a detailed analysis of the EUV
observations. The January 22 observation was part of an on-going
campaign to observe the onset of coronal mass ejections (CMEs) using
extreme ultraviolet spectroscopy. A high-temperature fan-like jet
was first detected in emission lines from plasmas at one million K
and over, and it appears to be the onset of a narrow mass ejection
identified later in coronagraph data. This was followed by a dramatic
jet or finger of cool (&lt;=250 000 K), rotating plasma which extended
vertically, high into the corona. It extended well beyond the field of
view of the instrument and appears to relate to a small ejected cloud
which is detected in subsequent coronagraph data. The spectroscopic
characteristics are used to provide plasma diagnostic information for
these two events, and this combined with images for a wide range of
temperatures allows a thorough investigation of the processes leading
to such eruptions. A simple accreting magnetic field model is used to
descibe the basic features of the jet activity.

---------------------------------------------------------
Title: Solar Orbiter EUV/UV wavelength selection and instrumentation -
report of Payload Splinter Group 4
Authors: Harrison, R. A.; Vial, J. -C.
2001ESASP.493..151H Altcode: 2001sefs.work..151H
We present here a summary of the discussions concerning the extreme
ultraviolet (EUV) and ultraviolet (UV) wavelength selection and
instrumentation for Solar Orbiter, held at the Tenerife meeting. These
issues were assigned to Payload Splinter Group 4 and to the Wavelength
Selection Working Group. Concerning the wavelength selection, a number
of critical wavelength ranges were highlighted and discussed. Great
emphasis was placed on good atmospheric coverage, from the chromosphere
to the hottest coronal lines. A number of wavelength ranges were
presented but the wide temperature range demands the inclusion of
wavelengths longer than 912 Å as well as prime coronal lines in
much shorter wavelength ranges, such as 170-250 Å. Regarding the
instrumentation, the group agreed that Solar Orbiter should carry both
imaging and spectroscopic capability in the EUV/UV and the two strawman
instruments were presented and discussed. A number of alternatives
were considered as were developments in technology, which could be of
use for these instruments.

---------------------------------------------------------
Title: Solar Orbiter, a high-resolution mission to the Sun and
inner heliosphere
Authors: Marsch, E.; Harrison, R.; Pace, O.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Fleck, B.; Langevin, Y.; Marsden, R.; Schwenn,
R.; Vial, J. -C.
2001ESASP.493D..11M Altcode: 2001sefs.workD..11M
Solar Orbiter will provide, at very high spatial (35 km pixel size)
and temporal resolution, novel observations of the solar atmosphere
and unexplored inner heliosphere. It will achieve its wide-ranging
scientific aims with a suite of sophisticated instruments through an
innovative orbit design. Unprecedented observations will be made in
the heliosynchronous segments of the orbits at heliocentric distances
near 45 Rsolar and out of the ecliptic plane at the highest
heliographic latitudes of 30° - 38°. The first near-Sun interplanetary
measurements together with concurrent remote-sensing observations of
the Sun and its corona will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in the source regions on the Sun. Solar Orbiter will deliver
the first images of the polar regions and the far side of the Sun
invisible from the Earth.

---------------------------------------------------------
Title: Joint EUV/Radio Observations of a Solar Filament
Authors: Chiuderi Drago, F.; Alissandrakis, C. E.; Bastian, T.;
Bocchialini, K.; Harrison, R. A.
2001SoPh..199..115C Altcode:
In this paper we compare simultaneous extreme ultraviolet (EUV) line
intensity and microwave observations of a filament on the disk. The
EUV line intensities were observed by the CDS and SUMER instruments on
board SOHO and the radio data by the Very Large Array and the Nobeyama
radioheliograph. The main results of this study are the following: (1)
The Lyman continuum absorption is responsible for the lower intensity
observed above the filament in the EUV lines formed in the transition
region (TR) at short wavelengths. In the TR lines at long wavelengths
the filament is not visible. This indicates that the proper emission of
the TR at the filament top is negligible. (2) The lower intensity of
coronal lines and at radio wave lengths is due to the lack of coronal
emission: the radio data supply the height of the prominence, while EUV
coronal lines supply the missing hot matter emission measure (EM). (3)
Our observations support a prominence model of cool threads embedded
in the hot coronal plasma, with a sheath-like TR around them. From the
missing EM we deduce the TR thickness and from the neutral hydrogen
column density, derived from the Lyman continuum and He i absorption,
we estimate the hydrogen density in the cool threads.

---------------------------------------------------------
Title: Transition Region Blinkers
Authors: Parnell, C. E.; Bewsher, D.; Harrison, R. A.; Hood, A. W.
2001IAUS..203..359P Altcode:
Blinkers are small bright emission events observed best in the O V
transition region line that occur above the supergranular network. They
were first observed using SoHO/CDS data and were identified manually
by Harrison (1997). They are believed to be density enhancements,
but how they are created and what their properties are is not well
known. We have developed the first program to automatically identify
blinkers and their characteristics. The evolution of the magnetic
field observed by SoHO/MDI below these blinkers has then be analysed to
determine what magnetic field configuration is required for a blinker
to occur. Also, the coronal emission above has been investigated using
SoHO/CDS and TRACE data to determine the relation between blinkers,
x-ray bright points and nanoflares. All three of these events are
known to occur at the network, but as yet the relation between them
is not understood. Putting together the results from these multi-wave
length studies we have been able to determine a model for how blinkers
occur and what their effect is on the transition region around and
the corona above.

---------------------------------------------------------
Title: Solar Orbiter, a High-Resolution Mission to the Sun and
Inner Heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Marsden, R.; Schwenn, R.; Vial, J. -C.
2001IAUS..203..565M Altcode:
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rodot and
out-of-ecliptic at the highest heliographic latitudes of 38 degrees. The
SO will achieve its many and varied aims with a suite of small and
innovative instruments through a clever choice of orbits. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind and
energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. The SO will, during
the high-latitude orbital passes, provide the first observations of
the Sun's polar regions as seen from outside the ecliptic and also
measure the magnetic field at the poles.

---------------------------------------------------------
Title: On the Detection of Solar Coronal High-Velocity Fields Using
the XUV Doppler Telescope
Authors: Kobayashi, Ken; Hara, Hirohisa; Kano, Ryohei; Nagata,
Shin'ichi; Sakao, Taro; Shimizu, Toshifumi; Tsuneta, Saku; Yoshida,
Tsuyoshi; Harrison, Richard
2000PASJ...52.1165K Altcode:
The XUV Doppler Telescope (XDT) is a sounding rocket experiment
designed to detect flows in the solar corona using filter ratios. The
XDT, successfully launched on 1998 January 31, is a normal incidence
telescope composed of narrow-bandpass multilayer mirrors and capable
of obtaining images 2 Å\ above and 2 Å\ below the Fe XIV 211 Å\
(T = 1.7 MK) emission line. It has the potential to make a velocity map
of the entire solar disk with just a few minutes of observation. The
image ratio maps show features that translate to Doppler shifts of
200 km s-1 or more, including several `redshift' features
located near footpoints of coronal loops. However, no corresponding
velocity features were seen by the Solar and Heliospheric Observatory
(SOHO) Coronal Diagnostic Spectrometer (CDS) in the Mg IX 368 Å (T =
1 MK) line, suggesting that the features are not caused by Doppler
shift. Instead, the features seem to be related to contamination
of lower temperature (T &lt; 1 MK) emission lines and the nearby
density-sensitive Fe XIII lines. We conclude that while no flows were
positively identified by the XDT, this observing technique is capable
of detecting flows of 1000 km s^{-1} independently, and 200 km s^{-1}$
when combined with simultaneous plasma diagnostic observation.

---------------------------------------------------------
Title: Solar Coronal Mass Ejection: Observations
Authors: Harrison, R.
2000eaa..bookE2029H Altcode:
The Sun ejects matter into space. There appear to be two basic ejection
classes, the first leading to the SOLAR WIND outflow, and the second
leading to the occasional ejection of huge, discrete clouds known as
coronal mass ejections (CMEs). First identified in the early 1970s,
a typical CME can carry 1 000 000 000 t of plasma into space as part
of the Sun's atmosphere erupts. The CME source regio...

---------------------------------------------------------
Title: Long-duration cosmic ray modulation from a Sun-Earth L1 orbit
Authors: Pike, C. D.; Harrison, R. A.
2000A&A...362L..21P Altcode:
We analyse cosmic ray hits impacting the detector system of the Coronal
Diagnostic Spectrometer aboard the Solar and Heliospheric Observatory
spacecraft. These observations allow us to study the modulation of
cosmic rays over a 4 year period (1996-2000) running from solar minimum
to maximum, from a Sun-Earth L1 Lagrangian orbit. The modulation,
at the 45-50% level is consistent with cosmic rays of energy 1 GeV.

---------------------------------------------------------
Title: A spectroscopic study of coronal dimming associated with a
coronal mass ejection
Authors: Harrison, R. A.; Lyons, M.
2000A&A...358.1097H Altcode:
Extreme ultraviolet spectroscopic observations of one coronal
mass ejection event are used to examine the onset phase of the
eruption. We find significant dimming of million K plasmas in the
low corona under the ascending CME, the activation of an adjacent
prominence and 2 million K `hot spots' which may be associated with
the CME footpoints. In particular, we show that the dimming is due
to a density decrease from million K plasma loss. We compare the mass
loss with the CME mass. The observations suggest that the interaction
of adjacent coronal loops plays an important role in CME activity and
may allow us to pinpoint the source of the CME material.

---------------------------------------------------------
Title: A study of opacity in SOHO-SUMER and SOHO-CDS spectral
observations. I. Opacity deduction at the limb
Authors: Brooks, D. H.; Fischbacher, G. A.; Fludra, A.; Harrison,
R. A.; Innes, D. E.; Landi, E.; Landini, M.; Lang, J.; Lanzafame,
A. C.; Loch, S. D.; McWhirter, R. W. P.; Summers, H. P.
2000A&A...357..697B Altcode:
A study is presented of the optical thickness of spectral lines of
carbon, nitrogen and oxygen ions in the quiet sun. The observations
consist of cross limb scans by the SUMER and CDS spectrometers on
the SOHO spacecraft. A maximum likelihood spectral line fitting code
has been adapted to analyse the multiplet profiles and to provide an
assessment of errors in the count rates, especially of close lying
components. Branching multiplet component ratios are presented as a
function of position across the limb and contrasted with theoretical
ratios in the optically thin case. The emergent fluxes are analysed
in an escape probability model to deduce the optical thicknesses in
the various spectral lines. Different specifications of the escape
probability are examined. These are used to compare the observations
with a geometric model of the emitting layer thickness across the limb
and the thinning of the emitting layer above the limb. Classification
of the deviations of quiet sun spectral line intensities from the
optically thin case is given to assist in the critical selection of
lines for differential emission measure analysis. This is linked to
a general purpose code for the calculation of the influence of the
line radiation fields on the local excited state population structure
of the selected ions so that the fluxes in any spectral lines can be
predicted. The Atomic Data and Analysis Structure (ADAS) was used for
the atomic calculations and data of the paper.

---------------------------------------------------------
Title: Solar Orbiter --- A High Resolution Mission to the Sun and
Inner Heliosphere
Authors: Fleck, B.; Marsch, E.; Schwenn, R.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Harrison, R. A.; Marsden, R.; Vial, J. -C.
2000SPD....31.0296F Altcode: 2000BAAS...32..828F
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rsun and
out-of-ecliptic at heliographic latitudes of up to 38o. By
going to 45 Rsun the SO will allow remote sensing of the
solar atmosphere with unprecedented spatial resolution, and the almost
heliosynchronous orbit segments will permit us to disentangle spatial
and temporal variations in the solar wind in close linkage with the
plasma and radiation conditions in the source regions of the Sun. The
strawman payload encompasses two instrument packages: Heliospheric
Instruments --- high-res visible light telescope and magnetograph
(&lt;40 km), high-res X-ray/EUV imager (&lt;30 km), high-res EUV
spectrometer (&lt;100 km), EUV and visible-light coronagraphs, solar
neutron and γ -ray detectors, radiometers. Heliospheric Instruments
--- solar wind analyzer, magnetometer, energetic particle detectors, IP
dust detector, plasma wave analyser, radio experiment, neutral particle
detector. Using solar electric propulsion (SEP) in conjunction with
multiple planet swing-by manoeuvres, it will take SO two years to reach
a perihelion of 45 Rsun at an orbital period of 149 days,
with an inclination ranging from 6.7o to 23.4o
w.r.t. the ecliptic. During an extended mission phase of about 2
years the inclination will increase to 31.7o, leading to
a maximum heliographic latitude of 38.3o. The SO was one
of the about 40 responses to the Call for Proposals for the next two
"flexi-missions" (F2 and F3) within ESA's Scientific Programme. At
its meeting on 1 March 2000, ESA's Space Science Advisory Committee
recommended the Solar Orbiter among 5 other proposals for an assessment
study. Launch is expected by the end of the decade.

---------------------------------------------------------
Title: EUV brightness variations in the quiet Sun
Authors: Brković, A.; Rüedi, I.; Solanki, S. K.; Fludra, A.;
Harrison, R. A.; Huber, M. C. E.; Stenflo, J. O.; Stucki, K.
2000A&A...353.1083B Altcode:
The Coronal Diagnostic Spectrometer (CDS) onboard the SOHO satellite has
been used to obtain movies of quiet Sun regions at disc centre. These
movies were used to study brightness variations of solar features at
three different temperatures sampled simultaneously in the chromospheric
He I 584.3 Ä (2 * 104 K), the transition region O V 629.7
Ä (2.5 * 105 K) and coronal Mg IX 368.1 Ä (106
K) lines. In all parts of the quiet Sun, from darkest intranetwork to
brightest network, we find significant variability in the He I and O
V line, while the variability in the Mg IX line is more marginal. The
relative variability, defined by rms of intensity normalised to the
local intensity, is independent of brightness and strongest in the
transition region line. Thus the relative variability is the same
in the network and the intranetwork. More than half of the points
on the solar surface show a relative variability, determined over a
period of 4 hours, greater than 15.5% for the O V line, but only 5%
of the points exhibit a variability above 25%. Most of the variability
appears to take place on time-scales between 5 and 80 minutes for the
He I and O V lines. Clear signs of “high variability” events are
found. For these events the variability as a function of time seen
in the different lines shows a good correlation. The correlation is
higher for more variable events. These events coincide with the (time
averaged) brightest points on the solar surface, i.e. they occur in
the network. The spatial positions of the most variable points are
identical in all the lines.

---------------------------------------------------------
Title: Emerging Flux and Coronal Heating: Small-Scale Transient
Events in the Low Solar Atmosphere
Authors: Harrison, R. A.
1999ESASP.448..531H Altcode: 1999mfsp.conf..531H; 1999ESPM....9..531H
No abstract at ADS

---------------------------------------------------------
Title: A study of extreme ultraviolet blinker activity
Authors: Harrison, R. A.; Lang, J.; Brooks, D. H.; Innes, D. E.
1999A&A...351.1115H Altcode:
In a previous paper (Harrison, 1997a), we reported on the existence
of extreme ultraviolet (EUV) flashes, known as blinkers, which were
identified in the quiet Sun network using the CDS instrument on board
the Solar and Heliospheric Observatory. Since then a number of dedicated
observations have been made and we report here on an analysis of 97
blinker events. We identify blinker spectral, temporal and spatial
characteristics, their distribution, frequency and general properties,
across a broad range of temperatures, from 20,000 K to 1,200,000 K. The
most significant brightenings were found in the transition region
temperature lines of O III, O IV and O V, with modest or no detectable
increases at higher or lower temperatures. A typical blinker event
has a duration of order 1000 s, though the detection of short-duration
blinkers may well be limited by the observation methods. However, a long
tail of longer-duration blinkers puts the average blinker duration at
almost 2400 s. Comparisons to plasma cooling times establish firmly that
there is a continuous energy input throughout the blinker event. The
projected blinker onset rate for the entire solar surface is 1.24
s-1 i.e. 3,000 blinker events may be in progress at any
point in time. An examination of the line ratios shows a remarkable
feature. Ratios of lines from O III, O IV and O V show no significant
change throughout the blinker event and this indicates that the
blinkers are predominantly caused by inceases in density or filling
factor. The intensity signatures of the blinkers are modelled using a
basic time dependent code and this confirms that the lack of a change
in the oxygen line ratios is consistent with a density or filling factor
increase in a plasma cooling from a temperature above 5 x 105
K. We estimate the thermal energy content of an average blinker at 2 x
1025 erg and consider this figure and the total blinker rate
in the light of the energy required for coronal heating. The results
are used to compare blinker activity to reported micro-flare, network
flare and explosive event activity, and to discuss their potential
role in coronal heating and solar wind acceleration processes. Finally,
a blinker model is presented which consists of the merging of a closed
magnetic system with pre-existing open field lines in the network.

---------------------------------------------------------
Title: Wavelet Analysis Of Active Region Oscillations
Authors: Ireland, J.; Walsh, R. W.; Priest, E. R.; Harrison, R. A.
1999ESASP.446..363I Altcode: 1999soho....8..363I
The wavelet transform is applied to the analysis of active region
oscillations. The localised (in time) nature of the wavelet transform
allows us to study both the duration of any statistically significant
oscillations as well as their period. Time series arising from SOHO
(Solar and Heliospheric Observatory) CDS-NIS (Coronal Diagnostic
Spectrometer Normal Incidence Spectrometer) active region observations
on 14th-15th November 1996 are used to demonstrate the applicability of
wavelet methods. High cadence (approximately 14 seconds) observations
were made in He I 584.33 Angstroms (log T = 4.3, T being the electron
temperature), O V 629.73 Angstroms(log T = 5.3), Mg IX 368.06 Angstroms
(log T = 6.0), Fe XVI 360.76 Angstroms (log T = 6.4) provide detailed
intensity information on the active region over a wide range of
temperatures. The distribution of statistically significant periods
found varies from line to line, as does their duration.

---------------------------------------------------------
Title: The quiet Sun extreme ultraviolet spectrum observed in normal
incidence by the SOHO coronal diagnostic spectrometer
Authors: Brooks, D. H.; Fischbacher, G. A.; Fludra, A.; Harrison,
R. A.; Innes, D. E.; Landi, E.; Landini, M.; Lang, J.; Lanzafame,
A. C.; Loch, S. D.; McWhirter, R. W. P.; Summers, H. P.; Thompson,
W. T.
1999A&A...347..277B Altcode:
The extreme ultraviolet quiet Sun spectrum, observed at normal incidence
by the Coronal Diagnostic Spectrometer on the SOHO spacecraft, is
presented. The spectrum covers the wavelength ranges 308-381 Ä and
513-633 Ä and is based on data recorded at various positions on the
solar disk between October 1996 and February 1997. Datasets at twelve
of these `positions' were judged to be free from active regions and
data faults and selected for detailed study. A constrained maximum
likelihood spectral line fitting code was used to analyse the spectral
features. In all over 200 spectrum lines have been measured and about
50% identified. The line identification process consisted of a number
of steps. Firstly assignment of well known lines was made and used to
obtain the primary wavelength calibration. Variations of wavelengths
with position were used to assess the precision of calibration
achievable. Then, an analysis method first used in studies with the
CHASE experiment, was applied to the new observations. The behaviour
of the intensities of lines from like ions over the twelve positions,
called `position patterns', were used to distinguish probable emitters
of weaker lines and extend the identifications. Spectral line widths
and expected multiplet intensities were examined to identify lines and
probable blends. The product of the study is a table which includes all
clearly observed emission lines, their measured wavelengths, widths
and count rates. Adopted laboratory wavelengths, ion and transition
designations are also presented for identified lines. The table has an
estimate of the uncertainty of the count rates based on a statistical
analysis of the variability of each line. A marked spectrum is also
provided.

---------------------------------------------------------
Title: A wavelet analysis of active region oscillations
Authors: Ireland, J.; Walsh, R. W.; Harrison, R. A.; Priest, E. R.
1999A&A...347..355I Altcode:
The wavelet transform is applied to the analysis of active region
oscillations. The localised (in time) nature of the wavelet transform
allows us to study both the duration of any statistically significant
oscillations as well as their period. Time series arising from SOHO
(Solar and Heliospheric Observatory) CDS-NIS (Coronal Diagnostic
Spectrometer Normal Incidence Spectrometer) active region observations
on 14th-15th November 1996 are used to demonstrate the applicability of
wavelet methods. High cadence (approximately 14 seconds) observations
were made in {He I} 584.33 Ä (log Te=4.3), {O V} 629.73 Ä
(log Te=5.3), {Mg IX} 368.06 Ä (log Te=6.0),
{Fe XVI} 360.76 Ä (log Te=6.4) provide detailed intensity
information on the active region over a wide range of temperatures. The
distribution of statistically significant periods found varies from
line to line, as does their duration.

---------------------------------------------------------
Title: Multi-wavelength observations of the onset phase of a coronal
mass ejection
Authors: Innes, D. E.; Inhester, B.; Srivastava, N.; Brekke, P.;
Harrison, R. A.; Matthews, S. A.; Noëns, J. C.; Schmieder, B.;
Thompson, B. J.
1999SoPh..186..337I Altcode:
The structure and dynamics of the initial phases of a coronal mass
ejection (CME) seen in soft X-ray, extreme ultraviolet and optical
emission are described. The event occurred on the SW limb of the Sun in
active region AR 8026 on 9 April 1997. Just prior to the CME there was
a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging
Telescope (EIT) reveal the emergence of a candle-flame shaped extreme
ultraviolet (EUV) cavity at the time of the flare. Yohkoh images,
taken about 15 min later, show that this cavity is filled with hot
X-ray emitting gas. It is most likely that this is the site of the
flare. Almost simultaneous to the flare, an Hα surge or small filament
eruption occurs about 50 arc sec northwards along the limb from the EUV
cavity. At both the site of the core of the hot, EUV cavity and the
filament ejection are X-ray jets. These jets seem to be connected by
hot loops near their bases. Both jets disappear within a few minutes
of one another.

---------------------------------------------------------
Title: Future Directions in Solar EUV/UV Spectroscopy
Authors: Harrison, R. A.
1999AAS...194.6505H Altcode: 1999BAAS...31..927H
Studies of the extreme ultraviolet (EUV) and ultraviolet (UV) spectrum
of the Sun provide a unique and powerful means to investigate plasma
properties, such as density, temperature, abundance and flow speeds
throughout the low solar atmosphere, from chromsphere to corona. In
particular, with the SOHO mission, recent EUV/UV spectroscopic
studies have paved the way for significant advances in numerous
areas of solar physics research, such as active region structure
and evolution, quiet Sun transient processes, mass ejection onset,
and so on... and the wealth of data will guarantee that we will be
reaping the rewards for some time to come. However, spectroscopy
demands relatively high mass, high telemetry instrumentation, and
the products are not readily understood by the non-specialist. Thus,
with the new breed of lighter missions and a greater need to enhance
public awareness, what is the future for solar EUV/UV spectroscopy? The
NASA STEREO mission due for launch in 2004 is not expected to carry
a spectrometer. The Japanese Solar-B mission will be carrying an
EUV spectrometer. The need for such instruments for the possible
ESA Solar Orbiter, the NASA Solar Probe and other future missions
must be addressed. SOHO comes from mid-1980's technology so we can
readily enhance our current performances with the use of multilayers,
improved CCD technology, multi-line-of-sight observations etc... So, as
well as advertising the success of solar spectroscopy in recent years,
an outline of possible directions willl be given which will underline
the strong case for including such experiments in future solar missions.

---------------------------------------------------------
Title: A new view of our star: observations from SOHO.
Authors: Harrison, R. A.
1999PhyEd..34..112H Altcode:
The ESA/NASA Solar and Heliospheric Observatory (SOHO) spacecraft
is revolutionizing our view of our star, the Sun. Its 12 instrument
payload allows one to delve into the body of the Sun itself, to observe
the mysterious solar atmosphere and to investigate the influence of the
Sun on interplanetary space. The mission has come up with a string of
new discoveries and has shown that in many ways the Sun is not quite
as we expected it to be. The authors glance at our closest star and
review the results, in particular, from a British-led instrument.

---------------------------------------------------------
Title: New views of our nearest star.
Authors: Harrison, R.
1999AsNow..13R..52H Altcode: 1999AstNw..13R..52H
"Focus: Basking in the Sun". A large range of instruments on board
SOHO have produced spectacular results.

---------------------------------------------------------
Title: Brightness Variations in the Solar Atmosphere as Seen by SOHO
Authors: Brkovic, A.; Rüedi, I.; Solanki, S. K.; Huber, M. C. E.;
Stenflo, J. O.; Stucki, K.; Harrison, R.; Fludra, A.
1999ASSL..239..231B Altcode: 1999msa..proc..231B
We present preliminary results of a statistical analysis of the
brightness variations of solar features at different levels in
the solar atmosphere. We observed quiet Sun regions at disc centre
using the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and
Heliospheric Observatory (SOHO). We find significant variability at all
time scales in all parts of the quiet Sun, from darkest intranetwork
to brightest network. Such variations are observed simultaneously in
the chromospheric He I 584.33 Angstroms (2 \cdot 10^4 K) line, the
transition region O V 629.74 Angstroms (2.5 \cdot 10^5 K) and coronal
Mg IX 368.06 Angstroms (10^6 K) line. The relative variability is
independent of brightness and most of the variability appears to take
place on time scales longer than 5 minutes for all 3 spectral lines. No
significant differences are observed between the different data sets.

---------------------------------------------------------
Title: Our New View of the Sun - Results from the Solar and
Heliospheric Observatory
Authors: Harrison, R. A.
1999JBIS...52..434H Altcode:
Over the last three years the Solar and Heliospheric Observatory (SOHO)
has been revolutionising our view of our star, the Sun. A review of
some of the new results from SOHO is given here, with a particular
emphasis on the solar atmosphere - the source of the so-called
`space weather'. The results include a rather unexpected feature of
the nature of so-called active regions on the Sun, the discovery of
new solar phenomena, such as solar tornadoes and jets, a new view of
the nature of the quiet Sun, and a new insight into the way the Sun
ejects vast clouds known as coronal mass ejections into space.

---------------------------------------------------------
Title: SOHO Observations of the Connection Between Line Profile
Parameters in Active and Quiet Regions and the Net Red Shift in EUV
Emission Lines
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Wilhelm, K.
1998SoPh..181...23B Altcode:
We present high spatial and spectral resolution observations of
one active and one quiet-Sun region, obtained with CDS and SUMER on
SOHO. The connections between the line profile parameters are studied
and a systematic wavelength shift towards the red with increasing peak
line intensity (line broadening) is detected. The large scatter in
the data calls for another approach. We apply conditional probability
analysis to a series of EUV emission lines and find significant
correlations between line profile parameters. For a given interval in
wavelength shift we find that: (1) line profiles with large intensities
(line widths) and red shifts above the average constitute an increasing
fraction of the profiles as the relative wavelength shift increases,
(2) line profiles with large intensities (line widths) and blue
shifts compared to the average, on the other hand, constitute a
decreasing fraction of the profiles as the relative wavelength shift
increases. These results extend the findings of an earlier quiet-Sun
study from one to several emission lines and expand the validity to
include the active region. Interestingly, the active region observations
show correlations between peak line intensity and wavelength shift in
the coronal lines.

---------------------------------------------------------
Title: First Results from the TRACE Mission
Authors: Title, A.; Tarbell, T.; Schrijver, C.; Wolfson, J.; Shine,
R.; Hurlburt, N.; Golub, L.; Deluca, E.; Bookbinder, J.; Handy, B.;
Acton, L.; Harrison, R.; Delaboudinere, J. -P.
1998AAS...192.1507T Altcode: 1998BAAS...30..841T
The TRACE spacecraft was launched on 1 April and all systems are
functioning as designed. The initial outgassing period will conclude
on 20 April and the science program will then begin. TRACE is a UV-EUV
imager with one arc second spatial resolution and is capable of taking
images with a cadence as high as two seconds. We will present images
and image sequences. We hope to present initial comparisons of magnetic
evolution and transition region and coronal brightenings.

---------------------------------------------------------
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
II. Velocities and Line Profiles
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
1998SoPh..179..279B Altcode:
We have studied the dynamics in the sunspot transition region between
the chromosphere and the corona and investigated the extension of
the flow field into the corona. Based on EUV spectra of a medium size
sunspot and its surroundings, NOAA 7981, observed with CDS and SUMER
on SOHO, we derive line-of-sight velocities and study the line profiles
for a series of emission lines.

---------------------------------------------------------
Title: EUV Spectroscopy of the Sunspot Region NOAA 7981 Using SOHO -
I. Line Emission and Time Dependence
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
1998SoPh..179...43B Altcode:
EUV spectra of a medium-size sunspot and its surroundings, NOAA 7981,
were obtained on 2 August 1996 with the Coronal Diagnostic Spectrometer
(CDS) and the Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) on the Solar and Heliospheric Observatory (SOHO). The spectral
lines formed in the transition region and corona show considerable
structure and large deviations from a uniform spatial distribution over
the active region. Enhanced EUV emissions in transition region lines
are concentrated in small regions outside the umbra of the sunspot
throughout most of the observing sequence. Only during a short,
active period do we find an enhanced line emission that reaches into
the umbra. Preliminary values for the umbral intensity are given.

---------------------------------------------------------
Title: Coordinated Observations with SOHO, YOHKOH and VLA
Authors: Aschwanden, Markus J.; Bastian, Tim S.; Nitta, Nariaki;
Newmark, Jeff; Thompson, Barbara J.; Harrison, Richard A.
1998ASPC..155..311A Altcode: 1998sasp.conf..311A
No abstract at ADS

---------------------------------------------------------
Title: 3-Dimensional Models of Active Region Loops
Authors: Aschwanden, M. J.; Neupert, W. M.; Newmark, J.; Thompson,
B. J.; Brosius, J. W.; Holman, G. D.; Harrison, R. A.; Bastian, T. S.;
Nitta, N.; Hudson, H. S.; Zucker, A.
1998ASPC..155..145A Altcode: 1998sasp.conf..145A
No abstract at ADS

---------------------------------------------------------
Title: Three Dimensional EUV Imaging of Sunspot Regions Observed
with SOHO
Authors: Brynildsen, N.; Brekke, P.; Haugan, S. V. H.; Kjeldseth-Moe,
O.; Maltby, P.; Harrison, R. A.; Rimmele, T.; Wilhelm, K.
1998ASPC..155..171B Altcode: 1998sasp.conf..171B
No abstract at ADS

---------------------------------------------------------
Title: EUV and Microwave Observations of a Filament
Authors: Chiuderi-Drago, F.; Bocchialini, K.; Lamartinie, S.;
Vial, J. -C.; Bastian, T.; Alissandrakis, C. E.; Harrison, R.;
Delaboudiniere, J. -P.; Lemaire, P.
1998ASPC..150...55C Altcode: 1998IAUCo.167...55C; 1998npsp.conf...55C
No abstract at ADS

---------------------------------------------------------
Title: Quiescent filament diagnostic.
Authors: Lamartinie, S.; Bocchialini, K.; Vial, J. -C.; Chiuderi-Drago,
F.; Harrison, R.; Alissandrakis, C. E.
1998joso.proc..139L Altcode:
UV observations of a quiescent filament were performed on July 28,
1996 by SUMER and CDS, two spectrometers onboard SOHO.

---------------------------------------------------------
Title: EUV Spectral Variability and Non-Equilibrium Ionisation in the
'Quiet' Sun
Authors: Brooks, D. H.; Summers, H. P.; Harrison, R. A.; Lang, J.;
Lanzafame, A. C.
1998Ap&SS.261...91B Altcode: 1999Ap&SS.261...91B
Recent spectroscopic observations by the Solar and Heliospheric
Observatory (SOHO) have revealed the dynamic nature of even the
'quiet' Sun. Spectral variability data clearly show that dynamics in
the solar upper atmosphere take place on timescales shorter than those
of ionisation relaxation. Accuracy in the interpretation of diagnostic
spectral data can only be maintained through detailed quantitative
modelling of the relevant atomic physics. In particular, dynamical
plasma models of the solar plasma require matching dynamic atomic
models to underpin conclusions drawn from the spectral reduction. The
inclusion of important effects such as finite plasma electron density
and the influence of metastable levels is essential to reduce the
uncertainties associated with equilibrium assumptions.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1998CIBu..142....2H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: European Plans for the Solar/Heliospheric Stereo Mission
Authors: Bothmer, V.; Bougeret, J. -L.; Cargill, P.; Davila, J.;
Delaboudiniere, J. -P.; Harrison, R.; Koutchmy, S.; Liewer, P.;
Maltby, P.; Rust, D.; Schwenn, R.
1998ESASP.417..145B Altcode: 1998cesh.conf..145B
No abstract at ADS

---------------------------------------------------------
Title: The Coronal Diagnostic Spectrometer on SOHO
Authors: Phillips, K. J. H.; Harrison, R. A.
1998ASSL..229..227P Altcode: 1998opaf.conf..227P
No abstract at ADS

---------------------------------------------------------
Title: Scientific Achievements of SOHO: The Solar Atmosphere
Authors: Harrison, R. A.
1998ESASP.417...19H Altcode: 1998cesh.conf...19H
No abstract at ADS

---------------------------------------------------------
Title: Overview of Results from IACG Campaign 3: CME Onsets
Authors: Harrison, R. A.
1997ESASP.415..121H Altcode: 1997cpsh.conf..121H
No abstract at ADS

---------------------------------------------------------
Title: Active Regions Observed in Extreme Ultraviolet Light by the
Coronal Diagnostic Spectrometer on SOHO
Authors: Fludra, A.; Brekke, P.; Harrison, R. A.; Mason, H. E.; Pike,
C. D.; Thompson, W. T.; Young, P. R.
1997SoPh..175..487F Altcode:
We present observations of five active regions made by the Coronal
Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory
(SOHO). CDS observes the Sun in the extreme ultraviolet range 150-780
Å. Examples of active region loops seen in spectral lines emitted at
various temperatures are shown. Several classes of loops are identified:
those that are seen in all temperatures up to 2 x 106 K;
loops seen at 106 K but not reaching 1.6 x 106
K; those at temperatures 2- 4 x 10-5 K and occasionally at
6 x 10-5 K but not reaching 106 K. An increasing
loop size with temperature and the relationship between the cool and
hot structures is discussed. CDS observations reveal the existence of
loops and other unresolved structures in active regions, at temperatures
between 1.5- 4 x 10-5 K, which do not have counterparts in
lines emitted above 8 x 10-5 K. Bright compact sources only
seen in the transition region lines are investigated. These sources can
have lifetimes of up to several days and are located in the vicinity
of sunspots. We study the variability of active region sources on time
scales from 30 sec to several days. We find oscillatory behaviour of Hei
and Ov line intensities in an active region on time scales of 5-10 min.

---------------------------------------------------------
Title: EUV Observations of a Macrospicule: Evidence for Solar Wind
Acceleration?
Authors: Pike, C. D.; Harrison, R. A.
1997SoPh..175..457P Altcode:
We present a unique observation of a macrospicule, recorded in
extreme ultraviolet light on 11 April 1996, using the Coronal
Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric
Observatory (SOHO). The observation was made by chance as part
of a daily, large-area mapping sequence. Although the feature
has some characteristics of the class of events which have become
known as X-ray jets, we argue that the feature observed here is a
macrospicule. This being the case, the observation demonstrates several
new features of macrospicule observation. Emission is detected from
the macrospicule to temperatures of 1 million degrees. In addition,
some footpoint structure is detected at the root of the macrospicule,
and the edges or sides of the macrospicule appear brighter than the
central regions. A velocity analysis shows high speed flows within
the macrospicule. Velocities are seen to increase with altitude until
a plateau is achieved. Coincident with this, there is evidence for
emission line narrowing. The significance of these observations for
solar wind acceleration processes is discussed.

---------------------------------------------------------
Title: EUV Blinkers: The Significance of Variations in the Extreme
Ultraviolet Quiet Sun
Authors: Harrison, Richard A.
1997SoPh..175..467H Altcode:
A search for microflare activity in the extreme ultraviolet (EUV)
quiet Sun using the Coronal Diagnostic Spectrometer (CDS) aboard the
Solar and Heliospheric Observatory (SOHO) spacecraft has not resulted
in the identification of microflare activity, but has resulted in
the identification of a hitherto unknown phenomenon: enhancements
of a factor of 2-3 in the flux of transition region lines at network
junctions. A total of some 6 hours of observation of 5 different target
areas showed this `blinker' activity at each area, with durations
ranging from 1 to 30 min and averaging 13 min, and thermal energy
content of order 10-6 that of a `standard' flare. Assuming
that the observations are of typical quiet Sun, and projecting these
data to predict a distribution of these events over the entire Sun,
the total thermal energy content of these `blinkers' is insignificant
when compared to the energy required to heat the corona. The nature
of these events and their significance are discussed in this paper.

---------------------------------------------------------
Title: High-Velocity Flows in an Active Region Loop System Observed
with the Coronal Diagnostic Spectrometer (Cds) on SOHO
Authors: Brekke, P.; Kjeldseth-Moe, O.; Harrison, R. A.
1997SoPh..175..511B Altcode:
EUV spectra of coronal loops above an active region show clear evidence
of strong dynamical activity. We present an example where the Ov
629 Å line, formed at 240 000 K, is shifted from its reference
position corresponding to line-of-sight velocities greater than 50
km s-1 with the shift extending over a large fraction
of a loop. The observations were made with the Coronal Diagnostic
Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO),
and are from active region NOAA 7981 on the east solar limb on 27
July 1996. An animation has been prepared showing the variation of the
shift or flow velocity along the loop. This animation is to be found
on the enclosed CD-ROM and gives a clear impression of the dynamical
condition present in the loop. The appearance of the loop system in
different lines formed over a range in temperature as well as the
observed dynamics indicates that loops at different temperatures are
not closely co-located. Finally, the results are discussed and related
to mechanisms that may cause line shifts.

---------------------------------------------------------
Title: Solar physics
Authors: Harrison, R. A.
1997Obs...117..279H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: First Observations of Coronal Hole Structure and Evolution
Using Soho-Cds
Authors: Insley, J. E.; Moore, V.; Harrison, R. A.
1997SoPh..175..437I Altcode:
We report on initial observations of coronal holestructure and evolution
by the Coronal Diagnostic Spectrometer (CDS) instrument on board the
Solar and Heliospheric Observatory (SOHO). The data show that there
is coronal activity on time scales of tens of minutes, manifested
as brightenings at chromospheric network cell junctions in extreme
ultraviolet (EUV) wavelengths. There are also significant differences
in structure seen in different wavelengths in coronal holes. Finally,
we show coronal hole EUV spectra and compare them to quiet-Sun spectra,
also taken by CDS.

---------------------------------------------------------
Title: IACG Campaign III: solar events and their manifestation in
interplanetary space and in geospace
Authors: Harrison, R. A.
1997AdSpR..20..623H Altcode:
In Spring 1994 the Inter Agency Consultative Group Campaign III was
set up at a kick-off meeting in Sagamihara, Japan. The basic idea of
Campaign III was to coordinate solar, interplanetary and near-Earth
spacecraft in an effort to link solar and near-Earth observations
relating to activity such as solar mass ejections, and features such as
co-rotating interaction regions. The Campaign was split into two basic
activities, namely (i) studies of the onset of mass ejections, and (ii)
studies of the effects of mass ejections and other solar phenomena at
the Earth. The onset of the Campaign activities was effectively linked
to the launch date of the Solar and Heliospheric Observatory (SOHO)
spacecraft, since most of the planned activities centred on use of
SOHO data linked to other spacecraft. SOHO was launched in December
1995 and the onset of full scientific operations was in March/April
1996. At the time of writing the more complex, time consuming multiple
instrument operations such as the ones required for the IACG campaign
have not been run, though pilot studies between selected instruments
have been performed. Thus, we have preliminary observations relevant to
the Campaign, and we anticipate the full campaign tobe run on several
occasions before the end of the year. In this paper, we report on
the IACG Campaign III concept and on the preliminary results from the
pilot studies.

---------------------------------------------------------
Title: Wave Propagation in the Chromosphere and Transition Region:
Where Have All the Shock Waves Gone?
Authors: Fleck, B.; Steffens, S.; Deubner, F. -L.; Wilhelm, K.;
Harrison, R.; Gurman, J.
1997SPD....28.0120F Altcode: 1997BAAS...29..882F
We present first results from a joint observing program (SOHO JOP 26)
involving SUMER, CDS and EIT on SOHO, coordinated with ground-based
observations at the Vacuum Tower Telescope at Iza{\ n}a, Tenerife. The
objective of this study is to characterize the wave propagation
properties in the solar atmosphere, from the photosphere through the
chromosphere up into the transition region. Particular emphasis is laid
on the 3-min shock waves observed in the Ca II K line. How do they
impact the transition region and what signature do they leave there
and in the lower corona? The ground-based measurements comprise high
resolution time series (both filtergrams and spectrograms) in Ca II K,
Hα and Mgb_2. With SUMER we ran four sequences covering different
temperature regimes: a) O I 1302, O I 1306, Si II 1309, C I 1311,
C II 1334, C II 1335, b) Si I 1256, N V 1242, O V 629 c) He I 584,
C III 1175, O I 1152, d) H I 1025, O VI 1031, O VI 1037. With CDS we
took spectral time series in O VI 554, He I 584, He II 607, Mg IX 368,
and O V 629 as well as wide-slit (90x240”) “movies” in He I 584,
Mg IX 368 and O V 629, while EIT ran sub-field high cadence sequences
in He II 304.

---------------------------------------------------------
Title: Uses of microchannel plate intensified detectors for imaging
applications in the X-ray, EUV and visible wavelength regions
Authors: Read, P. D.; Carter, M. K.; Pike, C. D.; Harrison, R. A.;
Kent, B. J.; Swinyard, B. M.; Patchett, B. E.; Redfern, R. M.; Shearer,
A.; Colhoun, M.
1997NIMPA.392..359R Altcode:
The Rutherford Appleton Laboratory Photon Counting Detector (RALPCD)
has been refined to meet project requirements for a flexible imaging
arrangement with applications at X-ray, EUV and visible wavelengths. The
basic detector design comprises commercially available high gain
microchannel plate intensifiers fibre optically coupled to CID or CCD
cameras, to form a modular detector arrangement with the appropriate
RAL detection and centroiding software. Frames of data from the cameras
are detected and centroided in a Transputer or C40 parallel processor
array where correction algorithms use look up tables to produce pattern
free images at high resolution. Data from completed applications are
used to illustrate the performance and future advances are discussed.

---------------------------------------------------------
Title: The Non-Uniformity in the Sunspot Transition Region
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Rimmele, T.;
Wilhelm, K.
1997ESASP.404..257B Altcode: 1997cswn.conf..257B
No abstract at ADS

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1997CIBu..140....7H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1997CIBu..138....5H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ground and Space-Based Studies of Solar Wind Acceleration
Authors: Breen, A. R.; Coles, W. A.; Grall, R. R.; Harrison, R. A.;
McKenzie, J. F.; Markkanen, J.; Moran, P. J.; Varley, C. A.; Williams,
P. J. S.
1997ESASP.404..223B Altcode: 1997cswn.conf..223B
No abstract at ADS

---------------------------------------------------------
Title: Transition Region Velocities and Line Profiles in the Sunspot
Region 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T. Thompson, W. T.; Wilhelm, K.
1997ESASP.404..251B Altcode: 1997cswn.conf..251B
No abstract at ADS

---------------------------------------------------------
Title: One Year of CDS: Highlights from Observations using the
Coronal Diagnostic Spectrometer on SOHO
Authors: Harrison, R. A.
1997ESASP.404....7H Altcode: 1997soho....5....7H; 1997cswn.conf....7H
No abstract at ADS

---------------------------------------------------------
Title: Active Region Blinkers: Transient Events in the Solar
Atmosphere
Authors: Walsh, R. W.; Ireland, J.; Harrison, R. A.; Priest, E. R.
1997ESASP.404..717W Altcode: 1997cswn.conf..717W
No abstract at ADS

---------------------------------------------------------
Title: Periodicities in Active Regions
Authors: Ireland, J.; Walsh, R. W.; Harrison, R. A.; Priest, E. R.
1997ESASP.404..433I Altcode: 1997cswn.conf..433I
No abstract at ADS

---------------------------------------------------------
Title: CDS Observations of the Connection Between Line Intensity
and Doppler Shift in the Active Region NOAA 7981
Authors: Fredvik, T.; Brynildsen, N.; Maltby, P.; Kjeldseth-Moe, O.;
Brekke, P.; Haugen, S. V. H.; Harrison, R. A.
1997ESASP.404..391F Altcode: 1997cswn.conf..391F
No abstract at ADS

---------------------------------------------------------
Title: Flows with High Velocities in an Active Region Loop Observed
with the Coronal Diagnostic Spectrometer
Authors: Kjeldseth-Moe, O.; Brekke, P.; Harrison, R. A.
1997ESASP.404..457K Altcode: 1997cswn.conf..457K
No abstract at ADS

---------------------------------------------------------
Title: CME Onset Studies
Authors: Harrison, R. A.
1997ESASP.404...85H Altcode: 1997cswn.conf...85H; 1997soho....5...85H
No abstract at ADS

---------------------------------------------------------
Title: First Results from SOHO on Waves Near the Solar Transition
Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.;
Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten,
R. J.
1997ASPC..118..284S Altcode: 1997fasp.conf..284S
We present first results from simultaneous observations with the
CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995)
for a description of the instruments} onboard SOHO and the VTT at
Tenerife. Our aim is to study the wave propagation, shock formation,
and transmission properties of the upper chromosphere and transition
region. The preliminary results presented here include the variation
of velocity power spectra with height, difference in power between
internetwork and network regions, and variations in mean flows displayed
by different spectral lines.

---------------------------------------------------------
Title: The Net Redshifts in EUV Emission Lines and the Connection
Between Intensity and Doppler Shift
Authors: Brynildsen, N.; Fredvik, T.; Maltby, P.; Kjeldseth-Moe, O.;
Brekke, P.; Haugan, S. V. H.; Harrison, R. A.; Wilhelm, K.
1997ESASP.404..263B Altcode: 1997cswn.conf..263B
No abstract at ADS

---------------------------------------------------------
Title: EUV Line Emission and Time Dependence in the Sunspot Region
NOAA 7981
Authors: Brynildsen, N.; Brekke, P.; Fredvik, T.; Haugan, S. V. H.;
Kjeldseth-Moe, O.; Maltby, P.; Harrison, R. A.; Pike, C. D.; Rimmele,
T.; Thompson, W. T.; Wilhelm, K.
1997ESASP.404..245B Altcode: 1997cswn.conf..245B
No abstract at ADS

---------------------------------------------------------
Title: Temporal Variability in the Quiet Sun Transition Region
Authors: Wikstoøl, Ø.; Hansteen, V. H.; Brynildsen, N.; Maltby,
P.; Kyeldseth-Moe, O.; Harrison, R. A.; Wilhelm, K.; Tarbell, T. D.;
Scherrer, P. H.
1997ESASP.404..733W Altcode: 1997cswn.conf..733W
No abstract at ADS

---------------------------------------------------------
Title: Properties of Brightenings Seen in CDS Movies
Authors: Rüedi, I.; Brkovic, A.; Solanki, S. K.; Harrison, R.;
Fludra, A.; Huber, M. C. E.; Stenflo, J. O.; Stucki, K.
1997ESASP.404..641R Altcode: 1997cswn.conf..641R
No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Observations of the Extreme Ultraviolet Sun
Authors: Harrison, R. A.; Fludra, A.; Pike, C. D.; Payne, J.;
Thompson, W. T.; Poland, A. I.; Breeveld, E. R.; Breeveld, A. A.;
Culhane, J. L.; Kjeldseth-Moe, O.; Huber, M. C. E.; Aschenbach, B.
1997SoPh..170..123H Altcode:
This paper presents first results of the Coronal Diagnostic Spectrometer
(CDS) recently launched aboard the Solar and Heliospheric Observatory
(SOHO). CDS is a twin spectrometer, operating in the extreme ultraviolet
range 151-785 Å. Thus, it can detect emission lines from trace
elements in the corona and transition region which will be used to
provide diagnostic information on the solar atmosphere. In this paper,
we present early spectra and images, to illustrate the performance of
the instrument and to pave the way for future studies.

---------------------------------------------------------
Title: Flows and Dynamics in the Corona Observed with the Coronal
Diagnostic Spectrometer (cds)
Authors: Brekke, P.; Kjeldseth-Moe, O.; Brynildsen, N.; Maltby, P.;
Haugan, S. V. H.; Harrison, R. A.; Thompson, W. T.; Pike, C. D.
1997SoPh..170..163B Altcode:
EUV spectra obtained with the Coronal Diagnostic Spectrometer (CDS)
on the Solar and Heliospheric Observatory (SOHO) show significant flows
of plasma in active region loops, both at coronal and transition region
temperatures. Wavelength shifts in the coronal lines Mgix 368 Å and
Mgx 624 Å corresponding to upflows in the plasma reaching velocities
of 50 km s-1 have been observed in an active region. Smaller
velocities are detected in the coronal lines Fexvi 360 Å and Sixii
520 Å. Flows reaching 100 km s-1 are observed in spectral
lines formed at transition region temperatures, i.e., Ov 629 Å and
Oiii 599 Å, demonstrating that both the transition region and the
corona are clearly dynamic in nature. Some high velocity events show
even higher velocities with line profiles corresponding to a velocity
dispersion of 300-400 km s-1. Even in the quiet Sun there
are velocity fluctuations of 20 km s-1 in transition region
lines. Velocities of the magnitude presented in this paper have never
previously been observed in coronal lines except in explosive events
and flares. Thus, the preliminary results from the CDS spectrometer
promise to put constraints on existing models of the flows and energy
balance in the solar atmosphere. The present results are compared to
previous attempts to observe flows in the corona.

---------------------------------------------------------
Title: Wave Propagation in the Chromosphere and Transition Region
Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.;
Harrison, R.; Gurman, J.
1997ESASP.404..679S Altcode: 1997cswn.conf..679S
No abstract at ADS

---------------------------------------------------------
Title: Application of Spectroscopic Diagnostics to Early Observations
with the SOHO Coronal Diagnostic Spectrometer
Authors: Mason, H. E.; Young, P. R.; Pike, C. D.; Harrison, R. A.;
Fludra, A.; Bromage, B. J. I.; Del Zanna, G.
1997SoPh..170..143M Altcode:
The Coronal Diagnostic Spectrometer (CDS) has as a scientific goal
the determination of the physical parameters of the solar plasma
using spectroscopic diagnostic techniques. Absolute intensities and
intensity ratios of the EUV spectral emission lines can be used to
obtain information on the electron density and temperature structure,
element abundances, and dynamic nature of different features in the
solar atmosphere. To ensure that these techniques are accurate it is
necessary to interface solar analysis programs with the best available
atomic data calculations. Progress is reported on this work in relation
to CDS observations.

---------------------------------------------------------
Title: Microwave and UV observations of filaments with SOHO and
the VLA
Authors: Alissandrakis, C. E.; Drago, F.; Bastian, T.; Bocchialini,
K.; Delaboudiniere, J. -P.; Lemaire, P.; Vial, J. -C.; Harrison,
R. A.; Thompson, B.
1997ASPC..118..289A Altcode: 1997fasp.conf..289A
Observations performed in coordination between SOHO instruments and
ground-based observatories offer the unique possibility to derive
information simultaneously in several wavelengths formed at different
altitudes and/or temperatures in the solar atmosphere. The SUMER and
CDS spectrometers, the imaging telescope EIT aboard SOHO, and the VLA
provide complementary information in the UV and the radio ranges. We
illustrate such a coordination with observations of filaments in the
transition region, performed in July 1996. The observations in the UV
between 10(4) and 10(6) K provide the differential emission measure
as a function of temperature; this can be used to compute the expected
brightness temperature in the microwave range and check models of the
filament-corona transition region.

---------------------------------------------------------
Title: Extreme ultraviolet observations of the solar corona: first
results from the coronal diagnostic spectrometer on SOHO
Authors: Harrison, R. A.; Fludra, A.; Sawyer, E. C.; Culhane, J. L.;
Norman, K.; Poland, A. I.; Thompson, W. T.; Kjeldseth-Moe, O.;
Aschenbach, B.; Huber, M. C. E.; Gabriel, A. H.; Mason, H. E.
1997AdSpR..20.2239H Altcode:
We present first results from the Coronal Diagnostic Spectrometer (CDS)
aboard the ESA/NASA Solar and Heliospheric Observatory (SOHO). CDS is
a double spectrometer operating in the 151-785 A˚ range. This region
of the solar spectrum is rich in emission lines from trace elements
in the solar atmosphere, which can be used to derive diagnostic
information on coronal and transition region plasma. Early spectra are
presented and well identified lines are listed. In addition, examples
of images in selected wavelength ranges are shown, for a prominence,
a loop system and a bright point, demonstrating well the power of such
extreme ultraviolet observations.

---------------------------------------------------------
Title: Coronal Magnetic Storms: a New Perspective on Flares and the
`Solar Flare Myth' Debate
Authors: Harrison, Richard A.
1996SoPh..166..441H Altcode:
Recently Gosling (1993) examined the interplanetary consequences of
solar activity, and suggested that the coronal mass ejection (CME) was
the prime driver of most disturbances (i.e., interplanetary shocks,
high-energy particles, geomagnetic storms, etc.) and that the solar
flare was relatively unimportant in this context. He coined the phrase
`Solar Flare Myth'. Since that paper there has been much debate on the
origin of interplanetary disturbances - most people sitting squarely
in the flare or CME camp. Švestka (1995) has attacked Gosling's
conclusions on the grounds that it is misleading to ignore the flare,
and that past flare classifications were perfectly adequate for
explaining the observations described by Gosling. This paper is a
comment on Švestka's report and an attempt to put the Solar Flare
Myth into perspective - indeed it is an attempt to view the solar
flare/CME phenomena in a more constructive light.

---------------------------------------------------------
Title: Coordinated SOHO Observations of Polar Plumes
Authors: Deforest, C. E.; Scherrer, P. H.; Tarbell, T.; Harrison,
R. A.; Fludra, A.; Delaboudiniere, J. P.; Gurman, J. B.; Wilhelm,
K.; Lemaire, P.; Hassler, D. M.; Kohl, J. L.; Noci, G.; Fineschi,
S.; Brueckner, G. E.; Howard, R. A.; Cyr, O. C. St.
1996AAS...188.4909D Altcode: 1996BAAS...28R.898D
On 7 and 8 March 1996, SOHO instruments engaged in their first
joint science operation, a 12-hr observation of polar plumes
over the South polar coronal hole. The observing mini-campaign
included observations from SOHO, other spacecraft, and ground-based
observatories. Contributing SOHO instruments -- in order of altitude,
MDI, CDS, SUMER, EIT, UVCS, and LASCO -- made overlapping, simultaneous
observations of plume structures from the photosphere out to the
LASCO C3 limit of 32 solar radii. MDI provided line-of-sight surface
magnetograms with a one-min cadence and 0.6 arcsec resolution;
CDS, SUMER, and EIT supplied temperature-sensitive images of the
lower corona with varying cadences and resolutions; UVCS measured
fluctuations in Ly B intensity across the coronal hole with a one-min
cadence at 1.4 R0; and LASCO imaged the entire corona out to 30 R0 in
various visible passbands. Plume footpoints in the lower corona are
observed by EIT and CDS to vary by a factor of two in EUV brightness
with a timescale of tens of minutes, while the structures above are
(as as been previously observed) quiescent on at least a ten-hr time
scale. We present preliminary results of cross-instrument analysis
of the observed plumes, and suggest how this and similar future data
sets can be used to constrain quiet-sun wind acceleration and coronal
heating models for the coronal hole. This research is supported by
the SOI-MDI NASA contract NAG5-3077 at Stanford University. SOHO is
project of international cooperation between NASA and ESA.

---------------------------------------------------------
Title: TRACE: the Transition Region and Coronal Explorer
Authors: Schrijver, C.; Title, A.; Acton, L.; Bruner, M.; Fischer,
R.; Golub, L.; Harrison, R.; Lemen, J.; Rosner, R.; Scharmer, G.;
Scherrer, P.; Strong, K.; Tarbell, T.; Wolfson, J.
1996AAS...188.6704S Altcode: 1996BAAS...28..934S
The TRACE mission is designed to obtain images of the solar
transition region and corona of unprecedented quality. With these
images we will be able to explore quantitatively the connections
between the photospheric magnetic field and the associated hot and
tenuous structures in the outer atmosphere. The TRACE telescope has
an aperture of 30 cm, and will observe an 8.5 x 8.5 arcminute field of
view with a resolution of one arcsecond. Finely tuned coatings on four
quadrants on the primary and secondary normal--incidence mirrors will
allow observations in narrow EUV and UV spectral bands. The passbands
are set to Fe IX, XII, and XV lines in the EUV band, while filters
allow observations in C IV, Ly alpha , and the UV continuum using
the UV mirror quadrant. The data thus cover temperatures from 10(4)
K up to 10(7) K. The Sun--synchronous orbit allows long intervals of
uninterrupted viewing. Observations at different wavelengths can be
made in rapid succession with an alignment of 0.1 arcsec. Coordinated
observing with TRACE, SoHO and YOHKOH will give us the first opportunity
to observe all temperature regimes in the solar atmosphere, including
magnetograms, simultaneously from space. TRACE is currently scheduled
to be launched in October 1997. More information can be found on the
web at “http://pore1.space.lockheed.com/TRACE/welcome.html”.

---------------------------------------------------------
Title: High Velocity Event Observed with CDS on SOHO
Authors: Kjeldseth-Moe, O.; Brynildsen, N.; Brekke, P.; Harrison, R. A.
1996AAS...188.3714K Altcode: 1996BAAS...28..880K
The Coronal Diagnostic Spectrometer, CDS, on SOHO has observed its
first strong High Velocity Event. The event occurred on 22 March
1996 at approximately 13.36 UT and was located in the leg of an
active region loop. The spectral signature is extremely wide emission
lines corresponding to a velocity dispersion of approximately 300-450
km/s. As measured in the 386 A line from Mg IX, the emission also seems
shifted in wavelength with a redshift corresponding to 65 km/s. The
intensity contrast in the line is a factor 2 compared to the surrounding
areas. The spatial extent is small, less than or corresponding to the
angular resolution of CDS of 4". The event occur in all available lines
from He I to Fe XV, i.e. over a temperature range from 10 000 K to
2.2 MK. This is a new result which has not been reported before. The
relation of this type of event to the well studied explosive events
is discussed.

---------------------------------------------------------
Title: The Coronal Diagnostic Spectrometer for the Solar and
Heliospheric Observatory: experiment description and calibration.
Authors: Harrison, R. A.; Kent, B. J.; Sawyer, E. C.; Hollandt, J.;
Kuhne, M.; Paustian, W.; Wende, B.; Huber, M. C. E.
1996Metro..32..647H Altcode:
The Coronal Diagnostic Spectrometer (CDS) to be flown aboard the
ESA/NASA Solar and Heliospheric Observatory (SOHO) is designed
to probe the solar atmosphere through the detection of spectral
emission lines in the extreme ultraviolet (EUV) wavelength range
15 nm to 80 nm. By observing the absolute and relative radiance of
selected lines and line profiles, one is able to derive temperature,
density, flow and abundance information for the plasmas in the solar
atmosphere. Spatial and temporal resolutions of down to a few arcseconds
and 1 second, respectively, allow such studies to be made within
the fine-scale structure of the solar corona. Simultaneous coverage
of large-wavelength bands provides the capability for simultaneously
observing the properties of plasmas across the wide temperature ranges
of the solar atmosphere. The pre-launch calibration is achieved through
the use of a hollow cathode discharge source which is used as a transfer
standard to allow calibration of the CDS against the primary standard
of the BESSY electron storage ring. By the use of different selected
gases in the discharge tube, each of the detector wavelength intervals
in the CDS can be covered adequately. The pre-delivery calibration of
the CDS has been performed and some results are shown.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1996CIBu..135....4H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The nature of solar flares associated with coronal mass
ejection.
Authors: Harrison, R. A.
1995A&A...304..585H Altcode:
An analysis is presented of solar X-ray flares associated with coronal
mass ejections through the period 1986-1987. The nature of the flares
apparently associated with mass ejection is explored. In particular the
relationships between flare duration and intensity and the association
with mass ejection are investigated. We believe that this study tackles
the flare-CME analysis in a way that is uniquely unbiased. Past studies
of a similar nature are discussed and a criticism of their approach
is given. In particular, the author believes that the continual bias
toward the so-called Long Duration Events and the brightest flares is
misleading. The analysis supports the view that the flare and CME are
signatures of the same magnetic "disease", that is, they represent the
responses in different parts of the magnetic struture, to a particular
activity; they do not drive one another but are closely related. The
present statistical analysis allows a chance association to be given
for a mass ejection event when an X-ray flare is observed. The use of
such information in the prediction of geomagnetic activity generated
when mass ejecta interact with the Earth is discussed.

---------------------------------------------------------
Title: The Coronal Diagnostic Spectrometer for the Solar and
Heliospheric Observatory
Authors: Harrison, R. A.; Sawyer, E. C.; Carter, M. K.; Cruise,
A. M.; Cutler, R. M.; Fludra, A.; Hayes, R. W.; Kent, B. J.; Lang,
J.; Parker, D. J.; Payne, J.; Pike, C. D.; Peskett, S. C.; Richards,
A. G.; Gulhane, J. L.; Norman, K.; Breeveld, A. A.; Breeveld, E. R.; Al
Janabi, K. F.; Mccalden, A. J.; Parkinson, J. H.; Self, D. G.; Thomas,
P. D.; Poland, A. I.; Thomas, R. J.; Thompson, W. T.; Kjeldseth-Moe,
O.; Brekke, P.; Karud, J.; Maltby, P.; Aschenbach, B.; Bräuninger,
H.; Kühne, M.; Hollandt, J.; Siegmund, O. H. W.; Huber, M. C. E.;
Gabriel, A. H.; Mason, H. E.; Bromage, B. J. I.
1995SoPh..162..233H Altcode:
The Coronal Diagnostic Spectrometer is designed to probe the solar
atmosphere through the detection of spectral emission lines in the
extreme ultraviolet wavelength range 150 - 800 å. By observing
the intensities of selected lines and line profiles, we may derive
temperature, density, flow and abundance information for the plasmas
in the solar atmosphere. Spatial and temporal resolutions of down to
a few arcseconds and seconds, respectively, allow such studies to be
made within the fine-scale structure of the solar corona. Futhermore,
coverage of large wavelength bands provides the capability for
simultaneously observing the properties of plasmas across the wide
temperature ranges of the solar atmosphere.

---------------------------------------------------------
Title: Book-Review - the High Latitude Heliosphere
Authors: Marsden, R. G.; Harrison, R. A.
1995Obs...115..346M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coronal Diagnostic Spectrometer: an extreme-ultraviolet
spectrometer for the Solar and Heliospheric Observatory
Authors: Kent, Barry J.; Harrison, Richard A.; Sawyer, Eric C.;
Hayes, R. W.; Richards, Anthony G.; Culhane, John L.; Norman, K.;
Breeveld, A. A.; Thomas, P. D.; Poland, Arthur I.; Thomas, Roger J.;
Thompson, William T.; Aschenbach, Bernd R.; Braeuninger, Heinrich
W.; Kjeldseth-Moe, O.; Kuehne, Mikhael; Hollandt, J.; Paustian, W.;
Bromage, B. J.
1995SPIE.2517...12K Altcode:
The coronal diagnostic spectrometer is designed to probe the solar
atmosphere through the detection of spectral emission lines in the
extreme ultraviolet wavelength range 15.0 - 80.0 nm. By observing
the intensities of selected lines and line profiles, it is possible
to derive temperature, density, flow, and abundance information for
the plasmas in the solar atmosphere. Spatial resolution down to
a few arcseconds and temporal resolution of seconds, allows such
studies to be made within the fine-scale structure of the solar
corona. Furthermore, coverage of a large wavelength band provides
the capability for simultaneously observing the properties of plasma
across the wide temperature ranges of the solar atmosphere. The
CDS design makes use of a Wolter-Schwarzschild II telescope which
simultaneously illuminates two spectrometer systems, one operating
in normal incidence the other in grazing incidence. In this paper we
describe the salient features of the design of the CDS instrument and
discuss the performance characteristics of CDS as established through
pre-delivery test and calibration activities.

---------------------------------------------------------
Title: The differential rotation of the corona as indicated by
coronal holes
Authors: Insley, J. E.; Moore, V.; Harrison, R. A.
1995SoPh..160....1I Altcode:
The rotation of the corona can be determined either directly by using
Doppler methods or indirectly by using tracers, i.e., structures
within the corona. In this study the rotational characteristics of the
corona are determined using coronal holes as tracers, for the period
1978-1991. The coronal data used here are from an atlas of coronal
holes mapped in HeI 10830 å data. A comparison is made between our
results and previous determinations of the coronal rotation rate,
e.g., by Sime (1986), using white-light K-coronameter observations,
by Timothy, Krieger, and Vaiana (1975), using soft X-ray observations,
and by Shelke and Pande (1985) and Navarro-Peralta and Sanchez-Ibarra
(1994), using HeI 10830 å data. For the atlas of coronal holes used in
this study the nature of the coronal hole distributions in number and
latitude, in yearly averages, has been determined. These distributions
show that at solar minimum the polar coronal holes dominate and the
few non-polar holes are confined to a narrow band near the equator. At
solar maximum, however, mid-latitude coronal holes dominate, with a
large spread in latitudes. Given these distributions we consider the
differential rotation data only as an average over a solar cycle. This
removes spurious effects caused by having only a small number of coronal
holes contributing to the results, or by having a narrow latitude
band for the observations, thus limiting the results to that narrow
latitude band. By considering these coronal holes as tracers of the
differential rotation we show that the mid-latitude corona rotates
more rigidly than the photosphere, but still exhibits significant
differential rotation, with an equatorial rate of 13.30 ± 0.04°
day−1, and at 45° latitude a rate of 12.57 ± 0.13°
day−1. These results are comparable, within errors, to
the Sime (1986) results which have an equatorial rate of approximately
13.2 ± 0.2° day−1 and a rate of approximately 12.9 ±
0.3° day−1 at 45° latitude.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1995CIBu..134....8H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mars Microrover navigation: performance evaluation and
enhancement.
Authors: Matthies, L.; Gat, E.; Harrison, R.; Wilcox, B.; Volpe, R.;
Litwin, T.
1995AuRob...2..291M Altcode:
The Mars Pathfinder spacecraft will carry a rover to explore the
immediate vicinity of the lander. To assess the capabilities of the
rover, as well as to set priorities for future rover research, it is
essential to evaluate the performance of its autonomous navigation
system as a function of terrain characteristics. The authors have
constructed a new Microrover testbed. In this paper, the authors outline
current plans for Mars exploration over the next decade, summarize
the design of the lander and rover for the 1996 Pathfinder mission,
and introduce a decomposition of rover navigation into four major
functions: goal designation, rover localization, hazard detection
and path selection. They then describe the Pathfinder approach to
each function, present results to date of evaluating the performance
of each function and outline their approach to enhancing performance
for future missions. The results show key limitations in the quality
of rover localization, the speed of hazard detection and the ability
of behaviour control algorithms for path selection to negotiate the
rock frequencies likely to be encountered on Mars. The facilities,
methodologies and, to some extent, the specific performance results
presented in this paper provide valuable examples for efforts to
evaluate robotic vehicle performance in other applications.

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1995CIBu..133...59H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Preface
Authors: Harrison, Richard
1995CIBu..132....2H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Inter Agency Consultative Group campaign to study coronal
mass ejection onsets
Authors: Harrison, R. A.
1994ESASP.373..355H Altcode: 1994soho....3..355H
No abstract at ADS

---------------------------------------------------------
Title: Book Review: Infrared solar physics / Kluwer, 1993
Authors: Harrison, R. A.
1994Obs...114..189H Altcode: 1994Obs...114..189R
No abstract at ADS

---------------------------------------------------------
Title: A statistical study of the coronal mass ejection phenomenon
Authors: Harrison, R. A.
1994AdSpR..14d..23H Altcode: 1994AdSpR..14...23H
The coronal mass ejection (CME) phenomenon represents a major
component of the evolution of the solar corona, yet the mechanisms
leading to such events remain something of a mystery. To understand
the onset phase of these ejecta, many studies have focused on the
relationship between CMEs and other, apparently related activity. A
typical CME occurs on a very large spatial scale and involves the
expulsion of up to 1012kg of matter, and the release of up
to 1025J from the coronal magnetic field. A solar flare
is an explosive event at the base of the atmosphere involving the
release of up to 1025J of energy. Since there is an apparent
association between these two phenomena and the time-scale for flares
is comparable to that of the acceleration phase of the mass ejections,
the questions arise as to what precise relationship exists between the
two and what does this indicate about the physics of each. Many earlier
studies of this kind were compromised by unfortunate assumptions,
poor data coverage or instrumental limitations. This study attempts
to identify purely formal correlations between parameters relating to
flare and mass ejection observations through the period 1986-1987. In
spite of a strong association between flares and CME onsets, we find
that no single type of flare shows a preferred association with mass
ejections, and the relative locations and timing of the two phenomena
show no systematic ordering.

---------------------------------------------------------
Title: On the potential of interplanetary scintillation for predicting
geomagnetic activity
Authors: Hapgood, Mike; Harrison, Richard
1994GeoRL..21..637H Altcode:
A survey of IPS, geomagnetic and inter-planetary medium data has
been used to interpret the weak correlation between IPS data and
geomagnetic activity. Our results indicate that: (i) we can use IPS
data to predict the maximum possible level of geomagnetic activity,
given the state of the solar wind; but (ii) to predict the actual level
of activity we also require an estimate the coupling between the solar
wind and the magnetosphere. This is the first time that the potential
(and the limitations) of IPS for predicting geomagnetic activity have
been demonstrated quantitatively in a comprehensive survey.

---------------------------------------------------------
Title: The study of the solar wind using interplanetary scintillation
observations from the MRAO, Cambridge, array.
Authors: Moore, V.; Lucek, E. A.; Sime, D. G.; Harrison, R. A.
1994JBIS...47..164M Altcode:
The daily monitoring of short time intensity fluctuations of
astronomical radio sources by an array at the Mullard Radio Astronomy
Observatory (MRAO), Cambridge, provides one of the few remote sensing
techniques for studying the large scale structure of the near-Earth
heliosphere. After an introduction to the interplanetary scintillation
(IPS) technique the authors review the overall character of the IPS
results for 1991. As the corona is the source of the solar wind the
authors indicate how large scale changes in the solar corona in 1991,
from a near maximum to a more minimum like structure, were reflected in
the IPS data. They also show, by way of a case study for two discrete
events, how the MRAO IPS data may be used to investigate the solar
sources and subsequent geomagnetic response to specific interplanetary
plasma features.

---------------------------------------------------------
Title: A characterization of discrete solar wind events detected by
interplanetary scintillation mapping
Authors: Moore, V.; Harrison, R. A.
1994JGR....99...27M Altcode:
We examine the large-scale solar wind density and velocity
characteristics which are associated with interplanetary disturbances
detected by interplanetary scintillation (IPS) mapping. Our aim
here is to characterize these remotely sensed events in order to
provide a better foundation on which to consider both the origin of
such phenomena and their influence on the near-Earth environment. We
select those events from a list published by Hewish and Bravo (1986)
that appear to be Earth crossing and consider the average density and
velocity in the solar wind at the time. We find density (and often
velocity) enhancements in association with the majority of these IPS
events, though the changes are modest. Postevent conditions commonly
show a slight velocity increase and density decrease with respect to
preevent conditions.

---------------------------------------------------------
Title: Foreword
Authors: Harrison, Richard
1994CIBu..130....2H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Daily Interplanetary Scintillation Activity Index and its
Relation to Solar and Geomagnetic Activity
Authors: Harrison, R. A.; Hapgood, M. A.
1994step.conf..269H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: International solar terrestrial energy programme and the
UK participation
Authors: Lester, M.; Coates, A. J.; Harrison, R. A.; Rees, D.;
Roederer, J. G.; Rycroft, M. J.; Saunders, M. A.
1993SGeo...14..555L Altcode:
The Solar Terrestrial Energy Programme (STEP) aims to improve
our general understanding of how mass, energy and momentum are
transferred between the various regions that form the Solar Terrestrial
environment. STEP began in 1990 and will continue until 1997, during
which time a number of major new spacecraft and ground-based projects
will become operational. Six Working Groups form the basis of STEP,
covering topics such as the Sun as a source of energy and disturbance,
energy and mass transfer through the interplanetary medium and the
magnetosphere-ionosphere system, ionosphere-thermosphere coupling and
response to energy and momentum inputs, middle atmosphere responses to
forcing from above and below, solar variability effects in the human
environment, and informatics. A Royal Astronomical Society Geophysics
Discussion meeting took place in March 1992 to draw to the attention of
UK scientists the diverse nature of STEP and the opportunities offered
by STEP. This paper consists of individual sections prepared by the
speakers at the meeting and which cover most of the STEP Working Group
topics. The main aims of each section are to provide a “benchmark”
for the present status of the research area and to look ahead to the
possible contributions that UK scientists can make during STEP.

---------------------------------------------------------
Title: An active solar prominence in 1.3 MM radiation
Authors: Harrison, R. A.; Carter, M. K.; Clark, T. A.; Lindsey, C.;
Jefferies, J. T.; Sime, D. G.; Watt, G.; Roellig, T. L.; Becklin,
E. E.; Naylor, D. A.; Tompkins, G. J.; Braun, D.
1993A&A...274L...9H Altcode:
We present new millimetre-wavelength observations of an active solar
prominence. Observations made over a two-day period with the James
Clerk Maxwell Telescope on Manna Kea, Hawaii, give a unique view in
1.3 mm radiation of the spectacular prominence that appeared on the
west solar limb in the total solar eclipse of 11 July 1991.

---------------------------------------------------------
Title: Book Review: The sun: a laboratory for astrophysics /
Kluwer, 1992
Authors: Harrison, R. A.
1993Obs...113...87H Altcode: 1993Obs...113...87S
No abstract at ADS

---------------------------------------------------------
Title: The SOHO interdisciplinary science matrix.
Authors: Harrison, Richard A.; Schultz, G.
1992ESASP.348..397H Altcode: 1992cscl.work..397H
To pursue the goals of SOHO, we are required to compare and analyse
data-sets from very different experiments. Such interdisciplinary
studies require careful planning, prior to the observations, and involve
complex analysis procedures. In recognition of this, the SOHO Coronal
and Particle Working Group has initiated a study to provide an overview
of the nature of such activities. The first results of this study are
presented here.

---------------------------------------------------------
Title: The coronal diagnostic spectrometer for the Solar and
Heliospheric Observatory.
Authors: Harrison, Richard A.; Sawyer, Eric C.
1992ESASP.348...17H Altcode: 1992cscl.work...17H
The Coronal Diagnostic Spectrometer is designed to probe the solar
atmosphere through the analysis of spectral emission lines in the
extreme ultraviolet wavelength range 150 - 800 Å. By observing the
absolute and relative intensities of selected lines, and line profiles,
one may derive temperature, density, flow and abundance information for
the plasmas in the solar atmosphere. Simultaneous coverage of large
wavelength bands combined with spatial and temporal resolutions of a
few arc sec and down to 1 sec will provide a unique tool for pursuing
the goals of SOHO.

---------------------------------------------------------
Title: Measurement of the Height of the Solar CO Layer During the
11 July 1991 Eclipse
Authors: Clark, T. A.; Naylor, D. A.; Tompkins, G. J.; Lindsey, C. A.;
Becklin, E. E.; Jefferies, J. T.; Harrison, R. A.; Roellig, T. L.;
Carter, M.; Braun, D. C.; Watt, G.
1992AAS...181.8108C Altcode: 1992BAAS...24.1253C
No abstract at ADS

---------------------------------------------------------
Title: Coronal mass ejecta and flares: a statistical study.
Authors: Harrison, R. A.; Sime, D. G.
1992ESASP.346..289H Altcode: 1992ssts.rept..289H
A typical solar coronal mass ejection (CME) occurs on a very large
spatial scale and involves the expulsion of up to 1012kg,
and the release of up to 1025J from the coronal magnetic
field. A solar flare is an explosive event at the base of the atmosphere
involving the release of up to 1025J of energy. Since
there is an observed association between these two phenomena and
the time-scale for flares is comparable to that of the acceleration
phase of the mass ejections, the questions arise as to what precise
relationship exists between the two and what does this indicate about
the physics of each. This study attempts to identify purely formal
correlations between parameters relating to flare and mass ejection
observations through the period 1986-7. In spite of a strong association
between flares and CME onsets, no single type of flare shows preferred
association with mass ejections and the relative locations and timing
of the two phenomena show no systematic ordering.

---------------------------------------------------------
Title: Detecting and tracking changes in solar wind conditions using
interplanetary scintillation.
Authors: Harrison, Richard A.; Hapgood, M. A.; Sime, D. G.
1992ESASP.346..207H Altcode: 1992ssts.rept..207H
Using the recently refurbished 81.5 MHz radio telescope at Cambridge the
authors are able to monitor the scintillation of ≡1000 radio sources
to identify regions of excessive scintillation due to the passage of
enhanced density fluctuations in the interplanetary medium. Analysis of
whole sky scintillation maps to reveal individual events has met with
modest success. However, the maps are adversely affected by noise
and can be difficult to interpret. As a result the cause of such
disturbances, perhaps in the form of mass ejection from the Sun, and
their effects are difficult to determine. For comparisons to geomagnetic
activity and for prediction of such activity, the use of a single
index to describe regions within the map promises to avoid many of the
difficulties presented by visual inspection. The use of such a global
descriptor is also more appropriate for comparison with geomagnetic
indices. We have developed such a scintillation activity index.

---------------------------------------------------------
Title: An interplanetary scintillation activity index.
Authors: Harrison, R. A.; Hapgood, M. A.; Moore, V.; Lucek, E. A.
1992AnGeo..10..519H Altcode: 1992AnG....10..519H
Using interplanetary scintillation (IPS) data obtained from the
Cambridge 81.5 MHz array, the authors have developed an activity index
in which they identify (i) discrete structures, most likely relating to
transient density enhancements, and (ii) periodic activity, relating
to co-rotating interplanetary structure. They find significant, yet
weak correlations between the index and geomagnetic activity. Their
results suggest that the persuit of such an index could result in a
valuable tool for the prediction of geomagnetic events and highlight
several potential future developments.

---------------------------------------------------------
Title: Extreme-infrared brightness profile of the solar chromosphere
obtained during the total eclipse of 1991
Authors: Lindsey, C.; Jefferies, J. T.; Clark, T. A.; Harrison, R. A.;
Carter, M. K.; Watt, G.; Becklin, E. E.; Roellig, T. L.; Braun, D. C.;
Naylor, D. A.
1992Natur.358..308L Altcode:
THE solar chromosphere is a thin layer of gas that is several thousand
degrees hotter than the underlying photosphere, and responsible for
most of the Sun's ultraviolet emission. The mechanism by which it is
heated to temperatures exceeding 10,000 K is not understood. Millimetre
and submillimetre radiometry can be used to obtain the chromospheric
temperature profile, but the diffraction-limited resolution for the
largest telescopes is at best 17 arcsec, or ~12,500 km at the Sun's
distance. This is greater than the thickness of the quiet chromosphere
itself. The total eclipse of July 1991, which passed over the Mauna
Kea Observatory in Hawaii, provided a rare opportunity to make limb
occultation observations with a large submillimetrewavelength telescope,
the 15-m James Clerk Maxwell Telescope, and in this way we obtained a
temperature profile in 1.3-mm radiation with ~300 km resolution at the
Sun. Our observations indicate that spicules (magnetically entrained
funnels of gas) reach a temperature of 8,000 K at 3,000-4,000 km above
the photosphere, a temperature lower than those of many spicule models.

---------------------------------------------------------
Title: Hα Activity and Global X-Ray Luminosity Flaring on the Sun
Authors: Pearce, G.; Harrison, R. A.; Bromage, B. J. I.; Pickering,
A. G. M.
1992sers.conf..440P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High resolution observations of solar ejecta.
Authors: Harrison, Richard A.
1992ESASP.344...91H Altcode: 1992spai.rept...91H
In the solar atmosphere, the ejection of matter occurs on a variety of
spatial scales. Indeed, it is useful to regard the phenomenon within the
framework of a spectrum. At one extreme one finds the huge, discrete
events known as coronal mass ejecta, involving spatial scales of over
one hundred thousand km and timescales of up to tens of minutes. At
the other extreme one is concerned with the microscopic processes
which accumulate to become the apparently continuous solar wind,
involving spatial scales of, perhaps, much less than 1000 km and
timescales of seconds. In the intermediate portions of the spectrum
one finds the high velocity events which have been identified in the
transition zone and, probably, in the corona with spatial scales of
1000 km or more and timescales of order tens of seconds. One also finds
surge and spray activity as chromospheric matter is expelled high into
the corona, with spatial scales ranging from one thousand to tens of
thousands of km and timescales often of order minutes. The larger scale
phenomena, such as the surges, sprays and coronal mass ejecta, often
display intricate fine scale features and, no doubt, as the spatial
resolution improves one will identify structure within the finer scale
ejection phenomena. The author explores the need for understanding
these ejection events, the need for high resolution observation of
them and will discuss the use of SIMURIS in making such observations.

---------------------------------------------------------
Title: Book Review: Opening the frontiers in solar research /
Pergamon, 1991
Authors: Machado, M. E.; Mattig, W.; Simon, G. W.; Harrison, R. A.
1992Obs...112...70F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Design Rationale of the Solar Ultraviolet Network / Sun
Authors: Dame, L.; Acton, L.; Bruner, M. E.; Connes, P.; Cornwell,
T. J.; Curdt, W.; Foing, B. H.; Hammer, R.; Harrison, R.; Heyvaerts,
J.; Karabin, M.; Marsch, E.; Martic, M.; Mattic, W.; Muller, R.;
Patchett, B.; Roca-Cortes, T.; Rutten, R. J.; Schmidt, W.; Title,
A. M.; Tondello, G.; Vial, J. C.; Visser, H.
1992ESOC...39..995D Altcode: 1992hrii.conf..995D
No abstract at ADS

---------------------------------------------------------
Title: Preface
Authors: Harrison, R. A.; Argent, C. R.
1992CIBu..125....3H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The relationship between global X-ray luminosity and flaring
on the sun
Authors: Pearce, G.; Harrison, R. A.; Bromage, B. J. I.; Pickering,
A. G. M.
1992A&A...253..601P Altcode:
The relationship between solar global flaring activity and X-ray
luminosity is investigated as part of a solar-stellar investigation. In
keeping with previous suggestions, it is found that the rate of
flaring on the sun is closely related to X-ray luminosity with a
positive correlation. This is in contrast to relationships found on
dMe stars, and can be interpreted in terms of flare activity both on
a microscopic and macroscopic scale varying sympathetically, rather
than macroscopic flare energy storage subduing smaller scale energy
release. The microscopic activity has significance for outstanding
problems such as coronal heating.

---------------------------------------------------------
Title: Cylindrical fabric-confined soil structures
Authors: Harrison, Richard A.
1992ecos.proc..123H Altcode: 1992ecos....1..123H
A cylindrical fabric-soil structural concept for implementation on
the moon and Mars which provides many advantages is proposed. The
most efficient use of fabric is to fashion it into cylindrical
tubes, creating cylindrical fabric-confined soil structures. The
length, diameter, and curvature of the tubes will depend on the
intended application. The cylindrical hoop forces provide radial
confinement while end caps provide axial confinement. One of the ends
is designed to allow passage of the soil into the fabric tube before
sealing. Transportation requirements are reduced due to the low mass
and volume of the fabric. Construction requirements are reduced due to
the self-erection capability via the pneumatic exoskeleton. Maintenance
requirements are reduced due to the passive nature of the concept. The
structure's natural ductility is well suited for any seismic activity.

---------------------------------------------------------
Title: Coronal Mass Ejection
Authors: Harrison, Richard A.
1991RSPTA.336..401H Altcode:
We summarize the observational aspects of the transient solar coronal
features known as coronal mass ejections. Recognizing the importance of
understanding this form of solar activity, particularly in the light of
relations to flare and prominence activity, and geomagnetic effects,
we consider the spectrum of models which have been used to describe
these events and assess their viability. We find most models to be
unphysical and all represent a gross over simplification of solar
conditions. In conclusion we set up a cartoon model which best fits
the observations and which we feel should be further developed.

---------------------------------------------------------
Title: Book Review: Dynamics of quiescent prominences / Springer, 1991
Authors: Harrison, R. A.
1991Obs...111..198H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar plasma energisation: basic concepts.
Authors: Harrison, Richard A.
1991AnGeo...9..170H Altcode: 1991AnG.....9..170H
The author describes the basic properties of the solar atmosphere and
outlines the mechanisms which may operate to produce the solar wind,
to heat the corona and to drive the transient events which we observe,
such as flares and coronal mass ejections. The aim of this review is
to provide a useful perspective for the solar physicist as well as an
introduction for those not familiar with the Sun.

---------------------------------------------------------
Title: European Geophysical Society, Symposium on Acceleration and
Heating Processes in Solar System Plasmas, Copenhagen, Denmark,
Apr. 23-27, 1990, Proceedings
Authors: Harrison, Richard A.; Saunders, Mark
1991AnGeo...9.....H Altcode:
The present symposium on acceleration and heating processes in solar
system plasmas discusses magnetic reconnection (solar flares, coronal
mass ejections, coronal heating, the earth's dayside magnetopause,
and substorms). Attention is given to shocks (coronal mass ejections,
interplanetary and planetary shocks), parallel electric fields (auroral
acceleration), and wave heating (wave particle interactions). Topics
addressed include cometary plasma energization, acceleration and
heating of space plasmas, wave activity in the solar atmosphere,
the solar wind mass flux problem, and auroral energization processes.

---------------------------------------------------------
Title: Book Review: Solar astrophysics / Wiley Interscience, 1990
Authors: Harrison, R. A.
1991Obs...111...45H Altcode: 1991Obs...111...45F
No abstract at ADS

---------------------------------------------------------
Title: The Detection of Wave Activity in the Solar Corona Using
Ultraviolet Spectra
Authors: McClements, K. G.; Harrison, R. A.; Alexander, D.
1991SoPh..131...41M Altcode:
The SUMER and CDS instruments on the Solar and Heliopheric Observatory
spacecraft (SOHO), due to be launched in 1995, may enable us to identify
the dominant mechanism responsible for solar coronal heating. In
this paper we examine, in particular, the possibility that Alfvén or
acoustic waves, propagating through the corona and heating the ambient
plasma, could be detected through the measurement of ultra-violet
line widths. The contribution of wave broadening to the total line
width depends on the orientation of the magnetic field with respect
to the line of sight. CDS may be used to identify the magnetic field
geometry in a particular region. The spatial resolution provided by
SUMER, superior to that of previous instruments, should then make it
possible to discriminate between different broadening mechanisms. In
the case of lines produced by heavy ions in the low corona, we find
that the line width produced by an Alfvén wave flux sufficiently high
to heat the active corona corresponds to a Doppler temperature of up
to twenty times the kinetic temperature.

---------------------------------------------------------
Title: Coronal transients and their relation to solar flares
Authors: Harrison, R. A.
1991AdSpR..11a..25H Altcode: 1991AdSpR..11...25H
Our understanding of the relationship between coronal transient
events and flare activity is severely restricted by a complex web
of preconception, mythology and misinterpretation. In principle, for
some time we have had access to the observations needed to develop a
good knowledge of coronal activity at the time of flaring. However,
this has required the combination of rather incompatible data-sets -
a stumbling block for many. In this paper, we attempt to clear some
of the dead-wood and simply ask the question: what happens in the
low corona at about the time of a coronal mass ejection? There is
no attempt to provide a thorough review of the literature; we simply
re-examine several large data-sets and draw conclusions. We supplement
this analysis with comments on related phenomena which have been the
target of some controversy, e.g long duration X-ray events, flare
precursors and X-ray arches, in an effort to gain a better perspective.

---------------------------------------------------------
Title: Preface
Authors: Harrison, R. A.
1991CIBu..121....1H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coronal mass ejection.
Authors: Harrison, R. A.
1991psf..conf..401H Altcode:
The author summarizes the observational aspects of the transient
solar coronal features known as coronal mass ejections. Recognizing the
importance of understanding this form of solar activity, particularly in
the light of relations to flare and prominence activity, and geomagnetic
effects, he considers the spectrum of models which have been used to
describe these events and assess their viability. The author finds most
models to be unphysical and all represent a gross over simplification
of solar conditions. In conclusion he sets up a cartoon model which
best fits the observations and which should be further developed.

---------------------------------------------------------
Title: Pamela Rothwell Martelli 1926-1991
Authors: Harrison, R.
1991CIBu..121....6H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The surge events of June 28 and October 30, 1980
Authors: Harrison, R. A.; Sime, D. G.; Pearce, G.
1990A&A...238..347H Altcode:
Similarities between two surge events, observed using the High
Altitude Observatory's Prominence Monitor on Mauna Loa, Hawaii and
the Hard X-ray Imaging Spectrometer on NASA's Solar Maximum Mission,
are discussed. In both events, a soft X-ray burst occurs adjacent to
a large quiescent prominence structure. After the onset of the burst,
a surge occurs in loop structures adjacent to the burst side and on
the side remote from the prominence. It is observed that, even though
the surge is removed physically from the burst side, it appears to be
related to the burst activity. It is suggested that the burst activity
and H-alpha ejecta are different manifestations of a single event
involving a large-scale structure. These results are not consistent
with those obtained using previous models of such events.

---------------------------------------------------------
Title: Fine-scale structure on the Sun
Authors: Harrison, R. A.
1990Obs...110...84H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The coronal diagnostic spectrometer - a solar EUV experiment
for the SOHO mission.
Authors: Patchett, B. E.; Harrison, R. A.; Sawyer, E. C.
1990JBIS...43..181P Altcode:
The scientific background of the Solar and Heliospheric Observatory
(SOHO) mission, a joint operation of NASA and ESA planned for 1995, is
given, and the main goals of the mission are defined. Two out of three
fundamental problems addressed, such as the existence and heating of
the solar corona, and causes and locations of the solar-wind stream
acceleration, will be examined by the major SOHO instrument, the
coronal diagnostic spectrometer (CDS). The CDS is designed to obtain
the intensity ratios of selected diagnostic line-pairs in the EUV,
at spatial and temporal resolutions appropriate to the fine scale
features of the solar atmosphere. Its design is a hybrid instrument,
with an astigmatic grazing incidence spectrometer to access the
important coronal line below 300 A and a stigmatic normal incidence
spectrometer to view the lines larger than 300 A.

---------------------------------------------------------
Title: The Source Regions of Solar Coronal Mass Ejections
Authors: Harrison, Richard A.
1990SoPh..126..185H Altcode:
Knowledge of the origin of the solar coronal mass ejection (CME) may be
crucial to our understanding of several active solar phenomena, such as
flares, as well as to the structure and stability of the corona and the
prediction of interplanetary disturbances. In recent years, two camps
of opinion have emerged, based on the belief that CMEs either commonly
originate from structures intimately linked to active regions or they
originate from coronal hole regions. This present study investigates
the locations of 95 CME events observed during 1984-1986 relative
to coronal hole and active region features. We find no evidence to
support the coronal hole hypothesis and many indications that active
regions are indeed associated with the source regions of CMEs.

---------------------------------------------------------
Title: Sympathetic flaring
Authors: Pearce, G.; Harrison, R. A.
1990A&A...228..513P Altcode:
An examination of the relationship between the flaring of 15 active
region pairs and their physical separations is found to support the
existence of sympathetic flare activity on the sun. In general, active
region pairs separated by less than 35 heliographic degrees show a
significant departure from random coincident flare activity. These
regions represent one extreme of a spectrum which suggests that there
is an inverse correlation between the pair separation and the degree
of coincident flare activity.

---------------------------------------------------------
Title: The launch of solar coronal mass ejections: Results from the
coronal mass ejection onset program
Authors: Harrison, R. A.; Hildner, E.; Hundhausen, A. J.; Sime, D. G.;
Simnett, G. M.
1990JGR....95..917H Altcode:
We describe a set of solar coronal mass ejection (CME) events where
coincident data sets from both X ray and white light instruments have
been made available through deliberate planning. Using these we have
been able to put tight limits on possible descriptions of the typical
sequence of events, and these we relate to interpretations of models
involving flares and CMEs. Our findings confirm recent suggestions
that CME onsets precede any related flare activity and that the
associated flaring commonly lies to one side of the CME span. The CME
launch appears to be associated with minor X ray (flare precursor)
activity. Although this scenario has been previously discussed (see
Harrison, 1986, and references therein), the abundance of flare and
CME models which are not compatible with this picture demands that
confirmation be sought using programs such as this.

---------------------------------------------------------
Title: Book Review: The physics of solar flares. / CUP, 1988
Authors: Harrison, R.
1989Obs...109..107H Altcode: 1989Obs...109..107T
No abstract at ADS

---------------------------------------------------------
Title: The launch of coronal mass ejections: White light and x ray
observations in the low corona
Authors: Harrison, R. A.; Sime, D. G.
1989JGR....94.2333H Altcode:
As part of an ongoing program to determine the processes which lead
to the launch of solar coronal mass ejections (CMEs) we present a
thorough examination of periods where there are observations from the
hard X ray imaging spectrometer on the Solar Maximum Mission which
are complementary to observations made by the MkIII K-coronameter on
Hawaii. At the time of the observations no attempt was made to produce
compatible data sets so the analysis is hampered by unfortunate timing
and pointing. Nevertheless, with the analysis of six events we are able
to draw some useful conclusions which agree with the findings of our
previous work but dispute the scenarios presented by most theoretical
models of the CME launch and the CME/flare relationship. To summarize
briefly our results: (1) None of the CME launches occur in coincidence
with a flare onset, (2) flares which do occur in the vicinity of a
CME launch site occur both after the CME onset and in one foot of the
CME structure, (3) there is weak X ray activity also associated with
the footpoints of the CME structures and these indicate the presence
of large coronal structures which underlie the CME structures, (4)
there are X ray enhancements after all of the CME onsets; in some
cases these are bright enough to be classed as flares, and in others
they are lesser brightenings which we refer to as subflares.

---------------------------------------------------------
Title: A statistical analysis of the soft X-ray profiles of solar
flares.
Authors: Pearce, G.; Harrison, R. A.
1989sasf.confP.161P Altcode: 1989IAUCo.104P.161P; 1988sasf.conf..161P
The authors undertake a statistical analysis of the soft X-ray (3.5
- 5.5 keV) profiles of solar flares as observed with the Hard X-ray
Imaging Spectrometer on the SMM. The durations, maximum intensities and
intensity profiles of the flares are examined. The properties of the
"typical" solar flare are discussed.

---------------------------------------------------------
Title: Comments on coronal mass ejection onset studies
Authors: Harrison, R. A.; Sime, D. G.
1989A&A...208..274H Altcode:
The relationship between solar Coronal Mass Ejections (CMEs) and other
solar activity, such as flares and prominences, is not yet clear. Recent
analyses have highlighted the complexity of the initial stages of
the CME, and this has demanded a reexamination of past studies where
clear relationships were claimed. A number of studies are shown where
preconceived ideas have damaged the interpretation of the data. The
message is one of caution, for both reader and researcher, to recognize
bias in CME analyses.

---------------------------------------------------------
Title: Coronal mass ejections and coronal structures.
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Stewart,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
1989epos.conf..493H Altcode:
The work of this team was concerned with modelling of post-flare arches,
the reconnection theory of flares, the slow variation of coronal
structure, and the coronal and interplanetary detection, evolution,
and consequences of mass ejections.

---------------------------------------------------------
Title: Largescale Magnetic Field Phenomena
Authors: Harrison, R. A.; Bentley, R. D.; Brosius, J.; Dwivedi,
B. N.; Jardine, M.; Klimchuk, J. A.; Kundu, M. R.; Pearce, G.; Saba,
J.; Sakurai, T.; Schmahl, E. J.; Schmelz, J.; Sime, D. G.; Steele,
C. D. C.; Sun, M. T.; Tappin, S. J.; Waljeski, K.; Wang, A. H.; Wu,
S. T.
1989tnti.conf....1H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The solar-stellar connection: the relationship between flaring
rates, flare power and quiescent X-ray background.
Authors: Harrison, R. A.; Pearce, G.; Skumanich, A.
1989sasf.confP..13H Altcode: 1988sasf.conf...13H; 1989IAUCo.104P..13H
The aim of this study is to extend the dMe analysis to the sun, to
explore relationships between the flaring-rate, flare power-loss and
quiescent X-ray luminosity for different solar active regions.

---------------------------------------------------------
Title: CDS: The Coronal Diagnostic Spectrometer
Authors: Patchett, B. E.; Harrison, R. A.; Sawyer, E. C.; Aschenbach,
B.; Culhane, J. L.; Doschek, G. A.; Gabriel, A. H.; Huber, M. C. E.;
Jordan, C.; Kjeldseth-Moe, O.
1988sohi.rept...39P Altcode:
The prime objective of the Coronal Diagnostic Spectrometer (CDS) is to
obtain intensity ratios of selected extreme-ultraviolet line pairs, with
spatial and temporal scales appropriate to the fine-scale features of
the solar atmosphere. This will be done simultaneously across a large
portion of the solar atmosphere. From this, density and temperature
information will be derived which coupled with a modest capability for
the detection of flows will be used to study the energy and mass balance
of the atmosphere. Understanding the heating of the solar corona and the
acceleration of the solar wind are the ultimate goals of this research.

---------------------------------------------------------
Title: A statistical analysis of the soft X-ray profiles of solar
flares
Authors: Pearce, G.; Harrison, R. A.
1988A&A...206..121P Altcode:
The authors undertake a statistical analysis of the soft X-ray (3.5
- 5.5 keV) profiles of solar flares as observed with the Hard X-ray
Imaging Spectrometer on the Solar Maximum Mission. Data are presented
for 59 flares. The durations, maximum intensities and intensity profiles
of the flares are examined. The properties of the "typical" solar flare
are discussed. The distributions of the measured parameters with respect
to one another reveal some interesting results. In common with past
studies, it is concluded that there is no evidence to suggest that more
than one type of event is being viewed, despite a desire evident in the
literature to place events into distinct groups. It is also concluded
that commonly held views about the relationships between flare duration
and intensity, profile asymmetries and intensity etc., are in error.

---------------------------------------------------------
Title: Active Region Coronal Loops: Structure and Variability
Authors: Haisch, Bernhard M.; Strong, Keith T.; Harrison, Richard A.;
Gary, G. A.
1988ApJS...68..371H Altcode:
X-ray images of a pair of active region loops are studied which show
significant, short time-scale variability in the line fluxes of O VIII,
Ne IX, and Mg XI and in the 3.5-11.5 keV soft X-ray bands. Vector
magnetograms and high-resolution UV images were used to model the
three-dimensional characteristics of the loops. X-ray light curves were
generated spanning four consecutive orbits for both loops individually,
and light curves of the loop tops and brightest points were also
generated. The largest variations involve flux changes of up to several
hundred percent on time scales of 10 minutes. No significant H-alpha
flare activity is reported, and loop temperatures remain in the four
to six million K range. The decay phases of the light curves indicate
radiative cooling, inhibition of conduction, and some type of 'continued
heating' due to ongoing, underlying activity at the microflare level.

---------------------------------------------------------
Title: The Solar-Stellar Connection: The Relationship between Flaring
Rates, Flare Power, and Quiescent X-Ray Background
Authors: Harrison, Richard A.; Pearce, Gillian; Skumanich, Andrew
1988ApJ...332.1058H Altcode:
The flaring rates, flare powers, and quiescent X-ray luminosities of dMe
(red dwarf) stars are compared with those of solar active regions. In
dMe stars, these properties are found to be closely related, and this
may have a significant influence on the understanding of the flare
process and coronal heating. For example, a correlation between flare
rate and quiescent X-ray luminosity suggests that both may be driven
by similar processes on a differing scale. It is a natural extension
of this work to investigate similar relationships for the sun. The
results are mixed. The relationships between the various parameters
are certainly not as clear for the sun as for the dMe stars. Some solar
properties appear to vary in a manner similar to the dMe analysis, and
some contradict the dMe case. The implications of this are discussed.

---------------------------------------------------------
Title: X-ray emission associated with solar prominences, sprays
and surges
Authors: Harrison, R. A.; Rompolt, B.; Garczynska, I.
1988SoPh..116...61H Altcode:
Using Hα observations made at the Astronomical Observatory of Wroclaw
University, and 3.5-5.5 keV X-ray data from the Hard X-ray Imaging
Spectrometer on board the Solar Maximum Mission, sites of solar X-ray
emission are identified which are associated with active Hα features,
such as prominences, sprays and surges. The X-ray emission is found to
be highly localized within the active (Hα) structures. For example,
in the prominences examined, 3.5-5.5 keV X-rays were found only in
compact sites near the feet of the prominences. Models predicting that,
during the active phase of these structures, the energy release should
be evenly distributed along the structure are clearly brought into
question. It is argued that these X-ray sites are indicative of the
cause of the expulsion and transport of chromospheric material. Models
which satisfy these observations are discussed.

---------------------------------------------------------
Title: A glimpse at the complexity and role of solar coronal mass
ejections, through the analysis of one event.
Authors: Harrison, R. A.
1988hmas.conf...81H Altcode:
The Mk III K-Coronameter on Mauna Loa (Hawaii) operates with a
fundamentally different approach to the traditional coronagraph and
has been able to observe coronal mass ejections (CMEs) down to ≡0.2
Rsun above the solar limb. A recent inspection of the Mk
III K-Coronameter data revealed a particularly well viewed event on
August 8, 1980. The author describes this event in detail, as a way
of illustrating the complexity of the CME problem and to highlight
the role of the CME in solar activity.

---------------------------------------------------------
Title: Solar soft X-ray pulsations
Authors: Harrison, R. A.
1987A&A...182..337H Altcode:
Using data from the Hard X-ray Imaging Spectrometer on the Solar Maximum
Mission, soft X-ray (3.5 - 5.5 keV) pulsations are identified, which
originate from a compact active region which lies at one footpoint of
a large coronal loop. It is believed that this is the first report of
soft X-ray pulsations from the non-flaring sun. The pulsations were
of period 24 min and were detected for six hours. The periodicity is
thought to be produced by a standing wave or a travelling wave "packet"
which exists within the loop. The candidates for the wave are fast or
Alfvén MHD modes of Alfvénic surface waves.

---------------------------------------------------------
Title: Interplanetary Effects of Coronal Mass Ejections
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
1986epos.conf.6.52H Altcode: 1986epos.confF..52H
No abstract at ADS

---------------------------------------------------------
Title: Initiations of Coronal Mass Ejections
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
1986epos.conf.6.27H Altcode: 1986epos.confF..27H
No abstract at ADS

---------------------------------------------------------
Title: Coronal manifestations of preflare activity
Authors: Schmahl, E. J.; Webb, D. F.; Woodgate, B.; Waggett, P.;
Bentley, R.; Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.;
Martens, P.
1986epos.conf.1.48S Altcode: 1986epos.confA..48S
A variety of coronal manifestations of precursors or preheating for
flares are discussed. Researchers found that almost everyone with a
telescope sees something before flares. Whether an all-encompassing
scenario will ever be developed is not at all clear at present. The
clearest example of preflare activity appears to be activated filaments
and their manifestations, which presumably are signatures of a changing
magnetic field. But researchers have seen two similar eruptions, one
without any evidence of emerging flux (Kundu et al., 1985) and the
other with colliding poles (Simon et al., 1984). While the reconnection
of flux is generally agreed to be required to energize a flare, the
emergence of flux from below (at least on short timescales and in
compact regions) does not appear to be a necessary condition. In some
cases the cancelling of magnetic flux (Martin, 1984) by horizontal
motions instead may provide the trigger (Priest, 1985) Researchers
found similarities and some differences between these and previous
observations. The similarities, besides the frequent involvement of
filaments, include compact, multiple precursors which can occur both at
and near (not at) the flare site, and the association between coronal
sources and activity lower in the atmosphere (i.e., transition zone
and chromosphere).

---------------------------------------------------------
Title: The Slowly Varying Corona Near Solar Activity Maximum
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
1986epos.conf.6.57H Altcode: 1986epos.confF..57H
No abstract at ADS

---------------------------------------------------------
Title: Modelling of Coronal Mass Ejections and POST Flare Arches
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
1986epos.conf6.366H Altcode: 1986epos.confF.366H
No abstract at ADS

---------------------------------------------------------
Title: Coronal mass ejections and coronal structures
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.
1986epos.conf..6.1H Altcode: 1986epos.confF...1H
Research on coronal mass ejections (CMF) took a variety of forms, both
observational and theoretical. On the observational side there were:
case studies of individual events, in which it was attempted to provide
the most complete descriptions possible, using correlative observations
in diverse wavelengths; statistical studies of the properties CMEs and
their associated activity; observations which may tell us about the
initiation of mass ejections; interplanetary observations of associated
shocks and energetic particles even observations of CMEs traversing
interplanetary space; and the beautiful synoptic charts which show to
what degree mass ejections affect the background corona and how rapidly
(if at all) the corona recovers its pre-disturbance form. These efforts
are described in capsule form with an emphasis on presenting pictures,
graphs, and tables so that the reader can form a personal appreciation
of the work and its results.

---------------------------------------------------------
Title: Spectral Line Profiles of Fe XXI 1354.1 Angstrom from the
Solar Maximum Mission
Authors: Mason, H. E.; Shine, R. A.; Gurman, J. B.; Harrison, R. A.
1986ApJ...309..435M Altcode:
Observations of the Fe XXI 1354.1 A line were obtained for several
flares using the SMM-UVSP instrument with varying spectral and spatial
resolution. Of special interest are spectral line profiles from the
footpoints of flare loops taken during the impulsive phase. These
data show blueshifted Fe XXI profiles coincident and cospatial with
the impulsive brightening of chromospheric material. The present
analysis supports the hypothesis that the blueshifted component of the
high temperature emission is an integral part of the flare, possibly
associated with chromospheric evaporation.

---------------------------------------------------------
Title: Solar coronal mass ejections and flares
Authors: Harrison, R. A.
1986A&A...162..283H Altcode:
Recent work has indicated that a solar coronal mass ejection begins to
rise during a weak, soft X-ray burst which often precedes a flare by
several tens of minutes. Using data from the Coronagraph/Polarimeter
and the Hard X-ray Imaging Spectrometer, both on board the Solar Maximum
Mission, it is shown that the burst originates from a coronal arch which
has a very close spatial relationship to the loop-like features of the
coronal mass ejection. The data suggest, in fact, that the ejection
arises directly from a destabilization or lack of equilibrium reached
by the arch. For the three examples discussed, with both X-ray and
coronagraph observations, a subsequent flare occurs in one foot of
the arch indicating a flare-ejection asymmetry. This asymmetry is
common in examples of flare associated coronal mass ejections that
can be found in the literature. The data suggest a picture which is
inconsistent with most models of the mass ejection phenomenon.

---------------------------------------------------------
Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
1986NASCP2439....1P Altcode:
Contents: 1. Introduction: the preflare state - a review of previous
results. 2. Magnetohydrodynamic instability: magnetic reconnection,
nonlinear tearing, nonlinear reconnection experiments, emerging flux and
moving satellite sunspots, main phase reconnection in two-ribbon flares,
magnetic instability responsible for filament eruption in two-ribbon
flares. 3. Preflare magnetic and velocity fields: general morphology of
the preflare magnetic field, magnetic field shear, electric currents in
the preflare active region, characterization of the preflare velocity
field, emerging flux. 4. Coronal manifestations of preflare activity:
defining the preflare regime, specific illustrative events, comparison
of preflare X-rays and ultraviolet, preflare microwave intensity and
polarization changes, non-thermal precursors, precursors of coronal
mass ejections, short-lived and long-lived HXIS sources as possible
precursors.

---------------------------------------------------------
Title: Coronal mass ejections and coronal structures.
Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.;
Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing,
R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos,
P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Stewart,
R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T.
1986NASCP2439....6H Altcode:
Contents: 1. Introduction. 2. Observations. 3. Initiation of
coronal mass ejections - observations. 4. Modelling of coronal mass
ejections and post-flare arches. 5. Interplanetary effects of coronal
mass ejections. 6. The slowly varying corona near solar activity
maximum. 7. Summary.

---------------------------------------------------------
Title: The Onset of Coronal Mass Ejections
Authors: Simnett, G. M.; Harrison, R. A.
1985SoPh...99..291S Altcode:
This study addresses the onset of coronal mass ejections. From
examination of sensitive X-ray images from the Solar Maximum
Mission around the projected onset time of coronal mass ejections
we identify two important new features: (1) there is usually a weak,
soft X-ray enhancement 15-30 min prior to the linearly extrapolated
chromospheric departure time of the ejection; (2) this activity is
generally from two widely separated (≥ 105 km) parts
of the Sun. Possible physical mechanisms for these phenomena are
examined and it is concluded that a plausible explanation is that
the initial energy release is converted first into kinetic energy of
suprathermal protons, 102-103 keV. The protons
are trapped in a large magnetic loop which later breaks open as the
mass ejection; Coulomb losses are the destabilizing agent but the
mass ejection is probably magnetically driven. Protons that escape
into the loss cone will impact the loop footpoints to heat the upper
chromospheric material to a sufficiently high temperature to generate
the weak soft X-ray emission. There will also be an Hα signature,
and this is observed in a number of events. There is in general no
radio emission or hard X-ray emission accompanying the soft X-ray
precursor. When the coronal mass ejection is followed by a flare,
then this is generally from a point close to, but not identical to,
one of the points with the earlier soft X-ray enhancement.

---------------------------------------------------------
Title: The X-Ray Signature of Solar Coronal Mass Ejections
Authors: Harrison, R. A.; Waggett, P. W.; Bentley, R. D.; Phillips,
K. J. H.; Bruner, M.; Dryer, M.; Simnett, G. M.
1985SoPh...97..387H Altcode:
The coronal response to six solar X-ray flares has been investigated. At
a time coincident with the projected onset of the white-light coronal
mass ejection associated with each flare, there is a small, discrete
soft X-ray enhancement. These enhancements (precursors) precede by
typically ∼20 m the impulsive phase of the solar flare which is
dominant by the time the coronal mass ejection has reached an altitude
above 0.5 R⊙. We identify motions of hot X-ray emitting
plasma, during the precursors, which may well be a signature of the
mass ejection onsets. Further investigations have also revealed a
second class of X-ray coronal transient, during the main phase of the
flare. These appear to be associated with magnetic reconnection above
post-flare loop systems.

---------------------------------------------------------
Title: White Light and X-ray Studies of the Coronal Mass Ejection
Onset Phase
Authors: Harrison, R. A.
1985BAAS...17..636H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The X-ray signature of solar coronal mass ejections.
Authors: Harrison, R. A.; Waggett, P. W.; Bentley, R. D.; Phillips,
K. J. H.; Bruner, M.; Dryer, M.; Simnett, G. M.
1985RALR...84.....H Altcode:
The coronal response to six solar X-ray flares has been investigated. At
a time coincident with the projected onset of the white-light coronal
mass ejection with each flare, there is a small, discrete soft X-ray
enhancement. These enhancements (precursors) precede by typically
≡20 m the impulsive phase of the solar flare which is dominant by
the time the coronal mass ejection has reached an altitude above 0.5
R_sun;. The authors identify motions of hot X-ray emitting plasma,
during the precursors, which may well be a signature of the mass
ejection onsets. Further investigations have also revealed a second
class of X-ray coronal transients, during the main phase of the
flare. These appear to be associated with magnetic reconnection above
post-flare loop systems.

---------------------------------------------------------
Title: A study of the morphology of solar flares as observed by the
hard X-ray imaging spectrometer.
Authors: Harrison, R. A.; Simnett, G. M.
1984ESASP.220..281H Altcode: 1984ESPM....4..281H
The authors have conducted an analysis of solar flares in the 3.5 -
30 keV energy region. They show that the majority of flares appear to
conform to the following scenario: in 3.5 - 30 keV X-rays, the impulsive
burst defines a system of low lying coronal magnetic loops. The soft
X-ray (&lt;10 keV) flare subsequently expands into a larger, well
resolved loop system and frequently an even larger overlying structure
is involved with footpoints separated by several hundred thousand km.

---------------------------------------------------------
Title: Do all flares occur within a hierarchy of magnetic loops?
Authors: Harrison, R. A.; Simnett, G. M.
1984AdSpR...4g.199H Altcode: 1984AdSpR...4..199H
X-ray events observed by the Hard X-ray Imaging Spectrometer on the
Solar Maximum Mission frequently indicate the following scenario for
solar flares: The initial energy release occurs in a compact magnetic
loop and during the impulsive phase may spread rapidly to involve a
larger structure. In later phases the soft X-ray emission is from
a much larger structure encompassing these initial features and,
overlying them all is a huge loop with footpoints separated by up
to several hundred thousand km. In the light of these observations,
we believe a flare model involving a single magnetic loop is rarely,
if ever appropriate.

---------------------------------------------------------
Title: Hard X-Ray Studies of the Large Coronal Feature on June
29, 1980
Authors: Harrison, R. A.; Simnett, G. M.; Hoyng, P.; Lafleur, H.;
van Beek, H. F.
1984sii..conf..287H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Advanced regenerative environmental control and life support
systems: Air and water regeneration
Authors: Simnett, G. M.; Harrison, R. A.
1984AdSpR...4g.279S Altcode: 1984AdSpR...4..279S
Extended manned space missions will require regenerative life support
techniques. Past U.S. manned missions used nonregenerative expendables,
except for a molecular sieve-based carbon dioxide removal system
aboard Skylab. The resupply penalties associated with expendables
becomes prohibitive as crew size and mission duration increase. The
U.S. Space Station, scheduled to be operational in the 1990's, is
based on a crew of four to sixteen and a resupply period of 90 days or
greater. It will be the first major spacecraft to employ regenerable
techniques for life support. The paper uses the requirements for the
Space Station to address these techniques.

---------------------------------------------------------
Title: Evidence for Extensive Magnetic Structures Between Two Active
Regions from Studies of Flares on June 24, 1980
Authors: Simnett, G. M.; Harrison, R. A.; Hoyng, P.; van Beek, H. F.
1984sii..conf..273S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The structure and evolution of a solar flare as observed in
3.5 30 keV X-rays
Authors: Harrison, R. A.; Simnett, G. M.; Hoyng, P.; Lafleur, H.;
van Beek, H. F.
1983SoPh...84..237H Altcode:
On July 5, 1980 the Hard X-Ray Imaging Spectrometer on board the Solar
Maximum Mission observed a complex flare event starting at 22 : 32 UT
from AR 2559 (Hale 16955), then at N 28 W 29, which developed finally
into a 2-ribbon flare. In this paper we compare the X-ray images with
Hα photographs taken at the Big Bear Solar Observatory and identify
the site of the most energetic flare phenomena. During the early
phases of the event the hard X-rays (&gt;16 keV) came from a compact
source located near one of the two bright Hα kernels; we believe the
latter are at the footpoints of a compact magnetic loop. The kernel
identified with the X-ray source is immediately adjacent to one of the
principal sunspots and in fact appears to `rotate' around the sunspot
over 90° in the early phase of the flare. Two intense X-ray bursts
occur at the site of the rotating kernel, and following each burst
the loop fills with hot, X-ray emitting plasma. If the first burst is
interpreted as bremsstrahlung from a beam of electrons impinging on a
collisionally dominated medium, the energy in such electrons, &gt;16
keV, is ∼ 5 × 1030 erg. The altitude of the looptop is
7-10 × 103 km. The temperature structure of the flare is
extremely non-homogeneous, and the highest temperatures are found in
the top of the loop.

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Title: Multifarious Spatial Structure in a Compact Hard X-Ray Flare
Authors: Harrison, R. A.; Vanbeek, H. F.; Hoyng, P.; Lafleur, H.;
Simnett, G. M.
1980BAAS...12..911H Altcode:
No abstract at ADS

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Title: A Study of the Impulsive Flares and Homologous Flares From
AR2372 From April 6-13, Using Hard X-Ray Images
Authors: Simnett, G. M.; Machado, M.; Harrison, R. A.; Hoyng, P.;
Lafleur, H.; Svestka, Z.; Vanbeek, H. F.
1980BAAS...12S.899S Altcode:
No abstract at ADS