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.
Bibcode: 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.
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.
Bibcode: 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.
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.
Bibcode: 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.
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.
Bibcode: 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.
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.
Bibcode: 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.
Title: Exploring the dynamics of inward core solidification using
analogue tank experiments.
Authors: Dodds, Kathryn; Bryson, James; Neufeld, Jerome; Harrison,
Richard
Bibcode: 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.
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.
Bibcode: 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.
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
Bibcode: 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.
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.
Bibcode: 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.
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
Bibcode: 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.
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
Bibcode: 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.
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
Bibcode: 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.
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.
Bibcode: 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.
Title: IPSCAT: A Catalogue of Solar Transients Identified through
Interplanetary Scintillation Analysis
Authors: Barnes, David; Bisi, Mario; Davies, Jackie; Harrison, Richard
Bibcode: 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/).
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.
Bibcode: 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.
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
Bibcode: 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).
Title: Space Weather Awareness, Engagement, and Outreach Activities
at UKRI STFC RAL Space
Authors: Bisi, Mario M.; Hapgood, Mike; Harrison, Richard
Bibcode: 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.
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.
Bibcode: 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.
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.
Bibcode: 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.
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.
Bibcode: 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.
Title: IPSCAT: A Catalogue of Solar Transients Identified through
Interplanetary Scintillation Analysis
Authors: Barnes, D.; Bisi, M. M.; Davies, J. A.; Harrison, R. A.
Bibcode: 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.
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.
Bibcode: 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.
Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
Bibcode: 2020A&A...642A..14S
Altcode: 2019arXiv190901183A; 2019arXiv190901183S
Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission.
Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal.
Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing.
Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.
Title: The Solar Orbiter 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.
Bibcode: 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.
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.
Bibcode: 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.
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
Bibcode: 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.
Title: A Catalogue of Coronal Mass Ejections Observed by the
Heliospheric Imagers throughout the STEREO Mission
Authors: Barnes, David; Davies, Jackie; Harrison, Richard
Bibcode: 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.
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
Bibcode: 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.
Title: From heliophysics to space weather forecasts
Authors: Harrison, Richard; Davies, Jackie; Rae, Jonny
Bibcode: 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.
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.
Bibcode: 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.
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
Bibcode: 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.
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.
Bibcode: 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
Bibcode: 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.
Title: Space weather in the UK
Authors: Bisi, Mario; Hapgood, Mike; Bisi, Mario M.; Harrison, Richard
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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
Bibcode: 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
Bibcode: 2018EGUGA..20.7441B
Altcode:
The EU FP7 project HELCATS (HELIOSPHERIC CATALOGUING, ANALYSIS &
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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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
& 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
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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” (ApJ, 824,
2, 131)
Authors: Amerstorfer, T.; Möstl, C.; Isavnin, A.; Davies, J. A.;
Kubicka, M.; Amerstorfer, U. V.; Harrison, R. A.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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
Bibcode: 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
Bibcode: 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.
Bibcode: 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
Bibcode: 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
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
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.
Bibcode: 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.
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
Bibcode: 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.
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.
Bibcode: 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.
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
Bibcode: 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 <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 >20 µT over a period of ~4 -
10 Myr. The Imilac meteorite recorded a stronger field between 120 -
130 µT over a period of <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.
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
Bibcode: 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 & 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.
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.
Bibcode: 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.
Bibcode: 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.
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.
Bibcode: 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.
Bibcode: 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.
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.
Bibcode: 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 (<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
(>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.
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.
Bibcode: 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.
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
Bibcode: 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.
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.
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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 >30° elongation to obtain arrival time errors < ± 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 2010arXiv1011.4052L
Altcode:
We present the science case for a broadband X-ray imager with
high-resolution spectroscopy, including simulations of X-ray spectral
diagnostics of both active regions and solar flares. This is part of
a trilogy of white papers discussing science, instrument (Bandler et
al. 2010), and missions (Bookbinder et al. 2010) to exploit major
advances recently made in transition-edge sensor (TES) detector
technology that enable resolution better than 2 eV in an array that
can handle high count rates. Combined with a modest X-ray mirror, this
instrument would combine arcsecondscale imaging with high-resolution
spectra over a field of view sufficiently large for the study of
active regions and flares, enabling a wide range of studies such as
the detection of microheating in active regions, ion-resolved velocity
flows, and the presence of non-thermal electrons in hot plasmas. It
would also enable more direct comparisons between solar and stellar
soft X-ray spectra, a waveband in which (unusually) we currently have
much better stellar data than we do of the Sun.
Title: 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.
Bibcode: 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
<105 km to >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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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 (> 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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
Bibcode: 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.
Bibcode: 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
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.
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.
Bibcode: 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.
Bibcode: 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.
Bibcode: 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.