bewsher

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Author name code: bewsher
ADS astronomy entries on 2022-09-14
author:"Bewsher, Danielle"

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Title: Evidence for conservative mass transfer in the classical Algol
system δ Librae from its surface carbon-to-nitrogen abundance ratio
Authors: Dervişoǧlu, A.; Pavlovski, K.; Lehmann, H.; Southworth,
J.; Bewsher, D.
2018MNRAS.481.5660D Altcode: 2018MNRAS.tmp.2565D; 2018arXiv181001465D
Algol-type binary systems are the product of rapid mass transfer between
the initially more massive component to its companion. It is still
unknown whether the process is conservative, or whether substantial mass
is lost from the system. The history of a system prior to mass exchange
is imprinted in the photospheric chemical composition, in particular in
the carbon-to-nitrogen (C/N) ratio. We use this to trace the efficiency
of mass-transfer processes in the components of a classical Algol-type
system, δ Librae. The present analysis is based on new spectroscopic
data (ground-based high-resolution échelle spectra) and extracted
archival photometric observations (space-based measurements from the
STEREO satellites). In the orbital solution, non-Keplerian effects on
the radial-velocity variations were taken into account. This reduces
the primary's mass by 1.1 M_⊙ (∼23 per cent) significantly in
comparison to previous studies, and removes a long-standing discrepancy
between the radius and effective temperature. A spectral disentangling
technique is applied to the échelle observations and the spectra of
the individual components are separated. Atmospheric and abundance
analyses are performed for the mass-gaining component and we found C/N
=1.55 ± 0.40 for this star. An extensive set of evolutionary models
(3.5 × 106) for both components are calculated from which
the best-fitting model is derived. It is found that β, the parameter
that quantifies the efficiency of mass-loss from a binary system, is
close to zero. This means that the mass transfer in δ Lib is mostly
conservative with little mass-loss from the system.

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Title: The first study of 54 new eccentric eclipsing binaries in
our Galaxy
Authors: Zasche, P.; Wolf, M.; Uhlař, R.; Cagaš, P.; Juryšek, J.;
Mašek, M.; Hoňková, K.; Kučáková, H.; Lehký, M.; Kotková,
L.; White, G. J.; Bewsher, D.; Tylšar, M.; Jelínek, M.; Paschke, A.
2018A&A...619A..85Z Altcode: 2018arXiv181108471Z
We present an analysis of the apsidal motion and light curve parameters
of 54 never-before-studied galactic Algol-type binaries. This is the
first analysis of such a large sample of eccentric eclipsing binaries
in our Galaxy, and has enabled us to identify several systems that are
worthy of further study. Bringing together data from various databases
and surveys, supplemented with new observations, we have been able to
trace the long-term evolution of the eccentric orbit over durations
extending back up to several decades. Our present study explores a
rather different sample of stars to those presented in the previously
published catalogue of eccentric eclipsing binaries, sampling to fainter
magnitudes, covering later spectral types, sensitive to different
orbital periods with more than 50% of our systems having periods longer
than six days. The typical apsidal motion in the sample is rather slow
(mostly of order of centuries long), although in some cases this is
less than 50 yr. All of the systems, except one, have eccentricities
less than 0.5, with an average value of 0.23. Several of the stars
also show evidence for additional period variability. In particular we
can identify three systems in the sample, HD 44093, V611 Pup, and HD
313631, which likely represent relativistic apsidal rotators. The
full Table 1 is only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/A85">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/619/A85</A>

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Title: VizieR Online Data Catalog: 54 new eccentric galactic eclipsing
binaries (Zasche+, 2018)
Authors: Zasche, P.; Wolf, M.; Uhlar, R.; Cagas, P.; Jurysek, J.;
Masek, M.; Honkova, K.; Kucakova, H.; Lehky, M.; Kotkova, L.; White,
G. J.; Bewsher, D.; Tylsar, M.; Jelinek, M.; Paschke, A.
2018yCat..36190085Z Altcode:
We have derived the preliminary apsidal motion and light curve
parameters for 54 Algol-type binaries. This is the first time any such
analysis of such a large sample of eccentric eclipsing binaries has been
studied in our Galaxy using different sources of photometry. Bringing
together data from various databases and surveys has facilitated
estimation of the long-term evolution of the orbit and the apsidal
precession of our sample. (2 data files).

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Title: Temporal resolution of a pre-maximum halt in a classical nova:
V5589 Sgr observed with STEREO HI-1B
Authors: Eyres, S. P. S.; Bewsher, D.; Hillman, Y.; Holdsworth, D. L.;
Rushton, M. T.; Bresnahan, D.; Evans, A.; Mróz, P.
2017MNRAS.467.2684E Altcode: 2017arXiv170109026E
Classical novae show a rapid rise in optical brightness over a few
hours. Until recently the rise phase, particularly the phenomenon
of a pre-maximum halt, was observed sporadically. Solar observation
satellites observing coronal mass ejections enable us to observe the
pre-maximum phase in unprecedented temporal resolution. We present
observations of V5589 Sgr with STEREO HI-1B at a cadence of 40 min,
the highest to date. We temporally resolve a pre-maximum halt for the
first time, with two examples each rising over 40 min then declining
within 80 min. Comparison with a grid of outburst models suggests
that this double peak, and the overall rise time-scale, is consistent
with a white dwarf mass, central temperature and accretion rate close
to 1.0 M⊙, 5 × 107 K and 10-10
M⊙ yr-1, respectively. The modelling formally
predicts mass-loss onset at JD 245 6038.2391 ± 0.0139, 12 h before the
optical maximum. The model assumes a main-sequence donor. Observational
evidence is for a subgiant companion, meaning that the accretion
rate is underestimated. Post-maximum, we see erratic variations
commonly associated with much slower novae. Estimating the decline
rate is difficult, but we place the time to decline two magnitudes as
2.1 &lt; t2(d) &lt; 3.9, making V5589 Sgr a 'very fast'
nova. The brightest point defines 'day 0' as JD 245 6038.8224 ±
0.0139, although at this high cadence the meaning of the observed
maximum becomes difficult to define. We suggest that such erratic
variability normally goes undetected in faster novae due to the low
cadence of typical observations, implying that erratic behaviour is
not necessarily related to the rate of decline.

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Title: Mapping the circumsolar dust ring near the orbit of Venus
Authors: Jones, M. H.; Bewsher, D.; Brown, D. S.
2017Icar..288..172J Altcode:
Synoptic images obtained from the HI-2 instrument on STEREO-A and
-B between 2007 and 2014 have been used to further investigate the
circumsolar dust ring at the orbit of Venus that was reported by Jones
et al. (2013). The analysis is based on high signal-to-noise ratio
photometry of the zodiacal light, using data acquired over 10-day
intervals, followed by a process of extracting spatial variability on
scales up to about 6.5°. The resulting images provide information
about the structure of the ring at the location where it is viewed
tangentially. We identify 65 usable data sets that comprise about 11%
of the available HI-2 data. Analysis of these images show that the
orientation of the ring appears to be different to that of the orbit of
Venus, with an inclination of 2.1° and longitude of ascending node of
68.5°. We map the variation of ring density parameters in a frame of
reference that is co-rotating with Venus and find a pattern suggestive
of dust in a 3: 2 orbital resonance. However, the location of the
maxima of dust densities is not as expected from theoretical models,
and there is some evidence that the dust density distribution in the
ring has a pattern speed that differs from the mean motion of Venus.

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Title: Nova Light Curves From The Solar Mass Ejection Imager (SMEI)
- II. The extended catalog
Authors: Hounsell, R.; Darnley, M. J.; Bode, M. F.; Harman, D. J.;
Surina, F.; Starrfield, S.; Holdsworth, D. L.; Bewsher, D.; Hick,
P. P.; Jackson, B. V.; Buffington, A.; Clover, J. M.; Shafter, A. W.
2016ApJ...820..104H Altcode: 2015arXiv151203321H
We present the results from observing nine Galactic novae in eruption
with the Solar Mass Ejection Imager (SMEI) between 2004 and 2009. While
many of these novae reached peak magnitudes that were either at
or approaching the detection limits of SMEI, we were still able
to produce light curves that in many cases contained more data at
and around the initial rise, peak, and decline than those found in
other variable star catalogs. For each nova, we obtained a peak time,
maximum magnitude, and for several an estimate of the decline time
({t}{{2}}). Interestingly, although of lower quality than
those found in Hounsell et al., two of the light curves may indicate
the presence of a pre-maximum halt. In addition, the high cadence
of the SMEI instrument has allowed the detection of low-amplitude
variations in at least one of the nova light curves.

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Title: Imaging and mapping the circumsolar dust ring near the orbit
of Venus
Authors: Jones, M.; Bewsher, D.; Brown, D.
2014acm..conf..250J Altcode:
Asteroids and comets are the dominant source of dust feeding the
zodiacal cloud [1,2]. The orbits of grains of size 10--100 microns
are expected to decay by Poynting-Robertson drag [3], but in the
vicinity of planetary orbits dust may get trapped into exterior mean
motion resonances [4] to form a circumsolar dust ring. It has long
been known that such a ring exists close to the Earth's orbit [5],
but even now, little is known about its detailed structure. No such
ring or associated resonance feature has been detected at the orbits
of Mars or Jupiter [6]. While re-analysis of photometry data from
the Helios mission provided some evidence of a ring associated with
Venus [7], the existence of such a ring could not be conclusively
demonstrated. Here we report on recent work that confirms
the existence of a circumsolar ring at Venus from sensitive optical
photometry of the zodiacal cloud [8]. Our analysis uses synoptic images
from the HI-2 instrument on STEREO [9]. We discuss the techniques that
we have developed to extract images of the Venus ring, and describe
the approach taken towards creating a simple parametric model of the
ring. We note that the maximum over-density in the ring is about 10%
that of the smooth zodiacal cloud, and we highlight other aspects of
the ring structure that we have already determined. We demonstrate
that the STEREO HI-2 data allow the density structure of the Venus
ring to be mapped in much greater detail than the Earth ring. Thus the
Venus ring has the potential to provide a stringent test of models of
resonance ring formation. Not only is this relevant to understanding
the structure of the zodiacal cloud, it is of importance in the context
of exoplanetary systems which are also expected to display analogous
circumstellar dust rings [10,11]. We conclude by discussing current
progress in mapping the density distribution of the Venus circumsolar
ring.

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Title: STEREO/HI and optical observations of the classical nova
V5583 Sagittarii
Authors: Holdsworth, Daniel L.; Rushton, M. T.; Bewsher, D.; Walter,
F. M.; Eyres, S. P. S.; Hounsell, R.; Darnley, M. J.
2014MNRAS.438.3483H Altcode: 2014MNRAS.tmp..110H; 2013arXiv1312.5235H
The classical nova V5583 Sgr (Nova Sagittarii 2009 No 3)
has been observed during the rise phase and shortly after by NASA's
Solar TErrestrial RElations Observatory/Heliospheric Imager (STEREO/HI)
instruments, with later optical spectroscopy obtained with the R-C
Spectrograph at Cerro Tololo Inter-American Observatory, Chile. The
time of peak in the STEREO passband has been constrained to within 4
h, as a result of the high cadence data obtained by STEREO/HI. The
optical spectra show the nova evolving from the permitted to the
nebular phases. The neon abundance in the ejecta is [Ne/O] ≳ +1.0,
which suggests that V5583 Sgr was most likely a neon nova.

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Title: VizieR Online Data Catalog: STEREO non-magnetic chemically
peculiar stars (Paunzen+, 2013)
Authors: Paunzen, E.; Wraight, K. T.; Fossati, L.; Netopil, M.; White,
G. J.; Bewsher, D.
2014yCat..74290119P Altcode:
We have analysed the photometric data obtained with the STEREO
spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search
for rotational and pulsational variability. Applying the Lomb-Scargle
and the phase dispersion minimization methods, we have detected
photometric variability for 44 objects from which 35 were previously
unknown. The new objects are all bright stars on the ecliptic plane
(magnitude range 4.7&lt;V&lt;11.7) and will therefore be of great
interest to studies of stellar structure and evolution. In particular,
several show multiple signals consistent with hybrid δ Scuti and
γ Doradus pulsation, with different periodicities allowing very
different regions of the stellar interior to be studied. There are two
subgroups of stars in our sample: the cool metallic line Am (CP1) and
the hot HgMn (CP3) stars. These objects fall well inside the classical
instability strip where δ Scuti, γ Doradus and slowly pulsating
B-type stars are located. We also expect to find periods correlated
to the orbital period for CP1 objects as they are mostly members
of binary systems. For CP3 stars, rotationally induced variability
is still a matter of debate. Although surface spots were detected,
they are believed to produce only marginal photometric amplitudes. So,
periods from several hours to a few days were expected for these two
star groups. The STEREO/HI-1 data are well matched to studies of this
frequency domain, owing to the cadence of approximately 40-min and
multiple epochs over four and a half years. The remaining 514 stars are
likely to be constant in the investigated range from 0.1 to 10d. In
some cases, the presence of blending or systematic effects prevented
us from detecting any reliable variability and in those cases we
classified the star as constant. We discuss our results in comparison
to already published ones and find a very good agreement. Finally,
we have calibrated the variable stars in terms of the effective
temperature and luminosity in order to estimate masses and ages. For
this purpose, we used specifically developed calibrations for CP stars
and, when available, Hipparcos parallaxes. All but two objects cover
the stellar mass range from 1.5 to 5M⊙ and are located
between the zero- and terminal-age main sequence. (3 data files).

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Title: VizieR Online Data Catalog: STEREO magnetic chemically peculiar
stars (Wraight+, 2012)
Authors: Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.;
Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, G. J.
2014yCat..74200757W Altcode:
The stars were observed with the STEREO/HI-1 imager, on board of
the Stereo satellites, launched primarily to observe the coronal
mass ejections. The field of view is 20x20°, with a resolution
of 70arcsec/pix. mostly in the 630-730nm wavelength range. Over the
course of an orbit, almost 900,000 stars of 12th magnitude and brighter
are imaged within 10° of the ecliptic plane, at a cadence of about
40min. (3 data files).

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Title: Imaging of a Circumsolar Dust Ring Near the Orbit of Venus
Authors: Jones, M. H.; Bewsher, D.; Brown, D. S.
2013Sci...342..960J Altcode:
The gravitational interaction of dust in the zodiacal cloud with
individual planets is expected to give rise to ringlike features:
Such a circumsolar ring has been observed associated with Earth,
but such resonance rings have not been confirmed to exist for other
planets. Here, we report on sensitive photometric observations, based
on imaging from the STEREO mission, that confirm the existence of a
dust ring at the orbit of Venus. The maximum overdensity of dust in
this ring, compared to the zodiacal cloud, is ~10%. The radial density
profile of this ring differs from the model used to describe Earth’s
ring in that it has two distinct steplike components, with one step
being interior and the other exterior to the orbit of Venus.

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Title: On-Orbit Degradation of Solar Instruments
Authors: BenMoussa, A.; Gissot, S.; Schühle, U.; Del Zanna, G.;
Auchère, F.; Mekaoui, S.; Jones, A. R.; Walton, D.; Eyles, C. J.;
Thuillier, G.; Seaton, D.; Dammasch, I. E.; Cessateur, G.; Meftah,
M.; Andretta, V.; Berghmans, D.; Bewsher, D.; Bolsée, D.; Bradley,
L.; Brown, D. S.; Chamberlin, P. C.; Dewitte, S.; Didkovsky, L. V.;
Dominique, M.; Eparvier, F. G.; Foujols, T.; Gillotay, D.; Giordanengo,
B.; Halain, J. P.; Hock, R. A.; Irbah, A.; Jeppesen, C.; Judge,
D. L.; Kretzschmar, M.; McMullin, D. R.; Nicula, B.; Schmutz, W.;
Ucker, G.; Wieman, S.; Woodraska, D.; Woods, T. N.
2013SoPh..288..389B Altcode: 2013arXiv1304.5488B
We present the lessons learned about the degradation observed in
several space solar missions, based on contributions at the Workshop
about On-Orbit Degradation of Solar and Space Weather Instruments
that took place at the Solar Terrestrial Centre of Excellence (Royal
Observatory of Belgium) in Brussels on 3 May 2012. The aim of this
workshop was to open discussions related to the degradation observed
in Sun-observing instruments exposed to the effects of the space
environment. This article summarizes the various lessons learned
and offers recommendations to reduce or correct expected degradation
with the goal of increasing the useful lifespan of future and ongoing
space missions.

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Title: A photometric study of chemically peculiar stars with the
STEREO satellites - II. Non-magnetic chemically peculiar stars
Authors: Paunzen, E.; Wraight, K. T.; Fossati, L.; Netopil, M.; White,
G. J.; Bewsher, D.
2013MNRAS.429..119P Altcode: 2012arXiv1211.1535P
We have analysed the photometric data obtained with the STEREO
spacecraft for 558 non-magnetic chemically peculiar (CP) stars to search
for rotational and pulsational variability. Applying the Lomb-Scargle
and the phase dispersion minimization methods, we have detected
photometric variability for 44 objects from which 35 were previously
unknown. The new objects are all bright stars on the ecliptic plane
(magnitude range 4.7 &lt; V &lt; 11.7) and will therefore be of great
interest to studies of stellar structure and evolution. In particular,
several show multiple signals consistent with hybrid δ Scuti and
γ Doradus pulsation, with different periodicities allowing very
different regions of the stellar interior to be studied. There are two
subgroups of stars in our sample: the cool metallic line Am (CP1) and
the hot HgMn (CP3) stars. These objects fall well inside the classical
instability strip where δ Scuti, γ Doradus and slowly pulsating
B-type stars are located. We also expect to find periods correlated
to the orbital period for CP1 objects as they are mostly members of
binary systems. For CP3 stars, rotationally induced variability is
still a matter of debate. Although surface spots were detected, they
are believed to produce only marginal photometric amplitudes. So,
periods from several hours to a few days were expected for these
two star groups. The STEREO/HI-1 data are well matched to studies
of this frequency domain, owing to the cadence of approximately 40
min and multiple epochs over four and a half years. The remaining
514 stars are likely to be constant in the investigated range from
0.1 to 10 d. In some cases, the presence of blending or systematic
effects prevented us from detecting any reliable variability and
in those cases we classified the star as constant. We discuss our
results in comparison to already published ones and find a very good
agreement. Finally, we have calibrated the variable stars in terms of
the effective temperature and luminosity in order to estimate masses
and ages. For this purpose, we used specifically developed calibrations
for CP stars and, when available, Hipparcos parallaxes. All but two
objects cover the stellar mass range from 1.5 to 5 M⊙
and are located between the zero- and terminal-age main sequence.

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Title: Bright low mass eclipsing binary candidates observed by STEREO
Authors: Wraight, K. T.; Fossati, L.; White, Glenn J.; Norton, A. J.;
Bewsher, D.
2012MNRAS.427.2298W Altcode: 2012arXiv1209.2014W
Observations from the Heliospheric Imagers (HI-1) on both the STEREO
spacecraft have been analysed to search for bright low mass eclipsing
binaries (EBs) and potential brown dwarf transits and to determine the
radii of the companions. A total of nine EB candidates have been found,
ranging in brightness from V = 6.59 to 11.3 mag, where the radius of the
companion appears to be less than 0.4 R⊙, with a diverse
range of host temperatures, from 4074 to 6925 K. Both components of one
candidate, BD-07 3648, appear to be less than 0.4 R⊙ and
this represents a particularly interesting system for further study. The
shapes of the eclipses in some cases are not clear enough to be certain
they are total and the corresponding radii found should therefore be
considered as lower limits. The EBs reported in this paper have either
been newly found by the present analysis or previously reported to be
eclipsing by our earlier STEREO/HI-1 results. One of the new objects
has subsequently been confirmed using archival SuperWASP data. This
study was made possible by using an improved matched filter extraction
algorithm, which is described in this paper.

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Title: STEREO observations of long period variables
Authors: Wraight, K. T.; Bewsher, D.; White, Glenn J.; Nowotny, W.;
Norton, A. J.; Paladini, C.
2012MNRAS.426..816W Altcode: 2012arXiv1206.1485W
Observations from the Heliospheric Imagers (HI-1) on both the STEREO
spacecrafts have been analysed to search for very long period large
amplitude stellar variability, finding six new candidates. A total
of 85 objects, mostly previously known Mira variables, were found to
show convincing variability on time-scales of over a 100 days. These
objects range in peak brightness from about fourth magnitude to 10th
magnitude in R and have periods between about 170 and 490 d. There
is a period gap between 200 and 300 d where no objects were found
and this is discussed. 15 of the Miras in the sample are previously
recorded as having variable periods and the possibility for these and
two other stars to have undergone a period change or to be irregular is
discussed. In addition to the six stars in the sample not previously
recorded as variable, another seven are recorded as variable but with
no classification. Our period determination is the first to be made
for 19 of these 85 stars. The sample represents a set of very long
period variables that would be challenging to monitor from the Earth,
or even from Earth orbit, owing to their position on the ecliptic
plane and that their periods are often close to a year or an integer
fraction thereof. The possibility for the new candidates to possess
circumstellar shells is discussed.

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Title: Long-Term Evolution of the Photometric Calibration of the
STEREO Heliospheric Imagers: I. HI-1
Authors: Bewsher, D.; Brown, D. S.; Eyles, C. J.
2012SoPh..276..491B Altcode:
The aim of this paper is to determine whether the photometric
response of the STEREO HI-1A and HI-1B Heliospheric Imagers has
evolved or degraded during the mission to date. This is done using
the methodology of Bewsher et al. (Solar Phys.264, 433, 2010)
to calculate the photometric calibration factor, μ, over the four
complete STEREO heliocentric orbits between the start of the science
mission operations in April 2007 and June 2011, and to evaluate
whether this parameter has undergone any significant variation. It is
shown that the photometric response of the instruments has remained
stable to within ∼ 1%. The value of μ across different parts of
the field of view is also determined to evaluate the validity of the
calibrated large-scale flatfield determined by Bewsher et al. (Solar
Phys.264, 433, 2010). Based on the results, new revised values for
the photometric calibration factor and conversion factors for diffuse
sources are presented.

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Title: A photometric study of chemically peculiar stars with the
STEREO satellites - I. Magnetic chemically peculiar stars
Authors: Wraight, K. T.; Fossati, L.; Netopil, M.; Paunzen, E.;
Rode-Paunzen, M.; Bewsher, D.; Norton, A. J.; White, Glenn J.
2012MNRAS.420..757W Altcode: 2011MNRAS.tmp.2052W; 2011arXiv1110.6283W
About 10 per cent of upper main-sequence stars are characterized by
the presence of chemical peculiarities, often found together with a
structured magnetic field. The atmospheres of most of those chemically
peculiar stars present surface spots, leading to photometric variability
caused by rotational modulation. The study of the light curves of those
stars therefore permits a precise measurement of their rotational
period, which is important to study stellar evolution and to plan
further detailed observations. We analysed the light curves of 1028
chemically peculiar stars obtained with the STEREO spacecraft. We
present here the results obtained for the 337 magnetic chemically
peculiar stars in our sample. Thanks to the cadence and stability of
the photometry, STEREO data are perfectly suitable to study variability
signals with a periodicity typical of magnetic chemically peculiar
stars. Using a matched filter algorithm and then two different period
searching algorithms, we compiled a list of 82 magnetic chemically
peculiar stars for which we measured a reliable rotational period;
for 48 of them, this is the first measurement of their rotational
period. The remaining 255 stars are likely to be constant, although we
cannot exclude the presence of long-period variability. In some cases,
the presence of blending or systematic effects prevented us from
detecting any reliable variability and in those cases we classified
the star as constant. For each star we classified as variable, we
determined temperature, luminosity, mass and fractional age, but the
limited statistics, biased towards the shorter periods, prevented us
from finding any evolutionary trend of the rotational period. For a few
stars, the comparison between their projected rotational velocity and
equatorial velocity let us believe that their real rotational period
might be longer than that found here and previously obtained. For the
82 stars identified as variable, we give all necessary information
needed to plan further phase-dependent observations. Data obtained
with the Heliospheric Imager instruments on board the STEREO spacecraft.

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Title: What is the true nature of blinkers?
Authors: Subramanian, S.; Madjarska, M. S.; Doyle, J. G.; Bewsher, D.
2012A&A...538A..50S Altcode: 2011arXiv1111.2149S
 Aims: The aim of this work is to identify the true nature of the
transient EUV brightenings, called blinkers. Methods: Co-spatial
and co-temporal multi-instrument data, including imaging (EUVI/STEREO,
XRT and SOT/Hinode), spectroscopic (CDS/SoHO and EIS/Hinode) and
magnetogram (SOT/Hinode) data, of an isolated equatorial coronal hole
were used. An automatic program for identifying transient brightenings
in CDS O v 629 Å, EUVI 171 Å and XRT was applied. Results: We
identified 28 blinker groups in the CDS O v 629 Å raster images. All
CDS O v 629 Å blinkers showed counterparts in EUVI 171 Å and 304 Å
images. We classified these blinkers into two categories, one associated
with coronal counterparts and other with no coronal counterparts as seen
in XRT images and EIS Fe xii 195.12 Å raster images. Around two-thirds
of the blinkers show coronal counterparts and correspond to various
events like EUV/X-ray jets, brightenings in coronal bright points
or foot-point brightenings of larger loops. These brightenings occur
repetitively and have a lifetime of around 40 min at transition region
temperatures. The remaining blinker groups with no coronal counterpart
in XRT and EIS Fe xii 195.12 Å appear as point-like brightenings and
have chromospheric/transition region origin. They take place only once
and have a lifetime of around 20 min. In general, lifetimes of blinkers
are different at different wavelengths, i.e. different temperatures,
decreasing from the chromosphere to the corona. Conclusions: This
work shows that the term blinker covers a range of phenomena. Blinkers
are the EUV response of various transient events originating at coronal,
transition region and chromospheric heights. Hence, events associated
with blinkers contribute to the formation and maintenance of the
temperature gradient in the transition region and the corona.

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Title: STEREO observations of stars and the search for exoplanets
Authors: Wraight, K. T.; White, Glenn J.; Bewsher, D.; Norton, A. J.
2011MNRAS.416.2477W Altcode: 2011arXiv1103.0911W; 2011MNRAS.tmp.1348W
The feasibility of using data from the NASA STEREO mission for variable
star and asteroseismology studies has been examined. A data analysis
pipeline has been developed that is able to apply selected algorithms to
the entire data base of nearly a million stars to search for signs of
variability. An analysis limited to stars of magnitude 10.5 has been
carried out, which has resulted in the extraction of 263 eclipsing
binaries (EBs), of which 122 are not recorded as such in the SIMBAD
online data base. The characteristics of the STEREO observations are
shown to be extremely well suited to variable star studies with the
ability to provide continuous phase coverage for extended periods as
well as repeated visits that allow both short- and long-term variability
to be observed. This will greatly inform studies of particular stars,
such as the pre-cataclysmic variable V471 Tau, as well as the entire
classes of stars, including many forms of rotational variability. The
high-precision photometry has also revealed a potentially substellar
companion to a bright (R= 7.5 mag) nearby star (HD 213597), detected
with 5σ significance. This would provide a significant contribution to
the exoplanet research if follow-up observations ascertain the mass to
be within the planetary domain. Some particularly unusual EBs from the
recovered sample are discussed, including a possible reclassification
of a well-known star as an EB rather than a rotational variable (HR
7355) and several particularly eccentric systems, including very long
period EBs.

---------------------------------------------------------
Title: VizieR Online Data Catalog: STEREO observations of variable
stars (Wraight+, 2011)
Authors: Wraight, K. T.; White, G. J.; Bewsher, D.; Norton, A. J. .
2011yCat..74162477W Altcode:
Description of the analysis of stars brighter than R=10.5mag
from the Heliospheric Imager on the STEREO-Ahead spacecraft
(STEREO/HI-1A). Analysis of the effectiveness of the different
algorithms used. Analysis of different trends amongst the sample
of EBs detected. Photometric lightcurves of several individual
stars of interest given, including all measurably eccentric EBs
detected. Statistics for 263 eclipsing binaries. Lightcurves for all
EBs provided in supporting information in the electronic version of
the paper. (1 data file).

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

---------------------------------------------------------
Title: The UCLan SDO Data Hub
Authors: Dalla, S.; Walsh, R. W.; Chapman, S. A.; Marsh, M.; Regnier,
S.; Bewsher, D.; Brown, D. S.; Kelly, J.; Laitinen, T.; Alexander, C.
2010AGUFMSH23C1876D Altcode:
A data pipeline for the distribution of SDO data products has been
developed throughout a number of countries in the US, Europe and
Asia. The UK node within this pipeline is at the University of Central
Lancashire (UCLan), where a data center has been established to host a
rolling AIA and HMI archive, aimed at supplying data to the country's
large solar scientific community. This presentation will describe the
hardware and software structures of the archive, as well as the best
practice identified and feedback received from users of the facility. We
will also discuss algorithms that are run locally in order to identify
solar features and events.

---------------------------------------------------------
Title: Determination of the Photometric Calibration and Large-Scale
Flatfield of the STEREO Heliospheric Imagers: I. HI-1
Authors: Bewsher, D.; Brown, D. S.; Eyles, C. J.; Kellett, B. J.;
White, G. J.; Swinyard, B.
2010SoPh..264..433B Altcode: 2010SoPh..tmp..105B
The aim of this paper is to calculate an accurate large-scale
flatfield for the STEREO HI-1 instruments. This is done by analysing
the variation in intensity of stars in the background starfield as
they pass across the CCD. In order to use the background starfield,
a photometric calibration is performed which defines a HI magnitude
scale and a conversion between this scale and measured intensity. The
photometric calibration uses stellar spectra folded through the
instrument response to make initial intensity predictions. However,
a secondary prediction method based on the photometric calibration,
which blends the R-, V- and B-magnitudes of a star, is derived for
stars with no spectral information.

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

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

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

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

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

---------------------------------------------------------
Title: Magnetic coupling in the solar system
Authors: Matthews, Sarah; Bewsher, Danielle; Davis, Chris
2009A&G....50b..31M Altcode:
On 10 October 2008, UK solar, solar-terrestrial and planetary scientists
hosted a meeting at the RAS on the theme of “Magnetic coupling in
the solar system - from the Sun into the heliosphere”. This meeting
was proposed in order to stimulate discussion on how the variations
of the solar magnetic field influence other solar system bodies such
as comets, planets (including our own) and their moons. Energy from
within the convection zone is transferred through magnetic coupling
into the corona and the heliosphere beyond on a wide range of spatial
and temporal scales that are related to the different types of magnetic
field emergence at the solar surface. Thus in order to understand the
global heliospheric magnetic field and its influence throughout the
solar system, we have to understand the role that flux emergence on
all scales plays in structuring in the global field and the associated
solar wind. With the successful launch of two major new space-based
missions, Hinode and STEREO (Solar Terrestrial Relations Observatory),
scientists are well placed to study the emergence of the Sun's magnetic
field and track it into the heliosphere.

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

---------------------------------------------------------
Title: Calibrating the Pointing and Optical Parameters of the STEREO
Heliospheric Imagers
Authors: Brown, D. S.; Bewsher, D.; Eyles, C. J.
2009SoPh..254..185B Altcode: 2008SoPh..tmp..181B
The Heliospheric Imager (HI) instruments on the Solar TErrestrial
RElations Observatory (STEREO) observe solar plasma as it streams
out from the Sun and into the heliosphere. The telescopes point
off-limb (from about 4° to 90° elongation) and so the Sun is not
in the field of view. Hence, the Sun cannot be used to confirm the
instrument pointing. Until now, the pointing of the instruments have
been calculated using the nominal preflight instrument offsets from the
STEREO spacecraft together with the spacecraft attitude data. This paper
develops a new method for deriving the instrument pointing solutions,
along with other optical parameters, by comparing the locations of stars
identified in each HI image with the known star positions predicted
from a star catalogue. The pointing and optical parameters are varied in
an autonomous manner to minimise the discrepancy between the predicted
and observed positions of the stars. This method is applied to all HI
observations from the beginning of the mission to the end of April
2008. For the vast majority of images a good attitude solution has
been obtained with a mean-squared deviation between the observed and
predicted star positions of one image pixel or less. Updated values have
been obtained for the instrument offsets relative to the spacecraft,
and for the optical parameters of the HI cameras. With this method the
HI images can be considered as "self-calibrating," with the actual
instrument offsets calculated as a byproduct. The updated pointing
results and their by-products have been implemented in SolarSoft.

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

---------------------------------------------------------
Title: Explosive Events in the Quiet Sun as Seen by EIS and SUMER
Authors: Madjarska, M. S.; Boutry, C.; Bewsher, D.
2008ASPC..397..180M Altcode:
We present preliminary results on the capabilities of EIS to register
explosive events in the quiet Sun. The events were registered with
EIS/Hinode and SUMER/SoHO during the Hinode/SoHO observing campaign
in April 2007. First results on the coronal response of these events
are shown. Both SUMER and EIS were observing spectral lines from the
widest possible temperature range from a few thousand to a few million
degrees Kelvin.

---------------------------------------------------------
Title: Magnetic topology of blinkers
Authors: Subramanian, S.; Madjarska, M. S.; Maclean, R. C.; Doyle,
J. G.; Bewsher, D.
2008A&A...488..323S Altcode:
Context: Co-spatial and co-temporal spectroscopic, imaging and
magnetogram data enable us to better understand various solar transient
phenomena. Here, we study brightening events in the transition region
of the quiet Sun, also called “blinkers”. Aims: We aim
to investigate the physical mechanism responsible for blinkers. Methods: An automated blinker identification procedure (BLIP) is
used to identify blinker events in SoHO/CDS data. The 3D magnetic
topology of the magnetic field in the blinker region is reconstructed
based on SoHO/MDI magnetogram data. Results: During 3 h of
SoHO/CDS observations on 2006 January 18, 66 blinkers were identified
in the O v 629 Å emission line. Out of them, a group comprising of
16 events were modelled here. They were found to be associated with
the emergence of magnetic flux which gave rise to the appearance of,
and multiple magnetic reconnection events across, an upper atmosphere
(coronal) magnetic null point, along with a loop structure as observed
with TRACE. Conclusions: This blinker group results from the
release of energy that was accumulated during flux emergence, although
whether all blinkers follow the same formation scenario requires
further investigation using additional multi-instrument/multi-mission
studies. 2 movies are only available in electronic form at
http://star.arm.ac.uk/preprints/ and http://www.aanda.org

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

---------------------------------------------------------
Title: Observations of corotating interaction regions in the inner
heliosphere by the STEREO spacecraft.
Authors: Rouillard, A. P.; Rees, A.; Forsyth, R. J.; Davies, J. A.;
Davis, C. J.; Bewsher, D.
2008AGUSMSH43A..02R Altcode:
The images taken by the Heliospheric Imagers (HI) onboard the STEREO
spacecraft provide information on the latitudinal distribution of the
plasma compressed inside CIRs. In this study, the size and orientation
of the plasma waves associated with these CIRs are compared to in-situ
observations of density increase, non-radial flows and the orientation
of the stream interface. The implications of this study for forecasting
the magneto- hydrodynamic properties of CIRs impinging on the Earth's
magnetosphere are discussed.

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

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

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

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

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

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Title: A Coronal Mass Ejection at Venus observed with STEREO HI and
Venus Express
Authors: Davies, J. A.; Rouillard, A.; Bewsher, D.; Hapgood, M. A.;
Lockwood, M.
2007AGUFMSH52B..06D Altcode:
Observations of a CME interacting with comet Encke were made by the
STEREO HI cameras in April 2007. The position of the comet allowed
the direction of the CME to be determined even though it had only been
observed with one STEREO spacecraft. An examination of the planetary
positions indicated that the CME would intersect with Venus. Data from
the Venus Express spacecraft show the passage of a CME front at the
time predicted by the HI data.

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

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

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Title: Solar physics in STEREO
Authors: Davis, Chris; Bewsher, Danielle
2007A&G....48c..12D Altcode:
NASA's STEREO mission uses twin spacecraft observing the Sun and solar
neighbourhood from increasingly distant viewpoints to give a stereo
view of the solar chromosphere and corona, including coronal mass
ejections. UK researchers have provided the Heliospheric Imagers on
each spacecraft, comprising sensitive wide-field cameras able to track
coronal mass ejections right out to Earth's orbit. Here we describe the
instruments, data-handling procedures and results obtained so far. We
finish with a discussion of the potential of these instruments for a
wide range of astronomical observations during the two-and-a-half-year
mission.

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

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

---------------------------------------------------------
Title: On Deriving Plasma Velocity Information from CDS/NIS
Observations: Application to the Dynamics of Blinkers
Authors: Brooks, David Hamilton; Bewsher, Danielle
2006SoPh..234..257B Altcode:
Using standard instrument software and two independently developed
data reduction and analysis procedures, we re-examine the accuracy of
plasma velocity information derived from data obtained by the Solar
and Heliospheric Observatory (SOHO)-Coronal Diagnostic Spectrometer
(CDS). We discuss only the Ov 629 Å line data obtained by the Normal
Incidence Spectrometer (NIS) and analyse a quiet Sun (QS) and active
region (AR) dataset. Using the QS data, we demonstrate that the
well-known North-South tilt in wavelength along the NIS slit varies
significantly with time, which is not accounted for in the standard CDS
correction procedures. In addition, when residual N - S trends exist in
the data after processing, they may not be detected, nor removed, using
the standard analysis software. This underscores the need for careful
analysis of velocity results for individual datasets when using standard
correction procedures. Furthermore, even when the results obtained by
the two independent methods are well correlated (coefficients greater
than 0.9), discrepancies in the values of the derived Doppler velocities
can remain (95% within ±5 km s−1). Therefore, we apply the
results to examine the velocities obtained for EUV blinkers by previous
authors. It is found that a strong correlation exists in the patterns
of variation of the blinker velocities (&gt; 0.98), even though there
may be differences in their magnitudes. That is, in a clear majority of
cases, the methods agree that a blinker is red-shifted or blue-shifted,
although the uncertainty in the absolute velocity may be large.

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Title: Statistics of the Quiet Sun Intensity Distribution
Authors: Young, C. A.; Ireland, J.; Bewsher, D.
2005ESASP.600E..75Y Altcode: 2005ESPM...11...75Y; 2005dysu.confE..75Y
No abstract at ADS

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Title: Statistics of the quiet Sun intensity distribution.
Authors: Ireland, J.; Young, C.; Bewsher, D.
2005AGUSMSP21B..11I Altcode:
The statistics of the quiet Sun intensity distribution present an
interesting challenge. Some authors find that the observed distribution
is adequately represented by a two component model, which seems to fit
well with the notion of a network and internetwork being physically
distinct. Other authors find that a single component model fits
the intensity distribution data well, which seems to suggest that
the network and internetwork emission may in fact be due to the same
process. This paper examines the evidence for both these points of view,
using CDS EUV data and a mixture modeling technique. Some comments
are also made on the nature of the mechanism which may create the
observed distributions.

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Title: Comparison of blinkers and explosive events: A case study
Authors: Bewsher, D.; Innes, D. E.; Parnell, C. E.; Brown, D. S.
2005A&A...432..307B Altcode:
Blinkers are brightenings at network cell junctions that are
traditionally identified with SOHO/CDS and explosive events or high
velocity events are identified in high resolution UV spectra obtained
from HRTS and SOHO/SUMER. Criteria are determined to facilitate
objective automatic identification of both blinkers and explosive events
in both SOHO/CDS and SOHO/SUMER data. Blinkers are identified in SUMER
data, if the temporal resolution of the data is reduced to that of
CDS. Otherwise short lived, localised intensity enhancements that make
up the blinker are identified. Explosive events are identified in CDS
data when the line width is significantly increased, and occasionally if
there is an enhancement in the wing of the line profile. A theoretical
statistical model is presented which hypothesises that blinkers and
explosive events are random and not connected in any way. The results
given in this paper suggest that this hypothesis can not be rejected and
our probability interpretation of the recent results of Brković &amp;
Peter (2004, A&amp;A, 422, 709) are inconclusive. Appendices A and
B are only available in electronic form at http://www.edpscienc es.org

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Title: Probability Analysis of Coincident Blinkers and Explosive
Events
Authors: Bewsher, D.; Brown, D.; Innes, D.; Parnell, C.
2004ESASP.575..465B Altcode: 2004soho...15..465B
No abstract at ADS

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

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

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Title: Comparison of Blinkers and Explosive Events
Authors: Bewsher, D.; Innes, D.; Parnell, C. E.
2003SPD....34.1617B Altcode: 2003BAAS...35Q.836B
There has been much speculation over recent years as to whether blinkers
and explosive events are the same phenomena observed with different
instruments. Blinkers were first observed by Harrison (1997) by eye
using SOHO/CDS, but more recently Brković et al. (2001) and Bewsher
et al. (2002) have developed automated methods of identifying these
events. Blinkers are small scale intensity enhancements seen in the
transition region, with a mean area of 3 x 107 km2
and a mean lifetime of 16 minutes. The Doppler velocities of blinkers
are preferentially more red-shifted than the typical transition region
plasma. The range of these enhanced velocities, however, are no larger
than the typical spread of Doppler velocities in these regions. Explosive events were first observed using HRTS (Bruckener and Bartoe,
1983) as high energy turbulent events and jets. More recently, they
have been observed using SOHO/SUMER. They have a typical size of 2"
- 4" and have an average lifetime of 60 seconds. Line profiles of
explosive events show strong non-Gaussian enhancements of both wings of
the profile, and velocities associated with them range from +/- 50 -
+/- 250 km s-1. Examples will be presented showing
(i) a co-spatial and co-incident blinker and explosive event; (ii)
a blinker with no associated explosive event; and (iii) an explosive
event with no associated blinker. We investigate the lightcurves and
line profiles of the regions to explain the relationship, if any,
between blinkers and explosive events.

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Title: Magnetic structure of transition region blinkers
Authors: Bewsher, D.; Parnell, C. E.; Brown, D. S.; Hood, A. W.
2002ESASP.505..239B Altcode: 2002IAUCo.188..239B; 2002solm.conf..239B
Analysis of the photospheric magnetic field has shown that the
majority of blinkers, small-scale intensity enhancements seen in the
transition region, occur above single fragments. We investigate the
relationship between the strength of these single magnetic fragments
or the ratio of any mixed magnetic fields beneath blinkers and blinker
characteristics. In all cases, no correlation is found between the
strength of the magnetic field and the blinker properties. We suggest,
therefore, that blinkers are not caused by reconnection and that other
mechanisms should be explored further.

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

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

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Title: The Nature of Blinkers and the Solar Transition Region
Authors: Priest, E. R.; Hood, A. W.; Bewsher, D.
2002SoPh..205..249P Altcode:
Solar plasma that exists at around 105 K, which has
traditionally been referred to as the solar transition region, is
probably in a dynamic and fibril state with a small filling factor. Its
origin is as yet unknown, but we suggest that it may be produced
primarily by one of five different physical mechanisms, namely:
the heating of cool spicular material; the containment of plasma in
low-lying loops in the network; the thermal linking of cool and hot
plasma at the feet of coronal loops; the heating and evaporating of
chromospheric plasma in response to a coronal heating event; and the
cooling and draining of hot coronal plasma when coronal heating is
switched off. We suggest that, in each case, a blinker could be produced
by the granular compression of a network junction, causing subtelescopic
fibril flux tubes to spend more of their time at transition-region
temperatures and so to increase the filling factor temporarily.

---------------------------------------------------------
Title: Transition region blinkers
Authors: Bewsher, Danielle
2002PhDT.......234B Altcode:
No abstract at ADS

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