Author name code: bochsler
ADS astronomy entries on 2022-09-14
author:"Bochsler, Peter"
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Title: Secular Variability of the Solar Wind Composition? — The
Case of Xe/Kr in the Lunar Regolith
Authors: Wieler, R.; Bochsler, P.
Bibcode: 2022LPICo2678.1370W
Altcode:
We discuss possible causes for the secular decrease of Xe/Kr in the
lunar regolith and suggest a contribution of early terrestrial Xe to
be most likely.
Title: Do Lunar Regolith Samples Testify of a Contribution of Cometary
Xenon onto the Moon?
Authors: Wieler, R.; Bochsler, P.; Marty, B.
Bibcode: 2021LPI....52.1085W
Altcode:
We discuss the hypothesis that lunar soil samples contain a minor
addition of cometary Xe depleted in 134,136-Xe.
Title: Lunar Xenon from Ancient Earth-Wind
Authors: Bochsler, Peter; Rainer, Wieler
Bibcode: 2020EPSC...14..177B
Altcode:
Lunar Xenon from Ancient Earth-Wind The apparent secular variability
of the Xe/Kr abundance ratio in the solar wind implanted in grains of
the lunar regolith is a long-standing problem (Wieler, 2016): Recently
irradiated soils (<100 Ma ago) show Xe/Kr ratios comparable to the
ratio found in solar wind targets of the Genesis mission (Meshik et
al. 2014, Vogel et al. 2011), while lunar samples exposed billions
of years ago to the solar wind exhibit a Xe/Kr ratio about twice as
high. It has been argued that this observation is the consequence of
the variability of the solar wind composition. More recently it has
also been suggested that, over time, cometary impacts have contributed
significantly to the inventory of noble gases and other volatiles
of the lunar regolith.From our understanding of the development of
typical G-stars, such as the Sun, we consider it unlikely that such
a strong variation could have occurred several 100 My after the lunar
regolith had started to build up. Today, variations of this ratio even
in very different solar wind regimes are marginally distinguishable
(Vogel et al. 2019). On the other hand, it seems also unlikely that
early cometary impacts could have implanted sufficient amounts of
Xe to noticeably modify the Xe/Kr inventory in the regolith with the
correct isotopic compositions.While we are currently unable to clearly
outrule any of the above hypotheses, we here propose an alternative
explanation: The ancient lunar regolith has been exposed to a xenon-rich
Earth-Wind. An ancient Earth-Wind has been invoked previously (e.g.,
Geiss and Bochsler, 1991, Ozima et al. 2005) in order to explain the
secular variability of the isotopic composition of nitrogen in the
lunar regolith.The apparent secular depletion of light isotopes of
atmospheric xenon combined with the presumed large deficit of Xe in
the atmosphere (Avice et al. 2018) recently led Zahnle et al. (2019)
to postulate a loss of Xe ions over the first 3 Gy from the upper
atmosphere, concomitant with the hydrogen escape and the oxygenation
of the atmosphere. The loss mechanism devised by Zahnle and co-authors
selectively involves Xe without affecting the other noble gases. It
operates through resonant charge exchange of H+ with Xe, leading to a
low-lying excited state of Xe+.We believe that escaping terrestrial Xe
ions will undoubtedly be incorporated into the flow of the magnetotail
of the Earth and impact the lunar surface, whenever the Moon crosses
the tail directed away from the Sun. From the present cross section
of the magnetotail near the orbit of the Moon and the amount of xenon
lost from the terrestrial atmosphere over the first few Gy, we conclude
that the Xe-fluence of the Earth-Wind could be sufficient to account
for the apparent secular variation of the lunar Xe/Kr ratio. Since we
expect Earth-Wind-xenon to be strongly fractionated in favour of light
isotopes, we expect its isotopic composition to deviate significantly
from the present-day terrestrial atmosphere, approaching the composition
of the solar wind. Unfortunately, given the experimental uncertainties
of the isotopic composition of xenon in ancient lunar soil, it is
difficult to obtain conclusive evidence in favour or against the
Earth-Wind hypothesis from isotopic abundances. In a simple box model
as outlined in Figure 1, we investigate the potential contribution
of the Earth-Wind to the lunar regolith using the compilation of data
on the isotopic composition of Xe in the ancient atmosphere of Avice
et al. (2018) and the abundance of Xe in the mantle to determine free
parameters. Our first results indicate that the Earth-Wind is a viable
alternative to explain the apparent secular decrease of the Xe/Kr ratio
in the lunar regolith, even if the solar wind has decreased in intensity
over the life-time of the Sun.The Earth-Wind hypothesis could be tested
by investigation of ancient lunar regolith samples with present-day
state-of-the-art mass spectrometry and by analysis of lunar samples
at different lunar longitudes, particularly from the lunar backside,
which at least at present, is mostly shielded from the ion-flow in the
geotail. References:Avice G. et al. (2018) Geochimica et Cosmochimica
Acta 232, 82-100.Geiss J., and Bochsler P. (1991) In: The Sun in
Time, The University of Arizona Press, 98-117.Meshik A. et al. (2014)
Geochimica et Cosmochimica Acta 127, 326-347.Ozima M. et al. (2005)
Nature 436, 655-659.Vogel N. et al. (2011) Geochimica et Cosmochimica
Acta 75, 3057-3071.Vogel N. et al. (2019) Geochimica et Cosmochimica
Acta 263, 182-194.Wieler R. (2016) Chemie der Erde - Geochemistry 76,
463-480.Zahnle K.J., Gacesa M., and Catling D.C. (2019), Geochimica
et Cosmochimica Acta 244, 56-85.
Title: A Possible Contribution from the Ancient Terrestrial Atmosphere
to the Trapped Xenon Inventory of Lunar Soils
Authors: Wieler, R.; Bochsler, P.
Bibcode: 2020LPI....51.1076W
Altcode:
Lunar regolith samples exposed to the solar wind several Ga ago may
contain Xe from the terrestrial atmosphere, which would explain their
higher Xe/Kr ratios.
Title: Noble gas elemental abundances in three solar wind regimes
as recorded by the Genesis mission
Authors: Vogel, Nadia; Heber, Veronika S.; Bochsler, Peter; Burnett,
Donald S.; Maden, Colin; Wieler, Rainer
Bibcode: 2019GeCoA.263..182V
Altcode:
We discuss elemental abundances of noble gases in targets exposed to the
solar wind (SW) onboard the "Genesis" mission during the three different
SW "regimes": "Slow" (interstream, IS) wind, "Fast" (coronal hole,
CH) wind and solar wind related to coronal mass ejections (CME). To
this end we first present new Ar, Kr, and Xe elemental abundance data
in Si targets sampling the different regimes. We also discuss He, Ne,
and Ar elemental and isotopic abundances obtained on Genesis regime
targets partly published previously. Average Kr/Ar ratios for all
three regimes are identical to each other within their uncertainties
of about 1% with one exception: the Fast SW has a 12% lower Xe/Ar ratio
than do the other two regimes. In contrast, the He/Ar and Ne/Ar ratios
in the CME targets are higher by more than 20% and 10%, respectively,
than the corresponding Fast and Slow SW values, which among themselves
vary by no more than 2-4%. Earlier observations on lunar samples
and Genesis targets sampling bulk SW wind had shown that Xe, with a
first ionisation potential (FIP) of ∼12 eV, is enriched by about
a factor of two in the bulk solar wind over Ar and Kr compared to
photospheric abundances, similar to many "low FIP" elements with a
FIP less than ∼10 eV. This behaviour of the "high FIP" element Xe
was not easily explained, also because it has a Coulomb drag factor
suggesting a relatively inefficient feeding into the SW acceleration
region and hence a depletion relative to other high FIP elements
such as Kr and Ar. The about 12% lower enrichment of Xe in Genesis'
Fast SW regime observed here is, however, in line with the hypothesis
that the depletion of Xe in the SW due to the Coulomb drag effect is
overcompensated as a result of the relatively short ionisation time of
Xe in the ion-neutral separation region in the solar chromosphere. We
will also discuss the rather surprising fact that He and Ne in CME
targets are quite substantially enriched (by 20% and 10%, respectively)
relative to the other solar wind regimes, but that this enrichment
is not accompanied by an isotopic fractionation. The Ne isotopic
data in CMEs are consistent with a previous hypothesis that isotopic
fractionation in the solar wind is mass-dependent.
Title: Elemental Abundances of Noble Gases in Solar Wind Regimes
Collected by Genesis
Authors: Vogel, N.; Heber, V. S.; Bochsler, P.; Burnett, D. S.; Maden,
C.; Wieler, R.
Bibcode: 2019LPI....50.1232V
Altcode:
Noble gas elemental abundances in Genesis regime targets are presented
and discussed in terms of theories on elemental fractionation in the
solar wind.
Title: Charge States of Krypton and Xenon in the Solar Wind
Authors: Bochsler, Peter; Fludra, Andrzej; Giunta, Alessandra
Bibcode: 2017SoPh..292..128B
Altcode:
We calculate charge state distributions of Kr and Xe in a model for
two different types of solar wind using the effective ionization and
recombination rates provided from the OPEN_ADAS data base. The charge
states of heavy elements in the solar wind are essential for estimating
the efficiency of Coulomb drag in the inner corona. We find that xenon
ions experience particularly low Coulomb drag from protons in the inner
corona, comparable to the notoriously weak drag of protons on helium
ions. It has been found long ago that helium in the solar wind can be
strongly depleted near interplanetary current sheets, whereas coronal
mass ejecta are sometimes strongly enriched in helium. We argue that
if the extraordinary variability of the helium abundance in the solar
wind is due to inefficient Coulomb drag, the xenon abundance must
vary strongly. In fact, a secular decrease of the solar wind xenon
abundance relative to the other heavier noble gases (Ne, Ar, Kr)
has been postulated based on a comparison of noble gases in recently
irradiated and ancient samples of ilmenite in the lunar regolith. We
conclude that decreasing solar activity and decreasing frequency of
coronal mass ejections over the solar lifetime might be responsible
for a secularly decreasing abundance of xenon in the solar wind.
Title: Suprathermal helium in corotating interaction regions:
combined observations from SOHO/CELIAS/STOF and ACE/SWICS
Authors: Yu, J.; Berger, L.; Wimmer-Schweingruber, R.; Bochsler, P.;
Klecker, B.; Hilchenbach, M.; Kallenbach, R.
Bibcode: 2017A&A...599A..13Y
Altcode:
Context. Energetic particle enhancements that are associated with
corotating interaction regions (CIRs) are typically believed to arise
from the sunward propagation of particles that are accelerated
by CIR-driven shocks beyond 1 AU. It is expected that these
sunward-travelling particles will lose energy and scatter, resulting
in a turnover of the energy spectra below 0.5 MeV/nuc. However,
the turnover has not been observed so far, suggesting that the
CIR-associated low-energy suprathermal ions are accelerated locally
close to the observer.
Aims: We investigate the variability
of suprathermal particle spectra from CIR to CIR as well as their
evolution and variation as the observer moves away from the rear
shock or wave.
Methods: Helium data in the suprathermal energy
range from the Solar and Heliospheric Observatory/Charge, Element, and
Isotope Analysis System/Suprathermal Time-of-Flight (SOHO/CELIAS/STOF)
were used for the spectral analysis and were combined with data
from the Advanced Composition Explorer/ Solar Wind Ion Composition
Spectrometer (ACE/SWICS) in the solar wind energies.
Results:
We investigated sixteen events: nine clean CIR events, three CIR
events with possible contamination from upstream ion events or solar
energetic particles (SEPs), and four events that occurred during CIR
periods that were dominated by SEPs. Six of the nine clean CIR events
showed possible signs of a turnover between 10-40 keV/nuc in the fast
solar wind that trails the compression regions. Three of them even
showed this behaviour inside the compressed fast wind. The turnover
part of the spectra became flatter and shifted from lower to higher
energies with increasing connection distance to the reverse shock. The
remaining three clean events showed continuous power-law spectra in
both the compressed fast wind and fast wind regions, that is, the same
behaviour as reported from previous observations. The spectra of the
seven remaining events are more variable, that is, they show power law,
turnover, and a superposition of these two shapes.
Title: Noble gases Ar, Kr and Xe measured in the coma of Comet
67P/Churyumov-Gerasimenko: implications to early solar system
formation
Authors: Balsiger, H. R.; Altwegg, K.; Bar-Nun, A.; Berthelier, J. J.;
Bieler, A. M.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi, M. R.;
De Keyser, J.; Fiethe, B.; Fuselier, S. A.; Gasc, S.; Gombosi, T. I.;
Hansen, K. C.; Hässig, M.; Kopp, E.; Korth, A.; Le Roy, L.; Mall,
U.; Marty, B.; Mousis, O.; Owen, T. C.; Reme, H.; Rubin, M.; Semon,
T.; Tzou, C. Y.; Waite, J. H., Jr.; Wurz, P.
Bibcode: 2016AGUFM.P43D..08B
Altcode:
The role of comets in the formation of solar system planets, in
particular their contribution to the volatiles of the terrestrial
planets has been the subject of numerous models and speculations. Having
kept at least partially the volatile constituents of the solar nebula,
comets are among the most primitive objects in the solar system. Noble
gases in the cometary coma are key tracers for assessing origin
and processing of planetary atmospheres. We report the detection of
Ar, Kr and Xe in the coma of Comet 67P during the same period (May
2016) by the Double Focusing Mass Spectrometer (DFMS) of the ROSINA
experiment on ESA's Rosetta spacecraft, their relative abundance and
isotopic composition. First implications for the volatile inventory
of terrestrial planets and for solar system formation scenarios are
discussed.
Title: Interstellar O, He and Magnetic Field from IBEX and IMAP
Predictions
Authors: Schwadron, N.; Moebius, E.; McComas, D. J.; Bochsler, P. A.;
Bzowski, M.; Fuselier, S. A.; Livadiotis, G.; Frisch, P. C.; Mueller,
H. R.; Heirtzler, D.; Kucharek, H.; Lee, M. A.; Park, J.
Bibcode: 2016AGUFMSH23A..08S
Altcode:
The measurements of interstellar matter by IBEX have opened an important
chapter in our study of interactions that control the boundaries of our
heliosphere. Here we discuss recently derived quantitative information
about interstellar O flow parameters from IBEX low energy neutral
atom data for the first time along with recently derived parameters
for interstellar He and determinations of the secondary components
of He (the warm breeze) and O. We show that primary O parameters
exist along a relatively narrow range of covariant 4-D parameters
("parameter tube"). Along the parameter tube, we find a large
uncertainty in interstellar O flow longitude, 76.0°±3.4° from χ2
analysis and 76.5°±6.2° from a maximum likelihood fit, statistically
consistent with the flow longitude derived for primary interstellar
He, 75.6°±1.4°. The O and He primary component temperatures are
almost identical at a reference flow longitude (76°), indicating that
the local interstellar plasma is relatively unaffected by turbulent
heating. However, key differences include an O parameter tube with
slightly higher speeds than for He, and an upstream flow latitude for
O that is 0.7° southward of the upstream He flow latitude. Both of
these differences suggest enhanced filtration of interstellar O due to
its higher charge-exchange ionization rate. We find an interstellar
O density near the termination shock of 5.8+0.9-0.8×10-5 cm-3 ,
consistent with previous work. The flow directions of interstellar
primary O, primary He, secondary O, and secondary He all lie along
the so-called B-V plane, which also contains the direction of the IBEX
ribbon center, supporting the idea that the ribbon center is aligned
with the interstellar magnetic field. Thus we provide predictions for
IMAP that the primary and secondary components of interstellar O,
He in addition to H, Ne, and D will lie along the B-V plane, as we
advance our understanding of interstellar properties and interactions.
Title: Determination of Interstellar O Parameters Using the First
Two Years of Data From the Interstellar Boundary Explorer
Authors: Schwadron, N. A.; Möbius, E.; McComas, D. J.; Bochsler, P.;
Bzowski, M.; Fuselier, S. A.; Livadiotis, G.; Frisch, P.; Müller,
H. -R.; Heirtzler, D.; Kucharek, H.; Lee, M. A.
Bibcode: 2016ApJ...828...81S
Altcode:
The direct measurements of interstellar matter by the Interstellar
Boundary Explorer (IBEX) mission have opened a new and important
chapter in our study of the interactions that control the boundaries
of our heliosphere. Here we derive for the quantitative information
about interstellar O flow parameters from IBEX low-energy neutral
atom data for the first time. Specifically, we derive a relatively
narrow four-dimensional parameter tube along which interstellar O
flow parameters must lie. Along the parameter tube, we find a large
uncertainty in interstellar O flow longitude, 76.°0 ± 3.°4 from χ
2 analysis and 76.°5 ± 6.°2 from a maximum likelihood fit,
which is statistically consistent with the flow longitude derived for
interstellar He, 75.°6 ± 1.°4. The best-fit O and He temperatures
are almost identical at a reference flow longitude of 76°, which
provides a strong indication that the local interstellar plasma near
the Sun is relatively unaffected by turbulent heating. However, key
differences include an oxygen parameter tube for the interstellar speed
(relation between speed and longitude) that has higher speeds than
those in the corresponding parameter tube for He, and an upstream
flow latitude for oxygen that is southward of the upstream flow
latitude for helium. Both of these differences are likely the result of
enhanced filtration of interstellar oxygen due to its charge-exchange
ionization rate, which is higher than that for helium. Furthermore,
we derive an interstellar O density near the termination shock of
{5.8}-0.8+0.9× {10}-5 cm-3
that, within uncertainties, is consistent with previous estimates. Thus,
we use IBEX data to probe the interstellar properties of oxygen.
Title: Solar Wind Boron in Ilmenite Grains from Lunar Soil 71501
Authors: Fujiya, W.; Bochsler, P.; Wieler, R.; Hoppe, P.; Ott, U.
Bibcode: 2016LPICo1921.6381F
Altcode:
We measured abundances of solar wind boron implanted into ilmenite
grains from lunar soil 71501. The inferred B/Ar ratio of the solar
wind is ~3 x 10^-3, which is a factor of ~15 higher than the solar
photospheric ratio.
Title: Prebiotic chemicals--amino acid and phosphorus--in the coma
of comet 67P/Churyumov-Gerasimenko
Authors: Altwegg, K.; Balsiger, H.; Bar-Nun, A.; Berthelier, J. -J.;
Bieler, A.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi, M. R.;
Cottin, H.; De Keyser, J.; Dhooghe, F.; Fiethe, B.; Fuselier, S. A.;
Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Haessig, M.; Ja ckel,
A.; Kopp, E.; Korth, A.; Le Roy, L.; Mall, U.; Marty, B.; Mousis,
O.; Owen, T.; Reme, H.; Rubin, M.; Semon, T.; Tzou, C. -Y.; Waite,
J. Hunter; Wurz, P.
Bibcode: 2016SciA....2E0285A
Altcode:
The importance of comets for the origin of life on Earth has been
advocated for many decades. Amino acids are key ingredients in
chemistry, leading to life as we know it. Many primitive meteorites
contain amino acids, and it is generally believed that these are formed
by aqueous alterations. In the collector aerogel and foil samples of
the Stardust mission after the flyby at comet Wild 2, the simplest
form of amino acids, glycine, has been found together with precursor
molecules methylamine and ethylamine. Because of contamination issues
of the samples, a cometary origin was deduced from the 13C isotopic
signature. We report the presence of volatile glycine accompanied by
methylamine and ethylamine in the coma of 67P/Churyumov-Gerasimenko
measured by the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral
Analysis) mass spectrometer, confirming the Stardust results. Together
with the detection of phosphorus and a multitude of organic molecules,
this result demonstrates that comets could have played a crucial role
in the emergence of life on Earth.
Title: High-Time Resolution In-situ Investigation of Major Cometary
Volatiles around 67P/C-G at 3.1 - 2.3 AU Measured with ROSINA-RTOF
Authors: Mall, U.; Altwegg, K.; Balsiger, H.; Bar-Nun, A.; Berthelier,
J. -J.; Bieler, A.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi,
M. R.; Dabrowski, B.; De Keyser, J.; Dhooghe, F.; Fiethe, B.;
Fuselier, S. A.; Galli, A.; Garnier, P.; Gasc, S.; Gombosi, T. I.;
Hansen, K. C.; Hässig, M.; Hoang, M.; Jäckel, A.; Kopp, E.; Korth,
A.; Le Roy, L.; Magee, B.; Marty, B.; Mousis, O.; Rème, H.; Rubin,
M.; Sémon, T.; Tzou, C. -Y.; Waite, J. H.; Wurz, P.
Bibcode: 2016ApJ...819..126M
Altcode:
Comets considered to be pristine objects contain key information about
the early formation of the solar system. Their volatile components can
provide clues about the origin and evolution of gases and ices in the
comets. Measurements with ROSINA/RTOF at 67P/Churyumov-Gerasimenko have
now allowed, for the first time, a direct in situ high-time resolution
measurement of the most abundant cometary molecules originating
directly from a comet’s nucleus over a long time-period, much longer
than any previous measurements at a close distance to a comet between
3.1 and 2.3 au. We determine the local densities of H2O,
CO2, and CO, and investigate their variabilities.
Title: Evolution of H2O related species in the neutral coma of 67P
Authors: Bieler, A. M.; Altwegg, K.; Balsiger, H. R.; Bar-Nun, A.;
Berthelier, J. J.; Bochsler, P. A.; Briois, C.; Calmonte, U.; Combi,
M. R.; De Keyser, J.; van Dishoeck, E.; Fiethe, B.; Fuselier, S. A.;
Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Hässig, M.; Jäckel, A.;
Kopp, E.; Korth, A.; Le Roy, L.; Mall, U.; Maggiolo, R.; Marty, B.;
Mousis, O.; Owen, T. C.; Reme, H.; Rubin, M.; Sémon, T.; Tzou, C. Y.;
Waite, J. H., Jr.; Walsh, C.; Wurz, P.
Bibcode: 2015AGUFM.P33E..01B
Altcode:
The ROSINA-DFMS mass spectrometer has been probing the coma of 67Psince
the spacecraft arrived at the comet in August 2014.The acquired data
set covers a large range of viewing geometries forthe ever changing
conditions of 67P along its journey to pericenter. With the high
temporal resolutionof ROSINA-DFMS we are able to examine diurnal and
seasonal changesof different species in the gaseous coma.Large scale
heterogeneities in the coma have been reported since the very first
measurements of the neutral inventory at 67P.Many of the minor species
are seen to follow one of the major compounds,H2O, CO or CO2.In this
paper we will present the latest results on H2O related species.We
will discuss the possible trapping/building mechanisms responsible
for these species and why it is different from other species such
asCO, N2 or CO2. Acknowledgements:Work at the University of Michigan
was funded by NASA contract JPL-1266313.Work at UoB was funded by
the State of Bern, the Swiss National Science Foundationand the
European Space Agency PRODEX Program. Work at MPS was funded by the
Max-Planck Society and BMWI contract 50QP1302. Work at Southwest
Research institute was supported by subcontract #1496541 from the
Jet Propulsion Laboratory. Work at BIRA-IASB was supported by the
Belgian Science Policy Office via PRODEX/ROSINA PEA 90020. This work
has been carried out thanks to the support of the A*MIDEX project (n°
ANR-11-IDEX-0001-02) funded by the « Investissements d'Avenir » French
Government program, managed by the French National Research Agency
(ANR). This work was supported by CNES grants at IRAP, LATMOS, LPC2E,
UTINAM, CRPG, and by the European Research Council (grant no. 267255
to B. Marty). A. Bar-Nun thanks the Ministry of Science and the Israel
Space agency. Work by JHW at Southwest Research Institute was funded by
the NASA JPL subcontract NAS703001TONMO710889. EvD and CW are supported
by A-ERC grant 291141 CHEMPLAN and an NWO Veni award. We acknowledge
herewith the work of the whole ESA Rosetta team.
Title: Similarities and differences between the solar wind light
noble gas compositions determined on Apollo 15 SWC foils and on NASA
Genesis targets
Authors: Vogel, N.; Bochsler, P.; Bühler, F.; Heber, V. S.; Grimberg,
A.; Baur, H.; Horstmann, M.; Bischoff, A.; Wieler, R.
Bibcode: 2015M&PS...50.1663V
Altcode: 2015M&PS..tmp..222V
We compare the solar wind (SW) He, Ne, and Ar compositions
collected during the Apollo Solar Wind Composition (SWC)
experiments (1969-1972; Al- & Pt-foils) and the Genesis
mission (2002-2004; so-called DOS targets considered
here). While published SW 20Ne/22Ne
and 36Ar/38Ar ratios of both data sets
agree, differences exist in the 4He/3He,
4He/20Ne, and 20Ne/36Ar
ratios. However, 20Ne/36Ar ratios from
Apollo-16 Pt-foils, exclusively adopted as SW values by the SWC
team, are consistent with the Genesis results. We investigate if
the differences indicate a variability of the SW over the course of
about 30 yr, or systematic biases of the two data sets, which were
collected in different environments and measured several decades
apart in different laboratories (University of Bern; ETH Zurich). New
measurements of Apollo-15 SWC aluminum foils in Zurich generally agree
with the original measurements performed in Bern. Zurich samples show
slightly lower 4He concentrations suggesting a few percent
of diffusive loss of 4He during storage of the foils. A 3%
difference between the He isotopic ratios measured in Bern and in Zurich
possibly represents an analytical bias between the laboratories. The low
SW 4He/20Ne and 20Ne/36Ar
ratios in Apollo-15 Al-foils compared to Genesis data are consistent
with a mixture of Genesis-like SW and noble gases from small amounts of
lunar dust. Our data suggest that the mean SW He, Ne, and Ar isotopic
and elemental compositions have not significantly changed between the
overall Apollo and Genesis mission collection periods.
Title: Abundant molecular oxygen in the coma of comet
67P/Churyumov-Gerasimenko
Authors: Bieler, A.; Altwegg, K.; Balsiger, H.; Bar-Nun, A.;
Berthelier, J. -J.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi,
M.; de Keyser, J.; van Dishoeck, E. F.; Fiethe, B.; Fuselier, S. A.;
Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Hässig, M.; Jäckel, A.;
Kopp, E.; Korth, A.; Le Roy, L.; Mall, U.; Maggiolo, R.; Marty, B.;
Mousis, O.; Owen, T.; Rème, H.; Rubin, M.; Sémon, T.; Tzou, C. -Y.;
Waite, J. H.; Walsh, C.; Wurz, P.
Bibcode: 2015Natur.526..678B
Altcode:
The composition of the neutral gas comas of most comets is dominated
by H2O, CO and CO2, typically comprising as
much as 95 per cent of the total gas density. In addition, cometary
comas have been found to contain a rich array of other molecules,
including sulfuric compounds and complex hydrocarbons. Molecular oxygen
(O2), however, despite its detection on other icy bodies
such as the moons of Jupiter and Saturn, has remained undetected in
cometary comas. Here we report in situ measurement of O2
in the coma of comet 67P/Churyumov-Gerasimenko, with local abundances
ranging from one per cent to ten per cent relative to H2O and
with a mean value of 3.80 +/- 0.85 per cent. Our observations indicate
that the O2/H2O ratio is isotropic in the coma
and does not change systematically with heliocentric distance. This
suggests that primordial O2 was incorporated into the nucleus
during the comet's formation, which is unexpected given the low upper
limits from remote sensing observations. Current Solar System formation
models do not predict conditions that would allow this to occur.
Title: Molecular nitrogen in comet 67P/Churyumov-Gerasimenko indicates
a low formation temperature
Authors: Rubin, M.; Altwegg, K.; Balsiger, H.; Bar-Nun, A.; Berthelier,
J. -J.; Bieler, A.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi,
M.; De Keyser, J.; Dhooghe, F.; Eberhardt, P.; Fiethe, B.; Fuselier,
S. A.; Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Hässig, M.; Jäckel,
A.; Kopp, E.; Korth, A.; Le Roy, L.; Mall, U.; Marty, B.; Mousis, O.;
Owen, T.; Rème, H.; Sémon, T.; Tzou, C. -Y.; Waite, J. H.; Wurz, P.
Bibcode: 2015Sci...348..232R
Altcode:
Molecular nitrogen (N2) is thought to have been the
most abundant form of nitrogen in the protosolar nebula. It is the
main N-bearing molecule in the atmospheres of Pluto and Triton and
probably the main nitrogen reservoir from which the giant planets
formed. Yet in comets, often considered the most primitive bodies
in the solar system, N2 has not been detected. Here we
report the direct in situ measurement of N2 in the Jupiter
family comet 67P/Churyumov-Gerasimenko, made by the Rosetta Orbiter
Spectrometer for Ion and Neutral Analysis mass spectrometer aboard
the Rosetta spacecraft. A N2/CO ratio of (5.70±0.66)×10-3
(2σ standard deviation of the sampled mean) corresponds to depletion
by a factor of ~25.4 ± 8.9 as compared to the protosolar value. This
depletion suggests that cometary grains formed at low-temperature
conditions below ~30 kelvin.
Title: 67P/Churyumov-Gerasimenko, a Jupiter family comet with a high
D/H ratio
Authors: Altwegg, K.; Balsiger, H.; Bar-Nun, A.; Berthelier, J. J.;
Bieler, A.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi, M.;
De Keyser, J.; Eberhardt, P.; Fiethe, B.; Fuselier, S.; Gasc, S.;
Gombosi, T. I.; Hansen, K. C.; Hässig, M.; Jäckel, A.; Kopp, E.;
Korth, A.; LeRoy, L.; Mall, U.; Marty, B.; Mousis, O.; Neefs, E.; Owen,
T.; Rème, H.; Rubin, M.; Sémon, T.; Tzou, C. -Y.; Waite, H.; Wurz, P.
Bibcode: 2015Sci...347A.387A
Altcode:
The provenance of water and organic compounds on Earth and other
terrestrial planets has been discussed for a long time without reaching
a consensus. One of the best means to distinguish between different
scenarios is by determining the deuterium-to-hydrogen (D/H) ratios
in the reservoirs for comets and Earth’s oceans. Here, we report
the direct in situ measurement of the D/H ratio in the Jupiter family
comet 67P/Churyumov-Gerasimenko by the ROSINA mass spectrometer aboard
the European Space Agency’s Rosetta spacecraft, which is found to be
(5.3 ± 0.7) × 10-4—that is, approximately three times the
terrestrial value. Previous cometary measurements and our new finding
suggest a wide range of D/H ratios in the water within Jupiter family
objects and preclude the idea that this reservoir is solely composed
of Earth ocean-like water.
Title: Time variability and heterogeneity in the coma of
67P/Churyumov-Gerasimenko
Authors: Hässig, M.; Altwegg, K.; Balsiger, H.; Bar-Nun, A.;
Berthelier, J. J.; Bieler, A.; Bochsler, P.; Briois, C.; Calmonte,
U.; Combi, M.; De Keyser, J.; Eberhardt, P.; Fiethe, B.; Fuselier,
S. A.; Galand, M.; Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Jäckel,
A.; Keller, H. U.; Kopp, E.; Korth, A.; Kührt, E.; Le Roy, L.; Mall,
U.; Marty, B.; Mousis, O.; Neefs, E.; Owen, T.; Rème, H.; Rubin,
M.; Sémon, T.; Tornow, C.; Tzou, C. -Y.; Waite, J. H.; Wurz, P.
Bibcode: 2015Sci...347a0276H
Altcode: 2015Sci...347.0276H
Comets contain the best-preserved material from the beginning of our
planetary system. Their nuclei and comae composition reveal clues
about physical and chemical conditions during the early solar system
when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and
Neutral Analysis) onboard the Rosetta spacecraft has measured the coma
composition of comet 67P/Churyumov-Gerasimenko with well-sampled time
resolution per rotation. Measurements were made over many comet rotation
periods and a wide range of latitudes. These measurements show large
fluctuations in composition in a heterogeneous coma that has diurnal
and possibly seasonal variations in the major outgassing species:
water, carbon monoxide, and carbon dioxide. These results indicate
a complex coma-nucleus relationship where seasonal variations may be
driven by temperature differences just below the comet surface.
Title: Expected constraints on the outer solar system formation
conditions from the Rosetta-ROSINA measurements
Authors: Mousis, O.; Altwegg, K.; Balsiger, H. R.; Bar-Nun, A.;
Bertaux, J. L.; Berthelier, J. J.; Bieler, A. M.; Bochsler, P. A.;
Briois, C.; Calmonte, U.; Combi, M. R.; De Keyser, J.; Dhooghe, F.;
Fiethe, B.; Fuselier, S.; Gasc, S.; Gliem, F.; Gombosi, T. I.; Hässig,
M.; Jäckel, A.; Kopp, E.; Korth, A.; Le Roy, L.; Mall, U. A.; Marty,
B.; Rème, H.; Rubin, M.; Sauvaud, J. A.; Waite, J. H., Jr.; Wurz, P.
Bibcode: 2014AGUFM.P33D4051M
Altcode:
Formation scenarios of the protosolar nebula invoke two main reservoirs
of ices that took part in the production of icy planetesimals. The
first reservoir, located within the inner region of the protosolar
nebula, contains ices (dominated by H2O, CO, CO2, CH4, N2 and NH3)
originating from the ISM, which, due to their near solar vicinity, were
initially vaporized. With time, the decrease of temperature and pressure
allowed the water in this reservoir to condense at ~150 K in the form
of crystalline ice. It is postulated that a substantial fraction of the
volatile species were trapped as clathrates during this condensation
phase as long as free water ice was available and there was enough
time to overcome the slow kinetics of clathration. On the other hand,
the remaining volatiles that were not enclathrated (due to the lack of
available water ice or a low kinetics of clathration) probably formed
pure condensates at lower temperatures in this part of the nebula. The
second reservoir, located at larger heliocentric distances, is composed
of ices originating from the ISM that did not vaporize when entering
into the disk. In this reservoir, water ice was essentially in the
amorphous form and the other volatiles remained trapped in the amorphous
matrix. The location of the boundary between these two reservoirs is
loosely constrained and may vary between 5 and 30 AU from the Sun,
depending on the postulated nebula's thermodynamic conditions. The
uncertainty in the distance of the boundary implies that comets may
have formed from amorphous ice as well as from crystalline ices and/or
clathrates. Here we review the key in situ measurements that are within
the capabilities of the ROSINA (Rosetta Orbiter Spectrometer for Ion
and Neutral Analysis) instrument aboard the Rosetta spacecraft during
its approach of comet 67P/Churyumov-Gerasimenko. These key measurements
may allow disentangling between the different formation scenarios.
Title: The Variability of Suprathermal Pickup He+ Measured with
SOHO/CELIAS/STOF
Authors: Yu, J.; Berger, L.; Wimmer-Schweingruber, R. F.; Heber, B.;
Hilchenbach, M.; Kallenbach, R.; Bochsler, P. A.; Klecker, B.
Bibcode: 2014AGUFMSH13B4121Y
Altcode:
SOHO/CELIAS/STOF measures suprathermal ions which are preferentially
accelerated and end up as energetic particles. We have investigated
temporal variations of He+ which has its origin in interstellar and
inner-source pickup ions but could also - occasionally - be solar. We
found no interstellar pickup He+ during solar quiet times in the
energy-per-charge range from 35 to 660 keV/e. This gives an upper
limit to the efficiency of the Gloeckler-Fisk v-5 mechanism. Using a
combination of SOHO/CELIAS/PM and ACE/MAG data we investigate the He+
abundances in Co-rotating Interaction Regions (CIRs) during the years
1997 to 2007. We find that suprathermal pickup He+ mainly appears
inside the compressed and decelerated fast solar wind region of (CIRs)
and persists within the leading parts of the fast wind. This is also
found in CIRs which have no associated forward or reverse shocks, the
majority of CIRs at 1 AU. This observation could be explained by an
injection and acceleration process due to a statistical mechanism in
the compressed solar wind such as the Gloeckler-Fisk v-5 mechanism. In
addition, we find an increase in the He+/He++ ratio in December which
we believe to be a signature of SOHO crossing the focusing cone of
interstellar neutral He. This analysis is based on a re-evaluation
and careful modeling of the substantial background which is present in
SOHO/CELIAS/STOF. Using data from SOHO/COSTEP/EPHIN, SOHO/CELIAS/STOF,
and SOHO/CELIAS/SEM, we show that UV is not suppressed efficiently
by the collimator of STOF and triggers the Time-of-Flight unit by
generating photoelectrons. The second and third triggers are then
provided by penetrating energetic particles which hit STOF's silicon
solid-state detectors.
Title: The Composition of Inner-source Heavy Pickup Ions:
SOHO/CELIAS/CTOF Results
Authors: Taut, A.; Berger, L.; Bochsler, P. A.; Drews, C.; Klecker,
B.; Wimmer-Schweingruber, R. F.
Bibcode: 2014AGUFMSH13B4122T
Altcode:
It is commonly acknowledged that there is a source for pickup ions
in the inner heliosphere. These so-called inner-source pickup
ions are most probably created from solar wind ions interacting
with interplanetary dust particles, but a production scenario
consistent with all observations has not been found to date. As
the composition of inner-source pickup ions should depend on their
production, a precise knowledge of this could help identifying the
production mechanism. For this purpose the raw pulse-height analysis
data from the Charge-Time-Of-Flight (CTOF) sensor of the Charge,
ELement, and Isotope Analysis System (CELIAS) on board the SOlar
and Heliospheric Observatory (SOHO) was reanalyzed. An in-flight
calibration of the sensor was performed to identify heavy pickup
ions by their mass-per-charge. The composition of inner-source heavy
pickup ions was derived by a sophisticated statistical assignment of
the counts. Finally, this composition was compared to an estimated
composition one would expect from a production scenario involving
solar wind ions passing through nm-sized dust grains and a good
agreement was found. Due to the large geometry factor of CTOF it
was also possible to investigate the abundance ratio of the two most
prominent inner-source heavy pickup ions, C+ and O+, at different solar
wind speeds. A systematic increase of the O+/C+ abundance ratio with
higher solar wind speeds was found. This is likely to be a further
signature of the production mechanism of inner-source pickup ions.
Title: High-Time Resolution Measurements of Heavy Ions with
SOHO/CELIAS/CTOF
Authors: Janitzek, N. P.; Berger, L.; Drews, C.; Bochsler, P. A.;
Klecker, B.; Wimmer-Schweingruber, R. F.
Bibcode: 2014AGUFMSH33A4134J
Altcode:
The Charge Time-Of-Flight (CTOF) mass spectrometer as part of the
Charge, ELement and Isotope Analysis System (CELIAS) onboard the
SOlar and Heliospheric Observatory (SOHO) is designed to measure the
kinetic properties and elemental/ionic composition of solar wind ions
heavier than H+, which we refer to as heavy ions. This is achieved by
the combined measurement of the energy-per-charge, the time-of-flight
and the energy of the incident ions. The CTOF instrument combines a
remarkable time-of-flight resolution with a large effective area which
allows to determine the velocity distributions of a wide range of
heavy ions with 5 minute cadence. Based on a sophisticated in-flight
calibration and count rate analysis we derived 5-minute velocity
distributions for typical charge states of solar wind carbon, oxygen,
silicon and iron for the CTOF measurement period between day of year
150 and 220 in 1996. In contrast to previous studies we used pure
Pulse Height Analysis (PHA) data, which yields the full mass and
mass-per-charge and velocity information. We analyzed the velocity
spectra for differential streaming relative to the solar wind bulk
proton speed, measured simultaneously with the CELIAS Proton Monitor
(PM). Here we present our results which should provide experimental
constraints for theories of resonant wave-particle interaction and
preferential acceleration of heavy ions in the solar wind.
Title: Minor Ion Species in the Solar Wind As Seen with
SOHO/Celias/Mtof
Authors: Heidrich-Meisner, V.; Berger, L.; Wimmer-Schweingruber,
R. F.; Wurz, P.; Bochsler, P. A.; Ipavich, F. M.; Gloeckler, G.;
Klecker, B.; Paquette, J. A.
Bibcode: 2014AGUFMSH33A4128H
Altcode:
The continuous solar wind is typically categorized as either fast or
slow wind. Unlike the name implies the constitutive difference between
these types of solar wind streams lies not in their respective solar
wind velocity but in their elemental compositions. The long-term
averages of the dominant ions in the solar wind have been measured
with various instruments and are remarkably homogeneous. Here, we are
interested in investigating the minor species contained in the solar
wind. SOHO/CELIAS/MTOF is a high resolution mass spectrometer which has
been continuously operational from 1996 to the present day. The high
mass resolution and long life time of MTOF allows to complement the
existing observations with the abundances of less abundant species
for both typical slow and typical fast solar wind. This allows to
further strengthen the characteristics of both types of solar wind. In
principle MTOF's time resolution of up to five minutes facilitates to
investigate the short-term variability of the solar wind. However, MTOF
is a complex instrument that was intended to be in-flight calibrated
with its sister instrument SOHO/CELIAS/CTOF. But unfortunately CTOF
was only fully operable for about half a year in 1996. Instead we use
solar wind data from ACE/SWICS for the calibration of MTOF whenever
both instruments are sufficiently close to each other that we can
expect them to observe the same solar wind stream.
Title: Expected constraints on the outer solar system formation
conditions from the Rosetta-ROSINA measurements
Authors: Mousis, Olivier; Altwegg, Kathrin; Bertaux, Jean-Loup;
Berthelier, Jean-Jacques; Bieler, Andre; Bochsler, Peter; Briois,
Christelle; Calmonte, Ursina; Combi, Michael R.; De Keyser,
Joan; Dhooghe, Frederik; Fiethe, Bjorn; Fuselier, Stephen A.;
Gasc, Sébastien; Gliem, Fritz; Gombosi, Tamas I.; Haessig, Myrtha;
Jäckel, Annette; Korth, Axel; Le Roy, Lena; Mall, Urs; Marty, Bernard;
Mazelle, Christian; Owen, Tobias; Rème, Henri; Rubin, Martin; Sauvaud,
Jean-André; Waite, Jack H.; Wurz, Peter
Bibcode: 2014DPS....4620905M
Altcode:
Formation scenarios of the protosolar nebula invoke two main reservoirs
of ices that took part in the production of icy planetesimals. The
first reservoir, located within the inner region of the protosolar
nebula, contains ices (dominated by H2O, CO, CO2, CH4, N2 and NH3)
originating from the ISM, which, due to their near solar vicinity, were
initially vaporized. With time, the decrease of temperature and pressure
allowed the water in this reservoir to condense at ~150 K in the form
of crystalline ice. It is postulated that a substantial fraction of the
volatile species were trapped as clathrates during this condensation
phase as long as free water ice was available and there was enough
time to overcome the slow kinetics of clathration. On the other hand,
the remaining volatiles that were not enclathrated (due to the lack of
available water ice or a low kinetics of clathration) probably formed
pure condensates at lower temperatures in this part of the nebula. The
second reservoir, located at larger heliocentric distances, is composed
of ices originating from the ISM that did not vaporize when entering
into the disk. In this reservoir, water ice was essentially in the
amorphous form and the other volatiles remained trapped in the amorphous
matrix. The location of the boundary between these two reservoirs is
loosely constrained and may vary between 5 and 30 AU from the Sun,
depending on the postulated nebula’s thermodynamic conditions. The
uncertainty in the distance of the boundary implies that comets may
have formed from amorphous ice as well as from crystalline ices and/or
clathrates. Here we review the key in situ measurements that are within
the capabilities of the ROSINA (Rosetta Orbiter Spectrometer for Ion
and Neutral Analysis) instrument aboard the Rosetta spacecraft during
its approach of comet 67P/Churyumov-Gerasimenko. These key measurements
may allow disentangling between the different formation scenarios.
Title: Possible modification of the cooling index of interstellar
helium pickup ions by electron impact ionization in the inner
heliosphere
Authors: Chen, Jun Hong; Bochsler, Peter; Möbius, Eberhard; Gloeckler,
George
Bibcode: 2014JGRA..119.7142C
Altcode:
Interstellar neutrals penetrating into the inner heliosphere are
ionized by photoionization, charge exchange with solar wind ions, and
electron impact ionization. These processes comprise the first step in
the evolution of interstellar pickup ion (PUI) distributions. Typically,
PUI distributions have been described in terms of velocity distribution
functions that cool adiabatically under solar wind expansion, with a
cooling index of 3/2. Recently, the cooling index has been determined
experimentally in observations of He PUI distributions with Advanced
Composition Explorer (ACE)/Solar Wind Ion Composition Spectrometer and
found to vary substantially over the solar cycle. The experimental
determination of the cooling index depends on the knowledge of the
ionization rates and their spatial variation. Usually, ionization rates
increase with 1/r2 as neutral particles approach the Sun,
which is not exactly true for electron impact ionization, because
the electron temperature increases with decreasing distance from the
Sun due to the complexity of its distributions and different radial
gradients in temperature. This different dependence on distance may
become important in the study of the evolution of PUI distributions
and is suspected as one of the potential reasons for the observed
variation of the cooling index. Therefore, we investigate in this
paper the impact of electron ionization on the variability of the
cooling index. We find that the deviation of the electron ionization
rate from the canonical 1/r2 behavior of other ionization
processes plays only a minor role.
Title: Observation of High Iron Charge States at Low Energies in
Solar Energetic Particle Events
Authors: Guo, Z.; Möbius, E.; Klecker, B.; Bochsler, P.; Connell,
J. J.; Kartavykh, Y. Y.; Mason, G. M.; Popecki, M. A.
Bibcode: 2014ApJ...785...26G
Altcode:
The ionic charge states of solar energetic particles (SEPs) provide
direct information about the source plasma, the acceleration
environment, and their transport. Recent studies report that
both gradual and impulsive SEP events show mean iron charge
states langQ Ferang ~ 10-14 at low energies E <=
0.1 MeV nuc-1, consistent with their origin from typical
corona material at temperatures 1-2 MK. Observed increases of langQ
Ferang up to 20 at energies 0.1-0.5 MeV nuc-1 in
impulsive SEPs are attributed to stripping during acceleration. However,
Q Fe > 16 is occasionally found in the solar wind,
particularly coming from active regions, in contrast to the exclusively
reported langQ Ferang <= 14 for low energy SEPs. Here
we report results from a survey of all 89 SEP events observed with
Advanced Composition Explorer Solar Energetic Particle Ionic Charge
Analyzer (SEPICA) in 1998-2000 for iron charge states augmented at low
energy with Solar and Heliospheric Observatory CELIAS suprathermal
time-of-flight (STOF). Nine SEP events with langQ Ferang
>= 14 throughout the entire SEPICA and STOF energy range have
been identified. Four of the nine events are impulsive events
identified through velocity dispersion that are consistent with
source temperatures >=2 MK up to ~4 MK. The other five events
show evidence of interplanetary acceleration. Four of them involve
re-acceleration of impulsive material, whose original energy dependent
charge states appear re-distributed to varying extent bringing higher
charge states to lower energy. One event, which shows flat but elevated
langQ Ferang ~ 14.2 over the entire energy range, can
be associated with interplanetary acceleration of high temperature
material. This event may exemplify a rare situation when a second
shock plows through high temperature coronal mass ejection material.
Title: Erratum: "Solar Photoionization Rates for Interstellar
Neutrals in the Inner Heliosphere: H, He, O, and Ne" (2014, ApJS, 210, 12)
Authors: Bochsler, Peter; Kucharek, Harald; Möbius, Eberhard; Bzowski,
Maciej; Sokół, Justyna M.; Didkovsky, Leonid; Wieman, Seth
Bibcode: 2014ApJS..211...32B
Altcode:
No abstract at ADS
Title: The 13C/12C Isotopic Ratio in the Solar Wind
Authors: Wimmer-Schweingruber, R. F.; Berger, L.; Köten, M.; Bochsler,
P.; Gloeckler, G.
Bibcode: 2014LPI....45.1114W
Altcode:
We present the long-term slow solar wind carbon isotopic ratio 12C/13C ~
97 ± 10 as derived from ACE/SWICS. The value is consistent with the
terrestrial one.
Title: The Elemental Composition of Solar Wind with Implications
for Fractionation Processes During Solar Wind Formation
Authors: Heber, V. S.; McKeegan, K. D.; Bochsler, P.; Duprat, J.;
Burnett, D. S.
Bibcode: 2014LPI....45.2117H
Altcode:
We present bulk SW and SW regime elemental abundances measured in
Genesis collectors comprising a wide range of masses and ionization
properties.
Title: Solar Wind Boron Observed in a Hayabusa Sample and a Gas-Rich
Meteorite
Authors: Fujiya, W.; Hoppe, P.; Ott, U.; Meier, M. M. M.; Bochsler, P.
Bibcode: 2014LPI....45.1802F
Altcode:
Boron-10 excesses were found in asteroidal regolith, possibly due to
implanted solar wind. However, the isotopic ratios cannot be explained
by current models.
Title: VizieR Online Data Catalog: Solar photoionization rates
(Bochsler+, 2014)
Authors: Bochsler, P.; Kucharek, H.; Mobius, E.; Bzowski, M.; Sokol,
J. M.; Didkovsky, L.; Wieman, S.
Bibcode: 2014yCat..22100012B
Altcode:
Using the spectral data for solar extreme UV (EUV) routinely available
from Thermosphere Ionosphere Mesosphere Energetics and Dynamics/Solar
EUV Experiment (TIMED/SEE), we have derived the photoionization rates
of H, He, O, and Ne at the location of the Earth for the period from
the launch of TIMED in 2002 up through the end of 2012. We compared
these rates with a set of three proxies, count rates from the Solar
Extreme Ultraviolet Monitor (SEM) on the Charge, ELement, and Isotope
Analysis System (CELIAS) of the Solar and Heliospheric Observatory
(SOHO) spacecraft, the F10.7 cm radio flux, and the MgII core-to-wing
index. (2 data files).
Title: Solar Photoionization Rates for Interstellar Neutrals in the
Inner Heliosphere: H, He, O, and Ne
Authors: Bochsler, P.; Kucharek, H.; Möbius, E.; Bzowski, Maciej;
Sokół, Justyna M.; Didkovsky, Leonid; Wieman, Seth
Bibcode: 2014ApJS..210...12B
Altcode:
Extreme UV (EUV) spectra from the Thermosphere Ionosphere Mesosphere
Energetics and Dynamics (TIMED)/Solar EUV Experiment are used to
infer photoionization rates in the inner heliosphere. Relating
these rates to various proxies describing the solar EUV radiation,
we construct a multi-linear model which allows us to extrapolate
ionization rates back to periods when no routine measurements of the
solar EUV spectral distribution have been available. Such information
is important, e.g., for comparing conditions of the interstellar
neutral particles in the inner heliosphere at the time of Ulysses/GAS
observations with conditions during the more recent observations of the
Interstellar Boundary Explorer. From a period of 11 yr when detailed
spectra from both TIMED and three proxies—Solar and Heliospheric
Observatory/CELIAS/SEM-rates, F10.7 radio flux, and Mg II core-to-wing
indices—have been available, we conclude that the simple model is
able to reproduce the photoionization rates with an uncertainty of
typically 5%.
Title: Observational study of the cooling behavior of interstellar
helium pickup ions in the inner heliosphere
Authors: Chen, Jun Hong; Möbius, Eberhard; Gloeckler, George;
Bochsler, Peter; Bzowski, Maciej; Isenberg, Philip A.; Sokół,
Justyna M.
Bibcode: 2013JGRA..118.3946C
Altcode:
velocity distribution of interstellar pickup ions (PUIs) has typically
been described as evolving through fast pitch angle scattering followed
by adiabatic cooling while being transported radially outward with the
solar wind. In combination, the ionization rate, which controls the
radial profile of the interstellar neutrals, and the cooling process
determine the slope of the observed PUI distributions. Thus far, a
cooling index of 3/2 for the PUI velocity distributions has been used
in almost all studies. This value is based on the implicit assumptions
of immediate PUI isotropization due to pitch angle scattering
and solar wind expansion with the square of the distance from the
Sun. Here we determine the observed cooling index in a comparison
of He+ PUI distributions taken for 1 month in the upwind
direction with ACE SWICS from 1999 through 2010 over the past solar
cycle with such an isotropic PUI model, treating the cooling index
as a free parameter. The ionization rate is obtained simultaneously
from independent observations. To separate effects of slow pitch angle
scattering of PUIs, the comparison is repeated for times restricted to
perpendicular interplanetary magnetic field (IMF). When averaged over
the entire data set, the cooling index is very close to 3/2. However, it
varies substantially from 1.1 to 1.9 between samples, shows a distinct
variation with solar activity, and has a significant correlation with
sunspot number when data are restricted to nearly perpendicular IMF
(θBvSW>60°) excluding the slow pitch angle scattering in the radial
IMF direction. The potential influence of slow pitch angle scattering,
solar wind structures, and electron ionization on the cooling index
and its variations is discussed.
Title: Interstellar Neutral Gas Flow Measurements with the
Interstellar Boundary Explorer (IBEX) - Implications on Interstellar
Medium and Heliosphere Diagnostics
Authors: Moebius, E.; Bochsler, P. A.; Bzowski, M.; Fuselier, S. A.;
Heirtzler, D.; Hlond, M.; Kubiak, M.; Kucharek, H.; Lee, M. A.;
Leonard, T.; McComas, D. J.; Saul, L. A.; Schwadron, N. A.; Sokol,
J.; Wurz, P.
Bibcode: 2013AGUSMSH54B..06M
Altcode:
The Interstellar Boundary Explorer (IBEX) observes the interstellar
neutral gas flow tra-jectories at their perihelion in Earth's orbit
every year from December through late March, when the Earth moves
into the oncoming flow. Surprisingly, the initial quantita-tive
analysis resulted in a somewhat different interstellar flow vector
with noticeably lower speed than obtained previously. In comparison
with astronomical observations of the flow vectors of neighboring
interstellar clouds, this result locates the solar system within the
Local Interstellar Cloud (LIC), contrary to the previous determination,
which indicated values between the LIC and the G-Cloud. This year,
the fifth season is being accumulated, providing a database over
increasing solar activity and with varying view-ing strategies. These
recurring observations of the interstellar flow pattern and its spatial
distribution allow us to consolidate the derived physical conditions
of the surrounding interstellar medium. We can also track variations
in the flow at 1 AU that may arise from solar cycle related changes in
ionization and radiation pressure for H and explore any other variations
of the neutral gas flow. Based on the angular distributions in latitude
and longitude, the neutral flow observations also indicate the presence
of a secondary compo-nent for most of the species, which most probably
stems from charge exchange with ions in the outer heliosheath. We will
review our observations and discuss implications for the LIC and its
interaction with the heliosphere in the light of a growing data set
and improv-ing analysis techniques.
Title: A multi-timescale view on the slow solar wind with MTOF
Authors: Heidrich-Meisner, Verena; Wimmer-Schweingruber, Robert F.;
Wurz, Peter; Bochsler, Peter; Ipavich, Fred M.; Paquette, John A.;
Klecker, Bernard
Bibcode: 2013EGUGA..15.9237H
Altcode:
The solar wind is known to be composed of several different types of
wind. Their respective differences in speed gives rise to the somewhat
crude categories slow and fast wind. However, slow and fast winds also
differ in their composition and plasma properties. While coronal holes
are accepted as the origin of the fast wind (e.g. [Tu2005]), slow wind
is hypothesized to emanate from different regions and to be caused by
different mechanisms, although the average properties of slow wind are
remarkably uniform. Models for the origin of the slow solar wind fall
in three categories. In the first category, slow wind originates from
the edges of coronal holes and is driven by reconnection of open field
lines from the coronal hole with closed loops [Schwadron2005]. The
second category relies on reconnection as well but places the source
regions of the slow solar wind at the boundaries of active regions
[Sakao2007]. A topological argument underlies the third group which
requires that all coronal holes are connected by the so-called "S-web"
as the driver of the slow solar wind [Antiochos2011]. Solar wind
composition has been continuously measured by for example SOHO/CELIAS
and ACE/SWICS. In this work we focus on the mass time-of-flight
instrument of SOHO/CELIAS/MTOF [Hovestadt1995], which has been
collecting data from 1996 to the present day. Whereas much attention
in previous years has been focused on spectacular features of the
solar wind like (interplanetary) coronal mass ejections (ICMEs) our
main interest lies in understanding the slow solar wind. Although it is
remarkably homogeneous in its average properties (e.g. [vonSteiger2000])
it contains many short term variations. This motivates us to investigate
the slow solar wind on multiple timescales with a special focus on
identifying individual stream with unusual compositions. A first step
in this is to identify individual streams. A useful tool to do this
reliably is specific entropy [Pagel2004]. Consequently, this leads to
an extensive picture of individual streams from MTOF, which can be
combined with observations from other spacecraft in the future. In
particular, identifying and understanding short-term variations of
the slow solar wind has the potential to help distinguishing between
different possible source regions and mechanisms. Further, with the
long term goal of identifying possible different source mechanisms
or regions, we analyze and compare the properties of individual
streams on short time scales to focus on significant deviations from
the average properties of slow solar wind. References [Antiochos2011]
SK Antiochos, Z. Mikic, VS Titov, R. Lionello, and JA Linker. A model
for the sources of the slow solar wind. The Astrophysical Journal,
731(2):112, 2011. [Hovestadt1995] D. Hovestadt, M. Hilchenbach,
A. Bürgi, B. Klecker, P. Laeverenz, M. Scholer, H. Grünwaldt,
WI Axford, S. Livi, E. Marsch, et al. Celias-charge, element and
isotope analysis system for soho. Solar Physics, 162(1):441-481,
1995. [Pagel2004] AC Pagel, NU Crooker, TH Zurbuchen, and JT
Gosling. Correlation of solar wind entropy and oxygen ion charge
state ratio. Journal of geophysical research, 109(A1):A01113,
2004. [Sakao2007] T. Sakao, R. Kano, N. Narukage, J. Kotoku,
T. Bando, E.E. DeLuca, L.L. Lundquist, S. Tsuneta, L.K. Harra,
Y. Katsukawa, et al. Continuous plasma outflows from the edge of
a solar active region as a possible source of solar wind. Science,
318(5856):1585-1588, 2007. [Schwadron2005] NA Schwadron, DJ McComas,
HA Elliott, G. Gloeckler, J. Geiss, and R. Von Steiger. Solar wind
from the coronal hole boundaries. Journal of geophysical research,
110(A4):A04104, 2005. [Tu2005] C.Y. Tu, C. Zhou, E. Marsch, L.D. Xia,
L. Zhao, J.X. Wang, and K. Wilhelm. Solar wind origin in coronal
funnels. Science, 308(5721):519-523, 2005. [vonSteiger2000] R. Von
Steiger, N. Schwadron, LA Fisk, J. Geiss, G. Gloeckler, S. Hefti,
B. Wilken, RF Wimmer-Schweingruber, and TH Zurbuchen. Composition
of quasi-stationary solar wind flows from ulysses/solar wind ion
composition spectrometer. Journal of geophysical research, 105:27, 2000.
Title: Elemental Fractionation Processes in the Solar Wind Revealed
by Genesis Solar Wind Regime Samples
Authors: Heber, V. S.; McKeegan, K. D.; Bochsler, P.; Burnett, D. S.;
Guan, Y.; Reisenfeld, D. B.; Wieler, R.
Bibcode: 2013LPI....44.3028H
Altcode: 2013LPICo1719.3028H
We present for the first time Na, Al, and Mg fluences in the solar wind
(SW) measured in Genesis regime collectors. SW fractionation processes
are discussed.
Title: Solar Abundances of Volatile Elements Revisited After Genesis
Authors: Bochsler, P.; Heber, V. S.; Burnett, D. S.
Bibcode: 2013LPI....44.1277B
Altcode: 2013LPICo1719.1277B
Significant differences among elemental abundances from different
solar sources can be reduced or eliminated when results from the
Genesis mission are used.
Title: Application of Solar EUV-Spectra to the Study of
Photoionization of Interstellar Neutrals in the Heliosphere (invited)
Authors: Bochsler, Peter; Bzowski, Maciej; Kucharek, Harald; Möbius,
Eberhard; Sokół, Justyna M.
Bibcode: 2013enss.confE..49B
Altcode:
For investigations of neutral interstellar gas penetrating into
the inner solar system, as well for the study of so-called pickup
ions, which are produced from inflowing interstellar matter in the
heliosphere, it is crucial to determine the photoionization rates
of various elements by solar EUV-radiation. We routinely use the
EUV-spectra from TIMED/SEE to compute the photoionization rates of H,
He, O, and Ne. Since observations of interstellar neutrals and pickup
ions in the heliosphere are also available for periods long before
solar EUV-spectra became routinely available, it is also important to
find good proxies for photoionization rates. For this purpose we have
developed a linear model involving different proxies (F10.7, Mg IIc/w,
Lyman alpha and SOHO/CELIAS/SEM). For the past decade, for which
all proxies and the TIMED spectra are available, we typically find
average deviations of the model results from the TIMED/SEE-derived
values of the order of a few percent. However, this model does not
include systematic errors, e.g., from calibration uncertainties. We
also investigate the impact of temporal and spatial inhomogeneities
on photoionization rates and on the flow of interstellar gas through
the heliosphere and on the production of pickup ions.
Title: Solar Oxygen Isotopes After Genesis: Is the Final Word Out?
Authors: Bochsler, P.; Eggenberger, P.; Meynet, G.
Bibcode: 2013LPI....44.1557B
Altcode: 2013LPICo1719.1557B
We investigate "non-mass-dependent" mechanisms to shift isotopes of
the solar wind oxygen away from the terrestrial fractionation line.
Title: Reflection of solar wind hydrogen from the lunar surface
Authors: Funsten, H. O.; Allegrini, F.; Bochsler, P. A.; Fuselier,
S. A.; Gruntman, M.; Henderson, K.; Janzen, P. H.; Johnson, R. E.;
Larsen, B. A.; Lawrence, D. J.; McComas, D. J.; MöBius, E.;
Reisenfeld, D. B.; RodríGuez, D.; Schwadron, N. A.; Wurz, P.
Bibcode: 2013JGRE..118..292F
Altcode:
The solar wind continuously flows out from the Sun and directly
interacts with the surfaces of dust and airless planetary bodies
throughout the solar system. A significant fraction of solar wind ions
reflect from an object's surface as energetic neutral atoms (ENAs). ENA
emission from the Moon was first observed during commissioning of the
Interstellar Boundary Explorer (IBEX) mission on 3 December 2008. We
present the analysis of 10 additional IBEX observations of the Moon
while it was illuminated by the solar wind. For the viewing geometry and
energy range (> 250 eV) of the IBEX-Hi ENA imager, we find that the
spectral shape of the ENA emission from the Moon is well-represented
by a linearly decreasing flux with increasing energy. The fraction
of the incident solar wind ions reflected as ENAs, which is the ENA
albedo and defined quantitatively as the ENA reflection coefficient
RN, depends on the incident solar wind speed, ranging from
~0.2 for slow solar wind to ~0.08 for fast solar wind. The average
energy per incident solar wind ion that is reflected to space is 30
eV for slow solar wind and 45 eV for fast solar wind. Once ionized,
these ENAs can become pickup ions in the solar wind with a unique
spectral signature that reaches 3vSW. These results apply
beyond the solar system; the reflection process heats plasmas that
have significant bulk flow relative to interstellar dust and cools
plasmas having no net bulk flow relative to the dust.
Title: Solar Parameters for Modeling the Interplanetary Background
Authors: Bzowski, Maciej; Sokół, Justyna M.; Tokumaru, Munetoshi;
Fujiki, Kenichi; Quémerais, Eric; Lallement, Rosine; Ferron,
Stéphane; Bochsler, Peter; McComas, David J.
Bibcode: 2013ccfu.book...67B
Altcode: 2011arXiv1112.2967B
The goal of the working group on cross-calibration of past and
present ultraviolet (UV) datasets of the International Space
Science Institute (ISSI) in Bern, Switzerland was to establish a
photometric cross-calibration of various UV and extreme ultraviolet
(EUV) heliospheric observations. Realization of this goal required
a credible and up-to-date model of the spatial distribution of
neutral interstellar hydrogen in the heliosphere, and to that end,
a credible model of the radiation pressure and ionization processes
was needed. This chapter describes the latter part of the project:
the solar factors responsible for shaping the distribution of neutral
interstellar H in the heliosphere. In this paper we present the solar
Lyman-α flux and the topics of solar Lyman-α resonant radiation
pressure force acting on neutral H atoms in the heliosphere. We will
also discuss solar EUV radiation and resulting photoionization of
heliospheric hydrogen along with their evolution in time and the still
hypothetical variation with heliolatitude. Furthermore, solar wind and
its evolution with solar activity is presented, mostly in the context
of charge exchange ionization of heliospheric neutral hydrogen, and
dynamic pressure variations. Also electron-impact ionization of neutral
heliospheric hydrogen and its variation with time, heliolatitude, and
solar distance is discussed. After a review of the state of the art in
all of those topics, we proceed to present an interim model of the solar
wind and the other solar factors based on up-to-date in situ and remote
sensing observations. This model was used by Izmodenov et al. (2013,
this volume) to calculate the distribution of heliospheric hydrogen,
which in turn was the basis for intercalibrating the heliospheric
UV and EUV measurements discussed in Quémerais et al. (2013, this
volume). Results of this joint effort will also be used to improve
the model of the solar wind evolution, which will be an invaluable
asset in interpretation of all heliospheric measurements, including,
among others, the observations of Energetic Neutral Atoms by the
Interstellar Boundary Explorer (IBEX).
Title: Diagnostics of the Interstellar Gas with IBEX Neutral Atom
Observations in the Inner Heliosphere
Authors: Moebius, E.; Bochsler, P. A.; Bzowski, M.; Frisch, P. C.;
Fuselier, S. A.; Kucharek, H.; Leonard, T.; McComas, D. J.; Petersen,
L.; Saul, L. A.; Schwadron, N. A.; Wurz, P.
Bibcode: 2012AGUFMSH22A..01M
Altcode:
The Interstellar Boundary Explorer (IBEX) observes the interstellar gas
flow, which penetrates the heliosphere, every spring when the Earth
moves antiparallel to the flow direction. During the previous deep
solar minimum, four interstellar species, H, He, O, and Ne have been
observed. Based on the flux ratios obtained with the IBEX-Lo sensor
at the location of the spacecraft at 1 AU, the abundance ratios in
the gas phase of the local interstellar cloud can be inferred within
measurement and modeling uncertainties. Using independently obtained
ionization rates for the prevailing solar minimum conditions during
the observations, the ratios at the termination shock are obtained. To
infer the abundance ratios in the interstellar medium, the filtration
of the gas in the heliospheric interface and the degree of ionization
of the species also are taken into account. Here, we concentrate on
the first direct measurement of the neutral Ne/O abundance ratio
at 1 AU with IBEX. Including all uncertainties, our preliminary
estimate of the Ne/O ratio in the surrounding interstellar gas is
0.27±0.10, which is—within uncertainties—consistent with previous
results from pickup ions. Strategies to reduce the observational and
modeling uncertainties involving extended observations under varying
solar activity conditions will be discussed. Even with the large
uncertainties, the current abundance value is significantly different
from the solar and the average galactic abundance ratio; it is larger
than both values. This result may indicate that a significant fraction
of oxygen in the local interstellar medium is hidden in grains and/or
ices. The result may also tell us something about variations in the
composition of different interstellar gas environments.
Title: Radiation Pressure from IBEX Observations of Interstellar
Neutral Hydrogen
Authors: Lee, M. A.; Schwadron, N. A.; Saul, L. A.; Moebius, E.;
Bochsler, P. A.; Bzowski, M.; Fuselier, S. A.; Kucharek, H.; McComas,
D. J.; Wurz, P.
Bibcode: 2012AGUFMSH23A2219L
Altcode:
Neutral hydrogen atoms travel into the heliosphere from the local
interstellar medium and experience strong radiation pressure due
to resonant absorption and re-emission of Ly-alpha. This radiation
pressure roughly compensates solar gravity. As a result, interstellar
hydrogen atoms move along trajectories that are quite different than
those of heavier interstellar species such as helium and oxygen that
experience relatively weak radiation pressure. IBEX observations show
clear effects of radiation pressure in a large longitudinal shift in
the peak of interstellar hydrogen compared with that of interstellar
helium [Saul et al., 2012]. Here, we extend the Lee et al. [2012]
interstellar neutral model to describe the longitudinal distribution
of hydrogen near 1 AU and provide new estimates of solar radiation
pressure by comparing the model results with the hydrogen observations.
Title: Combined Maximum Likelihood Fitting and Analytical Modeling
of the Interstellar Neutral Gas Flow as Observed by IBEX
Authors: Leonard, T.; Moebius, E.; Bochsler, P. A.; Fuselier, S. A.;
Heirtzler, D.; Kucharek, H.; Lee, M. A.; McComas, D. J.; Schwadron,
N. A.
Bibcode: 2012AGUFMSH23A2217L
Altcode:
The Interstellar Boundary Explorer (IBEX) observes neutral interstellar
gas flow distributions at the Earth's orbit providing the most detailed
information on the physical parameters (flow direction, flow speed,
and temperature) of the surrounding interstellar medium (ISM) and
the interaction with the heliospheric boundary. IBEX has observed
interstellar neutral H, He, O, and Ne and has completed its fourth
observation season of the ISM flow. The maximum likelihood method has
been used for fitting the ISM flow distributions due to its substantial
advantages over least square fitting procedures when dealing with low
counting statistics which is often the case with the minor species. IBEX
is a spinning spacecraft with the spin axis aligned with the Earth-Sun
line at the beginning of each orbit, providing observations near
the perihelion of the interstellar atom trajectories. However, over
the course of the orbit, the spin axis pointing drifts away from the
Sun. As a result, the ISM flow observables, such as ISM peak rate and
location in latitude, vary slowly over the course of the orbit. The
spin axis drift is inserted into an analytical model of the ISM flow
(Lee et al. 2012) and fitted to each IBEX orbit such that the ISM flow
observables can be determined at the location where the spin axis is
aligned with the Sun-Earth line, the perihelion of the interstellar
trajectories. This is an improvement of the previous analysis of
the IBEX ISM flow observations using the analytical model (Möbius
et al. 2012), where the ISM flow observables were interpolated or
extrapolated to the location where the spin axis is aligned with the
Sun-Earth line. The application of the maximum likelihood method and
the use of the analytical model of the ISM flow will be described along
with a discussion of the He distribution results and plans for the O
(+Ne) distribution.
Title: Global Oxygen ENAs sky maps from IBEX-Lo: Implication on the
ENA sources
Authors: Park, J.; Kucharek, H.; Moebius, E.; Bochsler, P. A.
Bibcode: 2012AGUFMSH11A2197P
Altcode:
The Interstellar Boundary Explorer (IBEX) spacecraft is orbiting the
Earth on a highly elliptical trajectory carrying two highly sensitive
single-pixel ENA cameras: IBEX-Lo measures energetic neutral atoms
(ENAs) from ~10 eV to 2 keV and IBEX-Hi measures them from ~300 eV to 6
keV. The IBEX-Lo sensor can separate two ENA species (H and O) and we
completed all-sky ENA maps over more than three years. The H ENA maps
include the interstellar H and He gas flow at low energies (~10 to 135
eV) as well as the ribbon and distributed heliospheric ENAs over the
entire energy ranges. In contrast, our current analysis shows that all
sky neutral Oxygen maps only contain the interstellar gas flow but no
ribbon. There could be several potential reasons as to why the ribbon
may not appear in the O ENA maps. We have limited counting statistics
as well as a limited energy range. In order to improve counting
statistics we overlaid the O maps for three years and we integrated
over the upper energy range (~0.2 to 2.3 keV). Based on a commonly
accepted value for the charge exchange rate and the neutral density of
hydrogen, we estimate the expected fluxes, integrated along the line
of sight, and then compare them with the measured O ENA fluxes. That
comparison shows that we would have enough counting statistics to see
ribbon signature. To constrain the expected energy spectrum of O ENAs
from the ribbon, we assume a possible association of the ribbon with
the solar wind. Recent models such as Heerikuisen et al.(2010) and
Siewert et al. (2012) make this assumption. Since the H ribbon signal
peaks at 1.1 keV with the above-mentioned assumption, an O ribbon would
appear beyond the maximum energy limit of IBEX-Lo. However, signatures
of the ribbon in the H ENA maps are observed at lower energies down
to 0.2 keV. This would imply that signatures of the ribbon in the O
ENA maps could be expected in the energy range of IBEX-Lo. Although,
our current study does not shows the ribbon like feature in the all
sky O maps of IBEX-Lo, it will constraint the location and possible
production mechanism(s) of ENAs. References: Siewert, M. et al.,
A&A, 539, A75, 2012. Heerikhuisen, J. et al., ApJ, 708L, 126H, 2010
Title: Isotopic Mass Fractionation of Solar Wind: Evidence from Fast
and Slow Solar Wind Collected by the Genesis mission
Authors: Heber, Veronika S.; Baur, Heinrich; Bochsler, Peter; McKeegan,
Kevin D.; Neugebauer, Marcia; Reisenfeld, Daniel B.; Wieler, Rainer;
Wiens, Roger C.
Bibcode: 2012ApJ...759..121H
Altcode:
NASA's Genesis space mission returned samples of solar wind collected
over ~2.3 years. We present elemental and isotopic compositions of He,
Ne, and Ar analyzed in diamond-like carbon targets from the slow and
fast solar wind collectors to investigate isotopic fractionation
processes during solar wind formation. The solar wind provides
information on the isotopic composition for most volatile elements for
the solar atmosphere, the bulk Sun and hence, on the solar nebula from
which it formed 4.6 Ga ago. Our data reveal a heavy isotope depletion
in the slow solar wind compared to the fast wind composition by 63.1 ±
2.1‰ for He, 4.2 ± 0.5‰ amu-1 for Ne and 2.6 ± 0.5‰
amu-1 for Ar. The three Ne isotopes suggest that isotopic
fractionation processes between fast and slow solar wind are mass
dependent. The He/H ratios of the collected slow and fast solar wind
samples are 0.0344 and 0.0406, respectively. The inefficient Coulomb
drag model reproduces the measured isotopic fractionation between fast
and slow wind. Therefore, we apply this model to infer the photospheric
isotopic composition of He, Ne, and Ar from our solar wind data. We
also compare the isotopic composition of oxygen and nitrogen measured in
the solar wind with values of early solar system condensates, probably
representing solar nebula composition. We interpret the differences
between these samples as being due to isotopic fractionation during
solar wind formation. For both elements, the magnitude and sign of the
observed differences are in good agreement with the values predicted
by the inefficient Coulomb drag model.
Title: Inflow direction of interstellar neutrals deduced from pickup
ion measurements at 1 AU
Authors: Drews, Christian; Berger, Lars; Wimmer-Schweingruber,
Robert F.; Bochsler, Peter; Galvin, Antoinette B.; Klecker, Berndt;
Möbius, Eberhard
Bibcode: 2012JGRA..117.9106D
Altcode: 2012JGRA..11709106D
Observations of interstellar pickup ions inside the heliosphere
provide an indirect method to access information on the surrounding
interstellar medium. The so-called pickup ion focusing cone and
pickup ion crescent, which show an imprint of the related longitudinal
distribution of interstellar neutrals in form of two overabundances
on the down- and upwind side of the sun, are both believed to be
aligned along the inflow vector of the interstellar medium. By finding
their longitudinal positions, we can give an accurate value for the
inflow direction λISM of interstellar matter. For that we
performed an epoch analysis of interstellar pickup ions measured by
the PLAsma and SupraThermal Ion Composition instrument (PLASTIC) on
the Solar TErrestrial RElations Observatory mission (STEREO) and were
able to reveal in situ the longitudinal distribution of interstellar
He+, O+, and Ne+ pickup ions in the
ecliptic plane at 1 AU. The previously accepted values for the inflow
direction of interstellar matter in ecliptic longitude, as obtained
with Ulysses/GAS (λ = 75.4° ± 0.5°), Prognoz 6 (λ = 74.5° ±
1°), and ACE/SWICS (λ = 74.43° ± 0.33°), are currently debated,
especially in view of recent results from the Interstellar Boundary
Explorer (IBEX) mission that show an inflow direction of interstellar
neutral helium of λ = 79° + 3.0°(-3.5°). Four years of data
collected with PLASTIC aboard STEREO A provided statistics sufficient
not only to obtain values for the inflow direction of interstellar
helium (λCone = 77.4° ± 1.9° and λCrescent
= 80.4° ± 5.4°, deduced from an analysis of the He+
focusing cone and crescent, respectively) but also to derive values
for the inflow direction of interstellar neon (λCone =
77.4° ± 5.0° and λCrescent = 79.7° ± 2.6°) and oxygen
(λCrescent = 78.9° ± 3.1°). Although our values for
He+, O+, and Ne+ are consistent with
results from ACE, Ulysses, and Prognoz 6, considering the statistical
and systematic uncertainties (except λNe,Crescent), they
are systematically larger than the previously accepted values of 74.99
± 0.55° and show a better agreement with the values from IBEX.
Title: First look at the secondary population of neutral interstellar
helium observed by the Interstellar Boundary Explorer
Authors: Bzowski, Maciej; Izmodenov, Vladislav; McComas, David;
Bochsler, Peter; Alexashov, Dmitry; Schwadron, Nathan; Sokol, Justyna
M.; Heirtzler, David M.; Kubiak, MMarzena A.; Möbius, Eberhard
Bibcode: 2012cosp...39..265B
Altcode: 2012cosp.meet..265B
The Interstellar Boundary Explorer (IBEX) has recently discovered that
the flow neutral interstellar helium at the entrance to the heliosphere
is significantly different than previously thought. Furthermore,
a portion of the observed helium signal cannot be explained with a
single-population Maxwellian gas. This suggests that another source
of neutral helium exists in the vicinity of the heliosphere. This
source may be charge exchange between neutral interstellar atoms and
interstellar He^+ ions in the outer heliosheath, which results in
the creation of a secondary population of neutral He atoms. The flow
of this secondary population is expected to be more complex than the
simple solar gravity-modified flow of the primary, but at this early
phase of our investigation we assume that the secondary population
in its source region can be described by a homogeneous Maxwellian
distribution function. With this assumption, we start from the flow
parameters of the secondary He population predicted by the Moscow
Mote Carlo model of the heliosphere and fit them to the IBEX-Lo data
from orbits that precede the passage of the peak primary interstellar
flow where the secondary population is clearly visible. Preliminary
values of the fitted parameters are markedly different from the flow
parameters of the primary population both in the flow direction and
in the magnitudes of velocity and temperature. The slower speed and
increased temperature values that we obtain are in qualitative agreement
with expectations from modern heliospheric models, regardless of the
presence of the local interstellar magnetic field. The significant shift
in the inflow direction of the secondary population relative to the
primary suggests, however, a notable deformation of the heliospheric
interface from axial symmetry, which is most probably due to a strong
interstellar magnetic field. This seems consistent with the need to
increase one of the pressure components at the interstellar-side in
the pressure balance at the heliospheric boundary. Such a requirement
is suggested by the recent discovery that the local interstellar flow
velocity is markedly lower than previously thought.
Title: Survival probabilities of ENAs in the heliosphere
Authors: Sokol, Justyna M.; McComas, David; Bochsler, Peter; Tokumaru,
Munetoshi; Wurz, Peter; Fujiki, Kenichi; Bzowski, Maciej; Kubiak,
MMarzena A.
Bibcode: 2012cosp...39.1855S
Altcode: 2012cosp.meet.1855S
Energetic Neutral Atoms (ENAs) bring information about the processes at
the outskirts of the heliosphere to location where they can be directly
sampled. Such observations are now available from a few experiments,
including the Interstellar Boundary Explorer (IBEX) mission and the
ASPERA detectors onboard the Mars Express and Venus Express space
probes. The ENA flux registered in the inner heliosphere should be
quantified by including flux modifications due to the joint action of
solar gravity, radiation pressure, and ionization losses. The ionization
processes include photoionization, charge exchange between ENAs and
solar wind ions, and electron-impact ionization. The rates of these
processes decrease with radial distance and vary with solar cycle
phase. Thus, flux modifications depend on the heliocentric distance
and time. We retrieved the evolution of the solar factors affecting
ENAs from in-situ and remote-sensing observations. For solar wind
parameters in the ecliptic plane, we used the OMNI-2 database. For the
out-of-ecliptic solar wind, we took results of Ulysses measurements and
computer-assisted tomography analysis of interplanetary scintillation
data. The variations of the photoionization rate were derived from
multi-spacecraft, multi-spectral observations of the solar EUV flux,
with data gaps filled by proxies. The electron-impact ionization
rate was calculated based on radial profiles of solar wind electron
temperature measured by Ulysses and Helios. To calculate the resonant
radiation pressure force acting on ENAs, the profile of solar Lyman-α
line is needed. We adopted a profile obtained from SOHO observations,
modulated by the composite solar Lyman-α flux. We briefly present
the time and heliolatitude evolution of the solar factors returned by
the model, which covers the time interval from 1990 through the end
of 2011. Then we discuss survival probabilities of the heliospheric
ENA at the locations of IBEX and ASPERA and show sky maps of survival
probability of ENAs seen by IBEX. We point out changes that have
occurred since IBEX launch due to the increase in solar activity
from the deep minimum in 2008 to the present phase of increasing
activity. Finally, modifications of the ENA flux and flattening of the
energy spectrum in transit from the outer heliosphere to the detection
locations are presented.
Title: Solar wind evolution since 1990 and H ENA ionization rates
and survival probabilities in the heliosphere
Authors: Sokol, J. M.; Kubiak, M. A.; Bzowski, M.; Tokumaru, M.;
Fujiki, K.; McComas, D. J.; Bochsler, P.
Bibcode: 2012EGUGA..14.4723S
Altcode:
We derive the solar wind speed and density evolution in heliolatitude
and time from 1990 to the end of 2011 based on remote-sensing and
in-situ data sources in and out of the ecliptic plane and use it to
calculate survival probabilities of heliospheric Energetic Neutral H
Atoms (H ENA) in the energy range observed by the Interstellar Boundary
Explorer (IBEX). We determine the heliolatitude structure of the solar
wind speed using remote-sensing radio observations of interplanetary
scintillations processed using the Computer Assisted Tomography
algorithm and obtain yearly profiles on a 10-degree heliolatitude grid,
which agree well with the in-situ measurements by Ulysses. Since the
in-situ information on the solar wind density structure out of ecliptic
is only available from the Ulysses data, we derive correlation formulae
between solar wind speed and density profiles from Ulysses fast latitude
scans and calculate the 3D structure of solar wind density. For the
ecliptic heliolatitude band we use in-situ measurements from the OMNI-2
collection. Having obtained evolution of solar wind speed and density
in time and heliolatitude, to calculate the ionization rate of H ENA we
need the photoionization rate of H, which we obtain from TIMED SEE and
SOHO CELIAS/SEM measurements supplemented with proxies. With the history
of evolution of the solar factors responsible for the ionization of H
ENA derived, we calculate the survival probabilities of H ENA observed
by IBEX. To that end, we employ an atom-tracing approach. We track the
atom trajectories from IBEX backwards in time up to the termination
shock, solving the equation of motion and simultaneously calculating
the survival probability against ionization. The equation of motion
includes the forces of solar gravity and radiation pressure, which
is a function of the total solar flux in the Lyman-alpha line and of
radial velocity of the atom relative to the Sun due to the Doppler
effect. To model the radiation pressure, we use a composite time
series of the solar Lyman-alpha flux compiled by the Laboratory for
Atmospheric and Space Physics (LASP), University of Colorado, and a
model of the solar Lyman-alpha line evolution in time based on solar
Lyman-alpha observations from SOHO SUMER. The survival probabilities
are presented as a function of ENA energy, time, and heliolatitude.
Title: Secondary population of neutral interstellar helium observed
by IBEX-Lo: preliminary analysis
Authors: Kubiak, M. A.; Bzowski, M.; Sokol, J. M.; Moebius, E.;
Heirtzler, D.; Alexashov, D. B.; Izmodenov, V. V.; Bochsler, P.;
McComas, D. J.
Bibcode: 2012EGUGA..14.8033K
Altcode:
Interstellar Boundary Explorer (IBEX) recently discovered that the
flow parameters of neutral interstellar helium at the entrance to the
heliosphere are significantly different than previously thought and
additionally that a portion of the observed helium signal cannot be
explained on the grounds of a single-population Maxwellian gas. This
brought the conclusion that another source of neutral helium exists in
the vicinity of the heliosphere. This source may be charge exchange
between neutral interstellar atoms and interstellar He+ ions in
the outer heliosheath, which results in the creation of a secondary
population of neutral He atoms in a process similar to the creation
of the secondary component of neutral interstellar hydrogen. While
the flow of the secondary population of He is expected to be more
complex than the simple solar gravity-modified flow of the primary
population, we assume that the secondary population can be described
by a homogeneous Maxwellian distribution function. Starting from the
parameters of the secondary He population predicted by the Moscow MC
model of the heliosphere, we fit the flow parameters to the IBEX-Lo
data from the orbits in 2010 on which the secondary population is
clearly visible. Preliminary values of the flow parameters are markedly
different from the flow parameters of the primary population both in
the flow direction and in the magnitude of velocity and temperature,
which suggests a strong deformation of the heliosphere from axial
symmetry by interstellar magnetic field.
Title: Estimation of the Neon/Oxygen Abundance Ratio at the
Heliospheric Termination Shock and in the Local Interstellar Medium
from IBEX Observations
Authors: Bochsler, P.; Petersen, L.; Möbius, E.; Schwadron, N. A.;
Wurz, P.; Scheer, J. A.; Fuselier, S. A.; McComas, D. J.; Bzowski,
M.; Frisch, P. C.
Bibcode: 2012ApJS..198...13B
Altcode:
We report the first direct measurement of the Ne/O abundance ratio of
the interstellar neutral gas flowing into the inner heliosphere. From
the first year of Interstellar Boundary Explorer IBEX data collected
in spring 2009, we derive the fluxes of interstellar neutral oxygen and
neon. Using the flux ratio at the location of IBEX at 1 AU at the time
of the observations, and using the ionization rates of neon and oxygen
prevailing in the heliosphere during the period of solar minimum, we
estimate the neon/oxygen ratios at the heliospheric termination shock
and in the gas phase of the inflowing local interstellar medium. Our
estimate is (Ne/O)gas, ISM = 0.27 ± 0.10, which is—within
the large given uncertainties—consistent with earlier measurements
from pickup ions. Our value is larger than the solar abundance ratio,
possibly indicating that a significant fraction of oxygen in the local
interstellar medium is hidden in grains and/or ices.
Title: Neutral Interstellar Helium Parameters Based on IBEX-Lo
Observations and Test Particle Calculations
Authors: Bzowski, M.; Kubiak, M. A.; Möbius, E.; Bochsler, P.;
Leonard, T.; Heirtzler, D.; Kucharek, H.; Sokół, J. M.; Hłond,
M.; Crew, G. B.; Schwadron, N. A.; Fuselier, S. A.; McComas, D. J.
Bibcode: 2012ApJS..198...12B
Altcode: 2012arXiv1202.0415B
Because of its high ionization potential and weak interaction with
hydrogen, neutral interstellar helium (NISHe) is almost unaffected
at the heliospheric interface with the interstellar medium and freely
enters the solar system. This second most abundant species provides some
of the best information on the characteristics of the interstellar gas
in the local interstellar cloud. The Interstellar Boundary Explorer
(IBEX) is the second mission to directly detect NISHe. We present
a comparison between recent IBEX NISHe observations and simulations
carried out using a well-tested quantitative simulation code. Simulation
and observation results compare well for times when measured fluxes
are dominated by NISHe (and contributions from other species are
small). Differences between simulations and observations indicate a
previously undetected secondary population of neutral helium, likely
produced by interaction of interstellar helium with plasma in the outer
heliosheath. Interstellar neutral parameters are statistically different
from previous in situ results obtained mostly from the GAS/Ulysses
experiment, but they do agree with the local interstellar flow vector
obtained from studies of interstellar absorption: the newly established
flow direction is ecliptic longitude 79fdg2, latitude -5fdg1, the
velocity is ~22.8 km s-1, and the temperature is 6200
K. These new results imply a markedly lower absolute velocity of the
gas and thus significantly lower dynamic pressure on the boundaries of
the heliosphere and different orientation of the Hydrogen Deflection
Plane compared to prior results from Ulysses. A different orientation
of this plane also suggests a new geometry of the interstellar magnetic
field, and the lower dynamic pressure calls for a compensation by other
components of the pressure balance, most likely a higher density of
interstellar plasma and strength of interstellar magnetic field.
Title: Interstellar Gas Flow Parameters Derived from Interstellar
Boundary Explorer-Lo Observations in 2009 and 2010: Analytical
Analysis
Authors: Möbius, E.; Bochsler, P.; Bzowski, M.; Heirtzler, D.; Kubiak,
M. A.; Kucharek, H.; Lee, M. A.; Leonard, T.; Schwadron, N. A.; Wu,
X.; Fuselier, S. A.; Crew, G.; McComas, D. J.; Petersen, L.; Saul,
L.; Valovcin, D.; Vanderspek, R.; Wurz, P.
Bibcode: 2012ApJS..198...11M
Altcode:
Neutral atom imaging of the interstellar gas flow in the inner
heliosphere provides the most detailed information on physical
conditions of the surrounding interstellar medium (ISM) and its
interaction with the heliosphere. The Interstellar Boundary Explorer
(IBEX) measured neutral H, He, O, and Ne for three years. We compare
the He and combined O+Ne flow distributions for two interstellar
flow passages in 2009 and 2010 with an analytical calculation, which
is simplified because the IBEX orientation provides observations
at almost exactly the perihelion of the gas trajectories. This
method allows separate determination of the key ISM parameters:
inflow speed, longitude, and latitude, as well as temperature. A
combined optimization, as in complementary approaches, is thus
not necessary. Based on the observed peak position and width in
longitude and latitude, inflow speed, latitude, and temperature
are found as a function of inflow longitude. The latter is then
constrained by the variation of the observed flow latitude as
a function of observer longitude and by the ratio of the widths
of the distribution in longitude and latitude. Identical results
are found for 2009 and 2010: an He flow vector somewhat outside
previous determinations (λISM∞ = 79fdg0+3fdg0(-3fdg5),
β ISM∞ = -4fdg9 ± 0fdg2, V ISM∞ = 23.5 +
3.0(-2.0) km s-1, T He = 5000-8200 K), suggesting
a larger inflow longitude and lower speed. The O+Ne temperature range,
T O+Ne = 5300-9000 K, is found to be close to the upper
range for He and consistent with an isothermal medium for all species
within current uncertainties.
Title: Monte-Carlo Simulation of Pickup Ion Velocity Distributions
in the Inner Heliosphere
Authors: Bochsler, P. A.; Isenberg, P. A.; Moebius, E.
Bibcode: 2011AGUFMSH23B1955B
Altcode:
Using Monte-Carlo simulations with simple assumptions on the pitch-angle
scattering, we investigate the structure of pickup ion velocity
distributions from the inner source and from interstellar helium
penetrating inside 1 AU. A large body of pickup ion measurements from
Ulysses, ACE, and STEREO exists, and our motivation is to investigate
which scattering laws are best able to reproduce the observed
distributions. For inner source pickup ions, we assume the ions to
be generated in the region from 0.2 to 1 AU according to a plausible
distribution. For the pickup ions from interstellar helium, we use
realistic conditions of instreaming gas with a drift velocity of 22.8
km/s at infinity, and a temperature of 6000 K as recently determined
with IBEX. These ionization conditions correspond to periods of high
solar activity. The pickup ions are transported outward in a Parker
spiral magnetic field, undergoing adiabatic focusing and simultaneous
pitch-angle scattering. We choose Monte-Carlo coefficients for the
pitch-angle scattering events to correspond to various assumptions
of the quasilinear theory in typical solar wind wave spectra. We will
report on the results and the comparison with distributions observed
at 1 AU.
Title: Observation of Secondary O in the Interstellar Neutral Gas
Flow with the Interstellar Boundary Explorer (IBEX)
Authors: Moebius, E.; Bochsler, P. A.; Bzowski, M.; Funsten, H. O.;
Fuselier, S. A.; Heirtzler, D.; Kubiak, M. A.; Kucharek, H.; Lee,
M. A.; Leonard, T.; McComas, D. J.; Saul, L. A.; Schwadron, N. A.;
Valovcin, D.; Wu, X.; Wurz, P.
Bibcode: 2011AGUFMSH23B1956M
Altcode:
Neutral atom imaging observations of the interstellar gas flow in
the inner heliosphere provide the most detailed information about
the physical conditions of the surrounding interstellar medium and
the interaction of this flow with the outer heliosheath. Key to
the latter diagnostics is a secondary component of the interstellar
neutral gas flow that originates from charge exchange interstellar
neutrals with outer heliosheath ions, which are diverted around the
heliosphere. Thus their trajectories contain information about the
deceleration, deflection, and heating of interstellar plasma in the
outer heliosheath. The Interstellar Boundary Explorer (IBEX) intercepts
the interstellar neutral atom flow trajectories at their perihelion
at 1 AU and identifies the species with its low energy neutral atom
camera IBEX-Lo. We have now observed the interstellar neutral flow
with IBEX-Lo over three consecutive years and identified neutral
interstellar H, He, O, and Ne in the flow observations. Already over
the first two years, strong indications for a secondary flow component
of O and He emerged. Based on three ISM flow passages thus far, we
will characterize its strength relative to the primary interstellar
O flow and its arrival direction relative to the interstellar flow as
observed for primary interstellar He and O with IBEX. We will discuss
potential implications of these findings.
Title: New Neutral Interstellar Helium Flow Parameters Based on
IBEX-Lo Observations
Authors: Bzowski, M.; Kubiak, M. A.; Moebius, E.; Bochsler, P. A.;
Leonard, T.; Heirtzler, D.; Kucharek, H.; Crew, G. B.; Sokol, J. M.;
Hlond, M.; Schwadron, N. A.; Fuselier, S. A.; McComas, D. J.
Bibcode: 2011AGUFMSH21C..06B
Altcode:
Because of its high ionization potential and weak interaction with
hydrogen, Neutral Interstellar Helium (NISHe) is almost unaffected at
the heliospheric interface with the interstellar medium and freely
enters the solar system. This second most abundant species provides
some of the best information on the characteristics of the interstellar
gas in the Local Interstellar Cloud (LIC). The Interstellar Boundary
Explorer is the second mission to directly detect NISHe (after Ulysses)
and the first to directly detect other interstellar neutrals. We present
a comparison between recent IBEX NISHe observations and simulations
carried out using a well-tested quantitative simulation code. This
code includes motion of the spacecraft and the Earth relative to the
incident NISHe in the inner heliosphere and accounts for both major
and minor interactions between NISHe and its surrounding medium. The
interactions include gravitational attraction by the Sun and losses by
solar photoionization, electron impact ionization, and charge exchange
with solar wind protons and alphas. Simulation and observation results
compare well for times when measured fluxes are dominated by NISHe
(and contributions from other species are small). Differences between
simulations and observations indicate previously undetected secondary
population of neutral helium, likely produced by interaction of helium
with plasma in the outer heliosheath. Interstellar neutral parameters
are statistically different from previous results: the newly-established
flow direction is ecliptic longitude 79.2°, latitude -5.1°, velocity
22.8 km/s. These new results imply a markedly lower absolute velocity of
the gas and thus significantly lower dynamic pressure on the boundaries
of the heliosphere and different orientation of the Hydrogen Deflection
Plane (the plane that contains the inflow vectors of hydrogen and helium
in the inner heliosphere) compared to prior results from Ulysses. A
different orientation of this plane also suggests a new geometry of the
interstellar magnetic field and the lower dynamic pressure calls for a
compensation by other components of the pressure balance, most likely
a higher density of interstellar plasma and strength of interstellar
magnetic field.
Title: Investigation of the Cooling Behavior of Interstellar HE+
Pickup Ions in the Inner Heliosphere
Authors: Chen, J.; Moebius, E.; Bochsler, P. A.; Gloeckler, G.;
Isenberg, P. A.; Bzowski, M.; Sokol, J. M.
Bibcode: 2011AGUFMSH23B1954C
Altcode:
Interstellar neutral gas is streaming though the inner heliosphere
where it is ionized and picked up by solar wind via interaction with
the interplanetary magnetic field (IMF). The dominant ionization process
is solar EUV radiation, augmented slightly by charge exchange with the
solar wind and electron impact ionization. The resulting pickup ion
(PUI) distributions broaden as they are transported radially outward
with the solar wind and are cooled in this process. The ionization
rate, which controls the radial profile of the interstellar neutrals,
and the cooling process together determine the slope of the observed
PUI distributions. Thus far, a cooling index of 3/2 for the PUI
velocity distributions as a function of radial distance from the Sun
(Vasyliunas & Siscoe, JGR, 81,1247, 1976) has been used in almost
all studies. Here, we use the observations of PUI distributions from ACE
SWICS over one month in the upwind direction of the interstellar flow
and of the ionization rate at 1AU from solar maximum to solar minimum to
deduce the actual PUI cooling index. We start with an isotropic model
for interstellar He+ PUIs that is valid for the upwind region and then
compare the modeled phase space density spectrum after integration
over the instrument fields-of-view and energy steps with ACE SWICS
observations. To account for the influence of PUI transport processes we
sort the PUI distributions for IMF orientation and solar wind speed and
start with distributions for nearly perpendicular IMF. The comparison
between the simulated and the time averaged He+ PUI phase space density
contains the cooling index as free parameter because the ionization
rate is obtained simultaneously from observations. We find noticeable
differences of the cooling index from the previously used value of 3/2
and will discuss potential implications on PUI expansion and transport.
Title: Maximum Likelihood Fitting of the Interstellar Neutral Gas
Flow as Observed by IBEX for Comparison with Analytical Modeling
Authors: Leonard, T.; Moebius, E.; Bochsler, P. A.; Bzowski, M.;
Fuselier, S. A.; Heirtzler, D.; Kubiak, M. A.; Kucharek, H.; Lee,
M. A.; McComas, D. J.; Saul, L. A.; Schwadron, N. A.; Wu, X.; Wurz, P.
Bibcode: 2011AGUFMSH23B1958L
Altcode:
Observations of the neutral interstellar gas flow distributions
at the Earth's orbit provide the most detailed information on the
physical parameters (flow direction, flow velocity, and temperature)
of the surrounding interstellar medium (ISM) and the interaction with
the heliospheric boundary. The Interstellar Boundary Explorer (IBEX)
has observed interstellar neutral H, He, O, and Ne. For the often
low counting statistics of the minor species, fitting the model
distributions using a maximum likelihood method has substantial
advantages over least square fitting procedures. Here, we evaluate
the ISM flow observations with an analytical model of the flow,
which is greatly simplified when analyzing the flow trajectories
at their perihelion. The IBEX configuration, with the spin axis
oriented along the Earth-Sun line at the beginning of each orbit,
naturally provides observations near the perihelion of the interstellar
trajectories. However, over the course of the 7.5-day IBEX orbit around
the Earth, the spin axis pointing drifts away from the Sun and the
ISM flow observables, such as ISM peak rate and location in latitude,
vary slowly over the course of the orbit. Therefore, these observables
are interpolated or extrapolated to the location where the spin axis
is aligned with the Sun-Earth line in the ecliptic for comparison with
the analytical model. From the results of the maximum likelihood fits we
are able to deduce, among others, the location of the observed ISM flow
maximum and the latitude of the ISM distribution peak as function of
observer ecliptic longitude. The application of the maximum likelihood
method to IBEX observations will be described along with how the
results are used in the comparison with the analytical ISM flow model.
Title: Local Interstellar Neutral Hydrogen sampled in-situ by IBEX
Authors: Saul, L. A.; McComas, D. J.; Wurz, P.; Kucharek, H.; Moebius,
E.; Rodriguez, D.; Bzowski, M.; Kucharek, H.; Bochsler, P. A.;
Fuselier, S. A.; Crew, G. B.; Leonard, T.; Scheer, J.; Schwadron, N. A.
Bibcode: 2011AGUFMSH23B1957S
Altcode:
Hydrogen gas is the dominant component of the local interstellar
medium. However, due to ionization and interaction with the heliosphere,
direct sampling of the neutral material is more difficult than sampling
the local interstellar neutral Helium, which penetrates deep into the
heliosphere. In this paper we report on the first direct sampling of
the neutral Hydrogen component of the local interstellar medium. We
confirm that the arrival direction of Hydrogen is offset from the local
Helium component. We further report the discovery of a variation of the
penetrating Hydrogen over the first two years of IBEX observations. The
observations are consistent with the Hydrogen having an effective
ratio of outward solar radiation pressure to inward gravitational force
greater than unity (mu>1), and the temporal change observed in the
local interstellar hydrogen is consistent with solar variability as
the cause.
Title: He Pickup Ions in the Inner Heliosphere-Diagnostics of the
Local Interstellar Gas and of Interplanetary Conditions
Authors: Möbius, E.; Klecker, B.; Bochsler, P.; Gloeckler, G.;
Kucharek, H.; Simunac, K. D. C.; Galvin, A. B.; Ellis, L.; Farrugia,
C.; Kistler, L. M.; Luhmann, J. G.; Popecki, M. A.; Russell, C. T.;
Wimmer-Schweingruber, R. F.; Wurz, P.
Bibcode: 2010AIPC.1302...37M
Altcode:
The relative motion of the Sun through the Local Interstellar Cloud
(LIC) leads to a neutral wind through the heliosphere. Because of
its high ionization potential, He remains neutral to well within 1
AU, where it is deflected by the Sun's gravity and forms a focusing
cone on the downwind side. This flow pattern has been studied with
UV backscattering, through pickup ions (PUI), and atom imaging. A
consolidated set of the physical parameters of He in the LIC has
been derived combining all three methods. However, it is still poorly
understood why PUI fluxes and velocity distributions vary substantially
on temporal scales from hours to many days, which leads among other
phenomena to apparent changes in the appearance of the focusing
cone, even after averaging over several days. With the combination
of PLASTIC on STEREO A and B as well as SWICS on ACE, simultaneous
PUI observations over an increasing range of heliospheric longitudes
have become possible, for which we have initiated a cross-calibration
effort between the distributed sensors. With these data that feature
improved temporal resolution, spatial and temporal variations in the
PUI fluxes and spectra can be separated. Therefore, we can probe the
effects on PUI distributions and the observed structure of the focusing
cone that arise from solar wind structures, such as compressions and
rarefactions, from variations in magnetic field strength and direction,
and from changes in the ionization rates.
Title: On the Origin of Inner Source Pickup Ions
Authors: Bochsler, Peter; Möbius, Eberhard; Kucharek, Harald;
Wimmer-Schweingruber, Robert F.
Bibcode: 2010AIPC.1302...44B
Altcode:
Inner source pickup ions are thought to originate from the interaction
of solar wind ions with interplanetary dust grains in the inner
heliosphere. Processes which produce inner source pickup ions, and which
have been considered so far are implantation of solar wind on grains
and subsequent desorption, charge exchange of solar wind ions during
transit through submicron dust grains, sputtering and backscattering
of ions. A large fraction if not all of the dust crossing the sphere
of the Earth's orbit must end up as pickup ions as is evidenced from
the comparable order of magnitude of dust flux inward and pickup ion
flux outward at 1 AU. This suggests that the ultimate fate for a large
fraction of small interplanetary dust particles after evaporation
or sputtering is conversion into pickup ions. Sputtering becomes
particularly efficient when dust particles-after fragmentation by
collisions with each other-have diminished to sizes comparable to
the range of solar wind ions in dust material. The sputter products,
charged or neutral molecules, atoms or ions, ultimately will undergo
photodissociation, photoionization, ionization by charge exchange
with solar wind ions, and/or ionization by electron collisions. We
investigate the relative importance of various processes on pickup
ions on their way out of the inner heliosphere and the relevance of
inner source pickup ions for diagnostics of dust particles near the Sun.
Title: Observation of High Iron Charge States over <0.1 to ~1
MeV/nucleon in Solar Energetic Particle Events
Authors: Guo, Z.; Moebius, E.; Popecki, M.; Klecker, B.; Mason, G. M.;
Bochsler, P. A.
Bibcode: 2010AGUFMSH42B..07G
Altcode:
The ionic charge states of Solar Energetic Particle (SEP) events provide
direct information about the physical properties of the source plasma
and related acceleration processes. In gradual events iron consistently
shows <QFe> ~10-11 reflecting typical corona temperatures,
while impulsive events yield a sharp increase in QFe with energy,
indicating energy dependent stripping. Both types of events approach
similar values for <QFe> for E<0.1 MeV/nuc, indicating similar
source temperature of 1-3 MK. However, distributions with QFe>16
have frequently been found in the solar wind, particularly coming
from active regions. This observation suggests the presence of highly
charged iron ions in potential SEP source populations, while so far
such high QFe has not been observed at low SEP energies. Therefore,
we performed a survey of iron charge states in all SEP events observed
with ACE SEPICA during 1998 - 2000, complemented by ACE SWICS and SOHO
STOF. Out of 89 events we found a set of 6 with <QFe>>14 over
the entire SEPICA energy range of 0.08-0.54 MeV/nuc. The presence of
high charge states over the entire energy range would require either
extremely strong adiabatic deceleration with a very short mean free path
during interplanetary transport or high temperature source material. All
6 events show enhanced abundances in heavy ions and 3He, but only one of
these events exhibits the strong increase in charge state with energy
typically observed in impulsive events. The high temperature source
material may be well correlated to the hot active regions during flare
events. However, a consistent association with specific solar events
and a related acceleration mechanism for these SEPs has yet to be found.
Title: Two Years of Interstellar Flow Observations with the
Interstellar Boundary Explorer (IBEX) - Implications on the LIC
Parameters and the Boundary (Invited)
Authors: Moebius, E.; Bochsler, P. A.; Bzowski, M.; Funsten, H. O.;
Fuselier, S. A.; Heirtzler, D.; Kubiak, M. A.; Kucharek, H.; Lee,
M. A.; Leonard, T.; McComas, D. J.; Petersen, L.; Saul, L. A.;
Schwadron, N. A.; Witte, M.; Wu, X.; Wurz, P.
Bibcode: 2010AGUFMSH23D..08M
Altcode:
Due to the motion of the Sun relative to its neighborhood, the neutral
gas of the local interstellar cloud (LIC) flows through the inner
heliosphere where it is subject to ionization, the Sun’s gravity,
and radiation pressure. Observing the resulting spatial and angular
flow distribution of several interstellar gas species with direct
neutral atom imaging techniques in the inner heliosphere provides us
with the most detailed information on physical conditions of the LIC
and its interaction with the outer heliosheath. The primary interstellar
neutral gas flow reveals the original LIC velocity distribution, while
a secondary flow component from charge exchange with outer heliosheath
ions that are diverted around the heliosphere carries information
on deceleration, deflection, and heating of the interstellar plasma
in the boundary layer. IBEX has observed neutral gas distributions
for almost two years, with two primary interstellar flow passages in
winter 2009 and 2010, of several interstellar species, notably H, He, O,
and Ne, with its triple-coincidence time-of-flight IBEX-Lo sensor. To
unravel LIC parameters from these flow distributions, observations are
compared with test-particle simulations and an analytical calculation
of the gas trajectories, which is simplified by IBEX observations
at almost exactly perihelion of the flow. Both comparison methods
result in the best agreement for a small parameter range, with the
inflow speed functionally tied to the inflow direction in longitude,
approximately bounded by two parameter sets, with identical results
for 2009 and 2010. The first set features the same interstellar
flow vector as found previously for He in a concerted effort at the
International Space Science Institute (ISSI)(Moebius et al.; Witte,
A&A, Vol 426, 2004), but with substantially higher temperature,
and the second set shows the same temperature, but coming from ≈6°
larger longitude and at ≈4 km/s slower speed. Detailed comparison of
the distributions indicates a slight preference for a different flow
vector and the same temperature. For heavy species an approximate
50/50 split between O and Ne is found, which leads to the identical
tempera-ture as for He, when the flow distribution is analyzed
analogous to He, indicating an isothermal LIC for all species. Both
the He and O distribution contain a substantial secondary component,
which arrives from noticeably higher latitude than the primary flow,
indicating a diversion of the interstellar flow.
Title: Flow of neutral interstellar helium into the heliosphere as
inferred from IBEX-Lo observations and simulations
Authors: Bzowski, M.; Kubiak, M. A.; Hlond, M.; Moebius, E.; Leonard,
T.; Heirtzler, D.; Kucharek, H.; Bochsler, P. A.; Schwadron, N. A.;
Crew, G. B.; McComas, D. J.; Fuselier, S. A.
Bibcode: 2010AGUFMSH21A1791B
Altcode:
Previously, a team coordinated through the International Space Science
Institute (ISSI) examined direct neutral gas, pickup ion, and UV
backscatter observations to produce consensus values for the inflow
direction (λ, β), speed v, and temperature T of neutral interstellar
helium from the Local Interstellar Cloud (LIC) with relatively small
uncertainties. Since then, NASA’s Interstellar Boundary Explorer
(IBEX) has started to provide new observations of the interstellar
He flow in Earth orbit, with data currently available from the spring
seasons of 2009 and 2010. Using a test-particle simulation to compute
the spin-phase distributions that IBEX observes during each orbit,
we optimize input LIC parameters to best fit the observations. The
simulations take into account actual ionization rates as derived
from solar EUV observations by SOHO CELIAS SEM, the OMNI solar wind
data set, the positions and velocity vectors of the Earth during
the actual integration intervals for each orbit, and the IBEX-Lo
field-of-view. The simulations were performed on a grid of bulk flow
vectors and temperatures, starting with the ISSI team consensus values
based most heavily on Ulysses GAS observations (v = 26.4 km/s, T = 6318
K, and λ = 255.4o, β = -5.31o in J2000 coordinates). The Mach number
of the flow derived from the IBEX observations is generally lower than
derived from Ulysses measurements, which would be consistent with a
higher temperature (up to 10 000 K) and/or a lower flow speed (down
to ≈22.5 km/s) of the LIC. Based on these findings, the possible
LIC parameter sets most probably lie within a narrow range between
(λ = 255.4°, β = 5.3°, v = 26.4 km/s, M = 4.5 or T = 10,000 K)
and (λ = 261.2°, β = 4.9, v = 23.05 km/s, M = 4.9, or T = 6300
K). At one end of the acceptable range, the parameters agree with the
previous values except for the temperature, and at the other end, the
temperatures agree, but the direction is different by almost 6° and
the velocity is lower by ≈4 km/s. The simulations appear to agree
with the IBEX observations slightly better for the different inflow
direction. The results obtained separately from the two passes through
the He flow (in 2009 and 2010) are identical within observational
uncertainties. Potential reasons for the differences from previous
results will be discussed. Any modifications in these critical inflow
parameters will require modification of current global heliosphere
models. In particular, a reduced flow speed and thus reduced ram
pressure would require an increase in the total LIC density and/or the
magnetic field strength to maintain pressure balance at the heliopause.
Title: Escape of O+ Through the Distant Tail Plasma Sheet
Authors: Kistler, L. M.; Galvin, A. B.; Popecki, M.; Simunac, K. D.;
Farrugia, C. J.; Moebius, E.; Lee, M. A.; Blush, L. M.; Bochsler,
P. A.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.; Opitz,
A.; Sauvaud, J.; Russell, C. T.
Bibcode: 2010AGUFMSM33B1900K
Altcode:
During the early orbit phase of the STEREO mission, in February, 2007,
the STEREO-B spacecraft went down the deep magnetotail, and encountered
the magnetosheath, plasma sheet and plasma sheet boundary layer from
about 200 Re to 300 Re downtail, before finally exiting to the solar
wind. This time period was during solar minimum, and there was no
storm activity during this month. We have used the ion composition
data from the PLASTIC instrument to determine how much ionospheric
O+ is in the deep tail plasma sheet, and to calculate the loss rate
through this path. Surprisingly, we find that during this solar
and geomagnetically quiet time, O+ is a constant feature of the deep
magnetotail. We find that the O+ density is about 15% of the density in
the near-earth plasma sheet for similar conditions. The tailward flux
of the O+ is similar to the flux of O+ beams that have been observed
in the lobe/mantle region of the deep tail. The observations provide
a consistent picture that some O+ is transported into the distant tail
in the lobe/mantle region, and then enters the plasma sheet tailward of
the distant neutral line. The total outflow of the O+ down the plasma
sheet is a rate of 1.1x1024 ions/s, which is 10% of the total outflow
rate of 1x 1025 ions/s, and of the same order as the estimated loss
from dayside transport.
Title: Escape of O+ through the distant tail plasma sheet
Authors: Kistler, L. M.; Galvin, A. B.; Popecki, M. A.; Simunac,
K. D. C.; Farrugia, C.; Moebius, E.; Lee, M. A.; Blush, L. M.;
Bochsler, P.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.;
Opitz, A.; Sauvaud, J. -A.; Thompson, B.; Russell, C. T.
Bibcode: 2010GeoRL..3721101K
Altcode:
In February 2007, the STEREO-B spacecraft encountered the
magnetosheath, plasma sheet and plasma sheet boundary layer from
about 200 RE to 300 RE downtail. This time
period was during solar minimum, and there was no storm activity
during this month. Using data from the PLASTIC instrument, we find
that even during quiet times, O+ is a constant feature of
the deep magnetotail, with an O+ density of about 15% of
the O+ density in the near-earth plasma sheet for similar
conditions. The tailward flux of the O+ is similar to the
flux of O+ beams that have been observed in the lobe/mantle
region of the deep tail. The total outflow rate of the O+
down the plasma sheet is 1.1 × 1024 ions/s, which is 10%
of the total outflow rate of 1 × 1025 ions/s, and of the
same order as the estimated loss from dayside transport.
Title: Venusian bow shock as seen by the ASPERA-4 ion instrument on
Venus Express
Authors: Whittaker, I.; Guymer, G.; Grande, M.; Pintér, B.;
Barabash, S.; Federov, A.; Mazelle, C.; Sauvaud, J. A.; Lundin, R.;
Russell, C. T.; Futaana, Y.; Fränz, M.; Zhang, T. L.; Andersson, H.;
Grigoriev, A.; Holmström, M.; Yamauchi, M.; Asamura, K.; Baumjohann,
W.; Lammer, H.; Coates, A. J.; Kataria, D. O.; Linder, D. R.; Curtis,
C. C.; Hsieh, K. C.; Koskinen, H. E. J.; Kallio, E.; Riihelä, P.;
Schmidt, W.; Kozyra, J.; McKenna-Lawlor, S.; Thocaven, J. J.; Orsini,
S.; Cerulli-Irelli, R.; Mura, A.; Milillo, M.; Maggi, M.; Roelof,
E.; Brandt, P.; Frahm, R. A.; Sharber, J. R.; Wurz, P.; Bochsler, P.
Bibcode: 2010JGRA..115.9224W
Altcode: 2010JGRA..11509224W
The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-4) instrument
on Venus Express is used to determine bow shock position at Venus using
ion data alone, using data recorded during a solar minimum from the Ion
Mass Analyzer (IMA) which is part of the ASPERA-4 package. Previous
models constructed from solar minimum data using Venus Express,
Pioneer Venus Orbiter (PVO) and Venera 9 and 10 are also compared to
the current fit. An important feature of this new fit is a statistical
accuracy introduced in the form of a probability weighting function for
the data points, based on the time spent in particular locations. The
bow shock curve is then compared to two-dimensional ion maps. These
verify the accuracy of this and previous solar minimum fit curves
based on PVO and Venus Express magnetic data. Comparing all bow shock
models to the 2D ion maps shows that a combination of models produces
the best fit. Since all the fitted curves show differences in position
they are investigated relative to the solar conditions pertaining at
the times when the individual data sets were measured. The sub solar
point and terminator distance were thus found to vary linearly with
sunspot number and hence with solar activity. This relationship, which
was already known to exist between solar maximum and solar minimum,
is now shown to exist between different solar minima and even within
the same minimum. This indicates a need for the mechanisms for bow
shock maintenance and variance to be more closely modeled.
Title: Energetic Neutral Atoms: An Additional Source for Heliospheric
Pickup Ions
Authors: Bochsler, Peter; Möbius, Eberhard
Bibcode: 2010ApJ...721L...6B
Altcode:
Recently, Schwadron & McComas discussed the possibility of inner
source pickup particles originating from the ionization of energetic
neutral atoms (ENAs), based on new data from the IBEX mission. This
proposition has some interesting features, namely, it might be able
to explain why inner source pickup ions (PUIs) have a composition
resembling solar abundances and show no indication of overabundance
of refractory elements, although this should be expected, if the
conventional explanation of solar wind-dust interaction for the
origin of this heliospheric component were correct. In this Letter,
we explore further consequences for ENA-related PUIs and investigate
their velocity distributions. We conclude that this model will not
reproduce the observed velocity distributions of inner source PUIs
and point out a substantial deviation in their composition. However,
it seems likely that the ionization of ENAs as observed with IBEX
could contribute a significant amount of heliospheric suprathermal tail
ions. Some possible consequences of our investigation for heliospheric
particle populations are briefly discussed.
Title: Proton Enhancement and Decreased O6+/H at the
Heliospheric Current Sheet: Implications for the Origin of Slow
Solar Wind
Authors: Liu, Y. C. -M.; Galvin, A. B.; Popecki, M. A.; Simunac,
K. D. C.; Kistler, L.; Farrugia, C.; Lee, M. A.; Klecker, B.; Bochsler,
P.; Luhmann, J. L.; Jian, L. K.; Moebius, E.; Wimmer-Schweingruber,
R.; Wurz, P.
Bibcode: 2010AIPC.1216..363L
Altcode:
We investigated the proton enhancement and O6+/H depletion
in the vicinity of the heliospheric current sheet (HCS) using data
from STEREO/PLASTIC and STEREO/IMPACT. Three HCS crossing events
were studied. For the first two events, the proton enhancement
and O6+/H depletion are found to lie at one edge of the
HCS. The proton density has a steep slope both at the HCS and at
the other boundary of the enhancement. In the third event the proton
enhancement and O6+/H depletion surround the HCS and last
for 8 hours while the density profile is very different from the other
two events. Velocity shear is observed at the HCS for the first two
events but not for the third. The enhancement of hydrogen and depletion
of oxygen at the streamer belt in the solar corona have been reported
using UVCS observation. A potential connection with our observations is
based on the similar features observed at 1 AU. How the plasma flows
out of the streamer belt, and why there are different features in HCS
encounters remain open questions for future study.
Title: New Analyses of Helium, Neon, and Argon in Aluminum Foils of
the Apollo Solar Wind Composition Experiment
Authors: Vogel, N.; Baur, H.; Bochsler, P.; Bühler, F.; Grimberg,
A.; Wieler, R.
Bibcode: 2010LPI....41.1907V
Altcode:
We present new analyses of solar wind He, Ne, and Ar obtained by UV
laser ablation of Apollo 15 foils. The new data will be compared to
those obtained ~40 years ago and to Genesis solar wind data. Agreements
and potential discrepancies will be discussed.
Title: Kinetic temperatures of iron ions in the solar wind observed
with STEREO/PLASTIC
Authors: Bochsler, Peter; Lee, Martin A.; Karrer, Reto; Popecki,
Mark A.; Galvin, Antoinette B.; Kistler, Lynn M.; Möbius, Eberhard;
Farrugia, Charles J.; Kucharek, Harald; Simunac, Kristin D. C.;
Blush, Lisa M.; Daoudi, Hagar; Wurz, Peter; Klecker, Berndt;
Wimmer-Schweingruber, Robert F.; Thompson, Barbara; Luhmann, Janet G.;
Jian, Lan K.; Russell, Christopher T.; Opitz, Andrea
Bibcode: 2010AIPC.1216..257B
Altcode:
STEREO/PLASTIC provides detailed information on the three-dimensional
velocity distributions of solar wind iron ions with a time
resolution of 5 minutes. In general the distributions at 1 AU contain
complicated structures showing persistence over several records,
i.e., over intervals of up to 30 minutes, but no clear correlation
of the properties of these distributions with the direction of the
ambient magnetic field is evident. We have performed a statistical
analysis using nearly 9000 observations. Iron ions follow the
same trends as protons, alpha particles, and electrons: The ratio
T⊥/T|| seems to be limited by the ion cyclotron
instability, whereas T||/T⊥ is bounded by the
firehose instability.
Title: Inner-Source Pickup Ions as Sensitive Probes to the
Inner-Heliospheric Micro-State
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter
Bibcode: 2010AIPC.1216..506W
Altcode:
Inner-source pickup ions have been investigated by several workers who
all assumed an initial velocity distribution function which is dominated
by high velocities in the solar wind velocity frame. This non-thermal
velocity distribution is supposed to be due to the Lorentz force which
acts on the freshly ionized particles. However, the location where
inner-source pickup ions are ionized lies close to the Sun (probably
between 5 and 25 rsolar). The magnetic field and solar
wind velocity are near radial there and the Lorentz force acting on
freshly created ions is small. Particles sputtered or ejected with small
relative velocities (E<few eV) from interplanetary dust particles
only experience a very small mirror force in the inner heliosphere
which only succeeds to accelerate a very small fraction of them out
of the solar vicinity after typically tens of hours to days. This
would result in a higher charge state than observed for heavy ions and
further aggravates the problem of the high abundance of inner-source
pickup ions. Of course, the principal acceleration agent for
inner-source pickup ions has to be wave-particle interactions in the
inner heliosphere. As freshly created pickup ions encounter a wave,
their pitch angle is scattered and they will, in most cases, experience
a net gain in momentum which carries them outwards, out of the solar
system. As we will show, inner-source pickup ions are thus highly
sensitive probes of the turbulent microstate of the inner heliosphere.
Title: Nitrogen isotopes in the recent solar wind from the analysis
of Genesis targets: Evidence for large scale isotope heterogeneity
in the early solar system
Authors: Marty, Bernard; Zimmermann, Laurent; Burnard, Peter G.;
Wieler, Rainer; Heber, Veronika S.; Burnett, Donald L.; Wiens, Roger
C.; Bochsler, Peter
Bibcode: 2010GeCoA..74..340M
Altcode:
We have analyzed nitrogen, neon and argon abundances and isotopic
ratios in target material exposed in space for 27 months to solar wind
(SW) irradiation during the Genesis mission. SW ions were extracted by
sequential UV (193 nm) laser ablation of gold-plated material, purified
separately in a dedicated line, and analyzed by gas source static mass
spectrometry. We analyzed gold-covered stainless steel pieces from the
Concentrator, a device that concentrated SW ions by a factor of up to
50. Despite extensive terrestrial N contamination, we could identify
a non-terrestrial, 15N-depleted nitrogen end-member that
points to a 40% depletion of 15N in solar-wind N relative
to inner planets and meteorites, and define a composition for the
present-day Sun ( 15N/ 14N = [2.26 ± 0.67] × 10
-3, 2σ), which is indistinguishable from that of Jupiter's
atmosphere. These results indicate that the isotopic composition
of nitrogen in the outer convective zone of the Sun has not changed
through time, and is representative of the protosolar nebula. Large
15N enrichments due to e.g., irradiation, low temperature
isotopic exchange, or contributions from 15N-rich presolar
components, are therefore required to account for inner planet values.
Title: First Global Observations Of The Interstellar Interaction
From The Interstellar Boundary Explorer (IBEX)
Authors: Frisch, Priscilla C.; McComas, D. J.; Allegrini, F.; Bochsler,
P.; Bzowski, M.; Christian, E. R.; Crew, G. B.; DeMajistre, B.;
Fahr, H.; Fichtner, H.; Funsten, H.; Fuselier, S. A.; Gloeckler,
G.; Gruntman, M.; Heerikhuisen, J.; Izmodenov, V.; Janzen, P.;
Knappenberger, P.; Krimigis, S.; Kucharek, H.; Lee, M.; Livadiotis,
G.; Livi, S.; MacDowall, R. J.; Mitchell, D.; Moebius, E.; Moore, T.;
Pogorelov, N. V.; Reisenfeld, D.; Roelof, E.; Saul, L.; Schwadron,
N. A.; Valek, P. W.; Vanderspek, R.; Wurz, P.; Zank, G. P.
Bibcode: 2010AAS...21541520F
Altcode: 2010BAAS...42R.263F
The Sun moves through the local interstellar medium (ISM), continuously
emitting ionized, supersonic solar wind plasma and carving out a cavity
in interstellar space called the heliosphere. The border of this cavity
traces regions where the interstellar gas first interacts with the
solar wind. The Interstellar Boundary Explorer (IBEX) spacecraft has
just completed the first all-sky maps of this interstellar interaction
at the edge of the heliosphere, by imaging energetic neutral atoms
(ENAs) emanating from this region. The IBEX all-sky maps and energy
spectra provide detailed information about this interaction. Our
observations show globally distributed ENA fluxes ordered by the solar
wind structure, superimposed on an unexpected feature. This poster
summarizes the IBEX observations, shares our unexpected results, and
discusses the new information on stellar wind interactions with the
ISM that we have gleaned from these data. Acknowledgments: We thank
the IBEX team members. This work is primarily funded by the NASA
Explorer Program.
Title: Observation of Interstellar Flow through the He Focusing
Cone with the Interstellar Boundary Explorer (IBEX): Evidence for
a Secondary Neutral Component?
Authors: Moebius, Eberhard; Bochsler, P.; Heirtzler, D.; Kucharek, H.;
Lee, M. A.; Leonard, T.; Petersen, L.; Wu, X.; Bzowski, M.; Kubiak,
M. A.; Crew, G. B.; Funsten, H. O.; Fuselier, S. A.; Ghielmetti, A.;
Izmodenov, V. V.; McComas, D. J.; Saul, L.; Scheer, J. A.; Wurz, P.;
Schwadron, N.; Witte, M.
Bibcode: 2010cosp...38.1596M
Altcode: 2010cosp.meet.1596M
Due to the motion of the Sun relative to its neighborhood, the neutral
gas of the local interstellar medium (LISM) flows through the inner
heliosphere where it is subject to ionization, the Sun's gravity, and
radiation pressure. Observing the resulting spatial distribution and
flow pattern of several interstellar gas species with UV backscatter,
pickup ion, and neutral atom imaging techniques allows us to unravel
the physical conditions of the LISM and its interaction with the outer
heliosheath. A secondary component of the interstellar neutral gas
flow in the inner heliosphere stems from charge exchange with outer
heliosheath ions, which are diverted around the heliosphere. Therefore,
this component contains information of the deceleration, deflection,
and heating of the interstellar plasma in the boundary layer. IBEX
was launched in October 2008 and has now scanned the interstellar gas
flow at 1 AU twice from mid December 2008 through March 2009, and from
late November 2009 through March 2010, taking advantage of simultaneous
observations of several interstellar species with its triple-coincidence
time-of-flight IBEX-Lo sensor. First data demonstrated that IBEX-Lo is
observing interstellar O, He, along with secondary O. During the second
year, a substantial flux of interstellar He was observed extending
even before the passage of the gravitational focusing cone in early
December. The modeled He distribution, which was shown to agree with
the ISM flow peak observed by IBEX-Lo in February 2009 within 10%, is
exceeded by this flux by more than two orders of magnitude. The most
likely explanation for this new observation is a small, but significant,
secondary He component, consistent with the simultaneous observation
of a secondary O component.
Title: Modeling the local interstellar flow: comparisons to first
observations from IBEX
Authors: Saul, L. A.; Bochsler, P. A.; Bühler, F.; Bzowski, M.; Crew,
G. B.; Funsten, H. O.; Fuselier, S. A.; Ghielmetti, A.; Heirtzler, D.;
Kucharek, H.; Leonard, T.; McComas, D. J.; Moebius, E.; Moore, T. E.;
Petersen, L.; Prested, C. L.; Scheer, J.; Schwadron, N. A.; Wurz, P.
Bibcode: 2009AGUFMSH21B1511S
Altcode:
Neutral interstellar atoms enter the heliosphere unperturbed by the
heliospheric plasma system. These particles, subject to ionization
processes and the gravitational field of the Sun, form a “beam”
due to the relative motion of the Sun and the local interstellar
medium (LISM). We report here on numerical models of this LISM beam,
to determine the properties of this flow in the inner heliosphere. We
compare results with the first observations of the IBEX mission, in
particular the IBEX-LO sensor, and discuss implications for and the
next IBEX observation campaigns and constraints on the LISM parameters.
Title: Reflection and Neutralization of Solar Wind Ions from the Moon:
IBEX Observations
Authors: Janzen, P. H.; Funsten, H. O.; Allegrini, F.; Bochsler,
P. A.; Gruntman, M.; Henderson, K.; Johnson, R. E.; McComas, D. J.;
Reisenfeld, D. B.; Schwadron, N. A.
Bibcode: 2009AGUFM.P31E..05J
Altcode:
The solar wind continuously flows out from the Sun, filling
interplanetary space and directly interacting with the surfaces
of small planetary bodies and other objects throughout the solar
system. A significant fraction of these ions reflect from the surface
as energetic neutral atoms (ENAs). The first ever observations of
ENA emission from the Moon was recently made by the Interstellar
Boundary Explorer (IBEX) spacecraft on Dec. 3, 2008 [McComas et al.,
Geophys Res. Lett. 36 (2009) L12104]. These observations yielded a
lunar ENA albedo of ~10% and showed that the Moon reflects ~150 metric
tons of neutral hydrogen per year. Here, we present the analysis of
5 additional lunar observation periods from IBEX for different solar
wind and lunar viewing conditions. While the kinematics of reflection
at the atomic and microstructural scales are complex, simulations
indicate that the ENA albedo and energy distributions of reflected
hydrogen are largely insensitive to the regolith composition. These
observations and simulations are important for understanding the
universal processes of backscattering and neutralization from complex
surfaces, which occur wherever space plasmas interact with dust and
other small bodies throughout and beyond our solar system.
Title: Inner-Source Pickup Ions as Sensitive Probes to the
Inner-Heliospheric Micro-State
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P. A.
Bibcode: 2009AGUFMSH51C..03W
Altcode:
Inner-source pickup ions have been investigated by several workers
who all assumed an initial velocity distribution function which is
dominated by high velocities in the solar wind velocity frame. This
is supposed to be due to the Lorentz force which acts on the freshly
ionized particles. Because the location where inner-source pickup
ions are ionized lies close to the Sun (probably between 5 and 25
r⊙) and the magnetic field is near radial there, the
Lorentz force acting on freshly created ions is small. Therefore,
particles sputtered or ejected with small relative velocities (E <
few eV) from interplanetary dust particles only experience a very
small mirror force in the inner heliosphere which only succeeds to
accelerate a very small fraction of them out of the solar vicinity
after typically tens of hours to days. This would result in a higher
charge state than observed for heavy ions and further aggravates the
problem of the high abundance of inner-source pickup ions. Of course,
the principal acceleration agent for inner-source pickup ions has to be
wave-particle interactions in the inner heliosphere. As freshly created
pickup ions encounter a wave, their pitch angle is scattered and they
will, in most cases, experience a net gain in momentum which arries
them outwards, out of the solar system. As we will show, inner-source
pickup ions are highly sensitive probes to the turbulent mircorstate
of the inner heliosphere.
Title: Direct Observations of Interstellar H, He, and O by the
Interstellar Boundary Explorer (Invited)
Authors: Moebius, E.; Bochsler, P. A.; Bzowski, M.; Crew, G. B.;
Funsten, H. O.; Fuselier, S. A.; Ghielmetti, A.; Heirtzler, D.;
Izmodenov, V.; Kubiak, M.; Kucharek, H.; Lee, M. A.; Leonard, T.;
McComas, D. J.; Petersen, L.; Saul, L. A.; Scheer, J.; Schwadron,
N. A.; Witte, M.; Wurz, P.
Bibcode: 2009AGUFMSH31B..02M
Altcode:
Due to the motion of the Sun relative to its neighborhood,
the neutral gas of the local in-terstellar medium (LISM) flows
through the inner heliosphere where it is subject to ioni-zation,
the Sun’s gravity, and radiation pressure. Observing the resulting
spatial distribu-tion and flow pattern of several interstellar gas
species with UV backscatter, pickup ion, and neutral atom imaging
techniques allows us to unravel the physical conditions of the LISM
and its interaction with the heliosphere. Imaging of the neutral gas
flow directly with energetic neutral atom (ENA) cameras yields the
most accurate account of the ki-netic parameters of the interstellar
gas, but so far this has been carried out only for He using Ulysses
GAS. IBEX, which was launched in October 2008, provides the capability
for simultaneous flow observations of several interstellar species with
its triple-time-of-flight IBEX-Lo sensor. Because H and O are strongly
affected by the heliospheric inter-face while He is not, a direct
comparison between these species enables an independent assessment of
the slowdown and heating processes in the outer heliosheath. Likewise,
IBEX observations will constrain models of the heliospheric interaction
and provide a test of the heliospheric asymmetry - recently inferred
from Voyager and SOHO SWAN observations - that is seen as an indicator
for the interstellar magnetic field direction. During the first half
year of its mission IBEX has observed the interstellar He, O, and H
flow. We will present an overview and preliminary analysis of these
first interstellar mul-tispecies scans of the interstellar gas flow
in spring and fall 2009.
Title: Global Observations of the Interstellar Interaction from the
Interstellar Boundary Explorer (IBEX)
Authors: McComas, D. J.; Allegrini, F.; Bochsler, P.; Bzowski, M.;
Christian, E. R.; Crew, G. B.; DeMajistre, R.; Fahr, H.; Fichtner,
H.; Frisch, P. C.; Funsten, H. O.; Fuselier, S. A.; Gloeckler,
G.; Gruntman, M.; Heerikhuisen, J.; Izmodenov, V.; Janzen, P.;
Knappenberger, P.; Krimigis, S.; Kucharek, H.; Lee, M.; Livadiotis,
G.; Livi, S.; MacDowall, R. J.; Mitchell, D.; Möbius, E.; Moore, T.;
Pogorelov, N. V.; Reisenfeld, D.; Roelof, E.; Saul, L.; Schwadron,
N. A.; Valek, P. W.; Vanderspek, R.; Wurz, P.; Zank, G. P.
Bibcode: 2009Sci...326..959M
Altcode:
The Sun moves through the local interstellar medium, continuously
emitting ionized, supersonic solar wind plasma and carving out a
cavity in interstellar space called the heliosphere. The recently
launched Interstellar Boundary Explorer (IBEX) spacecraft has
completed its first all-sky maps of the interstellar interaction at
the edge of the heliosphere by imaging energetic neutral atoms (ENAs)
emanating from this region. We found a bright ribbon of ENA emission,
unpredicted by prior models or theories, that may be ordered by the
local interstellar magnetic field interacting with the heliosphere. This
ribbon is superposed on globally distributed flux variations ordered by
both the solar wind structure and the direction of motion through the
interstellar medium. Our results indicate that the external galactic
environment strongly imprints the heliosphere.
Title: Direct Observations of Interstellar H, He, and O by the
Interstellar Boundary Explorer
Authors: Möbius, E.; Bochsler, P.; Bzowski, M.; Crew, G. B.; Funsten,
H. O.; Fuselier, S. A.; Ghielmetti, A.; Heirtzler, D.; Izmodenov,
V. V.; Kubiak, M.; Kucharek, H.; Lee, M. A.; Leonard, T.; McComas,
D. J.; Petersen, L.; Saul, L.; Scheer, J. A.; Schwadron, N.; Witte,
M.; Wurz, P.
Bibcode: 2009Sci...326..969M
Altcode:
Neutral gas of the local interstellar medium flows through the inner
solar system while being deflected by solar gravity and depleted
by ionization. The dominating feature in the energetic neutral atom
Interstellar Boundary Explorer (IBEX) all-sky maps at low energies is
the hydrogen, helium, and oxygen interstellar gas flow. The He and O
flow peaked around 8 February 2009 in accordance with gravitational
deflection, whereas H dominated after 26 March 2009, consistent with
approximate balance of gravitational attraction by solar radiation
pressure. The flow distributions arrive from a few degrees above
the ecliptic plane and show the same temperature for He and O. An
asymmetric O distribution in ecliptic latitude points to a secondary
component from the outer heliosheath.
Title: In Situ Observations of Solar Wind Stream Interface Evolution
Authors: Simunac, K. D. C.; Kistler, L. M.; Galvin, A. B.; Lee, M. A.;
Popecki, M. A.; Farrugia, C.; Moebius, E.; Blush, L. M.; Bochsler,
P.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.; Thompson,
B.; Luhmann, J. G.; Russell, C. T.; Howard, R. A.
Bibcode: 2009SoPh..259..323S
Altcode:
The heliocentric orbits of the two STEREO satellites are similar in
radius and ecliptic latitude, with separation in longitude increasing
by about 45° per year. This arrangement provides a unique opportunity
to study the evolution of stream interfaces near 1 AU over time scales
of hours to a few days, much less than the period of a Carrington
rotation. Assuming nonevolving solar wind sources that corotate with
the Sun, we calculated the expected time and longitude of arrival of
stream interfaces at the Ahead observatory based on the in situ solar
wind speeds measured at the Behind observatory. We find agreement to
within 5° between the expected and actual arrival longitude until the
spacecraft are separated by more than 20° in heliocentric inertial
longitude. This corresponds to about one day between the measurement
times. Much larger deviations, up to 25° in longitude, are observed
after 20° separation. Some of the deviations can be explained by a
latitude difference between the spacecraft, but other deviations most
likely result from evolution of the source region. Both remote and in
situ measurements show that changes at the source boundary can occur on
a time scale much shorter than one solar rotation. In 32 of 41 cases,
the interface was observed earlier than expected at STEREO/Ahead.
Title: Solar wind ion trends and signatures: STEREO PLASTIC
observations approaching solar minimum
Authors: Galvin, A. B.; Popecki, M. A.; Simunac, K. D. C.; Kistler,
L. M.; Ellis, L.; Barry, J.; Berger, L.; Blush, L. M.; Bochsler, P.;
Farrugia, C. J.; Jian, L. K.; Kilpua, E. K. J.; Klecker, B.; Lee,
M.; Liu, Y. C. -M.; Luhmann, J. L.; Moebius, E.; Opitz, A.; Russell,
C. T.; Thompson, B.; Wimmer-Schweingruber, R. F.; Wurz, P.
Bibcode: 2009AnGeo..27.3909G
Altcode:
STEREO has now completed the first two years of its mission, moving
from close proximity to Earth in 2006/2007 to more than 50 degrees
longitudinal separation from Earth in 2009. During this time, several
large-scale structures have been observed in situ. Given the prevailing
solar minimum conditions, these structures have been predominantly
coronal hole-associated solar wind, slow solar wind, their interfaces,
and the occasional transient event. In this paper, we extend earlier
solar wind composition studies into the current solar minimum using
high-resolution (1-h) sampling times for the charge state analysis. We
examine 2-year trends for iron charge states and solar wind proton
speeds, and present a case study of Carrington Rotation 2064 (December
2007) which includes minor ion (He, Fe, O) kinetic and Fe composition
parameters in comparison with proton and magnetic field signatures at
large-scale structures observed during this interval.
Title: Analysis of Suprathermal Events Observed by STEREO/PLASTIC
with a Focus on Upstream Events
Authors: Barry, Joshua Adam; Galvin, Antoinette; Popecki, Mark; Ellis,
Lorna; Kucharek, Harald; Lee, Marty; Simunac, Kristin; Farrugia,
Charlie; Moebius, Eberhard; Kistler, Lynn; Klecker, Berndt; Luhmann,
Janet; Russell, Christopher T.; Bochsler, Peter; Wurz, Peter; Wimmer,
Robert; Thompson, Barbara
Bibcode: 2009shin.confE..94B
Altcode:
Since the late 1960's, suprathermal and energetic ion events with
energies ranging from just above the solar wind energies up to 2MeV
and lasting for several minutes to hours, have been detected upstream
of the Earth. Possible sources of these ions include magnetospheric
ions, solar wind ions accelerated between the Earth's bow shock and
hydromagnetic waves to energies just above the solar wind energies,
and remnant ions from heliospheric processes (such as Solar Energetic
Particle (SEP) events or Corotating Interaction Regions (CIRs)). The
unique orbits of both STEREO spacecraft, STEREO-A (STA) drifting ahead
in Earth's orbit and STEREO-B (STB) lagging behind in Earth's orbit,
allow for analysis of upstream events in these unexamined regions. Using
both the PLASTIC and IMPACT instruments on board STA/B we can examine
protons in the energy range of solar wind energies up to 80keV, their
spatial distribution, and attempt to determine if the spacecraft is
magnetically connected to the Earth's bow shock. Suprathermal events
observed by STEREO/PLASTIC on STA during solar minimum conditions are
examined for possible upstream events using anisotropy measurements,
velocity dispersion, magnetic connection to the bow shock, and frequency
of events as a function of time and distance.
Title: Pickup Helium at Stream Interfaces and Corotating Interaction
Regions.
Authors: Kucharek, Harald; Klecker, B.; Möbius, E.; Simunac, K. D. C.;
Galvin, A. B.; Barry, J.; Bochsler, P.; Blush, L.; Ellis, L.; Farrugia,
C.; Kistler, L. M.; Lee, M.; Luhmann, J.; Popecki, M. A.; Russell,
C. T.; Thompson, B.; Wimmer-Schweingruber, R.
Bibcode: 2009shin.confE..34K
Altcode:
Pickup ion measurements using AMPTE, Ulysses, SOHO, Wind and ACE
have demonstrated that pickup ion fluxes can vary over a wide range
and that the shape of the distributions can change substantially on
time scales from less than one hour to many days. These variations
have been attributed to changes in the interplanetary magnetic field
(IMF) which may manifest themselves in incomplete pickup, density
compressions or rarefactions, and shocks. Suprathermal tails may play a
significant role because these energetic ions could form a seed particle
population for further acceleration. Yet, the vast majority of the
observed temporal variations remain unexplained and it is unknown
at what distance of the spacecraft the acceleration occurs. High
resolution and simultaneous observations of pickup ion distributions
with the Plasma and Suprathermal Ion Composition (PLASTIC) instrument
on board STEREO A and B, two spatially-separated spacecraft, provide
an opportunity to follow the temporal and spatial structures of pickup
ion variations. Furthermore, its Wide Angle Partition (WAP) provides
direction information. STEREO spacecraft have encountered numerous
large-scale interplanetary disturbances such as Stream Interfaces
(SIs) and Corotating Interaction Regions (CIRs). In this presentation
we will present helium pickup ion spectra and fluxes as a function of
solar wind and IMF parameters, focusing on their spatial and temporal
evolution. For selected events we will also determine the location of
the acceleration region relative to the spacecraft location.
Title: The Energy Spectra and Directional Distributions of
Suprathermal Tails in Solar Wind Iron
Authors: Popecki, Mark; Galvin, A.; Bochsler, P.; Klecker, B.;
Kucharek, H.; Moebius, E.; Kistler, L. M.; Blush, L.
Bibcode: 2009shin.confE..98P
Altcode:
High speed suprathermal tails have been observed in the solar wind
in H, He, O and Fe. The formation of these tails is a subject of
current discussion. They represent a transition from the solar wind
to energetic particles.They may also participate in the interplanetary
shock acceleration process of energetic ions. Suprathermal tails have
been observed in solar wind Fe by STEREO PLASTIC. The energy spectra
for slow and fast wind will be shown. Directional distributions will
also be investigated for a transition from a beamlike solar wind type
at solar wind energies to a more isotropic type in the tail that would
be typical of energetic particles.
Title: IBEX—Interstellar Boundary Explorer
Authors: McComas, D. J.; Allegrini, F.; Bochsler, P.; Bzowski,
M.; Collier, M.; Fahr, H.; Fichtner, H.; Frisch, P.; Funsten,
H. O.; Fuselier, S. A.; Gloeckler, G.; Gruntman, M.; Izmodenov,
V.; Knappenberger, P.; Lee, M.; Livi, S.; Mitchell, D.; Möbius,
E.; Moore, T.; Pope, S.; Reisenfeld, D.; Roelof, E.; Scherrer, J.;
Schwadron, N.; Tyler, R.; Wieser, M.; Witte, M.; Wurz, P.; Zank, G.
Bibcode: 2009SSRv..146...11M
Altcode:
The Interstellar Boundary Explorer (IBEX) is a small explorer mission
that launched on 19 October 2008 with the sole, focused science
objective to discover the global interaction between the solar wind and
the interstellar medium. IBEX is designed to achieve this objective by
answering four fundamental science questions: (1) What is the global
strength and structure of the termination shock, (2) How are energetic
protons accelerated at the termination shock, (3) What are the global
properties of the solar wind flow beyond the termination shock and in
the heliotail, and (4) How does the interstellar flow interact with
the heliosphere beyond the heliopause? The answers to these questions
rely on energy-resolved images of energetic neutral atoms (ENAs), which
originate beyond the termination shock, in the inner heliosheath. To
make these exploratory ENA observations IBEX carries two ultra-high
sensitivity ENA cameras on a simple spinning spacecraft. IBEX’s very
high apogee Earth orbit was achieved using a new and significantly
enhanced method for launching small satellites; this orbit allows
viewing of the outer heliosphere from beyond the Earth’s relatively
bright magnetospheric ENA emissions. The combination of full-sky
imaging and energy spectral measurements of ENAs over the range from
∼10 eV to 6 keV provides the critical information to allow us to
achieve our science objective and understand this global interaction
for the first time. The IBEX mission was developed to provide the
first global views of the Sun’s interstellar boundaries, unveiling
the physics of the heliosphere’s interstellar interaction, providing
a deeper understanding of the heliosphere and thereby astrospheres
throughout the galaxy, and creating the opportunity to make even
greater unanticipated discoveries.
Title: The IBEX-Lo Sensor
Authors: Fuselier, S. A.; Bochsler, P.; Chornay, D.; Clark, G.;
Crew, G. B.; Dunn, G.; Ellis, S.; Friedmann, T.; Funsten, H. O.;
Ghielmetti, A. G.; Googins, J.; Granoff, M. S.; Hamilton, J. W.;
Hanley, J.; Heirtzler, D.; Hertzberg, E.; Isaac, D.; King, B.; Knauss,
U.; Kucharek, H.; Kudirka, F.; Livi, S.; Lobell, J.; Longworth,
S.; Mashburn, K.; McComas, D. J.; Möbius, E.; Moore, A. S.; Moore,
T. E.; Nemanich, R. J.; Nolin, J.; O'Neal, M.; Piazza, D.; Peterson,
L.; Pope, S. E.; Rosmarynowski, P.; Saul, L. A.; Scherrer, J. R.;
Scheer, J. A.; Schlemm, C.; Schwadron, N. A.; Tillier, C.; Turco,
S.; Tyler, J.; Vosbury, M.; Wieser, M.; Wurz, P.; Zaffke, S.
Bibcode: 2009SSRv..146..117F
Altcode:
The IBEX-Lo sensor covers the low-energy heliospheric neutral atom
spectrum from 0.01 to 2 keV. It shares significant energy overlap and
an overall design philosophy with the IBEX-Hi sensor. Both sensors
are large geometric factor, single pixel cameras that maximize
the relatively weak heliospheric neutral signal while effectively
eliminating ion, electron, and UV background sources. The IBEX-Lo sensor
is divided into four major subsystems. The entrance subsystem includes
an annular collimator that collimates neutrals to approximately 7°×7°
in three 90° sectors and approximately 3.5°×3.5° in the fourth
90° sector (called the high angular resolution sector). A fraction
of the interstellar neutrals and heliospheric neutrals that pass
through the collimator are converted to negative ions in the ENA to
ion conversion subsystem. The neutrals are converted on a high yield,
inert, diamond-like carbon conversion surface. Negative ions from the
conversion surface are accelerated into an electrostatic analyzer (ESA),
which sets the energy passband for the sensor. Finally, negative ions
exit the ESA, are post-accelerated to 16 kV, and then are analyzed in
a time-of-flight (TOF) mass spectrometer. This triple-coincidence, TOF
subsystem effectively rejects random background while maintaining high
detection efficiency for negative ions. Mass analysis distinguishes
heliospheric hydrogen from interstellar helium and oxygen. In normal
sensor operations, eight energy steps are sampled on a 2-spin per
energy step cadence so that the full energy range is covered in 16
spacecraft spins. Each year in the spring and fall, the sensor is
operated in a special interstellar oxygen and helium mode during
part of the spacecraft spin. In the spring, this mode includes
electrostatic shutoff of the low resolution (7°×7°) quadrants of
the collimator so that the interstellar neutrals are detected with
3.5°×3.5° angular resolution. These high angular resolution data
are combined with star positions determined from a dedicated star
sensor to measure the relative flow difference between filtered and
unfiltered interstellar oxygen. At the end of 6 months of operation,
full sky maps of heliospheric neutral hydrogen from 0.01 to 2 keV in 8
energy steps are accumulated. These data, similar sky maps from IBEX-Hi,
and the first observations of interstellar neutral oxygen will answer
the four key science questions of the IBEX mission.
Title: The Interstellar Boundary Explorer High Energy (IBEX-Hi)
Neutral Atom Imager
Authors: Funsten, H. O.; Allegrini, F.; Bochsler, P.; Dunn, G.; Ellis,
S.; Everett, D.; Fagan, M. J.; Fuselier, S. A.; Granoff, M.; Gruntman,
M.; Guthrie, A. A.; Hanley, J.; Harper, R. W.; Heirtzler, D.; Janzen,
P.; Kihara, K. H.; King, B.; Kucharek, H.; Manzo, M. P.; Maple, M.;
Mashburn, K.; McComas, D. J.; Moebius, E.; Nolin, J.; Piazza, D.;
Pope, S.; Reisenfeld, D. B.; Rodriguez, B.; Roelof, E. C.; Saul, L.;
Turco, S.; Valek, P.; Weidner, S.; Wurz, P.; Zaffke, S.
Bibcode: 2009SSRv..146...75F
Altcode:
The IBEX-Hi Neutral Atom Imager of the Interstellar Boundary Explorer
(IBEX) mission is designed to measure energetic neutral atoms (ENAs)
originating from the interaction region between the heliosphere and the
local interstellar medium (LISM). These ENAs are plasma ions that have
been heated in the interaction region and neutralized by charge exchange
with the cold neutral atoms of the LISM that freely flow through the
interaction region. IBEX-Hi is a single pixel ENA imager that covers
the ENA spectral range from 0.38 to 6 keV and shares significant energy
overlap and overall design philosophy with the IBEX-Lo sensor. Because
of the anticipated low flux of these ENAs at 1 AU, the sensor has a
large geometric factor and incorporates numerous techniques to minimize
noise and backgrounds. The IBEX-Hi sensor has a field-of-view (FOV)
of 6.5°×6.5° FWHM, and a 6.5°×360° swath of the sky is imaged
over each spacecraft spin. IBEX-Hi utilizes an ultrathin carbon foil to
ionize ENAs in order to measure their energy by subsequent electrostatic
analysis. A multiple coincidence detection scheme using channel electron
multiplier (CEM) detectors enables reliable detection of ENAs in the
presence of substantial noise. During normal operation, the sensor steps
through six energy steps every 12 spacecraft spins. Over a single IBEX
orbit of about 8 days, a single 6.5°×360° swath of the sky is viewed,
and re-pointing of the spin axis toward the Sun near perigee of each
IBEX orbit moves the ecliptic longitude by about 8° every orbit such
that a full sky map is acquired every six months. These global maps,
covering the spectral range of IBEX-Hi and coupled to the IBEX-Lo maps
at lower and overlapping energies, will answer fundamental questions
about the structure and dynamics of the interaction region between
the heliosphere and the LISM.
Title: Lunar backscatter and neutralization of the solar wind:
First observations of neutral atoms from the Moon
Authors: McComas, D. J.; Allegrini, F.; Bochsler, P.; Frisch, P.;
Funsten, H. O.; Gruntman, M.; Janzen, P. H.; Kucharek, H.; Möbius,
E.; Reisenfeld, D. B.; Schwadron, N. A.
Bibcode: 2009GeoRL..3612104M
Altcode:
The solar wind continuously flows out from the Sun, filling
interplanetary space and impinging directly on the lunar regolith. While
most solar wind ions are implanted into the lunar dust, a significant
fraction is expected to scatter back and be emitted as energetic
neutral atoms (ENAs). However, this population has never been observed,
let alone characterized. Here we show the first observations of
backscattered neutral atoms from the Moon and determine that the
efficiency for this process, the lunar ENA albedo, is ∼10%. This
indicates that the Moon emits ∼150 metric tons of hydrogen per
year. Our observations are important for understanding the universal
processes of backscattering and neutralization from complex surfaces,
which occur wherever space plasmas interact with dust and other small
bodies throughout our solar system as well as in exoplanetary systems
throughout the galaxy and beyond.
Title: Temporal Evolution of the Solar Wind Bulk Velocity at Solar
Minimum by Correlating the STEREO A and B PLASTIC Measurements
Authors: Opitz, A.; Karrer, R.; Wurz, P.; Galvin, A. B.; Bochsler,
P.; Blush, L. M.; Daoudi, H.; Ellis, L.; Farrugia, C. J.; Giammanco,
C.; Kistler, L. M.; Klecker, B.; Kucharek, H.; Lee, M. A.; Möbius,
E.; Popecki, M.; Sigrist, M.; Simunac, K.; Singer, K.; Thompson, B.;
Wimmer-Schweingruber, R. F.
Bibcode: 2009SoPh..256..365O
Altcode:
The two STEREO spacecraft with nearly identical instrumentation were
launched near solar activity minimum and they separate by about 45°
per year, providing a unique tool to study the temporal evolution of the
solar wind. We analyze the solar wind bulk velocity measured by the two
PLASTIC plasma instruments onboard the two STEREO spacecraft. During the
first half year of our measurements (March - August 2007) we find the
typical alternating slow and fast solar wind stream pattern expected at
solar minimum. To evaluate the temporal evolution of the solar wind bulk
velocity we exclude the spatial variations and calculate the correlation
between the solar wind bulk velocity measured by the two spacecraft. We
account for the different spacecraft positions in radial distance and
longitude by calculating the corresponding time lag. After adjusting
for this time lag we compare the solar wind bulk velocity measurements
at the two spacecraft and calculate the correlation between the two
time-shifted datasets. We show how this correlation decreases as the
time difference between two corresponding measurements increases. As
a result, the characteristic temporal changes in the solar wind bulk
velocity can be inferred. The obtained correlation is 0.95 for a time
lag of 0.5 days and 0.85 for 2 days.
Title: Investigation of the Cooling Behavior of Interstellar Pickup
Helium and Its Effect on the Determination of Neutral Density Profiles
and Ionization Rates
Authors: Moebius, E.; Bochsler, P.; Isenberg, P. A.; Saul, L.
Bibcode: 2009AGUSMSH24A..04M
Altcode:
The shape of pickup ion velocity distributions in the solar wind is
typically used to infer the radial profile of the neutral source
distributions sunward of the observing instrument. Since this
radial profile is a direct function of the ionization rate relative
to the neutral flow time, this information can also determine the
ionization rate. However, this analysis also makes the significant
assumption that the pickup distribution cools from the point of
ionization in the expanding solar wind as an isotropic adiabatic
gas. This isotropic-adiabatic assumption allows a simple mapping of
the pickup intensity in velocity space to the ion production rate in
radial position. However, the finding of substantial anisotropies of
pickup ion distributions, in particular under radial interplanetary
magnetic field conditions, and of large variations of pickup ion
distributions that are correlated with magnetic field conditions,
suggests that pitch-angle scattering of these particles is substantially
inhibited in contrast to the simple theory. These observations prompt
a re-evaluation of the existing models. Here, we explore the effect
of different cooling functions on the shape of interstellar pickup He
distributions under perpendicular magnetic field conditions. The shape
also depends on the ionization rate through the radial neutral density
profile. We show that pickup He observations over a solar activity
cycle, during which the ionization rate will vary by factors of 3 -
4, can strongly constrain the actual cooling behavior of the pickup
distribution and provide information on the extent of isotropization.
Title: The Energy Spectra of Suprathermal Tails in Solar Wind Iron
Authors: Popecki, M. A.; Galvin, A.; Bochsler, P.; Klecker, B.;
Kucharek, H.; Kistler, L.; Blush, L.; Moebius, E.
Bibcode: 2009AGUSMSH31B..07P
Altcode:
High speed suprathermal tails with a fixed energy spectrum have
been observed in solar wind H+ and He2+, as well as in He+ pickup
ions (e.g. Gloeckler et al., 2007). The presence of the tails have
implications for particle injection into the interplanetary shock
acceleration process. The suprathermal tails of solar wind Fe have been
investigated with the STEREO/PLASTIC mass spectrometer. The energy
spectra will be presented for periods of slow and fast solar wind,
and for the entire STEREO mission.
Title: In Search of Solar Wind Nitrogen in Genesis Material: Further
Analysis of a Gold Cross Arm of the Concentrator
Authors: Marty, B.; Zimmermann, L.; Burnard, P. G.; Burnett, D. L.;
Heber, V. S.; Wieler, R.; Bochsler, P.; Wiens, R. C.; Sestak, S.;
Franchi, I. A.
Bibcode: 2009LPI....40.1857M
Altcode:
We have analysed nitrogen and noble gases in another gold cross arm of
the Genesis concentrator by laser ablation - static MS. Results define
a correlation that points to a light N isotope composition within the
range of Jupiter atmospheric value.
Title: The STEREO/PLASTIC response to solar wind ions (Flight
measurements and models)
Authors: Daoudi, H.; Blush, L. M.; Bochsler, P.; Galvin, A. B.;
Giammanco, C.; Karrer, R.; Opitz, A.; Wurz, P.; Farrugia, C.;
Kistler, L. A.; Popecki, M. A.; Möbius, E.; Singer, K.; Klecker,
B.; Wimmer-Schweingruber, R. F.; Thompson, B.
Bibcode: 2009ASTRA...5....1D
Altcode:
The Plasma and Supra-Thermal Ion Composition (PLASTIC) instrument is
one of four experiment packages on board of the two identical STEREO
spacecraft A and B, which were successfully launched from Cape Canaveral
on 26 October 2006. During the two years of the nominal STEREO mission,
PLASTIC is providing us with the plasma characteristics of protons,
alpha particles, and heavy ions. PLASTIC will also provide key
diagnostic measurements in the form of the mass and charge state
composition of heavy ions. Three measurements (E/qk,
time of flight, ESSD) from the pulse height raw data are
used to characterize the solar wind ions from the solar wind sector,
and part of the suprathermal particles from the wide-angle partition
with respect to mass, atomic number and charge state. In this paper,
we present a new method for flight data analysis based on simulations
of the PLASTIC response to solar wind ions. We present the response of
the entrance system / energy analyzer in an analytical form. Based on
stopping power theory, we use an analytical expression for the energy
loss of the ions when they pass through a thin carbon foil. This
allows us to model analytically the response of the time of flight
mass spectrometer to solar wind ions. Thus we present a new version
of the analytical response of the solid state detectors to solar wind
ions. Various important parameters needed for our models were derived,
based on calibration data and on the first flight measurements obtained
from STEREO-A. We used information from each measured event that is
registered in full resolution in the Pulse Height Analysis words and we
derived a new algorithm for the analysis of both existing and future
data sets of a similar nature which was tested and works well. This
algorithm allows us to obtain, for each measured event, the mass, atomic
number and charge state in the correct physical units. Finally, an
important criterion was developed for filtering our Fe raw flight data
set from the pulse height data without discriminating charge states.
Title: Composition of matter in the heliosphere
Authors: Bochsler, Peter
Bibcode: 2009IAUS..257...17B
Altcode:
The Sun is by far the largest reservoir of matter in the solar
system and contains more than 99% of the mass of the solar
system. Theories on the formation of the solar system maintain that
the gravitational collapse is very efficient and that typically not
more than one tenth from the solar nebula is lost during the formation
process. Consequently, the Sun can be considered as a representative
sample of interstellar matter taken from a well mixed reservoir 4.6
Gy ago, at about 8 kpc from the galactic center. At the same time,
the Sun is also a faithful witness of the composition of matter at the
beginning of the evolution of the solar system and the formation of
planets, asteroids, and comets. Knowledge on the solar composition and
a fair account of the related uncertainties is relevant for many fields
in astrophysics, planetary sciences, cosmo- and geochemistry. Apart
from the basic interest in the chemical evolution of the galaxy and the
solar system, compositional studies have also led to many applications
in space research, i.e., it has helped to distinguish between different
components of diffuse heliospheric matter. The elemental, isotopic,
and charge state composition of heliospheric particles (solar wind,
interstellar neutrals, pickup ions) has been used for a multitude
of applications, such as tracing the source material, constraining
parameters for models of the acceleration processes, and of the
transport through the interplanetary medium. It is important to realize,
that the two mainstream applications, as outlined above - geochemistry
and cosmochemistry on one side, and tracing of heliospheric processes
on the other side - are not independent of each other. Understanding
the physical processes, e.g., of the fractionation of the solar wind,
is crucial for the interpretation of compositional data; on the other
hand, reliable information on the source composition is the basis for
putting constraints on models of the solar wind fractionation.
Title: Fractionation Processes in the Solar Wind Revealed by Noble
Gases Collected by Genesis Regime Targets
Authors: Heber, V. S.; Wiens, R. C.; Bochsler, P.; Wieler, R.; Burnett,
D. S.
Bibcode: 2009LPI....40.2503H
Altcode:
Significant differences in isotopic and elemental compositions of
noble gases among the different SW regimes were found. Here we discuss
fractionation processes in the solar wind.
Title: Comparison of Solar Wind Noble Gas Data from Genesis with
Apollo/SWC -- New Results from Implantation Experiments
Authors: Grimberg, A.; Bühler, F.; Wieler, R.; Bochsler, P.
Bibcode: 2009LPI....40.1537G
Altcode:
We will show new results from extensive implantation experiments to
adress differences of isotopic and elemental solar wind noble gas data
between Genesis and Apollo/SWC.
Title: Analysis of Suprathermal Events Observed by STEREO/PLASTIC
Authors: Barry, J. A.; Galvin, A. B.; Farrugia, C. J.; Popecki, M.;
Klecker, B.; Ellis, L.; Lee, M. A.; Kistler, L. M.; Luhmann, J. G.;
Russell, C. T.; Simunac, K.; Kucharek, H.; Blush, L.; Bochsler, P.;
Möbius, E.; Thompson, B. J.; Wimmer-Schweingruber, R.; Wurz, P.
Bibcode: 2008AGUFMSH31B1671B
Altcode:
Since the late 1960's, suprathermal and energetic ion events with
energies ranging from just above the solar wind energies up to 2MeV
and lasting for several minutes to hours, have been detected upstream
of the Earth. Possible sources of these ions include magnetospheric
ions, solar wind ions accelerated between the Earth's bow shock and
hydromagnetic waves to energies just above the solar wind energies,
and remnant ions from heliospheric processes (such as Solar Energetic
Particle (SEP) events or Corotating Interaction Regions (CIRs)). The
unique orbits of both STEREO spacecraft, STEREO-A (STA) drifting ahead
in Earth's orbit and STEREO-B (STB) lagging behind in Earth's orbit,
allow for analysis of upstream events in these unexamined regions. Using
both the PLASTIC and IMPACT instruments on board STA/B we can examine
protons in the energy range of solar wind energies up to 80keV, their
spatial distribution, and determine if the spacecraft is magnetically
connected to the Earth's bow shock. Suprathermal events observed by
STEREO/PLASTIC during solar minimum conditions are examined for possible
upstream events using anisotropy measurements, velocity dispersion,
magnetic connection to the bow shock, and frequency of events as a
function of time and distance.
Title: Temporal and Spatial Variations of Pickup Ions seen on
STEREO/PLASTIC
Authors: Kucharek, H.; Klecker, B.; Simunac, K.; Russell, C.; Moebius,
E.; Popecki, M.; Galvin, A.; Kistler, L.; Ellis, L.; Gustafson, A.;
Barry, J.; Singer, K.; Farrugia, C.; Lee, M.; Blush, L.; Karrer,
R.; Bochsler, P.; Wurz, P.; Wimmer-Schweingruber, R.; Thompson, B.;
Luhmann, J.
Bibcode: 2008AGUFMSH21B1605K
Altcode:
Pickup ions seem to be a perfect tracer of interplanetary
discontinuities in the heliosphere and they provide important
information on acceleration processes at these structures and in the
turbulent solar wind (i.e. suprathermal tails). Studies of pickup ions
using AMPTE, Ulysses, SOHO, Wind and ACE demonstrated that pickup ion
fluxes and the shape of their distributions can vary substantially on
time scales from less than one hour to many days. These variations have
been attributed to changes in the interplanetary magnetic field (IMF)
direction and strength in the sense of incomplete pickup and/or density
compressions and decompressions. For instance, at CIRs one observes
the most intense and most prolonged enhancements of energetic helium
pickup ions. At present, the vast majority of the observed temporal
variations remain unexplained. Furthermore, spatial variations of
pickup ion distributions could not be studied with single spacecraft
observation. Simultaneous observations of pickup ion distributions with
the PLASTIC instrument on STEREO A and B now provide the opportunity
to follow pickup ion variations on spatial scales from a few 106 km
to 108 km. In the early mission phase STEREO A and B were often along
the same magnetic field flux tubes. This allows us to study temporal
effects. With increasing spacecraft separation spatial effects can
be studied. In this presentation we will show STEREO observations of
helium pickup ion spectra and fluxes for 2007/8 in their dependence
on solar wind density, speed and flux as well IMF direction and
strength on both spacecraft. We then determined whether the observed
variations are mainly correlated features that are associated with
spatial structures passing the STEREO spacecraft at different times
(such as CIRs or the focusing cone), or whether they have a substantial
uncorrelated component indicative of temporal variations.
Title: Oxygen Observations by STEREO/PLASTIC in the Slow Solar Wind
Authors: Liu, Y. C.; Galvin, A. B.; Simunac, K. D.; Kistler, L. M.;
Popecki, M. A.; Farrugia, C. F.; Ellis, L.; Mobius, E.; Lee, M. A.;
Zurbuchen, T. H.; Lepri, S.; Blush, L. M.; Bochsler, P.; Daoudi, H.;
Wurz, P.; Wimmer-Schweingruber, R. F.; Klecker, B.; Thompson, B.
Bibcode: 2008AGUFMSH51B1604L
Altcode:
We have analyzed solar wind oxygen in the data from the STEREO Plasma
and Supra-thermal Ion Composition Experiment (PLASTIC). For this initial
study we concentrate on the slow solar wind where the ion composition
is stable, different ion species have nearly the same bulk speed,
and the kinetic temperature is usually low. The mass of the detected
ions is determined when the ions have both a valid time-of-flight
and a residual energy measured by a Solid State Detector (SSD). The
bulk speed, thermal speed and flow angles of O6+ are then calculated
using the electrostatic analyzer and position data. The STEREO data
are compared to similar measurement on ACE/SWICS.
Title: Suprathermal Tails in Solar Wind Oxygen and Iron
Authors: Popecki, M. A.; Galvin, A.; Klecker, B.; Kucharek, H.;
Kistler, L.; Bochsler, P.; Blush, L.; Möbius, E.
Bibcode: 2008AGUFMSH31B1672P
Altcode:
High speed suprathermal tails with a fixed energy spectrum have been
observed in solar wind H and He2+, as well as in He+ pickup ions
(e.g. Gloeckler et al., 2007). These tails appear to have a persistent
and constant power law energy spectrum, unchanged in a variety of solar
conditions. The presence of the tails have implications for particle
injection into the interplanetary shock acceleration process. The
suprathermal tails of solar wind Fe and O have been investigated with
the STEREO/PLASTIC mass spectrometer. The energy spectra of solar
wind O and Fe will be presented for periods of slow and fast solar
wind. Variations in energy spectra are observed in both species at
speeds up to 1.8 times the solar wind speed.
Title: The Effect Of Fast And Slow Solar Wind On The Venusian Upper
Atmosphere.
Authors: Whittaker, I. C.; Grande, M.; Guymer, G.; Pintér, B.;
Barabash, S.; Federov, A.; Mazelle, C.; Sauvaud, J.; Lundin, R.;
Russell, C.; Futaana, Y.; Fränz, M.; Zhang, T. L.; Andersson,
H.; Brinkfeldt, K.; Grigoriev, A.; Holmströ M, M.; Yamauchi, M.;
Asamura, K.; Baumjohann, W.; Lammer, H.; Coates, A. J.; Kataria, D. O.;
Linder, D. R.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Gunell,
H.; Koskinen, H. E.; Kallio, E.; Riihelä, P.; Säles, T.; Schmidt,
W.; Kozyra, J.; Krupp, N.; Woch, J.; Luhmann, J.; McKenna-Lawlor, S.;
Thocaven, J. J.; Orsini, S.; Cerulli-Irelli, R.; Mura, M.; Milillo,
M.; Maggi, M.; Roelof, E.; Brandt, P.; Szego, K.; Winningham, J. D.;
Frahm, R. A.; Scherrer, J.; Sharber, J.; Wurz, P.; Bochsler, P.
Bibcode: 2008AGUFM.P13B1311W
Altcode:
Using the ASPERA-4 instrument onboard Venus Express the change in the
atmospheric boundary layers are investigated. Using the instrument
when it is in the apoapsis period of the polar orbit allows pure Solar
Wind measurements to be taken. Composition ratios are determined thus
identifying periods of fast and slow solar wind. This is then applied
to ion maps of the Venusian atmosphere to determine the response after
noise calibration methods. The Species reactions to the differing
Solar Wind are also used to investigate the inner boundary movements.
Title: Temporal and Spatial Variation of the Solar Wind Bulk
Properties from STEREO SWEA/PLASTIC by Multi-Spacecraft Analysis
Authors: Opitz, A.; Sauvaud, J.; Wurz, P.; Karrer, R.; Lavraud, B.;
Luhmann, J. G.; Galvin, A. B.; Curtis, D. W.; Fedorov, A.; Kellogg,
P. J.; Larson, D. E.; Penou, E.; Schroeder, P.; Bochsler, P.; Farrugia,
C. J.; Klecker, B.; Kucharek, H.; Moebius, E. S.; Russell, C. T.
Bibcode: 2008AGUFMSH21A1565O
Altcode:
The two STEREO spacecraft with nearly identical instrumentation were
launched near solar activity minimum and they separate by about 45
degrees per year providing a unique tool to study the temporal and
spatial evolution of the solar wind. We analyzed the solar wind
bulk properties measured by the SWEA electron and the PLASTIC ion
plasma instruments on board. We calculate the timelag between the
STEREO A and B spacecraft considering their radial and longitudinal
separation and time-shift the B measurements in order to forecast the
A measurements. We show that the correlation between the forecasted
and the real A datasets is very good. It decreases slightly as their
timelag increases, which is due to the temporal evolution of the
solar wind. We also find that this correlation clearly decreases
when we compare structures of smaller spatial scales. As a result,
the characteristic temporal and spatial changes in the solar wind bulk
properties can be quantitatively determined.
Title: Nitrogen Isotopes in the Recent Solar Wind: Further Analysis
of Gold-platted Concentrator Frame from Genesis
Authors: Marty, B.; Zimmermann, L.; Burnard, P. G.; Burnett, D. L.;
Allton, J. H.; Wiens, R. C.; Heber, V. S.; Wieler, R.; Bochsler, P.;
Sestak, S.; Franchi, I. A.
Bibcode: 2008M&PSA..43.5281M
Altcode:
No abstract at ADS
Title: Observations of O+ in the Distant Tail from the STEREO
B Spacecraft
Authors: Kistler, L. M.; Galvin, A. B.; Popecki, M. A.; Simunac,
K.; Farrugia, C.; Klecker, B.; Bochsler, P.; Blush, L. M.;
Wimmer-Schweingruber, R. F.; Sauvaud, J. A.; Russell, C. T.
Bibcode: 2008AGUSMSM41A..06K
Altcode:
During the month of February, 2007, the STEREO B spacecraft traversed
the dusk-side magnetotail, from -100 Re to -300 Re. This month was
relatively quiet, with minimum Dst never below -39, and less than -20
for most of the month. Throughout this time, bursts of energetic O+
ions with energies up to 80 keV were observed using the Plasma and
Suprathermal Ion Composition (PLASTIC), instrument. The O+ bursts are
normally observed during time periods when density was low and the
Bx component of the magnetic field changed orientation, indicating
that the spacecraft was in the plasma sheet, crossing the neutral
sheet. The energy of the bursts was highest for the highest solar
wind speeds. During the most energetic events, O++ was also observed,
simultaneous with the O+. These results show that the ionosphere can
be a significant source for the plasma sheet, even in the deep tail
during quiet times.
Title: First observation of energetic neutral atoms in the Venus
environment
Authors: Galli, A.; Wurz, P.; Bochsler, P.; Barabash, S.; Grigoriev,
A.; Futaana, Y.; Holmström, M.; Gunell, H.; Andersson, H.; Lundin,
R.; Yamauchi, M.; Brinkfeldt, K.; Fraenz, M.; Krupp, N.; Woch,
J.; Baumjohann, W.; Lammer, H.; Zhang, T. L.; Asamura, K.; Coates,
A. J.; Linder, D. R.; Kataria, D. O.; Curtis, C. C.; Hsieh, K. C.;
Sandel, B. R.; Sauvaud, J. A.; Fedorov, A.; Mazelle, C.; Thocaven,
J. J.; Grande, M.; Kallio, E.; Sales, T.; Schmidt, W.; Riihela, P.;
Koskinen, H.; Kozyra, J.; Luhmann, J.; McKenna-Lawlor, S.; Orsini,
S.; Cerulli-Irelli, R.; Mura, A.; Milillo, A.; Maggi, M.; Roelof,
E.; Brandt, P.; Russell, C. T.; Szego, K.; Winningham, D.; Frahm,
R.; Scherrer, J.; Sharber, J. R.
Bibcode: 2008P&SS...56..807G
Altcode:
The ASPERA-4 instrument on board the Venus Express spacecraft
offers for the first time the possibility to directly measure
the emission of energetic neutral atoms (ENAs) in the vicinity of
Venus. When the spacecraft is inside the Venus shadow a distinct
signal of hydrogen ENAs usually is detected. It is observed as a
narrow tailward stream, coming from the dayside exosphere around
the Sun direction. The intensity of the signal reaches several
105cm-2sr-1s-1, which is
consistent with present theories of the plasma and neutral particle
distributions around Venus.
Title: Comparative analysis of Venus and Mars magnetotails
Authors: Fedorov, A.; Ferrier, C.; Sauvaud, J. A.; Barabash, S.; Zhang,
T. L.; Mazelle, C.; Lundin, R.; Gunell, H.; Andersson, H.; Brinkfeldt,
K.; Futaana, Y.; Grigoriev, A.; Holmström, M.; Yamauchi, M.; Asamura,
K.; Baumjohann, W.; Lammer, H.; Coates, A. J.; Kataria, D. O.; Linder,
D. R.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Thocaven, J. -J.;
Grande, M.; Koskinen, H.; Kallio, E.; Sales, T.; Schmidt, W.; Riihela,
P.; Kozyra, J.; Krupp, N.; Woch, J.; Luhmann, J.; McKenna-Lawlor,
S.; Orsini, S.; Cerulli-Irelli, R.; Mura, A.; Milillo, A.; Maggi, M.;
Roelof, E.; Brandt, P.; Russell, C. T.; Szego, K.; Winningham, J. D.;
Frahm, R. A.; Scherrer, J.; Sharber, J. R.; Wurz, P.; Bochsler, P.
Bibcode: 2008P&SS...56..812F
Altcode:
We have an unique opportunity to compare the magnetospheres of two
non-magnetic planets as Mars and Venus with identical instrument sets
Aspera-3 and Aspera-4 on board of the Mars Express and Venus Express
missions. We have performed both statistical and case studies of
properties of the magnetosheath ion flows and the flows of planetary
ions behind both planets. We have shown that the general morphology of
both magnetotails is generally identical. In both cases the energy of
the light ( H+) and the heavy ( O+, etc.) ions
decreases from the tail periphery (several keV) down to few eV in
the tail center. At the same time the wake center of both planets
is occupied by plasma sheet coincident with the current sheet of the
tail. Both plasma sheets are filled by accelerated (500-1000 eV) heavy
planetary ions. We report also the discovery of a new feature never
observed before in the tails of non-magnetic planets: the plasma sheet
is enveloped by consecutive layers of He+ and H+
with decreasing energies.
Title: Ionospheric photoelectrons at Venus: Initial observations by
ASPERA-4 ELS
Authors: Coates, A. J.; Frahm, R. A.; Linder, D. R.; Kataria, D. O.;
Soobiah, Y.; Collinson, G.; Sharber, J. R.; Winningham, J. D.; Jeffers,
S. J.; Barabash, S.; Sauvaud, J. -A.; Lundin, R.; Holmström, M.;
Futaana, Y.; Yamauchi, M.; Grigoriev, A.; Andersson, H.; Gunell, H.;
Fedorov, A.; Thocaven, J. -J.; Zhang, T. L.; Baumjohann, W.; Kallio,
E.; Koskinen, H.; Kozyra, J. U.; Liemohn, M. W.; Ma, Y.; Galli, A.;
Wurz, P.; Bochsler, P.; Brain, D.; Roelof, E. C.; Brandt, P.; Krupp,
N.; Woch, J.; Fraenz, M.; Dubinin, E.; McKenna-Lawlor, S.; Orsini,
S.; Cerulli-Irelli, R.; Mura, A.; Milillo, A.; Maggi, M.; Curtis,
C. C.; Sandel, B. R.; Hsieh, K. C.; Szego, K.; Asamura, A.; Grande, M.
Bibcode: 2008P&SS...56..802C
Altcode:
We report the detection of electrons due to photo-ionization of atomic
oxygen and carbon dioxide in the Venus atmosphere by solar helium 30.4
nm photons. The detection was by the Analyzer of Space Plasma and
Energetic Atoms (ASPERA-4) Electron Spectrometer (ELS) on the Venus
Express (VEx) European Space Agency (ESA) mission. Characteristic
peaks in energy for such photoelectrons have been predicted by
Venus atmosphere/ionosphere models. The ELS energy resolution (Δ
E/ E∼7%) means that these are the first detailed measurements of
such electrons. Considerations of ion production and transport in the
atmosphere of Venus suggest that the observed photoelectron peaks are
due primarily to ionization of atomic oxygen.
Title: Location of the bow shock and ion composition boundaries at
Venus—initial determinations from Venus Express ASPERA-4
Authors: Martinecz, C.; Fränz, M.; Woch, J.; Krupp, N.; Roussos, E.;
Dubinin, E.; Motschmann, U.; Barabash, S.; Lundin, R.; Holmström, M.;
Andersson, H.; Yamauchi, M.; Grigoriev, A.; Futaana, Y.; Brinkfeldt,
K.; Gunell, H.; Frahm, R. A.; Winningham, J. D.; Sharber, J. R.;
Scherrer, J.; Coates, A. J.; Linder, D. R.; Kataria, D. O.; Kallio,
E.; Sales, T.; Schmidt, W.; Riihela, P.; Koskinen, H. E. J.; Kozyra,
J. U.; Luhmann, J.; Russell, C. T.; Roelof, E. C.; Brandt, P.;
Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Sauvaud,
J. -A.; Fedorov, A.; Thocaven, J. -J.; Mazelle, C.; McKenna-Lawler,
S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Mura, A.; Milillo, A.;
Wurz, P.; Galli, A.; Bochsler, P.; Asamura, K.; Szego, K.; Baumjohann,
W.; Zhang, T. L.; Lammer, H.
Bibcode: 2008P&SS...56..780M
Altcode:
For the first time since 1992 when the Pioneer Venus Orbiter (PVO)
ceased to operate, there is again a plasma instrument in orbit around
Venus, namely the ASPERA-4 flown on Venus Express (inserted into an
elliptical polar orbit about the planet on April 11, 2006). In this
paper we report on measurements made by the ion and electron sensors
of ASPERA-4 during their first five months of operation and, thereby,
determine the locations of both the Venus bow shock (BS) and the ion
composition boundary (ICB) under solar minimum conditions. In contrast
to previous studies based on PVO data, we employ a 3-parameter fit
to achieve a realistic shape for the BS. We use a different technique
to fit the ICB because this latter boundary cannot be represented by
a conic section. Additionally we investigate the dependence of the
location of the BS on solar wind ram pressure (based on ASPERA-4 solar
wind data) and solar EUV flux (using a proxy from Earth).
Title: Mars Express and Venus Express multi-point observations of
geoeffective solar flare events in December 2006
Authors: Futaana, Y.; Barabash, S.; Yamauchi, M.; McKenna-Lawlor, S.;
Lundin, R.; Luhmann, J. G.; Brain, D.; Carlsson, E.; Sauvaud, J. -A.;
Winningham, J. D.; Frahm, R. A.; Wurz, P.; Holmström, M.; Gunell, H.;
Kallio, E.; Baumjohann, W.; Lammer, H.; Sharber, J. R.; Hsieh, K. C.;
Andersson, H.; Grigoriev, A.; Brinkfeldt, K.; Nilsson, H.; Asamura,
K.; Zhang, T. L.; Coates, A. J.; Linder, D. R.; Kataria, D. O.;
Curtis, C. C.; Sandel, B. R.; Fedorov, A.; Mazelle, C.; Thocaven,
J. -J.; Grande, M.; Koskinen, Hannu E. J.; Sales, T.; Schmidt, W.;
Riihela, P.; Kozyra, J.; Krupp, N.; Woch, J.; Fränz, M.; Dubinin,
E.; Orsini, S.; Cerulli-Irelli, R.; Mura, A.; Milillo, A.; Maggi,
M.; Roelof, E.; Brandt, P.; Szego, K.; Scherrer, J.; Bochsler, P.
Bibcode: 2008P&SS...56..873F
Altcode:
In December 2006, a single active region produced a series of proton
solar flares, with X-ray class up to the X9.0 level, starting on
5 December 2006 at 10:35 UT. A feature of this X9.0 flare is that
associated MeV particles were observed at Venus and Mars by Venus
Express (VEX) and Mars Express (MEX), which were ∼80° and ∼125°
east of the flare site, respectively, in addition to the Earth, which
was ∼79° west of the flare site. On December 5, 2006, the plasma
instruments ASPERA-3 and ASPERA-4 on board MEX and VEX detected a
large enhancement in their respective background count levels. This
is a typical signature of solar energetic particle (SEP) events, i.e.,
intensive MeV particle fluxes. The timings of these enhancements were
consistent with the estimated field-aligned travel time of particles
associated with the X9.0 flare that followed the Parker spiral to
reach Venus and Mars. Coronal mass ejection (CME) signatures that
might be related to the proton flare were twice identified at Venus
within <43 and <67 h after the flare. Although these CMEs did
not necessarily originate from the X9.0 flare on December 5, 2006,
they most likely originated from the same active region because these
characteristics are very similar to flare-associated CMEs observed on
the Earth. These observations indicate that CME and flare activities
on the invisible side of the Sun may affect terrestrial space weather
as a result of traveling more than 90° in both azimuthal directions
in the heliosphere. We would also like to emphasize that during
the SEP activity, MEX data indicate an approximately one-order of
magnitude enhancement in the heavy ion outflow flux from the Martian
atmosphere. This is the first observation of the increase of escaping
ion flux from Martian atmosphere during an intensive SEP event. This
suggests that the solar EUV flux levels significantly affect the
atmospheric loss from unmagnetized planets.
Title: Suprathermal Tails in Solar Wind Oxygen and Iron
Authors: Popecki, M.; Galvin, A. B.; Kistler, L. M.; Klecker, B.;
Bochsler, P.; Kucharek, H.; Blush, L.; Wimmer-Schweingruber, R. F.;
Moebius, E.
Bibcode: 2008AGUSMSH41A..13P
Altcode:
High speed suprathermal tails with a fixed energy spectrum have been
observed in solar wind H and He2+, as well as in He+ pickup ions
(e.g. Gloeckler et al., 2007). These tails appear to have a persistent
and constant power law energy spectrum, unchanged in a variety of solar
conditions. The presence of the tails have implications for particle
injection into the interplanetary shock acceleration process. The
suprathermal tails of ions heavier than H and He may be investigated
with the STEREO/PLASTIC mass spectrometer, for speeds up to several
times the solar wind speed. The energy spectra of solar wind O and Fe
are presented for periods of slow and fast solar wind. Variations in
energy spectra will be discussed.
Title: The Venusian induced magnetosphere: A case study of plasma
and magnetic field measurements on the Venus Express mission
Authors: Kallio, E.; Zhang, T. L.; Barabash, S.; Jarvinen, R.;
Sillanpää, I.; Janhunen, P.; Fedorov, A.; Sauvaud, J. -A.; Mazelle,
C.; Thocaven, J. -J.; Gunell, H.; Andersson, H.; Grigoriev, A.;
Brinkfeldt, K.; Futaana, Y.; Holmström, M.; Lundin, R.; Yamauchi,
M.; Asamura, K.; Baumjohann, W.; Lammer, H.; Coates, A. J.; Linder,
D. R.; Kataria, D. O.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.;
Grande, M.; Koskinen, H. E. J.; Säles, T.; Schmidt, W.; Riihelä,
P.; Kozyra, J.; Krupp, N.; Woch, J.; Luhmann, J. G.; McKenna-Lawlor,
S.; Orsini, S.; Cerulli-Irelli, R.; Mura, A.; Milillo, A.; Maggi, M.;
Roelof, E.; Brandt, P.; Russell, C. T.; Szego, K.; Winningham, J. D.;
Frahm, R. A.; Scherrer, J. R.; Sharber, J. R.; Wurz, P.; Bochsler, P.
Bibcode: 2008P&SS...56..796K
Altcode:
Plasma and magnetic field measurements made onboard the Venus Express
on June 1, 2006, are analyzed and compared with predictions of a global
model. It is shown that in the orbit studied, the plasma and magnetic
field observations obtained near the North Pole under solar minimum
conditions were qualitatively and, in many cases also, quantitatively
in agreement with the general picture obtained using a global numerical
quasi-neutral hybrid model of the solar wind interaction (HYB-Venus). In
instances where the orbit of Venus Express crossed a boundary referred
to as the magnetic pileup boundary (MPB), field line tracing supports
the suggestion that the MPB separates the region that is magnetically
connected to the fluctuating magnetosheath field from a region that
is magnetically connected to the induced magnetotail lobes.
Title: Theoretical modeling for the stereo mission
Authors: Aschwanden, Markus J.; Burlaga, L. F.; Kaiser, M. L.; Ng,
C. K.; Reames, D. V.; Reiner, M. J.; Gombosi, T. I.; Lugaz, N.;
Manchester, W.; Roussev, I. I.; Zurbuchen, T. H.; Farrugia, C. J.;
Galvin, A. B.; Lee, M. A.; Linker, J. A.; Mikić, Z.; Riley, P.;
Alexander, D.; Sandman, A. W.; Cook, J. W.; Howard, R. A.; Odstrčil,
D.; Pizzo, V. J.; Kóta, J.; Liewer, P. C.; Luhmann, J. G.; Inhester,
B.; Schwenn, R. W.; Solanki, S. K.; Vasyliunas, V. M.; Wiegelmann, T.;
Blush, L.; Bochsler, P.; Cairns, I. H.; Robinson, P. A.; Bothmer,
V.; Kecskemety, K.; Llebaria, A.; Maksimovic, M.; Scholer, M.;
Wimmer-Schweingruber, R. F.
Bibcode: 2008SSRv..136..565A
Altcode: 2006SSRv..tmp...75A
We summarize the theory and modeling efforts for the STEREO mission,
which will be used to interpret the data of both the remote-sensing
(SECCHI, SWAVES) and in-situ instruments (IMPACT, PLASTIC). The
modeling includes the coronal plasma, in both open and closed magnetic
structures, and the solar wind and its expansion outwards from the Sun,
which defines the heliosphere. Particular emphasis is given to modeling
of dynamic phenomena associated with the initiation and propagation
of coronal mass ejections (CMEs). The modeling of the CME initiation
includes magnetic shearing, kink instability, filament eruption, and
magnetic reconnection in the flaring lower corona. The modeling of CME
propagation entails interplanetary shocks, interplanetary particle
beams, solar energetic particles (SEPs), geoeffective connections,
and space weather. This review describes mostly existing models of
groups that have committed their work to the STEREO mission, but is by
no means exhaustive or comprehensive regarding alternative theoretical
approaches.
Title: The Plasma and Suprathermal Ion Composition (PLASTIC)
Investigation on the STEREO Observatories
Authors: Galvin, A. B.; Kistler, L. M.; Popecki, M. A.; Farrugia,
C. J.; Simunac, K. D. C.; Ellis, L.; Möbius, E.; Lee, M. A.; Boehm,
M.; Carroll, J.; Crawshaw, A.; Conti, M.; Demaine, P.; Ellis, S.;
Gaidos, J. A.; Googins, J.; Granoff, M.; Gustafson, A.; Heirtzler,
D.; King, B.; Knauss, U.; Levasseur, J.; Longworth, S.; Singer, K.;
Turco, S.; Vachon, P.; Vosbury, M.; Widholm, M.; Blush, L. M.; Karrer,
R.; Bochsler, P.; Daoudi, H.; Etter, A.; Fischer, J.; Jost, J.; Opitz,
A.; Sigrist, M.; Wurz, P.; Klecker, B.; Ertl, M.; Seidenschwang, E.;
Wimmer-Schweingruber, R. F.; Koeten, M.; Thompson, B.; Steinfeld, D.
Bibcode: 2008SSRv..136..437G
Altcode: 2008SSRv..tmp....5G
The Plasma and Suprathermal Ion Composition (PLASTIC) investigation
provides the in situ solar wind and low energy heliospheric
ion measurements for the NASA Solar Terrestrial Relations
Observatory Mission, which consists of two spacecraft (STEREO-A,
STEREO-B). PLASTIC-A and PLASTIC-B are identical. Each PLASTIC is
a time-of-flight/energy mass spectrometer designed to determine the
elemental composition, ionic charge states, and bulk flow parameters of
major solar wind ions in the mass range from hydrogen to iron. PLASTIC
has nearly complete angular coverage in the ecliptic plane and an energy
range from ∼0.3 to 80 keV/e, from which the distribution functions
of suprathermal ions, including those ions created in pick-up and
local shock acceleration processes, are also provided.
Title: Helium, Neon, and Argon Isotopic and Elemental Composition of
Solar Wind Regimes Collected by Genesis: Implications on Fractionation
Processes Upon Solar Wind Formation
Authors: Heber, V. S.; Baur, H.; Bochsler, P.; Burnett, D. S.;
Reisenfeld, D. B.; Wieler, R.; Wiens, R. C.
Bibcode: 2008LPI....39.1779H
Altcode:
Elemental and isotopic composition of He, Ne and Ar will be presented
for the three Genesis solar wind (SW) regimes and bulk SW. Special
emphasis will be given to the relative differences between SW regimes
to reveal fractionation processes in the SW.
Title: Solar wind helium, neon, and argon isotopic and elemental
composition: Data from the metallic glass flown on NASA's Genesis
mission
Authors: Grimberg, Ansgar; Baur, Heinrich; Bühler, Fritz; Bochsler,
Peter; Wieler, Rainer
Bibcode: 2008GeCoA..72..626G
Altcode:
Solar wind (SW) helium, neon, and argon trapped in a bulk metallic glass
(BMG) target flown on NASA's Genesis mission were analyzed for their
bulk composition and depth-dependent distribution. The bulk isotopic
and elemental composition for all three elements is in good agreement
with the mean values observed in the Apollo Solar Wind Composition (SWC)
experiment. Conversely, the He fluence derived from the BMG is up to 30%
lower than values reported from other Genesis bulk targets or in-situ
measurements during the exposure period. SRIM implantation simulations
using a uniform isotopic composition and the observed bulk velocity
histogram during exposure reproduces the Ne and Ar isotopic variations
with depth within the BMG in a way which is generally consistent
with observations. The similarity of the BMG release patterns with
the depth-dependent distributions of trapped solar He, Ne, and Ar
found in lunar and asteroidal regolith samples shows that also the
solar noble gas record of extraterrestrial samples can be explained
by mass separation of implanted SW ions with depth. Consequently,
we conclude that a second solar noble gas component in lunar samples,
referred to as the “SEP” component, is not needed. On the other
hand, a small fraction of the total solar gas in the BMG released from
shallow depths is markedly enriched in the light isotopes relative
to predictions from implantation simulations with a uniform isotopic
composition. Contributions from a neutral solar or interstellar
component are too small to explain this shallow sited gas. We
tentatively attribute this superficially implanted gas to low-speed,
current-sheet related SW, which was fractionated in the corona due to
inefficient Coulomb drag. This fractionation process could also explain
relatively high Ne/Ar elemental ratios in the same initial gas fraction.
Title: Suprathermal tails in solar wind oxygen and iron
Authors: Popecki, Mark; Galvin, Antoinette; Bochsler, Peter; Kucharek,
Harald; Moebius, Eberhard; Kistler, Lynn; Blush, Lisa
Bibcode: 2008cosp...37.2480P
Altcode: 2008cosp.meet.2480P
High speed suprathermal tails have been observed in solar wind H+
and He2+, as well as in He+ pickup ions (e.g. Gloeckler et al.,
2007). These tails have a persistent and constant power law spectrum,
unchanged in a variety of solar conditions. The presence of the tails
have implications for particle injection into the interplanetary shock
acceleration process. The suprathermal tails of ions heavier than H and
He may be investigated with the STEREO/PLASTIC mass spectrometer. The
energy spectra of solar wind O and Fe are presented for periods of slow
and fast solar wind. Variations in energy spectra will be discussed.
Title: Solar wind transport parameters determined by SOHO/CELIAS
observations of interstellar pickup ions
Authors: Saul, Lukas; Wurz, Peter; Moebius, Eberhard; Bochsler, Peter
Bibcode: 2008cosp...37.2746S
Altcode: 2008cosp.meet.2746S
We review studies of solar wind transport using interstellar pickup
ions as a diagnosic, using helium data from SOHO/CELIAS/CTOF. These
include new insights into pitch angle transport and acceleration
processes. Recent work has also shown progress in quantitative
measurement of adiabatic cooling of the solar wind in the inner
heliosphere.
Title: Solar Wind and Suprathermal Ion Populations at the STEREO
Spacecraft Approaching Solar Minimum
Authors: Galvin, A. B.; Popecki, M.; Kistler, L.; Simunac, K.;
Farrugia, C.; Gustafson, A.; Barry, J.; Ellis, L.; Moebius, E.; Blush,
L.; Klecker, B.; Bochsler, P.; Wurz, P.; Wimmer-Schweingruber, R.;
Thompson, B.; Luhmann, J.; Russell, C.
Bibcode: 2007AGUFMSH33A1083G
Altcode:
The two STEREO spacecraft, which were launched in October 2006, have
been gradually separating in longitude at a rate of about 22 degrees
per year. During this past year, the dominant heliospheric features
have been a series of recurrent high and slow speed solar wind and
their interaction regions, an occasional transient event (e.g., May
22), and "background" suprathermal populations such as interstellar
pick up ions. In this poster we present an overview of the plasma
and suprathermal signatures observed by the STEREO spacecraft using
data from the Plasma and Suprathermal Ion Composition (PLASTIC)
and Magnetometer (IMPACT/MAG) investigations. Complementary STEREO
PLASTIC related presentations in this session are by Popecki et al.,
Klecker et al. (invited), and Simunac et al.
Title: Solar Wind Charge State Composition Results from PLASTIC
Authors: Popecki, M.; Galvin, A. B.; Kistler, L. M.; Moebius, E.;
Klecker, B.; Kucharek, H.; Simunac, K.; Bochsler, P.; Blush, L.;
Karrer, R.; Daoudi, H.; Opitz, A.; Giammanco, C.; Wimmer-Schweingruber,
R.
Bibcode: 2007AGUFMSH52B..07P
Altcode:
The PLASTIC instrument on the STEREO spacecraft provides solar wind
proton moments and heavy ion composition. Using an electrostatic
analyzer with a time of flight and residual energy measurement,
it can supply mass and ionic charge state for solar wind heavy
ions. Preliminary results for iron will be shown for selected events,
including the possible flux rope passage on May 21-22, 2007, and a
near-magnetotail passage in February, 2007.
Title: Pickup Helium in the Inner Heliosphere: an Overview
Authors: Klecker, B.; Galvin, A. B.; Kucharek, H.; Kistler, L. M.;
Popecki, M. A.; Mouikis, C.; Farrugia, C.; Möbius, E.; Lee,
M. A.; Ellis, L.; Simunac, K.; Singer, K.; Blush, L. M.; Bochsler,
P.; Wurz, P.; Daoudi, H.; Giammanco, C.; Karrer, R.; Opitz, A.;
Wimmer-Schweingruber, R. F.; Koeten, M.; Hilchenbach, M.; Thompson,
B.; Acuna, M.; Luhman, J.
Bibcode: 2007AGUFMSH51B..01K
Altcode:
The CELIAS experiment onboard SOHO and the two Plasma and Suprathermal
Ion Composition (PLASTIC) experiments onboard STEREO-A/B provide
measurements of velocity, mass and ionic charge of solar wind ions
and of suprathermal particles up to energies of 80 keV/e (PLASTIC)
and 600 keV/e (CELIAS), respectively. Thus both the SOHO and STEREO
instrumentation covers the energy range of the pickup He particle
population of interstellar origin that is accelerated to suprathermal
energies at interplanetary shocks and corotating interaction regions
(CIRs). ACE and SOHO observations showed a large variability of both
the pickup He source and the flux of suprathermal particles that so
far could not be satisfactorily explained. In this overview we will
summarize recent pickup He observations with ACE and SOHO at 1 AU,
present first results of pickup He in CIRs obtained with STEREO, and
discuss open questions that can be tackled in the near future with
the new constellation of several spacecraft in the inner heliosphere.
Title: Probing the 2-D Geometry of CIRs at Solar Minimum: Observations
From STEREO
Authors: Simunac, K. D.; Galvin, A. B.; Kistler, L. M.; Popecki,
M. A.; Farrugia, C.; Moebius, E.; Ellis, L.; Blush, L. M.; Bochsler,
P.; Wurz, P.; Klecker, B.; Wimmer-Schweingruber, R. F.; Thompson,
B. J.; Luhmann, J. G.; Russell, C. T.; Jian, L. K.
Bibcode: 2007AGUFMSH33A1084S
Altcode:
The twin STEREO observatories provide a unique opportunity to study
the two-dimensional in-ecliptic geometry of structures in the solar
wind. At the start of 2007 the AHEAD (A) and BEHIND (B) satellites
were near Earth. By the end of the year they will each be separated
from Earth by about 20 degrees longitudinally, and from each other
by about 40 degrees. This arrangement is well suited to test the
conceptual picture of CIRs in the ecliptic plane. The orbital radius
of STEREO A is about 0.98 AU, while STEREO B is at about 1.03 AU. If
A and B were at the same line of longitude they would be less than
2000 Earth radii apart. Observations show this small radial separation
becomes important when predicting the arrival time at Earth of streams
observed with STEREO B; stream fronts were seen to arrive at A and B
almost simultaneously in mid 2007 when the spacecraft were separated
by about 7 degrees. This suggests the leading edge of the stream is
roughly aligned with the solar wind garden hose angle. We report on
observations of the leading edges of co-rotating high-speed streams,
and discuss the implications for space weather forecasting.
Title: Helium at Interplanetary Discontinuities: ACE STEREO
Observations and Simulations
Authors: Moebius, E.; Kucharek, H.; Allegrini, F.; Desai, M.; Klecker,
B.; Popecki, M.; Farrugia, C.; Galvin, A.; Bochsler, P.; Karrer, R.;
Opitz, A.; Simunac, K.
Bibcode: 2007AGUFMSH33A1089M
Altcode:
ACE/SEPICA observations showed that, on average, energetic He+
is after H+ and He2+ the third most abundant energetic particle
species in the heliosphere. Depending on the type of the energetic
population the He+/He2+ ratio can reach unusually high values in the
energy range 250 - 800keV/n ratios up to unity. As a major source of
energetic He+ interplanetary pickup ions have been identified that are
preferentially accelerated at co-rotating interaction regions (CIRs),
transient interaction regions (TIRs), and interplanetary traveling
shocks. Most recent data from STEREO/PLASTIC in the energy range of
0.2-80keV/Q show clear evidence of abundant He+ at interplanetary
discontinuities. Thus PLASTIC extends the energy range into injection
region of the source. Furthermore, ACE/ULEIS and ACE/SEPICA measurements
showed that very often 3He2+ and He+ are also accelerated simultaneously
at CME-driven IP shocks. This is surprising because, these to species
originate from different sources. However, this may indicate that
the injection, or the acceleration efficiency of the accelerator for
different source population may be similar. From observations, however,
this cannot be differentiated easily. In numerical simulations this
can be done because there is control over species and distribution
functions. In a numerical study we applied test particle simulations
and multi-dimensional hybrid simulations to address the contribution
of source, injection and acceleration efficiency at shocks to the
variability of the helium ratio. These, simulations with and without
superimposed turbulence in the shock region will be compared with
observations.
Title: The loss of ions from Venus through the plasma wake
Authors: Barabash, S.; Fedorov, A.; Sauvaud, J. J.; Lundin, R.;
Russell, C. T.; Futaana, Y.; Zhang, T. L.; Andersson, H.; Brinkfeldt,
K.; Grigoriev, A.; Holmström, M.; Yamauchi, M.; Asamura, K.;
Baumjohann, W.; Lammer, H.; Coates, A. J.; Kataria, D. O.; Linder,
D. R.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.;
Gunell, H.; Koskinen, H. E. J.; Kallio, E.; Riihelä, P.; Säles, T.;
Schmidt, W.; Kozyra, J.; Krupp, N.; Fränz, M.; Woch, J.; Luhmann,
J.; McKenna-Lawlor, S.; Mazelle, C.; Thocaven, J. -J.; Orsini, S.;
Cerulli-Irelli, R.; Mura, M.; Milillo, M.; Maggi, M.; Roelof, E.;
Brandt, P.; Szego, K.; Winningham, J. D.; Frahm, R. A.; Scherrer,
J.; Sharber, J. R.; Wurz, P.; Bochsler, P.
Bibcode: 2007Natur.450..650B
Altcode:
Venus, unlike Earth, is an extremely dry planet although both began
with similar masses, distances from the Sun, and presumably water
inventories. The high deuterium-to-hydrogen ratio in the venusian
atmosphere relative to Earth's also indicates that the atmosphere
has undergone significantly different evolution over the age of the
Solar System. Present-day thermal escape is low for all atmospheric
species. However, hydrogen can escape by means of collisions with hot
atoms from ionospheric photochemistry, and although the bulk of O and
O2 are gravitationally bound, heavy ions have been observed
to escape through interaction with the solar wind. Nevertheless, their
relative rates of escape, spatial distribution, and composition could
not be determined from these previous measurements. Here we report
Venus Express measurements showing that the dominant escaping ions
are O+, He+ and H+. The escaping
ions leave Venus through the plasma sheet (a central portion of the
plasma wake) and in a boundary layer of the induced magnetosphere. The
escape rate ratios are Q(H+)/Q(O+) = 1.9;
Q(He+)/Q(O+) = 0.07. The first of these implies
that the escape of H+ and O+, together with the
estimated escape of neutral hydrogen and oxygen, currently takes place
near the stoichometric ratio corresponding to water.
Title: The Analyser of Space Plasmas and Energetic Atoms (ASPERA-4)
for the Venus Express mission
Authors: Barabash, S.; Sauvaud, J. -A.; Gunell, H.; Andersson, H.;
Grigoriev, A.; Brinkfeldt, K.; Holmström, M.; Lundin, R.; Yamauchi,
M.; Asamura, K.; Baumjohann, W.; Zhang, T. L.; Coates, A. J.; Linder,
D. R.; Kataria, D. O.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.;
Fedorov, A.; Mazelle, C.; Thocaven, J. -J.; Grande, M.; Koskinen,
Hannu E. J.; Kallio, E.; Säles, T.; Riihela, P.; Kozyra, J.;
Krupp, N.; Woch, J.; Luhmann, J.; McKenna-Lawlor, S.; Orsini, S.;
Cerulli-Irelli, R.; Mura, M.; Milillo, M.; Maggi, M.; Roelof, E.;
Brandt, P.; Russell, C. T.; Szego, K.; Winningham, J. D.; Frahm,
R. A.; Scherrer, J.; Sharber, J. R.; Wurz, P.; Bochsler, P.
Bibcode: 2007P&SS...55.1772B
Altcode:
The general scientific objective of the ASPERA-4 (Analyser of
Space Plasmas and Energetic Atoms) experiment is to study the solar
wind-atmosphere interaction and characterise the plasma and neutral
gas environment in the near-Venus space through energetic neutral atom
(ENA) imaging and local charged particle measurements. The studies
to be performed address the fundamental question: How strongly do
the interplanetary plasma and electromagnetic fields affect the
Venusian atmosphere? The ASPERA-4 instrument comprises four sensors;
two ENA sensors, electron and ion spectrometers. The neutral particle
imager (NPI) provides measurements of the integral ENA flux (0.1-60
keV) with no mass and energy resolution but relatively high angular
resolution. The neutral particle detector (NPD) provides measurements of
the ENA flux, resolving velocity (0.1-10 keV) and mass (H and O) with a
coarse angular resolution. The electron spectrometer (ELS) is a standard
top-hat electrostatic analyser in a very compact design. These three
sensors are located on a scanning platform providing a 4π coverage. The
instrument also contains an ion mass composition sensor, IMA (ion mass
analyser). Mechanically, IMA is a separate unit electrically connected
with the ASPERA-4 main unit. IMA provides ion measurements in the
energy range 0.01-36 keV/ q for the main ion components H+,
He++, He+, and the ion group with M/q20-80amu/q.
Title: Solar abundances of oxygen and neon derived from solar wind
observations
Authors: Bochsler, P.
Bibcode: 2007A&A...471..315B
Altcode:
Context: Recently, a revision of the solar abundances of C, N, and O to
substantially lower values has led to a controversy on solar opacities
in the solar standard model and to the suggestion to revise the solar
abundance of neon upward by as much as a factor of 1.6 leading to
enhanced solar neon/oxygen abundance ratios by a factor of 3. Neon and
oxygen are neighboring elements with easily defined charged states in
the solar wind, and they have been well identified and measured for over
two decades in the solar wind under many circumstances and with several
instruments. The solar wind Ne/O ratio is 0.14 with a conservative
error estimate of ±0.03, consistent with the coronal value derived
from solar energetic particle measurements.
Aims: We investigate,
whether solar wind observations are consistent with the newly proposed
elemental solar abundances of neon and oxygen.
Methods: The
solar helium abundance has been derived from helioseismological
observations. Helium and neon abundances in the solar wind have
been well determined with the Apollo Foil experiments and, more
recently, confirmed with the Genesis sample return mission. With these
observations and the neon/oxygen solar wind abundance ratio determined
by in-situ mass-spectrometry and using a simple theoretical model
of Coulomb-drag fractionation for the solar wind, we estimate solar
abundances for neon and oxygen.
Results: From the variability of
the helium/oxygen and the helium/neon ratio in the solar wind and from
theoretical considerations, we conclude that the helium/neon ratio in
the outer solar convective zone is 900 ± 110. Our best estimates of
the solar neon and oxygen abundances in logarithmic dex-units are [Ne]
= 7.96 ± 0.13, and [O] = 8.87 ± 0.11.
Conclusions: Our solar
neon/oxygen abundance ratio is consistent with the ratio derived from
EUV-spectra from SOHO/CDS. However, our absolute abundance for oxygen
is only marginally compatible with the newly derived value for oxygen,
and our neon value is clearly incompatible with the recently proposed
enhancement of the solar neon abundance.
Title: Composition of Light Solar Wind Noble Gases in the Bulk
Metallic Glass flown on the Genesis Mission
Authors: Grimberg, A.; Burnett, D. S.; Bochsler, P.; Baur, H.;
Wieler, R.
Bibcode: 2007SSRv..130..293G
Altcode: 2007SSRv..tmp...88G
We discuss data of light noble gases from the solar wind implanted
into a metallic glass target flown on the Genesis mission. Helium
and neon isotopic compositions of the bulk solar wind trapped in
this target during 887 days of exposure to the solar wind do not
deviate significantly from the values in foils of the Apollo Solar
Wind Composition experiments, which have been exposed for hours to
days. In general, the depth profile of the Ne isotopic composition
is similar to those often found in lunar soils, and essentially very
well reproduced by ion-implantation modelling, adopting the measured
velocity distribution of solar particles during the Genesis exposure
and assuming a uniform isotopic composition of solar wind neon. The
results confirm that contributions from high-energy particles to the
solar wind fluence are negligible, which is consistent with in-situ
observations. This makes the enigmatic “SEP-Ne” component,
apparently present in lunar grains at relatively large depth,
obsolete. 20Ne/ 22Ne ratios in gas trapped very
near the metallic glass surface are up to 10% higher than predicted by
ion implantation simulations. We attribute this superficially trapped
gas to very low-speed, current-sheet-related solar wind, which has
been fractionated in the corona due to inefficient Coulomb drag.
Title: Determination of Sulfur Abundance in the Solar Wind
Authors: Giammanco, C.; Bochsler, P.; Karrer, R.; Ipavich, F. M.;
Paquette, J. A.; Wurz, P.
Bibcode: 2007SSRv..130..329G
Altcode: 2007SSRv..tmp..122G
Solar chemical abundances are determined by comparing solar photospheric
spectra with synthetic ones obtained for different sets of abundances
and physical conditions. Although such inferred results are reliable,
they are model dependent. Therefore, one compares them with the values
for the local interstellar medium (LISM). The argument is that they
must be similar, but even for LISM abundance determinations models
play a fundamental role (i.e., temperature fluctuations, clumpiness,
photon leaks). There are still two possible comparisons—one with
the meteoritic values and the second with solar wind abundances. In
this work we derive a first estimation of the solar wind element
ratios of sulfur relative to calcium and magnesium, two neighboring
low-FIP elements, using 10 years of CELIAS/MTOF data. We compare
the sulfur abundance with the abundance determined from spectroscopic
observations and from solar energetic particles. Sulfur is a moderately
volatile element, hence, meteoritic sulfur may be depleted relative to
non-volatile elements, if compared to its original solar system value.
Title: Nickel Isotopic Composition and Nickel/Iron Ratio in the
Solar Wind: Results from SOHO/CELIAS/MTOF
Authors: Karrer, R.; Bochsler, P.; Giammanco, C.; Ipavich, F. M.;
Paquette, J. A.; Wurz, P.
Bibcode: 2007SSRv..130..317K
Altcode:
Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the
Charge, Elements, Isotope Analysis System (CELIAS)—onboard the
Solar Heliospheric Observatory (SOHO) spacecraft, we derive the
nickel isotopic composition for the isotopes with mass 58, 60 and
62 in the solar wind. In addition we measure the elemental abundance
ratio of nickel to iron. We use data accumulated during ten years of
SOHO operation to get sufficiently high counting statistics and compare
periods of different solar wind velocities. We compare our values with
the meteoritic ratios, which are believed to be a reliable reference
for the solar system and also for the solar outer convective zone,
since neither element is volatile and no isotopic fractionation is
expected in meteorites. Meteoritic isotopic abundances agree with
the terrestrial values and can thus be considered to be a reliable
reference for the solar isotopic composition. The measurements show
that the solar wind elemental Ni/Fe-ratio and the isotopic composition
of solar wind nickel are consistent with the meteoritic values. This
supports the concept that low-FIP elements are fed without relative
fractionation into the solar wind. Our result also confirms the absence
of substantial isotopic fractionation processes for medium and heavy
ions acting in the solar wind.
Title: Initial Results from STEREO/PLASTIC
Authors: Popecki, Mark; Galvin, A.; Kistler, L. M.; Moebius, E.;
Simunac, K.; Bochsler, P.; Blush, L. M.; Karrer, R.; Daoudi, H.;
Opitz, A.; Giammanco, C.; Klecker, B.; Wimmer-Schweingruber, R. F.
Bibcode: 2007AAS...210.2806P
Altcode: 2007BAAS...39..136P
With the recent successful launch of the STEREO spacecraft, two new
solar-observing spacecraft are in operation, with remote sensing and
in-situ instruments. The PLASTIC instrument reports the solar wind
speed, temperature, direction and density. It also measures the mass and
ionic charge state of heavy ions in the solar wind. In addition, PLASTIC
detects suprathermal ions using two non-solar wind apertures. The
instrument obtains mass/charge from one aperture. From the other, it
measures mass, energy and ionic charge. An overview of PLASTIC data
products will be presented, with a focus on heavy ion observations.
Title: Bulk Properties of Solar Wind Protons: Inter-comparison of
Observations From STEREO, SOHO, ACE, and WIND
Authors: Simunac, K. D.; Galvin, A. B.; Kistler, L. A.; Popecki, M. A.;
Farrugia, C.; Moebius, E.; Lee, M.; Ellis, L.; Singer, K.; Walker,
C.; Blush, L. M.; Bochsler, P.; Wurz, P.; Daoudi, H.; Giammanco,
C.; Karrer, R.; Opitz, A.; Klecker, B.; Wimmer-Schweingruber, R. F.;
Koeten, M.; Thompson, B.
Bibcode: 2007AGUSMSH41A..10S
Altcode:
The twin STEREO observatories were launched in October 2006. The PLASTIC
experiment onboard both spacecraft analyzes ions with energies between
0.25 and 80 keV/charge, including solar wind protons. Information on
bulk properties such as density, speed, and temperature are obtained. In
early 2007 STEREO A was separated from SOHO, ACE, WIND, and STEREO
B by hundreds of earth radii within the ecliptic plane, and by tens
of earth radii out of the ecliptic plane. We report on comparisons of
bulk parameters between these spacecraft, and what they show us about
small-scale temporal and spatial variations in the solar wind.
Title: Observations of Energetic O+ in the Distant Tail Magnetosheath:
Results from STEREO/PLASTIC
Authors: Kistler, L. M.; Galvin, A. B.; Popecki, M. A.; Mouikis,
C.; Farrugia, C.; Moebius, E.; Lee, M. A.; Ellis, L.; Simunac, K.;
Singer, K.; Blush, L. M.; Klecker, B.; Wimmer-Schweingruber, R. F.;
Thompson, B.; Bochsler, P.; Wurz, P.; Karrer, R.; Opitz, A.; Luhmann,
J.; Acuna, M.; Russell, C. T.
Bibcode: 2007AGUSMSH34A..03K
Altcode:
Two identical Plasma and Suprathermal Ion Composition (PLASTIC)
instruments are now flying on the STEREO A and B observatories, which
launched in October 2006. PLASTIC is a solar wind and heliospheric
ion mass spectrometer that utilizes electrostatic deflection,
post-acceleration,time-of-flight, energy, and position measurements
in the energy-per-charge range of 0.25-80 keV/e. During the month
of February, 2007, as the spacecraft were approaching their final
heliocentric orbits, STEREO B traversed the dusk-side magnetosheath and
boundary layer from -100 Re to -300 Re down the tail. Throughout the
month, bursts of energetic O+ were observed in the magnetosheath. The
energy of the O+ extended to the upper range of the instrument, 80
keV. The occurrence of O+ correlated with periods of high solar wind
velocity. We will compare these observations with observations of O+
in the near-earth magnetosheath, as observed by CLUSTER, and discuss
the possible sources and transport paths for these ions.
Title: Solar Wind Helium, Neon and Argon Isotopic and Elemental
Composition: Data from the Metallic Glass flown on NASA's Genesis
Mission
Authors: Grimberg, A.; Bochsler, P.; Baur, H.; Buehler, F.; Wieler, R.
Bibcode: 2007AGUSMSH32A..02G
Altcode:
Solar wind helium, neon and argon trapped in a metallic glass target
flown on NASA's Genesis mission were analyzed for their bulk composition
and depth dependent distribution. The bulk isotopic and elemental
composition for all elements is in good agreement with the mean values
observed in the Apollo solar wind composition experiment. Adopting the
measured solar wind velocity histogram during exposure, the isotopic
composition of He, Ne, and Ar varies with depth within the metallic
glass in a way generally consistent with ion- irradiation simulations
of a solar wind of uniform composition. The similarity of the release
patterns with the depth dependent distribution of trapped solar He,
Ne, and Ar reported for lunar and asteroidal regolith samples shows
that also the solar noble-gas record of extraterrestrial samples
can be explained by mass separation of implanted solar wind with
depth. This result confirms that contributions from high-energy
particles to the solar wind fluence are minor, consistent with in-situ
flux observations. On the other hand, a small gas fraction of the total
solar gas in the metallic glass released from shallow depths is markedly
enriched in the light isotopes relative to predictions from uniform
isotopic implantation simulations. Contributions from interstellar
gas or from the neutral solar wind are too small to explain this gas
fraction. We tentatively attribute this superficially implanted gas to
low-speed, current-sheet related solar wind, which was fractionated
in the corona due to inefficient Coulomb drag, although the small
apparent penetration depths associated to this component may be in
conflict with this interpretation.
Title: On the Variability of Suprathermal He+: new Results From
STEREO and SOHO
Authors: Klecker, B.; Galvin, A. B.; Kistler, L. M.; Popecki, M. A.;
Mouikis, C.; Farrugia, C.; Moebius, E.; Lee, M.; Ellis, L.; Simunac,
K.; Singer, K.; Blush, L. M.; Bochsler, P.; Wurz, P.; Daoudi, H.;
Giammanco, C.; Karrer, R.; Opitz, A.; Wimmer-Schweingruber, R. F.;
Koeten, M.; Hilchenbach, M.; Thompson, B.; Acuna, M.; Luhmann, J.
Bibcode: 2007AGUSMSH34A..02K
Altcode:
The two Plasma and Suprathermal Ion Composition (PLASTIC) experiments
onboard STEREO-A and STEREO-B and the CELIAS experiment onboard SOHO
provide measurements of velocity, mass and ionic charge of solar
wind ions and of suprathermal particles up to energies of 80 keV/e
(PLASTIC) and 600 keV/e (CELIAS), respectively. The observations with
SOHO showed a large variability of the He+/He2+ -ratio at suprathermal
energies, with He+/He2+ > 1 in many interplanetary shock related
solar energetic particle (SEP) events. This variability is much
larger than the observed variations in the interstellar pickup He+
source and suggests that the different velocity distributions of
the two sources, i.e. solar wind and pickup ions of interstellar
origin, play an important role for the efficiency of injection and/or
acceleration of these ions. Thus PLASTIC onboard STEREO, covering the
energy range from solar wind to pickup ion and suprathermal energies,
has the potential for resolving some of the questions related to the
large variability of the He+/He2+-ratios. In this paper we will review
the SOHO measurements of pickup and suprathermal He+ ions at 1 AU, show
first results from PLASTIC onboard STEREO and discuss the perspective
to tackle some of the open questions.
Title: Early Solar Wind Observations from the Plasma and Suprathermal
Ion Composition (PLASTIC) Experiments on STEREO
Authors: Galvin, A. B.; Kistler, L. A.; Popecki, M. A.; Farrugia, C.;
Moebius, E.; Lee, M.; Ellis, L.; Simunac, K.; Singer, K.; Russell,
C.; Walker, C.; Blush, L.; Klecker, B.; Wimmer-Schweingruber, R. F.;
Thompson, B.; Bochsler, P.; Wurz, P.; Daoudi, H.; Giammanco, C.;
Karrer, R.; Opitz, A.; Koeten, M.; Luhmann, J.; Howard, R.; Wuelser,
J. P.; Acuna, M.
Bibcode: 2007AGUSMSH34A..01G
Altcode:
Two identical Plasma and Suprathermal Ion Composition (PLASTIC)
instruments are now flying on the STEREO A and B observatories, which
launched in October 2006. The STEREO observatories are drifting away
from the Earth and from each other, providing different longitudinal
perspectives. PLASTIC together with the IMPACT suite provides the
in-situ measurements for the STEREO mission, while SECCHI provides
remote imaging of the solar corona. The PLASTIC solar wind sector
measures solar wind proton bulk parameters and provides species
identification and relative abundances for the more dominant solar wind
minor (Z>2) ions. During this early part of the STEREO mission,
as we approach solar minimum conditions, there have been a series of
coronal- hole associated high speed streams and interstream sector
boundaries. In this talk we will provide initial observations of the
solar wind during selected time periods.
Title: Erratum to “Observations of magnetic anomaly signatures in
Mars Express ASPERA-3 ELS data” [Icarus 182 (2006) 396 405]
Authors: Soobiah, Y.; Coates, A. J.; Linder, D. R.; Kataria, D. O.;
Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.;
Barabash, S.; Lundin, R.; Holmström, M.; Andersson, H.; Yamauchi,
M.; Grigoriev, A.; Kallio, E.; Koskinen, H.; Säles, T.; Riihelä, P.;
Schmidt, W.; Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.; Livi,
S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter,
M.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler,
S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler,
P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2007Icar..187..623S
Altcode:
No abstract at ADS
Title: The Depth Distribution of Neon and Argon in the Bulk Metallic
Glass Flown on Genesis
Authors: Grimberg, A.; Baur, H.; Burnett, D. S.; Bochsler, P.;
Wieler, R.
Bibcode: 2007LPI....38.1270G
Altcode:
We present Ar and Ne data from the Genesis metallic glass, analyzed
to investigate the depth-dependant elemental and isotopic composition
of solar noble gases, which provides information about the dependence
of the solar wind composition on energy.
Title: Rosina Rosetta Orbiter Spectrometer for Ion and Neutral
Analysis
Authors: Balsiger, H.; Altwegg, K.; Bochsler, P.; Eberhardt, P.;
Fischer, J.; Graf, S.; Jäckel, A.; Kopp, E.; Langer, U.; Mildner, M.;
Müller, J.; Riesen, T.; Rubin, M.; Scherer, S.; Wurz, P.; Wüthrich,
S.; Arijs, E.; Delanoye, S.; de Keyser, J.; Neefs, E.; Nevejans, D.;
Rème, H.; Aoustin, C.; Mazelle, C.; Médale, J. -L.; Sauvaud, J. A.;
Berthelier, J. -J.; Bertaux, J. -L.; Duvet, L.; Illiano, J. -M.;
Fuselier, S. A.; Ghielmetti, A. G.; Magoncelli, T.; Shelley, E. G.;
Korth, A.; Heerlein, K.; Lauche, H.; Livi, S.; Loose, A.; Mall,
U.; Wilken, B.; Gliem, F.; Fiethe, B.; Gombosi, T. I.; Block, B.;
Carignan, G. R.; Fisk, L. A.; Waite, J. H.; Young, D. T.; Wollnik, H.
Bibcode: 2007SSRv..128..745B
Altcode: 2007SSRv..tmp....1B
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis
(ROSINA) will answer important questions posed by the mission’s main
objectives. After Giotto, this will be the first time the volatile
part of a comet will be analyzed in situ. This is a very important
investigation, as comets, in contrast to meteorites, have maintained
most of the volatiles of the solar nebula. To accomplish the very
demanding objectives through all the different phases of the comet’s
activity, ROSINA has unprecedented capabilities including very wide mass
range (1 to >300 amu), very high mass resolution ( m/Δ m > 3000,
i.e. the ability to resolve CO from N2 and 13C
from 12CH), very wide dynamic range and high sensitivity,
as well as the ability to determine cometary gas velocities, and
temperature. ROSINA consists of two mass spectrometers for neutrals and
primary ions with complementary capabilities and a pressure sensor. To
ensure that absolute gas densities can be determined, each mass
spectrometer carries a reservoir of a calibrated gas mixture allowing
in-flight calibration. Furthermore, identical flight-spares of all three
sensors will serve for detailed analysis of all relevant parameters,
in particular the sensitivities for complex organic molecules and
their fragmentation patterns in our electron bombardment ion sources.
Title: On Pitch-Angle Scattering Rates of Interstellar Pickup Ions
as Determined by in Situ Measurement of Velocity Distributions
Authors: Saul, Lukas; Möbius, Eberhard; Isenberg, Philip; Bochsler,
Peter
Bibcode: 2007ApJ...655..672S
Altcode:
Newly ionized interstellar atoms are acted upon by electromagnetic
forces in the solar wind. Measurements of these pickup ions enable study
of the transport processes controlling the evolution of charged particle
populations in solar wind plasma. Data from the CELIAS instruments on
board the SOHO spacecraft allow measurement of the velocity distribution
of singly charged helium ions. These observations are compared to the
predictions of a hemispheric model of pitch-angle diffusion. To justify
the use of the hemispheric model we show here that a ``resonance gap,''
which hinders cross-hemispheric scattering of protons by Alfvén waves,
can exist for the case of pickup helium scattered by outward-propagating
waves. We find that the observed shape of helium pickup ion velocity
distributions is consistent with the hemispheric model prediction. The
parallel mean free path is found to vary with wave power from values of
0.1 to over 1 AU, here presented as a first measurement of the parallel
mean free path as a function of magnetic wave power. Magnetic field
data from the Wind spacecraft enable comparison to the coincident
magnetic field wave power. The cross-hemispheric scattering rate is
found to be monotonic and exponentially dependent on wave power over
the dynamic range considered.
Title: Inner Source Pickup Ions: Sputtering Of Small Dust Particles
And Charge Exchange Of Solar Wind Ions
Authors: Bochsler, P.; Möbius, E.; Wimmer-Schweingruber, R. F.
Bibcode: 2007ESASP.641E..47B
Altcode:
The origin of inner-source pickup ions is generally attributed
to the interaction of solar wind ions with dust particles in
the inner heliosphere. We show that charge states and elemental
abundances of weakly ionized species in the solar wind can provide
valuable information on the properties of dust in the innermost
solar system. Sputtering of sub-micron sized grains by solar wind
and suprathermal solar ions plays an important role in shaping the
grain sized distribution in the corona. The velocity distribution of
inner-source ions reveals details on their production mechanisms. We
investigate reasons for the apparent overabundance of neon compared
to solar wind abundances in inner-source pickup ions. A plasma
instrument capable of measuring charge state distributions and elemental
abundances, as well as velocity distributions of weakly ionized species,
combined with a dust experiment, promises exciting new results from
Solar Orbiter.
Title: Composition of Light Solar Wind Noble Gases in the Bulk
Metallic Glass flown on the Genesis Mission
Authors: Grimberg, A.; Burnett, D. S.; Bochsler, P.; Baur, H.;
Wieler, R.
Bibcode: 2007coma.book..293G
Altcode:
We discuss data of light noble gases from the solar wind implanted
into a metallic glass target flown on the Genesis mission. Helium
and neon isotopic compositions of the bulk solar wind trapped in
this target during 887 days of exposure to the solar wind do not
deviate significantly from the values in foils of the Apollo Solar
Wind Composition experiments, which have been exposed for hours to
days. In general, the depth profile of the Ne isotopic composition
is similar to those often found in lunar soils, and essentially very
well reproduced by ion-implantation modelling, adopting the measured
velocity distribution of solar particles during the Genesis exposure
and assuming a uniform isotopic composition of solar wind neon. The
results confirm that contributions from high-energy particles to
the solar wind fluence are negligible, which is consistent with
in-situ observations. This makes the enigmatic "SEP-Ne" component,
apparently present in lunar grains at relatively large depth,
obsolete. 20Ne/ 22Ne ratios in gas trapped very
near the metallic glass surface are up to 10% higher than predicted by
ion implantation simulations. We attribute this superficially trapped
gas to very low-speed, current-sheet-related solar wind, which has
been fractionated in the corona due to inefficient Coulomb drag.
Title: Nickel Isotopic Composition and Nickel/Iron Ratio in the
Solar Wind: Results from SOHO/CELIAS/MTOF
Authors: Karrer, R.; Bochsler, P.; Giammanco, C.; Ipavich, F. M.;
Paquette, J. A.; Wurz, P.
Bibcode: 2007coma.book..317K
Altcode:
Using the Mass Time-of-Flight Spectrometer (MTOF)—part of the
Charge, Elements, Isotope Analysis System (CELIAS)—onboard the
Solar Heliospheric Observatory (SOHO) spacecraft, we derive the
nickel isotopic composition for the isotopes with mass 58, 60 and
62 in the solar wind. In addition we measure the elemental abundance
ratio of nickel to iron. We use data accumulated during ten years of
SOHO operation to get sufficiently high counting statistics and compare
periods of different solar wind velocities. We compare our values with
the meteoritic ratios, which are believed to be a reliable reference
for the solar system and also for the solar outer convective zone,
since neither element is volatile and no isotopic fractionation is
expected in meteorites. Meteoritic isotopic abundances agree with
the terrestrial values and can thus be considered to be a reliable
reference for the solar isotopic composition. The measurements show
that the solar wind elemental Ni/Fe-ratio and the isotopic composition
of solar wind nickel are consistent with the meteoritic values. This
supports the concept that low-FIP elements are fed without relative
fractionation into the solar wind. Our result also confirms the absence
of substantial isotopic fractionation processes for medium and heavy
ions acting in the solar wind.
Title: Determination of Sulfur Abundance in the Solar Wind
Authors: Giammanco, C.; Bochsler, P.; Karrer, R.; Ipavich, F. M.;
Paquette, J. A.; Wurz, P.
Bibcode: 2007coma.book..329G
Altcode:
Solar chemical abundances are determined by comparing solar photospheric
spectra with synthetic ones obtained for different sets of abundances
and physical conditions. Although such inferred results are reliable,
they are model dependent. Therefore, one compares them with the values
for the local interstellar medium (LISM). The argument is that they
must be similar, but even for LISM abundance determinations models
play a fundamental role (i.e., temperature fluctuations, clumpiness,
photon leaks). There are still two possible comparisons—one with
the meteoritic values and the second with solar wind abundances. In
this work we derive a first estimation of the solar wind element
ratios of sulfur relative to calcium and magnesium, two neighboring
low-FIP elements, using 10 years of CELIAS/MTOF data. We compare
the sulfur abundance with the abundance determined from spectroscopic
observations and from solar energetic particles. Sulfur is a moderately
volatile element, hence, meteoritic sulfur may be depleted relative to
non-volatile elements, if compared to its original solar system value.
Title: Minor ions in the solar wind
Authors: Bochsler, Peter
Bibcode: 2007A&ARv..14....1B
Altcode: 2006A&ARv.tmp....2B
Ions heavier than 4He are treated as “minors” in the
solar wind. This is justified for many applications since minor ions
have no significant influence on the dynamics of the interplanetary
plasma. However, minor ions carry information on many aspects of the
formation, on the acceleration and on the transfer of solar plasma from
the corona into the interplanetary space. This review concentrates on
various aspects of minor ions as diagnostic tracers. The elemental
abundance patterns of the solar wind are shaped in the chromosphere
and in the lower transition region by processes, which are not fully
understood at this moment. Despite this lack of detailed understanding,
observed abundance patterns have been classified and are now commonly
used to characterize the sources, and to trace back solar-wind flows
to their origins in the solar atmosphere. Furthermore, the solar
wind is the most important source of information for solar isotopic
abundances and for solar abundances of volatile elements. In order
to fully exploit this information, a comprehensive understanding of
elemental and isotopic fractionation processes is required. We provide
observational clues to distinguish different processes at work.
Title: The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3)
for the Mars Express Mission
Authors: Barabash, S.; Lundin, R.; Andersson, H.; Brinkfeldt, K.;
Grigoriev, A.; Gunell, H.; Holmström, M.; Yamauchi, M.; Asamura,
K.; Bochsler, P.; Wurz, P.; Cerulli-Irelli, R.; Mura, A.; Milillo,
A.; Maggi, M.; Orsini, S.; Coates, A. J.; Linder, D. R.; Kataria,
D. O.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Frahm, R. A.;
Sharber, J. R.; Winningham, J. D.; Grande, M.; Kallio, E.; Koskinen,
H.; Riihelä, P.; Schmidt, W.; Säles, T.; Kozyra, J. U.; Krupp, N.;
Woch, J.; Livi, S.; Luhmann, J. G.; McKenna-Lawlor, S.; Roelof, E. C.;
Williams, D. J.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.
Bibcode: 2007tmpe.book..113B
Altcode:
The general scientific objective of the ASPERA-3 experiment is to
study the solar wind — atmosphere interaction and to characterize
the plasma and neutral gas environment within the space near Mars
through the use of energetic neutral atom (ENA) imaging and measuring
local ion and electron plasma. The ASPERA-3 instrument comprises
four sensors: two ENA sensors, one electron spectrometer, and one ion
spectrometer. The Neutral Particle Imager (NPI) provides measurements of
the integral ENA flux (0.1-60 keV) with no mass and energy resolution,
but high angular resolution. The measurement principle is based on
registering products (secondary ions, sputtered neutrals, reflected
neutrals) of the ENA interaction with a graphite-coated surface. The
Neutral Particle Detector (NPD) provides measurements of the ENA flux,
resolving velocity (the hydrogen energy range is 0.1-10 keV) and mass
(H and O) with a coarse angular resolution. The measurement principle
is based on the surface reflection technique. The Electron Spectrometer
(ELS) is a standard top-hat electrostatic analyzer in a very compact
design which covers the energy range 0.01-20 keV. These three sensors
are located on a scanning platform which provides scanning through
180° of rotation. The instrument also contains an ion mass analyzer
(IMA). Mechanically IMA is a separate unit connected by a cable to
the ASPERA-3 main unit. IMA provides ion measurements in the energy
range 0.01-36 keV/charge for the main ion components H+,
He++, He+, 0+, and the group of
molecular ions 20-80 amu/q. ASPERA-3 also was its own DC/DC converters
and digital processing unit (DPU).
Title: Velocity Distributions, Charge States and Abundances of
Inner Source Pickup Ions as Obtained from the Solar Wind Charge
Exchange Model
Authors: Bochsler, P.; Moebius, E.; Wimmer-Schweingruber, R. F.
Bibcode: 2006AGUFMSH44A..04B
Altcode:
Generally the origin of inner-source pickup ions is attributed to
the interaction of solar wind ions with dust particles in the inner
heliosphere. We have further developed the charge-exchange model
of Wimmer- Schweingruber and Bochsler (2003) and quantified some
results using the constraints provided by observations of dust size
distributions, dust density distributions, and fluxes and abundances
of pickup ions. Specifically, we have investigated the production of
sputtered particles from small grains and find, that they could easily
supply the observed amount of inner-source pickup ions. However, the
apparent overabundance of neon among inner source pickup ions continues
to pose an enigma, which could possibly be solved by constraining the
production process to the outskirts of the solar corona.
Title: Solar Wind Neon from Genesis: Implications for the Lunar
Noble Gas Record
Authors: Grimberg, Ansgar; Baur, Heinrich; Bochsler, Peter; Bühler,
Fritz; Burnett, Donald S.; Hays, Charles C.; Heber, Veronika S.;
Jurewicz, Amy J. G.; Wieler, Rainer
Bibcode: 2006Sci...314.1133G
Altcode:
Lunar soils have been thought to contain two solar noble gas components
with distinct isotopic composition. One has been identified as implanted
solar wind, the other as higher-energy solar particles. The latter was
puzzling because its relative amounts were much too large compared with
present-day fluxes, suggesting periodic, very high solar activity in
the past. Here we show that the depth-dependent isotopic composition of
neon in a metallic glass exposed on NASA’s Genesis mission agrees with
the expected depth profile for solar wind neon with uniform isotopic
composition. Our results strongly indicate that no extra high-energy
component is required and that the solar neon isotope composition of
lunar samples can be explained as implantation-fractionated solar wind.
Title: The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3)
for the Mars Express Mission
Authors: Barabash, S.; Lundin, R.; Andersson, H.; Brinkfeldt, K.;
Grigoriev, A.; Gunell, H.; Holmström, M.; Yamauchi, M.; Asamura,
K.; Bochsler, P.; Wurz, P.; Cerulli-Irelli, R.; Mura, A.; Milillo,
A.; Maggi, M.; Orsini, S.; Coates, A. J.; Linder, D. R.; Kataria,
D. O.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Frahm, R. A.;
Sharber, J. R.; Winningham, J. D.; Grande, M.; Kallio, E.; Koskinen,
H.; Riihelä, P.; Schmidt, W.; Säles, T.; Kozyra, J. U.; Krupp, N.;
Woch, J.; Livi, S.; Luhmann, J. G.; McKenna-Lawlor, S.; Roelof, E. C.;
Williams, D. J.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.
Bibcode: 2006SSRv..126..113B
Altcode: 2007SSRv..tmp...64B
The general scientific objective of the ASPERA-3 experiment is to
study the solar wind - atmosphere interaction and to characterize the
plasma and neutral gas environment with within the space near Mars
through the use of energetic neutral atom (ENA) imaging and measuring
local ion and electron plasma. The ASPERA-3 instrument comprises
four sensors: two ENA sensors, one electron spectrometer, and one ion
spectrometer. The Neutral Particle Imager (NPI) provides measurements of
the integral ENA flux (0.1-60 keV) with no mass and energy resolution,
but high angular resolution. The measurement principle is based on
registering products (secondary ions, sputtered neutrals, reflected
neutrals) of the ENA interaction with a graphite-coated surface. The
Neutral Particle Detector (NPD) provides measurements of the ENA flux,
resolving velocity (the hydrogen energy range is 0.1-10 keV) and mass
(H and O) with a coarse angular resolution. The measurement principle
is based on the surface reflection technique. The Electron Spectrometer
(ELS) is a standard top-hat electrostatic analyzer in a very compact
design which covers the energy range 0.01-20 keV. These three sensors
are located on a scanning platform which provides scanning through
180∘ of rotation. The instrument also contains an ion
mass analyzer (IMA). Mechanically IMA is a separate unit connected
by a cable to the ASPERA-3 main unit. IMA provides ion measurements
in the energy range 0.01-36 keV/charge for the main ion components
H+, He++, He+, O+, and
the group of molecular ions 20-80 amu/q. ASPERA-3 also includes its
own DC/DC converters and digital processing unit (DPU).
Title: The interstellar boundary explorer (IBEX): Update at the end
of phase B
Authors: McComas, D. J.; Allegrini, F.; Bartolone, L.; Bochsler,
P.; Bzowski, M.; Collier, M.; Fahr, H.; Fichtner, H.; Frisch, P.;
Funsten, H.; Fuselier, Steve; Gloeckler, G.; Gruntman, M.; Izmodenov,
V.; Knappenberger, P.; Lee, M.; Livi, S.; Mitchell, D.; Möbius, E.;
Moore, T.; Pope, S.; Reisenfeld, D.; Roelof, E.; Runge, H.; Scherrer,
J.; Schwadron, N.; Tyler, R.; Wieser, M.; Witte, M.; Wurz, P.; Zank, G.
Bibcode: 2006AIPC..858..241M
Altcode:
The Interstellar Boundary Explorer (IBEX) mission will make the
first global observations of the heliosphere's interaction with the
interstellar medium. IBEX achieves these breakthrough observations by
traveling outside of the Earth's magnetosphere in a highly elliptical
orbit and taking global Energetic Neutral Atoms (ENA) images over
energies from ~10 eV to 6 keV. IBEX's high-apogee (~50 RE) orbit enables
heliospheric ENA measurements by providing viewing from far above
the Earth's relatively bright magnetospheric ENA emissions. This high
energy orbit is achieved from a Pegasus XL launch vehicle by adding the
propulsion from an IBEX-supplied solid rocket motor and the spacecraft's
hydrazine propulsion system. IBEX carries two very large-aperture,
single-pixel ENA cameras that view perpendicular to the spacecraft's
Sun-pointed spin axis. Each six months, the continuous spinning of
the spacecraft and periodic re-pointing to maintain the sun-pointing
spin axis naturally lead to global, all-sky images. Over the course of
our NASA Phase B program, the IBEX team optimized the designs of all
subsystems. In this paper we summarize several significant advances
in both IBEX sensors, our expected signal to noise (and background),
and our groundbreaking approach to achieve a very high-altitude orbit
from a Pegasus launch vehicle for the first time. IBEX is in full
scale development and on track for launch in June of 2008.
Title: Depth-dependant Fractionation of Light Solar Wind Noble Gases
in a Genesis Target
Authors: Grimberg, A.; Bühler, F.; Bochsler, P.; Burnett, D. S.;
Baur, H.; Wieler, R.
Bibcode: 2006M&PSA..41.5187G
Altcode:
No abstract at ADS
Title: Solar Neon Abundance Inferred from Apollo Foil Experiments
Authors: Bochsler, P.
Bibcode: 2006M&PSA..41.5043B
Altcode:
No abstract at ADS
Title: Helium/Hydrogen Fractionation in the Solar Wind-How Much is
Due to Inefficient Coulomb Drag?
Authors: Bochsler, P.; Auchère, F.; Skoug, R. M.
Bibcode: 2006ESASP.617E..28B
Altcode: 2006soho...17E..28B
No abstract at ADS
Title: Observations of Solar Wind Ni and Fe
Authors: Ipavich, F.; Bochsler, P.; Paquette, J.; Lasley, S.
Bibcode: 2006ESASP.617E..18I
Altcode: 2006soho...17E..18I
No abstract at ADS
Title: First ENA observations at Mars: Subsolar ENA jet
Authors: Futaana, Y.; Barabash, S.; Grigoriev, A.; Holmström, M.;
Kallio, E.; Brandt, P. C. :son; Gunell, H.; Brinkfeldt, K.; Lundin,
R.; Andersson, H.; Yamauchi, M.; McKenna-Lawler, S.; Winningham,
J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.; Coates, A. J.;
Linder, D. R.; Kataria, D. O.; Säles, T.; Riihelä, P.; Schmidt,
W.; Koskinen, H.; Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.;
Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.;
Carter, M.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.; Orsini,
S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp,
N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..413F
Altcode:
The Neutral Particle Detector (NPD), an Energetic Neutral Atom (ENA)
sensor of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3)
on board Mars Express, detected intense fluxes of ENAs emitted from
the subsolar region of Mars. The typical ENA fluxes are (4-7) × 10
5 cm -2 sr -1 s -1 in the
energy range 0.3-3 keV. These ENAs are likely to be generated in the
subsolar region of the martian exosphere. As the satellite moved away
from Mars, the ENA flux decreased while the field of view of the NPD
pointed toward the subsolar region. These decreases occurred very
quickly with a time scale of a few tens of seconds in two thirds
of the orbits. Such a behavior can be explained by the spacecraft
crossing a spatially constrained ENA jet, i.e., a highly directional
ENA emission from a compact region of the subsolar exosphere. This
ENA jet is highly possible to be emitted conically from the subsolar
region. Such directional ENAs can result from the anisotropic solar
wind flow around the subsolar region, but this can not be explained
in the frame of MHD models.
Title: Electric fields within the martian magnetosphere and ion
extraction: ASPERA-3 observations
Authors: Dubinin, E.; Lundin, R.; Fränz, M.; Woch, J.; Barabash, S.;
Fedorov, A.; Winningham, D.; Krupp, N.; Sauvaud, J. -A.; Holmström,
M.; Andersson, H.; Yamauchi, M.; Grigoriev, A.; Thocaven, J. -J.;
Frahm, R.; Sharber, J.; Asamura, K.; Coates, A.; Curtis, C.;
Hsieh, K. S.; Sandel, B.; Koskinen, H.; Kallio, E.; Riihelä, P.;
Schmidt, W.; Säles, T.; Kozyra, J.; Luhmann, J.; McKenna-Lawler, S.;
Cerulli-Irelli, R.; Orsini, S.; Maggi, M.; Roelof, E.; Williams, D.;
Livi, S.; Wurz, P.; Bochsler, P.; Dierker, C.; Grande, M.; Carter, M.
Bibcode: 2006Icar..182..337D
Altcode:
Observations made by the ASPERA-3 experiment onboard the Mars Express
spacecraft found within the martian magnetosphere beams of planetary
ions. In the energy ( E/q)-time spectrograms these beams are often
displayed as dispersive-like, ascending or descending (whether the
spacecraft moves away or approach the planet) structures. A linear
dependence between energy gained by the beam ions and the altitude from
the planet suggests their acceleration in the electric field. The values
of the electric field evaluated from ion energization occur close to
the typical values of the interplanetary motional electric field. This
suggests an effective penetration of the solar wind electric field deep
into the martian magnetosphere or generation of large fields within
the magnetosphere. Two different classes of events are found. At
the nominal solar wind conditions, a 'penetration' occurs near the
terminator. At the extreme solar wind conditions, the boundary of
the induced magnetosphere moves to a more dense upper atmosphere that
leads to a strong scavenging of planetary ions from the dayside regions.
Title: First ENA observations at Mars: Solar-wind ENAs on the
nightside
Authors: Brinkfeldt, K.; Gunell, H.; Brandt, P. C. :son; Barabash, S.;
Frahm, R. A.; Winningham, J. D.; Kallio, E.; Holmström, M.; Futaana,
Y.; Ekenbäck, A.; Lundin, R.; Andersson, H.; Yamauchi, M.; Grigoriev,
A.; Sharber, J. R.; Scherrer, J. R.; Coates, A. J.; Linder, D. R.;
Kataria, D. O.; Koskinen, H.; Säles, T.; Riihelä, P.; Schmidt, W.;
Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.; Livi, S.; Curtis,
C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; Sauvaud,
J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler, S.; Orsini,
S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp,
N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..439B
Altcode:
We present measurements with an Energetic Neutral Atom (ENA) imager on
board Mars Express when the spacecraft moves into Mars eclipse. Solar
wind ions charge exchange with the extended Mars exosphere to produce
ENAs that can spread into the eclipse of Mars due to the ions'
thermal spread. Our measurements show a lingering signal from the
Sun direction for several minutes as the spacecraft moves into the
eclipse. However, our ENA imager is also sensitive to UV photons and we
compare the measurements to ENA simulations and a simplified model of UV
scattering in the exosphere. Simulations and further comparisons with
an electron spectrometer sensitive to photoelectrons generated when UV
photons interact with the spacecraft suggest that what we are seeing
in Mars' eclipse are ENAs from upstream of the bow shock produced in
charge exchange with solar wind ions with a non-zero temperature. The
measurements are a precursor to a new technique called ENA sounding
to measure solar wind and planetary exosphere properties in the future.
Title: Carbon dioxide photoelectron energy peaks at Mars
Authors: Frahm, R. A.; Winningham, J. D.; Sharber, J. R.; Scherrer,
J. R.; Jeffers, S. J.; Coates, A. J.; Linder, D. R.; Kataria, D. O.;
Lundin, R.; Barabash, S.; Holmström, M.; Andersson, H.; Yamauchi,
M.; Grigoriev, A.; Kallio, E.; Säles, T.; Riihelä, P.; Schmidt, W.;
Koskinen, H.; Kozyra, J. U.; Luhmann, J. G.; Roelof, E. C.; Williams,
D. J.; Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande,
M.; Carter, M.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.;
McKenna-Lawler, S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz,
P.; Bochsler, P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.;
Dierker, C.
Bibcode: 2006Icar..182..371F
Altcode:
The ELectron Spectrometer (ELS) from the Analyzer of Space Plasmas and
Energetic Atoms (ASPERA-3) flown on the Mars Express spacecraft has
an 8% energy resolution, combined with the capability to oversample
the martian electron distribution. This makes possible the resolution
and identification of electrons generated as a result of the He 304
Å ionization of CO 2 at the martian exobase on the dayside
of the planet. Ionospheric photoelectrons were observed during almost
every pass into the ionosphere and CO 2 photoelectron peaks
were identified near the terminator. Atmospherically generated CO
2 photoelectrons are also observed at 10,000 km altitude in
the martian tail near the inner magnetospheric boundary. Observations
over a wide range of spacecraft orbits showed a consistent presence
of photoelectrons at locations along the inner magnetospheric boundary
and in the ionosphere, from an altitude of 250 to 10,000 km.
Title: Mass composition of the escaping plasma at Mars
Authors: Carlsson, E.; Fedorov, A.; Barabash, S.; Budnik, E.;
Grigoriev, A.; Gunell, H.; Nilsson, H.; Sauvaud, J. -A.; Lundin, R.;
Futaana, Y.; Holmström, M.; Andersson, H.; Yamauchi, M.; Winningham,
J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J.; Coates, A. J.;
Linder, D. R.; Kataria, D. O.; Kallio, E.; Koskinen, H.; Säles,
T.; Riihelä, P.; Schmidt, W.; Kozyra, J.; Luhmann, J.; Roelof, E.;
Williams, D.; Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.;
Grande, M.; Carter, M.; Thocaven, J. -J.; McKenna-Lawler, S.; Orsini,
S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp,
N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..320C
Altcode:
Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3
instrument suite on Mars Express have been analyzed to determine
the mass composition of the escaping ion species at Mars. We have
examined 77 different ion-beam events and we present the results
in terms of flux ratios between the following ion species: CO
+2/O + and O +2/O
+. The following ratios averaged over all events and energies
were identified: CO +2/O + = 0.2 and O
+2/O + = 0.9. The values measured are
significantly higher, by a factor of 10 for O +2/O
+, than a contemporary modeled ratio for the maximum fluxes
which the martian ionosphere can supply. The most abundant ion species
was found to be O +, followed by O +2
and CO +2. We estimate the loss of CO
+2 to be 4.0×10s(0.29 kgs) by using the previous
measurements of Phobos-2 in our calculations. The dependence of the
ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV,
indicated that no clear correlation was found.
Title: Structure of the martian wake
Authors: Fedorov, A.; Budnik, E.; Sauvaud, J. -A.; Mazelle, C.;
Barabash, S.; Lundin, R.; Acuña, M.; Holmström, M.; Grigoriev,
A.; Yamauchi, M.; Andersson, H.; Thocaven, J. -J.; Winningham, D.;
Frahm, R.; Sharber, J. R.; Scherrer, J.; Coates, A. J.; Linder, D. R.;
Kataria, D. O.; Kallio, E.; Koskinen, H.; Säles, T.; Riihelä, P.;
Schmidt, W.; Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.; Livi,
S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter,
M.; McKenna-Lawler, S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.;
Wurz, P.; Bochsler, P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura,
K.; Dierker, C.
Bibcode: 2006Icar..182..329F
Altcode:
We present the first results from the ion mass analyzer IMA of the
ASPERA-3 instrument on-board of Mars Express. More than 200 orbits
for May 2004-September 2004 time interval have been selected for the
statistical study of the distribution of the atmospheric origin ions
in the planetary wake. This study shows that the martian magnetotail
consists of two different ion regimes. Planetary origin ions of
the first regime form the layer adjacent to the magnetic pile-up
boundary. These ions are accelerated to energy greater than 2000 eV and
exhibit a gradual decreasing of energy down to the planetary tail. The
second plasma regime is observed in the planetary shadow. The heavy
ions (considered as planetary ones) are accelerated to the energy
of the solar wind protons. Obviously the acceleration mechanism
is different for the different plasma regimes. Study of two plasma
regimes in the frame referred to the interplanetary magnetic field (IMF)
direction (we used MGS magnetometer data to obtain the IMF clock angle)
clearly shows their spatial anisotropy. The monoenergetic plasma in
the planetary shadow is observed only in the narrow angular sector
around the positive direction of the interplanetary electric field.
Title: Electron oscillations in the induced martian magnetosphere
Authors: Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Coates,
A. J.; Linder, D. R.; Soobiah, Y.; Kallio, E.; Espley, J. R.;
Lundin, R.; Barabash, S.; Holmström, M.; Andersson, H.; Yamauchi,
M.; Grigoriev, A.; Scherrer, J. R.; Jeffers, S. J.; Kataria, D. O.;
Kozyra, J. U.; Luhmann, J. G.; Roelof, E. C.; Williams, D. J.;
Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Koskinen,
H.; Säles, T.; Riihelä, P.; Schmidt, W.; Grande, M.; Carter, M.;
Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler, S.;
Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.;
Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..360W
Altcode:
The Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment
flown on the Mars Express (MEX) spacecraft includes the Electron
Spectrometer (ELS) as part of its complement. The ELS instrument
measures the differential electron flux spectrum in a 128-level
logarithmic energy sweep within a time period of 4 s. The orbital path
of MEX traverses the martian sheath, cusps, and tail where ELS recorded
periodic electron intensity oscillations. These oscillations comprised
periodic variations of up to an order of magnitude (peak to valley)
in energy flux, with the largest amplitudes in the tens to hundreds
of eV range. The observed oscillations displayed periods ranging from
minutes down to the instrument sweep resolution of 4 s. In the cases
analyzed here, the frequency of the integrated electron energy flux
typically peaked between 0.01 and 0.02 Hz. This frequency range is
nearly the same as the typical O + gyrofrequency in the
magnetosheath, calculated using magnetometer data from Mars Global
Surveyor. Due to the motion of the spacecraft, it is unclear if the
wave structures observed were permanent standing waves or rather
constituted waves propagating past the spacecraft.
Title: Ion escape at Mars: Comparison of a 3-D hybrid simulation
with Mars Express IMA/ASPERA-3 measurements
Authors: Kallio, E.; Fedorov, A.; Budnik, E.; Säles, T.; Janhunen,
P.; Schmidt, W.; Koskinen, H.; Riihelä, P.; Barabash, S.; Lundin, R.;
Holmström, M.; Gunell, H.; Brinkfeldt, K.; Futaana, Y.; Andersson,
H.; Yamauchi, M.; Grigoriev, A.; Sauvaud, J. -A.; Thocaven, J. -J.;
Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.;
Coates, A. J.; Linder, D. R.; Kataria, D. O.; Kozyra, J.; Luhmann,
J. G.; Roelof, E.; Williams, D.; Livi, S.; Curtis, C. C.; Hsieh,
K. C.; Sandel, B. R.; Grande, M.; Carter, M.; McKenna-Lawler, S.;
Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.;
Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..350K
Altcode:
We have analysed ion escape at Mars by comparing ASPERA-3/Mars Express
ion measurements and a 3-D quasi-neutral hybrid model. As Mars Express
does not have a magnetometer onboard, the analysed IMA data are from
an orbit when the IMF clock angle was possible to determine from
the magnetic field measurements of Mars Global Surveyor. We found
that fast escaping planetary ions were observed at the place which,
according to the 3-D model, is anticipated to contain accelerated
heavy ions originating from the martian ionosphere. The direction
of the interplanetary magnetic field was found to affect noticeably
which regions can be magnetically connected to Mars Express and to
the overall 3-D Mars-solar wind interaction.
Title: Direct Measurements of Energetic Neutral Hydrogen in the
Interplanetary Medium
Authors: Galli, A.; Wurz, P.; Barabash, S.; Grigoriev, A.; Lundin,
R.; Futaana, Y.; Gunell, H.; Holmström, M.; Roelof, E. C.; Curtis,
C. C.; Hsieh, K. C.; Fedorov, A.; Winningham, D.; Frahm, R. A.;
Cerulli-Irelli, R.; Bochsler, P.; Krupp, N.; Woch, J.; Fraenz, M.
Bibcode: 2006ApJ...644.1317G
Altcode:
We present an analysis of hydrogen energetic neutral atoms (ENAs)
measured by the ASPERA-3 instrument on board Mars Express. We focus
on ENAs that have no Martian origin. The energy spectra of these
ENAs are all very similar and can be fitted well by a two-component
power law. The fluxes, integrated from 0.2 to 10 keV, vary between
5×103 and 105 cm-2 sr-1
s-1. We checked for possible sources for these ENAs, but we
can rule out a planetary origin, a solar wind origin, contamination by
UV from UV bright stars, and contamination by high-energy protons. With
our present knowledge we conclude that the heliospheric termination
shock is the most plausible source region.
Title: First ENA observations at Mars: Charge exchange ENAs produced
in the magnetosheath
Authors: Gunell, H.; Brinkfeldt, K.; Holmström, M.; Brandt,
P. C. :son; Barabash, S.; Kallio, E.; Ekenbäck, A.; Futaana, Y.;
Lundin, R.; Andersson, H.; Yamauchi, M.; Grigoriev, A.; Winningham,
J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.; Coates, A. J.;
Linder, D. R.; Kataria, D. O.; Säles, T.; Riihelä, P.; Schmidt, W.;
Koskinen, H.; Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.; Livi,
S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter,
M.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler,
S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler,
P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..431G
Altcode:
Measurements of energetic neutral atoms (ENA) generated in the
magnetosheath at Mars are reported. These ENAs are the result of charge
exchange collisions between solar wind protons and neutral oxygen
and hydrogen in the exosphere of Mars. The peak of the observed ENA
flux is 1.3×10 msrs. For the case studied here, i.e., the passage of
Mars Express through the martian magnetosheath around 20:15 UT on 3
May 2004, the measurements agree with an analytical model of the ENA
production at the planet. It is possible to find parameter values in
the model such that the observed peak in the ENA count rate during
the spacecraft passage through the magnetosheath is reproduced.
Title: Energetic Neutral Atoms (ENA) at Mars: Properties of the
hydrogen atoms produced upstream of the martian bow shock and
implications for ENA sounding technique around non-magnetized planets
Authors: Kallio, E.; Barabash, S.; Brinkfeldt, K.; Gunell, H.;
Holmström, M.; Futaana, Y.; Schmidt, W.; Säles, T.; Koskinen, H.;
Riihelä, P.; Lundin, R.; Andersson, H.; Yamauchi, M.; Grigoriev, A.;
Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.;
Coates, A. J.; Linder, D. R.; Kataria, D. O.; Kozyra, J.; Luhmann,
J. G.; Roelof, E.; Williams, D.; Livi, S.; Brandt, P. C. :son; Curtis,
C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; Sauvaud,
J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler, S.; Orsini,
S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp,
N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..448K
Altcode:
We have studied the interaction of fast solar wind hydrogen atoms
with the martian atmosphere by a three-dimensional Monte Carlo
simulation. These energetic neutral hydrogen atoms, H-ENAs, are
formed upstream of the martian bow shock. Both H-ENAs scattered and
non-scattered from the martian atmosphere/exosphere were studied. The
colliding H-ENAs were found to scatter both to the dayside and
nightside. On the dayside they contribute to the so-called H-ENA
albedo. On the nightside the heated and scattered hydrogen atoms
were found also in the martian wake. The density, the energy
distribution function and the direction of the velocity of H-ENAs
on the nightside are presented. The present study describes a novel
"ENA sounding" technique in which energetic neutral atoms are used
to derive information of the properties of planetary exosphere and
atmosphere in a similar manner as the solar wind photons are used to
derive atmospheric densities by measuring the scattered UV light. A
detailed study of the direction and energy of the scattered and
non-scattered H-ENAs suggest that the ENA sounding is a method to
study the interaction between the planetary atmosphere and the solar
wind and to monitor the density, and likely also the magnetization,
of the planetary upper atmosphere. Already present-day ENA instrument
should be capable to detect the analyzed particle fluxes.
Title: Observations of magnetic anomaly signatures in Mars Express
ASPERA-3 ELS data
Authors: Soobiah, Y.; Coates, A. J.; Linder, D. R.; Kataria, D. O.;
Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.;
Barabash, S.; Lundin, R.; Holmström, M.; Andersson, H.; Yamauchi,
M.; Grigoriev, A.; Kallio, E.; Koskinen, H.; Säles, T.; Riihelä, P.;
Schmidt, W.; Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.; Livi,
S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter,
M.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler,
S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler,
P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..396S
Altcode:
Mars Express (MEX) Analyser of Space Plasmas and Energetic Atoms
(ASPERA-3) data is providing insights into atmospheric loss on Mars
via the solar wind interaction. This process is influenced by both
the interplanetary magnetic field (IMF) in the solar wind and by
the magnetic 'anomaly' regions of the martian crust. We analyse
observations from the ASPERA-3 Electron Spectrometer near to such
crustal anomalies. We find that the electrons near remanent magnetic
fields either increase in flux to form intensified signatures or
significantly reduce in flux to form plasma voids. We suggest that
cusps intervening neighbouring magnetic anomalies may provide a location
for enhanced escape of planetary plasma. Initial statistical analysis
shows that intensified signatures are mainly a dayside phenomenon
whereas voids are a feature of the night hemisphere.
Title: First ENA observations at Mars: ENA emissions from the martian
upper atmosphere
Authors: Futaana, Y.; Barabash, S.; Grigoriev, A.; Holmström, M.;
Kallio, E.; Brandt, P. C. :son; Gunell, H.; Brinkfeldt, K.; Lundin,
R.; Andersson, H.; Yamauchi, M.; McKenna-Lawler, S.; Winningham,
J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.; Coates, A. J.;
Linder, D. R.; Kataria, D. O.; Säles, T.; Riihelä, P.; Schmidt,
W.; Koskinen, H.; Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.;
Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.;
Carter, M.; Sauvaud, J. -A.; Fedorov, A.; Thocaven, J. -J.; Orsini,
S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Galli,
A.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..424F
Altcode:
The neutral particle detector (NPD) on board Mars Express has observed
energetic neutral atoms (ENAs) from a broad region on the dayside
of the martian upper atmosphere. We show one such example for which
the observation was conducted at an altitude of 570 km, just above
the induced magnetosphere boundary (IMB). The time of flight spectra
of these ENAs show that they had energies of 0.2-2 keV/amu, with an
average energy of ∼1.1 keV/amu. Both the spatial distribution and
the energy of these ENAs are consistent with the backscattered ENAs,
produced by an ENA albedo process. This is the first observation of
backscattered ENAs from the martian upper atmosphere. The origin of
these ENAs is considered to be the solar wind ENAs that are scattered
back by collision processes in the martian upper atmosphere. The
particle flux and energy flux of the backscattered ENAs are 0.9-1.3×10
cms and ∼9.5×10 eVcms, respectively.
Title: Plasma intrusion above Mars crustal fields—Mars Express
ASPERA-3 observations
Authors: Fränz, M.; Winningham, J. D.; Dubinin, E.; Roussos, E.;
Woch, J.; Barabash, S.; Lundin, R.; Holmström, M.; Andersson, H.;
Yamauchi, M.; Grigoriev, A.; Frahm, R. A.; Sharber, J. R.; Scherrer,
J. R.; Coates, A. J.; Soobiah, Y.; Linder, D. R.; Kataria, D. O.;
Kallio, E.; Säles, T.; Riihelä, P.; Schmidt, W.; Koskinen, H. E. J.;
Kozyra, J.; Luhmann, J.; Roelof, E.; Williams, D.; Livi, S.; Curtis,
C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; Sauvaud,
J. -A.; Fedorov, A.; Thocaven, J. -J.; McKenna-Lawler, S.; Orsini,
S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp,
N.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..406F
Altcode:
Using data of the ASPERA-3 instrument on board the European Mars Express
spacecraft we investigate the effect of the martian crustal fields
on electrons intruding from the magnetosheath. For the crustal field
strength we use published data obtained by the Mars Global Surveyor
MAG/ER instrument for a fixed altitude of 400 km. We use statistics
on 13 months of 80-100 eV electron observations to show that the
electron intrusion altitude determined by a probability measure is
approximately linearly dependent on the total field strength at 400
km altitude. We show that on the dayside the mean electron intrusion
altitude describes the location of the Magnetic Pile-Up Boundary
(MPB) such that we can quantify the effect of the crustal fields on
the MPB. On the nightside we quantify the shielding of precipitating
electrons by the crustal fields.
Title: Solar wind plasma protrusion into the martian magnetosphere:
ASPERA-3 observations
Authors: Dubinin, E.; Winningham, D.; Fränz, M.; Woch, J.; Lundin,
R.; Barabash, S.; Fedorov, A.; Frahm, R.; Sharber, J. R.; Coates,
A. J.; Krupp, N.; Sauvaud, J. -A.; Holmström, M.; Andersson, H.;
Yamauchi, M.; Grigoriev, A.; Thocaven, J. -J.; Asamura, K.; Curtis,
C.; Hsieh, K. S.; Sandel, B.; Koskinen, H.; Kallio, E.; Riihelä, P.;
Schmidt, W.; Säles, T.; Kozyra, J.; Luhmann, J.; McKenna-Lawler, S.;
Cerulli-Irelli, R.; Orsini, S.; Maggi, M.; Roelof, E.; Williams, D.;
Livi, S.; Wurz, P.; Bochsler, P.; Dierker, C.; Grande, M.; Carter, M.
Bibcode: 2006Icar..182..343D
Altcode:
The ASPERA-3 experiment onboard the Mars Express spacecraft revealed,
near the wake boundary of Mars, a spatially narrow, strip-like plasma
structure composed of magnetosheath-like electrons and planetary
ions. The peak electron energy often exceeds the peak energy at the
bow shock that indicates a significant heating (acceleration) during
the structure formation. It is shown that this structure is formed
during efficient plasma penetration into the martian magnetosphere in
the region near the terminator. The penetration of sheath electrons
and their gradual heating (acceleration) is accompanied by a change
of the ion composition from a solar wind plasma to a planetary plasma
dominated by oxygen ions. A possible mechanism of plasma inflow to
the magnetosphere is discussed.
Title: Ionospheric plasma acceleration at Mars: ASPERA-3 results
Authors: Lundin, R.; Winningham, D.; Barabash, S.; Frahm, R. A.;
Andersson, H.; Holmström, M.; Grigoriev, A.; Yamauchi, M.; Borg, H.;
Sharber, J. R.; Sauvaud, J. -A.; Fedorov, A.; Budnik, E.; Thocaven,
J. -J.; Asamura, K.; Hayakawa, H.; Coates, A. J.; Linder, D. R.;
Kataria, D. O.; Curtis, C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.;
Carter, M.; Reading, D. H.; Koskinen, H.; Kallio, E.; Riihelä, P.;
Schmidt, W.; Säles, T.; Kozyra, J.; Krupp, N.; Woch, J.; Fränz,
M.; Luhmann, J.; McKenna-Lawler, S.; Cerulli-Irelli, R.; Orsini, S.;
Maggi, M.; Roelof, E.; Williams, D.; Livi, S.; Brandt, P. C. :son;
Wurz, P.; Bochsler, P.
Bibcode: 2006Icar..182..308L
Altcode:
The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on-board the
Mars Express spacecraft (MEX) measured penetrating solar wind plasma
and escaping/accelerated ionospheric plasma at very low altitudes (250
km) in the dayside subsolar region. This implies a direct exposure of
the martian topside atmosphere to solar wind plasma forcing leading to
energization of ionospheric plasma. The ion and electron energization
and the ion outflow from Mars is surprisingly similar to that over the
magnetized Earth. Narrow "monoenergetic" cold ion beams, ion beams with
broad energy distributions, sharply peaked electron energy spectra,
and bidirectional streaming electrons are particle features also
observed near Mars. Energized martian ionospheric ions (O +,
O +2, CO +2, etc.) flow
in essentially the same direction as the external sheath flow. This
suggests that the planetary ion energization couples directly to
processes in the magnetosheath/solar wind. On the other hand, the
beam-like distribution of the energized plasma implies more indirect
energization processes like those near the Earth, i.e., energization
in a magnetized environment by waves and/or parallel (to B) electric
fields. The general conditions for martian plasma energization are,
however, different from those in the Earth's magnetosphere. Mars has
a weak intrinsic magnetic field and solar wind plasma may therefore
penetrate deep into the dense ionospheric plasma. Local crustal
magnetization, discovered by Acuña et al. [Acuña, M.J., Connerey, J.,
Ness, N., Lin, R., Mitchell, D., Carlsson, C., McFadden, J., Anderson,
K., Rème, H., Mazelle, C., Vignes, D., Wasilewski, P., Cloutier, P.,
1999. Science 284, 790-793], provide some dayside shielding against the
solar wind. On the other hand, multiple magnetic anomalies may also
lead to "hot spots" facilitating ionospheric plasma energization. We
discuss the ASPERA-3 findings of martian ionospheric ion energization
and present evidences for two types of plasma energization processes
responsible for the low- and mid-altitude plasma energization near
Mars: magnetic field-aligned acceleration by parallel electric fields
and plasma energization by low frequency waves.
Title: Numerical interpretation of high-altitude photoelectron
observations
Authors: Liemohn, Michael W.; Frahm, R. A.; Winningham, J. D.; Ma,
Y.; Barabash, S.; Lundin, R.; Kozyra, J. U.; Nagy, A. F.; Bougher,
S. M.; Bell, J.; Brain, D.; Mitchell, D.; Luhmann, J.; Holmström,
M.; Andersson, H.; Yamauchi, M.; Grigoriev, A.; McKenna-Lawler,
S.; Sharber, J. R.; Scherrer, J. R.; Jeffers, S. J.; Coates, A. J.;
Linder, D. R.; Kataria, D. O.; Kallio, E.; Koskinen, H.; Säles, T.;
Riihelä, P.; Schmidt, W.; Roelof, E.; Williams, D.; Livi, S.; Curtis,
C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; Sauvaud,
J. -A.; Fedorov, A.; Thocaven, J. -J.; Orsini, S.; Cerulli-Irelli,
R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp, N.; Woch, J.; Fränz,
M.; Asamura, K.; Dierker, C.
Bibcode: 2006Icar..182..383L
Altcode:
The Electron Spectrometer (ELS) instrument of the ASPERA-3 package on
the Mars Express satellite has recorded photoelectron energy spectra up
to apoapsis ( ∼10,000 km altitude). The characteristic photoelectron
shape of the spectrum is sometimes seen well above the ionosphere in the
evening sector across a wide range of near-equatorial latitudes. Two
numerical models are used to analyze the characteristics of these
high-altitude photoelectrons. The first is a global, multi-species
MHD code that produces a 3-D representation of the magnetic field and
bulk plasma parameters around Mars. It is used here to examine the
possibility of magnetic connectivity between the high-altitude flanks
of the martian ionosheath and the subsolar ionosphere. It is shown that
some field lines in this region are draped interplanetary magnetic
lines while others are open field lines (connected to both the IMF
and the crustal magnetic field sources). The second model is a kinetic
electron transport model that calculates the electron velocity space
distribution along a selected, non-uniform, magnetic field line. It
is used here to simulate the high-altitude ELS measurements. It is
shown that the photoelectrons are essentially confined to the source
cone, as governed by magnetic field inhomogeneity along the field
line. Reasonable agreement is shown between the data and the model
results, and a method is demonstrated for inferring properties of
the local and photoelectron source region magnetic field from the
ELS measurements. Specifically, the number of sectors in which
photoelectrons are measured is a function of the magnetic field
intensity ratio and the field's angle with respect to the detector
plane. In addition, the sector of the photoelectron flux peak is a
function of the magnetic field azimuthal angle in the detector plane.
Title: On the Acceleration of Helium in the Heliosphere
Authors: Kucharek, H.; Moebius, E.; Allegrini, F.; Desai, M.; Smith,
C.; Klecker, B.; Farrugia, C.; Popecki, M.; Galvin, A.; Bochsler, P.
Bibcode: 2006AGUSMSH33B..06K
Altcode:
ACE/SEPICA and SOHO/CELIAS/STOF observations have revealed the
surprising result that on average energetic He+ is after H+ and
He2+ the third most abundant energetic particle population in the
heliosphere. Depending on the type of the source population the
energetic He+/He2+ ratio in the energetic particle population can
reach unusually high values; in the energy range of 250keV/n -
800keV/n ratios close to unity. Interplanetary pickup ions have
been identified to be the major source of the energetic He+ that
are preferentially accelerated at co-rotating interaction regions
(CIRs), transient interaction regions (TIRs), and interplanetary
traveling shocks. Furthermore, the ACE/ULEIS, ACE/SEPICA, and
Wind/STICS measurements showed that 3He and He+ ions are accelerated
at CME-driven IP shocks. More recently, enhanced He+/He2+ ratios have
been observed in association with current sheet crossings, flows, and
enhanced magnetic turbulence. The abundance ratio appears to be very
variable which indicates that either the source or the acceleration
efficiency of the accelerator may be different. Numerical simulations
and theoretical considerations provide evidence that there maybe other
critical parameters that govern acceleration such as the shock normal
direction. In this presentation we will concentrate on the acceleration
properties of the above- mentioned structures by using energetic
helium data and compared these results with numerical simulations,
and theoretical models.
Title: On the velocity distributions of dust-related inner-source
pickup ions
Authors: Bochsler, P.; Möbius, E.; Wimmer-Schweingruber, R. F.
Bibcode: 2006GeoRL..33.6102B
Altcode:
We simulate velocity distributions for inner-source pickup ions in
two scenarios for their origin. One scenario creates inner-source
pickup ions by charge exchange and energy loss in very small (typically
submicron-sized) dust grains (Wimmer-Schweingruber and Bochsler 2003),
while the other liberates solar wind ions previously implanted in larger
(typically 1 μm) dust grains (Geiss et al. 1995; and Gloeckler and
Geiss 1998). The two scenarios differ by the initial velocity with
which the pickup ions are created; the fine-dust model produces
a wide initial velocity distribution, while the coarse-dust model
releases them essentially at rest. We investigate the differences
in the distributions once these ions have been transported out to an
observer at 1 AU or beyond.
Title: Solar Wind Helium and Neon from Metallic Glass Flown on
Genesis - Preliminary Bulk and Velocity-Dependent Data
Authors: Grimberg, A.; Bühler, F.; Burnett, D. S.; Jurewicz, A. J. G.;
Hays, C. C.; Bochsler, P.; Heber, V. S.; Baur, H.; Wieler, R.
Bibcode: 2006LPI....37.1782G
Altcode:
He and Ne data have been obtained from a metallic glass flown on
Genesis. We present preliminary total extraction data from the bulk
solar wind and first results from studies on the putative solar
energetic particle component.
Title: Interstellar Helium Trapped with the COLLISA Experiment on
the MiR Space Station-Improved Isotope Analysis by In Vacuo Etching
Authors: Busemann, H.; Bühler, F.; Grimberg, A.; Heber, V. S.;
Agafonov, Y. N.; Baur, H.; Bochsler, P.; Eismont, N. A.; Wieler, R.;
Zastenker, G. N.
Bibcode: 2006ApJ...639..246B
Altcode:
We have redetermined the helium isotopic composition of
the local interstellar cloud (LIC) in the framework of the
Swiss-Russian Collection of Interstellar Atoms (COLLISA)
collaboration. Based on in vacuo etching analyses of
foils that have been exposed to the interstellar neutral
particle flux on board the Mir space station, we obtain
(3He/4He)LIC=(1.62+/-0.29)×10-4.
This is the most precise determination of the He isotopic composition of
the LIC, with errors being lower by more than a factor of 2 compared to
an earlier experiment on similar foils and compared to the analysis of
interstellar pick-up ions. Comparing our improved result with current
models of Galactic chemical evolution reveals that close to 100% of
all Galactic low-mass stars must have undergone extra mixing associated
with cool bottom processing. The 3He abundance relative to
4He in the LIC is within the uncertainty identical to the
value of (1.66+/-0.06)×10-4 inferred for the protosolar
cloud (PSC), showing that no significant evolution of the 3He
abundance took place since 4.6 Gyr ago at the solar distance (~8 kpc)
from the Galactic center. Our value sets new rigorous constraints on
Galactic evolution models. Since the Big Bang nucleosynthesis theory
predicts a value of <=(1.1+/-0.2)×10-4, a noticeable
increase of the relative abundance of 3He has apparently
occurred in the Galaxy before the formation of the solar system, but,
contrary to earlier expectations, only a modest or negligible increase
is registered after the formation of the solar system.
Title: Stream-limited transport of Solar Energetic Particles
Authors: Wang, X.; Bamert, K.; Bochsler, P.; Hilchenbach, M.; Ipavich,
F.; Klecker, B.; Moebius, E.; Wurz, P.; Celias Team
Bibcode: 2006cosp...36.2699W
Altcode: 2006cosp.meet.2699W
By using the SoHO CELIAS H STOF data we compare the behavior of He H
abundance ratio at different energy range and their relationship to
the evolution of the proton spectra in small and large solar energetic
events The enhancements of the ratio He H predicted by the stream-limit
theory Ng et al 1999 are shown in both small and large events with
the difference of their appearance at different energy range large
events at higher energy range i e 1600 4000 keV nuc while small events
at lower energy range i e 200 800 keV nuc This result indicates that
self-generated waves are general phenomena in the acceleration and
the transport of solar energetic particles in interplanetary space
Title: Pickup ion acceleration in the solar wind observed by
SOHO/CELIAS
Authors: Saul, L.; Möbius, E.; Bochsler, P.
Bibcode: 2006cosp...36.3352S
Altcode: 2006cosp.meet.3352S
Injection into the solar wind gives interstellar pickup ions a
non-maxwellian distribution allowing preferential injection into
acceleration mechanisms Interplanetary shocks and compressions as
well as quiet-time processes such as stochastic acceleration create
suprathermal tails on observed pickup ion velocity distributions However
the dynamic nature of the solar wind makes measurement of the relative
importance of acceleration mechanisms difficult In the inner heliosphere
these particles are diffuse enough to be effectively test particles
in the solar wind This allows us to use pickup ion observations
as a test of particle energization theories We present a survey of
SOHO CELIAS data taken during solar minimum allowing comparison of
acceleration rates to shock parameters turbulence parameters and solar
wind parameters
Title: Conversion surfaces for neutral particle imaging detectors
Authors: Scheer, J. A.; Wieser, M.; Wurz, P.; Bochsler, P.; Hertzberg,
E.; Fuselier, S. A.; Koeck, F. A.; Nemanich, R. J.; Schleberger, M.
Bibcode: 2006AdSpR..38..664S
Altcode:
Low-energy neutral particles must be ionized before they are analyzed
by mass spectrometric means. Within the limitations regarding space,
weight and power consumption onboard a spacecraft surface ionization
has been identified as the only viable ionization technique. In
the study presented here molecular oxygen and hydrogen ions were
scattered at grazing incidence from several diamond-like carbon (DLC)
surfaces in the energy range from 190 to 2400 eV. Most surfaces were
hydrogen terminated. For incident positive oxygen and hydrogen ions,
scattered negative ion fractions of up to 28% and more than 6%,
were measured, respectively. These values are among the highest
ever reported, especially for oxygen. Furthermore, though these
surfaces are amorphous, due to improved polishing techniques angular
scattering distributions of the scattered beam have been observed,
which were comparable to distributions of scattering experiments with
single-crystal surfaces. Therefore, these DLC surfaces are strong
candidates to work as conversion surfaces in a neutral particle imaging
detector for the BepiColombo mission.
Title: Evolution of the Distributions and Composition of Inner-Source
Pickup Ions
Authors: Bochsler, P.; Moebius, E.; Wimmer-Schweingruber, R.
Bibcode: 2006cosp...36.3330B
Altcode: 2006cosp.meet.3330B
Inner source pickup ions originate most likely from the interaction of
the solar wind with dust particles in interplanetary space They are
thought to be generated either through saturation of dust with solar
wind subsequent desorption and pickup or through penetration of small
dust grains by solar wind neutralization and subsequent re-ionization
In both cases a velocity distribution emerges which is genuinely
suprathermal but peaks below the solar wind speed Using Monte Carlo
simulations we investigate the properties of inner-source pickup ions
in more detail We apply experimental results for charge exchange of
solar wind ions with carbon foils as a proxy for the interaction of
ions with small interplanetary dust grains As the initial pickup ion
distributions we adopt the velocity distribution functions VDFs of
solar wind particles with which they exit from the grains Subsequent
pitch angle scattering and cooling will spread the distributions through
velocity space Since the emerging VDFs are narrower than VDFs of pickup
ions from interstellar gas or pickup ions desorbed from grains we also
expect a somewhat narrower distribution at the observer location at
1 AU or beyond The expected abundances of inner-source ions depend
strongly on the amount and on the composition of sputtered grains as
well as on the ionization properties of the pickup ions We will also
make another attempt to estimate the production rate of pickup ions
and compare our estimate with the observed grain densities
Title: The Interstellar Boundary Explorer (IBEX) Mission
Authors: McComas, D.; Allegrini, F.; Bartolone, L.; Bochsler,
P.; Bzowski, M.; Collier, M.; Fahr, H.; Fichtner, H.; Frisch, P.;
Funsten, H.; Fuselier, S.; Gloeckler, G.; Gruntman, M.; Izmodenov,
V.; Knappenberger, P.; Lee, M.; Livi, S.; Mitchell, D.; Möbius, E.;
Moore, T.; Pope, S.; Reisenfeld, D.; Roelof, E.; Runge, H.; Scherrer,
J.; Schwadron, N.; Tyler, R.; Wieser, M.; Witte, M.; Wurz, P.; Zank, G.
Bibcode: 2005ESASP.592..689M
Altcode: 2005ESASP.592E.138M; 2005soho...16E.138M
No abstract at ADS
Title: Solar Wind Noble Gases - Preliminary Results from Bulk Metallic
Glass Flown on Genesis
Authors: Grimberg, A.; Bühler, F.; Bochsler, P.; Heber, V. S.;
Tosatti, S.; Jurewicz, A. J. G.; Hays, C. C.; McNamara, K.; Allton,
J. H.; Burnett, D. S.; Baur, H.; Wieler, R.
Bibcode: 2005M&PSA..40.5222G
Altcode:
No abstract at ADS
Title: Trapping and Release Data of Artificially Implanted Noble
Gases into Metals -- Tests for Genesis Targets
Authors: Grimberg, A.; Bühler, F.; Bochsler, P.; Heber, V.; Baur,
H.; Wieler, R.
Bibcode: 2005LPI....36.1355G
Altcode:
Two noble gas irradiation experiments were carried out to determine
mass discrimination for different Genesis target materials and to
demonstrate the depth resolution of closed-system stepwise etching on
the metallic glass Ax1.
Title: 3He and4He in the local interstellar gas as observed with
the COLLISA foil experiment on the Mir space station
Authors: Bochsler, P.; Agafonov, Yu. N.; Bühler, F.; Busemann, H.;
Eismont, N. A.; Grimberg, A.; Heber, V. S.; Salerno, E.; Wieler, R.;
Zastenker, G. N.
Bibcode: 2005IAUS..228...77B
Altcode:
With the COLLISA foil experiment onboard the Mir space station we have
collected samples of interstellar helium, which have been returned to
the Earth and investigated by mass spectrometric analysis. Recently,
we have been able to reduce the experimental uncertainties as
given earlier (Salerno et al. 2003). Our improved estimate of
the helium isotopic ratio in the local interstellar medium is now
(3He/4He)LISM=(1.62 ± 0.29) ×
10-4 (Busemann et al. 2005).
Title: Development and calibration of major components for the
STEREO/PLASTIC (plasma and suprathermal ion composition) instrument
Authors: Blush, L. M.; Allegrini, F.; Bochsler, P.; Daoudi, H.;
Galvin, A.; Karrer, R.; Kistler, L.; Klecker, B.; Möbius, E.; Opitz,
A.; Popecki, M.; Thompson, B.; Wimmer-Schweingruber, R. F.; Wurz, P.
Bibcode: 2005AdSpR..36.1544B
Altcode:
The plasma and suprathermal ion composition (PLASTIC) instrument will
measure kinetic properties and charge states of solar wind ions and
suprathermal ions as part of the solar terrestrial relations observatory
(STEREO) mission. Two identical instruments located on separate
spacecraft will provide in situ plasma measurements at ∼1 AU to study
physical processes low in the corona and in the inner heliosphere. In
conjunction with the other in situ and remote sensing instruments
of STEREO, as well as existing near-Earth observatories, the PLASTIC
instrument measurements will contribute to the understanding of the
three-dimensional structure of the heliosphere, with particular focus
on Coronal Mass Ejections. As the primary solar wind instrument aboard
STEREO, PLASTIC will measure bulk solar wind plasma parameters (density,
velocity, temperature, temperature anisotropy, and alpha/proton ratio)
and the distribution functions and charge state distributions of major
heavy solar wind ions (e.g., C, O, Ne, Mg, Si, Fe). The measurement
apparatus includes an electrostatic deflection analyzer for energy
per charge measurement ( E/ q), a time-of-flight section utilizing
carbon foils and microchannel plate detectors for time of flight
measurement ( TOF), and solid-state detectors for energy measurement
( E). The instrument will provide a large instantaneous field of view
(in-ecliptic and out-of-ecliptic angles distinguished) with measurements
taken at high time resolution (1-5 min) spanning an ion energy range
of 0.25-87 keV/e. To accommodate a large range of particle fluxes, the
PLASTIC Entrance System employs collection apertures with different
geometric factors for the bulk solar wind (H ∼ 96%, He ∼ 4%) and
for the heavy, less-abundant ions (<1%) and suprathermal ions. This
paper focuses on the hardware development of major components for the
PLASTIC instrument. The PLASTIC measurement principle is explained
along with a presentation of the ion optic calibrations of the flight
model Entrance Systems as well as calibrations of the microchannel
plates and solid-state detectors.
Title: Effect of Coronal Mass Ejection Interactions on the
SOHO/CELIAS/MTOF Measurements
Authors: Wang, X.; Wurz, P.; Bochsler, P.; Ipavich, F.; Paquette,
J.; Wimmer-Schweingruber, R. F.
Bibcode: 2005IAUS..226..409W
Altcode:
By using the plasma composition data from SOHO/CELIAS/MTOF, charge
states data from ACE/SWICS, combining with the remote sensing
observations from SOHO/LASCO white-light image and WIND/WAVES radio
emission, we describe a coronal mass ejection (CME) observed on 2001
October 19 16:50 UT to show how the effect of CME interaction appears
in the <e1>in situ</e1> measurements. A new narrow shock
is formed while the rear CME passing through the core region of the
preceding one, which moves faster than the surrounding part and has a
new type II radio burst associated with it. Because of its distinguished
elemental abundance and unusual low charge states, we connect a density
hump observed by MTOF/PM with the preceding CME core. By comparing
the relative abundances of minor ions in shock compressive region,
ICME region and CME core region with respect to that in upstream slow
solar wind, we indicate mass-per-charge dependence of minor thermal
ions may be an important imprint of the characteristic velocity of
distant acceleration region.
Title: Enhancements of He+ at Interplanetary Disturbances:
A Survey
Authors: Kucharek, H.; Moebius, E.; Lu, Y.; Smith, C.; Klecker, B.;
Farrugia, C.; Popecki, M.; Galvin, A.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2004AGUFMSH31A1149K
Altcode:
Recent observations with ACE/SEPICA and SOHO CELIAS STOF have
shown that energetic He+ is after H+ and
He2+ the third most abundant energetic particle population
in the heliosphere. The He+/He2+ ratio in the
energetic particle population can reach unusually high values; in the
energy range of 250keV/n -800keV/n ratios close to unity. The major
source of the energetic He+ has been identified to be interplanetary
pickup ions that are preferentially accelerated at CIR's, TIR's, and
interplanetary traveling shocks. Since, compared to solar wind ions
pickup ions are already suprathermal, any accelerator can create an
enhancement in the energetic He+/He2+ ratio. In
our survey of energetic helium over three years (1998-2000) from STOF
and SEPICA we have identified additional discontinuities and magnetic
field signatures, such as current sheet crossings, flows, and enhanced
magnetic turbulence, which are associated with an enhancement in
He+/He2+ ratio.
Title: The Plasma and SupraThermal Ion Composition (PLASTIC)
Instrument: Final Diagnostic Development Phase for the STEREO Mission
Authors: Blush, L. M.; Bochsler, P.; Daoudi, H.; Galvin, A.; Karrer,
R.; Kistler, L.; Klecker, B.; Möbius, E.; Opitz, A.; Popecki, M.;
Thompson, B.; Wimmer-Schweingruber, R.; Wurz, P.
Bibcode: 2004AGUFMSH21B0410B
Altcode:
The PLAsma and SupraThermal Ion Composition (PLASTIC) instrument
project is entering the final phases of instrument development prior
to integration with the Solar Terrestrial Relations Observatory
(STEREO) spacecraft in early 2005. The STEREO mission will provide
a unique opportunity to investigate the 3-dimensional structure of
the heliosphere, with particular focus on the origin, evolution, and
propagation of Coronal Mass Ejections (CMEs). The mission also seeks to
determine the sites and mechanisms of energetic particle acceleration as
well as develop a 3-D time-dependent understanding of the ambient solar
wind properties. As one of four STEREO instrument packages coordinating
remote sensing and in situ measurements, the PLASTIC instruments
will diagnose properties of the solar wind and suprathermal protons,
alphas, and heavy ions. PLASTIC will determine bulk solar wind plasma
parameters (density, velocity, temperature, temperature anisotropy,
and alpha/proton ratio) and the distribution functions of major
heavy solar wind ions in the energy per charge range 0.25-100keV/e. A
full characterization of the solar wind and suprathermal ions will
be achieved with a system that measures ion energy per charge (E/q),
ion velocity distribution (ěc v), and ion energy (E). Two identical
PLASTIC instruments located on the separate spacecraft will provide
in situ plasma measurements in order to study physical processes low
in the corona and in the inner heliosphere. Elemental and charge state
abundances provide tracers of the ambient coronal plasma, fractionated
populations from coronal and heliospheric events, and local source
populations of energetic particle acceleration. In this presentation,
the PLASTIC operation principles and aims will be presented along with a
review of development status and current instrument calibration results.
Title: Inferences for Isotopic Fractionation Processes in the Solar
Wind Using the Full Solar Cycle Record of Abundances from Ulysses:
Anticipating Results from the Genesis Mission
Authors: Bochsler, P.; von Steiger, R.
Bibcode: 2004ESASP.575..372B
Altcode: 2004soho...15..372B
No abstract at ADS
Title: Variability of the Nitrogen Abundance in the Solar Wind and
Implications for Past Solar Activity
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.; Wurz, P.;
Gloeckler, G.; Geiss, J.; Kallenbach, R.; Zurbuchen, T. H.
Bibcode: 2004AGUFMSH33B..01W
Altcode:
The abundance of nitrogen in the heliosphere is an enigma. Laboratory
analysis of lunar soils shows that trapped nitrogen is overabundant
in them by about one order of magnitude relative to all noble gases,
which in turn are efficiently trapped in the lunar regolith. On the
other hand, the Solar Wind Ion Mass Spectrometer (SWIMS) on ACE has
successfully measured the elemental abundance of nitrogen in the solar
wind, N/O ≈0.121 ± 0.014, in good agreement with the photospheric
value of N/O ≈ 0.123 and with the SEP-dervied coronal value. In
this work we determine the abundance ratio N/Ne and investigate the
variability of N/O and of N/Ne in the solar wind. Nitrogen is not
readily measured in the solar wind with spaceborn TOF mass/mass per
charge spectrometers such as SWICS because it is not very abundant and
is neighbored in mass and in mass per charge by the more abundant heavy
ions, oxygen and carbon. For this reason, previous elemental abundance
determinations of nitrogen in the solar wind have had large intrinsic
uncertainties. However, with SWIMS, nitrogen is cleanly separated from
its neighbors and its abundance can be accurately measured. Analyzing
data from 1998 to 2004, we have found no unexpected variability of
N in the solar wind, the ratios N/O and N/Ne are consistent with a
constant value throughout this period of dramatically changing solar
activity. We apply this finding to different ideas relating nitrogen
in lunar soils to widely different solar input in the distant past and
find that our result provides further evidence for a non-solar origin
of most of nitrogen in lunar soils.
Title: Are Inner Source Pickup Ions further Accelerated in
Interplanetary Space?
Authors: Möbius, E.; Kucharek, H.; Popecki, M.; Bochsler, P.;
Kallenbach, R.; Klecker, B.; Wimmer-Schweingruber, R.
Bibcode: 2004AGUFMSH43B..07M
Altcode:
Inner source pickup ions originate most likely from the interaction
of the solar wind with dust particles in interplanetary space. They
are thought to be generated either through saturation of dust with
solar wind, subsequent desorption, and pickup, or through penetration
of small dust grains by solar wind, neutralization, and subsequent
re-ionization. In both cases a velocity distribution emerges, which is
genuinely suprathermal, but peaks below the solar wind speed. Based
on the realization that interstellar pickup ions are preferentially
injected for further acceleration it has been suggested that also inner
source ions may contribute visibly to the energetic particle populations
in interplanetary space. It has been shown that inner source ions do
not contribute significantly to the CIR population that is accelerated
mostly outside 1 AU and observed in Earth's orbit. Since inner source
ions are generated close to the sun one might expect that they could
contribute to energetic particles accelerated at traveling shocks. We
will present results from the search of such ions in traveling shocks
that have been identified to accelerate substantial amounts of He+. The
results will be discussed in the light of models for inner source
pickup ion distributions and for injection of ions into acceleration.
Title: Solar and solar wind isotopic compositions
Authors: Wiens, Roger C.; Bochsler, Peter; Burnett, Donald S.;
Wimmer-Schweingruber, Robert F.
Bibcode: 2004E&PSL.226..549W
Altcode:
With only a few exceptions, the solar photosphere is thought to have
retained the mean isotopic composition of the original solar nebula,
so that, with some corrections, the photosphere provides a baseline
for comparison of all other planetary materials. There are two sources
of information on the photospheric isotopic composition: optical
observations, which have succeeded in determining a few isotopic
ratios with large uncertainties, and the solar wind, measured either
in situ by spacecraft instruments or as implanted ions into lunar or
asteroidal soils or collection substrates. Gravitational settling from
the outer convective zone (OCZ) into the radiative core is viewed as
the only solar modification of solar-nebula isotopic compositions to
affect all elements. Evidence for gravitational settling is indirect,
as observations are presently less precise than the predictions of
<10‰ effects for the isotopes of solid-forming elements. Additional
solar modification has occurred for light isotopes (D, Li, Be, B)
due to nuclear destruction at the base of the convection zone, and
due to production by nuclear reactions of photospheric materials
with high-energy particles from the corona. Isotopic fractionation
of long-term average samples of solar wind has been suggested by
theory. There is some evidence, although not unambiguous, indicating
that interstream (slow) wind is isotopically lighter than high-speed
wind from coronal holes, consistent with Coulomb drag theories. The
question of fractionation has not been clearly answered, because the
precision of spacecraft instruments is not sufficient to clearly
demonstrate the predicted fractionations, which are <30‰/amu
between fast and slow wind for most elements. Analysis of solar wind
noble gases extracted from lunar and asteroidal soils, when compared
with the terrestrial atmospheric composition, also suggests solar wind
fractionation consistent with Coulomb drag theories. Observations of
solar and solar wind compositions are reviewed for nearly all elements
from hydrogen to iron, as well as the heavy noble gases. Other than Li
and the noble gases, there is presently no evidence for differences
among stable isotopes between terrestrial and solar photosphere
compositions. Although spacecraft observations of solar wind isotopes
have added significantly to our knowledge within the past decade,
more substantial breakthroughs are likely to be seen within the next
several years with the return of long-exposure solar wind samples
from the Genesis mission, which should yield much higher precision
measurements than in situ spacecraft instruments.
Title: Erratum to “Solar and solar-wind isotopic compositions”
[Earth Planet. Sci. Lett. 224 (2004) 697-712]
Authors: Wiens, Roger C.; Bochsler, Peter; Burnett, Donald S.;
Wimmer-Schweingruber, Robert F.
Bibcode: 2004E&PSL.226..547W
Altcode:
No abstract at ADS
Title: Solar Wind-Induced Atmospheric Erosion at Mars: First Results
from ASPERA-3 on Mars Express
Authors: Lundin, R.; Barabash, S.; Andersson, H.; Holmström, M.;
Grigoriev, A.; Yamauchi, M.; Sauvaud, J. -A.; Fedorov, A.; Budnik, E.;
Thocaven, J. -J.; Winningham, D.; Frahm, R.; Scherrer, J.; Sharber,
J.; Asamura, K.; Hayakawa, H.; Coates, A.; Linder, D. R.; Curtis,
C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; Reading,
D. H.; Koskinen, H.; Kallio, E.; Riihela, P.; Schmidt, W.; Säles,
T.; Kozyra, J.; Krupp, N.; Woch, J.; Luhmann, J.; McKenna-Lawler,
S.; Cerulli-Irelli, R.; Orsini, S.; Maggi, M.; Mura, A.; Milillo, A.;
Roelof, E.; Williams, D.; Livi, S.; Brandt, P.; Wurz, P.; Bochsler, P.
Bibcode: 2004Sci...305.1933L
Altcode:
The Analyzer of Space Plasma and Energetic Atoms (ASPERA) on board the
Mars Express spacecraft found that solar wind plasma and accelerated
ionospheric ions may be observed all the way down to the Mars Express
pericenter of 270 kilometers above the dayside planetary surface. This
is very deep in the ionosphere, implying direct exposure of the martian
topside atmosphere to solar wind plasma forcing. The low-altitude
penetration of solar wind plasma and the energization of ionospheric
plasma may be due to solar wind irregularities or perturbations,
to magnetic anomalies at Mars, or both.
Title: The Interstellar Boundary Explorer (IBEX)
Authors: McComas, David; Allegrini, Frederic; Bochsler, Peter;
Bzowski, Maciej; Collier, Michael; Fahr, Hans; Fichtner, Horst; Frisch,
Priscilla; Funsten, Herb; Fuselier, Steve; Gloeckler, George; Gruntman,
Mike; Izmodenov, Vlad; Knappenberger, Paul; Lee, Marty; Livi, Stefano;
Mitchell, Don; Möbius, Eberhard; Moore, Tom; Reisenfeld, Dan; Roelof,
Ed; Schwadron, Nathan; Wieser, Martin; Witte, Manfred; Wurz, Peter;
Zank, Gary
Bibcode: 2004AIPC..719..162M
Altcode:
The Interstellar Boundary Explorer (IBEX) is one of five Small Explorer
(SMEX) missions undergoing Phase A study for NASA's Office of Space
Science. Around November 2004, NASA expects to select at least one of
missions for development and flight. If selected, IBEX will provide
the first global views of the Sun's interstellar boundaries by taking
a set of global energetic neutral atom (ENA) images at a variety
of energies. Recent advances in ENA imaging have made it possible
to remotely image space plasmas and ENA imaging is now poised to
image the interstellar interactions and interstellar boundaries
at the edge of our heliosphere. IBEX makes these exploratory ENA
observations using two ultra-high sensitivity ENA cameras on a simple
spinning spacecraft. IBEX's highly elliptical Earth orbit allows
viewing of the outer heliosphere from beyond the Earth's relatively
bright magnetospheric ENA emissions. IBEX's sole, focused science
objective is to discover the global interaction between the solar
wind and the interstellar medium. IBEX achieves this objective by
answering four fundamental science questions: (1) What is the global
strength and structure of the termination shock? (2) How are energetic
protons accelerated at the termination shock? (3) What are the global
properties of the solar wind flow beyond the termination shock and in
the heliotail? and (4) How does the interstellar flow interact with
the heliosphere beyond the heliopause? The IBEX objective is central
to the Sun-Earth Connection (SEC) theme as demonstrated by both the
2003 SEC Roadmap and 2002 NRC's Decadal Survey and is specifically
identified in the 2003 NASA-wide Strategic Plan. In short, the IBEX
mission provides the first global views of the Sun's interstellar
boundaries, unveiling the physics of the heliosphere's interstellar
interaction, providing a deeper understanding of the heliosphere and
thereby astrospheres throughout the galaxy, and creating the opportunity
to make even greater unanticipated discoveries.
Title: Noble Gases from the Interstellar Medium Trapped on the MIR
Space Station and Analyzed by In Vacuo Etching
Authors: Busemann, H.; Bühler, F.; Agafonov, Y. N.; Baur, H.;
Bochsler, P.; Eismont, N. A.; Heber, V. S.; Wieler, R.; Zastenker,
G. N.
Bibcode: 2004M&PSA..39.5170B
Altcode:
No abstract at ADS
Title: ASPERA-3: analyser of space plasmas and energetic ions for
Mars Express
Authors: Barabash, S.; Lundin, R.; Andersson, H.; Gimholt, J.;
Holmström, M.; Norberg, O.; Yamauchi, M.; Asamura, K.; Coates, A. J.;
Linder, D. R.; Kataria, D. O.; Curtis, C. C.; Hsieh, K. C.; Sandel,
B. R.; Fedorov, A.; Grigoriev, A.; Budnik, E.; Grande, M.; Carter,
M.; Reading, D. H.; Koskinen, H.; Kallio, E.; Riihela, P.; Säles, T.;
Kozyra, J.; Krupp, N.; Livi, S.; Woch, J.; Luhmann, J.; McKenna-Lawlor,
S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Morbidini, A.; Mura,
A.; Milillo, A.; Roelof, E.; Williams, D.; Sauvaud, J. -A.; Thocaven,
J. -J.; Moreau, T.; Winningham, D.; Frahm, R.; Scherrer, J.; Sharber,
J.; Wurz, P.; Bochsler, P.
Bibcode: 2004ESASP1240..121B
Altcode: 2004mesp.book..121B
The ASPERA-3 (Analyser of Space Plasma and Energetic Atoms)
instrument of Mars Express is designed to study the solar wind-Mars
atmosphere interaction and to characterise the plasma and neutral
gas environment in near-Mars space through energetic neutral atom
(ENA) imaging and local charged-particle measurements. The studies
address the fundamental question: how strongly do the interplanetary
plasma and electromagnetic fields affect the martian atmosphere? This
question is directly related to the problem of martian dehydration. The
instrument comprises four sensors; two ENA sensors, and electron and
ion spectrometers. The Neutral Particle Imager (NPI) measures the
integral ENA flux (0.1-60 keV) with no mass and energy resolution
but with high angular resolution. The Neutral Particle Detector (NPD)
measures the ENA flux, resolving energy (0.1-10 keV) and mass (H and O)
with a coarse angular resolution. The electron spectrometer (ELS) is a
standard top-hat electrostatic analyser of a very compact design. These
three sensors are mounted on a scanning platform providing 4π
coverage. The instrument includes an ion mass composiotion sensor, IMA
(Ion Mass Analyser). Mechanically, IMA is a separate unit connected by
a cable to the ASPERA-3 main unit. IMA provides ion measuremets in the
energy range 0.01-40 keV/q for the main ion components H+,
He2+, He+, O+, with 20-80 amu/q.
Title: Solar and solar-wind isotopic compositions
Authors: Wiens, Roger C.; Bochsler, Peter; Burnett, Donald S.;
Wimmer-Schweingruber, Robert F.
Bibcode: 2004E&PSL.222..697W
Altcode:
With only a few exceptions, the solar photosphere is thought to have
retained the mean isotopic composition of the original solar nebula,
so that, with some corrections, the photosphere provides a baseline
for comparison of all other planetary materials. There are two sources
of information on the photospheric isotopic composition: optical
observations, which have succeeded in determining a few isotopic
ratios with large uncertainties, and the solar wind, measured either
in situ by spacecraft instruments or as implanted ions into lunar or
asteroidal soils or collection substrates. Gravitational settling from
the outer convective zone (OCZ) into the radiative core is viewed as
the only solar modification of solar-nebula isotopic compositions to
affect all elements. Evidence for gravitational settling is indirect,
as observations are presently less precise than the predictions of
<10‰ effects for the isotopes of solid-forming elements. Additional
solar modification has occurred for light isotopes (D, Li, Be, B)
due to nuclear destruction at the base of the convection zone, and
due to production by nuclear reactions of photospheric materials
with high-energy particles from the corona. Isotopic fractionation
of long-term average samples of solar wind has been suggested by
theory. There is some evidence, though not unambiguous, indicating
that interstream (slow) wind is isotopically lighter than high-speed
wind from coronal holes, consistent with Coulomb drag theories. The
question of fractionation has not been clearly answered because the
precision of spacecraft instruments is not sufficient to clearly
demonstrate the predicted fractionations, which are <30‰ per amu
between fast and slow wind for most elements. Analysis of solar-wind
noble gases extracted from lunar and asteroidal soils, when compared
with the terrestrial atmospheric composition, also suggests solar-wind
fractionation consistent with Coulomb drag theories. Observations of
solar and solar-wind compositions are reviewed for nearly all elements
from hydrogen to iron, as well as the heavy noble gases. Other than Li
and the noble gases, there is presently no evidence for differences
among stable isotopes between terrestrial and solar photosphere
compositions. Although spacecraft observations of solar-wind isotopes
have added significantly to our knowledge within the past decade,
more substantial breakthroughs are likely to be seen within the next
several years with the return of long-exposure solar-wind samples
from the Genesis mission, which should yield much higher precision
measurements than in situ spacecraft instruments.
Title: STEREO mission: overview, the plasma instrument, calibrations
and data
Authors: Opitz, A.; Karrer, R.; Bochsler, P.; Blush, L.; Fischer,
J.; Jost, J.; Sigrist, M.; Wurz, P.
Bibcode: 2004PADEU..14...35O
Altcode:
This is an overview of the next generation solar space mission called
STEREO. We focus on the plasma instrument and its calibrations at
the University of Bern. The management of the plasma data is also
discussed briefly.
Title: The Interstellar Boundary Explorer (IBEX)
Authors: McComas, D. J.; Allegrini, F.; Bochsler, P.; Bzowski, M.;
Collier, M. R.; Fahr, H.; Fichtner, H.; Frisch, P.; Funsten, H.;
Fuselier, S.; Gruntman, M.; Izmodenov, V.; Knappenberger, P.; Lee,
M.; Livi, S.; Mitchell, D.; Moebius, E.; Moore, T.; Reisenfeld, D.;
Roelof, E.; Schwadron, N.; Wieser, M.; Witte, M.; Wurz, P.; Zank, G.
Bibcode: 2004AGUSMSH13A..02M
Altcode:
The Interstellar Boundary Explorer (IBEX) is one of five Small Explorer
(SMEX) missions undergoing Phase A study for NASA's Office of Space
Science. Around November 2004, NASA expects to select two of these five
missions for development and flight. If selected, IBEX will provide
the first global views of the Sun's interstellar boundaries by taking
a set of global energetic neutral atom (ENA) images at a variety of
energies. Recent advances in ENA imaging have made it possible to
remotely image space plasmas and ENA imaging is now poised to image
the interstellar interactions and interstellar boundaries at the edge
of our heliosphere. On IBEX, these groundbreaking ENA observations
are achieved with high sensitivity measurements provided by two very
large aperture ENA cameras, using heritage technologies, on a simple
spinning spacecraft. IBEX's highly elliptical Earth orbit provides
viewing of the outer heliosphere from beyond the relatively bright
emissions of the Earth's magnetosphere. IBEX's sole, focused science
objective is to discover the global interaction between the solar
wind and the interstellar medium. IBEX achieves this objective by
answering four fundamental science questions: (1) What is the global
strength and structure of the termination shock, (2) How are energetic
protons accelerated at the termination shock, (3) What are the global
properties of the solar wind flow beyond the termination shock and in
the heliotail, and (4) How does the interstellar flow interact with
the heliosphere beyond the heliopause? The IBEX objective is central
to the Sun-Earth Connection (SEC) theme as demonstrated by both the
2003 SEC Roadmap and 2002 NRC's Decadal Survey and is specifically
identified in the 2003 NASA-wide Strategic Plan. In short, the IBEX
mission provides the first global views of the Sun's interstellar
boundaries, unveiling the physics of the heliosphere's interstellar
interaction, providing a deeper understanding of the heliosphere and
thereby astrospheres throughout the galaxy, and creating the opportunity
to make even greater unanticipated discoveries.
Title: Artificial Implantation of Noble Gases on Genesis Targets
Authors: Grimberg, A.; Bühler, F.; Bochsler, P.; Baur, H.; Wieler, R.
Bibcode: 2004LPI....35.1754G
Altcode:
We are simulating the implantation of various noble gas ions under
Solar Wind conditions to test for implantation efficiencies and
mass-fractionation of different Genesis collector materials.
Title: Solar and Solar-Wind Oxygen Isotopes and the Genesis Mission
Authors: Wiens, R. C.; Burnett, D. S.; McKeegan, K. D.; Thiemens,
M. H.; Franchi, I. A.; Bochsler, P.; Mao, P.
Bibcode: 2004LPI....35.1296W
Altcode:
The solar oxygen isotope composition is thought to hold important
clues to pre-planetary processing of materials in the solar nebula,
yet it is essentially unmeasured. Here we describe plans for O isotope
analyses of Genesis solar-wind samples.
Title: Observational evidence of pitch angle isotropization by
IMF waves
Authors: Saul, L.; Möbius, E.; Smith, C. W.; Bochsler, P.; Grünwaldt,
H.; Klecker, B.; Ipavich, F.
Bibcode: 2004GeoRL..31.5811S
Altcode: 2004GeoRL..3105811S; 2004astro.ph..2090S
A statistical analysis of interstellar He+ pickup ion
measurements from SOHO/CTOF combined with magnetic field data from
WIND/MFI enable quantitative study of wave-particle interactions in the
inner heliosphere for the first time. Magnetic field vector measurements
with a time resolution of 3 seconds are used to determine power spectrum
characteristics of interplanetary magnetic turbulence. These spectral
characteristics are then compared in superposed epoch and correlation
analyses with He+ fluxes and spectra. The observed pickup ion
velocity distributions can be explained consistently as a consequence
of pitch angle scattering of the interstellar pickup ions by Alfvénic
fluctuations.
Title: ICMEs with unusual, mass-fractionated composition
Authors: Wurz, P.; Wang, X.; Bochsler, P.; Ipavich, F.; Paquette,
J.; Wimmer-Schweingruber, R. F.
Bibcode: 2004cosp...35..257W
Altcode: 2004cosp.meet..257W
We present a study of the elemental composition of coronal mass
ejections (CMEs) during the present solar cycle, of the magnetic cloud
(MC) type and of the other CMEs (non-MC type). The study covers the
proton and heavy ion elemental abundances. Considerable variations
from event to event exist with regard to the density of the individual
species with respect to regular ``slow'' solar wind preceding the CME
plasma. The elemental composition of the investigated CMEs is generally
significantely different from slow solar wind, with MC showing a
mass-dependent fractionation and non-MC CMEs having a large variety
of compositions.
Title: Variability of N/O in the Solar Wind: ACE/SWIMS
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.; Wurz, P.;
Gloeckler, G.; Geiss, J.; Kallenbach, R.; Zurbuchen, T. H.
Bibcode: 2004cosp...35.2887W
Altcode: 2004cosp.meet.2887W
The Solar Wind Ion Mass Spectrometer (SWIMS) on ACE has successfully
measured the elemental abundance of nitrogen in the solar wind, N/O ≈
0.121 ± 0.014, in excellent agreement with the photospheric value of
N/O ≈ 0.123 and with the SEP-dervied coronal value. The abundance of
nitrogen in the heliosphere is an enigma. Laboratory analysis of lunar
soils shows that trapped nitrogen is overabundant in them by about one
order of magnitude relative to the heavy noble gases, which in turn are
efficiently trapped in the lunar regolith. In this work we investigate
the variability of N/O in the solar wind. Since Ne/O is known to vary
little, variations in N/O would translate directly to variations of N
with respect to noble gases. Small variations in N/O will therefore
provide further evidence for a non-solar origin of most of nitrogen
in lunar soils. Nitrogen is not readily measured in the solar wind
because it is not very abundant and it is neighbored in mass and in
mass per charge by the most abundant heavy ions, oxygen and carbon. For
this reason, previous elemental abundance determinations of nitrogen
in the solar wind have had large intrinsic uncertainties. However,
with SWIMS, nitrogen is cleanly separated from its neighbors and its
abundance can be accurately measured.
Title: Injection and acceleration of interstellar helium at
interplanetary shocks
Authors: Kucharek, H.; Moebius, E.; Li, W.; Farrugia, C.; Popecki,
M.; Galvin, A.; Klecker, B.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2004cosp...35.3226K
Altcode: 2004cosp.meet.3226K
Although, substantial progress has been made in the understanding of
particle injection and acceleration at shocks, the processes involved
are not fully understood. Meanwhile numerical simulations have become
powerful enough to include different species, such as heavy ions
and electrons, and observations are now more sensitive to resolve
individual ion species and charge states even during less intense solar
energetic particle events. As a consequence, the combination of theory,
simulations, and observations provides the tools to study the physical
processes at interplanetary discontinuities in detail. In this talk we
will report on recent results using ACE/SEPICA and SOHO/CELIAS/STOF to
observe interstellar pickup He+ as well as coronal and/or
solar wind He2+ at interplanetary discontinuities. Apparently
He+ is injected and accelerated with very high efficiency
compared with He2+. Therefore, this pair, He+ and
He2+, represents an ideal probe for the injection efficiency,
because it comes from two well-defined sources with different velocity
distributions. We will discuss the most recent findings as well as
their implications on shock structure and acceleration in comparison
with theory and numerical simulations.
Title: Conversion Surfaces for Neutral Particle Detectors
Authors: Scheer, J. A.; Wieser, M.; Wurz, P.; Bochsler, P.; Hertzberg,
E.; Fuselier, S. A.
Bibcode: 2004cosp...35.3945S
Altcode: 2004cosp.meet.3945S
To measure neutral particles, first of all one has to find a
suitable ionization technique. Surface ionization was identified
as the only viable ionization technique to meet the requirements
concerning ionization efficiency for the energy range of 10 eV to
1 keV within the limitations imposed by the resources available on
a satellite. In recent years high fractions of negative ions have
been observed while scattering neutral particles off several quite
different insulating surfaces, i. e., natural diamond and MgO. We will
present measurements which show a very good overall-performance for
Diamond-Like-Carbon surfaces (DLC) and thus recommend these surfaces
to be used as conversion surfaces for instruments on future missions
like BepiColombo and Interstellar Boundary Explorer (IBEX).
Title: Variability of N/O in the Solar Wind
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.; Wurz, P.;
Gloeckler, G.; Geiss, J.; Kallenbach, R.; Zurbuchen, T. H.
Bibcode: 2003AGUFMSH41B0468W
Altcode:
The Solar Wind Ion Mass Spectrometer (SWIMS) on ACE has successfully
measured the elemental abundance of nitrogen in the solar wind, N/O ≈
0.121 +/- 0.014, in excellent agreement with the photospheric value of
N/O ≈ 0.123 and with the SEP-dervied coronal value. The abundance of
nitrogen in the heliosphere is an enigma. Laboratory analysis of lunar
soils shows that trapped nitrogen is overabundant in them by about one
order of magnitude relative to the heavy noble gases, which in turn are
efficiently trapped in the lunar regolith. In this work we investigate
the variability of N/O in the solar wind. Since Ne/O is known to vary
little, variations in N/O would translate directly to variations of N
with respect to noble gases. Small variations in N/O will therefore
provide further evidence for a non-solar origin of most of nitrogen
in lunar soils. Nitrogen is not readily measured in the solar wind
because it is not very abundant and it is neighbored in mass and in
mass per charge by the most abundant heavy ions, oxygen and carbon. For
this reason, previous elemental abundance determinations of nitrogen
in the solar wind have had large intrinsic uncertainties. However,
with SWIMS, nitrogen is cleanly separated from its neighbors and its
abundance can be accurately measured.
Title: On the source and acceleration of energetic He+:
A long-term observation with ACE/SEPICA
Authors: Kucharek, H.; MöBius, E.; Li, W.; Farrugia, C. J.; Popecki,
M. A.; Galvin, A. B.; Klecker, B.; Hilchenbach, M.; Bochsler, P. A.
Bibcode: 2003JGRA..108.8040K
Altcode:
We report on a systematic study of the He+/He2+
abundance ratio in the energetic population during the years
1998-2000. For the investigation we have used data in the energy
range 0.25-0.8 MeV/n from SEPICA on board ACE and from CELIAS STOF
on SOHO in the energy range 0.085-0.28 MeV/q. The ratio is quite
variable, with values up to 1. Over the entire time period the
integral abundance ratio of the energetic population is 0.06, which
exceeds the abundance of He+ in the solar wind and corona
by several orders of magnitude and even surpasses substantially the
average relative contribution of He+ pickup ions. This
requires preferential injection and acceleration of He+
over He2+. In a case study of a CME with plasma rich in
He+, which drives a shock and is being overtaken by another
shock, the largest enhancement is found near the driven shock way ahead
of the ejecta. In addition, CMEs which are He+ rich are very
rare. This implies that the source of the energetic He+ is
primarily interstellar pickup ions and not ejecta material. However,
signatures of large-scale structures in the interstellar source, such
as the gravitational focusing cone, have not been identified in this
survey. Enhanced He+/He2+ ratios are associated
with interplanetary structures in the solar wind, such as stream-stream
interfaces and interplanetary traveling shocks. In fact, more than
90% of all shocks and stream interfaces show ratios that exceed our
lower limit of 0.04. This association points to local acceleration
of interplanetary He+, whose injection and acceleration
efficiency may vary substantially from event to event, thus probably
washing out large-scale structures of the source strength. While the
enhancements tend to be very localized at interplanetary traveling
shocks, they are much more prolonged in the case of CIRs.
Title: Composition of magnetic cloud plasmas during 1997 and 1998
Authors: Wurz, P.; Wimmer-Schweingruber, R. F.; Bochsler, P.; Galvin,
A. B.; Paquette, J. A.; Ipavich, F. M.; Gloeckler, G.
Bibcode: 2003AIPC..679..685W
Altcode:
We present a study of the elemental composition of a sub-set of coronal
mass ejections, namely events which have been identified of being of
the magnetic cloud type (MC). We used plasma density data from the
MTOF sensor of the CELIAS instrument of the SOHO mission and plasma
ionization data from the SWICS instrument of the ACE mission. So far we
have investigated MCs of 1997 and 1998. The study covers the proton and
heavy ion elemental abundances. Considerable variations from event to
event exist with regard to the density of the individual species with
respect to regular ``slow'' solar wind preceding the MC plasma. However,
two general features are observed. First, we observe for the heavy
elements (carbon through iron), which can be regarded as tracers in the
solar wind plasma, a mass-dependent enrichment of ions monotonically
increasing with mass. The enrichment can be explained by a previously
published theoretical model assuming coronal plasma loops on the solar
surface being the precursor structure of the MC. Second, when comparing
the MC plasma to regular solar wind composition preceding the event,
a net depletion of the lighter ions is always observed. Proton and
alpha particle abundances have to be regarded separately since they
represent the main plasma.
Title: Interstellar Pathfinder - A Mission to the Inner Edge of the
Interstellar Medium
Authors: McComas, D. J.; Bochsler, P. A.; Fisk, L. A.; Funsten, H. O.;
Geiss, J.; Gloeckler, G.; Gruntman, M.; Judge, D. L.; Krimigis, S. M.;
Lin, R. P.; Livi, S.; Mitchell, D. G.; Möbius, E.; Roelof, E. C.;
Schwadron, N. A.; Witte, M.; Woch, J.; Wurz, P.; Zurbuchen, T. H.
Bibcode: 2003AIPC..679..834M
Altcode:
Interstellar Pathfinder (ISP), our first step into the interstellar
medium, is a scientific investigation to study the outer boundary
of our heliosphere and the interstellar matter that flows into
it. A wind of interstellar neutral gas penetrates to within several
astronomical units (AU) of the Sun, giving us a direct sample of
present-day galactic matter. ISP is a mission to this inner edge of the
interstellar medium. Using highly sensitive instrumentation, ISP will
determine the composition of our local interstellar environment. It
will also take the first global images of the boundary region of
the heliosphere at 100 to 150 AU. These measurements will allow ISP
to answer fundamental questions about the origin of the solar system
and the stars, about the evolution of our galaxy and of the universe,
and about the characteristics of our local galactic environment and
its influence on the heliosphere.
Title: Relative Abundance Variations of Energetic
He+/He2+ in CME Related SEP Events
Authors: Kucharek, H.; Möbius, E.; Li, W.; Farrugia, C.; Popecki,
M.; Galvin, A.; Klecker, B.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2003AIPC..679..648K
Altcode:
We have investigated several CME-related SEP events with unusually
high abundance of He+ relative to He2+ in the
energetic particle population which have been observed between 1998
and 2000 with ACE/SEPICA and SOHO/CELIAS. Usually the abundance of
He+ is below a few percent whereas at these times the
He+/He2+ ratio can be closer to one. Possible
sources for He+ are interstellar pickup ions or cold plasma
in CME's. We have investigated in detail the temporal evolution
and the energy spectra of these events. We find that the maximum
of the He+/He2+ ratio usually coincides with
the arrival of the shock or a solar wind structure. This is a strong
indication for local acceleration of these ions. The He+
enhancement does not seem to be associated with cold plasma within
CME's itself. Therefore, most probably interstellar pickup ions
are the source for the He+ enhancement. Furthermore,
the He+/He2+ ratio appears to be consistently
lower at higher energies. Also, the observed temporal variability
decreases with increasing energy. These two results seem to indicate
two different populations for He+ and He2+
with different energy spectra.
Title: SOHO CTOF Observations of Interstellar He+ Pickup
Ion Enhancements in Solar Wind Compression Regions
Authors: Saul, L.; Möbius, E.; Litvinenko, Y.; Isenberg, P.; Kucharek,
H.; Lee, M.; Grünwaldt, H.; Ipavich, F.; Klecker, B.; Bochsler, P.
Bibcode: 2003AIPC..679..778S
Altcode: 2003astro.ph..4366S
We present a recent analysis with 1996 SOHO CELIAS CTOF data, which
reveals correlations of He+ pickup ion fluxes and spectra with the
magnetic field strength and solar wind density. The motivation is to
better understand the ubiquitous large variations in both pickup ion
fluxes and their velocity distributions found in interstellar pickup
ion datasets. We concentrate on time periods of that can be associated
with compression regions in the solar wind. Along with enhancements
of the overall pickup ion fluxes, adiabatic heating and acceleration
of the pickup ions are also observed in these regions. Transport
processes that lead to the observed compressions and related heating
or acceleration are discussed. A shift in velocity space associated
with traveling interplanetary compression regions is observed, and
a simple model presented to explain this phenomenon based on the
conserved magnetic adiabatic moment.
Title: Lunar Soils - An Archive for the Galactic Environment of the
Solar System?
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter
Bibcode: 2003ANS...324...85W
Altcode: 2003ANS...324..J08W
No abstract at ADS
Title: Elemental Fractionation in the Solar Wind: SOHO Observations
and Modelling
Authors: Wurz, P.; Bochsler, P.; Paquette, J. A.; Ipavich, F. M.
Bibcode: 2003EAEJA....13362W
Altcode:
We report on the abundace of heav yions in the solar wind for selected
tiime periods of about one day duration of slow (VSW <
400 km/s) and fast VSW > 500 km/s solar wind. These time
periods were selected to study elemental fractionation as a function
of the first ionization potential (FIP). Data were recorded with the
MTOF sensor of the CELIAS instrument on SOHO. Slow and fast solar wind
flows typically attributed to soolar wind originating from the streamer
belt or from coronal holes, respectively. However, we find that such a
simple assignement is not always possible and compositional information
is needed to decide on the type of solar wind.
Title: Measurement of 3He/4He in the Local
Interstellar Medium: the Collisa Experiment on Mir
Authors: Salerno, E.; Bühler, F.; Bochsler, P.; Busemann, H.; Bassi,
M. L.; Zastenker, G. N.; Agafonov, Yu. N.; Eismont, N. A.
Bibcode: 2003ApJ...585..840S
Altcode:
An accurate measurement of the noble gas isotopic composition in the
local interstellar medium (LISM) provides a constraint of primary
importance for modeling Galactic evolution and, in some cases, for
studying the production of light nuclei in the early universe. The
foil collection technique offers a direct way to measure some local
interstellar gas abundances. With this method thin metal foils are
exposed to the flux of neutral interstellar particles. Particles
with sufficient energy penetrate the foil and remain trapped
within its atomic structure. With the COLLISA experiment we have
used this technique to collect a sample of interstellar neutral
matter with the aim of determining the helium isotopic ratio
in the LISM. The foils were exposed on board the Russian space
station Mir. After exposure in space, the foils were brought back
to the Earth, and the amount of captured particles was determined
by mass spectrometric analysis at the University of Bern. The
analysis has allowed the detection of interstellar 3He
and 4He and the determination of the LISM isotopic number
ratio 3He/4He=(1.7+/-0.8)×10-4. This
value is consistent with protosolar ratios obtained from meteorites
and Jupiter's atmosphere, supporting the hypothesis that negligible
changes of the abundance of 3He occurred in the Galaxy
during the past 4.5 Gyr.
Title: Calcium Abundance in the Solar Wind
Authors: Wurz, P.; Bochsler, P.; Paquette, J. A.; Ipavich, F. M.
Bibcode: 2003ApJ...583..489W
Altcode:
We report on the calcium abundance in the solar wind for an extended
time period around the 1996 solar minimum. Data were recorded with the
Mass Time-of-Flight (MTOF) sensor of the Charge, Element, and Isotope
Analysis System (CELIAS) instrument on the SOHO spacecraft. The Ca/O
abundance is 0.017+/-0.003 for slow solar wind (VSW<400
km s-1) and 0.0053+/-0.0014 for fast solar wind
(VSW>500 km s-1). Compared to the photospheric
Ca/O abundance ratio of (Ca/O)PS=0.00421+/-0.00079,
the solar wind clearly shows strong first ionization potential (FIP)
fractionation as is expected for a low-FIP element. The Ca/H abundance
is ACa=6.63+/-0.05 and ACa=6.21+/-0.10 for slow
and fast solar winds, respectively. For comparison, the photospheric
Ca abundance is ACa=6.36+/-0.02.
Title: On the origin of inner-source pickup ions
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter
Bibcode: 2003GeoRL..30.1077W
Altcode: 2003GeoRL..30b..49W
In situ measurements of pickup ions (PUI) exhibit a component that has
nearly thermalized with the solar wind. This implies an origin close
to the Sun and is generally ascribed to interaction of the solar wind
with interplanetary dust particles (IDPs). We propose a scenario for
the origin of inner-source PUIs in which a population of very small
IDPs serves as the neutralizing agent for solar wind ions. The size
of these IDPs is less than or comparable to the penetration range,
of solar wind ions in IDP material. The interaction of the solar wind
with such particles results in a net charge exchange in which solar
wind ions exit the IDPs as predominantly neutral or singly-charged
ions. When the neutralized solar wind is reionized, it is picked up
and can then be measured as a PUI.
Title: Galactic Evolution of CNONe and the Composition of Heliospheric
Particles
Authors: Bochsler, P.; Wimmer-Schweingruber, R. F.
Bibcode: 2003ASPC..304..179B
Altcode: 2003cnou.conf..179B
No abstract at ADS
Title: The Sulfur Isotopic Composition of the Sun
Authors: Wimmer-Schweingruber, R. F.; Gloeckler, G.; Bochsler, P.;
Zurbuchen, T. H.
Bibcode: 2002AGUFMSH52A0442W
Altcode:
The Solar Wind Ion Mass Spectrometer (SWIMS) on the Advanced
Composition Explorer (ACE) has successfully measured the isotopic
composition of sulfur in the solar wind. Preliminary analysis yields
34S/32S ≈ (4.3 +/- 0.6)% which is in good
agreement with the meteoritc value of 34S/32S =
4.43%. As opposed to elemental composition which can be very accurately
measured spectroscopically, the isotopic composition of sulfur on
the Sun cannot be directly measured. Solar wind measurements are
thus the only means of determining solar isotopic abundances. For
refractory elements the meteoritic isotopic composition is thought to
represent the solar composition very well. This has been verified with
measurements of Mg and Si in the solar wind. In contrast to Mg and Si,
sulfur is a volatile element, and as such is especially susceptible
to processes that alter its isotopic composition, be it during the
formation of the solar system, or during the history of the sample
being studied. Thus the determination of its isotopic composition in
the Sun can yield valuable information on the original sulfur isotopic
composition in the protosolar nebula and on possible fractionation
mechanisms active during the formation of the early solar system. We
will compare the solar values of 33S/32S and
34S/32S with values derived from meteoritic
samples, for the GCR, the interstellar medium, and from SEPs.
Title: ACE/SEPICA Observations of Energetic He+ Associated
With Interplanetary Disturbances at 1AU
Authors: Kucharek, H.; Moebius, E.; Li, W.; Farrugia, C.; Popecki,
M.; Galvin, A.; Klecker, B.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2002AGUFMSH61A0423K
Altcode:
Solar Energetic Particle (SEP) events with unusually high
abundance in He+ that have been observed between 1998
and 2000 with ACE/SEPICA have been investigated in detail. Usually
He+/He2+ abundance ratio in the solar wind/corona
is of the order of 10e-4. However during SEP events the
He+/He2+ ratio can be closer to one. This survey
has shown that the increase of the He+/He2+
abundance ratio coincides with the arrival of the shock (either
driven by a CME or associated with a CIR) or a discontinuity. The
analysis strongly suggests local acceleration of these ions and
it is also shown that interstellar pickup ions are the main source
for the He+ enhancement. We have identified the types of
discontinuities which are predominantly associated with an increase
of the He+/He2+ ratio. A representative sample
of CMEs, CME-related disturbances as well as corotating/transient
streams has been examined in detail. We have investigated the observed
temporal and energy dependence of the He+/He2+
ratio at the disturbances and we will describe the implications for
the acceleration of He+ pickup ions in the Heliosphere.
Title: Method and Results of Direct Measurement of the Interstellar
Neutral Helium Abundance and Isotopic Composition
Authors: Zastenker, G. N.; Agafonov, Yu. N.; Eismont, N. A.;
Prudkoglyad, A. V.; Khrapchenkov, V. V.; Gevorkov, L. G.; Burguchev,
S. A.; Kochetkov, A. V.; Salerno, E.; Buehler, F.; Bochsler, P.;
Fisher, J.; Bassi, M.; Busemann, G.; Eugster, O.
Bibcode: 2002CosRe..40..347Z
Altcode:
One of the important astrophysical problems is the determination of
the abundance of helium isotopes 3He and 4He in
different regions of the Universe, because this abundance can reflect
its history by pointing to the intensity of various possible processes
of the creation and decay of light elements. This paper describes the
method and results of the determination (for the first time performed
by a direct method) of the helium isotopic abundance in the local
interstellar medium surrounding the Solar system. The experiment was
carried out on the manned Mir space station by long-term space exposure
of samples of metal foil with their subsequent recovery to the Earth
and detailed laboratory mass-spectrometric analysis. As a result, we
succeeded in obtaining an estimation of the 4He concentration
(about 7.5 × 10-3 cm-3) and the isotopic ratio
3He/4He (about1.7 × 10-4) for the
local interstellar medium.
Title: Measuring the ionization rate of in-flowing interstellar
helium with the SOHO/CELIAS/SEM
Authors: McMullin, D. R.; Judge, D. L.; Phillips, E.; Hilchenbach,
M.; Bochsler, P.; Wurz, P.; Moebius, E.; Ipavich, F.
Bibcode: 2002ESASP.508..489M
Altcode: 2002soho...11..489M
The absolute measurement of solar EUV flux and its time dependence
provide critical data on the solar driven photochemistry which results
in solar system objects. In addition, the SEM measurements also
provide the data required to determine the absolute photoionization
rate of neutral interstellar helium flowing into our solar system. After
hydrogen, helium is the most abundant substance found in interplanetary
space, and the interstellar medium. In the inner solar system
photoionization of helium is the dominant ionization process of the
inflowing interstellar neutral helium. Thus, an accurate determination
of the solar photoionization rate is a requirement in astrophysical
research. The daily averaged photoionization rate of helium at 1 AU,
derived from the SOHO CELIAS/SEM absolute solar extreme ultraviolet
(EUV) flux values is presented for the time period since the launch
of SOHO in December, 1995.
Title: Abundance Variations of Energetic He+ at 1AU: ACE/SEPICA
Observations
Authors: Kucharek, H.; Moebius, E.; Klecker, B.; Li, W.; Farrugia,
C.; Popecki, M.; Galvin, A.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2002AGUSMSH22C..08K
Altcode:
We have investigated Solar Energetic Particle (SEP) events with
unusually high abundance in He+ that have been observed between 1998
and 2000 with ACE/SEPICA. The typical He+/He2+ abundance ratio in the
solar wind/corona is of the order of 10e-4. During SEP events the
He+/He2+ ratio can be closer to one. We have determined an average
abundance ratio of the high energetic population over one year to be
of the order of 0.1. Possible sources for this substantially enhanced
He+ are interstellar pickup ions or solar ejecta (CMEs). We have
investigated the temporal evolution and the energy spectra of these
events in detail. Usually the increase of the He+/He2+ abundance ratio
coincides with the arrival of the shock (either driven by a CME or
associated with a CIR) or a discontinuity. This seems to suggest local
acceleration of these ions. The investigations show that interstellar
pickup ions are the source for the He+ enhancement because it does
not seem to be associated with ejecta material. A comparison with
SOHO/CELIAS/STOF observations shows that the He+/He2+ ratio appears to
be consistently lower at higher energies, and the observed temporal
variability decreases with increasing energy. We have identified
the type of discontinuities which are associated with an increase
of the He+/He2+ ratio, and we will discuss the implications for the
acceleration of He+ pickup ions.
Title: On the Origin of Inner-Source Pickup Ions
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.
Bibcode: 2002AGUSMSH22C..06W
Altcode:
In situ measurements of pickup ions (PUI) exhibit a component that has
nearly thermalized with the solar wind. This implies an origin close
to the Sun and is generally ascribed to interaction of the solar wind
with interplanetary dust particles (IDPs). We propose a scenario for
the origin of inner-source PUIs in which a population of very small
IDPs serves as the neutralizing agent for solar wind ions. The size
of these IDPs is less than or comparable to the penetration range of
solar wind ions in IDP material. The interaction of the solar wind
with such particles results in a net charge exchange in which solar
wind ions exit the IDPs as predominantly neutral or singly-charged
ions. When the neutralized solar wind is reionized, it is picked up and
can then be measured as a PUI. This scenario has the advantage that
it can also explain the large neutralizing cross section associated
with the remarkably large flux of inner-source PUIs.
Title: Interstellar Pathfinder: A Mission to Explore the Inner Edge
of the Interstellar Medium
Authors: Livi, S.; Gloeckler, G.; Bochsler, P.; Fisk, L.; Funsten, H.;
Geiss, J.; Gruntman, M.; Judge, D.; Krimigis, S.; Lin, R.; McComas,
D.; Mitchell, D.; Moebius, E.; Roelof, E.; Schwadron, N.; Witte, M.;
Woch, J.; Wurz, P.; Zurbuchen, T.; Haggerty, D.; McNutt, R.
Bibcode: 2002AGUSMSH22B..04L
Altcode:
The Interstellar Pathfinder (ISP) will explore the interstellar space
surrounding our solar system and investigate its dynamic interaction
with the heliosphere. A steady wind of interstellar atoms penetrates
to within several AU of the Sun where ISP's instruments will analyze
the composition of this unique sample of matter in detail. ISP will
take global images of the distant boundary of the heliosphere, the
termination shock of the solar wind. ISP will probe the consequences
of and thus the conditions in the region beyond the termination, where
the heliosphere merges with the interstellar medium. The instruments
on ISP can also reveal the properties of the other sources of pickup
ions in the solar wind, and may be able to make detailed observations
of the composition of comets. ISP is a mission to the inner edge of
the interstellar medium and is an indispensable precursor to robotic
mission to measure interstellar space directly.
Title: Test of a Prototype Instrument for the Direct Measurement of
the Neutral Interstellar Gas
Authors: Wieser, M.; Wurz, P.; Bochsler, P.; Mobius, E.; Quinn, J.;
Fuselier, S. A.; DeFazio, J.; Stephen, T. M.
Bibcode: 2002AGUSMSH22B..05W
Altcode:
We have constructed and tested a prototype instrument for the direct
measurement of neutral interstellar gas (ISG). The particle detection of
this instrument bases on the conversion of energetic neutral atoms to
negative ions using surface ionization. Special emphasis was put on the
actual conversion surfaces and the relevant energy range for the ISG as
seen from a spacecraft (10eV to 1keV). The created negative ions are
subsequently coarsely energy analyzed via electrostatic deflection
and mass analyzed using the time of flight technique. We present
data recorded with this instrument from two calibration facilities
providing neutral particle beams. From these data we calculate the
detection efficiencies and deduce the expected performance for the
direct measurement of the interstellar gas flow on future missions,
such as Interstellar Pathfinder, Outer heliospheric Imager, or
Interstellar Probe.
Title: The Relative Abundance of Chromium and Iron in the Solar Wind
as Measured With SOHO/CELIAS/MTOF
Authors: Paquette, J. A.; Ipavich, F. M.; Lasley, S. E.; Bochsler,
P.; Wurz, P.
Bibcode: 2002AGUSMSH21C..08P
Altcode:
Measurements are presented of the abundance ratio of chromium to
iron in the solar wind in various flow types, and also for several
approximately 1-year long intervals in restricted speed ranges. The mass
discrimination of the MTOF (Mass Time-Of-Flight) sensor of the CELIAS
investigation on the SOHO spacecraft easily allows solar wind chromium
and iron to be resolved from each other, despite the similarity in
these two elements' masses (Chromium's most common isotope is mass 52,
while the most common isotope of iron is mass 56). Taking the ratio
of the densities of these two elements - as opposed to considering
their absolute abundances - minimizes the effects of uncertainties in
instrument efficiency. The First Ionization Potential (FIP) of Chromium
is 6.76 eV, while the FIP of Iron is 7.87 eV. Since Cr and Fe both have
low FIPs the ratio of their abundances should not be biased by the FIP
effect which is well known in different solar wind flows. Therefore
the Cr/Fe ratio from the MTOF data should give a good measure of the
photospheric abundance ratio. We also compare the ratio measured in
this work to the meteoritic value. Use is made of the MTOF sensor's
retarding potential to extend the study to higher solar wind speed
regimes than in previous work. A more realistic estimate of the solar
wind charge states (taken from Mazzotta et al) is also used.
Title: Isotopic Composition and Abundance of Interstellar Neutral
Helium Based on Direct Measurements
Authors: Zastenker, G. N.; Salerno, E.; Buehler, F.; Bochsler, P.;
Bassi, M.; Agafonov, Yu. N.; Eismont, N. A.; Khrapchenkov, V. V.;
Busemann, H.
Bibcode: 2002Ap.....45..131Z
Altcode:
One of the important problems in astrophysics is the determination of
the abundances of the helium isotopes 3He and 4He in various regions
of the universe, since those abundances can provide evidence of the
intensities of various possible processes of the production and decay
of light elements and can thereby reflect their history. In this paper
we describe the procedure and results of the first determination by
a direct method of the abundances of helium isotopes in the local
interstellar medium surrounding the solar system. The experiment was
carried out on the piloted MIR station by the prolonged exposure in
open space of specimens of metallic foil with their subsequent return to
earth and detailed laboratory mass-spectrometric analysis. As a result,
we were able to obtain estimates of the 4He density (about 7.5·10-3
cm-3) and the 3He/4He isotopic ratio (about 1.7·10-4) for the local
interst ellar medium.
Title: Sungrazing Comets: Properties of Nuclei and in Situ
Detectability of Cometary Ions at 1 AU
Authors: Iseli, M.; Küppers, M.; Benz, W.; Bochsler, P.
Bibcode: 2002Icar..155..350I
Altcode: 2001astro.ph.10091I
A one-dimensional sublimation model for cometary nuclei is used
to derive size limits for the nuclei of sungrazing comets and to
estimate oxygen ion fluxes at 1 AU from their evaporation. Given that
none of the ≈300 sungrazers detected by the SOlar and Heliospheric
Observatory (SOHO) was observed after disappearing behind the sun,
and that small nuclei with a radius of ≈3.5 m could be observed,
it is assumed that all SOHO sungrazers were completely destroyed. For
the case that sublimation alone is sufficient for destruction, the
model yields an upper size limit as a function of nuclear density ϱ,
albedo A, and perihelion distance q. If the density of the nuclei is
that typical of porous ice (600 kg m -3), the maximum size
is 63 m. These results confirm similar model calculations by Weissman
(1983). An analytical expression is derived that approximates the
model results well. We discuss possible modifications of our results by
different disruption mechanisms. While disruption by thermal stress does
not change the upper size limits significantly, they may be somewhat
increased by tidal disruption (up to 100 m for a density of 600 kg m
-3), dependent on the isotropy of the sublimation process
and the tensile strength of the comet. Implications for the Kreutz
family of sungrazers are discussed. Oxygen ions from the sublimation of
sungrazing comets form a tail. Fluxes from this tail are sufficiently
high to be measured at 1 AU by particle detectors on spacecraft, but
the duration of a tail crossing is only about half an hour. Therefore,
the probability of a spacecraft actually encountering a tail of an
evaporating sungrazer is only of the order of 2% per year.
Title: Using Solar Wind Composition As A Tracer For Solar Processes:
Applications For Plastic On Stereo
Authors: Wimmer-Schweingruber, Robert F.; Allegrini, Frédéric;
Blush, Lisa; Bochsler, Peter; Fischer, Josef; Wurz, Peter; Galvin,
A. B.; Moebius, E.; Klecker, B.; Thompson, B.; Plastic Team
Bibcode: 2002EGSGA..27.2220W
Altcode:
Solar wind composition is increasingly being used as a tracer for
various processes in the solar atmosphere and in interplanetary
space. We will discuss applications of solar wind composition
measurements that are relevant for the STEREO mission and that will be
supplied by the PLASTIC sensor. Solar wind elemental abundances
are affected by processes acting in the solar interior, chromosphere,
and in the corona, while charge-state composition is largely determined
in the corona. Farther out in the inner heliosphere, composition
measurements can give information about interplanetary processes and
serves as an excellent tracer for the coronal and chromospheric origin
of the measured solar wind. Coronal mass ejections often exhibit
unusual charge-state and elemental composition that is indicative of
unusual conditions in the solar atmosphere prior and during the launch
of the ejection. We will discuss observational opportunities
unique to collaborative studies with vari- ous instruments on STEREO.
Title: A survey of energetic He+/He2+ abundance ratios at 1AU:
ACE/SEPICA observations
Authors: Kucharek, H.; Moebius, E.; Klecker, B.; Li, W.; Farrugia,
C.; Popecki, M.; Galvin, A.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2002cosp...34E1992K
Altcode: 2002cosp.meetE1992K
The typical He+/He2+ abundance ratio in the solar wind/corona is of
the order of 10e4. However, during some Solar Energetic Particle (SEP)
events the He+/He2+ ratio can even reach values larger than 1. We
have investigated such SEP events that have been observed between
1998 and 2000 with ACE/SEPICA, and carried out a general survey of
the He+/He2+ ratio. We have determined an average abundance ratio of
the energetic population at energies 0.25 - 0.8 MeV/nucleon to be of
the order of 0.1. The possible major sources for this substantially
enhanced He+ abundance can be interstellar pickup ions or solar ejecta
(CMEs). Therefore, we have studied in detail the energy spectra and
the temporal evolution of these events. The increase of the He+/He2+
abundance ratio coincides with the arrival of a shock or a discontinuity
(either associated with a CME or a co-rotating interaction region). This
strongly suggests local acceleration of these ions. In addition, the
results favor interstellar pickup ions as the likely source for the He+
enhancement because no direct association with cold ejecta material
is found. In comparison with lower energies from SOHO/CELIAS/STOF
observations we find that the He+/He2+ ratio consistently decreases with
energy for CME related events, while there is no substantial change
in the ratio with energy for co-rotating interaction regions. This
seems to indicate that the energy spectra of the pickup He+ and the
solar wind He++ population are different. We have identified the
discontinuities that are associated with an increase of the He+/He2+
ratio and their relation to the solar wind structure. We will discuss
the implications for the acceleration of He+ pickup ions.
Title: In-flight Comparisons of Solar EUV Irradiance Measurements
Provided by the CELIAS/SEM on SOHO
Authors: McMullin, D. R.; Judge, D. L.; Hilchenbach, M.; Ipavich,
F.; Bochsler, P.; Wurz, P.; Burgi, A.; Thompson, W. T.; Newmark, J. S.
Bibcode: 2002ISSIR...2..135M
Altcode: 2002ESASR...2..135M; 2002rcs..conf..135M
Since 1 January 1996, the Solar EUV Monitor (SEM) on the Solar and
Heliospheric Observatory (SOHO) has continuously measured the solar EUV
irradiance. The SEM monitors the full-disk irradiance from 0.1 nm to 50
nm in a broadband channel and also within an 8 nm wide bandpass centered
at 30.4 nm. SEM irradiance measurements have been monitored periodically
during the SOHO mission using sounding rockets. Through this in-flight
calibration program, modest instrument degradation has been identified
and corrected for in the published datasets. The relative standard
uncertainty (1 σ ) of SEM irradiance measurements is ≈ 10 %. The
81-d average of the calibrated SEM dataset shows an increase in EUV
irradiance of a factor of three during the rise phase of solar cycle
23. The absolute value of the solar irradiance in the two SEM bands is
also in agreement with measurements of the solar irradiance determined
by ionization cells. The calibrated SEM irradiance values have been
compared with irradiance values derived independently from SOHO/CDS
and SOHO/EIT observations. The CDS and EIT irradiance values agree
with the SEM within the combined uncertainties of the measurements.
Title: Solar orbiter, a high-resolution mission to the sun and
inner heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Langevin, Y.; Marsden, R.; Pace, O.; Schwenn,
R.; Vial, J. -C.
Bibcode: 2002AdSpR..29.2027M
Altcode:
The scientific rationale of the Solar Orbiter is to provide, at high
spatial (35 km pixel size) and temporal resolution, observations of the
solar atmosphere and unexplored inner heliosphere. Novel observations
will be made in the almost heliosynchronous segments of the orbits at
heliocentric distances near 45 R⊙ and out of the ecliptic plane at
the highest heliographic latitudes of 30° - 38°. The Solar Orbiter
will achieve its wide-ranging aims with a suite of sophisticated
instruments through an innovative design of the orbit. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. Over extended periods
the Solar Orbiter will deliver the first images of the polar regions
and the side of the Sun invisible from the Earth.
Title: Solar Orbiter: a high-resolution mission to the sun and
inner heliosphere
Authors: Fleck, Bernhard; Marsch, E.; Antonucci, Ester; Bochsler,
Peter A.; Bougeret, J. L.; Harrison, R.; Marsden, R. P.; Coradini,
M.; Pace, Oscar; Schwenn, Rainer; Vial, Jean-Claude
Bibcode: 2001SPIE.4498....1F
Altcode:
The key mission objective of the Solar Orbiter is to study the Sun
from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar
rotation in order to examine the solar surface and the space above from
a co-rotating vantage point at high spatial resolution. Solar Orbiter
will also provide images of the Sun's polar regions from heliographic
latitudes as high as 38 degrees. The strawman payload encompasses
two instrument packages: Solar remote-sensing instruments: EUV
full-sun and high resolution imager, high-resolution EUV spectrometer,
high-resolution and full-sun visible light telescope and magnetograph,
EUV and visible-light coronagraphs, radiometers. Heliospheric
instruments: solar wind analyzer, radio and plasma wave analyzer,
magnetometer, energetic particle detectors, interplanetary dust
detector, neutral particle detector, solar neutron detector. To
reach its novel orbit, Solar Orbiter will make use of low-thrust
solar electric propulsion (SEP) interleaved by Earth and Venus gravity
assists. Solar Orbiter was selected by ESA's Science Programme Committee
(SPC) in October 2000 as a Flexi-mission, to be implemented after the
BepiColombo cornerstone mission to Mercury before 2013. This paper
summarizes the science to be addressed with the Solar Orbiter, followed
by brief descriptions of the strawman payload, the mission profile,
and the spacecraft and ground segment designs.
Title: First Investigations for the Entrance System / Energy Analyzer
of the PLASTIC Sensor on STEREO
Authors: Allegrini, F.; Wimmer-Schweingruber, R. F.; Galvin, A.;
Moebius, E.; Fischer, J.; Bartanus, J.; Wurz, P.; Bochsler, P.
Bibcode: 2001AGUFMSH31B0716A
Altcode:
STEREO (Solar TErrestrial Relations Observatory) is the third of
five Solar-Terrestrial Probes that will accomplish the goals of the
international Sun-Earth Connections program. PLASTIC (PLAsma and
SupraThermal Ion Composition) consists of a top-hat E/q analyzer and
a Time-Of-Flight--Energy (TOF--E) section. This sensor realizes three
functions: a) charge-state and mass measurements of interplanetary
ions with a 360o field of view in the ecliptic plane,
b) charge-state, mass, and energy measurements of the solar wind
(SW) heavy (Z > 2) ions in the 45o centered on the SW
direction and +/- 20o out of the ecliptic plane, and c)
charge-state, mass, and energy measurements of the solar wind protons
and alpha particles by a separate low-gain entrance with the same
field of view as in b). This way, PLASTIC will cover a large dynamical
range from bulk solar wind protons to suprathermal particles. In order
to accomplish the three functions, the entrance system consists of
a complex geometry involving multiple toroidal sections. The use of
protruding deflection plates allows to scan for directions up to +/-
20o out of the ecliptic plane. We will present the results
of our first measurements with the laboratory prototype and compare
them with the electrostatic simulations.
Title: On the Acceleration of Pickup He+ at 1 AU
Authors: Klecker, B.; Bogdanov, A. T.; Hilchenbach, M.; Galvin, A. B.;
Möbius, E.; Ipavich, F. M.; Steinberg, J. T.; Bochsler, P.
Bibcode: 2001AGUFMSH12C..07K
Altcode:
We investigate the variation of suprathermal
He+/He2+ abundances in the energy range 85-280 keV
during the years 1997 to 2001 at 1 AU, using data from the CELIAS/STOF
experiment onboard SOHO. It has been shown that the He+ ions
in this energy range form the suprathermal tail of accelerated pickup
helium of interstellar origin. We observe a large variability of the
He+ abundance ranging from He+/He2+
<5% to He+/He2+ >1. We correlate 12 hour
averages of the He+ abundance at suprathermal energies for
all days with significant He+ flux with solar wind parameters
and find a general anti-correlation of He+ abundance with
the solar wind velocity and the solar wind thermal velocity. We discuss
possible causes of this variability, in particular variations of the
source strength of pickup ions and solar wind alphas and variations
of the acceleration efficiency for He+ and He2+.
Title: Measurement of neutral atoms and ions in Mercury's exosphere
Authors: Mildner, M.; Wurz, P.; Scherer, S.; Zipperle, M.; Altwegg,
K.; Bochsler, P.; Benz, W.; Balsiger, H.
Bibcode: 2001P&SS...49.1655M
Altcode:
The Mercury apparatus for ions and atoms (MAIA) is a linear
time-of-flight mass spectrometer operating in two modes, a neutral
mode and an ion mode, which are used alternatively. MAIA is designed
to determine the composition of Mercury's exosphere and possibly its
crust. The mass resolution of MAIA is sufficient to resolve all elements
up to mass 300 amu. In both optional modes the mass range extends from
1 to 100 amu, and, if required, it can be increased up to 300 amu by
changing the data acquisition mode. Even isotopes could be resolved,
however, the partial pressures at Mercury are most likely too low
for identification.
Title: Space weather observations using the SOHO CELIAS complement
of instruments
Authors: Judge, D. L.; McMullin, D. R.; Gangopadhyay, P.; Ogawa, H. S.;
Ipavich, F. M.; Galvin, A. B.; Möbius, E.; Bochsler, P.; Wurz, P.;
Hilchenbach, M.; Grünwaldt, H.; Hovestadt, D.; Klecker, B.; Gliem, F.
Bibcode: 2001JGR...10629963J
Altcode:
The Solar and Heliospheric Observatory (SOHO) spacecraft located at
L1 is well outside the Earth's magnetosphere and has been observing
the Sun continuously since December 1995, except for relatively
brief periods due to spacecraft operational interruptions. While
a variety of instruments on the SOHO spacecraft investigate the
solar properties important to an improved understanding of the Sun
and its effect on space weather, the present work is limited to the
observations provided by the Charge, Element, and Isotope Analysis
System (CELIAS) proton monitor (PM) and Solar Extreme Ultraviolet
Monitor (SEM) instruments and their relationship to other space
weather observations. The CELIAS observations consist of particle
and EUV/soft X-ray solar flux measurements. A brief description of
the CELIAS instrumentation and examples of the precursor information
signaling the possibility of coronal mass ejection events observed by
the CELIAS/SEM are presented. In addition, the entire SEM database since
commissioning is presented on both expanded and compressed timescales
in order to provide both the long-term weather trends and short-term
storm data. The SEM data presented are full-disk observations and have
a 15 s sampling rate.
Title: Investigations of the Origin of the "Inner Source" of
Heliospheric Pick-up Ions
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.
Bibcode: 2001AGUFMSH22B0753W
Altcode:
The recently discovered "inner source" of heliospheric pick-up ions
is currently ascribed to the liberation of implanted solar wind atoms
from interplanetary dust particles that are saturated with solar wind
gas. Since the launch of SOHO, the LASCO instrument has observed a
large number of sun-grazing comets; typically one is observed every
few days. Such comets contribute a significant amount of small dust
particles to the dust inventory of the inner heliosphere. Typical
lifetimes against the Poynting-Robertson effect for very small ( ~
100Å) particles are on the order of a few tens of years, resulting in
significant accumulation of small particles in the innermost parts of
the heliosphere. Such small particles dominate the geometrical cross
section of dust but do not saturate with solar wind because it is not
trapped. Typical solar wind ranges in dust (SiO2) are on the
order of few 100 Å. However, the solar wind that is not trapped but
transmitted through these particles looses a significant fraction of
its kinetic energy and all memory of its initial charge state. The most
probable charge state of the transmitted particles are neutral atoms
and singly charged ions. We investigate the validity of this scenario
as an alternative explanation of the inner source of pick-up ions.
Title: Abundance Variations of Energetic He+ in CME Related SEP Events
Authors: Kucharek, H.; Moebius, E.; Klecker, B.; Li, W.; Popecki,
M.; Galvin, A.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2001AGUFMSH12C..04K
Altcode:
We have investigated several CME related SEP events with unusually
high abundance in He+ in the energetic particle population which
have been observed between 1998 and 2000 with ACE SEPICA and SOHO
CELIAS. Usually the abundance of He+ is below a few percent whereas at
these times the He+/He2+ ratio can be closer to one. Possible sources
for He+ are interstellar pickup ions or cold solar ejecta in CMEs. The
temporal evolution and the energy spectra of these events have been
investigated in detail. The maximum of the He+/He2+ ratio usually
coincides with the arrival of the shock or a discontinuity. This seems
to suggest local acceleration of these ions. The He+ enhancement does
not seem to be associated with cold ejecta in the CME. Therefore,
most probably interstellar pickup ions are the source for the He+
enhancement. Furthermore, the He+/He2+ ratio appears to be consistently
lower at higher energies, and the observed temporal variability
decreases with increasing energy. This seems to indicate two different
populations for He+ and He2+ with different energy spectra.
Title: Determination of the 36Ar/ 38Ar isotopic
abundance ratio of the solar wind using SOHO/CELIAS/MTOF
Authors: Weygand, James M.; Ipavich, Fred M.; Wurz, Peter; Paquette,
John A.; Bochsler, Peter
Bibcode: 2001GeCoA..65.4589W
Altcode:
This study is on the first direct measurements of the
36Ar/38Ar isotopic ratio in both the interstream
(IS)-associated and coronal hole (CH)-associated solar wind. Two
summed mass spectra are compiled for each solar wind region using
the Mass Time-Of-Flight (MTOF) sensor of the Charge, Element,
and Isotope Analysis System (CELIAS) instrument on the Solar and
Heliospheric Observatory (SOHO) spacecraft. A detailed analysis of
over 9.2 d of nonconsecutive IS-associated solar wind speed (395 ±
25 km/s) places the 36Ar/38Ar ratio at 5.6 ±
0.7. A similar analysis for a CH-associated solar wind speed (525 ±
25 km/s), with ∼22.8 nonconsecutive days of CH-associated solar
wind speed data, derived a similar 36Ar/38Ar
ratio of 5.5 ± 0.6. The error associated with these measurements
is essentially the instrumental uncertainty. Both the solar wind
36Ar/38Ar isotopic ratios found in this study are
consistent with the terrestrial 36Ar/38Ar ratio
as well as previous reported ratios for solar wind examined in this
study. A comparison of these results suggests little or no isotopic
fractionation occurring between the two solar wind regimes. This
study presents the results in the context of solar wind fractionation
models and in relation to experimental evidence derived from in situ
observations on refractory elements.
Title: Solar wind iron isotopic abundances: Results from
SOHO/CELIAS/MTOF
Authors: Ipavich, F. M.; Paquette, J. A.; Bochsler, P.; Lasley, S. E.;
Wurz, P.
Bibcode: 2001AIPC..598..121I
Altcode: 2001sgc..conf..121I
The MTOF sensor uses time of flight measurements in a harmonic
potential region to identify elements and isotopes in the solar
wind with excellent mass resolution. The combination of MTOF's large
bandwidth electrostatic deflection system and the 3-axis stabilized
orientation of SOHO results in excellent counting statistics. We
report relative abundances of the iron isotopes with mass 54, 56
and 57 amu. Since these isotopes are chemically identical, we expect
little fractionation either in the solar wind or in the instrument,
resulting in relatively small estimated uncertainties. Our results
agree, within the measurement uncertainties, with terrestrial values. .
Title: Composition of magnetic cloud plasmas during 1997 and 1998
Authors: Wurz, P.; Wimmer-Schweingruber, R. F.; Issautier, K.;
Bochsler, P.; Galvin, A. B.; Paquette, J. A.; Ipavich, F. M.
Bibcode: 2001AIPC..598..145W
Altcode: 2001sgc..conf..145W
We present a study of the elemental composition of a sub-set of
coronal mass ejections, namely events which have been identified of
being of the magnetic cloud type (MC). We used plasma data from the
MTOF sensor of the CELIAS instrument of the SOHO mission. So far we
have investigated MCs of 1997 and 1998. The study covers the proton,
alpha, and heavy ion elemental abundances. Considerable variations
from event to event exist with regard to the density of the individual
species with respect to regular ``slow'' solar wind preceding the MC
plasma. However, two general features are observed. First, for the heavy
elements (carbon through iron), which can be regarded as tracers in the
solar wind plasma, a mass-dependent enrichment of ions monotonically
increasing with mass is observed. The enrichment can be explained by
a previously published theoretical model assuming coronal plasma loops
on the solar surface being the precursor structure of the MC. Second,
when comparing the MC plasma to regular solar wind composition, a
net depletion of the lighter ions, helium through oxygen, is always
observed. Proton and alpha particle abundances have to be regarded
separately since they represent the main plasma. .
Title: Lunar soils: A long-term archive for the galactic environment
of the heliosphere?
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter
Bibcode: 2001AIPC..598..399W
Altcode: 2001sgc..conf..399W
Solar wind implanted in surface layers (<~0.03 μm) of lunar soil
grains has often been analyzed to infer the history of the solar
wind. In somewhat deeper layers, and thus presumably at higher
implantation energies, a mysterious population, dubbed ``SEP''
for ``solar energetic particle,'' accounts for the majority of the
implanted gas-several orders of magnitude more than expected from
the present-day flux of solar energetic particles. In addition,
its elemental and isotopic composition is distinct from that
of the solar system. While the heavy Ne isotopes are enriched
relative to 20Ne, 15N is depleted relative to
14N-a behavior that is hard to explain with acceleration
of solar material. N is overabundant with respect to the noble gases
(especially Ar). Here we show that interstellar pick-up ions (PUIs)
which are ionized and accelerated in the heliosphere and subsequently
implanted in lunar regolith grains can account for the properties of
the ``SEP'' population. This implies that lunar soils preserve samples
of the galactic environment of the solar system and may eventually be
used as an archive for solar system ``climate''. .
Title: The relative abundance of chromium and iron in the solar wind
Authors: Paquette, J. A.; Ipavich, F. M.; Lasley, S. E.; Bochsler,
P.; Wurz, P.
Bibcode: 2001AIPC..598...95P
Altcode: 2001sgc..conf...95P
Chromium and iron are two heavy elements in the solar wind with
similar masses. The MTOF (Mass Time Of Flight) sensor of the CELIAS
investigation on the SOHO spacecraft easily allows these two elements
to be resolved from one another. Taking the ratio of the densities
of these two elements-as opposed to considering their absolute
abundances-minimizes the effects of uncertainties in instrument
efficiency. Measurements of the abundance ratio are presented here. The
First Ionization Potential (FIP) of chromium is 6.76 eV, while the FIP
of iron is 7.87 eV. Since Cr and Fe have similar FIPs the ratio of their
abundances should not be biased by the FIP effect which is well known
in different solar wind flows. Therefore the Cr/Fe ratio from the MTOF
data should give a good measure of the photospheric abundance ratio. We
also compare the ratio measured in this work to the meteoritic value. .
Title: Direct measurement of 3He/4He in the
LISM with the COLLISA experiment
Authors: Salerno, E.; Bühler, F.; Bochsler, P.; Busemann, H.; Eugster,
O.; Zastenker, G. N.; Agafonov, Yu. N.; Eismont, N. A.
Bibcode: 2001AIPC..598..275S
Altcode: 2001sgc..conf..275S
Results from direct measurements of the helium isotopic ratio
in the closest regions of the Local Intersteller Medium (LISM)
are presented. Neutral 3He and 4He atoms
coming from the LISM were captured in space by means of the foil
collection technique, a method already successfully used during the
Apollo missions to determine the noble gas isotopic ratios in the
solar wind. In the framework of the Swiss-Russian project COLLISA
(COLLection of InterStellar Atoms), beryllium-copper foils were
placed on the outer surface of the space station Mir and directly
exposed to the flux of interstellar neutrals. The neutral particles
of the LISM cross the heliopause and reach, almost unaltered, the
Mir orbit at 400 km height above the Earth. Here, the kinetic energy
of the interstellar flux ramming against the foils is sufficient to
trap the particles into the atomic structure of the metal. After an
exposure of ~60 hours, the foils were recovered by the cosmonauts and
brought back to Earth by the American space shuttle Atlantis. The
particles were then extracted with a stepwise heating procedure
and their abundances were measured in the mass spectrometric
laboratories of the University of Bern. The analysis performed so
far allowed the detection of 3He and 4He
atoms of interstellar origin. The measured interstellar ratio
3He/4He={1.70-0.42+0.50}×10-4
is consistent with protosolar values obtained from meteorites and
Jupiter's atmosphere. Such a result seems to confirm the hypothesis
that no significant change of the 3He abundance occurred
in the LISM during the last 4.6 Gy. .
Title: Sun, solar wind, meteorites and interstellar medium: What
are the compositional relations?
Authors: Bochsler, Peter; Wimmer-Schweingruber, R. F.; Wurz, Peter
Bibcode: 2001AIPC..598..381B
Altcode: 2001sgc..conf..381B
Atomic properties of elements determine their chemical behavior,
their ionization properties and their interaction with radiation
in the solar atmosphere. Whereas the chemical properties influence
the condensation process in the primordial solar nebula and, hence,
meteoritic abundances, ionization properties seem to provide the most
important ordering parameters for producing coronal -, solar wind -, and
solar energetic particle abundances from the solar reservoir. Finally,
since atomic properties also shape the interaction of solar matter
with radiation, understanding these properties determines largely the
experimental reliability of photospheric chemical abundances. Isotopic
abundances must be derived from nuclear properties, which are almost
insensitive to atomic processes. The solar spectrum is the result of
atomic processes in the solar atmosphere. The derivation of isotopic
abundances from the solar spectrum is impossible for most species,
conversely, the insensitivity to chemical processes makes isotopes the
first choice to trace the nucleosynthetic history and the degree of
mixing of galactic matter from different astrophysical sources prior to
formation of the solar system. The solar wind provides a representative
sample of solar isotopes and-to some degree-also a rather trustworthy
representation of elements with similar atomic properties, especially
volatiles, which are difficult to derive from meteoritic abundances
and from optical observations of the solar spectrum. .
Title: Measuring Solar Abundances
Authors: von Steiger, R.; Vial, J. -C.; Bochsler, P.; Chaussidon, M.;
Cohen, C. M. S.; Fleck, B.; Heber, V. S.; Holweger, H.; Issautier, K.;
Lazarus, A. J.; Ogilvie, K. W.; Paquette, J. A.; Reisenfeld, D. B.;
Teriaca, L.; Wilhelm, K.; Yusainee, S.; Laming, J. M.; Wiens, R. C.
Bibcode: 2001AIPC..598...13V
Altcode: 2001sgc..conf...13V
This is the rapporteur paper of Working Group 2 on Measuring Solar
Abundances. The working group presented and discussed the different
observations and methods for obtaining the elemental and isotopic
composition of the Sun, and critically reviewed their results and
the accuracies thereof. Furthermore, a few important yet unanswered
questions were identified, and the potential of future missions to
provide answers was assessed. .
Title: Determination of the Ar/Ca solar wind elemental abundance
ratio using SOHO/CELIAS/MTOF
Authors: Weygand, J. M.; Ipavich, F. M.; Wurz, P.; Paquette, J. A.;
Bochsler, P.
Bibcode: 2001AIPC..598..101W
Altcode: 2001sgc..conf..101W
This study examines the first direct measurements of the solar wind
(SW) Ar/Ca elemental abundance ratio with the Mass Time-Of-Flight
(MTOF) sensor of the Charge, Element, and Isotope Analysis System
(CELIAS) instrument on the Solar and Heliospheric Observatory
(SOHO) spacecraft. Two mass spectra are compiled for interstream (IS)
associated SW and coronal hole (CH) associated SW. A detailed analysis
of over 3.6 days of non-consecutive IS associated SW speed (395+/-25
km/s) places the Ar/Ca elemental ratio at 0.38+/-0.05. A similar
analysis for CH associated SW speed (525+/-25 km/s), with about 5.6
non-consecutive days of CH associated SW speed data, derived an Ar/Ca
ratio of 0.59+/-0.07. The results of this study are consistent with
most previously published Ar/Ca values from gradual solar energetic
particle events and spectroscopy studies. .
Title: Solar Orbiter, a high-resolution mission to the Sun and
inner heliosphere
Authors: Marsch, E.; Harrison, R.; Pace, O.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Fleck, B.; Langevin, Y.; Marsden, R.; Schwenn,
R.; Vial, J. -C.
Bibcode: 2001ESASP.493D..11M
Altcode: 2001sefs.workD..11M
Solar Orbiter will provide, at very high spatial (35 km pixel size)
and temporal resolution, novel observations of the solar atmosphere
and unexplored inner heliosphere. It will achieve its wide-ranging
scientific aims with a suite of sophisticated instruments through an
innovative orbit design. Unprecedented observations will be made in
the heliosynchronous segments of the orbits at heliocentric distances
near 45 Rsolar and out of the ecliptic plane at the highest
heliographic latitudes of 30° - 38°. The first near-Sun interplanetary
measurements together with concurrent remote-sensing observations of
the Sun and its corona will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind
and energetic particles in close linkage with the plasma and radiation
conditions in the source regions on the Sun. Solar Orbiter will deliver
the first images of the polar regions and the far side of the Sun
invisible from the Earth.
Title: Particle and field instruments - report of Payload Splinter
Group 1
Authors: Marsden, R. G.; Bochsler, P.
Bibcode: 2001ESASP.493..143M
Altcode: 2001sefs.work..143M
In this paper we present a summary of the presentations and
discussions in Payload Splinter Group 1, devoted to the particle and
field instruments for the Solar Orbiter model payload. An important
conclusion is that, given the pivotal role of in-situ measurements
in the scientific mission of the Orbiter, the resources allocated to
these instruments during the Assessment Study were insufficient. This
applies both to the available telemetry and to the fraction of the total
payload mass. The Splinter Group also recommended that, in addition
to the suite of instrument already included in the model payload, a
hard X-ray imaging experiment be considered. It was also suggested
to extend the energy range of proton and electron measurements
by adding a cosmic-ray sensor that would also provide solar-ray
observations. Regarding telemetry, the Splinter Group emphasised the
need for continuous measurements, and proposed that a form of quick-look
data be implemented that would allow scientifically interesting periods
to be selected from the data stored on board the Orbiter.
Title: Reconnection remnants in the magnetic cloud of October 18-19,
1995: A shock, monochromatic wave, heat flux dropout, and energetic
ion beam
Authors: Collier, Michael R.; Szabo, A.; Farrell, W. M.; Slavin,
J. A.; Lepping, R. P.; Fitzenreiter, R.; Thompson, B.; Hamilton,
D. C.; Gloeckler, G.; Ho, G. C.; Bochsler, P.; Larson, D.; Ofman, L.
Bibcode: 2001JGR...10615985C
Altcode:
Evidence is presented that the Wind spacecraft observed particle and
field signatures on October 18-19, 1995, due to reconnection near
the foot points of a magnetic cloud (i.e., between 1 and 5 solar
radii). These signatures include (1) an internal shock traveling
approximately along the axis of the magnetic cloud, (2) a simple
compression of the magnetic field consistent with the foot point
magnetic fields being thrust outward at speeds much greater than the
solar wind speed, (3) an electron heat flux dropout occurring within
minutes of the shock, indicating a topological change resulting from
disconnection from the solar surface, (4) a very cold 5 keV proton
beam, and (5) an associated monochromatic wave. We expect that given
observations of enough magnetic clouds, Wind and other spacecraft
will see signatures similar to the ones reported here indicating
reconnection. However, these observations require the spacecraft to
be fortuitously positioned to observe the passing shock and other
signatures and will therefore be associated with only a small fraction
of magnetic clouds. Consistent with this, a few magnetic clouds observed
by Wind have been found to possess internal shock waves.
Title: On the variability of suprathermal He+ ions at 1 AU
Authors: Klecker, B.; Bogdanov, A. T.; Hilchenbach, M.; Galvin, A. T.;
Moebius, E.; Ipavich, F. M.; Bochsler, P.
Bibcode: 2001ICRC....8.3100K
Altcode: 2001ICRC...27.3100K
Using data from the STOF sensor of the CELIAS experiment onboard SOHO we
investigate the variation of suprathermal He+ /He2+ abundance ratios in
the energy range 85-280 keV during the years 1997 to 1999. We observe
a large variability of the He+ abundances in solar energetic particle
events ranging from He+ /He2+ <5% to He+ /He2+ > 1. Large He+
abundances are closely related with the passage of interplanetary
shocks, whereas abundance ratios of ~ 0.15 have been observed at 1
AU during CIR events. Combining the data from STICS/WIND and SOHO/
CELIAS/STOF for one of the events with He+ /He2+ ~ 1, a pickup He+
distribution with the typical cutoff energy at twice the solar
wind velocity and a suprathermal tail extending to ~ 150 keV/nuc is
observed. We correlate 12 hour averages of the He+ abundances in the
suprathermal tail for all days with significant He flux with solar
wind parameters and find a general anti-correlation of He+ abundances
with the solar wind velocity and the solar wind thermal velocity,
with a large scatter superimposed on the general trend. We discuss
possible causes of this variability, in particular variations of the
solar wind and pickup ion source strength.
Title: Variable abundance of energetic HE+ in CME related SEP events
Authors: Kucharek, H.; Klecker, B.; Möbius, E.; Li, W.; Popecki,
M. A.; Galvin, A. B.; Hilchenbach, M.; Bochsler, P.
Bibcode: 2001ICRC....8.3439K
Altcode: 2001ICRC...27.3439K
We have investigated several coronal mass ejections (CME) related solar
energetic particle (SEP) events with unusually high abundance of He+
in the energetic particle population. There were observed between 1998
and 1999 with SEPICA on ACE and CELIAS/STOF on board SOHO. Whereas
usually the abundance of He+ is below a few percent, at these times
the He+ /He2+ ratio can be close to one. Possible sources for He+ are
interstellar pickup ions or cold solar ejecta in CMEs. The abundance
of He+ is expected to vary depending on where the major acceleration
occurs, i.e. close to the sun or mainly locally close to the observer.
Title: The isotopic composition of oxygen in the fast solar wind:
ACE/SWIMS
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter; Gloeckler,
George
Bibcode: 2001GeoRL..28.2763W
Altcode:
Oxygen is the most abundant element in the solar system after H and
He, and the lightest element with three stable isotopes. Oxygen is a
volatile element; it was not retained completely in meteorites or in
their predecessors during their formation in the early solar system. The
solar oxygen isotopic composition is important because the Sun is
by far the largest reservoir of oxygen in the solar system. Oxygen
occurs in highly volatile phases of the solar system, such as water,
as well as in refractory phases, for example in silicates. Because
of this, the differences between the isotopic composition of oxygen
in solar-system bodies and the Sun are a sensitive measure of the
gas to dust ratio in the early solar system. We report the first
measurements of the oxygen isotopic composition in the fast solar
wind with the Solar Wind Isotope Mass Spectrometer (SWIMS) on the
Advanced Composition Explorer (ACE). The fast solar wind is the least
fractionated type of solar wind. We obtain an isotopic abundance
ratio 16O/18O of 446±90 which is (within
the quoted uncertainties) consistent with the terrestrial value of
498. However, in combination with previously published values for
the photosphere (16O/18O=440±50 [Harris et
al., 1987]) and the isotopically more fractionated slow solar wind
(16O/18O=450±130[Collier et al., 1998]), this
new determination may suggest that the Sun is isotopically heavier
than terrestrial.
Title: Solar Wind Composition at Solar Maximum
Authors: Bochsler, Peter
Bibcode: 2001SSRv...97..113B
Altcode:
Although coronal mass ejections have traditionally been thought to
contribute only a minor fraction to the total solar particle flux,
and although such events mainly occur in lower heliographic latitudes,
the impressive spectacle of eruptions - observed with SOHO/LASCO even
at times of solar minimum - indicates that an important part of the
low-latitude solar corona is fed with matter and magnetic fields
in a highly transient manner. Elemental and isotopic abundances
determined with the new generation of particle instruments with high
sensitivity and strongly enhanced time resolution indicate that,
apart from FIP/FIT-fractionation, mass-dependent fractionation can
also influence the replenishment of the thermal ion population of the
corona. Furthermore, selective enrichment of the thermal coronal plasma
with rare species such as 3He can occur. Such compositional
features have until recently only been found in energetic particles
from impulsive flare events. This review will concentrate on this and
other aspects of the present solar maximum and conclude with some
outlook on future investigations of near-terrestrial space climate
(the generalized counterpart of ‘space weather’).
Title: Solar and Galactic Composition
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.
Bibcode: 2001AGUSM..SH52C01W
Altcode:
The joint SOHO/ACE workshop on solar and galactic composition took
place in Bern, Switzerland in early March 2001. The workshop focused on
compositional aspects of the Sun and the Galaxy obtained with in-situ
and optical instruments, derived from laboratory studies of meteorites,
dust, returned samples, or from theoretical approaches. Topics ranged
from the composition of the solar interior (e.g. from helioseismology),
of the solar corona (from optical and SEP observations), and of the
solar wind (from in-situ and laboratory measurements), to interstellar
and galactic composition (from ACRs, interstellar pick-up ions, and
galactic cosmic rays). We will summarize key findings of the workshop
and report scientific highlights.
Title: Detection of Energetic Helium Atoms of Heliospheric Origin
at 1 AU
Authors: Shaw, A. W.; Hsieh, K.; Hilchenbach, M.; Czechowski, A.;
Hovestadt, D.; Klecker, B.; Kallenbach, R.; Gloeckler, G.; Moebius,
E.; Bochsler, P.
Bibcode: 2001AGUSM..SH22F04S
Altcode:
The time-of-flight mass spectrometer CELIAS/HSTOF on the Solar and
Heliospheric Observatory (SOHO), which detected the energetic hydrogen
atoms of heliospheric origin in the energy range of 58-88 keV, has
also detected and measured the flux of energetic helium atoms of
heliospheric origin in the energy range of 90-150 keV. We report on
the time variations in the flux of these energetic He atoms in the
ecliptic. Plausible interpretation and implications of the observed
flux variations will be presented.
Title: Test of Neutral to Negative Ion Conversion Surfaces in a
Prototype Sensor for Interstellar Neutral Gas Measurement
Authors: Wieser, M.; Wurz, P.; Bochsler, P.; Moebius, E.; Quinn, J.;
Fuselier, S. A.; Ghielmetti, A.
Bibcode: 2001AGUSM..SH22F01W
Altcode:
We have tested three different conversion surfaces (CVD diamond,
barium zirconate and magnesium oxide) for an interstellar neutral
gas instrument in a prototype sensor. A neutral oxygen beam in the
energy range 30 - 300 eV was used. This energy range is typical for
the interstellar gas flow as seen from a spacecraft in the inner
heliosphere. The prototype sensor performs energy and time-of-flight
analysis of the negative ions generated on the conversion surface
and thus provides unambiguous mass determination. This combination
allows the distinction between intrinsic background, sputtered ions and
truly converted primary neutrals. For all three surfaces a substantial
conversion efficieny was observed that extended to the lowest energies
under investigation. The overall detection efficiencies are sufficient
to collect typical interstellar O distributions with meaningful
statistics within reasonable integration times (one to a few days).
Title: Measurement of the Ar/Ca Abundance Ratio From CELIAS/MTOF in
Slow and Fast Solar Wind
Authors: Weygand, J. M.; Wurz, P.; Bochsler, P.; Ipavich, F. M.;
Galvin, A. B.
Bibcode: 2001AGUSM..SH62B05W
Altcode:
We present measurements of the Ar/Ca abundance ratio in the solar
wind. The results are derived from data recorded with the MTOF sensor of
the CELIAS instrument on the SOHO mission. This abundance ratio combines
two very different elements. Firstly, Ar is a high-FIP (First Ionization
Potential) element and Ca is a low-FIP element. Secondly, Ar is a
volatile element and Ca is a refractory element. The former difference
is important for processes associated with the solar atmosphere (e.g.,
the FIP fractionation process), the latter difference is important
with regard to the composition of the solar system. We shall present
the Ar/Ca abundance ratio for the slow and for the fast solar wind,
derived from the CELIAS/MTOF data set presently available.
Title: Calibration facility for solar wind plasma instrumentation
Authors: Marti, Adrian; Schletti, Reto; Wurz, Peter; Bochsler, Peter
Bibcode: 2001RScI...72.1354M
Altcode:
Space-borne analysis of the composition of the solar wind offers
the unique possibility of direct measurement of material originating
from the sun. For development, testing, and calibration of solar wind
particle instrumentation, particle beams of highly charged ions for all
elements from hydrogen up to iron are needed. Although sources for these
ions have been available for some time, the special demands of space
instrumentation made it necessary to build a dedicated facility. We
built an electron-cyclotron-resonance ion source operating at 2.45
GHz. The ion source is installed on a high voltage platform allowing
for postacceleration potentials of up to 100 kV. Ions are produced
from elements in gaseous and solid phase; the latter from vapor emitted
from a high temperature furnace closely attached to the ion source.
Title: Energetic neutral helium of heliospheric origin at 1 AU
Authors: Shaw, A.; Hsieh, K. C.; Hilchenbach, M.; Czechowski, A.;
Hovestadt, D.; Klecker, B.; Kallenbach, R.; Möbius, E.; Bochsler, P.
Bibcode: 2001ohnf.conf..219S
Altcode:
No abstract at ADS
Title: Isotopic Fractionation in Slow and Coronal Hole Associated
Solar Wind
Authors: Kucharek, H.; Klecker, B.; Ipavich, F. M.; Kallenbach, R.;
Grüwaldt, H.; Aellig, M. R.; Bochsler, P.
Bibcode: 2001IAUS..203..562K
Altcode:
Solar matter is a geochemical reference for the original composition of
the protosolar nebula from which the solar system formed. Therefore,
the Sun represents the least biased sample of interstellar matter and
the solar wind provides the most comprehensive source of information
about solar isotopic abundance. From in situ measurements of the solar
wind one obtains informations on the present-day isotopic composition
of the outer convective zone of the Sun. The flow dynamic of the solar
wind is determined by the magnetic topology of the flux tubes and is
different for slow and fast solar wind, respectively. The slow solar
wind originates from closed field line regions whereas the high speed
solar wind is emitted from open flux tubes in coronal holes. Data from
the Mass Time-of-Flight spectrometers MTOF and CTOF on board SOHO have
been accumulated for time periods in which coronal hole and non-coronal
hole type plasma has been detected by using different methods in order
to determine the abundance ratios of magnesium isotopes in these two
different source regions of the solar wind. The results as well as
limits will be discussed in the context of extisting theories.
Title: Solar Orbiter, a High-Resolution Mission to the Sun and
Inner Heliosphere
Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.;
Fleck, B.; Harrison, R.; Marsden, R.; Schwenn, R.; Vial, J. -C.
Bibcode: 2001IAUS..203..565M
Altcode:
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rodot and
out-of-ecliptic at the highest heliographic latitudes of 38 degrees. The
SO will achieve its many and varied aims with a suite of small and
innovative instruments through a clever choice of orbits. The first
near-Sun interplanetary measurements together with concurrent remote
observations of the Sun will permit us to determine and understand,
through correlative studies, the characteristics of the solar wind and
energetic particles in close linkage with the plasma and radiation
conditions in their source regions on the Sun. The SO will, during
the high-latitude orbital passes, provide the first observations of
the Sun's polar regions as seen from outside the ecliptic and also
measure the magnetic field at the poles.
Title: Energetic neutral hydrogen of heliospheric origin observed
with SOHO/CELIAS at 1 AU
Authors: Hilchenbach, M.; Hsieh, K. C.; Hovestadt, D.; Kallenbach,
R.; Czechowski, A.; Möbius, E.; Bochsler, P.
Bibcode: 2001ohnf.conf..273H
Altcode:
No abstract at ADS
Title: A non-solar origin of the "SEP" component in lunar soils
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.
Bibcode: 2001ohnf.conf..507W
Altcode:
No abstract at ADS
Title: On the variability of suprathermal pickup He+ at
1 AU (Oral papers and posters which were given at the conference,
but for which no manuscripts were submitted)
Authors: Klecker, B.; Bogdanov, A. T.; Hilchenbach, M.; Galvin, A. B.;
Möbius, E.; Ipavich, F. M.; Bochsler, P.
Bibcode: 2001ohnf.confQ.229K
Altcode:
No abstract at ADS
Title: Model for the mass fractionation in the January 6, 1997,
coronal mass ejection
Authors: Wurz, Peter; Bochsler, Peter; Lee, Martin A.
Bibcode: 2000JGR...10527239W
Altcode:
For the coronal mass ejection (CME) of January 6, 1997, strong element
fractionation of the heavy ions was observed at 1 AU with the Mass
Time-of-Flight (MTOF) sensor of the Charge, Element, and Isotope
Analysis System (CELIAS) on the Solar and Heliospheric Observatory
(SOHO). During the passage of the CME plasma and the passage of the
erupted filament, which followed the CME, a mass-dependent element
fractionation was found with an enhancement of heavy elements,
increasing monotonically with atomic mass. Si/O and Fe/O ratios
around 0.5 were observed, which corresponds to an increase of about
a factor of 4 compared to regular slow solar wind. We present a
theoretical model with which we can reproduce the observed element
fractionation. The model assumes hot coronal loops with non-Maxwellian
electron distributions as the precursor structure of the CME on the
solar surface. Diffusion perpendicular to the magnetic field results in
the preferential loss of lighter ions from the loop, leading to mass
fractionation. To quantitatively reproduce the fractionation process,
the loops must have existed for ~28 hours before they became part of
the CME plasma, a time that is commensurate with optical observations
of loops in the active region from which the CME was launched.
Title: Solar Wind Composition
Authors: Bochsler, P.
Bibcode: 2000eaa..bookE2303B
Altcode:
To first order the solar wind composition reflects the composition of
the source material, which is photospheric (SOLAR ABUNDANCES). However,
there are some important distinctions between the solar wind and solar
abundances which will be discussed in the following paragraphs. Since
solar wind particles feed the CORONA, and solar energetic particles
(SEPs; see SOLAR WIND: ENERGETIC PARTICLES) larg...
Title: First Detection of 4He in a Sample of Interstellar Neutral
Gas Collected Onboard Mir Station
Authors: Bühler, F.; Bassi, M. L.; Bochsler, P.; Eugster, O.;
Salerno, E.; Zastenker, G. N.; Agafonov, Yu. N.; Gevorkov, L. G.;
Eismont, N. A.; Prudkoglyad, A. V.; Khrapchenkov, V. V.; Shvets, N. I.
Bibcode: 2000Ap&SS.274...19B
Altcode:
For the first time, the method of collecting impinging atoms in
pretreated foil surfaces during exposure from a spacecraft allowed to
detect in the laboratory, after retrieval of the foils,4He
gas of interstellar origin in the expected concentration.
Title: Is there a record of interstellar pick-up ions in lunar soils?
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.
Bibcode: 2000AIPC..528..270W
Altcode: 2000atep.conf..270W
Solar wind noble gases and nitrogen implanted in the surface layers
of lunar grains have frequently been studied to infer the history
of the solar wind. In sub-surface layers, and thus presumably from
particles with higher energies than solar wind, a mysterious population,
dubbed ``SEP,'' accounts for most of the implanted gas. This ``SEP''
population is mysterious for at least four reasons: i) In the case
of neon it accounts for several tens of percent of the total amount
of implanted gas, completely disproportionate from what is expected
from solar wind particles; ii) its isotopic composition is distinct
from solar; iii) while the heavy neon isotopes are enriched relative to
20Ne, 15N is depleted relative to 14N,
signatures which are unexpected from known fractionation processes in
particle acceleration; iv) the elemental abundance of N with respect to
the noble gases (e.g., Ar) is inconsistent with solar abundances. Many
attempts to explain the origin and nature of this mysterious component
seem unsatisfactory. In this work, we propose that pick-up ions from
interstellar neutrals, accelerated in the heliosphere and subsequently
implanted into grains of the lunar regolith might account for the large
amount of non-solar ``SEPs.'' The solar system must have encountered
various dense interstellar clouds throughout its history. If this
scenario is correct, lunar soils serve as a ``travel diary'' for the
voyage of the solar system through the galaxy, preserving records of
the isotopic and elemental composition of dense interstellar clouds. .
Title: Determination of the abundance of aluminum in the solar wind
with SOHO/CELIAS/MTOF
Authors: Bochsler, Peter; Ipavich, Fred M.; Paquette, John A.; Weygand,
James M.; Wurz, Peter
Bibcode: 2000JGR...10512659B
Altcode:
The Al/Mg abundance ratio provides an excellent test case for
investigating possible fractionation processes among low First
Ionization Potential (FIP) elements in the solar wind. Al and Mg are
refractory elements; their abundance ratio has been well determined in
solar system materials and inferences for the abundance ratio in the
solar atmosphere are reliable. Al and Mg are at neighboring masses
and have similar charge state properties in the solar corona; hence
mass fractionation effects in the solar wind acceleration process and
instrumental mass fractionation are minimal. From first observations
during two relatively short periods, one recorded in coronal hole
associated solar wind, the other in typical interstream solar wind, it
is concluded that the solar wind ratio in both regimes is consistent
with the solar system ratio. The Al/Mg ratio in interstream solar
wind is 0.081+/-0.012, and in the sample of coronal hole associated
solar wind it amounts to 0.076+/-0.011. A comparison of these results
with the solar system ratio of 0.079+/-0.005 gives no indication for
fractionation occurring among low FIP elements in the solar wind.
Title: Oxygen freeze-in temperatures measured with SOHO/CELIAS/CTOF
Authors: Hefti, S.; Grünwaldt, H.; Bochsler, P.; Aellig, M. R.
Bibcode: 2000JGR...10510527H
Altcode:
We use the charge time-of-flight (CTOF) mass and charge spectrometer of
the charge, element, and isotope analysis system (CELIAS) on board the
Solar and Heliospheric Observatory (SOHO) to determine the solar wind
oxygen freeze-in temperature T76 from the O7+
and O6+ abundance ratios in the period from days 92 to 229
of 1996 (Carrington Rotations 1908 to 1912). The freeze-in temperature
is a conserved property of the solar wind because the charge states
do not change after a distance of a few solar radii. Therefore it
is an ideal in situ diagnostic for remote sensing of the inner solar
corona. We determine the mean freeze-in temperature during the selected
period to be 1.6×106K. We use it to map coronal regions
of different temperatures and to determine the separation between
such regions based on our observation of abrupt transitions of the
freeze-in temperature. We find a upper limit for the separation in
the inner corona of 1000 km.
Title: Solar Orbiter --- A High Resolution Mission to the Sun and
Inner Heliosphere
Authors: Fleck, B.; Marsch, E.; Schwenn, R.; Antonucci, E.; Bochsler,
P.; Bougeret, J. -L.; Harrison, R. A.; Marsden, R.; Vial, J. -C.
Bibcode: 2000SPD....31.0296F
Altcode: 2000BAAS...32..828F
The scientific rationale of the Solar Orbiter (SO) is to provide,
at high spatial and temporal resolution, observations of the solar
atmosphere and unexplored inner heliosphere. The most interesting and
novel observations will be made in the almost heliosynchronous segments
of the orbits at heliocentric distances near 45 Rsun and
out-of-ecliptic at heliographic latitudes of up to 38o. By
going to 45 Rsun the SO will allow remote sensing of the
solar atmosphere with unprecedented spatial resolution, and the almost
heliosynchronous orbit segments will permit us to disentangle spatial
and temporal variations in the solar wind in close linkage with the
plasma and radiation conditions in the source regions of the Sun. The
strawman payload encompasses two instrument packages: Heliospheric
Instruments --- high-res visible light telescope and magnetograph
(<40 km), high-res X-ray/EUV imager (<30 km), high-res EUV
spectrometer (<100 km), EUV and visible-light coronagraphs, solar
neutron and γ -ray detectors, radiometers. Heliospheric Instruments
--- solar wind analyzer, magnetometer, energetic particle detectors, IP
dust detector, plasma wave analyser, radio experiment, neutral particle
detector. Using solar electric propulsion (SEP) in conjunction with
multiple planet swing-by manoeuvres, it will take SO two years to reach
a perihelion of 45 Rsun at an orbital period of 149 days,
with an inclination ranging from 6.7o to 23.4o
w.r.t. the ecliptic. During an extended mission phase of about 2
years the inclination will increase to 31.7o, leading to
a maximum heliographic latitude of 38.3o. The SO was one
of the about 40 responses to the Call for Proposals for the next two
"flexi-missions" (F2 and F3) within ESA's Scientific Programme. At
its meeting on 1 March 2000, ESA's Space Science Advisory Committee
recommended the Solar Orbiter among 5 other proposals for an assessment
study. Launch is expected by the end of the decade.
Title: Enhanced solar wind ³He2+ associated with coronal
mass ejections
Authors: Ho, George C.; Hamilton, Douglas C.; Gloeckler, George;
Bochsler, Peter
Bibcode: 2000GeoRL..27..309H
Altcode:
Using data from the MASS high-resolution solar
wind spectrometer on the WIND spacecraft, six enhanced
³He2+/4He2+ periods were identified
from January 1995 to May 1998. The ratios observed in these events are
four to ten times higher than previously reported average solar wind
values. All enhanced ³He2+ periods were associated with the
passage of CME-ejecta. The observed time periods were either within but
towards the end of the CME-associated magnetic clouds or trailing the
magnetic cloud by about 24 hours. All the enhanced ³He2+
periods have a mixture of low (cold) iron charge states along with
high (hot) oxygen charge states. The unusual charge state composition
of these enhanced ³He2+ events suggests the plasma came
from a relatively cold and dense solar region, or from a rapidly
expanding plasma parcel in the corona. We suggest that the enhanced
³He2+ plasma originated from the prominence core embedded
within the CME.
Title: The relation of temporal variations of soft X-ray emission
from comet Hyakutake to variations of ion fluxes in the solar wind
Authors: Neugebauer, M.; Cravens, T. E.; Lisse, C. M.; Ipavich, F. M.;
Christian, D.; von Steiger, R.; Bochsler, P.; Shah, P. D.; Armstrong,
T. P.
Bibcode: 2000JGR...10520949N
Altcode:
Both the Röntgen X-Ray Satellite (ROSAT) and the Extreme Ultraviolet
Explorer (EUVE) have detected soft X-ray emission from comet
C/Hyakutake 1996 B2. This emission varied by a factor of about 2 over
a few hours and by a factor of 4 from day to day. One explanation for
the excitation of cometary X rays is the charge transfer mechanism
suggested by Cravens. This process involves charge exchange collisions
between highly charged heavy ions in the solar wind and neutral
gas in the cometary coma. Oxygen ion fluxes observed by the Charge,
Element, and Isotope Analysis System (CELIAS) Mass Time-of-Flight
(MTOF) instrument on the SOHO spacecraft and proton fluxes measured
by near-Earth spacecraft are mapped to the location of the comet to
demonstrate that the comet X-ray variability can be explained on the
basis of variability in the solar wind. There is a good correlation
between cometary X-ray emission and oxygen ion fluxes and a poorer
correlation with proton flux. The correlation between the solar wind
oxygen flux and cometary X rays degrades with increasing latitudinal
separation of SOHO from the comet. Cometary X-ray emission is not
sensitive to variations in solar X-ray fluxes and is unlikely to
be caused by crossing of the heliospheric current sheet. The charge
transfer mechanism appears to be supported by all the data examined to
date. Cometary X rays have some shortcomings as remote sensors of the
solar wind, however, because of variations in cometary gas production
rates and in the charge states and abundances of heavy solar wind ions.
Title: Abundances and charge states of particles in the solar wind
Authors: Bochsler, Peter
Bibcode: 2000RvGeo..38..247B
Altcode:
The Sun is the only star from which matter can be collected in order to
investigate its elemental and isotopic composition. Solar elemental
abundances provide the most important benchmark for the chemical
evolution of the galaxy. They can be derived from photospheric
observations, from in situ investigations of the solar wind, and
from solar energetic particles. Solar isotopic abundances provide an
important reference for the galactic evolution and if available with
sufficient precision, also for the chemical and physical evolution of
the solar system. The abundances of isotopes in the solar atmosphere can
only be inferred from in situ observations of solar particles. This
review makes an attempt to summarize current knowledge about the
composition of the solar wind and shows how the elemental, isotopic,
and charge state composition of solar wind particles is shaped as the
solar corona expands throughout the heliosphere.
Title: Influence of Coulomb collisions on isotopic and elemental
fractionation in the solar wind acceleration process
Authors: Bodmer, Roland; Bochsler, Peter
Bibcode: 2000JGR...105...47B
Altcode:
In view of new observational evidence from isotope spectrometers
on WIND, SOHO (Solar Heliospheric Observatory), and ACE (Advanced
Composition Explorer), we explore the efficiency of isotope
fractionation processes in the inner corona. We reinvestigate the
role of Coulomb collisions in the acceleration of minor ions using a
multifluid model. To model the main gas, we study stationary solutions
for the continuity and momentum equations of electrons, protons, and
alpha particles. As a closure of the system of equations, we prescribe
expansion geometry and temperature profiles based on observations. The
behavior of minor ions, which are treated as test particles, depends
in a complicated manner on their mass and on their charge, structured
by the interplay of acceleration, gravity, pressure gradient,
electromagnetic fields, Coulomb drag, and thermal diffusion. We
compare the fractionation effects in different solar wind regimes:
In our model high-speed solar wind emanating from polar coronal holes,
Coulomb friction practically equalizes the velocities of all species,
and no substantial fractionation takes place. In the case of a rapidly
expanding magnetic field geometry, for example, in the vicinity of
a coronal streamer, the proton flux and thus the Coulomb friction on
minor ions is reduced, leading to depletion of heavy species in the
solar wind. The model also predicts a substantial depletion of alpha
particles relative to protons in the heliospheric current sheet,
consistent with observations. In such a situation, heavy elements
are depleted in the solar wind relative to protons as well, but the
effect is strongest for alpha particles. Isotopic fractionation of
helium of the order of 30% is possible, while the isotope effect on
heavier elements amounts at most to a few percent per mass unit.
Title: The Fe/O elemental abundance ratio in the solar wind as
observed with SOHO CELIAS CTOF
Authors: Aellig, M. R.; Hefti, S.; Grünwaldt, H.; Bochsler, P.;
Wurz, P.; Ipavich, F. M.; Hovestadt, D.
Bibcode: 1999JGR...10424769A
Altcode:
Using data of the Charge Time-of-Flight (CTOF) mass spectrometer
of the Charge, Element, and Isotope Analysis System (CELIAS) on
board the Solar and Heliospheric Observatory (SOHO) from ~80 days
of observation around solar minimum we derive a value for the Fe/O
abundance ratio for the inecliptic solar wind of 0.11+/-0.03. Since Fe
has a low first ionization potential (FIP) and O is a high-FIP element,
their relative abundance is diagnostic for the FIP fractionation
process. The unprecedented time resolution of the CELIAS CTOF sensor
allows a fine-scaled study of the Fe/O ratio as a function of the
solar wind bulk speed. On average, the Fe/O abundance ratio shows
a continuous decrease by a factor of 2 with increasing solar wind
speed between 350 and 500 km/s. This corresponds to the well-known FIP
effect dependence. Our value at ~500 km/s agrees with the previously
observed Fe/O ratio in the fast solar wind emerging from polar coronal
holes whereas the value for speeds below 350 km/s is consistent with a
remote abundance determination in the leg of a coronal streamer. The
variability of the Fe/O abundance ratio is much larger in the slow
than in the fast solar wind.
Title: Determination Of The Argon Isotopic Ratio Of The Solar Wind
Using SOHO/CELIAS/MTOF
Authors: Weygand, J. M.; Ipavich, F. M.; Wurz, P.; Paquette, J. A.;
Bochsler, P.
Bibcode: 1999ESASP.446..701W
Altcode: 1999soho....8..701W
This study is about the first direct measurements of the 36Ar/38Ar
ratio in the solar wind with the MTOF sensor of CELIAS on the SOHO
spacecraft. Argon is highly volatile and a minor element in the solar
wind. Because of its volatility, inferences about the solar argon
isotopic composition from planetary samples are problematic. However,
it is possible to determine the solar isotopic composition quite
reliably from solar wind observations. Such determinations have been
made with the Apollo foil experiment predominantly for periods of slow
solar wind and a value consistent with the terrestrial atmospheric
36Ar/38Ar ratio of 5.32 had been found. CELIAS/MTOF has already been
successfully used to examine the isotopic ratios of elements such as
magnesium, neon, calcium, silicon, as well as nitrogen. Lunar soil
derived 36Ar/38Ar ratios lie somewhat above the terrestrial value,
however, they represent flux averages which are integrated over long
time periods and could be affected by fractionation effects during
implantation and storage. Direct measurements provide the possibility
to set limits to the variability of isotopic abundance ratios with
different solar wind regimes, and hence, to obtain a clue on the
importance of fractionation effects occuring in the solar wind. From
this study a preliminary 36Ar/38Ar abundance ratio of 5.5 +/- 1.1 which
is consistent with indirect observations. This value is derived from
approximately one day of slow solar wind. Furthermore, 20Ne/22Ne ratios
as well as 20Ne/36Ar ratios are monitored and are found to be similar
to published results. The result will be discussed in the context of
solar wind fractionation models and of experimental evidence derived
from in situ observations on refractory elements.
Title: Direct evidence of the interstellar gas flow velocity in the
pickup ion cut-off as observed with SOHO CELIAS CTOF
Authors: Möbius, E.; Litvinenko, Y.; Grüwaldt, H.; Aellig, M. R.;
Bogdanov, A.; Ipavich, F. M.; Bochsler, P.; Hilchenbach, M.; Judge,
D.; Klecker, B.; Lee, M. A.; Ogawa, H.
Bibcode: 1999GeoRL..26.3181M
Altcode:
He+ pickup ions as observed with SOHO CELIAS CTOF have
been analyzed for the time period DOY 160-190, 1996. During this time
of the year the Earth is on the upwind side of the interstellar gas
flow with respect to the sun. The high-speed cut-off in the frame of
the sun is significantly higher v/Vsw = 2, predicted for
pickup ions. The difference increases with lower solar wind speeds. This
behavior is interpreted as an effect of the local interstellar gas flow
velocity (inflow at large distances including gravitational acceleration
by the sun) on the pickup ion distribution. The neutral velocity is
added to the solar wind velocity in the determination of the pickup
ion cut-off on the upwind side and subtracted on the downwind side of
the gas flow. This new observation will provide a valuable tool to
determine the interstellar gas flow and will thus complement direct
neutral gas measurements.
Title: Magnesium Isotopic Abundance In Slow And Coronal Hole
Associated Solar Wind: SOHO/CELIAS/MTOF Measurements.
Authors: Kucharek, H.; Ipavich, F. M.; Kallenbach, R.; Klecker, B.;
Grünwaldt, H.; Aellig, M. R.; Bochsler, P.
Bibcode: 1999ESASP.446..395K
Altcode: 1999soho....8..395K
The solar wind provides the most comprehensive source of information
about solar isotopic abundance. The flow dynamic of the solar wind is
determined by the magnetic topology of the flux tubes. The slow solar
wind originating from closed field line regions, has a slow bulk
velocity and high freeze-in temperature, and the high speed solar
wind which has a low freeze-in temperature and originates from open
flux tubes in coronal holes. In situ solar wind measurements provide
therefore important informations on the present-day isotopic composition
of the outer convective zone of the Sun. Data from the high resolution
Mass Time-of-Flight spectrometer MTOF and the Charge Time-Of-Flight
spectrometer on board SOHO have been accumulated for time periods in
which coronal hole or non-coronal hole type plasma has been detected
in order to investigate the abundance ratios of magnesium isotopes
originating from these two different source regions of the solar wind
in the context of isotope fractionation.
Title: The Solar Origin of Corotating Interaction Regions and Their
Formation in the Inner Heliosphere
Authors: Balogh, A.; Bothmer, V.; Crooker, N. U.; Forsyth, R. J.;
Gloeckler, G.; Hewish, A.; Hilchenbach, M.; Kallenbach, R.; Klecker,
B.; Linker, J. A.; Lucek, E.; Mann, G.; Marsch, E.; Posner, A.;
Richardson, I. G.; Schmidt, J. M.; Scholer, M.; Wang, Y. -M.;
Wimmer-Schweingruber, R. F.; Aellig, M. R.; Bochsler, P.; Hefti, S.;
Mikić, Z.
Bibcode: 1999SSRv...89..141B
Altcode:
Corotating Interaction Regions (CIRs) form as a consequence of the
compression of the solar wind at the interface between fast speed
streams and slow streams. Dynamic interaction of solar wind streams
is a general feature of the heliospheric medium; when the sources of
the solar wind streams are relatively stable, the interaction regions
form a pattern which corotates with the Sun. The regions of origin
of the high speed solar wind streams have been clearly identified
as the coronal holes with their open magnetic field structures. The
origin of the slow speed solar wind is less clear; slow streams may
well originate from a range of coronal configurations adjacent to,
or above magnetically closed structures. This article addresses
the coronal origin of the stable pattern of solar wind streams
which leads to the formation of CIRs. In particular, coronal models
based on photospheric measurements are reviewed; we also examine
the observations of kinematic and compositional solar wind features
at 1 AU, their appearance in the stream interfaces (SIs) of CIRs,
and their relationship to the structure of the solar surface and the
inner corona; finally we summarise the Helios observations in the
inner heliosphere of CIRs and their precursors to give a link between
the optical observations on their solar origin and the in-situ plasma
observations at 1 AU after their formation. The most important question
that remains to be answered concerning the solar origin of CIRs is
related to the origin and morphology of the slow solar wind.
Title: Isotopes in the solar wind: New results from ACE, SOHO,
and WIND
Authors: Wimmer-Schweingruber, R. F.; Bochsler, P.; Wurz, P.
Bibcode: 1999AIPC..471..147W
Altcode: 1999sowi.conf..147W
Measuring the isotopic composition of the solar wind is interesting
because it provides unique information on the isotopic composition
of the solar atmosphere, the outer convective zone of the Sun, and
the bulk Sun. Comparing the solar isotopic composition with other
solar system samples can give clues about the early history of the
solar system. If compared with the present-day interstellar medium,
e.g., derived from interstellar pick-up ions in the interplanetary
medium or from the anomalous cosmic-ray component, the solar isotopic
composition yields valuable information on the galactic chemical
evolution during the last 4.6 Gy and on the radial migration of the
Sun within the galaxy. Solar isotopic abundances of volatile elements
(He, Ne) have been used to put constraints on the internal transport
of matter during the entire history of the Main-Sequence Sun and on
the evolution of planetary atmospheres. More recently, the isotopic
composition of refractory elements in different solar wind regimes has
been used to infer the importance of fractionation processes operating
between the radiative solar core, the outer convective zone, and
the solar atmosphere, as well as between the solar atmosphere and the
interplanetary plasma. The analysis of the isotopes of Mg, Si, and Ca as
observed with the WIND/SMS, the SOHO/CELIAS, and the ACE/SWIMS isotope
spectrometers indicate that the variability of isotopic abundance ratios
in different solar wind regimes amounts to less than a few percent per
mass unit, and that the overall isotopic composition of refractories in
the solar wind is within the uncertainties identical to the terrestrial,
lunar, and meteoritic composition. From observational evidence and from
theoretical models on minor ion heating and acceleration in the corona
it seems clear that coronal hole high speed streams provide the most
authentic samples of the isotopic composition of the solar photosphere.
Title: The Fe/O elemental abundance ratio in the solar wind
Authors: Aellig, M. R.; Holweger, H.; Bochsler, P.; Wurz, P.;
Grünwaldt, H.; Hefti, S.; Ipavich, F. M.; Klecker, B.
Bibcode: 1999AIPC..471..255A
Altcode: 1999sowi.conf..255A
We analyze the Fe/O elemental abundance ratio in the solar wind from
SOHO/CELIAS/CTOF data. Analyzed in different solar wind regimes this
ratio is indicative of the strength of the FIP fractionation process
because iron is a low FIP element and oxygen is a high FIP element. It
is investigated whether there is a significant fractionation of the
Fe/O ratio in the coronal hole solar wind. For the first time, to our
knowledge, we attempt to eliminate the influence of model-dependent
parameters on the derivation of the photospheric Fe/O ratio thereby
increasing the accuracy of its determination. The Fe/O ratio in coronal
hole solar wind is slightly higher than in the photosphere. Even with
our optimistic estimates of the uncertainties of the photospheric Fe/O
ratio the observed fractionation is only marginally significant.
Title: The Solar Origin of Corotating Interaction Regions and their
Formation in the Inner Heliosphere
Authors: Balogh, A.; Bothmer, V.; Crooker, N. U.; Forsyth, R. J.;
Gloeckler, G.; Hewish, A.; Hilchenbach, M.; Kallenbach, R.; Klecker,
B.; Linker, J. A.; Lucek, E.; Mann, G.; Marsch, E.; Posner, A.;
Richardson, I. G.; Schmidt, J. M.; Scholer, M.; Wang, Y. -M.;
Wimmer-Schweingruber, R. F.; Aellig, M. R.; Bochsler, P.; Hefti, S.;
Mikić, Z.
Bibcode: 1999cir..book..141B
Altcode:
No abstract at ADS
Title: Working Group 4 Report: Composition and Elemental Abundance
Variations in the Solar Atmosphere and Solar Wind
Authors: Mason, Helen E.; Bochsler, Peter
Bibcode: 1999SSRv...87..105M
Altcode:
This paper contains a summary of the topics treated in the working
group on abundance variations in the solar atmosphere and in the solar
wind. The FIP bias (overabundance of particles with low First Ionization
Potentials over photospheric abundances) in coronal holes and coronal
hole associated solar wind amounts to values between 1 and 2. The FIP
bias in the slow solar wind is typically a factor 4, consistent with
optical observations in streamers. In order to distinguish between
different theoretical models which make an attempt to explain the FIP
bias, some observable parameters must be provided. Unfortunately,
many models are deficient in this respect. In addition to FIP
fractionation, gravitational settling of heavy elements has been
found in the core of long lived streamers. The so-called electron
'freeze in' temperatures derived from in situ observed ionization
states of minor ions in the fast wind are significantly higher than
the electron temperatures derived from diagnostic line ratios observed
in polar coronal holes. The distinction between conditions in plumes
and interplume lanes needs to be further investigated. The 'freeze in'
temperatures for the slow solar wind are consistent with the electron
temperatures derived for streamers.
Title: Unusual composition of the solar wind in the 2-3 May 1998
CME observed with SWICS on ACE
Authors: Gloeckler, G.; Fisk, L. A.; Hefti, S.; Schwadron,
N. A.; Zurbuchen, T. H.; Ipavich, F. M.; Geiss, J.; Bochsler, P.;
Wimmer-Schweingruber, R. F.
Bibcode: 1999GeoRL..26..157G
Altcode:
Elemental, isotopic and charge state abundances provide valuable
information about the source and acceleration mechanism of Coronal Mass
Ejections (CMEs). Even though the kinetic properties of the plasma
might be subject to changes because of dynamic effects occurring
during the expansion of the CME, the composition of the solar wind
remains unchanged after it leaves the low corona. Data from the
Solar Wind Ion Composition Spectrometer (SWICS) on ACE are used to
study the elemental and charge state composition of He, O, C, N, and
Fe as well as the isotopic ratio of He during the very large CME of
May 2-3, 1998. We find in this CME anomalously large enrichment of
³He++/4He++, He/O and Fe/O. During
the 28 hour long cloud portion of the CME unusually cold material
(4He+ and very low charge state heavy ions)
was observed together with hot (high charge state ions) and normal
solar wind plasma.
Title: On the bulk isotopic composition of magnesium and silicon
during the May 1998 CME: ACE/SWIMS
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter; Gloeckler,
George; Ipavich, Fred M.; Geiss, Johannes; Kallenbach, Reinald; Fisk,
Len A.; Hefti, Simon; Zurbuchen, Thomas H.
Bibcode: 1999GeoRL..26..165W
Altcode:
The coronal mass ejection (CME) observed at the Advanced Composition
Explorer (ACE) spacecraft on May 2 and 3, 1998, exhibited very high
as well as exceptionally low charge states of all ions. In addition,
³He was considerably enhanced by in the bulk material of the CME. High
³He/4He ratios in solar energetic particles have recently
been observed in some events to coincide with substantial enrichments
in the heavy isotopes of heavy elements. We use data from the Solar
Wind Ion Mass Spectrometer (SWIMS) on ACE to investigate whether
the enrichment of the heavy isotopes in solar energetic particles
is mirrored in the isotopic composition of solar wind Mg and Si. We
concentrate on the time period where the unusual mixture of charge
states and unusually high ³He/4He was observed to test for
isotopic fractionation in such extreme solar wind conditions. We find
very little or no enrichment of the neutron-rich isotopes with respect
to the main isotopes. Incidentally, this is also the first report on
the isotopic composition of ions with Z > 2 in the bulk material
in a CME.
Title: Kinetic properties of solar wind minor ions and protons
measured with SOHO/CELIAS
Authors: Hefti, S.; Grünwaldt, H.; Ipavich, F. M.; Bochsler, P.;
Hovestadt, D.; Aellig, M. R.; Hilchenbach, M.; Kallenbach, R.; Galvin,
A. B.; Geiss, J.; Gliem, F.; Gloeckler, G.; Klecker, B.; Marsch, E.;
Möbius, E.; Neugebauer, M.; Wurz, P.
Bibcode: 1998JGR...10329697H
Altcode:
Using observations of the Charge Time-of-Flight (CTOF) charge
and mass spectrometer of the Charge, Element and Isotope Analysis
System (CELIAS), and of CELIAS/proton monitor on board the Solar and
Heliospheric Observatory (SOHO), we present an overview of speeds
and kinetic temperatures of minor ions and protons in the solar wind
near solar minimum, covering the Carrington Rotations 1908 to 1912. In
the case of a collision-dominated solar wind the speed of minor ions
is expected to be lower or equal to the speed of the protons, and
all species are expected to have equal temperatures. On the other
hand, minor ions can be accelerated and heated by wave-particle
interaction. In this case, equal thermal speeds of all species are
expected. CTOF data allow the determination of the kinetic parameters of
various ions with high accuracy and with high time resolution. The mean
O6+ speed of the observed period is 390 kms-1. The
speeds of Si7+ and Fe9+ correlate well with
O6+, the linear correlation coefficient being 0.96 or
higher. Our results also indicate that silicon and iron tend to lag
behind oxygen with a speed difference of ~20 kms-1 at 500
kms-1. At the same time, the kinetic temperature of the
ions under investigation exhibit the well-known mass proportionality,
which is attributed to wave-particle interactions. During the period
of low solar activity in consideration, many cases are observed where
the kinetic temperature is extraordinarily low (104K for
O6+).
Title: Magnesium isotopic composition as observed with the CELIAS/MTOF
experiment on the SOHO spacecraft
Authors: Kucharek, H.; Ipavich, F. M.; Kallenbach, R.; Bochsler,
P.; Hovestadt, D.; Grünwaldt, H.; Hilchenbach, M.; Axford, W. I.;
Balsiger, H.; Bürgi, A.; Coplan, M. A.; Galvin, A. B.; Geiss, J.;
Gliem, F.; Gloeckler, G.; Hsieh, K. C.; Judge, D. J.; Klecker, B.;
Lee, M. A.; Livi, S.; Managadze, G. G.; Marsch, E.; Möbius, E.;
Neugebauer, M.; Ogawa, H. S.; Reiche, K. -U.; Scholer, M.; Verigin,
M. I.; Wilken, B.; Wurz, P.
Bibcode: 1998JGR...10326805K
Altcode:
Solar wind abundance ratios of magnesium isotopes measured with the
high resolution Mass Time-of-Flight spectrometer (MTOF) of the Charge,
Element, and Isotope Analysis System (CELIAS) experiment on board
the Solar and Heliospheric Observatory (SOHO) are presented. MTOF,
as part of CELIAS, is, because of its high time and mass resolution,
an excellent tool for isotope abundance measurements in the
solar wind. From the data analysis we have found that the isotopic
composition of magnesium in the solar wind agrees with the terrestrial
composition within the experimental uncertainty. We have obtained
isotopic ratios of 24Mg/25Mg=7.7+/-0.4
and 24Mg/26Mg=7.0+/-0.5. These
values are consistent with the terrestrial values
of 24Mg/25Mg=7.90+/-0.01 and
24Mg/26Mg=7.17+/-0.03. Furthermore, these
investigations also show that with the given uncertainties the abundance
ratios do not vary significantly within a solar wind velocity range
from 375 km/s to 530 km/s.
Title: Isotopic Composition of Solar Wind Nitrogen: First In Situ
Determination with the CELIAS/MTOF Spectrometer on board SOHO
Authors: Kallenbach, R.; Geiss, J.; Ipavich, F. M.; Gloeckler, G.;
Bochsler, P.; Gliem, F.; Hefti, S.; Hilchenbach, M.; Hovestadt, D.
Bibcode: 1998ApJ...507L.185K
Altcode:
Using the high-resolution Mass Time-of-Flight (MTOF) spectrometer of
the Charge, Element, and Isotope Analysis System (CELIAS) experiment on
board the Solar and Heliospheric Observatory (SOHO), we have determined
the solar wind isotope abundance ratio 14N/15N
= 200+/-55 (1 σ error), suggesting that the relative abundance of
15N in the terrestrial atmosphere is lower than in solar
matter. This result is compatible with the hypothesis that terrestrial
N (14N/15N = 272) and also N found in lunar
surface material are a mixture of a heavy component that is identical
to solar N and an unspecified light component. The large variations
of 14N/15N in solar system matter is caused by
special isotope enrichment processes, as in the case of Mars, as well
as by varying contributions of isotopically different components.
Title: The helium isotopic ratio in the solar wind and ion
fractionation in the corona by inefficient Coulomb drag
Authors: Bodmer, Roland; Bochsler, Peter
Bibcode: 1998A&A...337..921B
Altcode:
Using data obtained between 1991 and 1996 with the SWICS instrument
(Solar Wind Ion Composition Spectrometer) aboard the Ulysses spacecraft,
a long time average of the ((4) He / (3) He ) isotopic ratio of 2450
+/- 460 in coronal hole dominated solar wind is derived. To assess the
influence of inefficient Coulomb friction in the inner corona and to
infer the solar photospheric abundance ratio from the solar wind flux
ratio, the variation of the fluxes with different solar wind regimes
is investigated and limits for the long time fractionation effects
are given. Finally a present-day (4) He / (3) He abundance ratio in
the outer convective zone of ((4) He / (3) He)_OCZ = 2670 +/- 500)
is derived.
Title: First determination of the silicon isotopic composition of
the solar wind: WIND/MASS results
Authors: Wimmer-Schweingruber, Robert F.; Bochsler, Peter; Kern,
Olivier; Gloeckler, George; Hamilton, Douglas C.
Bibcode: 1998JGR...10320621W
Altcode:
Silicon is a common material in the solar system. For instance,
Si accounts for about 10% of the material in primitive meteorites
(CI chondrites). Since silicon is a refractory element, we expect
the meteoritic isotopic composition to be very similar to that of
the Sun. The isotopic composition of Si in meteorites is well known
and varies little. Thus the three stable isotopes of Si may serve as
powerful indicators to test fractionation of isotopes in the transition
from the solar atmosphere into the solar wind. We present, for the
first time, measurements of the isotopic composition of Si in the solar
wind. The data were obtained with the MASS instrument aboard the WIND
spacecraft and accumulated in exceedingly cold and slow wind. Such
wind is often associated with large superradial expansion factors and
with current sheet crossings which in turn are associated with the
most efficient isotopic fractionation processes in the solar wind
acceleration region. We detect little or no isotopic fractionation
between the solar surface assumed to be of meteoritic composition
and the solar wind. This constrains solar wind acceleration models
and puts stringent limits on possible secular changes in the isotopic
composition of the outer solar convective zone, the solar atmosphere,
and the solar wind.
Title: Detection of 55-80 keV Hydrogen Atoms of Heliospheric Origin
by CELIAS/HSTOF on SOHO
Authors: Hilchenbach, M.; Hsieh, K. C.; Hovestadt, D.; Klecker, B.;
Grünwaldt, H.; Bochsler, P.; Ipavich, F. M.; Bürgi, A.; Möbius,
E.; Gliem, F.; Axford, W. I.; Balsiger, H.; Bornemann, W.; Coplan,
M. A.; Galvin, A. B.; Geiss, J.; Gloeckler, G.; Hefti, S.; Judge,
D. L.; Kallenbach, R.; Laeverenz, P.; Lee, M. A.; Livi, S.; Managadze,
G. G.; Marsch, E.; Neugebauer, M.; Ogawa, H. S.; Reiche, K. -U.;
Scholer, M.; Verigin, M. I.; Wilken, B.; Wurz, P.
Bibcode: 1998ApJ...503..916H
Altcode:
The High-Energy Suprathermal Time-of-Flight sensor (HSTOF) of the
Charge, Element, and Isotope Analysis System (CELIAS) on the Solar
and Heliospheric Observatory (SOHO) near the Lagrangian point L1 is
capable of identifying energetic hydrogen atoms (EHAs) between 55 and 80
keV. Between 1996 February 13 and 1997 August 31, near solar minimum,
there were 285 ``quiet'' days when the interplanetary charged-particle
flux was low. During these quiet times, HSTOF scanned the apex of
the heliosphere once and the antiapex twice. The flux level and time
profile, and hence the arrival direction, of the EHAs accumulated during
these quiet times are best interpreted as fluxes of EHAs coming from
the heliosheath.
Title: Iron freeze-in temperatures measured by SOHO/CELIAS/CTOF
Authors: Aellig, M. R.; Grünwaldt, H.; Bochsler, P.; Wurz, P.;
Hefti, S.; Kallenbach, R.; Ipavich, F. M.; Axford, W. I.; Balsiger,
H.; Bürgi, A.; Coplan, M. A.; Galvin, A. B.; Geiss, J.; Gliem, F.;
Gloeckler, G.; Hilchenbach, M.; Hovestadt, D.; Hsieh, K. C.; Klecker,
B.; Lee, M. A.; Livi, S.; Managadze, G. G.; Marsch, E.; Möbius, E.;
Neugebauer, M.; Reiche, K. -U.; Scholer, M.; Verigin, M. I.; Wilken, B.
Bibcode: 1998JGR...10317215A
Altcode:
The CELIAS particle experiment on SOHO contains the Charge Time
Of Flight (CTOF) mass spectrometer which measures the ionic and
elemental composition of minor ions in the solar wind. In this paper
we present iron freeze-in temperatures derived with a time resolution
of 5 min. They indicate that some of the filamentary structures of the
inner corona observed in Hα survive in the interplanetary medium as
far as 1 AU.
Title: Solar wind measurements with SOHO: The CELIAS/MTOF proton
monitor
Authors: Ipavich, F. M.; Galvin, A. B.; Lasley, S. E.; Paquette, J. A.;
Hefti, S.; Reiche, K. -U.; Coplan, M. A.; Gloeckler, G.; Bochsler,
P.; Hovestadt, D.; Grünwaldt, H.; Hilchenbach, M.; Gliem, F.; Axford,
W. I.; Balsiger, H.; Bürgi, A.; Geiss, J.; Hsieh, K. C.; Kallenbach,
R.; Klecker, B.; Lee, M. A.; Managadze, G. G.; Marsch, E.; Möbius,
E.; Neugebauer, M.; Scholer, M.; Verigin, M. I.; Wilken, B.; Wurz, P.
Bibcode: 1998JGR...10317205I
Altcode:
The proton monitor, a small subsensor in the Charge, Element, and
Isotope Analysis System/Mass Time-of-Flight (CELIAS/MTOF) experiment
on the SOHO spacecraft, was designed to assist in the interpretation
of measurements from the high mass resolution main MTOF sensor. In
this paper we demonstrate that the proton monitor data may be used to
generate reasonably accurate values of the solar wind proton bulk speed,
density, thermal speed, and north/south flow direction. Correlation
coefficients based on comparison with the solar wind measurements from
the SWE instrument on the Wind spacecraft range from 0.87 to 0.99. On
the basis of the initial 12 months of observations, we find that the
proton momentum flux is almost invariant with respect to the bulk speed,
confirming a previously published result. We present observations of
two interplanetary shock events, and of an unusual solar wind density
depletion. This large density depletion, and the correspondingly
large drop in the solar wind ram pressure, may have been the cause
of a nearly simultaneous large increase in the flux of relativistic
magnetospheric electrons observed at geosynchronous altitudes by the
GOES 9 spacecraft. Extending our data set with a 10-year time span from
the OMNIWeb data set, we find an average frequency of about one large
density depletion per year. The origin of these events is unclear;
of the 10 events identified, 3 appear to be corotating and at least
2 are probably CME related. The rapidly available, comprehensive data
coverage from SOHO allows the production of near-real time solar wind
parameters that are now accessible on the World Wide Web.
Title: Investigation of the composition of solar and interstellar
matter using solar wind and pickup ion measurements with SWICS and
SWIMS on the ACE spacecraft
Authors: Gloeckler, G.; Cain, J.; Ipavich, F. M.; Tums, E. O.;
Bedini, P.; Fisk, L. A.; Zurbuchen, T. H.; Bochsler, P.; Fischer,
J.; Wimmer-Schweingruber, R. F.; Geiss, J.; Kallenbach, R.
Bibcode: 1998SSRv...86..497G
Altcode:
The Solar Wind Ion Composition Spectrometer (SWICS) and the Solar
Wind Ions Mass Spectrometer (SWIMS) on ACE are instruments optimized
for measurements of the chemical and isotopic composition of solar
and interstellar matter. SWICS determines uniquely the chemical and
ionic-charge composition of the solar wind, the thermal and mean speeds
of all major solar wind ions from H through Fe at all solar wind speeds
above 300 km s-1 (protons) and 170 km s-1 (Fe+16), and resolves H and
He isotopes of both solar and interstellar sources. SWICS will measure
the distribution functions of both the interstellar cloud and dust
cloud pickup ions up to energies of 100 keV e-1. SWIMS will measure
the chemical, isotopic and charge state composition of the solar wind
for every element between He and Ni. Each of the two instruments uses
electrostatic analysis followed by a time-of-flight and, as required, an
energy measurement. The observations made with SWICS and SWIMS will make
valuable contributions to the ISTP objectives by providing information
regarding the composition and energy distribution of matter entering the
magnetosphere. In addition, SWICS and SWIMS results will have an impact
on many areas of solar and heliospheric physics, in particular providing
important and unique information on: (i) conditions and processes in
the region of the corona where the solar wind is accelerated; (ii) the
location of the source regions of the solar wind in the corona; (iii)
coronal heating processes; (iv) the extent and causes of variations
in the composition of the solar atmosphere; (v) plasma processes in
the solar wind; (vi) the acceleration of particles in the solar wind;
(vii) the physics of the pickup process of interstellar He in the
solar wind; and (viii) the spatial distribution and characteristics
of sources of neutral matter in the inner heliosphere.
Title: Elemental composition of the January 6, 1997, CME
Authors: Wurz, P.; Ipavich, F. M.; Galvin, A. B.; Bochsler, P.; Aellig,
M. R.; Kallenbach, R.; Hovestadt, D.; Grünwaldt, H.; Hilchenbach,
M.; Axford, W. I.; Balsiger, H.; Bürgi, A.; Coplan, M. A.; Geiss,
J.; Gliem, F.; Gloeckler, G.; Hefti, S.; Hsieh, K. C.; Klecker, B.;
Lee, M. A.; Managadze, G. G.; Marsch, E.; Möbius, E.; Neugebauer,
M.; Reiche, K. -U.; Scholer, M.; Verigin, M. I.; Wilken, B.
Bibcode: 1998GeoRL..25.2557W
Altcode:
Using solar wind particle data from the CELIAS/MTOF sensor on the SOHO
mission, we studied the abundance of the elements O, Ne, Mg, Si, S,
Ca, and Fe for the time period around the January 6, 1997, coronal mass
ejection event (CME). In the interstream and coronal hole regions before
and after this event we found elemental abundances consistent with the
expected abundance patterns of the respective flow regimes. However,
during the passage of the CME and during the passage of the erupted
filament, which followed the CME, we found that the elemental
composition differed markedly from the interstream and coronal hole
regions before and after this event. During the passage of the CME and
the passage of the erupted filament we found a mass-dependent element
fractionation, with a monotonic increase toward heavier elements. We
observed Si/O and Fe/O abundance ratios of about one half during these
time periods, which is significantly higher than for typical solar wind.
Title: Structure of the Solar Wind and Compositional Variations
Authors: Bochsler, P.
Bibcode: 1998SSRv...85..291B
Altcode:
The composition of the solar wind is largely determined by the
composition of the source material, i.e. the present-day composition
of the outer convective zone. It is then modified by the processes
which operate in the transition region and in the inner corona. In situ
measurements of the solar wind composition give a unique opportunity
to obtain information on the isotopic and elemental composition of
the Sun. However, elemental — and to some degree also isotopic
— fractionation can occur in the flow of matter from the outer
convective zone into the interplanetary space. The most important
examples of elemental fractionation are the well-known FIP/FIT
effect (First Ionization Potential/Time) and the sometimes dramatic
variations of the helium abundance relative to hydrogen in the solar
wind. A thorough investigation of fractionation processes which cause
compositional variations in different solar wind regimes is necessary
to make inferences about the solar source composition from solar
wind observations. Our understanding of these processes is presently
improving thanks to the detailed diagnostics offered by the optical
instrumentation on SOHO. Correlated observations of particle instruments
on Ulysses, WIND, and SOHO, together with optical observations will
help to make inferences for the solar composition. Continuous in
situ observations of several isotopic species with the particle
instruments on WIND and SOHO are currently incorporated into an
experimental database to infer isotopic fractionation processes which
operate in different solar wind regimes between the solar surface and
the interplanetary medium. Except for the relatively minor effects of
secular gravitational sedimentation which works at the boundary between
the outer convective zone and the radiative zone, refractory elements
such as Mg can be used as faithful witnesses to monitor the magnitude
of these processes. With theoretical considerations it is possible to
make inferences about the importance of isotopic fractionation in the
solar wind from a comparison of optical and in situ observations of
elemental fractionation with the corresponding models. Theoretical
models and preliminary results from particle observations indicate
that the combined isotope effects do not exceed a few percent per mass
unit. In the worst case, which concerns the astrophysically important
3He/4He ratio, we expect an overall effect of at most several percent
in the sense of a systematic depletion of the heavier isotope. Continued
observations with WIND, SOHO, and ACE, and, with the revival of the foil
technique, with the upcoming Genesis mission will further consolidate
our knowledge about the relation between solar wind dynamics and solar
wind composition.
Title: Fractionation of SI, NE, and MG Isotopes in the Solar Wind
as Measured by Soho/Celias/MTOF
Authors: Kallenbach, R.; Ipavich, F. M.; Kucharek, H.; Bochsler, P.;
Galvin, A. B.; Geiss, J.; Gliem, F.; Gloeckler, G.; Grünwaldt, H.;
Hefti, S.; Hilchenbach, M.; Hovestadt, D.
Bibcode: 1998SSRv...85..357K
Altcode:
Using the high-resolution mass spectrometer CELIAS/MTOF on board SOHO
we have measured the solar wind isotope abundance ratios of Si, Ne,
and Mg and their variations in different solar wind regimes with
bulk velocities ranging from 330 km/s to 650 km/s. Data indicate
a small systematic depletion of the heavier isotopes in the slow
solar wind on the order of (1.4±1.3)% per amu (2σ-error) compared
to their abundances in the fast solar wind from coronal holes. These
variations in the solar wind isotopic composition represent a pure
mass-dependent effect because the different isotopes of an element
pass the inner corona with the same charge state distribution. The
influence of particle mass on the acceleration of minor solar wind
ions is discussed in the context of theoretical models and recent
optical observations with other SOHO instruments.
Title: Isotopic Composition of Solar Wind Calcium: First in Situ
Measurement by CELIAS/MTOF on Board SOHO
Authors: Kallenbach, R.; Ipavich, F. M.; Bochsler, P.; Hefti, S.; Wurz,
P.; Aellig, M. R.; Galvin, A. B.; Geiss, J.; Gliem, F.; Gloeckler,
G.; Grünwaldt, H.; Hilchenbach, M.; Hovestadt, D.; Klecker, B.
Bibcode: 1998ApJ...498L..75K
Altcode: 1998astro.ph..2090K
We present the first results of the Ca isotopic abundances derived
from the high-resolution Mass Time-of-Flight (MTOF) spectrometer of
the Charge, Element, and Isotope Analysis System (CELIAS) experiment
on board the Solar and Heliospheric Observatory (SOHO). We obtain
the isotopic ratios 40Ca/42Ca =128+/-47 and
40Ca/44Ca =50+/-8, consistent with terrestrial
values. This is the first in situ determination of the solar wind
calcium isotopic composition and is important for studies of stellar
modeling and solar system formation since the present-day solar
Ca isotopic abundances are unchanged from their original isotopic
composition in the solar nebula.
Title: Energetic Hydrogen Atoms from beyond the Termination of the
Solar Wind as Observed by SOHO/CELIAS
Authors: Hsieh, K. C.; Hilchenbach, M.; Shaw, A. W.; Hovestadt, D.;
Klecker, B.; Gruenwaldt, H.; Ipavich, F. M.; Bochsler, P.
Bibcode: 1998APS..APR..M708H
Altcode:
The detection of energetic hydrogen atoms (EHAs) between 55 and 80 keV
by the time-of-flight mass spectrometer HSTOF of the CELIAS experiment
on SOHO near the Lagrangian point L1 has been reported. The EHA flux
observed under quiet solar and interplanetary conditions is anisotropic
and peaked in the anti-apex direction of the heliosphere. This
observation is consistent with models of energetic neutral atom (ENA)
production from the anomalous cosmic-ray (ACR) protons transcharging
on the neutral atoms of the local interstellar medium. An attempt is
made to extend the observation beyond 80 keV to have a better view of
the EHA energy spectrum. The detection of heliospheric ENAs can provide
an independent means to study solar modulation and shock acceleration
of charged particles in and out of the heliosphere.
Title: Fractionation of Si, Ne, and Mg Isotopes in the Solar Wind
as Measured by SOHO/CELIAS/MTOF
Authors: Kallenbach, R.; Ipavich, F. M.; Kucharek, H.; Bochsler, P.;
Galvin, A. B.; Geiss, J.; Gliem, F.; Gloeckler, G.; Grünwaldt, H.;
Hefti, S.; Hilchenbach, M.; Hovestadt, D.
Bibcode: 1998sce..conf..357K
Altcode:
No abstract at ADS
Title: Surface Ionization with Cesiated Converters for Space
Applications
Authors: Aellig, M. R.; Wurz, P.; Schletti, R.; Bochsler, P.;
Ghielmetti, A. G.; Shelley, E. G.; Fuselier, S. A.; Quinn, J. M.;
Herrero, F.; Smith, M. F.
Bibcode: 1998GMS...103..289A
Altcode: 1998mtsf.conf..289A
Neutral particle imaging can be used for remote sensing of
magnetospheric plasmas. Due to the low fluxes of neutral particles
and the very transient nature of many phenomena in such environments,
a highly sensitive detection method is required. Neutral particles
in the energy range between 10eV and 1keV have not previously been
accessible to a mass, energy and angle analysis. Surface ionization, a
well-established laboratory technique, can efficiently convert neutral
particles in this energy range into negative ions to be analyzed with
mass spectrographs. This article describes surface ionization with low
work function surfaces as a method and discusses its applicability in
spaceborne instrumentation.
Title: Imaging Low-Energy (keV) Neutral Atoms: Ion-Optical Design
Authors: Smith, Ark F.; Chornay, D. J.; Keller, J. W.; Herrero, F. A.;
Aellig, M. R.; Bochsler, P.; Wurz, P.
Bibcode: 1998GMS...103..263S
Altcode: 1998mtsf.conf..263S
Neutral atom imaging allows plasma populations to be remotely sensed
enabling instantaneous images of Earth's magnetosphere and ionosphere to
be obtained. The technique has been widely discussed, particularly the
imaging of high energy neutrals. Much of the magnetosphere/ionosphere
plasma population, however, lies at energies below 1 keV. The most
promising development for neutral atom imaging at these low energies is
the surface interaction technique, which uses a conversion surface to
change the neutral atoms into negative ions. In this paper we discuss
the design of such an instrument. We focus on the ion optics required
to make such an instrument work and present new laboratory results
achieved with a novel ion optic system.
Title: Isochronous Mass Spectrometer for Space Plasma Applications
Authors: Wurz, P.; Gubler, L.; Bochsler, P.; Möbius, E.
Bibcode: 1998GMS...102..229W
Altcode: 1998mtsp.conf..229W
We have developed a new isochronous mass spectrometer and achieved
high geometric factor and high mass resolving power, significantly
exceeding the capabilities of isochronous spectrometers currently
in use for the analysis of space plasmas. Ions with energies up to
about 60keV can be detected. In combination with an electrostatic
energy analyzer, the instrument will be used for measurements of the
elemental, isotopic, and molecular composition of space plasmas. The
instrument is of cylindrical geometry, therefore 3-dimensional velocity
distributions of ions can be measured from a spinning spacecraft. We
compare the performance of our instrument with those isochronous mass
spectrometers currently in use on the WIND and SOHO spacecrafts.
Title: Structure of the Solar Wind and Compositional Variations
Authors: Bochsler, P.
Bibcode: 1998sce..conf..291B
Altcode:
No abstract at ADS
Title: Scientific Achievements of SOHO: In-situ Solar Wind
Authors: Bochsler, P.
Bibcode: 1998ESASP.417...35B
Altcode: 1998cesh.conf...35B
No abstract at ADS
Title: Oxygen 16 to oxygen 18 abundance ratio in the solar wind
observed by Wind/MASS
Authors: Collier, Michael R.; Hamilton, D. C.; Gloeckler, G.; Ho,
G.; Bochsler, P.; Bodmer, R.; Sheldon, R.
Bibcode: 1998JGR...103....7C
Altcode:
Measurements of the 16O and 18O distribution
functions in the solar wind at low to average solar wind speeds
from the MASS instrument on the Wind spacecraft are reported. The
16O/18O density ratio is 450+/-130, a value
consistent with terrestrial, solar photospheric, solar energetic
particle, and galactic cosmic ray 16O/18O isotopic
ratios. This study constitutes the first reported spacecraft measurement
of the isotope 18O in the core solar wind and may represent
the best determination of the solar 16O/18O
density ratio to date.
Title: Rosetta orbiter spectrometer for ion and neutral
analysis-rosina
Authors: Balsiger, H.; Altwegg, K.; Arijs, E.; Bertaux, J. -L.;
Berthelier, J. -J.; Bochsler, P.; Carignan, G. R.; Eberhardt, P.;
Fisk, L. A.; Fuselier, S. A.; Ghielmetti, A. G.; Gliem, F.; Gombosi,
T. I.; Kopp, E.; Korth, A.; Livi, S.; Mazelle, C.; Rème, H.; Sauvaud,
J. A.; Shelley, E. G.; Waite, J. H.; Wilken, B.; Woch, J.; Wollnik,
H.; Wurz, P.; Young, D. T.
Bibcode: 1998AdSpR..21.1527B
Altcode:
The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA)
will answer outstanding questions concerning the main objectives of
the mission. To accomplish the very demanding objectives, ROSINA will
have unprecedented capabilities, including: very wide mass range from
1 amu to >300 amu; very high mass resolution (ability to resolve
CO from N_2 and ^13C from ^12CH); very wide dynamic range and high
sensitivity; the ability to determine cometary gas and ion flow
velocities and temperatures.
Title: Ion Composition and Upstream Solar Wind Observations at comet
Giacobini-Zinner (JGR 92(A1) 1987)
Authors: Coplan, M. A.; Ogilvie, K. W.; A'Hearn, M. F.; Bochsler,
P.; Geiss, J.
Bibcode: 1998coen.book....5C
Altcode:
No abstract at ADS
Title: Elemental Composition Before, During, and After the January 6,
1997 CME Event Measured by CELIAS/SOHO
Authors: Wurz, P.; Ipavich, F. M.; Galvin, A. B.; Bochsler, P.; Aellig,
M. R.; Kallenbach, R.; Hovestadt, D.; Grünwaldt, H.; Hilchenbach,
M.; Axford, W. I.; Balsinger, H.; Bürgi, A.; Coplan, M. A.; Geiss,
J.; Gliem, F.; Gloeckler, G.; Hefti, S.; Hsieh, K. C.; Klecker, B.;
Lee, M. A.; Livi, S.; Managadze, G. G.; Marsch, E.; Möbius, E.;
Neugebauer, M.; Reiche, K. U.; Scholer, M.; Verigin, M. I.; Wilken, B.
Bibcode: 1997ESASP.415..395W
Altcode: 1997cpsh.conf..395W
No abstract at ADS
Title: Determination of Calcium and Silicon Charge States and
Elemental Abundances in the Solar Wind with the Mass Instrument
on Wind
Authors: Kern, O.; Wimmer-Schweingruber, R. F.; Bochsler, P.;
Gloeckler, G.; Hamilton, D. C.
Bibcode: 1997ESASP.415..345K
Altcode: 1997cpsh.conf..345K
No abstract at ADS
Title: Isotopic composition of solar wind neon measured by CELIAS/MTOF
on board SOHO
Authors: Kallenbach, R.; Ipavich, F. M.; Bochsler, P.; Hefti, S.;
Hovestadt, D.; Grünwaldt, H.; Hilchenbach, M.; Axford, W. I.;
Balsiger, H.; Bürgi, A.; Coplan, M. A.; Galvin, A. B.; Geiss, J.;
Gliem, F.; Gloeckler, G.; Hsieh, K. C.; Klecker, B.; Lee, M. A.;
Livi, S.; Managadze, G. G.; Marsch, E.; Möbius, E.; Neugebauer, M.;
Reiche, K. -U.; Scholer, M.; Verigin, M. I.; Wilken, B.; Wurz, P.
Bibcode: 1997JGR...10226895K
Altcode:
We present first results taken from the high-resolution mass
time-of-flight spectrometer (MTOF) of the charge, element, and
isotope analysis system (CELIAS) experiment on board the Solar and
Heliospheric Observatory (SOHO) spacecraft launched in December 1995,
concerning the abundance ratios of neon isotopes in the solar wind. We
obtain the isotopic ratios 20Ne/22Ne=(13.8+/-0.7)
and 20Ne/21Ne=(440+/-110), which agree with the
values obtained from the Apollo foil solar wind experiments and which
have been derived from measurements of solar particles implanted in
lunar and meteoritic samples.
Title: Solar Wind Minor Ion Charge States Observed with High Time
Resolution with SOHO/CELIAS/CTOF
Authors: Aellig, M. R.; Grünwaldt, H.; Bochsler, P.; Hefti, S.; Wurz,
P.; Kallenbach, R.; Ipavich, F. M.; Hovestadt, D.; Hilchenbach, M.;
CELIAS Team
Bibcode: 1997ESASP.415...27A
Altcode: 1997cpsh.conf...27A
No abstract at ADS
Title: Venus tail ray observation near Earth
Authors: Grünwaldt, H.; Neugebauer, M.; Hilchenbach, M.; Bochsler,
P.; Hovestadt, D.; Bürgi, A.; Ipavich, F. M.; Reiche, K. -U.; Axford,
W. I.; Balsiger, H.; Galvin, A. B.; Geiss, J.; Gliem, F.; Gloeckler,
G.; Hsieh, K. C.; Kallenbach, R.; Klecker, B.; Livi, S.; Lee, M. A.;
Managadze, G. G.; Marsch, E.; Möbius, E.; Scholer, M.; Verigin,
M. I.; Wilken, B.; Wurz, P.
Bibcode: 1997GeoRL..24.1163G
Altcode:
In June, 1996, Venus passed through a very close inferior conjunction
with the Sun. At that time the CTOF detector of the CELIAS mass
spectrometer experiment on the SOHO spacecraft near Earth's L1
Lagrangian point was measuring heavy ions in the solar wind ∼4.5 ×
107 km downstream of Venus. Close to the time predicted
by simple geometric arguments for passage of SOHO through the Venus
wake, CTOF made three encounters with unusual fluxes of O+
and C+ ions. Their energy distributions resembled those
of tail rays originating in the Venus ionosphere or ionopause region
rather than of ions produced in the corona of neutral atoms that
surrounds the planet. The C+ abundance was ≈ 10% of
O+. The observed O+ speed was very close to
the simultaneous solar wind speed and the O+ temperature
was a cool 5600 K/amu. The flux densities for the three events were
(2.4-4.4) × 10³ cm-2s-1.
Title: Solar Wind Iron Charge States Observed with High Time
Resolution with SOHO/CELIAS/CTOF
Authors: Aellig, M. R.; Grünwaldt, H.; Bochsler, P.; Wurz, P.; Hefti,
S.; Kallenbach, R.; Ipavich, F. M.; Hovenstadt, D.; Hilchenbach, M.;
CELIAS Team
Bibcode: 1997ESASP.404..157A
Altcode: 1997cswn.conf..157A
No abstract at ADS
Title: Magnesium Isotope Composition in the Solar Wind as Observed
with the MTOF Sensor on the CELIAS Experiment On Board the SOHO
Spacecraft
Authors: Kucharek, H.; Ipavich, F. M.; Kallenbach, R.; Bochsler,
P.; Hovestadt, D.; Grünwaldt, H.; Hilchenbach, M.; Axford, W. I.;
Balsiger, H.; Bürgi, A.; Coplan, M. A.; Galvin, A. B.; Geiss, J.;
Gloeckler, G.; Hsieh, K. C.; Klecker, B.; Lee, M. A.; Livi, S.;
Managadzem G. G.; Marsch, E.; Möbius, E.; Neugebauer, M.; Reiche,
K. U.; Scholer, M.; Verigin, M. I.; Wilkin, B.; Wurz, P.
Bibcode: 1997ESASP.404..473K
Altcode: 1997cswn.conf..473K
No abstract at ADS
Title: Particles in the Solar Wind
Authors: Bochsler, P.
Bibcode: 1997ESASP.404..113B
Altcode: 1997soho....5..113B; 1997cswn.conf..113B
No abstract at ADS
Title: The Isotopic Composition of Iron in the Solar Wind: First
Measurements with the MASS Sensor on the Wind Spacecraft
Authors: Oetliker, M.; Hovestadt, D.; Klecker, B.; Collier, M. R.;
Gloeckler, G.; Hamilton, D. C.; Ipavich, F. M.; Bochsler, P.;
Managadze, G. G.
Bibcode: 1997ApJ...474L..69O
Altcode:
The isotopic composition of iron in the solar wind has been measured for
the first time with the MASS sensor on the Wind spacecraft. Measurements
were made from 1994 December 22 to 1996 February 9 in the
energy range 0.55-1.3 keV nucleon-1 (320-500 km
s-1). We obtained the values 54Fe/56Fe
= 8.5+0.5-2.2% and 57Fe/56Fe
<= 5%. Previously, measurements were reported for meteoritic material
(e.g., Anders & Grevesse 1989, 54Fe/56Fe
= 6.3% and 57Fe/56Fe = 2.3%) and the
origin of Galactic cosmic rays (e.g., Connell & Simpson
1995, 54Fe/56Fe = 8.9% +/- 0.8% and
57Fe/56Fe = 3.8% +/- 0.5%).
Title: Advanced Solar Probe Experiment Module (AD SOLEM)
Authors: McNutt, Ralph L.; Gold, Robert E.; Keath, Edwin P.; Rust,
David M.; Krimigis, Stamatios M.; Zanetti, Lawrence J.; Willey, C. E.;
Williams, B. D.; Kurth, William S.; Gurnett, Donald A.; Acuna, Mario
H.; Burlaga, L.; Gloeckler, G.; Ipavich, Fred M.; Lazarus, Alan J.;
Steinburg, John T.; Brueckner, Guenter E.; Socker, Dennis G.; Holzer,
Tom E.; Bochsler, Peter A.; Kallenbach, Reinald; Roux, Alain
Bibcode: 1996SPIE.2804....2M
Altcode:
A small, low-power suite of fields and particles and imaging experiments
is required for fulfilling the critical science objectives for a
near-sun flyby mission. We discuss how an integrated instrument suite
using novel sensors and advanced detector/microelectronics/packaging
techniques can be implemented for such a payload. Critical tradeoffs
between science requirements, measurement strategies and these
resource limits are discussed, and critical enabling components are
identified. The instrument site consists of 6 major investigations, some
with multiple sensors, power conditioners for both high and low voltages
and a common DPU. The concept design is essentially a dress-rehearsal
of how a payload could realistically make the measurements needed
to answer the critical science questions while operating within a
real-world physics, engineering and technology context.
Title: Abundance of solar wind magnesium isotopes determined with
WIND/MASS
Authors: Bochsler, P.; Gonin, M.; Sheldon, R. B.; Zurbuchen, Th.;
Gloeckler, G.; Hamilton, D. C.; Collier, M. R.; Hovestadt, D.
Bibcode: 1996AIPC..382..199B
Altcode:
We present first results of the abundance ratios of Mg isotopes in
the solar wind using the high resolution mass spectrometer on the
WIND spacecraft. The isotopic composition of Mg in the solar wind
is consistent with terrestrial values. Our preliminary result is
24Mg:25Mg:26Mg=(0.792+/-0.006):(0.095+/-0.005):(0.113+/-0.005).
Title: Coronal hole differential rotation rate observed with
SWICS/Ulysses
Authors: Zurbuchen, Th.; Bochsler, P.; von Steiger, R.
Bibcode: 1996AIPC..382..273Z
Altcode:
We discuss the latitude variation of the coronal hole differential
rotation investigating persistent structures in high speed streams as
observed from SWICS Ulysses during its first passage of the southern
polar hole in 1993-1994. We find a slower rotation rate near the
ecliptic than what is inferred from averaged photospheric features,
e.g. from sunspots. At intermediate latitudes we find a rate similar to
the equatorial rotation rate indicating a quasi-rigid rotation of the
polar coronal hole. At latitudes >65° no persistent structures to
determine the polar rotation have been observed. For the passage of the
southern heliosphere in 1993/94 we find a latitudinal dependence of the
sidereal rotation rate of the coronal hole which can be approximated
by ωSW=[13.13+1.94 sin2(Θ)]°/day, where Θ denotes the
solar latitude.
Title: Test particle study of minor ions in the solar wind
Authors: Zurbuchen, Th.; Bochsler, P.; Politano, H.; Pouquet, A.
Bibcode: 1996AIPC..382..371Z
Altcode:
Using numerical simulations of test particles in a MHD turbulence model
we investigate the influence of nonlinear effects in the interaction of
MHD turbulence with minor ions. We conclude that non-linear interactions
lead to an efficient heating of minor ions.
Title: Diagnostics of Closed Magnetic Structures in the Solar Corona
Using Charge States of Helium and of Minor Ions
Authors: Neukomm, R. O.; Bochsler, P.
Bibcode: 1996ApJ...465..462N
Altcode:
The evolution of charge state distributions of minor ions within closed
diamagnetic structures (plasmoids) propagating under the influence
of buoyancy and gravity through the solar corona is investigated in
a theoretical study. A system of equations describing the dynamics,
the internal energy balance, and the ionization processes is solved
numerically. It is shown that plasmoids that gain sufficient kinetic
energy to reach distances of several solar radii from the solar surface
without being overheated often contain neutral or weakly ionized
species such as He+, C4+, and O2+
reminiscent of occasional observations of solar wind plasma originating
from coronal mass ejections.
Title: Features of small-scale solar wind mass flux fluctuations
Authors: Zurbuchen, Th.; Zastenker, G.; Eiges, P.; Bochsler, P.;
Avanov, L.; Astafyeva, N.
Bibcode: 1996AIPC..382..367Z
Altcode:
We analyze solar wind mass flux data measured with the PROGNOZ 8
satellite. The temporal resolution of the data reaches 0.02 sec, such
that also the range is probed where finite Larmor radius effects become
increasingly important. We find a general tendency for steepening
of the power spectra towards higher frequencies, similar to what is
observed in spectra of magnetic field fluctuations. A significant peak
is found near f=3.2 Hz in a high-resolution spectrum. Possible causes
for this feature are discussed. Using the same data we also study
the practical applicability of the wavelet transform as a tool for
the analysis of non-stationary data with the emphasis on the search
for transient spatial structures which are often not easily resolved
using spectral analysis.
Title: SWICS/Ulysses and MASS/Wind observations of solar wind sulfur
charge states
Authors: Cohen, C. M. S.; Galvin, A. B.; Hamilton, D. C.; Gloeckler,
G.; Geiss, J.; Bochsler, P.
Bibcode: 1996AIPC..382..281C
Altcode:
As Ulysses journeys from the southern to the northern solar pole,
the newly launched Wind spacecraft is monitoring the solar wind
near I AU, slightly upstream of the Earth. Different solar wind
structures pass over both spacecraft as solar features rotate
in and out of view. Ulysses and Wind are presently on opposing
sides of the sun allowing us to monitor these streams for extended
periods of time. Composition measurements made by instruments on both
spacecraft provide information concerning the evolution and properties
of these structures. We have combined data from the SWICS instrument
on Ulysses and the MASS sensor on Wind to determine the charge state
distribution of sulfur in the solar wind. Both instruments employ
electrostatic deflection with time-of-flight measurement. The two
instruments complement each other nicely in that MASS has the greater
mass resolution while SWICS has the better mass/charge resolution and
better statistics.
Title: Neon-20, oxygen-16, and helium-4 densities, temperatures,
and suprathermal tails in the solar wind determined with WIND/MASS
Authors: Collier, Michael R.; Hamilton, D. C.; Gloeckler, G.; Bochsler,
P.; Sheldon, R. B.
Bibcode: 1996GeoRL..23.1191C
Altcode:
Measurements from the MASS instrument on the WIND
spacecraft from late Dec. 94 through Aug. 95 are reported for
20Ne, 16O, and 4He. The average
4He/20Ne density ratio is 566±87 with
considerable variability. The average 16O/20Ne
density ratio is 8.0±0.6 and is independent, within experimental
uncertainty, of solar wind speed. The 20Ne/4He
and 16O/4He temperature ratios at the
lowest solar wind speeds are consistent with unity, increasing
with increasing speed to values exceeding that expected from mass
proportionality. 20Ne, 16O, and 4He
distribution functions exhibit high energy tails which are well-fit
by a kappa function.
Title: Solar Wind Composition: First Results from SOHO and Future
Expectations
Authors: Galvin, A. B.; Ipavich, F. M.; Gloeckler, G.; Coplan, M.;
Hovestadt, D.; Hilchenbach, M.; Buergi, A.; Klecker, B.; Scholer,
M.; Bochsler, P.; Balsiger, H.; Geiss, J.; Kallenbach, R.; Wurz, P.;
Gruenwaldt, H.; Axford, W. I.; Livi, S.; Marsch, E.; Wilken, B.;
Gliem, F.; Reiche, K. -U.; Lee, M. A.; Moebius, E.; Hsieh, K. C.;
Neugebauer, M.; Managadze, G. G.; Verigin, M. I.
Bibcode: 1996AAS...188.4905G
Altcode: 1996BAAS...28..897G
The SOHO payload includes three experiments designed to make "in situ"
particle measurements of the solar wind and solar energetic particles
(CELIAS, D. Hovestadt PI; COSTEP, H. Kunow PI; ERNE, J. Torsti
PI). The solar wind measurements that are the focus of this talk are
primarily provided by the CELIAS CTOF and MTOF sensors. (CELIAS/STOF
and COSTEP-ERNE measure solar and interplanetary suprathermal and
energetic particle populations.) CELIAS/CTOF measures solar wind
heavy ion elemental and charge state abundances, information which
is used (for example) in identifying the type of solar wind flow and
the ionization processes in the corona where the solar wind charge
states become "frozen-in". CELIAS/MTOF provides heavy ion elemental
and isotopic abundances that are important (for example) in the study
of fractionation factors in coronal abundances (as in the so-called
"FIP-effect") for the rarer elements not resolvable in conventional
solar wind composition instruments, and in determining the isotopic
make-up of the solar corona. MTOF is, by far, the most powerful solar
wind mass spectrometer flown to date, and already has new science
to report at the time of this writing. This happenstance is due to a
combination of (1) advanced technology in obtaining high mass resolution
for ions at solar wind energies, and (2) increased statistics. The
excellent counting statistics are largely due to continuous solar wind
monitoring (with its position at L1, ``the Sun never sets on SOHO''),
and the continuous sampling of the solar wind by the 3-axis stabilized
spacecraft further enhanced by MTOF's novel, never previously flown
deflection system that encompasses a very large dynamic range. As might
be expected, this unique opportunity has allowed MTOF to identify
a number of elements for the first time in the solar wind (e.g., P,
Ti, Cr and Ni). A rich assortment of solar wind isotopes have been
identified for the first time, many of which (e.g., Fe 54 and 56; Ni
58,60,62) have not been detected previously even in solar energetic
particle populations nor remotely using spectroscopic techniques.
Title: Solar corona diagnostic with solar wind ion charge spectra.
Authors: Aellig, M. R.; Gruenwaldt, H.; Hefti, S.; Wurz, P.; Bochsler,
P.; Axford, W. I.; Balsiger, H.; Buergi, A.; Coplan, M. A.; Galvin,
A. B.; Geiss, J.; Gliem, F.; Gloeckler, G.; Hilchenbach, M.; Hovestadt,
D.; Hsieh, K. C.; Ipavich, F. M.; Judge, D. L.; Kallenbach, R.;
Klecker, B.; Lee, M. A.; Livi, S.; Managadze, G. G.; Marsch, E.;
Moebius, E.; Neugebauer, M.; Ogawa, H. S.; Reiche, K. U.; Scholer,
M.; Verigin, M. I.; Wilken, B.
Bibcode: 1996AcHPh..69...49A
Altcode:
Matter flowing away from the solar surface becomes highly ionized in the
corona (T ≍ 2·106K) by collisions with electrons. Due to
the decreasing electron density with increasing distance from the solar
surface, the charge state distributions freeze and remain unaltered
throughout the interplanetary medium. This is why charge spectra
measured at 1 AU are a valuable diagnostic tool for temperature and
density variations in the inner solar corona. Preliminary results
of ion charge spectra obtained from the SOHO CELIAS CTOF mass
spectrometer indicate a patchy structure of the corona at scales of
≍104km.
Title: CELIAS - Charge, Element and Isotope Analysis System for SOHO
Authors: Hovestadt, D.; Hilchenbach, M.; Bürgi, A.; Klecker, B.;
Laeverenz, P.; Scholer, M.; Grünwaldt, H.; Axford, W. I.; Livi, S.;
Marsch, E.; Wilken, B.; Winterhoff, H. P.; Ipavich, F. M.; Bedini, P.;
Coplan, M. A.; Galvin, A. B.; Gloeckler, G.; Bochsler, P.; Balsiger,
H.; Fischer, J.; Geiss, J.; Kallenbach, R.; Wurz, P.; Reiche, K. -U.;
Gliem, F.; Judge, D. L.; Ogawa, H. S.; Hsieh, K. C.; Möbius, E.;
Lee, M. A.; Managadze, G. G.; Verigin, M. I.; Neugebauer, M.
Bibcode: 1995SoPh..162..441H
Altcode:
The CELIAS experiment on SOHO is designed to measure the mass, ionic
charge and energy of the low and high speed solar wind, of suprathermal
ions, and of low energy flare particles. Through analysis of the
elemental and isotopic abundances, the ionic charge state, and the
velocity distributions of ions originating in the solar atmosphere,
the investigation focuses on the plasma processes on various temporal
and spatial scales in the solar chromosphere, transition zone,
and corona. CELIAS includes 3 mass- and charge-discriminating
sensors based on the time-of-flight technique: CTOF for the
elemental, charge and velocity distribution of the solar wind,
MTOF for the elemental and isotopic composition of the solar wind,
and STOF for the mass, charge and energy distribution of suprathermal
ions. The instrument will provide detailed in situ diagnostics of the
solar wind and of accelerated particles, which will complement the
optical and spectroscopic investigations of the solar atmosphere on
SOHO. CELIAS also contains a Solar Extreme Ultraviolet Monitor, SEM,
which continously measures the EUV flux in a wide band of 17 - 70 nm,
and a narrow band around the 30.4 nm He II line.
Title: Element fractionation by diffusion in the solar chromosphere.
Authors: Marsch, E.; von Steiger, R.; Bochsler, P.
Bibcode: 1995A&A...301..261M
Altcode:
A new mechanism to explain the observed first ionization potential
(FIP) fractionation of coronal and solar wind element abundances
is proposed. By the FIP fractionation, low-FIP (<10eV) elements
are enriched in the solar corona and solar wind relative to the
photosphere. This effect has been located earlier to take place in the
chromosphere, at densities of N =~10^16^-10^18^m^-3^ and a temperature
of T=~10^4^K, where a large fraction of the gas is still neutral. We
discuss a new mechanism for the FIP fractionation in the form of
a stationary diffusion model. It is based on a weakly stratified
chromospheric layer of constant density of the element hydrogen and
constant temperature. This layer is permeated everywhere by ionizing
photons and contains a homogeneous vertical magnetic field. Otherwise,
our model does not invoke any particular geometry or special set up of
the system. It is thus founded solely on robust and well understood
atomic collisional physics. Technically, a boundary value problem
of four coupled differential equations is solved for each chemical
element, i.e. a continuity equation and a momentum equation for both
atoms and singly ionized particles. By splitting the system into a
main gas (hydrogen) and trace gases (16 elements from He to Xe), an
analytical solution for the former can be found. This then serves as
a background for the numerical integration of each trace gas system,
for which we consider collisions between its atoms and ions with the
main gas, i.e. protons and hydrogen. Boundary conditions are such that
the gas is neutral at the bottom of the slab and fully ionized at its
top, as a result of irradiation by the solar coronal EUV. Starting
with a uniform density at the bottom of the layer, we find that, after
a few hydrogen diffusion lengths, each minor species asymptotically
approaches a constant density. The ratios of these density values to
some reference trace element reproduce the observed FIP fractionation
pattern of heavy elements remarkably well. The step between low-FIP
and high-FIP element abundances is about a factor of 5, and He is
somewhat depleted relative to the high-FIP elements, in agreement
with the observations. The model fractionation pattern proves to be
remarkably stable against changes in the external parameters (within
reasonable chromospheric values), particularly N and T.
Title: SWICS/Ulysses and MASS/wind observations of solar wind sulfur
charge states
Authors: Cohen, C. M. S.; Galvin, A. B.; Hamilton, D. C.; Gloeckler,
G.; Geiss, J.; Bochsler, P.
Bibcode: 1995sowi.conf...73C
Altcode:
As Ulysses journeys from the southern to the northern solar pole,
the newly launched Wind spacecraft is monitoring the solar wind
near 1 AU, slightly upstream of the Earth. Different solar wind
structures pass over both spacecraft as coronal holes and other
features rotate in and out of view. Ulysses and Wind are presently
on opposing sides of the sun allowing us to monitor these streams for
extended periods of time. Composition measurements made by instruments
on both spacecraft provide information concerning the evolution and
properties of these structures. We have combined data from the Solar
Wind Ion Composition Spectrometer (SWICS) on Ulysses and the high mass
resolution spectrometer (MASS) on Wind to determine the charge state
distribution of sulfur in the solar wind. Both instruments employ
electrostatic deflection with time-of-flight measurement. The high
mass resolution of the MASS instrument (M/Delta-M approximately 100)
allows sulfur to be isolated easily while the stepping energy/charge
selection provides charge state information. SWICS measurements allow
the unique identification of heavy ions by their mass and mass/charge
with resolutions of M/Delta-M approximately 3 and M/q/Delta(M/q)
approximately 20. The two instruments complement each other nicely in
that MASS has the greater mass resolution while SWICS has the better
mass/charge resolution and better statistics.
Title: Test particle study of minor ions in solar wind turbulence
Authors: Zurbuchen, Th.; Bochsler, P.; Politano, H.; Pouquet, A.
Bibcode: 1995sowi.confR..82Z
Altcode:
We perform a parameter study of the temporal evolution of a test
particle distribution function in MHD turbulence. The turbulent fields
are calculated using a pseudo-spectral method and periodic boundary
conditions on a regular grid of 1803 points, appropriate
for incompressible, homogeneous and isotropic turbulence. Initially,
the kinetic and the magnetic energy are equal on the average. Both,
deterministic and random initial conditions are used, in the former case
with zeros of the magnetic field located at grid points, in the latter
case located by interpolation between grid points. The evolution of the
minor ion distribution function is studied in detail as these turbulent
fields evolve, developing strong current and vorticity sheets. Using
the full collisionless equation of motion for the test particles,
the efficiency of nonlinear interactions can be studied. The results
are compared to theoretical predictions and are then discussed in
connection with the observations of the dynamical properties of solar
wind minor ions derived from in situ observations.
Title: Dynamic properties of helium ions in the solar wind
Authors: Zurbuchen, Th.; Bochsler, P.; von Steiger, R.
Bibcode: 1995sowi.conf...73Z
Altcode:
We characterize the dynamic properties of He ions of the solar
wind. Because of the non-negligible abundance and the significant
fraction of momentum flux inherent in helium ions, this species has an
influence on the state of turbulence. Especially, we analyze the helium
dynamic properties of different solar wind types. After a discussion
of the influence of measurement errors on the statistical analysis of
He bulk velocities, we investigate the structure function dependency
on the solar wind state. We find a self-similar sealing in the range
of minutes to days with characteristic structure function slopes
deviating from the canonical Kolmogorov values. For comparison with
previous studies, we also analyze H structure functions of the same
time periods and discuss differences of coinciding He and H structure
functions in the framework of the concept of intermittency.
Title: Elemental composition in the slow solar wind measured with
the MASS instrument on WIND
Authors: Bochsler, P.; Gonin, M.; Sheldon, R. B.; Zurbuchen, Th.;
Gloeckler, G.; Galvin, A. B.; Hovestadt, D.
Bibcode: 1995sowi.conf...35B
Altcode:
The MASS instrument on WIND contains the first isochronous time-off
light spectrometer to be flown in the solar wind. The first spectra
obtained with this instrument has demonstrated its capability to
measure the abundances of several high-and low-FIP elements in the
solar wind. The derivation of these abundances requires a careful
calibration of the charge exchange efficiencies of the relevant ions
in carbon foils. These efficiencies and the corresponding instrument
functions have been determined in extensive calibration campaigns
at different institutions. We present first and preliminary results
obtained in slow solar wind streams and we compare these results with
those obtained from previous investigations of solar wind abundances and
of coronal abundances as derived from Solar Energetic Particles. Recent
models of the FIP related fractionation effect predict a depletion of
a factor of typically 4 to 5 for high-FIP elements (He, N, O, Ne, Ar,
etc.) relative to low-FIP elements (Mg, Fe, Si, etc.). We also compare
our results with the detailed predictions of the different models and we
discuss the resulting evidence to validate or to invalidate different
physical scenarios explaining the feeding and the acceleration of slow
stream solar wind.
Title: Elemental and charge state composition of the fast solar wind
observed with SMS instruments on WIND
Authors: Gloeckler, G.; Galvin, A. B.; Ipavich, F. M.; Hamilton,
D. C.; Bochsler, P.; Geiss, J.; Fisk, L. A.; Wilken, B.
Bibcode: 1995sowi.conf...35G
Altcode:
The elemental composition and charge state distributions of heavy
ions of the solar wind provide essential information about: (1)
atom-ion separation processes in the solar atmosphere leading to the
'FIP effect' (the overabundance of low First Ionization potential
(FIP) elements in the solar wind compared to the photosphere); and
(2) coronal temperature profiles, as well as mechanisms which heat the
corona and accelerate the solar wind. This information is required for
solar wind acceleration models. The SWICS instrument on Ulysses measures
for all solar wind flow conditions the relative abundance of about
8 elements and 20 charge states of the solar wind. Furthermore, the
Ulysses high-latitude orbit provides an unprecedented look at the solar
wind from the polar coronal holes near solar minimum conditions. The
MASS instrument on the WIND spacecraft is a high-mass resolution solar
wind ion mass spectrometer that will provide routinely not only the
abundances and charge state of all elements easily measured with SWICS,
but also of N, Mg, S. The MASS sensor was fully operational at the end
of 1994 and has sampled the in-ecliptic solar wind composition in both
the slow and the corotating fast streams. This unique combination of
SWICS on Ulysses and MASS on WIND allows us to view for the first time
the solar wind from two regions of the large coronal hole. Observations
with SWICS in the coronal hole wind: (1) indicate that the FIP effect
is small; and (2) allow us determine the altitude of the maximum in
the electron temperature profile, and indicate a maximum temperature
of approximately 1.5 MK. New results from the SMS instruments on Wind
will be compared with results from SWICS on Ulysses.
Title: Some features of the small-scale solar wind fluctuations
Authors: Zastenker, G.; Eiges, P.; Avanov, L.; Astafyeva, N.;
Zurbuchen, Th.; Bochsler, P.
Bibcode: 1995sowi.confQ..82Z
Altcode:
We have investigated small-scale variations of the solar wind ion
flux measured with Faraday cups onboard the Prognoz-8 satellite. These
measurements have a high time resolution of 1.24 seconds for intervals
with a duration of several hours and as high as 0.02 seconds for some
periods of about 1 hour duration. The main goal of this work is the
determination of the quantitative features of fast ion flux fluctuations
using mainly spectral analysis but also other methods. We also identify
their association with interplanetary plasma parameters. Particularly,
it is shown that the slope of the power spectra in the frequency range
from 1E-4 to 6E-2 Hz is close to the classical Kolmogorov (-5/3)
law. We also discuss some intervals with a very high level of the
relative amplitude of flux fluctuations (10-20 percent) which were
observed near the Earth's bow shock in the foreshock region. The use
of the wavelet method for the long time series allows us to study the
temporal evolution of power spectra.
Title: Solar wind helium isotopic composition from SWICS/ULYSSES
Authors: Bodmer, R.; Bochsler, P.; Geiss, J.; von Steiger, R.;
Gloeckler, G.
Bibcode: 1995SSRv...72...61B
Altcode:
This is the first study of the isotopic composition of solar wind
helium with the SWICS time-of flight mass spectrometer. Although the
design of SWICS is not optimized to measure3He abundances
precisely,4He/3He flux ratios can be deduced
from the data. The long term ratio is 2290±200, which agrees with the
results obtained with the ICI magnetic mass spectrometer on ISEE-3
and with the Apollo SWC foil experiments. The ULYSSES spacecraft
follows a trajectory which is ideal for the study of different solar
wind types. During one year, from mid-1992 to mid-1993, it was in a
range of heliographic latitudes where a recurrent fast stream from the
southern polar coronal hole was observed every solar rotation. Solar
wind bulk velocities ranged from 350 km/s to 950 km/s which would,
in principle allow us to identify velocity-correlated compositional
variations. Our investigation of solar wind helium, however, shows an
isotopic ratio which does not depend on the solar wind speed.
Title: The Solar Wind and Suprathermal Ion Composition Investigation
on the Wind Spacecraft
Authors: Gloeckler, G.; Balsiger, H.; Bürgi, A.; Bochsler, P.; Fisk,
L. A.; Galvin, A. B.; Geiss, J.; Gliem, F.; Hamilton, D. C.; Holzer,
T. E.; Hovestadt, D.; Ipavich, F. M.; Kirsch, E.; Lundgren, R. A.;
Ogilvie, K. W.; Sheldon, R. B.; Wilken, B.
Bibcode: 1995SSRv...71...79G
Altcode:
The Solar Wind and Suprathermal Ion Composition Experiment (SMS)
on WIND is designed to determine uniquely the elemental, isotopic,
and ionic-charge composition of the solar wind, the temperatures
and mean speeds of all major solar-wind ions, from H through Fe,
at solar wind speeds ranging from 175 kms-1 (protons)
to 1280 kms-1 (Fe+8), and the composition,
charge states as well as the 3-dimensional distribution functions of
suprathermal ions, including interstellar pick-up He+, of
energies up to 230 keV/e. The experiment consists of three instruments
with a common Data Processing Unit. Each of the three instruments
uses electrostatic analysis followed by a time-of-flight and, as
required, an energy measurement. The observations made by SMS will make
valuable contributions to the ISTP objectives by providing information
regarding the composition and energy distribution of matter entering
the magnetosphere. In addition SMS results will have an impact on
many areas of solar and heliospheric physics, in particular providing
important and unique information on: (i) conditions and processes in
the region of the corona where the solar wind is accelerated; (ii) the
location of the source regions of the solar wind in the corona; (iii)
coronal heating processes; (iv) the extent and causes of variations in
the composition of the solar atmosphere; (v) plasma processes in the
solar wind; (vi) the acceleration of particles in the solar wind; and
(vii) the physics of the pick-up process of interstellar He as well
as lunar particles in the solar wind, and the isotopic composition of
interstellar helium.
Title: The Charge, Element, and Isotope Analysis System CELIAS on SOHO
Authors: Hovestadt, D.; Bochsler, P.; Grünwaldt, H.; Gliem, F.;
Hilchenbach, M.; Ipavich, F. M.; Judge, D. L.; Axford, W. I.; Balsiger,
H.; Bürgi, A.; Coplan, M.; Galvin, A. B.; Geiss, J.; Gloeckler,
G.; Hsieh, K. C.; Kallenbach, R.; Klecker, B.; Lee, M. A.; Livi, S.;
Managadze, G. G.; Marsch, E.; Möbius, E.; Neugebauer, M.; Reiche,
K. -U.; Scholer, M.; Verigin, M. I.; Wilken, D.; Wurz, P.
Bibcode: 1995LNP...444..271H
Altcode: 1995cmer.conf..271H
No abstract at ADS
Title: Solar Wind Helium Isotopic Composition from SWICS/Ulysses
Authors: Bodmer, R.; Bochsler, P.; Geiss, J.; von Steiger, R.;
Gloeckler, G.
Bibcode: 1995hlh..conf...61B
Altcode:
No abstract at ADS
Title: Fractionation of Nitrogen Isotopes in Solar Energetic Particles
Authors: Bochsler, Peter; Kallenbach, Reinald
Bibcode: 1994Metic..29..653B
Altcode:
In a further step to assess processes leading to the complicated secular
trend of the isotopic composition of N implanted in lunar regolith,
we investigate mechanisms fractionating solar energetic particles
(SEPs). We conclude that such mechanisms are likely to occur, most
probably producing an enrichment of N-15 over N-14 in SEPs over the
photospheric abundance ratio. Simultaneously, Ne-22 is enriched over
Ne-20 but to a lesser extent. An enrichment of the heavy Ne isotope
is observed in the suprathermal solar particles, implanted in the
lunar regolith. Hence, the now well-established difference between the
isotopic composition of suprathermal Ne and solar wind Ne in the lunar
regolith might be taken as evidence for the validity of this model. The
present-day fluxes of energetic particles produced in impulsive flare
events, capable to produce such isotopic fractionations are, however,
orders of magnitude below the required amounts to explain the lunar
observations. The details of the secular variation of the N isotopic
composition remain an enigma.
Title: Solar wind composition from the moon
Authors: Bochsler, P.
Bibcode: 1994AdSpR..14f.161B
Altcode: 1994AdSpR..14..161B
The lunar regolith contains the best accessible record of the solar
wind composition of the past few billion years. Interpreting this
record crucially depends on our understanding of the implantation
mechanisms, potential alternative sources other than the solar wind,
storage and degradation processes, and transport- and loss-mechanisms
of trapped particles in the regolith. We therefore suggest that a
future mission to the Moon should contain the following objectives:
1) A thorough in-situ investigation of the contemporary solar wind
composition by means of long-duration exposure experiments with various
techniques as baseline for investigation of the historic and ancient
solar wind. 2) A multidisciplinary program, involving an experimental
investigation of implantation-, storage- and loss-processes of solar
particles at the conditions of the lunar environment. This program
is complementary to an elaborated systematic sampling of all layers
of the lunar regolith, based on the experience from the Apollo- and
the Luna-missions. Difficulties with the interpretation of the lunar
record are illuminated in the case of surface correlated nitrogen. 3)
A complementary goal for the extensive sampling of the lunar surface
is the documentation of the lunar regolith for future generations,
prior to extended human activities which could have detrimental effects
to the lunar environment.
Title: Imaging ion outflow in the high-latitude magnetosphere using
low-energy neutral atoms
Authors: Hesse, Michael; Smith, Mark F.; Herrero, Federico A.;
Ghielmetti, Arthur G.; Shelley, Edward G.; Wurz, Peter; Bochsler,
Peter; Gallagher, Dennis L.; Moore, Thomas E.; Stephen, Thomas S.
Bibcode: 1993SPIE.2008...83H
Altcode:
The measurement of neutral atom fluxes generated by charge exchange
with the Earth's geocorona has recently been shown to provide the
capability to image the magnetosphere. Here we investigate neutral
oxygen fluxes, produced by charge exchange from the cusp/cleft ion
fountain population. Using an empirical cusp/cleft ion fountain model,
an empirical variation of the geocoronal neutral hydrogen density
with distance, and typical values for charge exchange cross-sections,
line-of-sight integrations are performed to calculate the neutral
oxygen flux at arbitrary locations in space. The resulting images are
evaluated for a set of orbital positions of the proposed HI-LITE small
explorer spacecraft. It is shown that the resulting neutral oxygen
fluxes are high enough for imaging with a low energy neutral atom
imaging instrument (ILENA) on board the spacecraft.
Title: Mass spectrograph for imaging low-energy neutral atoms
Authors: Ghielmetti, Arthur G.; Shelley, Edward G.; Fuselier, Stephen
A.; Herrero, Federico A.; Smith, Mark F.; Wurz, Peter; Bochsler,
Peter; Stephen, Thomas S.
Bibcode: 1993SPIE.2008..105G
Altcode:
We describe an instrument concept for measuring low energy neutral H
and O atoms with kinetic energies ranging from about 10 eV to several
100 eV. The instrument makes use of a low work function surface to
convert neutral atoms to negative ions. These ions are then accelerated
away from the surface and brought to an intermediate focus by a large
aperture lens. After deflection in a spherical electrostatic analyzer,
the ions are post accelerated to approximately 25 keV final energy into
a time-of-flight mass analyzer. The latter consists of a thin carbon
foil at the entrance that provides the secondary electrons for the start
signal, a drift space, and a stop microchannel plate that detects the
primary particles. Mass resolution is adequate for resolving H, He, and
O, and the isotopes D and (superscript 3)He. The image created by the
spherical electrostatic analyzer is arc shaped with initial incident
direction dispersed in azimuth and energy dispersed radially. Energy
and azimuth information are obtained by position imaging the secondary
electrons produced at the foil. A large geometric factor combined with
simultaneous angle-energy-mass imaging that eliminates the need for
duty cycles provide the necessary high sensitivity. From a spinning
spacecraft this instrument is capable of producing a two-dimensional
map of low energy neutral atom fluxes.
Title: Development of an isochronous time-of-flight mass spectrometer
for determination of space plasma parameters.
Authors: Gubler, L.; Moebius, E.; Bochsler, P.
Bibcode: 1993AcHPh..66..429G
Altcode:
For plasma composition measurements in space, the usual magnet
spectrometers are increasingly replaced by time-of-flight (TOF)
instruments. The authors have developed a prototype for a cylindrical,
high-resolution (M/ΔM > 50) isochronous TOF-mass spectrometer,
to be used in combination with an electrostatic energy-analyzer. They
present numerical simulations and first experimental results.
Title: High-latitude ion transport and energetic explorer (HI-LITE):
a mission to investigate ion outflow from the high-latitude ionosphere
Authors: Smith, Mark F.; Herrero, Federico A.; Hesse, Michael; Baker,
Daniel N.; Bochsler, Peter; Wurz, Peter; Balsiger, Hans; Chakrabarti,
Supriya; Erickson, Gary; Cotton, Daniel M.; Stephen, Thomas S.; Jamar,
Claude A.; Gerard, Jean-Claude; Fuselier, Stephen A.; Ghielmetti,
Arthur G.; Mende, Stephen B.; Peterson, William K.; Shelley, Edward G.;
Vondrak, Richard R.; Gallagher, Dennis L.; Moore, Thomas E.; Pollock,
Craig; Arnoldy, Roger; Lockwood, Michael; Gladstone, Randy
Bibcode: 1993SPIE.2008...40S
Altcode:
The proposed HI-LITE Explorer will investigate the global ion outflow
from the high-latitude ionosphere, its relationship to auroral features,
and the consequences of this outflow on magnetospheric processes. The
unique nature of the HI-LITE Explorer images will allow temporal and
spatial features of the global ion outflow to be determined. The
mission's scientific motivation comes from the fundamental role
high-latitude ionospheric ions play in the dynamics of the solar wind
driven magnetospheric-ionospheric system. These outflows are a major
source of plasma for the magnetosphere and it is believed they play
an important role in the triggering of substorms. In addition this
paper describes the HI-LITE spacecraft and instruments.
Title: How to detect plasmoids in the solar corona?
Authors: Neukomm, R.; Bochsler, P.
Bibcode: 1993AcHPh..66..431N
Altcode:
The authors examine in a model the movement of closed magnetized
structures (plasmoids) in the solar atmosphere. They discuss the
development of the ionisation state distributions of oxygen and
silicon. Charge states of minor ions are generally important tracers
for processes and conditions to which these particles were exposed. In
the solar wind they carry information about the inner heliosphere which
can otherwise not be derived from other quantities mesurable at 1 AU.
Title: Prospects for future solar-wind missions.
Authors: Bochsler, P.; Moebius, E.
Bibcode: 1993ESASP1157...43B
Altcode: 1993srfs.book...43B
The aim of this paper is to discuss possible activities and future
goals for solar-wind research in the post-Soho era. Specifically two
major enterprises are addressed which will open up important fields
in the future study of the Sun. The first deals with in-situ study
of the solar corona. The second will be the setting up of a baseline
for the isotopic composition in the solar system by studing a sample
from the Sun in detail. In order to achieve these goals, the authors
propose to develop advanced composition experiments to investigate
the solar wind with enhanced mass resolution, considerably increased
geometrical factor, and improved time resolution. Furthermore, they
propose to place sophisticated mass/charge-spectrometers, with the
ability to investigate both charge and velocity distributions with
enhanced time resolution, in the solar-wind acceleration region.
Title: Interaction of solar wind ions with thin carbon foils -
calibration of time-of-flight spectrometers.
Authors: Gonin, M.; Buergi, Alfred; Oetliker, M.; Bochsler, P.
Bibcode: 1992ESASP.348..381G
Altcode: 1992cscl.work..381G
With the KAFKA (german: Karbon Folien Kollisions Analysator) experiment
the authors study charge exchange, energy loss and angular scattering of
solar wind ions in thin carbon foils. Such foils are extensively used
in time-of-flight mass spectrometry. The authors have investigated the
properties of H, He, B, C, N, O, F, Ne, Na, Mg, Al, Si, S, Cl, Ar, K,
Ti, Fe, and Ni in the 0.5 - 5 keV/u energy range.
Title: CELIAS: charge, element and isotope analysis system for the
SOHO mission.
Authors: Hovestadt, D.; Geiss, J.; Gloeckler, G.; Axford, W. I.;
Balsiger, H.; Bochsler, P.; Bürgi, A.; Canfield, R.; Coplan, M.;
Dinse, H.; Galvin, A. B.; Gliem, F.; Gringauz, K. I.; Grünwaldt, H.;
Hilchenbach, M.; Hsieh, K. C.; Ipavich, F. M.; Judge, D.; Klecker,
B.; Kühne, M.; Lee, M. A.; Livi, S.; Managadze, G. G.; Marsch, E.;
Neugebauer, M.; Möbius, E.; Reiche, K. V.; Scholer, M.; Wilken, B.
Bibcode: 1992ESASP.346..343H
Altcode: 1992ssts.rept..343H
The status and further development as well as first calibration of the
CELIAS experiment on SOHO is presented. CELIAS is designed to measure
the mass, ionic charge, and energy of low and high speed solar wind of
suprathermal ions and of low energy flare particles. Through analysis
of the elemental and isotopic abundances (the ionic charge state and
velocity distributions of ions originating on the solar atmosphere),
the investigation focuses on studying the plasma processes in various
temporal and spatial scales in the solar chromosphere, transition zone,
and corona. Additionally, the CELIAS experiment includes the Solar EUV
Monitor (SEM). This unit, which consists of an EUV transmission grating
spectrometer and three isolated silicon photodiodes as detectors,
is described. The three mass and charge discriminating sensors based
on the time of flight technique are also described.
Title: Modeling the evolution of N and 15N/14N
in the lunar regolith: mixing models involving two components.
Authors: Kerridge, J. F.; Bochsler, P.; Eugster, O.; Geiss, J.
Bibcode: 1992LPSC...22..239K
Altcode:
A computer simulation of N buildup on the lunar surface, employing
two independent sources of N, generates a good match with most, but
not all, aspects of N abundance and isotope systematics observed in
regolith samples. This suggests that a two-component model, at least
as tested here, is insufficient to explain the lunar data.
Title: Minor ions - Tracers for physical processes in the heliosphere
Authors: Bochsler, P.
Bibcode: 1992sws..coll..323B
Altcode:
Minor ions can be used as tracers for physical processes in the
heliosphere by monitoring their abundances, their charge states,
and their dynamic properties in the solar wind. Two applications
are discussed in some detail, more applications can be found in other
contributions of this session. Here, we discuss the case of He-3 in the
solar wind which is a particularly useful tracer for mixing processes
within the radiative interior of the sun. The second example deals
with the charge states of solar wind ions as temperature diagnostics
for the inner corona. Weakly ionized species are sensitive indicators
for various processes occurring in the inner heliosphere such as
evaporation of cometary debris and the ionization and pick-up of
infiltrated interstellar neutral gas. We also present results of a
model calculation which demonstrates the usefulness of weakly ionized
species as indicators for the formation and propagation of plasmoids
within the solar corona.
Title: Einige neuere Ergebnisse zur Entstehung des Sonnensystems.
Authors: Bochsler, P.
Bibcode: 1991Orion..49..224B
Altcode:
No abstract at ADS
Title: Variability of coronal structures and ion components in the
solar wind
Authors: Zastenker, G.; Avanov, L.; Yermolaev, Yu.; Bochsler, P.;
Nemecek, Z.; Safrankova, J.
Bibcode: 1991CzJPh..41.1001Z
Altcode:
The variations of solar wind ion fluxes of protons and α-particles
are studied in a wide timescale: from parts of a second to several
months. A “persistence time” of about 60 hours was obtained for
the large-scale variations of α-particles. Power density spectra of
velocity, density and magnetic field were studied in the frequency range
from 10-5 to 10-3 Hz. Middle-scale fluctuations
of both protons and α-particles are close to each other and the
spectrum for α-particles has a somewhat greater slope than that for
protons. Estimates of the variations of the flux power density are
given in the frequency range from 10-3 to 3 Hz.
Title: Modelling the Evolution of N and 15N/14N in the Lunar Regolith
Authors: Kerridge, J. F.; Bochsler, P.; Eugster, O.; Geiss, J.
Bibcode: 1991LPI....22..711K
Altcode:
No abstract at ADS
Title: Erratum - Space-Based Measurements of Elemental Abundances
and Their Relation to Solar Abundances
Authors: Coplan, M. A.; Ogilvie, K. W.; Bochsler, P.; Geiss, J.
Bibcode: 1991SoPh..132..203C
Altcode:
No abstract at ADS
Title: Long-Time Variations in Solar Wind Properties: Possible Causes
Versus Observations
Authors: Geiss, J.; Bochsler, P.
Bibcode: 1991suti.conf...98G
Altcode:
Measurements of the composition of the contemporary solar wind
have led to tentative identifications of causes for compositional
variations and have permitted the magnitude of systematic differences
between solar wind and solar composition to be estimated. Helium is
generally depleted by a factor of two relative to hydrogen, and in
low-speed solar wind the elements with ionization potentials below 10
eV are overabundant by a factor of about three. Isotopic abundances of
solar wind noble gases collected at the lunar surface during different
epochs show little variability, in agreement with expectations. There
is some evidence of a modest secular increase of about 10 percent in
the He-3/He-4 ratio. Possible reasons for this and for anomalies in
solar wind abundances are discussed.
Title: High mass resolution isochronous time-of-flight spectrograph
for three-dimensional space plasma measurements
Authors: Moebius, E.; Bochsler, P.; Ghielmetti, A. G.; Hamilton, D. C.
Bibcode: 1990RScI...61.3609M
Altcode:
By combining a toroidal electrostatic analyzer with a novel
cylindrically symmetric isochronous time-of-flight mass spectrometer,
an instrument was developed that simultaneously determines the
three-dimensional distribution function of ions and differentiates
species. The ion mass is determined to high resolution (M/Delta-M
greater than 50) from the time of flight within a harmonic field
configuration defined by hyperboloid equipotential surfaces. A second
conventional time-of-flight channel makes use of particles leaving the
thin entrance foil as neutrals. An additional solid state detector in
which the neutrals are stopped allows the total energy and thereby the
ionic charge of the incident ions to be determined as well. Information
from the neutral and the ion channels can be combined to determine
the total mass of an incident molecular ion and the mass of one atomic
fragment.
Title: The abundance of 3He in the solar wind - A
constraint for models of solar evolution
Authors: Bochsler, P.; Geiss, J.; Maeder, A.
Bibcode: 1990SoPh..128..203B
Altcode: 1990IAUCo.121P.203B
3He is an intermediate product in the proton-proton chain,
and standard models of the Sun predict a large bulge of enhanced
3He abundance near Mr/M0 = 0.6 in
the contemporary Sun. The relatively low abundance of 3He
at the solar surface, which is derived from solar wind observations,
poses severe constraints to non-standard solar models.
Title: Space-based measurements of elemental abundances and their
relation to solar abundances
Authors: Coplan, M. A.; Ogilvie, K. W.; Bochsler, P.; Geiss, J.
Bibcode: 1990SoPh..128..195C
Altcode: 1990IAUCo.121P.195C
The solar wind provides a source of solar abundance data that only
recently is being fully exploited. The Ion Composition Instrument (ICI)
aboard the ISEE-3/ICE spacecraft was in the solar wind continuously from
August 1978 to December 1982. The results have allowed us to establish
long-term average solar wind abundance values for helium, oxygen, neon,
silicon, and iron. The Charge-Energy-Mass (CHEM) instrument aboard
the CCE spacecraft of the AMPTE mission has measured the abundance of
these elements in the magnetosheath and has also added carbon, nitrogen,
magnesium, and sulfur to the list. There is strong evidence that these
magnetosheath abundances are representative of the solar wind. Other
sources of solar wind abundances are Solar Energetic Particle (SEP)
experiments and Apollo lunar foils. When comparing the abundances
from all of these sources with photospheric abundances, it is clear
that helium is depleted in the solar wind while silicon and iron are
enhanced. Solar wind abundances for carbon, nitrogen, oxygen, and neon
correlate well with the photospheric values. The incorporation of minor
ions into the solar wind appears to depend upon both the ionization
times for the elements and the Coulomb drag exerted by the outflowing
proton flux.
Title: Book Review: Reviews in modern astronomy I: Cosmic chemistry /
Springer, 1988
Authors: Bochsler, P.; Bochsler, P.
Bibcode: 1990SoPh..125..209B
Altcode: 1990SoPh..125..209K
No abstract at ADS
Title: Modelling the evolution of N and 15N/14N
in the lunar regolith
Authors: Kerridge, J. F.; Bochsler, P.; Geiss, J.
Bibcode: 1989Metic..24..285K
Altcode:
No abstract at ADS
Title: Solar Wind Observations with the Ion Composition Instrument
Aboard the ISEE-3/ICE Spacecraft
Authors: Ogilvie, K. W.; Coplan, M. A.; Bochsler, P.; Geiss, J.
Bibcode: 1989SoPh..124..167O
Altcode:
In this paper we use the observations of solar wind helium ions made
by the Ion Composition Instrument (ICI) on the ISEE-3/ICE spacecraft
to study the variation of helium abundance in the solar wind and to
arrive at an average value of that quantity for the period August
1978 to December 1982. The abundance varies in a similar way to that
observed in the previous solar cycle, but more detailed dependence
on velocity and solar cycle epoch is observed. The long-term average
helium abundance is used in conjunction with long term abundances of
3He, O, Ne, Si, and Fe, measured with respect to helium using
the same instrument, to compile abundances with respect to hydrogen
which can be reliably compared with solar system abundances. With the
extended data set we are able to show Si and Fe to be overabundant
by a factor of three with respect to solar system abundances and He
underabundant by a factor of two.
Title: Velocity and abundance of silicon ions in the solar wind
Authors: Bochsler, P.
Bibcode: 1989JGR....94.2365B
Altcode:
Using data from the ISEE-3 ion composition instrument (ICI),
velocities and abundances of silicon ions in the solar wind have been
determined. The period of investigation covers the maximum of solar
cycle 21, beginning with launch of ISEE-3 in August 1978 and ending
at the removal of the spacecraft from the Lagrangian Point L1 in June
1982. The results generally confirm previous ICI observations of iron,
the other heavy element with a low first ionization potential measured
with the ICI. Silicon ions (and other ions in the same M/Q range) tend
to stream at the bulk velocity of 4He++
in low-speed solar wind. At high-speed solar wind. Si lags by up to or
about 20 km/s after 4He++. By means
of a minimum variance estimation technique, fluxes (and densities) of
silicon in the solar wind have been obtained free of bias. An average
Si/O flux ratio of 0.19+/-0.04 is derived. This value is larger by a
factor of 3 or 4 than the Si/O abundance ratio at the solar surface.
Title: Modelling the Evolution of N and 15N 14N
in the Lunar Regolith
Authors: Kerridge, J. F.; Bochsler, P.; Geiss, J.
Bibcode: 1989LPICo.712..111K
Altcode:
No abstract at ADS
Title: Composition of the solar wind.
Authors: Bochsler, P.; Geiss, J.
Bibcode: 1989GMS....54..133B
Altcode: 1989sspp.conf..133B
Under normal circumstances the composition of the solar wind is
mainly determined by processes occurring in the chromosphere and
the transition region. From the apparent systematics of solar wind
abundances with respect to the first ionization potentials of the
elements, it is concluded that these processes involve an efficient
ion-neutral separation. Detailed models of these processes have been
partially successful in reproducing solar wind abundances. However, some
features, e.g., the relatively low carbon abundance of solar energetic
particles (SEPs) and solar wind ions, remain difficult to explain. The
isotopic composition of solar wind neon differs significantly from
SEP-neon. It is not known what causes the discrepancy, and this raises
the question of how closely the solar wind reflects solar surface
isotopic abundances. The question can probably be solved only with
precise measurements of other isotopic ratios in the solar wind by
new techniques. The charge states of solar wind ions are established
during the transfer of matter through the corona. The charge state of
elements depends sensitively on the energy distribution of electrons
in the lower corona. It is expected that future observations can yield
more detailed information about charge state distributions and that
charge states will therefore serve as an efficient diagnostic tool
for varying conditions in the inner corona.
Title: Solar wind observations with the ion composition instrument
aboard the ISEE-3 ICE spacecraft
Authors: Ogilvie, K. W.; Coplan, M. A.; Bochsler, P.; Geiss, J.
Bibcode: 1989STIN...8915852O
Altcode:
The principal observations obtained by the Ion Composition Instrument
(ICI) flown on the ISEE-3/ICE spacecraft, which was in the solar wind
from September 1978 to the end of 1982, before being directed to the far
magnetotail of the Earth are discussed. Almost continuous observations
were made of the abundances of 3He++, 4He++, O6+, O7+, Ne, Si and Fe in
various charge states, and of their bulk speeds and temperatures. The
results show that there is a strong tendency in the collisionless solar
wind for the ionic temperatures to be proportional to the masses. For
heavier ions these temperatures exceed typical coronal electron
temperatures. 4He++, especially in high speed streams, moves faster
than H+, and travels at the same speed as heavier ions. The mechanism
leading to this heating and rapid streaming is still not entirely clear.
Title: CELIAS: Charge, element and isotope analysis system for SOHO
Authors: Hovestadt, D.; Geiss, J.; Gloeckler, G.; Moebius, E.;
Bochsler, P.; Gliem, F.; Ipavich, F. M.; Wilken, B.; Axford, W. I.;
Balsiger, H.
Bibcode: 1988sohi.rept...69H
Altcode:
The CELIAS (charge, element, and isotope analysis system) experiment
on SOHO (solar and heliospheric observatory) is described. It is
designed to measure the mass, ionic charge and energy of the low and
high speed solar wind, of suprathermal ions, and of low energy flare
particles. Through analysis of the elemental and isotopic abundances,
the ionic charge state and velocity distributions of ions originating
in the solar atmosphere, the investigation focuses on studying the
plasma processes on various temporal and spatial scales in the solar
chromosphere, transition zone, and corona. CELIAS includes three
mass and charge discriminating sensors based on the time-of-flight
technique. These intruments provide detailed in situ diagnostics of the
solar wind and of accelerated particles, which complement the optical
and spectroscopic investigations of the solar atmosphere carried out
by SOHO.
Title: Abundance of Iron Ions in the Solar Wind
Authors: Schmid, J.; Bochsler, P.; Geiss, J.
Bibcode: 1988ApJ...329..956S
Altcode:
For a period of 4 yr near the maximum of solar cycle 21 iron and
helium fluxes were measured in the solar wind. The ratio of the
summed fluxes from 45,000 spectra is 400 (+50 percent, -30 percent)
which is approximately 5 times lower than estimates of the solar
surface value. This difference is attributed to the difference of
first ionization potentials between the two elements, which leads to
a preferential feeding of iron (with a lower ionization potential)
into the coronal plasma, whereas helium has a tendency to remain below
as a neutral species. A marked increase of the He/Fe ratio is observed
in the driver gas following interplanetary shocks. Marginal depletions
of helium relative to iron are found at the sector boundaries of the
interplanetary magnetic field.
Title: Velocity of iron ions in the solar wind
Authors: Schmid, J.; Bochsler, P.; Geiss, J.
Bibcode: 1987JGR....92.9901S
Altcode:
From a set of approximately 7000 spectra provided by the ISEE 3 ion
composition instrument at the time near the maximum of solar cycle
21 we have been able to derive iron velocities and to compare them
with velocities of helium ions obtained with the same instrument. We
find a strong correlation among these velocities (rcor
=0.975+/-0.001). Whereas no significant velocity differences between
helium and iron are found at low solar wind speeds, it appears
that iron tends to flow at a somewhat lower speed (Δv~10 km/s) in
high-speed streams.
Title: Speculations about the origin of H3O+
seen in cometary mass spectra
Authors: Murad, Edmond; Bochsler, Peter
Bibcode: 1987Natur.326..366M
Altcode:
Recent mass spectrometer measurements of the composition of the coma
of Giacombini-Zinner and Halley comets have indicated the presence
of large amounts of H3O+. Here, we suggest that
some of these ions arise from the photoionization of the water dimer,
which is formed by direct vaporization of ice from solid surfaces at
the cometary nucleus or from ice particles ejected in cometary jets.
Title: Ion composition and upstream solar wind observations at
comet Giacobini-Zinner
Authors: Coplan, M. A.; Ogilvie, K. W.; A'Hearn, M. F.; Bochsler,
P.; Geiss, J.
Bibcode: 1987JGR....92...39C
Altcode:
The observations by the ion composition instrument (ICI)
on the ICE spacecraft made during the encounter with comet
P/Giacobini-Zinner (Ogilvie et al., 1986) are discussed in
detail. Solar wind 4He++
kinetic temperatures, densities, and velocities before, during,
and after the encounter are presented. These data combined with
4He++ velocity distributions provide
evidence for the existence of a thick diffuse shock. Relative abundances
of water group ions and CO+ are derived along with an
estimate of the abundance of an ion with M/Q=24+/-1 amu/e. The ICI data
are compared with electron data from two other experiments (Bame et al.,
1986; Meyer-Verner et al., 1986) and found to be in reasonable agreement
in the region outside the tail. Spectroscopic data for several neutral
and ionic species are compared with the ICI results for the water
group ions and CO+. The spectroscopic data are also used to
eliminate Mg+ and CN+ as candidates for the M/Q=24
peak. The two most likely candidates are C2+
and Na+, but neither photoionization of parent neutrals
nor sputtering from dust grains is sufficient to explain the observed
abundance relative to H2O+.
Title: Solar wind ion composition.
Authors: Bochsler, P.
Bibcode: 1987PhST...18...55B
Altcode:
The author discusses recent results on solar wind ion composition which
have been obtained in three different domains: in situ measurements by
spacecraft borne instruments, investigation of lunar soils for surface
implanted gases, and theoretical models of solar wind generation and
acceleration. The general agreement of solar wind abundances with solar
energetic particle abundances is confirmed. Abundances and ionization
states of different elements in the solar wind depend on the coronal
temperature, on the coronal temperature gradient, and on the process
which feeds ions into the solar wind. Future goals for research in
the field of solar wind composition are discussed.
Title: Origin of metal ions in the coma of P/Giacobini-Zinner
Authors: Geiss, J.; Bochsler, P.; Ogilvie, K. W.; Coplan, M. A.
Bibcode: 1986A&A...166L...1G
Altcode:
During the crossing of the ICE spacecraft through the coma of the comet
Giacobini-Zinner, ions with a mass/charge ratio 24±1 were unexpectedly
found. Na+ and/or Mg+ would fit into this mass
range. The authors discuss processes that could lead to high metal
ion abundances in cometary comae and conclude that evaporation or
sputtering from silicate grains are not likely to be responsible. A
remaining possibility is the occurrence of alkali metals in the icy
phase as a result of either cometary differentiation or co-condensation
of these elements with the icy component prior to the accretion of
cometary bodies.
Title: Ion Composition Results during the International Cometary
Explorer Encounter with Giacobini-Zinner
Authors: Ogilvie, K. W.; Coplan, M. A.; Bochsler, P.; Geiss, J.
Bibcode: 1986Sci...232..374O
Altcode:
The International Cometary Explorer spacecraft passed through the
coma of comet Giacobini-Zinner about 7800 kilometers antisunward of
the nucleus on 11 September 1985. The ion composition instrument was
sensitive to ambient ions with mass-to-charge ratios in the ranges
1.4 to 3 atomic mass units per electron charge (amu e-1)
and 14 to 33 amu e-1. Initial interpretation of the
measurements indicates the presence of H2O+,
H3O+, probably CO+ and HCO+,
and ions in the mass range 23 to 24; possible candidates are
Na+ and Mg+. In addition to these heavy ions,
measured over the velocity range 80 to 223 kilometers per second,
the instrument measured He2+ of solar wind origin over
the range 237 to 463 kilometers per second. The heavy ions have a
velocity distribution which indicates that they have been picked up
by the motional electric field, whereas the light ions are steadily
decelerated as the comet tail axis is approached. These results are in
agreement with the picture of a comet primarily consisting of water
ice, together with other material, that sublimes, streams away from
the nucleus, becomes ionized, and interacts with the solar wind.
Title: Solar Wind Composition and What We Expect to Learn from
Out-of-Ecliptic Measurements
Authors: Geiss, J.; Bochsler, P.
Bibcode: 1986ASSL..123..173G
Altcode: 1986shtd.symp..173G
Elemental abundances in the solar wind are fractionated relative to
the solar abundances by atom-ion separation in the upper chromosphere
and by ion-ion separation in the corona, where the charge states of
the ions are also frozen in. Thus, solar wind composition and charge
states of the elements can be used to study conditions and processes
at the solar surface and in the corona. The velocity distributions of
individual ion species reflect wave-particle interactions, collisions
and stream-stream interactions in interplanetary space. The SWICS and
SWPE experiments carried by Ulysses are well equipped for measurements
of the abundances of a number of elements and their charge and velocity
distributions. The scan over virtually all solar latitudes effected
by Ulysses ought to give new insight into processes and conditions
in the solar wind source regions, and it will provide data for a
three-dimensional picture of solar wind expansion and heliospheric
processes which is also important for studying the interactions of
the galactic cosmic rays and the interstellar gas with the heliosphere.
Title: Abundances of carbon, oxygen, and neon in the solar wind
during the period from August 1978 to June 1982
Authors: Bochsler, P.; Geiss, J.; Kunz, S.
Bibcode: 1986SoPh..103..177B
Altcode:
From four years of data provided by the Ion Composition Instrument
on ISEE-3, we have derived flux ratios of minor elements in the
solar wind and found He/O = 75 ± 20 and Ne/O = 0.17 ± 0.02. These
results are compared with recent solar energetic particle composition
data and photospheric values, and they are discussed in the light of
theoretical models of ionization and acceleration of heavy ions in
the solar chromosphere and corona.
Title: Kinetic temperatures of heavy ions in the solar wind
Authors: Bochsler, P.; Geis, J.; Joos, R.
Bibcode: 1985JGR....9010779B
Altcode:
From a refined analysis of 4 years of data of the ion composition
instrument on board ISEE 3 we find that in the overwhelming
majority of observations kinetic temperatures of ions are
approximately proportional to their masses. The logarithmic
average for T(4He++) is 5.363; for
T(O6+) and T(O7+) it is
5.978 and 6.000, respectively, corresponding to T(O)/T(He)=4.2. For
<log T(Fe)> we find 6.52, corresponding to T(Fe)/T(He)=14. The
correlation coefficients between oxygen and helium kinetic temperatures
are high (~0.78 or above), whereas for the correlation log T(Fe)
versus log T(He) we find a value of only 0.44 due to the large
measurement uncertainties of T(He). Significant deviations from the
mass/temperature proportionality are found at occasions of cool and
dense solar wind flow when Coulomb collisions succeed to equilibrate
kinetic temperatures of different ions species.
Title: Ion composition in the solar wind in relation to solar
abundances
Authors: Geiss, J.; Bochsler, P.
Bibcode: 1985irss.rept..213G
Altcode:
Processes affecting the composition of the solar wind are reviewed. A
process operating in or directly above the chromosphere has to be
invoked to explain the observed dependency on the first ionization
potential of corona, solar energetic particle, and solar wind abundances
relative to the photospheric composition. The critical velocity process,
that would lead to this type of element fractionation, was proposed
by Alfven (1960). The possibility of explaining the evidence by a
diffusive ion-atom separation process in a solar plasma under non-LTE
condition is discussed. Element and isotope abundance measurements in
the solar wind are summarized.
Title: Interpretation of3He abundance variations in the
solar wind
Authors: Coplan, M. A.; Ogilvie, K. W.; Bochsler, P.; Geiss, J.
Bibcode: 1984SoPh...93..415C
Altcode:
The ion composition instrument (ICI) on ISEE-3 has observed the
isotopes of helium of mass 3 and 4 in the solar wind almost continuously
between August 1978 and July 1982. This period included the increase
towards the maximum of solar activity cycle 21, the maximum period,
and the beginning of the descent towards solar minimum. Observations
were made when the solar wind speed was between 300 and 620 km
s−1. For part of the period evidence for regular
interplanetary magnetic sector structure was clear and a number
of3He flares occurred during this time.