explanation blue bibcodes open ADS page with paths to full text
Author name code: vonsteiger
ADS astronomy entries on 2022-09-14
author:"von Steiger, Rudolf E."
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Title: Observations of the Outer Heliosphere, Heliosheath, and
Interstellar Medium
Authors: Richardson, J. D.; Burlaga, L. F.; Elliott, H.; Kurth, W. S.;
Liu, Y. D.; von Steiger, R.
2022SSRv..218...35R Altcode:
The Voyager spacecraft have left the heliosphere and entered the
interstellar medium, making the first observations of the termination
shock, heliosheath, and heliopause. New Horizons is observing the solar
wind in the outer heliosphere and making the first direct observations
of solar wind pickup ions. This paper reviews the observations of the
solar wind plasma and magnetic fields throughout the heliosphere and
in the interstellar medium.
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Title: The Early History of Heliospheric Science and the Spacecraft
That Made It Possible
Authors: Zank, G. P.; Sterken, V.; Giacalone, J.; Möbius, E.;
von Steiger, R.; Stone, E. S.; Krimigis, S. M.; Richardson, J. D.;
Linsky, J.; Izmodenov, V.; Heber, B.
2022SSRv..218...34Z Altcode:
Our understanding of the interaction of the large-scale heliosphere with
the local interstellar medium (LISM) has undergone a profound change
since the very earliest analyses of the problem. In part, the revisions
have been a consequence of ever-improving and widening observational
results, especially those that identified the entrance of interstellar
material and gas into the heliosphere. Accompanying these observations
was the identification of the basic underlying physics of how neutral
interstellar gas and interstellar charged particles of different
energies, up to and including interstellar dust grains, interacted with
the temporal flows and electromagnetic fields of the heliosphere. The
incorporation of these various basic effects into global models of the
interaction, whether focused on neutral interstellar gas and pickup
ions, energetic particles such as anomalous and galactic cosmic rays,
or magnetic fields and large-scale flows, has profoundly changed our
view of how the heliosphere and LISM interact. This article presents
a brief history of the conceptual and observation evolution of our
understanding of the interaction of the heliosphere with the local
interstellar medium, up until approximately 1996.
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Title: Linking the Sun to the Heliosphere Using Composition Data
and Modelling
Authors: Parenti, Susanna; Chifu, Iulia; Del Zanna, Giulio; Edmondson,
Justin; Giunta, Alessandra; Hansteen, Viggo H.; Higginson, Aleida;
Laming, J. Martin; Lepri, Susan T.; Lynch, Benjamin J.; Rivera, Yeimy
J.; von Steiger, Rudolf; Wiegelmann, Thomas; Wimmer-Schweingruber,
Robert F.; Zambrana Prado, Natalia; Pelouze, Gabriel
2021SSRv..217...78P Altcode: 2021arXiv211006111P
Our understanding of the formation and evolution of the corona and
the heliosphere is linked to our capability of properly interpret the
data from remote sensing and in-situ observations. In this respect,
being able to correctly connect in-situ observations with their source
regions on the Sun is the key for solving this problem. In this work
we aim at testing a diagnostics method for this connectivity.
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Title: Editorial to the Topical Collection on Star Formation
Authors: Bykov, A. M.; Charbonnel, C.; Hennebelle, P.; Marcowith,
A.; Meynet, G.; Falanga, M.; von Steiger, R.
2020SSRv..216...53B Altcode:
No abstract at ADS
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Title: Small satellites for space science. A COSPAR scientific roadmap
Authors: Millan, Robyn M.; von Steiger, Rudolf; Ariel, Meir; Bartalev,
Sergey; Borgeaud, Maurice; Campagnola, Stefano; Castillo-Rogez, Julie
C.; Fléron, René; Gass, Volker; Gregorio, Anna; Klumpar, David M.;
Lal, Bhavya; Macdonald, Malcolm; Park, Jong Uk; Sambasiva Rao, V.;
Schilling, Klaus; Stephens, Graeme; Title, Alan M.; Wu, Ji
2019AdSpR..64.1466M Altcode:
This is a COSPAR roadmap to advance the frontiers of science through
innovation and international collaboration using small satellites. The
world of small satellites is evolving quickly and an opportunity
exists to leverage these developments to make scientific progress. In
particular, the increasing availability of low-cost launch and
commercially available hardware provides an opportunity to reduce the
overall cost of science missions. This in turn should increase flight
rates and encourage scientists to propose more innovative concepts,
leading to scientific breakthroughs. Moreover, new computer technologies
and methods are changing the way data are acquired, managed, and
processed. The large data sets enabled by small satellites will
require a new paradigm for scientific data analysis. In this roadmap
we provide several examples of long-term scientific visions that could
be enabled by the small satellite revolution. For the purpose of this
report, the term "small satellite" is somewhat arbitrarily defined as
a spacecraft with an upper mass limit in the range of a few hundred
kilograms. The mass limit is less important than the processes used
to build and launch these satellites. The goal of this roadmap is
to encourage the space science community to leverage developments in
the small satellite industry in order to increase flight rates, and
change the way small science satellites are built and managed. Five
recommendations are made; one each to the science community, to space
industry, to space agencies, to policy makers, and finally, to COSPAR.
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Title: Linking the Sun to the heliosphere using composition data
and modelling: coronal jets as a test case
Authors: Wimmer-Schweingruber, Robert F.; Parenti, Susanna; Del Zanna,
G.; Edmondson, J.; Giunta, A.; Hansteen, V. H.; Higginson, A.; Lepri,
S.; Laming, M.; Lynch, B. J.; von Steiger, R. E.; Wiegelmann, T.;
Zambrana Prado, N.
2019shin.confE.231W Altcode:
Understanding the formation and evolution of the solar wind is still
a priority in the Solar and Heliospheric communities. We expect
a significant progress in terms of observations with the upcoming
Solar Orbiter mission (launch in 2020), which will provide detailed
in-situ measurements of the solar wind and several remote-sensing
observations. However, real progress will only be possible if we
improve our understanding of the physical link between what measured
in-situ and its source regions on the Sun. In this respect, the plasma
chemical and charge-state compositions are considered good diagnostic
tools. In this paper we present results obtained from an extensive team
work aiming at providing solid diagnostics for linking the in-situ and
the remote sensing measurements. For our test cases, we selected two
periods when a single active region produced, close to its sunspot,
jets which had a counterpart signature in the Heliosphere in the form
of type-III radio bursts. These jets therefore marked magnetically
open regions expanding in the heliosphere. Firstly, we looked for
signatures of the open field associated with the active regions in
in-situ data from ACE and WIND, finding potential tracers. Secondly,
we studied the magnetic topology of the full Sun and Heliosphere with
extrapolations of photospheric data and MHD modeling. We found that
the open field area is consistent with the source and evolution of the
jets, as observed with EUV imagers (SDO/AIA, STEREO/EUVI). Thirdly, we
analysed remote sensing EUV spectroscopic observations to measure the
plasma conditions (densities, temperatures and chemical composition)
whenever available. We then modeled the solar wind and charge
state evolution with the solar distance along the open fields to
establish a link between the in-situ signatures and the remote sensing
observations. We discuss the various difficulties associated with such
studies, and highlight how Solar Orbiter measurements can improve them.
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Title: The Scientific Foundation of Space Weather
Authors: Baker, Daniel; Balogh, André; Gombosi, Tamas; Koskinen,
Hannu E. J.; Veronig, Astrid; von Steiger, Rudolf
2019sfsw.book.....B Altcode:
No abstract at ADS
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Title: Supernovae
Authors: Bykov, Andrei; Roger, Chevalier; Raymond, John; Thielemann,
Friedrich-Karl; Falanga, Maurizio; von Steiger, Rudolf
2019supe.book.....B Altcode:
No abstract at ADS
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Title: Achievements and Challenges in the Science of Space Weather
Authors: Koskinen, Hannu E. J.; Baker, Daniel N.; Balogh, André;
Gombosi, Tamas; Veronig, Astrid; von Steiger, Rudolf
2019sfsw.book....1K Altcode:
No abstract at ADS
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Title: Geoeffective Properties of Solar Transients and Stream
Interaction Regions
Authors: Kilpua, E. K. J.; Balogh, A.; von Steiger, R.; Liu, Y. D.
2019sfsw.book..295K Altcode:
No abstract at ADS
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Title: Determination of Plasma, Pickup Ion, and Suprathermal Particle
Spectrum in the Solar Wind Frame of Reference
Authors: Zhang, Ming; Zhao, Lulu; von Steiger, R.;
Wimmer-Schweingruber, R. F.; Gloeckler, G. M.; Desai, M.; Pogorelov,
N. V.
2019ApJ...871...60Z Altcode:
Particle spectra directly measured by a plasma or low-energy particle
experiment on spacecraft often contain instrumental effects due to a
limited field of view or angular resolution. It is because the particle
distribution function at low energies is highly anisotropic in the
spacecraft frame of reference, in which the measurements are made. In
this paper, we present a new mathematical method of transforming
the particle spectrum to the solar wind frame of reference, where
the particle distribution can be assumed to be nearly isotropic. The
transformed particle spectrum allows us to investigate the properties of
the solar wind, pickup ions, and suprathermal particles without concern
for instrumental effects. We apply the method to the measurements made
by the Solar Wind Ion Composition Spectrometer on Ulysses. Our results
demonstrate that the transformed spectrum can improve the determination
of the solar wind density and temperature from the previously published
methods. A brief survey of Ulysses data shows that suprathermal ions
in the slow solar wind frequently display a velocity distribution very
close to the v <SUP>-5</SUP> power law.
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Title: Preface
Authors: Bykov, A. M.; Chevalier, R. A.; Raymond, J. C.; Thielemann,
F. -K.; Falanga, M.; von Steiger, R.
2019supe.book....1B Altcode:
No abstract at ADS
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Title: Small Satellites for Space Science (4S) COSPAR Roadmap
Authors: Millan, Robyn; Von Steiger, Rudolf; Castillo-Rogez, Julie;
Lal, Bhavya
2018cosp...42E2286M Altcode:
In 2016, COSPAR commissioned an international scientific roadmap on
Small Satellites for Space Science (4S), focusing particularly on
CubeSats and CubeSat-technology enabled small satellites. The report
is motivated by recent progress and results summarized in a published
paper (Zurbuchen, von Steiger et al., Performing High-Quality Science
on CubeSats, Space Research Today, Vol. 196, pp. 10-30, August 2016) and
a study by the US National Academies (Zurbuchen, Lal, et al., Achieving
Science with CubeSats: Thinking Inside the Box, The National Academies
Press, Washington, DC, 2016). The roadmap has been developed by a
study team that covers a broad range of scientific and technological
disciplines, from Earth to planetary science, and from solar system
science to astronomy. The team is composed of scientists and engineers
working in universities, public research institutions and industry. The
report is structured into three main parts: I. Our Neighborhood: current
status of technology and scientific potential of small satellites and
CubeSatsII. Visions for the Future: potential ideas for what small
satellites could be used for in the futureIII. Challenges to Further
Development and Progress, and Ways to Overcome Them: roles of agencies,
industry, policies, international collaboration and exchange In this
presentation, members of the study team will give an overview of the
roadmap and summarize the findings of the study team, concentrating
on the parts relating to planetary science in particular. The final
report is intended to be of value to space agencies internationally
and their supporting governments, as well as non-profits and other
private sector organizations that would be interested in promoting
global smallsat-based missions.
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Title: Long-term evolution of solar wind elemental and charge state
composition
Authors: Von Steiger, Rudolf; Gilbert, Jason A.
2018cosp...42E3559V Altcode:
Before the 1990s observations of heavy elements in the solar wind
(A>4) were limited to a small number of brief periods with favorable
conditions. This has changed with the launch of the Ulysses mission
in October 1990 and the ACE mission in August 1997, whose SWICS sister
instruments are providing us with composition data covering all charge
states of C, N, O, Ne, N, Mg, Si, S, and Fe. The nearly uninterrupted
data sets combined now cover almost three full decades: Ulysses was
operating until June 2009 and ACE continues to operate until today,
although with some limitations of SWICS since August 2011. We will
present an overview of these unique data sets and the interpretation
of the elemental and charge state composition therein.
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Title: Small Satellites for Space Science (4S) COSPAR Roadmap
Authors: Von Steiger, Rudolf; Millan, Robyn; Schilling, Klaus;
Borgeaud, Maurice
2018cosp...42E3560V Altcode:
In 2016 COSPAR commissioned an international scientific roadmap on
Small Satellites for Space Science (4S), focusing particularly on
CubeSats and CubeSat-technology enabled small satellites. The report
is motivated by recent progress and results summarized in a published
paper (Zurbuchen, von Steiger et al., Performing High-Quality Science
on CubeSats, Space Research Today, Vol. 196, pp. 10-30, August 2016)
and a study by the US National Academies (Zurbuchen, Lal, et al.,
Achieving Science with CubeSats: Thinking Inside the Box, The National
Academies Press, Washington, DC, 2016).The roadmap has been developed
by a study team that covers a broad range of scientific disciplines,
from Earth to planetary science and from solar system science to
astronomy. The team is composed of scientists and engineers working in
universities, public research institutions and industry. The report is
structured into three main parts:I. Our Neighborhood: current status
and scientific potential of small satellites and CubeSatsII. Visions
for the Future: potential ideas for what small satellites could be
in the futureIII. Challenges to Further Development and Progress,
and Ways to Overcome Them: roles of agencies, industry, policies,
international collaboration and exchangeIn this presentation, members
of the study team will give an overview of the roadmap and summarize
the findings of the study team with emphasis on the parts relating to
Earth observation in particular. The final report is intended to be
of value to space agencies, key actors, industries, and governments
involved in Small Satellites
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Title: Editorial to the Topical Collection on Supernovae
Authors: Bykov, A. M.; Chevalier, R. A.; Raymond, J. C.; Thielemann,
F. -K.; Falanga, M.; von Steiger, R.
2018SSRv..214...73B Altcode:
No abstract at ADS
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Title: Imaging Plasma Density Structures in the Soft X-Rays Generated
by Solar Wind Charge Exchange with Neutrals
Authors: Sibeck, David G.; Allen, R.; Aryan, H.; Bodewits, D.; Brandt,
P.; Branduardi-Raymont, G.; Brown, G.; Carter, J. A.; Collado-Vega,
Y. M.; Collier, M. R.; Connor, H. K.; Cravens, T. E.; Ezoe, Y.; Fok,
M. -C.; Galeazzi, M.; Gutynska, O.; Holmström, M.; Hsieh, S. -Y.;
Ishikawa, K.; Koutroumpa, D.; Kuntz, K. D.; Leutenegger, M.; Miyoshi,
Y.; Porter, F. S.; Purucker, M. E.; Read, A. M.; Raeder, J.; Robertson,
I. P.; Samsonov, A. A.; Sembay, S.; Snowden, S. L.; Thomas, N. E.;
von Steiger, R.; Walsh, B. M.; Wing, S.
2018SSRv..214...79S Altcode:
Both heliophysics and planetary physics seek to understand the complex
nature of the solar wind's interaction with solar system obstacles
like Earth's magnetosphere, the ionospheres of Venus and Mars, and
comets. Studies with this objective are frequently conducted with the
help of single or multipoint in situ electromagnetic field and particle
observations, guided by the predictions of both local and global
numerical simulations, and placed in context by observations from far
and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral
atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or
transient magnetic reconnection, local or global magnetic reconnection,
ion pick-up, or the Kelvin-Helmholtz instability) generates diagnostic
plasma density structures. The significance of each mechanism to the
overall interaction (as measured in terms of atmospheric/ionospheric
loss at comets, Venus, and Mars or global magnetospheric/ionospheric
convection at Earth) remains to be determined but can be evaluated on
the basis of how often the density signatures that it generates are
observed as a function of solar wind conditions. This paper reviews
efforts to image the diagnostic plasma density structures in the soft
(low energy, 0.1-2.0 keV) X-rays produced when high charge state solar
wind ions exchange electrons with the exospheric neutrals surrounding
solar system obstacles. <P />The introduction notes that theory, local,
and global simulations predict the characteristics of plasma boundaries
such the bow shock and magnetopause (including location, density
gradient, and motion) and regions such as the magnetosheath (including
density and width) as a function of location, solar wind conditions,
and the particular mechanism operating. In situ measurements confirm
the existence of time- and spatial-dependent plasma density structures
like the bow shock, magnetosheath, and magnetopause/ionopause at Venus,
Mars, comets, and the Earth. However, in situ measurements rarely
suffice to determine the global extent of these density structures
or their global variation as a function of solar wind conditions,
except in the form of empirical studies based on observations from many
different times and solar wind conditions. Remote sensing observations
provide global information about auroral ovals (FUV and hard X-ray),
the terrestrial plasmasphere (EUV), and the terrestrial ring current
(ENA). ENA instruments with low energy thresholds (∼1 keV) have
recently been used to obtain important information concerning the
magnetosheaths of Venus, Mars, and the Earth. Recent technological
developments make these magnetosheaths valuable potential targets
for high-cadence wide-field-of-view soft X-ray imagers. <P />Section
2 describes proposed dayside interaction mechanisms, including
reconnection, the Kelvin-Helmholtz instability, and other processes
in greater detail with an emphasis on the plasma density structures
that they generate. It focuses upon the questions that remain as yet
unanswered, such as the significance of each proposed interaction mode,
which can be determined from its occurrence pattern as a function of
location and solar wind conditions. Section 3 outlines the physics
underlying the charge exchange generation of soft X-rays. Section
4 lists the background sources (helium focusing cone, planetary,
and cosmic) of soft X-rays from which the charge exchange emissions
generated by solar wind exchange must be distinguished. With the help
of simulations employing state-of-the-art magnetohydrodynamic models
for the solar wind-magnetosphere interaction, models for Earth's
exosphere, and knowledge concerning these background emissions,
Sect. 5 demonstrates that boundaries and regions such as the bow shock,
magnetosheath, magnetopause, and cusps can readily be identified in
images of charge exchange emissions. Section 6 reviews observations by
(generally narrow) field of view (FOV) astrophysical telescopes that
confirm the presence of these emissions at the intensities predicted
by the simulations. Section 7 describes the design of a notional wide
FOV "lobster-eye" telescope capable of imaging the global interactions
and shows how it might be used to extract information concerning the
global interaction of the solar wind with solar system obstacles. The
conclusion outlines prospects for missions employing such wide FOV
imagers.
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Title: Minimal Magnetic States of the Sun and the Solar Wind:
Implications for the Origin of the Slow Solar Wind
Authors: Cliver, E. W.; von Steiger, R.
2018smf..book..227C Altcode:
No abstract at ADS
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Title: Jets and Winds in Pulsar Wind Nebulae, Gamma-Ray Bursts
and Blazars
Authors: Bykov, Andrei; Amato, Elena; Arons, Jonathan; Falanga,
Maurizio; Lemoine, Martin; Stella, Luigi; von Steiger, Rudolf
2018jwpw.book.....B Altcode:
No abstract at ADS
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Title: Solar Magnetic Fields
Authors: Balogh, André; Cliver, Edward; Petrie, Gordon; Solanki,
Sami; Thompson, Michael; von Steiger, Rudolf
2018smf..book.....B Altcode:
No abstract at ADS
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Title: Editorial: Measuring Solar Magnetic Fields—An Outline of
History, Current Status and Challenges
Authors: Balogh, André; von Steiger, Rudolf
2018smf..book....1B Altcode:
No abstract at ADS
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Title: Editorial: Topical Collection on Jets and Winds in Pulsar
Wind Nebulae, Gamma-Ray Bursts and Blazars
Authors: Bykov, A.; Amato, E.; Arons, J.; Falanga, M.; Lemoine, M.;
Stella, L.; von Steiger, R.
2018jwpw.book....1B Altcode:
No abstract at ADS
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Title: Achievements and Challenges in the Science of Space Weather
Authors: Koskinen, Hannu E. J.; Baker, Daniel N.; Balogh, André;
Gombosi, Tamas; Veronig, Astrid; von Steiger, Rudolf
2017SSRv..212.1137K Altcode: 2017SSRv..tmp...80K
In June 2016 a group of 40 space weather scientists attended the
workshop on Scientific Foundations of Space Weather at the International
Space Science Institute in Bern. In this lead article to the volume
based on the talks and discussions during the workshop we review some of
main past achievements in the field and outline some of the challenges
that the science of space weather is facing today and in the future.
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Title: Geoeffective Properties of Solar Transients and Stream
Interaction Regions
Authors: Kilpua, E. K. J.; Balogh, A.; von Steiger, R.; Liu, Y. D.
2017SSRv..212.1271K Altcode: 2017SSRv..tmp..161K
Interplanetary Coronal Mass Ejections (ICMEs), their possible shocks
and sheaths, and co-rotating interaction regions (CIRs) are the primary
large-scale heliospheric structures driving geospace disturbances at the
Earth. CIRs are followed by a faster stream where Alfvénic fluctuations
may drive prolonged high-latitude activity. In this paper we highlight
that these structures have all different origins, solar wind conditions
and as a consequence, different geomagnetic responses. We discuss
general solar wind properties of sheaths, ICMEs (in particular those
showing the flux rope signatures), CIRs and fast streams and how
they affect their solar wind coupling efficiency and the resulting
magnetospheric activity. We show that there are two different solar
wind driving modes: (1) Sheath-like with turbulent magnetic fields,
and large Alfvén Mach (M<SUB>A</SUB>) numbers and dynamic pressure,
and (2) flux rope-like with smoothly varying magnetic field direction,
and lower M<SUB>A</SUB> numbers and dynamic pressure. We also summarize
the key properties of interplanetary shocks for space weather and how
they depend on solar cycle and the driver.
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Title: Editorial: Measuring Solar Magnetic Fields—An Outline of
History, Current Status and Challenges
Authors: Balogh, André; von Steiger, Rudolf
2017SSRv..210....1B Altcode: 2017SSRv..tmp..163B
No abstract at ADS
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Title: Minimal Magnetic States of the Sun and the Solar Wind:
Implications for the Origin of the Slow Solar Wind
Authors: Cliver, E. W.; von Steiger, R.
2017SSRv..210..227C Altcode: 2015SSRv..tmp..116C
During the last decade it has been proposed that both the Sun and
the solar wind have minimum magnetic states, lowest order levels
of magnetism that underlie the 11-yr cycle as well as longer-term
variability. Here we review the literature on basal magnetic states at
the Sun and in the heliosphere and draw a connection between the two
based on the recent deep 2008-2009 minimum between cycles 23 and 24. In
particular, we consider the implications of the low solar activity
during the recent minimum for the origin of the slow solar wind.
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Title: Editorial: Topical Collection on Jets and Winds in Pulsar
Wind Nebulae, Gamma-Ray Bursts and Blazars. Physics of Extreme
Energy Release
Authors: Bykov, A.; Amato, E.; Arons, J.; Falanga, M.; Lemoine, M.;
Stella, L.; von Steiger, R.
2017SSRv..207....1B Altcode: 2017SSRv..tmp...45B
No abstract at ADS
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Title: Fundamental Physics of the Slow Solar Wind - What do we Know?
Authors: Ofman, L.; Abbo, L.; Antiochos, S. K.; Hansteen, V. H.;
Harra, L.; Ko, Y. K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;
von Steiger, R.; Wang, Y. M.
2016AGUFMSH42A..01O Altcode:
Fundamental physical properties of the slow solar wind (SSW), such
as density, temperature, outflow speed, heavy ion abundances and
charges states were obtained from in-situ measurements at 1AU in
the past from WIND, ACE, and other spacecraft. Plasma and magnetic
field measurement are available as close as 0.3 AU from Helios data,
Spektr-R, and MESSENGER spacecraft. Remote sensing spectroscopic
measurements are available in the corona and below from SOHO/UVCS,
Hinode, and other missions. One of the major objectives of the Solar
Orbiter and Solar Probe Plus missions is to study the sources of the
SSW close to the Sun. The present state of understanding of the physics
of the SSW is based on the combination of the existing observations,
theoretical and numerical 3D MHD and multi-fluid models, that connect
between the SSW sources in the corona and the heliosphere. Recently,
hybrid models that combine fluid electrons and kinetic ions of the
expanding solar wind were developed, and provide further insights of the
local SSW plasma heating processes that related to turbulent magnetic
fluctuations spectra and kinetic ion instabilities observed in the
SSW plasma. These models produce the velocity distribution functions
(VDFs) of the protons and heavier ions as well as the ion anisotropic
temperatures. I will discuss the results of the above observations
and models, and review the current status of our understanding of
the fundamental physics of the SSW. I will review the open questions,
and discuss how they could be addressed with near future observations
and models.
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Title: Solar Metallicity Derived from In-Situ Solar Wind Composition
Authors: von Steiger, R.; Zurbuchen, T.
2016AGUFMSH51B2578V Altcode:
Solar metallicity — the fraction per unit mass that is composed of
elements heavier than He — is a critical and fundamental quantity
indicative of the history and future evolution of the Sun. Over
the last decade spectroscopic observations of the solar photosphere
using inversion techniques of increasing sophistication have led to a
downward revision of the abundances of heavy elements, specifically C,
N, and O, and thus of the solar metallicity. This in turn has led to
a crisis of solar models, which became inconsistent with the results
of helioseismology as a consequence of the missing opacity from these
elements. We present recently released solar wind compositional data
to determine the metallicity of the Sun. We focus on a present-day
solar sample available to us, which is the least fractionated solar
wind from coronal holes near the poles of the Sun. Using these data,
we derive a metallicity of Z = 0.0196 ± 0.0014, which is signicantly
larger than recent published values based on photospheric spectroscopy,
but consistent with results from helioseismology.
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Title: Slow Solar Wind: Observations and Modeling
Authors: Abbo, L.; Ofman, L.; Antiochos, S. K.; Hansteen, V. H.;
Harra, L.; Ko, Y. -K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;
von Steiger, R.; Wang, Y. -M.
2016SSRv..201...55A Altcode: 2016SSRv..tmp...34A
While it is certain that the fast solar wind originates from coronal
holes, where and how the slow solar wind (SSW) is formed remains an
outstanding question in solar physics even in the post-SOHO era. The
quest for the SSW origin forms a major objective for the planned future
missions such as the Solar Orbiter and Solar Probe Plus. Nonetheless,
results from spacecraft data, combined with theoretical modeling, have
helped to investigate many aspects of the SSW. Fundamental physical
properties of the coronal plasma have been derived from spectroscopic
and imaging remote-sensing data and in situ data, and these results
have provided crucial insights for a deeper understanding of the origin
and acceleration of the SSW. Advanced models of the SSW in coronal
streamers and other structures have been developed using 3D MHD and
multi-fluid equations.
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Title: Composition of Coronal Mass Ejections
Authors: Zurbuchen, T. H.; Weberg, M.; von Steiger, R.; Mewaldt,
R. A.; Lepri, S. T.; Antiochos, S. K.
2016ApJ...826...10Z Altcode:
We analyze the physical origin of plasmas that are ejected from the
solar corona. To address this issue, we perform a comprehensive analysis
of the elemental composition of interplanetary coronal mass ejections
(ICMEs) using recently released elemental composition data for Fe,
Mg, Si, S, C, N, Ne, and He as compared to O and H. We find that
ICMEs exhibit a systematic abundance increase of elements with first
ionization potential (FIP) < 10 eV, as well as a significant increase
of Ne as compared to quasi-stationary solar wind. ICME plasmas have a
stronger FIP effect than slow wind, which indicates either that an FIP
process is active during the ICME ejection or that a different type of
solar plasma is injected into ICMEs. The observed FIP fractionation
is largest during times when the Fe ionic charge states are elevated
above Q <SUB>Fe</SUB> > 12.0. For ICMEs with elevated charge states,
the FIP effect is enhanced by 70% over that of the slow wind. We argue
that the compositionally hot parts of ICMEs are active region loops that
do not normally have access to the heliosphere through the processes
that give rise to solar wind. We also discuss the implications of
this result for solar energetic particles accelerated during solar
eruptions and for the origin of the slow wind itself.
---------------------------------------------------------
Title: Solar Metallicity Derived from in situ Solar Wind Composition
Authors: von Steiger, R.; Zurbuchen, T. H.
2016ApJ...816...13V Altcode:
We use recently released solar wind compositional data to determine the
metallicity of the Sun—the fraction per unit mass that is composed
of elements heavier than He. We focus on a present-day solar sample
available to us, which is the least fractionated solar wind from
coronal holes near the poles of the Sun. Using these data, we derive
a metallicity of Z = 0.0196 ± 0.0014, which is significantly larger
than recent published values based on photospheric spectroscopy,
but consistent with results from helioseismology.
---------------------------------------------------------
Title: Slow Solar Wind: Observable Characteristics for Constraining
Modelling
Authors: Ofman, L.; Abbo, L.; Antiochos, S. K.; Hansteen, V. H.;
Harra, L.; Ko, Y. K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;
von Steiger, R.; Wang, Y. M.
2015AGUFMSH11F..03O Altcode:
The Slow Solar Wind (SSW) origin is an open issue in the post SOHO
era and forms a major objective for planned future missions such as
the Solar Orbiter and Solar Probe Plus.Results from spacecraft data,
combined with theoretical modeling, have helped to investigate many
aspects of the SSW. Fundamental physical properties of the coronal
plasma have been derived from spectroscopic and imaging remote-sensing
data and in-situ data, and these results have provided crucial insights
for a deeper understanding of the origin and acceleration of the
SSW.Advances models of the SSW in coronal streamers and other structures
have been developed using 3D MHD and multi-fluid equations.Nevertheless,
there are still debated questions such as:What are the source regions
of SSW? What are their contributions to the SSW?Which is the role
of the magnetic topology in corona for the origin, acceleration and
energy deposition of SSW?Which are the possible acceleration and heating
mechanisms for the SSW?The aim of this study is to present the insights
on the SSW origin and formationarisen during the discussions at the
International Space Science Institute (ISSI) by the Team entitled
”Slowsolar wind sources and acceleration mechanisms in the corona”
held in Bern (Switzerland) in March2014--2015. The attached figure will
be presented to summarize the different hypotheses of the SSW formation.
---------------------------------------------------------
Title: New insights in the interstellar dust properties and
its interaction with the heliosphere from data, simulations and
experiments
Authors: Sterken, V. J.; Strub, P.; Krüger, H.; von Steiger, R.;
Frisch, P. C.; Moragas-Klostermeyer, G.
2015AGUFMSH53C..07S Altcode:
Interstellar dust moves through the heliosphere at velocities of
ca. 26 km/s due to the relative motion of the local interstellar
cloud and the solar system. On their way through the solar system,
these charged particles' trajectories are affected by solar radiation
pressure force, gravity and Lorentz force, causing them to deviate in
a temporal and in a spatial way that depends on the particle properties
and on the interplanetary magnetic field. Combining 16 years of Ulysses
interstellar dust data with Monte Carlo simulations of these particle
trajectories in the inner heliosphere have unveiled new insights in
the interstellar dust flow, the dust properties and it can be used to
explore the nature of the outer heliosphere.We start the talk with an
overview of the current state of the art of the local interstellar dust
research. We then explain the simulations and put them in the context
of the Ulysses data. Using these, we demonstrate that the particles
are likely to be porous, and we show why a model of dust propagation
through the outer heliosphere is needed to provide a final proof. Also,
we discuss the steps needed to determine from the simulations, data,
and experiments how porous or fluffy the interstellar dust is. Finally,
we explain how ISD data can be used as an extra 'measureable' to explore
the structure of the outer heliosphere and we conclude the talk with
a summary of how this enhances our knowledge of ISD and the LIC.
---------------------------------------------------------
Title: Variations in Solar Wind Fractionation as Seen by ACE/SWICS
Over a Full Solar Cycle and the Implications for Genesis Mission
Results
Authors: Reisenfeld, D. B.; Pilleri, P.; Zurbuchen, T.; Lepri, S. T.;
Shearer, P.; Gilbert, J. A.; von Steiger, R.; Wiens, R. C.
2015AGUFMSH22B..06R Altcode:
We use ACE/SWICS elemental composition data to compare the variations
in solar wind fractionation as measured by SWICS during the previous
solar maximum (1999-2001), solar minimum (2006-2009) and the period in
which the Genesis spacecraft was collecting solar wind (late 2001 -
early 2004). We differentiate our analysis in terms of solar wind
regimes (i.e. solar wind originating from interstream or coronal
hole flows, or coronal mass ejecta). Abundances are normalized to the
low-FIP ion magnesium to uncover correlations that are not apparent
when normalizing to high-FIP ions. We find that relative to magnesium,
the other low-FIP elements are measurably fractionated, but the degree
of fractionation does not vary significantly over the solar cycle. For
the high-FIP ions, variation in fractionation over the solar cycle is
significant: greatest for Ne/Mg and C/Mg, less so for O/Mg, and the
least for He/Mg. When abundance ratios are examined as a function of
solar wind speed, we find a strong correlation, with the remarkable
observation that the degree of fractionation follows a mass-dependent
trend. We will discuss the implications for correcting the Genesis
sample return results to photospheric abundances.
---------------------------------------------------------
Title: Variations in Solar Wind Fractionation as Seen by ACE/SWICS
and the Implications for Genesis Mission Results
Authors: Pilleri, P.; Reisenfeld, D. B.; Zurbuchen, T. H.; Lepri,
S. T.; Shearer, P.; Gilbert, J. A.; von Steiger, R.; Wiens, R. C.
2015ApJ...812....1P Altcode: 2015arXiv150804566P
We use Advanced Composition Explorer (ACE)/Solar Wind Ion Composition
Spectrometer (SWICS) elemental composition data to compare the
variations in solar wind (SW) fractionation as measured by SWICS during
the last solar maximum (1999-2001), the solar minimum (2006-2009),
and the period in which the Genesis spacecraft was collecting SW (late
2001—early 2004). We differentiate our analysis in terms of SW regimes
(i.e., originating from interstream or coronal hole flows, or coronal
mass ejecta). Abundances are normalized to the low-first ionization
potential (low-FIP) ion magnesium to uncover correlations that are not
apparent when normalizing to high-FIP ions. We find that relative to
magnesium, the other low-FIP elements are measurably fractionated,
but the degree of fractionation does not vary significantly over
the solar cycle. For the high-FIP ions, variation in fractionation
over the solar cycle is significant: greatest for Ne/Mg and C/Mg,
less so for O/Mg, and the least for He/Mg. When abundance ratios are
examined as a function of SW speed, we find a strong correlation, with
the remarkable observation that the degree of fractionation follows a
mass-dependent trend. We discuss the implications for correcting the
Genesis sample return results to photospheric abundances.
---------------------------------------------------------
Title: Sixteen Years of Ulysses Interstellar Dust Measurements in
the Solar System. III. Simulations and Data Unveil New Insights into
Local Interstellar Dust
Authors: Sterken, Veerle J.; Strub, Peter; Krüger, Harald; von
Steiger, Rudolf; Frisch, Priscilla
2015ApJ...812..141S Altcode:
Interstellar dust (ISD) in the solar system was detected in situ for
the first time in 1993 by the Ulysses dust detector. The study of
ISD is important for understanding its role in star and solar system
formation. The goal of this paper is to understand the variability in
the ISD observations from the Ulysses mission by using a Monte Carlo
simulation of ISD trajectories, with the final aim to constrain the
ISD particle properties from simulations and the data. The paper is
part of a series of three: Strub et al. describe the variations of the
ISD flow from the Ulysses data set, and Krüger et al. focus on its
ISD mass distribution. We describe and interpret the simulations of
the ISD flow at Ulysses orbit for a wide range of particle properties
and discuss four open issues in ISD research: the existence of very
big ISD particles, the lack of smaller ISD particles, the shift in
dust flow direction in 2005, and particle properties. We conclude that
the shift in the dust flow direction in 2005 can best be explained by
Lorentz force in the inner heliosphere, but that an extra filtering
mechanism is needed to fit the fluxes. A time-dependent filtering in
the outer regions of the heliosphere is proposed for this. Also, the
high charge-to-mass ratio values found for the heavier particles after
2003 indicate that these particles are lower in density than previously
assumed. This method gives new insights into the ISD properties and
paves the way toward getting a complete view on the ISD from the local
interstellar cloud. We conclude that in combination with the data and
simulations, also impact ionization experiments are necessary using
low-density dust, in order to constrain the density of the particles.
---------------------------------------------------------
Title: Introduction to the Solar Activity Cycle: Overview of Causes
and Consequences
Authors: Balogh, A.; Hudson, H. S.; Petrovay, K.; von Steiger, R.
2015sac..book....1B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Solar Activity Cycle
Authors: Balogh, André; Hudson, Hugh; Petrovay, Kristóf; von
Steiger, Rudolf
2015sac..book.....B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The role of the heliosphere for interstellar dust trajectories
- revisited
Authors: Sterken, V. J.; Strub, P.; Krüger, H.; von Steiger, R.;
Grün, E.
2014AGUFMSH13B4124S Altcode:
Interstellar dust (ISD) moves through the solar system due to the
relative motion of the solar system and the local interstellar cloud,
at a speed of about 26 km/s. Most of the knowledge on these ISD
trajectories and their interplay with the interplanetary magnetic field
come from dust impact measurements using the Ulysses dust detector
in combination with modelling of the ISD trajectories. In this talk
we explain the dynamics of interstellar dust in the heliosphere, we
discuss in detail the resulting fluxes and directions of the ISD flow
at the location of Ulysses, we put this in context with existing data,
review the influence of three different descriptions of the IMF on
the modelling, and finally we conclude with the role of the boundary
region of the heliosphere on the ISD flux.
---------------------------------------------------------
Title: Introduction to the Solar Activity Cycle: Overview of Causes
and Consequences
Authors: Balogh, A.; Hudson, H. S.; Petrovay, K.; von Steiger, R.
2014SSRv..186....1B Altcode: 2014SSRv..tmp...60B
The 11-year activity cycle is a dominant characteristic of the Sun. It
is the result of the evolution in time the solar dynamo that generates
the solar magnetic field. The nearly periodic variation in the sunspot
number has been known since the mid-1800s; as the observations of
the Sun broadened to cover an increasing number of phenomena, the
same 11-year periodicity was noted in most of them. The discovery of
solar magnetic fields introduced a 22-year periodicity, as the magnetic
polarities of the polar regions change sign every 11 years. Correlations
have been identified and quantified among all the measured parameters,
but in most cases such correlations remain empirical rather than
grounded in physical processes. This introductory paper and the reviews
in the volume describe and discuss the current state of understanding
of the causal chains that lead from the variable nature of the solar
magnetic fields to the variability of solar phenomena. The solar
activity cycle is poorly understood: predictions made for the current
Cycle 24 have proved to be generally wrong. However, the re-evaluation
of the relationships in the light of unexpected shortcomings is likely
to lead to a better physical understanding of solar physics. This
will help in the systematic reassessment of solar activity indices and
their usefulness in describing and predicting the solar activity cycle.
---------------------------------------------------------
Title: Solar Wind C, N, and O Abundances and the Solar Metallicity
Authors: von Steiger, R.; Zurbuchen, T.; Shearer, P.; Gilbert, J. A.
2014AGUFMSH33A4127V Altcode:
Solar wind composition provides important constraints to solar
composition and to the processes that modify such compositional patterns
in the atmospheres of the Sun and of active stars. There are a number
of ways that composition can be observed, including spectroscopy,
helioseismology, and the collection of solar samples either in the
form of solar wind or energetic particles. In either case, models
are needed to infer compositional constraints from observations. For
example, models are needed to interpret solar spectroscopy results,
and the evolution of these has recently led to significant changes to
the previously accepted solar composition. The collection of solar
samples requires a different type of consideration. Most solar wind
and energetic particle samples are fractionated according to first
ionization potential (FIP) as first pointed out by Hovestadt et
al. in the seventies - elements with FIP below 10 eV are enhanced
relative to elements at higher FIP, and He and possibly Ne are
further depleted. Besides FIP fractionation there are indications
from both isotopic and elemental data that mass fractionation, either
through gravitational and/or collisional processes, may also play a
role. Based on comparisons of in situ data with coronal spectroscopy it
is evident that most of these processes occur at the interface between
the photosphere and the corona. However, the high-latitude corona near
solar minimum appears to undergo much less fractionation, if any at
all. Thus it provides a heliospheric sample that is - to within our
observational constraints - photospheric in nature. The low-latitude
heliosphere further provides direct access to plasmas that have the
fractionation pattern qualitatively and quantitatively similar to
the one observed in the corona. We present a recent reanalysis of the
SWICS observations on both Ulysses and ACE using modern statistical
tools. Concentrating on C, N, and O, which together with the recently
published Ne (Shearer et al., ApJ, 2014) contribute 96% of the solar
metallicity, we find that the solar wind metallicity is significantly
higher than the recent compilation of spectroscopic abundances (Asplund
et al., ARAA, 2009). It is more in line with earlier spectroscopic
results and, more importantly, not incompatible with helioseismology
results of the solar interior.
---------------------------------------------------------
Title: Solar Corona/Wind Composition and Origins of the Solar Wind
Authors: Lepri, S. T.; Gilbert, J. A.; Landi, E.; Shearer, P.; von
Steiger, R.; Zurbuchen, T.
2014AGUFMSH33A4129L Altcode:
Measurements from ACE and Ulysses have revealed a multifaceted solar
wind, with distinctly different kinetic and compositional properties
dependent on the source region of the wind. One of the major outstanding
issues in heliophysics concerns the origin and also predictability of
quasi-stationary slow solar wind. While the fast solar wind is now
proven to originate within large polar coronal holes, the source of
the slow solar wind remains particularly elusive and has been the
subject of long debate, leading to models that are stationary and
also reconnection based - such as interchange or so-called S-web based
models. Our talk will focus on observational constraints of solar wind
sources and their evolution during the solar cycle. In particular,
we will point out long-term variations of wind composition and dynamic
properties, particularly focused on the abundance of elements with low
First Ionization Potential (FIP), which have been routinely measured on
both ACE and Ulysses spacecraft. We will use these in situ observations,
and remote sensing data where available, to provide constraints for
solar wind origin during the solar cycle, and on their correspondence
to predictions for models of the solar wind.
---------------------------------------------------------
Title: Tracking the direction of the interstellar wind over a full
solar cycle using pickup ions detected by ACE SWICS
Authors: Gilbert, J. A.; Gershman, D. J.; Gloeckler, G.; Shearer,
P.; Stakhiv, M.; von Steiger, R.; Zurbuchen, T.
2014AGUFMSH11C4059G Altcode:
Recent studies regarding the flow direction of interstellar wind through
the heliosphere have determined the longitudinal evolution using neutral
Helium as an indicator. Ionized interstellar helium that is picked up
by the solar wind has also been used to measure the helium focusing
cone and determine its longitudinal orientation. This study expands
previous pickup ion measurements and provides, for the first time,
more than a full solar cycle of continuous pickup ion tracking of the
interstellar wind direction. We discuss these results from ACE-SWICS
and show how they fit within the context of previous investigations.
---------------------------------------------------------
Title: The Solar Wind Neon Abundance Observed with ACE/SWICS and
Ulysses/SWICS
Authors: Shearer, Paul; von Steiger, Rudolf; Raines, Jim M.; Lepri,
Susan T.; Thomas, Jonathan W.; Gilbert, Jason A.; Landi, Enrico;
Zurbuchen, Thomas H.
2014ApJ...789...60S Altcode:
Using in situ ion spectrometry data from ACE/SWICS, we determine the
solar wind Ne/O elemental abundance ratio and examine its dependence
on wind speed and evolution with the solar cycle. We find that Ne/O
is inversely correlated with wind speed, is nearly constant in the
fast wind, and correlates strongly with solar activity in the slow
wind. In fast wind streams with speeds above 600 km s<SUP>-1</SUP>,
we find Ne/O = 0.10 ± 0.02, in good agreement with the extensive polar
observations by Ulysses/SWICS. In slow wind streams with speeds below
400 km s<SUP>-1</SUP>, Ne/O ranges from a low of 0.12 ± 0.02 at solar
maximum to a high of 0.17 ± 0.03 at solar minimum. These measurements
place new and significant empirical constraints on the fractionation
mechanisms governing solar wind composition and have implications for
the coronal and photospheric abundances of neon and oxygen. The results
are made possible by a new data analysis method that robustly identifies
rare elements in the measured ion spectra. The method is also applied
to Ulysses/SWICS data, which confirms the ACE observations and extends
our view of solar wind neon into the three-dimensional heliosphere.
---------------------------------------------------------
Title: The Solar EUV flux in the 3D Heliosphere
Authors: Auchere, Frederic; Von Steiger, Rudolf; McMullin, Donald;
Newmark, Jeffrey
2014cosp...40E.150A Altcode:
The absolute measurement of solar EUV flux and its time dependence
provide critical data on the solar driven photo chemistry which results
in solar system objects. For example, the Solar HeII 30.4 nm emission
is a major contributor to photo-ionization in the heliosphere, and thus
30.4 nm measurements provide the data required to determine the absolute
photoionization rate of neutral interstellar helium flowing into our
solar system. However, because of the orbit characteristics of the vast
majority of spacecraft, the solar irradiance has mostly been measured at
Earth or at least in the plane of the ecliptic. Therefore, the existing
data ignore the fact that the angular distribution of the solar flux
is largely anisotropic. Indeed, in the far and extreme ultraviolet,
the chromosphere and the corona display very contrasted structures. At
solar minimum, the polar regions are darkened by large coronal holes,
and in the most active part of the solar cycle, bright active regions
are scattered around the solar globe at low heliocentric latitudes. To
date, due to the small number of off- ecliptic measurements, very
few attempts have been made to investigate these variations. The
implications of the anisotropy of the solar irradiance are diverse. For
example, in the case of the 121.6 nm line of H I, the latitudinal
anisotropy must be taken into account when modeling the Lyman alpha
resonantly backscattered sky background. Identically, the anisotropy
must be included in the modeling of the intensity of the HI 121.6 nm
and He II 30.4 nm resonantly scattered coronal lines. We present here
a generalization of an earlier work on the anisotropy of the 30.4
nm EUV flux. Our empirical model, is now able to synthethize solar
spectra as seen from any point in the heliosphere in the 10 to 50 nm
wavelength range. The model is based on a Differential Emission Measure
resonstruction of the spectrum from reprojected EUV Carrington maps of
the Sun. We present the results obtained on the 3D distribution of the
Solar EUV flux during solar cycle 23. We discuss their consequences
on the GAS/Ulysses measurements of the Helium abundance in the Local
Interstellar Medium.
---------------------------------------------------------
Title: Cosmic Rays in the Heliosphere
Authors: Heber, Bernd; Kóta, József; von Steiger, Rudolf
2014crh..book.....H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Foreword
Authors: Heber, Bernd; Kóta, József; von Steiger, Rudolf
2014crh..book....1H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sources of the solar wind - the heliospheric point of view
Authors: Von Steiger, Rudolf; Shearer, Paul; Zurbuchen, Thomas
2014cosp...40E3557V Altcode:
The solar wind as observed in the heliosphere has several properties
that can be interpreted as signatures of conditions and processes
at its source in the solar atmosphere. Traditionally it has been
customary to distinguish between solar wind types solely based on its
speed, "fast" and "slow" wind. Over the last couple of decades new
instruments resolving not only the main constituents (protons and alpha
particles) but also heavy ions from C to Fe have added new observables,
in particular the charge state and elemental composition of these
ions. The charge states are indicators of the coronal temperature at
the source region; they have confirmed that the "fast" wind emanates
from the relatively cool coronal hole regions, while the "slow"
wind originates from hotter sources such as the streamer belt and
active regions. Thus they are more reliable indicators of solar wind
source than the speed alone could be because they readily discriminate
between "fast" wind from coronal holes and fast coronal mass ejections
(CMEs). The elemental composition in the solar wind compared to
the abundances in the photosphere shows a typical fractionation that
depends on the first ionization potential (FIP) of the elements. Since
that fractionation occurs beneath the corona, in the chromosphere,
its strength is indicative of the conditions in that layer. While
the "fast" wind is very similar to photospheric composition, the
fractionation of the "slow" wind and of CMEs is higher and strongly
variable. We will review the observations of the SWICS composition
instruments on both the ACE and the Ulysses missions, which have made
composition observations between 1 and 5 AU and at all latitudes in the
heliosphere over the last two decades. Specifically, analysis of the
"slow" wind observations at all time scales, from hours to complete
solar cycles, will be used to better characterize its source regions.
---------------------------------------------------------
Title: Foreword
Authors: Heber, Bernd; Kóta, József; von Steiger, Rudolf
2013SSRv..176....1H Altcode: 2013SSRv..tmp...69H
No abstract at ADS
---------------------------------------------------------
Title: Foreword
Authors: Burgess, David; Drake, James; Marsch, Eckart; Velli, Marco;
von Steiger, Rudolf; Zurbuchen, Thomas H.
2013mspc.book....1B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Multi-scale Physics in Coronal Heating and Solar Wind
Acceleration
Authors: Burgess, David; Drake, James; Marsch, Eckart; von Steiger,
Rudolf; Velli, Marco; Zurbuchen, Thomas
2013mspc.book.....B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Sources of Solar Wind at Solar Minimum: Constraints from
Composition Data
Authors: Zurbuchen, Thomas H.; von Steiger, Rudolf; Gruesbeck, Jacob;
Landi, Enrico; Lepri, Susan T.; Zhao, Liang; Hansteen, Viggo
2013mspc.book...41Z Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spatially Dependent Heating and Ionization in an ICME Observed
by Both ACE and Ulysses
Authors: Lepri, Susan T.; Laming, J. Martin; Rakowski, Cara E.;
von Steiger, Rudolf
2012ApJ...760..105L Altcode:
The 2005 January 21 interplanetary coronal mass ejection (ICME)
observed by multiple spacecraft at L1 was also observed from January
21-February 4 at Ulysses (5.3 AU). Previous studies of this ICME have
found evidence suggesting that the flanks of a magnetic cloud like
structure associated with this ICME were observed at L1 while a more
central cut through the associated magnetic cloud was observed at
Ulysses. This event allows us to study spatial variation across the
ICME and relate it to the eruption at the Sun. In order to examine the
spatial dependence of the heating in this ICME, we present an analysis
and comparison of the heavy ion composition observed during the passage
of the ICME at L1 and at Ulysses. Using SWICS, we compare the heavy ion
composition across the two different observation cuts through the ICME
and compare it with predictions for heating during the eruption based
on models of the time-dependent ionization balance throughout the event.
---------------------------------------------------------
Title: Origin of the most strongly FIP-fractionated solar wind:
Ulysses SWICS results
Authors: von Steiger, R.; Zurbuchen, T.
2012AGUFMSH52A..03V Altcode:
The slow solar wind is one of two quasi-stationary states whose
origin - unlike the one of fast wind, which clearly emanates from
coronal holes - is much less understood, but must be associated with
the coronal streamer belt. The slow wind is also much more variable
than its fast counterpart in virtually all parameters, both kinetic
and compositional. In order to better pinpoint and characterize its
sources and establish observational constraints for the origin of this
unusual solar wind plasma we investigate in this paper periods of the
most metal-rich solar wind. During such periods ions with a low First
Ionization Potential (FIP) such as Fe, Mg, and Si are observed to be
enhanced well over the average coronal ratios. We find that these
time periods occur in two different heliospheric contexts: within
Coronal Mass Ejections (CMEs) and near the Heliospheric Current Sheet
(HCS). The CME-associated enhancements have highly elevated Fe charge
states (average QFe > 11.5) and also exhibit the well-reported
enhancements in alpha particles (α/p > 8 %). Similarly, ionic charge
state ratios of C and O are also enhanced, suggesting the presence of
intense heating near the Sun. On the other hand, HCS-associated events
exhibit some of the coolest Fe charge states observed during the entire
mission (QFe < 9.5) and, and exhibit depletions of alpha particles
(α/p < 3%). The ionic charge state ratios of C and O do not show
any enhancements as compared to the ambient wind that has nominal
Mg/O. We put this observational result in the context of theories
that predict the origin, heating and acceleration of the slow solar
wind. We conclude that highly fractionated CME plasma and the slow
wind near the HCS have a common origin in the closed corona and are
both intermittently released into the heliosphere.
---------------------------------------------------------
Title: Foreword
Authors: Burgess, David; Drake, James; Marsch, Eckart; Velli, Marco;
von Steiger, Rudolf; Zurbuchen, Thomas H.
2012SSRv..172....1B Altcode: 2012SSRv..tmp...85B
No abstract at ADS
---------------------------------------------------------
Title: Sources of Solar Wind at Solar Minimum: Constraints from
Composition Data
Authors: Zurbuchen, Thomas H.; von Steiger, Rudolf; Gruesbeck, Jacob;
Landi, Enrico; Lepri, Susan T.; Zhao, Liang; Hansteen, Viggo
2012SSRv..172...41Z Altcode: 2012SSRv..tmp...25Z
In this discussion of observational constraints on the source regions
and acceleration processes of solar wind, we will focus on the
ionic composition of the solar wind and the distribution of charge
states of heavy elements such as oxygen and iron. We first focus on
the now well-known bi-modal nature of solar wind, which dominates
the heliosphere at solar minimum: Compositionally cool solar wind
from polar coronal holes over-expands, filling a much larger solid
angle than the coronal holes on the Sun. We use a series of remote and
in-situ characteristics to derive a global geometric expansion factor of
∼5. Slower, streamer-associated wind is located near the heliospheric
current sheet with a width of 10-20°, but in a well-defined band with
a geometrically small transition width. We then compute charge states
under the assumption of thermal electron distributions and temperature,
velocity, and density profiles predicted by a recent solar wind model,
and conclude that the solar wind originates from a hot source at around
1 million K, characteristic of the closed corona.
---------------------------------------------------------
Title: Composition of the Solar Corona, Solar Wind, and Solar
Energetic Particles
Authors: Schmelz, J. T.; Reames, D. V.; von Steiger, R.; Basu, S.
2012ApJ...755...33S Altcode:
Along with temperature and density, the elemental abundance is a basic
parameter required by astronomers to understand and model any physical
system. The abundances of the solar corona are known to differ from
those of the solar photosphere via a mechanism related to the first
ionization potential of the element, but the normalization of these
values with respect to hydrogen is challenging. Here, we show that the
values used by solar physicists for over a decade and currently referred
to as the "coronal abundances" do not agree with the data themselves. As
a result, recent analysis and interpretation of solar data involving
coronal abundances may need to be revised. We use observations from
coronal spectroscopy, the solar wind, and solar energetic particles
as well as the latest abundances of the solar photosphere to establish
a new set of abundances that reflect our current understanding of the
coronal plasma.
---------------------------------------------------------
Title: The Ulysses Legacy
Authors: Von Steiger, Rudolf
2012cosp...39.2102V Altcode: 2012cosp.meet.2102V
The Ulysses mission was the first space mission to reach genuine
high latitudes in the heliosphere, and is the only one to do so to
this day. Launched in 1990, it has provided nearly two decades of
unprecedented and groundbreaking observations. Thus it has added to
our picture of the heliosphere not only the third, out-of-ecliptic,
dimension, but also the fourth, time, of almost a full magnetic (Hale)
cycle of the Sun. Now that Ulysses has ceased to operate and as we
are thinking about future out-of-ecliptic missions it is a good time
to pause and review the Ulysses legacy. We will present and review the
highlights of what Ulysses has been teaching us about the heliosphere:
e.g., the two states of the solar wind, there unexpected structure of
the polar magnetic field and what it means for access of cosmic rays,
how the magnetic field reverses polarity at solar maximum, and even
fortuitous encounters with the tails of distant comets. Finally, we
will also review the impact of the lack of imaging instrumentation
on Ulysses.
---------------------------------------------------------
Title: Cosmogenic Radionuclides
Authors: Beer, Jürg; McCracken, Ken; von Steiger, Rudolf
2012cora.book.....B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Cosmogenic Radionuclides
Authors: Beer, Jürg; McCracken, Ken; von Steiger, Rudolf
2012crta.book.....B Altcode: 2012cora.book.....B
No abstract at ADS
---------------------------------------------------------
Title: Variability of the solar wind
Authors: von Steiger, R.; Zurbuchen, T.; Balogh, A.
2011AGUFMSH11C..03V Altcode:
Using data from the entire Ulysses mission (1990-2009) we quantify the
variability of the solar wind using distributions of mass, momentum,
and total energy measurements in the wind. For this analysis, we
separate solar wind measurements according to its two dynamic states -
"fast" and "slow" wind. With the advent of composition instrumentation
it could be shown that heavy ion charge states are a significantly
improved and more physical way for the distinction of these two
states. "Fast" wind originates in relatively cool coronal holes,
while the source of the "slow" wind is much less clear but must be
near or above the streamer belt. Reflecting the properties of their
coronal source regions, the "slow" wind is much more variable than its
"fast" counterpart. In extreme cases the "slow" wind can have a speed
of close to 1000 km/s. We typically find log-normal distributions of
these parameters that are about three times wider in the "slow" wind,
even for the momentum flux, which was often considered the least
variable solar wind parameter. These data should provide important
constraints for studies of solar wind turbulence.
---------------------------------------------------------
Title: Polar coronal holes during the past solar cycle: Ulysses
observations
Authors: von Steiger, Rudolf; Zurbuchen, Thomas H.
2011JGRA..116.1105V Altcode:
During its nearly 19-year mission, Ulysses pioneered novel measurements
of the three-dimensional heliosphere and particularly in situ
observations of high-latitude solar wind from polar coronal holes
(PCHs). Winds from PCHs exhibit constant elemental abundances to within
the limits of the measurements, indicative of the fact that such winds
truly provide a ground state of solar wind composition. However, these
solar wind streams show long-term variability in the composition of
ionic charge states frozen into the low corona. The C and O freeze-in
temperatures measured in high-latitude solar wind have decreased ∼10%
as compared to the previous solar minimum and are now around 0.87
and 1.01 MK, respectively. The ionization states of Si and Fe also
exhibit a substantial cooling with a reduction of 0.4 and 0.5 charge
states, respectively. We show that these observations are indicative
of an overall decrease of coronal temperature, forming a trend toward
cooler PCH temperature persisting for over 14 years. We support these
observations with a detailed and comprehensive description of the data
analysis processes relevant for Ulysses SWICS and similar instruments.
---------------------------------------------------------
Title: Oxygen Flux in the Solar Wind: Ulysses Observations
Authors: von Steiger, R.; Zurbuchen, T.; McComas, D. J.
2010AGUFMSH33C..01V Altcode:
We use the complete set of Ulysses solar wind data to conduct a
comprehensive determination of the oxygen flux in relation to the
proton flux in the solar wind during a wide range of solar activity
levels. The data cover the heliosphere between 1.3 and 5.4 AU and,
due to the unique orbit of Ulysses, all of the heliographic latitudes
within ±80°. We find log-normal distributions for O and H daily
flux values, but with significant differences between slow and fast
wind. Coronal hole-associated fast wind has a distribution that is
approximately three times narrower than the one of slow wind associated
with streamers. Finally, we derive the solar oxygen abundance, finding
a value of H/O=1500±300, and discuss this value in comparison with
the results of spectroscopic determinations.
---------------------------------------------------------
Title: Oxygen flux in the solar wind: Ulysses observations
Authors: von Steiger, Rudolf; Zurbuchen, Thomas H.; McComas, David J.
2010GeoRL..3722101V Altcode:
We use the complete set of Ulysses solar wind data to conduct a
comprehensive determination of the oxygen flux in relation to the
proton flux in the solar wind during a wide range of solar activity
levels. The data cover the heliosphere between 1.3 and 5.4 AU and,
due to the unique orbit of Ulysses, all of the heliographic latitudes
within ±80°. We find log-normal distributions for O and H daily
flux values, but with significant differences between slow and fast
wind. Coronal hole-associated fast wind has a distribution that is
approximately three times narrower than the one of slow wind associated
with streamers. Finally, we derive the solar oxygen abundance, finding
a value of 8.82 ± 0.08, and discuss this value in comparison with
the results of spectroscopic determinations.
---------------------------------------------------------
Title: Turbulence in the Solar Atmosphere and Solar Wind
Authors: Petrosyan, A.; Balogh, A.; Goldstein, M. L.; Léorat, J.;
Marsch, E.; Petrovay, K.; Roberts, B.; von Steiger, R.; Vial, J. C.
2010SSRv..156..135P Altcode: 2010SSRv..tmp..117P
The objective of this review article is to critically analyze turbulence
and its role in the solar atmosphere and solar wind, as well as to
provide a tutorial overview of topics worth clarification. Although
turbulence is a ubiquitous phenomenon in the sun and its heliosphere,
many open questions exist concerning the physical mechanisms of
turbulence generation in solar environment. Also, the spatial and
temporal evolution of the turbulence in the solar atmosphere and solar
wind are still poorly understood. We limit the scope of this paper
(leaving out the solar interior and convection zone) to the magnetized
plasma that reaches from the photosphere and chromosphere upwards to
the corona and inner heliosphere, and place particular emphasis on
the magnetic field structures and fluctuations and their role in the
dynamics and radiation of the coronal plasma. To attract the attention
of scientists from both the fluid-dynamics and space-science communities
we give in the first two sections a phenomenological overview of
turbulence-related processes, in the context of solar and heliospheric
physics and with emphasis on the photosphere-corona connection and
the coupling between the solar corona and solar wind. We also discuss
the basic tools and standard concepts for the empirical analysis and
theoretical description of turbulence. The last two sections of this
paper give a concise review of selected aspects of oscillations and
waves in the solar atmosphere and related fluctuations in the solar
wind. We conclude with some recommendations and suggest topics for
future research.
---------------------------------------------------------
Title: Solar Wind Properties During the Current Solar Minimum:
Ulysses Observations
Authors: von Steiger, Rudolf; Zurbuchen, Thomas H.
2010EGUGA..12.5006V Altcode:
During its nearly 19 year mission, Ulysses pioneered novel measurements
of the three-dimensional heliosphere and particularly first in situ
observations of solar wind from polar coronal holes (PCHs). It is
thus possible to compare observations in the current, peculiar solar
minimum with those obtained in 1994-95. It has been reported earlier
that, during the current minimum, there is a ~ 15% reduction of the
heliospheric magnetic field (Smith and Balogh, 2008), and ~ 17% and ~
14% reduction in density and temperature, respectively (McComas et al.,
2008), as compared to the previous minimum. But the PCH-associated solar
wind streams show long-term variability not only in dynamic, but also
in compositional signatures. From 1995 to 2008, the C and O freeze-in
temperatures measured in high-latitude solar wind have decreased by ~
15% and are now around 0.86 MK and 1.0 MK, respectively. Si and Fe
ionization states also exhibit a substantial cooling with a reduction
of 0.2 and 0.3 charge states, respectively. Thus it appears that
the PCH of cycle 23 are cooler overall than those of cycle 22. It
is more difficult to assess whether there are significant changes
of the elemental composition of the solar wind, as exhibited through
the First Ionization Potential fractionation effect, which seems to
have remained at f = 1.8 ± 0.3 during both sets of polar passages,
i.e., enhanced to the photospheric composition (f = 1). If this can be
confirmed the streams from PCH would truly be the 'ground state' of the
solar wind. These observations provide a unique test for theories of the
solar wind and its composition. We will present results from this data
analysis and also provide a discussion of their scientific implications.
---------------------------------------------------------
Title: Division II: Sun and Heliosphere
Authors: Melrose, Donald B.; Martinez Pillet, Valentin; Webb, David
F.; Bougeret, Jean-Louis; Klimchuk, James A.; Kosovichev, Alexander;
van Driel-Gesztelyi, Lidia; von Steiger, Rudolf
2010IAUTB..27..146M Altcode:
This report is on activities of the Division at the General Assembly
in Rio de Janeiro. Summaries of scientific activities over the past
triennium have been published in Transactions A, see Melrose et
al. (2008), Klimchuk et al. (2008), Martinez Pillet et al. (2008) and
Bougeret et al. (2008). The business meeting of the three Commissions
were incorporated into the business meeting of the Division. This
report is based in part on minutes of the business meeting, provided
by the Secretary of the Division, Lidia van Driel-Gesztelyi, and it
also includes reports provided by the Presidents of the Commissions
(C10, C12, C49) and of the Working Groups (WGs) in the Division.
---------------------------------------------------------
Title: Solar Wind Properties During the Current Solar Minimum:
Ulysses Observations
Authors: von Steiger, Rudolf; Zurbuchen, Thomas H.
2010cosp...38.1705V Altcode: 2010cosp.meet.1705V
Using Ulysses solar wind composition data it is possible to compare
observations in the current, unusual solar minimum with those obtained
during the minimum in 1994-95. It has been re-ported earlier that,
during the current minimum, there is a ∼ 15% reduction of the
heliospheric magnetic field (Smith and Balogh, 2008), and ∼ 17%
and ∼ 14% reduction in density and temperature, respectively
(McComas et al., 2008), as compared to the previous minimum. But
the polar coronal hole (PCH)-associated solar wind streams show
long-term variability not only in dynamic, but also in compositional
properties. The observed trends provide powerful tools to investigate
the properties of the underlying corona during this time. From 1995
to 2008, the C and O freeze-in temperatures measured in high-latitude
solar wind have steadily decreased by ∼ 15% and are now around 0.86
MK and 1.0 MK, respectively. Si and Fe ionization states also exhibit
a substantial cooling with a reduction of 0.2 and 0.3 charge states,
respectively. Thus it appears that all observed PCHs of cycle 23 are
cooler overall than those of cycle 22. It is more difficult to assess
whether there are significant changes of the elemental composition of
the solar wind, as exhibited through the First Ionization Potential
fractionation effect, which seems to have remained at f = 1.8 ± 0.3
during all polar passages. These observations provide a unique test
for theories of the solar wind and its composition. Furthermore,
the comparative analysis of the corona with these data provides
important insights about the physical processes that link the Sun and
its heliosphere.
---------------------------------------------------------
Title: Polar Coronal Holes during the Past Solar Cycle: Ulysses
Observations
Authors: von Steiger, R.; Zurbuchen, T.
2009AGUFMSH14A..02V Altcode:
During its nearly 19 year mission, Ulysses pioneered novel measurements
of the three-dimensional heliosphere and particularly provided the
first in situ observations of solar wind from polar coronal holes
(PCHs). These PCH-associated solar wind streams show long-term
variability in both dynamic and also compositional signatures. Between
the polar passages in 1994-95 and in 2007-08, the C and O freeze-in
temperatures measured in high-latitude solar wind have decreased by
~15 % and are now around 0.86 MK and 1.0 MK, respectively. Si and Fe
ionization states also exhibit a substantial cooling with a reduction
of 0.4 and 0.5 charge states on average, respectively. On the other
hand, there no significant changes of the elemental composition of
the solar wind, as exhibited through the First Ionization Potential
fractionation effect, which has remained at f = 1.8±0.3 during both
sets of polar passages, i.e., enhanced to the photospheric composition
(f = 1). Thus, it appears that the PCH of cycle 23 are cooler overall
than those of cycle 22, while their elemental composition has remained
unchanged, thus confirming their status as the “ground state” of
the solar wind. These observations, together with the observed ~15
% reduction of the heliospheric magnetic field (Smith and Balogh,
2008), and the ~17 % and ~14 % reductions in density and temperature,
respectively (McComas et al., 2008), provide a unique test for theories
of the solar wind and its composition, in particular for the concept
of freezing-in of charge states and of the FIP fractionation effect. We
will present results from this analysis of SWICS data and also discuss
the scientific implications of these novel results.
---------------------------------------------------------
Title: Turbulence and intermittency in the heliospheric magnetic
field in fast and slow solar wind
Authors: Yordanova, E.; Balogh, A.; Noullez, A.; von Steiger, R.
2009JGRA..114.8101Y Altcode: 2009JGRA..11408101Y
We study the nonuniform solar wind turbulence using high-resolution
Ulysses magnetic field data measured at different solar activity
level, heliospheric latitudes, and distance. We define several types
of solar wind dependent of the coronal region of origin and also of
the dynamical behavior of the different streams, namely, “pure”
fast wind, fast streams, “pure” slow wind, and slow streams. The
turbulent properties of the solar wind types were investigated in terms
of their scaling properties and spatial inhomogeneity. A clear trend
in the power spectrum of the solar wind magnetic field magnitude is
observed: the “pure” fast wind has a slope ∼-1.33 (1/f-like),
the fast streams ∼-1.48 (Kraichnan-like), the “pure” slow wind
∼-1.67 (Kolmogorov-like), and the slow streams ∼-1.72. We find
that the “pure” fast wind in the polar heliolatitudes is less
intermittent than the other types: “pure” slow wind and both
slow and fast streams, which is because of the absence of dynamical
interactions between streams with different speeds. On the other hand,
fast streams are more intermittent than the “pure” fast wind, and
slow streams are less intermittent than the “pure” slow winds. A
clear radial and latitudinal evolution of the intermittency is observed
only for the “pure” fast wind, while in the equatorial plane,
the fast streams, the “pure” slow wind, and the slow streams do
not show evolution either in heliolatitude or in heliocentric distance.
---------------------------------------------------------
Title: Quiescent current sheets in the solar wind and origins of
slow wind
Authors: Suess, S. T.; Ko, Y. -K.; von Steiger, R.; Moore, R. L.
2009JGRA..114.4103S Altcode: 2009JGRA..11404103S
Solar wind near the heliospheric current sheet is investigated using
Ulysses and ACE data in a superposed epoch analysis for several days
on either side of the current sheets. Only data near sunspot minima
are used, minimizing the influence of transients. New results are
shown for composition and ionization state. Existing results showing
a ∼2 day wide depletion in He/H (He<SUP>++</SUP>/H<SUP>+</SUP>) at
the current sheet are confirmed, although the depletion is generally
more narrow. A recent finding of a broad 5-10 day wide reduction in
He/H around the current sheet is also confirmed. An important result
is that the narrow depletion is not a real phenomenon but is instead
a statistical consequence of the superposition of transient depletions
that also create the broad reduction in the averages. These transient
depletions last from a few hours up to several days, come from the core
of streamers, and are embedded in a quasi-steady flow from streamers'
legs. Most depletions contain a current sheet just inside one edge,
leading to the apparent narrow depletion at the current sheet in the
superposed epoch analysis. These results lead us to a hypothesis for
how the He/H depletions form with a current sheet just inside one
edge. Fe/O fluctuations associated with the He/H fluctuations further
show that mixing of plasma from coronal holes adjacent to streamer
brightness boundaries into outflow inside the brightness boundary is
not an important process.
---------------------------------------------------------
Title: Division II: Sun and Heliosphere
Authors: Melrose, Donald B.; Martínez Pillet, Valentin; Webb, David
F.; van Driel-Gesztelyi, Lidia; Bougeret, Jean-Louis; Klimchuk,
James A.; Kosovichev, Alexander; von Steiger, Rudolf
2009IAUTA..27...73M Altcode:
Division II of the IAU provides a forum for astronomers and
astrophysicists studying a wide range of phenomena related to the
structure, radiation and activity of the Sun, and its interaction with
the Earth and the rest of the solar system. Division II encompasses
three Commissions, 10, 12 and 49, and four Working Groups.
---------------------------------------------------------
Title: From the Outer Heliosphere to the Local Bubble
Authors: Linsky, J. L.; Izmodenov, V. V.; Möbius, E.; von Steiger, R.
2009fohl.book.....L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Commission 49: Interplanetary Plasma and Heliosphere
Authors: Bougeret, Jean-Louis; von Steiger, Rudolf; Webb, David
F.; Ananthakrishnan, Subramanian; Cane, Hilary V.; Gopalswamy,
Natchimuthuk; Kahler, Stephen W.; Lallement, Rosine; Sanahuja, Blai;
Shibata, Kazunari; Vandas, Marek; Verheest, Frank
2009IAUTA..27..124B Altcode:
Commission 49 covers research on the solar wind, shocks and particle
acceleration, both transient and steady-state, e.g., corotating,
structures within the heliosphere, and the termination shock and
boundary of the heliosphere.
---------------------------------------------------------
Title: Quiescent Current Sheets in the Solar Wind and Origins of
Slow Wind
Authors: Suess, S. T.; Ko, Y. -; von Steiger, R.; Moore, R. L.
2008AGUFMSH43B..03S Altcode:
Solar wind near the heliospheric current sheet is investigated using
Ulysses and ACE data, in a superposed epoch analysis for several days
on either side of the current sheets. Only data near sunspot minima
are used, minimizing the influence of transients. New results are
shown for composition and ionization state. Existing results showing
a ~2 day wide depletion in He/H at the current sheet are confirmed,
although the depletion is generally more narrow. A recent finding of
a broad 5-10 day wide reduction in He/H around the current sheet is
also confirmed. An important result is that the narrow depletion is
not a real phenomenon, but is instead a statistical consequence of
the superposition of transient depletions that also create the broad
reduction in the averages. These transient depletions last from
a few hours up to several days, come from the core of streamers,
and are embedded in a quasi-steady flow from streamers legs. Most
depletions contain a current sheet just inside one edge, leading to
the apparent narrow depletion at the current sheet in the superposed
epoch analysis. These results lead us to a hypothesis for how the
He/H depletions form with a current sheet just inside one edge. Fe/O
fluctuations associated with the He/H fluctuations further show that
mixing of plasma from coronal holes adjacent to streamer brightness
boundaries into outflow inside the brightness boundary is not an
important process.
---------------------------------------------------------
Title: Solar EUV Spectral Irradiance Throughout The 3-Dimensional
Heliosphere
Authors: McMullin, D. R.; Auchere, F.; Cook, J. W.; Newmark, J. S.;
Quemerais, E.; von Steiger, R.; Witte, M.
2008AGUFMSH13B1522M Altcode:
When Ulysses moved from 30 to 80 degrees in solar latitude (July
2001), the Ulysses GAS instrument measured an apparent increase
in the neutral He density. This is more naturally interpreted as
a latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than a true increase of the neutral He
density. This concept has been tested through the development of a
3-Dimensional solar EUV model for the Heliosphere. The model concept
has been presented earlier, and we are now presenting results and
applications of the new model. Using daily SOHO EIT observations,
over successive Carrington rotations, we have developed a three-
dimensional model for solar EUV fluxes observed at any heliospheric
position, projected to any heliospheric position. The combined
effects of solar rotational and latitude-dependent flux variability
are explicitly treated in this model. The flux model will be compared
with other direct spectral irradiance observations in the ecliptic
plane, such as those available from the TIMED SEE instrument as well
as broadband measurements available from the SOHO/SEM irradiance time
series. These comparisons will be used in part to validate the current
results. We then use this flux to compute the photoionization rate of
the in-flowing neutral Helium, and compare the modeled change with that
observed along the spacecraft trajectory with the direct measurements
from the out-of-ecliptic Ulysses GAS observations. The unique GAS
comparisons will provide validation of the original hypothesis as to
the latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than an increase of the neutral He density.
---------------------------------------------------------
Title: Fe, O, and C Charge States Associated With Quiescent Versus
Active Current Sheets in the Solar Wind
Authors: Suess, S. T.; Ko, Y.; von Steiger, R.
2008AGUSMSH44A..07S Altcode:
Ulysses MAG data were used to locate the heliospheric current sheet in
data from 1991 through 2006. The purpose was to characterize typical
charge states for Fe, O, and C in the vicinity of the current sheet
and provide insight into the physical sources for these charge states
in the corona. A study of He/H around the current sheets has led to
a clear distinction between quiescent current sheets at times of low
solar activity and active current sheets associated with magnetic clouds
(and, presumably, ICMEs). It has been shown that high ionization state
Fe is produced in the corona in current sheets associated with CMEs
through spectroscopic observations of the corona and through in situ
detection at Ulysses. Here we show that the ionization state of Fe is
typically only enhanced around active current sheets. The ionization
states of O and C are commonly enhanced around both quiescent and
active current sheets, but the enhancements are much larger around
active current sheets. This is consistent with UV coronal spectroscopy,
which has shown that reconnection in current sheets behind CMEs leads
to high temperatures not typically seen above quiet streamers.
---------------------------------------------------------
Title: Composition of the Solar Wind
Authors: von Steiger, Rudolf
2008cosp...37.3366V Altcode: 2008cosp.meet.3366V
The motivation for systematic observations of the solar wind
composition is twofold: (1) It may be used to deduce the composition
of the protosolar nebula from which the entire solar system was
made 4.6 gigayears ago, thus representing a sample of the galactic
chemical evolution at that time and location. (2) It is a tracer
of conditions and processes in the solar atmosphere where the solar
wind is accelerated, thus providing information about the structure
of the corona. With the launch of a new type of composition sensor on
the Ulysses mission in 1990 we have now a database of ten elements in
more than 30 charge states during more than a complete solar activity
cycle. Together with Ulysses' unique, high-inclination orbit that
database reveals much about the three-dimensional structure of not just
the solar atmosphere, but also of the heliosphere as a whole. We will
review the Ulysses observations of solar wind composition both in its
quasi-stationary states, steady fast streams and variable slow wind,
as well as in its transient states such as coronal mass ejections,
and their significance for the structure of the heliosphere.
---------------------------------------------------------
Title: Mercury
Authors: Balogh, André; Ksanfomality, Leonid; von Steiger, Rudolf
2008merc.book.....B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The solar wind throughout the solar cycle
Authors: von Steiger, Rudolf
2008hsac.book...41V Altcode:
The existence of solar corpuscular radiation (SCR) was conjectured
by Biermann (1951) based on the fact that the ion tails of comets
always point radially away from the Sun. Earlier it had been thought
that this was due to solar radiation pressure, but when the relevant
cross-sections were measured it became clear that these were far too
small. This is visible in Figure 3.1, where stars can be seen shining
through the ion tail of comet Hale-Bopp, one of the more spectacular
sights in the sky of the 20th century. Parker (1958) provided the
first theoretical description of the SCR in terms of a supersonic
magnetized fluid. He coined the term "solar wind" in order to set it
apart from other ideas of a (subsonic) solar breeze that were around
at the time. The solar wind was ultimately observed in the early 1960s
by the Soviets and independently with the American Mariner 2 mission
to Venus (Gringauz et al., 1961; Neugebauer and Snyder, 1962). An
excellent account of these early developments is given by Parker (2001).
---------------------------------------------------------
Title: Introduction
Authors: Balogh, André; Ksanfomality, Leonid; von Steiger, Rudolf
2008merc.book....1B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Calibration of Particle Instruments in Space Physics
Authors: Wüest, Martin; Evans, David S.; von Steiger, Rudolf
2007cpis.book.....W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Ulysses Transition into the Polar Coronal Holes
Authors: von Steiger, R.; Zurbuchen, T. H.
2007AGUFMSH14A1700V Altcode:
The Ulysses spacecraft has now half-completed its third polar
orbit around the Sun. Like the first polar orbit, in 1992-1998,
it is occurring at declining to minimum solar activity. Yet the two
transitions into the hole are remarkably different. The first transition
was substantially more regular than the second one is. This may be
understood in the context of the current sheet orientation, which was
generally flatter during the first transition, but is more strongly
warped during the second. We model the global distribution of slow and
fast solar wind streams starting from the Wilcox Solar Observatory maps
of the solar magnetic field at the source surface. The model assumes
slow solar wind to emanate from the vicinity of the current sheet with
a speed that increases as a function of angular distance from the CS,
i.e., with magnetic latitude, as it has been found on Helios. Fast solar
wind of constant speed is assumed to emanate from the coronal holes and
to expand superradially so as to fill the entire solid angle above a
certain magnetic latitude. Thus we obtain a model solar wind speed at
the position of Ulysses, and comparing to the observed solar wind speed
there we can optimize the model to finally obtain the angular width
of the belt of slow solar wind around the heliospheric current sheet.
---------------------------------------------------------
Title: Introduction
Authors: Balogh, André; Ksanfomality, Leonid; von Steiger, Rudolf
2007SSRv..132..183B Altcode: 2007SSRv..tmp..216B
No abstract at ADS
---------------------------------------------------------
Title: Encounter of the Ulysses Spacecraft with the Ion Tail of
Comet MCNaught
Authors: Neugebauer, M.; Gloeckler, G.; Gosling, J. T.; Rees, A.;
Skoug, R.; Goldstein, B. E.; Armstrong, T. P.; Combi, M. R.; Mäkinen,
T.; McComas, D. J.; von Steiger, R.; Zurbuchen, T. H.; Smith, E. J.;
Geiss, J.; Lanzerotti, L. J.
2007ApJ...667.1262N Altcode:
Comet McNaught was the brightest comet observed from Earth in the
last 40 years. For a period of five days in early 2007 February, four
instruments on the Ulysses spacecraft directly measured cometary ions
and key properties of the interaction of the comet's ion tail with the
high-speed solar wind from the polar regions of the Sun. Because of
the record-breaking duration of the encounter, the data are unusually
comprehensive. O<SUP>3+</SUP> ions were detected for the first time
in a comet tail, coexisting with singly charged molecular ions with
masses in the range 28-35 amu. The presence of magnetic turbulence
and of ions with energies up to ~200 keV indicate that at a distance
of ~1.6 AU from the comet nucleus, the ion tail of comet McNaught had
not yet reached equilibrium with the surrounding solar wind.
---------------------------------------------------------
Title: Encounter of Ulysses with Comet McNaught
Authors: Gosling, J. T.; Neugebauer, M.; McComas, D. J.; Goldstein,
B. E.; Skoug, R. M.; Gloeckler, G.; Zurbuchen, T.; von Steiger, R.;
Balogh, A.; Rees, A.; Combi, M. R.
2007AGUSMSH23C..05G Altcode:
Comet C/2006 P1 McNaught was the brightest comet observed from Earth
in the last 40 years. On February 3, 2007 the comet at a heliocentric
distance of ~0.71 AU was nearly radially aligned with the Ulysses
spacecraft at a heliocentric distance of ~2.40 AU and at 79 Deg south
heliographic latitude. Thus, during a ~4.5-day interval (February 5-9)
Ulysses encountered the tail region of this spectacular comet, the
region of disturbance in the solar wind produced by the comet being
nearly 10 Mkm wide at 2.4 AU. During the encounter the speed of the
solar wind dropped from ~750 km/s to a minimum of 360 km/s, the proton
density dropped by more than 2 orders of magnitude, and the proton
temperature increased from ~1.5x105 to ~4x105 K, while simultaneously
very large fluxes of cometary molecular and singly and doubly charged
atomic ions were detected. The slowing, depletion and heating of the
solar wind proton beam was a result of charge exchange with neutral
atoms and molecules in the cometary atmosphere and with the pickup up
by the wind of the newly-born cometary ions. Although no shocks were
observed during the encounter, the magnetic field strength was slightly
enhanced in broad regions at the leading and trailing edges of the tail
of the comet and was generally weaker than in the unobstructed solar
wind within the heart of the region of interaction. For most of the
encounter, the magnetic field direction was nearly radially inward,
and thus reversed from its normal outward direction in the southern
polar hemisphere at this phase of the present solar cycle. There
were, however, shorter periods when the field pointed nearly radially
outward, indicating a filamentary structure of the comet tail. One of
the intervals of radially outward field coincided with the interval
of minimum flow speed and maximum flux of picked up O+ ions.
---------------------------------------------------------
Title: Commission 49: Interplanetary Plasma and Heliosphere
Authors: Webb, David F.; Bougeret, Jean-Louis; Cane, Hilary V.;
Cramer, Neil F.; Kahler, Stephen W.; Kojima, Masayoshi; Sanahuja,
Blai; Vandas, Marek; Verheest, Frank; von Steiger, Rudolf
2007IAUTA..26..103W Altcode:
Commission 49 covers research on the solar wind, shocks and particle
acceleration, both transient and steady-state, e.g., corotating,
structures within the heliosphere, and the termination shock and
boundary of the heliosphere. During the last three years there was
considerable progress made in studies of solar energetic particles,
compositional and other signatures in the heliosphere, solar wind pickup
ions, the termination shock, which was finally crossed by a spacecraft,
and the boundary between the heliosphere and interstellar medium, and in
solar wind modeling and space weather. These topics have been summarized
here in five articles, each with extensive references that will guide
the reader who wants further details. Observations from the following
spacecraft have extensively used during this period: Ulysses, Cassini,
Voyager 1 and 2, MESSENGER, ACE, Genesis, SOHO, Wind, and RHESSI.
---------------------------------------------------------
Title: Solar Dynamics and Its Effects on the Heliosphere and Earth
Authors: Baker, D. N.; Klecker, B.; Schwartz, S. J.; Schwenn, R.;
von Steiger, R.
2007sdeh.book.....B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Composition of Matter: Symposium honouring Johannes Geiss
on the occasion of his 80th Birthday
Authors: von Steiger, Rudolf; Gloeckler, George; Mason, Glenn M.
2007coma.book.....V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Coronal Mass Ejections
Authors: Kunow, H.; Crooker, N. U.; Linker, J. A.; Schwenn, R.;
von Steiger, R.
2007cme..conf.....K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Foreword
Authors: von Steiger, R.; Gloeckler, G.; Mason, G. M.
2007coma.book....1V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Large-scale heliospheric structure in 2004-2006 and its
solar origin
Authors: Rother, O.; Wimmer-Schweingruber, R. F.; von Steiger, R.;
Zurbuchen, T. H.
2006AGUFMSH44A..01R Altcode:
As solar activity has begun to decline, the large-scale structure of the
heliosphere has begun to turn simpler again. Large coronal holes and
a more quiet streamer belt are structuring the heliosphere. Ulysses,
on its unique orbit, has again begun to measure recurrent high-speed
streams originating in coronal holes alternating with slow wind from
other regions. Here, we use simple back-mapping techniques to identify
the source regions of the solar wind measured by Ulysses. We relate
the observed stream interfaces to solar features and give a complete
list of stream interfaces for 2004 - 2006.
---------------------------------------------------------
Title: Ulysses Transition into the Newly Formed Southern Fast Stream
Observed with Ulysses- SWICS
Authors: von Steiger, R.; Zurbuchen, T. H.
2006AGUFMSH52A..07V Altcode:
The Ulysses spacecraft currently performs the third revolution on its
unique, high-inclination orbit around the Sun. Like on the first orbit
the current observations are taken during the declining to minimum
phase of the solar activity cycle, albeit with inverted magnetic
polarity. However, our observations show rather significant and
surprising differences between the configurations of the Heliosphere
during the first and the third orbits of Ulysses. In 1992-93 the
transition from the slow, variable solar wind into the high-speed stream
from the southern polar coronal hole was marked by a regular oscillation
from slow to fast solar wind and back once every solar rotation for
more than a year, indicating a relatively flat but tilted heliospheric
current sheet. The current transition has been much less regular,
with slow and variable solar wind pertaining to higher latitudes than
back then. The transition proper was much quicker, with duration of
only 2-3 solar rotations. Since early 2006 Ulysses is now immersed in
the polar fast stream, but this looks also somewhat different than the
previous one as it shows some variability and may even contain coronal
mass ejections with a composition signature, something that was never
observed during more than 2.5 years of polar stream observations in
the previous cycle.
---------------------------------------------------------
Title: Planetary Systems and Planets in Systems
Authors: Udry, Stéphane; Benz, Willy; von Steiger, Rudolf
2006psps.conf.....U Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Solar Wind Elemental Composition: Constraints on the
Origin of the Solar Wind
Authors: Zurbuchen, T. H.; von Steiger, R.
2006ESASP.617E...7Z Altcode: 2006soho...17E...7Z
No abstract at ADS
---------------------------------------------------------
Title: Foreword
Authors: Baker, D. N.; Klecker, B.; Schwartz, S. J.; Schwenn, R.;
von Steiger, R.
2006SSRv..124D...7B Altcode:
The topic of Solar Dynamics and its Effects on the Heliosphere and
Earth was addressed with a workshop at the International Space Science
Institute, under the auspices of the International Living with a Star
program, held in April 2005. It started out with an assessment and
description of the reasons for solar dynamics and how it couples into
the heliosphere. The three subsequent sections were each devoted to
following one chain of events from the Sun all the way to the Earth's
magnetosphere and ionosphere: The normal solar wind chain, the chain
associated with coronal mass ejections, and the solar energetic
particles chain. The final section was devoted to common physical
processes occuring both at the Sun and in the magnetosphere such as
reconnection, shock acceleration, dipolarisation of magnetic field,
and others.
---------------------------------------------------------
Title: Kinetic properties of heavy solar wind ions from Ulysses-SWICS
Authors: von Steiger, R.; Zurbuchen, T. H.
2006GeoRL..33.9103V Altcode:
The kinetic properties of heavy ions in the solar wind reflect the
plasma processes governing the solar wind in the heliosphere. We
use Ulysses-SWICS data that resolve heavy ions in a wide range of
mass-per-charge values, 2 <= m/q <= 9.33, to investigate the heavy
ions and their dynamic evolution throughout the heliosphere. While at
1 AU the imprint of Coulomb collisions is known to be present in the
slow solar wind, we show that is vanishes by the time the wind has
reached 5 AU. All ion species flow with equal bulk and thermal speeds
there. This is interpreted as a progressive dominance of wave-particle
interactions over Coulomb collisions.
---------------------------------------------------------
Title: Foreword
Authors: Kunow, H.; Crooker, N. U.; Linker, J. A.; Schwenn, R.;
von Steiger, R.
2006SSRv..123....1K Altcode: 2006SSRv..tmp...62K
No abstract at ADS
---------------------------------------------------------
Title: ICMEs in the Outer Heliosphere and at High Latitudes:
An Introduction
Authors: von Steiger, R.; Richardson, J. D.
2006SSRv..123..111V Altcode: 2006SSRv..tmp...65V
Interplanetary coronal mass ejections (ICMEs) are observed at all
latitudes and distances from which data are available. We discuss the
radial evolution of ICMEs out to large distances and ICME properties
at high latitudes. The internal pressure of ICMEs initially exceeds
the ambient solar wind pressure and causes the ICMEs to expand in
radial width to about 15~AU. Large ICMEs and series of ICMEs compress
the leading plasma and form merged interaction regions (MIRs) which
dominate the structure of the outer heliosphere at solar maximum. The
distribution of high-latitude ICMEs is solar cycle dependent. A
few overexpanding ICMEs are observed at high-latitude near solar
minimum. Near solar maximum ICMEs are observed at all latitudes,
but those above 40° do not have high charge states.
---------------------------------------------------------
Title: Understanding Interplanetary Coronal Mass Ejection Signatures.
Report of Working Group B
Authors: Wimmer-Schweingruber, R. F.; Crooker, N. U.; Balogh, A.;
Bothmer, V.; Forsyth, R. J.; Gazis, P.; Gosling, J. T.; Horbury, T.;
Kilchenmann, A.; Richardson, I. G.; Richardson, J. D.; Riley, P.;
Rodriguez, L.; von Steiger, R.; Wurz, P.; Zurbuchen, T. H.
2006SSRv..123..177W Altcode: 2006SSRv..tmp...66W
While interplanetary coronal mass ejections (ICMEs) are understood to
be the heliospheric counterparts of CMEs, with signatures undeniably
linked to the CME process, the variability of these signatures and
questions about mapping to observed CME features raise issues that
remain on the cutting edge of ICME research. These issues are discussed
in the context of traditional understanding, and recent results using
innovative analysis techniques are reviewed.
---------------------------------------------------------
Title: ICMEs at High Latitudes and in the Outer Heliosphere.
Report of Working Group H
Authors: Gazis, P. R.; Balogh, A.; Dalla, S.; Decker, R.; Heber,
B.; Horbury, T.; Kilchenmann, A.; Kota, J.; Kucharek, H.; Kunow, H.;
Lario, D.; Potgieter, M. S.; Richardson, J. D.; Riley, P.; Rodriguez,
L.; Siscoe, G.; von Steiger, R.
2006SSRv..123..417G Altcode: 2006SSRv..tmp...70G
Interplanetary coronal mass ejections (ICMEs) propagate into the outer
heliosphere, where they can have a significant effect on the structure,
evolution, and morphology of the solar wind, particularly during
times of high solar activity. They are known to play an important
role in cosmic ray modulation and the acceleration of energetic
particles. ICMEs are also believed to be associated with the large
global transient events that swept through the heliosphere during the
declining phases of solar cycles 21 and 22. But until recently, little
was known about the actual behavior of ICMEs at large heliographic
latitudes and large distances from the Sun. Over the past decade,
the Ulysses spacecraft has provided in situ observations of ICMEs at
moderate heliographic distances over a broad range of heliographic
latitudes. More recently, observations of alpha particle enhancements,
proton temperature depressions, and magnetic clouds at the Voyager
and Pioneer spacecraft have begun to provide comparable information
regarding the behavior of ICMEs at extremely large heliocentric
distances. At the same time, advances in modeling have provided new
insights into the dynamics and evolution of ICMEs and their effects
on cosmic rays and energetic particles.
---------------------------------------------------------
Title: Coronal Mass Ejections
Authors: Kunow, H.; Crooker, N. U.; Linker, J. A.; Schwenn, R.;
von Steiger, R.
2006cme..book.....K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: IHY Science and Organization in Europe
Authors: Bougeret, J. -L.; Briand, C.; Bonet Navaro, J. A.; Breen,
A.; Candidi, M.; Georgevia, K.; Harrison, R.; Marsden, R.; Schmieder,
B.; von Steiger, R.
2006cosp...36.3226B Altcode: 2006cosp.meet.3226B
We present the scientific and organizational approach to the
International Heliophysical Year in Europe A summary is given of the
First European General Assembly of the IHY that was held in Paris in
January 2006 Initiatives and expected returns are described
---------------------------------------------------------
Title: Dynamical processes in critical regions of the heliosphere
Authors: von Steiger, Rudolf; Gedalin, Michael
2006AdSpR..38....1V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: ICMEs at High Latitudes and in the Outer Heliosphere
Authors: Gazis, P. R.; Balogh, A.; Dalla, S.; Decker, R.; Heber,
B.; Horbury, T.; Kilchenmann, A.; Kota, J.; Kucharek, H.; Kunow, H.;
Lario, D.; Potgieter, M. S.; Richardson, J. D.; Riley, P.; Rodriguez,
L.; Siscoe, G.; von Steiger, R.
2006cme..book..417G Altcode:
Interplanetary coronal mass ejections (ICMEs) propagate into the outer
heliosphere, where they can have a significant effect on the structure,
evolution, and morphology of the solar wind, particularly during
times of high solar activity. They are known to play an important
role in cosmic ray modulation and the acceleration of energetic
particles. ICMEs are also believed to be associated with the large
global transient events that swept through the heliosphere during the
declining phases of solar cycles 21 and 22. But until recently, little
was known about the actual behavior of ICMEs at large heliographic
latitudes and large distances from the Sun. Over the past decade,
the Ulysses spacecraft has provided in situ observations of ICMEs at
moderate heliographic distances over a broad range of heliographic
latitudes. More recently, observations of alpha particle enhancements,
proton temperature depressions, and magnetic clouds at the Voyager
and Pioneer spacecraft have begun to provide comparable information
regarding the behavior of ICMEs at extremely large heliocentric
distances. At the same time, advances in modeling have provided new
insights into the dynamics and evolution of ICMEs and their effects
on cosmic rays and energetic particles.
---------------------------------------------------------
Title: In-situ and remote observations of CMEs
Authors: Rodriguez, Luciano; Zhukov, A. N.; Woch, J.; Krupp, N.;
von Steiger, R.; Forsyth, R.
2006IAUS..233..351R Altcode:
We present studies on a series of ICMEs detected by Ulysses and for
which the solar sources on the Sun could be identified. EUV and white
light data are used in order to correlate characteristics seen during
eruption with those measured in-situ. Particularly, an attempt was
made to find solar features that show a relationship with the type of
ICME seen later (i.e. cloud or non-cloud ICME). For magnetic clouds
(MC) the chirality of the magnetic field was then analyzed. Finally,
the charge states of oxygen ions contained in ICMEs were used to obtain
freezing-in temperatures and then compare these with the presence of
flares occurring close (spatially and temporally) to the CME eruption.We
have found no solar feature that could be used to predict the presence
of a MC in interplanetary space, they occur with the same frequency
for cloud and non-cloud ICMEs. The chirality of the clouds seems to
follow only weakly the hemisphere rule. The presence of solar flares
do not seem to be correlated with the oxygen freezing-in temperatures
seen in-situ.
---------------------------------------------------------
Title: Latitude Distribution of Interplanetary Coronal Mass Ejections
Authors: von Steiger, R.; Zurbuchen, T. H.; Kilchenmann, A.
2006cosp...36.2327V Altcode: 2006cosp.meet.2327V
We present an investigation of the latitude distribution of Coronal
Mass Ejections CMEs measured in the heliosphere The Interplanetary CMEs
ICMEs are identified and analyzed using combined solar wind plasma
parameters and composition data from the Ulysses spacecraft during
its solar maximum polar pass We first discuss this combined data set
and then analyze the latitude distribution of ICMEs found therein We
finally compare these results to coronagraph observations of CMEs and
to the results of a simple model of the three-dimensional distribution
and propagation of CMEs in the heliosphere at solar maximum
---------------------------------------------------------
Title: Understanding Interplanetary Coronal Mass Ejection Signatures
Authors: Wimmer-Schweingruber, R. F.; Crooker, N. U.; Balogh, A.;
Bothmer, V.; Forsyth, R. J.; Gazis, P.; Gosling, J. T.; Horbury, T.;
Kilchenmann, A.; Richardson, I. G.; Richardson, J. D.; Riley, P.;
Rodriguez, L.; von Steiger, R.; Wurz, P.; Zurbuchen, T. H.
2006cme..book..177W Altcode:
While interplanetary coronal mass ejections (ICMEs) are understood to
be the heliospheric counterparts of CMEs, with signatures undeniably
linked to the CME process, the variability of these signatures and
questions about mapping to observed CME features raise issues that
remain on the cutting edge of ICME research. These issues are discussed
in the context of traditional understanding, and recent results using
innovative analysis techniques are reviewed.
---------------------------------------------------------
Title: ICMEs in the Outer Heliosphere and at High Latitudes:
an Introduction
Authors: von Steiger, R.; Richardson, J. D.
2006cme..book..111V Altcode:
Interplanetary coronal mass ejections (ICMEs) are observed at all
latitudes and distances from which data are available. We discuss the
radial evolution of ICMEs out to large distances and ICME properties
at high latitudes. The internal pressure of ICMEs initially exceeds
the ambient solar wind pressure and causes the ICMEs to expand in
radial width to about 15 AU. Large ICMEs and series of ICMEs compress
the leading plasma and form merged interaction regions (MIRs) which
dominate the structure of the outer heliosphere at solar maximum. The
distribution of high-latitude ICMEs is solar cycle dependent. A
few overexpanding ICMEs are observed at high-latitude near solar
minimum. Near solar maximum ICMEs are observed at all latitudes,
but those above 40? do not have high charge states.
---------------------------------------------------------
Title: Thermal Properties of Heavy Ions throughout the Heliosphere:
39 Solar Wind Species from Ulysses-SWICS
Authors: von Steiger, R.; Zurbuchen, T. H.
2005AGUFMSH14A..06V Altcode:
The kinetic properties of heavy ions in the solar wind reflect the
kinetic processes governing the solar wind in the heliosphere. We use
Ulysses-SWICS data which resolves heavy ions in a wide range of mass
per charge, 2≤ m/q≤9.33. In particular, we look for deviations from
the canonical behavior of equal bulk speed and equal thermal speed for
all heavies. Such deviations are expected to carry signatures of all
important kinetic processes in the solar wind, such as wave-particle
interactions, and collisional processes. We also discuss a simple model
to assess the relative importance of these effects. The Ulysses-SWICS
data set is ideally suited for this task due to its extended m/q range,
and also its global coverage of the heliosphere up to 5 AU.
---------------------------------------------------------
Title: Latitude Distribution of Interplanetary Coronal Mass Ejections
during Solar Maximum
Authors: von Steiger, R.; Zurbuchen, T. H.; Kilchenmann, A.
2005ESASP.592..317V Altcode: 2005ESASP.592E..48V; 2005soho...16E..48V
No abstract at ADS
---------------------------------------------------------
Title: A Model for Solar EUV Flux Helium Photoionization Throughout
the 3-Dimensional Heliosphere
Authors: Auchère, F.; McMullin, D. R.; Cook, J. W.; Newmark, J. S.;
von Steiger, R.; Witte, M.
2005ESASP.592..327A Altcode: 2005soho...16E..49A; 2005ESASP.592E..49A
No abstract at ADS
---------------------------------------------------------
Title: Freezing-In Temperatures of Oxygen, Carbon and Iron in
Magnetic Clouds
Authors: Rodriguez, L.; Woch, J.; Krupp, N.; Fränz, M.; von Steiger,
R.; Cid, C.; Forsyth, R.; Glaß,eier
2005ESASP.592..759R Altcode: 2005soho...16E.155R; 2005ESASP.592E.155R
No abstract at ADS
---------------------------------------------------------
Title: Solar Wind from the Coronal Hole Boundaries
Authors: Schwadron, N. A.; McComas, D. J.; Elliott, H. A.; Gloeckler,
G.; Geiss, J.; von Steiger, R.
2005ESASP.592..645S Altcode: 2005soho...16E.127S; 2005ESASP.592E.127S
No abstract at ADS
---------------------------------------------------------
Title: The Heliospheric He II 30.4 nm Solar Flux During Cycle 23
Authors: Auchère, F.; Cook, J. W.; Newmark, J. S.; McMullin, D. R.;
von Steiger, R.; Witte, M.
2005ApJ...625.1036A Altcode:
Because of the orbit characteristics of the vast majority of
spacecraft, the solar flux has predominantly been measured at Earth
or at least in the plane of the ecliptic. Therefore, the existing
data do not directly demonstrate the fact that the latitudinal
distribution of the extreme-ultraviolet (EUV) solar flux is largely
anisotropic. Indeed, in the EUV the nonuniform distribution of very
contrasted bright features (i.e., active regions) and dark features
(i.e., coronal holes) at the surface of the Sun produces both the
obvious rotational (or longitudinal) modulation of the flux and also
a strong latitudinal anisotropy. Although largely ignored up to now,
the latitudinal anisotropy affects the physical conditions in the
corona and heliosphere and should therefore be taken into account in
several solar and heliospheric physics applications. We describe in this
paper a technique for computing the He II 30.4 nm flux at an arbitrary
position in the heliosphere from Solar and Heliospheric Observatory
(SOHO) EUV Imaging Telescope (EIT) images. This procedure was used to
produce daily all-sky maps of the 30.4 nm flux from 1996 January to 2003
August, covering the first 8 yr of solar cycle 23. As could be expected
from the examination of the EIT images, the 30.4 nm flux was found to
be strongly anisotropic. The anisotropy I<SUB>pol</SUB>/I<SUB>eq</SUB>
between the fluxes computed for viewpoints located above the solar
poles and within the solar equatorial plane ranges from 0.9 at solar
minimum to 0.6 at solar maximum. A 20% difference was also discovered
between the north and south polar fluxes. The generalization of this
technique to other lines of the EUV and far-ultraviolet (FUV) spectrum
is discussed.
---------------------------------------------------------
Title: Solar wind from the coronal hole boundaries
Authors: Schwadron, N. A.; McComas, D. J.; Elliott, H. A.; Gloeckler,
G.; Geiss, J.; von Steiger, R.
2005JGRA..110.4104S Altcode: 2005JGRA..11004104S
Recent studies using in situ observations established that the
interface between fast and slow wind in interplanetary space has two
distinct parts: a smoothly varying boundary layer flow that flanks
fast wind from coronal holes and a sharper plasma discontinuity
between intermediate and slow solar wind. Other studies using in
situ observations and modeling have demonstrated the existence of the
sub-Parker spiral structure of the heliospheric magnetic field in which
the magnetic connection between fast and slow wind created by foot
point motion at the Sun deforms field lines, making them significantly
less transverse than the Parker spiral. Here we model the formation
of corotating interaction regions, and by including a coronal hole
boundary layer (CHBL) and magnetic foot point motion across the coronal
hole boundary back at the Sun we explain the detailed, characteristic
variations in composition and magnetic field orientation observed in
interplanetary space. Our model accomplishes this using only two free
parameters, with all other quantities derived directly from solar wind
observations. Through the model we trace the observed interplanetary
variations back to an intrinsic two-part structure in the source of
solar wind at the Sun. These parts are (1) a CHBL that encircles the
coronal hole and has a smooth transition in the source properties that
produce the fast through intermediate speed (∼600 km s<SUP>-1</SUP>)
solar wind and (2) a sharp coronal hole discontinuity separating the
distinct sources of solar wind with intermediate speeds and temperatures
from slow solar wind. This study establishes the connection between
the characteristic variations of the solar wind speed, charge state
composition, and magnetic field orientation observed in situ near 5 AU
with their sources in the two-part structure of coronal hole boundaries
back at the Sun.
---------------------------------------------------------
Title: Bidirectional Proton Flows and Comparison of Freezing-in
Temperatures in ICMEs and Magnetic Clouds
Authors: Rodriguez, L.; Woch, J.; Krupp, N.; Fränz, M.; von Steiger,
R.; Cid, C.; Forsyth, R.; Glaßmeier, K. -H.
2005IAUS..226..420R Altcode:
From all the transient events identified in interplanetary space
by in-situ measurements, Magnetic Clouds (MCs) are among the most
intriguing ones. They are a special kind of Interplanetary Coronal
Mass Ejections (ICMEs), characterized by a well-defined magnetic field
configuration. We use a list of 40 MCs detected by Ulysses to study
bidirectional flows of protons in the ∼0.5 MeV energy range. Solar
wind ions are also analysed in order to compare cloud to non-cloud
ICMEs.</p>The enhancement in freezing-in temperatures inside the
clouds, obtained with data from the SWICS instrument, provides insights
into processes occurring early during the ejection of the material and
represents a complementary tool to differentiate cloud from non-cloud
ICMEs. At higher energies, directional information for protons obtained
with the EPAC instrument allows a comparison with previous results
concerning bidirectional suprathermal electrons. The findings are
qualitatively comparable. Apparently, the portion of bidirectional
flows inside magnetic clouds is neither heavily dependent on distance
from the Sun nor on parameters obtained from a flux rope model.
---------------------------------------------------------
Title: The Sun, from Core to Corona and Solar Wind
Authors: von Steiger, R.; Fröhlich, C.
2005ISSIR...3...99V Altcode: 2005ssb..book...99V; 2005ESASR...3...99V
No abstract at ADS
---------------------------------------------------------
Title: Model of the all-sky He II 30.4 nm solar flux
Authors: Auchère, F.; Cook, J. W.; Newmark, J. S.; McMullin, D. R.;
von Steiger, R.; Witte, M.
2005AdSpR..35..388A Altcode:
Because of the orbit characteristics of the vast majority of spacecraft,
the solar flux has been generally measured at Earth or in the plane
of the ecliptic. So far, most published studies did not consider
the fact that the extreme ultraviolet (EUV) solar flux is largely
anisotropic. Indeed, in the EUV, the distribution of very contrasted
bright and dark features at the surface of the Sun produces both the
obvious rotational (longitudinal) modulation of the flux, but also a
strong latitudinal anisotropy. Although largely ignored up to now, the
latitudinal anisotropy affects the physical conditions in the corona
and heliosphere. We describe an empirical model of the all-sky He II
30.4 nm flux based on EIT/ SOHO data. The 30.4 nm flux was found to be
strongly anisotropic. The anisotropy I<SUB>pol</SUB>/ I<SUB>eq</SUB>
between the fluxes computed for viewpoints located above the solar
poles and within the solar equatorial plane ranges from 0.9 at solar
minimum to 0.6 at solar maximum. A 20% asymmetry was also discovered
between the north and south polar fluxes.
---------------------------------------------------------
Title: A Model For EUV Flux Throughout The 3-Dimensional Heliosphere
Authors: McMullin, D. R.; Auchere, F.; Cook, J.; Newmark, J. S.;
Quemerais, E.; von Steiger, R.; Witte, M.
2004AGUFMSH21B0423M Altcode:
After July 2001, when Ulysses moved from 30 to 80 degrees in solar
latitude, the Ulysses GAS instrument measured an apparent increase
in the neutral He density. This is more naturally interpreted as
a latitudinal dependence (decrease) of the loss rate due to solar
photoionization rather than a true increase of the neutral He
density. We have developed a three-dimensional model for solar EUV
fluxes observed at any heliospheric position, using daily SOHO EIT
observations, over successive Carrington rotations, projected to
any heliospheric position. The combined effects of solar rotational
and latitude-dependent flux variability are explicitly treated in
this model. The flux model has been directly compared with other
direct irradiance observations in the ecliptic plane with the SOHO/SEM
irradiance time series for validation. We then use this flux to compute
the photoionization rate of the in-flowing neutral He, and compare the
modeled change with time along the spacecraft trajectory with the direct
measurements from the out -of -ecliptic Ulysses GAS observations. The
3-D model developed will be directly applicable to STEREO EUV images
from the SECCHI instrument suite. As the two spacecraft separate, the
amount of the solar surface observed will increase through the mission,
providing more accurate solar inputs.
---------------------------------------------------------
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.
2004ESASP.575..372B Altcode: 2004soho...15..372B
No abstract at ADS
---------------------------------------------------------
Title: Composition of Interplanetary Coronal Mass Ejections at Very
High Latitudes
Authors: von Steiger, R.; Zurbuchen, T. H.; Kilchenmann, A.
2004AGUFMSH33B..02V Altcode:
Composition signatures such as a high average iron charge state, a
high O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio, or a high alpha to proton
ratio are established tools for the identification of interplanetary
coronal mass ejections (ICMEs). However, their relation to the
classical signatures such as conterstreaming electrons, low plasma
beta, or magnetic field rotation, is far from being one-to-one,
and therefore deserves some attention. When Ulysses was traveling
to high latitudes it encountered ICMEs both during the first set of
polar passes at solar minimum and during the second set, which occurred
around the maximum of solar cycle 23. Six high-latitude ICMEs had been
observed in the large fast streams from the polar coronal holes at
solar minimum, defining a new class of overexpanding ICMEs, but none
had a compositional signature whatsoever. In this paper we analyze
five ICME events that were also embedded in a polar fast stream, but
occurred not far from solar maximum, in October to December 2001 at
a heliolatitude of >70<SUP>o</SUP> north. These five events show
a surprising variety of compositional signatures, from hardly any to
strong. They are ideally suited for the study of these signatures since
the background fast solar wind is compositionally uniform, making the
boundaries appear very sharp. This enables us to compare the two sets
of signatures to a high degree of accuracy.
---------------------------------------------------------
Title: Observations of the helium focusing cone with pickup ions
Authors: Gloeckler, G.; Möbius, E.; Geiss, J.; Bzowski, M.; Chalov,
S.; Fahr, H.; McMullin, D. R.; Noda, H.; Oka, M.; Ruciński, D.;
Skoug, R.; Terasawa, T.; von Steiger, R.; Yamazaki, A.; Zurbuchen, T.
2004A&A...426..845G Altcode:
The helium gravitational focusing cone has been observed using
pickup He<SUP>+</SUP>, first during the solar minimum in 1984-1985
with the AMPTE/IRM spacecraft, and again in more detail from 1998
to 2002 with ACE and in 2000 with Nozomi. Five traversals of the
cone allow us to obtain an accurate determination of the ecliptic
longitude of the interstellar wind flow direction, λ = 74.43 ° ±
0.33 ° , while observations of pickup He<SUP>++</SUP> with Ulysses
give us an estimate, relatively free of instrumental systematic
uncertainties, of the neutral He density, n<SUB>He</SUB> = 0.0151 ±
0.0015 cm<SUP>-3</SUP>, in the Local Interstellar Cloud. From best
fits to the measured velocity distributions of pickup He<SUP>+</SUP>
using time-stationary models we deduce the radial dependence and
magnitude of electron-impact ionization rates that cannot presently
be measured, and find this to be an important ionization process in
the inner (⪉0.5 AU) heliosphere. We obtain excellent model fits
to the 1998 cone profile using measured or deduced rates and known
interstellar He parameters, and from this conclude that cross-field
diffusion of pickup He<SUP>+</SUP> is small. Furthermore, we find no
evidence for extra sources of He in or near the cone region. Best fits
to the velocity distributions of He<SUP>+</SUP> are obtained assuming
isotropic solar-wind-frame distributions, and we conclude from this
that the scattering mean free path for pickup He<SUP>+</SUP> in the
turbulent slow solar wind is small, probably less than 0.1 AU. We
argue that application of 3D, time-dependent models for computation of
the spatial distribution of interstellar neutral helium in the inner
heliosphere may lead to excellent fits of short-term averaged pickup
He<SUP>+</SUP> data without assuming loss rates that are significantly
different from production rates.
---------------------------------------------------------
Title: Heliospheric conditions that affect the interstellar gas
inside the heliosphere
Authors: McMullin, D. R.; Bzowski, M.; Möbius, E.; Pauluhn, A.;
Skoug, R.; Thompson, W. T.; Witte, M.; von Steiger, R.; Rucinski,
D.; Judge, D.; Banaszkiewicz, M.; Lallement, R.
2004A&A...426..885M Altcode:
The interstellar gas that flows through the heliosphere is strongly
affected by ionization close to the Sun, in particular solar
photoionization, electron impact, and charge exchange. Therefore, the
interpretation of any observation of interstellar gas in the inner
heliosphere hinges upon the accurate knowledge of these effects and
their variations. In addition, the irradiance and line profile of the
relevant solar spectral line are needed to properly interpret resonant
backscattering observations of the interstellar neutral gas. With
instrumentation on ACE, SOHO and Wind, continuous monitoring of these
important environmental conditions simultaneously with a multitude
of interstellar gas observations has become possible for the first
time. In this paper we present a compilation of the processes and
parameters that affect the distribution of interstellar helium inside
the heliosphere and their observation, including the irradiance and
line profile of the He 58.4 nm line. We also make the connection to
proxies for these parameters and evaluate their accuracy in order to
expand the time period of coverage wherever possible.
---------------------------------------------------------
Title: Synopsis of the interstellar He parameters from combined
neutral gas, pickup ion and UV scattering observations and related
consequences
Authors: Möbius, E.; Bzowski, M.; Chalov, S.; Fahr, H. -J.; Gloeckler,
G.; Izmodenov, V.; Kallenbach, R.; Lallement, R.; McMullin, D.; Noda,
H.; Oka, M.; Pauluhn, A.; Raymond, J.; Ruciński, D.; Skoug, R.;
Terasawa, T.; Thompson, W.; Vallerga, J.; von Steiger, R.; Witte, M.
2004A&A...426..897M Altcode:
A coordinated effort to combine all three methods that are used
to determine the physical parameters of interstellar gas in the
heliosphere has been undertaken. In order to arrive at a consistent
parameter set that agrees with the observations of neutral gas, pickup
ions and UV backscattering we have combined data sets from coordinated
observation campaigns over three years from 1998 through 2000. The key
observations include pickup ions with ACE and Ulysses SWICS, neutral
atoms with Ulysses GAS, as well as UV backscattering at the He focusing
cone close to the Sun with SOHO UVCS and at 1 AU with EUVE. For the
first time also the solar EUV irradiance that is responsible for
photo ionization was monitored with SOHO CELIAS SEM, and the He I
58.4 nm line that illuminates He was observed simultaneously with
SOHO SUMER. The solar wind conditions were monitored with SOHO, ACE,
and WIND. Based on these data the modeling of the interstellar gas and
its secondary products in the heliosphere has resulted in a consistent
set of interstellar He parameters with much reduced uncertainties,
which satisfy all observations, even extended to earlier data sets. It
was also established that a substantial ionization in addition to photo
ionization, most likely electron impact, is required, with increasing
relative importance closer to the Sun. Furthermore, the total combined
ionization rate varies significantly with solar latitude, requiring
a fully three dimensional and time dependent treatment of the problem.
---------------------------------------------------------
Title: Heliospheric Magnetic Field Configuration at Solar Maximum
Conditions: Consequences for Galactic Cosmic Rays
Authors: Zurbuchen, T. H.; von Steiger, R.; Manchester, W. B.; Fisk,
L. A.
2004AIPC..719...70Z Altcode:
During solar maximum conditions, the heliosphere is highly structured
on all spatial scales. It is the purpose of this paper to summarize
our current understanding of these structures from global scales to
mesoscale, a fraction of 1 AU. We use theoretical considerations,
in situ observations near Earth and the Ulysses spacecraft, and
global heliosphere calculations to discuss the effects on both
global and mesoscales on the three-dimensional structure of the
heliospheric magnetic field and their effects on galactic cosmic
rays. These conclusions are in contrast to near-solar-minimum-like
heliospheric conditions that are currently assumed in modulation
and transport calculations even during solar maximum. The expected
complex heliospheric properties should be of major importance for
the interpretation of the heliospheric boundary events observed by
Voyager 1 since 2002. A companion paper by L. A. Fisk will explore
the effects of the mesoscale structures on particle acceleration in
the heliospheric boundary region.
---------------------------------------------------------
Title: Cometary Ions Trapped in a Coronal Mass Ejection
Authors: Gloeckler, G.; Allegrini, F.; Elliott, H. A.; McComas, D. J.;
Schwadron, N. A.; Geiss, J.; von Steiger, R.; Jones, G. H.
2004ApJ...604L.121G Altcode:
Ion tails of comets are known to extend radially away from the Sun
over very large distances. Crossing these tails by spacecraft not
specifically targeted to intercept them was believed to be extremely
improbable, since that requires precise angular alignment of the
spacecraft with a comet. We report here the fortuitous detection
of cometary ions at large angular separation far from the comet. To
explain this unexpected discovery, we conclude that these ions were
ducted laterally along magnetic fields that were randomly distorted
by a coronal mass ejection and that such transport increases the
probability of an unplanned detection of comets.
---------------------------------------------------------
Title: A statistical study of oxygen freezing-in temperature and
energetic particles inside magnetic clouds observed by Ulysses
Authors: Rodriguez, L.; Woch, J.; Krupp, N.; FräNz, M.; von Steiger,
R.; Forsyth, R. J.; Reisenfeld, D. B.; GlaßMeier, K. -H.
2004JGRA..109.1108R Altcode:
Interplanetary Coronal Mass Ejections (ICMEs) have proven to be
very complex phenomena, not easy to unveil using a single set of
observations. We combine Ulysses observations of medium energy
particles, solar wind plasma parameters, magnetic field, and
charge state distributions of heavy ions in order to identify and
characterize CME ejecta in the heliosphere. We focused on a special
class of ICMEs, so-called magnetic clouds (MC). The large number of
MCs detected by Ulysses allowed us to perform a statistical analysis
of the freezing-in temperature and energetic particle population within
MCs. Based on a larger statistical set of events covering a full solar
cycle and all heliolatitudes, we can confirm previous findings of a
significant temperature increase within MCs. Furthermore, we found
that this increase occurs at all latitudes and phases of the solar
cycle. Intensities of medium-energy particles are generally depleted
or not changed inside the MCs. This behavior is, again, found at all
latitudes and solar cycle phases.
---------------------------------------------------------
Title: Preface to: COSPAR 2002 D2.2-E3.3
Authors: Esser, R.; von Steiger, R.
2004AdSpR..33..667E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Charge States and Abundances of Heavy Ions as Signatures of
Interplanetary Coronal Mass Ejections
Authors: von Steiger, R.; Kilchenmann, A.; Zurbuchen, T. H.
2004cosp...35.1574V Altcode: 2004cosp.meet.1574V
Compositional signatures are by now a well-established tool for
the identification of Interplanetary Coronal Mass Ejections. An
alpha-to-proton ratio of >8 % is a sufficient criterion for the
presence of an ICME, as is an average charge state of iron ions of
< Q_Fe > ≥ 12; both of these signatures are not necessary
ones, though. An increased C and O freezing-in temperature is also
likely to be a robust ICME signature. Compositional signatures are
particulary attractive because, unlike kinetic and magnetic ones, they
remain essentially unchanged throughout the entire heliosphere. Using
data obtained with Ulysses-SWICS we evaluate the occurrence rate of
composition signatures in ICMEs as identified both by their classical
(kinetic and magnetic) as well as by their compositional signatures. We
then attempt to identify and define different classes of ICMEs based
on the presence of particular, characteristic combinations of such
signatures. Finally, the distribution of ICMEs with and without a
compositional signature as a function of heliographic latitude will
be evaluated.
---------------------------------------------------------
Title: Internal Structure of Magnetic Clouds seen by Ulysses
Authors: Rodriguez-Romboli, L.; Woch, J.; Krupp, N.; Fränz, M.;
von Steiger, R.; Cid, C.; Forsyth, R.; Glaßmeier, K. -H.
2004cosp...35.2285R Altcode: 2004cosp.meet.2285R
Magnetic clouds represent nearly one third of all the coronal mass
ejections seen by Ulysses. Among the many open questions regarding
their origin and evolution, one of the most challenging scientific
problems is to gain insights into their internal structure. On a first
approximation, the question is whether the intrinsic structure of CMEs
seen at the Sun still prevails in interplanetary space. We use data from
the SWICS and EPAC instruments onboard Ulysses to analyse intensities,
composition, anisotropies and spectra of ions from the plasma to the
1MeV/nuc energy range. These data are used in conjunction with a flux
rope model for the magnetic field, to order the obtained results in
a topological frame of reference.
---------------------------------------------------------
Title: The ICME Superevent 2003: A view from Ulysses
Authors: Kilchenmann, A.; von Steiger, R.; Zurbuchen, T. H.
2004cosp...35.1332K Altcode: 2004cosp.meet.1332K
In October-November 2003 a series of exceptionally large events took
place on the Sun. They led to a series of CMEs, which propagated
through interplanetary space and reached Ulysses, where they created
a very unusually strong ICME event. We will present the observations
from Ulysses, which was located at 5 AU close to the west limb of
the Sun. The speed resulting from this event, v<SUB>α</SUB>∼
999.2 km/s, was the highest 3-hour average ever observed at Ulysses
during its entire mission since late 1990. During almost a week,
events were arriving at Ulysses, which all had the same source region
at the Sun. We describe the superevent from Ulysses-SWICS data with
consideration of compositional signatures, such as Fe charge state,
O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio and the α/p ratio. Then we map
the in situ observations back to the Sun and identify them with events
observed from SOHO. We will discuss the detailed association of SOHO
CMEs and Ulysses in situ observations.
---------------------------------------------------------
Title: The October/November 2003 Events: ACE and Ulysses Results
Authors: Zurbuchen, T. H.; von Steiger, R.
2004cosp...35.1658Z Altcode: 2004cosp.meet.1658Z
The solar activity during a period of approximately 10 days starting in
late October 2003 is being discussed based on ACE and Ulysses data. The
solar events of interest were associated with a very large cluster of
highly complex active regions. These resulted in coronal mass ejections
that led to a number of the most spectacular events ever observed in
situ. It is the purpose of this talk to, first, summarize observations
from ACE. We will focus on measurements of solar wind dynamics, speeds
in excess of 1900 km/s, and plasma heating to levels not previously
observed. We will then discuss the compositional signatures of these
events. The ionic charge states of Fe were observed to reach record
levels, O and C were almost fully ionized, and there were unusual
elemental fractionation patterns observed during the most extreme
event. Finally, we will address the heliospheric consequences of
these events, by comparing ACE and Ulysses data. This time of very
unusual solar activity also led to record-breaking events in the outer
heliosphere, far off the Sun-Earth line. We will discuss the global
consequences of these events.
---------------------------------------------------------
Title: Charge states and abundances of heavy ions as signatures of
interplanetary coronal mass ejections
Authors: von Steiger, R.; Zurbuchen, T. H.
2003AGUFMSH11A..04V Altcode:
Interplanetary Coronal Mass Ejections (ICMEs) are not easy to
recognise. Several signatures are used to identify such events:
Counterstreaming electrons, magnetic field rotation and fluctuation,
low kinetic temperature, etc. However, an individual ICME rarely
shows them all, so identification remains a somewhat subjective art
form. Composition signatures were long known to provide a useful
identifier: An alpha-to-proton ratio of >8% is a sufficient
criterion for the presence of an ICME. More recently, a high average Fe
charge state was established as another sufficient (but not necessary)
signature, as is probably the case for an increased C and O freezing-in
temperature. Such signatures are particulary attractive because, unlike
kinetic and magnetic ones, they remain largely unchanged throughout the
entire heliosphere. Using data obtained with Ulysses-SWICS we evaluate
the occurrence rate of composition signatures in ICMEs as identified by
their classical signatures. The definition of the appropriate threshold
values of these signatures will receive particular attention. Finally,
the distribution of ICMEs with and without a compositional signature
as a function of heliographic latitude will be evaluated.
---------------------------------------------------------
Title: Solar wind composition measurements during one entire solar
cycle
Authors: Zurbuchen, T. H.; von Steiger, R.
2003AGUFMSH11A..03Z Altcode:
The Solar Wind Ion Composition Sensors on Ulysses and ACE have provided
the most comprehensive set of solar wind elemental composition data
to date. Solar wind elemental compositional variations have been
observed by these instruments since 1990 and 1997 respectively. All
solar wind is observed to be fractionated throughout the entire solar
cycle. However, the degree of fractionation varies as a function and
time and location throughout the solar cycle. We will review these
observations and discuss a theoretical model used to explain these
fractionation patterns. We will also discuss the implications of these
models on long-term averaged isotopic composition measurements, such
as to be provided by Genesis.
---------------------------------------------------------
Title: Earth Gravity Field from Space - from Sensors to Earth Sciences
Authors: Beutler, G.; Drinkwater, M. R.; Rummel, R.; von Steiger, R.
2003egfs.conf.....B Altcode:
The ESA explorer core mission GOCE, to be launched in 2006, will
enhance our knowledge of the global static gravity field and of the
geoid by orders of magnitude. The U.S. satellite gravity mission
GRACE (2002-2006) is currently measuring, in addition, the temporal
variations of the gravity field. With these new data a whole range
of fascinating new possibilities will be opened for solid Earth
physics, oceanography, geodesy and sea-level research. The new
generation of gravity missions employs sensor concepts for gravity
field measurement, orbit and attitude control and orbit determination
that show interesting similarities with space experiments planned
in the field of fundamental physics. This volume is the result of
a workshop that brought together some 50 acknowledged experts in
their field to discuss (1) strategies for ultra precision orbit
determination and gravity field modelling with the data of the
upcoming gravity field missions, (2) the use of accurate and high
resolution gravity models in Earth sciences whereby, in particular,
synergy is expected between the various science fields in their use
of this type of new information, and (3) gravity field requirements
and possible sensor and mission concepts for the time after GRACE and
GOCE. <P />Link: <A href="http://www.wkap.nl/prod/b/1-4020-1408-2">
http://www.wkap.nl/prod/b/1-4020-1408-2</A>
---------------------------------------------------------
Title: Composition signatures of interplanetary coronal mass ejections
Authors: von Steiger, Rudolf; Zurbuchen, Thomas H.
2003ESASP.535..835V Altcode: 2003iscs.symp..835V
The interplanetary counterparts of coronal mass ejections (ICMEs) are
complex phenomena that are not recognised or characterised easily. Many
signatures have been defined and used to identify them: kinetic,
magnetic, thermal, energetic particles, etc., but hardly any ICME
event shows a signal in all of them simultaneously. Another classical
ICME identifier is the abundance of alpha particles. It was shown that
an alpha-to-proton ratio of >8% is a sufficient criterion for ICME
detection, albeit not a necessary one. In recent years more composition
signatures for ICMEs were defined using the time-of-flight instruments
on Ulysses and ACE, and it could be shown that a high average iron
charge state is also a sufficient but no necessary ICME signature. The
same is probably true for an increased oxygen or carbon freezing in
temperature above a certain threshold value. Composition signatures
are particularly attractive since they are unlikely to change once the
SME has left the Sun, making them a robust tool for ICME identification
throughout the entire heliosphere. Using the data obtained with Ulysses
SWICS we assess which of the composition signatures are observed in
ICMEs defined by the classical signatures. Conversely, we search for
occurrences of composition signatures and assess whether or not an
ICME is associated with it. As a result we obtain a quality measure
for each composition signature.
---------------------------------------------------------
Title: Temperature Anisotropies of Heavy Solar Wind Ions from
Ulysses-SWICS
Authors: von Steiger, R.; Zurbuchen, T. H.
2003AIPC..679..526V Altcode:
We report the first in-situ measurements of temperature anisotropies
of heavy ions in the solar wind, obtained with the Solar Wind Ion
Composition Spectrometer (SWICS) on the Ulysses spacecraft. Since
SWICS measures only 1-dimensional cuts through the full, 3-d
velocity distribution functions we resort to a statistical approach,
separating the particle data according to the instantaneous magnetic
field angle. We apply this analysis to the ions of He<SUP>++</SUP>
and O<SUP>6+</SUP> during extended time periods in the fast streams
from both the south and the north polar coronal holes that Ulysses
traversed in 1993-96. In both cases we find anisotropies of the order
of T⊥/T∥ = 0.8. The results of this study are discussed in relation
to the observations made on Helios for He<SUP>++</SUP> in the 1970s, and
to recent observations made on SOHO-UVCS, which show extreme temperature
anisotropies of O VI, or O<SUP>5+</SUP>, at a few solar radii.
---------------------------------------------------------
Title: The Composition of Interplanetary Coronal Mass Ejections
Authors: Zurbuchen, Thomas H.; Fisk, L. A.; Lepri, S. T.; von
Steiger, R.
2003AIPC..679..604Z Altcode:
Interplanetary coronal mass ejection (ICME) associated plasma can
exhibit signatures in elemental, ionic and isotopic composition. These
signatures occur in less than 50% of all ICMEs, but are very indicative
of ICME plasma. We review these compositional anomalies and briefly
discuss a physical scenario that could be responsible for these
anomalies.
---------------------------------------------------------
Title: Foreword
Authors: Beutler, G.; Drinkwater, M. R.; Rummel, R.; von Steiger, R.
2003SSRv..108D...9B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Interplanetary and solar surface properties of coronal holes
observed during solar maximum
Authors: Zhang, J.; Woch, J.; Solanki, S. K.; von Steiger, R.;
Forsyth, R.
2003JGRA..108.1144Z Altcode:
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on board
the Ulysses spacecraft and synoptic maps from Kitt Peak are used to
analyze the relatively short-lived coronal holes which exist during
the maximum phase of the solar activity cycle 23. They are compared
with the persistent polar coronal holes which prevail around solar
minimum. A solar wind velocity increase coinciding with a shift of
the ionic charge composition toward lower charge states serves as a
robust criterion for identifying solar wind streams emanating from
solar maximum holes. This allows an unambiguous association of every
stream identified in interplanetary space with a coronal hole on the
solar surface with consistent magnetic polarity. Solar wind streams
emanating from the solar maximum holes generally show lower velocities
of 400 to 600 km/s compared to the polar hole stream velocities of
700 to 800 km/s. However, the SWICS O<SUP>7+</SUP>/O<SUP>6+</SUP>
charge-state ratios, which are a proxy for coronal temperatures, do not
reveal a consistent difference. Though a number of solar maximum holes
have a significantly, up to three times, higher temperature compared
to the polar coronal holes, the majority of the investigated holes and
specifically those with new cycle polarity have a coronal temperature
within the range of polar hole temperatures. Likewise, the magnetic flux
density in the solar maximum holes and in the polar coronal holes, as
derived from the synoptic maps, is not strikingly different. Therefore
any intrinsic difference between solar maximum holes and polar coronal
holes is small. The striking discrepancy in their kinetic properties,
namely the slower velocity of the solar wind streams emanating from
solar maximum holes, may partly be attributed to deceleration of the
solar wind during propagation to the spacecraft. The discrepancy may
also be influenced by active regions in close proximity to the coronal
holes, which presumably is more likely for smaller holes. There may,
however, be a tendency for the faster wind streams to emanate from
cooler holes.
---------------------------------------------------------
Title: Latitude Dependence of Element Abundances in the Slow
Solar Wind
Authors: von Steiger, R.; Zurbuchen, T. H.
2002AGUFMSH21A0515V Altcode:
Since 1992 the Ulysses spacecraft orbits the Sun on a high-inclination
orbit with an inclination of 80 degrees to the heliographic equator. The
first orbit, in 1992--98, took place around solar minimum and revealed
a highly ordered state of the heliosphere with large high-speed
streams poleward of about 30 degrees heliolatitude, emanating from the
relatively cool polar coronal holes, separated by a band of slow solar
wind at low latitudes. In the slow wind the abundances of elements
with a low first ionisation potential (FIP) such as Fe, Mg, and Si,
are found to be enhanced over the solar values relative to the high-FIP
elements by a significant factor of 2--5. On the other hand, this FIP
enrichment factor was found to be less than a factor of two, but still
significantly larger than one, in the polar high speed streams. On the
second orbit, which is now taking place around the maximum of solar
cycle 23, slow solar wind is found at all heliolatitudes, interspersed
with fast streams from fragmented coronal holes and from coronal mass
ejections, also at all latitudes. Using data from the SWICS sensor
on Ulysses, we have found that the strength of the FIP fractionation
factor appears to depend on the heliographic latitude, even if we
restrict ourselves to unequivocal slow solar wind. The strongest FIP
enrichments are found at low latitudes, which can also be observed from
the ecliptic plane, but they are becoming increasingly weaker at higher
latitudes. This was particularly evident during the second fast latitude
scan in 2000/01. We will present the observational data and discuss
their possible implications for the underlying coronal structure,
specifically in the framework of the Fisk model. In this model the slow
solar wind is pictured as made up from a sequence of prevoiusly closed
magnetic loops that are emptied onto open, migrating field lines. The
strength of the FIP fractionation of the loop material may expected to
be a function of loop parameters such as length, temperature, or age,
so therefore a systematic variation of the FIP fractonation factor
may reveal a dependence of these parameters on heliographic latitude.
---------------------------------------------------------
Title: Matter in the Universe
Authors: Jetzer, Ph.; Pretzl, K.; von Steiger, R.
2002maun.conf.....J Altcode:
The knowledge of the amount and nature of matter present in the Universe
is undoubtedly one of the most relevant topics in astrophysics and
cosmology. It started with the pioneering work of Zwicky in 1933,
who found the need for a large amount of dark matter in the Coma
cluster. An important step has been the recent finding through
the observation of distant type Ia supernovae of the presence of a
significant vacuum energy density causing an accelerating expansion
of the Universe. Nevertheless, the nature of most of the matter in
the Universe is still unknown. Its solution requires the interplay
of several fields of astrophysics and cosmology as well as particle
physics, all of which are covered in this volume: Cosmic Microwave
Background radiation, large scale structures, galaxy clusters,
intergalactic absorption, dark matter components of galaxies, globular
clusters, supernovae of type Ia distance measurements, gravitational
lensing, X-ray observations, Lyman-alpha observations, dark energy,
direct detection of weakly interacting massive particles (WIMPS),
detection of neutrino oscillations, particle candidates for dark
matter, and Big Bang nucleosynthesis of baryonic matter. Therefore,
the present volume presents a very useful synopsis on all constituents
of matter in the Universe. Link: http://www.wkap.nl/prod/b/1-4020-0666-7
---------------------------------------------------------
Title: Kinetic properties of heavy solar wind ions from Ulysses-SWICS
Authors: von Steiger, R.; Zurbuchen, T. H.
2002AdSpR..30...73V Altcode:
The kinetic properties of heavy ions in the solar wind reflect the
microphysical processes governing the solar wind in the heliosphere. We
use the unique data set of Ulysses-SWICS which provides data in a wide
rage of mass per charge, 2 ≤ m/q ≤ 9.33. In particular, we look
for slight deviations from the canonical behaviour of equal bulk speed
and equal thermal speed of all heavy ion species. Such deviations
are expected to carry signatures of the wave-particle interaction
processes in the solar wind, and to a lesser extent, to collisions
which tend to bring the particles closer to thermal equilibrium. The
data set of Ulysses-SWICS is ideal for this task because it spans not
only a large range in m/q, but also in time, solar wind speed (covering
extended time periods in slow and in fast wind), heliographic latitude,
and heliocentric distance.
---------------------------------------------------------
Title: The radiometric calibration and intercalibration of SOHO
Authors: Huber, M. C. E.; Pauluhn, A.; von Steiger, R.
2002ESASP.508..213H Altcode: 2002soho...11..213H
The radiometric calibration of spectrometric telescopes assures that
the observed spectral radiance (or irradiance) is measured on a scale
that is defined by the radiometric standards realised and used in
terrestrial laboratories. All SOHO instruments therefore have been
calibrated by use of source and detector standards that are traceable to
the primary radiometric standards. As any calibration, the laboratory
calibration has uncertainties. Moreover, environmental influences,
namely molecular and particulate contamination on the ground and effects
by photon and particle radiaton in space, do change the responsivity
of the instruments. In two workshops held at the International Space
Science Institute in Bern the individual instrument calibrations were
discussed and reconciled. The outcome of the workshops, to which
all instrument groups contributed, is summarised in a book that is
presented here before it goes to press.
---------------------------------------------------------
Title: Adaptive Systems for Detection and Forecasting of Coronal
Mass Ejections From Solar Mean Magnetic Field
Authors: Ganguli, S. B.; Gavrichtchaka, V. V.; Von Steiger, R.
2002AGUSMSH52A..01G Altcode:
Coronal mass ejections (CME) are important sources of dynamical
phenomena that collectively influence geo-space weather. For example,
large, nonrecurrent geomagnetic storms are caused by interplanetary
disturbances driven by fast CMEs. Therefore efficient techniques for
detection and forecasting of CME events can significantly increase the
performance of any realistic space weather forecasting system. Recently
it has been shown that wavelet analysis of the high-resolution solar
mean magnetic field (SMMF) data can provide valuable information for
CME detection. However not all CME events produce easy detectable
signatures in the wavelet transformed SMMF time series. Moreover CME
forecasting would require extracting information from the data prior
to CME onset where these signatures are even less obvious. Therefore
to achieve acceptable accuracy in CME detection/forecasting, multiple
features from the wavelet spectrum or raw SMMF data should be processed
with a powerful classifier based on statistical or machine learning
techniques. We applied neural network and support vector machine for
this purpose. Performance of the obtained systems will be discussed.
---------------------------------------------------------
Title: Solar wind from high-latitude coronal holes at solar maximum
Authors: McComas, D. J.; Elliott, H. A.; von Steiger, R.
2002GeoRL..29.1314M Altcode: 2002GeoRL..29i..28M
In this study we combine Ulysses' observations from the solar wind
plasma (SWOOPS) and ion composition (SWICS) instruments to study
high-latitude coronal holes near solar maximum for the first time. While
chromospheric and coronal composition signatures indicate that there is
a unique type of solar wind, which flows from coronal holes, variations
in the acceleration process produce a wide range of solar wind speeds
from these holes. High-speed wind (>700 km s<SUP>-1</SUP>) can be
produced in small as well as large holes, although the very highest
speed non-transient winds do come from the centers of the largest
holes. Along the edges of coronal holes, the acceleration decreases
and freezing-in temperatures increase relatively smoothly into the
surrounding solar wind, indicating a transition layer around the edges
of coronal holes.
---------------------------------------------------------
Title: The solar wind composition throughout the solar cycle:
A continuum of dynamic states
Authors: Zurbuchen, T. H.; Fisk, L. A.; Gloeckler, G.; von Steiger, R.
2002GeoRL..29.1352Z Altcode: 2002GeoRL..29i..66Z
Variations in the speed and elemental and ionic charge composition of
the solar wind are reported throughout the solar cycle, as observed by
the SWICS instrument on Ulysses. The apparent bimodal nature of the
solar wind during the solar minimum does not persist throughout the
solar cycle. Rather, with increasing solar activity, a continuum of
solar wind speeds and charge states is observed. The exception is the
elemental composition which is noticeably less enhanced in elements
with low first ionization potential (FIP) in material from coronal
holes throughout the solar cycle. These observations are consistent
with theories in which the solar wind originates from coronal loops
that reconnect with open magnetic field lines.
---------------------------------------------------------
Title: The Sun at solar minimum: North - south asymmetry of the
polar coronal holes
Authors: Zhang, J.; Woch, J.; Solanki, S. K.; von Steiger, R.
2002GeoRL..29.1236Z Altcode: 2002GeoRL..29h..77Z
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on
Ulysses and synoptic charts derived from Kitt Peak magnetograms are
used to compare the south and north polar coronal holes which existed
during the declining/minimum phase of the solar activity cycle from
1992 to 1997. The kinetic properties of the solar wind emanating from
the two polar coronal holes, as represented by solar wind speed, do
not differ significantly. However, the electron temperature in the
two coronal holes inferred from ionic charge composition data, namely
the O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio, show consistent differences,
with the south polar hole being 10 to 15% hotter. The ground-based
magnetograms show that the north polar coronal hole covers a larger
part of the solar surface than the southern one. The total magnetic
flux and, specifically, the flux density of the north polar coronal
hole is considerably lower for the whole interval of time between 1992
and 1997. This strongly indicates that the difference in coronal hole
temperature between the southern and northern coronal hole is intrinsic
and is not due to the fact that the Ulysses observations in the south
and north coronal hole streams were made at different phases of the
solar cycle. Thus the differences found represent a real north-south
asymmetry during this time period.
---------------------------------------------------------
Title: The Astrophysics of Galactic Cosmic Rays
Authors: Diehl, Roland; Parizot, Etienne; Kallenbach, Reinald; von
Steiger, Rudolf
2002agcr.conf.....D Altcode:
This volume together with the ones on Cosmic Rays in the Heliosphere
and on Cosmic Rays at Earth, rounds off a trilogy devoted to cosmic
rays. It specifically deals with the astrophysical sources and
acceleration processes of CRs. The principal aims are to examine the
cosmic ray phenomenon in the context of our evolving understanding of
the Galaxy as an astrophysical system. Observations of cosmic rays,
and theoretical models of their origin and propagation, are critically
reviewed. The extent to which these reinforce, or conflict with, other
astronomical information about the Galaxy is addressed. Other themes
are the extent to which galactic-scale processes can be illuminated by
studies or analogous heliospheric processes, and the identification
of key questions for future investigations. The workshop assembled
physicists working in the fields of cosmic rays origin and propagation,
structure evolution and composition of the Galaxy and the interstellar
medium. In addition, researchers working in relevant areas of radio,
optical, X-ray and gamma-ray astronomy, attended the workshops. This
has strengthened the interdisciplinary links between these scientific
communities. Link: http://www.wkap.nl/prod/b/1-4020-0107-X
---------------------------------------------------------
Title: Foreword
Authors: Pauluhn, A.; Huber, M. C. E.; von Steiger, R.
2002ISSIR...2D...7P Altcode: 2002ESASR...2D...7P; 2002rcs..confD...7P
No abstract at ADS
---------------------------------------------------------
Title: The solar wind
Authors: Neugebauer, M.; von Steiger, R.
2002css1.book.1115N Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Radiometric Calibration of SOHO
Authors: Pauluhn, A.; Huber, M. C. E.; von Steiger, R.
2002ISSIR...2.....P Altcode: 2002ESASR...2.....P; 2002rcs..conf.....P
No abstract at ADS
---------------------------------------------------------
Title: Foreword
Authors: Pauluhn, A.; Huber, M. C. E.; von Steiger, R.
2002ISSIR...2D...5P Altcode: 2002ESASR...2D...5P; 2002rcs..confD...5P
No abstract at ADS
---------------------------------------------------------
Title: The Sun At Solar Minimum: North - South Asymmetry of The
Polar Coronal Holes
Authors: Woch, J.; Zhang, J.; Solanki, S. K.; von Steiger, R.
2002EGSGA..27.4007W Altcode:
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses
and synoptic charts derived from Kitt Peak magnetograms are used to
compare the south and north polar coronal holes which existed during
the declining/minimum phase of the solar activity cycle from 1992 to
1997. The kinetic properties of the solar wind emanating from the two
polar coronal holes, as represented by solar wind speed, do not differ
significantly. However, the electron temperature in the two coronal
holes inferred from ionic charge composition data, namely the O7+/O6+
ratio, show consis- tent differences, with the south polar hole being
10 to 15% hotter. The ground-based magnetograms show that the north
polar coronal hole covers a larger part of the so- lar surface than
the southern one. The total magnetic flux and, specifically, the flux
density of the north polar coronal hole is considerably lower for the
whole interval of time between 1992 and 1997. This strongly indicates
that the difference in coronal hole temperature between the southern
and northern coronal hole is intrinsic and is not due to the fact that
the Ulysses observations in the south and north coronal hole streams
were made at different phases of the solar cycle Thus the differences
found represents a real north-south asymmetry.
---------------------------------------------------------
Title: Interplanetary and solar surface properties of coronal holes
Authors: Woch, J.; Zhang, J.; Solanki, S.; von Steiger, R.
2002cosp...34E.967W Altcode: 2002cosp.meetE.967W
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on
Ulysses and synoptic maps from Kitt Peak are used to analyse coronal
holes throughout the solar activity cycle. The large polar coronal
holes existing during the declining/minimum phase of solar cycle 22
show a persistent north-south asymmetry. The coronal temperature,
inferred from ionic charge-state distributions, and the magnetic flux
density are significantly lower in the north polar coronal hole. The
temperature of the emerging north polar hole of solar cycle 23 is
remarkably similar to that of solar cycle 22, confirming that the
coronal temperatures of the polar coronal holes do not evolve in the
course of the activity cycle. Solar wind streams emanating from the
small-scale coronal holes observed around solar maximum generally show
lower velocities compared to the polar coronal hole streams. However,
the coronal temperatures do not reveal a consistent difference. Though
a large number of solar maximum holes have a significantly higher
temperature compared to the polar coronal holes the majority has a
coronal temperature within the range of polar hole temperatures. Above
all, the latter holds for solar maximum coronal holes having a magnetic
polarity consistent with the polarity of the new solar cycle. Likewise,
the magnetic flux density in the solar maximum holes and in the polar
coronal holes, as derived from the synoptic maps, is not strikingly
different. Therefore, it can be concluded that there is no indication
for an intrinsic difference of solar maximum and polar coronal holes.
---------------------------------------------------------
Title: Latitude dependence of element abundances in the slow
solar wind
Authors: von Steiger, R.; Zurbuchen, T.; Schwadron, N.; Gloeckler,
G.; Geiss, J.; Fisk, L.
2002cosp...34E1205V Altcode: 2002cosp.meetE1205V
Since 1992 the Ulysses spacecraft orbits the Sun on a high-inclination
orbit with an inclination of 80 degrees to the heliographic equator. The
first orbit, in 1992-1998, took place around solar minimum and revealed
a highly ordered state of the heliosphere with large high-speed
streams poleward of30 heliolatitude, emanating from the relatively
cool polar coronal holes, separated by a band of slow solar wind
at low latitudes. In the slow wind the abundances of elements with
a low first ionisation potential (FIP) such as Fe, Mg, and Si, are
found to be enhanced over the solar values relative to the high-FIP
elements by a significant factor of 2-5. On the other hand, this FIP
enrichment factor was found to be less than a factor of two, but still
significantly >1, in the polar high speed streams. On the second
orbit, which is now taking place around the maximum of solar cycle 23,
slow solar wind is found at all heliolatitudes, interspersed with fast
streams from fragmented coronal holes and from coronal mass ejections,
also at all latitudes. Using data from the SWICS sensor on Ulysses, we
have found that the strength of the FIP fractionation factor appears to
depend on the heliographic latitude, even if we restrict ourselves to
unequivocal slow solar wind. The strongest FIP enrichments are found
at low latitudes, which can also be observed from the ecliptic plane,
but they are becoming increasingly weaker at higher latitudes. This
was particularly evident during the second fast latitude scan in
2000/01. We will present the observational data and discuss their
possible implications for the underlying coronal structure, specifically
in the framework of the Fisk model. In this model the slow solar wind
is pictured as made up from a sequence of prevoiusly closed magnetic
loops that are emptied onto open, migrating field lines. The strength
of the FIP fractionation of the loop material may expected to be a
function of loop parameters such as length, temperature, or age, so
therefore a systematic variation of the FIP fractonation factor may
reveal a dependence of these parameters on heliographic latitude.
---------------------------------------------------------
Title: Solar wind at solar maximum
Authors: von Steiger, R.
2002cosp...34E1201V Altcode: 2002cosp.meetE1201V
During the last solar minimum in 1996 Ulysses, on its first polar orbit,
found a heliosphere that was relatively simply structured. Large fast
streams emanating from the polar coronal holes dominated the heliosphere
poleward of30 , separated by a zone of generally slow and very variable
solar wind within20 from the solar equator. Composition data were
essential in defining these two quasi-stationary stream types and in
particular the boundary between them, which appears to be remarkably
sharp and well-defined from down in the chromosphere out to Ulysses at 5
AU. Now, around the time of solar maximum activity of cycle 23, Ulysses
is on its second polar orbit, and the picture of the heliosphere that we
obtain this time around is radically different. Superficially it looks
as if the fast streams had almost completely vanished and the slow,
variable solar wind subtended the full solid angle. Yet composition
data of both Ulysses- and ACE-SWICS reveal that the fast streams are,
and have been, present all along. As the solar magnetic field reverses
around maximum activity, the large polar coronal holes fragment and
are replaced by a number of smaller coronal holes at low latitudes
(possibly of about equal integrated area). The fast streams emanating
from these equatorial coronal holes are affected by stream-stream
interaction due to the solar rotation and their kinetic signature
may be altered thereby. But compositional signatures such as a low
O7+ /O6+ charge state ratio are unaffected by such interactions and
clearly indicate their coronal hole origin. Moreover, the solar wind
around solar maximum is interspersed with interplanetary coronal mass
ejections of any speed, and again compositional signatures such as a
high average Fe charge state can be used to identify many of these.
---------------------------------------------------------
Title: Coronal Holes During Solar Maximum: Swics/ulysses and Kitt
Peak Observations
Authors: Zhang, J.; Woch, J.; Solanki, S. K.; von Steiger, R.
2002EGSGA..27.4034Z Altcode:
Synoptic maps of the solar coronal magnetic field from Kitt Peak show
the existence of small-scale coronal holes at low and mid latitudes
during the maximum phase of the present solar cycle. The solar
wind originating from the most prominent holes can be unambiguously
identified in interplanetary space at distances of 2 to 4 AU with
the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses. The
coronal hole plasma is characterized by an enhanced velocity and a
decreased O7+/O6+ ratio com- pared to the ambient solar wind. The
decreased ratio is indicative for a lower coronal temperature in the
source region on the Sun. Though clearly distinguishable from the
ambient solar wind plasma, the solar wind originating from small
scale coronal holes has a lower velocity and less reduced O7+/O6+
ratio than the solar wind emanating from the large-scale polar coronal
holes during solar minimum. This difference is re- flected in synoptic
coronal hole maps and magnetograms. The magnetic flux density of the
small scale coronal holes is considerably lower compared to the flux
density of the polar coronal holes. We suggest that the two types of
coronal holes are intrinsically different.
---------------------------------------------------------
Title: Temperatures and Temperature Anisotropies of Heavy Solar Wind
Ions From Ulysses-SWICS
Authors: von Steiger, R.; Zurbuchen, T. H.
2001AGUFMSH21A0732V Altcode:
The kinetic properties of heavy ions in the solar wind are indicative
of processes affecting their distribution functions in interplanetary
space. Observations at 1 AU reported earlier have established that
all heavy ion species flow approximately at the same bulk speed
and have approximately equal thermal speeds (i.e., mass-proportional
temperatures), with exceptions at times when the solar wind density was
unusually high. At 5 AU such exceptions no longer occur and the basic
picture (of equal bulk speeds and thermal speeds) applies with very high
accuracy. This was interpreted as evidence for the growing dominance
of wave-particle interactions over Coulomb collisions with increasing
heliocentric distance. Moreover, ubiquitous supra-thermal tails on
the distribution functions of heavy ions (without any association to
shocks) were interpreted as evidence for wave-particle interactions
referentially heating and accelerating heavy ions from thermal energies
to energies where they become amenable to shock acceleration, at about
2--3 v<SUB></SUB> SW. In this work we examine yet another property of
heavy ion distribution functions: their thermal anisotropy. This is
not a straightforward matter since with SWICS only 1-dimensional cuts
through the full, 3-d velocity distribution functions are measured. We
therefore have to resort to a statistical approach, separating the
particle data according to the instantaneous magnetic field pitch
angle (and restricting ourselves to periods when this angle remains
sufficiently constant over an instrument cycle of 13 minutes). We apply
this analysis to the ions of He<SUP>++</SUP> and O<SUP>6+</SUP> during
extended time periods in both the fast streams from the south and the
north polar coronal holes observed by Ulysses in 1993--96. The results
of this study are interpreted in relation to the observations made on
Helios for He<SUP>2+</SUP> in the 1970s, and to recent observations
made on SOHO-UVCS, which show extreme temperature anisotropies of O vi,
or O<SUP>5+</SUP>, at a few solar radii.
---------------------------------------------------------
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.
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: The Astrophysics of Galactic Cosmic Rays
Authors: Diehl, R.; Kallenbach, R.; Parizot, E.; Von Steiger, R.
2001SSRv...99....3D Altcode:
Observations of cosmic rays and their related radio to gamma-ray
signatures are surveyed and discussed critically, and compared to
theoretical models of the cosmic-ray origin and propagation. The
analogous heliospheric processes are included as a well-studied case
of the principal physical processes of energetic particle acceleration
and propagation. Reinforcements, or conflicts, in the interpretations
of cosmic-ray spectral and compositional characteristics arise
when cosmic-ray source and propagation models are confronted with
astronomical information about the Galaxy as a whole and from potential
source sites, i.e., supernova remnants or regions with high massive-star
density. This volume represents the outcome of two workshops held at
ISSI. In this chapter we summarize the introductory papers presented
below, and include insights from the workshop discussions.
---------------------------------------------------------
Title: An ICME observed by Voyager 2 at 58 AU and by Ulysses at 5 AU
Authors: Paularena, K. I.; Wang, C.; von Steiger, R.; Heber, B.
2001GeoRL..28.2755P Altcode:
Between days 175 and 180 (June 24 through 29) of 1999, the PLS
instrument on Voyager 2 observed alpha particle enhancements with
fractional percentages of alpha to proton number densities exceeding
10%. Ulysses (located at 5.3 AU) observed at least two candidate
source features for these enhancements. To identify the correct
source structure, a 1D MHD model was used to propagate the Ulysses
plasma data to the Voyager radial position (58.2 AU). An ICME-related
alpha enhancement observed by Ulysses beginning on day 331 (November
27), 1998 appears to be the correct feature. While a speed jump and
cosmic ray decreases were observed by Ulysses in conjunction with this
alpha enhancement, the timing of these features differed markedly at
Voyager 2. The speed jump arrival-time difference is due to the faster
propagation of the shock relative to the rest of the ejecta. It is
unclear what mechanism is responsible for the delay in the cosmic ray
decrease. Nevertheless, we have demonstrated that alpha enhancement
signatures of ICMEs can be used to track these features to heliospheric
distances >50 AU.
---------------------------------------------------------
Title: Ionization state and magnetic topology of coronal mass
ejections
Authors: Henke, T.; Woch, J.; Schwenn, R.; Mall, U.; Gloeckler, G.;
von Steiger, R.; Forsyth, R. J.; Balogh, A.
2001JGR...10610597H Altcode:
Charge state distributions of heavy solar wind ions measured in
interplanetary space can be used to probe the physical conditions
in the solar corona. This paper presents a study of the charge state
distributions and the magnetic topology of 56 coronal mass ejections
(CMEs) observed in interplanetary space by the Ulysses spacecraft. The
analysis of the data from the Solar Wind Ion Composition Spectrometer
(SWICS) instrument and the Vector Helium Magnetometer (VHM) experiment
onboard Ulysses shows a clear correlation between the charge state
distributions and the magnetic topology of CMEs. Almost all CMEs whose
charge state distributions are shifted to higher charge states with
respect to the ambient solar wind have the structure of magnetic clouds,
whereas CMEs with the same charge state distributions as the surrounding
solar wind do not show magnetic cloud structure. This correlation
is found for CMEs observed at low, mid, and high solar latitudes. On
the basis of the numerical solution of the ionization/recombination
equations for oxygen and silicon, it is investigated which changes of
the electron temperature, electron density, and the speed of the ions
in the source region of the CMEs can reproduce the observations. It is
shown that the main reason for the observed enhancement of higher charge
states in the cloud CMEs is an increased electron temperature. However,
the evolution of the density and velocity of the CMEs before the charge
states freeze in cannot be neglected.
---------------------------------------------------------
Title: Solar Wind Source Diversity as Revealed by its Composition
Authors: von Steiger, R.; Zurbuchen, T. H.
2001AGUSM..SH61B01V Altcode:
The solar wind is a bimodal stream that is either called fast if it
originates from coronal holes, or slow if it originates above the
streamer belt. The two quasi-stationary modes are interspersed with
transient streams with a duration of several hours to days that may
differ radically in their properties: the coronal mass ejections. The
stream types are traditionally defined by their kinetic and magnetic
properties, perhaps supplemented (in the case of CMEs) by particle
signatures. But over the last decade new instrumentation has added
heavy ion composition as a diagnostic tool to describing the solar
wind. We present the compositional signatures that are associated
with the different stream types and the boundaries between them, and
we show that in many cases they do more than just adding evidence to
an otherwise clear-cut case. Compositional signatures identify stream
interfaces, CMEs, or fast streams even in cases where the kinetic
signatures are unclear. Moreover, they are a powerful tool for decoding
the solar wind origin and acceleration: The charge states of heavy
elements are indicative of the coronal temperature and its profile,
whereas the elemental abundances probe the conditions and the processes
in the chromosphere and lower transition region.
---------------------------------------------------------
Title: The 3-D Heliosphere from the Ulysses and ACE Solar Wind Ion
Composition Experiments
Authors: von Steiger, R.; Zurbuchen, T. H.; Geiss, J.; Gloeckler,
G.; Fisk, L. A.; Schwadron, N. A.
2001SSRv...97..123V Altcode:
The source region of solar wind plasma is observed to be directly
reflected in the compositional pattern of both elemental and charge
state compositions. Slow solar wind associated with streamers shows
higher freeze-in temperatures and larger FIP enhancements than
coronal hole associated wind. Also, the variability of virtually all
compositional parameters is much higher for slow solar wind compared
to coronal hole associated wind. We show that these compositional
patterns persist even though stream-stream interactions complicate
the identification based on in situ plasma parameters.
---------------------------------------------------------
Title: Coronal hole boundaries from the Sun to the Heliosphere:
Constraints on the sources and structure of the solar wind
Authors: Zurbuchen, T. H.; Von Steiger, R.; Riley, P.; Raymond, J.;
Geiss, J.; Antonucci, E.; Abbo, L.
2001AGUSM..SH21B06Z Altcode:
Coronal holes are known to be a source of fast, relatively homogenous
solar wind. A more variable slow solar wind emerges from the corona
adjacent to these fast streams and dominates the low latitude
heliosphere. The relation between these two qualitatively different
solar wind types is best studied by investigating in detail the
structure and evolution of the coronal hole boundaries from the
low atmosphere of the Sun, through the corona and into the deep
heliosphere. We present a comprehensive data-study combining data from
He I 10830A, EIT, UVCS and in situ plasma and composition measurements
from SWICS on Ulysses and ACE. First, the location and structure of the
coronal hole boundary is determined in each of the remote data-sets. We
then project the in situ plasma and composition measurements to 30
Rs using a sophisticated 2D MHD tracing technique. This technique
then allows a direct comparison of solar and in situ coronal hole
boundaries. We particularly concentrate on UVCS and SWICS data of heavy
ions in the solar wind that allow the most rigorous comparisons of solar
and in situ data, using the same measurement in the corona as in the
solar wind. We will then discuss these data in the context of models
and theories of the structure of the three-dimensional structure of
the corona and the solar wind. We will also compare the observations
with an 3D MHD calculation that predicts super-radial expansion of the
fast solar wind associated with coronal holes. This paper is a report
of an ISSI International Team on coronal hole boundaries.
---------------------------------------------------------
Title: An ICME Observed by Voyager~2 at 58~AU and by Ulysses at 5~AU
Authors: Paularena, K. I.; Wang, C.; von Steiger, R.; Heber, B.
2001AGUSM..SH62A04P Altcode:
Between days 175 and 180 of 1999, the PLS instrument on Voyager~2
observed alpha particle enhancements with fractional percentages of
alpha to proton number densities exceeding 10%. Ulysses (located at
5.3~AU) observed at least two candidate source features for these
enhancements. To identify the correct source structure, a 1D MHD
model was used to propagate the Ulysses plasma data to the Voyager
radial position (58.2~AU). An ICME-related alpha enhancement observed
by Ulysses beginning on day 331, 1998 appears to be the correct
feature. While a speed jump and cosmic ray decreases were observed
by Ulysses in conjunction with this alpha enhancement, the timing
of these features differed markedly at Voyager~2. The speed jump
arrival-time difference is due to the faster propagation of the shock
relative to the rest of the ejecta. It is unclear what mechanism is
responsible for the delay in the cosmic ray decrease. Nevertheless,
we have demonstrated that alpha enhancement signatures of ICMEs can
be used to track these features to heliospheric distances of over 50~AU.
---------------------------------------------------------
Title: The Astrophysics of Galactic Cosmic Rays
Authors: Diehl, R.; Kallenbach, R.; Parizot, E.; Von Steiger, R.
2001agcr.book....3D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Astrophysics of Galactic Cosmic Rays
Authors: Diehl, Roland; Parizot, Etienne; Kallenbach, Reinald; Von
Steiger, Rudolf
2001agcr.book.....D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Composition of quasi-stationary solar wind flows from
Ulysses/Solar Wind Ion Composition Spectrometer
Authors: von Steiger, R.; Schwadron, N. A.; Fisk, L. A.; Geiss, J.;
Gloeckler, G.; Hefti, S.; Wilken, B.; Wimmer-Schweingruber, R. F.;
Zurbuchen, T. H.
2000JGR...10527217V Altcode:
Using improved, self-consistent analysis techniques, we determine the
average solar wind charge state and elemental composition of nearly
40 ion species of He, C, N, O, Ne, Mg, Si, S, and Fe observed with the
Solar Wind Ion Composition Spectrometer on Ulysses. We compare results
obtained during selected time periods, including both slow solar wind
and fast streams, concentrating on the quasi-stationary flows away from
recurrent or intermittent disturbances such as corotating interaction
regions or coronal mass ejections. In the fast streams the charge state
distributions are consistent with a single freezing-in temperature for
each element, whereas in the slow wind these distributions appear to be
composed of contributions from a range of temperatures. The elemental
composition shows the well-known first ionization potential (FIP) bias
of the solar wind composition with respect to the photosphere. However,
it appears that our average enrichment factor of low-FIP elements
in the slow wind, not quite a factor of 3, is smaller than that in
previous compilations. In fast streams the FIP bias is found to be
yet smaller but still significantly above 1, clearly indicating that
the FIP fractionation effect is also active beneath coronal holes
from where the fast wind originates. This imposes basic requirements
upon FIP fractionation models, which should reproduce the stronger and
more variable low-FIP bias in the slow wind and a weaker (and perhaps
conceptually different) low-FIP bias in fast streams. Taken together,
these results firmly establish the fundamental difference between the
two quasi-stationary solar wind types.
---------------------------------------------------------
Title: Transition Region: First Ionization Potential Effect
Authors: von Steiger, R.
2000eaa..bookE2265V Altcode:
The first ionization potential (FIP) effect causes a fractionation,
i.e. a change of the relative abundances, of elements with a low FIP in
the corona and solar wind as compared with the SOLAR PHOTOSPHERE. These
elements (specifically Mg, Si and Fe) are becoming enriched somewhere
in the solar atmosphere by an average factor of 2-5 relative to the
high-FIP elements (specifically oxygen). The proc...
---------------------------------------------------------
Title: Pick-up Ion Measurements in the Heliosphere - A Review
Authors: Kallenbach, R.; Geiss, J.; Gloeckler, G.; von Steiger, R.
2000Ap&SS.274...97K Altcode:
Measurements of the composition and spatial distribution of pick-up
ions inside the heliosphere are reviewed. The first interstellar ^4He^+
pick-up ions were detected with the SULEICA instrument on the AMPTE
spacecraft near Earth's orbit. Most data on pick-up ions were taken
in the solar-wind and suprathermal energy range of SWICS on Ulysses
while the spacecraft cruised from 1.4 to 5.4 AU and explored the
high-latitude heliosphere and solar wind from the ecliptic to +/- 80^°
heliolatitude. This includes the discovery of H^+, ^4He^++, ^3He^+,
N^+, O^+, and Ne^+ pick-up ions that originate from the interstellar
neutral gas penetrating the heliosphere. From their fluxes properties
of the interaction region between the heliosphere and the Local
Interstellar Cloud such as the limits on filtration and the strength of
the interstellar magnetic field have been revealed. Detailed analysis
of the velocity distributions of pick-up ions led to 1) the discovery
of a new distinct source, the so-called Inner Source, consisting of
atoms released from interstellar and interplanetary dust inside the
heliosphere, 2) the determination of pick-up ion transport parameters
such as the long mean free path for pitch-angle scattering of order
1 AU, and 3) detailed knowledge on the very preferential injection
and acceleration of pick-up ions during interplanetary energetic
particle events such as Co-rotating Interaction Regions and Coronal
Mass Ejections. SWICS measurements have fully confirmed the theory
of Fisk, Koslovsky, and Ramaty that pick-up ions derived from the
interstellar gas are the dominant source of the Anomalous Cosmic Rays;
they are pre-accelerated inside the heliosphere and re-accelerated
at the solar-wind Termination Shock according to Pesses, Eichler,
and Jokipii. The data indicate that the Inner Source of pick-up ions
is largely responsible for the occurence of C^+ in the Anomalous
Cosmic Rays. The abundances of recently discovered Inner-Source Mg^+
and Si^+ are solar-wind like and consistent with their abundances
in the energetic particles associated with Co-rotating Interaction
Regions. Knowledge on the injection and acceleration processes in
Co-rotating Interaction Regions is applied to discuss the current
observational evidence for the Interplanetary Focusing Cone of the
interstellar neutral gas due to the Sun's gravitational force. The
25-150 keV/amu suprathermal ^4He^+ pick-up ion fluxes measured by
CELIAS/STOF on board SOHO over 360^° of ecliptic longitude represent
a `local' ionization and acceleration of interstellar atoms at 1
AU or smaller heliocentric distances. Completing the first limited
data set of SULEICA/AMPTE on ^4He^+ pick-up ions they indicate a
density enhancement in the Interplanetary Focusing Cone which is
confirmed by recent SWICS/ACE data. Clear evidence for signatures in
ecliptic longitude are found in the data on energetic neutral H fluxes
observed with the CELIAS/HSTOF sensor on board SOHO. These fluxes are
enhanced in the upstream and downstream directions of the interstellar
wind. Detection of energetic H atoms, which propagate unaffected by the
Heliospheric Magnetic Field, provided for the first time a diagnostic
tool for observations near Earth to analyze the structure in ecliptic
longitude of the interface region between the heliosphere and the
Local Interstellar Cloud.
---------------------------------------------------------
Title: Inner source distributions: Theoretical interpretation,
implications, and evidence for inner source protons
Authors: Schwadron, N. A.; Geiss, J.; Fisk, L. A.; Gloeckler, G.;
Zurbuchen, T. H.; von Steiger, R.
2000JGR...105.7465S Altcode:
A new and important source of pickup ions has been recently observed
for the first time, the so-called inner source. We examine properties
of inner source ions at high heliographic latitudes through analysis
of data from the Solar Wind Ion Composition Spectrometer on the
Ulysses satellite for a period extending through the year of 1994
while Ulysses achieved its southernmost latitudes. As demonstrated
by Gloeckler et al. [this issue], the relative abundances of inner
source ions resemble those of the solar wind, which implies that the
dominant production mechanism for the inner source ions involves the
absorption and reemission of solar wind ions from interplanetary dust
grains. A simple transport model is devised that compares favorably to
observed distribution functions and provides an important consistency
check for the previously mentioned production mechanism. The model
comparison also allows for constraints to be placed on the total
dust geometric cross section. The observed distribution function of
protons reveals a significant contribution from the inner source,
but the abundance of inner source protons relative to oxygen falls
significantly below the universal abundance. We postulate causes of
this low relative abundance. We also find that inner source protons
have a sizable pressure and may constitute an important energetic
population in the solar wind, particularly near the their source.
---------------------------------------------------------
Title: Interception of comet Hyakutake's ion tail at a distance of
500 million kilometres
Authors: Gloeckler, G.; Geiss, J.; Schwadron, N. A.; Fisk, L. A.;
Zurbuchen, T. H.; Ipavich, F. M.; von Steiger, R.; Balsiger, H.;
Wilken, B.
2000Natur.404..576G Altcode:
Remote sensing observations and the direct sampling of material from a
few comets have established the characteristic composition of cometary
gas. This gas is ionized by solar ultraviolet radiation and the solar
wind to form `pick-up' ions, ions in a low ionization state that retain
the same compositional signatures as the original gas. The pick-up ions
are carried outward by the solar wind, and they could in principle be
detected far from the coma. (Sampling of pick-up ions has also been
used to study interplanetary dust, Venus' tail and the interstellar
medium.) Here we report the serendipitous detection of cometary pick-up
ions, most probably associated with the tail of comet Hyakutake,
at a distance of 3.4 AU from the nucleus. Previous observations have
provided a wealth of physical and chemical information about a small
sample of comets, but this detection suggests that remote sampling of
comet compositions, and the discovery of otherwise invisible comets,
may be possible.
---------------------------------------------------------
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.
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: Solar Variability and Climate
Authors: Friis-Christensen, E.; Fröhlich, C.; Haigh, J. D.;
Schüssler, M.; Von Steiger, R.
2000svc..book.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Wind Composition
Authors: von Steiger, R.; Schwadron, N. A.
2000ASPC..206...54V Altcode: 2000hesp.conf...54V
No abstract at ADS
---------------------------------------------------------
Title: Origin, Injection, and Acceleration of CIR Particles:
Observations Report of Working Group 6
Authors: Mason, G. M.; von Steiger, R.; Decker, R. B.; Desai, M. I.;
Dwyer, J. R.; Fisk, L. A.; Gloeckler, G.; Gosling, J. T.; Hilchenbach,
M.; Kallenbach, R.; Keppler, E.; Klecker, B.; Kunow, H.; Mann, G.;
Richardson, I. G.; Sanderson, T. R.; Simnett, G. M.; Wang, Y. -M.;
Wimmer-Schweingruber, R. F.; Fränz, M.; Mazur, J. E.
1999SSRv...89..327M Altcode:
This report emphasizes new observational aspects of CIR ions revealed
by advanced instruments launched on the Ulysses, WIND, SOHO, and
ACE spacecraft, and by the unique vantage point of Ulysses which
carried out the first survey of Corotating Interaction Region (CIR)
properties over a very wide range of heliolatitudes. With this more
complete observational picture established, this review is the basis
to consider the status of theoretical models on origin, injection, and
acceleration of CIR particles reported by Scholer, Mann et al. (1999)
in this volume.
---------------------------------------------------------
Title: Corotating Interaction Regions at High Latitudes
Authors: Kunow, H.; Lee, M. A.; Fisk, L. A.; Forsyth, R. J.; Heber, B.;
Horbury, T. S.; Keppler, E.; Kóta, J.; Lou, Y. -Q.; McKibben, R. B.;
Paizis, C.; Potgieter, M. S.; Roelof, E. C.; Sanderson, T. R.; Simnett,
G. M.; von Steiger, R.; Tsurutani, B. T.; Wimmer-Schweingruber, R. F.;
Jokipii, J. R.
1999SSRv...89..221K Altcode:
Ulysses observed a stable strong CIR from early 1992 through 1994
during its first journey into the southern hemisphere. After the rapid
latitude scan in early 1995, Ulysses observed a weaker CIR from early
1996 to mid-1997 in the northern hemisphere as it traveled back to the
ecliptic at the orbit of Jupiter. These two CIRs are the observational
basis of the investigation into the latitudinal structure of CIRs. The
first CIR was caused by an extension of the northern coronal hole into
the southern hemisphere during declining solar activity, whereas
the second CIR near solar minimum activity was caused by small
warps in the streamer belt. The latitudinal structure is described
through the presentation of three 26-day periods during the southern
CIR. The first at ∼24°S shows the full plasma interaction region
including fast and slow wind streams, the compressed shocked flows
with embedded stream interface and heliospheric current sheet (HCS),
and the forward and reverse shocks with associated accelerated ions
and electrons. The second at 40°S exhibits only the reverse shock,
accelerated particles, and the 26-day modulation of cosmic rays. The
third at 60°S shows only the accelerated particles and modulated
cosmic rays. The possible mechanisms for the access of the accelerated
particles and the CIR-modulated cosmic rays to high latitudes above
the plasma interaction region are presented. They include direct
magnetic field connection across latitude due to stochastic field
line weaving or to systematic weaving caused by solar differential
rotation combined with non-radial expansion of the fast wind. Another
possible mechanism is particle diffusion across the average magnetic
field, which includes stochastic field line weaving. A constraint on
connection to a distant portion of the CIR is energy loss in the solar
wind, which is substantial for the relatively slow-moving accelerated
ions. Finally, the weaker northern CIR is compared with the southern
CIR. It is weak because the inclination of the streamer belt and HCS
decreased as Ulysses traveled to lower latitudes so that the spacecraft
remained at about the maximum latitudinal extent of the HCS.
---------------------------------------------------------
Title: Composition variations in fast solar wind streams
Authors: von Steiger, R.; Fisk, L. A.; Gloeckler, G.; Schwadron,
N. A.; Zurbuchen, T. H.
1999AIPC..471..143V Altcode: 1999sowi.conf..143V
The Ulysses spacecraft has now completed its first revolution around the
Sun on its nearly-polar orbit. Thereby it has traversed the extended
high speed streams from the polar coronal holes (south in 1993/94,
north in 1995/96) which were well-developed during that time of close
to minimal solar activity. It is evident that the fluctuations of
both the kinetic and the compositional parameters are much weaker in
the high-speed streams than they are in the slow solar wind, leading
Bame to use the term “structure-free” for describing it. It was only
the extended time periods Ulysses spent in the polar streams that led
to the detection of some structure, the microstreams. From remote
observations of the Sun it is clear that the high latitude corona
is quite unstructured. The most remarkable features are the polar
plumes, which are well detectable because of their higher density
and brightness. Also, they are characterized by a difference in
composition relative to the coronal hole plasma. These features should
in principle be observable in interplanetary space, e.g. by the SWICS
mass spectrometer, in the form of abundance variations of heavy ions
as well as variations in their charge state composition, which serves
as a proxy for the coronal temperature at the site where the stream
originated. Using the unique data set of SWICS we examine to what extent
polar plumes contribute to fast, coronal hole associated wind. We also
study the possible connection between microstreams and polar plumes.
---------------------------------------------------------
Title: Identification of trailing edge solar wind stream interfaces:
A comparison of Ulysses plasma and composition measurements
Authors: Burton, M. E.; Neugebauer, M.; Crooker, N. U.; von Steiger,
R.; Smith, E. J.
1999JGR...104.9925B Altcode:
Measurements of the specific entropy argument of the solar wind
protons, T/n<SUP>γ-1</SUP>, reveal that nearly every occurrence of a
high-speed stream seen at Ulysses in 1992-1993 is characterized by an
abrupt interface at its trailing edge. These observations, made by the
solar wind plasma instrument (SWOOPS), at a heliocentric range of 4.5
to 5 AU show that there is a discontinuous drop in specific entropy
at the interface from a high value in the high-speed wind to a lower
value in the slow interstream wind. This interface is coincident with,
but much more abrupt than, compositional changes measured by the Solar
Wind Ion Composition Spectrometer (SWICS) [Geiss et al., 1995]. These
results suggest that a relatively thin interface can be identified which
separates two plasmas of distinctly different origins as determined by
the compositional measurements. A superposed epoch analysis performed
on seventeen events reveal the interface is characterized by (1) an
abrupt drop in entropy by a factor of ~1/3 due to an enhancement in
density along with gradually declining temperature, (2) a distinct
drop in the alpha/proton ratio from a value of ~5%, typical of the
fast wind, to ~4% characteristic of the slow solar wind, and (3)
relative changes in Mg<SUP>10+</SUP>/O<SUP>6+</SUP> at the interface
which are as large as the variations in the total Mg/O ratio and the
freezing-in temperature derived from O<SUP>7+</SUP>/O<SUP>6+</SUP>. The
specific entropy argument, a combination of commonly measured solar
wind parameters, gives a strong signature of the trailing edge interface
which is preserved as far out in the heliosphere as 5 AU and may provide
useful information regarding the coronal origin of solar wind streams.
---------------------------------------------------------
Title: Solar wind stream interfaces in corotating interaction regions:
New SWICS/Ulysses results
Authors: Wimmer-Schweingruber, Robert F.; von Steiger, Rudolf;
Paerli, Raoul
1999JGR...104.9933W Altcode:
We have analyzed data from the solar wind ion composition spectrometer
(SWICS)/Ulysses instrument taken between August 1996 and May 1997. In
this period the Ulysses spacecraft traveled from 28° to 11°N and
encountered a highly regular pattern of high-speed streams alternating
with slow solar wind. Heliocentric distance varied between 4.3 and
5.1 astronomical units (AU). Using proton and alpha-particle kinetic
parameters (density, speed, and kinetic temperatures) as well as
charge state and elemental composition data, we identify the stream
interfaces in the corotating interaction regions (CIRs) observed in
this period. As Wimmer-Schweingruber et al. [1997] previously reported
for a similar period in 1992/1993, stream interfaces are the sites
of compositional changes between values typical of the slow solar
wind and values typical of high-speed streams. During that period,
Ulysses traveled from 13° to 34°S and from 4.5 to 5.4 AU. In spite
of the similarity of the heliospheric regions probed during 1992/1993
and 1996/1997 the corotating interaction regions observed in 1996/1997
are quite different from those observed in 1992/1993. We observe fewer
(11) CIRs in 1996/1997 than in the previous period (15); the CIRs are
less evolved, i.e., the kinetic signatures at the stream interface
are less clear; and mainly, only 3 out of the 11 CIRs are bounded
by forward-reverse shock pairs, whereas in 1992/1993, 13 out of 15
were. This may have important consequences for particle acceleration
in CIRs in the inner heliosphere.
---------------------------------------------------------
Title: The Transition Between Fast and Slow Solar Wind from
Composition Data
Authors: Zurbuchen, T. H.; Hefti, S.; Fisk, L. A.; Gloeckler, G.;
von Steiger, R.
1999SSRv...87..353Z Altcode:
The transition between coronal hole associated fast solar wind and
slow solar wind is studied using data from the high resolution mass
spectrometer SWICS on ACE. We discuss the data in the framework
of a recent theory about the global heliospheric magnetic field and
conclude that the data are consistent with magnetic connections between
field-lines in the fast and in the slow wind.
---------------------------------------------------------
Title: Origin, Injection, and Acceleration of CIR Particles:
Observations
Authors: Mason, G. M.; Von Steiger, R.; Decker, R. B.; Desai, M. I.;
Dwyer, J. R.; Fisk, L. A.; Gloeckler, G.; Gosling, J. T.; Hilchenbach,
M.; Kallenbach, R.; Keppler, E.; Klecker, B.; Kunow, H.; Mann, G.;
Richardson, I. G.; Sanderson, T. R.; Simnett, G. M.; Wang, Y. -M.;
Wimmer-Schweingruber, R. F.; Fränz, M.; Mazur, J. E.
1999cir..book..327M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Corotating Interaction Regions at High Latitudes
Authors: Kunow, H.; Lee, M. A.; Fisk, L. A.; Forsyth, R. J.; Heber, B.;
Horbury, T. S.; Keppler, E.; Kóta, J.; Lou, Y. -Q.; McKibben, R. B.;
Paizis, C.; Potgieter, M. S.; Roelof, E. C.; Sanderson, T. R.; Simnett,
G. M.; von Steiger, R.; Tsurutani, B. T.; Wimmer-Schweingruber, R. F.;
Jokipii, J. R.
1999cir..book..221K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Differences in the O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio of
magnetic cloud and non-cloud coronal mass ejections
Authors: Henke, T.; Woch, J.; Mall, U.; Livi, S.; Wilken, B.; Schwenn,
R.; Gloeckler, G.; von Steiger, R.; Forsyth, R. J.; Balogh, A.
1998GeoRL..25.3465H Altcode:
On its trajectory to Jupiter and over the poles of the Sun
the Ulysses spacecraft has observed a considerable number of
Coronal Mass Ejection (CME) transients in slow and in fast solar
wind streams. The analysis of the magnetic field topology and the
O<SUP>7+</SUP>/O<SUP>6+</SUP> charge state ratio of 56 of these events
has yielded strong evidence for a systematic connection between the
two features. Coronal mass ejections with magnetic cloud structure
have an increased O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio with respect
to the ambient solar wind whereas non-cloud CMEs do not show enhanced
O<SUP>7+</SUP>/O<SUP>6+</SUP> ratios. We discuss possible mechanisms
based on the freezing-in concept that can account for the observation.
---------------------------------------------------------
Title: Spatial structure of the solar wind and comparisons with
solar data and models
Authors: Neugebauer, M.; Forsyth, R. J.; Galvin, A. B.; Harvey,
K. L.; Hoeksema, J. T.; Lazarus, A. J.; Lepping, R. P.; Linker,
J. A.; Mikic, Z.; Steinberg, J. T.; von Steiger, R.; Wang, Y. -M.;
Wimmer-Schweingruber, R. F.
1998JGR...10314587N Altcode:
Data obtained by instruments on the Ulysses spacecraft during its rapid
sweep through >90° of solar latitude, crossing the solar equator
in early 1995, were combined with data obtained near Earth by the
Wind spacecraft to study the spatial structure of the solar wind and
to compare to different models of the interplanetary magnetic field
derived from solar observations. Several different source-surface
models matched the double sinusoidal structure of the heliospheric
current sheet (HCS) but with differences in latitude as great as
21°. The source-surface model that included an interplanetary
current sheet gave poorer agreement with observed current-sheet
crossings during this period than did the other source-surface models
or an MHD model. The differences between the calculated and observed
locations of the HCS were minimized when 22° of solar rotation was
added to the constant-velocity travel time from the source surface to
the spacecraft. The photospheric footpoints of the open field lines
calculated from the models generally agreed with observations in the
He 10,830 Å line of the locations of coronal holes with the exceptions
that (1) in some places, open field lines originated outside the coronal
hole boundaries and (2) the models show apparently closed-field regions
just inside some coronal hole boundaries. The patterns of mismatches
between coronal hole boundaries and the envelopes of open field lines
persisted over at least three solar rotations. The highest-speed wind
came from the polar coronal holes, with the wind originating deeper
within the hole being faster than the wind coming from near the
hole boundary. Intermediate and slow streams originated in smaller
coronal holes at low latitudes and from open field regions just
outside coronal hole boundaries. Although the HCS threaded regions
of low speed, low helium abundance, high ionization temperature,
and a high ratio of magnesium to oxygen densities (a surplus of an
element with low first-ionization potential), there was a great deal
of variation in these parameters from one place to another along
the HCS. The gradient of speed with latitude varied from 14 to 28
kms<SUP>-1</SUP>deg<SUP>-1</SUP>.
---------------------------------------------------------
Title: Composition Aspects of the Upper Solar Atmosphere Rapporteur
Paper III
Authors: von Steiger, R.
1998SSRv...85..407V Altcode:
This rapporteur paper discusses the solar corona and the solar wind in
the context of their chemical composition. The abundances of elements,
both obtained by optical and by in situ observations, are used to infer
the sources of the slow solar wind and of the fast streams. The first
ionisation potential (FIP) fractionation effect is also discussed,
in particular the agreed basics and the open questions.
---------------------------------------------------------
Title: The Expansion of Coronal Plumes in the Fast Solar Wind
Authors: Del Zanna, L.; von Steiger, R.; Velli, M.
1998SSRv...85..349D Altcode:
Coronal plumes are believed to be essentially magnetic features: they
are rooted in magnetic flux concentrations at the photosphere and are
observed to extend nearly radially above coronal holes out to at least
15 solar radii, probably tracing the open field lines. The formation of
plumes itself seems to be due to the presence of reconnecting magnetic
field lines and this is probably the cause of the observed extremely
low values of the Ne/Mg abundance ratio.
---------------------------------------------------------
Title: Foreword
Authors: Fröhlich, C.; Huber, M. C. E.; Solanki, S. K.; von Steiger,
R.
1998SSRv...85...11F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: O<SUP>5+</SUP> in High Speed Solar Wind Streams: SWICS/Ulysses
Results
Authors: Wimmer-Schweingruber, Robert F.; von Steiger, Rudolf; Geiss,
Johannes; Gloeckler, George; Ipavich, Fred M.; Wilken, Berend
1998SSRv...85..387W Altcode:
Recent observations with UVCS on SOHO of high outflow velocities of
O<SUP>5+</SUP> at low coronal heights have spurred much discussion
about the dynamics of solar wind acceleration. On the other hand,
O<SUP>6+</SUP> is the most abundant oxygen charge state in the solar
wind, but is not observed by UVCS or by SUMER because this helium-like
ion has no emission lines falling in the wave lengths observable
by these instruments. Therefore, there is considerable interest in
observing O<SUP>5+</SUP> in situ in order to understand the relative
importance of O<SUP>5+</SUP> with respect to the much more abundant
O<SUP>6+</SUP>. High speed streams are the prime candidates for the
search for O<SUP>5+</SUP> because all elements exhibit lower freezing-in
temperatures in high speed streams than in the slow solar wind. The
Ulysses spacecraft was exposed to long time periods of high speed
streams during its passage over the polar regions of the Sun. The
Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses is capable
of resolving this rare oxygen charge state. We present the first
measurement of O<SUP>5+</SUP> in the solar wind and compare these
data with those of the more abundant oxygen species O<SUP>6+</SUP>
and O<SUP>7+</SUP>. We find that our observations of the oxygen charge
states can be fitted with a single coronal electron temperature in the
range of 1.0 to 1.2 MK assuming collisional ionization/recombination
equilibrium with an ambient Maxwellian electron gas.
---------------------------------------------------------
Title: Primordial nuclei and their Galactic
evolution. Proceedings. 4th ISSI Workshop, Bern (Switzerland), 6 -
10 May 1997.
Authors: Prantzos, N.; Tosi, M.; von Steiger, R.
1998SSRv...84.....P Altcode:
The following topics are dealt with: early Universe, extragalactic
objects, low-Z stars, Galactic disk and Galactic evolution, solar
nebula, and the local interstellar medium.
---------------------------------------------------------
Title: Solar Composition and Its Evolution -- From Core to Corona
Authors: Fröhlich, C.; Huber, M. C. E.; Solanki, S. K.; von Steiger,
R.
1998sce..conf.....F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: MHD models of coronal plumes
Authors: Del Zanna, L.; Hood, A.; Velli, M.; von Steiger, R.
1998ESASP.421..359D Altcode: 1998sjcp.conf..359D
No abstract at ADS
---------------------------------------------------------
Title: Cosmic rays in the heliosphere. Proceedings. ISSI
(International Space Science Institute) Workshop, Bern (Switzerland),
17 - 20 Sep 1996 and 10 - 14 Mar 1997.
Authors: Fisk, L. A.; Jokipii, J. R.; Simnett, G. M.; von Steiger,
R.; Wenzel, K. -P.
1998SSRv...83.....F Altcode:
The following topics were dealt with: solar modulation; solar wind;
magnetic fields; heliosphere; galactic cosmic rays; anomalous cosmic
rays.
---------------------------------------------------------
Title: O<SUP>5+</SUP> in High Speed Solar Wind Streams: SWICS/Ulysses
Results
Authors: Wimmer-Schweingruber, R. F.; von Steiger, R.; Geiss, J.;
Gloeckler, G.; Ipavich, F. M.; Wilken, B.
1998sce..conf..387W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Primordial Nuclei and their Galactic Evolution
Authors: Prantzos, Nikos; Tosi, Monica; von Steiger, Rudolf
1998pnge.conf.....P Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Composition Aspects of the Upper Solar Atmosphere
Authors: von Steiger, R.
1998sce..conf..407V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Latitude Manifestations of the Solar Wind
Authors: von Steiger, R.
1998HiA....11..842V Altcode:
Dependencies of solar wind parameters as a function of latitude are
presented and discussed, based on measurement of the Ulysses mission
during times of declining or minimum solar activity. The heliosphere is
found to be structured into a band of slow solar wind at low latitudes
and two large high-speed streams from the polar coronal holes. Only
small trends of solar wind parameters with heliolatitude are found
within these streams. A small but significant temperature difference
is seen between the south and the north polar coronal hole.
---------------------------------------------------------
Title: Solar composition and its evolution - from core to
corona. Proceedings. ISSI (International Space Science Institute)
Workshop, Bern (Switzerland), 26 - 30 Jan 1998.
Authors: Fröhlich, C.; Huber, M. C. E.; Solanki, S. K.; von Steiger,
R.
1998SSRv...85.....F Altcode:
The following topics were dealt with: solar composition, solar
evolution, the solar interior, helioseismology, photosphere,
chromosphere, solar corona, solar wind, the Sun as a Sun-like star.
---------------------------------------------------------
Title: The Expansion of Coronal Plumes in the Fast Solar Wind
Authors: del Zanna, L.; von Steiger, R.; Velli, M.
1998sce..conf..349D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar wind stream interfaces in corotating interaction regions:
SWICS/Ulysses results
Authors: Wimmer-Schweingruber, Robert F.; von Steiger, Rudolf;
Paerli, Raoul
1997JGR...10217407W Altcode:
Motivated by the well-known differences in charge state and even
elemental composition of the slow solar wind as compared to high-speed
streams, we have analyzed observations made by the Solar Wind Ion
Composition Spectrometer (SWICS)/Ulysses mass spectrometer of the
series of corotating interaction regions (CIRs) encountered by Ulysses
in 1992/1993 at 4.5-5.4 AU from the Sun. Stream interfaces (SIs)
are first identified within each CIR using the kinetic parameters
(density and thermal speed) of the main components, protons and
alpha particles. We then show that SIs are also the location of the
expected compositional changes in the heavy ion components, such
as the freezing-in temperatures of C and O and the strength of FIP
fractionation as given by the Mg/O abundance ratio, to within the time
resolution with which these parameters may be obtained by SWICS. The
changes in freezing-in temperatures are so clear that they in turn
may be used as a robust indicator of the SI location and even reveal
that some of the SI crossings were in fact multiple. We conclude that
the heavy ion composition of the solar wind changes abruptly at the
SI and remains well preserved out to large heliocentric distances.
---------------------------------------------------------
Title: Composition of the Solar Wind
Authors: von Steiger, R.; Geiss, J.; Gloeckler, G.
1997cwh..conf..581V Altcode: 2006mslp.conf..581V
No abstract at ADS
---------------------------------------------------------
Title: Search for the Origin of Quiet-Time Particle Fluxes in the
Inner Heliosphere
Authors: Kiraly, P.; Bothmer, V.; Kecskemety, K.; Keppler, E.;
Kudela, K.; Kunow, H.; Logachev, Yu. I.; sMüller-Mellin, R.;
Rodriguez-Pacheco, J.; von Steiger, R.; Torsti, J.; Valtonen, E.;
Zeldovich, M. A.
1997ICRC....2..477K Altcode: 1997ICRC...25b.477K
No abstract at ADS
---------------------------------------------------------
Title: Foreword by the volume editors
Authors: von Steiger, R.; Lallement, R.; Lee, M.
1996SSRv...78D..13V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The heliosphere in the local interstellar
medium. Proceedings. 1. ISSI (International Space Science Institute)
Workshop, Bern (Switzerland), 6 - 10 Nov 1995.
Authors: von Steiger, R.; Lallement, R.; Lee, M. A.
1996SSRv...78.....V Altcode:
The following topics were dealt with: outer heliosphere, solar
wind-heliosphere interaction, interstellar pickup ions, interplanetary
magnetic field, radio emissions, ionization processes, the termination
shock, the local interstellar medium, interstellar dust.
---------------------------------------------------------
Title: Origin of C<SUP>+</SUP> ions in the heliosphere
Authors: Geiss, J.; Gloeckler, G.; von Steiger, R.
1996SSRv...78...43G Altcode:
C<SUP>+</SUP> pickup ions were investigated with the SWICS instrument
along the trajectory of Ulysses, covering a broad range of solar
latitude and distance. Whereas nearly all the observed H<SUP>+</SUP>,
He<SUP>+</SUP>, N<SUP>+</SUP>, O<SUP>+</SUP> and Ne<SUP>+</SUP> pickup
ions are created from the interstellar gas penetrating deep into the
heliosphere, C<SUP>+</SUP> comes primarily from an “inner source”
which is located at a solar distance below a few AU and extends over
all heliospheric latitudes investigated up to now. We present evidence
that the C<SUP>+</SUP> originates from carbon compounds evaporating
from interstellar grains. This inner source also produces some
O<SUP>+</SUP> and N<SUP>+</SUP> with estimated relative abundances
ofC<SUP>+</SUP>/O<SUP>+</SUP> ∼ 1 and N<SUP>+</SUP>/O<SUP>+</SUP>
∼ 0.2. However, the total amount of O<SUP>+</SUP> and N<SUP>+</SUP>
produced by this inner source is only of the order of 10<SUP>-3</SUP>
as compared to the total production of O<SUP>+</SUP> and N<SUP>+</SUP>
from the interstellar gas in the heliosphere, respectively. Thus the
inner source does not significantly contribute to oxygen or nitrogen
in the anomalous cosmic rays (ACR) but its contribution to ACR-carbon
may not be negligible.
---------------------------------------------------------
Title: Coronal hole differential rotation rate observed with
SWICS/Ulysses
Authors: Zurbuchen, Th.; Bochsler, P.; von Steiger, R.
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 sin<SUP>2</SUP>(Θ)]°/day, where Θ denotes the
solar latitude.
---------------------------------------------------------
Title: Solar wind composition and charge states
Authors: von Steiger, R.
1996AIPC..382..193V Altcode:
The abundances and charge states of the heavy ions present in the
solar wind are important tracers for conditions and processes in the
solar corona and chromosphere. The elemental abundances are known to be
fractionated with respect to the photosphere, with the fractionation
being organized best by the first ionization time. Since the first
ionization occurs in the upper the chromosphere, the solar wind
abundances are indicative for the conditions at this site. On the
other hand, the solar wind charge states provide information about
the coronal temperature, where they are frozen-in at altitudes between
1.5 and 3.5 solar radii. The charge state distributions of different
elements can thus be used to infer a coronal temperature profile. The
two types of steady solar wind, fast streams from coronal holes and
slow, interstream wind, are significantly different in both of these
signatures. This implies that they are separated by a boundary extending
through the corona and down into the chromosphere, i.e. that the slow
wind is not merely emanating from the coronal hole boundary regions.
---------------------------------------------------------
Title: Kinetic temperature ratios of O<SUP>6+</SUP> and
He<SUP>2+</SUP>: Observations from Wind/MASS and Ulysses/SWICS
Authors: Cohen, C. M. S.; Collier, M. R.; Hamilton, D. C.; Gloeckler,
G.; Sheldon, R. B.; von Steiger, R.; Wilken, B.
1996GeoRL..23.1187C Altcode:
We present results from a two spacecraft study of the ratio of
O<SUP>6+</SUP> and He<SUP>2+</SUP> kinetic temperatures as a function of
solar wind speed. Data from the Wind/MASS and Ulysses/SWICS instruments
both indicate the O<SUP>6+</SUP>/He<SUP>2+</SUP> kinetic temperature
ratio increases with increasing solar wind speed, peaking near 500
km/s. Above 500 km/s, the ratio appears to decrease slightly. Values
near unity were obtained for slow solar wind while fast wind yielded
ratios substantially higher than what is expected from the general rule
FD1 TiTj≈MiMj.(1) Although averaging over all data would result in the
nominal ratio of 4, deviations from equation (1) appear to be common and
the assumption of equal thermal velocities should not be made a priori.
---------------------------------------------------------
Title: Solar wind abundances from ULYSSES
Authors: von Steiger, R.
1996ASPC..109..491V Altcode: 1996csss....9..491V
No abstract at ADS
---------------------------------------------------------
Title: Proton Temperatures, Electron Temperatures and Outflows in
the Extended Solar Corona.
Authors: Kohl, J. L.; Gardner, L. D.; Strachan, L.; Cohen, C. M. S.;
Galvin, A. B.; Gloeckler, G.; Guhathakurta, M.; Fisher, R. R.; Ko,
Y. -K.; Geiss, J.; von Steiger, R.
1996ASPC..109...99K Altcode: 1996csss....9...99K
No abstract at ADS
---------------------------------------------------------
Title: Element fractionation by diffusion in the solar chromosphere.
Authors: Marsch, E.; von Steiger, R.; Bochsler, P.
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: Radial gradients of ion densities and temperatures derived
from SWICS/Ulysses observations
Authors: Liu, S.; Marsch, E.; Livi, S.; Woch, J.; Wilken, B.; von
Steiger, R.; Gloeckler, G.
1995GeoRL..22.2445L Altcode:
Mean density and temperature gradients of solar wind protons and α
particles are derived from SWICS/Ulysses observations between 1.2
and 5.4 AU in the ecliptic plane during declining solar activity. All
parameters are sorted in solar wind speed classes. The radial gradients
show a similar behavior for both ion species. In the slow solar wind
protons as well as α particles are found to expand adiabatically
all the way out to many AUs, while in the fast wind ions evolve
non-adiabatically and are heated by interplanetary sources. The
α particle to proton temperature and density ratios are also
determined. They do not show any clear radial dependence.
---------------------------------------------------------
Title: Observations of the solar wind and interstellar pick-up ion
populations in the heliosphere with ULYSSES
Authors: Gloeckler, G.; Geiss, J.; von Steiger, R.
1995AdSpR..16i.343G Altcode: 1995AdSpR..16..343G
The solar wind (SW) and interstellar pick-up ions (IPI) are the dominant
ion populations in the heliosphere. While SW ions are by far the most
abundant at low thermal energies and closer to the sun, IPI ions with
thermal speeds exceeding the SW bulk speed become dynamically more and
more important beyond a few AU. Measurements of the characteristics
(composition, charge states and distribution functions) of these ion
populations provide essential information about (1) solar abundances,
acceleration of the solar wind and conditions in the corona, (2)
local heliospheric processes that shape the distribution functions of
SW ions and IPI, (3) conditions in the outer heliosphere, including
acceleration processes that produce the anomalous cosmic rays, and (4)
characteristics and composition of the local interstellar cloud. The
orbit and timing of Ulysses is particularly well suited for these
observations: Polar passes of Ulysses at solar minimum allow us to
study the solar wind from polar coronal holes under the simplest
conditions. Extended time periods at heliocentric distances between
~3 and 5 AU make it possible to observe in addition to He^+ a number
of new IPI species (H^+, O^+, N^+, Ne^+, and He^++). We will discuss a
number of results based on ion composition and energy spectra measured
from 0.6 to 60 keV/e with the time-of-flight vs. energy Solar Wind Ion
Composition Spectrometer (SWICS). We find that (a) the composition of
the solar wind from coronal holes is least biased compared to the solar
photospheric composition and (b) the composition in the interstellar
medium deduced from IPI measurements resembles to better than a factor
of two solar system abundances. These observations show that SW and
IPI are a relatively unbiased samples of the solar and interstellar
material respectively which can be used to study the isotopic and
chemical compositions in these remote regions.
---------------------------------------------------------
Title: Abundance variations in the solar wind
Authors: von Steiger, R.; Schweingruber, R. F. Wimmer; Geiss, J.;
Gloeckler, G.
1995AdSpR..15g...3V Altcode: 1995AdSpR..15Q...3V
The solar wind (SW) allows us to probe the solar material in situ,
particularly its composition, without the need to fly a spacecraft to
inhospitably small heliocentric distances. However, it turns out that
this plasma source is biased with respect to the photosphere. Elements
with a low first ionization potential (FIP) are overabundant by a factor
of 3-5 relative to high-FIP elements in the slow SW, but only by a
factor of 1.5-2 in the fast streams emanating from coronal holes. It is
thus important to have a good understanding of this FIP fractionation
effect, which operates between the photosphere and the corona. Such
a theory may improve on our understanding of the solar atmosphere and
SW acceleration. We present SW measurements, concentrating on results
of the SWICS mass spectrometer on Ulysses, which is currently sampling
the SW on a highly inclined orbit. In 1992/93, Ulysses was traversing
a recurrent high-speed stream once per solar rotation, alternating
with slow SW, providing an unique opportunity to compare these two
SW types. We find a strongly positive correlation of low- to high-FIP
element ratios (such as Mg/O) with coronal temperature, which in turn
is anticorrelated with the SW speed. The correlation of these three
parameters--one chromospheric, one coronal, and one from the SW--points
at a common cause for their variations, and provides a challenge to
theorists to model these three domains in an unified approach. Further,
abundance variations found in the SW from coronal streamers and
in coronal mass ejections are presented and discussed. Finally, we
address the question of abundance variations within the fast streams,
looking for abundance gradients with heliographic latitude.
---------------------------------------------------------
Title: Dynamic properties of helium ions in the solar wind
Authors: Zurbuchen, Th.; Bochsler, P.; von Steiger, R.
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: Large-scale variations of solar wind elemental composition
and charge states with heliospheric latitude
Authors: Woch, J.; Wilken, B.; Livi, S.; von Steiger, R.; Geiss, J.;
Gloeckler, G.
1995sowi.confQ..74W Altcode:
The Solar Wind Ion Composition Spectrometer (SWICS) onboard Ulysses
allows determination of the elemental composition of the solar wind
and the charge states of all major solar wind ion species. Ulysses
left the ecliptic plane in early 1992, crossed the Sun's south polar
region in late 1994 and made a fast approach back towards the ecliptic
in the first half of 1995. Data from this period were investigated for
long-term variations in the solar wind composition. At midlatitudes
Ulysses encountered periodically the fast solar wind stream emerging
from the south coronal hole. As a consequence, dramatic variations
in the charge-states arise, between high charge-states dominating in
the current sheet solar wind and low charge states in the coronal hole
stream. However, the initial analysis indicates that from midlatitudes
onwards, with Ulysses permanently immersed in the coronal hole stream,
the charge state and elemental abundance ratios of the major solar
wind ion species stayed essentially constant. This implies that the
temperature profile in the coronal hole at solar wind source altitudes
exhibit no variation with solar latitude. It confirms that the south
coronal hole is essentially unstructured down to scale lengths of
several degrees in solar latitude.
---------------------------------------------------------
Title: The Southern High-Speed Stream: Results from the SWICS
Instrument on Ulysses
Authors: Geiss, J.; Gloeckler, G.; von Steiger, R.; Balsiger, H.;
Fisk, L. A.; Galvin, A. B.; Ipavich, F. M.; Livi, S.; McKenzie, J. F.;
Ogilvie, K. W.; Wilken, B.
1995Sci...268.1033G Altcode:
The high-speed solar wind streaming from the southern coronal hole was
remarkably uniform and steady and was confined by a sharp boundary that
extended to the corona and chromosphere. Charge state measurements
indicate that the electron temperature in this coronal hole reached
a maximum of about 1.5 million kelvin within 3 solar radii of the
sun. This result, combined with the observed lack of depletion of heavy
elements, suggests that an additional source of momentum is required
to accelerate the polar wind.
---------------------------------------------------------
Title: Solar wind helium isotopic composition from SWICS/ULYSSES
Authors: Bodmer, R.; Bochsler, P.; Geiss, J.; von Steiger, R.;
Gloeckler, G.
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 measure<SUP>3</SUP>He abundances
precisely,<SUP>4</SUP>He/<SUP>3</SUP>He 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: Solar Wind Charge States Measured by Ulysses/SWICS in the
South Polar Hole
Authors: Galvin, A. B.; Ipavich, F. M.; Cohen, C. M. S.; Gloeckler,
G.; von Steiger, R.
1995SSRv...72...65G Altcode:
The Ulysses mission now has an extensive data base covering several
passes of the south polar coronal hole as the spacecraft proceeds
to higher latitudes. Using composition measurements from the SWICS
experiment on the Ulysses spacecraft, we have obtained charge state
distributions, and hence inferred coronal ionization temperatures,
for several solar wind species. In particular, we present an
overview of Oxygen ionization temperature measurements, based on the
O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio, for the period January 1993 until
April 1994 (∼23°S to ∼61°S heliographic latitude), and detailed
Oxygen, Silicon and Iron charge state distributions of the south polar
hole during a two month period of nearly continuous hole coverage,
Dec 1993 Jan 1994 (∼45°S to 52°S heliographic latitude).
---------------------------------------------------------
Title: Kinetic Properties of Heavy Ions in the Solar Wind From
SWICS/Ulysses
Authors: von Steiger, R.; Geiss, J.; Gloeckler, G.; Galvin, A. B.
1995SSRv...72...71V Altcode:
The kinetic properties of heavy ions in the solar wind are known to
behave in a well organized way under most solar wind flow conditions:
Their speeds are all equal and faster than that of hydrogen by
about the local Alfvén speed, and their kinetic temperatures are
proportional to their mass. The simplicity of these properties points to
a straightforward physical interpretation; wave-particle interactions
with Alfvén waves are the probable cause. With the SWICS sensor on
board Ulysses, it is now possible to investigate the kinetic properties
of many more ion species than before. Furthermore, the transition of
Ulysses into the fast stream emanating from the south polar coronal
hole since 1992 allows us to study these properties both in the slow,
interstream solar wind, as well as in an unambiguously identified
fast stream. We present data from SWICS/Ulysses on the dominant ions
of He, C, O, Ne, and Mg. As a result we find that, both in the slow
wind and in fast streams, the isotachic property is obeyed even better
than it could be determined by the ICI instrument on ISEE-3. The mass
proportionality ofT <SUB>kin</SUB> is also shown to hold for these ions,
including the newly identified C and Mg.
---------------------------------------------------------
Title: Origin of the Solar Wind From Composition Data
Authors: Geiss, J.; Gloeckler, G.; von Steiger, R.
1995SSRv...72...49G Altcode:
The ESA/NASA spacecraft Ulysses is making, for the first time,
direct measurements in the solar wind originating from virtually all
places where the corona expands. Since the initial two polar passes
of Ulysses occur during relatively quiet solar conditions, we discuss
here the three main regimes of quasi-stationary solar wind flow: the
high speed streams (HSSTs) coming out of the polar coronal holes, the
slow solar wind surrounding the HSSTs, and the streamers which occur
at B-field reversals. Comparisons between H-α maps and data taken
by Ulysses demonstrate that as a result of super-radial expansion,
the HSSTs occupy a much larger solid angle than that derived from
radial projections of coronal holes. Data obtained with SWICS-Ulysses
confirm that the strength of the FIP effect is much reduced in the
HSSTs. The systematics in the variations of elemental abundances
becomes particularly clear, if these are plotted against the time
of ionisation (at the solar surface) rather than against the first
ionisation potential (FIP). We have used a superposed-epoch method to
investigate the changes in solar wind speed and composition measured
during the 9-month period in 1992/93 when Ulysses regularly passed
into and out of the southern HSST. We find that the patterns in the
variations of the Mg/O and O<SUP>7+</SUP>/O<SUP>6+</SUP> ratios are
virtually identical and that their transition from high to low values is
very steep. Since the Mg/O ratio is controlled by the FIP effect and the
O<SUP>7+</SUP>/O<SUP>6+</SUP> ratio reflects the coronal temperature,
this finding points to a connection between chromospheric and coronal
conditions.
---------------------------------------------------------
Title: New Results for Outflow and LOS Velocities in the Solar Wind
Acceleration Region of the Corona
Authors: Strachan, L.; Gardner, L. D.; Kohl, J. L.; Guhathakurta,
M.; Fisher, R. R.; Cohen, C. M. S.; Galvin, A. B.; Gloeckler, G.;
Ko, Y. -K.; Geiss, J.; von Steiger, R.
1995SPD....26..719S Altcode: 1995BAAS...27..970S
No abstract at ADS
---------------------------------------------------------
Title: C<SUP>+</SUP> pickup ions in the heliosphere and their origin
Authors: Geiss, J.; Gloeckler, G.; Fisk, L. A.; von Steiger, R.
1995JGR...10023373G Altcode:
C<SUP>+</SUP> pickup ions were discovered with the solar wind ion
composition spectrometer flying on Ulysses. Whereas the other nonlocally
occurring pickup ions are produced from the interstellar gas penetrating
deep into the heliosphere, C<SUP>+</SUP> comes from an “inner source”
which is located at a solar distance of a few AU and extends over all
heliospheric latitudes investigated so far. The total production of
C<SUP>+</SUP>, N<SUP>+</SUP>, and O<SUP>+</SUP> by this inner source
is of the order of 10<SUP>-3</SUP> relative to the total production of
O<SUP>+</SUP> from the interstellar gas in the heliosphere. Thus the
inner source does not significantly contribute to oxygen or nitrogen
in the anomalous cosmic rays (ACR), but its contribution to ACR carbon
may not be negligible. We propose that the inner source material is
carbon compounds evaporating from grains. At this time, the evidence
points to interstellar grains as the major source, but we do not want
to exclude yet a contribution from grains of solar system origin.
---------------------------------------------------------
Title: Kinetic Properties of Heavy Ions in the Solar Wind From
SWICS/Ulysses
Authors: von Steiger, R.; Geiss, J.; Gloeckler, G.; Galvin, A. B.
1995hlh..conf...71V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Fractionation of the solar wind
Authors: von Steiger, R.
1995HiA....10..310V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Origin of the Solar Wind From Composition Data
Authors: Geiss, J.; Gloeckler, G.; von Steiger, R.
1995hlh..conf...49G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Wind Charge States Measured by Ulysses/SWICS in the
South Polar Hole
Authors: Galvin, A. B.; Ipavich, F. M.; Cohen, C. M. S.; Gloeckler,
G.; von Steiger, R.
1995hlh..conf...65G Altcode:
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.
1995hlh..conf...61B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar and Heliospheric Processes from Solar Wind Composition
Measurements
Authors: Geiss, J.; Gloeckler, G.; von Steiger, R.
1994RSPTA.349..213G Altcode:
Composition measurements in the solar wind provide important information
for solar system science and astrophysics. We show in this report how
ion composition data are used to investigate chromospheric and coronal
processes. Isotopic abundances in the Sun can best be derived from
solar wind measurements. <SUP>3</SUP>He/<SUP>4</SUP>He is an isotopic
ratio with far-reaching implications. It allows us to determine the
deuterium abundance in the proto-solar nebula, which in turn leads
to an estimate of deuterium production in the early universe. The
interstellar gas is the second most important source of heliospheric
ions. Atomic abundances in the local interstellar gas are derived
from ion composition measurements, and processes in the solar wind
termination region and beyond are studied.
---------------------------------------------------------
Title: Diffusive fractionation in the chromosphere
Authors: von Steiger, R.; Marsch, E.
1994SSRv...70..341V Altcode:
A new mechanism for the FIP fractionation in the solar wind in the form
of a stationary diffusion model is proposed. It is based on a weakly
stratified chromospheric layer of constant density and temperature,
permeated everywhere by ionizing photons and a homogeneous magnetic
field. Our model does not invoke any particular geometry or special set
up of the system and is founded solely on robust and well understood
atomic collisonal 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. For the main gas (hydrogen), an
analytical solution can be found. This then serves as a background for
the numerical integration of each trace gas system (several elements
from He to Fe). 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 element reproduce
the observed FIP fractionation pattern remarkably well.
---------------------------------------------------------
Title: Acceleration of interstellar pickup ions in the disturbed
solar wind observed on Ulysses
Authors: Gloeckler, G.; Geiss, J.; Roelof, E. C.; Fisk, L. A.; Ipavich,
F. M.; Ogilvie, K. W.; Lanzerotti, L. J.; von Steiger, R.; Wilken, B.
1994JGR....9917637G Altcode:
Acceleration of interstellar pickup H<SUP>+</SUP> and He<SUP>+</SUP>
as well as of solar wind protons and alpha particles has been observed
on Ulysses during the passage of a corotating interaction region
(CIR) at ~4.5 AU. Injection efficiencies for both the high thermal
speed interstellar pickup ions (H<SUP>+</SUP> and He<SUP>+</SUP>)
and the low thermal speed solar wind ions (H<SUP>+</SUP> and
He<SUP>+</SUP><SUP>+</SUP>) are derived using velocity distribution
functions of protons, pickup He<SUP>+</SUP> and alpha particles
from <1 to 60 keV/e and of ions (principally protons) above ~60
keV. The observed spatial variations of the few keV and the few hundred
keV accelerated pickup protons across the forward shock of the CIR
indicate a two stage acceleration mechanism. Thermal ions are first
accelerated to speeds of 3 to 4 times the solar wind speed inside the
CIR, presumably by some statistical mechanism, before reaching higher
energies by a shock acceleration process. Our results also indicate that
(1) the injection efficiencies for pickup ions are almost 100 times
higher than they are for solar wind ions, (2) pickup H<SUP>+</SUP> and
He<SUP>+</SUP> are the two most abundant suprathermal ion species and
they carry a large fraction of the particle thermal pressure, (3) the
injection efficiency is highest for protons, lowest for He<SUP>+</SUP>,
and intermediate for alpha particles, (4) both H<SUP>+</SUP> and
He<SUP>+</SUP> have identical spectral shapes above the cutoff speed for
pickup ions, and (5) the solar wind frame velocity distribution function
of protons has the form F(w)=F<SUB>O</SUB>w<SUP>-</SUP><SUP>4</SUP>
for 1<w<~5, where w is the ion speed divided by the solar wind
speed. Above w~5-10 the proton spectrum becomes steeper. These results
have important implications concerning acceleration of ions by shocks
and CIRs, acceleration of anomalous cosmic rays, and particle dynamics
in the outer heliosphere.
---------------------------------------------------------
Title: Interstellar oxygen, nitrogen and neon in the heliosphere
Authors: Geiss, J.; Gloeckler, G.; Mall, U.; von Steiger, R.; Galvin,
A. B.; Ogilvie, K. W.
1994A&A...282..924G Altcode:
Oxygen, nitrogen and neon pick-up ions of interstellar origin were
detected for the first time with the Solar Wind Ion Spectrometer (SWICS)
on board Ulysses. The interstellar origin of these ions is established
by the following criteria: (a) they are singly charged, (b) they have
the broad velocity distributions characteristic of pick-up ions, with an
upper limit of twice the solar wind speed, (c) their relative abundance
as a function of distance from the sun corresponds to the theoretical
expectation, and (d) there is no relation to a planetary or cometary
source. The interstellar abundance ratios He(+)/O(+), N(+)/O(+),
Ne(+)/O(+) were investigated. At approximately 5.25 AU in the outermost
part of Ulysses' trajectory He(+)/O(+) = 175<SUP>+70</SUP><SUB>-50</SUB>
N(+)/O(+) = 0.13<SUP>+0.05</SUP><SUB>-0.05</SUB> and Ne(+)/O(+)
= 0.18<SUP>+0.10</SUP><SUB>-0.07</SUB> were determined. For the
interstellar gas passing through the termination region and entering the
heliosphere (He/O)<SUB>0</SUB> = 290<SUP>+190</SUP><SUB>-100</SUB>,
(N/O)<SUB>0</SUB> = 0.13<SUP>+0.06</SUP><SUB>-0.06</SUB> and
(Ne/O)<SUB>0</SUB> = 0.20<SUP>+0.12</SUP><SUB>-0.09</SUB> were obtained
from the pick-up ion measurements. Upper limits for the relative
abundances of C(+) and C were also determined.
