Description of ISCS, proposal accepted by SCOSTEP
INTERNATIONAL SOLAR CYCLE STUDIES (ISCS)
Project Summary
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Steering Committee
V. Obridko Co-chairman Russia
M.A. Shea Co-chairman USA
B. Schmieder France
T. Watanabe Japan
S.T. Wu USA
SCIENTIFIC OBJECTIVE: To conduct basic research directed toward understanding
the underlying and resulting processes associated with the rising and maximum
phase of a solar cycle.
ASSOCIATED APPLICATIONS: An improved understanding of the processes associated
with a solar cycle can be applied to many aspects of Earth's environment such as
predicting solar proton intensities, and geomagnetic disturbances. In addition
the scientific results may have long term applications from planning extended
spacecraft missions to global climate effects.
PROPOSED TIME PERIOD FOR STUDY: 1998-2002
POSSIBLE PARTICIPANTS: Scientists who have already agreed to participate in
various aspects of the ISCS project:
P. Brandt Germany I. Chertok Russia
E. Cliver USA M. Dryer USA
E. Flueckiger Switzerland K. Harvey USA
S. Kahler USA M. Kojima Japan
G. Kuklin Russia H. Kunow Germany
P. Lantos France M. Pick France
B. Sanahuja Spain E. Sarris Greece
R. Schwenn Germany G. Smolkov Russia
M. Storini Italy J. Sykora Slovakia
R. Thompson Australia B. Tsurutani USA
I. Veselovsky Russia
The steering committee invites interested scientists to participate in the
implementation of the International Solar Cycle Study. Organization of specific
projects within the framework of this program are encouraged, particularly for
any event-oriented studies to be undertaken by the ISCS group as a whole.
Participants are expected to work within their own resources since SCOSTEP
funding is extremely limited.
RESEARCH PROGRAM SUMMARY:
WORKING GROUP 1. SOLAR ENERGY FLUX STUDY: FROM THE INTERIOR TO THE OUTER LAYER
Coordinators: C. Froehlich (Switzerland), J. Pap (USA)
- main reference points of the cycle in different solar indices;
- irradiance variability;
- physical cause of solar indices and irradiance variability;
- mass-energy output: particles and waves;
- irradiance (or other possible solar agents) and climate.
WORKING GROUP 2. SOLAR MAGNETIC FIELD VARIABILITY STUDY: FROM THE LOWER
ATMOSPHERE THROUGH THE INNER CORONA
Coordinators: R. Harrison (UK), S.T. Wu (USA) (interium)
- Magnetic phenomena having different space and time scales; - Solar flares,
mass ejections and interplanetary consequences.
WORKING GROUP 3. SOLAR EMISSIONS: ORIGINS AND TRANSPORT THROUGH THE HELIOSPHERE
Coordinators: G. Simnett (UK), D. Webb (USA)
- Dynamic solar emissions in the increasing and maximum portion of solar cycle 23.
- Propagation in the interplanetary medium (coronal mass ejections,
interplanetary shocks, and energetic particles). - Interaction of coronal mass
ejections and solar wind streams with the magnetosphere.
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ISCS PROJECT DOCUMENTATION
INTRODUCTION
Solar activity has long been observed to occur in approximate 11-year cycles.
The advantage of this knowledge is the ability to plan, over a short time scale,
specific programs aimed to increase our knowledge of the solar activity cycle.
Solar cycle 22 has been one of the shortest cycles in history with the expected
minimum, based on the smoothed sunspot number, to have occurred in late 1996.
Over the past 21 years, SCOSTEP has coordinated several successful solar and
interplanetary programs such as FBS, SERF, STIP, SMY, SMA and the SOLERS22 and
SOLTIP projects under STEP. However, it has not coordinated any program
directed toward understanding solar processes throughout the rise and maximum of
the solar cycle and the resulting phenomena that affect the interplanetary
medium and planet Earth. To the best of our knowledge there are currently no
national or international projects being conducted with an emphasis on
understanding solar and interplanetary processes during the rising and maximum
of the 23rd solar cycle.
We are unable to accurately predict the magnitude of the 23rd solar cycle.
Sunspots have been observed at high solar latitudes thus announcing the onset of
new cycle phenomena. Solar activity (and interplanetary phenomena) typically
occur from both old and new cycle regions during the initial period of each
solar cycle (as defined by the smoothed sunspot number). Also they typically
occur during relatively quiet conditions making these disturbances ideal
candidates for studying an isolated event.
The first few months of 1997 have produced these type of phenomena. The
interesting solar activity in January 1997 occurred in a cycle 22 spot region
near the solar equator and had many unusual features. The solar activity in
April 1997 occurred in a cycle 23 spot region and was more typical of solar
induced phenomena.
Significant energetic solar proton events also seldom occur during the first
year of a "new" cycle although major solar flares (and coronal mass ejections)
are observed. During the second year of a cycle, proton events typically occur
in isolation associated with one solar activity event. As the cycle progresses,
one solar active region often produces episodes of similar activity such as
similar X-ray emissions, coronal mass ejections, solar proton events, and
interplanetary disturbances. What underlying solar feature(s) evolves
differently between these three types of solar emission phenomena is an
unanswered question.
Similarly interplanetary disturbances usually occur in relative isolation during
the initial phase of the rising portion of a solar cycle. As the cycle
progresses, the increased solar activity, often from more than one region at a
time, results in considerable turbulence in the interplanetary medium. The
transport of these solar emissions through the interplanetary medium is of
importance in predicting which and when various phenomena will interfere with
spacecraft operations and the geophysical environment.
In addition to the particle output of the Sun, the study of variability of the
solar radiation over a solar cycle is an equally important issue. The total
radiative output of the Sun establishes Earth's radiation environment, and it
controls its temperature and atmospheric composition. Recent studies indicate
that small but persistent variations in the solar energy flux may play an
important role in climate changes. Unfortunately, we lack the fundamental
understanding of the physical mechanism beneath the solar convective zone that
causes solar variability. We need to conduct further research to answer
important questions like "Could the solar irradiance change by a larger amount
during the next solar cycle?" or "Are the catastrophic climate changes observed
in prehistoric isotopic records related to changes that occur in the Sun?" A
comprehensive study of the emergence, evolution, eruption and decay of solar
magnetic active regions, related irradiance changes and particle effects will
help to achieve our ultimate goal: to understand why, how and what mechanisms
govern solar variability which controls many of the terrestrial processes.
Study of the solar cycle also includes the analysis of physical parameters and
indices at various reference points of the cycle where their behavior changes
drastically. It is important to determine the relationship between the fields
of various scales, including global fields. We still do not know exactly when a
solar cycle begins. Equally puzzling are the processes underlying the solar
polarity reversal near the maximum of solar activity. Questions like "What
processes give rise to polarity reversal?" and "Why doesn't the polarity at each
pole change aimultaneously?" need to be addressed. Studies of the relation of
differential and rigid rotation and the variation of rotation characteristics
with depth may help explain the reversal process at different solar latitudes.
Although the programs planned by each of the Working Group leaders are
fundamental and basic research, there is an underlying theme of connectivity
between the solar emissions and selected geophysical phenomena (i.e. space
weather). There is little doubt that increased knowledge of the
solar-interplanetary environment, particularly during the rising and maximum
portions of the solar cycle, will enhance our knowledge and hence our ability to
better forecast not only the occurrence of terrestrial phenomena (e.g.
geomagnetic disturbances) but also to help predict the magnitude and possible
consequences of various perturbations. In addition, coordinated studies of
solar phenomena and solar emission propagation to Earth and other spacecraft
will enhance our knowledge of the propagation of these phenomena throughout the
heliosphere.
This project is planned for the rising portion of the 23rd solar cycle through
the projected maximum in solar activity and is designed to improve our
understanding of how the Sun dramatically evolves from a quiet Sun to an
extremely active Sun over a period of five years. This time period presents a
superb opportunity to capitalize on an armada of strategically positioned
spacecraft located in a variety of orbits from near-Earth space to the distant
heliosphere. Measurements from these spacecraft and ground-based observations
coupled with theoretical and modelling efforts will lead to a better
understanding of the solar effects on the heliosphere. Appendices A and B are
summaries of some of the relevant spacecraft and ground-based observations
expected to be in operation between 1998 and 2002.
ENVIRONMENTAL AND OTHER APPLICATIONS
The three working groups under this proposed study will be coordinating their
efforts. Results from Working Group 1 will be transmitted to Working Group 2;
results from Working Group 2 will be transmitted to Working Group 3. Together
these three groups provide a seamless environmental study from the interior of
the Sun to Earth's magnetosphere. Participants in this project are willing to
cooperate with any other SCOSTEP study of the magnetosphere, ionosphere, or
upper atmosphere, offering suggestions on the transfer of solar energy and
emissions to the magnetosphere.
In addition, the participants of this project are dedicated to conducting a
responsible study that will help improve our knowledge of Earth's environment.
We anticipate this will be accomplished in several ways as summarized in the
following paragraphs.
Solar irradiance variations below 300 nm, although it represents only 1% of the
Sun's total electromagnetic output, are especially important since the
irradiance is totally absorbed in various layers of Earth's atmosphere.
Consequently, it plays a significant role in heating Earth's atmosphere and
establishing its chemical composition through photodissociation and
photoionization processes. The UV irradiance between 200 and 285 nm penetrates
to the stratosphere and is the major source of the stratospheric heating and the
ozone photodissociation. Radiation between 165 and 205 nm photodissociates the
oxygen molecules and other important odd oxygen constituents of the stratosphere
and the mesosphere. In addition, the 165 to 300 nm UV flux variations are of
primary interest for research into a possible connection between solar activity
and climate via solar control of the stratosphere and lower mesosphere and
coupling from these layers to the troposphere. The solar energy radiated below
200 nm represents less than 0.01% of the total flux, but it is aeronomically
important since it heats the lower thermosphere through the production of oxygen
by O2 absorption in the Schuman-Runge continuum. One of the most important
tasks will be to understand the variations in the Lyman-alpha emission line at
121.6 nm since in the mesosphere it photodissociates water vapor, which
contributes to the destruction of ozone at about 70 km altitude. Between 60 and
90 km of Earth's atmosphere, the ionization of NO by Lyman-alpha is responsible
for the formation of the ionospheric D region. The various EUV emissions at
wavelengths shorter than Lyman alpha and down to X-ray are entirely absorbed
above 90 km in Earth's atmosphere and they are responsible for the ionization of
the E and F regions. The most variable part of the solar spectrum is the X-ray
which is emitted principally from coronal regions of closed magnetic flux loops.
The X-ray radiation penetrates deeper to Earth's atmosphere playing an
important part in the ionization of the D-region. In principle it ionizes all
the atmospheric constituents, but is most effective in ionizing O2 and N2. Rapid
changes in X-ray related to solar flares have been identified as primary causes
of the sudden ionospheric disturbances which cause fadeouts in high frequency
radio propagation. Each increment of understanding these irradiance emissions
will contributed to Earth's atmosphere and possibly to climate.
Other solar emissions are important to our everyday lives as we move from one
century to the next. Technologies not even imaginable at the close of the last
century are routinely providing an improvement in our everyday lives. However,
these technologies are increasingly more susceptible to environmental
perturbations. Solar X-rays disrupt high frequency communications and
techniques for navigation. Solar particles, which also affect high frequency
communications, degrade solar cells on spacecraft as well as interfering with
spacecraft electronics, often in unpredictable ways. Degradation of solar cells
can lead to shortened satellite operational lifetimes, necessitating more
launches which translates to additional costs. Interference with spacecraft
electronics can generate a gambit of problems ranging from re-programming
satellite operational procedures, to the ultimate loss of an entire spacecraft
capability. When we consider the range of satellite applications - telephone,
FAX, television communications, scientific studies, weather observations, etc. -
we realize how much these spacecraft contribute to our everyday lives. It is
now firmly established that a fast and energetic coronal mass ejection generates
an interplanetary shock. If this interplanetary shock intersects Earth and if
there is a southward component of the interplanetary magnetic field, a
geomagnetic storm will occur. These geomagnetic disturbances can result in
electrical power grid problems as well as mid and low latitude communication
problems.
For reasons such as those in the above paragraph, many nations have implemented
Space Weather programs. The scientific results from this proposed ISCS project
can contribute to these Space Weather programs. An improved knowledge of the
solar processes and solar emission transport in the interplanetary medium can
improve space weather prediction techniques. These prediction methods can
assist in determining periods of radio, navigation, and communication
interferences, satellite and space systems hazards, and potential problems with
electrical power grids. It will assist in refining satellite drag calculations,
and perhaps offer insight into other ionospheric and atmospheric effects.
Finally, although the Sun has been studied for centuries, we really know very
little about how the solar cycle is initiated, maximizes, and decays. Some
scientists believe this is a chaotic process; others disagree. We do not
propose to resolve this problem. However, spacecraft engineers need solar cycle
predictions - particularly those long term predictions which will help determine
launch times for extended space missions. We do not expect to be able to
predict the onset or amplitude of solar cycles 24, 25, 26 and beyond. However,
we do hope to contribute to the overall understanding of the processes involved
in the creation of the solar cycle itself - from the solar interior to the
effects on Earth and the heliosphere. Each new result will add an additional
piece to the solar cycle puzzle.
CONCLUDING REMARKS
This is the first SCOSTEP scientific program that seeks to not only investigate
the underlying phenomena leading to the onset and maximum of the solar cycle but
also to extend the new scientific knowledge to societal problems. The
scientific results are anticipated to be useful in many areas of our society -
from the planning of long term spacecraft missions, to improved satellite
operations, to links to ozone depletion, and even to climatic changes. Each
improvement in our understanding of the solar cycle will aid humankind in one or
more ways - as well as giving rise to new and exciting scientific problems to be
studied in the future.
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WORKING GROUP 1: RESEARCH PROGRAM PLANS
Solar Energy Flux Study: From the Interior to the Outer Layer
Coordinators: Claus Frohlich and Judit Pap
The Sun, a fairly typical star, dominates the physical conditions throughout the
solar system due to its influence on planetary atmospheres and interplanetary
medium. The Sun's energy output takes two principal forms: electromagnetic
radiation and the emission of charged particles. Measurements of the solar
energy flux and understanding its variability are essential since they provide
important information about the physical processes and structural changes taking
place below, in, and above the photosphere. In addition to the astrophysical
importance of the solar energy flux measurements, these measurements are
important for solar-terrestrial physics. As the flux is deposited with
different fractions in Earth's atmosphere, the oceans and land, the energy flux
of the Sun (both solar radiation and particles) controls the heating, ionization
, radiative, chemical, and dynamical processes in the terrestrial atmosphere-
ocean-land system. Measurements of the solar energy flux over the last decades
have demonstrated that it varies with the eleven year solar activity cycle, and
it has been established conclusively that Earth's climate, radiative environment
, and upper atmospheric chemistry are influenced by the varying solar energy
flux. The solar variability together with the accumulation of anthropogenic
trace gases determine the human milieu of the future.
The main objective of ISCS's Working Group 1 is to coordinate and support
comprehensive international research of the variations in the solar energy flux
during the rising portion and maximum of solar cycle 23. The research
activities of ISCS's Working Group 1 will concentrate on the following tasks:
1. Measure and study the variations in the solar radiative and mass output and
solar activity indices during the solar activity cycle.
2. Understand why the solar radiative and mass output and the solar activity
indices vary during the solar cycle.
3. Study the role of solar variability in solar-terrestrial changes and its
contribution to global change.
The total radiative output of the Sun establishes Earth's radiation environment
and controls Earth's temperature and atmospheric composition. Therefore, the
accurate knowledge of solar radiation received by Earth, and its temporal
variations, is critical to understanding the role solar variability plays in
climate change. Although the value of the integrated solar energy flux over the
entire solar spectrum, hence total irradiance, is known with high precision, we
only know the solar energy flux within about a +/-0.2% absolute accuracy. The
knowledge of the spectral irradiance below 300 nm is only >1%. On the other
hand, it is well known that coronal mass ejections are responsible for many
major effects on Earth. These coronal mass ejections, if accompanied by fast
and powerful interplanetary shocks can result in major magnetic disturbances on
Earth. These phenomena are related to the Sun and its activity cycle. Thus, the
study of solar phenomena with respect to the solar cycle is needed to understand
the solar influence in its full consequences.
In order to achieve the goals set forth above, one has to understand the
physical processes inside the Sun. Although the bulk of the solar energy is
radiated into space from the photosphere, chromosphere and corona, it is
generated in the central core. The outer one third of the Sun consists of a
convective envelope. Thermal, kinetic and magnetic energy are available
throughout this envelope and conversion between these energy reservoirs is
possible but not yet described by any well-established theory. Measurements of
the solar energy flux, emitted in the form of electromagnetic radiation and
particles, and analysis of its variability will help to discover the underlying
physical processes. As we learn more about the causes of the changes in the
solar energy flux, we can provide better guides for experimentalists carrying
out the measurements.
In addition to the astrophysical significance of studying the solar energy flux
variations, this has a great importance for solar-terrestrial physics as well.
The general level of solar radiation determines the temperature of Earth. Long-
term changes in this energy output can be responsible for slow climatic changes
such as produced the Little Ice Ages. Short-term changes over days, weeks and a
few years appear to have little climatic effect, but Earth's upper atmosphere is
very responsive to solar activity variations in general via the effect of UV and
EUV radiation and energetic solar particles. The changes in Earth's upper
atmosphere may be quite large and rapid, especially related to intense outbursts
of solar flares and coronal mass ejections.
Since the space observations cover only a few decades and there are
interruptions in the measurements, one also has to rely on ground-based indices
of solar activity. These indices are used as surrogates for the changes in the
solar energy flux. This is an especially important issue because of the lack of
adequate physical models of the solar energy flux variability. However, the
fundamental question is whether such empirical models of the solar energy flux
variability can reasonably describe and predict the energy flux changes.
Considering the importance of the variation in the total energy flux in climate
changes, it is questionable whether the irradiance surrogates can predict the
irradiance changes with the long-term precision required by climatic studies.
The largest obstacle in modeling the solar energy flux is the different
magnitude and time behavior of the various forms of the solar energy flux.
Analyses have demonstrated that all parts of the solar energy change are in
parallel with the solar magnetic activity, being higher during maximum activity
conditions; however, there may be different physical reasons for these cyclic
changes. While the changes in the total solar radiation is about 0.2% over the
solar cycle, the relative changes can be orders of magnitude larger at UV/EUV
wavelengths and for particle fluxes. These differences in the shape and fferent
physical conditions of the solar atmosphere where they are emitted. In addition
, there is a phase shift between the variation of the solar energy flux and
magnetic activity indices, which makes the modeling and prediction more
difficult. Because of all these difficulties, ISCS's WG1 will devote
considerable effort to the study of solar energy flux changes as a function of
solar cycle and to improve the models used for climate and solar-terrestrial
studies. Combination of the measured solar energy flux and its models will thus
enable more advanced studies of the terrestrial and climate effects of solar
variability.
An extremely successful international program, the "Solar Electromagnetic
Radiation Study for Solar Cycle 22 (SOLERS22)", has been operating under the
auspices of the STEP project within SCOSTEP. SOLERS22 will end its activities
at the end of 1997. SOLERS22 helped in many ways to organize, continue and
start new observational programs of solar irradiance from space and also from
the ground. The new SCOSTEP project "Solar Energy Flux Study: From the Interior
to the Outer Layer" within ISCS is based on the results gained during the
SOLERS22 project; however, it will address much broader scientific issues than
SOLERS22. Introducing a new project within SCOSTEP on the topic of solar energy
flux variability and its terrestrial effects is very timely considering the
on-going and extremely successful SOHO and UARS missions and the forthcoming
EOS, TIMED, SOLAR-B, Solar Probe and additional solar-terrestrial missions.
Since the operation of both the space and ground-based solar energy monitoring
programs requires international cooperation, its is essential to have an
international research project coordinating the research based on the
international solar energy monitoring programs.
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WORKING GROUP 2: RESEARCH PROGRAM PLANS
Solar Magnetic Field Variability Study:From the Lower Atmosphere to the Inner
Corona
Coordinators: R. Harrison and S.T. Wu (interium)
It is recognized that solar atmospheric structures are dominated by magnetic
fields. The variability of the solar magnetic field must be investigated to
understand the physics of solar activity. For these studies we will classify
the variability in different time and spatial scales. For example, we need to
study the solar magnetic field variability on both a global spatial scale and on
a long time scale to understand the changes during the rising and maximum
portions of a solar cycle. We also must study the magnetic field variability on
a short time scale (hours, days, or even months) in both small and global
spatial scales. This would improve our knowledge of the fundamental physical
processes for the evolution of active regions and coronal magnetic fields
leading to a better understandin of disturbances in the lower solar atmosphere (
i.e. UV, EUV and X-Ray emissions) and in the inner corona (e.g. coronal mass
ejections).
Another important aspect of near-Sun coronal phenomena is the prolonged post-CME
(Coronal Mass Ejection) energy release in the corona. During this phase, the
magnetic field in the extended region of the corona, strongly disturbed by a
large CME, relaxes via the magnetic reconnection in vertical coronal current
sheets. The post-eruption energy release is a process which appears to occur in
any eruptive event, including a CME, irrespective of whether a CME is associated
by impulsive flare energy release, by filament (i.e. prominence) eruption, or by
the destabilization of a large-scale coronal structure. An investigation of the
magnetic structure of solar active regions both pre- and post- coronal mass
ejections may offer insights as to if an when a region will produce a similar
eruption.
The objective of this working group is to investigate solar magnetic field
variabilities for small and global spatial structures and for both long and
short time scales. In the initial phase of this project, we will focus on the
short time scale solar features with small and global spatial structures. To
conduct these studies, we will utilize data collected by the experiments on-
board various space missions (SOHO, YOHKOH, TRACE, ULYSSES, WIND, and GOES) in
addition to data from ground-based measurements.
Specific tasks are cited below.
1. Coronal loop structures and evolution.
The coronal loops are fundamental elements of the solar atmosphere. In order to
understand the physics (i.e. UV, EUV, X-Ray emissions) of the non-coronal hole
corona, it is essential to investigate the structures and evolution of coronal
loops. These loops are formed by the plasmas confined by the solar magnetic
fields. These studies are particularly important for the understanding of flare
physics.
2. Initiation and propagation of coronal mass ejections (CMEs) and their
interplanetary consequences.
It has been suggested that most CMEs are caused by the destabilization of
coronal streamers on the basis of previous observations. The current space
instrument LASCO/EIT on-board the SOHO mission has a field-of-view of the Sun in
the range from 1 solar radii to 32 solar radii which, in collaboration with
coronal spectrometers also on SOHO, provides an unprecedented opportunity to
investigate the initiation and propagation of CMEs and their interplanetary
consequences. Therefore, we suggest utilization of these observations to answer
the following questions:
(i) What physical processes lead to global scale coronal magnetic field
rearrangement? This could lead to an understanding of the initiation of CMEs.
(ii) What is a coronal mass ejection?
(iii) What is the CME rate? How does it relate to the solar cycle?
3. Frequency of the occurrence of the CMEs during the rising phase of the solar
cycle 23.
The CME is a major restructuring of the corona. It is important to assess the
role of CMEs in the solar cycle. SOHO is ideally suited to this work.
4. Theoretical Modeling and Numerical Simulations.
In order to carry out the above objectives, we will also focus our attention to
the development of theoretical and numerical simulation models to quantify the
interpretation of the observation in order to reveal the hidden physics. It is
also to emphasize that this group will work closely with both WG1 and WG3 by
taking the solar surface input from WG1 and delivering the outputs of WG2 to WG3
.
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WORKING GROUP 3: RESEARCH PROGRAM PLANS
Solar Emissions: Origins and Transport Through the Heliosphere
Coordinators: G. Simnett and D. Webb
The objectives of Working Group 3 are to study the following topics on the
heliospheric aspects of solar emissions and how they depend on the solar
activity cycle during the rise and maximum phases of cycle 23:
(1) the origins of solar dynamic phenomena;
(2) the interplanetary propagation of coronal mass ejections (CMEs),shocks and
solar energetic particles (SEPs); and
(3) the interaction of these disturbances and solar wind streams with the
magnetosphere.
Solar activity provides the driving force for disturbances in the interplanetary
medium and geomagnetic storms. The Sun has been well observed during the past
two decades with data obtained by many spacecraft, including SMM, YOHKOH and
SOHO, and ground-based observatories. In addition the interplanetary medium has
been probed by many spacecraft: the inner heliosphere by HELIOS and the outer
and high latitude heliosphere by Ulysses and the Pioneer and Voyager spacecraft.
The most recent near-Earth missions collecting solar wind data are SOHO and WIND
. Starting late this year the TRACE and ACE missions will be launched, and later
in solar cycle 23 several new missions, such as SMEI, Solar-B and STEREO, are
planned. We propose to use these observations of solar, interplanetary and
geomagnetic phenomena to address specific questions of importance to studies of
solar and interplanetary disturbances and their coupling to the magnetosphere,
including recent new initiatives on "Space Weather".
Past observations such as from ISEE-3, HELIOS, IPS (Interplanetary
Scintillations) and at long radio wavelengths, have shown that CMEs inject vast
amounts of plasma and magnetic field into the heliosphere in correspondence with
the sunspot cycle. The resulting disturbances are the most likely cause of
sporadic geomagnetic storms and, therefore, a key component of space weather.
CMEs are linked to other solar activity including eruptive filaments, large
flares, long-duration X-ray events, transient coronal holes and shock waves.
There is a broad spectrum of solar mass ejecta, ranging from small transient
outflows primarily at low latitudes to large, extended events with widths of
over 90 degrees. Most large CMEs arise from closed coronal magnetic fields such
as streamers. But we know little about how the global magnetic field evolves
and leads to the opening of these structures and the loss of material to space.
The coronal observations from SOHO (LASCO, EIT, CDS, UVCS) are providing new
data on CME source regions and streamers and how this material is accelerated
along with the solar wind. Observations of Sun-centered activity and "halo"
CMEs also provide an important new way of evaluating the origin and propagation
of material toward Earth.
An important class of mass ejecta are erupting prominences, which have been
modeled as expanding flux ropes whose signature in the heliosphere is a magnetic
cloud. Recently, the twist (helicity) of filaments has been found to have both
hemispherical and solar cycle dependencies and to be correlated with the
helicity of magnetic clouds at 1 AU. We propose to study the relationship of
filament eruptions and CMEs to flux ropes and magnetic clouds, and to shedding
of the Sun's flux and helicity built up over the cycle. In addition, we need to
study patterns in the long-term evolution of magnetic polarity boundaries and of
filament eruptions, and their roles as sites of CME and other eruptive activity.
The effects and signatures of individual CMEs on the interplanetary medium
remain uncertain. Major CMEs, especially if accompanied by large flares, can
produce large interplanetary disturbances. However, since the typical CME is
often not associated with a flare or interplanetary shock, its interplanetary
characteristics are likely more subtle than those associated with large flares.
At present we know that these signatures consist of abnormal flows relative to
the average solar wind, with about half of all transient interplanetary
disturbances accompanied by shocks, magnetic clouds or clear "piston"-like
plasma enhancements. We need to study and model the magnetic topology of these
structures using both the interplanetary magnetic field and energetic particles
as "tracers". During solar cycle 23 in-situ measurements from Ulysses, WIND,
SOHO and other deep space missions should greatly improve our understanding of
these transient flows and how they vary over the cycle. Perspective views from
one or more STEREO-type missions would provide valuable complementary data on
the 3-D structure of interplanetary CMEs and shocks.
We also need to understand the role of reconnection in coronal and CME evolution
. This is important in the heliospheric context since the injection of magnetic
flux should increase the interplanetary flux indefinitely, which is clearly not
observed. Evidence of the disconnection of solar fields is observed in only a
small fraction of all CMEs, but intermingling of both open and closed fields may
be common in interplanetary ejecta. The SOHO observations of CMEs within 30
solar radii combined with in-situ interplanetary magnetic field and plasma
measurements will be ideal for studies of magnetic reconnection and topologies
during solar cycle 23.
We know that geomagnetic storms can have two causes: transient solar eruptions (
mainly CMEs) from streamers that form the base of the heliospheric current sheet
, and recurrent interaction regions and high-speed wind streams which arise from
solar coronal streamers and holes, respectively. However, we do not understand
the interplanetary conditions necessary to produce geomagnetic storms and other
geoactivity. Good associations have been found between geomagnetic storms and
other interplanetary signatures of ejecta, especially magnetic clouds. Although
magnetic clouds with their strong southward fields are clearly related to the
coupling of these disturbances to the magnetosphere, we do not have a detailed
physical understanding of this process. We propose to utilize the many space
observations to be obtained during solar cycle 23 to investigate the
characteristics of geoeffective interplanetary phenomena and the coupling
process and how they vary over the cycle.
Finally, we propose to study the relationships among interplanetary shocks, CMEs
, solar flares and solar energetic particles utilizing these data sets. Coronal
shocks must propagate through coronal streamers and neutral sheets which extend
into the interplanetary medium. The streamers extend from the corona into the
interplanetary medium and become the heliospheric current sheet. Since the
trajectories of CMEs and the production and propagation of SEPs may depend
significantly on the presence of a neutral sheet in space, we propose to
investigate the effects of neutral sheets on CME, shock and SEP propagation
during solar cycle 23. We also need to understand how and where solar energetic
particles are accelerated, e.g., the fraction produced in the corona vs the
interplanetary medium, and how they are transported in the low corona. In the
outer heliosphere corotating interaction regions play an important role in
producing charged particles.
Important questions to be addressed by Working Group 3 include:
(1) What are the solar origins of interplanetary disturbances and what are
their interplanetary manifestations?
(2) How do these ejecta propagate through the heliosphere both radially and
latitudinally?
(3) How and where do CMEs originate and how are the previously closed magnetic
fields opened and the material accelerated?
(4) How can the intensity and duration of SEPs be predicted?
(5) What is the relative importance of CME shocks vs the flare impulsive phase
in SEP production and does it depend on the solar cycle?
(6) How and where are the relativistic SEPs accelerated?
(7) Can the strength and direction of the Bz component of the interplanetary
magnetic field be predicted?
(8) How can the intensity and duration of geomagnetic storms be predicted?
(9) How do interplanetary disturbances couple to the magnetosphere and drive a
geomagnetic storm?
(10) What are the characteristics of geoeffective solar source regions, what
are their key interplanetary signatures, and how do these vary over the cycle?
(11) What is the relative importance of solar flares and filament eruptions to
geomagnetic storms?
-------------------------------------
APPENDIX A:
SPACECRAFT EXPECTED TO BE IN OPERATION 1998-2002
The following list of spacecraft is in alphabetical order. For new spacecraft,
anticipated launch dates are given whenever available. Scientists planning
specific coordinated studies involving future spacecraft are advised to keep
informed of any changes in launch schedules.
1. ACE. Scheduled for launch in 1997, this spacecraft will measure the
composition of the solar wind at the L1 position.
2. CGRO. Launched in 1991, this spacecraft can monitor the highest energy
emissions from the Sun.
3. CORONAS-F. Anticipated launch in 1998. Will provide information on the
structure of solar activity, X-ray imaging, helioseismology, solar radio
spectrometer, and a spectrometer of solar cosmic rays.
4. GOES. Spacecraft at geosynchronous orbit monitoring solar X-rays and solar
particles. If the GOES-M spacecraft is launched in the 1998-2002 time period, X
-ray imaging will be available.
5. IMP-8. Launched in 1973, this spacecraft is located at 30 Earth-radii and
measures interplanetary plasma and particles when beyond the magnetospheric bow
shock.
6. INTERBALL-1. Launched in 1995.
INTERBALL-2 with subsatellite MAGION-4.
The subsatellite is at changeable distances to the mother spacecraft.
The INTERBALL satellite program is a series of satellites for the study of
Earth's magnetosphere, solar wind and the heliosphere.
7. INTERHELIOS. Possible launch in 2002. Will investigate solar and
heliospheric plasmas on the way to the Sun and very close to the Sun.
8. PROTON. Anticipated launch in 1999 or 2000. Will provide measurements of
solar soft and hard X-ray and gamma ray radiation.
9. SMEI. The Solar Mass Ejection Imager is being developed by NASA and the
USAF to detect and track CMEs between Sun and Earth. The goal is to provide 1-3
days warning of CME arrival at Earth; launch is planned for 2000.
10. SOHO. Launched in 1995, this spacecraft provides information on the
structure of the solar interior, surface magnetic fields, inner corona, coronal
mass ejections, and the solar wind.
11. SOLAR PROBE. Possible launch in 2001. Will investigate solar and
heliospheric plasmas on the way to the Sun and very close to the Sun.
12. STEREO. A class of deep-space mission which, in conjunction with near-
Earth spacecraft would provide 3-D views of solar phenomena and disturbances
traveling in the inner heliosphere. The launch of one or more such missions is
possible in this solar cycle.
13. SYSTEMA-STEREOSCOP. Possible launch in 2002. Will investigate three-
dimensional structure and dynamics of phenomena and processes in the solar
atmosphere.
14. TRACE. Scheduled for launch in 1997, this is a high resolution EUV/UV
imager that will be able to follow the structure of the solar magnetic field
into the corona. This is a USA spacecraft.
15. UARS. Launched in 1991, this is an upper atmospheric research satellite
that carries solar flux monitors to measure solar variability at UV wavelengths.
16. ULYSSES. Launched in 1990, this spacecraft measures plasma and particles
in the solar wind. The spacecraft operates out of the ecliptic plane and is
scheduled to return to the solar polar regions during the next solar maximum.
17. VOYAGER 1 and 2. Measures particles and fields in the distant heliosphere
(i.e. beyond Pluto's orbit).
18. WIND. Launched in 1994, periodically samples the solar wind upstream of
the magnetosphere from an eccentric orbit that goes from within the
magnetosphere to the L1 position.
19. YOHKOH. Launched in 1991, this spacecraft provides information on solar
soft and hard X-ray imaging in addition to spectroscopy of coronal activity.
In addition to these specific spacecraft and space probes, related
investigations will continue on the International Space Station and Space
Shuttle.
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APPENDIX B:
GROUND-BASED PROGRAMS EXPECTED TO BE IN OPERATION 1998-2002
Throughout the period 1998-2002 there will be continued and new ground-based
programs some of which are now operational or planned for the near future. In
some cases, an upgrading of existing equipment will facilitate improved or new
measurements.
No attempt is made to list individual ground-based detectors that will provide
correlative data for the studies planned for this project. Solar optical,
magnetic and radio observations are being conducted by many groups throughout
the world and these data will contribute to the overall database. Of particular
interest are the following:
1. GONG. A world-wide network of ground based helioseismology observatories
that monitor the structure and dynamics of the solar interior.
2. SEON. Solar optical and radio observatories with real-time patrol data
transmitted to the Space Environment Center at NOAA, Boulder, Colorado. This
equipment is being upgraded during the ISCS time period.
-----------------------------------
APPENDIX C:
Meetings of the Steering Committee will be held primarily in conjunction with
other scientific assemblies where many of the participants might be in
attendance. The initial meeting was held in conjunction with the SCOSTEP
Steering Committee Meeting in the UK in July 1996.
Meetings of the Steering Committee
April 97, France
August 97, Uppsala
Possibilities of future meetings:
1998 - SOHO/COSPAR (Nagoya) and/or
SCOSTEP meeting in Taiwan during Western Pacific AGU
1999 - IUGG meeting in UK and/or
1st ISCS Workshop
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APPENDIX D
BUDGETARY INFORMATION
Budget 2 K$ 1997
10 K$ 1998
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Last revised: September 13 2002
