International Space Science Institute Research Articles

Towards the definition of a solar forcing dataset for CMIP7

Abstract. The solar forcing prepared for Phase 6 of the Coupled Model Intercomparison Project (CMIP6) has been used extensively in climate model experiments and has been tested in various intercomparison studies. Recently, an International Space Science Institute (ISSI) working group has been established to revisit the solar forcing recommendations, based on the lessons learned from CMIP6, and to assess new datasets that have become available, in order to define a road map for building a revised and extended historical solar forcing dataset for the upcoming Phase 7 of CMIP. This paper identifies the possible improvements required and outlines a strategy to address them in the planned new solar forcing dataset. Proposed major changes include the adoption of the new Total and Spectral Solar Irradiance Sensor (TSIS-1) solar reference spectrum for solar spectral irradiance and an improved description of top-of-the-atmosphere energetic electron fluxes, as well as their reconstruction back to 1850 by means of geomagnetic proxy data. In addition, there is an urgent need to consider the proposed updates in the ozone forcing dataset in order to ensure a self-consistent solar forcing in coupled models without interactive chemistry. Regarding future solar forcing, we propose consideration of stochastic ensemble forcing scenarios, ideally in concert with other natural forcings, in order to allow for realistic projections of natural forcing uncertainties.

Quantifying errors in 3D CME parameters derived from synthetic data using white-light reconstruction techniques

Current efforts in space weather forecasting of CMEs have been focused on predicting their arrival time and magnetic structure. To make these predictions, methods have been developed to derive the true CME speed, size, position, and mass, among others. Difficulties in determining the input parameters for CME forecasting models arise from the lack of direct measurements of the coronal magnetic fields and uncertainties in estimating the CME 3D geometric and kinematic parameters after eruption. White-light coronagraph images are usually employed by a variety of CME reconstruction techniques that assume more or less complex geometries. This is the first study from our International Space Science Institute (ISSI) team “Understanding Our Capabilities in Observing and Modeling Coronal Mass Ejections”, in which we explore how subjectivity affects the 3D CME parameters that are obtained from the Graduated Cylindrical Shell (GCS) reconstruction technique, which is widely used in CME research. To be able to quantify such uncertainties, the “true” values that are being fitted should be known, which are impossible to derive from observational data. We have designed two different synthetic scenarios where the “true” geometric parameters are known in order to quantify such uncertainties for the first time. We explore this by using two sets of synthetic data: 1) Using the ray-tracing option from the GCS model software itself, and 2) Using 3D magnetohydrodynamic (MHD) simulation data from the Magnetohydrodynamic Algorithm outside a Sphere code. Our experiment includes different viewing configurations using single and multiple viewpoints. CME reconstructions using a single viewpoint had the largest errors and error ranges overall for both synthetic GCS and simulated MHD white-light data. As the number of viewpoints increased from one to two, the errors decreased by approximately 4° in latitude, 22° in longitude, 14° in tilt, and 10° in half-angle. Our results quantitatively show the critical need for at least two viewpoints to be able to reduce the uncertainty in deriving CME parameters. We did not find a significant decrease in errors when going from two to three viewpoints for our specific hypothetical three spacecraft scenario using synthetic GCS white-light data. As we expected, considering all configurations and numbers of viewpoints, the mean absolute errors in the measured CME parameters are generally significantly higher in the case of the simulated MHD white-light data compared to those from the synthetic white-light images generated by the GCS model. We found the following CME parameter error bars as a starting point for quantifying the minimum error in CME parameters from white-light reconstructions: Δθ (latitude)=6°-3°+2°, Δϕ (longitude)=11°-6°+18°, Δγ (tilt)=25°-7°+8°, Δα(half-angle)=10°-6°+12°, Δh (height)=0.6-0.4+1.2R⊙, and Δκ (ratio)=0.1-0.02+0.03.

Decoding the Pre-Eruptive Magnetic Field Configurations of Coronal Mass Ejections

A clear understanding of the nature of the pre-eruptive magnetic field configurations of Coronal Mass Ejections (CMEs) is required for understanding and eventually predicting solar eruptions. Only two, but seemingly disparate, magnetic configurations are considered viable; namely, sheared magnetic arcades (SMA) and magnetic flux ropes (MFR). They can form via three physical mechanisms (flux emergence, flux cancellation, helicity condensation) . Whether the CME culprit is an SMA or an MFR, however, has been strongly debated for thirty years. We formed an International Space Science Institute (ISSI) team to address and resolve this issue and report the outcome here. We review the status of the field across modeling and observations, identify the open and closed issues, compile lists of SMA and MFR observables to be tested against observations and outline research activities to close the gaps in our current understanding. We propose that the combination of multi-viewpoint multi-thermal coronal observations and multi-height vector magnetic field measurements is the optimal approach for resolving the issue conclusively. We demonstrate the approach using MHD simulations and synthetic coronal images. Our key conclusion is that the differentiation of pre-eruptive configurations in terms of SMAs and MFRs seems artificial. Both observations and modeling can be made consistent if the pre-eruptive configuration exists in a hybrid state that is continuously evolving from an SMA to an MFR. Thus, the 'dominant' nature of a given configuration will largely depend on its evolutionary stage (SMA-like early-on, MFR-like near the eruption).

Guest Editorial: International Space Science Institute (ISSI) Workshop on Geohazards and Risks Studied from Earth Observations

Guest Editorial: International Space Science Institute (ISSI) Workshop on Geohazards and Risks Studied from Earth Observations

Tropical Widening: From Global Variations to Regional Impacts

AbstractOver the past 15 years, numerous studies have suggested that the sinking branches of Earth’s Hadley circulation and the associated subtropical dry zones have shifted poleward over the late twentieth century and early twenty-first century. Early estimates of this tropical widening from satellite observations and reanalyses varied from 0.25° to 3° latitude per decade, while estimates from global climate models show widening at the lower end of the observed range. In 2016, two working groups, the U.S. Climate Variability and Predictability (CLIVAR) working group on the Changing Width of the Tropical Belt and the International Space Science Institute (ISSI) Tropical Width Diagnostics Intercomparison Project, were formed to synthesize current understanding of the magnitude, causes, and impacts of the recent tropical widening evident in observations. These working groups concluded that the large rates of observed tropical widening noted by earlier studies resulted from their use of metrics that poorly capture changes in the Hadley circulation, or from the use of reanalyses that contained spurious trends. Accounting for these issues reduces the range of observed expansion rates to 0.25°–0.5° latitude decade‒1—within the range from model simulations. Models indicate that most of the recent Northern Hemisphere tropical widening is consistent with natural variability, whereas increasing greenhouse gases and decreasing stratospheric ozone likely played an important role in Southern Hemisphere widening. Whatever the cause or rate of expansion, understanding the regional impacts of tropical widening requires additional work, as different forcings can produce different regional patterns of widening.

Promoting Transdisciplinary and Transeultural Cooperation In Space Science in Face of COVID-19-Interview with Prof.Wing-Huen Ip,Executive Director of ISSI-BJ

Prof.Wing-Huen Ip,a world-renown scientist in cometary physics,planetary science,solar system evolution and exoplanets,took the post of the Executive Director of the International Space Science Institute一Beijing(ISSI-BJ)in June.As the only partner of the well-known International Space Science Institute(ISSI)in Bern outside Switzerland,ISSI-BJ has adopted the same tools as ISSI to facilitate international cooperation and academic exchanges:workshops,forums,and others that rely on in-person communications.

Lunar Seismology: An Update on Interior Structure Models

An international team of researchers gathered, with the support of the International Space Science Institute (ISSI), (1) to review seismological investigations of the lunar interior from the Apollo-era and up until the present and (2) to re-assess our level of knowledge and uncertainty on the interior structure of the Moon. A companion paper (Nunn et al. in Space Sci. Rev., submitted) reviews and discusses the Apollo lunar seismic data with the aim of creating a new reference seismic data set for future use by the community. In this study, we first review information pertinent to the interior of the Moon that has become available since the Apollo lunar landings, particularly in the past ten years, from orbiting spacecraft, continuing measurements, modeling studies, and laboratory experiments. Following this, we discuss and compare a set of recent published models of the lunar interior, including a detailed review of attenuation and scattering properties of the Moon. Common features and discrepancies between models and moonquake locations provide a first estimate of the error bars on the various seismic parameters. Eventually, to assess the influence of model parameterisation and error propagation on inverted seismic velocity models, an inversion test is presented where three different parameterisations are considered. For this purpose, we employ the travel time data set gathered in our companion paper (Nunn et al. in Space Sci. Rev., submitted). The error bars of the inverted seismic velocity models demonstrate that the Apollo lunar seismic data mainly constrain the upper- and mid-mantle structure to a depth of ∼1200 km. While variable, there is some indication for an upper mantle low-velocity zone (depth range 100–250 km), which is compatible with a temperature gradient around 1.7 ∘C/km. This upper mantle thermal gradient could be related to the presence of the thermally anomalous region known as the Procellarum Kreep Terrane, which contains a large amount of heat producing elements.

Beyond planetary protection: What is planetary sustainability and what are its implications for space research?

This paper presents recent developments in the interdisciplinary topic of “planetary sustainability” and discusses its potential implications for space research.The current COSPAR Planetary Protection Policy address scientific space exploration only and is primarily concerned with the issue of contamination with micro-organisms. Other impacts of human space exploration that may be detrimental to space exploration itself are not covered. The best known example is the anthropogenic space debris orbiting Earth, but similar problems will occur in other places due to scientific and commercial space exploration in the near future.One possible approach to discuss and mitigate the impact of space exploration on the environment is to consider the space environment as integral part of sustainable development. The resulting concept of “planetary sustainability” and its ethical, scientific, economic, and legal ramifications were discussed during a workshop co-sponsored by the International Space Science Institute in March 2018. In this paper, we first summarize the results of this workshop. Then we propose potential implications of this concept for space research and report reactions and suggestions by members of the space research community during the COSPAR assembly 2018.

Sulfur dioxide in the Venus atmosphere: I. Vertical distribution and variability

Recent observations of sulfur containing species (SO2, SO, OCS, and H2SO4) in Venus’ mesosphere have generated controversy and great interest in the scientific community. These observations revealed unexpected spatial patterns and spatial/temporal variability that have not been satisfactorily explained by models. Sulfur oxide chemistry on Venus is closely linked to the global-scale cloud and haze layers, which are composed primarily of concentrated sulfuric acid. Sulfur oxide observations provide therefore important insight into the on-going chemical evolution of Venus’ atmosphere, atmospheric dynamics, and possible volcanism.This paper is the first of a series of two investigating the SO2 and SO variability in the Venus atmosphere. This first part of the study will focus on the vertical distribution of SO2, considering mostly observations performed by instruments and techniques providing accurate vertical information. This comprises instruments in space (SPICAV/SOIR suite on board Venus Express) and Earth-based instruments (JCMT). The most noticeable feature of the vertical profile of the SO2 abundance in the Venus atmosphere is the presence of an inversion layer located at about 70–75km, with VMRs increasing above. The observations presented in this compilation indicate that at least one other significant sulfur reservoir (in addition to SO2 and SO) must be present throughout the 70–100km altitude region to explain the inversion in the SO2 vertical profile. No photochemical model has an explanation for this behaviour. GCM modelling indicates that dynamics may play an important role in generating an inflection point at 75km altitude but does not provide a definitive explanation of the source of the inflection at all local times or latitudesThe current study has been carried out within the frame of the International Space Science Institute (ISSI) International Team entitled ‘SO2 variability in the Venus atmosphere’.

Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields

This paper summarizes the results obtained by the team "Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields" supported by the International Space Science Institute in Bern, Switzerland. We focus on the physical processes occurring in the outer heliosphere, especially at its boundary called the heliopause (HP), and in the LISM. The importance of magnetic field, charge exchange between atoms and ions, and solar cycle on the heliopause topology and observed heliocentric distances to different heliospheric discontinuities are discussed. It is shown that time-dependent boundary conditions are necessary to describe the heliospheric asymmetries detected by the Voyager spacecraft. We also discuss the structure of the HP, especially due to its instability and magnetic reconnection. It is demonstrated that the Rayleigh-Taylor instability of the nose of the HP creates consecutive layers of the interstellar and heliospheric plasma which are magnetically connected to different sources. This may be a possible explanation of abrupt changes in the galactic and anomalous cosmic ray fluxes observed by Voyager 1 when it was crossing the HP structure for a period of about one month in the summer of 2012. This paper also discusses the plausibility of fitting simulation results to a number of observational data sets obtained by in situ and remote measurements. The distribution of magnetic field in the vicinity of the HP is discussed in the context of Voyager measurements. We discuss the transport of energetic particles in the inner and outer heliosheath, concentrating on the anisotropic spatial diffusion diffusion tensor and the pitch-angle dependence of perpendicular diffusion and demonstrate that the latter can explain the observed pitch-angle anisotropies of both the anomalous and galactic cosmic rays in the outer heliosheath.

International Space Science Institute (ISSI) Workshop on Integrative Study of the Mean Sea Level and its Components

Because it integrates changes in several components of the climate system in response to external forcing factors and internal climate variability, sea level is one of the best indicators of global climate change.

Satellites provide the big picture.

INSIGHTS Mountain range formation p. 687 Rethinking vascular therapy for cancer p. 694 ▶ PERSPECTIVES WATER Downloaded from www.sciencemag.org on September 14, 2015 Watching water: From sky or stream? Monitoring and management of freshwater resources has long depended upon on-the-ground measurements. Satellite remote sensing has brought new complementing capabilities. In this final of three debates, Science invited arguments about the appropriate roles for, and balance between, each approach. By J. S. Famiglietti, 1, 2, 3 * A. Cazenave, 4, 5 A. Eicker , 6 J. T. Reager, 1 M. Rodell , 7 I. Velicogna 1 ,2 Satellite observations have revolutionized our understanding of hydrology, water availability, and global change, while catalyzing modern advances in weather, flood, drought, and fire prediction in ways that would not have occurred with relatively sparse POLICY ground-based measurements alone. Earth-observing satellites provide the necessary “big-picture” spatial coverage, as well as the regional-to-global understanding essential for improving predictive models and informing policy-makers, re- source managers, and the general public. Sustained investments in a robust satellite hydrology program have enabled a plethora of discoveries, along with modernization of water management, that have increased the human, economic, and water security of many nations. We now recognize distinct human- and climate-driven fingerprints on the water landscape that are dramatically changing the distribution of freshwater on Earth ( 1). Improved understanding and heightened societal aware- ness of the global extent of sea-level rise ( 2), ice sheet and glacial melt ( 3), changing rainfall patterns ( 4), declining snow cover ( 5), groundwater depletion ( 6), and the changing extremes of flooding ( 7) and drought ( 8) simply would not have occurred without satel- lite observations. As we look ahead, ongoing and near-future missions will soon provide routine global monitoring of the stocks of soil moisture ( 9), surface water ( 10), and total water storage ( 11)—which will im- prove estimates of groundwater storage changes ( 12)—and of the fluxes of precipitation ( 4) and evapotranspiration ( 13). Taken to- NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA. Department of Earth System Science, University of California, Irvine, CA, USA. 3 Department of Civil and Environmental Engineering, University of California, Irvine, CA, USA. 4 Centre National d’Etudes Spatiales–Laboratoire d’Etudes Geophysique et Oceanographique Spatiales (CNES/ LEGOS), Toulouse, France. 5 International Space Science Institute, Bern, Switzerland. 6 Institute of Geodesy and Geoinformation, University of Bonn, Germany. 7 NASA Goddard Space Flight Center, Greenbelt, MD, USA. *Corresponding author. E-mail: james.famiglietti@jpl.nasa.gov. sciencemag.org SCIENCE 14 AUGUST 2015 • VOL 349 ISSUE 6249 Published by AAAS ILLUSTRATION: DAVIDE BONAZZI Satellites provide the big picture

Foreword: A Conclusion to the ISSI Series on Astrophysical Magnetic Fields

Magnetic fields are a fundamental component of the physical world on all scales—as constituents of the electromagnetic environment of all matter. The interaction between the magnetic fields and matter is at the heart of many dynamic processes that shape astrophysical objects and their environments. Regions of space threaded by magnetic fields control or at least influence the interactions that take place between them. Observing and understanding magnetic fields and the role they play in physical processes in the solar system and beyond have been the subject of a series of Workshops and publications by the International Space Science Institute since 2008. The first three volumes covered the origin and dynamics of solar magnetism, the magnetic fields of the planets, and the magnetic field of the Earth. These were meant to constitute a trilogy of magnetic fields within the confines of the solar system. Then came the fourth volume which extended the coverage to the whole Universe, but concentrating on large-scale magnetic fields, comparable to, or smaller in magnitude than those directly measured within the solar system. The four volumes are:

Solar Coronal Plumes and the Fast Solar Wind

The spectral profiles of the coronal Ne viii line at 77 nm have different shapes in quiet-Sun regions and Coronal Holes (CHs). A single Gaussian fit of the line profile provides an adequate approximation in quiet-Sun areas, whereas, a strong shoulder on the long-wavelength side is a systematic feature in CHs. Although this has been noticed since 1999, no physical reason for the peculiar shape could be given. In an attempt to identify the cause of this peculiarity, we address three problems that could not be conclusively resolved, in a review article by a study team of the International Space Science Institute (ISSI) (Wilhelm et al. 2011): (1) The physical processes operating at the base and inside of plumes, as well as their interaction with the Solar Wind (SW). (2) The possible contribution of plume plasma to the fast SW streams. (3) The signature of the First-Ionization Potential (FIP) effect between plumes and inter-plume regions (IPRs). Before the spectroscopic peculiarities in IPRs and plumes in Polar Coronal Holes (PCHs) can be further investigated with the instrument Solar Ultraviolet Measurements of Emitted Radiation (SUMER) aboard the Solar and Heliospheric Observatory (SOHO), it is mandatory to summarize the results of the review to place the spectroscopic observations into context. Finally, a plume model is proposed that satisfactorily explains the plasma flows up and down the plume field lines and leads to the shape of the neon line in PCHs.

Giant Planet Magnetodiscs and Aurorae—An Introduction

This volume contains the reports discussed during the Workshop “Giant Planet Magnetodiscs and Aurorae” held 26–30 November 2012, at the International Space Science Institute, organised together with the Europlanet project, supported by FP7 (Grant No. 228319). Magnetodiscs are large current sheets surrounding Jupiter and Saturn (also Uranus and Neptune) that are filled with plasma principally originating in the natural satellites of these worlds. They are also solar system analogues for astrophysical discs. Magnetodiscs are special features of the fast rotating giant planets, a special feature of rotationally driven magnetospheres. Their structure is modified by variability in their plasma sources and by the solar wind. Auroral signatures in the optical and radio wavebands allow a diagnostic of these dynamical processes and enable the visualisation of these large plasma and field structures.

Atmospheric Drag, Occultation ‘N’ Ionospheric Scintillation (ADONIS) mission proposal

The Atmospheric Drag, Occultation 'N' Ionospheric Scintillation mission (ADONIS) studies the dynamics of the terrestrial thermosphere and ionosphere in dependency of solar events over a full solar cycle in Low Earth Orbit (LEO). The objectives are to investigate satellite drag with in-situ measurements and the ionospheric electron density profiles with radio occultation and scintillation measurements. A constellation of two satellites provides the possibility to gain near real-time data (NRT) about ionospheric conditions over the Arctic region where current coverage is insufficient. The mission shall also provide global high-resolution data to improve assimilative ionospheric models. The low-cost constellation can be launched using a single Vega rocket and most of the instruments are already space-proven allowing for rapid development and good reliability. From July 16 to 25, 2013, the Alpbach Summer School 2013 was organised by the Austrian Research Promotion Agency (FFG), the European Space Agency (ESA), the International Space Science Institute (ISSI) and the association of Austrian space industries Austrospace in Alpbach, Austria. During the workshop, four teams of 15 students each independently developed four different space mission proposals on the topic of "Space Weather: Science, Missions and Systems", supported by a team of tutors. The present work is based on the mission proposal that resulted from one of these teams' efforts.

The Summer School Alpbach

Sixty young, highly qualified European science and engineering students converge annually for stimulating 10 days of work in the Austrian Alps. Four teams are formed, each of which designs a space mission, which are then judged by a jury of experts. Students learn how to approach the design of a satellite mission and explore new and startling ideas supported by experts. The Summer School Alpbach enjoys more than 30 years of tradition in providing in-depth teaching on different topics of space science and space technology, featuring lectures and concentrated working sessions on mission studies in self-organised working groups. The Summer School is organised by the Austrian Research Promotion Agency (FFG) and co-sponsored by the European Space Agency (ESA), the International Space Science Institute (ISSI), and the national space authorities of its member and cooperating states.

Erratum to: Foreword: International Space Science Institute (ISSI) Workshop on the Earth’s Hydrological Cycle

On the first page of the original article one of the sentences reads: In comparison, the total amount of water vapor in the atmosphere is small; it amounts to *2.5 kg/m, or the equivalent of 25 mm water for each column of air. It should have read: In comparison, the total amount of water vapor in the atmosphere is small; it amounts to *25 kg/m, or the equivalent of 25 mm water for each column of air. Everything else in the paper remains correct.

The Science of Exoplanets and Their Systems

A scientific forum on "The Future Science of Exoplanets and Their Systems," sponsored by Europlanet and the International Space Science Institute (ISSI) and co-organized by the Center for Space and Habitability (CSH) of the University of Bern, was held during December 5 and 6, 2012, in Bern, Switzerland. It gathered 24 well-known specialists in exoplanetary, Solar System, and stellar science to discuss the future of the fast-expanding field of exoplanetary research, which now has nearly 1000 objects to analyze and compare and will develop even more quickly over the coming years. The forum discussions included a review of current observational knowledge, efforts for exoplanetary atmosphere characterization and their formation, water formation, atmospheric evolution, habitability aspects, and our understanding of how exoplanets interact with their stellar and galactic environment throughout their history. Several important and timely research areas of focus for further research efforts in the field were identified by the forum participants. These scientific topics are related to the origin and formation of water and its delivery to planetary bodies and the role of the disk in relation to planet formation, including constraints from observations as well as star-planet interaction processes and their consequences for atmosphere-magnetosphere environments, evolution, and habitability. The relevance of these research areas is outlined in this report, and possible themes for future ISSI workshops are identified that may be proposed by the international research community over the coming 2-3 years.

Cosmic Plasmas and Particle Acceleration: An Introduction

The topic of this volume, Particle Acceleration in Cosmic Plasmas, is the first in a series of three broad topics, each intended for a volume in Space Science Reviews and the Space Science Series of ISSI, that cover aspects of astrophysical plasma phenomena on all scales, from the Earth’s magnetosphere to the scale of clusters of galaxies. The other two topics cover “The Microphysics of Cosmic Plasmas” and “Structure Formation and Dynamics in Cosmic Plasmas”. The motivation for the series can be found in the conclusions of a discussion Forum held in the International Space Science Institute, Bern, Switzerland, in March 2009. The topic of the Forum was the question “Is there a future for magnetospheric research?”, originally formulated at a meeting of COSPAR’s Scientific Advisory Committee in March 2008. The discovery, exploration and detailed understanding of the Earth’s magnetosphere have been key scientific goals and the focus of significant activities in scientific space research in