Gottingen, Germany

The Max Planck Institute for Solar System Research is a research institute in astronomy and astrophysics located in Göttingen, Germany, where it relocated in February 2014 from the nearby village of Lindau. The exploration of the solar system is the central theme for research done at this institute.MPS is a part of the Max Planck Society, which operates 80 research facilities in Germany.Over the last five years, members of the Institute have each year published about 270 articles in international journals and books and given 360 conference presentations. Wikipedia.

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News Article | April 21, 2017

Of all the stars in the sky, you might assume the closest to the sun would be the easiest to visit. But this may not be the case. René Heller at the Max Planck Institute for Solar System Research in Göttingen, Germany, says we could reach and orbit Sirius, the brightest star in our night sky, in just 69 years. This is despite the fact that it is twice as far away as our nearest stars in the Alpha Centauri system, which would take at least 90 years to reach. A private enterprise called Breakthrough Starshot is hoping to send a fleet of small, wafer-thin spacecraft to visit Alpha Centauri and explore its tantalising planets. Previous estimates by Breakthrough Starshot have indicated they could reach Alpha Centauri in just 20 years, travelling at a fifth of the speed of light. But this estimate was calculated for a flyby mission, passing by in just a few seconds. That’s not much use if you actually want to observe anything when you’re there: the spacecraft would need to slow down. Earlier this year, Heller and independent researcher Michael Hippke showed how light from the stars themselves could be used to slow down a solar-sail powered spacecraft. That technique might put Alpha Centauri at a disadvantage. Such a mission to put the spacecraft in orbit there around the star Proxima Centauri, for example, would take around 140 years, Heller has calculated. Sirius is 8 light years away, twice as far as Alpha Centauri, but 16 times as bright, so its light would help the spacecraft both speed up and then decelerate. The results surprised Heller at first, but the maths is simple, he says. The time it takes to travel to the star system and then stay there is a function of the distance divided by the square root of the luminosity, so it would take less time to travel to Sirius compared to Alpha Centauri. The idea is “innovative and interesting”, says Avi Loeb at Harvard University. “However, the concept requires an extremely thin sail if the goal is to reach a fraction of the speed of light.” Heller and Hippke say the key to cracking this issue lies in material science. “We need a very light, solid, temperature-resistant, and highly reflective sail material that can span an area of several hundred metres squared,” says Heller. The material could possibly be based on graphene with a metamaterial coating, he says. “If this works out, then humanity can really go interstellar.”

News Article | April 18, 2017

Massive landslides, similar to those found on Earth, are occurring on the asteroid Ceres, according to a new study. The work adds to the growing evidence that Ceres retains a significant amount of water ice. Published in Nature Geoscience, the study uses data from NASA’s Dawn spacecraft to identify three different types of landslides, or flow features, on the Texas-sized asteroid. Type I are relatively round, large, and have thick “toes” at their ends. They look similar to rock glaciers and icy landslides in Earth’s arctic. Type I landslides are mostly found at high latitudes, which is also where the most ice is thought to reside near Ceres’ surface. Type II features are the most common of Ceres’ landslides and look similar to deposits left by avalanches on Earth. They are thinner and longer than Type I and found at mid-latitudes. The authors affectionately call one such Type II landslide “Bart” because of its resemblance to the elongated head of Bart Simpson from The Simpsons. Ceres’ Type III features appear to form when some of the ice melts during impact events. These landslides at low latitudes are always found coming from large-impact craters. Britney Schmidt, assistant professor at Georgia Tech and Dawn science team associate, believes it provides more proof that the asteroid’s shallow subsurface is a mixture of rock and ice. “Landslides cover more area in the poles than at the equator, but most surface processes generally don’t care about latitude,” says Schmidt, a faculty member in the School of Earth and Atmospheric Sciences. “That’s one reason why we think it’s ice affecting the flow processes. There’s no other good way to explain why the poles have huge, thick landslides; mid-latitudes have a mixture of sheeted and thick landslides; and low latitudes have just a few.” The study’s researchers were surprised at just how many landslides Ceres has in general. About 20 percent to 30 percent of craters greater than 6 miles (10 kilometers) wide have some type of landslide associated with them. Such widespread features formed by “ground ice” processes, made possible because of a mixture of rock and ice, have only been observed before on Earth and Mars. Based on the shape and distribution of landslides on Ceres, the authors estimate that the upper layers of Ceres may range from 10 percent to 50 percent ice by volume. “These landslides offer us the opportunity to understand what’s happening in the upper few kilometers of Ceres,” says Georgia Tech PhD student Heather Chilton, a coauthor of the paper. “That’s a sweet spot between information about the upper meter or so provided by the GRaND (Gamma Ray and Neutron Detector) and VIR (Visible and Infrared Spectrometer) instrument data, and the tens of kilometers-deep structure elucidated by crater studies.” “It’s just kind of fun that we see features on this small planet that remind us of those on the big planets, like Earth and Mars,” Schmidt says. “It seems more and more that Ceres is our innermost icy world.” NASA’s Science Mission Directorate in Washington, DC manages the Dawn mission for JPL. Dawn is a project of the directorate’s Discovery Program, which NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency, and Italian National Astrophysical Institute are international partners on the mission team.

Van Noort M.,Max Planck Institute for Solar System Research
Astronomy and Astrophysics | Year: 2012

Context. When inverting solar spectra, image degradation effects that are present in the data are usually approximated or not considered. Aims. We develop a data reduction method that takes these issues into account and minimizes the resulting errors. Methods. By accounting for the diffraction PSF of the telescope during the inversions, we can produce a self-consistent solution that best fits the observed data, while simultaneously requiring fewer free parameters than conventional approaches. Results. Simulations using realistic MHD data indicate that the method is stable for all resolutions, including those with pixel scales well beyond those that can be resolved with a 0.5 m telescope, such as the Hinode SOT. Application of the presented method to reduce full Stokes data from the Hinode spectro-polarimeter results in dramatically increased image contrast and an increase in the resolution of the data to the diffraction limit of the telescope in almost all Stokes and fit parameters. The resulting data allow for detecting and interpreting solar features that have so far only been observed with 1m class ground-based telescopes. Conclusions. A new inversion method was developed that allows for accurate fitting of solar spectro-polarimetric imaging data over a large field of view, while simultaneously improving the noise statistics and spatial resolution of the results significantly. © 2012 ESO.

Christensen U.R.,Max Planck Institute for Solar System Research
Icarus | Year: 2015

Ganymede's internal magnetic field is dominated by the axial dipole. The measurements by the Galileo spacecraft only place an upper limit on the quadrupole moment. Ganymede's magnetic field has the lowest ratio of quadrupole power to dipole power for all known planetary dynamos, not only at the planetary surface but possibly also at the top of the dynamo region. The dynamo operates in a fluid iron core that probably contains a significant amount of sulfur. Crystallization of the core will then proceed from the top by formation of iron snow in a layer that develops a stable compositional gradient. Remelting of the snow at the bottom of this layer enriches the underlying fluid in iron and drives compositional convection. Here we explore the consequences for the dynamo process of this scenario by numerical modeling. Convection is driven by an imposed buoyancy flux at the top of a convecting core region that is surrounded by a conducting fluid shell with a strongly stabilizing density gradient. Only horizontal flow is allowed in the outer shell. It is shown that this is a valid approximation in the case where the stabilizing density contrast in the upper shell exceeds by far the unstable density contrast in the convecting region. We vary the basic control parameters, concentrating on the regime where the magnetic field is dominantly dipolar. Compared to reference cases without an extra layer above the dynamo, we find that a stable fluid conducting layer with a thickness of 100km or larger reduces the ratio of quadrupole power R2 to dipole power R1 by a factor of at least four. With a stable outer layer R2/R1 is compatible with the Galileo observations for all tested dipolar models, whereas in the absence of such layer R2/R1 is too large or at best marginally compatible. For plausible values of the buoyancy flux the models reproduce Ganymede's observed dipole moment. A stable layer that is comparable in thickness to the unstable region is found to promote a hemispherical type of dynamo whose field in incompatible with observations. This may indicate that the snow layer in Ganymede's core has a moderate depth extent. © 2014 Elsevier Inc..

Vasyliunas V.M.,Max Planck Institute for Solar System Research
Annales Geophysicae | Year: 2012

The conventional equations of ionospheric electrodynamics, highly succesful in modeling observed phenomena on sufficiently long time scales, can be derived rigorously from the complete plasma and Maxwell's equations, provided that appropriate limits and approximations are assumed. Under the assumption that a quasi-steady-state equilibrium (neglecting local dynamical terms and considering only slow time variations of external or aeronomic-process origin) exists, the conventional equations specify how the various quantities must be related numerically. Questions about how the quantities are related causally or how the stress equilibrium is established and on what time scales are not anwered by the conventional equations but require the complete plasma and Maxwell's equations, and these lead to a picture of the underlying physical processes that can be rather different from the commonly presented intuitive or ad hoc explanations. Particular instances include the nature of the ionospheric electric current, the relation between electric field and plasma bulk flow, and the interrelationships among various quantities of neutral-wind dynamo. © Author(s) 2012.

Marsch E.,Max Planck Institute for Solar System Research
Space Science Reviews | Year: 2012

The radial evolution of the velocity distribution functions of the protons, electrons and ions, as they were measured during the Helios mission in the solar wind between 0.3 and 1.0 AU, is discussed and analysed. Emphasis is placed on the detailed plasma measurements, and on the non-thermal features of the particles and the kinetic processes they undergo in the expanding solar wind. As the plasma is multi-component and nonuniform, complexity prevails and the observed distributions exhibit, owing to their low number densities, significant deviations from local thermal equilibrium, and reveal such suprathermal particles as the strahl electrons, as well as ion beams and temperature anisotropies. The distribution functions still carry imprints of their solar boundaries that are reflected locally, but also have ample free energy driving in situ plasma instabilities which are triggered and modulated by wave-particle interactions. The ion temperatures and their anisotropies and the non-adiabatic radial evolution of the solar wind internal energy are discussed in detail. © 2010 Springer Science+Business Media B.V.

Christensen U.R.,Max Planck Institute for Solar System Research
Physics of the Earth and Planetary Interiors | Year: 2011

Self-consistent models of the dynamo process in the Earth's core have reached a state where they can be used to understand specific morphological and temporal properties of the geomagnetic field. Even though several parameters in the models are far from Earth values, systematic parameter studies resulted in scaling laws that suggest that the dynamical regime in the models is not dissimilar to that in the core dynamo. In some dynamo models the magnetic field shows a close similarity with the structure of the geomagnetic field at the core-mantle boundary and the models are used to infer the underlying flow pattern inside the core. They support the concept of convection columns aligned with the rotation axis that concentrate magnetic flux into four strong lobes near ±65° latitude, and of rising plumes at the poles that are associated with low magnetic flux and westward vortex motion in the polar cap regions. Predictions for the field strength inside Earth's core from dynamo models and inferences from observations of short-term changes of the field and changes in Earth's rotation seem to converge at values of a few milliTesla. Dynamo models support the idea that the inhomogeneous thermal structure of the lower mantle has a significant influence on the dynamo and leads to a breaking of the longitudinal symmetry in the long-term geomagnetic field. In a limited range of control parameters the models show dipole polarity reversals that agree in detail with what is known about geomagnetic reversals, although the precise reversal mechanism in the models remains an open question. © 2011 Elsevier B.V.

Peter H.,Max Planck Institute for Solar System Research
Astronomy and Astrophysics | Year: 2010

Context. The profiles of emission lines formed in the corona contain information on the dynamics and the heating of the hot plasma. Only recently has data with sufficiently high spectral resolution become available for investigating the details of the profiles of emission lines formed well above 106 K. These show enhanced emission in the line wings, which has not been understood yet. Aims. We study the underlying processes leading to asymmetric line profiles, in particular the responsible plasma flows and line broadening mechanisms in a highly filamentary and dynamic atmosphere. Methods. Line profiles of Fe XV formed at 2.5 MK acquired by the Extreme ultraviolet Imaging Spectrometer (EIS) onboard the Hinode solar space observatory are studied using multi Gaussian fits, with emphasis on the resulting line widths and Doppler shifts. Results. In the major part of the active region, the spectra are best fit by a narrow line core and a broad minor component. The latter contributes some 10% to 20% to the total emission, is about a factor of 2 broader than the core, and shows strong blueshifts of up to 50 km s -1, especially in the footpoint regions of the loops. On average, the line width increases from the footpoints to the loop top for both components. A component with high upflow speeds can be found also in small restricted areas. Conclusions. The coronal structures consist of at least two classes that are not resolved spatially but only spectroscopically and that are associated with the line core and the minor component. Because of their huge line width and strong upflows, it is proposed that the major part of the heating and the mass supply to the corona is actually located in source regions of the minor component. It might be that these are identical to type II spicules. The siphon flows and draining loops seen in the line core component are consistent with structures found in a three-dimensional magneto-hydrodynamic (3D MHD) coronal model. Despite the quite different appearance of the large active region corona and small network elements seen in transition region lines, both show similar line profile characteristics. This indicates that the same processes govern the heating and dynamics of the transition region and the corona. © 2010 ESO.

Nathues A.,Max Planck Institute for Solar System Research
Icarus | Year: 2010

Reflectance spectra in visible and near-infrared wavelengths of 97 nominal members of the Eunomia asteroid family have been obtained and analyzed. According to these investigations, 94% of the observed dynamic family members belong to the Tholen S-class, only 4% to the C-class and 2% to the M-class. The S-asteroids are believed to be " genetic" members of the Eunomia family and thus are fragments of 15 Eunomia. The fragments show different 1- and 2-μm absorption band characteristics, which are likely attributed to their place of origin within the parent body. The major volume fraction of the investigated members seems to originate from the " crust" of the parent body while the volume fraction of " mantle" material is less. Previous spectral investigations (Nathues, A., Mottola, S., Kaasalainen, M., Neukum, G. [2005], Icarus 175 (2), 452-463) of the family's main body, 15 Eunomia, revealed variations of olivine and pyroxene on a hemispherical scale. These findings, together with the conclusion that the major mineral component of 15 Eunomia and its fragments is olivine, suggest that a large fraction of the original pyroxene-enriched crust layer has been lost due to a major collision that created the asteroid family. Significant spectral evidences consistent with high concentrations of metals have not been found in the rotational resolved spectra of 15 Eunomia and in its fragments. This led to the conclusion that either a core, which consists mainly of metals, does not exist or that an eventual one has not yet been unearthed by an impact. The absence of V-type asteroids, the low number of M-types among the dynamic family members and the lack of distinct feldspar absorption features in the S-asteroid spectra suggest that the parent body of the Eunomia family was partially differentiated rather than fully differentiated. © 2010 Elsevier Inc.

Christensen U.R.,Max Planck Institute for Solar System Research
Space Science Reviews | Year: 2010

Scaling laws for planetary dynamos relate the characteristic magnetic field strength, characteristic flow velocity and other properties to primary quantities such as core size, rotation rate, electrical conductivity and heat flux. Many different scaling laws have been proposed, often relying on the assumption of a balance of Coriolis force and Lorentz force in the dynamo. Their theoretical foundation is reviewed. The advent of direct numerical simulations of planetary dynamos and the ability to perform them for a sufficiently wide range of control parameters allows to test the scaling laws. The results support a magnetic field scaling that is not based on a force balance, but on the energy flux available to balance ohmic dissipation. In its simplest form, it predicts a field strength that is independent of rotation rate and electrical conductivity and proportional to the cubic root of the available energy flux. However, rotation rate controls whether the magnetic field is dipolar or multipolar. Scaling laws for velocity, heat transfer and ohmic dissipation are also discussed. The predictions of the energy-based scaling law agree well with the observed field strength of Earth and Jupiter, but for other planets they are more difficult to test or special pleading is required to explain their field strength. The scaling law also explains the very high field strength of rapidly rotating low-mass stars, which supports its rather general validity. © 2009 The Author(s).

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