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Geophysics and Astronomy

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The scientists study the interstellar medium and star formation, stellar astrophysics, galaxy formation, planetary system, space physics, solid earth and the hydrosphere. Two significant events took place in 2011: A new Assistant Professor in Astrophysics was recruited within the newly-established tenure-track system of the University, and a “new openings” programme titled The Active Suns started as one of two such programmes in the whole University.

Astronomy and space physics

For our astronomers the telescopes of the European Southern Observatory (ESO) in Chile, the space-borne observing facilities of the European Space Agency (ESA), and the Nordic Optical Telescope (NOT) in La Palma are the key sources of data. The ESO-related research is conducted in close co-operation with the Finnish Centre for Astronomy with ESO (FINCA). By the end of 2011 five of our astronomers were FINCA employees.

In studies of interstellar medium our focus is on the early stages of the star formation process. Observations are carried out from optical to radio wavelengths using major international facilities, in particular, the ESO telescopes and various spacecraft. Data from ESA’s astrophysics missions Herschel and Planck were intensively used for studies of the Milky Way. The first results from the Planck mission were published in 2011, including a new catalogue of Galactic pre-stellar sources.

In stellar astrophysics we conduct observational and theoretical studies of stellar magnetic activity. We have access to data from two state-of-the-art spectropolarimeters: HARPS of ESO and SOFIN of NOT. Solar and stellar magnetic activity is also studied using numerical magnetohydrodynamic simulations of varying complexity. This requires the use of high-performance computing facilities (e.g., CSC - IT Center for Science). Recently, our simulations in spherical coordinates have shown cyclic dynamo action, reminiscent that of the Sun.

Numerical simulations are also used to study galaxy formation and evolution. Highlights include studies of the  formation and assembly of massive early-type galaxies at high redshifts and demonstrating that they form in two phases, with the central parts forming at very high redshifts and the outer parts being assembled at lower redshifts through minor merging of lower-mass galaxies. In addition, detailed investigations were undertaken on the role of the central supermassive black holes in regulating star formation activity in massive elliptical galaxies. 

In planetary system research our focus is on asteroids and comets as well as on small particles in regoliths and atmospheres, including the atmosphere of the Earth. In 2011 studies on electromagnetic scattering by small particles and random media composed of such particles resulted in two Ph.D theses. Astronomical observations are carried out using modern ground-based telescopes (e.g., VLT of ESO) and satellite instruments. Analysis of observations with ESA’s Moon mission SMART-1 has continued and our future spacecraft involvement includes ESA’s astrometry mission Gaia and the Mercury mission BepiColombo. We also assess the risk of near-Earth asteroid collisions and participate in the upcoming Canadian NEOSSat mission as well as in the proposed ESA near-Earth asteroid sample return mission MarcoPolo-R. Furthermore, light scattering methods are used in preparations for the Global Precipitation Measurement mission of NASA by modelling radar backscattering from winter-type precipitating particles. We also study how terrestrial dust and ice particles scatter solar radiation and quantify their direct radiative impacts.

In space physics we study the dynamics of Solar System plasmas in close co-operation with space physics research at the Finnish Meteorological Institute. Our key research questions are lift-off, propagation and geoefficiency of coronal mass ejections (CMEs), solar-wind interaction with the Earth's magnetosphere and other planetary environments, physics of shock waves and solar energetic particle acceleration. We develop state-of-the-art numerical simulations and use them to analyse observations from several ESA and NASA spacecraft. This has allowed us to reach greatly improved understanding, e.g., on the propagation of CMEs and their shocks in the solar corona and solar wind, on the response of the magnetosphere to CMEs, their shocks and their sheath regions, and on solar-wind energy transfer through the magnetopause. A highlight in 2011 was the publication by Springer/PRAXIS of the monograph “Physics of Space Storms – From the Solar System to the Earth” authored by Hannu Koskinen.

We are currently involved in three projects within EU’s 7th Framework Programme. Two projects are coordinated by our scientists: In the E-SQUID project an improved SQUID-based readout suitable for large X-ray to infrared detector arrays in space research is being developed. In the SEPServer project an integrated web-based interface to a comprehensive set of solar energetic particle data, related data on electromagnetic solar emissions and tools on analysing these data will be established. Furthermore, we participate within a consortium led by the British Antarctic Survey in the SPACECAST project to produce improved forecasting methods for space weather.

As a leading Finnish scientific satellite instrument provider we presently work intensively with a solar X-ray and particle instrument onboard ESA’s Mercury mission BepiColombo to be launched in 2014. In addition to its main task to provide background information to a UK-led X-ray instrument to determine the elemental composition of the surface of Mercury, the instrument can be used independently in studies of solar eruptions. Furthermore, we participate in the upcoming ESA missions Solar Orbiter to study the Sun from a near distance and Euclid, whose goal is study the nature of dark energy and dark matter and the evolution of galaxies up to a redshift of z~2. Furthermore, we provide instrumentation for the student satellite project Aalto-1 of the Aalto University.

Geophysics

In Solid Earth Geophysics laboratory the key subjects of research are: (i) the study of supercontinents during the geological past; (ii) testing the Geocentric Axial Dipole (GAD) hypothesis of the Earth´s magnetic field during the Precambrian; (iii) research of physical properties of meteorite impact structures and meteorites; and (iv) studies of magnetic properties of the urban dust, which contains magnetic particles composed of various heavy metals which are harmful to human health. The highlights of the achievements include (1) to show, for the first time, that the GAD hypothesis stands for the Precambrian era with minor modifications by second order zonal harmonics; (2) the proposal, based on our novel database, that the supercontinent Nuna did exist during the period 1.84-1.27 Ga ago; and (3) the revelation that the density decrease, as seen in many impact structures, is due to increase of shock induced porosity and fracture density in the rocks.  Furthermore, we were able to show that the magnetic “halos”, as often seen to surround the central melt sheets, are partly due to weakened susceptibility in the fractured target rocks and partly by shock demagnetization. The laboratory continues to develop high quality physical measurements of meteorites and impact rocks by installing several new instruments, such as the gas pycnometer, the pulse magnetizer and the Ar- and N-lines to the laboratory. One of the highlights was the recent discovery of low temperature magnetic transitions in troilite (FeS) and alabandite (MnS), which are common minerals in cometary dust and meteorites. Understanding their physical properties is important in interpretation of their parent asteroids and comet observations. While the existence of magnetic transition in troilite was confirmed, the anomalous magnetic behavior of alabandite was attributed to presence on manganese oxides.

Hydrospheric research goes into cryosphere science, hydrology and oceanography. The main field is cryosphere. In sea ice dynamics basic research is performed and field data are analysed from Arctic and subarctic seas. The 2nd edition of the widely used textbook “The Drift of Sea Ice” authored by Matti Leppäranta was published by Springer-Praxis. The coastal zone of freezing seas is examined with applications to ecology and engineering. Ice-covered boreal lakes are examined in northern Eurasia, with emphasis on the role of the ice season in the annual cycle of lake ecology, and also supraglacial lakes are studied in Antarctica. Snow research includes seasonal snow in Finland and the snow surface layer (10 m) in the Dronning Maud Land. Two scientists participated in FINNARP expedition to Dronning Maud Land in austral summer 2010/2011, based in the research station Aboa. Topics in our oceanographic research include circulation and mixing processes in the Arctic Sea, and the exchange processes between the Nordic Seas and the North Atlantic.

Highlights of research

A composite image illustrating the Coronal Mass Ejection (CME) studies of the Space Physics group. CMEs are large bursts of plasma released from the Sun into interplanetary space that can, if they hit Earth, drive severe space storms.
(a) Results of the forward modeling of a CME using the SOHO LASCO C2 coronagraph observations. (A. Isavnin)
(b) Numerical magnetohydrodynamic (MHD) model capturing the coronal dynamics related to the CME lift-off. (J. Pomoell)
c) Combined image of three CME events using SDO AIA composite image of the Sun disk and SOHO LASCO C2 (red) and C3 (blue) coronagraph observations. (A. Isavnin)
The formula summarizes the equations of MHD.
(Credit: Alexey Isavnin/Jens Pomoell/Heli Hietala)

The all-sky distribution of the cold Galactic sources detected by the Planck satellite. The objects represent the dense parts of the interstellar clouds were the formation of new stars is possible. The number of sources per area is encoded in colours from blue to red. More than 10000 objects have been detected and the list of the most secure detections was made public in January (Planck Collaboration, 2011).

Paleomagnetic reconstruction of supercontinent (Columbia) Nuna at 1.53 Ga. Data available from Laurentia (L), Baltica (B), Amazonia (Am), Siberia (S), Australia (A) and North China (NC). The ca. 1.55-1.50 Ga  rapakivi intrusions and related dykes are shown as red circles and sticks, respectively. (b) Geologically made reconstruction of the ca. 1.8-1.3 Ga "SAMBA" consisting of Laurentia-Baltica-Amazonia (see Pesonen et al., 2011).