Picture of the Month

The highly dynamic magnetised solar atmosphere exhibits a wealth of oscillatory magneto-hydrodynamic (MHD) waves. These MHD waves are thought to play an important role in the transport of energy to the solar chromosphere and corona since they are channeled by the magnetic fields.

Read more

Finding life on other planets is one of the ultimate goals of modern astrophysics. Prof. Dr. Svetlana Berdyugina and her team have proposed and developed a new approach for searching life on other planets. They have measured in the laboratory samples of terrestrial plants containing various biological photosynthetic pigments (biopigments, BP) and found that these biopigments modify reflected light in such a way that it becomes linearly polarized to a high degree. This means that the reflected electromagnetic wave oscillates preferably within one plane, and an external observer can see a very conspicuous signal of biopigments if the planet is observed in polarized light. The team has also measured non-biological samples like sand and rocks containing different mineral pigments. The measured data were used to model polarized and unpolarized spectra of Earth-like planets.

In contrast to biopigments, minerals do no show a very high polarization degree in the reflected light of planets and can be well distinguished from biopigments. This is an excellent news for ...

Read more

Close binary stars with late-type, solar-like components are among the most active stellar objects known. The combination of vigorous convective motions with rapid rotation promotes efficient dynamo operation, which entails a plethora of magnetic activity considerably stronger than on the Sun. Examples include extensive dark spots in the photosphere, enhanced chromospheric emission, and high-energetic flaring events in the corona. The magnetic field has a decisive influence on the structural, dynamical and thermal properties of the atmosphere of these stars. However, since even in the case of the Sun direct observations of coronal magnetic fields are difficult to accomplish, extrapolation methods are frequently used to infer them from observed magnetic field distributions in the photosphere.

We have extended the potential field source surface extrapolation technique, a basic method which was originally developed for the case of the Sun, to binary star systems to...

Read more

As of recently, the new German 1.5 m GREGOR telescope at the Observatorio del Teide (Tenerife) is fully operational. The first scientific data was taken in May of this year with hitherto unparalleled precision.

Read more

Das KIS ist Gastgeber für das 12. Solar Orbiter PHI Team Meeting. Es findet im Hotel Brugger in Titisee statt, vom 1. bis 3. Juli 2014.

Read more

At GREGOR, the largest European solar telescope, another essential instrument is now operational: the slit scanner. Up to now, the slit of the spectropolarimeter GRIS (GRegor Infrared Spectrograph) could only stare at one position on the solar surface. Therefore, only spectra in one spatial dimension could be taken.

Read more

The 11-year solar cycle has been known for centuries. During this time the activity level (measured as sunspot number) changed dramatically from the Maunder minimum (1650-1700) to the Modern maximum in mid 20th century. The extended minimum of the last solar cycle alerted solar physicists about possible long-term variations in the solar magnetic activity. While some argue that the Sun was unusually active in mid 20th century, others find it unusually inactive now. This caused speculations whether the solar activity cycle is overlaid with a long-term decline that may lead to another grand minimum in the near future. Some linear extrapolations predicted that there would be no sunspots in the next cycle. Since solar magnetic activity and space weather have a direct impact on our life, it is important to understand such variations. To this end, we compared the present cycle 24 with the previous one. We measured sunspot intensity, area, and magnetic field strength, seeking for...

Read more

In the solar subsurface layers one can observe a meridional flow which stretches from the equator to the poles. In our group we developed and applied a new helioseismic analysis method to measure the extension of the meridional flow in the deeper solar interior. The method uses the deformation of deeply penetrating solar acoustic waves due to the flow. We have analyzed 6 consecutive years of doppler velocity data with this method. The data were obtained between 2004-2010 by the Michelson Doppler Imager (MDI) on board of the Solar and Heliospheric Observatory (SoHO), a spacecraft of ESA/NASA. Figure 1 depicts a cross-section of the meridional flow measured below the solar surface between 0.82-0.97 solar radii in the radius-latitude-plane. A dashed line marks the solar surface; dashed-dotted lines mark heliographic latitudes of +/-60 degree. Positive (negative) velocities correspond to a northward (southward) directed flow. Our measurement shows a complex flow profile in the solar interior with horizontal velocities less than 50 m/s. It is composed of multiple flow cells of larger and smaller scales.

The meridional flow is present at greater depths than depicted in Figure 1, but the current analysis does not yet allow measurements of the large-scale flow component at depths beyond 126 Mm.

In Figure 2 (bottom), we show the flow component consisting of small flow cells as a function of latitude and depth below the solar surface; positive (negative) values again correspond to a northward (southward) directed flow. For this flow component we obtain significant velocities down to a depth of about 200 Mm. Hence, the result provides evidence for a deeply penetrating meridional flow that permeates the whole solar convection zone. We compared our measurement with a subsurface measurement of the small-scale flow component (Bild 2, top) published by Komm et. al. (2004). This measurement reaches from 0.5-14 Mm depth. Near the surface, both results are in good agreement. The small-scale flow cells observed already near the surface stretch deep down into the interior and change their flow direction at a depth of about 100 Mm.

References:

Schad A., Timmer J., Roth M.: "Global helioseismic evidence for a deeply penetrating meridional flow consisting of multiple flow cells", ApJL, 778, L38-L44 (2013)

Komm, R., Howe, R., Hill, F., González Hernández, I., & Toner, C., ApJ, 631, 636 (2005) ...

Read more

In collaboration with the Istituto Ricerche Solari Locarno (IRSOL) another instrument has been installed for the first time at the GREGOR telescope: ZIMPOL. First successful observations have been carried out.

The new instrument is a polarimeter for the visible wavelength range (390-700 nm) combined with the spectrograph at GREGOR. The polarimeter is based on technologies originally developed at ETH Zurich. It has been used for many years at IRSOL and is further developed in collaboration with SUPSI (University of Applied science in Locarno-Manno).

The system consists of two main components: a fast polarization modulator (composed of two ferro-electric liquid crystal modulators and two retarder plates) and a polarizer. It transforms polarization signals into modulated intensity signals. The second component is a camera system with a special masked CCD sensor. It demodulates the modulated intensity signal directly on the sensor. This concept allows a fast polarization modulation of 1 kHz, fast enough to avoid any disturbing seeing effects for the polarization measurements. Thus the polarimeter achieves a high sensitivity and is especially suited for the measurement of very small polarimetric signals.

End of October 2013 the new system has been installed at GREGOR for the first time with the goal to integrate the instrument into the other components (telescope, spectrograph and AO). Several observations have been recorded to demonstrate the performance of the instrument.

Another important point was the calibration of the measurements. Modern solar telescopes like GREGOR often have many inclined mirrors which change the polarisation state. Generally this is a difficult calibration problem. GREGOR, however, has the great advantage that there is a calibration unit installed before of the first tilted mirror. So the telescope and the polarimeter can be fully calibrated. The signals in the recorded data show that the system is already working successfully....

Read more

Das Kiepenheuer-Institut für Sonnenphysik bildet nicht nur im wissenschaftlichen Bereich Studierende aus, sondern engagiert sich auch im gewerblich-technischen Bereich als Ausbildungseinrichtung.

Insgesamt 5 Ausbildungsstellen in der Form der dualen Ausbildung sind am Kiepenheuer-Institut etabliert.

Es werden Auszubildende in den Berufsfeldern Feinmechanik (2 Auszubildende), Elektronik, Fachinformatiker / Systemintegration und Fachinformatiker / Anwendungsentwicklung ausgebildet.

Im Rahmen ihrer Ausbildung haben die Auszubildenden am KIS die Möglichkeit in einem technisch wissenschaftlichen Bereich zu lernen und hierbei an technischen Entwicklungen und Produktionen mitzuwirken, die zu den führenden im Bereich der Astrophysik zählen.

Diese Aufgabenstellung motiviert die Auszubildenden und Ausbilder, was sich nun auch im Abschneiden  unseres Fachinformatiker /Systemintegration Auszubildenden  Marco Günter, der mit einer Gesamtpunktzahl 93 von 100 Punkten seine Prüfung abschloss zeigt....

Read more