Picture of the Month

The Schauinsland observatory is used not only for solar observations: In 2013, an additional 14" Maksutov-Cassegrain telescope was installed that is used for night-time observations. It has a parallactical mount and is located in the old refractor tower. The telescope is connected to a GoTo software which allows the observer to easily point at different objects.

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NOAA 12192 is the identification number of one of the largest regions of strong magnetic activity seen in the current solar cycle 24, which started back in January 2008. The NOAA 12192 active region appeared on the solar disc on 17 October 2014, harbouring several large sunspots visible even to the naked eye. The size of the active region was gigantic, with an area extending over 2750 millionths of the visible solar hemisphere (MHS). The largest umbral diameter reached up to 22000 km, almost twice as big as the diameter of Earth. By 27 October 2014, NOAA 12192 ranked 33rd in the list of active region sizes since 1874.

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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.

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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 ...

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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...

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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.

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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.

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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.

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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...

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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) ...

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