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Collection of talks
KIS Colloquium Free Conference is closed
Conference is closed
KIS.Colloquium
Hosted by Markus Roth
Affiliation Thüringer Landessternwarte Tautenburg
Freiburg, Germany
22.02.2016 - 27.02.2017

Organizing institutions

Kiepenheuer-Institut für Sonnenphysik

Main category Natural Sciences (Astrophysics and Astrononmy)
Conference/Workshop objectives

The astrophysicsal colloquium of the Kiepenheuer-Institut für Sonnenphysik usually takes place on Thursdays at 11:30 if not stated otherwise.

 

Local organizing committee

Markus Roth

Scientific organizing committee (SOC)

Markus Roth

Sessions
  • Colloquium
Programme
Invited speakers

Speakers in 2016:

Roland Gredel

Maud Langlois

Mathieu Ossendrijver

Johny Setiawan

Irina Kitiashvili

 

Important dates
Registration and payment information
Conference venue Freiburg, Germany
Hotel information

We are happy to support all speakers in the KIS Colloquium in finding accommodation in a hotel nearby the institute.

Travel information
There are no uploaded videos yet.
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robertus erdelyi

Session: Colloquium

1214 views
Date of upload:
20.04.2016
Co-author:
Korsos, M., Gyenge, N., Erdelyi, R.
Abstract:
The most probable sites of flare onset are the regions of high horizontal magnetic led gradients in ARs. Flare and CME forecast methods are based on magnetograms. Our objective is a new type of measure for the description of non-potentiality by using the detailed Debrecen sunspot data catalogue. This catalogue enables us to follow the evolution of the internal magnetic con guration of the ARs in high spatial and temporal resolution. Next, our aim is to carry out a detailed statistical analysis of the photospheric cursors of pre-flare and pre-CME dynamics of a large sample of sunspot groups observed by SOHO/MDI and SDO/AIA to further develop, improve and validate the prediction method developed by Korsos et al. [2015b,a]. To make a leap forward in Space Weather forecast, we will generalise our forecast method, by applying it to the Interface Region and low corona in 3D, in order to identify the optimum height for flare/CME lift-o ff prediction in the solar atmosphere. Here, we expect to considerably increase the forecast capability, with having massive practical implications in our high-tech-driven world. Speci cally, we aim (i) to investigate the pre-flare/CME dynamics and the related physical processes in the 3D solar atmosphere by constructing the magnetic topology above ARs (see Figure 4), and (ii) to track their temporal evolution by applying WGM and the shear and twist motion of opposite polarity of sunspots before flare and CME. We tested the idea by investigating AR 11158. The active region produced M6.6 energetic flare on 13/02/2011 at 17:28 and X2.2 flare on 15/02/2011 at 01:44. We track the temporal evolutionWGM, distance and net flux at various heights. We demonstrate that the starting time of the converging phase changes as function of height. We found that at about 1 Mm level the converging starts much earlier than at the photosphere or at other heights. If we are able to identify the optimum height in the solar atmosphere for flare/CME lift-off then may considerably increase the forecast time. This would be a signi cant progress.
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Saskia Hekker

Session: Colloquium

990 views
Date of upload:
05.06.2016
Co-author:
Abstract:
Asteroseismology — the study of stellar interiors through their global oscillations — has been revolutionised with the launch of dedicated space missions. The CoRoT and Kepler satellites perform(ed) high precision photometric measurements of tens to hundreds of thousands of stars with the aim to detect both stellar oscillations and planets. In this talk I will present the main breakthroughs with respect to solar-like oscillators — stars that have convective outer layers in which oscillations are stochastically excited.
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Paul Rajaguru

Session: Colloquium

1022 views
Date of upload:
06.06.2016
Co-author:
Abstract:
After reviewing the well established observational results on solar meridional flows in the near surface layers, I discuss recent time-distance helioseismic measurements on the deep structure of the circulation. I also discuss the limitations of such analyses due to noise and large systematics of unknown origins. Finally, I discuss implications for theoretical/numerical models of meridional circulation as well as for those which use it in modeling the solar dynamo.
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Volker Bothmer

Session: Colloquium

995 views
Date of upload:
05.07.2016
Co-author:
Abstract:
Fast coronal mass ejections (CMEs) are the prime source of space storms and their associated space weather effects. Over the past decades, a variety of solar and heliospheric space missions, such as SOHO, STEREO, SDO or ACE have provided unprecedented remote sensing and in-situ observations of CMEs. The analysis of multipoint space observations has led to a new understanding of their 3D topology. Understanding the 3D topology and interplanetary evolution of CMEs is of key importance to help establish reliable space weather forecasts and to develop methods with which hazardous effects on our modern day technological infrastructure can be mitigated. In my presentation I will summarize the state-of-the-art understanding of CMEs and its scientific and societal benefits.
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Matthias Johannes Schubert

Session: Colloquium

1233 views
Date of upload:
22.09.2016
Co-author:
Abstract:
Context: Our Sun is an unique high-energy plasma physics laboratory, which can be studied with exceptional spatial and temporal resolution. Using dedicated telescopes, it is possible to verify and enhance our knowledge about aspects of modern physics unaccessible to any experiments on earth. State of the art magneto-hydrodynamic simulations of the solar photosphere have a spatial resolution of 6km at a wavelength $\lambda$ = 500nm and model the dynamics of solar pores, sunspots and coronal mass ejections. The theoretical models have to be evaluated in different atmospheric heights with highly resolving spectro-polarimetric observations. Therefore, the international solar community started to build a 4 m-class telescope. Furthermore an imaging spectro-polarimeter for visible light is developed. This is an unique tool to access highly dynamical, small scale processes on the solar photosphere and chromosphere for ground breaking scientific research. Method: Since a similar, yet smaller instrument is operated at the Vacuum-Tower- Telescope on the Canarian Island Tenerife, it was used as a test bed to characterize realistic instrumental induced errors. This defined the relevant parameters of the filter instrument for scientific research which were modelled: the etalons surface micro roughness, a varying reflectivity, plate figure errors, the photon noise, the relative aperture and the distance of the individual etalons to a defined focal plane of the telescope. Micro roughness, reflectivity and plate figure errors will shift and broaden the observed line profiles. Thus an instrumental error is induced in calculated Doppler velocity and full width half maximum maps of the solar surface. Additionally, the magnetic measurement sensitivity is limited by noise . Therefore, simulated observations of the quiet Sun were performed for two instrument configurations to study their measurement capabilities. One instrument is simulated with three etalons and a spectral bandwidth of $\delta\ambda$ = 3.8pm and the other with two etalons and $\delta\ambda$ = 6.1pm (spectral bandwidth is given for wavelength $\lambda$=630 nm). To study the effect of a defocused mounting of the etalons on the optical axis, the simulations were carried out for the instruments theoretical in a focal plane and at specified distances.
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Marian Martinez Gonzalez

Session: Colloquium

986 views
Date of upload:
18.11.2016
Co-author:
Abstract:
Solar prominences are clouds of cold and dense chromospheric plasma suspended in the very tenuous ambient corona. They are called prominences when they are seen at the limb and scatter light from the underlying atmosphere, and filaments when they are observed as absorption features above the solar disk. They are supported against gravity and isolated from the hot environment by the magnetic field. Though maintaining such structures and governing their evolution, little is known about the actual magnetic field topology (and strength) of solar prominences. One of the reasons is that measuring full spectropolarimetry of such tenuous structures is extremely challenging and very few data sets are available. Also, the subsequent interpretation of the polarimetric signatures (in the Hanle-Zeeman regime) is not straightforward. In this talk I will review the present state of knowledge on solar prominence magnetic fields. Since the late 80s, it is well known that the corona of rapidly rotating stars also hold clouds of dense material, probing that the corona of late-type stars is a complex medium with non-homogeneous density and temperature distributions. These clouds were first reported by Collier Cameron & Robinson in 1995 and they are commonly called ``stellar prominences'', since their physical properties present some similarities with solar prominences. Though much more observationally challenging, stellar prominences have been detected and characterised on several fast rotators. In this talk, I will briefly review this research field and show very preliminar analysis of the prominences on a dwarf M star (HK Aqr). I will show that large amplitude oscillations similar to those reported in the Sun are also present in the prominences of HK Aqr.
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Travis Metcalfe

Session: Colloquium

1078 views
Date of upload:
03.03.2017
Co-author:
Ricky Egeland, Jennifer van Saders
Abstract:
Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation-age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro~2). We have compiled chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation-age relations. We use these data along with a sample of well-characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.
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Jorge Sanchez Almeida

Session: Colloquium

919 views
Date of upload:
28.04.2017
Co-author:
Abstract:
Galaxies are born in the very early Universe. Depending on their properties (mainly on their mass and environment), most of them are still forming today. Galaxies are systems that transform gas into stars, and they are still doing so despite the fact that the galaxies exhaust their gas reservoir in a very short time-scale. The question arises as to where the gas that keep them alive comes from. The answer is clear from the point of view of the numerical simulations of galaxy formation: metal-poor gas is continuously accreted from the cosmic web filaments (e.g., Dekel+09). However, the hypothetical cosmological gas inflow has been extremely difficult to detect observationally (e.g., SA+14). The talk will describe the theoretical framework that explains the formation of galaxies in a cosmological context, the key role played by the accretion of cosmic web gas, and the evidence that we have of the process at work. (Some of this evidence has been gathered by our group; e.g., SA+15.) In a sense, the situation is similar the 'quiet revolution' that happened in Solar Physics around the year 2000, when the quiet sun magnetic fields were theoretically predicted (Cattaneo 99) but when observations only hinted at their existence (e.g., SA+ 11).
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Alexei Pevtsov

Session: Colloquium

1357 views
Date of upload:
04.05.2017
Co-author:
Abstract:
It is not uncommon to see the references to recent (cycle 24) solar activity as “exceptionally low” or as an “extended long-term decline”. But how would we know that the current level of activity is unusual if we did not have historical data taken over many cycles? How would we know, for example, what are the strongest field strengths in sunspots and how they change with time or that the amplitude of next cycle could be defined by the strength of polar field in previous cycle if we did not have long-term records of solar activity? Truly, synoptic observations feed future research to solve issues that may not be identified at the time when data are acquired. In my talk, I will discuss the current state of long-term synoptic programs and present results of my recent projects on reconstructing the solar activity using historical data.
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Arnold Hanslmeier

Session: Colloquium

1318 views
Date of upload:
13.07.2017
Co-author:
Carina Fian, Evencio Mediavilla
Abstract:
We describe principles of gravitational lensing, macrolensing and microlensing. The physics of Quasars is shortly discussed and then quasar macro- and microlensing by galaxies is described. Own observations consist of photometric observations and spectroscopic observations. We show how from the lensing parameters quantities like the Hubble constant, the mass of the lensing galaxy, the size of the accretion disc and the mass of the supermassive black hole at the center of the quasar can be derived.
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Nobumitsu Yokoi

Session: Colloquium

998 views
Date of upload:
11.08.2017
Co-author:
Abstract:
Turbulent helicity (velocity–vorticity correlation) represents breaking mirror-symmetry in turbulence. With the aid of an analytical statistical theory for inhomogeneous turbulence, an expression of the Reynolds stress in non-mirror-symmetric turbulence is obtained from the fundamental hydrodynamic equations. It is shown that the helicity gradient enters the Reynolds stress as the coupling coefficient of the mean absolute vorticity Ω* (system rotation and mean relative vorticity). Using this analytical expression, a turbulence model (helicity model) is constructed, which is validated by direct numerical simulations (DNS) of rotating turbulence with helical forcing. This result implies that inhomogeneous turbulent helicity coupled with the mean absolute vorticity Ω* may induce a global flow in the direction of Ω*. This effect is generic in rotating turbulence with inhomogeneous helicity, and is expected to be relevant to several astro- and geo-physical flows, which include cyclones and solar convective motion. The angular-momentum transport in the solar convection zone is discussed from the view point of this helicity effect.
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Michael Thompson

Session: Colloquium

864 views
Date of upload:
25.06.2018
Co-author:
Abstract:
Helioseismology has been spectacularly successful at revealing many aspects of the Sun's internal structure and dynamics. What then are the new challenges and opportunities for the field? In this talk I will briefly review the current state of helioseismology, and will then discuss science opportunities and future directions for observations from the ground and space.
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Stefaan Poedts

Session: Colloquium

862 views
Date of upload:
21.09.2018
Co-author:
Abstract:
Solar Coronal Mass Ejections (CMEs) are large-scale eruptive events in which large amounts of plasma (up to 1013-1016 g) and magnetic field are expelled into interplanetary space at very high velocities (typ. 450 km/s, but up to 3000 km/s). When sampled in situ by a spacecraft in the interplanetary medium, they are termed Interplanetary CMEs (ICMEs). They are nowadays considered to be the major drivers of “space weather” and the associated geomagnetic activity. The detectable space weather effects on Earth appear in a broad spectrum of time and length scales and have various harmful effects for human health and for our technologies on which we are ever more dependent. Severe conditions in space can hinder or damage satellite operations as well as communication and navigation systems and can even cause power grid outages leading to a variety of socio-economic losses. CME models) and its integration in the ESA Virtual Space Weather Modeling Centre and coupling to other models (effects, magnetosphere, etc.), and focus on the latest parameter studies of the effects of the cone CME model shape and the inclusion of an internal magnetic structure of the CMEs and the potential of these features to fit the in-situ wind parameter data at L1 and other locations. References [1] J. Pomoell and S. Poedts: "EUHFORIA: EUropean Heliospheric FORecasting Information Asset", J. of Space Weather and Space Climate, Accepted, in press (2018).
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Luis Eduardo Vieira

Session: Colloquium

4368 views
Date of upload:
15.11.2018
Co-author:
Abstract:
The solar electromagnetic and corpuscular emissions are strongly modulated by the evolution of the magnetic structure of the solar atmosphere, which is imprinted in the solar surface. The evolution of the magnetic structure leads to gradual changes in the solar activity (space climate) as well as violent events (space weather) that affect the whole Heliosphere. In particular, the solar output affects the ionized and neutral components of the Earth’s atmosphere that have a direct impact on human activities from agriculture to high-technological systems. The solar magnetism is driven by the energy transport from the inner layers to the solar atmosphere. Although systematic observations have revealed several features related to the evolution of solar activity, there is not a complete explanation of the physical processes that lead to solar activity cyclic variability and its long-term changes. Here we present a brief description of the development of a magnetograph and visible-light imager instrument to study the solar dynamo processes through observations of the solar surface magnetic field distribution. The instrument will provide measurements of the vector magnetic field and the line-of-sight velocity in the solar photosphere. As the magnetic field anchored at the solar surface produces most of the structures and energetic events in the upper solar atmosphere and significantly influences the Heliosphere, the development of this instrument plays an essential role in reaching the scientific goals of The Atmospheric and Space Science Coordination (CEA) at the Brazilian National Institute for Space Research (INPE). In particular, the INPE’s Space Weather program will benefit most from the development of this technology. Additionally, we expect that this project will be the starting point to establish a robust research program on Solar System Research at INPE. The proposed instrument has been designed to operate on the ground, but with a conceptual design flexible enough to be adapted to work on a balloon and space-based platforms. In this way, our main aim is acquiring know-how progressively to build state-of-art solar vector magnetograph and visible-light imagers for space-based platforms to contribute to the efforts of the solar-terrestrial physics community to address the main unanswered questions on how our nearby Star works.
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