Sunspot Formation: Theory, Simulations and Observations

Session

Penumbra formation. Magnetic effects, umbral dots, light bridges, etc.

Session 7

12 Mar 2015, 14:30

Oskar Klein Auditorium (Albanova, Stockholm)

Conveners

Penumbra formation. Magnetic effects, umbral dots, light bridges, etc.

• Aaron Birch (Max Planck Institute for Solar System Research)

Penumbra formation. Magnetic effects, umbral dots, light bridges, etc.

• Aaron Birch (Max Planck Institute for Solar System Research)

Penumbra formation. Magnetic effects, umbral dots, light bridges, etc.

• Illa Losada (Nordita & Stockholm University)

Penumbra formation. Magnetic effects, umbral dots, light bridges, etc.

• Hannah Schunker (Max Planck Institute for Solar System Research)

308. Clustering of Flares and Clustering of Sunspots

Alan Title (Stanford Lockheed Institute)

12/03/2015, 14:30

In this study we tested for groups of flares (flare clusters) in which successive flares occur within a fixed time - the linking window. The data set used is the flare waiting times provided by the X-ray flare detectors on the Geostationary Operational Environmental Satellites (GOES). The study was limited to flares of magnitude C5 and greater obtained during cycle 23. While many flares...

297. Penumbra formation

Rolf Schlichenmaier (Kiepenheuer-Institut fuer Sonnenphysik)

12/03/2015, 16:45

The various ways of energy transport in radiatively driven magnetoconvection determine the structure of sunspots. At first glance, sunspots are composed of a dark umbra and a brighter penumbra. The darkness of the umbra is readily explained by the tension of the magnetic field lines that supresses convection. Yet, it is clear that even in the darkest part of the umbra, radiative and...

298. Peeking at small-scale convection in sunspot penumbrae with high-resolution spectropolarimetry

Sara Esteban Pozuelo (Instituto de Astrofísica de Andalucía (IAA-CSIC))

12/03/2015, 17:25

We study the evolution of small-scale convective motions in a sunspot located close to disk center using a temporal sequence of high resolution observations acquired at the SST. We calculate Dopplergrams in photospheric layers and filter them for subsonic oscillations. Lateral downflows appear everywhere in the center side penumbra as small, weak, redshifted patches next to blueshifted...

302. On the penumbra - Evershed flow - moat connection: A modeling perspective

Matthias Rempel (HAO/NCAR)

13/03/2015, 09:00

We present a series of high-resolution sunspot simulations that cover a time span of up to 100 hours. The simulation domain covers the upper 18 Mm of the convection zone and we use open boundaries that do not maintain the initial field structure against decay driven by convective motions. We consider two setups: A sunspot simulation with penumbra, a "naked-spot" simulation in which we...

319. On sunspots and penumbrae

Åke Nordlund

13/03/2015, 09:40

Discussion of factors that influence the structure of (model an real) sunspots and their penumbrae

301. Physical properties of a sunspot chromosphere with umbral flashes

Jaime de la Cruz Rodriguez (Institute for Solar Physics, Stockholm University)

13/03/2015, 10:00

We present new high-resolution spectro-polarimetric Ca II 8542 observations of umbral flashes in sunspots. At nearly 0.18", and spanning about one hour of continuous observation, this is the most detailed dataset published thus far. Our study involves non-LTE inversions to quantify temperatures, mass flows and the full magnetic field vector geometry.

320. SST observations and interpretations of penumbral fine structure

Göran Scharmer (Kungliga Vetenskapsakademien)

13/03/2015, 10:50

During the last ten years, our understanding of sunspot fine structure and heating through convection has improved dramatically thanks to a combination of numerical MHD simulations and high-resolution imaging and spectropolarimetric data. I will summarise some of the recent observations, with emphasis on data from the Swedish 1-m Solar Telescope (SST), and how these and simple...

303. Observational Diagnostics of Magnetoconvection in a Sunspot Umbra

Nikola Vitas (Instituto de Astrofísica de Canarias)

13/03/2015, 11:10

The three-dimensional simulation of magnetoconvection in a sunspot umbra by V\"ogler and Sch\"ussler (2006) was an important step towards more realistic sunspot and active-region simulations. In spite of the idealized boundary conditions in this simulation (it describes a periodic umbra-like atmosphere isolated from the surrounding quiet sun) it predicted the typical coffee-bean shape...

299. Single sunspot structures and dynamics from the SOT (Hinode) and AIA (SDO) observations

Serge Koutchmy (Institut d'Astrophysique de Paris CNRS & UPMC)

13/03/2015, 11:30

The free of seeing effects high resolution images of a single sunspot observed near the centre of the Sun with the SOT (Hinode) are accuratly deconvolved. The new PSF deduced from the transit of Venus and from the extreme limb data takes into account both the diffraction of origin smearing and the stray light from the optics. It considerably improved the details near the diffraction...