Conveners
Local flux concentration: theoretical results and local helioseismology
- Serge Koutchmy (Institut d'Astrophysique de Paris CNRS & UPMC)
Local flux concentration: theoretical results and local helioseismology
- Gustavo Guerrero (Universidade Federal de Minas Gerais)
Local flux concentration: theoretical results and local helioseismology
- Dhrubaditya Mitra (NORDITA)
Local flux concentration: theoretical results and local helioseismology
- Robert Cameron (MPS)
Junwei Zhao
(Stanford University)
11/03/2015, 09:00
Through cross-correlating oscillation signals at different
locations, we are able to reconstruct how waves propagate
away from a virtual wave source inside a sunspot in the
photospheric level. Before helioseismic waves are visible
from the source inside the sunspot, a surprisingly
fast-moving wave is detected propagating along the sunspot's
radial direction from the inside to the...
Paul Cally
(Monash University)
11/03/2015, 09:40
Magnetic field dominates wave behaviour in sunspots. The
direction of the magnetic field has profound effects on mode
conversion, "travel times" (as inferred from local
helioseismology), and on wave polarization. These in turn
affect what we see when observing spots from different
orientations. I will discuss recent work at Monash on both
travel time dependence on field direction, and...
Aaron Birch
(Max Planck Institute for Solar System Research)
11/03/2015, 10:40
We have carried out a study of about one hundred emerging
sunspot regions observed by the HMI instrument. For each
active region, we measure flows by applying helioseismic
holography to time series of Doppler images and also by
applying local correlation tracking to intensity images. We
show that these two methods give very similar results in
non-magnetic regions. We find that the active...
Neal Hurlburt
(Lockheed Martin Solar & Astrophysics Laboratory)
11/03/2015, 11:20
Flows in the vicinity of sunspots are investigated, focusing
on the statistical behavior of radial and rotational
motions. We identify datasets for study using the sunspot
records captured in the Heliophysics Events Knowledgebase
(HEK) using the sunspot detection method developed under the
EGSO and SDO/FFT projects.
Jörn Warnecke
(Max-Planck-Institut für Sonnesystemforschung)
11/03/2015, 12:10
Abstract: This work presents an extensive study of the
previously discovered formation of bipolar flux
concentrations in a two-layer model. We relate the formation
process to the negative effective magnetic pressure
instability (NEMPI), which is a possible mechanism to
explain the origin of sunspots. In our simulations we use a
Cartesian domain of isothermal stratified gas which...
Petri Käpylä
(University of Helsinki)
11/03/2015, 12:30
We present preliminary results from high resolution
magneto-convection simulations where we find the formation
of flux concentrations from an initially uniform magnetic
field. We compute the effective magnetic pressure but find
that the concentrations appear also in places where it is
positive. The structures appear in roughly ten convective
turnover times and live close to a turbulent...
Alexander Kosovichev
(New Jersey Institute of Technology)
12/03/2015, 09:00
I will present results of helioseismology analysis of
subsurface flows and sound-speed structures of the largest
emerging active regions observed by Solar Dynamics Observatory.
Aneta Wisniewska
(Kiepenheuer-Institut fuer Sonnenphysik)
12/03/2015, 09:50
We present our preliminary results from multi-height
observations taken for active regions with the HELLRIDE
(HELioseismology Large Regions Interferometric Device)
Instrument at the Vacuum Tower Telescope (VTT). The goal of
our work is to study the differences between propagation of
solar acoustic waves in the case of the quiet Sun atmosphere
and the atmosphere above the active regions.
Dhrubaditya Mitra
12/03/2015, 10:40
We show, from direct numerical simulations of stratified
MHD, that bipolar structures can emerge from from dynamo
simulations. The emerged structures show intriguing
dynamical behaviour. The emergence may be attributed to the
Negative Effective Magnetic Pressure Instability (NEMPI).
Sarah Jabbari
(PhD student)
12/03/2015, 11:10
We study a system of a highly stratified turbulent plasma.
In such a system, when the magnetic Reynolds number is large
enough and there is a background field of suitable strength,
a new effect will play role in concentrating magnetic fields
such that it leads to the formation of magnetic spots and
bipolar regions. This effect is due to the fact that the
turbulent pressure is suppressed...
Igor Rogachevskii
(Ben-Gurion University of the Negev)
12/03/2015, 11:30
A review of different theories of sunspots formation is
presented. Comparisons with numerical simulations is made.
