M1-H2: Magnetic Activity

Science Goals and Approaches

Chairs:

Abbett/Hoeksema/Komm

Overall goal of today’s session:

• To bring together theorists and modelers, observers, and helioseismologists to foster collaboration, identify scientific challenges, and determine how HMI data products can be best used to address these challenges.

• To do this in an informal, workshop style atmosphere (participate!!)

HMI science objectives directly relevant to M1:

• Understand the formation and structure of long-lived complexes of solar activity (active longitudes)

– What is the relationship between active longitudes and large-scale circulation patterns deep in the CZ?

– Are there systematic large-scale variations in cs deep in the interior below these complexes?

– How are the formation of these regions related to flux emergence, meridional circulation, and flux transport to high latitudes?

– Can we understand irradiance variations around these complexes?

• Theoretical / computational tools– Global models of the interior extending down to the overshoot layer; flux

transport models, coupled radiative MHD models of the upper CZ and atmosphere.

HMI science objectives directly relevant to M1:

• Understand the evolution of active region magnetic fields

– Can we accurately track the sub-surface evolution of ARs, and if so, how do standard theoretical and computational models compare to the observed behavior?

– Do ARs show signs of disconnection of magnetic flux? What is the physics of AR decay? When do ARs lose their sub-surface connection? Is there a systematic change in flow patterns below ARs during this dynamic disconnection?

– What is the dynamic, energetic and magnetic connection between AR fields below the surface, those observed at the surface, and those inferred from observations of the corona?

– What is the physics of flux cancellation? Can we reliably detect the signatures of flux emergence, submergence, and cancellation?

• Theoretical / computational tools– Local AR-scale MHD models of the interior, surface layers, and corona; static

extrapolations of the magnetic field in the corona; flux transport models; realistic radiation MHD models of the upper CZ and low atmosphere

HMI science objectives directly relevant to M1:

• Understand the formation and dynamic evolution of sunspots

– What is the relationship between flows and flux concentrations in sunspots; between vortex flows, magnetic twist and coronal activity; between the Evershed effect and deeper flow patterns?

– What is the magnetic connectivity between photospheric magnetic fields in and around sunspots and the overlying atmosphere and low corona?

– Can we predict the onset and subsequent lifetime of a sunspot?– What is the effect of magnetic field and temperature perturbations on

sound speed images? *

• Theoretical / computational tools– Local AR-scale MHD models of the interior, surface layers, and corona;

static extrapolations of the magnetic field in the corona; large-scale (simplified) radiative MHD models of the upper CZ and low atmosphere

* Can we determine well-defined hare-and-hound exercises between compressible MHD models and specific inversion techniques?

HMI science objectives directly relevant to M1:

• Understand the physics of highly-sheared structures and δ–type sunspots

– Is there a signature in the flow pattern of an emerging δ-spot that would allow us to understand the physics and morphology of the underlying structure?

– What is the origin of the magnetic twist?

– Can we understand in a quantitative way the relationship between the evolving, twisted sub-surface structure and the observed photospheric shear, the energization of the atmosphere, and the resulting topological changes in the corona?

• Theoretical / computational tools– AR-scale MHD models of the interior, surface layers, and corona; static

extrapolations of the magnetic field in the corona; large-scale (simplified) radiative MHD models of the upper CZ and low atmosphere.

HMI science objectives directly relevant to M1:

• Understand the physics of flux emergence at both large (AR) and small scales

– Do we understand signatures in the sub-surface flow pattern well enough to allow for the reliable prediction of an emerging AR?

– How does emerging magnetic flux interact with the pre-existing magnetic field of the corona? Can we make predictions of eruptive or transient events based on a physical understanding of this interaction?

– Can we characterize the emergence and cancellation of magnetic flux at small scales in terms of idealized emergence, submergence, or diffusive processes? How is the energy balance of the atmosphere affected by the Joule heating of small, concentrated magnetic elements? How many observed emergence/cancellation events are simply due to instrumental effects?

• Theoretical / computational tools– MHD models (both idealized and realistic, over small and large, AR-scale

spatial scales) that incorporate sub-surface layers, low-atmosphere and corona into a single domain; static extrapolations of the magnetic field in the corona.

The plan for this session:

• Common threads among the M1 HMI scientific goals:– Understanding the dynamic, energetic, and magnetic connectivity

between sub-surface fields and flows and the solar atmosphere (over both large and small spatial scales).

– Using observations of sub-surface and surface magnetic fields and flows (along with atmospheric emission) to constrain theoretical models of active region formation and evolution

• Progress so far (theoretical and observational):– invited speakers:

• Mats Carlsson: will discuss progress/challenges in realistically modeling the CZ below the visible surface and low atmosphere (20 min)

• Doug Braun: will discuss progress/challenges using helioseismology to probe magnetic structures (20 min)

• Neal Hurlburt: Linking models and observations

• Tom Berger: High resolution photospheric observations

• Brian Welsch: Inferring surface flows from vector magnetograms

The Near Future:

• Where do we go from here to make real progress on the (many!) stated M1 HMI scientific goals and objectives?

• Where should we concentrate our effort?

• What technical challenges do we need to address in order to make real progress on the science questions?

– Should we form working groups?

– Share data/resources?

– Pursue additional funding for collaborative projects?

– Schedule follow-up meetings/splinter groups?

Sub-surface signatures of flux emergence: