Helioseismology with Synoptic Network Observations

HELIOSEISMOLOGY WITHSYNOPTIC NETWORK OBSERVATIONS

Rachel Howe

SYNOPSIS Why do we need to continue

observing? Why ground-based? Requirements for a new network

WHY CONTINUE OBSERVING?

LONG-TERM VARIATIONSDynamics changes – rotation-rate variationsPart of the puzzle for the dynamoUseful for “preview” of activity cycle timing

LONG-TERM VARIATIONS -- DYNAMICSRotation-rate variations near the tachocline

TORSIONAL OSCILLATION (LOCAL HELIOSEISMOLOGY)

Torsional oscillation from ring-diagram analysis: MDI-GONG combo that I showed at the AGU meeting. MDI before mid-2001, GONG after. The flows are averaged in depth over 4-10 Mm. Bands of faster (or slower) rotation move toward the equator. The fast band of cycle 24 appears before there is any surface activity present. The new fast band is stronger in the northern hemisphere indicating that the activity will be stronger in this hemisphere.

Courtesy of R. Komm

Figure 2 from Meridional Circulation During the Extended Solar Minimum: Another Component of the Torsional Oscillation?I. González Hernández et al. 2010 ApJ 713 L16 doi:10.1088/2041-8205/713/1/L16

MERIDIONAL CIRCULATION VARIATION

Temporal variation of the fitted polynomial to the meridional circulation observations at a depth of 5.8 Mm. (Bottom panel symmetrized; poleward velocities positive.)

FREQUENCY SHIFTS WITH SOLAR CYCLE ACRIM (Woodard &

Noyes 1985, 1988, Gelly, Fossat & Grec 1988)

BiSON, Mark I (Palle et al. 1989, Elsworth et al. 1990)

Chaplin et al. 2007

ASPHERICITY VARIATIONS

Normalized even-a coefficients vary as Legendre decomposition of magnetic field distribution

ASPHERICITY VARIATIONS

Normalized even-a coefficients vary as Legendre decomposition of magnetic field distribution – but fit isn’t perfect; residuals correlated between GONG, MDI

LONG-TERM VARIATIONS (STRUCTURE)Localized GONG frequency shifts

WHY GROUND-BASED?

WHY GROUND-BASED?Redundancy/ease of repair -- lose one site for a few months, still get usable data

WHY GROUND-BASED? Longevity

BiSON – courtesy W. Chaplin

WHY GROUND-BASED? Redundancy

REQUIREMENTS FOR A FUTURE NETWORK

BASIC REQUIREMENTS Minimum for global: continuation

of GONG classic cadence/resolution/duty cycle

For local: > 75% duty cycle, <0.1 deg angular drift Overlap between sites for cross-

calibration Minimum 1-year overlap with

predecessor Improved peak fitting

MULTI-WAVELENGTH Work for example with AIA UV intensity

has shown how mode behavior varies through the atmosphere

COHERENCE WITH HMI V

PHASE RELATIVE TO HMI V

POWER MAPS

HMI V

HMI Ic

HMI Lc

AIA 1700

3mHz 5mHz 7mHz