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Transcript of Rachel Howe. Why do we need to continue observing? Why ground-based? Requirements for a new...
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 VARIATIONS
Dynamics 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