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Decay of sunspots

Martínez Pillet, V.

The photometric decay of sunspots is studied in some detail. Aspects related to leader vs. follower sunspot decay are presented and our current understanding of the physical mechanisms involved critically reviewed. The intrinsic instability of follower spots to form a stable sunspot cannot be understood in terms of the fluting stability as propose…

Subsurface structure of sunspots

Kosovichev, A. G.

The subsurface structure of sunspots is probed by measuring travel-time delays of acoustic waves propagating beneath the spots, and using a helioseismic inversion method to infer the internal sound-speed perturbations and mass flows. The initial results obtained from the MDI instrument on SOHO reveal under sunspots zones of the relatively low soun…

Solar irradiance variability and climate

Fröhlich, C.; Lean, J.

Since November 1978 a complete set of total solar irradiance (TSI) measurements from space is available, yielding a time series of more than 23 years. From measurements made by different space-based radiometers (HF on NIMBUS 7, ACRIM I on SMM, ACRIM II on UARS and VIRGO on SOHO) a composite record of TSI is compiled with an overall precision of or…

New radio instrumentation for the study of sunspots and starspots

White, S. M.

Much of the radio emission from the Sun and similar stars depends directly on magnetic fields for its origin. For this reason, radio emission contains important diagnostic information on solar and stellar magnetic fields. This paper reviews radio measurements of coronal magnetic fields and discusses new radio instrumentation that will exploit this…