Physical conditions in the infrared at 1.5 microns, including maximum magnetic field strength and temperature, have been observed spectroscopically in 1391 sunspots 1990 to 2009 (1). We emphasize the quantitative difference between our IR sunspot measurements and the visible light results from most solar magnetographs employed world-wide. The latter are compromised by scattered light and measure flux, not field strength. A lower limit of ~1800 Gauss is required to form spot umbra.
The umbral maximum field strength has declined over the above interval, perhaps because spots have on average diminished in size. The present condition of solar activity minimum has more spotless days than since the 1910s (2). The Cheshire Cat
behavior is related to magnetic surface fields often appearing without accompanying dark spots.
Sunspots recently are behaving like a Cheshire Cat: the smile is there (magnetic fields) but the body is missing (no dark markings). We are unsure about past cycles but at present sunspots, with their usual umbrae and penumbrae, are failing to materialize.
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