HR: 1340h
AN: SH13A-1109    [Abstracts]
TI: Origins of the Wolf Sunspot Number Series: Geomagnetic Underpinning
AU: Cliver, E W
EM: edward.cliver@hanscom.af.mil
AF: Space Vehicles Directorate, Air Force Research Laboratory, 29 Randolph Rd, Hanscom AFB, MA 01731-3010, United States
AU: * Svalgaard, L
EM: leif@leif.org
AF: Easy Tool Kit, Inc., 6927 Lawler Ridge, Houston, TX 770055, United States
AB: The Wolf or International sunspot number (SSN) series is based on the work of Swiss astronomer Rudolf Wolf (1816-1893). Following the discovery of the sunspot cycle by Schwabe in 1843, Wolf culled sunspot counts from journals and observatory reports and combined them with his own observations to produce a SSN series that extended from 1700-1893. Thereafter the SSN record has been maintained by the Zurich Observatory and, since 1981, by the Royal Observatory of Belgium. The 1700-1893 SSN record constructed by Wolf has not been modified since his death. Here we show that Wolf's SSNs were not based solely on reports of sunspots but were calibrated by reference to geomagnetic range observations which closely track the sunspot number. Nor were these corrections small; for example Wolf multiplied the long series (1749-1796) of sunspot counts obtained by Staudacher by factors of 2.0 and 1.25, in turn, to obtain the numbers in use today. It is not surprising then that a competing SSN series obtained by Hoyt and Schatten based on group sunspot numbers is different, generally lower than that of Wolf. Comparison of the International number with current magnetic range observations indicates that, as Wolf found, the magnetic range (specifically, the average annual Y-component of mid-latitude stations) can be used as an independent check on the validity and stability of the SSN series. Moreover, the geomagnetic range series, which in itself is a long-term proxy of solar EUV emission, can be used to resolve discrepancies between the Wolf and Group SSN series during the 19th century.
DE: 7536 Solar activity cycle (2162)
DE: 7537 Solar and stellar variability (1650)
DE: 7549 Ultraviolet emissions
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting