Secular variation of the aurora for the past 500 years
- Boston College, Chestnut Hill, MA (United States)
Direct observations of the Sun exist only since about 1700. Understanding of long-term solar variability thus depends on proxy data, such as visual auroral observations, measurements of magnetic activity, and the radiocarbon record. These also give information on the interaction between the solar wind, interplanetary field, and terrestrial magnetosphere, as well as, for the radiocarbon record, heliospheric conditions. This paper uses a data base of visual auroral observations for a period of about 500 years, from 1450 to 1948, comprising about 45,000 observations, in addition to the well-known sunspot series and the magnetic activity index [ital aa], from 1868 to 1990. The secular variation of the aurora is examined and compared to sunspot data and magnetic activity data. Blackman-Tukey power spectra are used to determine periodicities. The study confirms the variability of the periodicities in frequency and amplitude. The 11.1-year cycle disappears during the Mounder minimum and at the end of the eighteenth and beginning of the nineteenth century. While the 11.1-year period is normally strongly dominant for sunspots, other shorter periods become important for auroras and magnetic activity. Prolonged solar activity minima are clearly evident. In addition to the known Sporer, Mounder, Dalton, and 1901-1913 minima, a previously unrecognized minimum about 1765 is clearly evident in the data. Comparison of the depth of these minima shows that the Dalton minimum may rival the Mounder minimum in importance. Combining the polar data base with that of mid-latitudes provides a globally comprehensive historical record of auroral occurrence. The data provide confirmation of the anticorrelation of auroral occurrence in the polar regions with sunspot activity. The data provide a basis for understanding the variation over time of the general magnetic field of the Sun, in particular the polar field. 59 refs., 29 figs.
- OSTI ID:
- 6076466
- Journal Information:
- Reviews of Geophysics (1985); (United States), Journal Name: Reviews of Geophysics (1985); (United States) Vol. 30:4; ISSN REGEEP; ISSN 8755-1209
- Country of Publication:
- United States
- Language:
- English
Similar Records
Auroral changes during the eighteenth and nineteenth centuries and their implications for the solar wind and the long-term variation of sunspot activity
Magnetic activity and solar wind velocity at and preceding solar minimum for the past 500 years
Related Subjects
540000 -- Environment-- (1990-)
661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
AURORAL OVAL
COMPILED DATA
CRYOSPHERE
DATA
DOCUMENT TYPES
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ENVIRONMENTAL EFFECTS
HISTORICAL ASPECTS
INFORMATION
MAGNETIC FIELDS
MAIN SEQUENCE STARS
NUMERICAL DATA
POLAR REGIONS
REVIEWS
SOLAR ACTIVITY
SOLAR WIND
STARS
SUN
VARIATIONS