The statistic of the observed auroras during the time of the so-called
Maunder-Minimum shows a regular solar cyclus and similar auroral and geomagnetic
Keywords: Maunder-Minimum, auroras, solar cycle, geomagnetic activity
Recently Letfus (2000) presents a review of
auroral data during the so-called Maunder-Minimum (1645-1715) which needs some
additional modification. His limited knowledge of international literature gives
a result which cannot be accepted in detail. Because of his interpretation of
auroral data during the so-called Maunder- Minimum some clarifications seems to
be useful. First we must remember that the Thirty-year war (1618-1648) ravaged
great parts of middle Europe, and destroyed libraries, churches, archives, and
other possible sources of scientific records. During these times the people
looked to the skies and its fearful portents such as great meteors, halos, or
remarkabie auroras. Often these remarkable, unusual events were described in
printed colour or black-white pamphlets or leaflets. These must be examined and
analyzed for interpretation of auroral statistics in this time. - Also, it must
be pointed out that the aurora and sunspots were not subjects of prime interest
for natural researchers; they had other fields of scientific interest.
In this connection we must consider the real chance to
observe an aurora in middle latitudes (54-48 N). Frorn long-term German data for
the years 1882-1966 the annual variation for middle latitude in general are well
described, and can be used for comparison for the data of other centuries.
This showed that mostly great auroras were noted with
intense colours and variable forms, these similar to the examples which have
been observed of the time but were not published in a newspaper, book or leaflet.
From the German statistics it is also clear that during low geomagnetic activity
(Kp 5) auroras can sometimes appear in these latitudes. Thus, in middle
latitudes during solar maxima, up to 15 auroras can be observed but during
decreased solar activity only a few.
With this background we can look at auroras in the
so-called Maunder minimum. Letfus, discussion was based mainly on the tables
published by Krivsky who collected data from different papers to prepare a
catalogue mostly without any examination of the vents, their description or
sources in original.
A more detailed source analysis has been presented by
Schroeder (1984, 2000) who has collected data from 1615-1715. From this a
chronology of realistic auroral data can be constructed and examined for
possible solar cycle effects (Table 1). The times with maximal and minimal
auroral reports are indicated together with years of maxima or minima in solar
activity (Table 2). This data are mostly from sporadic observation and usually
relate to the more spectular events which people described at that time. On the
other hand, it is well-known that we can conclude that the sun was active in
years of maximal auroral data and showed lower activity during other years (those
of minimal or zero auroras). The great auroras are thus indicators of the active
sun during the time of the so-called Maunder-minimum. From the available auroral
data we can conclude a) large auroras were frequently observed and described in
the period between 1645-1715, and b) these auroras can be understood as
indicators of an active sun and related geomagnetic disturbances. This must be
emphasised more clearly than Letfus has done, and these carefully checked
auroral data confirm the existence of a regular solar cycle during the so-called
M., R. S. Cecchini, M. Galli and T. Nanni, Solar activity variations in
historical aurorae records and tree radiocarbons. In: Schroeder, W. (Ed.)
Advances in Geosciences. Bremen, 28-35.
Letfus, V. (2000), Sunspot and auroral activity during Maunder minimum. Solar Phys. 197, 203-213.
Schove, D. J. (1983), Sunspot Cycles. Stroudburg and New York, Ross and Comp.
Schroeder, W. (1997), Catalogue of auroras. Bremen, Science Edition.
Schroeder, W. (2000), Changes in the interpretation of aurora. Bremen, Science Edition, 100 p.
Waldmeier, M. (1955), Ergebnisse und Probleme der Sonnenforschung. Leipzig, Akad. Verlagsgesellschaft.
Wittmann, A. (1978a), Sterne und Weltraum 12, 412.
Wittmann, A. (1978b), The sunspot cycle before the Maunder Minimum. Astron. Astrophys. 66, 93-97.
TABLE 1: Table of auroral and sunspots maxima/minima
|Sunspot Max. Epoch||Maximal Auroras||Sunspot Max. Epoch||Maximal Auroras|
|1549 (1547a)||1548f||1554 (1554+)||1552/53
|1593 (1593a)||1592/93||1600 (1598a)||1600/01??
|1604 (1604.7b)||1604||1610 (?)||1610/11
|1615 (1615.8)||?||1619 (?)||1619/20
|1626 (1626.9b)||1626||1634 (?)||1636
|1638 (1638.1b)||1639||1645 (?)||1644
|1649 (1649.2b)||1648||1655 (?)||1654
|1704 (1704.7b)||1704/05||1710 (?)||1710/11
|1715 (1715.9b)||1716||1721 (?)||1721/22
see SCHOVE (1979); b) VVITTMANN and XU's catalogue;
Maxima given with p: 11.116 years by WITTMANN/XU.
Aurora Maxima determined with 5 auroras and more.
TABLE 2: Aurora during Maunder-Minimum in Middle Europe
|Year||Number of Aurorae||Year||Number of Aurorae||Year||Number of Aurorae|
|1648||5 (6)||1671||1 (2?)||1694||?|
|1649||2||1672||1 (2?)||1695||2 (3?)|