Bibcode
Claverie, A.; Isaak, G. R.; McLeod, C. P.; van der Raay, H. B.; Roca-Cortés, T.
Referencia bibliográfica
Solar Physics, Volume 82, Issue 1-2, pp. 233-234
Advertised on:
1
1983
Revista
Número de citas
2
Número de citas referidas
1
Descripción
An analysis of 28 contiguous days of whole disk observations of the
solar surface by means of optical resonant scattering in the K 769.9 nm
line, taken at the Teide Observatory at Izana during July-August 1980,
have thus far yielded two significant facts. Firstly when the results of
an iterative sine-wave fitting procedure are considered in the period
range 2-3 h, although the expected daily harmonics corresponding to 1/8,
1/10, 1/11, and 1/12 of a day are clearly seen the l/9th contribution is
significantly absent. It is suggested that this results from an
interference between a signal of 160 min (1/9th of a day) with the daily
harmonic. It is further pointed out that the observatories at which the
160 min oscillation has been seen, Crimea, Pic du Midi, and Stanford are
all separated by integral numbers of 160 min, and thus the phase of the
160 min oscillation relative to the daily observation window is
constant. However, the Teide Observatory is situated at a half integral
number of 160 min periods relative to the others. Thus when constructive
interference exist at the first three sites destructive interference
will exist at the latter. It is thus concluded that the non-existence of
a peak corresponding to the 1/9th harmonic of a day in the sine-wave fit
data is strong indirect evidence for the existence of the 160 min
signal. An analysis of those same data in the 5 min region has revealed
the now well established pattern of discrete frequencies and with the
increased resolution obtainable from 28 contiguous days of data, clearly
showed the existence of splitting by rotational effects. In all 33
discrete lines were considered in the frequency range 2.4-3.85 mHz,
which could be divided up into 3 groups, each of 11 lines, corresponding
to the l = 0, l = 1, and l= 2 modes. This definitive classification was
possible as the lines are split into (2l + 1) components yielding easily
identifiable singlets, triplets and quintuplets. This first observation
of the rotational splitting of solar oscillations gave the further
information that the splitting of 0.75 ± 0.10 μHz indicated
that the solar interior is rotating more rapidly than the observable
surface (uniform rotation would yield a splitting of 0.4 μHz). A
comparison of the widths of the individual peaks, with the intrinsic
resolution of the data string (˜ 1/T where T = length of the data
string), showed that these were consistent with a high Q value
oscillation, a fact which is further confirmed by the very existence of
singlets triplets and quintuplets in the data. The exact value of the
speed of internal rotation of the Sun can only be deduced from these
data by a model dependent calculation. The simplest of these would
suggest that if the core were almost equal to the solar diameter then it
is rotating twice as fast as the surface, whereas if the core were only
15% of the solar diameter, it would be rotating at 9 times the surface
rate.