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[7] On 23 March 1974 a coronal formation in the vicinity of a long-living prominence was observed at the coronograph of the Sakramento Peak observatory in the Fe ion lines 5303 Å, 6374 Å, 7059 Å, and 7892 Å [Tsubaki, 1975]. The spectrograph slit was positioned in parallel to the solar limb. At all cuts passing the prominence, a local minimum of the intensity of the coronal lines and Doppler temperature TD corresponding to the prominence position were observed. The value of TD was determined from
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The electron temperature value was determined from the ratio of the intensities of the lines l 7059/l 5303. Usually, an equality of ionization and electron temperatures is taken for the coronal plasma. Using this assumption the values of x averaged over cuts parallel to the limb are calculated from the value of TD = T+x2m/2k. The value of the nonthermal velocity varies (depending on the cut number) within the limits from 6 to 16 km s-1, the mean value of x being 13 km s-1.
[8] We can assume with some stretch that this value characterizes nonthermal velocities in the cavity surrounding the quiet prominence. Actually, these estimates are contaminated by the contribution from the quiet corona with different weight for different cuts.
[9] For the cut closest to the limb this contribution is minimal. For this cut x= 6 km s-1. According to Delone et al. [2003] the mean value of x for the quiet corona in the temperature region 6.0< log Te <6.4 is 18 km s -1. We see that the nonthermal velocities in the cavity surrounding a quiet prominence are less than in the quiet corona.
[10] We reconsidered the results of our observations of solar
eclipses and obtained a confirmation to the conclusions discussed
above. Observations during eclipses were carried out at installations
using Fabry-Perot etalons and narrow interference filters as
premonochromators. Using the interferogram of the corona in the
l = 5303 Å line obtained by
Delone and Makarova [1975]
during the
1968 eclipse, we measured 26 profiles around a quiet prominence.
The mean Doppler half width in this region is
DlD= 0.604 Å.
At the
corona temperature of
2 
106 K
the turbulent velocity in the
vicinity of the quiet prominence is 24 km s-1.
Far from the
prominence we obtained
DlD = 0.720 Å
and, respectively, the mean
calculated velocity
x = 32 km s
-1. The line profiles above the
southern pole at altitude
90'' above the limb had larger Doppler half
widths (averaged
DlD = 0.948 Å)
and turbulent velocity ( x = 50 km s-1 ).
Using the interferograms obtained in the
l = 5303 Å line during
the 1981 eclipse
[Delone et al., [1988],
we obtained the nonthermal velocity around a
quiet prominence
x by 25% less than in other coronal regions.
[11] During the 11 August 1999 eclipse, two quiet prominences
were observed. In the eastern region according to the Solar
Geophysical Data, there were two small coronal holes located close
to the limb on the disk. This provided a chance to compare the
nonthermal velocities obtained from the 5303 Å line half widths for
all studied coronal structures (CH, coronal cavity around the quiet
prominence, and quiet corona) in the same system. Assuming in all
formations that
T = 2 106 K,
we obtain in the vicinity of the quiet
prominences
x = 14.4 km s-1.
In quiet (undisturbed) region of the
corona
x = 20 km s-1 and in CH
x = 28 km s-1.
It is known from a
series of publications that the temperature in a coronal hole is lower
than the temperature of quiet corona. Therefore the turbulent
velocity in CH should have been even higher than the temperature
determined with the same
T =2 106 K for all regions. If one
assumes the temperature in a coronal hole
T =1.3 106 K
[Tu et al., 1998],
the nonthermal velocity in the CH would be
x = 31 km s-1.
Apparently, in 1968
[Delone and Makarova, 1975]
a coronal hole
also existed over the southern pole. That is why the Doppler half
widths in this place of the corona were higher than in the adjacent
regions.
[12] Observations on board Solar Ultraviolet Measurements of
Emitted Radiation (SUMER) Solar and Heliospheric Observatory
(SOHO) during several months in 1996-1997 in the lines: Mg IX
(706 Å and 750 Å) and Si VIII (1440 Å and 1445 Å) near the
southern and northern poles
of the Sun over coronal holes showed
that the electron temperature along plumes
Te < 0.8 106 K,
whereas in interplume lanes
Te < (0.75 - 0.88) 106 K
[Wilhelm et al., 1998].
Typical velocities obtained from Doppler half widths of
the line were
VD 
43 km s-1 within the plumes and
VD 55 km s-1 in
the interplume regions.
Wilhelm et al. [1998]
noted that the
assumption on the ionization equilibrium provided by collisions
(and so the equality
Te = Ti ) apparently is not fulfilled within a CH.
This is emphasized also by some other authors on the basis of
observations. On this basis,
Wilhelm et al. [1998]
did not try to
separate the line half width to the thermal and turbulent
components. The values presented above are the total velocities.
However, if one assumes that
Ti is equal to the commonly accepted
temperature of formation of the lines ( log Ti( Mg XI) = 5.95 and
log Ti( Si IX) = 5.99 ),
then on the basis of the data of
Wilhelm et al. [1998]
one can calculate the values of the nonthermal velocities in
coronal holes. The values of
x vary from 30 to 60 km s-1. The
average value
x = 45 km s-1, which is higher than in the ambient
corona.
[13] According to numerous publications dedicated to studying of
nonthermal velocities in coronal holes, the value of
x increases with
height. For example, according to the data by
Banerjee et al. [1998]
based on SUMER SOHO measurements in the line Si VIII
( l =1445.75 Å) and the assumption on homogeneous temperature
( T 106 K) in CH, the turbulent velocities are
x = 27 km s
-1 at an altitude
of
27'' over the limb and
x = 46 km s-1 at an altitude of
250''. The
nonthermal velocities are higher in the interplume regions and
higher than in quiet corona.
[14] Using the observations at Norikura coronograph in the
x =6374 Å line conducted on 3 November 1998 by the CCD matrix in
the vicinity of the north pole of the Sun in a large coronal hole and
adjacent quiet corona during 6.3 hours,
Raju et al. [2000]
obtained
that the nonthermal velocities within CH and quiet corona lie in the
limits from 14 to 36 km s-1 and from 10 to 30 km s-1, respectively.
The average values of
x are 24 km s-1 in CH and 15 km s-1 in quiet
corona. The temperatures are about
1.08 106 K in CH and
1.2 106 K in quiet corona.
[15] The corona images in the lines l = 171 Å (Fe IX, Fe X) and l = 195 Å (Fe XII) obtained at the Extreme Ultraviolet Imaging Telescope (EUIT) SOHO were used to draw temperature charts of the corona for the moments of observations at the Norikura coronograph in the l = 6374 Å. The temperature of formation of the UV lines of Fe ions is about 106 K, that is the same as the temperature of formation of the red line.
[16] Using the profiles of the lines of Si VIII (1446 Å) and Fe X,
Fe XI, and Fe XII in the range of
l 1242-1467 Å, observed on
board the Skylab spacecraft (the spatial resolution
2'' 60'' ),
Doschek and Feldman [1977]
obtained
x = 18.3 and 22 km s-1 in the
quiet region and coronal hole, respectively. The temperature was
taken the same both for CH and quiet region:
T 1 106 (Si VIII)
to
1.7 106 (Fe XII) K.
[17] Using the observations at Sakramento Peak observatory in
the 6374 Å line carried out in September 1992 in the CH near the
southern pole,
Hassler and Moran [1994]
obtained that the
nonthermal velocities are varying in the range from 40 to 60 km s
-1 with an increase of the distance over the limb (up to
r = 1.16 R
).
Thus the turbulent velocities in a coronal cavity around quiet
prominence are lower than in the ambient quiet corona, whereas the
velocities in CH are higher than in the quiet corona.
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