[2] It is widely known that the observed profiles of coronal lines almost always are wider than one would expect if their widths were determined only by thermal motions of the emitting ions. This "excess'' is usually explained by the presence of nonthermal velocities in the corona.
[3] Chae et al. [1998]
studied long observations of 17 lines of
various ions ( l= 625-1551 Å). The temperature of formation of
these lines (from
104 K to
2 
106 K) covers a large height range
from the chromosphere to the upper layers of the transition region
and coronal layers.
Chae et al. [1998]
found that the nonthermal
velocities
x increase with an increase of
T reaching a maximum of
~30 km s-1 at
T = 3 105 K and decrease to
~20 km s-1 in the
corona.
Delone et al. [2003]
collected data on 18 publications
confirming this result.
[4] The increase in the nonthermal velocity
x with an increase in
the temperature in the transition region agrees with theoretical
predictions. For example, it was demonstrated by
Mariska et al. [1978]
considering propagation of Alfvén or sonic waves without
dissipation. However, the decrease of
x with
T in the region of
coronal temperatures
log Te 
(5.8-6.4 ) is not understandable
especially taking into account that at further increase of the
temperature ( log Te >6.4 ) an increase in
x is observed again
[Hara and Ichimoto, 1999;
Harra-Murnion et al., 1999].
Possible this
increase is related to the fact that the temperature and nonthermal
velocity are higher in active regions than in the quiet corona
[Delone et al., 2003;
Dere and Mason, 1993].
[5] In this paper we analyze the observations of nonthermal velocities in quiet corona, in coronal holes (CH), and in the regions adjacent to quiet prominences. The results that we obtained during the total solar eclipses in 1968, 1981, and 1999, and also the results of noneclipse observations in the visual, IR, and far UV regions carried out both on the ground and in space (using publications of various authors) are used. The relation of nonthermal velocities to characteristics of the magnetic field is also considered.
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