Fine structure of convective motions in the solar photosphere
The granulation brightnesses and convective velocities in the solar photosphere between the levels of formation of the continuum radiation and the temperature minimum are examined. The properties of the brightness and velocity are analysed in a sixteen-column model. Four sorts of motions are most ty...
Збережено в:
| Опубліковано в: : | Кинематика и физика небесных тел |
|---|---|
| Дата: | 2005 |
| Автор: | |
| Формат: | Стаття |
| Мова: | Англійська |
| Опубліковано: |
Головна астрономічна обсерваторія НАН України
2005
|
| Теми: | |
| Онлайн доступ: | https://nasplib.isofts.kiev.ua/handle/123456789/79619 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Fine structure of convective motions in the solar photosphere / R.I. Kostik // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 134-137. — Бібліогр.: 2 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860253797221138432 |
|---|---|
| author | Kostik, R.I. |
| author_facet | Kostik, R.I. |
| citation_txt | Fine structure of convective motions in the solar photosphere / R.I. Kostik // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 134-137. — Бібліогр.: 2 назв. — англ. |
| collection | DSpace DC |
| container_title | Кинематика и физика небесных тел |
| description | The granulation brightnesses and convective velocities in the solar photosphere between the levels of formation of the continuum radiation and the temperature minimum are examined. The properties of the brightness and velocity are analysed in a sixteen-column model. Four sorts of motions are most typical and efficient. In the first two, only the sign of the relative contrast of the material changes, which occurs, on the average, at a height of 270 km. In the last two motions, both the sign of the contrast and the direction of the motions are reversed near ~350 km. The convective motions maintain their column structure throughout the photosphere, right to the temperature minimum.
|
| first_indexed | 2025-12-07T18:46:37Z |
| format | Article |
| fulltext |
FINE STRUCTURE OF CONVECTIVE MOTIONS
IN THE SOLAR PHOTOSPHERE
R. I. Kostik
Main Astronomical Observatory, NAS of Ukraine
27 Akademika Zabolotnoho Str., 03680 Kyiv, Ukraine
e-mail: kostik@mao.kiev.ua
The granulation brightnesses and convective velocities in the solar photosphere between the levels of
formation of the continuum radiation and the temperature minimum are examined. The properties
of the brightness and velocity are analysed in a sixteen-column model. Four sorts of motions are
most typical and efficient. In the first two, only the sign of the relative contrast of the material
changes, which occurs, on the average, at a height of 270 km. In the last two motions, both the sign
of the contrast and the direction of the motions are reversed near ∼350 km. The convective motions
maintain their column structure throughout the photosphere, right to the temperature minimum.
INTRODUCTION
Numerous researchers studied intensities and velocities of motions in the photosphere, using various instruments
and applying various data-processing techniques and interpretations. In all these studies the complex intensities
and velocities of the motions were analysed with the help of a very simple two-column model. Here, we consider
more complicated sixteen-column model. Our study is based on the data obtained with high spatial and
temporal resolutions.
OBSERVATIONAL DATA
We used spectrograms with high spatial (0.5′′) and temporal (9 s) resolutions obtained in 1996 and 2001 on
the German Vacuum Tower Telescope (VTT) in Izana (Tenerife, Spain). Spectral observations of the centre
of the solar disc were carried out in an unperturbed region. A CCD camera with 1024×1024 pixels connected
in pairs was used. The spatial resolution of a single pair-connected pixel was 0.174′′. The entrance slit of
the spectrograph cut off an area of 0.38′′×98′′ on the solar disc. The spectra were recorded for a single point on
the solar disc. For the observations in 1996, we chose the Fe i λ 532.418 nm line, for which we obtained 31 min
recordings. The observations in 2001 were carried out with two cameras, which recorded 158 min of data for
the Fe i λ 639.361 nm and Fe ii λ 523.462 nm lines. After the usual preliminary spectral data reduction, we
determined the fluctuations in the intensities and velocities of all three lines for each position along the spectro-
graph slit and for each moment in time at 11 heights in the solar atmosphere using “lambda-meter” technique
discussed in detail in [2]. The spatial and temporal variations in the intensities and velocities are due to
convective and wave motions. To separate these different types of variations, we constructed a diagnostic
diagram that presents the power as a function of the temporal and spatial frequencies. Our further analysis
deals only with the convective components. We took motions toward the observer to be positive.
RESULTS OF OBSERVATIONS
If we assume that relatively hot or cool material at two heights H = 10 km and H = 500 km can move both
upward and downward, we find 16 types of convective motions, shown schematically at the bottom of Fig. 1.
Ascending material is denoted by a plus sign and descending material by a minus sign. We also used plus
and minus signs to denote material whose temperature is higher or lower than the average temperature for
a given height. It turns out that all 16 types of convective motions are indeed observed in convective columns
on the Sun. The upper plot in Fig. 1 shows the number of cases corresponding to each of 16 convective motions,
while the second and third plots from the top show the average absolute values of the velocity and contrast
at H = 10 km. The fourth plot in Fig. 1 shows a parameter that we have called the “efficiency”, and that
is the product of five quantities: the number of cases for each type of convective motions, their velocity and
intensity with respect to the average values at H = 10 km and the same two quantities for H = 500 km. This
efficiency varies widely, from nearly zero to almost 30%.
c© R. I. Kostik, 2004
134
Figure 1. Motions in the solar atmosphere according to the 16-column model. The upper plot shows the number of
cases corresponding to each of 16 types of convective motions. The second and third plots from above show the average
absolute values of the velocity Vc and contrast Ic for the motions at H = 10 km. The signs of Ic and Vc are shown in
the diagram at the bottom of the figure. The fourth plot shows the “efficiency” of the motions, which is the product
of five quantities: the number of cases, the velocity and contrast at H = 10 km, and the velocity and contrast at
H = 500 km
135
Figure 2. The heights at which ascending material that is hot near the continuum height becomes comparatively cool
as a function of continuum velocity (a) and continuum intensity (b). The heights at which descending material that is
hot at the temperature minimum becomes comparatively cool as a function of continuum velocity (c) and continuum
intensity (d). The heights separating hot ascending material and cool descending material near the continuum height as
a function of continuum velocity (e) and continuum intensity (f). The heights separating cool descending material and
hot ascending material near the continuum as a function of continuum velocity (g) and continuum intensity (h)
136
Four types of motions are most efficient. In two of them, the material changes only the sign of its relative
contrast, while both the sign of the contrast and the direction of the motion change with height in two others.
In detail, these four motions are the following:
• material that is hot at the continuum height and cool at the temperature minimum ascending at all heights
in the photosphere (motion 14, with an efficiency of 18%);
• material that is hot at H = 500 km and cool at H = 10 km descending at all heights (motion 10, 28%);
• hot material ascending at the continuum height and cool material descending at the temperature minimum
(motion 8, 15%);
• cool material at H = 10 km descending and hot material at H = 500 km ascending (motion 7, 13%).
The total efficiency of these four motions is 74%. Thus, we can understand that two-column models for
the solar photosphere with hot ascending (motion 1) and cool descending (motion 2) materials cannot explain
the observed asymmetry and shifts of the Fraunhofer lines, since the total efficiency of these motions does not
exceed 10%. At the same time, the semiempirical four-column model (see [1]), which admits both upward and
downward motions of cool and hot materials, can successfully explain almost all features of the fine structure
of the absorption lines observed in the solar spectrum, and has predicted some features of the fine structure of
the Fraunhofer lines that have been verified by observations.
Let us consider in detail these four most efficient motions. Figure 2 (left panels) presents heights where
the material changes the sign of its relative contrast in convective columns with motions 14 and 10. We can see
in Fig. 2a and Fig. 2b that the height where ascending (at all heights) material that is hot, near the continuum
height becomes cool (motion 14), depends only slightly on the velocity and contrast in the continuum.
On the average, this height is H14 = 280±105 km. This is also true for descending material; namely, the height
where material that is hot, near the temperature minimum becomes cool is almost independent of both velocity
and contrast in the continuum. The contrast sign reversals occur, on the average, at H10 = 260 ± 100 km.
Figure 2 (right panels) presents the heights in columns with motions 8 and 7, in which there is a sign reversal
of both the contrast of the material and the velocity of the convective motions. In contrast to the previous
case, the corresponding heights depend significantly on the velocity at the continuum height and, in a less
degree, on the contrast in the continuum. Figure 2e shows that the higher the velocity of ascending hot
material is, the larger is the height of the sign reversals for the contrast and direction of motion. This height
is H8 = 360 ± 130 km, on the average. We would expect this behaviour based on general reasoning. However,
it is difficult to understand the behaviour in Fig. 2f: the lower is the contrast of the granule in the continuum,
the larger is the height for the sign reversals of both the direction of motion and the relative contrast of
the material. Figures 2g and 2h show the heights of layers separating cool descending material and hot ascending
material near the continuum height. These heights depend on velocity at the continuum height, and are virtually
independent of the contrast in the continuum.
CONCLUSIONS
There are various combinations of the direction of motion and relative brightness of materials in the solar
photosphere. We have analysed 16 cases and shown that four motions are most typical and “efficient”. In the first
two cases, the material reverses only the sign of its relative contrast at the mean height H = 270 km. In the last
two cases, both the sign of the contrast and the direction of the motions are reversed near the height H = 350 km.
Our study shows that the convective motions maintain their column structure in the lower photosphere right
to the height of the temperature minimum.
Acknowledgements. The author are grateful to N. Shchukina and E. Khomenko for providing me with the ob-
servational data. This work was partially supported by the Fundamental Research State Fund of the Ministry
of Ukraine for Education and Science (project No. 02.07/00044) and INTAS (project 00–00084).
[1] Kostyk R. I. Asymmetry of Fraunhofer lines and structure of the solar photosphere // Sov. Astron.–1985.–29.–
P. 65–76.
[2] Stebbins R. T., Goode P. R. Waves in the solar photosphere // Solar Phys.–1987.–110.–P. 237–253.
137
|
| id | nasplib_isofts_kiev_ua-123456789-79619 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0233-7665 |
| language | English |
| last_indexed | 2025-12-07T18:46:37Z |
| publishDate | 2005 |
| publisher | Головна астрономічна обсерваторія НАН України |
| record_format | dspace |
| spelling | Kostik, R.I. 2015-04-03T15:51:44Z 2015-04-03T15:51:44Z 2005 Fine structure of convective motions in the solar photosphere / R.I. Kostik // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 134-137. — Бібліогр.: 2 назв. — англ. 0233-7665 https://nasplib.isofts.kiev.ua/handle/123456789/79619 The granulation brightnesses and convective velocities in the solar photosphere between the levels of formation of the continuum radiation and the temperature minimum are examined. The properties of the brightness and velocity are analysed in a sixteen-column model. Four sorts of motions are most typical and efficient. In the first two, only the sign of the relative contrast of the material changes, which occurs, on the average, at a height of 270 km. In the last two motions, both the sign of the contrast and the direction of the motions are reversed near ~350 km. The convective motions maintain their column structure throughout the photosphere, right to the temperature minimum. The author are grateful to N. Shchukina and E. Khomenko for providing me with the observational data. This work was partially supported by the Fundamental Research State Fund of the Ministry of Ukraine for Education and Science (project No. 02.07/00044) and INTAS (project 00–00084). en Головна астрономічна обсерваторія НАН України Кинематика и физика небесных тел MS2: Physics of Solar Atmosphere Fine structure of convective motions in the solar photosphere Article published earlier |
| spellingShingle | Fine structure of convective motions in the solar photosphere Kostik, R.I. MS2: Physics of Solar Atmosphere |
| title | Fine structure of convective motions in the solar photosphere |
| title_full | Fine structure of convective motions in the solar photosphere |
| title_fullStr | Fine structure of convective motions in the solar photosphere |
| title_full_unstemmed | Fine structure of convective motions in the solar photosphere |
| title_short | Fine structure of convective motions in the solar photosphere |
| title_sort | fine structure of convective motions in the solar photosphere |
| topic | MS2: Physics of Solar Atmosphere |
| topic_facet | MS2: Physics of Solar Atmosphere |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79619 |
| work_keys_str_mv | AT kostikri finestructureofconvectivemotionsinthesolarphotosphere |