Sodium emission from Comet Shoemaker-Levy 9 in the magnetosphere of Jupiter

On July 20, 1994, before the Q fragments of Comet Shoemaker-Levy 9 fell to Jupiter, more than 200 spectra of the Jovian features were obtained at the Crimean Astrophysical Observatory in the wavelength range 5700–7600 Å with a 26 s exposure time and a spectral resolution of 20 Å. We found a time-varying Na D line emission in the form of two components with Doppler shifts of about 30 Å. The brightest and most frequent sodium flares were detected when the Q fragments passed through the Jovian inner magnetosphere at a distance of about three the Jovian radii (3R_J) from its center, where they crossed the Io-Jupiter current tube. A frequency analysis of our data revealed a flare recurrence time scale of 1 min. We conclude that sodium was released from the cometary dust and from the surfaces of numerous cometary debris and that its amount was enough to produce the observed emission. The observed high-speed clouds of sodium atoms are assumed to have been formed through ionization, ion acceleration by the bidirectional electric fields of Alfvén waves in the Io-Jupiter current tube, and their neutralization.     

Lithium abundance in sunspots

The observations of lithium were carried out with the TST-2 telescope at CrAO on August 15–20, 2006. A sunspot model was calculated for the dates of observations. The lithium abundance in a sunspot and in the undisturbed photosphere was determined. It is log(N _Li) = 1.35 for the sunspot and log (N _Li) = 1.05 for the undisturbed photosphere.     

Physical conditions in the chromosphere of a two-ribbon solar flare accompanied by a surge: 1

We studied changes in thermodynamic parameters of the chromosphere at the initial stage of the two-ribbon solar flare accompanied by a surge that occurred on September 4, 1990. The inhomogeneous semiempirical models of the flare chromosphere and surge are constructed for four observation moments. The spectra were obtained with the ATsU-26 horizontal solar telescope of the Main Astronomical Observatory of the National Academy of Sciences of Ukraine (Terskol Peak). Photometric transections of the spectra passed through two bright kernels of one of the flare ribbons and through the surge. The comparison of the observed profiles of the line H_α in the solar active and quiet-Sun regions reveals the substantial emission in the line wings (up to 1–1.2 nm) with a residual intensity of 0.6–0.77 at the center of the line profiles. Calculations within the two-component models of the chromosphere have shown that this may be the evidence of the existence of the details (unresolved by the telescope and occupying 5–12% of the total area) with a deep heating of the chromosphere layers. A strong asymmetry of the line profiles and the shift with respect to the line profile for the quiet-Sun region are explained by peculiarities of the line-of-sight velocity distribution over the height. It is found that the motion is directed to the observer in the upper chromosphere (10–30 km/s) and from the observer in the lower chromosphere (5–20 km/s) for the larger part of the active region under study. According to the models calculated for the surge, the line-of-sight velocities reach a value of 70 km/s.     

Determination of lithium abundance in sunspots: Observations in 1973

Spectra of sunspots in the region of the lithium 6708 ? line, as well as certain CaI, AlI, FeI, YI, ScI, VI lines, were studied. The observations were performed on July 8, 1973 using a BST-2 telescope at the Crimean Astrophysical Observatory. A sunspot model was developed based on the observed profiles of CaI, AlI, FeI, YI, ScI, and VI lines. Using the developed model and observed profile of the Li 6708 ? line, the abundance of lithium was determined. The obtained result is log(N_Li) = 0.95.     

Filaments and the underlying surface from He I and H<Emphasis Type="Italic">α</Emphasis> line observations

Bright bands are observed along filaments in the He I 1083 nm line, while both bright and dark bands are observed along Hα 656.3 nm filaments. The range of brightness variations near He I filaments is 1.005–1.10 times the unperturbed brightness, with an average of 1.031 ± 0.01, while this range is 0.91–1.5 times the unperturbed brightness for Hα filaments. The physical state of the matter in these bands is investigated. Computations of the band brightness have been carried out for various chromospheric models, aimed at explaining the observed features of the bands. Two types of models are considered: with temperature or density variations in the upper chromosphere, and with temperature variations in the middle and lower chromosphere. In the first type of model, the brightness in the He I line is changed, but the Hα brightness is not. In the second type of model, only the Hα brightness is changed. Using the variations of the chromospheric parameters and both types of models, we obtained various combinations of band brightnesses in the He I line and in Hα. The brightnesses of regions were estimated by calculating the profiles of the He I and Hα lines in the corresponding models in a non-LTE approximation. A comparison of the observed and calculated quantities indicates that the enhancement in the brightness in the He I line is due to a decrease in temperature or density in the upper chromosphere (where the temperatures are about 10 000–24 000 K). The enhancement and dimming of the brightness in Hα are due to an increase or decrease of the temperature in the middle and lower chromosphere (where the temperatures are 6000–9000 K) by 800–1000 K. The dependence of the band brightness on distance from the center of the solar disk is also considered. The brightness in the He I line increases from the center to the limb by 2–4%. Computations of the center–limb brightness variaions correspond to the observed results.     

Three Periods in Asteroid 4197 Brightness Variations

In 1996, photometric observations of the near-Earth asteroid NEA 4197 (1982 TA) were performed at the Crimean Astrophysical Observatory. More than 2000 brightness measurements in the V band were made. The harmonic data analysis at a fairly high significance level revealed two close periods, P ₁= 3^h _.5372 ± 0^h _.0005 (amplitude 0 ^m _.4) and P ₂= 4^h _.367 ± 0^h _.001 (amplitude 0 ^m _.2). The third period, P ₃= 20^h _.26 ± 0^h _.05 (amplitude about 0 ^m _.15), was found at a lower significance level. The conclusion was drawn that the asteroid is a binary system. Its components rotate with the periods P ₁and P ₂, and P ₃is probably related to the orbital motion of the components. Assuming that the diameters of both components are equal to 2 km, the orbital radius equals 4.4 km.     

A method for the determination of the lithium abundance in sunspots: Observations for 2011

Sunspot spectra for LiI 6708Å lines and for several FeI and CaI lines were obtained. Observations were performed in January and in August, 2011 using the TST-2 telescope with a charge-coupled camera at the Crimean Astrophysical Observatory. The sunspot models were calculated by using the observing profiles of FeI and CaI lines. Lithium abundance was determined by using the calculated sunspot models and LiI 6708Å observed profiles; this equals log(N _Li) = 0.98 and 0.95 (in the scale logA(H) = 12.0).     

Simulation of photosphere and chromosphere of two powerful solar flares (October 28, 2003 and September 1, 1990)

The spectra of two powerful flares with approximately the same intensities in the optical region but with different spectral features and power in other regions are studied. One of them is the unique flare which occurred on October 28, 2003, importance X17.2/4B, ranking third in magnitude among the recorded flares. Another occurred on September 1, 1990, 3B importance. The flares vary in the Balmer decrement. The flare of October 28, 2003, has a ratio of I(H_β)/I(H_α) = 1.47. This is the largest value for solar flares ever observed. The flares also differ in magnitude of the D Na I lines emission: the emission of the flare of October 28, 2003, is substantially larger than that of the other flare. The chromosphere models of the flares are computed using the observed profiles of Balmer lines and D Na I lines. The satisfactory agreement of the calculated and observed profiles is obtained for the two-component models in which a hot component occupies 6% of the area. The hot component of the chromosphere model is characterized with the dense condensation available in the upper layers. For the flare of October 28, 2003, this condensation is located deeper and its substance concentration is greater than that for another flare. The H_α line intensity for the model hot component alone is approximately 30 and the continuous spectrum intensity is approximately 3% of the undisturbed level. The photosphere model is computed using the observed profiles of photosphere lines for the flare of October 28, 2003. It is found that very broad profiles of individual sigma-components of the Fe I λ 525.0 nm line may be only explained by the presence of magnetic fields having different directions. A great difference is detected between values of the magnetic field strength obtained in the splitting of sigma-components and those provided by simulation.     

Physical conditions in the chromosphere of a two-strand solar flare with ejection

Chromosphere layers of solar flares were investigated according to the observed profiles of the H_α line. A two-strand flare was observed on September 4, 1990. Spectra were obtained with the ATsU-26 solar horizontal telescope at Terskol Peak Observatory (3100 m). Spectra photometry is performed for two bright nodes of one strand of the flare. Some profiles are superposed to the ejection. The observed profiles are characterized by high emissions in the wings of the H_α line (up to 10–12 Å) under relatively low intensity in the center of H_α (r = 0.35–0.6). To explain such profile behavior we calculated flare models with two or three components. Separate components of the model correspond to unresolved details in the flare area and therefore the averaged profile is calculated. Emission in the far wings is explained by model components with deep heating of chromosphere layers. These occupy 5–12% of the total area. Noticeable emission asymmetry is explained by ray velocities of up to 70 km/s and more. The models are determined by agreement of the observed and calculated profiles. We processed several photometric profiles for seven observations. The temperature in the models with deep heating in the lower cromosphere is increased by 1000–2500 K with respect to the model with an undisturbed chromosphere VAL-C. The second feature of the observed profiles is their high asymmetry and shift with respect to the undisturbed profiles. This can be explained by the opposite motion of the material. We revealed that for the most of the profiles the line-of-sight velocities were directed to the observer in the upper chromosphere (10–100 km/s) and from the observer in the lower chromosphere (5–20 km/s).     

Photon excitation of sodium emission in Comets

We consider the possibility of the excitation of sodium resonance emission in cometary matter under solar radiation at a heliocentric distance of 5 AU, as was observed when a fragment of Comet Shoemaker-Levy 9 plunged into Jupiter. When the sodium emission is calculated, the multiple scattering in the cometary cloud is taken into account. We use a non-LTE radiative transfer code for a two-level model sodium atom. A comparison of the computed and observed Na I D emission line profiles allows the column density of the sodium atoms for specific times of observations of Comet Shoemaker-Levy 9 to be determined. The observed Na I(D₁+D₂) line profile was found to agree well with the computed profile for an optically thick sodium cloud. We calculated the column density of the sodium atoms for three comets from the observed intensity of the D₂ line emission. We also calculated the D₂/D₁ intensity ratio for various optical depths of the sodium cloud and various phase angles.