For the first time, Russian and Italian scientists managed to establish with the help of the Venera-Express station the influence of relief on the dynamic processes of Venus at altitudes of 90-110 kilometers, an article with the results of the work was published in the journal Geophysical Research Letters.
“It became known that practically the entire gas envelope of the planet, from the surface to 85–90 kilometers, rapidly rotates along the parallels from east to west. At the upper boundary of the clouds, air currents move at a speed of about 100 m / s (360 km / h) and overtake the rotation of the planet's solid body by more than 50 times. This is the so-called super-rotation regime, which captures cloud layers in the lower troposphere and the mesosphere following it,”the researchers note.
Starting from an altitude of about 110 km (mesopause), atmospheric currents begin to move differently: from a sunflower point on the illuminated side to an antisolar point on the night side. Between them, at altitudes of 90–110 km, there is a transition layer, the dynamics of which is supposed to be inherent in both modes.
Specific glow
To find out what is happening in this area, researchers - employees of the Institute of Space Research (IKI RAS) Dmitry Gorinov, Igor Khatuntsev, Lyudmila Zasova, Alexander Tyurin and their colleague Giuseppe Piccioni from the National Institute of Astrophysics of Italy - drew attention to a specific glow at a wavelength of 1.27 microns in the infrared, which emits atomic oxygen on the night side of the planet.
As it was found out, its appearance is connected precisely with atmospheric currents. On the daytime side of Venus, under the influence of solar radiation, oxygen atoms appear, which at high altitudes "drift" to the night side. There, in the descending atmospheric flow, they go down and combine into oxygen molecules (recombine), this process is accompanied by radiation in the infrared range.
This glow was observed by the VIRTIS-M mapping spectrometer aboard the Venera Express spacecraft (European Space Agency), which entered the planet's orbit in 2006. The average height at which the radiation was born was estimated at about 97 kilometers above the surface. In addition, even then they noticed that the glow is distributed unevenly along the night side of Venus, which means that it is interesting to study the patterns of this distribution, the speed of movement of individual parts of the "pattern".
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Wind speed and direction
This was done in the new work. Dmitry Gorinov and his colleagues tracked the movement of individual bright details in the images of the Venus disk and thus got an idea of the direction and speed of the wind at altitudes of about 97 kilometers. Observational data from July 2006 to September 2008 were used. Due to the peculiarities of the Venus-Express orbit, the southern hemisphere and the equatorial part of the northern hemisphere were studied in particular detail up to approximately 20 parallel.
The picture that opened up on the received maps turned out to be very complex and asymmetrical about midnight. This means that the circulation from the side of the morning terminator (the line separating the light part of the cosmic body from the unlit one) differs from the evening one. According to VIRTIS-M data, on the "morning" side, atmospheric masses at this altitude move mainly towards the pole and towards the midnight point (eastward). On the "evening" side - also towards the midnight point (to the west), but towards the equator. These streams meet, but not at the midnight line, but a little earlier, approximately at the 22 o'clock line, where they diverge towards the pole and the equator.
Relief affects the atmosphere
But an even more interesting and important result of the work is evidence that the atmospheric circulation at such an altitude (almost 100 km) is affected by the relief of the underlying surface. Some images show that the streams seem to "flow around" invisible obstacles, which are located above the topographic elevations of the planet's surface.
And although the Venus-Express data is not enough to confidently speak about the relationship between the relief and atmospheric currents at an altitude of about 100 km, the researchers tried to study in detail the movements of some bright regions, suggesting that they are associated with high mountains, in particular, with the Phoebe region (Phoebe Regio). If this assumption is correct, then we can say that the bright areas serve as a kind of "indicator" of heights, taking into account possible displacements.
The Venera-Express automatic interplanetary station (European Space Agency) was launched on November 9, 2005 from the Baikonur cosmodrome using a Soyuz launch vehicle with a Fregat upper stage. The device entered the first elongated orbit around Venus on April 11, 2006. In February 2015, the device entered the Venusian atmosphere, but its data processing continues.
Specialists from IKI RAS took part in the development, manufacture and testing of two scientific instruments of the orbiter: a universal spectrometer and a high-resolution spectrometer SPICAV / SOIR and a planetary Fourier spectrometer PFS (made in Italy with the participation of Russia).
