There are phenomena on Earth whose intensity on Venus is much higher. The European spacecraft Venus Express, which is about to end its life, discovered many of them
The European spacecraft Venus Express is about to end its life soon As a meteor in Venus' atmosphere After the European Space Agency lost control of it due to running out of fuel.
The spacecraft operated for eight and a half years and yielded many insights into the closest celestial neighbor to Earth, which for some reason is discriminated against Mars in the number of missions sent to it. In this review, consisting of two parts, we will present the main findings that resulted from these eight years of research.
Explosions in the atmosphere
It recently became clear that the weather in space (there is such a thing) at the outer edge of the Earth's magnetosphere also has implications in terms of what is happening in the atmosphere of Venus. It turned out that the huge explosions observed in the Earth's magnetosphere, called hot flow anomalies, have parallels on Venus as well, except that they are so large that they can envelop the entire planet and occur several times a day. The difference between the two planets is that Venus does not have a magnetosphere to protect it from the solar wind. All this planet has is the ionosphere to protect it from this phenomenon. On Venus there is a delicate balance between the ionosphere and the solar wind (1).
ionosphere
Observations made by the Pioneer Venus spacecraft in 1978 showed that the ionosphere of Venus has two states. One state where the magnetic field lines are long and a second state where there are no long magnetic field lines. In their place are many small magnetic structures known as flux ropes. Observations made by the Venus Express in 2008-2009 revealed a third state that is also magnetic, but with giant flux ropes. In this state there are strong magnetic fields with a diameter of hundreds of kilometers. It is not clear how they were formed (2).
Pioneer Venus discovered an extremely strange phenomenon. In the biosphere there is a hole, a region in which the density is very low compared to its surroundings. For 30 years, a similar phenomenon was not observed until the entry of the Venus Express spacecraft into orbit around Venus. The spacecraft's flight path around the planet is different from that of its predecessor. He is taller. It turned out that this black hole still exists and that there are other holes, although larger that reach greater depths than thought and are probably more common than expected. When Pioneer Venor observed the phenomenon the sun was at its maximum (solar maximum) and when Venus Express observed it the sun was at its minimum (solar minimum). To understand the phenomenon one must take into account the nature of the reaction of Venus with its environment in space, where the solar wind is very dominant. The particles of wind The Sun's magnetic fields can affect charged particles and other magnetic fields they encounter on their way. Earth is protected from this by its strong magnetic field and Venus has no magnetic field. For this reason, when the solar wind reaches Venus it accumulates in the ionosphere and creates a thinner and weaker magnetic layer. than that of the earth.
The observations of Venus Express led to the assumption that these are not holes, but long cylindrical formations of low pressure that start on the ground and reach space. It appears that these are magnetic structures that cause charged particles to be pushed up from the ground like toothpaste being squeezed out of a tube. It is not clear what the nature of these magnetic structures is and how they were created(3).
the wind of the sun
The measurements made by the spacecraft shed light on the interaction between the solar wind and Venus. In one observation when the density of the solar wind was low, the ionosphere of Venus was elongated downstream and it looked like a long tail of a comet. Usually the density of the solar wind is 5-10 particles per cm1999 near the Earth's orbit and sometimes the solar wind disappears as happened in May 2010. This unusual phenomenon near the Earth has been measured quite a bit. There have been very few opportunities to explore this near Venus. Such a rare opportunity was on the 0.1rd and 0.2th of August 50, following a series of large masses thrown from the Sun's corona. The American spacecraft STEREO-B observed that the density of the solar wind near the Earth drops sharply to 150 particles per cubic meter and remains so for an entire day. Venus Express could track the interaction between the thin solar wind and Venus' ionosphere. The spacecraft's instruments showed that the density of the solar wind near Venus drops to 300 particles per cubic centimeter. When the dynamic pressure is 4 times smaller than normal pressure. It turned out that the nightside ionospheric tail no longer exists during this period of thin solar wind. The observations made in the past showed that the plasma supply at night is made by the movement of plasma along the terminator from the day side through the plasma pressure drops. The flow towards the night side with positive oxygen ions occurs at an altitude of 2011-300 km and the speed of the flow is several km per second. On August 1500, 0 this pattern was interrupted. When the spacecraft passed behind the terminator at altitudes between 4 - XNUMX, the instruments showed that the + XNUMX plasma (ionized oxygen) was moving slower than normal for this area (XNUMX).
Spirits
Ultraviolet monitoring made it possible to measure the many powerful winds surrounding Venus at the top of the clouds, 70 km above the ground. An in-depth analysis of the winds made it possible to measure long-term and daily changes (in terms of Venus), changes between one lap of Venus and the next, and cyclical changes. In low latitudes the wind moves in an east-west direction and its speed is 338 km/h. If you look from the North Pole the direction of movement is clockwise and if you look from the South Pole the direction is anti-clockwise. The same wind we mentioned reaches its peak at latitudes 40 - 50 south 367 km/h. From a latitude of 50 degrees to the south. The wind speed drops sharply. This means that the cloud-top wind takes five days to circle Venus at the equator and three days at mid-latitudes. The wind in the main block of meridians from the equator to the pole gradually increases from zero km/h at the equator to 36 km/h at 50 south latitude. At high latitudes the meridian wind gradually decreases and reaches zero km/h near the fast eye of the polar vortex.
The measurements showed significant changes in the wind speed throughout the lap of Venus. At low latitudes the changes in the main regional block increase to more than 90 km. This change corresponds to dramatic changes in the atmospheric circulation time from 3.9 days to 5.3 days. During the circulation of the atmosphere Venus. The latitude of the jet winds also changes dramatically from 38 degrees south to 57 degrees south. The most dramatic change was the steady increase in the main mass of clouds in low latitudes at altitudes from 300 km to almost 400 km above the ground, in the period between 2006 and 2013. Such a dramatic change has never been observed. Wind speed varies in the short and long term. This includes changes related to the local time of day and the sun's height above the horizon.
Explanations for changes in wind speed do not yet exist. In some places the wind speed at the equator varies from 360 to 396 km/h to less than 180 km/h in the polar regions, while in other places the wind speed is almost constant. up to latitude 40 degrees with a prominent jet stream at latitude 50 degrees south. The differences in speeds observed between successive orbits of the spacecraft in the region of the jet winds can be 100 km/h. Between the equator and 35 south latitude the speed changes about every 4.8 days similar to the high rotational speed at the equator. This cycle appears to be related to waves in the upper atmosphere. There is evidence of a smaller cyclical oscillation that occurs every Venusian year, the zonal wind speed changes cyclically by more than 72 km/h every 225 days (5).
Temperatures
The temperature on the ground is 450 degrees and the wind speed is 3-4 km/h and at the top of the clouds the temperature is 70 degrees below zero and the wind speed is 300-400 km/h. It was estimated that there is little connection between the atmosphere near the ground and the upper atmosphere at an altitude of 60-70 km. Observations made over decades have concluded that the type of connection is ocean-like between the lower atmosphere and the layer of clouds above it. The lower atmosphere is like the surface of an ocean. Ripples and many air currents below visible at the top of the clouds provide clues as to various processes and effects coming from below.
Early evidence of atmospheric waves generated by air currents just above large topographic formations was provided in 1985 by two balloons launched to Venus by two Russian spacecraft released at an altitude of 54 km above the ground and experienced tremors over the southern highlands of Aphrodita Terra . The Venus Express spacecraft provided evidence for the upward propagation of gravitational waves from the ground toward the main cloud layer. These waves can only exist in a stratified and stable atmosphere. They can be transported from the bottom up by means of convection currents or by horizontal currents passing over obstacles such as a mountain, similar in principle to creating ripples in the bottom of a river when they pass over a large rock (boulder).
The importance of gravity waves is that they can transfer energy and momentum by spreading horizontally and vertically through the atmosphere. This is a common phenomenon in the upper layers of rocky planets like Earth. Sometimes they are in the form of wave trains)), a series of waves moving in the same direction and the space between one wave and another is constant like train cars.
A report on these waves in the atmosphere of Venus was in November 2012 when an international research team used the spacecraft's radio device (radio science experiment) to find profiles of the atmosphere at heights of 40-90 km. 500 profiles were made between 2006 and July with the arrival of the spacecraft to Venus until 2011. This study allowed the calculation of differences in atmospheric pressure and temperatures at different heights and in different places above the ground. From these measurements of the upper atmosphere it is possible to learn about a possible dependence of small vertical temperature changes on the local clock and latitude and to learn about changes in individual degrees of heat and at vertical wavelengths of 1-4 km and a very large number of gravitational waves were discovered. It turned out that they are very common in latitudes 60 - 75 degrees and the most activity on the side of mountains protected from winds in the Northern Hemisphere. These findings have been confirmed in other studies of waves observed in cloud tops. In the photographs taken by the Visible Monitoring Camera. This device recognized four types of waves, long, medium short and long irregular waves. The longest ones are hundreds of kilometers long. They are narrow and the wavelength is 7-17 km. The medium waves have an irregular front, their length is more than 100 km. And the wavelength is 8-21 km. The short waves The short waves are tens of kilometers wide, hundreds of kilometers long and the wavelength is 3-16 km. The origin of the irregular waves is in disturbances at the interface between the waves. One of the conclusions they reached is that topography has a significant effect on the circulation of the atmosphere. This phenomenon has been observed in various models and this is the first time that the phenomenon has been observed practically (6).
Sources
1. "Planet sized space weather explosion at Venus" 20.2.2014
http://www.spacedaily.com/releases/2014/140220194027.html
2. "A new state of Venus's atmosphere" 27.12.2012
http://www.spacedaily.com/reports/A_New_State_Of_Venus_Atmosphere_999.html
3. "NASA research helps unravel mysteries of the Venusian atmosphere" 12.9.2014
http://www.spacedaily.com/reports/NASA_Research_Helps_Unravel_Mysteries_Of _The _Venusian_ Atmosphere_999.html
4. "The tail of Venus and weak solar wind" 1.2.2013
http://www.spacedaily.com/reports/The_Tail_Of_Venus_And_Weak_Solar_Wind_999.html
5. "Super hurricane force winds on Venus are getting stronger" 18.6.2013
http://sci.esa.int/science -e/www/object.index.cfm?fobjecid=51937
6. "Venus mountains create wave trains" 13.1.2014
http://sci.esa.int/venus – express 53597- venus -mountains- create- wave -trains/
