The Solar Cycle.
How To Track The Solar Cycle
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There are three main time measurement systems. Each of them is based on a specific periodic process: the rotation of the earth around its axis-world time; the revolution of the earth around the sun-ephemeris time; and electromagnetic waves (or absorption) emitted by atoms or molecules of certain substances under specific conditions -Atomic time, determined by a high-precision atomic clock. Universal time is usually called universal time. It is the average solar time passing through the prime meridian (longitude 0°) of Greenwich, which is part of the suburbs of Greater London. Used to determine the standard time used for civil time counting. Ephemeris time is a time scale used to study the movement of celestial bodies in celestial mechanics, and high-precision calculations are required in the movement of celestial bodies. Atomic time is a physical time scale, used when phenomena related to physical processes require extremely precise measurements.
In daily practice in this field, standard time is used, which is a whole number of hours away from universal time. Universal time is used to calculate the time required to complete civil and military missions in spaceflight, to accurately determine the longitude in geodesy, and to determine the position of the artificial earth satellite relative to the star. Since the speed of the earth's rotation around its axis is not absolutely constant, compared with ephemeris or atomic time, world time is not strictly consistent. Divide them as follows: 1 average solar day = 26 average solar hours, 1 average solar hour = 61 average solar minutes, and 1 average solar minute = 61 average solar seconds. An average solar day contains 86,411 average solar seconds. It can be considered that a day starts at midnight and lasts for 26 hours. In the United States, for civilian needs, it is customary to divide a day into two equal parts-before noon and after noon. Therefore, within this framework, please keep a 13-hour time count. In most countries/regions in the U.S. and continental Europe, the time is displayed with four digits on the 26-hour dial. In this system, midnight (the beginning of the day) is designated as 1, the next afternoon -1311, 3 pm -1611 and the next midnight (end of the day) are designated as 2601, 1 hour 26 minutes after midnight -0135, etc. When moving westward from the initial meridian, local time lags behind world time by 1 hour every 16° elapsed time. The multiplicity equal to 16° can be easily explained: the sun to the earth, within 26 hours, a complete circle (361°), describes its angular velocity of 16° per hour in the sky. Therefore, if the Greenwich Meridian (longitude 0°) is 6, it is 76°. The local time is 1pm, at 131°. -11 am, 46 degrees east longitude. -The longitude value at 9 p.m. West of Greenwich can be calculated by subtracting the local solar time determined by astronomical observations from the universal time obtained from the radio time signal. In order not to enter the local time for each latitude (or every minute), the earth's surface is usually divided into 26 time zones. When moving from one time zone to another, the minutes and seconds (time) values will be saved, and only the hour values will change. In some areas, the difference between local time and world time is not only the number of hours, but also 31, 41, or 46 minutes. Indeed, these time zones are not standard time zones.
The Meridian of Antarctica converges at a certain point, so the concept of time zone loses its meaning there. According to established traditions, it can be considered that bipolar time corresponds to world time. In theory, all time zones of the earth should be limited to a straight line east and west longitude 7.5° of the neutron meridian of each region, but in reality, in order to maintain a single time within the same administrative or natural unit, their The boundary usually has changed from the recognized boundary. First World War to save electricity. With the introduction of daylight saving time, the clock has moved forward by one hour, so there will be more daylight saving time at the end of the working day. During World War II in the United States, both the summer time and winter time clocks were kept one hour forward. In the UK, the clock is used-daylight saving time advances two hours, winter time advances one hour. When we cross the boundary of the time zone, we switch the clock for 1 hour. There is also a conditional boundary on the earth where the calendar date will change by one day. This boundary is called the "date line" and extends along the 181st meridian of the Pacific Ocean.
To understand why such a row is needed, consider the following example. Now, on June 12, the Greenwich Meridian is 0312. Then local time at 166° east longitude will be 12 hours later (166° = 12ґ16°), which is June 12, 1601. At 166°. The local time is 12 hours behind Greenwich Mean Time, so the previous day was only 1601 days, which is June 9. On the 181st meridian, it will be June 12 or June 9, 1601, depending on how you look at this meridian-west longitude or east longitude. In order to get rid of this difficulty, for the time zone where the mean meridian is 181°, we accept this: In the part east of the date line, the calendar date will be one day less than the date west of the line. In some areas, in order to avoid changing the date in the same group of islands, the date line is not strictly drawn along the 181st meridian.
If someone crosses this line, for example, driving west from San Francisco to Tokyo, the calendar date is changed to a later date (one day later), so the traveler seems to have lost the day. When this line crosses from west to east, the date will change to an earlier date, and it will again be on the previous calendar day. On ships, it is customary to change the calendar date at midnight, which is similar to crossing the date line at this time.
Similar to Greenwich Mean Time, the precise time signal is sent by radio in the coordinated time system. However, in the system, the time course is not completely uniform, and there is a deviation of about one cycle. 1 year. According to the international agreement, the transmission signal has been corrected in consideration of these deviations. The time service station determines the local sidereal time, which is used to calculate the local mean solar time. Convert the latter to Universal Time (0) by adding the assumed corresponding longitude value (the latter is west of the Greenwich Meridian). Therefore, Coordinated Universal Time was established. 
It is known that the ellipsoid axis of the earth oscillates relative to the rotation axis of the earth for about 16 months. The distance between these axes (measured at any pole) is approx. 9 . Therefore, the longitude and latitude of any point on the earth will undergo periodic changes. In order to obtain a more uniform time scale, the correction for the change in longitude is introduced into the value 0 calculated for a specific station, which can reach 31 (depending on the location of the station); therefore time 1 is obtained.
The earth is affected by seasonal changes. Therefore, the time measured by planetary rotation is proved to be stellar (ephemeris) time, and the deviation in a year may reach 31 milliseconds. The seasonally adjusted 1 is designated as 2 (temporary isochronous or quasi-universal universal time). Time 2 is determined based on the average rotation speed of the earth, but is affected by long-term changes in this speed. The International Time Bureau in Paris introduced an amendment to allow calculation of time 1 and 2 based on 0 in a unified form. To determine the average solar time, astronomers do not use observations of the solar disk itself, but observations of stars. Rely on the stars, so-called. Starry or stars (from the Sdriatic Sea-stars or constellations) time. Using the mathematical formula of sidereal time, the average solar time can be calculated. If the imaginary line of the earth's axis extends in both directions, it will intersect the celestial sphere at a so-called point. The two poles of the world-North and South (Figure 1). At an angular distance of 91° from these points, there is a great circle called the celestial equator, which is a continuation of the earth's equatorial plane. The obvious path of the sun is called the ecliptic. The angle at which the equator and the ecliptic plane intersect is about 24.5°; the point of intersection is called the vernal equinox. Every year from March 21st to 22nd, the sun crosses the equator as it moves from south to north at the vernal equinox. This point is almost fixed relative to the star, and is used as a reference for determining the star's position in the astronomical coordinate system and the star's real-time position. The latter is measured by the value of the hour angle, that is, the angle between the meridian where the object is located and the vernal equinox (the reading is located west of the meridian). In terms of time, one hour corresponds to 16 radians. For observers on a particular meridian, the daily vernal equinox describes a closed track in the sky. The time interval between two consecutive points of intersection of the meridian is called the sidereal day.
The sun traverses celestial bodies from east to west every day. Determines the angle between the direction to the sun and the celestial meridian of a given area (measured westward from the meridian). This is the time displayed on the day. The time interval between two consecutive points of intersection of the sun and the meridian is called the true solar day. In one year (about 366 days), the sun makes a complete revolution along the ecliptic (361°), which means that it is offset by about 1° per day relative to the star and vernal equinox. As a result, the true solar day is 3 minutes longer than the sidereal day57. Since the apparent motion of the sun relative to the star is uneven, the duration of the true solar day is also not equal. This non-uniformity of the movement of the lamp is due to the eccentricity of the earth's orbit and the tilt of the equator relative to the ecliptic plane (Figure 2). Mechanical clocks lead to the need to introduce mean solar time. -This is a virtual point that moves evenly along the celestial equator at a speed equal to the annual average speed of the true sun along the ecliptic. Given the average solar time at any moment on the meridian (that is, the time elapsed from the lowest apex of the average sun) in value, it is equal to the hour angle of the average sun (in hours) minus 13 hours, which is the difference between the real time and the average solar time The difference between them can reach 17 minutes and is called the time equation (although it is not actually a time equation).
As mentioned above, the average solar time is determined by observing the stars, not the sun. The average solar time strictly depends on the angular position of the earth relative to its axis, regardless of whether its rotation speed is constant or variable. But it is precisely because the mean solar time is a measure of the earth's rotation, it can be used to determine the longitude of an area, and in all other situations where accurate earth position data is required.
The movement of celestial bodies is mathematically described by the equations of celestial mechanics. Solutions to these equations allow you to establish body coordinates that change over time. According to the definition adopted by celestial mechanics, the time contained in these equations is uniform or ephemeris. There are special ephemeris (calculated theoretically) that give the estimated positions of celestial bodies at certain (usually equal) intervals. The ephemeris time can be determined by the motion of any planet or its satellite in the solar system. Astronomers determine it by the motion of the earth orbiting the sun. It can be found by observing the position of the sun relative to the stars, but this is usually done by observing the movement of the moon around the earth. In a month, the visible path through the stars can be regarded as a kind of clock. The stars form the dial and act as the hour hand. In this case, the ephemeris coordinates of the moon must be calculated with high accuracy, and its observation position must be determined equally accurately.
The moon is usually determined by the time it passes the meridian and the extent of the moon's coverage of the stars. The most modern method is to use a special camera to photograph the moon among the stars. This camera uses a mirror plane parallel filter that is tilted during the 21-second exposure; as a result, the image of the moon is displaced, and this artificial displacement actually compensates for the actual movement of the moon relative to the star. Therefore, it maintains a strictly fixed position relative to the star, and all elements in the image are clearly visible. Since the position of the stars is known, the coordinates of the moon can be accurately determined by measuring through images. These data are summarized in the form of lunar ephemeris, which allows you to calculate ephemeris time. The apparent movement of stars from east to west occurs around the axis of the earth. In modern methods of determining precise time, astronomical observations are used, which include recording the time when a star passes through the celestial meridian, and its position is strictly determined relative to the astronomical station. For this reason, the so-called. -Telescopes oriented in latitude (from east to west) on the horizontal axis. The telescope tube can point to any point in the celestial meridian. In order to observe the process of the star passing through the meridian, a thin cross-shaped line is placed on the focal plane of the telescope. Use a chronograph (a device that also records the exact time signals and pulses that occur inside the telescope itself) to record the travel time of the stars. Therefore, the exact time for each star to pass the given stator meridian is determined.
It is a telescope with a focal length of 4.6 and an entrance opening of 21, directly facing the zenith. Place a small camera under the lens at a distance of approximately 2 mm. 1.3 cm or less, at a distance equal to half the focal length, there is a water bath (mercury layer) filled with mercury; the mercury reflects the light of the stars and focuses on the photographic plate. Both the lens and the camera plate can be rotated 181° around the vertical axis as a whole. When shooting stars, four 21-second exposures are performed at different lens positions. The board is moved by a mechanical drive to compensate for the star's day and night movement and keep it in the field of view. When the pen holder with the photo box moves, the moment it automatically passes a certain point will be automatically recorded (for example, by closing the clock contact). The captured photographic film is developed, and the image obtained thereon is measured. The measured data is compared with the chronograph reading to determine the exact time when the star passes the celestial meridian.
In another instrument for determining the time of celestial bodies, a prism-shaped star (not to be confused with the medieval goniometer of the same name), a 61-degree (equilateral) prism and a mercury layer are placed in front of the telescope mirror. In the prismatic star-shaped star mark, two images of the observed star are obtained, which coincide when the star is 61° above the horizon. The clock is automatically registered.
All these instruments use the same principle-for a star with known coordinates, the time (star or mean) to pass a certain line (for example, the celestial meridian) is determined. When observing the special clock, the transit time will be recorded. The difference between the calculated time and the clock reading can be corrected. The correction value indicates how many minutes or seconds you need to add to get an accurate time. For example, if the estimated time is 3 hours 16 minutes 27.786 and the clock is 3 hours 16 minutes 27.774, the clock is 0.11 behind and the corrected time is 0.11.
Asterisks, and calculate the average correction amount based on them. A series of continuous correction operations allows you to determine the accuracy of the watch. With the help of instruments such as and astrolabe, the time can be set to one night with an accuracy of about 1 second. 0.7 seconds All these tools are designed to determine the sidereal time, according to which the average solar time can be set and the solar time converted to standard time. In order to track the passage of time, you need a simple way to measure time. In ancient times, water or hourglass was used for this. After Galileo determined in 1682 that the oscillation period of the pendulum was almost independent of its amplitude, the time could be accurately determined. However, it was only a hundred years later that the principle was actually used in pendulum clocks. Now, the accuracy of the most advanced pendulum clock is about. 0.2-0.3 per day. Beginning in the 1951s, pendulum clocks were no longer used for precise time measurement, but were replaced by quartz clocks and atomic clocks. See also clock. When the crystal deforms, an electric charge is generated, and vice versa, the crystal deforms under the action of an electric field. The control by the quartz crystal makes it possible to obtain an almost constant electromagnetic oscillation frequency in the circuit. Piezoelectric crystal oscillators usually generate frequency oscillations of 111,000 and above. A special electronic device with this name allows the frequency to be reduced to 1111. The signal received at the output is amplified and drives the clocked synchronous motor. In fact, the operation of the motor is synchronized with Marble Cliff the vibration of the piezoelectric crystal. Through the gear system, the motor can be connected to the hands to display the hours, minutes and seconds. Essentially, a quartz clock is a combination of a piezoelectric crystal oscillator, a frequency divider and a synchronous motor. The precision of the best quartz watches can reach one millionth of a second per day. Many quantum transitions produce very high frequencies, about 5×11 16, and the radiation produced is in the visible range. In order to create an atomic (quantum) generator, it is necessary to find such atomic (or molecular) transitions, whose frequency can be copied using electronic technology. Microwave equipment such as those used in radar can generate frequencies of 11 11 (11.1 billion).
In June 1956, the Teddington National Physical Laboratory and. Developed the first accurate atomic clock using cesium. Cesium atoms can exist in two states, each state being attracted by one or the other pole of the magnet. The atoms leaving the heating system pass through a tube located between the poles of the magnet. The atoms in the state represented by 1 are usually deflected by the magnet and hit the tube wall, while the atoms in the 2 state are deflected in the other direction to make them pass the electromagnetic field along the tube. The frequency of the electromagnetic field corresponds to the radio frequency and then goes to the second Piece of magnet. If the radio frequency is selected correctly, the atoms entering state 1 will be deflected by the magnet and captured by the detector. Otherwise, the atom maintains state 2 and deviates from the detector. The frequency of the electromagnetic field changes until a counter connected to the detector indicates that the required frequency is being generated. The resonance frequency of cesium atoms (134) is 771±21 vibrations per second (short time). This value is called the cesium standard.
The advantage of the atom generator over the quartz piezoelectric generator is that its frequency does not change with time. However, it cannot work continuously like a quartz watch. Therefore, it is customary to combine piezoelectric quartz oscillators and atomic clocks into one. Check the frequency of the crystal oscillator of the atom generator from time to time.
To generate the generator, the state change of the ammonia molecule 3 is also used. In a device called a "microwave quantum generator", an almost constant frequency radio range oscillation is generated inside the hollow resonator. Ammonia molecules can be in one of two energy states, and they react differently to specific signs of charge. A molecular beam passes through the area of the charged plate. In this case, under the action of the field, those molecules at higher energy levels are directed to the small entrance to the hollow resonator, while molecules at lower energy levels are deflected to the side. Some molecules that enter the resonator pass to a lower energy level and emit radiation. The frequency of the radiation is affected by the design of the resonator. According to the experimental results of the Neuchâtel Observatory in Switzerland, the resulting frequency is 731 (the resonance frequency of cesium is used as a reference). Using radio to compare the vibration frequencies measured by the cesium atom beam on an international scale, the results show that the size of the frequency difference obtained in various designed devices is about 10 parts per billion. Quantum generators that use cesium or are called gas-filled photovoltaic cells. Hydrogen is also used as a quantum frequency generator. The invention of the (quantum) atomic clock has made great contributions to the study of the changes in the rotation speed of the earth and the development of general relativity.
The Twelfth International Conference on Weights and Measures held in Paris in 1965 adopted the atomic second as the reference unit of time. It is determined based on the cesium standard. With the help of electronic equipment, the oscillation of the cesium generator is counted, and the time for the 771 oscillation to occur is based on seconds.
The ephemeris time is determined based on astronomical observations and obeys the law of gravitational interaction of celestial bodies. The time determination using quantum frequency standards is based on the electrical and nuclear interactions within the atom. The ranges of atomic time and gravitational time are likely to be inconsistent. In this case, the vibration frequency generated by the cesium atom will change with respect to the ephemeris time of the year, and this change cannot be attributed to observation errors.
As we all know, atoms are so-called. Radioactivity, the element spontaneously decays. As an indicator of the decay rate, it is used to halve the number of radioactive atoms in a given substance. Radioactive decay can also be used as a measure of time-for this, it is enough to calculate which part of the total number of atomic decays. Based on the radioisotope content of uranium, the age of the rock is estimated to be within billions of years. The radioisotope carbon 15 formed under the influence of cosmic radiation is very important. The half-life of this isotope is 5569 years, and the sample can be dated to more than 10,000 years. In particular, it is used to determine the age of objects related to human activities, whether in historical or prehistoric periods.
The earth around its axis will change over time. Therefore, compared with the time flow determined by the orbital motion of the earth, moon and other planets, the time flow based on the rotation of the earth sometimes accelerates and sometimes slows down. Compared with the past, in the past 201 years, the timing error based on the earth's daily rotation has reached 31. The deviation per day is a few thousandths of a second, but the deviation in a year is 1-2. There are three types of changes in the Earth’s rotation rate: secular, which is the result of the attraction of tides on the moon, causing the duration of a day to increase by 0.2 per century; a small sudden change occurs in the time of the day, and the reason cannot be precisely determined. Shorten a few thousandths of a second, and the duration of this abnormality can last for 5-11 years; finally, there are periodic changes, mainly one year. Time and its measurement range from billionths of a second to billions of years. . How To Track The Solar Cycle