Solar constant, fluctuations

Very little is known about fluctuations of the solar constant and even less about fluctuations of the ultraviolet part of the solar constant. Until now, periodicities of the sun have been evaluated solely from the sun spot cycles, observed over some four hundred years (except for a few desultory observations in ancient China), but the sun has many ways to vary besides sunspot variations. 

The atmospheric 14C/C ratio during the last 50,000 y was sufficiently constant to make radiocarbon a remarkably reliable dating tool. Evidence for fluctuations of the 14C/C ratio could be found by high precision measurements on samples of known age. These fluctuations can be attributed to variations of processes in the solar system (solar activity) and on earth (fluctuations of C02 distribution among the atmospheric, oceanic, and biospheric reservoirs). Both fluctuations of solar activity and of the atmospheric C02 content may have contributed to past climatic changes. 

Fast Response CO Sensor. The sensor requirements for eddy covariance measurements are extreme. To be used within a few meters of a plant canopy, the sensor must have a frequency response in excess of 20 Hz. Additionally, because the large mean density of CO2 in the atmosphere (about 560 mg m-3) and the deviations around the mean associated with turbulent transfer are small (>10 mg m-3), the sensor must have a signal to noise ratio in excess of 3500 1. The sensor must maintain these specifications for long durations, while mounted on a tower above the canopy, where it is exposed to constant changes in temperature, solar irradiation, and background gas concentrations. The instrument must unobtrusively sense the natural turbulant fluctuations of the atmosphere. To effectively accomplish this it must be small and streamlined. 

Chondrites, the most primitive of all meteorites, formed in dynamic energetic, dust-rich zones in the solar nebula. In this environment, dust/gas ratios were constantly changing, temperatures fluctuated through 1,000 K, with multiple cycles of melting, evaporation, condensation, and aggregation. In addition there were influxes of matter from the interstellar dust and the periodic removal of batches of chondritic material to small planetesimals. In this section we explore how the most primitive materials of the solar system were formed and what they can tell us about processes during the condensation of the solar nebula. These materials include chondrules, refractory inclusions (CAIs), and amoeboid olivine aggregates (AOAs), the oldest component parts of chondritic meteorites. 

A new use for ammonia, NHS, has been foundf. The mean solar day is not absolutely constant. Owing to variations in the rate of rotation of the earth on its axis there is a fluctuation of 1 second in every 20 to 30 million seconds. In addition to this there is a slight lengthening of the solar day due to a slowing down of the earth s rotation, through tidal action mainly, which amounts to about 1 second per day every 120,000 years. This has raised the question as to whether or not it might be possible to check time intervals by some absolutely constant wave motion on the lines adopted for measurements of length (p. 308). This problem is in course of solution by the invention of the atomic clock , as it is... 

The mass of living matter fluctuates about a constant value over geological time. It depends on the quantity of solar energy absorbed by living matter. 

In radiocarbon dating, a reasonable assumption is that the ratio of carbon-14 to carbon-12 in the atmosphere has been relatively constant for the past 50,000 yr. However, because variations in solar activity control the amount of carbon-14 produced in the atmosphere, that ratio can fluctuate. We can correct for this effect by using other kinds of data. Recently scientists have compared carbon-14 data with data from tree rings, corals, lake sediments, ice cores, and other natural sources to correct variations in the carbon-14 clock back to 26,000 yr. 

If it can be assumed that the rate of production has not varied over time, and thus that a dynamic equilibrium has formed, and if it is possible to extract clean sample carbon, unaltered apart from the decline in and to measure its current concentration, it is possible using eqn [1] to calculate the elapsed time since the death of the organism. In practice, the process is far more complicated than this brief description indicates. Principally, one of the basic assumptions, that the rate of formation is constant, is known to be incorrect. The rate has, in fact, varied over time in response to a number of effects, principally fluctuations in the cosmic-ray flux with changes in the geomagnetic field and in solar activity. Because of this, no radiocarbon measurement equates directly with a calendar date, and all such measurements must be calibrated before use. 

Socially living ants establish above-ground and underground colonies to guarantee an effective development of their brood in varying climates. These colonies are often characterized by hills of considerable size and an appropriate shape to collect solar irradiation. Measurements show that the temperature in the central brood zone remains rather constant inspite of fluctuating ambient values. Moreover, these temperatures are significantly above the environment, typically around 25 °C in nests of the wood ant Formica polyctena. Several theories were developed to explain the increased temperature in the nest ... 

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