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At the base of the convection zone is a zone of rotational shear, known as the tachocline, which now plays a central role in theories of the solar dynamo (4).Despite valuable attempts, none of the above solar features were confidently predicted by models.Those simulations, and the seismological evidence with which they are being confronted, are reviewed elsewhere in this volume.
4.5 billion years, both for the Earth and for the solar system in general.
We do research in a variety of topics in solar astronomy, some of which are described below.
It contains as well an file with: - column 1: the series index associated to the frequency table; - column 2, 3, 4: respectively the year, month, and day of the starting date of each 365-day time series; - column 5: the associated duty cycle in %; - column 6: the corresponding radio flux averaged over the same 365-day periods. (2015) and were updated as longer time series were available.
They were calculated for 4 different frequency ranges: [1800-3790μHz]; the low-frequency range [1800-2450μHz]; the mid-frequency range [2450-3110μHz]; and the high-frequency range [3110-3790μHz].
Another spectacular achievement was the inference of solar rotation as a function of radius and latitude.
The bulk of the convective envelope rotates differentially, faster at the equator than at high latitudes.
The age of the Earth has been calculated to 4.54 ± 0.05 billion years, which is only approximately a 1% uncertainty.
Now the exact numbers may be refined slightly as more detailed investigations are completed, there is now so much data backing up a 4.5 billion year age, that the chances of it being substantially inaccurate are very low.
Nevertheless, some progress has been made, and seismological inference has provided us with evidence of more to come.
Some of that I summarize here, mentioning in passing hints that are pointing the way to the future.
Historically, great advances in our understanding of the solar interior have been due to helioseismology, the study of 5-minute solar internal oscillations (3).