Cycles of the Solar Wind Flux at the Front of the Earth’s Magnetosphere

Abstract

We studied various long solar wind proxy records in order to reveal prolonged solar wind cycles. Inverted rate of atmospheric 14C production as derived from the standard radiocarbon calibration curve represents good proxy record of the past variations of the solar wind flux at the upper atmosphere because it modulates the galactic cosmic rays flux, which produces the radiocarbon there. We made periodogramme time series analysis of the inverted rate of atmospheric 14C production record in order to obtain the solar wind cycles. In such a way, we found cycles of 11 500, 1670, 1420, 1280, 924, 835, 787, 750, 663, 610, and 545 years in this solar wind proxy record.Records of the intensity of the geomagnetic dipole are also proxy records of variations of the solar wind flux, because it modulates the geomagnetic field. We made periodogramme time series analysis of the one long record of the intensity of the geomagnetic dipole in order to obtain the solar wind cycles. In this way we found cycles of 11 500, 4400, 3950, 2770, 2500, 2090, 1960, 1670, 1460, 1280, 1195, 1145, 1034, 935, and 835 yrs in this solar wind proxy record. We have confirmed the solar origin of all this cycles by their detection in an independent solar luminosity proxy record.The 11 500‐yr cycle was found previously to be the most intensive cycle in the 14C calibration record and was interpreted to be of geomagnetic origin. Our studies suggest that this is a solar cycle modulating the geomagnetic field. We determined the solar origin of strong cycles with duration of 11500, 4400, 3950, 2770, 2500, 2300, 2090, 1960, 1670, 1460, 1280, 1195, 1145, 1034, 935, 835, 814, 775, 750, 660, 610, 550, and 538 years and of many weak cycles with duration from one to five centuries. This was achieved by their detection in proxy records of solar luminosity, atmospheric 14C production and the intensity of the geomagnetic dipole. The main variations in the last two records are known to be produced by the solar wind while the first record is absolutely independent on the geomagnetic field, so non of these cycles can be of terrestrial origin.The main variations in the 14C and geomagnetic field records are produced by the solar wind. Known decadal and even centennial solar cycles have negligible intensity (100 times less intensive) relative to these cycles. These millennial solar luminosity cycles can produce climatic variations with intensity comparable to that of the orbital variations known to produce the glacial periods on Earth.We discovered a sub‐annual cycle of 27 days in very high‐resolution soil surface temperature proxy records, attributed to solar rotation, which causes the periodic appearance of active zones on the visible solar surface, which are the major emitters of solar wind. Solar wind modulates cosmic ray flux at the Earth, while cosmic rays influence the atmospheric transparency, thus producing a multiplication of solar variations in insolation. Hence small variations of the solar activity can produce a measurable influence on insolation.