Cornelis de Jager
| Cornelis de Jager | |
|---|---|
Kees de Jager in 1967
|
|
| Born |
29 April 1921 Den Burg, Texel, Netherlands |
| Residence | Den Burg |
| Fields | astrophysics, climate change |
| Institutions | Utrecht University |
| Alma mater | Utrecht University |
| Doctoral advisor | Marcel Minnaert |
| Spouse | Doetie Rienks |
Cornelis "Kees" de Jager (born 29 April 1921) is a Dutch astronomer who specializes in predicting solar variation to assess the Sun's impact on future climate. He was the General Secretary of the IAU from 1967 to 1973 and former director of the observatory at Utrecht. He is a fellow with the Committee for Skeptical Inquiry.
Born in Den Burg, de Jager spent his school years in the Dutch East Indies. From 1939 to 1945 he studied mathematics, physics and astronomy at Utrecht University. On 13 October 1952 he obtained his PhD with a thesis called "The Hydrogen Spectrum of the Sun". His supervisor was Marcel Minnaert.
De Jager did work on stars and solar physics, in relation to which he was a founding editor of the journal Solar Physics. In 1980 he was principal investigator of the Hard X-ray Imaging Spectrometer (HXIS) on board the Solar Maximum Mission satellite.
From 1978 onward de Jager did noted work on the most luminous stars, known as hypergiants. From 1960 to 1986 de Jager was a professor at Utrecht University. In 1969 he became member of the Royal Netherlands Academy of Arts and Sciences.
De Jager's current research focuses on predicting solar variation to assess the Sun's impact on future climate. Usually solar activity is defined in terms of the Sun's toroidal magnetic field, the field component parallel to the solar equator. Sunspots are one expression of this component. De Jager introduces the poloidal field of the Sun, which connects its two poles, as a factor of possibly similar importance. He uses proxies for both components and takes 19-year running averages to eliminate all effects that last only one or two solar cycles. Next he plots both components in a diagram, thus creating an experimental phase portrait. The track of the two components went from low to high activity around 1925. Around 2009 the same point has been passed in the opposite direction. Thus solar activity in the 21st century is expected to be lower than it was for most of the 20th century. A reduction in solar activity means less energy input to the Earth, thus counteracting global warming. A book, Grand Phases On The Sun: The case for a mechanism responsible for extended solar minima and maxima, was written to outline some of de Jager's research in this regard, along with contributory papers from Bas van Geel and Sylvia Duhau in 2013.
...
Wikipedia