Ted Molczan wrote: "The rate of orbital decay depends strongly upon atmospheric density, which varies as the solar flux varies. The active regions on the sun that cause high solar flux are not evenly distributed, so the solar flux experienced at the Earth varies over roughly the same period as the sun's period of rotation of 27 days." Would not the bulk of the ions from the sun be deflected by the earth's magnetic field, since the ISS's orbit is well inside the Van Allen radiation belt? Is there some data that speaks to the relative effects of the earth's atmosphere at the altitude of the ISS's orbit, vs. the solar wind? I suppose what Ted is saying is that a strong solar flux compresses the earth's magnetic field, which in turn compresses the trace atmosphere at orbital altitudes. Also, from http://csep10.phys.utk.edu/astr162/lect/sun/sunspots.html "Because the Sun is not a solid body, it does not have a well defined rotational period. Modern measurements indicate that the rotational period of the Sun is about 25 days near its equator, 28 days at 40 degrees latitude, and 36 days near the poles." So whatever you want to call the rotational period of the sun, it's not 20 days (or a multiple thereof), so I'd be inclined to look for another explanation. ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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