Research of the solar activity influence on the upper atmosphere of the Earth

In the work the variations of the upper atmosphere density influencing orbit form and drag value of a satellite
were investigated. The time series of orbital parameters received by NORAD (North American Aerospace
Defense Command) system from 1975 to 2004 were considered.
Some satellites were excluded from the consideration due to:
1. Observation series of less then 11-year solar activity cycle;
2. With high eccentricity (only satellites with circular orbits);
3. Beyond 600 to 1100 km range (above 1100 km the atmosphere has weak influence, below 600 km the
lifetime of a satellite is less than the period of solar activity);
4. With signs of intended orbital correction during operation.
For each of 38 selected satellites the changes of the apogee and perigee orbital heights within a single solar
activity cycle were calculated. Significant correlation between time series of drag values of satellites and Wolf’s
numbers was found (0,72 ± 0,05).
To discover the physical reasons influencing the density of the given atmosphere layer of the Earth, the
following time series have been studied: solar wind, solar cosmic rays, and magnitude of general magnetic field
of the Sun (as a star) (GMF). For all the time series the long-term components comparable with the length
of solar activity cycle and short-term ones comparable with the period of the Sun rotation were considered.
Significant correlation was found only for GMF value and satellite drag. A considerable response in atmospheric
density due to the phenomenon of solar flares was shown.