Earth's Atmosphere
© Wikimedia CommonsEarth's atmosphere and ionosphere.
Earth's ionosphere is a "conducting layer" that can transmit radio signals. To ensure the reliability of these transmissions, scientists must first understand how ionospheric variations influence radio signals and the drivers behind these variations.

One hypothesis holds that long-term trends in the ionosphere are related to the increase of carbon dioxide in lower layers of Earth's atmosphere. Perrone and Mikhailov take a different approach and consider the origin of long-term variations in the ionosphere as they relate to solar and geomagnetic activity—the so-called "geomagnetic control concept."

The authors scrutinized reliable observations of critical frequencies on European ionosondes for five solar cycles (around 55 years). Through their analysis, they've become the first to retrieve a consistent set of parameters—temperature and neutral composition—for the F layer, the region of the ionosphere transmitting the signals.

They found that their data reflect trends seen in long-term variations in solar and geomagnetic activity for the whole period, including the last deep solar minimum in 2008 - 2009.

The analysis confirms that the long-term variations have a natural origin: They existed in the past and presumably will continue in future, reflecting the long-term variations in solar activity.

Reference:

Journal of Geophysical Research: Space Physics, doi:10.1002/2016JA022715, 2016