Speaker
Description
Ionospheric absorption degrades high frequency radio wave propagation following solar events that enhance either photoionization or energetic particle precipitation. The high-latitude region poleward of 50° magnetic latitude is particularly vulnerable because of the frequency and widespread effects of auroral and polar cap absorption events. Shortwave fadeout, auroral absorption and polar cap absorption were independently modelled at 30 MHz in 5-minute increments between 1986 and 2017. The combined total absorption was evaluated to determine the overall and yearly probability of exceeding 0.5 dB, 1.0 dB, and 2.0 dB thresholds. At the 1.0 dB threshold the highest probability (>1%) is observed in an oval poleward of ~60° magnetic latitude coincident with the low-latitude cut-off for polar cap absorption. Enhancements of > 2% are observed along an oval-shaped ring centered at 65° magnetic latitude, which is the latitude of maximum enhancement for auroral absorption. Shortwave fadeout contributes minimally to the probability distribution with an occurrence of < 0.03% and peak values near the most equatorward portions of the high-latitude region. Yearly probability statistics are reflective of the solar cycle with values ranging from near 0% in 2009 to >10% in 1991 and nearly 30% in 1989.
| Keyword-1 | ionosphere |
|---|---|
| Keyword-2 | absorption |
| Keyword-3 | space weather |
