Space Weather Advisories (SWX ADVISORY)
The ICAO Manual on Space Weather Information in Support of International Air Navigation (ICAO DOC 10100), describes the hazards of space-weather as follows:
- HF communications
HF radio blackout (absorption)
Compressed HF bandwidth (depression) - Satellite communications
Ionospheric scintillation - GNSS-based navigation and surveillance
Positioning errors (ionospheric delay)
GNSS loss of lock (scintillation*) - Elevated radiation dose rates on polar flights
A 2100 m decrease in altitude lowers the radiation dose by approximately 50%.
(*): Severe scintillation conditions can prevent a GPS receiver from locking on to the signal and can make it impossible to calculate a position. Less severe scintillation conditions can reduce the accuracy and the confidence of positioning results.
SWX Advisories have a standardized format: they are transmitted directly to aircraft operators and flight crew throughout the flight as standard meteorological information. They are only issued whenever space weather conditions get bad with moderate and severe impacts, and only when operations above FL250 are affected. They are activated for comms, GNSS and radiation interference.
They predict the effect of space weather at six hourly intervals across a twenty-four-hour period. To define the areas affected, SWX advisories divide the world into six bands of latitude, and tell you how wide the box is with longitude.
HNH: High Latitude Northern Hemisphere
HSH: High Latitude Southern Hemisphere
