Information

The sun is a big mass of energy. The sun produces high energy protons, and the solar wind carries these protons towards our planet. However during solar flare activity, energetic protons are blown violently outwards.. sometimes towards earth. Energetic protons can reach Earth within 30 minutes of a major flare's peak. During such an event (big ones are also known as Solar Proton Events), Earth is showered with highly energetic solar particles (primarily protons) released from the flare site. When these protons arrive at Earth and enter the atmosphere over the polar regions, much enhanced ionization is produced at altitudes below 100 km. Ionization at these low altitudes is particularly effective in absorbing HF radio signals and can render HF communications impossible throughout the polar regions. This effect is called Radio Blackouts. This type of event is also known as a Polar Cap Absorption Event or PCA.

Open the GOES-11 Proton page in a new window. http://www.sec.noaa.gov/rt_plots/pro_3d.html