Polar Cap Absorption

A polar cap absorption event results from the ionisation of the D-layer of the polar ionosphere by high energy protons. A PCA causes a HF radio blackout for trans polar circuits and can last several days. PCAs are almost always preceded by a major solar flare with the time between the flare event and the onset of the PCA ranging from few minutes to several hours.

See Real Time Riometer Data from Antarctic Stations.

The icon below indicates the estimated absorption in db of a 30 MHz riometer from Casey station in Antarctica. These figures give an indication of the severity of the PCA. The background colour of the icon is red when absorption exceeds 1db and green otherwise.

Details of any current proton event are given below:

(last updated 30 May 2023 13:50 UT)

10MeV (S1) Proton/PCA Event Began 25 02 2023 2100UT and is in progress 10MeV (S1) Proton/PCA Event Ended 26 02 2023 1830UT 10MeV Maximum proton flux of 5.88E+01 PFU (S1) observed at 26 02 2023 0440UT 10MeV (S1) Proton/PCA Event Began 26 02 2023 1935UT and is in progress 10MeV (S1) Proton/PCA Event Ended 26 02 2023 2005UT 10MeV Maximum proton flux of 1.58E+01 PFU (S1) observed at 26 02 2023 1925UT 10MeV (S1) Proton/PCA Event Began 26 02 2023 2035UT and is in progress 10MeV (S1) Proton/PCA Event Ended 26 02 2023 2245UT 10MeV Maximum proton flux of 1.58E+01 PFU (S1) observed at 26 02 2023 2115UT 10MeV (S1) Proton/PCA Event Began 13 03 2023 1400UT and is in progress 10MeV (S1) Proton/PCA Event Ended 13 03 2023 1500UT 10MeV Maximum proton flux of 1.32E+01 PFU (S1) observed at 13 03 2023 1435UT 10MeV (S1) Proton/PCA Event Began 13 03 2023 1615UT and is in progress 10MeV (S1) Proton/PCA Event Ended 13 03 2023 1700UT 10MeV Maximum proton flux of 1.22E+01 PFU (S1) observed at 13 03 2023 1645UT 10MeV (S1) Proton/PCA Event Began 14 03 2023 1145UT and is in progress 10MeV (S1) Proton/PCA Event Ended 14 03 2023 1220UT 10MeV Maximum proton flux of 1.28E+01 PFU (S1) observed at 14 03 2023 1205UT 10MeV (S1) Proton/PCA Event Began 14 03 2023 1355UT and is in progress 10MeV (S1) Proton/PCA Event Ended 14 03 2023 1435UT 10MeV Maximum proton flux of 1.30E+01 PFU (S1) observed at 14 03 2023 1425UT 10MeV (S1) Proton/PCA Event Began 14 03 2023 1555UT and is in progress 10MeV (S1) Proton/PCA Event Ended 14 03 2023 1630UT 10MeV Maximum proton flux of 1.12E+01 PFU (S1) observed at 14 03 2023 1630UT 10MeV (S1) Proton/PCA Event Began 14 03 2023 1740UT and is in progress 10MeV (S1) Proton/PCA Event Ended 15 03 2023 0515UT 10MeV Maximum proton flux of 2.20E+01 PFU (S1) observed at 15 03 2023 0425UT 10MeV (S1) Proton/PCA Event Began 23 04 2023 1800UT and is in progress 10MeV (S1) Proton/PCA Event Ended 23 04 2023 1900UT 10MeV Maximum proton flux of 2.62E+01 PFU (S1) observed at 23 04 2023 1820UT 10MeV (S1) Proton/PCA Event Began 08 05 2023 1220UT and is in progress 10MeV (S1) Proton/PCA Event Ended 08 05 2023 1405UT 10MeV Maximum proton flux of 1.67E+01 PFU (S1) observed at 08 05 2023 1400UT 10MeV (S1) Proton/PCA Event Began 08 05 2023 1435UT and is in progress 10MeV (S1) Proton/PCA Event Ended 09 05 2023 1220UT 10MeV Maximum proton flux of 3.84E+01 PFU (S1) observed at 09 05 2023 0150UT 10MeV (S1) Proton/PCA Event Began 09 05 2023 2325UT and is in progress 10MeV (S1) Proton/PCA Event Ended 11 05 2023 0350UT 10MeV Maximum proton flux of 8.35E+01 PFU (S1) observed at 10 05 2023 1250UT

(last updated 30 May 2023 13:50 UT)

No proton event in progress

Note: Proton event descriptive text will lag realtime due to data smoothing.

Current proton fluxes are as follows:

(last updated 30 May 2023 13:50 UT)

GOES (Gp16) satellite energetic Proton Flux (Courtesy of SWPC, Boulder Colorado, USA) Data Date/Time: 30 05 2023 1340 UT Proton Energy Current Proton Level Flux Event Status 10MeV 2.90e-01PFU No proton event in progress 100MeV 2.33e-01PFU No proton event in progress 500MeV 2.25e-01PFU No proton event in progress Units: PFU = protons/cm2/sec/ster MeV = million electron volts Proton energy levels and PFU event thresholds: Proton Energy Proton Flux Level Threshold 10MeV 10PFU 100MeV 1PFU 500MeV 1PFU Gp: GOES primary Gs: GOES secondary Solar proton events can impact satellite operations and transpolar HF communications.

GOES satellite proton flux data for this page are provided by US Space Weather Prediction Center in Boulder.