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 21 Dec 2024 11:59 UT)

10MeV (S1) Proton/PCA Event Began 03 01 2024 1955UT and is in progress 10MeV (S1) Proton/PCA Event Ended 03 01 2024 2205UT 10MeV Maximum proton flux of 1.24E+01 PFU (S1) observed at 03 01 2024 2150UT 10MeV (S1) Proton/PCA Event Began 03 01 2024 2250UT and is in progress 10MeV (S1) Proton/PCA Event Ended 04 01 2024 2155UT 10MeV Maximum proton flux of 2.01E+01 PFU (S1) observed at 04 01 2024 0835UT 10MeV (S1) Proton/PCA Event Began 04 01 2024 2225UT and is in progress 10MeV (S1) Proton/PCA Event Ended 05 01 2024 0125UT 10MeV Maximum proton flux of 2.53E+01 PFU (S1) observed at 05 01 2024 0035UT 10MeV (S1) Proton/PCA Event Began 29 01 2024 0605UT and is in progress 10MeV (S2) Proton/PCA Event Began 29 01 2024 1725UT and is in progress 10MeV (S2) Proton/PCA Event Ended 29 01 2024 1850UT 10MeV Maximum proton flux of 1.37E+02 PFU (S2) observed at 29 01 2024 1805UT 10MeV (S1) Proton/PCA Event Ended 30 01 2024 0405UT 10MeV Maximum proton flux of 1.37E+02 PFU (S2) observed at 29 01 2024 1805UT 10MeV (S1) Proton/PCA Event Began 09 02 2024 1515UT and is in progress 10MeV (S2) Proton/PCA Event Began 09 02 2024 1810UT and is in progress 10MeV (S2) Proton/PCA Event Ended 09 02 2024 1900UT 10MeV Maximum proton flux of 1.13E+02 PFU (S2) observed at 09 02 2024 1825UT 10MeV (S2) Proton/PCA Event Began 09 02 2024 2300UT and is in progress 10MeV (S2) Proton/PCA Event Ended 10 02 2024 1610UT 10MeV Maximum proton flux of 1.87E+02 PFU (S2) observed at 09 02 2024 2355UT 10MeV (S2) Proton/PCA Event Began 11 02 2024 0230UT and is in progress 10MeV (S2) Proton/PCA Event Ended 11 02 2024 0345UT 10MeV Maximum proton flux of 1.34E+02 PFU (S2) observed at 11 02 2024 0315UT 10MeV (S1) Proton/PCA Event Ended 11 02 2024 1750UT 10MeV Maximum proton flux of 1.87E+02 PFU (S2) observed at 09 02 2024 2355UT 10MeV (S1) Proton/PCA Event Began 12 02 2024 0755UT and is in progress 10MeV (S2) Proton/PCA Event Began 13 02 2024 0545UT and is in progress 10MeV (S2) Proton/PCA Event Ended 13 02 2024 0635UT 10MeV Maximum proton flux of 1.18E+02 PFU (S2) observed at 13 02 2024 0615UT 10MeV (S2) Proton/PCA Event Began 13 02 2024 0830UT and is in progress 10MeV (S2) Proton/PCA Event Ended 13 02 2024 0900UT 10MeV Maximum proton flux of 1.12E+02 PFU (S2) observed at 13 02 2024 0840UT 10MeV (S1) Proton/PCA Event Ended 14 02 2024 1930UT 10MeV Maximum proton flux of 1.18E+02 PFU (S2) observed at 13 02 2024 0615UT 10MeV (S1) Proton/PCA Event Began 16 03 2024 0015UT and is in progress 10MeV (S1) Proton/PCA Event Ended 16 03 2024 1450UT 10MeV Maximum proton flux of 1.67E+01 PFU (S1) observed at 16 03 2024 0635UT 10MeV (S1) Proton/PCA Event Began 23 03 2024 0805UT and is in progress 10MeV (S2) Proton/PCA Event Began 23 03 2024 1355UT and is in progress 10MeV (S2) Proton/PCA Event Ended 24 03 2024 1845UT 10MeV Maximum proton flux of 9.56E+02 PFU (S2) observed at 23 03 2024 1820UT 10MeV (S1) Proton/PCA Event Ended 25 03 2024 1405UT 10MeV Maximum proton flux of 9.56E+02 PFU (S2) observed at 23 03 2024 1820UT 10MeV (S1) Proton/PCA Event Began 10 05 2024 1350UT and is in progress 10MeV (S1) Proton/PCA Event Ended 11 05 2024 0050UT 10MeV Maximum proton flux of 2.07E+02 PFU (S2) observed at 10 05 2024 1745UT 10MeV (S1) Proton/PCA Event Began 11 05 2024 0210UT and is in progress 10MeV (S1) Proton/PCA Event Ended 12 05 2024 1125UT 10MeV Maximum proton flux of 1.16E+02 PFU (S2) observed at 11 05 2024 0910UT 10MeV (S1) Proton/PCA Event Began 13 05 2024 1355UT and is in progress 10MeV (S2) Proton/PCA Event Began 14 05 2024 0335UT and is in progress 10MeV (S2) Proton/PCA Event Ended 14 05 2024 0640UT 10MeV Maximum proton flux of 1.21E+02 PFU (S2) observed at 14 05 2024 0505UT 10MeV (S1) Proton/PCA Event Ended 16 05 2024 1410UT 10MeV Maximum proton flux of 1.21E+02 PFU (S2) observed at 14 05 2024 0505UT 10MeV (S1) Proton/PCA Event Began 08 06 2024 0250UT and is in progress 10MeV (S2) Proton/PCA Event Began 08 06 2024 0445UT and is in progress 10MeV (S2) Proton/PCA Event Ended 08 06 2024 2240UT 10MeV Maximum proton flux of 1.03E+03 PFU (S3) observed at 08 06 2024 0800UT 10MeV (S1) Proton/PCA Event Ended 09 06 2024 1930UT 10MeV Maximum proton flux of 1.03E+03 PFU (S3) observed at 08 06 2024 0800UT 10MeV (S1) Proton/PCA Event Began 23 07 2024 0250UT and is in progress 10MeV (S1) Proton/PCA Event Ended 23 07 2024 2335UT 10MeV Maximum proton flux of 2.48E+01 PFU (S1) observed at 23 07 2024 1040UT 10MeV (S1) Proton/PCA Event Began 09 09 2024 1625UT and is in progress 10MeV (S1) Proton/PCA Event Ended 10 09 2024 0410UT 10MeV Maximum proton flux of 3.42E+01 PFU (S1) observed at 09 09 2024 2250UT 10MeV (S1) Proton/PCA Event Began 17 09 2024 0735UT and is in progress 10MeV (S1) Proton/PCA Event Ended 17 09 2024 1425UT 10MeV Maximum proton flux of 3.36E+01 PFU (S1) observed at 17 09 2024 1050UT 10MeV (S1) Proton/PCA Event Began 09 10 2024 0455UT and is in progress 10MeV (S2) Proton/PCA Event Began 09 10 2024 0730UT and is in progress 10MeV (S3) Proton/PCA Event Began 09 10 2024 2035UT and is in progress 10MeV (S3) Proton/PCA Event Ended 09 10 2024 2240UT 10MeV Maximum proton flux of 1.14E+03 PFU (S3) observed at 09 10 2024 2215UT 10MeV (S3) Proton/PCA Event Began 10 10 2024 0235UT and is in progress 10MeV (S3) Proton/PCA Event Ended 10 10 2024 0455UT 10MeV Maximum proton flux of 1.15E+03 PFU (S3) observed at 10 10 2024 0325UT 10MeV (S3) Proton/PCA Event Began 10 10 2024 1310UT and is in progress 10MeV (S3) Proton/PCA Event Ended 10 10 2024 1535UT 10MeV Maximum proton flux of 1.81E+03 PFU (S3) observed at 10 10 2024 1515UT 10MeV (S2) Proton/PCA Event Ended 10 10 2024 2100UT 10MeV Maximum proton flux of 1.81E+03 PFU (S3) observed at 10 10 2024 1515UT 10MeV (S1) Proton/PCA Event Ended 11 10 2024 0045UT 10MeV Maximum proton flux of 1.81E+03 PFU (S3) observed at 10 10 2024 1515UT 10MeV (S1) Proton/PCA Event Began 11 10 2024 0205UT and is in progress 10MeV (S1) Proton/PCA Event Ended 11 10 2024 0300UT 10MeV Maximum proton flux of 1.29E+01 PFU (S1) observed at 11 10 2024 0225UT 10MeV (S1) Proton/PCA Event Began 26 10 2024 1850UT and is in progress 10MeV (S2) Proton/PCA Event Began 27 10 2024 0900UT and is in progress 10MeV (S2) Proton/PCA Event Ended 29 10 2024 1225UT 10MeV Maximum proton flux of 3.64E+02 PFU (S2) observed at 28 10 2024 1350UT 10MeV (S2) Proton/PCA Event Began 29 10 2024 1345UT and is in progress 10MeV (S2) Proton/PCA Event Ended 29 10 2024 1435UT 10MeV Maximum proton flux of 1.07E+02 PFU (S2) observed at 29 10 2024 1425UT 10MeV (S1) Proton/PCA Event Ended 31 10 2024 1955UT 10MeV Maximum proton flux of 3.64E+02 PFU (S2) observed at 28 10 2024 1350UT 10MeV (S1) Proton/PCA Event Began 31 10 2024 2025UT and is in progress 10MeV (S1) Proton/PCA Event Ended 01 11 2024 0610UT 10MeV Maximum proton flux of 1.51E+01 PFU (S1) observed at 01 11 2024 0125UT 10MeV (S1) Proton/PCA Event Began 21 11 2024 1915UT and is in progress 10MeV (S2) Proton/PCA Event Began 22 11 2024 0305UT and is in progress 10MeV (S2) Proton/PCA Event Ended 22 11 2024 0510UT 10MeV Maximum proton flux of 1.25E+02 PFU (S2) observed at 22 11 2024 0350UT 10MeV (S1) Proton/PCA Event Ended 22 11 2024 1820UT 10MeV Maximum proton flux of 1.25E+02 PFU (S2) observed at 22 11 2024 0350UT

(last updated 21 Dec 2024 11:59 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 21 Dec 2024 11:59 UT)

GOES (Gp16) satellite energetic Proton Flux (Courtesy of SWPC, Boulder Colorado, USA) Proton event detection will lag data time by approximately 1 hour due to data smoothing. Data Date/Time: 21 12 2024 1150 UT Proton Energy Current Proton Level Flux Event Status 10MeV 1.88e+00PFU No proton event in progress 100MeV 1.71e-01PFU No proton event in progress 500MeV 1.60e-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.