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 03 Dec 2023 00:35 UT)

10MeV (S1) Proton/PCA Event Began 16 07 2023 0625UT and is in progress 10MeV (S1) Proton/PCA Event Ended 16 07 2023 0855UT 10MeV Maximum proton flux of 1.80E+01 PFU (S1) observed at 16 07 2023 0735UT 10MeV (S2) Proton/PCA Event Began 18 07 2023 0145UT and is in progress 10MeV (S1) Proton/PCA Event Began 18 07 2023 0105UT and is in progress 10MeV (S2) Proton/PCA Event Ended 18 07 2023 1425UT 10MeV Maximum proton flux of 6.20E+02 PFU (S2) observed at 18 07 2023 0615UT 10MeV (S1) Proton/PCA Event Ended 20 07 2023 0335UT 10MeV Maximum proton flux of 6.20E+02 PFU (S2) observed at 18 07 2023 0615UT 10MeV (S1) Proton/PCA Event Began 29 07 2023 0035UT and is in progress 10MeV (S2) Proton/PCA Event Began 29 07 2023 0520UT and is in progress 10MeV (S2) Proton/PCA Event Ended 29 07 2023 1150UT 10MeV Maximum proton flux of 1.54E+02 PFU (S2) observed at 29 07 2023 0920UT 10MeV (S1) Proton/PCA Event Ended 30 07 2023 1615UT 10MeV Maximum proton flux of 1.54E+02 PFU (S2) observed at 29 07 2023 0920UT 10MeV (S1) Proton/PCA Event Began 05 08 2023 1105UT and is in progress 10MeV (S1) Proton/PCA Event Ended 05 08 2023 2000UT 10MeV Maximum proton flux of 1.85E+01 PFU (S1) observed at 05 08 2023 1745UT 10MeV (S1) Proton/PCA Event Began 05 08 2023 2340UT and is in progress 10MeV (S1) Proton/PCA Event Ended 06 08 2023 0435UT 10MeV Maximum proton flux of 1.77E+01 PFU (S1) observed at 06 08 2023 0140UT 10MeV (S1) Proton/PCA Event Began 08 08 2023 0105UT and is in progress 10MeV (S1) Proton/PCA Event Ended 10 08 2023 0915UT 10MeV Maximum proton flux of 4.77E+01 PFU (S1) observed at 09 08 2023 0025UT 10MeV (S1) Proton/PCA Event Began 01 09 2023 0425UT and is in progress 10MeV (S1) Proton/PCA Event Ended 01 09 2023 2000UT 10MeV Maximum proton flux of 2.58E+01 PFU (S1) observed at 01 09 2023 0610UT

(last updated 03 Dec 2023 00:35 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 03 Dec 2023 00:35 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: 03 12 2023 0025 UT Proton Energy Current Proton Level Flux Event Status 10MeV 2.20e-01PFU No proton event in progress 100MeV 1.82e-01PFU No proton event in progress 500MeV 1.75e-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.