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Coloured scaled plot of ap values showing in grey colour past 72 hours (actual data provided by GFZ) and the forecasted values for the next 72 hours starting (time = 0) at the time of the most recent output/run. Colour Cyan corresponds to ap values 0-3, lime to 4-7, yellow 9-15, Orange 18-32, Red 39-154 and Magenta >179.
Tabulated data of forecasting ap values

This forecasting technique utilizes state-of-the-art machine learning techniques (Long Short Term Memory algorithm) to predict three-hour time intervals of ap geomagnetic index values for the next 72 hours with a time resolution of 3 hours.It is noted that the algorithm is aided by Human/forecaster in case of CME or/and CH event.
Description

1.-Introduction
Daily regular magnetic field variation arises from current systems caused by regular solar radiation changes. Other irregular current systems produce magnetic field changes caused by the interaction of the solar wind with the magnetosphere, by the magnetosphere itself, by the interactions between the magnetosphere and ionosphere. Magnetic activity indices were designed to describe variation in the geomagnetic field caused by these irregular current systems.

2.- Methodology
A new product based on a machine learning approach is provided to forecast ap index values with prediction lead time up to 72 hours. This product is utilizing the archived time series of the ap index with a 3-hour time interval resolution based on archived data of the solar cycles 23 and 24 to train the Long short-term memory (LSTM) model and predict the future values (forecasts) from t0 (the time of the most recent run of the code) up to three days in total (24 values of 3-hour time interval forecasts) in the future. The model is capable of reproducing and forecasting quiet or active conditions. In case of extreme Space Weather events (i.e., Coronal Mass Ejection (CME) arrival and/or high-speed streams of solar wind originating from coronal holes (CH)) the model is aided by human intervention. In particular, the on-duty forecaster operating from the Athens Cosmic Ray Group (NKUA) provides inputs that are ingested in the model via two modules:
• The CME_arr module reads the file which created by the duty forecaster with the following information: Onset Date and Time of the CME, CME linear speed, angular width and predicted Time-of-Arrival of the CME at Earth.
• The CH_arr module reads the file which created by the duty forecaster with the following information: Date and Time of the first appearance of the coronal hole on the first meridian of the visible solar disk and an estimated speed of the solar wind from this CH.

3.- Caveats and Limitations
In case of extreme Space Weather events (i.e.. Coronal Mass Ejection(CME)arrival and/or high-speed streams of solar wind originating from coronal holes (CH) the model is aided by the on-duty forecaster operating from the Athens Cosmic ray Group (NKUA). The forecaster's input is ingested via the modules presented in the previous section. When the forecaster's intervention is needed the prediction lead time is shortened from 72 hours to 24-48 hours.

Bibliography:
  • Rostoker, G. :1972. Geomagnetic Indices. Reviews of Geophysics and Space Physics 10 (4), 935. doi:10.1029/RG010i004p00935

  • Paouris, E. , Abunina, M. ,Belov, A. ,Mavromichalaki, H.: 2021, Statistical analysis on the current capability to predict the Ap Geomagnetic Index,  New Astronomy, Vol.86, article id. 101570. doi: 10.1016/j.newast.2021.101570
Frequently Asked Questions

1. What are geomagnetic indices?
Geomagnetic indices are a measure of geomagnetic activity, which is a signature of the response of the Earth magnetosphere and ionosphere to solar forcing. They play a significant role in describing the magnetic configuration of the Earth’s ionized environment.


    2. What is Ap and ap index?
    The 3-hourly ap and the daily Ap indices are planetary magnetic activity indices, with units of 2nT. Related to the Kp index, they are average values of the irregular disturbance levels in the horizontal field components, observed at selected magnetic observatories worldwide.


      3. Why we are interested in ap prediction?
      The geomagnetic index ap is related to effects of the Space Weather such as satellite drag and sensor degradation, effects of geomagnetically, induced currents (GICs) on the power grids and pipelines, radiation threat to polar flight crews and astronauts, as well as high-frequency, communication outages in polar regions
        Publications

        • E. Paouris and H. Mavromichalaki: ‘Effective Acceleration Model for the arrival time of interplanetary shocks driven by coronal mass ejections’, Solar Physics, 292, 180, 2017, doi 10.1007/s11207-017-1212-2
        • E. Paouris and H. Mavromichalaki: ‘Interplanetary coronal mass ejections resulting from Earth-Directed CMEs Using SOHO and ACE Combined Data During Solar Cycle 23’ Solar Physics, 292, 30, 2017, doi: 10.1007/s11207-017-1050-2
        • E. Paouris, A. Belov, M. Abunin, H. Mavromichalaki: ‘Statistical analysis on the current capability to predict the Ap Geomagnetic Index’ New Astronomy, 86, 2021. doi10.1016/j.newast.2021.101570
        • A.Stassinakis, M.Livada, M.Gerontidou, A.Tezari,H.Mavromichalaki, E.Paouris,P.Makrantoni: ‘Forecast of the Geomagnetic Index ap during CME events’, European Space Weather Week, 2023. Click here.
        • H. Mavromichalaki, M.Livada, A.Stassinakis, M.Gerontidou, M-C Papailiou,L. Drude, Aikaterini Karmi: ‘The ap Prediction Tool Implemented by the A.Ne.Mo.S NKUA Group, 2024. Click here.
        • H. Mavromichalaki, M-C Papailiou, M.Livada, M.Gerontidou, P. Paschalis, A.Stassinakis, M. Abunina, N. Shlyk, A. Abunin, A. Belov, V. Yanke, N. Crosby, M. Dierckxsens, L. Drude: ‘Unusual Forbush Decreases and Geomagnetic Storms on 24 March,2024 and 11 May,2024, 2024. Click here.

         Reports

        • Strong geomagnetic storm conditions (G3) were observed on 05-06 November 2023 following the arrival of a CME. Click here to read the report
        • Severe geomagnetic storm conditions (G4) were observed on 24 March 2024 Click here to read the report
        • An Extreme Geomagnetic storm (G5) on10-11 May 2024 Click here to read the report
        • The Severe Geomagnetic Storm (G4) on September 17, 2024 Click here to read the report
        • The Severe Geomagnetic Storm (G4) on October 10-11, 2024 Click here to read the report
        Acknowledgments

        This web site forms part of the European Space Agency's network of space weather services and service development activities, and is supported under ESA contract number 4000134036/21/D/MRP. For further product-related information or enquiries contact helpdesk. Email: helpdesk.swe@esa.int
        All publications and presentations using data obtained from this site should acknowledge the ANEMOS/NKUA group and the ESA Space Safety Programme.
        For further information about space weather in the ESA Space Safety Programme see: https://www.esa.int/Safety_Security/Space_weather
        NKUA is thankful to the German Research Center of Geoscience,GFZ (https://kp.gfz-potsdam.de/en/) for providing ap index data.
        Frequently Asked Questions

        1. What are geomagnetic indices?
        Geomagnetic indices are a measure of geomagnetic activity, which is a signature of the response of the Earth magnetosphere and ionosphere to solar forcing. They play a significant role in describing the magnetic configuration of the Earth’s ionized environment.


          2. What is Ap and ap index?
          The 3-hourly ap and the daily Ap indices are planetary magnetic activity indices, with units of 2nT. Related to the Kp index, they are average values of the irregular disturbance levels in the horizontal field components, observed at selected magnetic observatories worldwide.


            3. Why we are interested in ap prediction?
            The geomagnetic index ap is related to effects of the Space Weather such as satellite drag and sensor degradation, effects of geomagnetically, induced currents (GICs) on the power grids and pipelines, radiation threat to polar flight crews and astronauts, as well as high-frequency, communication outages in polar regions
              Publications

              • E. Paouris and H. Mavromichalaki: ‘Effective Acceleration Model for the arrival time of interplanetary shocks driven by coronal mass ejections’, Solar Physics, 292, 180, 2017, DOI 10.1007/s11207-017-1212-2
              • E. Paouris and H. Mavromichalaki: ‘Interplanetary coronal mass ejections resulting from Earth-Directed CMEs Using SOHO and ACE Combined Data During Solar Cycle 23’ Solar Physics, 292, 30, 2017, DOI: 10.1007/s11207-017-1050-2
              • E. Paouris, A. Belov, M. Abunin, H. Mavromichalaki: ‘Statistical analysis on the current capability to predict the Ap Geomagnetic Index’ New Astronomy, 86, 2021 https://doi.org/10.1016/j.newast.2021.101570
              Acknowledgments

              This web site forms part of the European Space Agency's network of space weather services and service development activities, and is supported under ESA contract number 4000134036/21/D/MRP. For further product-related information or enquiries contact helpdesk. Email: helpdesk.swe@esa.int
              All publications and presentations using data obtained from this site should acknowledge the ANEMOS/NKUA group and the ESA Space Safety Programme.
              NKUA is thankful to the German Research Center of Geoscience,GFZ (https://kp.gfz-potsdam.de/en/) for providing ap index data.