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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 automated and uses CME inputs from different catalogues and services.
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 a module that automates the procedure of importing the corresponding data and estimating the maximum ap index is triggered. In particular, this module scans the most recent CME events from a real-time database and is triggered when a new CME event is recorded. Then the algorithm imports all the need data and parameters for this CME event (i.e velocity, angular width etc) and estimates the maximum value of the ap index and the time of arrival. The results of this module are imported in the main algorithm.

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 affected by the limitations of the CACTus and CCMC CME Scoreboard limitations.. Furthermore, the coronal hole solar wind impacts and high speed streams (HSS) has not been assessed yet for this product version

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
  • Robbrecht E., Berghmans D., Van der Linden R.A.M.: 2009, Automated LASCO CME Catalog for Solar Cycle 23: Are CMEs Scale Invariant?, ApJ 691, 1222
    • Robbrecht E., Berghmans D., Van der Linden R.A.M.: 2006, Objective CME detection over the solar cycle: A first attempt, AdSpR 38, 475
  • Robbrecht E. & Berghmans D.: 2004, Automated recognition of coronal mass ejections (CMEs) in near-real-time data, A&A 425, 1097
  • Berghmans D., Foing B.H., Fleck B.: 2002, Automated detection of CMEs in LASCO data Proc. of SOHO-11 workshop, Davos, ESA SP-508
  • Kay C., Palmerio E., Riley P., Mays M.L., Nieves-Chinchilla T., Romano M. et al.: 2024, Updating measures of CME arrival time errors. Space Weather, 22, e2024SW003951
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

        • Berghmans D., Foing B.H., Fleck B.: 2002, Automated detection of CMEs in LASCO data Proc. of SOHO-11 workshop, Davos, ESA SP-508
        • Kay C., Palmerio E., Riley P., Mays M.L., Nieves-Chinchilla T., Romano M. et al.: 2024, Updating measures of CME arrival time errors. Space Weather, 22, e2024SW003951. https://doi.org/10.1029/2024SW003951
        • Paouris E., Abunina M., Belov A., Mavromichalaki H.: 2021, Statistical analysis on the current capability to predict the Ap Geomagnetic Index, New Astronomy, 86, article id. 101570. Doi: 10.1016/j.newast.2021.101570
        • Robbrecht E., Berghmans D., Van der Linden R.A.M.: 2009, Automated LASCO CME Catalog for Solar Cycle 23: Are CMEs Scale Invariant?, The Astrohysical JJournal, 691, 1222. Doi: 10.1088/0004-637X/691/2/1222
        • Robbrecht E., Berghmans D., Van der Linden R.A.M.: 2006, Objective CME detection over the solar cycle: A first attempt, Adv Space Res 38, 475. https://doi.org/10.1016/j.asr.2005.02.005
        • Robbrecht E. & Berghmans D.: 2004, Automated recognition of coronal mass ejections (CMEs) in near-real-time data, Astron & Astrophys 425, 1097. https://doi.org/10.1051/0004-6361:20041302
        • Rostoker G.: 1972, Geomagnetic Indices. Reviews of Geophysics and Space Physics 10 (4), 935. Doi:10.1029/RG010i004p00935

         Reports

        • Strong geomagnetic storm conditions (G3) were observed on 05-06 November 2023 following the arrival of a CME.
        • Severe geomagnetic storm conditions (G4) were observed on 24 March 2024
        • An Extreme Geomagnetic storm (G5) on10-11 May 2024
        • The Severe Geomagnetic Storm (G4) on September 17, 2024
        • The Severe Geomagnetic Storm (G4) on October 10-11, 2024
        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.
        This product uses data from the CACTus CME catalog, generated and maintained by the SIDC at the Royal Observatory of Belgium.
        We acknowledge the use of the Community Coordinated Modeling Center (CCMC) at Goddard Space Flight Center for the use of the CME Arrival Time Scoreboard, the Arrival Time Scoreboard is available at https://kauai.ccmc.gsfc.nasa.gov/CMEscoreboard/ and to the existing sources or the teams at the CCMC and M2M Space Weather Analysis Office for populating and maintaining the online database.
        For further information about space weather in the ESA Space Safety Programme see: https://www.esa.int/Safety_Security/Space_weather
        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. This product uses data from the CACTus CME catalog, generated and maintained by the SIDC at the Royal Observatory of Belgium. We acknowledge the use of the CCMC CME Scoreboard, the Arrival Time Scoreboard is available at https://kauai.ccmc.gsfc.nasa.gov/CMEscoreboard/ and the existing sources or the teams at the CCMC and M2M Space Weather Analysis Office for populating and maintaining the online database.