Speaker
Description
The flux of cosmic rays (CRs) is modulated by solar activity. The heliospheric modulation parameter ϕ is a useful quantity to assess the level and variation of the modulation. It is based on the force-field approximation, which simplifies the Parker equation and complex modulation to a single quantity. In spite of the heavy approximations, the modulation potential still stands as a useful and fast method to accurately model the GCR fluxes measured, e.g., by neutron monitors and other intstruments.
Due to the heavy approximations, the parameter was usually considered only at a monthly or yearly resolution. Recently, however, the ϕ-parameter was also computed and published and validated on a daily scale [1]. The results were promising and were further validated by comparison to daily measurements of the Alpha Magnetic Spectrometer (AMS-02) in the International Space Station [2].
In this work we present the ongoing work to improve the accuracy and time-resolution of the heliospheric modulation and how this can be utilized in monitoring space weather in real time. The new process will involve a wider selection of NM stations to improve validity of the ϕ and better assess the effect of geomagnetic rigidity cutoff, atmospheric depth and the quality of data. Preliminarily, the new estimation will use 38 neutron monitor stations instead of 10, and extend the dataset back to 1953, when the first 1-hour measurements began. The rigidity cutoff will also be determined at 1-hour resolution via backtracing, which will take into account magnetospheric and Earth’s rotational effects. This will help us to discover the best way to answer the outstanding obstacle for reliable 1-hour estimations, which is the diurnal variation caused by anisotropy. The new version also has the aim to offer real-time modulation potential estimations, which can have many applications in assessing space weather, radiation environment and the conditions of the local near-Earth space.
References:
[1] Väisänen, P., Usoskin, I., Kähkönen, R., Koldobskiy, S., & Mursula, K. (2023). Revised reconstruction of the heliospheric modulation potential for 1964–2022. Journal of Geophysical Research: Space Physics, 128, e2023JA031352. https://doi.org/10.1029/2023JA031352
[2] Väisänen, P., Bertucci, B., Tomassetti, N., Orcinha, M., Usoskin, I., & Koldobskiy, S. (2025). Simulation of galactic cosmic ray proton fluxes with the daily modulation parameter: Validation with AMS-02 data for 2011–2019. Journal of Geophysical Research: Space Physics, 130, e2025JA033805. https://doi.org/10.1029/2025JA033805
