Speaker
Description
The magnetic activity of the Sun modulates the fluxes of galactic cosmic rays (GCRs) arriving to the heliosphere and Earth. This modulation of GCR can be estimated by a straightforward force-field approach, which reduced the modulation to a single parameter φ with units in megavolts. Even though the physical interpretation of this modulation parameter can be unclear, it can still assess the overall modulation efficiently and relatively accurately.
Since the GCR particles can take from weeks to months to travel from the heliospheric boundary to Earth, the heliospheric modulation parameter is usually recorded in monthly and yearly resolution. Recent work, however, has revealed that the parameter also functions very successfully even in daily, hourly and even minute resolutions during quiet conditions, which can be utilized to monitor the near-Earth radiation environment and related events. The higher cadences mean that parameter is biased to near-Earth space, due to which we call the higher resolution version the near-Earth modulation (NEM) index.
We present recent results of the NEM index at daily, hourly and minute cadences, used methodology and related datasets of neutron monitor data and rigidity cutoff computations. The hourly resolution result includes data from 38 neutron monitors stations from years 1951- 2026, total up to 1491 years of hourly cadence observetations. We find that the parameter performs well with up to +-1 % accuracy to expected values during quiet times. During Forbush decreases and other disruptions there are station-specific deviations from the expected values during the shock and flux rope phases, revealing information about anisotropy during the events. We discuss potential use cases, such as the analysis of Forbush decreases and CME’s, NM data quality assessment and real-time-monitoring of the near- Earth radiation environment and dose rates. We also discuss preliminary results on 5-minute and higher resolutions.