Main Properties of Forbush Effects Related to High-Speed Streams from Coronal Holes

The IZMIRAN database of Forbush effects and interplanetary disturbances was used to study features of the action of high-speed solar wind streams from coronal holes on cosmic rays. Three hundred and fifty Forbush effects created by coronal holes without other actions were distinguished. The mean values and distributions have been found for different characteristics of events from this group and compared with all Forbush effects and Forbush effects caused by coronal ejections. Despite the great differences in high-speed streams from coronal holes, this group turned out to be more compact and uniform as compared to events related to coronal ejections. Regression dependences and correlation relations between different parameters of events for the studied groups have been obtained. It has been shown that Forbush effects caused by coronal ejections depend considerably more strongly on the characteristics of interplanetary disturbances as compared to Forbush effects related to coronal holes. This suggests a significant difference between the modulation mechanisms of Forbush effects of different types and corroborates earlier conclusions based on indirect data.     

Ring of Station Method in Research of Cosmic Ray Variations: 1. General Description

Geomagnetism and Aeronomy - For over 60 years, neutron monitors have remained the main standard, stable instrument for the measurement of cosmic rays with energies from 400 MeV to hundreds of GeV....     

Behavior of the Speed and Temperature of the Solar Wind during Interplanetary Disturbances Creating Forbush Decreases

Geomagnetism and Aeronomy - Forbush decreases of cosmic rays are caused by two types of solar sources: coronal holes and coronal mass ejections. In some cases, the identification of the solar...     

Similarities and Differences between Forbush Decreases Associated with Streams from Coronal Holes,Filament Ejections,and Ejections from Active Regions

Geomagnetism and Aeronomy - The Forbush decreases for the period from 1997 to 2020 were studied based on data from the database on Forbush effects and interplanetary disturbances created and...     

Bedding Angle Identification from BIF Marker Shales via Modified Dynamic Time Warping

Mathematical Geosciences - When modelling a stratified orebody, accurately representing the dip and dip direction is important for accurate resource estimation. In the banded iron formation-hosted...     

Boundary Identification and Surface Updates Using MWD

Mathematical Geosciences - In the banded iron formation-hosted iron ore deposits in the Hamersley Range of Western Australia, the stratigraphic boundaries are generally modelled using data from...     

Sample Truncation Strategies for Outlier Removal in Geochemical Data: The MCD Robust Distance Approach Versus t-SNE Ensemble Clustering

Mathematical Geosciences - The presence of outliers in geochemical data can impact the accuracy of grade models and influence the interpretation of mine assay data. Removal of outliers is therefore...     

Long-Term Changes in the Number and Magnitude of Forbush-Effects

The IZMIRAN database of Forbush effects and interplanetary disturbances has been used to study long-term changes in the number and magnitude of Forbush effects in the last six solar cycles (1957–2016) for cosmic rays of rigidity of 10 GV. Solar activity cycles have been shown to be well expressed in data of Forbush effects, especially in large magnitude events that almost disappear in minima. The changes in the distribution of Forbush effects and the decrease in their average values from solar activity maximum to minimum are explained by the predominance of cosmic-ray variations due to the action of coronal holes at low activity. It should be noted that the current cycle involves fewer and generally weaker Forbush effects than in the previous five cycles. For each month, an FD index combining the magnitude and number of Forbush effects and convenient for studying long-term variations has been proposed and calculated.