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4 papers · 1 filter
The First Four Ground-Level Enhancements in the 1940s: Investigation, Digitisation, and Analysis of Forgotten Data
Hisashi Hayakawa, Stepan Poluianov, Sergey Koldobskiy +4
Intense solar eruptions occasionally accelerate solar energetic particles (SEPs) and can trigger ground-level enhancements (GLEs). Among the 77 known GLEs, the first four GLEs, #1…
Reconstructing solar magnetic fields from historical observations VIII. AIA 1600 Å contrast as a proxy of solar magnetic fields
Ismo Tähtinen, Ilpo Virtanen, Alexei A. Pevtsov +1
The bright regions in the solar chromosphere and temperature minimum have a good spatial correspondence with regions of intense photospheric magnetic field. Their observation start…
Asymmetric distribution of weak photospheric magnetic field values
Tibebu Getachew, Ilpo Virtanen, Kalevi Mursula
We use the synoptic maps of the photospheric magnetic field observed at Wilcox Solar Observatory, Mount Wilson Observatory, Kitt Peak, SOHO/MDI, SOLIS/VSM, and SDO/HMI to study the…
A new method to estimate annual solar wind parameters and contributions of different solar wind structures to geomagnetic activity
Lauri Holappa, Kalevi Mursula, Timo Asikainen
In this paper, we study two sets of local geomagnetic indices from 26 stations using the principal component (PC) and the independent component (IC) analysis methods. We demonstrat…