Sq and EEJ—a review on the daily variation of the geomagnetic field caused by ionospheric dynamo currents

Y Yamazaki, A Maute - Space Science Reviews, 2017 - Springer
A record of the geomagnetic field on the ground sometimes shows smooth daily variations
on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are …

Principal component analysis of sunspot cycle shape

J Takalo, K Mursula - Astronomy & Astrophysics, 2018 - aanda.org
Aims. We study the shape of sunspot cycles using the Wolf sunspot numbers and group
sunspot numbers of solar cycles 1–23. We determine the most typical “model” cycles and the …

Ionospheric current variations by empirical orthogonal function analysis: Solar activity dependence and longitudinal differences

C Owolabi, H Ruan, Y Yamazaki… - Journal of …, 2022 - Wiley Online Library
The solar quiet (Sq) ionospheric current variations exhibit spatial and temporal patterns that
can be identified by the prevailing eigenmodes based on the empirical orthogonal function …

Empirical modeling of ionospheric current using empirical orthogonal function analysis and artificial neural network

C Owolabi, H Ruan, Y Yamazaki, J Li, J Zhong… - Space …, 2021 - Wiley Online Library
Given the potential importance of solar quiet (Sq) ionospheric current in geomagnetic field
modeling, it is vital to obtain accurate parameters characterizing its variations, particularly …

Re‐visiting EEJ and CEJ occurrences pattern under the influence of Sq variations of both hemispheres

RK Archana, M Lingala, K Arora - Journal of Geophysical …, 2023 - Wiley Online Library
The present study investigated the variability in Equatorial electrojet (EEJ) and Counter
electrojet (CEJ) extracted at the Indian equatorial station Tirunelveli (TIR) using low‐latitude …

Spatial and temporal distribution of solar green-line corona for Solar Cycles 18–24

J Takalo - Solar Physics, 2022 - Springer
The homogeneous coronal data set (HCDS) of the green corona (Fe xiv) and the coronal
index of solar activity (CI) have been used to study the time–latitudinal distribution in Solar …

An Improved Halo Coronal Mass Ejection Geoeffectiveness Prediction Model Using Multiple Coronal Mass Ejection Features Based on the DC-PCA-KNN Method

D Ye, H Li, L Guo, X Jiang - The Astrophysical Journal, 2024 - iopscience.iop.org
Coronal mass ejections (CME) are regarded as the main drivers of geomagnetic storms
(GSs). In the prediction of geoeffectiveness, various CME features have been introduced …

Analysis of the solar flare index for solar cycles 18–24: extremely deep Gnevyshev gap in the chromosphere

J Takalo - Solar Physics, 2023 - Springer
We study the solar flare index (SFI) for the Solar Cycles 18–24. We find that SFI has deeper
Gnevyshev gap (GG) in its first principal component than other atmospheric parameters. The …

Extracting hale cycle related components from cosmic-ray data using principal component analysis

J Takalo - Solar Physics, 2022 - Springer
We decompose the monthly cosmic-ray data, using several neutron-monitor count rates, of
Cycles 19–24 with principal component analysis (PCA). Using different cycle limits, we show …

On the occurrence of afternoon counter electrojet over Indian longitudes during June solstice in solar minimum

K Pandey, R Sekar, BG Anandarao… - Journal of …, 2018 - Wiley Online Library
Studies made earlier using ground‐based observations of geomagnetic field over the Indian
longitudes revealed that the occurrence of equatorial counter electrojet (CEJ) events in …