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Polar Crown Filaments (PCFs) form above the magnetic polarity inversion line, which separates the unipolar polar fields and the nearest dispersed fields from trailing part of active regions with opposite polarity. The statistical properties…

Solar and Stellar Astrophysics · Physics 2018-08-08 Yan Xu , Werner Potzi , Hewei Zhang , Nengyi Huang , Ju Jing , Haimin Wang

In this paper, we apply Principal Component Analysis (PCA) to experimental data recorded by the KASCADE experiment to reconstruct the mass composition of cosmic rays around the \textit{knee} region. A set of four extensive air shower…

High Energy Astrophysical Phenomena · Physics 2025-10-10 Nicusor Arsene

We study the differences in the heavy ion composition of solar energetic particle (SEP) events between solar cycles 23 and 24. We have surveyed the SOHO/ERNE heavy ion data from the beginning of solar cycle 23 until the end of June 2015,…

Solar and Stellar Astrophysics · Physics 2016-04-27 O. Raukunen , E. Valtonen , R. Vainio

Using data from the Geostationary Operational Environmental Satellites (GOES) spacecraft in the 1-8 \AA\ wavelength range for Solar Cycles 23, 24, and part of Cycles 21 and 22, we compare mean temporal parameters (rising, decay times,…

Solar and Stellar Astrophysics · Physics 2017-10-19 I. M. Chertok , A. V. Belov

The south-north travel-time differences are measured by applying time-distance helioseismology to the MDI and HMI medium-degree Dopplergrams covering May 1996-April 2017. Our data analysis corrects for several sources of systematic effects:…

Solar and Stellar Astrophysics · Physics 2018-11-14 Zhi-Chao Liang , Laurent Gizon , Aaron C. Birch , Thomas L. Duvall , S. P. Rajaguru

In the present paper a systematic study is carried out to validate the similarity or degree of relationship between daily terrestrial cosmic rays intensity and three characteristics of about evolution of solar corona, like a number of…

Solar and Stellar Astrophysics · Physics 2019-06-05 D. Sierra-Porta

We report the identification of cyclical changes in the orbital period of the eclipsing cataclysmic variable HT Cas. We measured new white dwarf mid-eclipse timings and combined with published measurements to construct an…

Astrophysics · Physics 2009-11-13 B. W. Borges , R. Baptista , C. Papadimitriou , O. Giannakis

Long observational series for bipolar active regions (ARs) provide significant information about the mutual transformation of the poloidal and toroidal components of the global solar magnetic field. The direction of the toroidal field…

Solar and Stellar Astrophysics · Physics 2022-03-14 A. Zhukova , A. Khlystova , V. Abramenko , D. Sokoloff

We have statistically analyzed 379 radio-loud (RL) CMEs and their associated flares during the period 1996 - 2019 covering both solar cycles (SC) 23 and 24. We classified them into two sets of populations based on the observation period: i)…

Solar and Stellar Astrophysics · Physics 2022-05-25 P. Pappa Kalaivani , O. Prakash , A. Shanmugaraju , G. Michalek , G. Selvarani

The maximum of a solar cycle contain two or more peaks, known as Gnevyshev peaks. Studies of this property of solar cycles may help for better understanding the solar dynamo mechanism. We analysed the 13-month smoothed monthly mean…

Solar and Stellar Astrophysics · Physics 2023-02-27 J. Javaraiah

Context. The variations of solar activity over long time intervals using a solar activity reconstruction based on the cosmogenic radionuclide 10Be measured in polar ice cores are studied. Methods. By applying methods of nonlinear dynamics,…

Solar and Stellar Astrophysics · Physics 2015-06-18 A. Hanslmeier , R. Brajsa , J. Calogovic , B. Vrsnak , D. Ruzdjak , F. Steinhilber , C. L. MacLeod , Z. Ivezic , I. Skokic

This paper presents a statistical analysis of Soft X-ray (SXR) flares during the period January 1976 to December 2007 covering solar cycles (SCs) 21, 22, and 23. We have analysed north-south (N-S) and east-west (E-W) asymmetry of SXR at low…

Solar and Stellar Astrophysics · Physics 2015-05-13 Navin Chandra Joshi , Neeraj Singh Bankoti , Seema Pande , Bimal Pande , Kavita Pandey

In our previous article (Priyal et al. in Solar Phys. 289, 127, 2014) we have discussed the details of observations and methodology adopted to analyze the Ca-K spectroheliograms obtained at the Kodaikanal Observatory (KO) to study the…

Solar and Stellar Astrophysics · Physics 2017-07-04 Muthu Priyal , Jagdev Singh , Ravindra Belur , Somasundaram Kameshwaran Rathina

Measurements of Ra-226 activity from eight HPGe gamma ray detectors at the NC State University PULSTAR Reactor were analyzed for evidence of periodic variations, with particular attention to annual variations. All measurements were made…

Nuclear Experiment · Physics 2017-01-10 Daniel D. Stancil , Sümeyra Balci Yegen , David A. Dickey , Chris R. Gould

To better understand the influence of the activity cycle on the solar atmosphere, we report the time variation of the radius observed at 37 GHz ($\lambda$=8.1 mm) obtained by the Mets\"ahovi Radio Observatory (MRO) through Solar Cycles 22…

Solar and Stellar Astrophysics · Physics 2019-12-17 Caius L. Selhorst , Juha Kallunki , C. G. Giménez de Castro , Adriana Valio , Joaquim E. R. Costa

We have observed selected Fraunhofer lines, both integrated over the Full Disk and for a small circular region near the center of the solar disk, on 1,215 days for the past 30 years. Full Disk results: Ca II K 393 nm nicely tracks the 11…

Astrophysics · Physics 2008-11-26 W. Livingston , L. Wallace , O. R. White , M. S. Giampapa

It is known that the weak state of the heliosphere due to diminished solar activity in cycle 24 back-reacted on coronal mass ejections (CMEs) to make them appear wider for a given speed. One of the consequences of the weak state of the…

Solar and Stellar Astrophysics · Physics 2023-08-02 Nat Gopalswamy , Grzegorz Michalek , Seiji Yashiro , Pertti Mäkelä , Sachiko Akiyama , Hong Xie

In the paper, a comparative primary cosmic rays (PCR) comparative analysis by $E_0$ and the spectra of variable stars by periods is carried out in order to establish the causes of irregularities in the spectrum of PCR by $E_0$. The study…

High Energy Astrophysical Phenomena · Physics 2023-05-31 S. E. Pyatovsky

The last solar minimum was, by recent standards, unusually deep and long. We are now close to the maximum of the subsequent solar cycle, which is relatively weak. In this article we make comparisons between different global (unresolved)…

Solar and Stellar Astrophysics · Physics 2015-07-13 A. -M. Broomhall , V. M. Nakariakov

Prior to the epoch of reionisation, the 21-cm signal of the cosmic dawn is dominated by the Lyman-$\alpha$ coupling and gas temperature fluctuations caused by the first sources of radiation. While early efforts to model this epoch relied on…

Cosmology and Nongalactic Astrophysics · Physics 2021-05-05 Aurel Schneider , Sambit K. Giri , Jordan Mirocha