Related papers: Unusual Polar Conditions in Solar Cycle 24 and the…
Using magnetic and microwave butterfly diagrams, we compare the behavior of solar polar regions to show that (i) the polar magnetic field and the microwave brightness temperature during the solar minimum substantially diminished during the…
We report on the status of solar cycle 24 based on polar prominence eruptions (PEs) and microwave brightness enhancement (MBE) information obtained by the Nobeyama radioheliograph. The north polar region of the Sun had near-zero field…
The Sun's polar magnetic fields change their polarity near the maximum of sunspot activity. We analyzed the polarity reversal epochs in Solar Cycles 21 to 24. There was a triple reversal in the N-hemisphere in Solar Cycle 24 and single…
Aims: To investigate solar polar fields during cycle 24, using measurements of solar magnetic fields in the latitude range 55 - 90 degree and 78 - 90 degree, to report a prolonged and unusual hemispheric asymmetry in the polar field…
The solar activity in Cycle 23--24 shows differences from the previous cycles that were observed with modern instruments, e.g. long cycle duration and a small number of sunspots. To appreciate the anomalies further, we investigated the…
Solar cycle activity forecasting, mainly its magnitude and timing, is an essential issue for numerous scientific and technological applications: in fact, during an active solar period, many strong eruptions occur on the Sun with increasing…
We use microwave imaging observations from the Nobeyama Radioheliograph at 17 GHz for long-term studies of solar activity. In particular, we use the polar and low-latitude brightness temperatures as proxies to the polar magnetic field and…
The solar polar fields reverse because magnetic flux from decaying sunspots moves towards the poles, with a preponderance of flux from the trailing spots. Let us assume that there is a strong asymmetry in the sense that all activity is in…
The "extended" solar cycle 24 began in 1999 near 70 degrees latitude, similarly to cycle 23 in 1989 and cycle 22 in 1979. The extended cycle is manifested by persistent Fe XIV coronal emission appearing near 70 degrees latitude and slowly…
As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33--2014.33) of…
The onset of the "Rush to the Poles" of polar-crown prominences and their associated coronal emission is a harbinger of solar maximum. Altrock (Solar Phys. 216, 343, 2003) showed that the "Rush" was well-observed at 1.15 Ro in the Fe XIV…
Analysis of synoptic data from the Vector Stokes Magnetograph (VSM) of the Synoptic Optical Long-term Investigations of the Sun (SOLIS) and the NASA/NSO Spectromagnetograph (SPM) at the NSO/Kitt Peak Vacuum Telescope facility shows that the…
In this paper, we have made a statistical analysis of solar H$\alpha$ flares that occurred during the period 1996 to 2005 to investigate their spatial distribution with respect to northern and southern hemispheres of the Sun. The analysis…
The flare activity and the ultraviolet emission of the sun during its 24-th cycle are analysed. As compared to cycles 21-23, where the most powerful flares were observed during the decay phase, in cycle 24 the greatest number of powerful…
Solar variability occurs over a broad range of spatial and temporal scales, from the Sun's brightening over its lifetime to the fluctuations commonly associated with magnetic activity over minutes to years. The latter activity includes most…
The process of the Sun's polar field cancellation reversal commences with the emergence of new cycle Hale's polarity active regions. Once the Sun undergoes polarity reversal, typically occurring near the peak of solar activity, it begins…
Here we present the results of the study of the north-south (N-S) distribution and asymmetry of GOES soft X-ray (SXR) flares during solar cycle 24. The period of study includes ascending, maximum and descending phases of the cycle. During…
We present evidence that $>25$ MeV solar proton events show a clustering in time at intervals of $\approx$ six months that persisted during the rising and peak phases of Solar Cycle 24. This phenomenon is most clearly demonstrated by…
The forthcoming solar cycle (SC) 25 was beleived to be rather low when using the sunspot number (SN) as a measurement of the level of activity. The most popular prediction was made by the panel of NASA in 2019, including works based on…
Synoptic magnetograms and relevant proxy data were analyzed to study the evolution of the Sun's polar magnetic fields. Time-latitude analysis of large-scale magnetic fields demonstrates cyclic changes in their zonal structure and the…