The Sun is the most important energy source for the Earth. Since the incoming solar radiation is not equally distributed and peaks at low latitudes the climate system is continuously transporting energy towards the polar regions. Any variability in the Sun-Earth system may ultimately cause a climate change. There are two main variability components that are related to the Sun. The first is due ...

The validity of a technique developed by the authors to identify historical occurrences of intense geomagnetic storms, which is based on finding approximately coincident observations of sunspots and aurorae recorded in East Asian histories, is corroborated using more modern sunspot and auroral observations. Scientific observations of aurorae in Japan during the interval 1957–2004 are used to id...

We report novel spectropolarimetric observations of sunspots carried out with the Tenerife Infrared Polarimeter (TIP) in a near-IR spectral region around 15410 Å, which is known to contain two groups of prominent OH lines that show circular polarization signals of opposite polarity. Surrounding these well-known OH lines, we have discovered the presence of CN lines of the ∆v = 1 band which show ...

this analysis was conducted on 31 synoptic stations in iran. initially, the mann-kendall test was administered in order to analyse the trend of alterations of these two components over time and the results suggest that 16% of the stations show significant relationship with annual precipitation (positive and negative). more stations showed significant relationships between sunspots and minimum a...

Transient microwave brightenings (TMBs) are small-scale energy releases from the periphery of sunspot umbrae, with a flux density two orders of magnitude smaller than that from a typical flare. Gopalswamy et al (1994) first reported the detection of the TMBs and it was pointed out that the radio emission implied a region of very high magnetic field so that the emission mechanism has to be gyror...

A number of methods of flare prediction rely on classification of physical characteristics of an active region, in particular optical classification of sunspots, and historical rates of flaring for a given classification. However, these methods largely ignore the number of flares the active region has already produced, in particular the number of small events. The past history of occurrence of ...

The Sun’s magnetic cycle manifests itself in an year periodic variation in the number of sunspots seen on the solar surface and a periodic reversal in the polarity of its large-scale magnetic fields. Exploring the origins of this magnetic cycle can unravel the physical mechanisms at work in the interior of magnetized stars like the Sun. Such studies are also important for understanding how the ...

The relaxation dynamics of a magnetized plasma system is a subject of fundamental importance in magnetohydrodynamics—with applications ranging from laboratory plasma devices such as the toroidal-field pinch and spheromaks to astrophysical plasmas, stellar flaring activity, and coronal heating. Taylor in 1974 proposed that the magnetic field in a plasma, subject to certain constraints, relaxes t...

We study the temporal evolution of downflows observed at the lateral edges of penumbral filaments in a sunspot located very close to the disk center. Our analysis is based on a sequence of nearly diffraction-limited scans of the Fe I 617.3 nm line taken with the CRisp Imaging Spectro-Polarimeter at the Swedish 1 m Solar Telescope. We compute Dopplergrams from the observed intensity profiles usi...

The relationship between bipolar magnetic regions (BMRs) and their sunspots is an important property of the solar field, but it not well constrained. One consequence that a challenge for surface flux transport models (SFTMs) based on sunspot observations to determine details BMR emergence, which they require as input, from such data. We aimed establish amount in newly emerged BMRs area enclosed...