Eleven-year Schwabe cycle in solar activity is not yet fully understood despite of its almost two century discovery. It is generally interpreted as owing to some sort of magnetic dynamo operating below or inside the convection zone. The magnetic field strength in the dynamo layer may determine the importance of the tachocline in the model which is responsible for the cyclic magnetic field, but ...

Received: October 20, 2016 Revised: March 07, 2017 Accepted: March 11, 2017 Abstract: Background: Nitric oxide concentration in the upper atmosphere is known to be highly dependent on the solar activity. It can be transported to the stratosphere by the atmospheric circulation. In the stratosphere it is responsible for the destruction of ozone and consequently stratospheric heating rates are aff...

The authors present an interesting spatio-temporal analysis of 4-dim solar data, for a flaring event, the preflare phase, and a Quiet Sun region. They use a Singular Value Decomposition method and investigate the multi-scale behavior of the physical parameter of the temperature T, and attempt to extract information on the heat flow dT/dx in a flare. The description of the method is clear, and t...

We present model calculations of facular and sunspot contrasts as a function of wavelength and limb angle on the Sun. These are the first such calculations; they assume LTE and are based on opacity distribution functions (ODFs). The calculated facular contrasts as a function of limb angle fit into the general picture of contrast measurements, and the behaviour of the contrast with wavelength at...

The solar polar fields reverse because magnetic flux from decaying sunspots moves towards the poles, with a preponderance of flux from the trailing spots. If there is a strong asymmetry in the sense that most activity is in the Northern Hemisphere, then that excess flux will move to the North Pole and reverse that pole first. If later on, there is more activity in the South, then that flux will...

We study the response of the low-degree, solar p-mode frequencies to the unusually extended minimum of solar surface activity since 2007. A total of 4768 days of observations collected by the space-based, Sun-as-a-star helioseismic GOLF instrument are analyzed. A multi-step iterative maximum-likelihood fitting method is applied to subseries of 365 days and 91.25 days to extract the p-mode param...

We report the first observation of a ~27 day period component in daily maximum temperature recorded at widely spaced locations in Australia. The ~27 day component, extracted by band pass filtering, is correlated with the variation of daily solar radio flux during years close to solar minimum. We demonstrate that the correlation is related to the emergence of regions of solar activity on the Sun...

The effects of solar flares on the propagation of subionospheric VLF signals from NWC and NLK transmitter stations monitored at a low-latitude station, Suva (18.2°S, 178.4°E), Fiji, between December 2006 and December 2010 (an unprecedented solar minimum of solar cycles 23 and 24) and between January 2012 and December 2013 (moderate solar activity at the peak of solar cycle 24) have been analyze...