English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The distribution of the sunspot group size (area) and its dependence on thelevel of solar activity is studied. It is shown that the fraction of smallgroups is not constant but decreases with the level of solar activity so thathigh solar activity is largely defined by big groups. We study the possibleinfluence of solar activity on the ability of a realistic observer to see andreport the daily number of sunspot groups. It is shown that the relationbetween the number of sunspot groups as seen by different observers withdifferent observational acuity thresholds is strongly non-linear and cannot beapproximated by the traditionally used linear scaling ($k-$factors). Theobservational acuity threshold [$A_{\rm th}$] is considered to quantify thequality of each observer, instead of the traditional relative $k-$factor. Anonlinear $c-$factor based on $A_{\rm th}$ is proposed, which can be used tocorrect each observer to the reference conditions. The method is tested on apair of principal solar observers, Wolf and Wolfer, and it is shown that thetraditional linear correction, with the constant $k-$factor of 1.66 to scaleWolf to Wolfer, leads to an overestimate of solar activity around solar maxima.

Dependence of the Sunspot-group Size on the Level of Solar Activity and its Influence on the Calibration of Solar Observers