The signature of the stable auroral red arc (SAR arc) as it appears on ionograms is described. The key features are a very significant increase in the amount of spread-F and a reduction in the maximum plasma density compared with regions just equatorward and poleward of the SAR arc Identification of the SAR arc signature is made by using complementary data from the global auroral imaging instrument on board the Dynamics Explorer-1 satellite. At sunspot minimum there is a positive correlation between the occurrence of spread-F on ionograms from Argentine Islands, Antarctica (65°S, 64°W; L = 2.3) and magnetic activity. In contrast, at sunspot maximum there is a weak negative correlation when the K magnetic index is less than 6. but a significant increase in spread-F occurrence at K ⩾ 6. Detailed study of ionograms shows that there are two distinct regions where considerable spread-F is observed. These are the region where SAR arcs occur and the poleward edge of the mid-latitude ionospheric trough. They are separated by a region associated with the trough minimum, where comparatively little spread-F is seen. It is suggested that the movement of these features to lower latitudes with increasing magnetic and solar activity can explain the lack of correspondence between variations of spread-F occurrence as a function of magnetic activity at sunspot maximum compared with that at sunspot minimum at Argentine Islands.
World Maritime News Staff
Related Manchester United and Real Madrid are set to do battle at the Philip II Arena in Skopje, Macedonia, as both teams prepare for their UEFA Super Cup game tonight.Europa League winners, Manchester United, who will be without Eric Bailly, Phil Jones, Rojo, Shaw, and Ashley Young due to injuries and suspensions, will hope to win their first UEFA Super Cup trophy since 1991, having lost their last two appearances in 1999 and 2008. Preparing for the #SuperCup! pic.twitter.com/ecHrIWqnOx— Manchester United (@ManUtd) August 7, 20173-time UEFA Super Cup winners and Champions League champions, Real Madrid, will be making their sixth appearance in the season curtain raiser cup, as manager, Zinedine Zidane declares that his side “aren’t tired of winning”. Zidane: “Every year it gets harder for us, but we have personality and hunger and we aren’t tired of winning.”#SuperCup #LaysUnited pic.twitter.com/F7Ug2SqCzf— Champions League (@ChampionsLeague) August 8, 2017Just over two weeks ago, both teams faced each other at the International Champions Cup (ICC) pre-season friendly in the USA, with United edging Real on penalties after the game ended 1-1 in regulation time.