2016 schedule


Solar Flaring in SC24: End of an Era?

Harry Roberts

ASNSW, SCS(BAA, NSW), Shoalhaven Astronomers

This paper revisits the question of Solar Flaring where the NACAA2008 paper, “Anomalous Flaring in Solar Cycle 23”, left off. That paper concluded that flaring in solar cycle 23 (SC23, 1997-2008) was unusually strong compared to earlier cycles. Reasons for this were advanced. As well as being a thermonuclear reactor, the Sun contains a dynamo, and magnetism drives most solar activity - including sunspots and their flares. Data collected since SC23 (2008 – 2016) will show that the power of current flaring in SC24 (GOES satellite X-ray flux, 2008 - 2016) has fallen dramatically when compared to the earlier cycles, particularly SC23: indeed to levels not seen since X-ray flux data have been available (~40yrs). We examine some of the strong flares of SC24, as logged in H-alpha, contrasting them with earlier SC23 events. This will be supported by data from other channels, notably the strength of sunspot umbral-fields from Mt Wilson and Kitt Peak facilities. We will conclude that an era of steadily increasing flare power peaked in SC23, and that SC24 activity is now about an order of magnitude weaker by comparison. This prompts the idea that the Sun has a way of accumulating magnetic power over several solar cycles, despite the general belief that no such mechanism exists. A mechanism for the steady increase in flare power over the latter part of the 20thC will be suggested. The paper will support the 2008 conclusion that flaring in SC23 was anomalously strong. It will also confirm that an era of steadily stronger flaring, over successive solar cycles, ended in 2008 – suggesting a reason for that abrupt decline.