Ephemeral Active Regions During the Solar Minimum. I. General Properties and Trends Over the Solar Cycle. II. Characteristics of Individual Ephemeral Regions.
Abstract
General properties of ephemeral active regions were studied using Kitt Peak daily magnetograms from Apr.-Nov. 1975. Although this interval was prior to sunspot minimum, ephemeral regions related to incoming cycle 21 were already more numerous than ephemeral regions related to outgoing cycle 20. The transition between the old and new solar cycle was identified by a reversal of the statistically dominant orientation of regions and sometimes by a minimum in the latitude distribution where adjacent cycles overlapped. During this interval the transition between cycle 20 and 21 was at N18 deg and S24 deg. Comparing this 1975 data with previously studied data from 1970 and 1973, we find evidence that incoming cycle 21 was already present on the sun at middle and high latitudes in 1973 and 1970. Extrapolating backward and forward in time from these three periods, we find that it is conceivable that two solar cycles may be present on the sun at all times. It appears that further statistical studies of ephemeral active regions may yield long-term prognostic information on the future course of solar activity. The birth of 90 ephemeral regions was recorded. Prior to the birth of regions, existing network was found to disappear or show lateral displacement. The growth and decay rates of regions were comparable. In the decaying phase, some flux elements simply disappeared; some merged with network or other elements of regions of similar polarity; some collided and simultaneously disappeared with network or elements of other regions of opposite polarity. All clearly identifiable ephemeral regions dissipated by these processes while continuing to expand.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 28, 1976
- Accession Number
- ADA038124
Entities
People
- Karen L. Harvey
- Sara F. Martin