Average Properties of Bipolar Magnetic Regions during Sunspot Cycle-21
Abstract
We examine the statistical properties of some 2700 bipolar magnetic regions (BMRs) with magnetic fluxes ≥3 × 1020 Mx which erupted during 1976-1986. Empirical rules were used to estimate the fluxes visually from daily magnetograms obtained at the National Solar Observatory/Kitt Peak. Our analysis shows the following: (i) the average flux per BMR declined between 1977 and 1985; (ii) the average tilts of BMRs relative to the east-west line increase toward higher latitudes; (iii) weaker BMRs had larger root-mean-square tilt angles than stronger BMRs at all latitudes; (iv) over the interval 1976-1986, BMRs with their leading poles equatorward of their trailing poles contributed a total of 4 times as much flux as BMRs with `inverted' tilts, but the relative amount of flux contributed by BMRs with inverted or zero tilts increased as the sunspot cycle progressed; (v) only 4% of BMRs had `reversed' east-west polarity orientations; (vi) although the northern hemisphere produced far more flux during the rising phase of the sunspot cycle, the southern hemisphere largely compensated for this imbalance during the declining phase; (vii) southern-hemisphere BMRs erupted at systematically higher latitudes than northern-hemisphere ones through most of sunspot cycle 21.
- Publication:
-
Solar Physics
- Pub Date:
- March 1989
- DOI:
- 10.1007/BF00146521
- Bibcode:
- 1989SoPh..124...81W
- Keywords:
-
- Magnetic Field Configurations;
- Magnetic Flux;
- Solar Magnetic Field;
- Sunspot Cycle;
- Dynamo Theory;
- Magnetic Field Inversions;
- Solar Activity;
- Solar Cycles;
- Solar Physics;
- Magnetic Flux;
- Average Property;
- Sunspot Cycle;
- Empirical Rule;
- Magnetic Region