Dynamic power spectral analysis of solar measurements from photospheric, chromospheric, and coronal sources.
Abstract
An important aspect in the power spectral analysis of solar variability is the quasistationary and quasiperiodic nature of solar periodicities. In other words, the frequency, phase, and amplitude of solar periodicities vary on time scales ranging from active region lifetimes to solar cycle time scales. In this study the authors employ a dynamic, or running, power spectral density analysis to determine many periodicities and their time-varying nature in the projected area of active sunspot groups (Sact), the SMM/ACRIM total solar irradiance (S), the Nimbus-7 Mg II center-to-wing ratio (R(Mg IIc/w)), the Ottawa 10.7 cm flux (F10.7), and the GOES background X-ray flux (Xb) for the maximum, descending, and minimum portions of solar cycle 21 (i.e., 1980-1986). This technique dramatically illustrates several previously unrecognized periodicities. For example, a relatively stable period at about 51 days has been found in those indices which are related to emerging magnetic fields. The majority of solar periodicities, particularly around 27, 150 and 300 days are quasiperiodic because they vary in amplitude and frequency throughout the solar cycle. Finally, it is shown that there are clear differences between the power spectral densities of solar measurements from photospheric, chromospheric, and coronal sources.
- Publication:
-
NASA Conference Publication
- Pub Date:
- August 1990
- Bibcode:
- 1990NASCP3086..125B
- Keywords:
-
- Chromosphere;
- Periodic Variations;
- Photosphere;
- Solar Activity;
- Solar Activity Effects;
- Solar Corona;
- Solar Cycles;
- Solar Radiation;
- Spectrum Analysis;
- Sunspots;
- Irradiance;
- Magnetic Fields;
- Monitors;
- Nimbus 7 Satellite;
- Radiometers;
- Solar Maximum Mission;
- Stability;
- X Rays;
- Solar Physics;
- Sun: Variability