The ACRIM data in the context of stellar variability

The Active Cavity Radiometer Irradiance Monitor (ACRIM) total-irradiance data from the Solar Maximum Mission have given a first comprehensive view of solar variability in the stellar sense. Five types of solar variability have been identified thus far. These have small amplitudes, less than a few tenths of one percent, and are at levels generally not yet detectable on other stars. The possible stellar analogs are interesting physically, and in particular may help us to understand solar behavior on longer time scales. The ACRIM data is described from the stellar point of view. The present state of stellar time-series photometry is discussed

Scientific tradeoffs in pinhole/occulter facility accommodation

The Pinhole/Occulter Facility (P/OF) consists of state-of-the-art instruments for the study of particle acceleration in the solar corona, and uses a large structure to obtain very high angular resolution. P/OF has been studied in the past as an attached payload for the Space Shuttle, and has been the subject of study by a NASA Science Working Group (P/OFSWG). Appendix A lists various technical studies and reports carried out under the auspices of P/OFSWG and the Program Development Office of NASA Marshall Space Flight Center. Under the rationalization of NASA flight opportunities following the Challenger disaster, and the beginning of the Space Station Freedom program, the sortie-mode deployment of P/OF seemed less efficient and desirable. Thus, NASA decided to reconsider P/OF for deployment on the Space Station Freedom. The technical studies for this deployment continue at the present and will evolve as our knowledge of Space Station architecture and capabilities increase. MSFC contracted with Teledyne Brown Engineering for these technical studies

Prominences in SDO/EVE spectra: contributions from large solar structures

The EVE instrument on SDO is making accurate measurements of the solar spectral irradiance in the EUV between 30 and 1069 Å, with 1 Å spectral resolution and 10 s sampling rate. These data define solar variability in the “Sun-as-a-star” mode and reveal many interesting kinds of variation. Its high sensitivity also makes it suitable for spectroscopic diagnostics of solar features such as flares. Here we present EVE's potential contribution to the diagnostics of large-scale, slowly evolving features such as prominences and active regions, and what we can learn from this

Cycle 23 Variation in Solar Flare Productivity

The NOAA listings of solar flares in cycles 21-24, including the GOES soft X-ray magnitudes, enable a simple determination of the number of flares each flaring active region produces over its lifetime. We have studied this measure of flare productivity over the interval 1975-2012. The annual averages of flare productivity remained approximately constant during cycles 21 and 22, at about two reported M or X flares per region, but then increased significantly in the declining phase of cycle 23 (the years 2004-2005). We have confirmed this by using the independent RHESSI flare catalog to check the NOAA events listings where possible. We note that this measure of solar activity does not correlate with the solar cycle. The anomalous peak in flare productivity immediately preceded the long solar minimum between cycles 23 and 24