English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

How much energy do solar active regions (ARs) typically radiate duringquiescent periods? This is a fundamental question for storage and releasemodels of flares and ARs, yet it is presently poorly answered by observations.Here we use the "Sun-as-a-point-source" spectra from the EUV VariabilityExperiment (EVE) on the Solar Dynamics Observatory (SDO) to provide a novelestimate of radiative energy losses of an evolving active region. Although EVEprovides excellent spectral (5-105nm) and temperature (2-25MK) coverage for ARanalysis, to our knowledge, these data have not been used for this purpose dueto the lack of spatial resolution and the likelihood of source confusion. Herewe present a way around this problem. We analyze EVE data time series, whenonly one large AR 11520 was present on the disk. By subtracting the quiet Sunbackground, we estimate the radiative contribution in EUV from the AR alone. Weestimate the mean AR irradiance and cumulative AR radiative energy losses inthe 1-300A and astronomical standard ROSAT-PSPC, 3-124A, passbands and comparethese to the magnetic energy injection rate through the photosphere, and tovariations of the solar cycle luminosity. We find that while AR radiativeenergy losses are ~100 times smaller than typical magnetic energy injectionrates at the photosphere, they are an order of magnitude larger or similar tothe bolometric radiated energies associated with large flares. This study isthe first detailed analysis of AR thermal properties using EVE Sun-as-a-starobservations, opening doors to AR studies on other stars.

Active Region Irradiance During Quiescent Periods: New Insights from Sun-as-a-star Spectra