The Sun is the dominant source of energy for Earth’s atmosphere. Scientists are interested in determining how the Sun’s output affects Earth’s climate and the ways specific events can disrupt space weather applications, space-based technologies, and radio communications. New observations of solar extreme ultraviolet (EUV) irradiance from the LASP-designed and built EUV Variability Experiment (EVE) on NASA’s Solar Dynamics Observatory (SDO) are adding another piece to this complicated puzzle that may help scientists more accurately predict space weather events.
Using observations from EVE, LASP researchers have discovered an extra enhancement, or energy emission, that occurs up to five hours after the main phase of some solar flare occurrences and can increase the total EUV irradiance by 30 to 60 percent. Solar flares are intense bursts of radiation from the release of magnetic energy associated with sunspots. The frequency and importance of the EUV late phase to the total spectral irradiance had not been fully recognized until the first flare observations by SDO EVE—launched in February 2010—which provides a much more comprehensive time coverage and resolution of solar energy output.
According to LASP Senior Research Associate and EVE principal investigator, Tom Woods, the new EUV irradiance observations from SDO EVE have exciting potentials for expanding our understanding of how different EUV emissions vary during flares, how these variations can cause changes in Earth’s ionosphere and thermosphere, and how the Sun’s energy can impact human activities and technologies.
“If we can get these new results into space weather prediction models, we should be able to more reliably forecast solar events and their effects on our communication and navigation systems on Earth,” said Woods. “It will take some time and effort, but it is important.”
While not all solar flares demonstrate the EUV late phase phenomenon—they occur in about 15% of all measurable flares—the new EVE observations have drawn a clear distinction between late phase EUV and long-duration flares and will provide a much more accurate estimation of the total energy input into Earth’s environment.
“We are seeing something that is new and surprising about the physics of solar flares,” said LASP graduate student and EVE instrument scientist Rachel Hock. “When we looked at the observations from our instruments aboard SDO and compared them with our physical models, the results were consistent with each other,” said Hoch. “That was good news to us.”
The results of the research appear in the September 7 online edition of The Astrophysical Journal.
Woods, T. N., et al. New Solar Extreme-Ultraviolet Irradiance Observations During Flares. The Astrophysical Journal advance online publication, 1 October 2011 (DOI 10.1088/0004-637X/739/2/59)
- Tom Woods, EVE PI: Tom.Woods@colorado.edu
- Rachel Hock, EVE Scientist: Rachel.Hock@colorado.edu
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