Solar Flare Soft X-ray Irradiance and its Impact on the Earth's Upper Atmosphere
Abstract
Solar flares dramatically enhance the soft X-ray region of the solar spectrum. A differential emission measure technique is used to determine flare spectra from Thermosphere Ionosphere Mesosphere Energetics Dynamics (TIMED) and Solar Radiation and Climate Experiment (SORCE) solar observations. Results show that flares primarily enhance the soft X-ray irradiance in the 0.1-2 nm range, and rapidly modify the energy input to the lower thermosphere. Most of the excess flare 0.1-2 nm irradiance comes from 1-2 nm, thus flares deposit a large amount of their energy between 100-110 km. One of the key effects of this energy deposition is to modify nitric oxide (NO), which plays an important role in the energy balance of the thermosphere as it is a source of radiative cooling through infrared emissions. The density of NO is highly variable as a function of time and latitude, and reaches a maximum in the same altitude region where the flare irradiance is absorbed. Valid comparisons between Student Nitric Oxide Explorer (SNOE) satellite NO observations and those predicted by a photochemical thermospheric model provide a better understanding of low latitude flare enhanced NO density. Results show that large flares can deposit the same amount of 0.1-2 nm energy to the thermosphere during a relatively short time as the Sun normally deposits in one day, thus doubling the energy, which doubles the NO density.
- Publication:
-
37th COSPAR Scientific Assembly
- Pub Date:
- 2008
- Bibcode:
- 2008cosp...37.2627R