National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Understanding the Thermospheric and Ionospheric Response to Solar Flares

ROSES ID: NNH08ZDA001N      Selection Year: 2009      

Program Element: Focused Science Topic

Principal Investigator: Aaron Ridley

Affiliation(s): University of Michigan

Project Member(s):
Chamberlin, Phillip C Co-I NASA
Forbes, Jeffrey M Collaborator University of Colorado
Woods, Thomas N. Collaborator University of Colorado
Paxton, Larry J Co-I Johns Hopkins University
Bernstein, Dennis S Co-I University of Michigan


An understanding of both the thermosphere and the ionosphere, two tightly coupled, overlapping regions of the atmosphere, is important for a number of research and space weather applications: (1) examining increased satellite drag due to heating of the atmosphere (2) examining where and when GPS signal degrading caused by strong gradients of electron density will occur; (3) determining when and where high frequency signals will be strongly scattered or lost due to ionospheric scintillation; (4) examining the role of ionospheric and thermospheric dynamics on the climatology of the lower atmosphere; and (5) determining how the ionosphere influences the magnetosphere through ionospheric conductance and outflow.

Energy enters the thermosphere and ionosphere through many different sources, but two of the most important are the solar extreme ultraviolet (EUV) brightness and the high-latitude Joule heating. The solar EUV is present at relative high levels all of the time, while the high-latitude Joule heating primarily occurs during aurorally active time periods. For many years, models have been run assuming that the solar EUV driving is constant, or slowly varying, for long periods of time (e.g., 24 hours), utilizing proxy models of the flux based on single wavelengths in the solar spectrum (i.e., F10.7). Recently, many researchers have realized that significant variations in the solar spectrum may be missed by doing this, and therefore, much of the physical driving of the model was lacking. Because there has been so little research done on the thermospheric and ionospheric response to the variability in the solar EUV spectrum, there is significant uncertainty in how the upper atmosphere behaves during impulsive increases in the EUV brightness (i.e., during flare events). We propose to address the following four questions related to this topic:

- What effect do solar flares have on the thermospheric density, temperature structure and winds?

- How long does the atmospheric effect of solar flares last?

- How does preconditioning of the thermosphere and ionosphere affect the response of the atmosphere to solar flares?

- How does the shape of the temporal behavior of the flare affect the thermospheric and ionospheric reaction to the solar EUV?

- How does the spectral distribution of the flare affect the thermosphere and ionosphere response?

In order to study these topics, we will utilize a global ionosphere thermosphere model (GITM), data from multiple NASA and ESA supported instruments (i.e., GUVI and SEE on the TIMED satellite, EVE data from SDO, when and if available, and data from the CHAMP satellite), a rigorous data analysis program and newly developed data assimilation techniques, which will allow us to better determine whether preconditioning of the thermosphere and ionosphere has an important effect on the response to solar flares.


Performance YearReferenceInvestigation TypeActions
1Pawlowski, David J.; Ridley, Aaron J.; (2009), Modeling...
not set
1Pawlowski, David J.; Ridley, Aaron J.; (2011), The effe...
not set
1Zhu, Jie; Ridley, Aaron J.; (2014), The effect of backgr...
not set
1Zhu, Jie; Ridley, Aaron J.; (2014), Modeling subsolar t...
not set


Performance YearReferenceActions
1Pawlowski, D. J.; Ridley, A. J.; (2009), The effect of ...
1Pawlowski, David; Bougher, Stephen; Ridley, Aaron; (201...
1Ridley, A. J.; Zhu, J.; Yigit, E.; Drob, D. P.; Co...
1Zhu, J.; Ridley, A. J.; (2012), Study of the Influences ...
1Burrell, A. G.; Zhu, J.; Ridley, A. J.; Stoneback, ...
1Ridley, A. J.; Zhu, J.; (2013), Exploring the Sources of...

Export to PDF