HAO 2010 PROFILES IN SCIENCE: Dr. Liying Qian
Contact
303-497-15291
lqian@ucar.edu
Dr. Liying Qian is a Project Scientist I at the High Altitude Observatory at NCAR. Her specialty is in the use of upper atmospheric numerical models to study global changes in the coupled thermosphere/ionosphere system, including investigation of vertical coupling of the thermosphere/ionosphere and the lower atmosphere. She performs calculations of thermospheric neutral density for comparison with satellite drag data.
Publication:
Figure: Simulated I/T responses to the X17 limb flare and X17 center flare in the equatorial region (2.5°N) at local noon. Upper panel: ion production rates, ion loss rates, and electron density profiles under pre-flare condition (black), at flare peak of the X17center flare (red), and at flare peak of the X17 limb flare (blue); lower panel: percentage increases of neutral temperature, O/N2, and neutral density from pre-flare condition to flare peaks; Red: center flare; Blue: limb flare.
(1) Modeling the Thermospheric and Ionospheric Response to Solar Flare
Qian, L., A. G. Burns, P. C. Chamberlin, and S. C. Solomon (2010), Flare location on the solar disk: Modeling the thermosphere and ionosphere response, J. Geophys. Res., 115, A09311, doi: 10.1029/2009JA015225.
Abstract: Solar flare enhancements to the soft X-ray (XUV) and extreme-ultraviolet (EUV) spectral irradiance depend on the location of the flare on the solar disk. Most emission lines in the XUV region (~0.1 to ~25 nm) are optically thin, and are weakly dependent on the location of the flare, but in the EUV region (~25 to ~120 nm), many important lines and continua are optically thick, so enhancements are relatively smaller for flares located near the solar limb, due to absorption by the solar atmosphere. The Flare Irradiance Spectral Model (FISM, Chamberlin et al., 2008) was used to illustrate these location effects, assuming two X17 flares that are identical except that one occurs near disk center and the other near the limb. FISM spectra of these two flares were used as solar input to the NCAR thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) to investigate the ionosphere/thermosphere (I/T) response. Model simulations showed that in the
E region ionosphere, where XUV dominates ionization, flare location does not affect I/T response. However, flare-driven changes in the
F region ionosphere, total electron content (TEC), and neutral density in the upper thermosphere, are 2 to 3 times stronger for a disk-center flare than for a limb flare, due to the importance of EUV enhancement. Space weather implications of solar flares, such as satellite drag, radio communications, as well as accuracy of the GPS, are related to neutral density in the upper thermosphere, electron density in the
F region, and TEC; therefore, flare location is an important factor in determining space weather consequences of flare effects.
Publication:
Figure: (a) Model simulated neutral density perturbation at 400 km, (b) neutral density perturbation at 120 km, (c) neutral temperature perturbation at 400 km, and (d) perturbation of column number density ratio of O and N2 (O/N2), at 12:00 local time and 0:00 UT, from day 51 to day 110 of 2005. Dotted lines are geomagnetic Ap index
(2) Simulations of Thermospheric Response to Recurrent Geomagnetic Forcing
Qian, L., S. C. Solomon, and M. G. Mlynczak (2010), Model simulation of thermospheric response to recurrent geomagnetic forcing, J. Geophys. Res., 115, A10301, doi:10.1029/2010JA015309.
Abstract: We assess model capability in simulating thermospheric response to recurrent geomagnetic forcing driven by modulations in the solar wind speed and the interplanetary magnetic field. Neutral density and nitric oxide (NO) cooling rates are simulated for the declining phase of solar cycle 23. The simulated results are compared to neutral density derived from satellite drag and to NO cooling measured by the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) sounding of the atmosphere using broadband emission radiometry (SABER) instrument. Model—data comparisons show good agreement between the model and the measurements for multiday oscillations, as well as good agreement for longer-term variations. The simulations demonstrate that the multiday oscillation of density is globally distributed in the upper thermosphere but restricted to high latitudes in the lower thermosphere. The density variation in the upper thermosphere exhibits less latitude dependence than the temperature variation because of the effects of composition changes. Model simulations also show that NO density and temperature play primary roles in the multiday oscillation of NO cooling rates.
