HAO 2012 Profiles In Science: Dr. Gang Lu
Contact:
303-497-1554
ganglu@ucar.edu
Dr. Gang Lu obtained a B.S. degree in Physics from Zhejiang University in China in 1982, and a Ph.D. degree in Space Physics from Rice University in 1991. She has worked at HAO since 1992, where she was a Postdoctoral visitor from 1992-1993, and a research scientist from 1993 to the present.
Dr. Lu has worked actively on the analysis and interpretation of various ground- and space-based observations, including ground magnetometers, coherent and incoherent scatter radars, satellite electric and magnetic fields and particles, and auroral images. She also has extensive experience in numerical modeling, including the Assimilative Mapping of Ionospheric Electrodynamics (AMIE), the Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIEGCM), and the Thermosphere-Ionosphere-Mesosphere Electrodynamics General Circulation Model (TIMEGCM).
Her primary research interests are in high-latitude ionospheric electrodynamics, solar wind-magnetosphere-ionosphere thermosphere coupling, and space weather.
Publications
(1) Lu, G., L. Goncharenko, M. J. Nicolls, A. Maute, A. Coster, and L. J. Paxton 2012: Ionospheric and thermospheric variations associated with prompt penetration electric fields, J. Geophys. Res., 117, A08312, doi:10.1029/2012JA017769.
Abstract: This paper presents a comprehensive modeling investigation of ionospheric and thermospheric variations during a prompt penetration electric field (PPEF) event that took place on 9 November 2004, using the Thermosphere-Ionosphere-Mesosphere Electrodynamic General Circulation Model (TIMEGCM). The simulation results reveal complex latitudinal and longitudinal/local-time variations in vertical ion drift in the middle- and low-latitude regions owing to the competing influences of electric fields and neutral winds. It is found that electric fields are the dominant driver of vertical ion drift at the magnetic equator; at midlatitudes, however, vertical ion drift driven by disturbance meridional winds exceeds that driven by electric fields. The temporal evolution of the UT-latitude electron density profile from the simulation depicts clearly a super-fountain effect caused by the PPEF, including the initial slow-rise of the equatorial F-layer peak height, the split of the F-layer peak density, and the subsequent downward diffusion of the density peaks along magnetic field lines. Correspondingly, low-latitude total electron content (TEC) becomes bifurcated around the magnetic equator. The O/N2 column density ratio, on the other hand, shows very little variations during this PPEF event, excluding composition change as a potential mechanism for the TEC variations. By using realistic, time-dependent, high-latitude electric potential and auroral precipitation patterns to drive the TIMEGCM, the model is able to successfully reproduce the large vertical ion drift of ~120 m/s over the Jicamarca incoherent radar (IS) in Peru, which is the largest daytime ion drift ever recorded by the radar.
Figure 1 caption: Altitude distributions of electron density at selected UT times on 9 November 2004 show the super-fountain effect associated with the prompt penetration electric fields. The white lines indicate the geomagnetic field lines.
(2) He, M., J. Vogt, H. Lühr, E. Sorbalo, A. Blagau, G. Le, and G. Lu 2012: A high-resolution model of field-aligned currents through empirical orthogonal functions analysis (MFACE), Geophys. Res. Lett., 39, L18105, doi:10.1029/2012GL053168.
Abstract: Ten years of CHAMP magnetic field measurements are used to develop a new empirical model of field-aligned currents (FACs) using empirical orthogonal functions (EOFs). Our results show that the first principal component of EOFs (e.g., EOF1) depicts the basic Region-1/Region-2 pattern varying mainly with the interplanetary magnetic field Bz component, whereas the second principal component (e.g., EOF2) captures separately the cusp current signatures and By-related variability. Compared to existing models, the new model has significantly better spatial resolution, reproduces typically observed FAC thickness and intensity, improves on the magnetic local time (MLT) distribution, and shows the seasonal dependence of FAC latitudes and the northward Bz (NBZ) current signature. Our MFACE method further reveals systematic dependences on By, including 1) Region-1/Region-2 topology modifications around noon; 2) imbalance between upward and downward maximum current density; 3) MLT location of the Harang discontinuity. Furthermore, our procedure allows quantifying response times of FACs to solar wind driving at the bow shock nose.
Figure 2 caption: Polar distributions of FAC density in the (left) Northern and (right) Southern hemispheres as organized by IMF clock angle (marked on left margin) and season (marked on top). Maximum upward and downward current peaks are marked by crosses, and the green and magenta arrows point out two types of noon-time FAC topology.