HAO 2011 Profiles In Science: Dr. Gang Lu
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.
Figure 1: High resolution
(1) G. Lu, W.H. Li, J. Raeder, Y. Deng, F. Rich, D. Ober, Y.L. Zhang, L. Paxton, M. Ruohoniemi, M. Hairston, and P. Newell, 2011:Reversed two-cell convection in the northern and southern hemisphere during northward IMF, J. Geophys. Res., doi:10.1029/2011JA017043, in press.
Abstract: Gang Lu and her collaborators (including Wenhui Li and Jimmy Raeder at University of New Hampshire, Yue Deng at University of Texas at Arlington, Fred Rich and Dan Ober at Air Force Research Laboratory, Yongliang Zhang, Larry Paxton, and Patrick Newell at Applied Physics Laboratory of Johns Hopkins University, Mike Ruohoniemi at Virginia Tech, and Marc Hairston at University of Texas at Dallas) presented a case study of large-scale ionospheric convection in the northern and southern hemispheres under strongly northward interplanetary magnetic field (IMF) conditions on 9 November 2004. Using a comprehensive data set from both ground- and space-based instruments, the study shows the formation of reversed two-cell convection in both northern and southern hemispheres that lasted for nearly 2 hours. Examination of the concurrent satellite energy-time spectrograms of precipitating particles reveals that reverse convection occurs in the region filled mostly with the boundary plasma sheet (BPS) type precipitating electrons except that the electron number flux is much smaller than that in the normal BPS. They named this region the northward Bz boundary layer (NBZBL) as a consequence of double lobe reconnection. This interpretation is corroborated by the global MHD simulations, which show that the NBZBL consists of mostly closed field lines, resulting from double lobe reconnection in both hemispheres, together with intermittent presence of overdraped open field lines, resulting from single lobe reconnection in one of the hemispheres. In addition to reversed two-cell convection, the distribution of field-aligned currents (FACs) shows clearly the presence of a pair of the northward Bz (NBZ) currents near the central polar region in both hemispheres. Intense downward Poynting flux with a peak value around 100 mW/m2 is also seen in the high-latitude polar region, which tends to surround the upward leg of the NBZ currents. Finally, the potential drop between the two reverse convection cells exceeds 100 kV, which is far larger than the values reported in any previous studies of reverse convection under northward IMF conditions. The unusually large reverse potential drop in this case is attributed in part to the strong northward Bz component of 35~40 nT and in part to the unusually large solar wind dynamic pressure that is about 5 times its nominal value.
Figure 1 caption: Consecutive ionospheric convection patterns from 2040 UT to 2350 UT in the southern hemisphere, with a contour interval of 10 kV. The positive and negative values below each pattern correspond to the electric potentials in the locations marked by the '+' and '−' signs, which are not necessary the maximum and minimum potentials.
Figure 2: High resolution
(2) D. Bermejo-Pantaleon, B. Funke, M. Lopez-Puertas, M. Garcia-Comas, G. P. Stiller, T. von Clarmann, A. Linden, U. Grabowski, M. Höpfner, M. Kiefer, N. Glatthor, S. Kellmann, and G.Lu. 2011: Global Observations of Thermospheric Temperature and Nitric Oxide from MIPAS spectra at 5.3 µm, J. Geophys. Res., doi:10.1029/2011JA016752.
Abstract: This study led by colleagues at Instituto de Astrofisica de Andalucia in Granada, Spain. It presents vertically resolved thermospheric temperatures and NO abundances in terms of volume mixing ratio retrieved simultaneously from spectrally resolved 5.3 µm emissions recorded by the Michelson Interferometer for Passive Atmospheric Spectroscopy (MIPAS) in its upper atmospheric observation mode during 2005–2009. These measurements are unique since they represent the first global observations of temperature and NO for both day and night conditions taken from space. The study found that temperature and NO profiles observed under auroral conditions are rather insensitive to smoothing errors related to the mapping of a priori profile shapes. However, for extra-polar and low Ap conditions, a potential systematic bias in the retrieved nighttime temperature and NO profiles related to smoothing errors has been identified from a comparison to Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME–GCM) model simulations. A solar minimum monthly climatology of thermospheric temperature and NO have been constructed based on MIPAS observations taken during 2008–2009. MIPAS temperature distributions agree well, on average, with the Mass Spectrometer and Incoherent Scatter radar model (NRLMSISE–00), but some systematic differences exist. MIPAS temperatures are generally colder than NRLMSISE-00 in the polar middle thermosphere (mainly in the summer polar region) by up to 40 K; and are warmer than NRLMSISE–00 in the lower thermosphere around 120–125 km by 10–40 K. Thermospheric NO daytime distributions agree well with the Nitric Oxide Empirical Model (NOEM), based on Student Nitric Oxide Explorer (SNOE) observations. A comparison of MIPAS NO number density with the previous climatology for the declining phases of the solar cycle based on HALOE and SME data shows that MIPAS is generally larger with values ranging from 10 to 40%, except in the auroral region and at the equatorial latitudes above 130 km where the MIPAS/HALOE+SME ratio varies from 1.6 to 2. Day-night differences in MIPAS NO show daytime enhancements of up to 140% in the tropical and mid-latitudes middle thermosphere. In the lower thermosphere, the diurnal amplitude is smaller and NO concentrations are generally higher during night by about 10–30%, particularly in the auroral regions.
Figure 2 caption: NO volume mixing ratio (vmr) zonal mean distributions for 22 July 2005. From left to right: MIPAS observations, MIPAS observations adjusted to TIME-GCM atomic oxygen concentrations, TIME-GCM simulations, and the difference between the adjusted MIPAS observations and TIME-GCM simulations.