HAO 2012 Profiles In Science: : Dr. Arthur Richmond

Contact:

303-497-1570
richmond@ucar.edu

Dr. Arthur D. Richmond has research interests in upper atmospheric dynamics and electrodynamics. He received his B.S. in physics in 1965 and Ph.D. in meteorology in 1970 from UCLA. After various visiting scientist positions, including ones at HAO between 1972 and 1976, and after working as a physicist at the NOAA Space Environment Laboratory from 1980 to 1983, he became a scientist at NCAR in 1983, and joined HAO in 1984.

FY12 Research Highlights

(1) Relation of equatorial lunar geomagnetic perturbations to stratospheric sudden warmings

Yamazaki et al. (2012) carried out a quantitative comparison of the geomagnetic lunar tide and lower stratospheric parameters (zonal mean air temperature T and zonal mean zonal wind U ) for the period 1958–2007. The correlation between the amplitude of the geomagnetic lunar tide at an equatorial station, Addis Ababa, and the lower stratospheric parameters from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis is positive for T and negative for U in northern high latitudes during December and January. The results suggest that variability of the geomagnetic lunar tide during the northern winter is closely linked with dynamical changes in the lower stratospheric parameters associated with stratospheric sudden warmings.

Figure 1 caption: Variations in (top) the zonal mean zonal wind at 60°N at 10 hPa, (middle) air temperature at 90°N at 10 hPa, and (bottom) the amplitude of the lunar semidiurnal variation in the geomagnetic perturbation at Addis Ababa, from October 1 through March 31 for different years. For the stratospheric parameters, the black line indicates the variation for a given time period, while the magenta line indicates the climatological mean for 1948–2010.

(2) Intense day-side Joule heating identified with multi-instrument observations.

Intense day-side Joule heating identified with multi-instrument observations (Wilder et al. [2012]) identified occurrences of intense, but highly localized, energy deposition into the dayside ionosphere during two geomagnetic storms when the interplanetary magnetic field was northward with a strong By component, using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) as an input to the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) algorithm. The intense Joule heating was associated with an intense field-aligned current pair near the noon meridian, and was large enough to lead to anomalous thermospheric density enhancements. This figure shows how the addition of AMPERE data to AMIE greatly improves the estimate of field-aligned current into the ionosphere (left) and of Joule heating (right), as seen in the plots that do not (top) or do (bottom) include AMPERE data. The minimum magnetic latitude shown is 60°. MLT is magnetic local time.

Figure 2 caption: Wilder et al. (2012) identified occurrences of intense, but highly localized, energy deposition into the dayside ionosphere during two geomagnetic storms when the interplanetary magnetic field was northward with a strong By component, using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) as an input to the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) algorithm. The intense Joule heating was associated with an intense field-aligned current pair near the noon meridian, and was large enough to lead to anomalous thermospheric density enhancements. This figure shows how the addition of AMPERE data to AMIE greatly improves the estimate of field-aligned current into the ionosphere (left) and of Joule heating (right), as seen in the plots that do not (top) or do (bottom) include AMPERE data. The minimum magnetic latitude shown is 60°. MLT is magnetic local time.

(3) The dependence of the coupled magnetosphere-ionosphere-thermosphere system on the Earth's magnetic dipole moment

Cnossen et al. (2012) used simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere model to investigate how the magnetosphere, upper atmosphere, and solar quiet (Sq) geomagnetic variation respond as the geomagnetic dipole moment M varies between 2×1022 and 10×10^22 Am2, for solar minimum, medium and maximum conditions. The figure shows how the magnetopause stand-off distance Rs decreases and the shape of the magnetosphere changes as M decreases. While a decrease in Rs is expected from a theoretical balance between the solar wind dynamic pressure and the magnetic pressure inside the magnetosphere (indicated by the black line), the model shows a stronger dependence on M. This may be due to enhanced magnetopause erosion and/or to strong changes in the ionospheric conductance, which affect the field-aligned currents. The magnetic fields created by the field-aligned currents in the magnetosphere modify the magnetic pressure inside the magnetosphere, which changes the dependence of Rs on M as well as the shape of the magnetosphere, here indicated by the ratio of the distance to the magnetopause in the solar magnetic y- and x-directions. Changes in M also affect the ionosphere-thermosphere system. E×B drift velocities, Joule heating power, the global mean thermospheric temperature and the global mean height of the peak of the ionospheric F2 layer, hmF2, all increase with increasing M for low dipole moments, but all decrease with increasing M for larger dipole moments.The peak electron density of the F2 layer, NmF2, shows the opposite behaviour. The Sq amplitude decreases with increasing M and this dependence can be roughly described by a power law scaling. Most scaling relations show a weak dependence on the solar activity level, which is likely associated with a change in the relative contributions to the Pedersen conductance from the upper and lower ionosphere, which scale differently with M.

Figure 3 caption: The stand-off distance Rs (top) and the ratio between the stand-off to the flank and nose of the magnetosphere (bottom) as a function of dipole moment for solar minimum (blue), medium (green) and maximum (red) conditions. The black line indicates the theoretical relationship Rs µ M1/3.

(4) Forcing the TIEGCM with Birkeland currents from AMPERE

Marsal et al. (2012) used geomagnetic field-aligned currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellite mission to drive the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). They presented a comparison between ground magnetic signatures computed by the model and observations at four different geomagnetic observatories, for different magnetic disturbance levels. Results show the ability of the model to pick up the gross features of the magnetic variations, improving its performance with increasing disturbance level and from low to high latitudes. During geomagnetically quiescent conditions a baseline noise of about 5 nT is evident in reconstructed ground magnetic field signatures, which are attributed to the baseline noise level in the AMPERE currents. For variations shorter than about 30 min the modeled signals are often significantly lower than observed by a factor up to 3 to 4, possibly reflecting localized ionization structures not captured in the TIEGCM conductance modules, or missing small-scale and rapid temporal variations in auroral currents. While the observed horizontal field variations are reflected in the model, the vertical component is consistently underestimated, possibly indicating errors in the estimates for ground induction currents. Comparison with the standard version of the TIEGCM was also carried out, showing that time variations shorter than 6 h and down to the 10 min resolution of the AMPERE data (which do not appear in the standard version of TIEGCM) are reflected in the AMPERE-driven model.

Figure 4 caption: (Top) Observed field-aligned currents in the northern hemisphere from AMPERE, compared with the currents calculated from the TIEGCM when the sum of northern and southern AMPERE currents are used to drive the electrodynamics. (Bottom) Comparison between simulated (dashed) and observed (solid) ground magnetic perturbations at College, Alaska.

(5) Sources of low-latitude ionospheric E×B drifts and their variability

Maute et al. 2012) examined how upward propagating tropospheric tides affect vertical ExB ionospheric drifts via the ionospheric wind dynamo, gravity and plasma pressure gradient driven current, the geomagnetic main field, and longitudinal variation in the conductivities, using March equinox results from the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model. Gravity and plasma pressure gradient driven current and the longitudinal variation of the conductivities excluding the variation due to the geomagnetic main field do not change the longitudinal variation of the vertical drift significantly. Modifying the geomagnetic main field will change the vertical drift at 5–6 LT, 18–19 LT and 23–24 LT at almost all longitudes. In general the influence of the geomagnetic main field on the vertical drift is larger, with respect to the maximum difference, at 18–19 LT and 23–24 LT, equal at 5–6 LT, and smaller at 14–15 LT than the influence due to nonmigrating tidal components in the neutral winds. Examination of the contribution from E- and F-region neutral winds to the vertical drift shows that their importance depends on the local time and the solar activity.

Figure 5 caption: Average upward ExB drift [m/s] between +/- 30 deg magnetic latitude due to neutral wind for 5-6 LT (blue/ long dashed), 13–14 LT (brown/dotted), 18–19 LT (red/dasheddotted), and 23–24 LT (green/solid) with migrating and nonmigrating tidal components (thick lines) and with migrating components (thin lines).

(6) Atmospheric Semidiurnal Lunar Tide Climatology Simulated by the Whole Atmosphere Community Climate Model

Pedatella et al. (2012a) added the atmospheric semidiurnal lunar tide to the Whole Atmosphere Community Climate Model (WACCM) through inclusion of an additional forcing mechanism and presented the simulated climatology of the tide in surface pressure and zonal and meridional winds in the mesosphere and lower thermosphere (MLT). Prior observations and modeling results demonstrate characteristic seasonal and latitudinal variability of the semidiurnal lunar tide in surface pressure, and the WACCM reproduces these features. In the MLT, the WACCM simulations reveal a primarily semiannual variation with maxima near December and June solstice. The peak amplitudes in the MLT zonal and meridional winds are 5–10 ms−1, and occur at mid to high latitudes in the summer hemisphere. The WACCM simulation results in the MLT were further compared with those from the Global Scale Wave Model (GSWM). The overall latitude and seasonal variations are consistent between these two models. However, the GSWM peak amplitudes are 2–3 times larger than those in the WACCM. This is thought to be related to deficiencies in the GSWM and not the WACCM simulations. With the exception of smaller amplitudes during Northern Hemisphere summer months, the WACCM simulations of the semidiurnal lunar tide in the MLT are also shown to be generally consistent with prior observations and modeling results. The reduced amplitudes in the WACCM simulations during Northern Hemisphere summer months are thought to be related to the influence of the cold-pole bias in WACCM on the propagation of the lunar tide during these months.

Figure 6 caption: Seasonal and latitudinal variability of the migrating semidiurnal lunar tide amplitude in zonal neutral wind at (a) 90 km, (b) 95 km, (c) 105 km, and (d) 125 km.

(7) Quasi-two-day wave coupling of the mesosphere and lower thermosphere-ionosphere in the TIME-GCM: Two-day oscillations in the ionosphere

Yue et al. (2012) used the Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM to simulate the quasi-two-day wave (QTDW) modulation of the ionospheric dynamo and electron density. The QTDW can directly penetrate into the lower thermosphere and modulate the neutral winds at a period of two days. The QTDW modulation of the tidal amplitudes is not evident. The QTDW in zonal and meridional winds results in a quasi-two-day oscillation (QTDO) of the dynamo electric fields at southern midlatitudes, which is mapped into the conjugate northern magnetic midlatitudes. The QTDO of the electric fields in the E region is transmitted along the magnetic field lines to the F region and leads to the QTDOs of the vertical ion drift and total electron content (TEC) at low and mid latitudes. The QTDO of the vertical ion drift near the magnetic equator leads to the 2-day oscillation of the fountain effect. The QTDO of the TEC has two peaks at +/-25 magnetic latitude (Mlat) and one near the dip equator. The equatorial peak is nearly out of phase with the ones at +/-25 Mlat. The vertical ion drift at midlatitudes extends the QTDW response of the TEC to midlatitudes from the Equatorial Ionospheric Anomaly. Most differently from previous reports, it was discovered that the QTDW winds couple into the F region ionosphere through both the fountain effect and the middle latitude dynamos.

Figure 7 caption: (a) Amplitude (m/s) and (b) phase (UT hour) of the QTDO of the vertical ion drift in the F region. The phase is defined as the UT when the maximum amplitude is obtained. The interval is 0.1 m/s and 4 h, respectively.

(8) Simulations of solar and lunar tidal variability in the mesosphere and lower thermosphere during sudden stratospheric warmings and their influence on the low-latitude ionosphere

Pedatella et al. (2012b) used Whole Atmosphere Community Climate Model (WACCM) simulations to investigate solar and lunar tide changes in the mesosphere and lower thermosphere (MLT) that occur in response to sudden stratosphere warmings (SSWs). The average tidal response is demonstrated based on 23 moderate to strong Northern Hemisphere SSWs. The migrating semidiurnal lunar tide is enhanced globally during SSWs, with the largest enhancements (~60–70%) occurring at mid to high latitudes in the Northern Hemisphere. Enhancements in the migrating solar semidiurnal tide (SW2) also occur up to an altitude of 120 km. Above this altitude, the SW2 decreases in response to SSWs. The SW2 enhancements are 40–50%, making them smaller in a relative sense than the enhancements in the migrating semidiurnal lunar tide. Changes in nonmigrating solar tides are, on average, generally small and the only nonmigrating tides that exhibit changes greater than 20% are the diurnal tide with zonal wave number 0 (D0) and the westward propagating semidiurnal tide with zonal wave number 1 (SW1). D0 is decreased by ~20–30% at low latitudes, while SW1 exhibits a similar magnitude enhancement at mid to high latitudes in both hemispheres. The tidal changes are attributed to a combination of changes in the zonal mean zonal winds, changes in ozone forcing of the SW2, and nonlinear planetary wave-tide interactions. The influence of the lunar tide enhancements on generating perturbations in the low latitude ionosphere during SSWs was further investigated by using the WACCM-X thermosphere to drive an ionosphere-electrodynamics model. For both solar maximum and solar minimum simulations, the changes in the equatorial vertical plasma drift velocity are similar to observations when the lunar tide is included in the simulations. However, when the lunar tide is removed from the simulations, the low latitude ionosphere response to SSWs is unclear and the characteristic behavior of the low latitude ionosphere perturbations that is seen in observations is no longer apparent. The results thus indicate the importance of variability in the lunar tide during SSWs, especially for the coupling between SSWs and perturbations in the low latitude ionosphere.

Figure 8 caption: (a) Change in the zonal mean vertical drift velocity at the magnetic equator and 300 km. The zonal means are calculated at fixed local times. The changes are with respect to the average local time variation in the vertical drift velocity over the interval shown. (b) 10 hPa daily zonal mean temperature at 90°N (solid) and 60°N (dashed), and zonal wind at 60°N (dotted). Results are for solar minimum simulation with lunar tidal forcing.

(9) Height distribution of Joule heating and its influence on the  thermosphere

Huang et al. (2012) employed the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General Circulation Model (NCAR TIE-GCM) to quantify the influence of Joule heating at different altitudes on the neutral  temperature and density at 400 km for solar minimum and maximum conditions. The results show that high-altitude Joule heating is more efficient than low-altitude heating in affecting the upper thermosphere. Most of the Joule heating is deposited under 150 km, and the largest Joule heating deposition per scale height happens at about 125 km, independent of solar activity. However, the temperature and density changes at 400 km are largest for heat deposited at ~140 km for solar minimum and ~263 km for solar maximum. The time scale for the thermospheric response varies with the altitude of heating. Joule heating deposited at lower heights needs more time to conduct upward, and it takes more time for the thermosphere at 400 km to approach a steady state. A simple one-dimensional model is utilized to explain how the amplitude and characteristic time scale of the upper-thermosphere response to Joule heating depends on the height of heat input. The characteristic response time scale for heat deposited around 135 km is ~6 hours, while that for heat deposited around 238 km is ~0.5 hours. The initial temperature response at 400 km to the high-altitude heating is much stronger than the response to the low-altitude heating, but the responses become comparable after about 4 days.

Figure 9 caption: Temporal variation of globally averaged temperature perturbations at 400 km due to heat deposited in one scale height centered at pressure level 0 (blue lines) or −3 (red lines).

(10) How changes in the tilt angle of the geomagnetic dipole affect the coupled magnetosphere-ionosphere-thermosphere system

Ingrid Cnossen and Arthur Richmond investigated the effects of changes in dipole tilt angle on the magnetosphere, ionosphere and thermosphere, using the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model. A change in dipole tilt angle changes the inclination of the magnetic field in a geographic reference frame. Because charged particles move much more easily along magnetic field lines than across them, this affects the vertical component of plasma transport processes, which in turn alters the vertical plasma distribution. This leads to changes in the height of the peak of the F2 layer, hmF2, and its peak electron density, NmF2. An example for tilt angles of 0° (T0, dipole axis aligned with the rotation axis) and a tilt angle of 30° (T30) and the difference between them is shown in the figure. About 2/3 of the changes in NmF2, and most of the low to mid-latitude changes in hmF2, are due to changes in the vertical component of plasma diffusion along the magnetic field. The remainder is associated with changes in the amount of Joule heating, arising from changes in the efficiency of solar wind-magnetosphere coupling, and its geographic distribution, as the locations of the magnetic poles and auroral ovals change. Joule heating effects are only important when Joule heating is relatively high, as under southward Interplanetary Magnetic Field (IMF). Under northward IMF they are negligible.

Figure 10 caption: HmF2 and NmF2 for 0° dipole tilt (T0) and 30° dipole tilt (T30) and the difference between them (T30-T0) for equinox under southward Interplanetary Magnetic Field (IMF) conditions.

(11) Assimilation of FORMOSAT-3/COSMIC electron density profiles into a coupled Thermosphere/Ionosphere model using ensemble Kalman filtering

I-Te Lee, Arthur Richmond, and colleagues presented an effort to assimilate FORMOSAT-3/COSMIC (F3/C) GPS Occultation Experiment observations into the National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) by means of ensemble Kalman filtering (EnKF). The F3/C EDP are combined with the TIE-GCM simulations by EnKF algorithms implemented in the NCAR Data Assimilation Research Testbed open-source community facility to compute the expected value of electron density, which is 'the best' estimate of the current ionospheric state. Assimilation analyses obtained with real F3/C electron density profiles are compared with independent ground-based observations as well as the F3/C profiles themselves. The comparison shows the improvement of the primary ionospheric parameters, such as NmF2 and hmF2. This paper further discusses the limitations of the model and the impact of ensemble member creation approaches on the assimilation results, and proposes possible methods to avoid these problems for future work.

Figure 11 caption: Global NmF2 maps from 2008/04/12 06:00UT to 2008/04/13 04:00UT before and after assimilating the FORMOSAT-3/COSMIC electron density profiles. The upper and lower row of each panel displays the posterior and control, respectively. The black dots indicate the observation locations.

(12) Comparative Studies of Theoretical Models in the Equatorial Ionosphere

Richmond participated in a study by Tzu-Wei Fang et al., who compared two sets of ionospheric models including six non-self-consistent models and five self-consistent models with ionosonde data and the International Reference Ionosphere (IRI).  The comparisons were focused on the low latitudes in March equinox under quiet geomagnetic activity and moderate solar activity (F10.7=120). They compared the NmF2 and hmF2 from all theoretical models, the IRI, and observations at four different local times at equatorial region in the American sector (75 W). For the non-self-consistent model, they further compared simulation results in the Asian sector (120 E). To identify the causes of differences in the non-self-consistent models, runs without neutral wind and/or electric field were conducted at the Asian sector.  Results show that the non-self-consistent models are in good agreement with each other and with the IRI especially in the daytime. Large discrepancies are shown in the self-consistent model results which imply very different electric fields and neutral atmosphere in these models. Also, the daytime NmF2 values at the crests of the equatorial anomaly calculated by the self-consistent models are substantially lower than those in the non-self-consistent models. This paper reviews the current status of each theoretical model and examines their capability in simulating the quiet time equatorial ionosphere.

Figure 12 caption: Comparisons of NmF2 (m−3, left) and hmF2 (km, right) at 2, 10, 14, 20 LT from five self-consistent models (colored lines), the IRI (black lines) and observations (triangles). Gray lines are the one standard deviation of the observations.

(13) The NCAR TIE-GCM: A Community Model of the Coupled Thermosphere/Ionosphere System

The Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) is a community model developed and maintained at the National Center for Atmospheric Research (NCAR). It also can be run at the NASA Community Coordinated Modeling Center (CCMC), and is a component of the Coupled Magnetosphere-Ionosphere-Thermosphere Model (CMIT). Richmond participated in a paper by Liying Qian et al. that describes the TIE-GCM development history, model elements, model input and output, the equations solved, boundary conditions, and numerical techniques. Some model validation examples are shown, and future improvements and developments are discussed.

Figure 13 caption: NmF2 observed by COSMIC, estimated by IRI, and simulated by TIE-GCM, during 2008. NmF2 is averaged over 10:00–13:00 LT and over the months shown in each panel.

(14) Ionospheric electrodynamics modeling

Arthur Richmond and Astrid Maute described the modeling of quasi-static ionospheric electric fields,currents, and magnetic perturbations associated with thermospheric winds, plasma gravitational and pressure-gradient (G/P) forces, and coupling with the magnetosphere, using examples from the National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General-Circulation Model. A two-dimensional partial differential equation (PDE) for the electric potential is obtained in magnetic coordinates, with source terms related to the winds, plasma G/P forces, and net field-aligned currents (FAC) from the magnetosphere. Three ways of representing the net FAC in the PDE are discussed: as a specified input FAC distribution, as a FAC distribution derived from a specified distribution of high-latitude electric potential, and as a representation of the FAC from the inner magnetosphere in terms of equivalent magnetospheric conductances. The plasma G/P source is generally weaker than the other sources of electric field and current, but can produce significant effects on the electric field at night and measurable geomagnetic perturbations at satellite heights. The calculation of geomagnetic perturbations below and above the ionosphere is illustrated with simplified calculations that reduce the three-dimensional current to a horizontal thin current sheet at ~110 km altitude, connected to FAC above. This simplified current system can be divided into an "equivalent" current flowing in the sheet, plus a "residual" current composed of the FAC plus divergent sheet current. By definition the ground-level magnetic perturbations are related only to the equivalent current, while magnetic perturbations above the ionosphere are produced both by the equivalent current and the residual current, with the latter often dominant.

Figure 14 caption: TIEGCM simulation of ionospheric currents (left) and geomagnetic perturbations
(right) as a function of magnetic local time and magnetic latitude for solar minimum, June 8, 17 UT, (when the subsolar point is at its northern-most magnetic latitude). For currents, arrows show the height-integrated sheet current density, K, and colors show the upward component of field-aligned current density at the top of the current sheet, Jqr. For magnetic perturbations, arrows show the horizontal components and colors the vertical component (positive downward). On the left are shown the total density (top), the residual current (middle), and the equivalent current (bottom).  On the right are shown magnetic perturbations at 400 km altitude due to equivalent current (top) and residual current (middle), and magnetic perturbations at the ground (bottom), which by definition are due only to the equivalent current.

(15) Sq current system during stratospheric sudden warming events in 2006 and 2009

Yosuke Yamazaki, Arthur Richmond, and colleagues examined ionospheric Sq current systems during unusually strong and prolonged stratospheric sudden warming (SSW) events in January 2006 and January 2009 by analyzing ground-magnetometer data. During these SSW events, a significant decrease and increase of the Sq equivalent current intensity are observed in the Northern and Southern Hemispheres, respectively, along with a reduction in longitudinal displacement of the northern and southern current vortices. If the observed changes are attributed to migrating tides, the solar anti-symmetric (2,3) semidiurnal tide is most likely to be the main contributor.

Figure 15 caption: (Top) Sq current functions at the American sector (355-degree E magnetic longitude) simulated by the NCAR/TIE-GCM for solar-minimum February conditions (DoY =46, Kp=2.0, and F10.7=70), (a) with (1,1), (2,2), (2,3), (2,4), (2,5) modes from the GSWM at the lower boundary, and (b) with (1,1), (2,2), (2,4), (2,5) modes from the GSWM and the (2,3) mode adjusted with the phase reversed and the amplitude multiplied by 6 at the lower boundary.  (Bottom) Sq current functions derived from ground-magnetometer data at the American sector for (c) late December of 2005, and (d) middle February of 2006. Current flow contours are drawn with 25 kA steps in latitude versus local time coordinates.

Publications

Alken, P., S. Maus, A.D. Richmond, and A. Maute (2011), The ionospheric gravity and diamagnetic current systems, J. Geophys. Res., 116, A12316, doi:10.1029/2011JA017126.

Cnossen, I., A.D. Richmond, M. Wiltberger, W. Wang, and P. Schmitt (2011), The response of the coupled magnetosphere-ionosphere-thermosphere system to a 25% reduction in the dipole moment of the Earth's magnetic field, J. Geophys. Res., 116, A12304, doi:10.1029/2011JA017063.

Cnossen, I., A.D. Richmond, and M. Wiltberger (2012), The dependence of the coupled magnetosphere-ionosphere-thermosphere system on the Earth's magnetic dipole moment, J. Geophys. Res., 117, A05302, doi:10.1029/2012JA017555.

Huang, Y., A.D. Richmond, Y. Deng, and R. Roble (2012), Height distribution of Joule heating and its influence on the thermosphere, J. Geophys. Res., 117, A08334, doi:10.1029/2012JA017885.

Lei, J., J.P. Thayer, W. Wang, A.D. Richmond, R. Roble, X. Luan, X. Dou, X. Xue, and T. Li (2012), Simulations of the equatorial thermosphere anomaly: Field-aligned ion drag effect, J. Geophys. Res., 117, A01304, doi:10.1029/2011JA017114.

Marsal, S., A.D. Richmond, A. Maute, and B.J. Anderson (2012), Forcing the TIEGCM model with Birkeland currents from the Active Magnetosphere and Planetary Electrodynamics Response Experiment, J. Geophys. Res., 117, A06308, doi:10.1029/2011JA017416.

Maute, A., A.D. Richmond, and R.G. Roble (2012), Sources of low-latitude ionospheric ExB drifts and their variability, J. Geophys. Res., 117, A06312, doi:10.1029/2011JA017502.

Pedatella, N.M., J.M. Forbes, A. Maute, A.D. Richmond, T.-W. Fang, K.M. Larson, and G. Millward (2011), Longitudinal variations in the F region ionosphere and the topside ionosphere-plasmasphere: Observations and model simulations, J. Geophys. Res., 116, A12309, doi:10.1029/2011JA016600.

Pedatella, N.M., H.-L. Liu, and A.D. Richmond (2012), Atmospheric semidiurnal lunar tide climatology simulated by the Whole Atmosphere Community Climate Model, J. Geophys. Res., 117, A06327, doi:10.1029/2012JA017792.

Pedatella, N.M., H.-L. Liu, A.D. Richmond, A. Maute, and T.-W. Fang (2012), Simulations of solar and lunar tidal variability in the mesosphere and lower thermosphere during sudden stratosphere warmings and their influence on the low-latitude ionosphere, J. Geophys. Res., 117, A08326, doi:10.1029/2012JA017858.

Wilder, F.D., G. Crowley, B.J. Anderson, and A.D. Richmond (2012), Intense dayside Joule heating during the April 5, 2010 geomagnetic storm recovery phase observed by AMIE and AMPERE, J. Geophys. Res., 117, A05207, doi:10.1029/2011JA017262.

Yamazaki, Y., A.D. Richmond, and K. Yumoto (2012), Stratospheric warmings and the geomagnetic lunar tide: 1958-2007, J. Geophys. Res., 117, A04301, doi:10.1029/2012JA017514.

Yue, J., W. Wang, A.D. Richmond, and H.-L. Liu (2012), Quasi-two-day wave coupling of the mesosphere and lower thermosphere-ionosphere in the TIME-GCM: Two-day oscillations in the ionosphere, J. Geophys. Res., 117, A07305, doi:10.1029/2012JA017815.