HAO 2011 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.

Publications

(1) 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., accepted, doi:10.1029/2011JA016600.

Abstract: Pedatella et al. [2011] used Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) observations of the total electron content (TEC) above and below 800 km to study the local time and seasonal variation of longitude structures in both the F-region ionosphere as well as the top-side ionosphere and plasmasphere. The COSMIC observations reveal the presence of distinct longitude variations in the topside ionosphere/plasmasphere TEC and these further exhibit a seasonal and local time dependence. The predominant feature observed at all local times in the topside ionosphere/plasmasphere TEC is a substantial maximum (minimum) during Northern Hemisphere winter (summer) around 300–360° geographic longitude. Around equinox, at a fixed local time, a wave-4 variation in longitude prevails in the daytime F-region TEC as well as the topside ionosphere/plasmasphere TEC. The wave-4 variation in longitude persists into the nighttime in the F-region; however, the nighttime topside ionosphere/plasmasphere TEC exhibits two maxima in longitude. The COSMIC observations clearly reveal the presence of substantial longitude variations in the F-region and topside ionosphere/plasmasphere and, to elucidate the source of the longitude variations, results are presented based on the coupling between the Global Ionosphere Plasmasphere model and the Thermosphere Ionosphere Electrodynamics General Circulation Model. The model simulations demonstrate that the orientation of the geomagnetic field plays a fundamental role in generating significant longitude variations in the topside ionosphere/plasmasphere but does not considerably influence longitude variations in the F-region ionosphere. The model results further confirm that nonmigrating tides are the primary mechanism for generating longitude variations in the F-region ionosphere. The coupled model additionally demonstrates that nonmigrating tides are also of considerable importance for the generation of longitude variations in the topside ionosphere/plasmasphere TEC.

Figure 1 caption: Geographic longitude and magnetic latitude variations of the TEC between 16-18 LT around September equinox (top) and the December solstice (bottom) for (a) COSMIC observations below 800 km, (b) COSMIC observations above 800 km, (c) GIP-TIEGCM simulation below 800 km, (d) GIP-TIEGCM simulation above 800 km.

(2) Pedatella, N.M., J.M. Forbes, and A.D. Richmond. 2011: Seasonal and longitudinal variations of the solar quiet (Sq) current system during solar minimum determined by CHAMP satellite magnetic field observations, J. Geophys. Res., 116, A04317, doi:10.1029/2010JA016289.

Abstract: Pedatella et al. [2011] used vector magnetometer observations from  the CHAllenging Mini- satellite Payload (CHAMP) satellite to determine the solar quiet (Sq) current system during the recent solar minimum. Observations from 2006-2008 are combined and after removal of a main field model and accounting for field aligned currents, the longitudinal and seasonal variation of the Sq currents are determined through the method of spherical harmonic analysis. Comparison with Sq currents derived from ground based magnetometers in the African/European longitude sector reveals similar amplitudes and seasonal variations, indicating that the CHAMP observations can reliably determine the Sq current system. The seasonal variation is consistent with prior observations during solar minimum conditions and in the Northern Hemisphere exhibits a primarily annual variation with peak currents during local summer. The seasonal variation in the Southern Hemisphere is characterized by a semiannual variation with the maxima occurring around the equinoxes. Significant longitudinal variations are also observed and they display a seasonal variability. During Northern Hemisphere summer the predominant structure is a wave-1 feature. During the remainder of the year, wave-3 and wave-4 longitudinal structures are observed. The longitudinal variations are considered to be due to a combination of the orientation and strength of the geomagnetic field as well as the tidal winds in the lower thermosphere. Variations in tidal winds due to nonmigrating tides may influence the dynamo generated electric fields and currents, resulting in longitudinal variations of the Sq current system. The study represents the first time that satellite magnetic field observations have been used to 28 determine the global Sq current system. Furthermore, the use of satellite observations allows for the first determination of the complete longitudinal variation of the global Sq current system.

Figure 2 caption: Sq current systems during June solstice for (a) CHAMP zonal mean and (b) ground based magnetometers. (c) and (d) are the same as (a) and (b) except for December solstice.

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

Abstract: Patrick Alken and Stefan Maus (National Geophysical Data Center, NOAA) worked with Art Richmond and Astrid Maute at HAO to model the ionospheric electric currents and magnetic perturbations driven by gravitational and pressure-gradient forces on the ionospheric plasma. The magnetic perturbations are large enough to affect precision measurements of the geomagnetic field by low-Earth-orbiting satellites. The researchers created a numerical model by combining the electrodynamic solver from the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) together with empirical models of thermospheric densities and winds and of ionospheric densities. For gravitationally-driven currents the model shows how polarization electric fields are established in the F-region ionosphere which maintain eastward low-latitude current flow throughout the night, in spite of low conductivity, and which weaken the net low-latitude eastward current during the day and evening, as seen in the figure. For diamagnetic currents and magnetic perturbations associated with plasma pressure gradients, the researchers found that the model gives results in rough agreement with estimates based on the simplified concept of a magnetic-pressure reduction equal to the plasma pressure. However, the researchers noted that changes in the magnetic tension force also enter into the force balance, creating discrepancies between the simplified concept and the predictions of their model.

Figure 3 caption: Height-integrated gravity-driven ionospheric currents that either include (top) or neglect (bottom) the effects of polarization electric fields, simulated for 0 UT on March 21, 2003. The center portion of the figures lies on the night-side of the Earth, and the red line indicates the magnetic equator. When the polarization field is neglected, the current is proportional to the height-integrated plasma mass density (bottom). The polarization field generally increases eastward current during the early-morning hours and reduces the current during the day and evening (top).

(4) Kondo, T., A.D. Richmond, H. Liu, J. Lei, and S. Watanabe. 2011: On the formation of a fast thermospheric zonal wind at the magnetic dip equator, Geophys. Res. Lett., 38, L10101, doi:10.1029/2011GL047255.

Abstract: Kondo et al. [2011] carried out simulations with the NCAR Thermosphere – Ionosphere – Electrodynamics General Circulation Model (TIEGCM) to understand the cause of strong thermospheric zonal wind at the magnetic dip equator. The simulations show that the zonal winds blow strongly at the magnetic dip equator instead of at the geographic equator due to the latitude structure of ion drag. The fast winds at the dip equator are seen throughout the altitude between 280km and 600km, and the wind above 400km is mainly accelerated via viscosity. A test simulation without viscosity verifies that the extension of the fast equatorial wind to heights above 400 km is maintained by viscous coupling with the winds at lower altitudes, in spite of there being an ion-drag maximum instead of relative minimum at the dip equator at high altitudes. Basically, viscosity is not so large compared to the pressure gradient and ion drag, but dynamics causes the pressure gradient and ion drag approximately to balance, and viscosity becomes important. The simulation results are consistent with the observations by the DE-2 and CHAMP satellites. Therefore they suggest that the zonal wind velocity in the low latitude region is controlled by ion drag and viscosity.

Figure 4 caption: The eastward wind (left) and electron density (right) altitude-latitude profiles at 20 LT and −15° longitude. The upper panels are for normal TIEGCM simulations, while the lower panels have viscosity set to zero. The magnetic dip equator is at about 10° geographic latitude. The fast zonal wind around the magnetic equator forms where the electron density and ion drag are low on the bottom side of the ionosphere; viscosity drags the air along at higher altitudes.

(5) Lei, J., J.P. Thayer, W. Wang, A.D. Richmond, R. Roble, X. Luan, X. Dou, X. Xue, and T. Li. 2011: Simulations of the equatorial thermosphere anomaly: 1. Field-aligned ion drag effect, J. Geophys. Res., submitted, doi:10.1029/2011JA017114.

Abstract: Lei et al. [2011] quantitatively investigated the impact of the field-aligned ion drag on thermosphere temperature and density on the basis of NCAR-TIEGCM simulations under high solar activity (F107=180). The increment of upward vertical winds over the magnetic equator associated with the additional divergence of meridional winds causes additional adiabatic cooling due to the inclusion of the field-aligned ion drag, consequently leading to the equatorial reduction of thermosphere temperature and density. They found that the field-aligned ion drag has obvious impact on the thermosphere only over the equatorial region and in the daytime, whereas it has little contribution on the Equatorial Thermosphere Anomaly (ETA) crests. The daytime neutral temperature over the magnetic equator is reduced by about 30 K above the altitude of 250 km without significant altitudinal variations, when the field-aligned ion drag is included in the simulation. For thermosphere density in the equatorial region, it starts to change slightly at 300 km and depletes by about 5% at 400 km; it has a greater decrease at higher altitudes. Meanwhile, the trough produced in neutral temperature and density corresponds well with the dip equator, with little longitudinal dependence. The ETA features during 1200–1800 local time become obvious as a result of the inclusion of the field-aligned ion drag. Specifically, their results showed that at 400 km the crest-trough differences in neutral temperature are about 30–60 K, and the crest-trough ratios in thermosphere density are 1.03–1.06, comparable with observations.

Figure 5 caption: Thermospheric temperature (left) and density (right) at 400 km at 1800 UT for TIEGCM simulations that either exclude (top) or include (bottom) ion drag along the direction of the geomagnetic field. Temperature is in units of K; density is in units of 10⁻¹² kg·m⁻³. The dashed white lines indicate the location of the magnetic equator.

(6) Oberheide, J., M. Hagan, J. Forbes, and A. Richmond. 2011: Atmospheric Tides, submitted to Encyclopedia of Atmospheric Sciences, Elsevier Science Ltd.

Abstract: Oberheide et al. [2011] gave an overview of atmospheric tides in an encyclopedia article. They covered classical tidal theory, migrating and non-migrating tides, lunar tides, and ionospheric effects of the tides.

Figure 6 caption: Surface pressure (hPa) at Batavia (Jakarta, Indonesia) against time during the first 5 days of January 1925.

(7) Fuller-Rowell, T., H. Wang, R. Akmaev, F. Wu, T.-W. Fang, M. Iredell, and A. Richmond. 2011: Forecasting the dynamic and electrodynamic response to the January 2009 sudden stratospheric warming, Geophys. Res. Lett., 38, L13102, doi:10.1029/2011GL047732.

Abstract: A whole atmosphere model was used by Fuller-Rowell et al. [2011] to simulate the changes in the global atmosphere dynamics and electrodynamics during the January 2009 sudden stratospheric warming (SSW). In a companion paper, it has been demonstrated that the neutral atmosphere response to the 2009 warming can be simulated with high fidelity and forecast several days ahead. The 2009 warming was a particularly large event with the polar stratospheric temperature increasing by 70K. The neutral dynamics changes from the whole atmosphere model (WAM) have been used to drive the ionosphere and electrodynamics. The WAM simulation shows that there is a substantial increase in the amplitude of the 8-hour ter-diurnal tide in the lower thermosphere dynamo in response to the warming, at the expense of the more typical semi-diurnal tides. The increase in the ter-diurnal mode has a significant impact on the diurnal variation of the electrodynamics at low latitude. The changes in the winds in the dayside ionospheric E-region tend to increase the eastward electric field, or upward vertical plasma drift, early in the morning, and drive a westward electric field, or downward plasma drift, in the afternoon. As the SSW evolves, the initial large increase in upward drifts that appears early on the dayside gradually moves to later local times, and at the same time decreasing in magnitude. The change in the amplitude and phase of the electrodynamic response to the SSW is in excellent agreement with observations from the Jicamarca coherent scatter radar observations. In the absence of comprehensive direct measurements of the neutral winds in the mesosphere and lower thermosphere, the agreement of the electrodynamics with observations serves to validate the whole atmosphere dynamic response. Since WAM can accurately forecast the neutral dynamics several days ahead, the simulations indicate that the ionospheric and electrodynamic response to large-scale lower atmospheric processes, and their impact on space weather, can also be forecast several days in advance.

Figure 7 caption: Illustration of excellent agreement between observed and modeled electrodynamic response to the January 2009 SSW. The upper panel shows the time variation of the observed dayside (8 to 18 local time) response of the vertical plasma drift at the Jicamarca incoherent scatter observation on the magnetic equator, from Chau et al., 2010; the lower panel shows the simulation results using WAM winds to drive the electrodynamics in the CTIPe coupled thermosphere ionosphere model.

(8) Cnossen, I., A.D. Richmond, M. Wiltberger, W. Wang, and P. Schmitt. 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., accepted, doi:10.1029/2011JA017063.

Abstract: In order to understand how changes in the dipole moment of the Earth's magnetic field may affect the magnetosphere-ionosphere-thermosphere system, Ingrid Cnossen and colleagues performed simulations with the Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model, first using a dipole moment of 8•10²² Am²², close to the present-day value ("strong dipole"), and then a dipole moment of 6•10²² Am²², which may be its value a few centuries in the future ("weak dipole"). Both simulations were run under the same solar wind conditions, for intermediate solar activity (F10.7 = 150), at equinox. Substantial differences are predicted for the ionosphere. The left column of the figure shows ionospheric quantities for the "strong dipole", averaged over the two hours 13–15 UT: the height of the peak of the F2 layer, hmF2 (top); the vertical component of the neutral wind parallel to the magnetic field, v_n,par,v (middle), which forces the plasma up and down field lines; and the vertical component of the E×B drift (bottom). The right column shows the changes in these quantities when the dipole moment is reduced. Changes in v_n,par,v, explain the changes in hmF2 over the Pacific, off the south-east coast of Australia, and over east Asia. The changes in the neutral wind themselves are caused partly by an enhancement in E×B ion drift velocities (through ion-neutral collisions) and partly through an increase in the meridional pressure gradient, in response to stronger high-latitude Joule heating. Changes in the vertical component of the E×B drift, which is most effective in changing hmF2 at low latitudes, may be responsible for the decrease in hmF2 over the Indian Ocean. There is also a global mean uplift of the ionosphere, due to an increase in global mean temperature, which causes the thermosphere to expand.

Figure 8 caption: The left column of the figure shows ionospheric quantities for the “strong dipole”, averaged over the two hours 13-15 UT:  the height of the peak of the F2 layer, hmF2 (top); the vertical component of the neutral wind parallel to the magnetic field, vn,par,v (middle), which forces the plasma up and down field lines; and the vertical component of the ExB drift (bottom).  The right column shows the changes in these quantities when the dipole moment is reduced.