Dr. Astrid Maute has research interests in the modeling of the ionospheric electrodynamics, ionospheric current systems and their associated magnetic perturbations. She studies the upper atmosphere response due to metrological and geospace forcing, and is interested in the high-latitude magnetosphere-ionosphere energgy transfer.


Figure 1: 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).

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

Abstract: The complete mechanism of how upward propagating tropospheric tides connect to the upper atmosphere is not yet fully understood. One proposed mechanism is via ionospheric wind dynamo. However, other sources can potentially alter the vertical ExB drift: gravity and plasma pressure gradient driven current, the geomagnetic main field, and longitudinal variation in the conductivities. In this study we examine the contribution to the vertical drift from these sources, and compare them. We use March equinox results from the Thermosphere Ionosphere Mesosphere Electrody namics General Circulation Model. We found that the 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. This implies that the vertical drift has to be analyzed at specific local times to examine the relation between the wavenumber in the vertical drift and in the neutral winds.

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Figure 2: Comparison between observed (black line) and modeled (blue line) ground magnetic perturbations at different latitudes for the highly disturbed day August 4th, 2010 with Ap = 49: results are shown for TRO (66.5 deg. magn. latitude) and CMO (64.9 deg. magn. latitude).

(2) 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., 116, A12309, doi:10.1029/2011JA017416.

Abstract: 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). The modeled ground magnetic perturbations at four differenct locations are compared with observations for different magentic disturbance levels. Comparison with the standard version of TIEGCM shows that temporal variations of the ground geomagnetic perturbations between 6h and down to 10 min can now be simulated. In general, the AMPERE-driven TIEGCM can model the gross features of the geomagnetic variations. Temporal variations less than 30 min are often underestimated in the model, which could possibly caused by local ionization not capture by the GCM.

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Figure 3: Results for solar minimum simulation with lunar tidal forcing: (a)Change in the zonal mean vertical drift velocity at the magnetic equator and 300 km. 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).

(3) Pedatella, N. M., H.-L. Liu, A. D. Richmond, A. I. 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.

Abstract: 23 Whole Atmosphere Community Climate Model (WACCM) simulations of sudden stratosphere warmings (SSWs) are used to investigate the solar and lunar tide changes in the mesosphere and lower thermosphere (MLT) due to SSW events. Pedatella et al. [2012] found that 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) by 40–50% also occur up to an altitude of 120 km. Changes in nonmigrating solar tides are, on average, smaller than 20% with the exception of the diurnal tide with zonal wave number 0 (D0) which decrease by 20–30% at low latitudes and the westward propagating semidiurnal tide with zonal wave number 1 (SW1) which is enhanced at mid to high latitudes in both hemispheres by approximately the same magnitude. The study indicates the importance of the lunar tide during SSWs, especially for the coupling between SSWs and perturbations in the low latitude ionosphere.

Figure 4: Variability of the (top) vertical and (middle) zonal plasma drifts in the Peruvian longitudinal sector (-75°E). (bottom) The two-dimensional plasma flow pattern.

(4) Rodrigues, F., G. Crowley, R. Heelis, A. Maute, and A. Reynolds (2012), On TIE-GCM simulation of the evening equatorial plasma vortex, J. Geophys. Res., 117, A05307, doi:10.1029/2011JA017369.

Abstract: Rodrigues et al. [2012] could simulate the post-sunset vortex using the Thermosphere-Ionosphere-Electrodynamics general Circulation Model (TIE-GCM). The comparison between observed plasma flow pattern and simulation in the Peruvian sector showed that the overall features can be reproduced, but the simulated vortex center occures earlier in local time.

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Figure 5: Modeled vertical ion drifts at the IS radar locations, with the blue dashed lines representing the wind-driven vertical drift component, the red dashed lines representing the electric field-driven component, and the black lines for the total vertical drift.

(5) 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: Lu et al. [2012] investigated the ionospheric and thermospheric response due to the prompt penetrations electric field (PPEF) event on November 9, 2004 using the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIME-GCM). By using realistic, time-dependent, high-latitude electric potential and auroral precipitation patterns, derived from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure, 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. The simulation results are validated with several key observations from IS radars, ground GPS-TEC network, and the TIMED-GUVI O/N2 column density ratio. 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.

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Figure 6: Schematic illustration of the current and electric field associated with a zonal wind in the F region, as a function of local time. The pre-reversal enhancement appears in a local time region prior to the E region terminator when the E region cannot effectively short the F region current and cannot effectively polarize the F region to eliminate it.

(6) Heelis, R. A., G. Crowley, F. Rodrigues, A. Reynolds, R. Wilder, I. Azeem, and A. Maute (2012), The role of zonal winds in the production of a pre-reversal enhancement in the vertical ion drift in the low latitude ionosphere, J. Geophys. Res., 117, A08308, doi:10.1029/2012JA017547.

Abstract: Heelis et al. [2012] used the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) to study the evolution of the pre-reversal enhancement in the vertical ion drift in the equatorial F region via an examination of the current systems. They found that the pre-reversal enhancement is produced by a reversal in the F region zonal wind that results in an additional upward current where the E region Pedersen conductivity is declining across the dusk sector. The continuity of the total current is maintained through an enhancement in the eastward zonal current and an associated upward drift of the ions.

Figure 7: Longitude variation of the simulated vertical E×B drift velocity at the magnetic equator and 300 km altitude. The results shown are for the average between 12 and 15 local time. Individual lines correspond to the TIME-GCM simulation results, climatology from Scherliess and Fejer [1999], and the simulation results for the ionosphere-electrodynamics model.

(7) Pedatella, N. M., M. E. Hagan, and A. I. Maute (2012), The comparative importance of DE3, SE2, and SPW4 on the generation of wavenumber-4 longitude structures in the low-latitude ionosphere during September equinox, Geophys. Res. Lett., 39, L19108, doi:10.1029/2012GL053643.

Abstract: Pedatella et al. [2012] investigated the generation of the wave-4 longitude variation in the low-latitude ionosphere due to the diurnal eastward propagating nonmigrating tide with zonal wavenumber 3 (DE3), semidiurnal eastward propagating nonmigrating tide with zonal wavenumber 2 (SE2), and stationary planetary wave 4 (SPW4) using the Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM). Both the DE3 and SPW4 are found to produce significant wave-4 variations in the equatorial vertical E×B drift velocity, and in the ionospheric peak density (NmF2) at 15°N magnetic latitude. The daytime wave-4 variation in NmF2 is driven by the combination of vertical E×B drift variability and in-situ effects due largely to meridional neutral winds. The SPW4 in the model is generated due to the nonlinear interaction between the migrating diurnal tide and the DE3.