Geophysics

Permanent URI for this collectionhttps://digital.lib.washington.edu/handle/1773/4926

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Self-consistent modeling of ice-sheet evolution and paleoclimate
(2012-08-10) Lundin, Jessica; Waddington, Edwin D
A self-consistent approach has been developed to determine past climate histories while simultaneously determining the past ice-sheet evolution. We recognize that multiple physical processes are affected by the same climate history and ice-sheet evolution. By combining several processes into one self-consistent model based on physics of ice-sheet flow, heat flow, grain growth, and firn compaction, I can infer the climate history (accumulation rate and delta-age) and ice-sheet evolution (thickness and divide position), that match data sets from ice cores and ice-penetrating radar layers. Ice-sheet behavior has not previously been modeled to enforce self consistency. The self-consistent approach consists of modules, or subroutines, representing physical processes. I have developed forward models to simulate firn densification, grain growth, heat transfer, and ice flow, and inverse models to infer histories including the spatial pattern of accumulation, and the depth-age relationship for ice cores and radar layers. While individual modules can be replaced with modules based on a variety of physical approximations, I provide here proof of the concept that multiple data sets and multiple processes can be combined to provide improved estimates of ice-sheet histories that cannot be directly measured. This new approach provides a way to improve ice-core chronologies from Greenland and Antarctica, and to infer self-consistent histories of climate and ice-sheet evolution at those locations.
Theoretical calculations of magnetic hysteresis and critical sizes for transitions between single-domain and multi-domain properties in titanomagnetites
(1997) Newell, Andrew James
In this dissertation, I develop some theoretical tools to interpret measurements of magnetization in rocks, sediments and soils. I show that the magnetization curve for an ensemble of superparamagnetic particles depends only on odd moments of the volume distribution $\rm(\langle V\rangle,\langle V\sp3\rangle,\...).$ As long as the ensemble is isotropic, the magnetic anisotropies of individual particles do not affect the curve. I derive analytical expressions for acquisition and loss of isothermal remanent magnetization in single-domain (SD) particles with uniaxial anisotropy. These curves depend only on the volume-average anisotropy. Plots of acquisition against loss of remanence can be used to distinguish uniaxial anisotropy from cubic anisotropy. I show that existing multi-domain (MD) hysteresis models, including the theory of Neel (1955) for thermoremanent magnetization, are internally inconsistent. I develop a simple self-consistent two-domain model and show that the slope of the hysteresis curve is always $1/N,$ where N is the demagnetizing factor for a two-domain particle.Using micromagnetic theory, I derive analytical expressions for the critical sizes $L\rm\sb{sw},$ the upper limit for SD hysteresis, and $L\rm\sb{n},$ the upper limit for stability of the SD remanent state. $L\rm\sb{sw}$ depends weakly on elongation and not at all on magnetocrystalline anisotropy, but$$L\sb{\rm n} = L\sb{\rm sw}\ \left({N\sb{\rm b}\over N\sb{\rm a}}\right)\sp{\sp{1/2}}\left(1-{2\kappa\over\mu\sb0M{\sbsp{\rm s}{2}}N\sb{\rm a}}\right)\sp{\sp{-1/2}}$$where $N\sb{\rm a} > N\sb{\rm b}$ are demagnetizing factors and $\kappa$ depends on the combined magnetocrystalline and magnetoelastic anisotropy. Mainly because of the the difference in $Ms,\ L\rm\sb{n}$ is orders of magnitude larger for a particle of $\rm Fe\sb{2.4}Ti\sb{0.6}O\sb4$ than for a particle of magnetite with the same aspect ratio.I develop a technique for eliminating unstable solutions of three-dimensional numerical micromagnetic models. I show that nucleation theory can be extended to non-ellipsoidal particles. The nucleation field $H\sb{\rm n}$ for a cuboid can be precisely located by a change in slope dM/dH and the appearance of curl in the magnetization. For a cube with $K\sb1 = 0,$ the plot of $H\sb{\rm n}$ against $1/L\sp2$ has the same slope as for a sphere, but the intercept is lower, reflecting a smaller average demagnetizing field. $H\sb{\rm n}$ is not affected by the demagnetizing field in the corners of the particle.
Folding of stratigraphic layers in ice domes
(2001) Jacobson, Herbert Paul
This dissertation presents a two part model of the formation of recumbent folds in stratigraphic layers of ice sheets such as those in Greenland and Antarctica. The initial disturbances in the stratigraphy have their roots in transient dynamic processes and local rheological inhomogeneities, but the kinematics of even a simple ice flow model can deform these disturbances enough to alter paleoclimatic interpretation of an ice core. This study focuses on this deformation, treating the disturbed strati-graphic layers as passive markers in the large-scale flow.The two major tools that I use to study overturning are core-relative isochrones (precores) and the deformation gradient tensor along a particle path. This tensor is used to calculate the rotation of stratigraphic segments of various orientations. It is also used in a stochastic model to derive the probability distribution of observing overturned segments given a probability distribution of the initial disturbances.Overturn probabilities increase downstream along a path. They also increase with depth, unless the initial disturbance processes are concentrated at a particular depth. Because of rapid rate of rotation of near-vertical segments, the probability of seeing obvious overturning in a small ice-core cross-section is low even if recumbent folds are present. Gentle disturbances are more likely to be overturned if they occur deep in the ice where the shear is strongest.Overlaying precores on divide arch isochrones shows that ice divide movement can produce recumbent folds. This movement must have a stop-start quality, with enough stability to produce mature arching, but also enough movement to leave an orphaned disturbance on the flank where it can be overturned. Such folding may be most likely downstream from ice ridges bounded by variable ice streams.The variation in the vertical thickness of a disturbed layer is also examined. Even if a disturbance is not overturned, some portions will be thinned more than undisturbed layers while other portions will be thickened. Passive deformation may reduce or exaggerate certain aspects of dynamically produced stratigraphic disturbances, but it does not obliterate them.
Interpretation of infrasound generated by erupting volcanoes and seismo-acoustic energy partitioning during strombolian explosions
(2000) Johnson, Jeffrey B., 1972-
Infrasonic signals provide a valuable tool for the study of volcanic eruptions because volcanoes generate the majority of their acoustic energy in the infrasonic bandwidth and infrasound is only slightly affected by propagation filters, transmission losses, dispersion, and instrument site responses. Though changing atmospheric properties can influence infrasonic amplitudes and arrival times, they do not significantly distort the original waveform. Because of the simplicity of acoustic propagation filters (compared to seismic propagation filters), recorded infrasonic pressure waveforms can reveal the overpressure time history at the vent which may be integrated to estimate explosive gas mass flux. Digitized video records are able to substantiate the relationship between infrasound intensity and the rate change of gas mass flux released during an explosion.This dissertation analyzes and interprets the radiated infrasound and seismicity produced by five different active volcanoes. The case studies encompass low-viscosity Strombolian activity (Erebus, Antarctica), medium viscosity Strombolian activity (Karymsky, Russia and Sangay, Ecuador), a more vigorous Vulcanian eruption (Tungurahua, Ecuador), and degassing explosions from an active dacitic dome (Pichincha, Ecuador). The complexity of both the infrasonic and seismic waveforms at these five volcanoes appears related to the viscosity and volatile content of the different magmas. Erebus explosion signals are uniform, short-duration bursts because gas is able to easily escape the low-viscosity magma. Conversely, extended-duration degassing signals at the other volcanoes can be attributed to higher magma viscosity.At both Erebus and Karymsky, arrays of low-frequency microphones and seismometers were deployed within several kilometers of the degassing source to quantify the elastic energy that propagates into the ground and into the atmosphere. Acoustic efficiency (relative to the radiated seismic energy) is attributed to shallow explosion sources with associated impulsive gas outflux. Strombolian explosions at Erebus appear acoustically efficient compared to Karymsky because gas release occurs at the surface of the lava lake. Karymsky explosion sources emanate from shallow depths within the conduit diminishing the impulsivity of gas release from the vent of the volcano. Scatter in the seismic-acoustic energy radiation at Karymsky reveals that conditions in the conduit change during the course of an explosion.
Juan de Fuca subducting plate geometry and intraslab seismicity
(2006) Medema, Guy Frederick
The geometry of the subducting Juan de Fuca plate beneath the Olympic Peninsula of Western Washington is modeled using wide-angle P mP reflections off the slab Moho. Active-source reflection data collected from the 1998 WET SHIPS project were augmented with earthquake-source reflections to increase the spatial distribution of reflection points over the Juan de Fuca arch structure. Approximately 1100 WET SHIPS and 500 earthquake-source reflections were used in our inversion. PmP travel-times from active sources and PmP--P differential times from earthquakes sources were simultaneously inverted for slab-Moho depth, using a combination of finite-difference and 3-D ray-tracing methods. Results show a tighter arch structure than in previous models with the shallowest dipping portion (∼ 10° dip) concentrated directly beneath the Olympic Mountains. Comparison of our slab model to intraslab earthquake hypocenters reveals a southwest-northeast trending lineament of seismicity situated just beneath the subducted Moho in the slab mantle. We interpret this seismicity as the manifestation of a subducting pseudofault along which high levels of upper mantle hydration occurred prior to subduction. Most of the remaining intraslab seismicity is concentrated on the northern and southern flanks of the arch and is likely due to increased strain rates in these regions from the combined effect of slab arch and subsequent steepening of slab dip. Earthquakes in the northern region appear to occur above the slab Moho in the crust of the oceanic plate, while uncertainties in earthquake locations and 3-D velocities in the southern region prevent an unambiguous interpretation at this time. The southern patch is especially important as it contains 3 large (magnitude 6.5 to 7.1) earthquakes during that past 60 years, including the 2001, Mw 6.8, Nisqually earthquake. Earthquakes occurring between 45 and 65 km depth in these two regions also systematically produce an anomalous low-frequency, high-amplitude secondary P arrival on updip stations with an average horizontal velocity of 6.0 km/s. We identified 13 earthquakes producing this anomalous phase. These arrivals are typically observed for rays that pass under the Olympic Mountains. 2-D ray-tracing was used to interpret travel times of these arrivals as S-to-P conversions at the interface between the top of the subducted oceanic crust and mantle wedge. Efficient conversion from S-to-P required high velocity oceanic crust and an anomalously low velocity mantle wedge. We therefore interpret this secondary phase to indicate eclogitization of the oceanic crust and serpentinization of the mantle wedge in the vicinity of earthquakes producing the phase. Along paths where these phases are observed, 3-D tomography models exhibit a dipping low-velocity zone formed by accretionary sediments underthrusting high-velocity Eocene volcanics. 2-D ray tracing indicates that this acts as a wave guide along which high-amplitude, low-frequency waves can propagate great distances to the seismic stations.
High pressure and low temperature equations of state for aqueous magnesium sulfate: applications to the search for life in extraterrestrial oceans, with particular reference to Europa
(2007) Vance, Steven, 1978-
A prevalence of cold, high pressure (P > 100 MPa) environments in the Solar System, and beyond, is discussed in the context of contemporary efforts to understand the origin and abundance of life in the Universe. Constraints on the depths of fluid circulation in extraterrestrial seafloors are explored through a model for the development of microfractures in olivine through cooling. For the example of Europa, we estimate a factor of four in per-unit-area hydrogen flux from serpentinization as compared with calculations for Earth's seafloor. Uptake of seafloor salt by an incipient thermal plume is suggested as a stay on buoyancy and a driver for stratification in the Europa's ocean. An apparatus for optical measurements in deep-ocean analogue materials is described. Laser-induced phonon spectroscopy is applied to the determination of the velocity of sound in water and in aqueous solutions of MgSO4. The equation of state is deduced for concentrations from 0 to 2.0137 m for temperatures from -20 to 100°C and pressures as high as 700 MPa. Debye Huckel theory is employed for calculating partial molal volume at infinite dilution. The volumetric contribution of MgSO4 is less than expected above 200 MPa and at the extremes of temperature, indicating a change in ion-water interaction due to increased confinement under these conditions.
Kinetic processes in the plasma sheet observed during auroral activity
(2002) Fillingim, Matthew Owen
In this dissertation we analyze plasma sheet magnetic field and plasma data observed during varying levels of auroral activity from very small, isolated events known as pseudobreakups to large, global events known as substorms. The plasma and magnetic field data are taken from instruments onboard the WIND spacecraft while it traverses the near-Earth plasma sheet. Simultaneous global auroral images from POLAR/UVI allow us to determine the auroral activity level. The goal of this dissertation is to provide the most complete set of plasma sheet observations during auroral activity currently available. The kinetic aspects of the plasma dynamics which have largely been ingnored in other works are emphasized here. We have the capability to resolve changes in the three dimensional ion distribution functions with a time resolution comparable to or faster than the local ion gyroperiod. In addition, we consider the typically neglected electron dynamics when relating plasma sheet processes to the aurora. We find that the plasma sheet signatures of both pseudobreakups and substorms appear very similar. During both types of events, increases in auroral precipitation into the ionosphere are associated with large amplitude, high frequency magnetic field fluctuations, large Earthward ion 〈 v〉, increases in the fluxes of high energy ions and electrons, and hardening of the electron spectrum. Both ion and electron distributions appear to be composed of multiple components. Electromagnetic waves with power at frequencies up to and above the local proton gyrofrequency area also observed. Additionally, the ion distributions can change significantly in one gyroperiod. Together, these results imply that the microphysical processes occurring in the plasma sheet during pseudobreakups and substorms are the same and that kinetic effects are important. Therefore, magnetohydrodynamics (MHD) cannot adequately describe the physics occurring during large ion 〈 v〉 events.
The effect of vertical mixing on along channel transport in a layered flow
(1998) Cudaback, Cynthia Nova
The Columbia River has a large, biologically productive estuary whose ecosystem depends on the balance of salt and fresh water. Outflow from the river also forms a vast buoyant plume which affects circulation for hundreds of miles along the coast. Both the estuarine salt balance and the initial state of the plume are determined by flow through the narrow entrance channel. I have made a three-part study of the effects of interfacial turbulence and bottom friction on along-channel transport through the Columbia River entrance channel.My observations in the Columbia River entrance channel show that both interfacial mixing and bottom friction significantly affect circulation. The pycnocline is thinned by lateral advection on flood and thickened by vertical mixing on ebb and flow. On late flood, the pycnocline is close to the surface and quite thin; on late ebb, its center is below mid-depth and it fills 3/4 of the water column. Bottom friction retards the near-bottom currents, so early flood currents are strongest at mid-depth, and peak flood currents are strongest at the surface. At peak ebb and peak flood, salinity transport is strongest at mid-depth.A two-layer time-dependent model (Helfrich, 1995) simulates along-channel currents and layer thicknesses. By assuming a near-critical bulk Richardson number, I estimated the pycnocline thickness from the two-layer model results. Bottom friction raises the pycnocline and causes tidal variations in vertical shear, which drive the changes in pycnocline thickness. This model replicates the observed pycnocline quite well, but cannot simulate mid-depth currents.I created a new three-layer time-dependent model, in which the middle layer represents the pycnocline. Mixing of salt and fresh water creates water of intermediate density, which is modeled as entrainment from the top and bottom layers into the middle layer. This model simulates along-channel circulation at all stages of the tide, including the mid-depth maximum at early flood. It also simulates the vertical distribution and tidal average of salinity transport. For the best fit to observations, the three-layer model requires significantly more bottom friction than the two-layer model; this is consistent with the formulation of the bottom roughness coefficient.
The indepth magnetotelluric experiment on the Tibetan Plateau and its implications
(2001) Li, Shenghui
This dissertation focus on the application of the magnetotelluric method to tectonic studies on the Tibetan Plateau. The framework of this thesis composes three parts. The first part concentrates on magnetotelluric data inversion in the presence of strong topographic or bathymetric distortions. A new approach is described to invert magnetotelluric data with strong topographic distortions and a few examples are shown to demonstrate the capability of this algorithm. The second part of this dissertation illustrates how magnetotelluric data can be used to constrain the nature of the conductive middle crustal zone in southern Tibet. Seismic bright spots have been identified in the middle crust of southern Tibet, but the nature of these bright spots can not be resolved by seismic data alone. Using minimum conductance derived from magnetotelluric data, important thickness constraints are developed for the middle crustal conductive zone. Combining these constraints with other geophysical data, the seismic bright spots in southern Tibet may be best explained by a thin layer of aqueous fluid overlaying a thick partially molten system. Study of the electrical structures in central Tibet is presented in part three. High regional conductance is observed in central Tibet and the best candidate for the high conductance is partial melt. The dissertation ends with main conclusions from these studies.
Imaging mid-mantle discontinuities: implications for mantle chemistry, dynamics, rheology, and deep earthquakes
(1998) Castle, John C
Using teleseismic network data and new signal processing techniques, I investigated mantle structure in the vicinity of subduction zones. The 660-km seismic discontinuity in the Izu-Bonin region is depressed by up to 80 km, indicative of material 1000$\sp\circ$K colder than ambient mantle. A broad depression of the discontinuity near 33$\sp\circ$N suggests that the subducting slab extends to the west upon the discontinuity from 139$\sp\circ$E to at least 135$\sp\circ$E. Farther to the south near 26$\sp\circ$N, a narrow and confined discontinuity depression suggests local penetration. Along the entire Mariana-Bonin-Izu-Japan-Kuril Trench, the dip of the slab changes to vertical at the deepest earthquake, regardless of the depth of the earthquakes. This observation implies that the slab loses strength at the seismicity cutoff. A grain size reduction due to the olivine to spinel phase change would create a weak zone within the slab, eliminate the slab membrane strength, and thus provide a mechanism allowing the slab to fall vertically downward. The 660-km discontinuity is less than 3 km thick and the shear wave jump across the discontinuity is.40 km/sec $\pm$.05 km/sec. This jump agrees with the velocity jump predicted of a pyrolite mantle containing 4% cation aluminum at the bottom of the transition zone. I observed the 410-km discontinuity infrequently, suggesting this discontinuity broadens in the subduction zone, possibly due to high water content. There exists no consistent sharp ($<$10 km) discontinuity between 660 km and 410 km depth and between 410 km and the crust. Beneath the 660-km discontinuity in Izu-Bonin, there does not exist another horizontal discontinuity to at least 1300 km. If a chemical change is associated with the 660-km discontinuity, it produces a very small change in shear velocity ($\delta Vs<1\%).$ The absence of a discontinuity in the 660 km-1300 km depth range shows that a hypothesized global discontinuity does not exist at these depths. Applying new migration and stacking techniques to global waveform data, I used S-to-P scattered arrivals to image a deep dipping structure beneath Izu-Bonin, which I interpret as an ancient slab. Reinterpretations of S wave tomography, P wave tomography, and plate reconstructions all confirm this result.
Upper-mantle structure of the Cascadia subduction zone from non-linear teleseismic travel-time inversion
(1991) VanDecar, John Callaway
The tectonic evolution of the Juan de Fuca plate system has undergone dramatic changes over the past several million years as evidenced by seafloor geomagnetic data. If there are large geodynamic forces active in the subduction of oceanic lithosphere, corresponding changes in the structure of the Cascadia subduction zone should also be dramatic. In light of the seismic hazard normally presented by active subduction zones and the Pacific Northwest population centers potentially affected by such a hazard, it is important that we understand this subduction zone structure in order to properly evaluate the seismic potential of the region. We have approximated a non-linear inversion for variations in seismic wave speed over the upper-mantle portion of the Cascadia subduction zone by alternately performing linear travel-time inversions, via an efficient conjugate gradient method, and three-dimensional ray tracing. We employ regularization through minimizing the Laplacian of the final solution. We parameterize the three-dimensional model at over 10,000 knots with velocities between knots represented by spline interpolation. The culled data set consists of approximately 10,000 relative arrival times of teleseismic P and PKP waves recorded from 1980 to 1990 at 146 station locations of a short-period vertical-component seismic network in Washington and Northern Oregon. We obtain accurate relative arrival-time data (standard errors $\approx$0.01 sec) and associated data covariance estimates via the use of a new multi-channel cross-correlation technique. The most prominent and robust characteristic of our models is a 3-4% fast, planar feature that dips steeply to the east (at $\approx$60$\sp\circ$) with a width of approximately 100 km. We infer this to be the seismic manifestation of a thermal and compositional anomaly associated with the subducting Juan de Fuca oceanic plate. At shallow depths ($\approx$80 km) this feature is consistent with the projections of models of shallow slab structure. The high velocity zone is located at a depth of 100-120 km beneath the Cascade volcanos, consistent with other subduction zones. Under central Washington the slab extends to depths of 400 km or more, while there is an apparent lack of deep slab material beneath southern Washington and northern Oregon. The latter, when taken together with the tectonic history of the region and other geophysical observations, is consistent with a deep slab that has torn away from the shallow portion of the slab.
Behavior of the atomic oxygen 5577 Ångström emission intensity at mid-latitudes: a climatological view
(2000) Deutsch, Kerry Ann
A global mid-latitude study of the atomic oxygen green line emission intensity at 5577 A has been undertaken with the goal of developing a climatological understanding of the emission behavior and its usefulness as a tracer for the atmosphere near 97 km. Long-term observations have been analysed at nine stations covering periods of ∼8--12 years, for a total of over 90 years of measurements. The results of this investigation show that the emission typically exhibits a maximum near the summer solstice and again near the fall equinox, before falling to a low winter-time level that persists into the middle of spring. Importantly, the oft-reported maximum at the spring equinox is not a statistically significant feature on the climatological time scale. This finding has implications on our understanding of the dominant processes operating in the region. Specifically, the role of seasonally varying vertical diffusion caused by breaking gravity waves must be readdressed in light of the absence of a strong maximum at the spring equinox.This work also addresses the relationship between the green line emission intensity and geomagnetic and solar activity. Results show that failing to exclude observations taken under high geomagnetic activity conditions leads to increased springtime emission levels and may be one explanation for this feature as has been reported by others. The influence of solar activity on the green line emission over the long term is shown to exhibit a hysteresis effect within a given solar cycle, confirming that there is not a simple linear relationship between the two processes.Finally, a critical examination is made of how long of a data series is necessary to fully achieve a climatological understanding of this emission and how this understanding may reasonably be used to advance our understanding of the upper middle atmosphere region. After ∼10 years, features with periods less than one year become stable (or achieve climatology), but the data examined here show unresolved power at periods approaching the series length which need longer data coverage to fully characterize.
Effects of firn ventilation on geochemistry of polar snow
(2003) Neumann, Thomas A., 1973-
The effects of air motion in firn on geochemical species is examined. Stable isotope data from Taylor Mouth, Antarctica are compared with data from nearby Taylor Dome and are found to be significantly different. Three possible reasons for the difference between these two records are presented: (1) the standard stable isotope - surface temperature relationship, (2) mixing precipitation from several sources and (3) post-depositional isotopic change.A two-dimensional model to estimate condensation and sublimation rates of water in firn based on firn-ventilation theory is presented. This model is used to investigate preservation characteristics of chemical species in snow and quantify the effects of post-depositional water-vapor motion. Results demonstrate the sensitivity of sublimation and condensation rates in the firn to hand-to-hand diffusion, grain size, wind speed and temperature.The sensitivity of stable isotope ratios to firn ventilation quantify what other investigators have suggested: isotopic exchange in the upper few meters is more rapid than can be explained by existing models, isotopic equilibration with atmospheric vapor is an important component of isotopic exchange and ventilation enhances exchange by creating regions of relatively rapid sublimation and condensation in the firn.The concentration of irreversibly deposited species (e.g. non-sea-salt-sulfate) is decreased by condensation in pore spaces and increased by sublimation of surrounding ice grains. Results suggest that concentration changes induced by firn ventilation are on the order of 3%, making it unlikely that this effect can be detected in field data.The concentration of reversibly-deposited species in snow (e.g. H 2O2) is generally decreased by sublimation of the surrounding ice grain. Condensation increases the diffusion path from the grain interior to the surface and can scavenge species which exist as trace gasses from pore-space air. Results suggest that firn ventilation has little effect on H2O 2 concentration in firn, but may be more important to the preservation of other reversibly-deposited species.In summary, results show that firn-ventilation induced water vapor motion is a key component of isotopic change in the firn, and may be important for reversibly-deposited geochemical species; but is probably not important for irreversibly-deposited geochemical species.
Fluid and particle simulations of the interaction of the solar wind with magnetic anomalies on the surface of the Moon and Mars
(2003) Harnett, Erika Megan
Simulations of the solar wind interacting with the Moon and Mars indicate that the presence of magnetic anomalies on the surface can lead to the formation of mini-magnetospheres around the anomalies. These mini-magnetospheres are not just small scale versions of planetary magnetospheres, but rather their small size leads to merged boundaries. Mini-magnetospheres also posses an increased sensitivity to solar wind parameters, the IMF direction in particular. The small scale size also leads to non-ideal MHD behavior, such as localized charge separation, which modifies particle acceleration, and ion cyclotron effects that lead to evolution of the magnetic field.This thesis presents results that show that mini-magnetospheres at the Moon, while small in comparison to the size of the Moon, can change the size and shape of the wake region even when the anomalies are on the day side. Some magnetic field configurations can completely prevent solar wind access to the surface of the Moon, suggesting that the regions of surface magnetization may provide a source of material that has been exposed only to cosmic radiation.The magnetic anomalies at Mars create a mini-magnetopause in place of the magnetic pileup boundary, and depending on IMF configuration lead to either an increase of decrease in the scale height of the ionosphere opposite the magnetized region. Non-ideal MHD plasma behavior is associated with both the magnetic pileup boundary and the mini-magnetopause. The location of the magnetic anomalies greatly effects the plasma in the tail, leading to plasma voids and density enhancements that are several Martian radii in size.

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