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Sample records for polar cap region

  1. Pulsar gamma rays from polar cap regions

    NASA Technical Reports Server (NTRS)

    Chiang, James; Romani, Roger W.

    1992-01-01

    The production is studied of pulsar gamma rays by energetic electrons flowing in the open field region above pulsar polar caps. The propagation was followed of curvature radiation from primary electrons, as well as hard synchrotron radiation generated by secondary pairs, through the pulsar magnetosphere for vacuum dipole open field geometries. Using data from radio and optical observations, models were constructed for the specific geometries and viewing angles appropriate to particular pulsars. These detailed models produce normalized spectra above 10 MeV, pulse profiles, beaming fractions and phase resolved spectra appropriate for direct comparison with COS-B and GRO data. Models are given for the Crab, Vela, and other potentially detectable pulsars; general agreement with existing data is good, although perturbations to the simplified models are needed for close matches. The calculations were extended to the millisecond pulsar range, which allows the production of predictions for the flux and spectra of populations of recycled pulsars and search strategies are pointed out.

  2. POLAR/TIDE Perigee Observations of Thermal O(+) Characteristics in the Polar Cap Region

    NASA Technical Reports Server (NTRS)

    Stevenson, B. A.; Horwitz, J. L.; Su, Y. J.; Elliott, Heather A.; Comfort, Richard H.; Craven, Paul D.; Chandler, Michael O.; Moore, Thomas E.; Giles, Barbara L.; Pollock, Craig J.

    1998-01-01

    We analyze in situ moment measurements of thermal O(+) from the Thermal Ion Dynamics Experiment (TIDE) on POLAR for April - May, 1996. These measurements were obtained near 5000 km altitude within the polar cap ionosphere - magnetosphere interface region. Su explored certain aspects of O(+) parameters in this region. In this report, we hope to expand our knowledge of the O(+) behavior by examining relationships of densities, parallel velocities, and temperatures to the convection velocities, IMF By and Bz components. Preliminary studies with the convection velocities currently require further analysis. In doing so, we are guided in part by the Cleft Ion Fountain paradigm and model developed by which involves downward O(+) flows in the polar magnetosphere. Initial results tend to indicate that in the extreme antisunward region of the polar cap, the density decreases with increasing convection velocity.

  3. Swarm in situ observations of F region polar cap patches created by cusp precipitation

    NASA Astrophysics Data System (ADS)

    Goodwin, L. V.; Iserhienrhien, B.; Miles, D. M.; Patra, S.; Meeren, C.; Buchert, S. C.; Burchill, J. K.; Clausen, L. B. N.; Knudsen, D. J.; McWilliams, K. A.; Moen, J.

    2015-02-01

    High-resolution in situ measurements from the three Swarm spacecraft, in a string-of-pearls configuration, provide new insights about the combined role of flow channel events and particle impact ionization in creating F region electron density structures in the northern Scandinavian dayside cusp. We present a case of polar cap patch formation where a reconnection-driven low-density relative westward flow channel is eroding the dayside solar-ionized plasma but where particle impact ionization in the cusp dominates the initial plasma structuring. In the cusp, density features are observed which are twice as dense as the solar-ionized background. These features then follow the polar cap convection and become less structured and lower in amplitude. These are the first in situ observations tracking polar cap patch evolution from creation by plasma transport and enhancement by cusp precipitation, through entrainment in the polar cap flow and relaxation into smooth patches as they approach the nightside auroral oval.

  4. Plasma density enhancements in the high-altitude polar cap region observed on Akebono

    NASA Astrophysics Data System (ADS)

    Ichikawa, Yoh-ichi; Abe, Takumi; Yau, Andrew W.

    2002-05-01

    The plasma density in the polar cap ionosphere is generally low (<103 cm-3 above 3000 km), mainly because of plasma escape from the ionosphere along open magnetic-field lines. The Akebono satellite occasionally encounters regions of unusually high plasma density (>=103 cm-3) above 4000 km altitude, in which the thermal plasma exhibits a distinctively low electron temperature (<3000 K) and low parallel ion drift velocity (<=1 km/s). Such events are almost always observed on the dusk side. The occurrence of low electron temperature and ion drift velocity appears to suggest the antisunward convection of high-density plasma into the polar cap, and the decrease in electron temperature due to the disruption of field-aligned heat flux in the high-altitude polar cap.

  5. North Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    1997-01-01

    North polar ice cap of Mars, as seen during mid summer in the northern hemisphere. The reddish areas consist of eolian dust, bright white areas consist of a mixture of water ice and dust, and the dark blue areas consist of sand dunes forming a huge 'collar' around the polar ice cap. (The colors have been enhanced with a decorrelation stretch to better show the color variability.) Shown here is an oblique view of the polar region, as seen with the Viking 1 spacecraft orbiting Mars over latitude 39 degrees north. The spiral bands consist of valleys which form by a combination of the Coriolis forces, wind erosion, and differential sublimation and condensation. In high-resolution images the polar caps are seen to consist of thick sequences of layered deposits, suggesting that cyclical climate changes have occurred on Mars. Cyclical climate changes are readily explained by quasi-periodic changes in the amount and distribution of solar heating resulting from perturbations in orbital and axial elements. Variations in the Earth's orbit have also been linked to the terrestrial climate changes during the ice ages.

  6. Some photometric properties of the Martian south polar cap region during the 1971 apparition

    NASA Technical Reports Server (NTRS)

    Lumme, K.; James, P. B.

    1984-01-01

    High-quality earth-based photographs from the Lowell Observatory Planetary Research Center collection have been analyzed to derive some photometric parameters for the Martian south polar cap region during the 1971 apparition. The optical thickness of the atmosphere above the cap varied with wavelength from 0.35 + or - 0.05 in red light to 0.58 + or 0.06 in UV light. The effective geometric albedo is calculated from the 30 deg phase data assuming isotropic scattering: it varies from 0.85 + or - 0.04 (in red light) to 0.63 + or 0.05 (in UV light).

  7. Swarm In Situ Observations of F-Region Polar Cap Patches Created by Cusp Ionization

    NASA Astrophysics Data System (ADS)

    Goodwin, L. V.; Iserhienrhien, B.; Miles, D. M.; Patra, S.; van der Meeren, C.; Buchert, S. C.; Burchill, J. K.; Clausen, L.; Knudsen, D. J.; McWilliams, K. A.; Moen, J.

    2014-12-01

    Multi-point in situ measurements from the Swarm spacecraft provide a novel tool to investigate the creation, transport, and evolution of polar cap patches. The string-of-pearls spacecraft configuration allow the motion and dynamics of electron density to be resolved on a one minute timescale. Swarm flew northward through the Scandinavian dayside cusp, passing through auroral features and high frequency radar backscatter. The observations reveal that plasma flow channels, the transport of photoionized plasma, and cusp particle precipitation are all important processes involved in creating the structures which become polar cap patches. Newly created electron density structures are transported across the polar cap via convection. The observed time-history of density structure indicates that particle impact ionization can add structure to both photoionized plasma and lower density polar cap plasma. Newly created and highly structured plasma evolves into lower density, less structured polar cap patches as they transit the polar cap.

  8. Polar Cap Formation on Ganymede

    NASA Technical Reports Server (NTRS)

    Pilcher, C. B.; Shaya, E. J.

    1985-01-01

    Since thermal migration is not an effective mechanism for water transport in the polar regions at the Galilean satellites, some other process must be responsible for the formation of Ganymede's polar caps. It is proposed that Ganymede's polar caps are the optical manifestation of a process that began with the distribution of an ice sheet over the surface of Ganymede. The combined processes of impact gardening and thermal migration led, in regions at latitudes less than 40 to 45 deg., to the burial of some fraction of this ice, the migration of some to the polar caps margins, and a depletion of free ice in the optical surface. At higher latitudes, no process was effective in removing ice from the optical surface, so the remanants of the sheet are visible today.

  9. Dual radar investigation of E region plasma waves in the southern polar cap

    NASA Astrophysics Data System (ADS)

    Forsythe, Victoriya V.; Makarevich, Roman A.

    2015-10-01

    Origins and characteristics of small-scale plasma irregularities in the polar ionosphere are investigated using a dual radar setup in which the E region is probed from opposite directions by two Super Dual Auroral Radar Network facilities at the McMurdo and Dome Concordia Antarctic stations. In certain time intervals, velocity agreement is observed when velocities are compared at the same physical location in the horizontal plane. Such an agreement is widely expected if velocity at a given location is largely controlled by the convection electric field. In other cases, however, velocity agreement is unexpectedly observed when measurements are considered at the same slant range (distance along the radar beam) for both radars. This implies that it is not the electric field at a given location that is a controlling factor. Raytracing results show that the same range agreement may be explained for certain E region density conditions when echo altitude increases with radar range. Backscatter observations under generally unfavorable conditions for irregularity generation and the critical role of propagation conditions in the polar cap are discussed. The observed E region velocity in the polar cap is demonstrated to depend indirectly on the plasma density distribution, which is important for establishing the fundamental dependence on the convection electric field.

  10. Polar cap formation on Ganymede

    NASA Technical Reports Server (NTRS)

    Shaya, E. J.; Pilcher, C. B.

    1984-01-01

    It is argued that Ganymede's polar caps are the remnants of a more extensive covering of water ice that formed during a period in which the satellite was geologically active. It is inferred that the initial thickness of this covering was a significant fraction of the gardening depth since the covering formed. This suggests an initial thickness of at least a few meters over heavily cratered regions such as the south polar grooved terrain. The absence of similar polar caps on Callisto apparently reflects the absence of comparable geologic activity in the history of this satellite.

  11. 2-D Visualization of Global D-region and Polar Cap Absorption

    NASA Astrophysics Data System (ADS)

    Baek, J.-H.; Choi, S.; Lee, J.; Bong, S.-C.

    2015-09-01

    We have visualized global D-region and polar cap absorption in two dimensions. We use the empirical relationship between solar x-ray flux (0.1-0.8 nm) and highest affected frequency at sub-solar point to calculate global D-region absorption. We also use the relation between the integral proton fluxes above certain energy thresholds and polar cap absorption. The calculation code was developed by C++ and refers to the result of Solar Position Algorithm (SPA) code of National Renewable Energy Laboratory (NREL) in C. We also consider the relation between the angles of the geomagnetic system and the geographical one. We calculate the attenuation at 8.83 MHz because it is used in High Frequency (HF) communications by airplanes. The code needs input data such as x-ray flux, proton flux, and Kp index of Geostationary Operational Environmental Satellite (GOES) and National Oceanic and Atmospheric Administration (NOAA). The attenuation is displayed in a world map, the Korean peninsula, and polar route.

  12. Creation of polar cap patches

    NASA Astrophysics Data System (ADS)

    Hosokawa, K.; Taguchi, S.; Ogawa, Y.

    2014-12-01

    Polar cap patches, which are islands of enhanced plasma density drifting anti-sunward, are one of the outstanding phenomena in the polar cap F region ionosphere. In the last decade, data from all-sky airglow imagers have been extensively used for better understanding the propagation of patches in the central polar cap region. But still, it has been rather difficult to capture the birth of patches in their generation region near the dayside cusp, because, in most places, the dayside part of the polar cap ionosphere is sunlit even in winter. In Longyearbyen (78.1N, 15.5E), Norway, however, optical observations are possible near the dayside cusp region in a limited period around the winter solstice. This enables us to directly image how polar cap patches are born in the cusp. In this paper, we present a few intervals of daytime optical observations, during which polar cap patches were generated within the field-of-view of an all-sky imager in Longyearbyen. During all the intervals studied here, we identified several signatures of poleward moving auroral forms (PMAF) in the equatorward half of the field-of-view, which are known as ionospheric manifestations of dayside reconnection. Interestingly, patches were directly produced from such poleward moving auroral signatures and propagated poleward along the anti-sunward convection near the cusp. In the literature, Lorentzen et al. (2012) first reported such a direct production of patches from PMAFs. During the current observations, however, we succeeded in tracking the propagation of patches until they reached the poleward edge of the field-of-view of the imager. This confirms that the faint airglow structures produced from PMAFs were actually transported for a long distance towards the central polar cap area; thus, polar cap patches were produced. From this set of observations, we suggest that polar cap patches during moderately disturbed conditions (i.e, non-storm time conditions) can be directly produced by the

  13. South Polar Cap, Summer 2000

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This is the south polar cap of Mars as it appeared to the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) on April 17, 2000. In winter and early spring, this entire scene would be covered by frost. In summer, the cap shrinks to its minimum size, as shown here. Even though it is summer, observations made by the Viking orbiters in the 1970s showed that the south polar cap remains cold enough that the polar frost (seen here as white) consists of carbon dioxide. Carbon dioxide freezes at temperatures around -125o C (-193o F). Mid-summer afternoon sunlight illuminates this scene from the upper left from about 11.2o above the horizon. Soon the cap will experience sunsets; by June 2000, this pole will be in autumn, and the area covered by frost will begin to grow. Winter will return to the south polar region in December 2000. The polar cap from left to right is about 420 km (260 mi) across.

  14. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information: VIS instrument. Latitude 86.5, Longitude 64.5 East (295.5 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation

  15. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information:VIS instrument. Latitude 86.5, longitude 57.4 East (302.6 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is

  16. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information: VIS instrument. Latitude 84.3, Longitude 314.4 East (45.6 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation

  17. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This week we will be looking at five examples of laminar wind flow on the north polar cap. On Earth, gravity-driven south polar cap winds are termed 'catabatic' winds. Catabatic winds begin over the smooth expanse of the cap interior due to temperature differences between the atmosphere and the surface. Once begun, the winds sweep outward along the surface of the polar cap toward the sea. As the polar surface slopes down toward sealevel, the wind speeds increase. Catabatic wind speeds in the Antartic can reach several hundreds of miles per hour.

    In the images of the Martian north polar cap we can see these same type of winds. Notice the streamers of dust moving downslope over the darker trough sides, these streamers show the laminar flow regime coming off the cap. Within the trough we see turbulent clouds of dust, kicked up at the trough base as the winds slow down and enter a chaotic flow regime.

    The horizontal lines in these images are due to framelet overlap and lighting conditions over the bright polar cap.

    Image information: VIS instrument. Latitude 84.2, Longitude 57.4 East (302.6 West). 40 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation

  18. Polar Cap Pits

    NASA Technical Reports Server (NTRS)

    2005-01-01

    17 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows kidney bean-shaped pits, and other pits, formed by erosion in a landscape of frozen carbon dioxide. This images shows one of about a dozen different patterns that are common in various locations across the martian south polar residual cap, an area that has been receiving intense scrutiny by the MGS MOC this year, because it is visible on every orbit and in daylight for most of 2005.

    Location near: 86.9oS, 6.9oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  19. South Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-337, 21 April 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the 'swiss cheese' pattern of frozen carbon dioxide on the south polar residual cap. Observation of these materials over two Mars years has revealed that the scarps that bound the mesas and small buttes are retreating-the carbon dioxide ice is subliming away-at a rate of about 3 meters (3 yards) per Mars year in some places. The picture covers an area about 900 m (about 900 yards) wide near 87.1oS, 93.7oW. Sunlight illuminates the scene from the upper left.

  20. The nature of GPS differential receiver bias variability: An examination in the polar cap region

    NASA Astrophysics Data System (ADS)

    Themens, David R.; Jayachandran, P. T.; Langley, Richard B.

    2015-09-01

    While modern GPS receiver differential code bias estimation techniques have become highly refined, they still demonstrate unphysical behavior, namely, notable solar cycle variability. This study investigates the nature of these seasonal and solar cycle bias variabilities in the polar cap region using single-station bias estimation methods. It is shown that the minimization of standard deviation bias estimation technique is linearly dependent on the user's choice of shell height, where the sensitivity of this dependence varies significantly from 1 total electron content unit (1 TECU = 1016 el m-2) per 4000 km in solar minimum winter to in excess of 1 TECU per 90 km during solar maximum summer. Using an ionosonde, we find appreciable shell height variability resulting in bias variabilities of up to 2 TECU. Comparing northward face Resolute Incoherent Scatter Radar (RISR-N) measurements to a collocated GPS station, we find that RISR-derived GPS receiver biases vary seasonally but not with solar cycle. RMS differences between bias estimation methods and observation between 2009 and 2013 were found to range from 2.7 TECU to 3.4 TECU, depending on method. To account for the erroneous solar cycle variability of standard bias estimation approaches, we linearly fit these biases to sunspot number, removing the trend. RMS errors after sunspot detrending these biases are reduced to 1.91 TECU. Also, these ISR-derived and sunspot-detrended biases are fit to ambient temperature, where a significant correlation is found. By using these temperature-fitted biases we further reduce RMS errors to 1.66 TECU. These results can be taken as further evidence of temperature-dependent dispersion in the GPS cabling and antenna hardware.

  1. MARCI and MOC observations of the atmosphere and surface cap in the north polar region of Mars

    NASA Astrophysics Data System (ADS)

    Cantor, Bruce A.; James, Philip B.; Calvin, Wendy M.

    2010-07-01

    We used MGS-MOC and MRO-MARCI daily mapping images of the North Polar Region of Mars from 16 August 2005 ( Ls = 270°) to 21 May 2009 ( Ls = 270°), covering portions of three consecutive martian years (MY 27-MY 29), to observe the seasonal behavior of the polar ice cap and atmospheric phenomena. The rate of cap regression was similar in MY 28 and MY 29, but was advanced by 3.5° of Ls (˜7-8 sols) in MY 29. The spatial and temporal behaviors of dust and condensate clouds were similar in the two years and generally in accord with prior years. Dust storms (>100 km 2) were observed in all seasons, with peak activity occurring at Ls = 10-20° from 50°N to 70°N and at Ls = 135-140° from 70°N to 90°N. The most active quadrant was 0-90°W in MY 28, shifting to 180-270°W in MY 29. The majority of regional storms in both years developed in longitudes from 10°W to 60°W. During late summer the larger storms obscure the North Polar Region in a cloud of dust that transitions to north polar hood condensate clouds around autumnal equinox. Changes in the distribution of perennial ice deposits, especially in Olympia Planum, were observed between the 2 years, with the MY 29 ice distribution being the most extensive observed to date. Modeling suggests that the small, bright ice patches on the residual cap are not the result of slope or elevation effects. Rather we suggest that they are the result of local meteorological effects on ice deposition. The annual darkening and brightening of peripheral areas of the residual cap around summer solstice can be explained by the sublimation of a brighter frost layer revealing an underlying darker, ice rich layer that itself either sublimes to reveal brighter material below or acts as a cold trap, attracting condensation of water vapor that brightens the surface. An alternative explanation invokes transport and deposition of dust on the surface from the cap interior, and later removal of that dust. The decrease in cap albedo and

  2. Topography of the South Polar Cap and Layered Deposits of Mars: Viking Stereo Grametry at Regional and Local Scales

    NASA Astrophysics Data System (ADS)

    Schenk, P.; Moore, J.; Stoker, C.

    1998-01-01

    Layered deposits and residual polar caps on Mars may record the deposition of ice and sediment modulated by periodic climate change. Topographic information relating to layer thicknesses, erosional processes, and formation of dark spirals within these deposits has been sparce or unreliable until the arrival of MOLA in orbit in September 1997. To assist in evaluating these terrains prior to launch and to assess formation and erosion processes in the polar deposits, we have assembled Viking stereo mosaics of the region and have produced the first reliable DEM models of the south polar deposits using automated stereogrammetry tools. Here we report our preliminary topographic results, pending final image pointing updates. The maximum total thickness of the layered deposits in the south polar region is 2.5 km. The thick layered deposits consist of a series of megaterraces. Each terrace is several tens of kilometers wide and is flat or slopes very gently toward the pole. These terraces step downward from a central plateau near the south pole. Terraces are bounded by relatively steep scarps 100-500 meters high that face toward the equator. These scarps correspond to the pattern of dark spirals observed within the residual cap in southern summer, and are interpreted as ice or frost-free surfaces warmed by solar insolation. Several tongue-shaped troughs, with rounded cirquelike heads, are observed near the margins of the deposit. These troughs are 300-600 meters in deep and may be similar to troughs observed in the northern polar deposit.

  3. Northern Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 13 May 2004 This nighttime visible color image was collected on November 26, 2002 during the Northern Summer season near the North Polar Cap Edge.

    The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    Image information: VIS instrument. Latitude 80, Longitude 43.2 East (316.8 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for

  4. Polar Cap Colors

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 12 May 2004 This daytime visible color image was collected on June 6, 2003 during the Southern Spring season near the South Polar Cap Edge.

    The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    Image information: VIS instrument. Latitude -77.8, Longitude 195 East (165 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA

  5. Volatile-rich Crater Interior Deposits in the Polar Regions of Mars: Evidence for Ice Cap Advance and Retreat

    NASA Technical Reports Server (NTRS)

    Russell, Patrick S.; Head, James W.; Hecht, Michael H.

    2003-01-01

    Many craters on Mars are partially filled by distinctive material emplaced by post-impact processes. This crater fill material is an interior mound which is generally separated from the walls of the crater by a trough that may be continuous along the crater circumference (i.e. a ring-shaped trough), or which may only partially contact the crater walls (i.e. a crescent-shaped trough). The fill deposit is frequently offset from the crater center and may be asymmetric in plan view. Populations of such craters include those in the circum-south polar cap region, in Arabia Terra, associated with the Medusae Fossae Formation, and in the northern lowlands proximal to the north polar cap. We focus on those craters in circumpolar regions and assess their relationship to polar cap advance and retreat, especially the possibility that fill material represents remnants of a formerly larger contiguous cap. Volatile-rich deposits have the property of being modifiable by the local stability of the solid volatile, which is governed by local energy balance. Here we test the hypothesis that asymmetries in volatile fill shape, profile, and center-location within a crater result from asymmetries in local energy balance within the crater, due mainly to variation of solar insolation and radiative effects of the crater walls over the crater interior. Model profiles of crater fill are compared with MOLA topographic profiles to assess this hypothesis. If asymmetry in morphology and location of crater fill are consistent with radiative-dominated asymmetries in energy budget within the crater, then 1) the volatile-rich composition of the fill is supported (this process should not be effective at shaping volcanic or sedimentary deposits), and 2) the dominant factor determining the observed shape of volatile-rich crater fill is the local radiative energy budget (and erosive processes such as eolian deflation are secondary or unnecessary). We also use a geographic and energy model approach to

  6. Coherence scales of wavefield during propagation through naturally disturbed ionosphere in the polar cap, auroral, and equatorial regions

    SciTech Connect

    Basu, S.; Basu, S.; Livingston, R.C.

    1990-05-03

    Phase and intensity scintillation measurements have been made at low latitudes in the equatorial anomaly region, and at high latitudes in the auroral oval and the polar cap regions, using phase coherent transmissions at 250 MHz from stationary and near stationary satellites. The observations pertain to periods of high solar activity when intense scintillation activity is recorded at each of the above observing sites. This data set has been utilized to study the reduction of coherence times of intensity and complex amplitude scintillation with increasing strength of scattering. Estimates of coherence scales of intensity and complex amplitude scintillation at 250 MHz are provided which indicate that coherent scales of scintillation are typically of the order of hundreds of meters at high latitudes but approach values as small as tens of meters in the equatorial anomaly region. The phase spectral index in the nightside auroral oval is observed to be much steeper (p sub psi = .4) than those typically observed in the equatorial (p sub psi = 2.4) or polar cap regions (p sub psi approx. -2.3). It shows the importance of large scale phase variations in the nightside auroral oval. Under strong scatter conditions, the coherence times of complex amplitude scintillation are shown to asymptotically approach a value which is 1.4 times the coherence time of intensity scintillation. This result is consistent with the theoretical predictions for Rayleigh statistics.

  7. The Enigmatic Martian Polar Caps

    SciTech Connect

    James, Philip

    2005-08-17

    The Martian polar caps have puzzled astronomers for over a century. Extensive study by many instruments on various spacecraft has resolved many questions but has at the same time created a new generation of puzzles. The polar caps are intimately coupled to the current Martian climate and volatile cycles. They also hold clues to climate variations on a variety of longer time scales. The results of recent missions will be reviewed, and the potential outlook for resolution of the outstanding questions will be examined.

  8. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 28 May 2004 This image was collected February 29, 2004 during the end of southern summer season. The local time at the location of the image was about 2 pm. The image shows an area in the South Polar region.

    The THEMIS VIS camera is capable of capturing color images of the martian surface using its five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from the use of multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    Image information: VIS instrument. Latitude -84.7, Longitude 9.3 East (350.7 West). 38 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet

  9. Polar Rain Gradients and Field-Aligned Polar Cap Potentials

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.; Wing, S.; Newell, P. T.; Ruohoniemi, J. M.; Gosling, J. T.; Skoug, R. M.

    2008-01-01

    ACE SWEPAM measurements of solar wind field-aligned electrons have been compared with simultaneous measurements of polar rain electrons precipitating over the polar cap and detected by DMSP spacecraft. Such comparisons allow investigation of cross-polarcap gradients in the intensity of otherwise-steady polar rain. The generally good agreement of the distribution functions, f, from the two data sources confirms that direct entry of solar electrons along open field lines is indeed the cause of polar rain. The agreement between the data sets is typically best on the side of the polar cap with most intense polar rain but the DMSP f's in less intense regions can be brought into agreement with ACE measurements by shifting all energies by a fixed amounts that range from tens to several hundred eV. In most cases these shifts are positive which implies that field-aligned potentials of these amounts exist on polar cap field lines which tend to retard the entry of electrons and produce the observed gradients. These retarding potentials undoubtedly appear in order to prevent the entry of low-energy electrons and maintain charge quasi-neutrality that would otherwise be violated since most tailward flowing magnetosheath ions are unable to follow polar rain electrons down to the polar cap. In more limited regions near the boundary of the polar cap there is sometimes evidence for field-aligned potentials of the opposite sign that accelerate polar rain electrons. A solar electron burst is also studied and it is concluded that electrons from such bursts can enter the magnetotail and precipitate in the same manner as polar rain.

  10. The nonuniform recession of the south polar cap of Mars

    NASA Technical Reports Server (NTRS)

    Veverka, J.; Goguen, J.

    1973-01-01

    The nature of the irregular springtime recession of the Martian polar caps is investigated, with particular reference to the southern polar cap. Our current knowledge about the composition of the caps is outlined, and the historical record of their springtime recession is reviewed. An attempt is made to correlate the irregularities of the recession pattern of the southern polar cap with the features of the terrain revealed by Mariner 9 photography at a time when the southern cap was at its minimum extent. The results are interpreted in terms of the physical and meteorological processes active in the polar regions.

  11. Energetic particles over Io's polar caps

    NASA Astrophysics Data System (ADS)

    Williams, D. J.; Thorne, R. M.

    2003-11-01

    We present results obtained from the Galileo satellite's Energetic Particles Detector during its final two encounters in 2001 with Jupiter's moon Io. These encounters returned the first data from just above Io's polar caps. They complement previous low-latitude data and provide a new perspective of Io's interaction with Jupiter's magnetosphere and ionosphere. The evolution of electron and ion distributions was measured from the upstream region throughout the polar cap traversals. From the time of initial field contact with Io and continuing throughout the encounter these distributions evolve in a manner consistent with adiabatic motion along the Io-Jupiter field line. At encounter all particles develop narrow trapped-like distributions indicative of the creation of a near-Io magnetic bottle caused by an enhancement of field at Io's upstream surface. The measured pitch angle distributions indicate a field enhancement of up to 10%-15% higher than the field observed at Galileo's position. Distribution evolution times agree roughly with particle bounce times on the Io-Jupiter field line. The ion distribution evolution times provide an estimate of ˜3-7 km/s for the field line convection speed across Io's polar caps, a value small (˜10%) compared with the upstream convection speed. Along with these trapped distributions, beams of ions and electrons are observed streaming into Io's polar caps throughout the encounters. The continued observation of ion beams across the polar cap is consistent with their half-bounce times. The data further indicate that the convection speed may vary as the polar cap is traversed. The one exception to the adiabatic particle behavior discussed above is the observation of intense electron beams streaming into Io's polar caps. The polar cap electron beams are similar to those previously measured in Io's wake [, 1996] and apparently originate from the same source. The source has been located at low (˜0.5 RJ) altitudes on the Io-Jupiter field

  12. Lobe cell convection and polar cap precipitation

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peria, W. J.; Bonnell, J. W.; Su, Y.-J.; Ergun, R. E.; Tung, Y.-K.; Parks, G. K.; Carlson, C. W.

    2003-05-01

    The characteristic electric and magnetic field signature of lobe cells as observed by the low-altitude FAST satellite in 55 dawn-dusk passes are compared with Polar ultraviolet images of polar cap auroral activity. Initial results from 34 events of UV image coverage suggest that there is an intimate coupling between the sunward convection flow of the lobe cell and transpolar auroral arcs or diffuse polar cap precipitation in ˜62% of these cases. However, in some cases where the field signatures are suggestive of lobe cell convection, there is no detectable particle precipitation either in Polar UVI or the FAST data sets. Moreover, the presence of lobe cells coincide with UV data intensifications in the premidnight 2000-2400 MLT sector and/or the postnoon 1500 MLT region in ˜59% of all cases with UVI coverage. The magnetic local time dependence of the lobe cells and polar cap precipitation on the interplanetary magnetic field (IMF) are examined using the upstream Wind monitor. The relative importance of the IMF By and Bz components are investigated and compared with the predictions of the antiparallel merging model and strongly suggests a connection with the magnetospheric sash, as is further implied by the mapping of magnetic field lines using the [2002] (T01) model. It was also noted that a majority of lobe cell events occurred during enhanced AE index substorm-like conditions and that generally stronger AE indices are measured for stronger IMF By magnitudes during these events.

  13. High-Resolution South Polar Cap Mosaics

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The layered terrains of the polar regions of Mars are among the most exotic planetary landscapes in our Solar System. The layers exposed in the south polar residual cap, vividly shown in the top view, are thought to contain detailed records of Mars' climate history over the last 100 million years or so. The materials that comprise the south polar layers may include frozen carbon dioxide, water ice, and fine dust. The bottom picture shows complex erosional patterns that have developed on the south polar cap, perhaps by a combination of sublimation, wind erosion, and ground-collapse. Because the south polar terrains are so strange and new to human eyes, no one (yet) has entirely adequate explanations as to what is being seen.

    These images were acquired by the Mars Orbiter Camera aboard the Mars Global Surveyor spacecraft during the southern spring season in October 1999. Each of these two pictures is a mosaic of many individual MOC images acquired at about 12 m/pixel scale that completely cover the highest latitude (87oS) visible to MOC on each orbital pass over the polar region. Both mosaics cover areas of about 10 x 4 kilometers (6.2 x 2.5 miles) near 87oS, 10oW in the central region of the permanent--or residual--south polar cap. They show features at the scale of a small house. Sunlight illuminates each scene from the left.'Gaps' at the upper and lower right of the second mosaic, above, are areas that were not covered by MOC in October 1999.

  14. Polar cap size metrics study at CCMC

    NASA Astrophysics Data System (ADS)

    Rastaetter, L.; Kuznetsova, M. M.; Hesse, M.; Gombosi, T. I.; Raeder, J.; Weimer, D.

    2005-12-01

    The Community-Coordinated Modeling Center (CCMC) tests space physics models covering space from the Sun's corona to the Earth's ionosphere and makes them available for researchers through a run-on-request capability. The polar cap size and location as observed by global auroral imagers is used as a basis model to study the performance of global MHD simulation models and statistical models of the auroral ionosphere. With good confidence one can assume that auroral emissions are located within the closed magnetic field lines in a narrow region adjacent to the boundary of the open field line region of the polar cap. In this study we are using imager data from POLAR (FUV) for several events from 1997 to 2000 for which reasonable coverage is available. Simulation runs have been performed using the global magnetospheric models BATSRUS (T. Gombosi et al., U. Michigan) and OpenGGCM (J. Raeder, U. New Hampshire) as well as the Weimer (2000,2005) field-aligned current models (D. Weimer, Mission Research Corp.) fed with upstream solar wind data from the ACE or Geotail satellites. In addition to direct field line tracings available from the 3D MHD model outputs, we use field-aligned currents from both MHD models and the Weimer-2K model to determine the polar cap boundary by using the position of the maximum absolute FAC value in 16 local time sectors. We define skill scores that measure the agreement in the polar cap sizes and location between measurements and models as an example of implementations of metrics to track model performance and apply the analysis to a number of storm event days.

  15. Periodicities of polar cap patches

    NASA Astrophysics Data System (ADS)

    Hosokawa, K.; Taguchi, S.; Ogawa, Y.; Aoki, T.

    2013-01-01

    A highly sensitive all-sky electron multiplier charge-coupled device airglow imager has been operative in Longyearbyen, Norway since October 2011. The imager captures 630.0 nm all-sky images with an exposure time of 4 s, which is about 10 times shorter than that achieved by conventional cooled CCD imagers. This allows us to visualize the structure of polar cap patches without blurring effects and better estimate their periodicities. We present, as one of the first results from the imager, an event of successive appearance of patches on the night of 21 December 2011. A time series of the optical intensity at zenith showed modulations having two distinguished periods, one at 40 min and the other at 5-12 min. One possible explanation is that such a coexistence of two different periodicities is a manifestation of simultaneous occurrence of patch generation processes on the 40 min periodicity was created by large-scale reconfiguration of the dayside convection pattern while the 5-12 min modulations were closely associated with mechanisms driven by pulsed reconnection on the dayside magnetopause. Such a combined effect of multiple patch generation processes may play a role in structuring patches; thus, it would be of particular importance for evaluating the space weather effects in the trans-ionospheric communications environment in the polar cap.

  16. Lobe Cell Convection and Polar cap Precipitation

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peria, W. J.; Su, Y.; Ergun, R. E.; Tung, Y.; Parks, G.; Carlson, C. W.

    2002-12-01

    The characteristic electric and magnetic field signature of lobe cells as observed by the low-altitude FAST satellite are compared with Polar ultraviolet images of polar cap auroral activity. Initial results from 55 events suggest that there is an intimate coupling between the sunward convection flow of the lobe cell and transpolar auroral arcs or diffuse polar cap precipitation. Moreover, the presence of lobe cells coincide with UV data intensifications in the premidnight 2100-2400 MLT sector and/or the postnoon 1500 MLT region in ~54% of all cases with UVI coverage. The magnetic local time dependence of the lobe cells and polar cap precipitation on the interplanetary magnetic field (IMF) are examined using the upstream Wind monitor. The relative importance of the IMF By and Bz components are investigated and compared with the predictions of the antiparallel merging model and strongly suggests a connection with the magnetospheric sash, as is further implied by the mapping of magnetic field lines using the Tsyganenko [2002] (T01) model. It was also noted that a majority of events occurred during enhanced AE index substorm-like conditions and that generally stronger AE indices are measured for stronger IMF By magnitudes.

  17. Mars South Polar Cap 'Fingerprint' Terrain

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This picture is illuminated by sunlight from the upper left.

    Some portions of the martian south polar residual cap have long, somewhat curved troughs instead of circular pits. These appear to form in a layer of material that may be different than that in which 'swiss cheese' circles and pits form, and none of these features has any analog in the north polar cap or elsewhere on Mars. This picture shows the 'fingerprint' terrain as a series of long, narrow depressions considered to have formed by collapse and widening by sublimation of ice. Unlike the north polar cap, the south polar region stays cold enough in summer to retain frozen carbon dioxide. Viking Orbiter observations during the late 1970s showed that very little water vapor comes off the south polar cap during summer, indicating that any frozen water that might be there remains solid throughout the year.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was obtained in early southern spring on August 4, 1999. It shows an area 3 x 5 kilometers (1.9 x 3.1 miles) at a resolution of about 7.3 meters (24 ft) per pixel. Located near 86.0oS, 53.9oW.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  18. Textures in south polar ice cap #2

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Textures of the south polar permanent residual ice cap and polar layered terrains. This 15 x 14 km area image (frame 7306) is centered near 87 degrees south, 341 degrees west.

    Figure caption from Science Magazine

  19. Textures in south polar ice cap #1

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Textures of the south polar permanent residual ice cap and polar layered terrains. This 30 x 29 km area image (frame 7709) is centered near 87 degrees south, 77 degrees west.

    Figure caption from Science Magazine

  20. The Role of Polar Cap Flux Tube Deformation and Magnetosheath Plasma Beta in the Saturation of the Region 1 Field-Aligned Current System

    NASA Astrophysics Data System (ADS)

    Wilder, F. D.; Eriksson, S.; Wiltberger, M. J.

    2014-12-01

    The phenomena of cross-polar cap potential (CPCP) and ionospheric field-aligned current (FAC) saturation remains largely unexplained. In this study, we expand upon the Alfvén Wing model of CPCP saturation by investigating its impact on the magnetosphere-ionosphere current system, particularly the Region 1 FAC input into the polar cap. Our hypothesis is that the ability of open flux tubes to deform in response to applied fluid stress from the magnetosheath is governed by the magnetosheath plasma beta, which in turn governs the Maxwell stress imposed on ionospheric plasma from the magnetosphere. This leads both the Region 1 FAC input as well as the ionospheric convection strength, as represented by the CPCP, to saturate in response to the interplanetary magnetic field (IMF) driving. We perform 32 simulations using the Lyon-Fedder-Mobarry (LFM) Magnetohydrodynamic (MHD) model with varying solar wind density and IMF strength, and demonstrate that the plasma beta does govern the deformation of polar cap and lobe field lines, as well as the non-linear response of the Region 1 FAC system to increasingly southward IMF. Further, we show that the current-voltage relationship in the ionosphere also shows a dependence on the plasma beta in the magnetosheath, with the ionosphere becoming more resistive at lower beta.

  1. Edge of polar cap patches

    NASA Astrophysics Data System (ADS)

    Hosokawa, K.; Taguchi, S.; Ogawa, Y.

    2016-04-01

    On the night of 4 December 2013, a sequence of polar cap patches was captured by an all-sky airglow imager (ASI) in Longyearbyen, Norway (78.1°N, 15.5°E). The 630.0 nm airglow images from the ASI of 4 second exposure time, oversampled the emission of natural lifetime (with quenching) of at least ˜30 sec, introduce no observational blurring effects. By using such high-quality ASI images, we succeeded in visualizing an asymmetry in the gradients between the leading/trailing edges of the patches in a 2-D fashion. The gradient in the leading edge was found to be 2-3 times steeper than that in the trailing edge. We also identified fingerlike structures, appearing only along the trailing edge of the patches, whose horizontal scale size ranged from 55 to 210 km. These fingers are considered to be manifestations of plasma structuring through the gradient-drift instability (GDI), which is known to occur only along the trailing edge of patches. That is, the current 2-D observations visualized, for the first time, how GDI stirs the patch plasma and such a mixing process makes the trailing edge more gradual. This result strongly implies a close connection between the GDI-driven plasma stirring and the asymmetry in the large-scale shape of patches and then suggests that the fingerlike structures can be used as markers to estimate the fine-scale structure in the plasma flow within patches.

  2. Why is the north polar cap on Mars different than the south polar cap?

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1994-01-01

    One of the most puzzling mysteries about the planet Mars is the hemispherical asymmetry in the polar caps. Every spring the seasonal polar cap of CO2 recedes until the end of summer, when only a small part, the residual polar cap, remains. During the year that Viking observed Mars, the residual polar cap was composed of water ice in the northern hemisphere but was primarily carbon dioxide ice in the southern hemisphere. Scientists have sought to explain this asymmetry by modeling observations of the latitudinal recession of the polar cap and seasonal variations in atmospheric pressure (since the seasonal polar caps are primarily frozen atmosphere, they are directly related to changes in atmospheric mass). These models reproduce most aspects of the observed annual variation in atmospheric pressure fairly accurately. Furthermore, the predicted latitudinal recession of the northern polar cap in the spring agrees well with observations, including the fact that the CO2 ice is predicted to completely sublime away. However, these models all predict that the carbon dioxide ice will also sublime away during the summer in the southern hemisphere, unlike what is observed. This paper will show how the radiative effects of ozone, clouds, airborne dust, light penetration into and through the polar cap, and the dependence of albedo on solar zenith angle affect CO2 ice formation and sublimation, and how they help explain the hemispherical asymmetry in the residual polar caps. These effects have not been studied with prior polar cap models.

  3. ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and its Implication to the Cross-Polar Cap Pedersen Currents

    NASA Technical Reports Server (NTRS)

    Le, Guan; Slavin, J. A.; Strangeway, Robert

    2010-01-01

    In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar windmagnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approximately 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  4. ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and Its Implication to the Cross-Polar Cap Pedersen Currents

    NASA Technical Reports Server (NTRS)

    Le, Guan; Slavin, J. A.; Strangeway, Robert

    2011-01-01

    In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  5. Polar cap arcs: Sun-aligned or cusp-aligned?

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Paxton, L. J.; Zhang, Qinghe; Xing, Zanyang

    2016-08-01

    Polar cap arcs are often called sun-aligned arcs. Satellite observations reveal that polar cap arcs join together at the cusp and are actually cusp aligned. Strong ionospheric plasma velocity shears, thus field aligned currents, were associated with polar arcs and they were likely caused by Kelvin-Helmholtz waves around the low-latitude magnetopause under a northward IMF Bz. The magnetic field lines around the magnetopause join together in the cusp region so are the field aligned currents and particle precipitation. This explains why polar arcs are cusp aligned.

  6. The effect of polar caps on obliquity

    NASA Technical Reports Server (NTRS)

    Lindner, B. L.

    1993-01-01

    Rubincam has shown that the Martian obliquity is dependent on the seasonal polar caps. In particular, Rubincam analytically derived this dependence and showed that the change in obliquity is directly proportional to the seasonal polar cap mass. Rubincam concludes that seasonal friction does not appear to have changed Mars' climate significantly. Using a computer model for the evolution of the Martian atmosphere, Haberle et al. have made a convincing case for the possibility of huge polar caps, about 10 times the mass of the current polar caps, that exist for a significant fraction of the planet's history. Since Rubincam showed that the effect of seasonal friction on obliquity is directly proportional to polar cap mass, a scenario with a ten-fold increase in polar cap mass over a significant fraction of the planet's history would result in a secular increase in Mars' obliquity of perhaps 10 degrees. Hence, the Rubincam conclusion of an insignificant contribution to Mars' climate by seasonal friction may be incorrect. Furthermore, if seasonal friction is an important consideration in the obliquity of Mars, this would significantly alter the predictions of past obliquity.

  7. Polar cap auroral arcs: Observations, theories, and a numerical model

    SciTech Connect

    Berg, G.A.

    1993-12-31

    This thesis reports the results of probably the most completely documented study of auroras near the polar cap boundary performed to date. Three fully instrumented rockets flew into the morning sector of the polar cap, complemented on the ground by a digital all-sky camera and incoherent scatter radar. Additionally, DMSP satellite passes over the polar cap bracketed the launches. We use these data to address two main issues: (1) the relationship between the state of the magnetosphere and the formation of polar cap arcs, and (2) the character of the current systems associated with polar cap arcs. The data indicate that in a decaying magnetosphere sun-aligned arcs erupt into the polar cap at high velocity from regions of enhanced brightness in the auroral oval. Two bright polar cap arcs formed in this manner in the region sampled by the rockets. The most equatorward of the arcs, sampled by two of the rockets during its lifetime, erupted into a region already characterized by strong sunward convection. The most poleward, however, which formed after the rockets had passed, pushed into a region where anti-sunward convection pertained less than two minutes earlier. It is likely that the boundary between sunward and anti-sunward convection shifted poleward so that sunward convection pertained at this arc as well. One of the payloads measured, with high resolution, both E and {delta}B as well as energetic particle flux. This permitted an in-depth study of the current systems flown through. The correlation between {delta}E and {delta}B is classic, both fields indicating upward field-aligned currents in virtually every region of enhanced electron precipitation. However, the currents deduced from the electrons do not agree in magnitude with those deduced from the fields. The conclusion is that for arcs embedded in a region of low {Sigma}{sub P} a current composed of upward thermal electrons flows concurrently with the precipitating electrons.

  8. Effects of Atmospheric Dust on Residual South Polar Cap Stability

    NASA Technical Reports Server (NTRS)

    Bonrv, B. P.; Bjorkman, J. E.; Hansen, G. B.; James, P. B.; Wolff, M. J.

    2005-01-01

    The Martian polar caps have been studied from the time of Herschel. Neither polar cap normally disappears in summer. The Residual North Polar Cap (portion that remains through summer) is composed of a mixture of water ice and dust, and its interannual stability is due to its low sublimation rate at the summer temperatures in the North Polar Region. The Residual South Polar Cap (RSPC) is more enigmatic, surviving the relatively hot perihelic summer season despite being composed of much more volatile CO2. It is able to do so because of its unusually high albedo, which is larger than that of other bright regions in the seasonal cap (e.g. Mountains of Mitchel). The proximity of the albedo of the RSPC to the critical albedo for stability raises the question of whether the RSPC exists in every Martian year. The ground based record is somewhat ambivalent. Douglass and Lowell reported that RSPC suddenly vanished at Ls=297deg in 1894 and did not reappear until Ls=0deg [1], and Kuiper reported that it disappeared in 1956 [2]; but both observations were questioned by contemporaries, who tended to attribute them to obscuring dust. Barker [3] reported a large amount of water vapor over the south polar cap in 1969 that could be attributed to exposure of near surface water ice during partial removal of the CO2 in the RSPC in 1969.

  9. O+ transport across the polar cap

    NASA Astrophysics Data System (ADS)

    Elliott, H. A.; Jahn, J.; Pollock, C. J.; Moore, T. E.; Horwitz, J. L.

    2006-12-01

    The plasma sheet, inner magnetosphere, and high latitude magnetosphere all contain significant amounts of O+ ions during active times. Singly charged oxygen ions unambiguously come from the ionosphere making them an excellent tracer species. As the solar wind dynamic pressure increases, the O+ density in the in the cleft, high altitude polar cap, and plasma sheet also increases. We test the "cleft ion fountain" model, which asserts that O+ ions escape from the cleft, cross the polar cap, and then enter the plasma sheet against a mo of outflows originating from the entire polar cap. We use observations of O+ transport across the polar cap from TIDE polar cap ion outflow measurements. The Tsyganenko magnetic field model, driven with ACE solar wind parameters is used to provide magnetic mapping and organization of the observations. We calculate the distance between the cleft and the foot-points of magnetic field lines mapped from the Polar spacecraft along the noon-midnight meridian. Using the observed outflow speed and magnetic field line length we calculate travel time for the ions. We then plot the distance from the cleft versus the travel time for an entire pass. For O+ this plot is quite linear, and the slope of the line is the average convection speed of the magnetic field lines across the polar cap. The convection speed we determined is consistent with the convection speed measured in the ionosphere. We conclude that O+ ions emanating principally from the cleft are transported across the polar cap, and these O+ ions have access to the ring current and plasma sheet.

  10. Polar cap precursor of nightside auroral oval intensifications using polar cap arcs

    NASA Astrophysics Data System (ADS)

    Zou, Ying; Nishimura, Yukitoshi; Lyons, Larry R.; Donovan, Eric F.; Shiokawa, Kazuo; Ruohoniemi, J. Michael; McWilliams, Kathryn A.; Nishitani, Nozomu

    2015-12-01

    Recent radar and optical observations suggested that localized fast flows in the polar cap precede disturbances within the nightside auroral oval. However, how commonly this connection occurs has been difficult to examine due to limited coverage of radar flow measurements and diffuse and dim nature of airglow patches. Polar cap arcs are also associated with fast flows in the polar cap and appear much brighter than patches, allowing evaluation of the interaction between polar cap structures and nightside aurora more definitively. We have surveyed data during six winter seasons and selected quasi-steady polar cap arcs lasting >1 h. Thirty-four arcs are found, and for the majority (~85%) of them, as they extend equatorward from high latitude, their contact with the nightside auroral poleward boundary is associated with new and substantial intensifications within the oval. These intensifications are localized (< ~1 h magnetic local time (MLT)) and statistically occur within 10 min and ±1 h MLT from the contact. They appear as poleward boundary intensifications in a thick auroral oval or an intensification of the only resolvable arc within a thin oval, and the latter can also exhibit substantial poleward expansion. When radar echoes are available, they corroborate the association of polar cap arcs with localized enhanced antisunward flows. That the observed oval intensifications are major disturbances that only occur after the impingement of polar cap arcs and near the contact longitude suggest that they are triggered by localized fast flows coming from deep in the polar cap.

  11. Eddy intrustion of hot plasma into the polar cap and formation of polar-cap arcs

    NASA Technical Reports Server (NTRS)

    Chiu, Y. T.; Gorney, D. J.

    1983-01-01

    Under the simple postulate that multiple large scale detachable magnetospheric convection eddies can exist in the vicinity of the convection reversal boundary and in the polar cap, by Kelvin-Helmholtz instability or otherwise, it is shown that a number of seemingly disconnected plasma and electric field observations in the polar cap can be organized into a theory of magnetosheath and plasmasheet plasma intrusion into the polar cap. Current theory of inverted V structures then predicts existence of similar, but weaker, structures at the eddy convection reversal boundaries in the polar cap. A possible consequence is that the polar cap auroras are natural offshoots from discrete oval arcs and evidently are formed by similar processes. The two arc systems can occassionally produce an optical image in the form of the theta aurora.

  12. INFLUENCE OF THE POLAR CAP CURRENT ON PULSAR POLARIZATION

    SciTech Connect

    Kumar, D.; Gangadhara, R. T. E-mail: ganga@iiap.res.in

    2012-07-20

    We have developed a model for the polarization of curvature radiation by taking into account the polar-cap-current-induced perturbation on the dipolar magnetic field. We present the effects of the polar cap current on the pulsar radio emission in an artificial case when the rotation effects, such as aberration and retardation, are absent. Our model indicates that the intensity components and the polarization angle inflection point can be shifted to either the leading or the trailing side depending upon the prevailing conditions in the viewing geometry, the non-uniformity in source distribution (modulation), and the polar-cap-current-induced perturbation. Also, we find evidence for the origin of symmetric-type circular polarization in addition to the antisymmetric type. Our model predicts a stronger trailing component compared to that on the leading side of a given cone under some specific conditions.

  13. Cassini multi-instrument assessment of Saturn's polar cap boundary

    NASA Astrophysics Data System (ADS)

    Jinks, S. L.; Bunce, E. J.; Cowley, S. W. H.; Provan, G.; Yeoman, T. K.; Arridge, C. S.; Dougherty, M. K.; Gurnett, D. A.; Krupp, N.; Kurth, W. S.; Mitchell, D. G.; Morooka, M.; Wahlund, J.-E.

    2014-10-01

    We present the first systematic investigation of the polar cap boundary in Saturn's high-latitude magnetosphere through a multi-instrument assessment of various Cassini in situ data sets gathered between 2006 and 2009. We identify 48 polar cap crossings where the polar cap boundary can be clearly observed in the step in upper cutoff of auroral hiss emissions from the plasma wave data, a sudden increase in electron density, an anisotropy of energetic electrons along the magnetic field, and an increase in incidence of higher-energy electrons from the low-energy electron spectrometer measurements as we move equatorward from the pole. We determine the average level of coincidence of the polar cap boundary identified in the various in situ data sets to be 0.34° ± 0.05° colatitude. The average location of the boundary in the southern (northern) hemisphere is found to be at 15.6° (13.3°) colatitude. In both hemispheres we identify a consistent equatorward offset between the poleward edge of the auroral upward directed field-aligned current region of ~1.5-1.8° colatitude to the corresponding polar cap boundary. We identify atypical observations in the boundary region, including observations of approximately hourly periodicities in the auroral hiss emissions close to the pole. We suggest that the position of the southern polar cap boundary is somewhat ordered by the southern planetary period oscillation phase but that it cannot account for the boundary's full latitudinal variability. We find no clear evidence of any ordering of the northern polar cap boundary location with the northern planetary period magnetic field oscillation phase.

  14. Plasma structuring in the polar cap

    SciTech Connect

    Basu, S.; Basu, S.; Weber, E.J.; Bishop, G.J.

    1990-01-01

    Propagation experiments providing scintillation, total electron content and drift data in the field of view of an all-sky imager near the magnetic polar in Greenland are utilized to investigate the manner in which ionospheric plasma becomes structured within the polar cap. It is found that under IMF Bz southward conditions, large scale ionization patches which are convected through the dayside cusp into the polar cap get continually structured. The structuring occurs through the ExB gradient drift instability process which operates through an interaction between the antisunward plasma convection in the neutral rest frame and large scale plasma density gradients that exist at the edges of the ionization patches. It is shown that with the increase of solar activity the strength of the irregularities integrated through the ionosphere is greatly increased. Under the IMF Bz northward conditions, the plasma structuring occurs around the polar cap arcs in the presence of inhomogeneous electric field or disordered plasma convection. In that case, the irregularity generation is caused by the competing processes of non-linear Kelvin-Helmholtz instability driven by sheared plasma flows and the gradient drift instability process which operates in the presence of dawn-dusk motion of arc structures. The integrated strength of this class of irregularities also exhibits marked increase with increasing solar activity presumably because the ambient plasma density over the polar cap is enhanced.

  15. The polar cap environment of outflowing O(+)

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.; Pollock, C. J.; Moore, T. E.; Peterson, W. K.; Burch, J. L.; Winningham, J. D.; Craven, J. D.; Frank, L. A.; Persoon, A.

    1992-01-01

    The properties of the core (0-50 eV) and 'energetic' (0-1 keV) ions, plasma waves, and auroral images obtained from Dynamics Explorer 1 (DE-1) and those of electrons, obtained from DE-2, are examined in the context of the polar cap environment. Results indicate the presence of two populations: high-speed (10-30 eV, or higher, streaming energies) polar beams and low-speed (generally less than 10-eV streaming energies) streams. The high-speed polar beams show an auroral connection (i.e., they are observed on or near the field lines threading auroral arcs), while the low-speed streams are on or near the field lines threading the dark polar cap and may be converted from the cleft ion fountain. Compared to the high-speed streams, the low-speed streams are significantly more stable with respect to energy and flux.

  16. DEAD ZONE IN THE POLAR-CAP ACCELERATOR OF PULSARS

    SciTech Connect

    Chen, Alexander Y.; Beloborodov, Andrei M.

    2013-01-10

    We study plasma flows above pulsar polar caps using time-dependent simulations of plasma particles in the self-consistent electric field. The flow behavior is controlled by the dimensionless parameter {alpha} = j/c{rho}{sub GJ}, where j is the electric current density and {rho}{sub GJ} is the Goldreich-Julian charge density. The region of the polar cap where 0 < {alpha} < 1 is a {sup d}ead zone{sup -}in this zone, particle acceleration is inefficient and pair creation is not expected even for young, rapidly rotating pulsars. Pulsars with polar caps near the rotation axis are predicted to have a hollow-cone structure of radio emission, as the dead zone occupies the central part of the polar cap. Our results apply to charge-separated flows of electrons (j < 0) or ions (j > 0). In the latter case, we consider the possibility of a mixed flow consisting of different ion species, and observe the development of two-stream instability. The dead zone at the polar cap is essential for the development of an outer gap near the null surface {rho}{sub GJ} = 0.

  17. Polar Cap Precursor of Nightside Auroral Oval Intensifications Using Polar Cap Arcs

    NASA Astrophysics Data System (ADS)

    Zou, Y.; Nishimura, T.; Lyons, L. R.; Donovan, E.; Shiokawa, K.; Ruohoniemi, J. M.; McWilliams, K. A.; Nishitani, N.

    2015-12-01

    Recent radar and optical observations have revealed that localized fast flows in the polar cap can closely relate to disturbances within the nightside auroral oval. However, how commonly this connection occurs has been difficult to examine due to limited coverage of radar flow measurements and diffuse and dim nature of airglow patches. This question can now be addressed by using polar cap arcs, which are also associated with fast flows and appear much brighter than patches, allowing evaluation of the interaction between polar cap flows and nightside aurora more definitively. Utilizing an array of high-resolution 630.0 nm all-sky imagers, we have selected quasi-steady polar cap arcs lasting >1 h from six winter seasons. Thirty four arcs are found and for the majority (~85%) of them, as they extend equatorward from magnetic pole, their contact with the nightside auroral poleward boundary is associated with new and substantial intensifications within the oval, in contrast to the otherwise quiet oval. These intensifications are localized (<~1 h MLT) and statistically occur within 10 min and ±1 h MLT from the contact. They appear as poleward boundary intensifications (PBIs) in a thick auroral oval or an intensification of the only resolvable arc in a thin oval, and the latter can also exhibit substantial poleward expansion. When radar echoes are available, they corroborate the association of polar cap arcs with localized enhanced anti-sunward polar cap flows. That the observed oval intensifications are major disturbances that only occur after and initiate near the impingement of polar cap arcs suggest that they are triggered by localized fast flows coming from deep in the polar cap. Such observation suggests that meso-scale fast flows in the lobe can traverse the open-closed field line boundary through enhanced magnetic reconnection and closely couple with disturbances in the plasma sheet.

  18. Lithospheric Loading by the Northern Polar CAP on Mars

    NASA Astrophysics Data System (ADS)

    Johnson, C. L.; Solomon, S. C.; Head, J. W.; Smith, D. E.; Zuber, M. T.

    1999-03-01

    Loading of the martian lithosphere by the northern polar cap is investigated using elastic and viscoelastic models and constraints from MOLA data and geology. Implications for basement topography, polar cap volume and the gravity field are discussed.

  19. Formation of the Carbon Dioxide Ice Seasonal Polar Caps

    NASA Astrophysics Data System (ADS)

    Forget, F.

    1998-01-01

    One of the key processes controlling the geology of the martian polar regions is the seasonal condensation of the atmosphere into CO2 ice caps. These polar caps mostly condense during the polar night, when surface and atmospheric temperature become cold enough to reach the frost point of CO2. Thus, almost all that is known about the formation of the polar caps has come from the Mariner 9 and Viking infrared measurements. These observations showed that the physical processes controlling the condensation are complex, because of the unique radiative and microphysical properties Of CO2 ice condensing in a CO2 atmosphere. For instance, the Infrared Thermal Mapper (IRTM). One of the key processes controlling the geology of the martian polar regions is the seasonal condensation of the atmosphere into CO2 ice caps. These polar caps mostly condense during the polar night, when surface and atmospheric temperature become cold enough to reach the frost point of CO2. Thus, almost all that is known about the formation of the polar caps has come from the Mariner 9 and Viking infrared measurements. These observations showed that the physical processes controlling the condensation are complex, because of the unique radiative and microphysical properties Of CO2 ice condensing in a CO2 atmosphere. For instance, the IRTM instrument observed variable structures exhibiting brightness temperatures far below the physical temperature appropriate for condensed CO, in vapor pressure equilibrium at the expected atmospheric pressure. A detailed analysis of the data suggests that these low brightness temperatures result from the radiative properties of the SMO CO2 ice particles that condense in the atmosphere rather than directly on the surface New observations are being transmitted by Mars Global Surveyor. TES and MOLA data should greatly improve our understand- ing of what is really going on during the cap formation. instrument observed variable structures exhibiting brightness temperatures

  20. Water Ice Albedo Variations on the Martian Northern Polar Cap

    NASA Technical Reports Server (NTRS)

    Hale, A. S.; Bass, D. S.; Tamppari, L. K.

    2003-01-01

    The Viking Orbiters determined that the surface of Mars northern residual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain. Early studies of the ice coverage and albedo of the northern residual Martian polar cap using Mariner 9 and Viking images reported that there were substantial internannual differences in ice deposition on the polar cap, a result which suggested a highly variable Martian climate. However, some of the data used in these studies were obtained at differing values of heliocentric solar longitude (L(sub s)). Reevaluation of this dataset indicated that the residual cap undergoes seasonal brightening throughout the summer, and indicated that this process repeats from year to year. In this study we continue to compare Mariner 9 and Viking Orbiter imaging observations and thermal data of the north residual polar cap to data acquired with Mars Global Surveyor s Mars Orbiter Camera (MOC) instrument. In the current study, our goal is to examine all released data from MGS MOC in the northern summer season, along with applicable TES data in order to better understand the albedo variations in the northern summer and their implications on water transport. To date, work has focused primarily on the MOC dataset. In 1999, data acquisition of the northern polar regions began at L(sub s) = 107, although there was little north polar data acquired from L(sub s)= 107 to L(sub s) = 109. We examined a total of 409 images from L(sub s) = 107 to L(sub s)=148. We have also examined data from 2000 from L(sub s)= 93 to L(sub s)= 110; additional progress is ongoing. Here we present a progress report of our observations, and continue to determine their implications for the Martian water cycle.

  1. The phase composition of Triton's polar caps

    NASA Technical Reports Server (NTRS)

    Duxbury, N. S.; Brown, R. H.

    1993-01-01

    Triton's polar caps are modeled as permanent nitrogen deposits hundreds of meters thick. Complex temperature variations on Triton's surface induce reversible transitions between the cubic and hexagonal phases of solid nitrogen, often with two coexisting propagating transition fronts. Subsurface temperature distributions are calculated using a two-dimensional thermal model with phase changes. The phase changes fracture the upper nitrogen layer, increasing its reflectivity and thus offering an explanation for the surprisingly high southern polar cap albedo (approximately 0.8) seen during the Voyager 2 flyby. The model has other implications for the phase transition phenomena on Triton, such as a plausible mechanism for the origin of geyser-like plume vent areas and a mechanism of energy transport toward them.

  2. The phase composition of Triton's polar caps

    NASA Astrophysics Data System (ADS)

    Duxbury, N. S.; Brown, R. H.

    1993-08-01

    Triton's polar caps are modeled as permanent nitrogen deposits hundreds of meters thick. Complex temperature variations on Triton's surface induce reversible transitions between the cubic and hexagonal phases of solid nitrogen, often with two coexisting propagating transition fronts. Subsurface temperature distributions are calculated using a two-dimensional thermal model with phase changes. The phase changes fracture the upper nitrogen layer, increasing its reflectivity and thus offering an explanation for the surprisingly high southern polar cap albedo (approximately 0.8) seen during the Voyager 2 flyby. The model has other implications for the phase transition phenomena on Triton, such as a plausible mechanism for the origin of geyser-like plume vent areas and a mechanism of energy transport toward them.

  3. The Phase Composition of Triton's Polar Caps.

    PubMed

    Duxbury, N S; Brown, R H

    1993-08-01

    Triton's polar caps are modeled as permanent nitrogen deposits hundreds of meters thick. Complex temperature variations on Triton's surface induce reversible transitions between the cubic and hexagonal phases of solid nitrogen, often with two coexisting propagating transition fronts. Subsurface temperature distributions are calculated using a two-dimensional thermal model with phase changes. The phase changes fracture the upper nitrogen layer, increasing its reflectivity and thus offering an explanation for the surprisingly high southern polar cap albedo (approximately 0.8) seen during the Voyager 2 flyby. The model has other implications for the phase transition phenomena on Triton, such as a plausible mechanism for the origin of geyser-like plume vent areas and a mechanism of energy transport toward them. PMID:17757213

  4. South Polar Cap Erosion and Aprons

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This scene is illuminated by sunlight from the upper left.

    While Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images have shown that the north and south polar cap surfaces are very different from each other, one thing that the two have in common is that they both seem to have been eroded. Erosion in the north appears mostly to come in the form of pits from which ice probably sublimed to vapor and was transported away from the polar cap by wind. Erosion in the south takes on a wider range of possible processes that include collapse, slumping and mass-movement on slopes, and probably sublimation. Among the landforms created by these process on the south polar cap are the 'aprons' that surround mesas and buttes of remnant layers such as the two almost triangular features in the lower quarter of this image. The upper slopes of the two triangular features show a stair-stepped pattern that suggest these hills are layered.

    This image shows part of the south polar residual cap near 86.9oS, 78.5oW, and covers an area approximately 1.2 by 1.0 kilometers (0.7 x 0.6 miles) in size. The image has a resolution of 2.2 meters per pixel. The picture was taken on September 11, 1999.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  5. Polar cap F layer patches: structure and dynamics

    SciTech Connect

    Weber, E.J.; Klobuchar, J.A.; Buchau, J.; Carlson, H.C.; Livingston, R.C.

    1986-11-01

    Coordinated measurements of F-region plasma patches were conducted on February 3/4, 1984, from Thule and Sondrestrom, Greenland. Optical, ionsonde, amplitude scintillation, total electron content (TEC), and incoherent scatter radar measurements were combined to reveal several new aspects of the structure and transport of these localized regions of enhanced F region ionization. For the first time, these patches were directly tracked flowing in the antisunward direction over distances of 3000 km from the center of the polar cap to the poleward edge of the auroral oval. Quantative measurements of TEC show increases of 10-15 TEC units within the patches, above a background polar cap value of 5 TEC units. Amplitude scintillation measurements show the presence of ionospheric irregularities through the entire patch, with a weak indication of stronger scintillation on the trailing (or E x B unstable) edge.

  6. Polar cap F layer patches: structure and dynamics

    SciTech Connect

    Weber, E.J.; Klobuchar, J.A.; Buchau, J.; Carlson H.C. Jr.; Livingston, R.C.; De La Beaujardiere, O.; McCready, M.; Moore, J.G.; Bishop, G.J.

    1986-11-01

    Coordinated measurements of F region plasma patches were conducted on February 3/4, 1984, from Thule and Sondrestrom, Greenland. Optical, ionosonde, amplitude scintillation, total electron content (TEC), and incoherent scatter radar measurements were combined to reveal several new aspects of the structure and transport of these localized regions of enhanced F region ionization. For the first time these patches were directly tracked flowing in the antisunward direction over distances of 3000 km from the center of the polar cap to the poleward edge of the auroral oval. Quantitative measurements of TEC show increases of 10--15 TEC units within the patches, above a background polar cap value of 5 TEC units. Amplitude scintillation measurements show the presence of ionospheric irregularities through the entire patch, with a weak indication of stronger scintillation on the trailing (or E x B unstable) edge.

  7. Polar Cap Disturbances: Mesosphere and Thermosphere-Ionosphere Response to Solar-Terrestrial Interactions

    NASA Technical Reports Server (NTRS)

    Sivjee, G.; McEwen, D.; Walterscheid, R.

    2003-01-01

    The Polar Cap is the Upper-Atmosphere cum Mag-netosphere region which is enclosed by the poleward boundary of the Auroral Oval and is threaded by open geomagnetic tield lines. In this region, there is normally a steady precipition (Polar "drizzle") of low energy (w 300eV) electrons that excite optical emissions from the ionosphere. At times, enhanced ionization patches are formed near the Dayside Cusp regions that drift across the Polar Cap towards the Night Sector of the Auroral Oval. Discrete auroral arcs and auroras formed during Solar Magnetic Cloud (SMC)/Coronal Mass Ejection (CME) events are also observed in the Polar Cap. Spectrophotometric observations of all these Polar Cap phenomena provide a measure of the average energy as well a energy flux of the electrons precipitating in the Polar Cap region during these disturbances. Such measurements also point to modulations of the Polar Cap Mesosphere-Lower Thermosphere (MLT) air density and temperature by zonally symmetric tides whose Hough functions peak in the Polar region. MLT cooling during Stratospheric Warming events and their relation to Polar Vortex and associated Gravity wave activities are also observed at the Polar Cap sites.

  8. Frost streaks in the south polar cap of Mars

    NASA Technical Reports Server (NTRS)

    Thomas, P.; Veverka, J.; Campos-Marquetti, R.

    1979-01-01

    Viking Orbiter images of the annual south polar cap on Mars exhibit elongated bright features that are associated with craters and resemble wind streaks observed elsewhere on Mars. The study focuses on the well-documented frost streaks. The discussion covers the morphology of frost streaks, occurrence, seasonal behavior, thickness of frost in streak deposits, wind patterns inferred from frost streaks and other eolian features in the south polar region, formation of frost streaks, and other locales of preferential frost accumulation. The form and seasonal behavior of the bright elongated albedo markings which extend from the rims of many craters in the south polar cap suggest that they are accumulations of CO2 frost in the lee of craters. The frost streaks appear in the fall, increasing in length but not changing in direction during fall and winter. The frost streaks indicate a prograde circulation pattern of near-surface winds around the pole. Other details are also presented.

  9. Space weather challenges of the polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Moen, Jøran; Oksavik, Kjellmar; Alfonsi, Lucilla; Daabakk, Yvonne; Romano, Vineenzo; Spogli, Luca

    2013-01-01

    This paper presents research on polar cap ionosphere space weather phenomena conducted during the European Cooperation in Science and Technology (COST) action ES0803 from 2008 to 2012. The main part of the work has been directed toward the study of plasma instabilities and scintillations in association with cusp flow channels and polar cap electron density structures/patches, which is considered as critical knowledge in order to develop forecast models for scintillations in the polar cap. We have approached this problem by multi-instrument techniques that comprise the EISCAT Svalbard Radar, SuperDARN radars, in-situ rocket, and GPS scintillation measurements. The Discussion section aims to unify the bits and pieces of highly specialized information from several papers into a generalized picture. The cusp ionosphere appears as a hot region in GPS scintillation climatology maps. Our results are consistent with the existing view that scintillations in the cusp and the polar cap ionosphere are mainly due to multi-scale structures generated by instability processes associated with the cross-polar transport of polar cap patches. We have demonstrated that the SuperDARN convection model can be used to track these patches backward and forward in time. Hence, once a patch has been detected in the cusp inflow region, SuperDARN can be used to forecast its destination in the future. However, the high-density gradient of polar cap patches is not the only prerequisite for high-latitude scintillations. Unprecedented high-resolution rocket measurements reveal that the cusp ionosphere is associated with filamentary precipitation giving rise to kilometer scale gradients onto which the gradient drift instability can operate very efficiently. Cusp ionosphere scintillations also occur during IMF BZ north conditions, which further substantiates that particle precipitation can play a key role to initialize plasma structuring. Furthermore, the cusp is associated with flow channels and

  10. Spatial variability in the seasonal south polar CAP of Mars

    NASA Astrophysics Data System (ADS)

    Calvin, Wendy M.; Martin, Terry Z.

    1994-10-01

    The first comprehensive discussion of the south seasonal polar cap spectra obtained by the Mariner 7 infrared spectrometer in the short-wavelength region (2-4 microns) is presented. The infrared spectra is correlated with images acquired by the wide-angle camera. Significant spectral variation is noted in the cap interior and regions of varying water frost abundance, CO2 ice/frost cover, and CO2-ice path length can be distinguished. Many of these spectral variations correlate with heterogeneity noted in the camera images, but certain significant infrared spectral variations are not discernible in the visible. Simple reflectance models are used to classify the observed spectral variations into four regions. Region I is at the cap edge, where there is enhanced absorption beyond 3 microns inferred to be caused by an increased abundance of water frost. The increase in water abundance over that in the interior is on the level of a few parts per thousand or less. Region II is the typical cap interior characterized by spectral features of CO2 ice at grain sizes of several millimeters to centimeters. These spectra also indicate the presence of water frost at the parts per thousand level. A third, unusual region (III), is defined by three spectra in which weak CO2 absorption features are as much as twice as strong as in the average cap spectra and are assumed to be caused by an increased path length in the CO2. Such large paths are inconsistent with the high reflectance in the visible and at 2.2 microns and suggest layered structures or deposition conditions that are not accounted for in current reflectance models. The final region (IV) is an area of thinning frost coverage or transparent ice well in the interior of the seasonal cap. These spectra are a combination of CO2 and ground signatures.

  11. Electron polar cap and the boundary of open geomagnetic field lines.

    NASA Technical Reports Server (NTRS)

    Evans, L. C.; Stone, E. C.

    1972-01-01

    A total of 333 observations of the boundary of the polar access region for electrons (energies greater than 530 keV) provides a comprehensive map of the electron polar cap. The boundary of the electron polar cap, which should occur at the latitude separating open and closed field lines, is consistent with previously reported closed field line limits determined from trapped-particle data. The boundary, which is sharply defined, seems to occur at one of three discrete latitudes. Although the electron flux is generally uniform across the polar cap, a limited region of reduced access is observed about 10% of the time.

  12. Monitoring the perennial martian northern polar cap with MGS MOC

    NASA Astrophysics Data System (ADS)

    Hale, A. Snyder; Bass, D. S.; Tamppari, L. K.

    2005-04-01

    We have used the Mars Global Surveyor Mars Orbiter Camera Wide Angle (MGS MOC WA) dataset to study albedo trends on the martian northern residual cap. Six study regions were selected, the Chasma Boreale source region, three regions near the center of the cap ("fish hook" region, latitude = 87°; "bottle opener" region, latitude = 87°, "steep-shallow" region, latitude = 85°), and two lower latitude regions (crater, latitude = 77°, and polar outlier, latitude = 82°), and the albedos of these six regions were examined. These regions were chosen due to their good temporal coverage in the MOC dataset, as well as having been studied by other researchers (Bass et al., 2000, Icarus 144, 382-396; Calvin and Titus, 2004, Lunar Planet. Sci. XXXV, Abstract 1455). The picture which emerges is complex. Most areas experience a combination of darkening and brightening through the northern summer; only one area consistently brightens (the polar outlier region). A good deal of interannual repeatability in each region's albedo behavior is seen, however. Possible causes for the observed complex behaviors include dust deposition from late summer storms, sintering of frost grains over the course of the summer, and cold trapping of volatiles on bright, cold surfaces.

  13. Interannual variability of Mars' south polar CAP

    NASA Astrophysics Data System (ADS)

    James, P. B.; Malolepszy, K. M.; Martin, L. J.

    1987-08-01

    Published observational data on the seasonal recession of the south polar cap on Mars (covering the period 1903-1977) are compiled in tables and graphs and analyzed statistically. The basic data set (photographic observations obtained at Lowell Observatory) of Fischbacher et al. (1960) and James and Lumme (1982) and the reduction procedures described by Baum and Martin (1973) are employed, and Viking data from 1977 are used for comparison; the early onset (relative to the mean) of the 1956 recession is characterized in detail. A list of photographically documented large dust storms is provided, and it is suggested that in years with early spring storms, recession may be slower than in years without such storms.

  14. Application of Polar Cap (PC) indices in analyses and forecasts of geophysical conditions

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2016-07-01

    The Polar Cap (PC) indices could be considered to represent the input of power from the solar wind to the Earth's magnetosphere. The indices have been used to analyse interplanetary electric fields, effects of solar wind pressure pulses, cross polar cap voltages and polar cap diameter, ionospheric Joule heating, and other issues of polar cap dynamics. The PC indices have also been used to predict auroral electrojet intensities and global auroral power as well as ring current intensities. For specific space weather purposes the PC indices could be used to forecast substorm development and predict associated power line disturbances in the subauroral regions. The presentation shall outline the general background for applying the PC indices in analyses or forecasts of solar wind-magnetosphere-ionosphere interactions and provide illustrative examples of the use of the Polar Cap indices in specific cases

  15. Plasma density increase in the high altitude polar cap

    NASA Astrophysics Data System (ADS)

    Kitanoya, Yugo; Abe, Takumi; Mukai, Toshifumi

    In general situation, the electron density in the ionosphere decreases with altitude. As for the latitudinal variation, the electron density is generally smaller in the polar cap than in the midor low-latitude region. Few reliable measurements have been made to estimate thermal electron density and temperature with a simple instrument such as Langmuir probe in the highaltitude polar cap region. For example, only the limited amount of the electron temperature and density data are available for the high-altitude (> 3000 km) polar cap, where the density is generally less than 2.0*103 [/cm3 ]. Since the plasma density significantly correlates with the solar activity, thermal plasma density becomes smaller for the minimum solar activity period. Thermal Electron energy Distribution (TED) instrument onboard "AKEBONO" (EXOS-D) satellite has been operated in two modes; 1) DC mode to obtain the probe characteristic, 2) SH (second harmonic) mode to estimate the electron energy distribution function based on Druyvesteyn method, from which the electron temperature and density can be estimated even on the condition of low electron density. On the basis of statistical study of the Akebono observation for over 10 years, it is found that the electron number density occasionally increases up to 3.0-4.0*103 [/cm3 ] above altitude of 3000 km. While the electron temperature is believed to be about 8000 K at such a high altitude, the temperature inside the high density region is observed to be lower than that by several thousand degrees. It is noticeable that such a density enhancement occurs during the geomagnetically active period at solar maximum. The high density region is observed to exist not in whole but in part of the polar cap. In addition, it is obvious from the Suprathermal Mass Spectrometer (SMS) observations that the H+ velocity parallel to the upward field aligned direction is observed to be lower in the high density region than the surrounding region. Also, it is

  16. Observational and theoretical analyses of polar cap/auroral region f(sub p) and 2 f(sub p) emissions using the polar and DE 1 satellites

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    2001-01-01

    The objective of this proposal was to conduct a comprehensive observational and theoretical investigation, including 2-D numerical simulations of emissions that occur near f(sub p) and 2 f(sub p) as observed by the Dynamics Explorer 1 (DE 1) spacecraft in the mid-altitude polar magnetosphere. Electrostatic electron plasma waves (or Langmuir waves) and associated electromagnetic (ETD) radiation near f(sub p) and 2 f(sub p) have previously been observed associated with the Earth's foreshock and in coronal/solar wind type II and III solar radio bursts. The observations of similar emissions in the terrestrial polar magnetosphere have not been previously reported and are important for a better understanding of the range of generation processes. We have been cataloging the location, electric and magnetic intensity, polarization, bandwidth, etc. of the emissions. The theoretical analysis included linear and nonlinear plasma theory. The goal was to fully describe the generation processes for both the f(sub p) (PF component) and 2 f(sub p) (H component) emissions. Although this goal was not completely accomplished, we have made significant advances in our understanding of these emissions.

  17. Polar cap auroral arcs: Observations, theories, and a numerical model. Ph.D. Thesis

    SciTech Connect

    Berg, G.A.

    1993-01-01

    This thesis reports the results of probably the most completely documented study of auroras near the polar cap boundary performed to date. Three fully instrumented rockets flew into the morning sector of the polar cap, complemented on the ground by a digital all-sky camera and incoherent scatter radar. Additionally, DMSP satellite passes over the polar cap bracketed the launches. The authors use these data to address two main issues: (1) the relationship between the state of the magnetosphere and the formation of polar cap arcs, and (2) the character of the current systems associated with polar cap arcs. The data indicate that in a decaying magnetosphere sun-aligned arcs erupt into the polar cap at high velocity from regions of enhanced brightness in the auroral oval. Two bright polar cap arcs formed in this manner in the region sampled by the rockets. The most equatorward of the arcs, sampled by two of the rockets during its lifetime, erupted into a region already characterized by strong sunward convection. The most poleward, however, which formed after the rockets had passed, pushed into a region where anti-sunward convection pertained less than two minutes earlier. It is likely that the boundary between sunward and anti-sunward convection shifted poleward so that sunward convection pertained at this arc as well. The formation of polar cap arcs may be tied closely to the reconfiguration of the magnetosphere into a system characterized by a smaller polar cap. One of the payloads measured, with high resolution, both E and delta B as well as energetic particle flux. This permitted an in-depth study of the current systems flown through. The correlation between delta E and delta B is classic, both fields indicating upward field-aligned currents in virtually every region of enhanced electron precipitation. However, the currents deduced from the electrons do not agree in magnitude with those deduced from the fields.

  18. Substorm Bulge/Surge Controlled by Polar Cap Flow Channels

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Nishimura, T.; Zou, Y.; Gallardo-Lacourt, B.; Donovan, E.; Shiokawa, K.; Nicolls, M. J.; Chen, S.; Ruohoniemi, J. M.; Nishitani, N.; McWilliams, K. A.

    2015-12-01

    Previous studies have provided evidence that localized channels of enhanced polar cap flow drive plasma sheet/auroral oval flow channels, auroral poleward boundary intensifications and streamers, and substorm onset. Evidence has also indicated that a persistence of such flow channels after substorm onset may enhance post-onset auroral poleward expansion and activity. Here, we combine auroral imager and radar observations to show evidence that polar-cap flow channels can directly feed the substorm bulge westward motion, i.e., the westward traveling surge, and its poleward expansion well into the pre-existing polar cap. By taking advantage of the capability of tracing polar cap arcs and patches over long distances with red line imaging, we are able to trace flow features that strongly affect the substorm bulge across the polar cap for up to ~1-1.5 hr prior to their impacting and affecting the substorm bulge.

  19. Localized polar cap flow enhancement tracing using airglow patches: Statistical properties, IMF dependence, and contribution to polar cap convection

    NASA Astrophysics Data System (ADS)

    Zou, Ying; Nishimura, Yukitoshi; Lyons, Larry R.; Shiokawa, Kazuo; Donovan, Eric F.; Ruohoniemi, J. Michael; McWilliams, Kathryn A.; Nishitani, Nozomu

    2015-05-01

    Recent radar observations have suggested that polar cap flows are highly structured and that localized flow enhancements can lead to nightside auroral disturbances. However, knowledge of these flows is limited to available echo regions. Utilizing wide spatial coverage by an all-sky imager at Resolute Bay and simultaneous Super Dual Auroral Radar Network measurements, we statistically determined properties of such flows and their interplanetary magnetic field (IMF) dependence. We found that narrow flow enhancements are well collocated with airglow patches with substantially larger velocities (≥200 m/s) than the weak large-scale background flows. The flow azimuthal widths are similar to the patch widths. During the evolution across the polar cap, the flow directions and speeds are consistent with the patch propagation directions and speeds. These correspondences indicate that patches can optically trace localized flow enhancements reflecting the flow width, speed, and direction. Such associations were found common (~67%) in statistics, and the typical flow speed, propagation time, and width within our observation areas are 600 m/s, tens of minutes, and 200-300 km, respectively. By examining IMF dependence of the occurrence and properties of these flows, we found that they tend to be observed under By-dominated IMF. Flow speeds are large under oscillating IMF clock angles. Localized flow enhancements are usually observed as a channel elongated in the noon-midnight meridian and directed toward premidnight (postmidnight) for +By (-By). The potential drops across localized flow enhancements account for ~10-40% of the cross polar cap potential, indicating that they significantly contribute to polar cap plasma transport.

  20. The Role of Viscous Deformation in the Morphology of the Martian North Polar Cap

    NASA Technical Reports Server (NTRS)

    Zuber, M. T.; Lim, L.; Zwally, H. J.

    1998-01-01

    The first detailed topographic measurements of Mars' north polar cap have recently been collected by the Mars Orbiter Laser Altimeter (MOLA), an instrument on Mars Global Surveyor (MGS). These new data provide the opportunity to address in a quantitative way the processes responsible for the origin and evolution of the martian polar caps. On the basis of imaging and spectral observations from the Mariner 9 and Viking orbiters, it was recognized that a number of physical mechanisms. including radiative transfer, wind erosion, and viscous flow, represent possible or probable contributors to the morphology of the polar cap. Here we review rheological data for H2O and CO2 at conditions relevant to the martian polar regions. We then use MOLA topographic profiles to perform a preliminary assessment of the role of power law flow in contributing to the regional-scale planform of the north polar cap.

  1. Tracking the Martian CO2 Polar Ice Caps in Infrared Images

    NASA Technical Reports Server (NTRS)

    Wagstaff, Kiri L.; Castano, Rebecca; Chien, Steve

    2006-01-01

    Researchers at NASA s Jet Propulsion Laboratory have developed a method for automatically tracking the polar caps on Mars as they advance and recede each year (see figure). The seasonal Mars polar caps are composed mainly of CO2 ice and are therefore cold enough to stand out clearly in infrared data collected by the Thermal Emission Imaging System (THEMIS) onboard the Mars Odyssey spacecraft. The Bimodal Image Temperature (BIT) histogram analysis algorithm analyzes raw, uncalibrated data to identify images that contain both "cold" ("polar cap") and "warm" ("not polar cap") pixels. The algorithm dynamically identifies the temperature that separates these two regions. This flexibility is critical, because in the absence of any calibration, the threshold temperature can vary significantly from image to image. Using the identified threshold, the algorithm classifies each pixel in the image as "polar cap" or "not polar cap," then identifies the image row that contains the spatial transition from "polar cap" to "not polar cap." While this method is useful for analyzing data that has already been returned by THEMIS, it has even more significance with respect to data that has not yet been collected. Instead of seeking the polar cap only in specific, targeted images, the simplicity and efficiency of this method makes it feasible for direct, onboard use. That is, THEMIS could continuously monitor its observations for any detections of the polar-cap edge, producing detections over a wide range of spatial and temporal conditions. This effort can greatly contribute to our understanding of long-term climatic change on Mars.

  2. Comparisons of the North Polar Cap of Mars and the Earth's Northern Hemisphere snow cover

    NASA Technical Reports Server (NTRS)

    Foster, J.; Owe, M.; Capen, C.

    1985-01-01

    The boundaries of the polar caps of Mars have been measured on more than 3000 photographs since 1905 from the plate collection at the Lowell Observatory. For the Earth the polar caps have been accurately mapped only since the mid 1960's when satellites were first available to synoptically view the polar regions. The polar caps of both planets wax and wane in response to changes in the seasons, and interannual differences in polar cap behavior on Mars as well as Earth are intimately linked to global energy balance. In this study data on the year to year variations in the extent of the polar caps of Mars and Earth were assembled and analyzed together with data on annual variations in solar activity to determine if associations exist between these data. It was found that virtually no correlation exists between measurements of Mars north polar cap and solar variability. An inverse relationship was found between variations in the size of the north polar caps of Mars and Earth, although only 6 years of concurrent data were available for comparison.

  3. Fourier analysis of polar cap electric field and current distributions

    NASA Technical Reports Server (NTRS)

    Barbosa, D. D.

    1984-01-01

    A theoretical study of high-latitude electric fields and currents, using analytic Fourier analysis methods, is conducted. A two-dimensional planar model of the ionosphere with an enhanced conductivity auroral belt and field-aligned currents at the edges is employed. Two separate topics are treated. A field-aligned current element near the cusp region of the polar cap is included to investigate the modifications to the convection pattern by the east-west component of the interplanetary magnetic field. It is shown that a sizable one-cell structure is induced near the cusp which diverts equipotential contours to the dawnside or duskside, depending on the sign of the cusp current. This produces characteristic dawn-dusk asymmetries to the electric field that have been previously observed over the polar cap. The second topic is concerned with the electric field configuration obtained in the limit of perfect shielding, where the field is totally excluded equatorward of the auroral oval. When realistic field-aligned current distributions are used, the result is to produce severely distorted, crescent-shaped equipotential contours over the cap. Exact, analytic formulae applicable to this case are also provided.

  4. Geology of the southern hemisphere of Triton: No polar cap

    NASA Technical Reports Server (NTRS)

    Schenk, P.; Moore, J. M.

    1993-01-01

    The bright southern hemisphere, comprising Uhlanga Regio, is perhaps the most poorly understood geologic province on Triton. The entire bright southern hemisphere has been described as a bright polar 'cap', implying a seasonal origin, or as a permanent geologic terrain distinct from the equatorial terrains. Also, thermal models have predicted seasonal migration of frosts and ices from the presently sun-lit south latitudes to the dark northern latitudes. The distribution of frosts and geologic history of this region must be determined observationally. We reexamine the geology of this terrain with the goal of answering these questions.

  5. Characteristics of GPS TEC variations in the polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Watson, Chris; Jayachandran, P. T.; MacDougall, John W.

    2016-05-01

    This paper presents statistical characteristics (occurrence rate, amplitude, and frequency) of low-frequency (<100 mHz) variations in total electron content (TEC) observed in the polar cap ionosphere. TEC variations were primarily associated with mesoscale (tens to hundreds of kilometers) ionization structures and were observed by five Global Positioning System (GPS) receivers over a 6 year period (2009-2014). The altitude of ionization structures was estimated by using colocated ionosonde radars. High data rate receivers combined with broad spatial coverage of multisatellite TEC measurements provided high-resolution magnetic local time/latitude maps of TEC variation characteristics, which were examined as a function of solar cycle and season. These high-resolution maps improve upon the current observational picture of mesoscale structuring in the polar cap and provide accurate links to particular magnetospheric source regions. Occurrence of TEC variations was consistently highest in dayside regions mapping to low latitude and plasma mantle boundary layers, while largest-amplitude TEC variations were observed in dayside regions close to the polar cusp, and lower latitudes around midnight. Occurrence and amplitude of TEC variations increased significantly during the ascending phase of the solar cycle, independent of solar wind conditions, while seasonal statistics showed highest dayside occurrence and amplitude in winter months, lowest in summer, and highest nightside occurrence and amplitude around equinox. A surprising result in the frequency distributions of TEC variations was discrete frequencies of about 2 and 4 mHz, which appeared to originate from regions corresponding to the plasma mantle, immediately poleward of the polar cusp.

  6. Variations of the polar cap potential measured during magnetospheric substorms

    SciTech Connect

    Weimer, D.R.; Kan, J.R.; Akasofu, S.I. )

    1992-04-01

    Measurements of the polar cap potential drop and size have been obtained during magnetospheric substorms. Using double-prove electric field measurements on the DE 2 satellite, 148 measurements have been obtained at random times preceding, during, and after 64 substorms. The polar cap potentials are graphed as a function of the difference between the time of the polar cap measurement and the time of the expansion onset of the corresponding substorm. The ratios of the auroral electrojet (AE) indices and the potential are also determined. The results show that on the average the polar cap potential starts to increase at 1.5 hours before onset. However, on a case-by-case basis there are substantial variations from the average, as polar cap potentials over 1,200 kV were measured as early as 1 hour before substorm onset and values as low as 40 kV were observed during the expansion phase. The size of the polar cap ranged from 23{degree} to 38{degree} invariant latitude at the time of onset, and had an average value of 31{degree}. The AE/{Phi}{sub PC} ratio is nearly constant before and after substorms, but decreases slightly during the substorm growth phase and increases greatly during the expansion phase. This increase is most likely due to a higher conductivity and westward electric field within the electrojet during expansion, which causes AE to increase without a corresponding change in the polar cap potential.

  7. Earth's polar cap ionization patches lead to ion upflow

    NASA Astrophysics Data System (ADS)

    Zhang, Q. H.; Zong, Q.; Lockwood, M. M.; Liang, J.; Zhang, B.; Moen, J. I.; Zhang, S.; Zhang, Y.; Ruohoniemi, J. M.; Thomas, E. G.; Liu, R.; Dunlop, M. W.; Yang, H. G.; Hu, H.; Liu, Y.; Lester, M.

    2014-12-01

    The Earth constantly losses matter through ions escaping from the polar ionosphere. This makes the ionosphere as an important source of plasma for the magnetosphere and could modulate atmospheric isotope abundances on geological timescales, depending on what fraction of the upflowing ions subsequently return to the ionosphere and what fraction are ejected into interplanetary space. It has been proposed that the magnetosphere is dynamically modulated by the presence of the ionospheric ions, particularly heavy ions O+, during magnetic substorms and storms. The origin and formation mechanism of ionospheric ion upflow is, however, poorly understood, particularly under disturbed space weather conditions. We report simultaneous direct observations of ion upflow and a patch of ionization at the center of the polar cap region during a geomagnetic storm. Our observations indicate enhanced fluxes of upwelling O+ ions originate from the patch and were accelerated by the enhanced ambipolar electric field. This enhancement is caused by soft electron precipitations. Polar cap patches therefore provide an important source of upwelling ions for accelerations mechanisms at greater altitudes which can eject the ions. These observations give new insight into the processes of ionosphere-magnetosphere coupling and the potential loss of terrestrial water dissociation products into space which, although extremely slow in the case of Earth, may be significant for other planets and moons.

  8. Response of northern winter polar cap to auroral substorms

    NASA Astrophysics Data System (ADS)

    Liou, Kan; Sotirelis, Thomas

    2016-05-01

    The three-phase substorm sequence has been generally accepted and is often tied to the Dungey cycle. Although previous studies have mostly agreed on the increase and decrease in the polar cap area during an episode of substorm, there are disparate views on when the polar cap starts to contract relative to substorm onset. Here we address this conflict using high-resolution (~1-3 min) snapshot global auroral images from the ultraviolet imager on board the Polar spacecraft. On the basis of 28 auroral substorm events, all observed in the Northern Hemispheric winter, it is found that the polar cap inflated prior to onset in all events and it attained the largest area ~6 min prior to the substorm expansion phase onset, while the dayside polar cap area remained steady around the onset. The onset of nightside polar cap deflation is found to be attributed to intensifications of aurora on the poleward edge of the nightside oval, mostly in the midnight sector. Although this result supports the loading-unloading and reconnection substorm models, it is not clear if the initial polar cap deflation and the substorm expansion are parts of the same process.

  9. Formation of the Carbon Dioxide Ice Seasonal Polar Caps

    NASA Astrophysics Data System (ADS)

    Foster, J.; Chang, A.; Hall, D.; Tait, A.; Klein, A.

    1998-01-01

    One of the key processes controlling the geology of the martian polar regions is the seasonal condensation of the atmosphere into CO, ice caps. These polar caps mostly condense during the polar night, when surface and atmospheric temperature become cold enough to reach the frost point of CO2. Thus, almost all that is known about the formation of the polar caps has come from the Mariner 9 and Viking infrared measurements. These observations showed that the physical processes controlling the condensation are complex, because of the unique radiative and microphysical properties of CO2 ice condensing in a CO2 atmosphere. For instance, the Infrared Thermal Mapper (IRTM) instrument observed variable structures exhibiting brightness temperatures far below the physical temperature appropriate for condensed CO2 in vapor pressure equilibrium at the expected atmospheric pressure. A detailed analysis of the data suggests that these low brightness temperatures result from the radiative properties of the small CO2 ice particles that condense in the atmosphere rather than directly on the surface. Indeed, simulations performed with General Circulation Models have shown that a fraction of the total CO2 condensation can take place in the atmosphere. Atmospheric condensation can result from radiative cooling on the one hand (especially when the atmosphere is dust laden) and from adiabatic cooling in upward motions on the other . The resulting CO2 snowfalls could create the observed features, because the CO2 ice particles that condense in the atmosphere can be efficient scatterers at infrared wavelengths (whether they are airborne or have just fallen to the ground) carbon dioxide ice deposits composed of nonporous solid ice, however, having directly condensed on the ground or having undergone frost metamorphism should behave almost like blackbody emitters, or, more likely, be transparent in the infrared so that the ground beneath can radiate through. In fact, by simply parametrizing

  10. Model-observation comparison study of multiple polar cap arcs

    NASA Astrophysics Data System (ADS)

    Zhu, L.; Valladares, C. E.; Sojka, J. J.; Schunk, R. W.; Crain, D. J.

    1996-01-01

    A quantitative model-observation comparison of multiple polar cap arcs has been conducted by using a time-dependent theoretical model of polar cap arcs. In particular, the electrodynamical features of multiple polar cap arcs with various spacings are simulated and the results are compared with the images obtained from the All-Sky Intensified Photometer at Qaanaaq. The results show that the observed and simulated arcs are quite similar, both spatially and temporally. The results support the theory proposed by Zhu et al. [1993a, 1994b] that the structure of polar cap arcs is mainly determined by the magnetosphere-ionosphere (M-I) coupling processes and that the spacing of multiple polar cap arcs is closely related to the hardness of the primary magnetospheric precipitation. It is found that for the multiple polar cap arcs with both narrow and wide spacings, the associated field-aligned currents are mainly closed by Pedersen currents. It is also found that a hard precipitation can lead to a highly structured secondary arc because of the nonlinear M-I coupling processes.

  11. The hemispherical asymmetry of the residual polar caps on Mars

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1991-01-01

    A model of the polar caps of Mars was created which allows: (1) for light penetration into the cap; (2) ice albedo to vary with age, latitude, hemisphere, dust content, and solar zenith angle; and (3) for diurnal variability. The model includes the radiative effects of clouds and dust, and heat transport as represented by a thermal wind. The model reproduces polar cap regression data very well, including the survival of CO2 frost at the south pole and reproduces the general trend in the Viking Lander pressure data.

  12. Wind erosion in the Martian polar regions

    NASA Technical Reports Server (NTRS)

    Cutts, J. A.

    1973-01-01

    Photographic evidence suggests that many topographic features of the polar regions of Mars may have been sculptured by wind action. In the case of the pitted terrain, this is established by relating the orientations of elongate basins and grooves to patterns of albedo markings that are generally accepted to be wind-formed. Small-scale flutes and other textures of laminated terrain recognized outside the perennial ice cap in the south polar region are also attributed to eolian action. Winds flowing off the polar cap and spiraling toward the west seem to be responsible. More speculatively the large-scale circumpolar features which underlie the residual polar caps may be related to wind erosion. Rotational motion localized on circular segments of the perennial frost deposits are proposed as a mechanism.

  13. Idealized model of polar cap currents, fields, and auroras

    NASA Technical Reports Server (NTRS)

    Cornwall, J. M.

    1985-01-01

    During periods of northward Bz, the electric field applied to the magnetosphere is generally opposite to that occurring during southward Bz and complicated patterns of convection result, showing some features reversed in comparison with the southward Bz case. A study is conducted of a simple generalization of early work on idealized convection models, which allows for coexistence of sunward convection over the central polar cap and antisunward convection elsewhere in the cap. The present model, valid for By approximately 0, has a four-cell convection pattern and is based on the combination of ionospheric current conservation with a relation between parallel auroral currents and parallel potential drops. Global magnetospheric issues involving, e.g., reconnection are not considered. The central result of this paper is an expression giving the parallel potential drop for polar cap auroras (with By approximately 0) in terms of the polar cap convection field profile.

  14. Modeling the Quiet Time Outflow Solution in the Polar Cap

    NASA Technical Reports Server (NTRS)

    Glocer, Alex

    2011-01-01

    We use the Polar Wind Outflow Model (PWOM) to study the geomagnetically quiet conditions in the polar cap during solar maximum, The PWOM solves the gyrotropic transport equations for O(+), H(+), and He(+) along several magnetic field lines in the polar region in order to reconstruct the full 3D solution. We directly compare our simulation results to the data based empirical model of Kitamura et al. [2011] of electron density, which is based on 63 months of Akebono satellite observations. The modeled ion and electron temperatures are also compared with a statistical compilation of quiet time data obtained by the EISCAT Svalbard Radar (ESR) and Intercosmos Satellites (Kitamura et al. [2011]). The data and model agree reasonably well. This study shows that photoelectrons play an important role in explaining the differences between sunlit and dark results, ion composition, as well as ion and electron temperatures of the quiet time polar wind solution. Moreover, these results provide validation of the PWOM's ability to model the quiet time ((background" solution.

  15. POLAR/TIDE Survey of Thermal O+ Characteristics near 5000km Altitude over the Polar Cap

    NASA Technical Reports Server (NTRS)

    Stevenson, B. A.; Horwitz, J. L.; Su, Y. J.; Elliott, Heather A.; Comfort, Richard H.; Moore, Thomas E.; Giles, Barbara A.; Craven, Paul D.; Chandler, Michael O.; Pollock, Craig J.

    1998-01-01

    We analyze measurements of thermal 0+ parameters from the Thermal Ion Dynamics Experiment (TIDE) on POLAR for April - May, 1996 obtained near 5000 km altitude within the polar cap ionosphere - magnetosphere interface region. Certain aspects of O+ parameters in this region were explored by Su et. al. [1998]. In this report, we hope to extend our understanding of the O+ behavior by examining relationships of densities, parallel velocities, and temperatures to the convection velocities, IMF By and Bz components. Preliminary results with the convection velocities are currently being analyzed. In doing so, we are guided in part by the Cleft Ion Fountain paradigm and model developed by Horwitz and Lockwood [1985] which involves downward O+ flows in the polar magnetosphere.

  16. A study of auroral activity in the nightside polar cap

    SciTech Connect

    Wu, Q.

    1989-01-01

    Using various ground observations at South Pole, Antarctica (invariant magnetic latitude -74{degree}) and its conjugate point, Frobisher Bay, Canada, the author has studied the following aspects of nightside polar cap auroral activity: the appearance and disappearance of polar cap auroras (diffuse and discrete) associated with substorms and interplanetary magnetic field (IMF) variations; auroral optical emission line intensities; and the seasonal variation of auroral conjugacy. The observations show that the polar cap auroras usually fade away before the expansive phase of a substorm and bright auroral arcs reach high latitude (-74{degree}) near the recovery phase. Just before the auroras fade away the discrete polar cap auroral arcs, which are usually on the poleward boundary of the diffuse aurora, intensify for 1 to 2 minutes. The observations also indicate the IMF may have stronger control over polar cap auroral activity than do substorms. A search for energy spectral variation of precipitating electrons using the intensities of 630.0 nm (0) and 427 nm (N{sub 2}{sup +}) auroral emission lines reveals no dramatic changes in the energy spectrum; instead, the data show possible atmospheric scattering and geometric effects on the photometric measurements while the bright auroral arc is moving into the polar cap. The conjugate observations show that the stormtime auroral electrojet current, which is associated with the bright auroral arc, in most cases reaches higher (lower) latitudes in the winter (summer) hemisphere. An asymmetric plasma sheet (with respect to the neutral sheet) is proposed, which expands deeper into the winter lobe, under a tilted geomagnetic dipole. Accordingly, the winter polar cap would have smaller area and the auroral electrojet would be at higher latitude.

  17. Direct Observations of the Evolution of Polar Cap Ionization Patches

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Zhang, B.; Lockwood, M. M.; Hu, H.; Moen, J. I.; Ruohoniemi, J.; Thomas, E. G.; Zhang, S.; Yang, H.; Liu, R.; McWilliams, K. A.; Baker, J. B.

    2013-12-01

    Patches of ionization are common in the polar ionosphere where their motion and associated density gradients give variable disturbances to High Frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a 'tongue' of ionization (TOI).

  18. Intense field-aligned currents in the polar cap as evidenced from the Swarm satellite constellation

    NASA Astrophysics Data System (ADS)

    Luhr, H.; Kervalishvili, G.; Huang, T.

    2015-12-01

    Traditionally the polar cap has been considered as a region of low activity and reduced energy input. More recent observations, however, evidence more and more exceptions from that. For example, CHAMP and GRACE recorded significant mass density anomalies over the polar cap practically during every magnetic storm. The question is, which process provides enough Joule heating and/or particle precipitation along the open field lines. A promising mechanism is field-aligned currents (FACs). In the past it has been difficult to make reliable estimates of FACs in the polar cap from single satellite magnetic field measurements. An important assumption that the currents are organized in sheets is often not fulfilled in the polar cap. As a consequence current densities are largely underestimated. Only recently ESA's Swarm constellation mission offers reliable FAC estimates from dual-satellite measurements. Significant differences between single and dual-satellite estimates are found in the polar cap. We will show the relation between polar cap FAC patches and IMF orientation and solar wind conditions. Based on these results suggestions for possible current drivers are made.

  19. Heating of the Sunlit Polar Cap Ionosphere by Reflected Photoelectrons

    NASA Astrophysics Data System (ADS)

    Varney, R. H.; Solomon, S. C.; Nicolls, M. J.

    2014-12-01

    Photoelectrons escape from the ionosphere on sunlit polar cap field lines. In order for those field lines to carry zero current without significant heavy ion outflow or cold electron inflow, field-aligned potential drops must form to reflect a portion of the escaping photoelectron population back to the ionosphere. Using a 1-D ionosphere-polar wind model and measurements from the Resolute Bay Incoherent Scatter Radar (RISR-N), this paper shows that these reflected photoelectrons are a significant source of heat for the sunlit polar cap ionosphere. The model includes a kinetic suprathermal electron transport solver, and it allows energy input from the upper boundary in three different ways: thermal conduction, soft precipitation, and potentials that reflect photoelectrons. The simulations confirm that reflection potentials of several 10s of eV are required to prevent cold electron inflow and demonstrate that the flux tube integrated change in electron heating rate (FTICEHR) associated with reflected photoelectrons can reach 109 eV cm-2s-1. Soft precipitation can produce FTICEHR of comparable magnitudes, but this extra heating is divided among more electrons as a result of electron impact ionization. Simulations with no reflected photoelectrons and with downward field-aligned currents (FAC) primarily carried by the escaping photoelectrons have electron temperatures which are ~250-500 K lower than the RISR-N measurements in the 300-600 km region; however, simulations with reflected photoelectrons, zero FAC, and no other form of heat flux through the upper boundary can satisfactorily reproduce the RISR-N data.

  20. Heating of the sunlit polar cap ionosphere by reflected photoelectrons

    NASA Astrophysics Data System (ADS)

    Varney, R. H.; Solomon, S. C.; Nicolls, M. J.

    2014-10-01

    Photoelectrons escape from the ionosphere on sunlit polar cap field lines. In order for those field lines to carry zero current without significant heavy ion outflow or cold electron inflow, field-aligned potential drops must form to reflect a portion of the escaping photoelectron population back to the ionosphere. Using a 1-D ionosphere-polar wind model and measurements from the Resolute Bay Incoherent Scatter Radar (RISR-N), this paper shows that these reflected photoelectrons are a significant source of heat for the sunlit polar cap ionosphere. The model includes a kinetic suprathermal electron transport solver, and it allows energy input from the upper boundary in three different ways: thermal conduction, soft precipitation, and potentials that reflect photoelectrons. The simulations confirm that reflection potentials of several tens of eV are required to prevent cold electron inflow and demonstrate that the flux tube integrated change in electron heating rate (FTICEHR) associated with reflected photoelectrons can reach 109eV cm-2s-1. Soft precipitation can produce FTICEHR of comparable magnitudes, but this extra heating is divided among more electrons as a result of electron impact ionization. Simulations with no reflected photoelectrons and with downward field-aligned currents (FAC) primarily carried by the escaping photoelectrons have electron temperatures which are ˜250-500 K lower than the RISR-N measurements in the 300-600 km region; however, simulations with reflected photoelectrons, zero FAC, and no other form of heat flux through the upper boundary can satisfactorily reproduce the RISR-N data.

  1. Testing the Expanding-Contracting Polar Cap Paradigm

    NASA Astrophysics Data System (ADS)

    Sotirelis, T.; Keller, M. R.; Smith, D.; Barnes, R. J.; Talaat, E. R.; Newell, P. T.; Baker, J. B.

    2013-12-01

    The expanding-contracting polar cap (ECPC) paradigm is tested. Under the ECPC paradigm ionospheric convection in the polar cap is driven by the combined effects of dayside merging and nightside reconnection, as opposed to being mapped down from higher altitudes. The ECPC paradigm is tested by separately examining convection when the polar cap is expanding versus contracting. The open magnetic flux is estimated from SuperDARN observations of the convection reversal boundary (CRB) made simultaneously at different local times. (Sotirelis et al. [2005] established the CRB as a proxy for the Open-Closed Boundary (OCB).) The correlation of the ionospheric convection potential with solar wind/IMF driving is indeed found to depend on whether the polar cap is expanding or contracting. Specifically, when the polar cap is expanding, ionospheric convection correlates best (0.86) with the most recent 10 minutes of solar wind/IMF driving (versus 0.57 for contracting). When contracting, convection correlates best (0.87) with 90-minute averages of solar wind/IMF driving (versus 0.51 for expanding). This is consistent with ECPC expectations.

  2. Measurements of the north polar cap of Mars and the earth's Northern Hemisphere ice and snow cover

    NASA Technical Reports Server (NTRS)

    Foster, J.; Owe, M.; Capen, C.

    1986-01-01

    The boundaries of the polar caps of Mars have been measured on more than 3000 photographs since 1905 from the plate collection at the Lowell Observatory. For the earth, the polar caps have been accurately mapped only since the mid 1960s when satellites were first available to synoptically view the polar regions. The polar caps of both planets wax and wane in response to changes in the seasons, and interannual differences in polar cap behavior on Mars as well as earth are intimately linked to global energy balance. Data on the year to year variations in the extent of the north polar caps of Mars and earth have been assembled and compared, although only 6 years of concurrent data were available for comparison.

  3. Morphology of Mars North Polar Ice Cap

    NASA Astrophysics Data System (ADS)

    Zwally, H. J.; Fountain, A.; Kargel, J.; Kouvaris, L.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Saba, J. L.

    2000-08-01

    The northern ice cap of Mars consists of a parabolic dome centered within 13 km of the pole, plus an arm-like ridge extending from the dome between about 135 and 225 east. Chasma Boreale lies between the dome and the extended ridge. The base of the dome is approximately elliptical with a major axis of 1100 km along the 90 east to 270 east direction and minor axis of 700 km along zero east to 180 deg. The heights of the dome and the extended ridge are respectively 2900 inches and 1700 inches above the surrounding basin. Least-squares fitting of a parabola through height profiles of the dome along longitudes 90 deg to 270 deg and zero deg to 180 deg gives an elliptic-paraboloid equation for the dome: Z(m) = 2800 - [(X-x)2/113.6] - [(Y-y)2/50.3], where X is the 90 deg to 270 deg axis, x = 9.90 km, y = 13.32 km, and the slightly-different fitted heights for the two axes are averaged. The center of the dome is shifted 13.32 km from the pole along zero deg longitude and 9.90 km along 90 deg longitude. Typical mean surface slopes on the ice cap are the order of 1/100 (0.6 deg), A small central portion of the cap, about 100 km by 200 km, extends in elevation about 200 inches above the parabolic shape of the cap. Additional information is contained in the original extended abstract.

  4. Polar cap auroral electron fluxes observed with Isis 1

    NASA Technical Reports Server (NTRS)

    Winningham, J. D.; Heikkila, W. J.

    1974-01-01

    Three types of auroral particle precipitation have been observed over the polar caps, well inside the auroral oval, by means of the soft particle spectrometer on the Isis 1 satellite. The first type is a uniform, very soft (about 100 eV) electron 'polar rain' over the entire polar cap; this may well be present with very weak intensity at all times, but it is markedly enhanced during worldwide geomagnetic storms. A second type of precipitation is a structured flux of electrons with energies near 1 keV, suggestive of localized 'polar showers'; it seems likely that these are the cause of the sun-aligned auroral arcs that have been observed during moderately quiet conditions. During periods of intense magnetic disturbance this precipitation can become very intense and exhibit a characteristic pattern that we have come to call a 'polar squall'.

  5. Mercury's South Polar Region

    NASA Video Gallery

    This animation shows 89 wide-angle camera (WAC) images of Mercury’s south polar region acquired by the Mercury Dual Imaging System (MDIS) over one complete Mercury solar day (176 Earth days). Thi...

  6. Radiation Near 2f(sub p) and Intensified Emissions Near f(sub p) in the Dayside and Nightside Auroral Region and Polar Cap

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Menietti, J. D.

    1997-01-01

    This paper reports the discovery in the DE 1 data of propagating radiation near 2f(sub p) (the H component) and relatively intense electromagnetic waves near f(sub p) with fields typically less than or approximately equal to 1 mV/m (the PF or plasma frequency component) on both the dayside and the nightside of Earth. These emissions are observed at auroral and polar cap latitudes for radial distances ranging from 2.5 to 4.5 R(sub E). The H component is unique in that no other 2f(sub p) emissions are known to be generated where the electron gyrofrequency f(sub g) exceeds 2f(sub p). Since existing theories for 2f(sub p) radiation assume f(sub g)/f(sub p) less than 1, new theories will be required to explain the H component. The PF waves near f(sub p) are electromagnetic, but with large ratios E/cB approximately 20. On the basis of cold plasma theory, the wave frequencies and the ratios E/cB, the PF component plausibly consists of zeta-mode and/or whistler mode waves near f(sub p), presumably driven by an electron instability. The H emissions have modest bandwidths of approximately 50% at frequencies ranging from 5 to 20 kHz. Grounds for interpreting the H component as emissions generated near 2f(sub p) are provided by the very good frequency tracking of the PF and H components and typical frequency ratios near 2.0. Strong evidence exists that part of the H component is propagating, electromagnetic radiation, based on propagation effects and spin modulation patterns. However, no magnetic signals have yet been detected for the H component, so that it could be partly electrostatic. Cold plasma theory and the observed wave characteristics favor interpreting the H component as composed of omicron mode and/or zeta mode signals. Combining the DE 1 observations with rocket observations, it is predicted that the much more intense Langmuir-like fields observed in the low altitude auroral zones should also generate observable 2f(sub p) radiation. This prediction should be

  7. North-Polar Martian Cap as Habitat for Elementary Life

    NASA Astrophysics Data System (ADS)

    Wallis, M. K.; Wickramasinghe, J. T.; Wickramasinghe, N. C.

    2008-09-01

    North-polar cap over millenia Atmospheric water in Mars tends currently as for the past millenia to distil onto the polar caps and be buried under dust deposits. Diffusive release from ground-ice (and its excavation in meteorite impacts [1]) replenishes atmospheric water, allowing the gradual build up of polar ice-dust deposits. When sunlit, this warmed and sublimating ice-dust mix has interest as a potential habitat for micro-organisms. Modelling shows precipitable vapour at 10-50μm/yr, varying sensitively with small changes in orbitable obliquity around the present 25° [2]. The modelling applies to a globe with regionally uniform albedo, unlike the steep topography and dark layering of the north polar cap whose upper 300m have accumulated over the last 500 kyr [3]. The cliffs and ravines of the north-polar cap are thought to form through south-facing slopes sublimating and gaining a dirt-encrusted surface, while horizontal surfaces brighten through frost deposits. The two-phase surface derives from the dust and frost feedback on surface albedo [4] and the resulting terrain develops over diurnal cycles of frosting and sublimation, and over annual seasonal cycles. The steep south-facing sides of observed ravines when unshadowed would see for a few hours the full intensity of sunlight at near normal incidence, without the atmospheric dimming at similar inclinations on Earth. As exposed ice sublimates at T > 200K (partial pressure exceeds typical martian 0.1 Pa), a crust of dirt develops to maintain quasi-stability. The dirt crust's main function is to buffer the ice against diurnal temperature fluctuations, but it also slows down vapour diffusion - analogous to south polar ice sublimation [5] and the growth of ground-ice [6]. We envisage 1-10 mm/yr as the net sublimation rate, compatible with the 100 kyr life and scales of the north polar ravines. Modelling of icy-dirt crusts in the polar cap Plane-parallel layers have been used to model the changing temperature

  8. F-layer polar-cap arcs. Master's thesis

    SciTech Connect

    Fite, D.D.

    1987-09-01

    Two types of ionospheric anomalies were discovered recently in the polar cap: patches and arcs. Polar-cap arcs are the focus of this study, which seeks correlation between arcs and total election content (TEC) enhancements and amplitude scintillation effects. Simultaneous optical and radio-frequency measurements were taken at Thule AFB and Qanaaq, Greenland, using the All-Sky Imaging Photometer (ASIP) and a specially equipped Global Positioning System (GPS) receiver. Arcs were discovered to produce significant, rapidly varying TEC increases, and small but measurable amplitude scintillation.

  9. High spatial resolution radar observations of ultralow frequency waves in the southern polar cap

    NASA Astrophysics Data System (ADS)

    Bland, Emma C.; McDonald, Andrew J.

    2016-05-01

    We present an analysis of ultralow frequency (ULF) waves detected in the southern polar cap using the Super Dual Auroral Radar Network (SuperDARN). These waves manifest as quasi-sinusoidal oscillations in the Doppler velocity, which arise due to the oscillating ULF wave electric field in the F region ionosphere. The event reported in this study occurred during the southern polar winter under quiet geomagnetic conditions. The 1.1-1.3 mHz oscillations were observed throughout the polar cap by the McMurdo, Dome C East, and South Pole Station SuperDARN radars and also by the Dome Concordia and Scott Base magnetometers at corrected geomagnetic latitudes of ˜89°S and ˜80°S, respectively. In contrast to large-scale toroidal field line resonances observed at auroral latitudes, we find that the magnetic perturbation vector of the polar cap oscillations did not undergo a 90° rotation upon transmission from the ionosphere to the ground and was instead rotated by about 30°. The polar cap oscillations were also accompanied by simultaneous field line resonance (FLR) activity in the dayside auroral zone, in the field of view of the Zhongshan SuperDARN radar. This FLR occurred at the same frequency and exhibited a similar azimuthal phase velocity to the polar cap oscillations, indicating that they may have been driven by the same source mechanism.

  10. Mars Polar Cap During Transition Phase Instrument Checkout

    NASA Technical Reports Server (NTRS)

    2006-01-01

    During the last week of September and the first week or so of October 2006, scientific instruments on NASA's Mars Reconnaissance Orbiter were turned on to acquire test information during the transition phase leading up to full science operations. The mission's primary science phase will begin the first week of November 2006, following superior conjunction. (Superior conjunction is where a planet goes behind the sun as viewed from Earth.) Since it is very difficult to communicate with a spacecraft when it is close to the sun as seen from Earth, this checkout of the instruments was crucial to being ready for the primary science phase of the mission.

    Throughout the transition-phase testing, the Mars Color Imager (MARCI) acquired terminator (transition between nighttime and daytime) to terminator swaths of color images on every dayside orbit, as the spacecraft moved northward in its orbit. The south polar region was deep in winter shadow, but the north polar region was illuminated the entire Martian day. During the primary mission, such swaths will be assembled into global maps that portray the state of the Martian atmosphere -- its weather -- as seen every day and at every place at about 3 p.m. local solar time. After the transition phase completed, most of the instruments were turned off, but the Mars Climate Sounder and MARCI have been left on. Their data will be recorded and played back to Earth following the communications blackout associated with conjunction.

    Combined with wide-angle image mosaics taken by the Mars Orbiter Camera on NASA's Mars Global Surveyor at 2 p.m. local solar time, the MARCI maps will be used to track motions of clouds.

    This image is a composite mosaic of four polar views of Mars, taken at midnight, 6 a.m., noon, and 6 p.m. local Martian time. This is possible because during summer the sun is always shining in the polar region. It shows the mostly water-ice perennial cap (white area), sitting atop the north polar layered

  11. Polar cap magnetic field reversals during solar grand minima: could pores play a role?

    NASA Astrophysics Data System (ADS)

    Švanda, Michal; Brun, Allan Sacha; Roudier, Thierry; Jouve, Laurène

    2016-02-01

    We study the magnetic flux carried by pores located outside active regions with sunspots and investigate their possible contribution to the reversal of the global magnetic field of the Sun. We find that they contain a total flux of comparable amplitude to the total magnetic flux contained in polar caps. The pores located at distances of 40-100 Mm from the closest active region systematically have the correct polarity of the magnetic field to contribute to the polar cap reversal. These pores can be found predominantly in bipolar magnetic regions. We propose that during grand minima of solar activity, such a systematic polarity trend, which is akin to a weak magnetic (Babcock-Leighton-like) source term, could still be operating but was missed by the contemporary observers because of the limited resolving power of their telescopes.

  12. Perennial water ice identified in the south polar cap of Mars.

    PubMed

    Bibring, Jean-Pierre; Langevin, Yves; Poulet, François; Gendrin, Aline; Gondet, Brigitte; Berthé, Michel; Soufflot, Alain; Drossart, Pierre; Combes, Michel; Bellucci, Giancarlo; Moroz, Vassili; Mangold, Nicolas; Schmitt, Bernard

    2004-04-01

    The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2 km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap. PMID:15024393

  13. Reduction of the field-aligned potential drop in the polar cap during large geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Kitamura, N.; Seki, K.; Nishimura, Y.; Hori, T.; Terada, N.; Ono, T.; Strangeway, R. J.

    2013-12-01

    We have studied photoelectron flows and the inferred field-aligned potential drop in the polar cap during 5 large geomagnetic storms that occurred in the periods when the photoelectron observations in the polar cap were available near the apogee of the FAST satellite (~4000 km) at solar maximum, and the footprint of the satellite paths in the polar cap was under sunlit conditions most of the time. In contrast to the ~20 V potential drop during geomagnetically quiet periods at solar maximum identified by Kitamura et al. [JGR, 2012], the field-aligned potential drop frequently became smaller than ~5 V during the main and early recovery phases of the large geomagnetic storms. Because the potential acts to inhibit photoelectron escape, this result indicates that the corresponding acceleration of ions by the field-aligned potential drop in the polar cap and the lobe region is smaller during the main and early recovery phases of large geomagnetic storms compared to during geomagnetically quiet periods. Under small field-aligned current conditions, the number flux of outflowing ions should be nearly equal to the net escaping electron number flux. Since ions with large flux originating from the cusp/cleft ionosphere convect into the polar cap during geomagnetic storms [e.g., Kitamura et al., JGR, 2010], the net escaping electron number flux should increase to balance the enhanced ion outflows. The magnitude of the field-aligned potential drop would be reduced to let a larger fraction of photoelectrons escape.

  14. Unsolved problems: Mesoscale polar cap flow channels' structure, propagation, and effects on space weather disturbances

    NASA Astrophysics Data System (ADS)

    Lyons, L. R.; Nishimura, Y.; Zou, Y.

    2016-04-01

    Recent evidence indicates that the magnetosphere-ionosphere system is frequently driven by dynamic mesoscale flow structures that are first seen near the dayside cusps, move across the open field line regions of the polar caps, and then enter the plasma sheet where they lead to a large variety of space weather disturbances. It will be important to uncover the features of these flow enhancements, including their structure, how they propagate across the polar cap, and what controls their dynamic effects after reaching the nightside plasma sheet.

  15. Topography of Impact Structures on the Northern Polar Cap of Mars

    NASA Technical Reports Server (NTRS)

    Sakimoto, S. E. H.; Garvin, J. B.

    1998-01-01

    The north polar residual ice deposits of mars are thought to be relatively young, based on the reported lack of any fresh impact craters in Viking Orbiter images. A handful of possible impact features were identified, but available data were inconclusive. Determining the number and current topographic characteristics of any craters on the polar residual ice surface is important in constraining the surface age, relative importance of polar cap resurfacing processes and ice flow dynamics, and the role of the cap deposits in the global volatile and climate cycles. Subsequent image processing advances and new Mars Orbiter Laser Altimeter (MOLA) data in the north polar region are now a considerable aid in impact feature identification. This study reconsiders the abundant Viking high-resolution polar images along with the new altimetry data. We examine possible impact features, compare their topography with known mars high-latitude impact features, and use their morphology as a constraint on crater modification processes.

  16. Field-Aligned Electric Potential in the Polar Cap

    NASA Astrophysics Data System (ADS)

    Wing, S.; Hildebrand, L.

    2014-12-01

    Reconnection with the interplanetary magnetic field (IMF) on the dayside magnetosphere opens the previously closed Earth's field line, allowing solar wind particles to enter the magnetosphere, some of which precipitate into the ionosphere. As the open-field line ExB convects to the nightside, fewer ions can enter the magnetosphere. As a result, field-aligned (parallel) electric potential increases with latitude to prevent more electrons from entering, in order to maintain charge quasi-neutrality. The APL open-field line model predicts that the parallel potential drop increases from cusp to mantle to polar rain. This trend has been confirmed in a study that compared phase space densities of ACE solar wind electrons to those of DMSP precipitating electrons. However, the same study also found that sometimes there is an anomaly: the parallel potential drop would have the opposite polarity such that solar wind electrons are accelerated downward in the afternoon polar cap. Using DMSP magnetometer and particle precipitation data, we show that this accelerating potential drop can be found often in the poleward upward field-aligned current region. The velocity shear at the magnetopause boundary leads to a voltage drop across the boundary, which drives the upward field-aligned currents. At higher latitude or further away from noon, the field line maps to the magnetopause location that is further down the magnetotail where the magnetosheath velocity shear is higher and density is lower. When the velocity shear and hence field-aligned current density (J//) is too high or density too low, parallel potential develops to accelerate more electron downward, in accordance with Knight relation.

  17. Effective area for northern Polar Cap index data

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2016-07-01

    The northern (PCN) and southern (PCS) Polar Cap indices are used, among other, in applications to forecast geomagnetic storms and substorms. The index values are based on geomagnetic observations that for the forecast are transmitted in real-time from selected stations, PCN on data from Qaanaaq (Thule) in Greenland and PCS on geomagnetic data from Vostok in Antarctica. Observational conditions in the harsh polar environments are difficult and data transmission links are vulnerable. Hence, it could be advantageous to base real-time PC index values on data from multiple sites in order to safeguard the forecasts. The presentation shall compare PCN index values derived from a range of further observatories in Greenland and Canada in order to delimit an effective Polar Cap area for providing geomagnetic data for a useful index and to settle whether reliable (preliminary) index values could be derived from other than the standard observatories particularly during strongly disturbed conditions.

  18. Direct observations of the evolution of polar cap ionization patches.

    PubMed

    Zhang, Qing-He; Zhang, Bei-Chen; Lockwood, Michael; Hu, Hong-Qiao; Moen, Jøran; Ruohoniemi, J Michael; Thomas, Evan G; Zhang, Shun-Rong; Yang, Hui-Gen; Liu, Rui-Yuan; McWilliams, Kathryn A; Baker, Joseph B H

    2013-03-29

    Patches of ionization are common in the polar ionosphere, where their motion and associated density gradients give variable disturbances to high-frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication. Their formation and evolution are poorly understood, particularly under disturbed space weather conditions. We report direct observations of the full evolution of patches during a geomagnetic storm, including formation, polar cap entry, transpolar evolution, polar cap exit, and sunward return flow. Our observations show that modulation of nightside reconnection in the substorm cycle of the magnetosphere helps form the gaps between patches where steady convection would give a "tongue" of ionization (TOI). PMID:23539601

  19. The spatial coherence of Schumann activity in the polar cap

    NASA Astrophysics Data System (ADS)

    Holtham, P. M.; McAskill, B. J.

    1988-02-01

    The spatial coherence of the first two Schumann resonant modes has been studied at two locations in the polar cap separated by 1100 km. Measurements were made at Assistance Bay and Mould Bay, which have geomagnetic latitudes of 83 and 79 deg, respectively, and satellite time-keeping was employed to accurately synchronize the field stations. The coherence was found to be high, typically 95 percent for the first Schumann mode, and was unaffected by changes in Kp, a storm sudden commencement, or a solar flare event. Polarization rotations were observed between the two stations, which could most likely be attributed to the coastline effect. The results are consistent with a stable propagation of Schumann activity from midlatitudes to high latitudes that is relatively unaffected by changes in the polar cap ionosphere.

  20. Low-energy electron intensities at large distances over the earth's polar cap

    NASA Technical Reports Server (NTRS)

    Yeager, D. Y.; Frank, L. A.

    1976-01-01

    The eccentric-orbiting satellite Imp 5 penetrated the distant polar magnetosphere at positions corresponding to those for magnetic field lines which intersect the earth's northern polar cap. Measurements of electron intensities with E not less than 250 eV in these regions of extremely low plasma densities were gained with an electrostatic analyzer. The observational period was January-October 1970. Electron intensities within the energy range 250 eV-50 keV were less by orders of magnitude than those typically encountered within the plasma sheet and over the auroral oval. However, dramatic temporal variations of average electron intensities in the polar cap region were found for orbit-to-orbit comparisons. The observed intensity variations showed a remarkable correlation with the polarity of the magnetic sector structure in the interplanetary medium: high intensities for 'away from the sun' sectors and low intensities for 'toward' sectors.

  1. The Martian North Polar Cap in Summer - One Year Later

    NASA Technical Reports Server (NTRS)

    2001-01-01

    In the middle of January 2001, Mars Global Surveyor (MGS) completed one Mars year in its 380 km-high (236 mi) mapping orbit. The mapping orbit was originally achieved in late February 1999. In March of that year, MGS conducted a series of operations in preparation for full-up mapping, first calibrating its scientific instruments and then operating in a mode in which the high gain antenna was held fixed against the body of the spacecraft. During this Fixed High Gain Antenna period, 'contingency science' observations were made in case the high gain antenna failed to properly deploy. The wide angle view of the martian north polar cap shown on the left was acquired on March 13, 1999, during early northern summer. The image on the right was acquired almost exactly one Mars year later, on January 26, 2001. The light-toned surfaces are residual water ice that remains through the summer season. The nearly circular band of dark material surrounding the cap consists mainly of sand dunes formed and shaped by wind. The north polar cap is roughly 1100 kilometers (680 miles) across. Close inspection will show that there are differences in the frost cover between the two images (for example, in the upper center of each image, and on the left edge center). Although these changes appear small, they are in fact quite large--the change in frost covering is equivalent to the amount of frost that would be evaporated (in the case of areas that are darker) or deposited (in areas where frost is still on the ground) in almost 5 months. What gives rise to such large changes in the heat budget for the polar caps from one year to the next is not known. Changes in the coloration and brightness of the polar cap suggest dust, deposited perhaps by dust storms during critical periods of the year, may play an important role.

  2. When is O+ Observed in the High Altitude Polar Cap?

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    2000-01-01

    Solar wind and IMF properties are correlated with the properties of O+ and H+ in the polar cap at altitudes greater than 5.5 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. O+ is of primary interest in this study because the fraction of O+ present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. O+ is observed to be most abundant at lower latitudes when the solar wind speed is low and across most of the polar cap at high solar winds speeds and Kp. As the solar wind dynamic pressures increases more O+ is present in the polar cap. The O+ density is also shown to be more highly correlated with the solar wind dynamic pressure when IMF Bz is positive. H+ was not as well correlated with solar wind and IMF parameters although some correlation with IMF By is observed. H+ is more plentiful when IMF By is negative than when it is positive. In this data set H+ is very dominate so that if this plasma makes it to the plasma sheet its contribution to the plasma sheet would have a very low O+ to H+ ratio.

  3. Martian polar and circum-polar sulfate-bearing deposits: Sublimation tills derived from the North Polar Cap

    NASA Astrophysics Data System (ADS)

    Massé, M.; Bourgeois, O.; Le Mouélic, S.; Verpoorter, C.; Le Deit, L.; Bibring, J. P.

    2010-10-01

    Previous spectroscopic studies have shown the presence of hydrated minerals in various kinds of sedimentary accumulations covering and encircling the martian North Polar Cap. More specifically, gypsum, a hydrated calcium sulfate, has been detected on Olympia Planum, a restricted part of the Circum-Polar Dune Field. To further constrain the geographical distribution and the process of formation and accumulation of these hydrated minerals, we performed an integrated morphological, structural and compositional analysis of a key area where hydrated minerals were detected and where the main polar landforms are present. By the development of a spectral processing method based on spectral derivation and by the acquisition of laboratory spectra of gypsum-ice mixtures we find that gypsum-bearing sediment is not restricted to the Olympia Planum dunes but is also present in all kinds of superficial sediment covering the surface of the North Polar Cap and the Circum-Polar Dune Field. Spectral signatures consistent with perchlorates are also detected on these deposits. The interpretation of landforms reveals that this gypsum-bearing sediment was released from the ice cap by sublimation. We thus infer that gypsum crystals that are now present in the Circum-Polar Dune Field derive from the interior of the North Polar Cap. Gypsum crystals that were initially trapped in the ice cap have been released by sublimation of the ice and have accumulated in the form of ablation tills at the surface of the ice cap. These gypsum-bearing sublimation tills are reworked by winds and are transported towards the Circum-Polar Dune Field. Comparison with sulfates found in terrestrial glaciers suggests that gypsum crystals in the martian North Polar Cap have formed by weathering of dust particles, either in the atmosphere prior to their deposition during the formation of the ice cap, and/or in the ice cap after their deposition.

  4. Reversed-polarity regions

    NASA Technical Reports Server (NTRS)

    Tang, F.

    1982-01-01

    It is found by a statistical study of 58 reversed-polarity regions (RPRs) covering the 11-year period 1969-1979 that RPRs (1) have a lifespan comparable to normal active regions, (2) do not show a tendency to rotate toward a more normal alignment, and (3) have stable configurations that do not suggest stress due to their anomalous magnetic alignment. As in normal regions, RPR magnetic complexity is found to be the primary factor in flare productivity. Weak-field RPRs produce no flares, and regions with complex spots produce more flares than regions with non-complex spots by a factor of five. The main difference between RPRs and normal regions lies in complex spot frequency, with less that 17% of normal active regions having such spots and fewer than 1.8% having long-lived complex ones, while 41% of RPRs have complex spots and 24% have long-lived complex spots.

  5. Power grid disturbances and polar cap index during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2013-06-01

    The strong geomagnetic storm in the evening of 30 October 2003 caused high-voltage power grid disturbances in Sweden that expanded to produce hour-long power line outage in Malmö located in the southern part of the country. This was not a unique situation. The geomagnetic storm on 13 March 1989 caused extensive disruptions of high-voltage power circuits especially in the Province of Quebec, Canada, but also to a lesser degree in Scandinavia. Similar events have occurred earlier, among others, during the great storms of 13-14 July 1982 and 8-9 February 1986. These high-voltage power grid disturbances were related to impulsive magnetic variations accompanying extraordinarily intense substorm events. The events were preceded by lengthy intervals of unusually high values of the Polar Cap (PC) index caused by enhanced transpolar ionospheric convection. The transpolar convection transports magnetic flux from the dayside to nightside which causes equatorward displacements of the region of auroral activity enabling the substorms to hit vital power grids. During the 30 October 2003 event the intense solar proton radiation disabled the ACE satellite observations widely used to provide forecast of magnetic storm events. Hence in this case the alarmingly high PC index could provide useful warning of the storm as a back-up of the missing ACE-based forecast. In further cases, monitoring the PC index level could provide supplementary storm warnings to the benefit of power grid operators.

  6. Condensation phase of the Martian south polar cap

    NASA Technical Reports Server (NTRS)

    Capuano, J.; Reed, M.; James, P. B.

    1992-01-01

    One type of database that can be useful in limiting models of the Mars surface-atmosphere system is the time dependent boundary of CO2 frost for the polar caps. Data acquired by the thermal infrared sensors on spacecraft are not limited by the lighting problems that hamper visual observations. The surface temperature of solid CO2 is limited by Clapeyron's equation as a function of the local partial pressure of CO2 gas. The growth was studied of the Martian south polar cap using the Viking IRTM dataset. These data are available in five bands, four of which should correspond to surface radiation in clear conditions; the 20 micron data was examined in the first phase.

  7. Review of methods to derive a Polar Cap (PC) index.

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2016-07-01

    Since a Polar Cap (PC) index was introduced in 1985, several different methods have been used to derive index values. Basically, the northern (PCN) and southern (PCS) are based on geomagnetic recordings at Qaanaaq (Thule) and Vostok, respectively. However, different derivation methods can give index values differing by more than a factor 2. The PC indices are used, among other, in scientific analyses to link solar wind conditions to relevant geophysical effects and in forecast efforts to establish numerical criteria for imminent risk of geomagnetic storms and substorms. Thus, it is unfortunate that several different versions of the PC index have been in use, often without specifically mentioning the index version being used or without ensuring that proper documention and specification of the derivation method is available. The presentation shall briefly describe the basic calculation of a Polar Cap index and point specifically to the differences between the different derivation methods and to the consequences for the index values

  8. On magnetic pair production above fast pulsar polar caps

    NASA Technical Reports Server (NTRS)

    An, S.

    1985-01-01

    Magnetic pair production is one of high-energy electromagnetic conversion processes important to the development of pair-photon cascades in pulsars. On the basis of current polar cap models, the properties of magnetic pair production in fast pulsars are discussed. Suppose there is a roughly dipole magnetic field at the stellar surface, the author estimate the effects on non-zero curvature of magnetic field lines upon curvature radiation from primary particles and pair production rate near the surface of pulsars.

  9. Pulsar Polar Cap and Slot Gap Models: Confronting Fermi Data

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2012-01-01

    Rotation-powered pulsars are excellent laboratories for studying particle acceleration as well as fundamental physics of strong gravity, strong magnetic fields and relativity. I will review acceleration and gamma-ray emission from the pulsar polar cap and slot gap. Predictions of these models can be tested with the data set on pulsars collected by the Large Area Telescope on the Fermi Gamma-Ray Telescope over the last four years, using both detailed light curve fitting and population synthesis.

  10. Seasonal Changes in Mars' North Polar Ice Cap

    NASA Technical Reports Server (NTRS)

    1997-01-01

    These images, which seem to have been taken while NASA's Hubble Space Telescope (HST) was looking directly down on the Martian North Pole, were actually created by assembling mosaics of three sets of images taken by HST in October, 1996 and in January and March, 1997 and projecting them to appear as they would if seen from above the pole. This first mosaic is a view which could not actually be seen in nature because at this season a portion of the pole would have actually been in shadow; the last view, taken near the summer solstice, would correspond to the Midnight Sun on Earth with the pole fully illuminated all day. The resulting polar maps begin at 50 degrees N latitude and are oriented with 0 degrees longitude at the 12 o'clock position. This series of pictures captures the seasonal retreat of Mars' north polar cap.

    October 1996 (early spring in the Northern hemisphere): In this map, assembled from images obtained between Oct. 8 and 15, the cap extends down to 60 degrees N latitude, nearly it's maximum winter extent. (The notches are areas where Hubble data were not available). A thin, comma-shaped cloud of dust can be seen as a salmon-colored crescent at the 7 o'clock position. The cap is actually fairly circular about the geographic pole at this season; the bluish 'knobs' where the cap seems to extend further are actually clouds that occurred near the edges of the three separate sets of images used to make the mosaic.

    January 1997 (mid-spring): Increased warming as spring progresses in the northern hemisphere has sublimated the carbon dioxide ice and frost below 70 degrees north latitude. The faint darker circle inside the cap boundary marks the location of circumpolar sand dunes (see March '97 map); these dark dunes are warmed more by solar heating than are the brighter surroundings, so the surface frost sublimates from the dunes earlier than from the neighboring areas. Particularly evident is the marked hexagonal shape of the polar cap at this season

  11. IR spectral properties of dust and ice at the Mars south polar cap

    NASA Astrophysics Data System (ADS)

    Titus, T. N.; Kieffer, H. H.

    2001-11-01

    Removal of atmospheric dust effects is required to derive surface IR spectral emissivity. Commonly, the atmospheric-surface separation is based on radiative transfer (RT) spectral inversion methods using nadir-pointing observations. This methodology depends on a priori knowledge of the spectral shape of each atmospheric aerosol (e.g. dust or water ice) and a large thermal contrast between the surface and atmosphere. RT methods fail over the polar caps due to low thermal contrast between the atmosphere and the surface. We have used multi-angle Emission Phase Function (EPF) observations to estimate the opacity spectrum of dust over the springtime south polar cap and the underlying surface radiance, and thus, the surface emissivity. We include a few EPFs from Hellas Basin as a basis for comparisons between the spectral shape of polar and non-polar dust. Surface spectral emissivities over the seasonal cap are compared to CO2 models. Our results show that the spectral shape of the polar dust opacity is not constant, but is a two-parameter family that can be characterized by the 9 um and 20 um opacities. The 9 um opacity varies from 0.15 to 0.45 and characterizes the overall atmospheric conditions. The 9 um to 20 um opacity ratio varies from 2.0 to 5.1, suggesting changes in dust size distribution over the polar caps. Derived surface temperatures from the EPFs confirm that the slightly elevated temperatures (relative to CO2 frost temperature) observed in ``cryptic'' regions are a surface effect, not atmospheric. Comparison of broad-band reflectivity and surface emissivities to model spectra suggest the bright regions (e.g. perennial cap, Mountains of Mitchell) have higher albedos due to a thin surface layer of fine-grain CO2 (perhaps either frost or fractured ice) with an underlying layer of either coarse grain or slab CO2 ice.

  12. Mariner 9 observations of the south polar cap of Mars - Evidence for residual CO2 frost

    NASA Technical Reports Server (NTRS)

    Paige, D. A.; Herkenhoff, K. E.; Murray, B. C.

    1990-01-01

    The first spacecraft observations of the south residual polar cap of Mars were obtained by the Mariner 9 orbiter during the Martian southern summer season, 1971-1972. Analyses of Viking orbiter observations obtained 3 Mars years later have shown that residual carbon dioxide frost was present at the south polar cap in 1977. In this study, Mariner 9 infrared interferometer spectrometer spectra and television camera images are used in conjuction with multispectral thermal emission models to constrain the temperatures of dark bare ground and bright frost regions within the south residual cap. The results provide strong evidence that carbon dioxide frost was present throughout the summer season despite the fact that the residual frost deposits observed by Mariner 9 were less extensive than those observed by Viking.

  13. Field-Line Tracing from Locations of Polar Cap Neutral Density Anomalies to the Magnetosphere

    NASA Astrophysics Data System (ADS)

    Sutton, E. K.; Lin, C. S.; Huang, C. Y.; Cooke, D. L.

    2015-12-01

    Localized neutral density enhancement in the polar cap above 70o magnetic latitude have been frequently observed during major geomagnetic storms. It has been suggested that energy input responsible for producing localized neutral density spikes is the dominant energy deposition in the polar cap. To better understand the origin of polar cap neutral density anomalies (PCNDAs) we trace magnetic field lines from the polar cap region at about 400 km to the magnetosphere using the data-based Tsyganenko magnetic field model TS05 [Tsyganenko and Sitnov, 2005] for the periods when CHAMP detected PCNDAs during major magnetic storms with the minimum Dst < -100 nT. The magnetopause boundary is specified according to the three-dimensional asymmetric magnetopause model recently developed by Lin et al. [2010]. The closest distance to the magnetopause along the traced field line path is determined as a function of time. The tracing results indicate that depending on Dst and locations PCNDAs could be connected through magnetic field lines either to the nightside magnetopause or to the magnetotail lobe. For some events field lines originating from a portion of the PCNDA region are found to cross the equatorial plane in the near earth tail region. We discuss the results to help elucidate the coupling between the magnetosphere and the thermosphere and its roles in producing polar cap density anomalies. ReferencesLin, R. L., X. X. Zhang, S. Q. Liu, Y. L. Wang, and J. C. Gong (2010), A three-dimensional asymmetric magnetopause model, J. Geophys. Res., 115, A04207, doi:10.1029/2009JA014235.Tsyganenko, N. A., and M. I. Sitnov (2005), Modeling the dynamics of the inner magnetosphere during strong geomagnetic storms, J. Geophys. Res., 110, A03208, doi:10.1029/2004JA010798.

  14. Interplanetary magnetic field dependency of stable Sun-aligned polar cap arcs

    NASA Technical Reports Server (NTRS)

    Valladares, C. E.; Carlson, H. C., Jr.; Fukui, K.

    1994-01-01

    06-12 and the 12-18 quadrants of the CG coordinate system point toward the cusp. The B(sub y) dependency of the arc alignment is consistent with a cusp displacement in local time according to the sign of B(sub y). We found that the arc direction of motion depended both on B(sub y) and the arc location within the polar cap. For a given value of B(sub y) two well-defined regions (or cells) exist. Within each cell the arcs move in the same direction toward the boundary between the cells. The arcs located in the duskside move dawnward; those in the dawnside move duskward. The relative size of these dusk and dawn regions (or cells) are controlled by the magnitude of B(sub y). This persistent dusk-dawn motion fo the polar cap arcs is interpreted in terms of newly open flux tubes entering the polar cap and exerting a displacement of the convective cells and the polar cap arcs that are embedded within them.

  15. The Residual Polar Caps of Mars: Geological Differences and Possible Consequences

    NASA Technical Reports Server (NTRS)

    Thomas, P. C.; Sullivan, R.; Ingersoll, A. P.; Murray, B. C.; Danielson, G. E.; Herkenhoff, K. E.; Soderblom, L.; Malin, M. C.; Edgett, K. S.; James, P. B.

    2000-01-01

    The Martian polar regions have been known to have thick layered sequences (presumed to consist of silicates and ice), CO2 seasonal frost, and residual frosts that remain through the summer: H2O in the north, largely CO2 in the south. The relationship of the residual frosts to the underlying layered deposits could not be determined from Viking images. The Mars Orbiter Camera on Mars Global Surveyor has provided a 50-fold increase in resolution that shows more differences between the two poles. The north residual cap surface has rough topography of pits, cracks, and knobs, suggestive of ablational forms. This topography is less than a few meters in height, and grades in to surfaces exposing the layers underneath. In contrast, the south residual cap has distinctive collapse and possibly ablational topography emplaced in four or more layers, each approx. two meters thick. The top surface has polygonal depressions suggestive of thermal contraction cracks. The collapse and erosional forms include circular and cycloidal depressions, long sinuous troughs, and nearly parallel sets of troughs. The distinctive topography occurs throughout the residual cap area, but not outside it. Unconformities exposed in polar layers, or other layered materials, do not approximate the topography seen on the south residual cap. The coincidence of a distinct geologic feature, several layers modified by collapse, ablation, and mass movement with the residual cap indicates a distinct composition and/or climate compared to both the remainder of the south polar layered units and those in the north.

  16. The Residual South Polar Cap of Mars: Stable or Transitory?

    NASA Astrophysics Data System (ADS)

    Glenar, David A.; Bonev, B. P.; Hansen, G. B.; James, P. B.; Bjorkman, J. E.

    2006-09-01

    It remains uncertain whether the CO2 residual south polar cap (RSPC) is a permanent feature of the present Mars climate, or whether it occasionally sublimes completely during years marked by dramatic dust storm activity. While there is no firm evidence for complete disappearance of the cap in the past, observations show that the residual cap lost significant CO2 material in the spring / summer season prior to the Mariner 9 encounter. On the other hand, little interannual change has been observed in the RSPC during the MGS mission [1], despite the massive early-spring dust storm which occurred in 2001. We discuss whether a global dust storm beginning near perihelion could enhance the net CO2 sublimation sufficiently to completely remove the RSPC. We utilize a surface-plus-aerosol radiative transfer model under conditions of both modest and heavy atmospheric dust loading. The sublimination behavior depends critically on the extended (visible to thermal IR) albedo spectrum of the polar CO2 ice, which we have strongly constrained [2] from a combination of HST photometric imaging, ground based near-IR imaging spectroscopy and spectroscopic measurements by the Mars Express PFS. The extension of the cap spectrum to thermal IR wavelengths was accomplished by forward modeling using a semi-infinite grid of scattering grains. Results of this analysis depend on the strength of possible feedback mechanisms (increased surface dust content; exposure of water ice) as well as on the possibility of dust confinement by the polar vortex; but the general conclusion is that it would require multiple, intense dust storms in a given year in order to completely remove the CO2 ice veneer layer. This work has been supported by the NASA Planetary Astronomy and Mars Data Analysis Programs. [1] Benson and James, Icarus 174, 513, 2005; [2] Bonev et al., Planet Space Sci. 2006 (accepted).

  17. The Martian polar CAP - Radiative effects of ozone, clouds, and airborne dust

    NASA Astrophysics Data System (ADS)

    Lindner, B. L.

    1990-02-01

    The solar and thermal flux striking the polar cap of Mars is computed for various ozone, dust, and cloud abundances and for three solar zenith angles. Ozone does not significantly affect the total energy budget of the polar cap. Hence the observed hemispherical asymmetry in ozone abundance causes only an insignificant hemispherical asymmetry in the polar caps. Vertical optical depths of dust and cloud ranging from zero to 1 cause little change in the total flux absorbed by the polar cap near its edge but increase the absorbed flux significantly as one travels poleward. Hemispherical asymmetries in dust abundance, cloud cover, and surface pressure combine to cause a significant hemispherical asymmetry in the total flux absorbed by the residual polar caps, which helps to explain the dichotomy in the residual polar caps on Mars. Other processes which affect the energy budget of the polar cap are proposed and reviewed, particularly with respect to their interaction with the radiative effects of clouds and dust.

  18. The quiet time polar cap: DE 1 observations and conceptual model

    SciTech Connect

    Burch, J.L. ); Saflekos, N.A. ); Gurnett, D.A.; Frank, L.A. ); Craven, J.D. )

    1992-12-01

    Auroral activity increases over the polar caps during quiet times, which are associated with northward interplanetary magnetic field (IMF) components. Polar cap auroras (Sun-aligned arcs, theta auroras, and horse collar auroras) occur under these conditions. DE 1 data have provided partial characterization of these events. A conceptual northward IMF merging model containing lobe cells, merging cells, and viscous cells is shown to be consistent with the observations. As the IMF becomes more northward, the polar arc configuration changes from the horse collar pattern to the theta aurora pattern in the model, and this is shown to be generally true for the set of published data on these phenomena. The model involves dayside merging both at high latitudes on open field lines and at lower latitudes on closed field lines. The ratio between the merged flux produced by the high-latitude merging to that produced by the lower-latitude merging increases as the IMF becomes more northward. Two types of open field lines, equator-crossing and non-equator-crossing, are produced by the higher- and lower-latitude merging, respectively. The equator-crossing field lines have a strong azimuthal component of convection as they flow around the magnetopause, while the non-equator-crossing field lines can convect more or less directly across the polar cap, leading to an antisunward flow channel across the central polar cap. This antisunward flow region grows as the IMF becomes less northward, causing dual polar cap arcs to spread out into the horse collar configuration.

  19. Fourier spectra from exoplanets with polar caps and ocean glint

    NASA Astrophysics Data System (ADS)

    Visser, P. M.; van de Bult, F. J.

    2015-07-01

    Context. The weak orbital-phase dependent reflection signal of an exoplanet contains information on the planet surface, such as the distribution of continents and oceans on terrestrial planets. This light curve is usually studied in the time domain, but because the signal from a stationary surface is (quasi)periodic, analysis of the Fourier series may provide an alternative, complementary approach. Aims: We study Fourier spectra from reflected light curves for geometrically simple configurations. Depending on its atmospheric properties, a rotating planet in the habitable zone could have circular polar ice caps. Tidally locked planets, on the other hand, may have symmetric circular oceans facing the star. These cases are interesting because the high-albedo contrast at the sharp edges of the ice-sheets and the glint from the host star in the ocean may produce recognizable light curves with orbital periodicity, which could also be interpreted in the Fourier domain. Methods: We derive a simple general expression for the Fourier coefficients of a quasiperiodic light curve in terms of the albedo map of a Lambertian planet surface. Analytic expressions for light curves and their spectra are calculated for idealized situations, and dependence of the spectral peaks on the key parameters inclination, obliquity, and cap size is studied. Results: The ice-scattering and ocean glint contributions can be separated out, because the coefficients for glint are all positive, whereas ice sheets lead to even-numbered, higher harmonics. An in-view polar cap on a planet without axial tilt only produces a single peak. The special situation of edge-on observation, which is important for planets in transit, leads to the most pronounced spectral behavior. Then the respective spectra from planets with a circumventing ocean, a circular ocean (eyeball world), polar caps, and rings, have characteristic power-law tails n-2, n-7/2, n-4, and (-1)n + 1n-2. Conclusions: Promising recently discovered

  20. Earth's ion upflow associated with polar cap patches: Global and in situ observations

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-He; Zong, Qiu-Gang; Lockwood, Michael; Heelis, Roderick A.; Hairston, Marc; Liang, Jun; McCrea, Ian; Zhang, Bei-Chen; Moen, Jøran; Zhang, Shun-Rong; Zhang, Yong-Liang; Ruohoniemi, J. Michael; Lester, Mark; Thomas, Evan G.; Liu, Rui-Yuan; Dunlop, Malcolm W.; Liu, Yong C.-M.; Ma, Yu-Zhang

    2016-03-01

    We report simultaneous global monitoring of a patch of ionization and in situ observation of ion upflow at the center of the polar cap region during a geomagnetic storm. Our observations indicate strong fluxes of upwelling O+ ions originating from frictional heating produced by rapid antisunward flow of the plasma patch. The statistical results from the crossings of the central polar cap region by Defense Meteorological Satellite Program F16-F18 from 2010 to 2013 confirm that the field-aligned flow can turn upward when rapid antisunward flows appear, with consequent significant frictional heating of the ions, which overcomes the gravity effect. We suggest that such rapidly moving patches can provide an important source of upwelling ions in a region where downward flows are usually expected. These observations give new insight into the processes of ionosphere-magnetosphere coupling.

  1. The Polar Cap Tongue of Ionization: A survey of GPS TEC mappings from 2000 to 2014

    NASA Astrophysics Data System (ADS)

    David, M.; Sojka, J. J.; Schunk, R. W.; Coster, A. J.

    2015-12-01

    The tongue of ionization (TOI) is a sporadic large-scale feature of the F-region polar ionosphere; a volume of high density plasma transported anti-sunward across the polar cap by the magnetospheric convection electric field. Sometimes the TOI may exist in the form of polar cap patches, owing to the solar wind and M-I coupling causing variations in convection, breaking up the TOI into discrete patchy structures. Figure 1 shows an example of a TOI under quiet geomagnetic conditions, from the GPS TEC map for 1637 UT on 05 Nov 2012, a day on which the Kp index was never higher than 1.7. The data is taken from Millstone Hill's on-line Madrigal data base. The TOI is often thought of as a storm-time phenomenon; this work challenges that assumption by examining observations from all levels of geomagnetic activity throughout the period of availability of the GPS TEC maps (2000-2014).Sojka et al [1994] carried out a modeling study to determine the seasonal and universal time dependence of the tongue of ionization (and polar cap patches); Figure 2 is reproduced from that paper. In essence, this figure is intended to indicate the times when a TOI may and may not exist. A notable feature is the "hole" that is seen during winter days between 0600 and 1200 UT. At the time of that publication it was not possible to test the prediction, but there now exists a wealth of data in the form of maps of total electron content (TEC), available from the on-line Madrigal data base. These TEC maps, especially in the northern hemisphere, cover the mid-latitude and polar cap regions with sufficient resolution to determine whether or not a TOI exists, for nearly every day from the year 2000 to the present time, at 5 minute intervals. In this study we make a comprehensive survey of this immense data base and outline the conditions under which TOIs have been seen in the northern hemisphere, based on seasonal and UT dependencies, as well as levels of geomagnetic disturbance. The winter "hole" in

  2. The 1997 Spring Regression of the Martian South Polar Cap: Mars Orbiter Camera Observations

    NASA Astrophysics Data System (ADS)

    James, P. B.; Cantor, B. A.; Edgett, K.; Malin, M. C.

    1999-09-01

    The Mars Orbiter Cameras on Mars Global Surveyor observed the south polar cap of Mars during its spring recession in 1997. The images acquired by the Wide Angle Cameras reveal a pattern of recession that is qualitatively similar to that observed by Viking in 1977 but that does differ in at least two respects. The 1977 recession in the 0 deg to 120 deg longitude sector was accelerated relative to the 1997 observations after LS = 240 deg the Mountains of Mitchel also detached from the main cap earlier in 1997. Comparison of the MOC images with MOLA data shows that the Mountains of Mitchel feature is controlled by local topography. Relatively dark, low albedo regions well within the boundaries of the seasonal cap were observed to have red to violet ratios that characterize them as frost units rather than unfrosted or partially frosted ground; this suggests the possibility of regions covered by CO2 frost having different grain sizes.

  3. South Polar Residual Cap Geomorphology and Inferred Environmental Changes

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ingersoll, A.; Pathare, A.

    2003-12-01

    this varies from area to area. These features are smaller in scale than SCF?s and so may have information pertaining to more recent environmental events. We will present results from several avenues of research that we are pursuing: We are investigating the overall mass budget of the SRC. If the mass lost from expanding depressions is not condensed elsewhere on the cap then the SRC will disappear within a few Martian centuries. It seems unlikely to us that we are observing Mars at such a special time in its history. A large range of expansion rates is possible depending on the subsurface albedo profile (3,5). We will attempt to measure the subsurface albedo by examining images of exposed SCF walls. We are also improving our model to more accurately date features and by extension the environmental events that triggered their initiation. Previously we always initiated our modeled depressions from small pre-existing surface features. We are more closely investigating the genesis of SRC features and what environmental changes are required to cause them. We will continue to catalogue new population statistics for different regions in the SRC Each distinct feature population that we can identify may give us information on previous environmental events. Investigations into SRC features have the potential to describe changes in the Martian polar environment over timescales of millennia. It will provide a link from present conditions to longer-term variations in Martian climate, which are perhaps recorded in the layered deposits. [1] Thomas et al., Nature, 404. [2] Malin et al., Science, 294. [3] Byrne and Ingersoll, GRL, 30. [4] Malin and Edgett, JGR, 106. [5] Byrne and Ingersoll, Science, 299.

  4. Origin of density enhancements in the winter polar-cap ionosphere

    SciTech Connect

    Anderson, D.N.; Buchau, J.; Heelis, R.A.

    1987-05-07

    Coherent and incoherent ground-based radar measurements of the winter polar cap ionosphere at Thule and Sondrestrom, Greenland, have established the existence of patches of enhanced ionization that drift across the polar cap in an antisunward, noon-midnight direction. Associated with these patches is strong radio scintillation activity which severely disrupts ground-to-satellite communication systems and interferes with the operation of space surveillance radar at high latitudes. Several recent studies have shown that the source of enhanced ionization is the sunlit sub-cusp ionosphere rather than production by precipitating energetic particles. This problem is studied by solving the time-dependent plasma continuity equation including production by solar ultraviolet radiation, loss through charge exchange and transport by diffusion and convection E X B drifts. Time and spatially varying, horizontal E X B drift patterns are imposed and subsequent ionospheric responses are calculated to determine enhanced plasma densities. In the dark polar cap could result from extended transit of relevant flux tubes through regions of significant solar production. A density enhancement in NMAX from 70,000 to 500,000 el/cu cm occurs at Thule when a time-varying convection pattern is included in the simulation. The patch of ionization is generated when an initial convection pattern characterized by an 80-kV crosstail potential and a 12/degree/ polar cap radius is abruptly changed to a 100-kV crosstail potential and a 15/degree/ polar-cap radius. The horizontal extent of the patch is related to the length of time the new convection pattern remains turned-on.

  5. Magnetohydrostatics in the polar caps of accreting magnetized white dwarfs

    NASA Astrophysics Data System (ADS)

    Hameury, J. M.; Lasota, J. P.

    1985-04-01

    The mechanism of quasi-periodic luminosity variations seen in cataclysmic variable stars is investigated theoretically. Numerical calculations are performed for the model proposed by Livio (1984), in which matter accreted onto the polar caps of a magnetized white dwarf causes repeated breaking of the magnetic-field lines; the method is based (by analogy) on the analysis of magnetic-field disruption in magnetized neutron stars of Hameury et al. (1983). It is found that any such magnetic-field breaking gives recurrence times orders of magnitude greater than those actually observed in magnetized cataclysmic variables suggesting that some other mechanism must be found for the quasi-periodic variations.

  6. Seasonal recession of Mars' south polar cap in 1986

    NASA Technical Reports Server (NTRS)

    James, Philip B.; Martin, Leonard J.; Henson, Jean R.; Birch, Peter V.

    1990-01-01

    Photographs of Mars obtained during the 1986 opposition of the planet have been used to derive the regression curve for the south polar cap between Ls = 190 deg and Ls = 255 deg. The 1986 regression appears to have been unexceptional until after Ls = 230 deg, when it becomes retarded relative to the normal established by the 1971 and 1977 regressions. A study of the data as a function of the filter used suggests that circumpolar clouds were present in early spring, unlike the case in the 1977 recession.

  7. Polar Cap Pair Production for an Axisymmetric Pulsar Requires General Relativity

    NASA Astrophysics Data System (ADS)

    Belyaev, Mikhail

    2016-04-01

    Using an analytical approach coupled to a condition for pair production derived from particle in cell simulations, we show that pair production by curvature photons on magnetic field lines at the polar cap is inactive if general relativity is ignored. In particular, general relativisitic frame-dragging lowers the value of the Goldreich-Julian density at the polar cap compared to its value for a flat spacetime. This leads to a region of space-like current near the surface of the neutron star where pair production is possible.However, even when general relativity is included, we show analytically that pair production on magnetic field lines is suppressed near the outer edge of the polar cap. This leads to the possibility of a ``vacuum" region of unscreened parallel electric field on open field lines near the last open field line. Such a vacuum region has indeed been observed in particle in cell simulations of the pulsar magnetosphere.Because of the generality of our analytical approach (which does not assume a dipolar surface field), our conclusions are true independent of the detailed structure of the magnetic field at the surface of the neutron star. We confirm our analytical results by comparing them to force-free simulations of a pulsar with a dipolar surface field.

  8. The Changing South Polar Cap of Mars: 1999-2005

    NASA Technical Reports Server (NTRS)

    2005-01-01

    13 July 2005 The south polar residual cap of Mars is composed of layered, frozen carbon dioxide. In 1999, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) showed that the carbon dioxide layers have been eroded to form a variety of circular pits, arcuate scarps, troughs, buttes, and mesas. In 2001, MOC images designed to provide repeated views of the areas imaged in 1999 -- with the hope of creating stereo (3-D) images, so that the height of scarps and depth of pits could be measured -- showed that the scarps had retreated, pits enlarged, and buttes and mesas shrank. Only carbon dioxide is volatile enough in the martian environment to have caused such dramatic changes -- the scarps were seen to retreat at an average rate of 3 meters (about 3 yards) per Mars year. Most of the scarp retreat occurs during the southern summer season; in some areas the scarps move as much as 8 meters, in others, only 1 meter per Mars year.

    Three Mars years have now elapsed since MOC first surveyed the south polar cap in 1999. Over the past several months, MGS MOC has been re-imaging areas that were seen in 1999, 2001, and 2003, to develop a detailed look at how the landscape has been changing. This animated GIF provides an example of the dramatic changes that have occurred during the past three martian years. The first image, a sub-frame of M09-05244, was acquired on 21 November 1999. The second image, a sub-frame of S06-00973, was obtained on 11 May 2005. The animation shows the changes that have occurred between 1999 and 2005. Each summer, the cap has lost more carbon dioxide. This may mean that the carbon dioxide content of the martian atmosphere has been increasing, bit by very tiny little bit, each of the years that MGS has been orbiting the red planet. These observations also imply that there was once a time, in the not-too-distant past (because there are no impact craters on the polar cap), when the atmosphere was somewhat thinner and colder, to permit the layers

  9. Composition of Auroral Polar Cap Boundary Ion Conics

    NASA Astrophysics Data System (ADS)

    Tung, Y.; Carlson, C. W.; McFadden, J. P.; Parks, G. K.; Lund, E. J.; Eriksson, S.; Ergun, R. E.

    2002-12-01

    Ion conics have frequently been observed by FAST on the auroral polar cap boundary, which we have defined as where the ion energy flux sharply drops off. These polar cap boundary (PCB) ion conics are particularly prevalent in the nightside sector near midnight. Of medium energies (100 eV to 1 keV), these ion conics are characterized by intense number fluxes and often constitute the majority of the outflow from the nightside auroral oval. An earlier study has reported that the PCB ion outflow consisted predominantly of H+ and He+, while a separate study presented data that showed PCB ion conics that consisted primarily of oxygen ions. Possible explanations for the composition change include solar cycle variation or seasonal variation. We will explore through a systematic consideration of FAST orbits from 1997 through 2000 the change in composition of PCB ion conics. Since neither the solar cycle nor the seasons alone seem to explain the variation in ion composition of the PCB ion conics, we will consider alternative possibilities such as convection, IMF dependence, or auroral activity level and history.

  10. Does a "substorm precursor" exist in the polar cap?

    NASA Astrophysics Data System (ADS)

    Nosikova, Nataliya; Lorentzen, Dag; Yagova, Nadezda; Baddeley, Lisa; Pilipenko, Vyacheslav; Kozyreva, Olga

    2015-04-01

    An isolated auroral substorm, which occurs without external triggering, can develop as a result of inner instabilities in the geomagnetic tail. The comparative analysis of presubstorm variations of the geomagnetic field and particle flux in the geomagnetic tail along with geomagnetic and auroral disturbances in the polar caps is of key importance for the discrimination between direct triggering and intra-magnetospheric processes in a substorm onset. In the present study we compare the auroral disturbances and geomagnetic pulsations in the frequency range 1-5 mHz (Pc5/Pi3) at nighttime high latitudes during both quiet geomagnetic intervals preceding isolated substorms and non-substorm intervals. Superposed epoch analysis is applied to reveal pre-substorm variations ("substorm precursors"). The data from IMAGE magnetometer network, the Meridian Scanning photometer (Svalbard), and particle flux measured by GEOTAIL, has been used. The effect of presubstorm activation (Yagova, 2000) is reproduced during the solar minimum conditions. References Yagova N., V. Pilipenko, A. Rodger, V. Papitashvili, J. Watermann, Long period ULF activity at the polar cap preceding substorm, in: Proc. 5th International Conference on Substorms, St. Peterburg, Russia (ESA SP-443), 603-606, 2000.

  11. Gravity Waves Near 300 km Over the Polar Caps

    NASA Technical Reports Server (NTRS)

    Johnson, F. S.; Hanson, W. B.; Hodges, R. R.; Coley, W. R.; Carignan, G. R.; Spencer, N. W.

    1995-01-01

    Distinctive wave forms in the distributions of vertical velocity and temperature of both neutral particles and ions are frequently observed from Dynamics Explorer 2 at altitudes above 250 km over the polar caps. These are interpreted as being due to internal gravity waves propagating in the neutral atmosphere. The disturbances characterized by vertical velocity perturbations of the order of 100 m/s and horizontal wave lengths along the satellite path of about 500 km. They often extend across the entire polar cap. The associated temperature perturbations indicate that the horizontal phase progression is from the nightside to the dayside. Vertical displacements are inferred to be of the order of 10 km and the periods to be of the order of 10(exp 3) s. The waves must propagate in the neutral atmosphere, but they usually are most clearly recognizable in the observations of ion vertical velocity and ion temperature. By combining the neutral pressure calculated from the observed neutral concentration and temperature with the vertical component of the neutral velocity, an upward energy flux of the order of 0.04 erg/sq cm-s at 250 km has been calculated, which is about equal to the maximum total solar ultraviolet heat input above that altitude. Upward energy fluxes calculated from observations on orbital passes at altitudes from 250 to 560 km indicate relatively little attenuation with altitude.

  12. Macroscale modeling and mesoscale observations of plasma density structures in the polar cap

    SciTech Connect

    Basu, S.; Basu, S.; Sojka, J.J.

    1995-04-15

    The seasonal and UT variation of mesoscale structures (10 km - 100 m) in the central polar cap has been obtained from an analysis of 250-MHz intensity scintillation observations made at Thule, Greenland. It has been established earlier that mesoscale structures causing scintillations of satellite signals may develop at the edges of macroscale structures (several hundred km) such as discrete polar cap plasma density enhancements or patches through the gradient drift instability process. As such, the authors examined the seasonal and UT variation of polar cap patches simulated by using the USU Time Dependent Ionospheric Model (TDIM) under conditions of southward B{sub z}. A fairly remarkable similarity is found between the scintillation observations and the model predictions of patch occurrence. For instance, both the patch and scintillation occurrences are minimized during the winter solstice (northern hemisphere) between 0800-1200 UT while also having their largest seasonal intensity between 2000-2400 UT. Little UT dependence of patches and scintillations is seen at equinox with high intensity being observed throughout the day, while during local summer the intensity of macroscale patches and mesoscale irregularities are found to be a minimum at all UT. These results indicate that macroscale features in the polar cap are routinely associated with plasma instabilities giving rise to smaller scale structures and that the specific patch formation mechanism assumed in the simulation is consistent with the observations. This ability to bridge between macroscale modeling and mesoscale observations provides a natural framework for the modeling of mesoscale structures themselves. This mesoscale modeling, in turn, can be utilized in a variety of radar and communication systems applications in the polar region. 25 refs., 3 figs.

  13. Polar cap patches observed during the magnetic storm of November 2003: observations and modeling

    NASA Astrophysics Data System (ADS)

    Valladares, C. E.; Pedersen, T.; Sheehan, R.

    2015-09-01

    We present multi-instrumented measurements and multi-technique analysis of polar cap patches observed early during the recovery phase of the major magnetic storm of 20 November 2003 to investigate the origin of the polar cap patches. During this event, the Qaanaaq imager observed elongated polar cap patches, some of which containing variable brightness; the Qaanaaq digisonde detected abrupt NmF2 fluctuations; the Sondrestrom incoherent scatter radar (ISR) measured patches placed close to but poleward of the auroral oval-polar cap boundary; and the DMSP-F13 satellite intersected topside density enhancements, corroborating the presence of the patches seen by the imager, the digisonde, and the Sondrestrom ISR. A 2-D cross-correlation analysis was applied to series of two consecutive red-line images, indicating that the magnitude and direction of the patch velocities were in good agreement with the SuperDARN convection patterns. We applied a back-tracing analysis to the patch locations and found that most of the patches seen between 20:41 and 21:29 UT were likely transiting the throat region near 19:41 UT. Inspection of the SuperDARN velocities at this time indicates spatial and temporal collocation of a gap region between patches and large (1.7 km s-1) line-of-sight velocities. The variable airglow brightness of the patches observed between 20:33 and 20:43 UT was investigated using the numerical Global Theoretical Ionospheric Model (GTIM) driven by the SuperDARN convection patterns and a variable upward/downward neutral wind. Our numerical results indicate that variations in the airglow intensity up to 265 R can be produced by a constant 70 m s-1 downward vertical wind.

  14. Multi-instrument, high-resolution imaging of polar cap patch transportation

    NASA Astrophysics Data System (ADS)

    Thomas, E. G.; Hosokawa, K.; Sakai, J.; Baker, J. B. H.; Ruohoniemi, J. M.; Taguchi, S.; Shiokawa, K.; Otsuka, Y.; Coster, A. J.; St.-Maurice, J.-P.; McWilliams, K. A.

    2015-09-01

    Transionospheric radio signals in the high-latitude polar cap are susceptible to degradation when encountering sharp electron density gradients associated with discrete plasma structures, or patches. Multi-instrument measurements of polar cap patches are examined during a geomagnetic storm interval on 22 January 2012. For the first time, we monitor the transportation of patches with high spatial and temporal resolution across the polar cap for 1-2 h using a combination of GPS total electron content (TEC), all-sky airglow imagers (ASIs), and Super Dual Auroral Radar Network (SuperDARN) HF radar backscatter. Simultaneous measurements from these data sets allow for continuous tracking of patch location, horizontal extent, and velocity despite adverse observational conditions for the primary technique (e.g., sunlit regions in the ASI data). Spatial collocation between patch-like features in relatively coarse but global GPS TEC measurements and those mapped by high-resolution ASI data was very good, indicating that GPS TEC can be applied to track patches continuously as they are transported across the polar cap. In contrast to previous observations of cigar-shaped patches formed under weakly disturbed conditions, the relatively narrow dawn-dusk extent of patches in the present interval (500-800 km) suggests association with a longitudinally confined plasma source region, such as storm-enhanced density (SED) plume. SuperDARN observations show that the backscatter power enhancements corresponded to the optical patches, and for the first time we demonstrate that the motion of the optical patches was consistent with background plasma convection velocities.

  15. Effect of high-latitude ionospheric convection on Sun-aligned polar caps

    NASA Technical Reports Server (NTRS)

    Sojka, J. J.; Zhu, L.; Crain, D. J.; Schunk, R. W.

    1994-01-01

    A coupled magnetospheric-ionospheric (M-I) magnetohydrodynamic (MHD) model has been used to simulate the formation of Sun-aligned polar cap arcs for a variety of interplanetary magnetic field (IMF) dependent polar cap convection fields. The formation process involves launching an Alfven shear wave from the magnetosphere to the ionosphere where the ionospheric conductance can react self-consistently to changes in the upward currents. We assume that the initial Alfven shear wave is the result of solar wind-magnetosphere interactions. The simulations show how the E region density is affected by the changes in the electron precipitation that are associated with the upward currents. These changes in conductance lead to both a modified Alfven wave reflection at the ionosphere and the generation of secondary Alfven waves in the ionosphere. The ensuing bouncing of the Alfven waves between the ionosphere and magnetosphere is followed until an asymptotic solution is obtained. At the magnetosphere the Alfven waves reflect at a fixed boundary. The coupled M-I Sun-aligned polar cap arc model of Zhu et al.(1993a) is used to carry out the simulations. This study focuses on the dependence of the polar cap arc formation on the background (global) convection pattern. Since the polar cap arcs occur for northward and strong B(sub y) IMF conditions, a variety of background convection patterns can exist when the arcs are present. The study shows that polar cap arcs can be formed for all these convection patterns; however, the arc features are dramatically different for the different patterns. For weak sunward convection a relatively confined single pair of current sheets is associated with the imposed Alfven shear wave structure. However, when the electric field exceeds a threshold, the arc structure intensifies, and the conductance increases as does the local Joule heating rate. These increases are faster than a linear dependence on the background electric field strength. Furthermore

  16. A Novel Approach to Exploring the Mars Polar Caps

    NASA Technical Reports Server (NTRS)

    Brophy, John R.; Carsey, Frank D.; Rodgers, David H.; Soderblom, L. A.; Wilcox, Brian H.

    2000-01-01

    The Martian polar caps contain some of the most important scientific sites on the planet. There is much interest in exploring them with a view to understanding their role in the Mars climate system. By gaining access to the stratigraphy of the polar terrain, it is probable that one can access the climate history of the planet. Additionally, investigations aimed at localizing subsurface water--liquid or solid--are not only of great scientific interest but are also germane to the long-term interests of the manned space flight program. A major difficulty with polar exploration is access. Current techniques using chemical propulsion, Holman transfers, and direct-entry landers with aeroshells have limited capability to access the polar terrain. For the near term the authors propose a new approach to solving this transportation issue by using Solar Electric Propulsion (SEP), recently flight demonstrated on NASA's DS1 Mission to an asteroid and a comet. For a longer-term approach there are additional ways in which access to Mars, as well as other planets, can be significantly improved. These include the use of Chaos orbit theory to enable transportation between LaGrange points in the solar system, gossamer structures enabling very low-mass mobility, and advanced ascent vehicles. In this paper the authors describe how a 1000-kG payload can be transported to the surface of Mars and a polar sample obtained and returned to Earth in less than five years using SEP. A vision of how this approach can be integrated into a long-term Mars exploration strategy building toward the future is also discussed.

  17. Effects of Polar Cap Absorption of Energetic Particles on December 2006

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. V.; Yeh, H. C.; Tsai, L. C.

    2009-05-01

    Ionization effects produced at the northern polar ionosphere and upper atmosphere by energetic particles during December 2006 were studied. That period was accompanied by several solar flares and solar energetic particle (SEP) events as well as by several weak and one strong magnetic storms. Fluxes and spectra of energetic protons and electrons precipitating to the high-latitude and polar regions were measured by a constellation of four POES satellites at low-altitude orbit. The precipitating particles of solar, interplanetary and magnetospheric origin demonstrate different spectral properties and spatial distributions that permit us to study their dynamics separately. Magnetospheric particles are electrons having soft spectra and precipitating predominantly at auroral ionosphere. SEP together with particles accelerated at leading edge of interplanetary transients are characterized by higher energies and harder spectra. They penetrate to the magnetosphere in the polar cap region and causing abundant ionization of the lower ionosphere and upper atmosphere. Using POES data and standard models of the ionosphere and atmosphere we calculated height profiles of specific ionization produced by the SEP in the polar cap. The dynamics of SEP ionization reveals three intensifications at heights from 50 to 100 km in 7 to 8, 13 and 14 December. At the same time the ionization was measured as electron content (EC) by the COSMIC/FORMOSAT-3 constellation of six satellites. That experiment provides a 3- D tomography of the ionosphere and upper atmosphere on the base of radio occultation technique, which makes use of radio signals transmitted by the GPS satellites. We found that the observed temporal and spatial patterns of EC are pretty close to the dynamics of specific ionization, produced by the SEP and in particular by the electrons. Namely, the spatial region of enhanced ionization is overlapped pretty well with the enhancements of the electrons penetrating to the bottom

  18. Polar cap plasma patch primary linear instability growth rates compared

    NASA Astrophysics Data System (ADS)

    Burston, Robert; Mitchell, Cathryn; Astin, Ivan

    2016-04-01

    Four primary plasma instability processes have been proposed in the literature to explain the generation of phase scintillation associated with polar cap plasma patches. These are the gradient drift, current convective, and Kelvin-Helmholtz instabilities and a small-scale "turbulence" process. In this paper the range of possible values of the linear growth rates for each of these processes is explored using Dynamics Explorer 2 satellite observations. It is found that the inertial turbulence instability is the dominant process, followed by inertial gradient drift, collisional turbulence, and collisional shortwave current convective instabilities. The other processes, such as Kelvin-Helmholtz, collisional gradient drift, and inertial shortwave current convective instabilities, very rarely (<1% of the time) give rise to a growth rate exceeding 1/60, that is deemed to be significant (in publications) to give rise to GPS scintillation.

  19. Properties of localized polar cap flow enhancements and their connection to nightside poleward boundary intensifications and substorms

    NASA Astrophysics Data System (ADS)

    Zou, Y.; Nishimura, Y.; Lyons, L. R.; Shiokawa, K.; Donovan, E.; Ruohoniemi, J. M.; McWilliams, K. A.; Nishitani, N.

    2014-12-01

    Previous radar observations have shown that polar cap flows are highly structured and that localized flow enhancements are related to nightside auroral disturbances. However, such studies are limited to available echo regions. Utilizing wide spatial coverage by an all-sky imager at Resolute Bay and simultaneous SuperDARN radar measurements, we determined properties of such localized flow enhancements and their statistical association with nightside auroral activity. We found that narrow flow enhancements are well collocated with airglow patches with substantially larger velocities (>~200 m/s up to ~700 m/s) than the weak large-scale polar cap convection. The flow widths are similar to the patch widths. During the evolution across nightside the polar cap, the flow directions and speeds are consistent with the patch propagation directions and speeds. These correspondences indicate that patches can visualize localized flow enhancements reflecting the flow width, speed and direction. Such associations were prevalent (~67%) in our survey and tended to be observed under By-dominated IMF. The typical flow channel speed, propagation time, and width within our observation areas were 600 m/s, tens of minutes, and 200-300 km, respectively. Localized flow enhancements were usually observed as a channel elongated in the noon-midnight meridian and directed towards pre-midnight (post-midnight) for +By (-By), and accounted for ~10-40% of the plasma transport across the entire polar cap. Utilizing airglow patches as tracers of localized flow enhancements, we also found that as localized polar cap structures move across the polar cap and impinge on the poleward boundary of the nightside auroral oval, they are followed by poleward boundary intensifications (PBIs), which can extend equatorward as auroral streamers, some of which further propagate equatorward and are followed by a substorm auroral onset. This suggests that localized flow enhancements within the polar cap can contribute

  20. Periodic creation of polar cap patches from auroral transients in the cusp

    NASA Astrophysics Data System (ADS)

    Hosokawa, K.; Taguchi, S.; Ogawa, Y.

    2016-06-01

    On 24 November 2012, an interval of polar cap patches was identified by an all-sky airglow imager located near the dayside cusp. During the interval, the successive appearance of poleward moving auroral forms (PMAFs) was detected, which are known to represent ionospheric manifestations of pulsed magnetic reconnections at the dayside magnetopause. All of the patches observed during the interval appeared from these transient auroral features (i.e., there was a one-to-one correspondence between PMAFs and newly created baby patches). This fact strongly suggests that patches can be directly and seamlessly created from a series of PMAFs. The optical intensities of the baby patches were 100-150 R, which is slightly lower than typical patch luminosity on the nightside and may imply that PMAF-induced patches are generally low density. The generation of such patches could be explained by impact ionization due to soft particle precipitation into PMAFs traces. In spite of the faint signature of the baby patches, two coherent HF radars of the SuperDARN network observed backscatter echoes in the central polar cap, which represented signatures of plasma irregularities associated with the baby patches. These indicate that patches created from PMAFs have the potential to affect the satellite communications environment in the central polar cap region.

  1. Comparison of auroral latitude convection to central polar cap convection. (Invited)

    NASA Astrophysics Data System (ADS)

    Bristow, W. A.; Amata, E.

    2013-12-01

    The SuperDARN radar at McMurdo station has been providing convection observations in the central polar cap since January 2010. The Antarctic magnetic pole lies in the center of the radar field of view at about 1000 km range, which is optimum for convection observations. A new pair of SuperDARN radars was constructed in the Antarctic summer of 2012/2013, which add highly complimentary fields of view. The radars, one located at the Italian station at Dome-C, and one located at the US South Pole Station, are directed into a region directly equatorward of the McMurdo field of view. The radars came on line in late January 2013 and are producing excellent convection observations. This paper presents initial results combining the three radar's convection observations. Intervals when the IMF clock angle was between 135 and 225 for periods of more than an hour were selected for study. Just under 50 hours of observations met this criteria since the radars began operation. Convection vectors were formed using the standard SuperDARN algorithm [Ruohoniemi and Baker, 1998] and the auroral-zone flows were compared to those in the central polar cap. Central polar cap flows are typically spatially uniform though highly variable in time, even though the lower latitude observations were spatially structured. The central polar cap average flow velocity is less than 500 m/s, though it often exceeds 1000 m/s. Conditions that lead to the high-speed flow are presented. In addition, correlation with the IMF and solar wind are presented. At times the correlation exceeds 80% while at others it is near zero.

  2. Electron density enhancements in the polar cap during periods of dayside reconnection

    NASA Astrophysics Data System (ADS)

    Clausen, L. B. N.; Moen, J. I.

    2015-06-01

    Using field-aligned current data, we monitor the location of the region 1 current oval which is related to the location of the polar cap boundary (PCB). We identify intervals when the current oval and hence the PCB moved equatorward for extended periods lasting at least 75 min, and we term these intervals sustained dayside reconnection events (SDRE). We find 1059 SDREs between 2010 and 2012 and go on to study the dynamics of the total electron content (TEC) in the high-latitude region in a superposed epoch sense. Immediately after the beginning of a SDRE, a plasma density increase forms at the poleward edge of the PCB and its edge moves from the location of the dayside PCB antisunward at speeds of about 500 m/s, consistent with ionospheric convection measurements. Our results show that the TEC inside the polar cap locally increases by up to 20%. Averaged over the entire polar region poleward of 55° magnetic latitude, however, we find no significant increase in the TEC, indicating that local increases and decreases are formed by transport and rearrangement of existing plasma rather than by impact ionization due to particle precipitation. We also observe a latitudinally narrow region between the TEC increases equatorward and poleward of the dayside PCB in which the TEC stagnates. This stagnation trough may be due to local flow channels associated with bursty dayside reconnection.

  3. Electron Density Enhancements in the Polar Cap During Periods of Dayside Reconnection

    NASA Astrophysics Data System (ADS)

    Clausen, L. B. N.; Moen, J.

    2015-12-01

    Using field-aligned current data we monitor the location of the region 1 current oval which is related to the location of the polar cap boundary (PCB). We identify intervals when the current oval and hence the PCB moved equatorward for extended periods lasting at least 75 minutes and we term these intervals sustained dayside reconnection events (SDRE). We find 1059 SDREs between 2010 and 2012 and go on to study the dynamics of the total electron content (TEC) in the high-latitude region in a superposed epoch sense. Immediately after the beginning of a SDRE a plasma density increase forms at the poleward edge of the PCB and its edge moves from the location of the dayside PCB anti-sunward at speeds of about 500 m/s, consistent with ionospheric convection measurements. Our results show that the TEC inside the polar cap locally increases by up to 20%. Averaged over the entire polar region poleward of 55 degrees magnetic latitude, however, we find no significant increase in the TEC, indicating that local increases and decreases are formed by transport and rearrangement of existing plasma rather than by impact ionization due to particle precipitation. We also observe a latitudinally narrow region between the TEC increases equatorward and poleward of the dayside PCB in which the TEC stagnates. This stagnation trough may be due to local flow channels associated with bursty dayside reconnection.

  4. Diurnal Albedo Variations of the Martian North Polar Water Ice Cap

    NASA Technical Reports Server (NTRS)

    Troy, R. F.; Bass, D.

    2002-01-01

    Presentation of findings regarding diurnal variations in the north polar water ice cap of Mars as part of a larger study of the interannual and seasonal variations of the Martian north polar water ice cap. Additional information is contained in the original extended abstract.

  5. Complex Burial and Exhumation of South Polar Cap Pitted Terrain

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This image is illuminated by sunlight from the upper left. The two prominent bright stripes at the left/center of the image are covered with bright frost and thus create the illusion that they are sunlit from the lower left.

    The large pits, troughs, and 'swiss cheese' of the south polar residual cap appear to have been formed in the upper 4 or 5 layers of the polar material. Each layer is approximately 2 meters (6.6 feet) thick. Some Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images of this terrain show examples in which older pitted and eroded layers have been previously buried and are now being exhumed. The example shown here includes two narrow, diagonal slopes that trend from upper left toward lower right at the left/center portion of the frame. Along the bottoms of these slopes are revealed a layer that underlies them in which there are many more pits and troughs than in the upper layer. It is likely in this case that the lower layer formed its pits and troughs before it was covered by the upper layer. This observation suggests that the troughs, pits, and 'swiss cheese' features of the south polar cap are very old and form over long time scales.

    The picture is located near 84.6oS, 45.1oW, and covers an area 3 km by 5 km (1.9 x 3.1 mi) at a resolution of about 3.8 meters (12 ft) per pixel. The image was taken during southern spring on August 29, 1999.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  6. Observation of polar cap patches and calculation of gradient drift instability growth times: A Swarm case study

    NASA Astrophysics Data System (ADS)

    Spicher, A.; Cameron, T.; Grono, E. M.; Yakymenko, K. N.; Buchert, S. C.; Clausen, L. B. N.; Knudsen, D. J.; McWilliams, K. A.; Moen, J. I.

    2015-01-01

    The Swarm mission represents a strong new tool to survey polar cap patches and plasma structuring inside the polar cap. In the early commissioning phase, the three Swarm satellites were operated in a pearls-on-a-string configuration making noon-midnight transpolar passes. This provides an unparalleled opportunity to examine the potential role of the gradient drift instability (GDI) process on polar cap patches by systematically calculating GDI growth times during their transit across the pole from day to night. Steep kilometer-scale gradients appeared in this study as initial structures that persisted during the approximate 90 min it took a patch to cross the polar cap. The GDI growth times were calculated for a selection of the steep density gradients on both the dayside and the nightside. The values ranged from 23 s to 147 s, which is consistent with recent rocket measurements in the cusp auroral region and provides a template for future studies. Growth times of the order of 1 min found both on the dayside and on the nightside support the existing view that the GDI may play a dominant role in the generation of radio wave scintillation irregularities as the patches transit the polar cap from day to night.

  7. Chasma Boreale in the North Polar Region

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This images shows a Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) full-resolution 'targeted image' of the edge of Mars' north polar cap. The region in the image, Chasma Boreale, is a valley several kilometers or miles deep that cuts about 400 kilometers (about 250 miles) into the edge of the cap.

    This image was acquired at 0851 UTC (4:51 a.m. EDT) on Oct. 1, 2006, near 84.6 degrees north latitude, 3.6 degrees east longitude. It covers an area about 13 kilometers (8 miles) long and, at the narrowest point, about 9 kilometers (5.6 miles) wide. At the center of the image the spatial resolution is as good as 18 meters (60 feet) per pixel. The image was taken in 544 colors covering wavelengths of 0.36 to 3.92 micrometers. Two renderings of the data are shown here, both draped over topography without vertical exaggeration, and then viewed from a perspective diagonally above the site. The top view is an approximately true-color representation. The bottom view, constructed from infrared wavelengths, shows strength of the spectral signature of ice. Brighter areas are rich in ice, and dark areas have little ice.

    The polar cap has long been recognized to contain layers composed of dust and ice, and hence has been named the polar layered deposit. This sits atop an underlying 'basal unit.' The upper part of the basal unit is dark at visible wavelengths and steeply sloped, whereas the lower part of the basal unit is brighter, redder, and layered like the polar layered deposits. The chasma floor is cratered, and in the foreground it is covered by dunes that are outliers of a north polar sand sea that surrounds the polar cap. The polar layered deposits and the basal unit form a steeply sloping scarp about 1.1 kilometers (0.7 miles) high.

    CRISM's image of this region shows a number of previously unrecognized characteristics of the polar layered deposits and the basal unit. First, the ice-rich polar layered deposits exhibit coherent banding both at

  8. Plasma turbulence and coherent structures in the polar cap observed by the ICI-2 sounding rocket

    NASA Astrophysics Data System (ADS)

    Spicher, A.; Miloch, W. J.; Clausen, L. B. N.; Moen, J. I.

    2015-12-01

    The electron density data from the ICI-2 sounding rocket experiment in the high-latitude F region ionosphere are analyzed using the higher-order spectra and higher-order statistics. Two regions of enhanced fluctuations are chosen for detailed analysis: the trailing edge of a polar cap patch and an electron density enhancement associated with particle precipitation. While these two regions exhibit similar power spectra, our analysis reveals that their internal structures are significantly different. The structures on the edge of the polar cap patch are likely due to nonlinear wave interactions since this region is characterized by intermittency and significant coherent mode coupling. The plasma enhancement subjected to precipitation, however, exhibits stronger random characteristics with uncorrelated phases of density fluctuations. These results suggest that particle precipitation plays a fundamental role in ionospheric plasma structuring creating turbulent-like structures. We discuss the physical mechanisms that cause plasma structuring as well as the possible processes for the low-frequency part of the spectrum in terms of plasma instabilities.

  9. The quiet time polar cap - DE 1 observations and conceptual model

    NASA Technical Reports Server (NTRS)

    Burch, J. L.; Saflekos, N. A.; Gurnett, D. A.; Craven, J. D.; Frank, L. A.

    1992-01-01

    A conceptual merging model of the magnetosphere is developed which explains DE-1 observations on polar cap plasmas and waves made during a quiet period with a northward IMF when multiple adjacent regions of sunward and antisunward convection were observed. The model involves dayside merging both at high latitudes on open field lines (the usual northward IMF merging) and at lower latitudes on closed field lines. The ratio between the merged flux produced by the high-latitude merging to that produced by the lower-latitude merging increases as the IMF becomes more northward.

  10. Low-energy electron intensities at large distances over the earth's polar cap

    NASA Technical Reports Server (NTRS)

    Yeager, D. M.; Frank, L. A.

    1975-01-01

    The results of the character and temporal fluctuations study of electron intensities in the energy range of hundreds of electron volts, are reported which were measured at high latitudes and altitudes on geomagnetic field lines corresponding to those of the polar cap and magnetotail lobes. It is concluded that such electron intensities are diminutive relative to those found in other regions of the magnetosphere. Severe variations of intensities were found and the magnitudes of electron intensities appear to be strongly coupled to the directions of the interplanetary magnetic fields.

  11. Case study of polar cap scintillation modeling using DE 2 irregularity measurements at 800 km

    SciTech Connect

    Basu, S.; Basu, S.; Weber, E.J.; Coley, W.R.

    1988-08-01

    High-resolution in situ Dynamics Explorer 2 data on thermal plasma densities are used here to study the small-scale irregularity structure of the F layer patches. It is shown that spatially discrete density structures associated with polar cap patches can be detected fairly high in the topside by an in situ irregularity sensor and that they correspond to temporally discrete scintillation patches. It is also shown that it is possible to model phase and amplitude scintillation occurrence from a knowledge of irregularity amplitude at a satellite altitude of about 800 km provided that independent measurements of the peak density and scale height of the F region are available. 19 references.

  12. The role of rotation and polar-cap currents on pulsar radio emission and polarization

    SciTech Connect

    Kumar, D.; Gangadhara, R. T. E-mail: ganga@iiap.res.in

    2013-06-01

    Perturbations such as rotation and polar-cap current (PC-current) have been believed to greatly affect the pulsar radio emission and polarization. The two effects have not been considered simultaneously in the literature; each one of these has been considered separately, and a picture has been deduced by simply superposing them, but such an approach can lead to spurious results. Hence, by considering pulsar rotation and PC-current perturbations together instead of one at a time, we have developed a single particle curvature radiation model, which is expected to be much more realistic. By simulating a set of typical pulse profiles, we have made an attempt to explain most of the observational results of pulsar radio emission and polarization. The model predicts that due to the perturbations the leading side component can become either stronger or weaker than the corresponding trailing one in any given cone, depending on the passage of the sight line and modulation (nonuniform source distribution). Further, we find that the phase delay of the polarization angle inflection point with respect to the core component greatly depends on the viewing geometry. The correlation between the sign reversal of circular polarization and the polarization angle swing in the case of core-dominated pulsars becomes obscure once the perturbations and modulation become significant. However, the correlation between the negative circular polarization and the increasing polarization angle and vice versa is very clear in the case of conal-double pulsars. The 'kinky'-type distortions in polarization angle swing could be due to the incoherent superposition of modulated emission in the presence of strong perturbations.

  13. Reversed-polarity regions

    NASA Technical Reports Server (NTRS)

    Tang, F.

    1980-01-01

    The 58 RPRS studied have a lifespan comparable to normal active regions and have no tendency to rotate toward a more normal alignment. They seem to have stable configurations with no apparent evidence suggesting stress due to their anomalous magnetic alignment. Magnetic complexity in RPRs is the key to flare productivity just as it is in normal regions - weak field RPRs produced no flares and regions with complex spots produced more flares than regions with noncomplex spots by a factor of 5. The RPRs however, differ from normal regions in the frequency of having complex spots, particularly the long lived complex spots, in them. Less than 17 percent of normal ARs have complex spots; less than 1.8 percent have long lived complex spots. In contrast, 41 percent of RPRs have complex spots and 24 percent have long lived complex spots.

  14. Day-night coupling by a localized flow channel visualized by polar cap patch propagation

    NASA Astrophysics Data System (ADS)

    Nishimura, T.; Lyons, L. R.; Zou, Y.; Wang, B.; Oksavik, K.; Moen, J. I.; Clausen, L.; Donovan, E.; Angelopoulos, V.; Shiokawa, K.; Ruohoniemi, J. M.; Nishitani, N.; McWilliams, K. A.; Lester, M.

    2014-12-01

    Although plasma convection in the polar cap is often thought of large-scale two-cell convection, recent radar observations have shown that dynamic meso-scale fast flows of the order of 100 km size are embedded within the large-scale convection. Those flow channels are colocated with polar cap airglow patches in many cases, and thus optical measurements can be used to track the origin of such flows, evolution in the polar cap, and their influence on nightside auroral activity. We present unique coordinated observations of the dayside auroral oval, polar cap, and nightside auroral oval by three All-Sky Imagers (ASIs), two SuperDARN radars, and DMSP. This dataset revealed that a dayside Poleward-Moving Auroral Form (PMAF) evolved into a polar cap airglow patch that propagated across the polar cap, and then nightside poleward boundary intensifications (PBIs). Radar observations detected fast anti-sunward flows associated with the PMAF, and the DMSP satellite, whose conjunction occurred within a few minutes after the PMAF initiation, measured enhanced Low-Latitude Boundary Layer (LLBL) precipitation and enhanced plasma density with a strong anti-sunward flow burst. The polar cap patch was spatially and temporally coincident with a localized anti-sunward flow channel. The propagation across the polar cap and the subsequent PBIs suggest that the flow channel originated from dayside reconnection and then reached the nightside open-closed boundary, triggering localized nightside reconnection and flow bursts within the plasma sheet. In addition, we have also statistically investigated the property of dayside and nightside polar cap flow channels using imagers, radars and low-altitude satellites. The flow channels are typically found to have a ~300 km width, propagate a few hundred km/s faster than background flows, and to occur during a By-dominant IMF with a weak southward component.

  15. Polar gypsum on Mars : wind-driven exhumation from the North Polar Cap and redistribution in the Circumpolar Dune Field

    NASA Astrophysics Data System (ADS)

    Masse, M.; Bourgeois, O.; Le Mouélic, S.; Verpoorter, C.; Le Deit, L.; Mercier, E.; Bibring, J.

    2010-12-01

    The North Polar Cap of Mars is associated with different kinds of superficial sediments, including the Circumpolar Dune Field and sedimentary veneers scattered over the ice cap. In order to resolve the mineralogical composition of these sediments, we processed OMEGA and CRISM hyperspectral data with an original method based on spectral derivation (Huguenin and Jones, 1986). We find that gypsum is present in all areas where undefined hydrated minerals had been previously detected (Poulet et al., 2008; Horgan et al., 2009; Calvin et al., 2010), including the superficial sedimentary veneers found on the North Polar Cap and the whole Circumpolar Dune Field. Integrated morphological and structural analyses reveal that these gypsum crystals derive directly from the interior of the ice cap (Massé et al., 2010). The source of sedimentary veneers is the dust that was previously contained in the upper part of the ice cap, the ice-rich North Polar Layered Deposits (NPLD). This gypsum-bearing dust was exhumed, on south-facing slopes of spiral troughs and arcuate scarps, by ice ablation induced by katabatic winds. By the analysis of all associations of erosional scarps and dune fields over the North Polar Cap, we also demonstrate that the source of the polar dunes are sand-sized particles that were previously contained in the sediment-rich BU (Basal Unit), corresponding to the lower part of the ice cap. These particles were exhumed from the BU, by regressive ablation of the ice at marginal scarps that border the North Polar Cap, or by vertical ablation of the ice on Olympia Planum. From a reconstruction of wind flow lines over and around the ice cap, we infer that katabatic winds descending from the polar high and rotating around the North Polar Cap are responsible for the exhumation of this gypsum-bearing sand and for its redistribution in the Circumpolar Dune Field. The intensity of gypsum diagnostic spectral absorption bands decreases along wind flow lines in the

  16. The 1997 Spring Regression of the Martian South Polar Cap: Mars Orbiter Camera Observations

    USGS Publications Warehouse

    James, P.B.; Cantor, B.A.; Malin, M.C.; Edgett, K.; Carr, M.H.; Danielson, G.E.; Ingersoll, A.P.; Davies, M.E.; Hartmann, W.K.; McEwen, A.S.; Soderblom, L.A.; Thomas, P.C.; Veverka, J.

    2000-01-01

    The Mars Orbiter cameras (MOC) on Mars Global Surveyor observed the south polar cap of Mars during its spring recession in 1997. The images acquired by the wide angle cameras reveal a pattern of recession that is qualitatively similar to that observed by Viking in 1977 but that does differ in at least two respects. The 1977 recession in the 0?? to 120?? longitude sector was accelerated relative to the 1997 observations after LS = 240??; the Mountains of Mitchel also detached from the main cap earlier in 1997. Comparison of the MOC images with Mars Orbiter Laser Altimeter data shows that the Mountains of Mitchel feature is controlled by local topography. Relatively dark, low albedo regions well within the boundaries of the seasonal cap were observed to have red-to-violet ratios that characterize them as frost units rather than unfrosted or partially frosted ground; this suggests the possibility of regions covered by CO2 frost having different grain sizes. ?? 2000 Academic Press.

  17. Pulsar Pair Cascades in Magnetic Fields with Offset Polar Caps

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alex G.

    2012-01-01

    Neutron star magnetic fields may have polar caps (PC) that are offset from the dipole axis, through field-line sweepback near the light cylinder or non-symmetric currents within the star. The effects of such offsets on electron-positron pair cascades are investigated, using simple models of dipole magnetic fields with small distortions that shift the PCs by different amounts or directions. Using a Monte Carlo pair cascade simulation, we explore the changes in the pair spectrum, multiplicity and energy flux across the PC, as well as the trends in pair flux and pair energy flux with spin-down luminosity, L(sub sd). We also give an estimate of the distribution of heating flux from returning positrons on the PC for different offsets. We find that even modest offsets can produce significant increases in pair multiplicity, especially for pulsars that are near or beyond the pair death lines for centered PCs, primarily because of higher accelerating fields. Pair spectra cover several decades in energy, with the spectral range of millisecond pulsars (MSPs) two orders of magnitude higher than for normal pulsars, and PC offsets allow significant extension of all spectra to lower pair energies. We find that the total PC pair luminosity L(sub pair) is proportional to L(sub sd), with L(sub pair) approximates 10(exp -3) L(sub sd) for normal pulsars and L(sub pair) approximates 10(exp -2) L(sub sd) for MSPs. Remarkably, the total PC heating luminosity for even large offsets increases by less than a factor of two, even though the PC area increases by much larger factors, because most of the heating occurs near the magnetic axis.

  18. The Martian polar caps: Stability and water transport at low obliquities

    NASA Astrophysics Data System (ADS)

    Henderson, B. G.; Jakosky, B. M.

    1992-12-01

    The seasonal cycle of water on Mars is regulated by the two polar caps. In the winter hemisphere, the seasonal CO2 deposits at a temperature near 150 K acts as a cold trap to remove water vapor from the atmosphere. When summer returns, water is pumped back into the atmosphere by a number of mechanisms, including release from the receding CO2 frost, diffusion from the polar regolith, and sublimation from a water-ice residual cap. These processes drive an exchange of water vapor between the polar caps that helps shape the Martian climate. Thus, understanding the behavior of the polar caps is important for interpreting the Martian climate both now and at other epochs. Mars' obliquity undergoes large variations over large time scales. As the obliquity decreases, the poles receive less solar energy so that more CO2 condenses from the atmosphere onto the poles. It has been suggested that permanent CO2 condenses from the atmosphere onto the poles. It has been suggested that permanent CO2 caps might form at the poles in response to a feedback mechanism existing between the polar cap albedo, the CO2 pressure, and the dust storm frequency. The year-round presence of the CO2 deposits would effectively dry out the atmosphere, while diffusion of water from the regolith would be the only source of water vapor to the atmosphere. We have reviewed the CO2 balance at low obliquity taking into account the asymmetries which make the north and south hemispheres different. Our analysis linked with a numerical model of the polar caps leads us to believe that one summertime cap will always lose its CO2 cover during a Martian year, although we cannot predict which cap this will be. We conclude that significant amounts of water vapor will sublime from the exposed cap during summer, and the Martian atmosphere will support an active water cycle even at low obliquity.

  19. Simultaneous observations of sun-aligned polar cap arcs in both hemispheres by EXOS-C and viking

    SciTech Connect

    Obara, T.; Kitayama, M.; Mukai, T.; Kaya, N.; Murphree, J.S.; Cogger, L.L.

    1988-07-01

    On September 25, 1986, the EXOS-C satellite traversed an intense electron precipitation in the southern polar cap, while the Viking satellite simultaneously obtained image data of the polar cap arc in the northern hemisphere. The energy spectrum of the precipitation, measured by instrumentation aboard EXOS-C, was very similar to that of adjacent (typical) auroral arcs, and the precipitation in the southern polar cap was observed in the same local time sector in which the arc was found in the northern polar cap. Observations seem to support the view that the polar cap arc occurs on closed field lines and is conjugate in both hemispheres. copyright American Geophysical Union 1988

  20. Seasonal aldedo variations on the Martian north polar cap as seen by MGS

    NASA Technical Reports Server (NTRS)

    Hale, Amy S.; Bass, Deborah S; Tamppari, Leslie K.

    2003-01-01

    The Viking Orbiters determined that the surface of Mars' northern redisual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain.

  1. The Mars water cycle at other epochs - Recent history of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1993-01-01

    A numerical model is presented of the integrated role of seasonal water cycle on the evolution of polar deposits on Mars over the last 10 million years. From the model, it is concluded that the only major difference between the polar caps which affects their long-term behavior is ultimately the difference in their elevations. Because of that difference, there is a preference for CO2 frost to stay longer on the northern polar cap. The average difference in sublimation at the caps results in a net south-to-north transport of water ice over long time scales. Superimposed on any long-term behavior is a transfer of water ice between the caps on the 10 exp 5 - 10 exp 6 yr time scales. The amount of water exchanged is small compared to the total ice content of the polar deposits.

  2. Pair Cascades and Deathlines in Magnetic Fields with Offset Polar Caps

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alex G.

    2012-01-01

    We present results of electron-positron pair cascade simulations in a dipole magnetic field whose polar cap is offset from the dipole axis. In such a field geometry, the polar cap is displaced a small fraction of the neutron star radius from the star symmetry axis and the field line radius of curvature is modified. Using the modified parallel electric field near the offset polar cap, we simulate pair cascades to determine the pair deathlines and pair multiplicities as a function of the offset. We find that the pair multiplicity can change dr;unatically with a modest offset, with a significant increase on one side of the polar cap. Lower pair deathlines allow a larger fraction of the pulsar population, that include old and millisecond pulsars, to produce cascades with high multiplicity. The results have some important implications for pulsar particle production, high-energy emission and cosmic-ray contribution.

  3. CO_2 Frost Halos on the South Polar Residual Cap of Mars

    NASA Astrophysics Data System (ADS)

    Becerra, P.; Byrne, S.; HiRISE Team

    2012-03-01

    We present observational analysis, and a numerical model to explain the formation of bright CO_2 frost halos seen by HiRISE on the edges of scarps and "swiss cheese" features in the south polar residual cap of Mars.

  4. Polar cap electric field distributions related to the interplanetary magnetic field direction

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.

    1972-01-01

    The correlations between the azimuthal direction of the interplanetary magnetic field and the most simple polar cap signatures are discussed. Only the spatial distribution of the dawn-dusk polar cap field is considered. For each OGO 6 traverse across the northern or southern polar cap, the simultaneous values of the interplanetary magnetic field in solar-equatorial coordinates were recorded by the Explorer 33 magnetometer. Histograms of these values are presented and are discussed. The high degree of correlation with the longitudinal angle indicates that the relative geometry of the interplanetary magnetic field and magnetospheric magnetic fields must be fundamental to explaining the distribution of polar cap electric fields. The sign of the solar-equatorial component perpendicular to the sun-earth line appears to be a more critical parameter than the sign of the component toward the sun. The Svalgaard-Mansurov correlation and the correspondence between fast convection and parallel magnetospheric and interplanetary magnetic fields are described.

  5. Comparison of polar cap potential drops estimated from solar wind and ground magnetometer data - CDAW 6

    NASA Technical Reports Server (NTRS)

    Reiff, P. H.; Spiro, R. W.; Wolf, R. A.; Kamide, Y.; King, J. H.

    1985-01-01

    It is pointed out that the maximum electrostatic potential difference across the polar cap, Phi, is a fundamental measure of the coupling between the solar wind and the earth's magnetosphere/ionosphere sytem. During the Coordinated Data Analysis Workshop (CDAW) 6 intervals, no suitably instrumented spacecraft was in an appropriate orbit to determine the polar-cap potential drop directly. However, two recently developed independent techniques make it possible to estimate the polar-cap potential drop for times when direct spacecraft data are not available. The present investigation is concerned with a comparison of cross-polar-cap potential drop estimates calculated for the two CDAW 6 intervals on the basis of these two techniques. In the case of one interval, the agreement between the potential drops and Joule heating rates is relatively good. In the second interval, however, the agreement is not very good. Explanations for this discrepancy are discussed.

  6. SeaWinds - Oceans, Land, Polar Regions

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The SeaWinds scatterometer on the QuikScat satellite makes global radar measurements -- day and night, in clear sky and through clouds. The radar data over the oceans provide scientists and weather forecasters with information on surface wind speed and direction. Scientists also use the radar measurements directly to learn about changes in vegetation and ice extent over land and polar regions.

    This false-color image is based entirely on SeaWinds measurements obtained over oceans, land, and polar regions. Over the ocean, colors indicate wind speed with orange as the fastest wind speeds and blue as the slowest. White streamlines indicate the wind direction. The ocean winds in this image were measured by SeaWinds on September 20, 1999. The large storm in the Atlantic off the coast of Florida is Hurricane Gert. Tropical storm Harvey is evident as a high wind region in the Gulf of Mexico, while farther west in the Pacific is tropical storm Hilary. An extensive storm is also present in the South Atlantic Ocean near Antarctica.

    The land image was made from four days of SeaWinds data with the aid of a resolution enhancement algorithm developed by Dr. David Long at Brigham Young University. The lightest green areas correspond to the highest radar backscatter. Note the bright Amazon and Congo rainforests compared to the dark Sahara desert. The Amazon River is visible as a dark line running horizontally though the bright South American rain forest. Cities appear as bright spots on the images, especially in the U.S. and Europe.

    The image of Greenland and the north polar ice cap was generated from data acquired by SeaWinds on a single day. In the polar region portion of the image, white corresponds to the largest radar return, while purple is the lowest. The variations in color in Greenland and the polar ice cap reveal information about the ice and snow conditions present.

    NASA's Earth Science Enterprise is a long-term research and technology program designed to

  7. On the interpretation of low-energy particle access to the polar caps

    NASA Technical Reports Server (NTRS)

    Michel, F. C.; Dessler, A. J.

    1975-01-01

    Neither particle access to the polar caps by motion along magnetospheric field lines connected to the interplanetary field (in the 'open' model) nor particle access to the polar caps by combined diffusive and convective motion across magnetospheric field lines (in the 'closed' model) adequately explains the available data. The fact that data exist that are difficult to interpret with one model does not automatically confirm the other model.

  8. Recession of Martian north polar cap - 1979-1980 Viking observations

    NASA Technical Reports Server (NTRS)

    James, P. B.

    1982-01-01

    The polar regression curve for the Martian northern polar cap, derived from Viking observations for the 1979-1980 regression, is discussed, and comparisons with previous regression curves are made. Differences in the curves may be due to dust storms affecting the deposition of the cap. It is not possible to unambiguously ascribe differences between the curves to dynamical effects, since detailed information on the longitudinal dependence, which was an uncontrolled variable, is not available.

  9. Martian circumpolar sulfate-rich deposits: sublimation tills derived from the North Polar Cap

    NASA Astrophysics Data System (ADS)

    Masse, M.; Bourgeois, O.; Le Mouélic, S.; Verpoorter, C.; Le Deit, L.

    2009-12-01

    The North Polar Cap of Mars is an accumulation of ice layers with various amounts of interstratified dust particles. A dune field surrounds this polar cap. On one of the densest part of this dune field, Olympia Undae, Langevin et al. (Science, 2005) have detected calcium-rich sulfates (gypsum). To constrain the origin of these gypsum deposits, we performed an integrated morphological, structural and compositional analyses of a key area where it is possible to see the circum-polar dune field, the surface of the ice cap and a cross-section through the ice cap. The mineralogical composition of this area is investigated by applying a spectral derivative method to data acquired by OMEGA and CRISM hyperspectral imaging spectrometers. These are compared to laboratory spectra of ice-gypsum mixtures in simulated martian pressure and temperature conditions. We find that dunes of the circumpolar field and dust interstratified in the ice cap have the same composition. Both contain gypsum. Landforms produced by sublimation of ice are also visible on dust-rich layers of the ice cap. We therefore infer that the superficial circumpolar dust deposits correspond to a sublimation till produced by the ice cap. Circumpolar gypsum-rich deposits thus derive directly from the ice cap. Gypsum crystals are released at the surface of the cap as the ice sublimes. This material is then reworked by winds and forms the circumpolar dunes. There are two hypotheses for the ultimate origin of the gypsum crystals. (1) Pre-existing gypsum crystals might have been deposited together with ice crystals during the formation of the ice cap. (2) Authigenic gypsum crystals might have grown within the ice cap by weathering of dust trapped in the ice. The second hypothesis is consistent with the existence of authigenic sulfate inclusions in terrestrial polar ice (Ohno et al., GRL, 2006) and with the formation process suggested by Niles et al. (Nature, 2009) for martian equatorial sulfates.

  10. IMF B(y) and day-night conductivity effects in the expanding polar cap convection model

    NASA Technical Reports Server (NTRS)

    Moses, J. J.; Gorney, D. J.; Siscoe, G. L.; Crooker, N. U.

    1987-01-01

    During southward B(z) periods the open field line region in the ionosphere (polar cap) expands due to increased dayside merging. Ionospheric plasma flow patterns result which can be classified by the sign of the interplanetary magnetic field (IMF) B(y) component. In this paper, a time-dependent ionospheric convection model is constructed to simulate these flows. The model consists of a spiral boundary with a gap in it. The sign of the IMF B(y) component determines the geometry of the gap. A potential is applied across the gap and distributed around the boundary. A flow results which enters the polar cap through the gap and uniformly pushes the boundary outward. Results of the model show that B(y) effects are greatest near the gap and virtually unnoticeable on the nightside of the polar cap. Adding a day-night ionospheric conductivity gradient concentrates the polar cap electric field toward dawn. The resulting flow curvature gives a sunward component that is independent of B(y). These patterns are shown to be consistent with published observations.

  11. The response of ionospheric convection in the polar cap to substorm activity

    NASA Technical Reports Server (NTRS)

    Lester, M.; Lockwood, M.; Yeoman, T. K.; Cowley, S. W. H.; Luehr, H.; Bunting, R.; Farrugia, C. J.

    1995-01-01

    We report multi-instrument observations during an isolated substorm on 17 October 1989. The European Incoherent Scatter (EISCAT) radar operated in the SP-UK-POLI mode measuring ionospheric convection at latitudes 71 deg Lambda - 78 deg Lambda. Sub-Auroral Magnetometer Network (SAMNET) and the EISCAT Magnetometer Cross provide information on the timing of substorm expansion phase onset and subsequent intensifications, as well as the location of the field aligned and ionospheric currents associated with the substorm current wedge. Interplanetary Monitoring Platform-8 (IMP-8) magnetic field data are also included. Evidence of a substorm growth phase is provided by the equatorward motion of a flow reversal boundary across the EISCAT radar field of view at 2130 MLT, following a southward turning of the interplanetary magnetic field (IMF). We infer that the polar cap expanded as a result of the addition of open magnetic flux in the tail lobes during this interval. The flow reversal boundary, which is a lower limit to the polar cap boundary, reached an invariant latitude equatorward of 71 deg Lambda by the time of the expansion phase onset. We conclude that the substorm onset region in the ionosphere, defined by the westward electrojet, mapped to a part of the tail radially earthward of the boundary between open and closed magnetic flux, the distant neutral line. Thus the substorm was not initiated at the distant neutral line, although there is evidence that it remained active during the expansion phase.

  12. Black carbon aerosols and the third polar ice cap

    SciTech Connect

    Menon, Surabi; Koch, Dorothy; Beig, Gufran; Sahu, Saroj; Fasullo, John; Orlikowski, Daniel

    2010-04-15

    Recent thinning of glaciers over the Himalayas (sometimes referred to as the third polar region) have raised concern on future water supplies since these glaciers supply water to large river systems that support millions of people inhabiting the surrounding areas. Black carbon (BC) aerosols, released from incomplete combustion, have been increasingly implicated as causing large changes in the hydrology and radiative forcing over Asia and its deposition on snow is thought to increase snow melt. In India BC emissions from biofuel combustion is highly prevalent and compared to other regions, BC aerosol amounts are high. Here, we quantify the impact of BC aerosols on snow cover and precipitation from 1990 to 2010 over the Indian subcontinental region using two different BC emission inventories. New estimates indicate that Indian BC emissions from coal and biofuel are large and transport is expected to expand rapidly in coming years. We show that over the Himalayas, from 1990 to 2000, simulated snow/ice cover decreases by {approx}0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is {approx}36%, similar to that simulated for 2000 to 2010. Spatial patterns of modeled changes in snow cover and precipitation are similar to observations (from 1990 to 2000), and are mainly obtained with the newer BC estimates.

  13. Centrifugal acceleration at high altitudes above the polar cap: A Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Abudayyeh, H. A.; Barghouthi, I. A.; Slapak, R.; Nilsson, H.

    2015-08-01

    A Monte Carlo simulation was used to study the outflow of O+ and H+ ions along three flight trajectories above the polar cap up to altitudes of about 15 RE. Barghouthi (2008) developed a model on the basis of altitude and velocity-dependent wave-particle interactions and a radial geomagnetic field which includes the effects of ambipolar electric field and gravitational and mirror forces. In the present work we improve this model to include the effect of the centrifugal force, with the use of relevant boundary conditions. In addition, the magnetic field and flight trajectories, namely, the central polar cap (CPC), nightside polar cap (NPC), and cusp, were calculated using the Tsyganenko T96 model. To simulate wave-particle interactions, the perpendicular velocity diffusion coefficients for O+ ions in each region were determined such that the simulation results fit the observations. For H+ ions, a constant perpendicular velocity diffusion coefficient was assumed for all altitudes in all regions as recommended by Nilsson et al. (2013). The effect of centrifugal acceleration was simulated by considering three values for the ionospheric electric field: 0 (no centrifugal acceleration), 50, and 100 mV/m. It was found that the centrifugal acceleration increases the parallel bulk velocity and decreases the parallel and perpendicular temperatures of both ion species at altitudes above about 4 RE. Centrifugal acceleration also increases the temperature anisotropy at high altitudes. At a given altitude, centrifugal acceleration decreases the density of H+ ions while it increases the density of O+ ions. This implies that with higher centrifugal acceleration more O+ ions overcome the potential barrier. It was also found that aside from two exceptions centrifugal acceleration has the same effect on the velocities of both ions. This implies that the centrifugal acceleration is universal for all particles. The parallel bulk velocities at a given value of ionospheric electric field

  14. The Mars water cycle at other epochs: History of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through the atmosphere, integrated over long timescales, must be the driving force behind the long-term evolution of the polar caps; clearly, this feeds back into the evolution of the layered terrain. We have investigated the behavior of the seasonal water cycle and the net integrated behavior at the pole for the last 10 exp 7 years. Our model of the water cycle includes the solar input, CO2 condensation and sublimation, and summertime water sublimation through the seasonal cycles, and incorporates the long-term variations in the orbital elements describing the Martian orbit.

  15. Observations of aspect sensitive RF-enhanced incoherent backscatter in the polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Dhillon, Ranvir; Robinson, T. R.; Yeoman, Timothy K.

    RF-induced plasma instabilities give rise to characteristic spectral enhancements in incoherent scatter spectra. The aspect sensitivity of these enhancements provides valuable information regarding the physical processes that occur within the RF-affected ionospheric patch. These direction-dependent signatures exhibit significant variability and help shed light on possible coupling between artificial field-aligned irregularities generated at the upper-hybrid height and RF-induced instabilities excited near the reflection height for O-mode-polarized radio waves. This directional dependence of RF-enhanced incoherent radar backscatter has been shown using data from the high-latitude ionosphere, and the significant features included consistent field-aligned signatures that may be related to the presence of artificial field-aligned irregularities. These earlier high-latitude results provided motivation for repeating the investigation in the different geophysical conditions that obtain in the polar cap ionosphere. The Space Plasma Exploration by Active Radar (SPEAR) facility is located within the polar cap and has provided observations of RF-enhanced ion and plasma line spectra recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. We present observations of aspect sensitive E-and F-region SPEAR-induced ion and plasma line enhance-ments from several directions in the magnetic meridian plane, centred on field-aligned. These enhancements indicate excitation of both the purely growing mode and the parametric decay instability, together with sporadic E-layer results that may indicate the presence of cavitons. We note consistent enhancements from field-aligned, vertical and also from 5 degrees south of field-aligned. We attribute the prevalence of vertical scatter to the importance of the Spitze region, and of that from field-aligned to possible wave/irregularity coupling.

  16. Structures in Ionospheric Number Density and Velocity Associated with Polar Cap Ionization Patches

    NASA Technical Reports Server (NTRS)

    Kivanc, O.; Heelis, R. A.

    1997-01-01

    Spectral characteristics of polar cap F region irregularities on large density gradients associated with polar ionization patches are studied using in situ measurements made by the Dynamics Explorer 2 (DE 2) spacecraft. The 18 patches studied in this paper were identified by the algorithm introduced by Coley and Heelis, and they were encountered during midnight-noon passes of the spacecraft. Density and velocity spectra associated with these antisunward convecting patches are analyzed in detail. Observations indicate the presence of structure on most patches regardless of the distance between the patch and the cusp where they are believed to develop. Existence of structure on both leading and trailing edges is established when such edges exist. Results, which show no large dependence of Delta N/N power on the sign of the edge gradient del N, do not allow the identification of leading and trailing edges of the patch. The Delta N/N is an increasing function of gradient del N regardless of the sign of the gradient. The correlation between Delta N/N and Delta V is generally poor, but for a given intensity in Delta V, Delta N/N maximizes in regions of large gradients in N. There is evidence for the presence of unstructured patches that seem to co-exist with unstructured horizontal velocities. Slightly smaller spectral indices for trailing edges support the presence of the E X B drift instability. Although this instability is found to be operating in some cases, results suggest that stirring may be a significant contributor to kilometer-size structures in the polar cap.

  17. Transient bright "halos" on the South Polar Residual Cap of Mars: Implications for mass-balance

    NASA Astrophysics Data System (ADS)

    Becerra, Patricio; Byrne, Shane; Brown, Adrian J.

    2015-05-01

    Spacecraft imaging of Mars' south polar region during mid-southern summer of Mars year 28 (2007) observed bright halo-like features surrounding many of the pits, scarps and slopes of the heavily eroded carbon dioxide ice of the South Polar Residual Cap (SPRC). These features had not been observed before, and have not been observed since. We report on the results of an observational study of these halos, and spectral modeling of the SPRC surface at the time of their appearance. Image analysis was performed using data from MRO's Context Camera (CTX), and High Resolution Imaging Science Experiment (HiRISE), as well as images from Mars Global Surveyor's (MGS) Mars Orbiter Camera (MOC). Data from MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) were used for the spectral analysis of the SPRC ice at the time of the halos. These data were compared with a Hapke reflectance model of the surface to constrain their formation mechanism. We find that the unique appearance of the halos is intimately linked to a near-perihelion global dust storm that occurred shortly before they were observed. The combination of vigorous summertime sublimation of carbon dioxide ice from sloped surfaces on the SPRC and simultaneous settling of dust from the global storm, resulted in a sublimation wind that deflected settling dust particles away from the edges of these slopes, keeping these areas relatively free of dust compared to the rest of the cap. The fact that the halos were not exhumed in subsequent years indicates a positive mass-balance for flat portions of the SPRC in those years. A net accumulation mass-balance on flat surfaces of the SPRC is required to preserve the cap, as it is constantly being eroded by the expansion of the pits and scarps that populate its surface.

  18. Ir Spectral Mapping of the Martian South Polar Residual CAP Using Crism

    NASA Astrophysics Data System (ADS)

    Campbell, Jacqueline; Sidiropoulos, Panagiotis; Muller, Jan-Peter

    2016-06-01

    Polycyclic aromatic hydrocarbons (PAHs) are considered to be important in theories of abiogenesis (Allamandola, 2011) . There is evidence that PAHs have been detected on two icy Saturnian satellites using the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft (Cruikshank et al., 2007). The hypothesised presence of PAHs in Mars south polar cap has not been systematically examined even though the Mars south polar cap may allow the preservation of organic molecules that are typically destroyed at the Martian surface by UV radiation (Dartnell et al. 2012). This hypothesis is supported by recent analyses of South Polar Residual Cap (SPRC) structural evolution (Thomas et al., 2009) that suggest the possibility that seasonal and long term sublimation may excavate dust particles from within the polar ice. Periodic sublimation is believed to be responsible for the formation of so-called "Swiss Cheese Terrain", a unique surface feature found only in the Martian south polar residual cap consisting of flat floored, circular depressions (Byrne, 2009). We show the first examples of work towards the detection of PAHs in Swiss Cheese Terrain, using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA's Mars Reconnaissance Orbiter (MRO). CRISM is designed to search for mineralogical indications of past and present water, thus providing extensive coverage of the south polar cap. In this work, we discuss whether CRISM infrared spectra can be used to detect PAHs in Swiss Cheese Terrain and demonstrate a number of maps showing shifts in spectral profiles over the SPRC.

  19. Yearly Comparisons of the Mars North Polar Cap: 1999, 2001, and 2003 MOC Observations

    NASA Technical Reports Server (NTRS)

    Benson, J. L.; James, P. B.

    2003-01-01

    The seasonal cycle of the martian north polar cap has been studied since the time of William Herschel, who published the first quantitative observations of the seasonal recession of the polar caps in 1784. Ground-based observations made after Herschel were summarized by Slipher in 1962. More recent ground-based observations of the north polar cap have been done by Iwasaki et al. Mariner 9 and Viking also made north polar observations. Cantor et al. used Hubble Space Telescope observations between 1990 and 1997 to determine several north polar recessions and Lambert albedos of the cap. Mars Global Surveyor went into orbit around Mars in September 1997. The wide-angle cameras on the Mars Orbiter Camera (MOC) acquire images of the entire planet every day at a resolution of approx. 7.5 km/pixel in both red (575 nm - 625 nm) and blue (400 nm - 450 nm) bandpasses (WAR and WAB). Some polar cap observations were acquired during the aerobraking (AB) and science phasing (SPO) of MGS before systematic mapping began in March, 1999 at Ls = 110 .

  20. Mars Climate Orbiter's Investigation of the Atmosphere and Polar Caps

    NASA Technical Reports Server (NTRS)

    McCleese, D. J.; Moroz, V.; Schofield, T.; Taylor, F.; Zurek, R.

    1999-01-01

    The Mars Climate Orbiter (MCO) is now on its way to Mars. It carries an atmospheric sounder whose observations will provide a continuous, global data set on weather and climate for a full Martian year. This paper describes the observation strategy and anticipated results from the Pressure Modulator Infrared Radiometer (PMIRR). PMIRR will measure vertical profiles of atmospheric infrared radiance in the 7 to 50 micron wavelength region extending from the surface of Mars to 80-km altitude. The observations have a vertical resolution of 5 km, or one-half the atmospheric scale height. From these radiance profiles we will retrieve profiles of atmospheric temperature, pressure, and the amounts of dust, condensates and water vapor. In addition, PMIRR will measure the radiative balance of the polar regions of Mars in an effort to better understand the short-term climate variability of the planet. The information obtained with PMIRR on MCO will be complementary to data obtained by the Thermal Emission Spectrometer (TES) and Radio Science (RS) experiments on the Mars Global Surveyor. A major emphasis of our research will be the assimilation of PMIRR data into numerical models of the Martian atmosphere. Assimilation schemes, of which several are currently in development, will permit the extension of measurements to spatial and temporal scales and to phenomena (e.g. winds) not observed directly by PMIRR.

  1. Dynamics of Saturn's polar regions

    NASA Astrophysics Data System (ADS)

    Antuñano, A.; Río-Gaztelurrutia, T.; Sánchez-Lavega, A.; Hueso, R.

    2015-02-01

    We analyze data retrieved by the imaging science system onboard the Cassini spacecraft to study the horizontal velocity and vorticity fields of Saturn's polar regions (latitudes 60-90°N in June-December 2013 and 60-90°S in October 2006 and July-December 2008), including the northern region where the hexagonal wave is prominent. With the aid of an automated two-dimensional correlation algorithm we determine two-dimensional maps of zonal and meridional winds and deduce vorticity maps. We extract zonal averages of zonal winds, providing wind profiles that reach latitudes as high as 89.5° in the south and 89.9° in the north. Wind measurements cover the intense polar cyclonic vortices that reach similar peak velocities of 150 m s-1 at ±88.5°. The hexagonal wave lies in the core of an intense eastward jet at planetocentric latitude 75.8°N with motions that become nonzonal at the hexagonal feature. In the south hemisphere the peak of the eastward jet is located at planetocentric latitude 70.4°S. A large anticyclone (the south polar spot, SPS), similar to the north polar spot (NPS) observed at the Voyager times (1980-1981), has been observed in images from April 2008 to January 2009 in the south polar region at latitude -66.1° close to the eastward jet. The SPS does not apparently excite a wave on the jet. We analyze the stability of the zonal jets, finding potential instabilities at the flanks of the eastward jets around 70°, and we measure the eddy wind components, suggesting momentum transfer from eddy motion to the westward jets closer to the poles.

  2. Water-ice clouds in the Martian North Polar Region

    NASA Astrophysics Data System (ADS)

    Tamppari, L. K.; Qu, Z.; Smith, M. D.; Bass, D. S.; Hale, A. S.

    2004-11-01

    There has been uncertainty about the amount of water cycling in and out of the polar region during the northern spring/summer timeframe, as evidenced by visible brightness changes in the residual polar cap from year to year which were originally though to be interannual variations (James and Martin, 1995; Kieffer, 1990). Subsequently, through comparison of Viking and Mariner 9 data sets, these variations were thought to be late season water deposition (Bass et al., 2000: Bass and Paige, 2000), perhaps in the form of direct condensation or snowfall. More recently, examination of multi-year MGS MOC data (Hale et al., 2004) opens this question again. Water cycling can be assessed using data sets by examination of water vapor, polar cap changes, and water-ice clouds. In this presentation, we examine the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) nadir pointed data in the north polar region of Mars during northern spring and summer to find and map water-ice clouds. Water-ice clouds, in the north polar region, have previously been tentatively identified in the Viking data (Tamppari and Bass, 2000), and some water-ice clouds identifications have been made in the north polar region during the MGS era (M. Smith, pers. comm., 2001). We present our results of water-ice clouds for 3 Mars years' spring and summer times, including opacities, spatial and temporal variations.

  3. Identifying Surface Changes on HRSC Images of the Mars South Polar Residual CAP (sprc)

    NASA Astrophysics Data System (ADS)

    Putri, Alfiah Rizky Diana; Sidiropoulos, Panagiotis; Muller, Jan-Peter

    2016-06-01

    The surface of Mars has been an object of interest for planetary research since the launch of Mariner 4 in 1964. Since then different cameras such as the Viking Visual Imaging Subsystem (VIS), Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC), and Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) have been imaging its surface at ever higher resolution. The High Resolution Stereo Camera (HRSC) on board of the European Space Agency (ESA) Mars Express, has been imaging the Martian surface, since 25th December 2003 until the present-day. HRSC has covered 100 % of the surface of Mars, about 70 % of the surface with panchromatic images at 10-20 m/pixel, and about 98 % at better than 100 m/pixel (Neukum et. al., 2004), including the polar regions of Mars. The Mars polar regions have been studied intensively recently by analysing images taken by the Mars Express and MRO missions (Plaut et al., 2007). The South Polar Residual Cap (SPRC) does not change very much in volume overall but there are numerous examples of dynamic phenomena associated with seasonal changes in the atmosphere. In particular, we can examine the time variation of layers of solid carbon dioxide and water ice with dust deposition (Bibring, 2004), spider-like channels (Piqueux et al., 2003) and so-called Swiss Cheese Terrain (Titus et al., 2004). Because of seasonal changes each Martian year, due to the sublimation and deposition of water and CO2 ice on the Martian south polar region, clearly identifiable surface changes occur in otherwise permanently icy region. In this research, good quality HRSC images of the Mars South Polar region are processed based on previous identification as the optimal coverage of clear surfaces (Campbell et al., 2015). HRSC images of the Martian South Pole are categorized in terms of quality, time, and location to find overlapping areas, processed into high quality Digital Terrain

  4. 24/7 Solar Minimum Polar Cap and Auroral Ion Temperature Observations

    NASA Technical Reports Server (NTRS)

    Sojka, Jan J.; Nicolls, Michael; van Eyken, Anthony; Heinselman, Craig; Bilitza, Dieter

    2011-01-01

    During the International Polar Year (IPY) two Incoherent Scatter Radars (ISRs) achieved close to 24/7 continuous observations. This presentation describes their data sets and specifically how they can provide the International Reference Ionosphere (IRI) a fiduciary E- and F-region ionosphere description for solar minimum conditions in both the auroral and polar cap regions. The ionospheric description being electron density, ion temperature and electron temperature profiles from as low as 90 km extending to several scale heights above the F-layer peak. The auroral location is Poker Flat in Alaska at 65.1 N latitude, 212.5 E longitude where the NSF s new Poker Flat Incoherent Scatter Radar (PFISR) is located. This location during solar minimum conditions is in the auroral region for most of the day but is at midlatitudes, equator ward of the cusp, for about 4-8 h per day dependent upon geomagnetic activity. In contrast the polar location is Svalbard, at 78.2 N latitude, 16.0 E longitude where the EISCAT Svalbard Radar (ESR) is located. For most of the day the ESR is in the Northern Polar Cap with a noon sector passage often through the dayside cusp. Of unique relevance to IRI is that these extended observations have enabled the ionospheric morphology to be distinguished between quiet and disturbed geomagnetic conditions. During the IPY year, 1 March 2007 - 29 February 2008, about 50 solar wind Corotating Interaction Regions (CIRs) impacted geospace. Each CIR has a two to five day geomagnetic disturbance that is observed in the ESR and PFISR observations. Hence, this data set also enables the quiet-background ionospheric climatology to be established as a function of season and local time. These two separate climatologies for the ion temperature at an altitude of 300 km are presented and compared with IRI ion temperatures. The IRI ion temperatures are about 200-300 K hotter than the observed values. However, the MSIS neutral temperature at 300 km compares favorably

  5. Comparison between the polar cap index, PC and the auroral electrojet indices AE, AL, and AU

    SciTech Connect

    Vennerstrom, S.; Friis-Christensen, E. ); Troshichev, O.A.; Andresen, V.G. )

    1991-01-01

    The newly introduced index PC for magnetic activity in the polar cap has been examined to establish to which extent it can serve as an indicator of auroral electrojet activity. PC is derived from a single nearpole station, as a 15-min average index. The authors have derived it for two stations, one in the northern hemisphere (Thule) and one in the southern hemisphere (Vostok). The simplicity of the PC index enables us to make a large data base for statistical investigations. They have thus used 7 years of PC values for the two stations to analyze the relationship between PC and the auroral zone indices AE, AU, and AL statistically. They find a very high correlation between PC and AE during winter and equinox, the linear correlation coefficient being {approximately} 0.8-0.9 for Thule and {approximately} 0.7-0.8 for Vostok. During summer the correlation is less because the PC index is then disturbed by polar cap currents controlled by the northward and east-west components of the interplanetary magnetic field. They therefore stress the importance of having PC available from both the northern and southern hemisphere. From event studies they find that PC is sensitive both to DP 2 type electrojet activity and to substorm intensifications of the westward electrojet in the midnight or postmidnight sector but less sensitive to substorm intensifications of the westward electrojet in the midnight or post midnight sector. They conclude that PC can serve as a fast available indicator of DP 2 and DP 1 activity in the polar regions, excluding intrusions of the westward electrojet in the premidnight sector.

  6. A complicated evolution of a newly created Polar Cap Ionization Patch

    NASA Astrophysics Data System (ADS)

    Zhang, Q. H.; Moen, J. I.; Lockwood, M. M.; Zhang, B.; Zong, Q.; Zhang, S.; Ruohoniemi, J. M.; Thomas, E. G.; Dunlop, M. W.; Liu, R.; Yang, H. G.; Hu, H.; Lester, M.

    2014-12-01

    Polar cap patches is a common phenomenon in the Earth polar ionosphere. They are associated with turbulent instabilities giving rise to severe disturbances to High Frequency (HF) radio communications, over-the-horizon radar location errors, and disruption and errors to satellite navigation and communication systems. Their formation and evolution are still poorly understood, particularly under disturbed space weather conditions, and there is not yet established any forecasting tool to predict their occurrence. Here we report the first direct and continuous monitoring of a complicated evolution of a newly created patch during a geomagnetic storm. The observations reveal that the patch was segmented from the high density "tongue" of ionization (TOI) by a subauroral polarization stream (SAPS) near the polar cap boundary associated with a substorm . The patch did not follow the expected route across the polar cap from dayside to nightside, but instead was halted by a local disturbance in the polar cap due to a rapidly changing in interplanetary magnetic field (IMF) condition and evolved in a particular way with quickly fading associated with the high-latitude lobe reconnection. These results give essential new insight into the formation of the patches and their evolution as controlled by the IMF, and offer a key opportunity for improving polar ionospheric modeling and Global Navigation Satellite System (GNSS) scintillation and space weather forecasts.

  7. O+ and H+ above the polar cap: Observations and semikinetic simulations

    NASA Astrophysics Data System (ADS)

    Barghouthi, I. A.; Abudayyeh, H. A.; Slapak, R.; Nilsson, H.

    2016-01-01

    A one-dimensional direct simulation Monte Carlo model is used to study the outflow of O+ and H+ ions from 1.2 RE to 15.2 RE along two flight trajectories originating from the polar cap, namely, the central polar cap (CPC) and the cusp. To study the effect of varying geophysical conditions and to deduce the proper set of parameters, several parameters were varied, and the results were compared to corresponding data from Cluster spacecraft. First, several sets of diffusion coefficients were considered based on using diffusion coefficients calculated by Barghouthi et al. (1998), Nilsson et al. (2013), and Abudayyeh et al. (2015b) for different altitude intervals. It was found that in the central polar cap using the diffusion coefficients reported by Barghouthi et al. (1998) for altitudes lower than 3.7 RE, zero diffusion coefficients between 3.7 and 7.5 RE and diffusion coefficients from Nilsson et al. (2013) for altitudes higher than 7.5 RE provide the best fit for O+ ions. For O+ ions in the cusp the best fit was obtained for using Barghouthi et al. (1998) diffusion coefficients for altitudes lower than 3.7 RE and Nilsson et al. (2013) diffusion coefficients for altitudes higher than that. The best fit for H+ ions in both regions was obtained by using the diffusion coefficients calculated by Abudayyeh et al. (2015b). Also, it was found that along an ion's trajectory the most recent heating dominates. Second, the strength of centrifugal acceleration was varied by using three values for the ionospheric electric field, namely, 0, 50, and 100 MV/m. It was found that the value of 50 MV/m provided the best fit for both ion species in both regions. Finally, the lower altitude boundary conditions and the electron temperature were varied. Increasing the electron temperature and the lower altitude O+ parallel velocity were found to increase the access of O+ ions to higher altitudes and therefore increase the density at a given altitude. The variation of all other boundary

  8. Mars south polar spring and summer behavior observed by TES: seasonal cap evolution controlled by frost grain size

    USGS Publications Warehouse

    Kieffer, Hugh H.; Titus, Timothy N.; Mullins, Kevin F.; Christensen, Philip R.

    2000-01-01

    Thermal Emission Spectrometer (TES) observations of the recession phase of Mars' south polar cap are used to quantitatively map this recession in both thermal and visual appearance. Geographically nonuniform behavior interior to the cap is characterized by defining several small regions which exemplify the range of behavior. For most of the cap, while temperatures remain near the CO2 frost point, albedos slowly increase with the seasonal rise of the Sun, then drop rapidly as frost patches disappear over a period of ∼20 days. A “Cryptic” region remains dark and mottled throughout its cold period. TES observations are compared with first-order theoretical spectra of solid CO2 frost with admixtures of dust and H2O. The TES spectra indicate that the Cryptic region has much larger grained solid CO2 than the rest of the cap and that the solid CO2 here may be in the form of a slab. The Mountains of Mitchel remain cold and bright well after other areas at comparable latitude, apparently as a result of unusually small size of the CO2 frost grains; we found little evidence for a significant presence of H2O. Although CO2 grain size may be the major difference between these regions, incorporated dust is also required to match the observations; a self-cleaning process carries away the smaller dust grains. Comparisons with Viking observations indicate little difference in the seasonal cycle 12 Martian years later. The observed radiation balance indicates CO2 sublimation budgets of up to 1250 kg m−2. Regional atmospheric dust is common; localized dust clouds are seen near the edge of the cap prior to the onset of a regional dust storm and interior to the cap during the storm.

  9. Sunlight penetration through the Martian polar caps: Effects on the thermal and frost budgets

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

  10. Sunlight penetration through the Martian polar caps - Effects on the thermal and frost budgets

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard L.

    1992-01-01

    An energy balance model of the seasonal polar caps on Mars is modified to include penetration of solar radiation into and through the ice. Penetration of solar radiation has no effect on subsurface temperature or total frost sublimation if seasonal ice overlies a dust surface. An effect is noted for seasonal ice which overlies the residual polar caps. For the case of an exposed water-ice residual polar cap, the temperature at depth is calculated to be up to several degrees warmer, and the calculated lifetime of seasonal CO2 frost is slightly lower when penetration of sunlight is properly treated in the model. For the case of a residual polar cap which is perennially covered by CO2 frost, the calculated lifetime of seasonal CO2 frost is very slightly increased as a result of sunlight penetration through the ice. Hence, penetration of sunlight into the ice helps to stabilize the observed dichotomy in the residual polar caps on Mars, although it is a small effect.

  11. Martian Polar Caps: Folding, Faulting, Flowing Glaciers of Multiple Interbedded Ices

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    2001-12-01

    The Martian south polar cap (permanent CO2 cap and polar layered deposits), exhibit abundant, varied, and widespread deformational phenomena. Folding and boudinage are very common. Strike-slip or normal faults are rarer. Common in the vicinity of major troughs and scarps are signs of convergent flow tectonics manifested as wrinkle-ridge-like surface folds, thrust faults, and viscous forebulges with thin-skinned extensional crevasses and wrinkle-ridge folds. Such flow convergence is predicted by theory. Boudinage and folding at the 300-m wavelength scale, indicating rheologically contrasting materials, is widely exposed at deep levels along erosional scarps. Independent morphologic evidence indicates south polar materials of contrasting volatility. Hence, the south polar cap appears to be a multiphase structure of interbedded ices. The north polar cap locally also exhibits flow indicators, though they are neither as common nor as varied as in the south. The large-scale quasi-spiral structure of the polar caps could be a manifestation of large-scale boudinage. According to this scenario, deep-level boudinage continuously originates under the glacial divide (the polar cap summit). Rod-like boudin structures are oriented transverse to flow and migrate outward with the large-scale flow field. Troughs develop over areas between major boudins. A dynamic competition, and possibly a rough balance, develops between the local flow field in the vicinity of a trough (which tends to close the trough by lateral closure and upwelling flow) and sublimation erosion (which tends to widen and deepen them). Over time, the troughs flow to the margins of the polar cap where they, along with other polar structures, are destroyed by sublimation. Major ice types contributing to rheological and volatility layering may include, in order of highest to lowest mechanical strength, CO2 clathrate hydrate, water ice containing inert/insoluble dust, pure water ice, water ice containing traces of

  12. Azimuthal Structure of the Sand Erg that Encircles the North Polar Water-Ice Cap

    NASA Astrophysics Data System (ADS)

    Teodoro, L. A.; Elphic, R. C.; Eke, V. R.; Feldman, W. C.; Maurice, S.; Pathare, A.

    2011-12-01

    The sand erg that completely encircles the perennial water-ice cap that covers the Martian north geographic pole displays considerable azimuthal structure as seen in visible and near-IR images. Much of this structure is associated with the terminations of the many steep troughs that cut spiral the approximately 3 km thick polar ice cap. Other contributions come from the katabatic winds that spill over steep-sided edges of the cap, such as what bounds the largest set of dunes that comprise Olympia Undae. During the spring and summer months when these winds initiate from the higher altitudes that contain sublimating CO2 ice, which is very cold and dry, heat adiabatically when they compress as they lose altitude. These winds should then remove H2O moisture from the uppermost layer of the sand dunes that are directly in their path. Two likely locations where this desiccation may occur preferentially is at the termination of Chasma Boreale and the ice cap at Olympia Undae. We will search for this effect by sharpening the spatial structure of the epithermal neutron counting rates measured at northern high latitudes using the Mars Odyssey Neutron Spectrometer (MONS). The epithermal range of neutron energies is nearly uniquely sensitive to the hydrogen content of surface soils, which should likely be in the form of H2O/OH molecules/radicals. We therefore convert epithermal counting rates in terms of Water-Equivalent-Hydrogen, WEH. However, MONS counting-rate data have a FWHM of ~550 km., which is sufficiently broad to prevent a close association of WEH variability with images of geological features. In this study, we reduce spurious features in the instrument smeared neutron counting rates through deconvolution. We choose the PIXON numerical deconvolution technique for this purpose. This technique uses a statistical approach (Pina 2001, Eke 2001), which is capable of removing spurious features in the data in the presence of noise. We have previously carried out a detailed

  13. Recession of Martian north polar cap - 1977-1978 Viking observations

    NASA Technical Reports Server (NTRS)

    James, P. B.

    1979-01-01

    The regression curve for the 1977-1978 sublimation of the north polar cap of Mars is extracted from Viking orbiter imaging data. The recession observed during the spring season is quite consistent with previous observations and is in excellent agreement with telescopic data obtained concurrently. A receding late winter boundary is identified, but owing to hood obscuration this boundary cannot be definitely attributed to a surface cap.

  14. Polar cap patches and the tongue of ionization: A survey of GPS TEC maps from 2009 to 2015

    NASA Astrophysics Data System (ADS)

    David, Michael; Sojka, J. J.; Schunk, R. W.; Coster, A. J.

    2016-03-01

    The source and structuring mechanisms for F region density patches have been subjects of speculation and debate for many years. We have made a survey of mappings of total electron content (TEC) between the years 2009 and 2015 from the web-based Madrigal data server in order to determine when patches and/or a tongue of ionization (TOI) have been present in the Northern Hemisphere polar cap; we find that there is a UT and seasonal dependence that follows a specific pattern. This finding sheds considerable light upon the old question of the source of polar cap patches, since it virtually eliminates potential patch plasma sources that do not have a UT/seasonal dependence, for example, particle precipitation or flux transfer events. We also find that the frequency of occurrence of patches or TOIs has little to do with the level of geomagnetic activity.

  15. RGS Proteins and Septins Cooperate to Promote Chemotropism by Regulating Polar Cap Mobility

    PubMed Central

    Kelley, Joshua B; Dixit, Gauri; Sheetz, Joshua B; Venkatapurapu, Sai Phanindra; Elston, Timothy C; Dohlman, Henrik G

    2014-01-01

    Summary Background Septins are well known to form a boundary between mother and daughter cells in mitosis, but their role in other morphogenic states is poorly understood. Results Using microfluidics and live cell microscopy, coupled with new computational methods for image analysis, we investigated septin function during pheromone-dependent chemotropic growth in yeast. We show that septins colocalize with the regulator of G-protein signaling (RGS) Sst2, a GTPase-activating protein that dampens pheromone receptor signaling. We show further that the septin structure surrounds the polar cap, ensuring that cell growth is directed toward the source of pheromone. When RGS activity is abrogated, septins are partially disorganized. Under these circumstances the polar cap travels toward septin structures and away from sites of exocytosis, resulting in a loss of gradient tracking. Conclusion Septin organization is dependent on RGS protein activity. When assembled correctly, septins promote turning of the polar cap and proper tracking of a pheromone gradient. PMID:25601550

  16. Water Cycling in the North Polar Region of Mars

    NASA Technical Reports Server (NTRS)

    Tamppari, L. K.; Smith, M. D.; Bass, D. S.

    2003-01-01

    To date, there has been no comprehensive study to understand the partitioning of water into vapor and ice clouds, and the associated effects of dust and surface temperature in the north polar region. Ascertaining the degree to which water is transported out of the cap region versus within the cap region will give much needed insight into the overall story of water cycling on a seasonal basis. In particular, understanding the mechanism for the polar cap surface albedo changes would go along way in comprehending the sources and sinks of water in the northern polar region. We approach this problem by examining Thermal Emission Spectrometer (TES) atmospheric and surface data acquired in the northern summer season and comparing it to Viking data when possible. Because the TES instrument spans the absorption bands of water vapor, water ice, dust, and measures surface temperature, all three aerosols and surface temperature can be retrieved simultaneously. This presentation will show our latest results on the water vapor, water-ice clouds seasonal and spatial distributions, as well as surface temperatures and dust distribution which may lend insight into where the water is going.

  17. Gamma-Ray Pulsar Light Curves in Offset Polar Cap Geometry

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; DeCesar, Megan; Miller, M. Coleman

    2011-01-01

    Recent studies have shown that gamma-ray pulsar light curves are very sensitive to the geometry of the pulsar magnetic field. Pulsar magnetic field geometries, such as the retarded vacuum dipole and force-free magnetospheres, used to model high-energy light curves have distorted polar caps that are offset from the magnetic axis in the direction opposite to rotation. Since this effect is due to the sweepback of field lines near the light cylinder, offset polar caps are a generic property of pulsar magnetospheres and their effects should be included in gamma-ray pulsar light curve modeling. In slot gap models (having two-pole caustic geometry), the offset polar caps cause a strong azimuthal asymmetry of the particle acceleration around the magnetic axis. We have studied the effect of the offset polar caps in both retarded vacuum dipole and force-free geometry on the model high-energy pulse profile. We find that. corn pared to the profile:-; derived from :-;ymmetric caps, the flux in the pulse peaks, which are caustics formed along the trailing magnetic field lines. increases significantly relative to the off-peak emission. formed along leading field lines. The enhanced contrast produces greatly improved slot gap model fits to Fermi pulsar light curves like Vela, which show very little off-peak emIssIon.

  18. A simple model for polar cap convection patterns and generation of theta auroras

    NASA Technical Reports Server (NTRS)

    Lyons, L. R.

    1985-01-01

    An addition of the uniform interplanetary magnetic field and the earth's dipole magnetic field is used to evaluate electric field convection patterns over the polar caps that result from solar wind flow across open geomagnetic field lines. The model also accounts for field-aligned patterns within, and auroral arcs across, the polar cap. The qualitative predictions derived from the model express the electric field magnitudes, aurora intensity, sunward and antisunward flow, and the dusk-side reversal of the convection field in terms of the x and y components of the interplanetary magnetic field.

  19. The Mars water cycle at other epochs: Recent history of the polar caps and layered terrain

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

    1992-01-01

    The Martian polar caps and layered terrain presumably evolves by the deposition and removal of small amounts of water and dust each year, the current cap attributes therefore represent the incremental transport during a single year as integrated over long periods of time. The role was studied of condensation and sublimation of water ice in this process by examining the seasonal water cycle during the last 10(exp 7) yr. In the model, axial obliquity, eccentricity, and L sub s of perihelion vary according to dynamical models. At each epoch, the seasonal variations in temperature are calculated at the two poles, keeping track of the seasonal CO2 cap and the summertime sublimation of water vapor into the atmosphere; net exchange of water between the two caps is calculated based on the difference in the summertime sublimation between the two caps (or on the sublimation from one cap if the other is covered with CO2 frost all year). Results from the model can help to explain (1) the apparent inconsistency between the timescales inferred for layer formation and the much older crater retention age of the cap and (2) the difference in sizes of the two residual caps, with the south being smaller than the north.

  20. 3-D Radar Imaging Reveals Deep Structures and Buried Craters Within the Martian Polar Caps

    NASA Astrophysics Data System (ADS)

    Putzig, N. E.; Foss, F. J., II; Campbell, B. A.; Phillips, R. J.; Smith, I. B.

    2015-12-01

    We use Shallow Radar (SHARAD) observations on thousands of orbital passes by the Mars Reconnaissance Orbiter to produce fully imaged 3-D data volumes encompassing both polar ice caps of Mars. Greatly clarifying the view of subsurface features, a completed volume for Planum Boreum provides new constraints on the nature and timing of emplacement of the northern polar deposits and their relationship to climate. The standard method of mapping subsurface features with single-pass 2-D radargrams has been very fruitful (see Brothers et al. 2015, JGR 120 in press, and references therein), but a full assessment of internal structures has been hindered by interfering off-nadir echoes from spiral troughs and other variable topography prevalent on both caps. By assembling the SHARAD radargrams into a volume and applying a 3-D imaging process (migration) borrowed from seismic processing techniques, we enhance the signal-to-noise ratio while repositioning the echoes to their proper locations, thereby unraveling the interference. As part of the process, we correct ionospheric distortions and delays of the radar echoes (Campbell et al. 2014, IEEE GRSL 11 #3). Interfaces painstakingly mapped in radargrams (e.g., the basal-unit surface, a buried chasma) are clearly visible in the 3-D volume, and new features are revealed. Structures may now be mapped through trough-rich regions, including a widespread sequence that provides corroborative evidence of recent ice ages (Smith et al. 2015, LPSC XLVI #2574). Distinctive radar signatures associated with known, partially buried craters also occur elsewhere in the volume but without surface expression. Presumably, these are fully buried craters that may provide a new means to estimate the age of the deposits. Preliminary work for Planum Australe demonstrates that the 3-D processing currently underway will illuminate deep structures that are broadly obfuscated in 2-D radargrams by a shallow scatterer (Campbell et al. 2015, LPSC XLVI #2366).

  1. Polar cap models of gamma-ray pulsars: Emision from single poles of nearly aligned rotators

    NASA Technical Reports Server (NTRS)

    Daugherty, Joseph K.; Harding, Alice K.

    1994-01-01

    We compare a new Monte Carlo simulation of polar cap models for gamma-ray pulsars with observations of sources detected above 10 MeV by the Compton Observatory (CGRO). We find that for models in which the inclination of the magnetic axis is comparable to the angular radius of the polar cap, the radiation from a single cap may exhibit a pusle with either a single broad peak as in PSR 1706-44 and PSR 1055-52, or a doubly peaked profile comparable to those observed from the Crab, Vela and Geminga pulsars. In general, double pulses are seen by observers whose line of sight penetrates into the cap interior and are due to enhanced emission near the rim. For cascades induced by culvature radiation, increased rim emission occurs even when electrons are accelerated over the entire cap, since electrons from the interior escape along magnetic field lines with less curvature and hence emit less radiation. However, we obtain better fits to the duty cycles of observed profiles if we make the empirical assumption that acceleration occurs only near the rim. In either case, the model energy spectra are consistent with most of the observed sources. The beaming factors expected from nearly aligned rotators, based on standard estimates for the cap radius, imply that their luminosities need not be as large as in the case of orthogonal rotators. However, small beam angles are also a difficutly with this model because they imply low detection probablities. In either case the polar cap radius is a critical factor, and in this context we point out that plasma loading of the field lines should make the caps larger than the usual estimates based on pure dipole fields.

  2. Thermosphere variation at different altitudes over the northern polar cap during magnetic storms

    NASA Astrophysics Data System (ADS)

    Huang, Yanshi; Wu, Qian; Huang, Cheryl Y.; Su, Yi-Jiun

    2016-08-01

    In this study, we report observations and simulation results of heated neutrals at various altitudes inside the polar cap during two magnetic storms in January 2005. The Poynting flux measurements from the Defense Meteorological Satellite Program (DMSP) satellites show enhanced energy input in the polar cap during the storm main phase, which is underestimated in the TIE-GCM simulation. Neutral temperature measurements at 250 km from the ground-based Fabry-Perot Interferometer (FPI) at Resolute Bay are presented, along with the neutral density observations at 360 km and 470 km from Challenging Minisatellite Payload (CHAMP) and the Gravity Recovery and Climate Experiment (GRACE) satellites, respectively. These data have been analyzed to demonstrate the altitudinal dependence of neutral response to the storm energy input. By comparing the TIE-GCM simulation results and the observations, we demonstrate that Poynting fluxes as well as the thermosphere response were underestimated in the model. The simulated neutral temperature at Resolute Bay increases by approximately 260° and 280° K for the two events, respectively, much lower than the observed temperature enhancements of 750° and 900° K. Neutral density enhancements with more than 30% increase over the background density were also observed at polar latitudes, with no clear distinction between the auroral zone and polar cap. All measurements indicate enhancements at high latitudes poleward of 80° magnetic latitude (MLAT) implying that substantial heating can occur within the polar cap during storms.

  3. Twin-vortex Convection in the Nightside High-Latitude Ionosphere Observed by the New Polar Cap SuperDARN Radar at Rankin Inlet

    NASA Astrophysics Data System (ADS)

    McWilliams, K. A.

    2006-12-01

    The opening and closing of magnetic flux by reconnection at the dayside magnetopause and in the magnetotail is the primary driver of convection in the magnetosphere and polar ionospheres. It is not the existence of open flux that excites convection; rather it is the creation or destruction of open flux that excites convection. These flows persist until a new equilibrium condition is reached, assuming no further reconnection occurs. The time scale for the excitation and decay of ionospheric flows depends on the time necessary for the polar cap to reconfigure following reconnection. The consequence of this zero-flow equilibrium concept (Cowley and Lockwood, 1992) has a powerful consequence when considering both bursty and steady-state reconnection. Newly created regions of open flux are appended contiguously to the polar cap adjacent to the previously reconnected region of open flux. Similarly, newly closed flux regions are appended contiguously to the closed field line region outside the polar cap on the nightside. The opening or closing of magnetic flux will create a perturbation of the polar cap boundary, and convection cells develop at the ends of the reconnection X-line. Convection is excited such that the newly created open flux is incorporated into the polar cap on the dayside or the newly closed flux is excluded from the polar cap on the nightside. The observation of the nightside convection response to reconnection has been very difficult to accomplish because (a) the nightside has a far more dynamic and complex response to reconnection, and (b) radar observations of convection in the midnight sector are difficult to achieve due to absorption of the radio waves during active conditions. The newest SuperDARN radar at Rankin Inlet is located at very high latitudes (73.2 magnetic), and it offers extensive and nearly continual observations of plasma convection in the poleward part of the nightside auroral region. Because of its high latitude, the Rankin Inlet

  4. Possible recent and ancient glacial ice flow in the south polar region of Mars

    NASA Technical Reports Server (NTRS)

    Kargel, J. S.

    1992-01-01

    Martian polar science began almost as soon as small telescopes were trained on the planet. The seasonal expansion and contraction of the polar caps and their high albedoes led most astronomers to think that water ice is the dominant constituent. In 1911 Lowell perceived a bluish band around the retreating edge of the polar caps, and interpreted it as water from melting polar ice and seasonal snow. An alternative idea in his time was that the polar caps consist of frozen carbonic acid. Lowell rejected the carbonic acid hypothesis on account of his blue band. He also pointed out that carbonic acid would sublimate rather than melt at confining pressures near and below one bar, hence, carbonic acid could not account for the blue band. In comparing Lowell's theories with today's knowledge, it is recognized that (1) sublimation is mainly responsible for the growth and contraction of Mars' polar caps, (2) carbon dioxide is a major component of the southern polar cap, and (3) Lowell's blue band was probably seasonal dust and/or clouds. Geomorphic evidence that glacial ice and glacial melt waters once flowed over broad areas of the southern polar region. Two aspects of the south polar region suggest possible glacial processes during two distinct eras in Mars' history.

  5. Albedo Variations on the Martian Northern Polar Cap as Seen by MGS

    NASA Technical Reports Server (NTRS)

    Hale, A. S.; Bass, D. S.; Tamppan, L. K.

    2003-01-01

    The Viking Orbiters determined that the surface of Mars northern residual cap is water ice. Many researchers have related observed atmospheric water vapor abundances to seasonal exchange between reservoirs such as the polar caps, but the extent to which the exchange between the surface and the atmosphere remains uncertain. Early studies of the ice coverage and albedo of the northern residual Martian polar cap using Mariner 9 and Viking images reported that there were substantial internannual differences in ice deposition on the polar cap, a result that suggested a highly variable Martian climate. However, some of the data used in these studies were obtained at differing values of heliocentric solar longitude (Ls). Reevaluation of this dataset in indicated that the residual cap undergoes seasonal brightening throughout the summer, and indicated that this process repeats from year to year. In this study we continue this work with data acquired with Mars Global Surveyor s Mars Orbiter Camera (MOC) and Thermal Emission Spectrometer (TES) instruments. We use MOC Wide Angel (WA) red filter images

  6. Mars Seasonal Polar Caps as a Test of the Equivalence Principle

    NASA Technical Reports Server (NTRS)

    Rubincam, Daivd Parry

    2011-01-01

    The seasonal polar caps of Mars can be used to test the equivalence principle in general relativity. The north and south caps, which are composed of carbon dioxide, wax and wane with the seasons. If the ratio of the inertial to gravitational masses of the caps differs from the same ratio for the rest of Mars, then the equivalence principle fails, Newton's third law fails, and the caps will pull Mars one way and then the other with a force aligned with the planet's spin axis. This leads to a secular change in Mars's along-track position in its orbit about the Sun, and to a secular change in the orbit's semimajor axis. The caps are a poor E6tv6s test of the equivalence principle, being 4 orders-of-magnitude weaker than laboratory tests and 7 orders-of-magnitude weaker than that found by lunar laser ranging; the reason is the small mass of the caps compared to Mars as a whole. The principal virtue of using Mars is that the caps contain carbon, an element not normally considered in such experiments. The Earth with its seasonal snow cover can also be used for a similar test.

  7. Year-to-year instability of the Mars south polar cap

    NASA Technical Reports Server (NTRS)

    Jakosky, Bruce M.; Haberle, Robert M.

    1990-01-01

    Models of the Mars polar cap energy balance suggest that the south cap has two possible configurations at the current epoch. It can be covered all year by CO2 frost, as was observed by the Viking spacecraft, or the CO2 frost can disappear at midsummer to expose an underlying surface. The difference between the two states depends on the role of energy conducted into the subsurface. If the cap was exposed the previous year, conducted energy will cause less CO2 frost to condense in winter, and the frost will disappear completely in summer. If the cap was covered the previous year, there will be no conducted energy, and it will stay covered again. Subtle effects in the atmosphere can perturb the cap energy balance sufficiently to cause the cap to jump between states. This behavior might provide an explanation for the large southern summer water vapor abundances observed in 1969. It also explains the observed differences between the north and the south residual caps as resulting in part from a difference in the role in the annual energy balance of energy conducted into the subsurface.

  8. Mars seasonal polar caps as a test of the equivalence principle

    NASA Astrophysics Data System (ADS)

    Rubincam, David Parry

    2011-08-01

    The seasonal polar caps of Mars can be used to test the equivalence principle in general relativity. The north and south caps, which are composed of carbon dioxide, wax and wane with the seasons. If the ratio of the inertial (passive) to gravitational (active) masses of the caps differs from the same ratio for the rest of Mars, then the equivalence principle fails, Newton’s third law fails, and the caps will pull Mars one way and then the other with a force aligned with the planet’s spin axis. This leads to a secular change in Mars’s along-track position in its orbit about the Sun, and to a secular change in the orbit’s semimajor axis. The caps are a poor Eötvös test of the equivalence principle, being 4 orders-of-magnitude weaker than laboratory tests and 7 orders-of-magnitude weaker than that found by lunar laser ranging; the reason is the small mass of the caps compared to Mars as a whole. The principal virtue of using Mars is that the caps contain carbon, an element not normally considered in such experiments. The Earth with its seasonal snow cover can also be used for a similar test.

  9. Driving Stresses in Mars Polar Ice Caps and Conditions for Ice Flow

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Saba, Jack L.

    1999-01-01

    Measurements of the topography of the North polar ice cap by the Mars Orbiter Laser Altimeter (MOLA) show that the ice cap is 2950 +/- 200 meters thick. The volume of the cap is about 1.2 x 10(exp 6) cu km covering an area of 1.04 x 10(exp 6) sq km, which is about 40 percent of the Greenland ice sheet in volume and 62 percent in area. The composition of the Northern cap was previously concluded to be predominately H2O, rather than CO2 ice, based on thermodynamic considerations of the insustainablity of CO2 during summer. Principal questions about the cap are: does the ice move and at what rate, is the cap currently growing or depleting in volume, and how and when was the cap formed? Recent research on terrestrial ice sheets indicates that rates of ice deformation at the low stress values characteristic of ice sheets are significantly higher than the rates given by the classic viscous-plastic flow laws commonly used.

  10. Macroscale modeling and mesoscale observations of plasma density structures in the polar cap

    SciTech Connect

    Basu, S.; Basu, S.; Sojka, J.J.; Schunk, R.W.; MacKenzie, E.

    1995-04-15

    The seasonal and UT variation of mesoscale structures (10 km - 100 m) in the central polar cap has been obtained from an analysis of 250-MHz intensity scintillation observations made at Thule, Greenland. It has been established earlier that mesoscale structures causing scintillations of satellite signals may develop at the edges of macroscale structures (several hundred km) such as discrete polar cap plasma density enhancements or patches through the gradient drift instability process. As such, the authrs examined the seasonal and UT variation of polar cap patches simulated by using the USU Time Dependent Ionospheric Model (TDIM) under conditions of southward B(sub z). A fairly remarkable similarity is found between the scintillation observations and the model predictions of patch occurrence. For instance, both the patch and scintillation occurrences are minimized during the winter solstice (northern hemisphere) between 0800-1200 UT while also having their largest seasonal intensity between 2000-2400 UT. Little UT dependence of patches and scintillations is seen at equinox with high intensity being observed throughout the day, while during local summer the intensity of macroscale patches and mesoscale irregularities are found to be a minimum at all UT. These results indicate that macroscale features in the polar cap are routinely associated with plasma instabilities giving rise to smaller scale structures and that the specific patch formation mechanism assumed in the simulation is consistent with the observations.

  11. Subsurface radar sounding of the martian polar cap: radiative transfer approach

    NASA Astrophysics Data System (ADS)

    Ilyushin, Ya. A.; Seu, R.; Phillips, R. J.

    2005-12-01

    The problem of subsurface radar sounding of the martian polar caps [Ilyushin, 2004. Martian northern polar cap: layering and possible implications for radar sounding. Planet. Space Sci. 52, 1195-1207] is considered from the point of view of incoherent radiative transfer theory. Since it has been previously shown that the radar signal field within the polar cap has diffuse structure, there is a need for a statistical approach to the problem. Radiative transfer theory, which is now well developed, seems to be the most appropriate formalism for this approach. Several physical models of polar caps have been formulated. The asymptotic solutions for all proposed models are derived here. In the present paper only the case of orbital ground penetrating radar is considered, because it is of great interest in relationship to currently developed radar experiments. In principle, the approach is believed to be applicable to a wide class of short pulse and compressed chirp radar experiments, including both orbital and landed instruments and media more complicated than a simple plane parallel geometry. This work, however, is postponed to future papers. Techniques for retrieval of physical properties of polar caps from the radar measurements are proposed. From the observational data, the macroscopic parameters of the medium appearing in radiative transfer theory, i.e. the single scattering albedo and volume extinction coefficient can be estimated. These estimates put certain constraints on the physical parameters of the medium model introduced in the paper. With some additional information, known a priori or from other observations, these estimates can be used to retrieve physically meaningful information, for example, the average content of impurities in the ice.

  12. Rocket measurements within a polar cap arc - Plasma, particle, and electric circuit parameters

    NASA Technical Reports Server (NTRS)

    Weber, E. J.; Ballenthin, J. O.; Basu, S.; Carlson, H. C.; Hardy, D. A.; Maynard, N. C.; Kelley, M. C.; Fleischman, J. R.; Pfaff, R. F.

    1989-01-01

    Results are presented from the Polar Ionospheric Irregularities Experiment (PIIE), conducted from Sondrestrom, Greenland, on March 15, 1985, designed for an investigation of processes which lead to the generation of small-scale (less than 1 km) ionospheric irregularities within polar-cap F-layer auroras. An instrumented rocket was launched into a polar cap F layer aurora to measure energetic electron flux, plasma, and electric circuit parameters of a sun-aligned arc, coordinated with simultaneous measurements from the Sondrestrom incoherent scatter radar and the AFGL Airborne Ionospheric Observatory. Results indicated the existence of two different generation mechanisms on the dawnside and duskside of the arc. On the duskside, parameters are suggestive of an interchange process, while on the dawnside, fluctuation parameters are consistent with a velocity shear instability.

  13. Seasonal recession of Mars' south polar cap as seen by Viking

    NASA Technical Reports Server (NTRS)

    James, P. B.; Briggs, G.; Barnes, J.; Spruck, A.

    1979-01-01

    The spring-summer retreat of the south polar cap of Mars is portrayed in photomosaics obtained by Viking Orbiter 2 during 1977. Comparisons of these data to Mariner 9 photos and to the record of telescopic observations attest that the polar retreat viewed by Viking was significantly slower than those previously reported. A global dust storm which occurred at an unusually early season may have effected this retarded recession by introducing dust into the atmosphere of Mars which modified the polar energy balance through scattering of incident radiation. The composition of the south residual cap cannot be unambiguously determined at this time; however, some data suggest that CO2 or clathrate survived the entire summer viewed by Viking.

  14. Correlation between south polar cap composition from OMEGA/MEX data and geomorphologic units

    NASA Astrophysics Data System (ADS)

    Mangold, N.; Poulet, F.; Forget, F.; Gendrin, A.; Gondet, B.; Langevin, Y.; Schmitt, B.; Bibring, J.-P.; OMEGA, Team

    A series of observations covering the south polar cap and part of the surrounding terrains have been recorded in the first weeks of OMEGA operation. From these first observations nearly pure H2O ice has been discovered in several areas surrounding the bright cap on which CO2 ice is mainly concentrated. A strong correlation exists between these compositional units and geomorphic features observed on MOC images acquired during the summer of the south hemisphere. As postulated by previous studies using MOC and THEMIS data, CO2 ice is strongly correlated with the geomorphic features called swiss-cheese terrains characterized by quasi-circular depressions. H2O ice, devoid of any CO2 ice, is observed with OMEGA in the periphery of these these swiss-cheese terrains. These H2O ice terrains on MOC images are very smooth and only affected by polygonal cracks which likely result of thermal contraction. The CO2 ice is apparently superimposed on these H2O ice layers confirming that the CO2 ice cap is restricted to a thin layer of few meters thick. Outside of the bright cap, patches of H2O ice are observed with OMEGA in correlation with grooved homogeneous surfaces on MOC images. They represent part of an H2O ice cap devoid of any overlying CO2 units which suggests an extension of the cap far beyond the bright polar cap. Preliminary results of the modeling of the sublimation processes of these different ices units will be presented.

  15. Variability of Mars' North Polar Water Ice Cap: I. Analysis of Mariner 9 and Viking Orbiter Imaging Data

    USGS Publications Warehouse

    Bass, D.S.; Herkenhoff, K. E.; Paige, D.A.

    2000-01-01

    Previous studies interpreted differences in ice coverage between Mariner 9 and Viking Orbiter observations of Mars' north residual polar cap as evidence of interannual variability of ice deposition on the cap. However, these investigators did not consider the possibility that there could be significant changes in the ice coverage within the northern residual cap over the course of the summer season. Our more comprehensive analysis of Mariner 9 and Viking Orbiter imaging data shows that the appearance of the residual cap does not show large-scale variance on an interannual basis. Rather we find evidence that regions that were dark at the beginning of summer look bright by the end of summer and that this seasonal variation of the cap repeats from year to year. Our results suggest that this brightening was due to the deposition of newly formed water ice on the surface. We find that newly formed ice deposits in the summer season have the same red-to-violet band image ratios as permanently bright deposits within the residual cap. We believe the newly formed ice accumulates in a continuous layer. To constrain the minimum amount of deposited ice, we used observed albedo data in conjunction with calculations using Mie theory for single scattering and a delta-Eddington approximation of radiative transfer for multiple scattering. The brightening could have been produced by a minimum of (1) a ???35-??m-thick layer of 50-??m-sized ice particles with 10% dust or (2) a ???14-??m-thick layer of 10-??m-sized ice particles with 50% dust. ?? 2000 Academic Press.

  16. Radiative Effects of CO_2 in the Martian Polar Caps from MGS

    NASA Astrophysics Data System (ADS)

    Hansen, G. B.

    1998-09-01

    We have examined data from two orbits in the assessment period of the Mars Global Surveyor (MGS), focusing on the known properties of pure CO_2 ice. For CO_2 snow surfaces with grains less than a few centimeters in size, there should be a depression in the thermal infrared brightness temperature with a minimum near 25 mu m. These grain-size properties of solid CO_2 may explain both the continuous and transient low-brightness-temperature regions discovered by the Viking orbiter infrared radiometers (IRTM). Using the Thermal Emission Spectrometer (TES) data from Orbit 21, we show how the spectra from an annulus near the edge of the retreating south polar cap are consistent with smaller CO_2 grain sizes. We suspect that this behavior results from the fracturing of nearly solid sheets of frozen CO_2 (formed in this way, or reaching this state by a process of grain-coarsening), as they are heated (mostly from below) by the rising sun. The unfractured layers near the pole behave more like a blackbody, and probably reflect visible light much like the surfaces underneath them, while the cracked surfaces should appear bright. We also investigated a low-altitude pass over the autumn north polar region in orbit 35, using data from both TES and the Mars Orbiter Laser Altimeter (MOLA). We found an area with properties similar to the Viking transient low-brightness-temperature regions, located precisely on the rim of a 22-km crater (from the MOLA profile) at the outlet of the Chasma Boreale. The MOLA reflectivity and the 30-mu m emissivity are anticorrelated across this feature (bright at 1 mu m, low emissivity at 30 mu m), implying that it is caused primarily by the CO_2 particle size. We propose that this region is characterized by a local change in particle size, and that it is correlated with topography, a fact hinted at but not proven by Viking IRTM studies. A likely cause of such a feature is the flow over the obstacle by a possibly dusty atmosphere near saturation

  17. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap.

    PubMed

    Kieffer, Hugh H; Christensen, Philip R; Titus, Timothy N

    2006-08-17

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. PMID:16915284

  18. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

    USGS Publications Warehouse

    Kieffer, H.H.; Christensen, P.R.; Titus, T.N.

    2006-01-01

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO 2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. ?? 2006 Nature Publishing Group.

  19. HiRISE Images of the Sublimation of the Southern Seasonal Polar Cap of Mars

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; McEwen, A. S.; Okubo, C.; Byrne, S.; Becker, T.; Kieffer, H.; Mellon, M.; HiRISE Team

    2007-12-01

    The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) has returned images with unprecedented resolution of Mars southern seasonal CO2 polar cap. Several high latitude sites were selected for systematic monitoring throughout the spring as the seasonal cap sublimed away. The capability of MRO to turn off-nadir enabled acquisition of stereo pairs to study the topography. HiRISE color capability distinguishes processes involving dust and frost. Color images show evidence of localized migration of frost as dark spots sublimate. Unique landforms are found in the cryptic terrain[1] region of Mars polar cap. These unusual landforms have narrow channels emanating radially, dubbed spiders[2]. Fans of dust blown by the prevailing wind are hypothesized to come from gas jets of CO2 subliming beneath translucent seasonal ice [3]. HiRISE images show a wide variety of morphologies of narrow channels. In some regions deep narrow channels converge radially, while in others the high channel density is more akin to lace. A smooth evolution of one form to another has been observed. Channels converge dendritically, often uphill, consistent with formation by flowing gas, not liquid. More dust fans are observed in regions of spiders than in lace, suggesting that the sublimating gas under the seasonal ice builds up more pressure and can entrain more dust in spidery areas. These differing terrain types are found within a single 6 x 10 km image, which has presumably homogeneous weather, thus a uniform layer of ice and exposure to atmospheric dust. HiRiSE images show that the dust fans tend to emerge from low spots, where the subsurface is accessed, then are blown up and out onto the surface of the seasonal ice. The fans evolve from a thin diffuse covering to thick blankets filling in the narrow channels. We hypothesize that dust collects in the channels, and that these relatively more permeable dust-filled channels form pathways for the next seasons

  20. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-08-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels ("araneiform" terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  1. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    USGS Publications Warehouse

    Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-01-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  2. Geomorphology of Titan's Polar Regions

    NASA Astrophysics Data System (ADS)

    Birch, S. P.; Hayes, A. G., Jr.; Dietrich, W. E.; Malaska, M. J.; Kirk, R. L.; Lucas, A.

    2014-12-01

    Numerous lakes and seas have been observed in Titan's polar regions (Stofan et al., 2007), primarily at the north pole (Hayes et al., 2008), while evidence for channelized fluid flow has been found at all latitudes (Lorenz et al., 2008), though primarily at the poles as well. We construct a geomorphologic map of both poles at latitudes higher than 600 using a combination of the Cassini Synthetic Aperture Radar images along with topographic data in the form of SARTopo (Stiles et al., 2009) and sparsely distributed Digital Terrain Models. Utilizing data from flybys Ta through T98, we define five governing morphologic units: plains, small depressions, large seas, mountains and ridge and valley networks. These units are subdivided according to their radar properties (bright or dark, uniformity), morphologies (degree of dissection, undulation, curvature and organization, regional slope), relative elevations and contact relations. These units are systematically mapped in a repeatable, quantitative manner along with various structural features such as remnant ridges, channels, alluvial fans and scarps. In combining SAR imagery with topographic data, our geomorphic map reveals a stratigraphic sequence from which we can infer processes. We find that the North Pole is dominated by an elevated, radar-dark plains unit, embedded by numerous filled, wet and dry small depressions with a sparse number of channels. The dark-plains unit transitions into a highly dissected radar-bright, lowland unit closer to the mare. A high density of radar-dark remnant ridges, channels and alluvial fans characterizes this unit. The South Pole is markedly different from the North, having far fewer lakes, no large filled seas, larger elevation gradients and a greater number of mountain regions while also being dominated by an organized ridge and valley network. Our work suggests the South Pole is not a drier version of the North. Rather the observed dichotomy between the two poles is likely the

  3. Field-aligned electron density irregularities near 500 km Equator to polar cap topside sounder observations

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1985-01-01

    In addition to spread F, evidence for field-aligned electron density irregularities is commonly observed on Alouette 2 topside sounder ionograms recorded near perigee (500 km). This evidence is provided by distinctive signal returns from sounder-generated Z mode waves. At low latitudes these waves become guided in wave ducts caused by field-aligned electron density irregularities and give rise to strong long-duration echoes. At high latitudes, extending well into the polar cap, these Z mode waves (and stimulated electrostatic waves at the plasma frequency) produce a series of vertical bars on the ionogram display as the satellite traverses discrete field-aligned density structures. The radio frequency (RF) noise environment to be expected in the 400 to 500 km altitude region from low to high latitudes was examined by analyzing perigee Alouette 2 topside sounder data. All observed noise bands were scaled on nearly 200 topside sounder ionograms recorded near perigee at low, mid, and high latitude telemetry stations. The minimum and maximum frequencies of each noise band were entered into a data base or computer analysis. The signals of primary interest in the perigee study were found to be sounder-generated.

  4. Seasonal Variation of Martian Polar Caps: 1999 and 2001 MOC Data

    NASA Technical Reports Server (NTRS)

    James, P. B.; Benson, J. L.; Cantor, B. A.

    2003-01-01

    The seasonal Martian polar caps wax and wane in response to condensation and sublimation of carbon dioxide resulting from seasonal insolation changes on Mars. Numerous data exist on observations of the recession or sublimation phases in the visible portion of the spectrum for the last two centuries. William Herschel published the first quantitative observations of the seasonal recession of the Martian polar caps in 1784. During the next 180 years, ground based observers used a variety of techniques to observe recessions; Slipher summarized these observations in 1962, on the eve of the first space exploration of Mars. Portions of the seasonal cycles of the surface caps that were observed by Mariners 7 and 9 and by Viking as well as ground based studies from 1971-1988 by the International Planetary Patrol were summarized in a review article following the Fourth International Conference on Mars in 1989. Hubble Space Telescope observed points in the seasonal recessions of the south and north caps during the 1990 s. Differences between different Martian regressions have been reported in the past; but, because many of the relevant data sets are localized in longitude, at least some of these results could be an artifact introduced by the considerable longitudinal asymmetry that observed during recessions.

  5. Effects of interplanetary magnetic field azimuth on auroral zone and polar cap magnetic activity

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1972-01-01

    During relatively quiet times in the period 1964-1968, AE is found to be greater when the interplanetary magnetic field (b sub IMF) is directed toward the sun in Jan., Feb., and Apr., and when B sub IMF is directed away from the sun in Oct. to Dec. Using Murmansk hourly H values and the AE components, AU and AL, it is shown that this sector dependence is present only in the negative H deviations. This observation supports the idea that negative bay magnitudes are determined chiefly by particle-produced ionization, while positive bay magnitudes are rather insensitive to increases in particle precipitation. The ratio of DP2-type magnetic activity in the southern polar cap to that in the northern polar cap is found to be greater by a factor of about 1.75 for B sub IMF toward the sun.

  6. The CAMEO barium release - E/parallel/ fields over the polar cap

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.; Miller, M. L.; Pongratz, M. B.; Smith, G. M.; Smith, L. L.; Mende, S. B.; Nath, N. R.

    1981-01-01

    Four successive thermite barium releases at an altitude of 965 km over polar cap invariant latitudes 84 to 76 deg near magnetic midnight were conducted from the orbiting second stage of the vehicle that launched Nimbus 7; the releases were made as part of the CAMEO (Chemically Active Material Ejected in Orbit) program. This was the first opportunity to observe the behavior of conventional barium release when conducted at orbital velocity in the near-earth magnetic field. The principal unexpected characteristic in the release dynamics was the high, 1.4 to 2.6 km/s, initial Ba(+) expansion velocity relative to an expected velocity of 0.9 km/s. Attention is also given to neutral cloud expansion, initial ion cloud expansion, convective motion, and the characteristics of field-aligned motion. The possibility of measuring parallel electric fields over the polar cap by observing perturbations in the motion of the visible ions is assessed.

  7. Auroral-polar cap environment and its impact on spacecraft plasma interactions

    NASA Technical Reports Server (NTRS)

    Garrett, H. B.

    1985-01-01

    The high density of the plasma at shuttle altitude is likely to increase greatly the possibility of arcing and shorting of exposed high voltage surfaces. For military missions over the polar caps and through the auoroal zones, the added hazards of high energy auroral particle fluxes or solar flares will further increase the hazard to shuttle, its crew, and its mission. A review of the role that the auroral and polar cap environment play in causing these interactions was conducted. A simple, though comprehensive attempt at modelling the shuttle environment at 400 km will be described that can be used to evaluate the importance of the interactions. The results of this evaluation are then used to define areas where adequate environmental measurements will be necessary if a true spacecraft interactions technology is to be developed for the shuttle.

  8. A new type of Doppler velocity fluctuations in HF ground scatter from the polar cap

    NASA Astrophysics Data System (ADS)

    Scoular, G.; Ponomarenko, P. V.; St.-Maurice, J. P.

    2013-10-01

    We report a new type of variations in Doppler velocity of HF ground scatter echoes from the polar cap at f˜10 mHz. Similar fluctuations from lower latitudes are usually associated with large-scale dayside Pc3-4 ULF waves. However, the polar cap oscillations exhibit a puzzling anisotropy in spatial coherence along and across the radar's line of sight. Furthermore, in contrast to Pc3-4 waves, these fluctuations show no ground magnetic signatures and display a pronounced gap in power/occurrence around local noon. We hypothesize that localized, ≤100 km, auroral particle precipitations near the radar site can modulate Doppler shift of the radio waves entering the ionosphere. In the ground scatter returns, due to the geometrical spread of the rays propagating through the ionosphere to the ground, these variations would appear to have a much larger line-of-sight scale.

  9. Dynamics of the correlation between polar cap radio absorption and solar energetic proton fluxes in the interplanetary medium

    NASA Astrophysics Data System (ADS)

    Kouznetsov, A.; Knudsen, D. J.; Donovan, E. F.; Spanswick, E.

    2014-03-01

    During solar energetic particle (SEP) events, large fluxes of energetic particles spreading throughout the interplanetary medium (IPM) have access to the upper polar atmosphere where they play important roles in physical and chemical processes. We examine the dynamics of the relation between solar energetic proton (SEP) fluxes detected outside the magnetosphere by SOHO, at geosynchronous orbit by GOES 8, and in low earth orbit by NOAA 15 (POES) satellites on one hand, and ionospheric absorption measured by a NORSTAR riometer in the polar cap on the other. We attempt to isolate SEP-related signals by rejecting periods influenced by electron precipitation and solar radio bursts. Under these conditions we find R2of up to 0.9 between the logarithms of SEP flux and absorption for all satellites, but with the additional restriction to periods beginning 10 h after event onsets and within tens of hours following times of maximum flux. We find that the flux-absorption correlation is poor during the first few hours of an event, which we attribute to the fact that SEP angular distributions are often highly peaked along the interplanetary magnetic field during the early stages of an event. Such highly anisotropic distributions map to small regions inside the polar caps, making it unlikely that the corresponding absorption signal will be detected by a single riometer. These observations suggest that riometers in combination with a suitable numerical tool can be used as a diagnostic of properties of energetic proton populations in the interplanetary medium.

  10. Dynamics of Saturn’s Polar Regions

    NASA Astrophysics Data System (ADS)

    Antuñano, Arrate; del Río Gaztelurrutia, Teresa; Sánchez Lavega, Agustin; Hueso, Ricardo

    2014-11-01

    In this study we analyze the horizontal velocity fields of Saturn’s North and South Polar regions, including the hexagonal wave and its jet. The studied regions cover 30° in latitude going from 60° to 90° in both hemispheres. Using an automated two dimensional brightness correlation we create 2D zonal and meridional wind maps and zonal wind profiles for both polar regions, obtaining information on the horizontal velocity field up to 89.9° latitude in the north polar region and -89.5° latitude in the south. The eastward jet in the north polar region has its peak of velocity at higher latitudes (closer to the pole) than that in the south polar region, and this could be one of the reasons for the formation of the hexagonal wave in the north. An anticyclone (South Polar Vortex) is observed in the south polar region, just outside the eastward jet and impinging on it, similar to the NPS anticyclone (north Polar Vortex observed in Voyager time). However, it does not excite a wave, showing that these anticyclones are not the cause of the formation of the hexagonal feature. We also deduce vorticity maps and analyze the stability of the zonal jets, finding potential instability at the flanks of the eastward jets. Finally, we study the transfer of momentum from the turbulent motion to the westward jets in these regions.

  11. MRO CRISM Investigation of Hydrated Materials Associated with the North Polar Residual Cap on Mars

    NASA Astrophysics Data System (ADS)

    Seelos, F. P.; Seelos, K. D.; Murchie, S. L.; Titus, T. N.; Calvin, W. M.; CRISM Team

    2007-12-01

    The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard the Mars Reconnaissance Orbiter (MRO) is a visible and near infrared hyperspectral imager with 544 channels from 362 to 3920 nm (6.55 nm spectral sampling). The MRO Primary Science Phase (PSP) began at Ls ~ 130° allowing for significant data acquisition at the high northern latitudes in advance of deteriorating atmospheric and illumination conditions. As a result of early PSP science priorities and operational constraints, the majority of the CRISM data acquired at that time were multispectral survey (200 m/pxl; 73 channel) observations. This allowed for the generation of a nearly complete multispectral survey mosaic for the north polar residual cap and the surrounding terrain (>75° latitude). CRISM multispectral mapping mosaics and related analysis products for the high northern latitudes reveal hydrated material within a number of troughs and reentrants into the north polar residual cap, as inferred from the depth and spatial coherency of the 1.9 μm absorption band. Although the identification of the hydrated exposures occurred after the close of the observing season at the high northern latitudes, a limited number of CRISM hyperspectral targeted (20-40 m/pxl; 544 channel) and multispectral window (100 m/pxl; 73 channel) observations were acquired at these locations. The higher spatial resolution data show that the hydration signature is most commonly associated with low-albedo dunes -- both in the vicinity of the Olympia Undae gypsum-bearing sand sea, and in distant polar cap reentrants. The ongoing evaluation of high resolution hyperspectral CRISM observations of hydrated materials in the vicinity of the north polar residual cap and further refinement of the multispectral mapping spectral analysis products will contribute to the targeting and acquisition of additional CRISM observations in the upcoming full northern summer of MRO operations.

  12. Influence of polar-cap albedo on past and current Martian climate

    NASA Technical Reports Server (NTRS)

    Kieffer, Hugh H.; Paige, David A.

    1987-01-01

    The finding that the observed albedo of the Martian polar caps increase with increasing isolation is reviewed. Models of the Martian climate system are greatly stabilized when an insolation-dependent frost albedo instead of a constant albedo is used in the energy budget. The authors views on microphysics of the process is then presented. Long term climate models must account for the variability of CO2 frost albedo.

  13. Three-dimensional numerical simulation of near-surface flows over the Martian north polar CAP

    NASA Astrophysics Data System (ADS)

    Parish, Thomas R.; Howard, A. D.

    Measurements made by Viking Lander VL-2 (48 N) have shown that the near-surface wind and temperature regime on Mars displays striking similarities to terrestrial counterparts. The diurnal radiative cycle is responsible for establishment of a well-defined thermal circulation in which downslope (Katabatic) flows prevail during the nighttime hours and weak upslope (anabatic) conditions prevail during the daytime. Previous work has indicated that the slope flows are much like those found on Earth, particularly the Katabatic winds, which show striking similarities to drainage flows observed over Antarctica. The low-level wind regime appears to be an important factor in the scouring of the martian landscape. The north polar cap shows evidence of eolian features such as dunes, frost streaks, and grooves from Viking imagery. The direction of the prevailing wind can in cases be inferred from the eolian features. We examine the thermally induced flows that result from the radiative heating and cooling of the martian north polar region using a comprehensive three-dimensional atmospheric mesoscale numerical model. The same model has been used previously for simulation of Antarctic Katabatic winds. The model equations are written in terrain-following coordinates to allow for irregular terrain; prognostic equations include the flux forms of the horizontal momentum equations, temperature, continuity. A surface energy budget equation is also incorporated in which the surface temperature is determined. Explicit parameterization of both terrestrial (longwave) and solar (shortwave) radiation is included. Turbulent transfer of heat and momentum in the martian atmosphere is assumed to follow the similarity expressions in the surface boundary layer on Earth. The terrain heights for the martian north polar region have been obtained from the U.S. Geological Survey map and digitized onto a 57x57 grid with a spacing of 75 km. The resulting terrain map is shown in Fig. 1. The vertical grid

  14. Three-dimensional numerical simulation of near-surface flows over the Martian north polar cap

    NASA Technical Reports Server (NTRS)

    Parish, Thomas R.; Howard, A. D.

    1993-01-01

    Measurements made by Viking Lander VL-2 (48 N) have shown that the near-surface wind and temperature regime on Mars displays striking similarities to terrestrial counterparts. The diurnal radiative cycle is responsible for establishment of a well-defined thermal circulation in which downslope (Katabatic) flows prevail during the nighttime hours and weak upslope (anabatic) conditions prevail during the daytime. Previous work has indicated that the slope flows are much like those found on Earth, particularly the Katabatic winds, which show striking similarities to drainage flows observed over Antarctica. The low-level wind regime appears to be an important factor in the scouring of the martian landscape. The north polar cap shows evidence of eolian features such as dunes, frost streaks, and grooves from Viking imagery. The direction of the prevailing wind can in cases be inferred from the eolian features. We examine the thermally induced flows that result from the radiative heating and cooling of the martian north polar region using a comprehensive three-dimensional atmospheric mesoscale numerical model. The same model has been used previously for simulation of Antarctic Katabatic winds. The model equations are written in terrain-following coordinates to allow for irregular terrain; prognostic equations include the flux forms of the horizontal momentum equations, temperature, continuity. A surface energy budget equation is also incorporated in which the surface temperature is determined. Explicit parameterization of both terrestrial (longwave) and solar (shortwave) radiation is included. Turbulent transfer of heat and momentum in the martian atmosphere is assumed to follow the similarity expressions in the surface boundary layer on Earth. The terrain heights for the martian north polar region have been obtained from the U.S. Geological Survey map and digitized onto a 57x57 grid with a spacing of 75 km. The resulting terrain map is shown in Fig. 1. The vertical grid

  15. Scintillation and irregularities from the nightside part of a Sun-aligned polar cap arc

    NASA Astrophysics Data System (ADS)

    Meeren, Christer; Oksavik, Kjellmar; Lorentzen, Dag A.; Paxton, Larry J.; Clausen, Lasse B. N.

    2016-06-01

    In this paper we study the presence of irregularities and scintillation in relation to the nightside part of a long-lived, Sun-aligned transpolar arc on 15 January 2015. The arc was observed in DMSP UV and particle data and lasted at least 3 h between 1700 and 2000 UT. The arc was more intense than the main oval during this time. From all-sky imagers on Svalbard we were able to study the evolution of the arc, which drifted slowly westward toward the dusk cell. The intensity of the arc as observed from ground was 10-17 kR in 557.7 nm and 2-3.5 kR in 630.0 nm, i.e., significant emissions in both green and red emission lines. We have used high-resolution raw data from global navigation satellite systems (GNSS) receivers and backscatter from Super Dual Auroral Radar Network (SuperDARN) radars to study irregularities and scintillation in relation to the polar cap arc. Even though the literature has suggested that polar cap arcs are potential sources for irregularities, our results indicate only very weak irregularities. This may be due to the background density in the northward IMF polar cap being too low for significant irregularities to be created.

  16. Polar volatiles on Mars - Theory versus observation. [solid carbon dioxide in north residual cap

    NASA Technical Reports Server (NTRS)

    Murray, B. C.; Malin, M. C.

    1973-01-01

    Synthesis of the results of the Mariner 9 mission, as they pertain to polar volatiles, and comparison of them with a description of the solid-vapor equilibrium relations believed to be presently active on Mars. The discovery by Mariner 9 of extensive volcanic deposits on portions of the Martian surface suggests that the total amount of CO2 liberated to the surface probably exceeds that now present in the atmosphere. Thus excess CO2 in the solid form is to be expected in the polar areas. Although the simplified model of Leighton and Murray (1966), which predicts a permanent CO2 cap, has significant deficiencies both theoretically and observationally, the seasonal caps are composed of CO2, as predicted, excess CO2 is quite likely, and a permanent deposit of solid CO2 evidently is in equilibrium with atmospheric CO2. It is suggested that there must be a large reservoir of solid CO2 in gaseous equilibrium with the atmosphere, but buried immediately below the exposed residual water-ice cap. This reservoir is believed to be located near the north pole. The principal effect of such a reservoir is to average out annual and longer-term fluctuations in the polar heat balance.

  17. Workshop on the Polar Regions of Mars: Geology, Glaciology, and Climate History, part 1

    NASA Technical Reports Server (NTRS)

    Clifford, S. M. (Editor); Howard, A. D. (Editor); Paterson, W. S. B. (Editor)

    1992-01-01

    Papers and abstract of papers presented at the workshop are presented. Some representative titles are as follows: Glaciation in Elysium; Orbital, rotational, and climatic interactions; Water on Mars; Rheology of water-silicate mixtures at low temperatures; Evolution of the Martian atmosphere (the role of polar caps); Is CO2 ice permanent; Dust transport into Martian polar latitudes; Mars observer radio science (MORS) observations in polar regions; and Wind transport near the poles of Mars (timescales of changes in deposition and erosion).

  18. Observations of the relationship between ionospheric central polar cap and dayside throat convection velocities, and solar wind/IMF driving

    NASA Astrophysics Data System (ADS)

    Bristow, W. A.; Amata, E.; Spaleta, J.; Marcucci, M. F.

    2015-06-01

    Convection observations from the Southern Hemisphere Super Dual Auroral Radar Network are presented and examined for their relationship to solar wind and interplanetary magnetic field (IMF) conditions, restricted to periods of steady IMF. Analysis is concentrated on two specific regions, the central polar cap and the dayside throat region. An example time series is discussed in detail with specific examples of apparent direct control of the convection velocity by the solar wind driver. Closer examination, however, shows that there is variability in the flows that cannot be explained by the driving. Scatterplots and histograms of observations from all periods in the year 2013 that met the selection criteria are given and their dependence on solar wind driving is examined. It is found that on average the flow velocity depends on the square root of the rate of flux entry to the polar cap. It is also found that there is a large level of variability that is not strongly related to the solar wind driving.

  19. Mars Water Ice and Carbon Dioxide Seasonal Polar Caps: GCM Modeling and Comparison with Mars Express Omega Observations

    NASA Technical Reports Server (NTRS)

    Forget, F.; Levrard, B.; Montmessin, F.; Schmitt, B.; Doute, S.; Langevin, Y.; Bibring, J. P.

    2005-01-01

    To better understand the behavior of the Mars CO2 ice seasonal polar caps, and in particular interpret the the Mars Express Omega observations of the recession of the northern seasonal cap, we present some simulations of the Martian Climate/CO2 cycle/ water cycle as modeled by the Laboratoire de Meteorologie Dynamique (LMD) global climate model.

  20. On the occurrence and motion of decametre-scale irregularities in the sub-auroral, auroral, and polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Parkinson, M. L.; Devlin, J. C.; Ye, H.; Waters, C. L.; Dyson, P. L.; Breed, A. M.; Morris, R. J.

    2003-08-01

    The statistical occurrence of decametre-scale ionospheric irregularities, average line-of-sight (LOS) Doppler velocity, and Doppler spectral width in the sub-auroral, auroral, and polar cap ionosphere ( - 57°L

  1. Results of current Mars studies at the IAU Planetary Research Center. [global dust storms, seasonal variations, and polar cap dissipation

    NASA Technical Reports Server (NTRS)

    Baum, W. A.

    1974-01-01

    Ground based images obtained hourly by seven observatories are used to study Martian phenomena. Maps of global dust storms show the degree of activity of the storm depends both on the region and on the time of day. Statistical analysis of regional contrast variations on the images supports the opinion that the contrasts in the brightness of the light and dark areas depends on the Martian season. Residual differences may be due to a phase angle dependence. Diagrams confirm the earlier finding that there is a systematic trend of regional contrast with the time of the Martian day and that the afternoon is not symmetric with the morning. The dissipation of Martian polar caps is also discussed.

  2. Structure and dynamics of polar-cap F-layer patches. Interim report, March 1985-March 1986

    SciTech Connect

    Weber, E.J.; Klobuchar, J.A.; Buchau, J.; Carlson, H.C.; Livingston, R.C.

    1986-03-31

    Coordinated measurements of F-region plasma patches were conducted on 3 and 4 February 1984 from Thule and Sondrestrom, Greenland. Optical, ionosonde, amplitude scintillation, Total Electron Content (TEC), and incoherent scatter radar measurements were combined to reveal several new aspects of the structure and transport of these localized regions of enhanced F-region ionization. These patches were directly tracked for the first time flowing anti-sunward from the center of the polar cap to the poleward edge of of the auroral oval. Amplitude scintillation caused by irregularities within these structured patches showed a systematic increase on the trailing edge of the patches consistent with an E X B instability mechanism. Equally important, significant scintillation was also observed on the loading edge and throughout the patch, requiring another instability mechanism to produce irregularities throughout the interior of the patch.

  3. Analysis of close conjunctions between dayside polar cap airglow patches and flow channels by all-sky imager and DMSP

    NASA Astrophysics Data System (ADS)

    Wang, Boyi; Nishimura, Yukitoshi; Lyons, Larry R.; Zou, Ying; Carlson, Herbert C.; Frey, Harald U.; Mende, Stephen B.

    2016-09-01

    Recent imager and radar observations in the nightside polar cap have shown evidence that polar cap patches are associated with localized flow channels. To understand how flow channels propagate from the dayside auroral oval into the polar cap, we use an all-sky imager in Antarctica and DMSP (F13, F15, F16, F17 and F18) to determine properties of density and flows associated with dayside polar cap patches. We identified 50 conjunction events during the southern winter seasons of 2007-2011. In a majority (45) of events, longitudinally narrow flow enhancements directed anti-sunward are found to be collocated with the patches, have velocities (up to a few km/s) substantially larger than the large-scale background flows (~500 m/s) and have widths comparable to patch widths (~400 km). While the patches start with poleward moving auroral forms (PMAFs) as expected, many PMAFs propagate azimuthally away from the noon over a few hours of MLT, resulting in formation of polar cap patches quite far away from the noon, as early as ~6 MLT. The MLT separation from the noon is found to be proportional to the IMF |By|. Fast polar cap flows of >~1500 m/s are predominantly seen during large IMF |By| and small |Bz|. The presence of fast, anti-sunward flow channels associated with the polar cap patches suggests that the flow channels form in the dayside auroral oval through transient reconnection and can be the source of flow channels propagating into the polar cap.

  4. Physical State of the ``Bright'' South Seasonal Polar Cap From OMEGA Observations

    NASA Astrophysics Data System (ADS)

    Doute, S.; Schmidt, F.; Schmitt, B.; Vincendon, M.; Langevin, Y.; Gondet, B.; Bibring, J.

    2009-12-01

    The composition, physical state and texture of the South Seasonal Polar Cap (SSPC) have important consequences on energy balance. The imaging spectrometer OMEGA on board Mars Express has acquired the most comprehensive set of observations to date in the near-infrared (0.93-5.1 microns) on the SSPC from mid-winter solstice (Ls=110° , December 2004) to the end of the recession at Ls=320° (November 2005) [1]. The time resolution is 3 days to one month and the spatial resolution ranges from 700m to 10 km/pixel. [1] showed that during southern spring and summer, there is a very complex evolution in terms of effective grain size of CO2 ice and contamination by dust or H2O ice. H2O ice does not play a significant role except close to the end of the recession. [2] systematically segmented the South Seasonal Polar Cap into different spectral units and tested diverse surface representations by the modeling of spectral end-members and average unit spectra. Here we focus on the “bright” part of the SSPC corresponding to spectral unit SSPC1 (I.b of [1]). Regions belonging to this unit have a very bright albedo (≈ 0.6-0.8) associated with strong CO2 ice absorption features. According to [1] such characteristics are compatible with granular CO2 deposits with grain size in the range of 5 cm implying an extremely low contamination by dust and water ice. Furthermore, from their study of a representative region at 34° E, 76° S, the albedo increases from Ls=223° up to a maximum at Ls=240° and then decreases until total disappearance of the ice. The albedo increase would require a decrease of grain size if the granular model is really relevant. However the mean free path within CO2 ice as well as its thermodynamic behavior would rather favor a porous CO2 slab model [3]. Then photometric effects could be expected that could explain the brightening. In this paper we propose to further study the physical state of the “bright” part of the SSPC and its evolution by

  5. A One Billion Year Martian Climate Model: The Importance of Seasonally Resolved Polar Caps and the Role of Wind

    NASA Technical Reports Server (NTRS)

    Armstrong, J. C.; Leovy, C. B.; Quinn, T. R.; Haberle, R. M.; Schaeffer, J.

    2003-01-01

    Wind deflation and deposition are powerful agents of surface change in the present Mars climate regime. Recent studies indicate that, while the distribution of regions of potential deflation (or erosion) and deposition is remarkably insensitive to changes in orbital parameters (obliquity, timing of perihelion passage, etc.), rates of aeolian surface modification may be highly sensitive to these parameters even if the atmospheric mass remains constant. But previous work suggested the atmospheric mass is likely to be sensitive to obliquity, especially if a significant mass of carbon dioxide can be stored in the regolith or deposited in the form of massive polar caps. Deflation and erosion are highly sensitive to surface pressure, so feedback between orbit variations and surface pressure can greatly enhance the sensitivity of aeolian modification rates to orbital parameters. We used statistics derived from a 1 Gyr orbital integration of the spin axis of Mars, coupled with 3D general circulation models (GCMs) at a variety of orbital conditions and pressures, to explore this feedback. We also employed a seasonally resolved 1D energy balance model to illuminate the gross characteristics of the longterm atmospheric evolution, wind erosion and deposition over one billion years. We find that seasonal polar cycles have a critical influence on the ability for the regolith to release CO2 at high obliquities, and find that the atmospheric CO2 actually decreases at high obliquities due to the cooling effect of polar deposits at latitudes where seasonal caps form. At low obliquity, the formation of massive, permanent polar caps depends critically on the values of the frost albedo, A(sub frost), and frost emissivity, E(sub frost). Using our 1D model with values of A(sub frost) = 0.67 and E(sub frost) = 0.55, matched to the NASA Ames GCM results, we find that permanent caps only form at low obliquities (< 10 degrees). Thus, contrary to expectations, the Martian atmospheric pressure

  6. Zonally averaged thermal balance and stability models for nitrogen polar caps on Triton

    NASA Technical Reports Server (NTRS)

    Stansberry, John A.; Lunine, J. I.; Porco, C. C.; Mcewen, A. S.

    1990-01-01

    Voyager four-color imaging data of Triton are analyzed to calculate the bolometric hemispheric albedo as a function of latitude and longitude. Zonal averages of these data have been incorporated into a thermal balance model involving insolation, reradiation, and latent heat of sublimation of N2 ice for the surface. The current average bolometric albedo of Triton's polar caps is 0.8, implying an effective temperature of 34.2 K and a surface pressure of N2 of 1.6 microbar for unit emissivity. This pressure is an order of magnitude lower than the surface pressure of 18 microbar inferred from Voyager data (Broadfoot et al., 1989; Conrath et al., 1989), a discrepancy that can be reconciled if the emissivity of the N2 on Triton's surface is 0.66. The model predicts that Triton's surface north of 15 deg N latitude is experiencing deposition of N2 frosts, as are the bright portions of the south polar cap near the equator. This result explains why the south cap covers nearly the entire southern hemisphere of Triton.

  7. Unloading Versus Driven Processes Derived from Auroral Energy Deposition and Polar Cap Size

    NASA Technical Reports Server (NTRS)

    Brittnacher, M. J.; Parks, G. K.; Fillingim, M. O.; Elsen, R.; Chua, D.; Germany, G. A.; Spann, J. F., Jr.

    1998-01-01

    The intensity of far ultraviolet auroral emissions at all local times during the three substorm phases has been monitored by the Ultraviolet Imager (UVI) on the Polar spacecraft for many substorms. Changes in the energy flux and characteristic energy of the precipitating electrons can be derived from these observations by modeling of the spectral emission processes. The global and local energy deposition is a new parameter that can be used in substorm studies since it provides a measure of energy transfer from the tail to the ionosphere due to precipitating electrons at a time resolution of three minutes. The polar cap area and area of auroral emissions can also be determined at high time resolution during substorms from the UVI images. An example of a substorm that appears to be driven by solar wind dynamic pressure alone will be presented. The polar cap area and other parameters do not indicate a growth phase prior to substorm onset. In another example, the slow growth phase followed by a very rapid increase in energy deposition during the expansion phase will be shown. This substorm was preceded by a southward IMF orientation. In these two examples, the role the solar wind in determining polar cap area is discussed. The time development of the area of auroral emissions is also discussed in relation to substorm phase and energy deposition. If the auroral emissions occur on closed field lines then the area of auroral emissions may provide an indication of changes in the thickness of the plasma sheet during each substorm phase.

  8. Ionospheric Ion Outflow from the Cusp and the Polar Cap Ionosphere: Current Observations, Knowledge Gaps, and Planned Observations (Invited)

    NASA Astrophysics Data System (ADS)

    Yau, A. W.; Abe, T.; Peterson, W. K.

    2009-12-01

    Satellite observations over the past few decades, notably those from ISIS, S3-3, Dynamics Explorer-1 and -2, Viking, Akebono, Freja, Polar, Fast, and Cluster, have demonstrated that ions of ionospheric origin represent a significant and at times dominant component of the magnetospheric plasma. In this overview, we will focus on our existing observations of ion outflows from the cusp and polar cap ionosphere, and their relationship with other low and high-energy ion outflow populations and with neutral upwelling and escapes in the high-latitude ionosphere-thermosphere. We will also discuss planned observations in the upcoming CASSIOPE/e-POP (Enhanced Polar Outflow Probe) mission on the acceleration, upflow, and outflow in the cusp and polar cap ionosphere in the context of gaps in our current knowledge in cusp and polar-cap ion outflow dynamics.

  9. A perchlorate brine lubricated deformable bed facilitating flow of the north polar cap of Mars: Possible mechanism for water table recharging

    NASA Astrophysics Data System (ADS)

    Fisher, David A.; Hecht, Michael H.; Kounaves, Samuel P.; Catling, David C.

    2010-02-01

    The Phoenix Wet Chemistry Lab (WCL) discovered substantial amounts of magnesium, calcium, and sodium perchlorate in the soil of polar Mars. Magnesium perchlorate is likely the dominant salt in the polar region's soils. But it could be that the cations are contributed by a mixture of Mg, Ca, and Na. Mg, Ca, and Na perchlorate brines can stay liquid as low as ˜-69, -74, -32°C, respectively. WCL reports 0.7 % (wt) of the soil is pure perchlorate, and if 5% of the northern permanent ice cap is soil, then the perchlorate could make about 1/2800 of the ice cap. This suggests there could be enough perchlorate in the ice cap to generate about 1-3 m of brine at the bed. Large areas under the north polar cap have basal temperatures above -69°C so the Mg and Ca perchlorate brines would be liquid. Because of its high density, the perchlorate brine would pool over impervious layers and make the bed into a perchlorate sludge, which could be mobilized and deformed by the weight of the overburden of ice and soil. The sludge would be deformed and moved outward and stop where the basal temperature dropped below -69°C. During the warmest climates, any frozen cold dam at the edge could be breached and the brine reintroduced to the polar surface. Some of the brine could have penetrated downward under the ice cap. This mobile sludge-bed ice cap has been modeled with a 2-D time-varying model. Results of such model runs have similarities to measured layers found by shallow subsurface radar.

  10. Contemporary Changes in Vegetation of Polar Regions

    NASA Astrophysics Data System (ADS)

    Olech, Maria; Węgrzyn, Michał; Lisowska, Maja; Słaby, Agnieszka; Angiel, Piotr

    2011-01-01

    Rapid climate changes which have been observed over the recent years in both polar regions of the Earth, directly or indirectly affect vegetation dynamics. This article presents the main directions of the changes taking place in the recent years in tundra communities of both polar regions, based on original research carried out in the Arctic in Spitsbergen and in the maritime Antarctic on King George Island.

  11. Study of the behavior of electron density of the lower ionosphere during absorption of the polar cap at latitudes in the Southern Hemisphere and the region of the South Atlantic Geomagnetic Anomaly

    NASA Astrophysics Data System (ADS)

    Mendesdacosta, Aracy

    1991-04-01

    A study is presented of the effect of Solar Proton events (PCA's) that occurred from September 1967 to November 1974, on the phase and amplitude records of very low frequency (VLF) signals on NWC (Australia) - Sao Paulo (Brazil) propagation path, crossing the Southern Hemisphere auroral zone. Twenty five of more than a hundred events of different intensities that occurred in this period were studied and the most relevant ones were described in detail. Simultaneous analysis of transequatorial VLF propagation paths received in Sao Paulo and Curitiba (Brazil) showed also the significant contribution of the South Atlantic Geomagnetic Anomaly to the ionization of the lower part of the ionospheric D-region during the PCA events. The outstanding results was the determination of day and nighttime electron density fitting exponential models to the data analyzed for two regions up to now poorly known: The Antarctic region and the South Atlantic Geomagnetic Anomaly.

  12. Self-sustaining Mars colonies utilizing the North Polar Cap and the Martian atmosphere.

    PubMed

    Powell, J; Maise, G; Paniagua, J

    2001-01-01

    A revolutionary new concept for the early establishment of robust, self-sustaining Martian colonies is described. The colonies would be located on the North Polar Cap of Mars and utilize readily available water ice and the CO2 Martian atmosphere as raw materials to produce all of the propellants, fuel, air, water, plastics, food, and other supplies needed by the colony. The colonists would live in thermally insulated large, comfortable habitats under the ice surface, fully shielded from cosmic rays. The habitats and supplies would be produced by a compact, lightweight (~4 metric tons) nuclear powered robotic unit termed ALPH (Atomic Liberation of Propellant and Habitat), which would land 2 years before the colonists arrived. Using a compact, lightweight 5 MW (th) nuclear reactor/steam turbine (1 MW(e)) power source and small process units (e.g., H2O electrolyzer, H2 and O2 liquefiers, methanator, plastic polymerizer, food producer, etc.) ALPH would stockpile many hundreds of tons of supplies in melt cavities under the ice, plus insulated habitats, to be in place and ready for use when the colonists landed. With the stockpiled supplies, the colonists would construct and operate rovers and flyers to explore the surface of Mars. ALPH greatly reduces the amount of Earth supplied material needed and enables large permanent colonies on Mars. It also greatly reduces human and mission risks and vastly increases the capability not only for exploration of the surrounding Martian surface, but also the ice cap itself. The North Polar Cap is at the center of the vast ancient ocean that covered much of the Martian Northern Hemisphere. Small, nuclear heated robotic probes would travel deep (1 km or more) inside the ice cap, collecting data on its internal structure, the composition and properties of the ancient Martian atmosphere, and possible evidence of ancient life forms (microfossils, traces of DNA, etc.) that were deposited either by wind or as remnants of the ancient ocean

  13. Quantitative Mapping of Surface Texture on the Northern Polar Residual Cap of Mars

    NASA Astrophysics Data System (ADS)

    Milkovich, S. M.; Byrne, S.; Russell, P. S.

    2010-12-01

    The northern polar residual cap (NPRC) of Mars is a water ice deposit with a rough surface made up of pits, knobs, and linear depressions on scales of tens of meters [1]. This roughness manifests as a series of bright and dark patches in visible images. Spectral data indicate that the surface of the NPRC is composed of large-grained (and therefore old) water ice. Due to the presence of this old ice, it is thought that the NPRC is in a current state of net loss of material [2]. The NPRC provides a link between the current martian climate and the historical climate recorded within the layers of the underlying north polar layered deposits. By characterizing and mapping the variations in surface texture of the NPRC, we seek to understand what factors (distance from the pole, GCM and mesoscale wind direction predictions, etc) are currently at work in resurfacing the deposit, and may have been at work in shaping the layers below. Maps of NPRC texture wavelength and orientation are being produced from HiRISE images. Two-dimensional Fourier analysis is performed upon a 256 meter x 256 meter region (corresponding to 512 x 512 pixels in 0.5 cm/pxl images, or 1024 x 1024 pixels in 0.25 cm/pxl images) within each image analyzed. The dominant wavelength of the resulting peak power spectrum corresponds to the average size of a pit-knob pair in the image, and so is a proxy for the scale of the surface roughness. The orientation of the surface roughness (i.e., the orientation of a chain of pits and mounds) is measured from a narrow range of wavelengths encompassing the dominant wavelength. We will report on how the dominant wavelengths and orientations of this surface texture vary with location and what that implies for the processes currently shaping this landscape. [1] P. C. Thomas et al, Nature 404, 161-164, 2000 [2]Y. Langevin et al, Science 307, 5715, 1581-1584, 2005.

  14. Ephemeral Liquid Water at the Surface of Martian North Polar Cap

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Czechowski, Leszek; Velbel, Michael A.

    2015-04-01

    Formation of large, young gypsum deposits within the Olympia Planum region has been an unsolved riddle since its discovery [1]. It was proposed that gypsum was formed by precipitation of water emanating from polar layered deposits [2]. However, it is improbable that a large amount of bulk water could exist under current Martian low atmospheric pressure sufficiently long to form the observed deposits [3]. One of the proposed solutions to this problem is that gypsum is formed due to weathering in the ice [3, 4, 5, 6]. However none of the previous papers have described this process in detail, tested whether it is possible under current Martian conditions, and defined the environmental properties required for this process to occur. The aim of this paper is to determine if solar irradiation available currently at the North Polar Cap (NPC) is sufficient to heat a basaltic dust grain enough to melt a thin layer of glacial ice located directly beneath it. The numerical model used here is based on a one dimensional, time-dependent equation of heat transfer [8]. The model is applicable for grains exposed on the south-facing side of the NPC spiral troughs, during the warmest days of the year (with average or low amount of dust in the atmosphere), when surface temperature reaches 215 K and solar radiation delivers >260 W m^-2 (on the inclined surface). Our calculations show that during the warmest days of summer, pure water-ice located below a dark dust particle lying on the equatorial-facing slopes of the Martian NPC can be melted. Melting occurs over a wide range of used parameters which shows that this phenomenon is relatively common (albeit localized). Our research shows that on the Martian NPC there can be a sufficient amount of transient, metastable liquid water for evaporites such as gypsum to form, as was hypothesized by [3, 4, 5, 6]. Additionally, bulk water surrounding dust grains near the surface and precipitating evaporitic minerals makes the NPC one of the most

  15. Examination of a Deep Subsurface Mars Polar Cap Mission to Address Climate History

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.; Nock, K.; Bearman, G.; Kossakovski, D.; Wilcox, B.

    2000-01-01

    We have examined the technological readiness of a mission to the Mars north polar area for the science objective of developing a climate history. We argue that the polar regions are scientifically extremely important mission sites from the perspectives of both climate history and astrobiology and that a polar deep subsurface mission would constitute a serious challenge and significant accomplishment. Thus a key question is: What is the technical readiness status of such a mission? Additional information is contained in original extended abstract.

  16. Mass balance of Mars' residual south polar cap from CTX images and other data

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Calvin, W.; Cantor, B.; Haberle, R.; James, P. B.; Lee, S. W.

    2016-04-01

    Erosion of pits in the residual south polar cap (RSPC) of Mars concurrent with deposition and fluctuating cap boundaries raises questions about the mass balance and long term stability of the cap. Determining a mass balance by measurement of a net gain or loss of atmospheric CO2 by direct pressure measurements (Haberle, R.M. et al. [2014]. Secular climate change on Mars: An update using one Mars year of MSL pressure data. American Geophysical Union (Fall). Abstract 3947), although perhaps the most direct method, has so far given ambiguous results. Estimating volume changes from imaging data faces challenges, and has previously been attempted only in isolated areas of the cap. In this study we use 6 m/pixel Context Imager (CTX) data from Mars year 31 to map all the morphologic units of the RSPC, expand the measurement record of pit erosion rates, and use high resolution images to place limits on vertical changes in the surface of the residual cap. We find the mass balance in Mars years 9-31 to be -6 to +4 km3/♂y, or roughly -0.039% to +0.026% of the mean atmospheric CO2 mass/♂y. The indeterminate sign results chiefly from uncertainty in the amounts of deposition or erosion on the upper surfaces of deposits (as opposed to scarp retreat). Erosion and net deposition in this period appear to be controlled by summertime planetary scale dust events, the largest occurring in MY 9, another, smaller one in MY 28. The rates of erosion and the deposition observed since MY 9 appear to be consistent with the types of deposits and erosional behavior found in most of the residual cap. However, small areas (<10%) of the cap are distinguished by their greater thickness, polygonal troughs, and embayed contacts with thinner units. These deposits may require extended periods (>100 ♂y) of depositional and/or erosional conditions different from those occurring in the period since MY 9, although these environmental differences could be subtle.

  17. Irregularity anisotropy and drifts from polar-cap scintillations during the current solar maximum

    SciTech Connect

    Basu, S.; Basu, S.; Costa, E.

    1990-05-03

    Spaced receiver scintillation measurements made at Thule, Greenland during two sunspot maximum CEDAR High Latitude Plasma Structure (HLPS) campaigns in Dec 1988 and Nov 1989 have been analyzed to yield phase and amplitude scintillation magnitude, decorrelation time, irregularity drifts and anisotropy of the ground diffraction pattern during well defined polar cap patch and sun-aligned arc events. It is found that all these parameters tend to be different in these two classes of events which are controlled by the Bz component of the interplanetary magnetic field.

  18. Relationship of O(+) Field-Aligned Flows and Densities to Convection Speed in the Polar Cap at 5000 km Altitude

    NASA Technical Reports Server (NTRS)

    Stevenson, B. A.; Horwitz, J. L.; Creel, B.; Elliott, H. A.; Comfort, R. H.; Su, Y. J.; Moore, T. E.; Craven, P. D.

    1999-01-01

    Measurements of thermal O(+) ion number fluxes, densities, field-aligned velocities, and convective velocities from the Thermal Ion Dynamics Experiment (TIDE) on POLAR obtained near 5000 km altitude over the Southern hemisphere are examined. We find that the O(+) parallel velocities and densities are strongly related to the convection speeds. The polar cap densities decrease rapidly with convection speed, with a linear least square fit formula to bin averaged data giving the relationship log(N(sub (sub _)O(+))) = -0.33* V(sub (sub _)conv)) + 0.07, with a linear regression coefficient of r = -0.96. The parallel bulk flow velocities are on average slightly downward (0 - 2 km/s) for V(sub (sub _)conv) < 2.5 km/s, but tend to be upward (0 - 4 km/s) for average V(sub (sub _)conv) > 2.5 km/s. We interpret these relationships in terms of the Cleft Ion Fountain paradigm [e.g., Horwitz and Lockwood, 1985]. The densities decline with convection speed owing to increased spreading and resulting dilution from the restricted cleft source over the polar cap area with convection speed. The parallel velocities tend to be downward for low convection speeds because they fall earthward after initial cleft injection at shorter distances into the polar cap for low convection speeds. At the higher convection speeds, the initially-upward flows are transported further into the polar cap and thus occupy a larger area of the polar cap.

  19. Correlation of Martian South Polar CO2 Seasonal Cap Retreat With Low Altitude Clouds: A Control On Annual Accumulation

    NASA Astrophysics Data System (ADS)

    Smith, Isaac; Spiga, Aymeric

    2014-05-01

    Both the north and south polar layered deposits (NPLD and SPLD) comprise the majority of surface ice on Mars and offer a historical record for understanding recent climate. Of importance, the deposits undergo seasonal variability, between winter (when CO2 ice frost covers the polar regions) and summer (when the CO2 ice has sublimed). Recent evidence has shown that winds and atmospheric deposition played major roles for forming the spiral troughs that cover the NPLD. Observations of low altitude clouds (or visible expressions of katabatic jumps), radar stratigraphy, and surface morphology, in combination with high resolution mesoscale simulations from the Laboratoire de Météorologie Dynamique, demonstrate that ice is transported across the NPLD by wind to form and modify the troughs [Smith et al., 2013]. We employ the same techniques on the SPLD to find that the processes affecting southern spiral troughs are very similar, although there is an additional seasonal component not detected on the NPLD. Clouds, as mechanisms of deposition, retreat pole-ward during southern spring and summer. The retreat is matched spatially to modeled high speed winds near the CO2 seasonal ice cap boundary. Our mesoscale simulations reveal that topographic heights of the SPLD primarily drive slope-wind (katabatic) circulations. This existing circulation is reinforced by an additional thermally-direct circulation driven by the retreating CO2 ice in proximity to nearby exposed low albedo deposits, explaining why enhanced winds (and trough clouds) are mostly found in the vicinity of the CO2 seasonal ice boundary. In one simulation, at Ls 290°, the ice line is located so that the slope winds produced by the SPLD topography are optimally enhanced (up to 20 ms-1) by thermally directed circulations caused by a nearly 100 K thermal contrast. This work, in combination with detailed stratigraphic analysis from ground penetrating radar indicates that sites of deposition and retention of ice on

  20. Elimination of surface band bending on N-polar InN with thin GaN capping

    SciTech Connect

    Kuzmík, J. Haščík, Š.; Kučera, M.; Kúdela, R.; Dobročka, E.; Adikimenakis, A.; Mičušík, M.; Gregor, M.; Plecenik, A.; Georgakilas, A.

    2015-11-09

    0.5–1 μm thick InN (0001) films grown by molecular-beam epitaxy with N- or In-polarity are investigated for the presence of native oxide, surface energy band bending, and effects introduced by 2 to 4 monolayers of GaN capping. Ex situ angle-resolved x-ray photo-electron spectroscopy is used to construct near-surface (GaN)/InN energy profiles, which is combined with deconvolution of In3d signal to trace the presence of InN native oxide for different types of polarity and capping. Downwards surface energy band bending was observed on bare samples with native oxide, regardless of the polarity. It was found that the In-polar InN surface is most readily oxidized, however, with only slightly less band bending if compared with the N-polar sample. On the other hand, InN surface oxidation was effectively mitigated by GaN capping. Still, as confirmed by ultra-violet photo-electron spectroscopy and by energy band diagram calculations, thin GaN cap layer may provide negative piezoelectric polarization charge at the GaN/InN hetero-interface of the N-polar sample, in addition to the passivation effect. These effects raised the band diagram up by about 0.65 eV, reaching a flat-band profile.

  1. Sedimentation Waves on the Martian North Polar Cap: Analogy with Megadunes in Antarctica

    NASA Astrophysics Data System (ADS)

    Herny, C.; Masse, M.; Bourgeois, O.; Carpy, S.; Le Mouelic, S.; Appéré, T.; Smith, I. B.; Spiga, A.; Perret, L.; Rodriguez, S.; Piquet, T.; Gaudin, D.; Le Menn, E.

    2014-12-01

    Complex feedbacks between katabatic winds and the cryosphere may lead to the development of sedimentation waves at the surface of ice sheets. These have been first described and named megadunes in Antarctica. Here we use topographic data, optical images, spectroscopic data and radar soundings, acquired by Mars orbiters, to show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. They have similarities with Antarctic megadunes regarding their surface morphology, texture, grain size, and internal stratigraphic architecture. Based on this analogy, we are currently developing a model of ice/wind interaction at the surface of ice sheets. In Antarctica the accumulation processes on megadunes fields is generally attributed to the wind-blown snow transport while on sedimentation waves of the North Polar Cap of Mars the accumulation seems to be dominated by sublimation/condensation processes at the surface. The model is designed to explore the implication of the water vapor mass transfer and heat transfer on the development of sedimentation waves both on Mars and Earth.

  2. Solar Cycle Variations in Polar Cap Area Measured by the SuperDARN Radars

    NASA Astrophysics Data System (ADS)

    Imber, S. M.; Milan, S. E.; Lester, M.

    2013-12-01

    We present a long term study, from January 1996 - August 2012, of the latitude of the Heppner-Maynard Boundary (HMB) measured at midnight using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection, and is used in this study as a measure of the global magnetospheric dynamics and activity. We find that the yearly distribution of HMB latitudes is single-peaked at 64° magnetic latitude for the majority of the 17-year interval. During 2003 the envelope of the distribution shifts to lower latitudes and a second peak in the distribution is observed at 61°. The solar wind-magnetosphere coupling function derived by Milan et al. (2012) suggests that the solar wind driving during this year was significantly higher than during the rest of the 17-year interval. In contrast, during the period 2008-2011 HMB distribution shifts to higher latitudes, and a second peak in the distribution is again observed, this time at 68° magnetic latitude. This time interval corresponds to a period of extremely low solar wind driving during the recent extreme solar minimum. This is the first statistical study of the polar cap area over an entire solar cycle, and the results demonstrate that there is a close relationship between the phase of the solar cycle and the area of the polar cap on a large scale statistical basis.

  3. Solar cycle variations in polar cap area measured by the superDARN radars

    NASA Astrophysics Data System (ADS)

    Imber, S. M.; Milan, S. E.; Lester, M.

    2013-10-01

    present a long-term study, from January 1996 to August 2012, of the latitude of the Heppner-Maynard Boundary (HMB) measured at midnight using the northern hemisphere Super Dual Auroral Radar Network (SuperDARN). The HMB represents the equatorward extent of ionospheric convection and is used in this study as a measure of the global magnetospheric dynamics. We find that the yearly distribution of HMB latitudes is single peaked at 64° magnetic latitude for the majority of the 17 year interval. During 2003, the envelope of the distribution shifts to lower latitudes and a second peak in the distribution is observed at 61°. The solar wind-magnetosphere coupling function derived by Milan et al. (2012) suggests that the solar wind driving during this year was significantly higher than during the rest of the 17 year interval. In contrast, during the period 2008-2011, HMB distribution shifts to higher latitudes, and a second peak in the distribution is again observed, this time at 68° magnetic latitude. This time interval corresponds to a period of extremely low solar wind driving during the recent extreme solar minimum. This is the first long-term study of the polar cap area and the results demonstrate that there is a close relationship between the solar activity cycle and the area of the polar cap on a large-scale, statistical basis.

  4. A Case for Microorganisms on Comets, Europa and the Polar Ice Caps of Mars

    NASA Technical Reports Server (NTRS)

    Hoover, Richard B.; Pikuta, Elena V.

    2003-01-01

    Microbial extremophiles live on Earth wherever there is liquid water and a source of energy. Observations by ground-based observatories, space missions, and satellites have provided strong evidence that water ice exists today on comets, Europa, Callisto, and Ganymede and in the snow, permafrost, glaciers and polar ice caps of Mars. Studies of the cryoconite pools and ice bubble systems of Antarctica suggest that solar heating of dark rocks entrained in ice can cause localized melting of ice providing ideal conditions for the growth of microbial communities with the creation of micro-environments where trapped metabolic gasses produce entrained isolated atmospheres as in the Antarctic ice-bubble systems. It is suggested that these considerations indicate that several groups of microorganisms should be capable of episodic growth within liquid water envelopes surrounding dark rocks in cometary ices and the permafrost and polar caps of Mars. We discuss some of the types of microorganisms we have encountered within the permafrost and snow of Siberia, the cryoconite pools of Alaska, and frozen deep within the Antarctic ice sheet above Lake Vostok.

  5. Testing Predictions of the Ionospheric Convection from the Expanding/Contracting Polar Cap Paradigm

    NASA Astrophysics Data System (ADS)

    Walach, M. T.; Milan, S. E.; Yeoman, T. K.; Hairston, M. R.; Hubert, B. A.

    2015-12-01

    The expanding/contracting polar cap (ECPC) paradigm, or the time-dependent Dungey cycle, provides a theoretical framework for understanding solar wind-magnetosphere-ionosphere coupling. The ECPC describes the relationship between magnetopause reconnection and substorm growth phase, magnetotail reconnection and substorm expansion phase, associated changes in auroral morphology, and ionospheric convective motions. Despite the many successes of the model, there has yet to be a rigorous test of the predictions made regarding ionospheric convection, which remains a final hurdle for the validation of the ECPC. In this study we undertake a comparison of ionospheric convection, as measured by ion driftmeters on board DMSP (Defense Meteorological Satellite Program) satellites, with motions predicted by a theoretical model (Milan, 2013). The model is coupled to measurements of changes in the size of the polar cap made using global auroral imagery from the IMAGE FUV (Imager for Magnetopause to Aurora Global Exploration Far Ultraviolet) instrument, as well as the dayside reconnection rate, calculated using the OMNI dataset. The results show that we can largely predict the magnitudes of ionospheric convection flows using the context of our understanding of magnetic reconnection at the magnetopause and in the magnetotail.

  6. Observations of the north polar region of Mars from the Mars orbiter laser altimeter.

    PubMed

    Zuber, M T; Smith, D E; Solomon, S C; Abshire, J B; Afzal, R S; Aharonson, O; Fishbaugh, K; Ford, P G; Frey, H V; Garvin, J B; Head, J W; Ivanov, A B; Johnson, C L; Muhleman, D O; Neumann, G A; Pettengill, G H; Phillips, R J; Sun, X; Zwally, H J; Banerdt, W B; Duxbury, T C

    1998-12-11

    Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography. PMID:9851922

  7. Observations of the north polar region of Mars from the Mars orbiter laser altimeter

    NASA Technical Reports Server (NTRS)

    Zuber, M. T.; Smith, D. E.; Solomon, S. C.; Abshire, J. B.; Afzal, R. S.; Aharonson, O.; Fishbaugh, K.; Ford, P. G.; Frey, H. V.; Garvin, J. B.; Head, J. W.; Ivanov, A. B.; Johnson, C. L.; Muhleman, D. O.; Neumann, G. A.; Pettengill, G. H.; Phillips, R. J.; Sun, X.; Zwally, H. J.; Banerdt, W. B.; Duxbury, T. C.

    1998-01-01

    Elevations from the Mars Orbiter Laser Altimeter (MOLA) have been used to construct a precise topographic map of the martian north polar region. The northern ice cap has a maximum elevation of 3 kilometers above its surroundings but lies within a 5-kilometer-deep hemispheric depression that is contiguous with the area into which most outflow channels emptied. Polar cap topography displays evidence of modification by ablation, flow, and wind and is consistent with a primarily H2O composition. Correlation of topography with images suggests that the cap was more spatially extensive in the past. The cap volume of 1.2 x 10(6) to 1.7 x 10(6) cubic kilometers is about half that of the Greenland ice cap. Clouds observed over the polar cap are likely composed of CO2 that condensed out of the atmosphere during northern hemisphere winter. Many clouds exhibit dynamical structure likely caused by the interaction of propagating wave fronts with surface topography.

  8. Identifications of the polar cap boundary and the auroral belt in the high altitude magnetosphere: A model for field aligned currents

    NASA Technical Reports Server (NTRS)

    Sugiura, M.

    1974-01-01

    Using the OGO-5 fluxgate magnetometer data, the polar cap boundary is identified in the high altitude magnetosphere by a sudden transition from a dipolar field to a more tail like configuration. The basic pattern of the magnetic field variations observed during the satellite's traversal of the auroral belt is presented. This pattern shows the existence of a field aligned current layer on the equator side of the polar cap boundary. Currents flow in the opposite directions in the two field aligned current layers. The current directions in these layers as observed by OGO-5 in the high-altitude magnetosphere are the same as those observed at low altitudes by the polar orbiting TRIAD satellite. The magnetic field in the region where the lower latitude field aligned current layer is situated is essentially meridional. Thus the equatorial current closure of this current system must be via the equatorial current sheet. The two field aligned current systems, one at the polar cap boundary and the other on the low latitude side of the auroral belt, are coupled through the Pedersen current in the ionosphere.

  9. Mapping the Martian Polar Ice Caps: Applications of Terrestrial Optical Remote Sensing Methods

    NASA Astrophysics Data System (ADS)

    Nolin, A. W.

    1998-01-01

    With improvements in both instrumentation and algorithms, methods for mapping terrestrial snow cover using optical remote sensing data have progressed significantly over the past decade. Multispectral data can now be used to determine not only the presence or absence of snow but the fraction of snow cover in a pixel. Radiative transfer models have been used to quantify the nonlinear relationship between surface reflectance and grain size, thereby providing the basis for mapping snow grain size from surface reflectance images Because subpixel mixtures of snow and other land cover types create erroneous estimates of snow grain-size, the snow fraction information can be used in tandem with the grain size algorithm to limit its use to only those pixels that have complete snow cover. Model-derived characterization of the bidirectional reflectance distribution function (BRDF) provides the means for converting measured bidirectional reflectance to directional-hemispherical albedo. In recent work, this approach has allowed climatologists to examine the large-scale seasonal variability of albedo on the Greenland ice sheet. This seasonal albedo variability results from increases in snow grain size and exposure of the underlying ice cap as the seasonal snow cover ablates away. it will soon be possible to apply some of these terrestrial mapping methods to learn more about martian polar caps. What is most needed for this purpose is multispectral optical imagery. The extent and variability of the ice caps and their seasonal CO2 frost covering can be mapped with only a few spectral bands distributed through the visible and near-infrared wavelengths. Imaging spectrometer data would provide the ability to quantify mineral-ice mixtures and to better characterize the martian atmosphere. These are both needed for albedo determinations while only the former is required for subpixel frost/ice mapping. Perhaps the most significant terrestrial mapping application is the potential use of

  10. Interannual Comparison of Water Vapor in the North Polar Region of Mars

    NASA Technical Reports Server (NTRS)

    Tamppari, L. K.; Smith, M. D.; Hale, A. S.; Bass, D. S.

    2003-01-01

    In order to better understand the current climate of Mars, we seek to understand atmospheric water in the north polar region. Our approach is to examine the water transport and cycling issues within the north polar region and in/out of the region on seasonal and annual timescales. Viking Mars Atmospheric Water Detector (MAWD) data showed that water vapor increased as the northern summer season progressed and temperatures increased, and that vapor appeared to be transported southward . However, there has been uncertainty about the amount of water cycling in and out of the north polar region, as evidenced by residual polar cap visible brightness changes between one Martian year (Mariner 9 data) and a subsequent year (Viking data). These changes were originally thought to be interannual variations in the amount of frost sublimed based on global dust storm activity . However, Viking thermal and imaging data were re-examined and it was found that 14-35 pr m of water -ice appeared to be deposited on the cap later in the summer season, indicating that some water may be retained and redistributed within the polar cap region. This late summer deposition could be due to adsorption directly onto the cap surface or due to snowfall. We seek to understand what happens to the water on seasonal and interannual timescales. We address these issues by examining water vapor in the north polar region of Mars during the north spring and summer period from MGS TES data and by comparing these results to the Viking MAWD results.

  11. Time scales of erosion and deposition recorded in the residual south polar cap of Mars

    NASA Astrophysics Data System (ADS)

    Thomas, P. C.; Calvin, W. M.; Gierasch, P.; Haberle, R.; James, P. B.; Sholes, S.

    2013-08-01

    The residual south polar cap (RSPC) of Mars has been subject to competing processes during recent Mars years of high resolution image coverage: continuing erosion of scarps while the maximum extent grows as well as shrinks (Piqueux, S., Christensen, P.R. [2008]. J. Geophys. Res. (Planets) 113, 2006; James, P.B., Thomas, P.C., Malin, M.C. [2010]. Icarus 208, 82-85). Additionally, the cap has a variety of morphologies and erosion (scarp retreat) rates (Thomas, P.C., James, P.B., Calvin, W.M., Haberle, R., Malin, M.C. [2009]. Icarus 203, 352-375). Do these different forms and competing processes indicate an aging and possibly disappearing cap, a growing cap, or a fluctuating cap, and is it possible to infer the timescales of the processes acting on the RSPC? Here we use the latest imaging data from Mars' southern summer in Mars year 30 (Calendar year 2011) to evaluate erosion rates of forms in the RSPC over 6 Mars years, and to map more fully features whose sizes can be used to predict deposit ages. Data through Mars year 30 show that scarp retreat rates in the RSPC have remained approximately the same for at least 6 Mars years and that these rates of erosion also apply approximately over the past 21 Mars years. The thicker units appear to have undergone changes in the locations of new pit formation about 30-50 Mars years ago. The thinner units have some areas that are possibly 80 Mars years old, with some younger materials having accumulated more than a meter in thickness since Mars year 9. Formation of the thicker units probably required over 100 Mars years. The upper surfaces of most areas, especially the thicker units, show little change at the few-cm level over the last 2 Mars years. This observation suggests that current conditions are substantially different from those when the thicker units were deposited. A prime characteristic of the evolution of the RSPC is that some changes are progressive, such as those involving scarp retreat, while others, such as the

  12. The earth's radiation belts, auroral zones, and polar caps: Particle models, event studies, and effects on materials

    NASA Astrophysics Data System (ADS)

    Carovillano, R. L.

    1992-04-01

    Some research activities are as follows. (1) An empirical DMSP data base of the most poleward ion precipitation boundary: The data base was analyzed statistically and analytically. At each MLT there is great variance, and the ion boundary correlates best with AE. The average boundary is a circle offset from the geomagnetic pole that expands with geomagnetic activity. (2) An analytical model of convection and currents in the height-integrated ionosphere coupled to field aligned currents: Results include the effect of auroral conductivity; the deterministic coupling between Region 1 and Region 2 currents; the generation of auroral electrojet currents; the electrical shielding of low latitudes; two cell and multiple cell convection patterns; and conductivity gradient effects. (3) Energy dispersion discovered at the ion polar cap boundary: Interpretations have the ions originating in the plasma sheet boundary layer. (4) Various tasks and services with Air Force data bases: Tasks included particle event studies, the auroral boundary index, the polar rain index, and several CRRES projects including the static radiation belt model. Services included algorithm development, provision for data storage, access, and documentation.

  13. The polar regions and the USGCRP

    SciTech Connect

    MacCracken, M. C.,

    1997-06-01

    The US Global Change Research Program provides interagency coordination for the ten federal agencies supporting research on global environmental change. Program activities are described annually in Our Changing Planet, which is a report submitted to Congress each year in support of the President`s budget request. The USGCRP also periodically prepares a multiyear research overview (referred to officially as a multiyear research plan even though it is more of a strategy) to provide a framework for organizing research over the next ten years. Consideration of the polar regions is of particular interest in pursuit of the goals of the USGCRP in each of the major environmental issue areas. Especially with the increased emphasis of the USGCRP on the regional aspects of global environmental change and the regional differentiation of consequences for the environment, the polar regions will be receiving intense attention in future research activities.

  14. Is Substorm Onset Seeded by Cross-Tail Current Enhancement Resulting from Parallel Energization of Oxygen Ion Polar Cap Outflow?

    NASA Astrophysics Data System (ADS)

    Sofko, G. J.; Hussey, G. C.; McWilliams, K. A.

    2015-12-01

    The parallel energization of polar cap outflow (PCO) has been shown to be highly effective along newly-created lobe lines where the geometry is such that the Coulomb force due to the dawn-to-dusk electric field is roughly parallel to the curvature drift of the ions. This "Coulomb-curvature" interaction can produce a parallel energization rate that raises the parallel energy of the ions to about 5-6 keV before they reach the Neutral Sheet (NSh) at about 11 earth radii downtail. Then, in the outer NSh, they produce a strong westward curvature current. When they enter the inner neutral sheet (INSh) where they become "unmagnetized", they are accelerated westward by the dawn-dusk electric field. This causes their perpendicular energy and their pitch angle to increase such that the ions essentially become trapped in the inner NSh while continuing to accelerate westward. This additional westward current in the inner NSh accompanies the westward curvature current produced in the two outer NSh layers. This total ion current is supplemented by the westward curvature current caused by the eastward curvature drift of the electrons. The combined total ion and electron current is sufficient to severely decrease the magnetic field near the earthward end of the NSh. The magnetic pressure decrease is compensated by the particle pressure increase due to inflow of oxygen ions from the northern and southern polar caps. The conditions near the earthward edge of the NSh and in the adjoining plasmasheet regions neighbouring the NSh become ideal for reconnection and the dipolarization that follows.

  15. Interannual observations and quantification of summertime H2O ice deposition on the Martian CO2 ice south polar cap

    NASA Astrophysics Data System (ADS)

    Brown, Adrian J.; Piqueux, Sylvain; Titus, Timothy N.

    2014-11-01

    The spectral signature of water ice was observed on Martian south polar cap in 2004 by the Observatoire pour l'Mineralogie, l'Eau les Glaces et l'Activite (OMEGA) (Bibring et al., 2004). Three years later, the OMEGA instrument was used to discover water ice deposited during southern summer on the polar cap (Langevin et al., 2007). However, temporal and spatial variations of these water ice signatures have remained unexplored, and the origins of these water deposits remains an important scientific question. To investigate this question, we have used observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO) spacecraft of the southern cap during austral summer over four Martian years to search for variations in the amount of water ice. We report below that for each year we have observed the cap, the magnitude of the H2O ice signature on the southern cap has risen steadily throughout summer, particularly on the west end of the cap. The spatial extent of deposition is in disagreement with the current best simulations of deposition of water ice on the south polar cap (Montmessin et al., 2007). This increase in water ice signatures is most likely caused by deposition of atmospheric H2O ice and a set of unusual conditions makes the quantification of this transport flux using CRISM close to ideal. We calculate a 'minimum apparent' amount of deposition corresponding to a thin H2O ice layer of 0.2 mm (with 70% porosity). This amount of H2O ice deposition is 0.6-6% of the total Martian atmospheric water budget. We compare our 'minimum apparent' quantification with previous estimates. This deposition process may also have implications for the formation and stability of the southern CO2 ice cap, and therefore play a significant role in the climate budget of modern day Mars.

  16. Palmer Quest: A Feasible Nuclear Fission "Vision Mission" to the Mars Polar Caps

    NASA Technical Reports Server (NTRS)

    Carsey, F. D.; Beegle, L. W.; Nakagawa, R.; Elliott, J. O.; Matthews, J. B.; Coleman, M. L.; Hecht, M. H.; Ivaniov, A. B.; Head, J. W.; Milkovich, S.

    2005-01-01

    We are engaged in a NASA Vision Mission study, called Palmer Quest after the American Antarctic explorer Nathaniel Palmer, to assess the presence of life and evaluate the habitability of the basal domain of the Mars polar caps. We address this goal through four objectives: 1. Determine the presence of amino acids, nutrients, and geochemical heterogeneity in the ice sheet. 2. Quantify and characterize the provenance of the amino acids in Mars ice. 3. Assess the stratification of outcropped units for indications of habitable zones. 4. Determine the accumulation of ice, mineralogic material, and amino acids in Mars ice caps over the present epoch. Because of the defined scientific goal for the vision mission, the Palmer Quest focus is astrobiological; however, the results of the study make us optimistic that aggressive multi-platform in-situ missions that address a wide range of objectives, such as climate change, can be supported by variations of the approach used on this mission. Mission Overview: The Palmer Quest baseline

  17. Pulsar Polar Cap Heating and Surface Thermal X-ray Emission. 1; Curvature Radiation Pair Fronts

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alexander G.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We investigate the effect of pulsar polar cap (PC) heating produced by positrons returning from the upper pair formation front. Our calculations are based on a self-consistent treatment of the pair dynamics and the effect of electric field screening by the returning positrons. We calculate the resultant X-ray luminosities and discuss the dependence of the PC heating efficiencies on pulsar parameters, such as characteristic spin-down age, spin period, and surface magnetic field strength. In this study we concentrate on the regime where the pairs are produced in a magnetic field by curvature photons emitted by accelerating electrons. Our theoretical results are not in conflict with the available observational x-ray data and suggest that the effect of PC heating should significantly contribute to the thermal x-ray fluxes from middle-aged and old pulsars. The implications for current and future x-ray observations of pulsars are briefly outlined.

  18. Plasma flow reversals at the dayside magnetopause and the origin of asymmetric polar cap convection

    NASA Technical Reports Server (NTRS)

    Gosling, J. T.; Thomsen, M. F.; Bame, S. J.; Elphic, R. C.; Russell, C. T.

    1990-01-01

    Events observed in a fast plasma experiment, where the y-component of the plasma flow within the low latitude boundary layer and magnetopause current layer was oppositely directed to that in the adjacent magnetosheath, are examined. The observations are shown to be qualitatively and quantitatively consistent with previous observations of accelerated flows at the magnetopause and with models of magnetic reconnection, with reconnection occurring at low latitudes near the GSE XY plane, independently of the magnitude or the sign of the y-component ot the local magnetosheath magnetic field. Local magnetic shears at the magnetopause for these events (in 60-180 deg range) and the fact that these events occur at low latitudes do not support the antiparallel merging hypothesis. The observations of B(y)-dependent flow reversals demonstrate how the asymmetric polar cap convection and related phenomena, such as the Svalgaard-Mansurov effect, originate in magnetic reconnection at the dayside magnetopause.

  19. Stratigraphy and evolution of the buried CO2 deposit in the Martian south polar cap

    NASA Astrophysics Data System (ADS)

    Bierson, C. J.; Phillips, R. J.; Smith, I. B.; Wood, S. E.; Putzig, N. E.; Nunes, D.; Byrne, S.

    2016-05-01

    Observations by the Shallow Radar instrument on Mars Reconnaissance Orbiter reveal several deposits of buried CO2 ice within the south polar layered deposits. Here we present mapping that demonstrates this unit is 18% larger than previously estimated, containing enough mass to double the atmospheric pressure on Mars if sublimated. We find three distinct subunits of CO2 ice, each capped by a thin (10-60 m) bounding layer (BL). Multiple lines of evidence suggest that each BL is dominated by water ice. We model the history of CO2 accumulation at the poles based on obliquity and insolation variability during the last 1 Myr assuming a total mass budget consisting of the current atmosphere and the sequestered ice. Our model predicts that CO2 ice has accumulated over large areas several times during that period, in agreement with the radar findings of multiple periods of accumulation.

  20. Variations in Surface Texture of the North Polar Residual Cap of Mars

    NASA Technical Reports Server (NTRS)

    Milkovich, S. M.; Byrne, S.; Russell, P. S.

    2011-01-01

    The northern polar residual cap (NPRC) of Mars is a water ice deposit with a rough surface made up of pits, knobs, and linear depressions on scales of tens of meters. This roughness manifests as a series of bright mounds and dark hollows in visible images; these bright and dark patches have a characteristic wavelength and orientation. Spectral data indicate that the surface of the NPRC is composed of large-grained (and therefore old) water ice. Due to the presence of this old ice, it is thought that the NPRC is in a current state of net loss of material a result potentially at odds with impact crater statistics, which suggest ongoing deposition over the past 10-20 Kyr.

  1. High-Energy Emission From the Polar Cap and Slot Gap

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2006-01-01

    Thirty-five years after the discovery of rotation-powered pulsars, we still do not understand the fundamentals of their pulsed emission at any wavelength. I will review the latest developments in understanding the high-energy emission of rotation-powered pulsars, with particular emphasis on the polar cap and slot gap models. Special and general relativistic effects play important roles in pulsar emission, from inertial frame-dragging near the stellar surface to aberration, time-of-flight and retardation of the magnetic field near the light cylinder. Understanding how these effects determine what we observe at different wavelengths is critical to unraveling the emission physics. I will discuss how the next generation of gamma-ray detectors, AGILE and GLAST, will test prediction of these models.

  2. Plasma drifts associated with a system of sun-aligned arcs in the polar cap

    SciTech Connect

    Mende, S.B.; Doolittle, J.H.; Robinson, R.M.; Vondrak, R.R.; Rich, F.J.

    1988-01-01

    A series of four sun-aligned arcs passed over Sondre Stromfjord, Greenland, on the night of the 17th and 18th of February, 1985. Observations of these arcs were made using the Sondrestrom incoherent scatter radar and an intensified all-sky imaging TV system that was operated at the radar site. The first of the four arcs crossed the Sondre Stromfjord meridian just before local midnight moving westward, and the other three arcs followed at approximately half-hour intervals. When we account for the earth's rotation, the arc drift in an inertial frame was eastward, or dusk to dawn. The half-hour interval between meridian crossings of the arcs implies that the mean spacing between the arcs was 180 km. A Defense Meteorological Satellite Program (DMSP) F6 satellite pass at 0110 UT revealed the presence of highly structured electron and ion precipitation throughout the polar cap. The DMSP visible imager detected a single, sun-aligned arc associated with the largest peak in precipitating electron flux. This arc was also observed at Thule, Greenland, with an intensified film camera. These observations suggest that at least one of the arcs that were observed at Sondre Stromfjord extended across a large part of the polar cap. The radar at Sondre Stromfjord measured electron density and ion drift velocities associated with the four arcs. The radar drift measurements were superimposed on the all-sky video images to determine the location of the measurements relative to the arcs. Plasma drifts outside the arcs were found to be both sunward and antisunward, while within the arcs the drifts were predominantly antisunward. The variability of the drifts in the direction parallel to the arcs indicates that the electric fields were highly structured even though the configuration and motion of the arcs were well behaved.

  3. Science goals for a Mars Polar Cap subsurface mission : optical approaches for investigations of inclusions in ice

    NASA Technical Reports Server (NTRS)

    Carsey, Frank; Mogensen, Claus T.; Behar, Alberto; Engelhardt, Hermann; Lane, Arthur L.

    2002-01-01

    The Mars Polar Caps are highly interesting features of Mars and have received much recent attention with new and exciting data on morphology, basal units, and layered outcroppings. We have examined the climatological, glaciological, and geological issues associated with a subsurface exploration of the Mars North Polar Cap and have determined that a finescale optical examination of ice in a borehole, to examine the stratigraphy, geochemistry and geochronology of the ice, is feasible. This information will enable reconstruction of the development of the cap as well as prediction of the properties of its ice. We present visible imagery taken of dust inclusions in archived Greenland ice cores as well as in-situ images of accreted lithologic inclusions in West Antarctica, and we argue for use of this kind of data in Mars climate reconstruction as has been successful with Greenland and Antarctic ice core analysis. .

  4. Science goals for a Mars Polar Cap subsurface mission : optical approaches for investiagations of inclusions in ice

    NASA Technical Reports Server (NTRS)

    Mogensen, Claus T.; Carsey, Frank D.; Behar, Alberto; Engelhardt, Hermann; Lane, Arthur L.

    2002-01-01

    The Mars Polar Caps are highly interesting features of Mars and have received much recent attention with new and exciting data on morphology, basal units, and layered outcroppings. We have examined the climatological, glaciological, and geological issues associated with a subsurface exploration of the Mars North Polar Cap and have determined that a finescale optical examination of ice in a borehole, to examine the stratigraphy, geochemistry and geochronology of the ice, is feasible. This information will enable reconstruction of the development of the cap as well as predication of the properties of its ice. We present visible imagery taken of dust inclusions in archived Greenland ice cores as well as in-situ images of accreted lithologic inclusions in West Antarctica, and we argue for use of this kind of data in Mars climate reconstruction as has been successful with Greenland and Antarctic ice core anlaysis.

  5. New evidence of dayside plasma transportation over the polar cap to the prevailing dawn sector in the polar upper atmosphere for solar-maximum winter

    NASA Astrophysics Data System (ADS)

    Yang, Sheng-Gao; Zhang, Bei-Chen; Fang, Han-Xian; Kamide, Y.; Li, Chong-Yin; Liu, Jun-Ming; Zhang, Shun-Rong; Liu, Rui-Yuan; Zhang, Qing-He; Hu, Hong-Qiao

    2016-06-01

    It is well known that owing to the transport of high-density sunlit plasma from dayside to nightside primarily by convection, polar cap tongue of ionization (TOI), polar cap patches, and blobs are common features in the polar ionosphere. The steep density gradients at the edges of these structures lead to severe problems in applications involving radio waves traversing the ionosphere. To better understand the evolution of TOI/patches/blobs, it is essential to examine how the transported sunlit plasma is distributed. Through averaging the hourly total electron content in solar-maximum winter, we present complete distribution of polar ionospheric plasma and find that the dayside plasma can be transported through cusp, over polar cap, and eventually to the prevailing dawnside, showing asymmetric distribution around magnetic midnight. The negative interplanetary magnetic field By or Bz component is favored for the plasma transportation from dayside to the prevailing dawn sector. This provides direct evidence for the plasma source of the dawnside high-density plasma structure. The same corotating convection direction as convection at auroral dawnside is responsible for the prevailing dawn sector transportation. This finding is significant for forecasting TOI/patches/blobs in conducting space weather in the polar ionosphere.

  6. Multiscale and cross entropy analysis of auroral and polar cap indices during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Gopinath, Sumesh; Prince, P. R.

    2016-01-01

    In order to improve general monoscale information entropy methods like permutation and sample entropy in characterizing the irregularity of complex magnetospheric system, it is necessary to extend these entropy metrics to a multiscale paradigm. We propose novel multiscale and cross entropy method for the analysis of magnetospheric proxies such as auroral and polar cap indices during geomagnetic disturbance times. Such modified entropy metrics are certainly advantageous in classifying subsystems such as individual contributions of auroral electrojets and field aligned currents to high latitude magnetic perturbations during magnetic storm and polar substorm periods. We show that the multiscale entropy/cross entropy of geomagnetic indices vary with scale factor. These variations can be attributed to changes in multiscale dynamical complexity of non-equilibrium states present in the magnetospheric system. These types of features arise due to imbalance in injection and dissipation rates of energy with variations in magnetospheric response to solar wind. We also show that the multiscale entropy values of time series decrease during geomagnetic storm times which reveals an increase in temporal correlations as the system gradually shifts to a more orderly state. Such variations in entropy values can be interpreted as the signature of dynamical phase transitions which arise at the periods of geomagnetic storms and substorms that confirms several previously found results regarding emergence of cooperative dynamics, self-organization and non-Markovian nature of magnetosphere during disturbed periods.

  7. The interplanetary electric field, cleft currents and plasma convection in the polar caps

    NASA Technical Reports Server (NTRS)

    Banks, P. M.; Clauer, C. R.; Araki, T.; St. Maurice, J. P.; Foster, J. C.

    1984-01-01

    The relationship between the pattern of plasma convection in the polar cleft and the dynamics of the interplanetary electric field (IEF) is examined theoretically. It is shown that owing to the geometrical properties of the magnetosphere, the East-West component of the IEF will drive field-aligned currents which connect to the ionosphere at points lying on either side of noon, while currents associated with the North-South component of the IEF will connect the two polar caps as sheet currents, also centered at 12 MLT. In order to describe the consequences of the Interplanetary Magnetic Field (IMF) effects upon high-latitude electric fields and convection patterns, a series of numerical simulations was carried out. The simulations were based on a solution to the steady-state equation of current continuity in a height-integrated ionospheric current. The simulations demonstrate that a simple hydrodynamical model can account for the narrow 'throats' of strong dayside antisunward convection observed during periods of southward interplanetary IMF drift, as well as the sunward convection observed during periods of strongly northward IMF drift.

  8. A Sublimation Model for the Martian Polar Swiss-Cheese Features. Observational and Modeling Studies of the South Polar Residual Cap

    NASA Technical Reports Server (NTRS)

    Byrne, Shane; Ingersoll, Andrew P.

    2002-01-01

    In their pioneering work Leighton and Murray argued that the Mars atmosphere, which is 95 percent CO2 today, is controlled by vapor equilibrium with a much larger polar reservoir of solid CO2. Here we argue that the polar reservoir is small and cannot function as a long-term buffer to the more massive atmosphere. Our work is based on modeling the circular depressions (Swiss-cheese features) in the south polar cap. We argue that a solid CO2 layer approximately 8 meters thick is being etched away to reveal water ice underneath. Preliminary results from the THEMIS (Thermal Emission Imaging System) instrument seem to confirm our model.

  9. South Polar Region of Mars: Topography and Geology

    NASA Technical Reports Server (NTRS)

    Schenk, P. M.; Moore, J. M.

    1999-01-01

    The polar layered deposits of Mars represent potentially important volatile reservoirs and tracers for the planet's geologically recent climate history. Unlike the north polar cap, the uppermost surface of the bright residual south polar deposit is probably composed of carbon dioxide ice. It is unknown whether this ice extends through the entire thickness of the deposit. The Mars Polar Lander (MPL), launched in January 1999, is due to arrive in December 1999 to search for water and carbon dioxide on layered deposits near the south pole (SP) of Mars. Additional information is contained in the original extended abstract.

  10. Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies

    NASA Technical Reports Server (NTRS)

    Killeen, T. L.; Won, Y.-I.; Niciejewski, R. J.; Burns, A. G.

    1995-01-01

    Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The

  11. 35 GHz Measurements of CO2 Crystals for Simulating Observations of the Martian Polar Caps

    NASA Technical Reports Server (NTRS)

    Foster, J. L.; Chang, A. T. C.; Hall, D. K.; Tait, A. B.; Barton, J. S.

    1998-01-01

    In order to learn more about the Martian polar caps, it is important to compare and contrast the behavior of both frozen H2O and CO2 in different parts of the electromagnetic spectrum. Relatively little attention has been given, thus far, to observing the thermal microwave part of the spectrum. In this experiment, passive microwave radiation emanating from within a 33 cm snowpack was measured with a 35 GHz hand-held radiometer, and in addition to the natural snow measurements, the radiometer was used to measure the microwave emission and scattering from layers of manufactured CO2 (dry ice). A 1 m x 2 m plate of aluminum sheet metal was positioned beneath the natural snow so that microwave emissions from the underlying soil layers would be minimized. Compared to the natural snow crystals, results for the dry ice layers exhibit lower' microwave brightness temperatures for similar thicknesses, regardless of the incidence angle of the radiometer. For example, at 50 degree H (horizontal polarization) and with a covering of 21 cm of snow and 18 cm of dry ice, the brightness temperatures were 150 K and 76 K, respectively. When the snow depth was 33 cm, the brightness temperature was 144 K, and when the total thickness of the dry ice was 27 cm, the brightness temperature was 86 K. The lower brightness temperatures are due to a combination of the lower physical temperature and the larger crystal sizes of the commercial CO2 Crystals compared to the snow crystals. As the crystal size approaches the size of the microwave wavelength, it scatters microwave radiation more effectively, thus lowering the brightness temperature. The dry ice crystals in this experiment were about an order of magnitude larger than the snow crystals and three orders of magnitude larger than the CO2 Crystals produced in the cold stage of a scanning electron microscope. Spreading soil, approximately 2 mm in thickness, on the dry ice appeared to have no effect on the brightness temperatures.

  12. Dust-Driven Halos on the Martian South Polar Residual CAP

    NASA Astrophysics Data System (ADS)

    Becerra, P.; Byrne, S.; Brown, A. J.

    2013-12-01

    The CO2 ice South Polar Residual Cap (SPRC) on Mars may be a sensitive indicator of inter-annual planetary climate variability. Imaging by HiRISE [1], and CTX [2] found that many scarps and pits in the 'Swiss cheese terrain' [3] of the SPRC exhibited a bright 'halo' around their edges. These halos appeared during Martian southern summer in Mars Year 28 (MY28, [4]), and have been observed in only one of eight mars years for which observations at high enough resolution exist. We hypothesize that the formation of these features is linked to the late-summer global dust storm of MY28 and report on observations and formation models. We surveyed HiRISE, CTX, and CRISM [5] data to constrain the optical properties and composition of the halos, as well as their time of appearance and location within the SPRC. The halos appeared throughout most of the surface area of the SPRC between Ls 280° and 330° in MY28. The widest portions of the halos occurred adjacent to north-facing walls, and the brightest parts adjacent to sun-facing walls, which points to a connection between insolation and halo appearance. CRISM spectral products rule out the presence of water ice as a factor in the halos' appearance. These data also imply larger CO2 ice grain sizes where the bright halos were seen, which are normally associated with lower, rather than higher, albedos [6]. Thus, we also ruled out CO2 ice grain size differences as the main cause for the halos. The remaining possibility is that the halos appeared due to differences in dust content between the terrain adjacent to the pit walls and the surrounding ice. To investigate this we made a Hapke [7] surface reflectance model in which the CO2 ice grain size, dust volumetric content and dust particle size were free parameters. We used the HiRISE and CRISM bandpass coefficients to simulate HiRISE I/F values and CRISM spectra, and attempted to match the HiRISE RED I/F, HiRISE BG/RED color ratio, and the CRISM 1.43 μm band depths. A self

  13. Band engineering in a van der Waals heterostructure using a 2D polar material and a capping layer

    PubMed Central

    Cho, Sung Beom; Chung, Yong-Chae

    2016-01-01

    Van der Waals (vdW) heterostructures are expected to play a key role in next-generation electronic and optoelectronic devices. In this study, the band alignment of a vdW heterostructure with 2D polar materials was studied using first-principles calculations. As a model case study, single-sided fluorographene (a 2D polar material) on insulating (h-BN) and metallic (graphite) substrates was investigated to understand the band alignment behavior of polar materials. Single-sided fluorographene was found to have a potential difference along the out-of-plane direction. This potential difference provided as built-in potential at the interface, which shift the band alignment between h-BN and graphite. The interface characteristics were highly dependent on the interface terminations because of this built-in potential. Interestingly, this band alignment can be modified with a capping layer of graphene or BN because the capping layer triggered electronic reconstruction near the interface. This is because the bonding nature is not covalent, but van der Waals, which made it possible to avoid Fermi-level pinning at the interface. The results of this study showed that diverse types of band alignment can be achieved using polar materials and an appropriate capping layer. PMID:27301777

  14. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, Heather A.; Comfort, Richard H.; Craven, Paul D.; Chandler, Michael O.; Moore, Thomas E.

    2000-01-01

    We correlate solar wind and IMF properties with the properties of O(+) and H(+) in the polar cap in early 1996 during solar minimum conditions at altitudes between 5.5 and 8.9 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the POLAR satellite. Throughout the high altitude polar cap, we observe H(+) to be more abundant than O(+). H(+) is a significant fraction of both the ionosphere and the solar wind, and O(+) is not a significant species in the solar wind. O(+) is the major species in the ionosphere so the faction of O(+) present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. For these reasons, 0+ is of primary interest in this study. We observe O(+) to be most abundant at lower latitudes when the solar wind speed is low (and low Kp), and at higher solar wind speeds (and high Kp) O(+) is observed across most of the polar cap. We also find that O(+) density and parallel flux are well organized by solar wind dynamic pressure; they both increase with solar wind dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, but H(+) density and parallel flux have some negative correlation with IMF By, and some positive correlation with VswBIMF. In this solar minimum data set, H(+) is dominant so that contributions of this plasma to the plasma sheet would have a very low O(+) to H(+) ratio.

  15. Band engineering in a van der Waals heterostructure using a 2D polar material and a capping layer

    NASA Astrophysics Data System (ADS)

    Cho, Sung Beom; Chung, Yong-Chae

    2016-06-01

    Van der Waals (vdW) heterostructures are expected to play a key role in next-generation electronic and optoelectronic devices. In this study, the band alignment of a vdW heterostructure with 2D polar materials was studied using first-principles calculations. As a model case study, single-sided fluorographene (a 2D polar material) on insulating (h-BN) and metallic (graphite) substrates was investigated to understand the band alignment behavior of polar materials. Single-sided fluorographene was found to have a potential difference along the out-of-plane direction. This potential difference provided as built-in potential at the interface, which shift the band alignment between h-BN and graphite. The interface characteristics were highly dependent on the interface terminations because of this built-in potential. Interestingly, this band alignment can be modified with a capping layer of graphene or BN because the capping layer triggered electronic reconstruction near the interface. This is because the bonding nature is not covalent, but van der Waals, which made it possible to avoid Fermi-level pinning at the interface. The results of this study showed that diverse types of band alignment can be achieved using polar materials and an appropriate capping layer.

  16. IMF effect on the polar cap contraction and expansion during a period of substorms

    NASA Astrophysics Data System (ADS)

    Aikio, A. T.; Pitkänen, T.; Honkonen, I.; Palmroth, M.; Amm, O.

    2013-06-01

    The polar cap boundary (PCB) location and motion in the nightside ionosphere has been studied by using measurements from the EISCAT radars and the MIRACLE magnetometers during a period of four substorms on 18 February 2004. The OMNI database has been used for observations of the solar wind and the Geotail satellite for magnetospheric measurements. In addition, the event was modelled by the GUMICS-4 MHD simulation. The simulation of the PCB location was in a rather good agreement with the experimental estimates at the EISCAT longitude. During the first three substorm expansion phases, neither the local observations nor the global simulation showed any poleward motions of the PCB, even though the electrojets intensified. Rapid poleward motions of the PCB took place only in the early recovery phases of the substorms. Hence, in these cases the nightside reconnection rate was locally higher in the recovery phase than in the expansion phase. In addition, we suggest that the IMF Bz component correlated with the nightside tail inclination angle and the PCB location with about a 17-min delay from the bow shock. By taking the delay into account, the IMF northward turnings were associated with dipolarizations of the magnetotail and poleward motions of the PCB in the recovery phase. The mechanism behind this effect should be studied further.

  17. Electrodynamic, thermal, and energetic character of intense sun-aligned arcs in the polar cap

    SciTech Connect

    Valladares, C.E.; Carlson, H.C.

    1991-02-01

    The electrodynamic, thermal and energetic character of stable Sun-aligned arcs in the polar cap can be meaningfully diagnosed by an incoherent scatter radar, provided a suitable observing scheme is selected. The authors report here such measurements of two intense Sun-aligned arcs. The two arcs were diagnosed on two different nights (February 26 and March 1, 1987) using the Sondre Stomfjord radar as a stand-alone diagnostic. Repeatable patterns are found in mesoscale area maps of altitude profiles for observed electron and ion gas number densities, temperatures, and line-of-sight velocities, and projected mesoscale area maps of derived electric fields, Pedersen and Hall conductivities, horizontal and field-aligned currents, Joule heating rate, and Poynting flux. They confirm, for the first time with continuous mesoscale area maps, that the arcs have the anticipated simple arc electrodynamics. That is, the visual and enhanced ionization signatures of the arc are produced by incoming energetic electrons carrying the outgoing current from the electric field convergence in the arc.

  18. Albedo of Surface CO2 Deposits in Mars' Residual South Polar Cap

    NASA Astrophysics Data System (ADS)

    James, P. B.; Wolff, M. J.; Bonev, B.

    2014-12-01

    The albedo of surface CO2 deposits in the Residual South Polar Cap (RSPC) of Mars controls their net condensation / sublimation over a martian year and is therefore a crucial parameter in determining RSPC stability. The albedo used in previous analyses is obtained by dividing I/F, determined from radiometrically calibrated imaging data, by the cosine of the incidence angle. Because of atmospheric aerosols, the albedo calculated from I/F above the atmosphere is not the surface albedo that enters into stability considerations. In order to determine the surface albedo, we interpolate optical depths determined from CRISM EPF measurements to provide estimates of the dust and ice opacities over the RSPC (Wolff et al., 2009) and use these to determine the actual surface albedos from MARCI images using the radiative transport program DISORT (Stamnes et al., 1988). Assuming that dust is the only contributor to atmospheric opacity, the retrieved surface albedos for the longer wavelength MARCI filters in MY 28 and 29 are found to be consistent despite very different dust opacities in the two years (James et al., 2014). However, this model fails to reproduce the short wavelength behavior in early summer. We consider possible modifications of the dust only model that could explain the discrepancy.

  19. Albedo of surface CO2 deposits in Mars' Residual South Polar Cap

    NASA Astrophysics Data System (ADS)

    James, P. B.; Wolff, M. J.; Bonev, B.

    2013-12-01

    The albedo of surface CO2 deposits in the Residual South Polar Cap (RSPC) controls their net condensation / sublimation over a martian year and is therefore a crucial parameter in determining RSPC stability. The Lambert albedo used in previous analyses is obtained by dividing I/F, determined from radiometrically calibrated imaging data, by the cosine of the incidence angle. Because of atmospheric dust, this albedo calculated from I/F above the atmosphere is not the surface albedo that enters into stability considerations. In order to investigate the real surface albedo, we interpolate optical depths determined from CRISM EPF measurements to provide estimates of the opacites over the RSPC and use these to determine the actual surface albedos from MARCI images using the radiative transport program DISORT (Stamnes et al., 1988). The assumption that the surface is a Lambertian diffuse reflector can then also be tested. MARCI images acquired in one-day span a significant range of emission angles; the set of images acquired during one sol is similar to EPF observations except that diurnal opacity variations could be important.

  20. Spectral albedo and emissivity of CO2 in Martian polar caps - Model results

    NASA Technical Reports Server (NTRS)

    Warren, Stephen G.; Wiscombe, Warren J.; Firestone, John F.

    1990-01-01

    In this paper, a snow albedo model previously developed for terrestrial snow is extended to the case of CO2 snow on Mars. Pure CO2 snow is calculated to have high albedo at visible wavelengths but not as high as that of water snow. At any given wavelength, the primary variable controlling albedo and emissivity is the snow grain size, with albedo decreasing and emissivity increasing as grain size increases. Observations that red albedo is much higher than blue albedo in the Martian south polar cap indicates that the snow or the atmosphere is contaminated with red dust. The absorption coefficient of CO2 ice in the thermal infrared is two to three orders of magnitude smaller than that measured for H2O ice. CO2 snow emissivity is therefore much lower than H2O snow, varying substantially with wavelength and quite sensitive to grain size and emission angle. Factors tending to increase emissivity are large grain size, small emission angle, and large concentrations of dust or water.

  1. A polar cap absorption event observed using the Southern Hemisphere SuperDARN radar network.

    NASA Astrophysics Data System (ADS)

    Breed, A.; Morris, R.; Parkinson, M.; Duldig, M.; Dyson, P.

    A large X5 class solar flare and coronal mass ejection were observed emanating from the sun on July 14, 2000. Approximately 10 minutes later a large cosmic ray ground level enhancement was observed using neutron monitors located at Mawson station (70.5°S CGM), Antarctica; Large increases in proton flux were also observed using satellites during this time. This marked the start of a large polar cap absorption event with cosmic noise absorption peaking at 30 dB, as measured by a 30 MHz riometer located at Casey station (80.4°S CGM), Antarctica. The spatial evolution of this event and its subsequent recovery were studied using the Southern Hemisphere SuperDARN radar network, including the relatively low latitude observation provided by the Tasman International Geospace Environment Radar (TIGER) located on Bruny Island (54.6°S GGM), Tasmania. When the bulk of the CME arrived at the Earth two days later it triggered an intense geomagnetic storm. This paper presents observations of the dramatic sequence of events.

  2. The Enigma of Io's Warm Polar Regions

    NASA Astrophysics Data System (ADS)

    Matson, D. L.; Veeder, G. J.; Davies, A. G.; Johnson, T. V.; Blaney, D. L.

    Io's polar temperatures are higher than expected for any passive surface. Data from the Galileo Photopolarimeter (PPR) show that minimum nighttime temperatures are in the range of 90 -95 K virtually everywhere [1]. This is particularly striking at high latitudes, within the polar regions. Furthermore, the distribution of minimum night- time temperatures across the surface of Io (away from the sunset terminator) shows little variation with latitude and/or time of night [1,2,3,4]. We consider suggested mechanisms for this elevated-minimum-temperature effect: 1) Polar terrain is warmer than expected because it is rough, 2) Higher latitudes have lower albedos, 3) Thermal inertia increases with latitude, and 4) Cooling lava controls nighttime temperatures. We find that the passive mechanisms fail. This leads to the suggestion that most of Io is covered by cooling lavas. In this context, lava cools to the observed temperature range on time scales of ten to ten thousand years depending upon the nature of the eruption scenario(s). Separately, analysis of thermal anomalies reveals that the trend of the data (log-cumulative-surface-area versus log-temperature) extrapolated to the entire surface area of Io predicts large- scale, ambient, temperatures in the 90-95 K range. Recent Galileo observations showing a myriad of small volcanic hot spots [7] provide strong support for the paradigm of ubiquitous volcanic activity with global, cooling-lava fields on Io. While explaining the high nighttime polar temperatures, this model displaces the previous explaination for Io's anomalously low 20 micron daytime emission. Explaining this emission is an important focus for current work. Warm polar regions appear to require some heat flow through very large areas in addition to the small, hot anomalies already known. This has implications for raising Io's global heat flow. Presently, the heat flow is constrained between a lower bound of ~2.5 W m -2[5] and an upper bound of ~13 W m -2

  3. Comparison of Energy Deposition in the Auroral Oval and Cap Regions for Cases Where Transpolar Structures Exist

    NASA Technical Reports Server (NTRS)

    Spann, J. F., Jr.; Germany, G. A.; Parks, G. K.; Brittnacher, M. J.

    1998-01-01

    For several cases where the full auroral zone is imaged and transpolar structures exist, we compare the total energy input to the auroral oval with the total energy input in the polar cap. This comparison is made for cases where auroral intensification near local midnight is and is not observed. Temporal evolution of the energy balance between the energy deposited in the oval and polar cap can be used to understand the mechanism that triggers substorms.

  4. On the field-aligned electric field in the polar cap

    NASA Astrophysics Data System (ADS)

    Wing, Simon; Fairfield, Donald H.; Johnson, Jay R.; Ohtani, Shin-I.

    2015-07-01

    The Johns Hopkins University Applied Physics Laboratory open-field line particle precipitation model predicts downward field-aligned electric field to maintain charge quasi-neutrality. Previous studies confirmed the existence of such electric fields. However, the present study shows that upward field-aligned electric field can be found within upward field-aligned current (FAC) region. In the upward FAC region, upward electric field that accelerates electron downward is seen with the occurrence rates of 82%-96%. In contrast, the occurrence rates in the downward FAC regions are 3%-11%. Polar rain electrons located in the upward FAC region adjacent to closed field lines often show a ramping up of energy with increasing latitude before reaching a plateau. This plateau may be attributed to the magnetosheath electrons that progressively have higher antisunward velocity and lower density with increasing distance from the subsolar point before they asymptotically reach the solar wind values.

  5. Field-aligned electron density irregularities near 500 km. Equator to polar cap topside sounder Z mode observations

    NASA Technical Reports Server (NTRS)

    Benson, R. F.

    1984-01-01

    In addition to spread F, evidence for field-aligned electron density irregularities is commonly observed on Alouette 2 topside sounder ionograms recorded near perigee (500 km). This evidence is provided by distinctive signal returns from sounder-generated Z mode waves. At low latitudes these waves become guided in wave ducts caused by field-aligned electron density irregularities and give rise to strong long-duration echoes. At high latitudes, extending well into the polar cap, these Z mode waves (and stimulated electrostatic waves at the plasma frequency) produce a series of vertical bars on the ionogram display as the satellite traverses discrete field-aligned density structures. The radio frequency (RF) noise environment to be expected in the 400 to 500 km altitude region from low to high latitudes was examined by analyzing perigee Alouette 2 topside sounder data. All observed noise bands were scaled on nearly 200 topside sounder ionograms recorded near perigee at low, mid, and high latitude telemetry stations. The minimum and maximum frequencies of each noise band were entered into a data base or compuer analysis. The signals of primary interest in the perigee study were found to be sounder-generated.

  6. Correlated observations of the boundary between polar cap and nightside auroral zone by HF radars and the DMSP satellite

    SciTech Connect

    Senior, C.; Cerisier, J.C. ); Hanuise, C. ); Villain, J.P. ); Greenwald, R.G.; Newell, P.T. ); Rich, F.J. )

    1994-02-01

    Simultaneous observations from HF radars and the DMSP satellite have been used to relate the ionospheric convection pattern and the nightside precipitation at the polar cap-auroral zone boundary. The convection is eastward in the poleward part of the radars field of view and predominantly westward at lower latitudes. The DMSP-F9 particle spectrograms exhibit energetic precipitating protons at the poleward edge of an inverted V'. The downward H[sup +] flow displays spatial filtering effects with a clear energy-latitude dispersion. Single-particle trajectory simulations in appropriate field models demonstrate that these ions were ejected from the neutral sheet near 120 R[sub E] geocentric distance. Most notably, the simulations reveal significant azimuthal dispersion during transport, and the source region in the magnetotail is found to extend over several Earth radii in the dawn-dusk direction, less energetic particles originating duskward of the high-energy ones. The longitudinal spread of the tail source suggests particle precipitation in the ionosphere over at least one hour magnetic local time. Also, as the downflowing protons travel near the lobeward edge of the plasma sheet, the observations suggest that the convection reversal lies inside the boundary layer plasma sheet (PSBL). 11 refs., 3 figs.

  7. VISIONS remote observations of a spatially-structured filamentary source of energetic neutral atoms near the polar cap boundary during an auroral substorm

    NASA Astrophysics Data System (ADS)

    Collier, Michael R.; Chornay, D.; Clemmons, J.; Keller, J. W.; Klenzing, J.; Kujawski, J.; McLain, J.; Pfaff, R.; Rowland, D.; Zettergren, M.

    2015-11-01

    We report initial results from the VISualizing Ion Outflow via Neutral atom imaging during a Substorm (VISIONS) rocket that flew through and near several regions of enhanced auroral activity and also sensed regions of ion outflow both remotely and directly. The observed neutral atom fluxes were largest at the lower energies and generally higher in the auroral zone than in the polar cap. In this paper, we focus on data from the latter half of the VISIONS trajectory when the rocket traversed the polar cap region. During this period, many of the energetic neutral atom spectra show a peak at 100 eV. Spectra with peaks around 100 eV are also observed in the Electrostatic Ion Analyzer (EIA) data consistent with these ions comprising the source population for the energetic neutral atoms. The EIA observations of this low energy population extend only over a few tens of km. Furthermore, the directionality of the arriving energetic neutral atoms is consistent with either this spatially localized source of energetic ions extending from as low as about 300 km up to above 600 km or a larger source of energetic ions to the southwest.

  8. VISIONS: Remote Observations of a Spatially-Structured Filamentary Source of Energetic Neutral Atoms near the Polar Cap Boundary During an Auroral Substorm

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Chornay, D.; Clemmons, J.; Keller, J. W.; Klenzing, J.; Kujawski, J.; McLain, J.; Pfaff, R.; Rowland, D.; Zettergren, M.

    2015-01-01

    We report initial results from the VISualizing Ion Outflow via Neutral atom imaging during a Substorm (VISIONS) rocket that flew through and near several regions of enhanced auroral activity and also sensed regions of ion outflow both remotely and directly. The observed neutral atom fluxes were largest at the lower energies and generally higher in the auroral zone than in the polar cap. In this paper, we focus on data from the latter half of the VISIONS trajectory when the rocket traversed the polar cap region. During this period, many of the energetic neutral atom spectra show a peak at 100 electronvolts. Spectra with peaks around 100 electronvolts are also observed in the Electrostatic Ion Analyzer (EIA) data consistent with these ions comprising the source population for the energetic neutral atoms. The EIA observations of this low energy population extend only over a few tens of kilometers. Furthermore, the directionality of the arriving energetic neutral atoms is consistent with either this spatially localized source of energetic ions extending from as low as about 300 kilometers up to above 600 kilometers or a larger source of energetic ions to the southwest.

  9. Measurements of trans-ionospheric propagation parameters in the polar-cap ionosphere. Final report, October 1982-November 1986

    SciTech Connect

    Klobuchar, J.A.; Anderson, D.N.; Bishop, G.J.; Doherty, P.H.

    1987-04-03

    Measurements of absolute TEC (Total Electron Content), were made for the first time from the polar-cap station located at Thule, Greenland in early 1984 using dual-frequency group delay measurements from high orbit satellites. Measurements of L-band amplitude scintillation and dual-frequency differential carrier-phase scintillation were also made. The variability of the TEC was extremely large, with increases above the background values of more than 100% observed frequently. Quasi-periodic TEC enhancements with periods as short as 10 min and with amplitudes exceeding 10**17 el/m**2 column were seen over several time intervals of more than two hours. The absolute values of TEC observed in the dark polar-cap ionosphere at times exceeded the diurnal maximum values from the mid-latitude ionosphere during this initial period of observations.

  10. An atlas of polar cap energetic particle observations. Volume 2: NOAA-6, 8 July 1979 to 10 May 1983

    NASA Astrophysics Data System (ADS)

    Sauer, H. H.

    1984-09-01

    This series presents graphical displays of the polar cap (herein defined as geomagnetic latitudes greater than 70 degrees) averages of the proton and electron fluxes precipitating into the polar atmosphere, over the energy range of 30 keV to greater than 80 MeV for protons and greater than 300 keV for electrons. Volume 2 presents data from the NOAA-6 spacecraft from 8 July 1979 to 10 May 1983. Subsequent volumes using data from the NOAA-6, -7 and -8 satellites will extend the data presentations.

  11. Aeolian Transport of Ferrous Minerals in the North Polar Region of Mars

    NASA Astrophysics Data System (ADS)

    Horgan, Briony H.; Bell, J. F., III; Noe Dobrea, E. Z.

    2008-09-01

    The north polar region of Mars contains two areally extensive, dark aeolian deposits: (1) the north polar sand seas that encircle the polar cap, and (2) the north polar veneers that drape over the polar cap itself. Both deposits have been previously identified as containing hydrated minerals, and exhibit spectral features consistent with gypsum, a hydrated calcium sulfate. However, it remains unclear whether or not the deposits have exchanged material in the past, and whether any portion of either deposit is active today. In this study, we are investigating the distribution of ferrous minerals in the north polar region using near-infrared spectral data from the Mars Express OMEGA imaging spectrometer. Ferrous minerals, such as olivine and pyroxene, are most readily identified by the presence of a wide absorption band around 1 micron. Observations of changes in the position, depth, and shape of the 1 micron absorption band may be used to track changes in composition. We have identified the presence of a strong 1 micron band in the veneers, the sand sea, and the surrounding plains. Initial results from study regions in Chasma Boreale and Olympia Planum suggest that the position, depth, and shape of the band do vary within the veneers and sand seas. These spectral differences may reflect: (1) compositional variations between the sources of the deposits, (2) the degree of modern activity of the deposits, or (3) changes in mineralogy due to breakdown of softer minerals during aeolian transport over long distances. By extending our observations of these spectral changes to the entire north polar region, we may be able to help identify sources of aeolian material, transport pathways, and the most active regions of modern aeolian activity.

  12. Sedimentation waves formed by katabatic winds on the North Polar Cap of Mars

    NASA Astrophysics Data System (ADS)

    Herny, Clémence; Carpy, Sabrina; Bourgeois, Olivier; Massé, Marion; Le Mouélic, Stéphane; Perret, Laurent; Spiga, Aymeric; Smith, Isaac; Appéré, Thomas; Rodriguez, Sébastien; Piquet, Thibault; Gaudin, Dominique; Le Menn, Erwan

    2015-04-01

    Complex feedbacks between katabatic winds and the cryosphere may lead to the development of sedimentation waves at the surface of ice sheets. These have been first described, and named snow megadunes, in Antarctica. Complementary investigations of topographic data, optical images, spectroscopic data and stratigraphic radar soundings reveal that these sedimentation waves generally migrate upwind in response to enhanced accumulation on their upwind sides and reduced (or net ablation) on their downwind sides. On Mars, the North Polar Cap exhibits two wavelengths of such sedimentations waves. (1) The larger ones are several tens of kilometers in wavelength and several hundreds of meters in amplitude. These large bedforms confer a stunning spiral-shaped topography to the NPC. They have been interpreted as cyclic steps systems associated with katabatic jumps. (2) The smaller ones are tens of kilometers in wavelength and several tens of meters in amplitude. They are superimposed on the larger ones and are probable Martian equivalents of terrestrial snow megadunes. These specific bedforms have morphologic, stratigraphic and dynamic similarities with underwater sedimentary antidunes. Sedimentation waves on Earth and Mars result from the interaction between katabatic winds and the redistribution of ice at the surface of the NPC. Ice sublimation and condensation play an important role in the development of sedimentation waves on the NPC, due to the low atmospheric pressure, low temperature and low water vapor content at the surface of Mars. We are currently developing a numerical model based on the coupled implementation of fluid dynamics and H2O mass transfer by sublimation and condensation. The model is designed to explore the implication of the interaction between katabatic winds and water vapor diffusion/transport on the development of sedimentation waves on Mars and could be extrapolated to Antarctic conditions.

  13. Sedimentation waves on the Martian North Polar Cap: Analogy with megadunes in Antarctica

    NASA Astrophysics Data System (ADS)

    Herny, C.; Massé, M.; Bourgeois, O.; Carpy, S.; Le Mouélic, S.; Appéré, T.; Smith, I. B.; Spiga, A.; Rodriguez, S.

    2014-10-01

    Complex interactions between katabatic winds and the cryosphere may lead to the formation of sedimentation waves at the surface of ice sheets. These have been first described and named snow megadunes in Antarctica. Here we use topographic data, optical images, subsurface radar soundings and spectroscopic data acquired by Mars orbiters, to show that the surface of the Martian North Polar Cap displays two superimposed sets of sedimentation waves with differing wavelengths. These sedimentation waves have similarities with Antarctic snow megadunes regarding their surface morphology, texture, grain size asymmetry, and internal stratigraphic architecture. Both sets of Martian sedimentation waves present young ice and occasional sastrugi fields, indicative of net accumulation, on their shallow-dipping upwind sides, their tops and the intervening troughs. Old layers of dusty ice, indicative of net ablation, are exhumed on the steep-dipping downwind sides of the larger waves. Smooth surfaces of coarse-grained ice, indicative of reduced accumulation associated with sublimation metamorphism, cover the steep-dipping downwind sides of the smaller waves. These surface characteristics and the internal stratigraphy revealed by radar soundings are consistent with the interpretation that both sets of Martian sedimentation waves grow and migrate upwind in response to the development of periodic accumulation/ablation patterns controlled by katabatic winds. The recognition of these sedimentation waves provides the basis for the development of a common model of ice/wind interaction at the surface of Martian and terrestrial glaciers. Martian smaller waves, characterized by reduced net accumulation on their downwind sides, are analogous to Antarctic snow megadunes that have been described so far. A terrestrial equivalent remains to be discovered for the larger Martian waves, characterized by net ablation on their downwind sides.

  14. Atmospheric Modeling of the Martian Polar Regions: One Mars Year of CRISM EPF Observations of the South Pole

    NASA Astrophysics Data System (ADS)

    Brown, A. J.; Wolff, M. J.

    2009-03-01

    We have used CRISM Emission Phase Function gimballed observations to investigate atmospheric dust/ice opacity and surface albedo in the south polar region for the first Mars year of MRO operations. This covers the MY28 "dust event" and cap recession.

  15. Observations of the plasma density enhancement in the high-altitude polar region during geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Kitamura, Naritoshi; Shinbori, Atsuki; Nishimura, Yukitoshi; Ono, Takayuki; Iizima, Masahide; Kumamoto, Atsushi; Yamada, Manabu; Watanabe, Shigeto; Abe, Takumi; Yau, Andrew W.

    Recent satellite observations have clarified that plasma outflows play an important role in abrupt changes in the ion composition in the plasmasheet and ring current during geomagnetic storms. In the present study, we perform case studies of enhancement of the plasma density and ion upflow in the high-altitude polar region during geomagnetic storms using the data observed by the Akebono satellite. We use the electron density data observed by the plasma wave and sounder experiments (PWS), and the ion composition and field-aligned velocity measured by the suprathermal ion mass spectrometer (SMS) onboard the Akebono satellite. We perform case studies for the geomagnetic storm events which occurred on June 6, June 9, 1989 and March 30, 1990. Enhancements of the electron density are identified in the entire polar cap associated with the period of the main phase of geomagnetic storms. The electron density in June 7 and 9 enhanced up to 100 times larger than the quiet-time level. During the main phase of the March 30 storm, Akebono crossed the dayside polar region directed from dawn to dusk, and the electron density enhanced up to 30 times larger than the quiet-time level in the auroral zone and dayside polar cap in an altitude range of 7000-10000 km. The SMS instrument measured ion upflows in the entire polar cap along the satellite path. Eighty percent of the upflowing ions were composed of oxygen ions and the field-aligned upward velocity of oxygen ions reached 5-10 km/s. Existence of ion upflows dominated by oxygen ions indicates that the plasma is originated from the ionosphere. The upflow flux of the oxygen ion mapped to 1000 km altitude corresponded to 1-4*109 /cm2 /s. The flux is about the same as the maximum flux observed by DE-1 [Pollock et al., 1990] and Polar during a geomagnetic storm [Moore et al., 1999], and the flux was observed continuously (8-16 h in magnetic local time) in the polar cap. These results indicate that a large amount of the ionospheric

  16. Influence of X-ray and polar cap absorptions on vertical and oblique sounding ionograms on different latitudes

    NASA Astrophysics Data System (ADS)

    Zaalov, N. Y.; Moskaleva, E. V.; Rogov, D. D.; Zernov, N. N.

    2015-12-01

    High frequency (HF) radio band is important for the long-range communications and over-the-horizon surveillance, particularly in the polar cap region where the ground infrastructure may be limited. However, the space weather events drastically affect the high frequency radio wave propagation so that the ability to provide now-casting and forecasting of HF radio wave absorption is important for users relying on the HF communications. During the space weather events such as solar proton events and X-ray flares the high-latitude ionosphere becomes a particularly efficient absorber of HF radio waves. There is therefore a need to develop accurate HF propagation prediction services. Absorption of the HF field caused by the X-ray flux, Solar Ultra-Violet flux and proton precipitations is investigated in this paper for the event of the solar flare observed on 11 April 2013. The effects of the X-ray flux and proton precipitations on the structure of the vertical and oblique ionograms for different latitudes are estimated. The simulation of the vertical and oblique ionograms was performed on the basis of the computational model of the ionosphere oriented to applications into the high frequency wave propagation problems. The absorption effects induced by the proton precipitations and X-ray flux are calculated according to the algorithm elaborated by Sauer and Wilkinson and D-region Absorption Model (D-RAP) available from the NOAA Space Weather Prediction Center. The simulated vertical and oblique ionograms with the absorption effects taken into account and the measured ionograms exhibit a fairly good similarity.

  17. PERSPECTIVE: Snow matters in the polar regions

    NASA Astrophysics Data System (ADS)

    Sodeau, John

    2010-03-01

    Antarctica is not quite as chemically pristine as might sometimes be thought (Jones et al 2008). For example, as elsewhere, reduced sulfur species such as dimethylsulfide (DMS) are emitted from biogenic marine sources at the poles (Read et al 2008). Somewhat less well known is that inland (as opposed to coastal) field campaigns have also detected, within the Antarctic boundary layer (ABL), emissions containing unexpectedly high levels of diverse, oxidizing chemicals such as NOx, nitrate ions, formaldehyde, ozone and hydrogen peroxide (Honrath et al 1999, Hutterli et al 2004, Sumner and Shepson 1999). And then there are the halogen-containing compounds (Simpson et al 2007). The transformation of DMS to sulfate aerosols capable of acting as cloud condensation nuclei often proceeds via one main oxidized product of DMS, namely methanesulfonic acid (MSA). Two specific reactions have been well studied to date in this regard, namely DMS plus either OH or NO3 radicals. Corresponding reactions with halogen radicals, which also contribute to the oxidizing capacity of our atmosphere, have generally been considered to be of less importance. The reason for this view is that even though the reactivity of bromine- and iodine-containing radicals is much greater than that of OH, the halogens were thought to be relatively scarce in the polar atmosphere. However both BrO (and IO) have been detected in the Antarctic CHABLIS campaign, as discussed in depth in the Atmospheric Chemistry and Physics special issue of 2008, see Jones et al (2008). It was subsequently shown that calculated MSA production from the DMS/BrO reaction may be about an order of magnitude greater than when the OH radical was the oxidizing reactant. The recent analytical measurements by Antony et al (2010) of MSA, Br and NO3 found in snow along the Ingrid Christensen Coast of East Antarctica are important in the above field context. Hence it would appear that the concentrations of these ions in ice-cap sites are up

  18. Influence of ice rheology and dust content on the dynamics of the north-polar cap of Mars

    NASA Astrophysics Data System (ADS)

    Greve, Ralf; Mahajan, Rupali A.

    2005-04-01

    The evolution and dynamics of the north-polar cap (residual-ice-cap/layered-deposits complex) of Mars is simulated with a thermomechanical ice-sheet model. We consider a scenario with ice-free initial conditions at 5 Ma before present due to the large obliquities which prevailed prior to this time. The north-polar cap is then built up to its present shape, driven by a parameterized climate forcing (surface temperature, surface mass balance) based on the obliquity and eccentricity history. The effects of different ice rheologies and different dust contents are investigated. It is found that the build-up scenarios require an accumulation rate of approximately 0.15-0.2 mm a -1 at present. The topography evolution is essentially independent of the ice dynamics due to the slow ice flow. Owing to the uncertainties associated with the ice rheology and the dust content, flow velocities can only be predicted within a range of two orders of magnitude. Likely present values are of the order of 0.1-1 mm a -1, and a strong variation over the climatic cycles is found. For all cases, computed basal temperatures are far below pressure melting.

  19. Energy balance of acoustic gravity waves above the polar caps according to the data of satellite measurements

    NASA Astrophysics Data System (ADS)

    Fedorenko, A. K.

    2010-02-01

    Wave disturbances of the Neutral Atmosphere above the polar caps are studied based on the Dynamic Explorer 2 satellite measurements. The characteristic spatial scales of these disturbances are 500— 600 km. Based on an analysis of the synchronous variations in different parameters, these disturbances were interpreted as propagating acoustic gravity waves (AGWs). The mass-spectrometer measurements of concentrations of individual atmospheric gases made it possible to determine the following AGW components: density of the acoustic compression, thermobaric, and average kinetic energies. It has been found out that the average (during the period) densities of the acoustic and thermobaric energies are approximately equal for polar AGWs. The results indicate that the contribution of these waves to the energy of the polar upper atmosphere is considerable.

  20. Convection and electrodynamic signatures in the vicinity of a Sun-aligned arc: Results from the Polar Acceleration Regions and Convection Study (Polar ARCS)

    NASA Technical Reports Server (NTRS)

    Weiss, L. A.; Weber, E. J.; Reiff, P. H.; Sharber, J. R.; Winningham, J. D.; Primdahl, F.; Mikkelsen, I. S.; Seifring, C.; Wescott, Eugene M.

    1994-01-01

    An experimental campaign designed to study high-latitude auroral arcs was conducted in Sondre Stromfjord, Greenland, on February 26, 1987. The Polar Acceleration Regions and Convection Study (Polar ARCS) consisted of a coordinated set of ground-based, airborne, and sounding rocket measurements of a weak, sun-aligned arc system within the duskside polar cap. A rocket-borne barium release experiment, two DMSP satellite overflights, all-sky photography, and incoherent scatter radar measurements provided information on the large-scale plasma convection over the polar cap region while a second rocket instrumented with a DC magnetometer, Langmuir and electric field probes, and an electron spectrometer provided measurements of small-scale electrodynamics. The large-scale data indicate that small, sun-aligned precipitation events formed within a region of antisunward convection between the duskside auroral oval and a large sun-aligned arc further poleward. This convection signature, used to assess the relationship of the sun-aligned arc to the large-scale magnetospheric configuration, is found to be consistent with either a model in which the arc formed on open field lines on the dusk side of a bifurcated polar cap or on closed field lines threading an expanded low-latitude boundary layer, but not a model in which the polar cap arc field lines map to an expanded plasma sheet. The antisunward convection signature may also be explained by a model in which the polar cap arc formed on long field lines recently reconnected through a highly skewed plasma sheet. The small-scale measurements indicate the rocket passed through three narrow (less than 20 km) regions of low-energy (less than 100 eV) electron precipitation in which the electric and magnetic field perturbations were well correlated. These precipitation events are shown to be associated with regions of downward Poynting flux and small-scale upward and downward field-aligned currents of 1-2 micro-A/sq m. The paired field

  1. An onboard data analysis method to track the seasonal polar caps on Mars

    USGS Publications Warehouse

    Wagstaff, K.L.; Castano, R.; Chien, S.; Ivanov, A.B.; Pounders, E.; Titus, T.N.

    2005-01-01

    The Martian seasonal CO2 ice caps advance and retreat each year. They are currently studied using instruments such as the THermal EMission Imaging System (THEMIS), a visible and infra-red camera on the Mars Odyssey spacecraft [1]. However, each image must be downlinked to Earth prior to analysis. In contrast, we have developed the Bimodal Image Temperature (BIT) histogram analysis method for onboard detection of the cap edge, before transmission. In downlink-limited scenarios when the entire image cannot be transmitted, the location of the cap edge can still be identified and sent to Earth. In this paper, we evaluate our method on uncalibrated THEMIS data and find 1) agreement with manual cap edge identifications to within 28.2 km, and 2) high accuracy even with a smaller analysis window, yielding large reductions in memory requirements. This algorithm is currently being considered as a capability enhancement for the Odyssey second extended mission, beginning in fall 2006.

  2. Studies of Martian polar regions. [using CO2 flow

    NASA Technical Reports Server (NTRS)

    Smith, C. I.; Clark, B. R.; Eschman, D. F.

    1974-01-01

    The flow law determined experimentally for solid CO2 establishes that an hypothesis of glacial flow of CO2 at the Martian poles is not physically unrealistic. Compression experiments carried out under 1 atmosphere pressure and constant strain rate conditions demonstrate that the strength of CO2 near its sublimation point is considerably less than the strength of water ice near its melting point. A plausible glacial model for the Martian polar caps was constructed. The CO2 deposited near the pole would have flowed outward laterally to relieve high internal shear stresses. The topography of the polar caps, and the uniform layering and general extent of the layered deposits were explained using this model.

  3. Growth and Decay of the South Polar Residual Cap of Mars

    NASA Astrophysics Data System (ADS)

    Byrne, S.; McEwen, A.; HiRISE Team

    2008-12-01

    The southern residual ice cap (SRC) is composed of high-albedo solid CO2, is a few meters thick and has areas at its margins and in its interior where the underlying water ice of the polar layered deposits shows through. Previous observations show that pits within the SRC expose sections of layering in the CO2 ice (up to 10m thick) and are expanding by meters/year (Thomas et al., Icarus, 2005). The expansion of these pits is a problem as their spatial density and expansion rates indicate that there should be nothing left of the SRC within a century or so. Our analysis of pit expansion rates indicates that they increase during periods of dust-storm activity. The sensitivity of SRC evolution to climate indicates that its stratigraphy is likely also a valuable source of information about recent climate variability. We are using HiRISE data to constrain landscape evolution models of CO2 ice landscapes to quantify the history of the SRC and the connection of its stratigraphy to martian climate. Here we report on two investigations utilizing different models. 1. We use a landscape evolution model to simulate growth of an accumulating CO2 deposit. This model shows pits naturally form in this landscape, without any associated change in climate, due to increases in surface roughness with time and the feedback between slope and ice ablation. Comparison of model results with the current SRC indicates the thickest sections of stratigraphy likely represent up to 100 martian years of accumulation. 2. HiRISE data shows that some pits expand by faster retreat of the lower ice layers, undercutting of the upper bright ice and subsequent mass-wasting. A separate model that can handle topographic overhangs has been developed and is being used to investigate this behavior. Using this model to reproduce the non- circular aspects of the pit-shapes and their expansion rates (which HiRISE can measure as a function of azimuth) constrains properties of the lower CO2 ice layers such as

  4. Biological rhythms during residence in polar regions.

    PubMed

    Arendt, Josephine

    2012-05-01

    At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relatively controlled artificial light conditions in winter are conducive to experimentation with different types of light treatment. The hormone melatonin and/or its metabolite 6-sulfatoxymelatonin (aMT6s) provide probably the best index of circadian (and seasonal) timing. A frequent observation has been a delay of the circadian system in winter. A skeleton photoperiod (2 × 1-h, bright white light, morning and evening) can restore summer timing. A single 1-h pulse of light in the morning may be sufficient. A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h. With regard to general health in polar regions, intermittent reports describe abnormalities in various physiological processes from the point of view of daily and seasonal rhythms, but positive health outcomes are also published. True winter depression (SAD) appears to be rare, although subsyndromal SAD is reported. Probably of most concern are the numerous reports of sleep problems. These have prompted investigations of the underlying mechanisms and treatment interventions. A delay of the circadian system with "normal" working hours implies sleep is attempted at a suboptimal phase. Decrements in sleep efficiency, latency, duration, and quality are also seen in winter. Increasing the intensity of ambient light exposure throughout the day advanced circadian phase and was associated with benefits for sleep: blue-enriched light was slightly more effective than standard white light. Effects on performance remain to be fully investigated. At 75°S, base personnel adapt the circadian system to night work within a week

  5. Hydrated Units in the Martian North Polar Region

    NASA Astrophysics Data System (ADS)

    Horgan, B. H. N.; Bell, J. F.; Noe Dobrea, E. Z.; Cloutis, E. A.; Bailey, D. T.; Craig, M. A.; Stewart, L.

    2008-03-01

    We show that the hydration signature detected in Olympia Undae extends to other units in the north polar region, including nearly the entirety of the north polar erg, dunes within reentrants in Planum Boreum, and in the north polar layered deposits.

  6. Satellite Data Sets in the Polar Regions

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.; Busalacchi, Antonio J. (Technical Monitor)

    2000-01-01

    We have generated about two decades of consistently derived geophysical parameters in the polar regions. The key parameters are sea ice concentration, surface temperature, albedo, and cloud cover statistics. Sea ice concentrations were derived from the Scanning Multichannel Microwave Radiometer (SMMR) data and the Special Scanning Cl Microwave Imager (SSM/I) data from several platforms using the enhanced Bootstrap Algorithm for the period 1978 through 1999. The new algorithm reduces the errors associated with spatial and temporal variations in the emissivity and surface temperatures of sea ice. Also, bad data at ocean/land interfaces are identified and deleted in an unsupervised manner. Surface ice temperature, albedo and cloud cover statistics are derived simultaneously from the Advanced Very High Resolution Radiometer (AVHRR) data from 1981 through 1999 and mapped at a higher resolution but the same format as the ice concentration data. The technique makes use these co-registered ice concentration maps to enable cloud masking to be done separately for open ocean, sea ice and land areas. The effect of inversion is minimized by taking into consideration the expected changes in the effect of inversion with altitude, especially in the Antarctic. A technique for ice type regional classification has also been developed using multichannel cluster analysis and a neural network. This provide a means to identify large areas of thin ice, first year ice, and older ice types. The data sets have been shown to be coherent with each other and provide a powerful tool for in depth studies of the currently changing Arctic and Antarctic environment.

  7. Modelling Ocean Surface Waves in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, Lucia; Aksenov, Yevgeny; Coward, Andrew; Bertino, Laurent; Williams, Timothy; Nurser, George A. J.

    2015-04-01

    agreement with observations. In addition to our global implementation, the method is currently also tested in the TOPAZ framework (Towards an Operational Prediction system for the North Atlantic European Coastal Zones). We will discuss the two modeling strategies (global 35 km resolution and pan-Arctic 3 km resolution) and analyse model biases. The study contributes to the EU FP7 project 'Ships and Waves Reaching Polar Regions (SWARP)', aimed at developing techniques for sea ice and waves modelling and forecasting in the MIZ in the Arctic. The method will be implemented as part of the EU Global Monitoring and Environmental Security system GMES.

  8. May the continuous trapping of atmospheric water on the permanent South polar cap affect the global atmospheric D/H ratio on Mars?

    NASA Astrophysics Data System (ADS)

    Chassefiere, E.; Montmessin, F.; Fouchet, T.; Forget, F.

    It is generally admitted that thermal escape is the only process responsible for hydrogen isotopic fractionation in Mars atmosphere (enrichment by a factor of 5.5 relative to SMOW value). The aim of the present paper is to show that thermodynamic processes (condensation/ sublimation) may potentially play a significant role in fractionating atmospheric H2O. The cycle of Martian H2O is complex. During northern summer, the North permanent water ice cap is assumed to release a few precipitable microns (pr. μ m), globally averaged, to the atmosphere. Part of this water vapor finally returns to North cap during northern winter, whereas a small fraction (<10%) is trapped in the South permanent carbonic ice cap, which acts as a permanent sink. Water vapor is probably cycled through regolith by adsorption/deposition and further sublimation/desorption. It is believed that the ultimate fate of water molecules released by the North water ice cap, and/or by the permafrost, is to stick to the South carbonic ice cap, with a time scale longer than one seasonal cycle. If so, a molecule released by the North cap must undergo a number of adsorption/desorption and deposition/sublimation cycles, through regolith and polar caps, before being trapped irreversibly in South cap carbonic ice. Recent IR observations of pure water ice on South polar cap by Mars-Express during southern spring show that water, migrating southward together with the edge of the retreating seasonal south CO2 cap, is finally deposited near cap edges in substantial amount. The fraction of this deposited water not released back to the atmosphere at later times (southern summer), therefore incorporated to carbonic ice, is not well known at present time. Because, during southern winter, water vapor above the South permanent cap is much depleted in deuterium, by at least a factor of 3 (Montmessin et al, AGU meeting, 2003), the polar cap tends to be depleted in deuterium (similarly to Earth's case), with a related

  9. Aerosol Remote Sensing in Polar Regions

    NASA Technical Reports Server (NTRS)

    Tomasi, Claudio; Kokhanovsky, Alexander A.; Lupi, Angelo; Ritter, Christoph; Smirnov, Alexander; O'Neill, Norman T.; Stone, Robert S.; Holben, Brent N.; Nyeki, Stephan; Wehrli, Christoph

    2014-01-01

    Multi-year sets of ground-based sun-photometer measurements conducted at 12 Arctic sites and 9 Antarctic sites were examined to determine daily mean values of aerosol optical thickness tau(lambda) at visible and near-infrared wavelengths, from which best-fit values of Ångström's exponent alpha were calculated. Analyzing these data, the monthly mean values of tau(0.50 micrometers) and alpha and the relative frequency histograms of the daily mean values of both parameters were determined for winter-spring and summer-autumn in the Arctic and for austral summer in Antarctica. The Arctic and Antarctic covariance plots of the seasonal median values of alpha versus tau(0.50 micrometers) showed: (i) a considerable increase in tau(0.50 micrometers) for the Arctic aerosol from summer to winter-spring, without marked changes in alpha; and (ii) a marked increase in tau(0.50 micrometer) passing from the Antarctic Plateau to coastal sites, whereas alpha decreased considerably due to the larger fraction of sea-salt aerosol. Good agreement was found when comparing ground-based sun-photometer measurements of tau(lambda) and alpha at Arctic and Antarctic coastal sites with Microtops measurements conducted during numerous AERONET/MAN cruises from 2006 to 2013 in three Arctic Ocean sectors and in coastal and off-shore regions of the Southern Atlantic, Pacific, and Indian Oceans, and the Antarctic Peninsula. Lidar measurements were also examined to characterize vertical profiles of the aerosol backscattering coefficient measured throughout the year at Ny-Ålesund. Satellite-based MODIS, MISR, and AATSR retrievals of tau(lambda) over large parts of the oceanic polar regions during spring and summer were in close agreement with ship-borne and coastal ground-based sun-photometer measurements. An overview of the chemical composition of mode particles is also presented, based on in-situ measurements at Arctic and Antarctic sites. Fourteen log-normal aerosol number size-distributions were

  10. Aerosol remote sensing in polar regions

    DOE PAGESBeta

    Tomasi, Claudio; Kokhanovsky, Alexander A.; Lupi, Angelo; Ritter, Christoph; Smirnov, Alexander; O'Neill, Norman T.; Stone, Robert S.; Holben, Brent N.; Nyeki, Stephan; Wehrli, Christoph; et al

    2015-01-01

    Multi-year sets of ground-based sun-photometer measurements conducted at 12 Arctic sites and 9 Antarctic sites were examined to determine daily mean values of aerosol optical thickness τ(λ) at visible and near-infrared wavelengths, from which best-fit values of Ångström's exponent α were calculated. Analysing these data, the monthly mean values of τ(0.50 μm) and α and the relative frequency histograms of the daily mean values of both parameters were determined for winter–spring and summer–autumn in the Arctic and for austral summer in Antarctica. The Arctic and Antarctic covariance plots of the seasonal median values of α versus τ(0.50 μm) showed: (i)more » a considerable increase in τ(0.50 μm) for the Arctic aerosol from summer to winter–spring, without marked changes in α; and (ii) a marked increase in τ(0.50 μm) passing from the Antarctic Plateau to coastal sites, whereas α decreased considerably due to the larger fraction of sea-salt aerosol. Good agreement was found when comparing ground-based sun-photometer measurements of τ(λ) and α at Arctic and Antarctic coastal sites with Microtops measurements conducted during numerous AERONET/MAN cruises from 2006 to 2013 in three Arctic Ocean sectors and in coastal and off-shore regions of the Southern Atlantic, Pacific, and Indian Oceans, and the Antarctic Peninsula. Lidar measurements were also examined to characterise vertical profiles of the aerosol backscattering coefficient measured throughout the year at Ny-Ålesund. Satellite-based MODIS, MISR, and AATSR retrievals of τ(λ) over large parts of the oceanic polar regions during spring and summer were in close agreement with ship-borne and coastal ground-based sun-photometer measurements. An overview of the chemical composition of mode particles is also presented, based on in-situ measurements at Arctic and Antarctic sites. Fourteen log-normal aerosol number size-distributions were defined to represent the average features of nuclei

  11. Aerosol remote sensing in polar regions

    SciTech Connect

    Tomasi, Claudio; Kokhanovsky, Alexander A.; Lupi, Angelo; Ritter, Christoph; Smirnov, Alexander; O'Neill, Norman T.; Stone, Robert S.; Holben, Brent N.; Nyeki, Stephan; Mazzola, Mauro; Lanconelli, Christian; Vitale, Vito; Stebel, Kerstin; Aaltonen, Veijo; de Leeuw, Gerrit; Rodriguez, Edith; Herber, Andreas B.; Radionov, Vladimir F.; Zielinski, Tymon; Petelski, Tomasz; Sakerin, Sergey M.; Kabanov, Dmitry M.; Xue, Yong; Mei, Linlu; Istomina, Larysa; Wagener, Richard; McArthur, Bruce; Sobolewski, Piotr S.; Kivi, Rigel; Courcoux, Yann; Larouche, Pierre; Broccardo, Stephen; Piketh, Stuart J.

    2015-01-01

    Multi-year sets of ground-based sun-photometer measurements conducted at 12 Arctic sites and 9 Antarctic sites were examined to determine daily mean values of aerosol optical thickness τ(λ) at visible and near-infrared wavelengths, from which best-fit values of Ångström's exponent α were calculated. Analysing these data, the monthly mean values of τ(0.50 μm) and α and the relative frequency histograms of the daily mean values of both parameters were determined for winter–spring and summer–autumn in the Arctic and for austral summer in Antarctica. The Arctic and Antarctic covariance plots of the seasonal median values of α versus τ(0.50 μm) showed: (i) a considerable increase in τ(0.50 μm) for the Arctic aerosol from summer to winter–spring, without marked changes in α; and (ii) a marked increase in τ(0.50 μm) passing from the Antarctic Plateau to coastal sites, whereas α decreased considerably due to the larger fraction of sea-salt aerosol. Good agreement was found when comparing ground-based sun-photometer measurements of τ(λ) and α at Arctic and Antarctic coastal sites with Microtops measurements conducted during numerous AERONET/MAN cruises from 2006 to 2013 in three Arctic Ocean sectors and in coastal and off-shore regions of the Southern Atlantic, Pacific, and Indian Oceans, and the Antarctic Peninsula. Lidar measurements were also examined to characterise vertical profiles of the aerosol backscattering coefficient measured throughout the year at Ny-Ålesund. Satellite-based MODIS, MISR, and AATSR retrievals of τ(λ) over large parts of the oceanic polar regions during spring and summer were in close agreement with ship-borne and coastal ground-based sun-photometer measurements. An overview of the chemical composition of mode particles is also presented, based on in-situ measurements at Arctic and Antarctic sites. Fourteen log-normal aerosol number size-distributions were defined to represent the average features of nuclei

  12. The role of sublimation and condensation on the development of ice sedimentation waves on the North Polar Cap of Mars

    NASA Astrophysics Data System (ADS)

    Herny, C.; Carpy, S.; Bourgeois, O.; Masse, M.; Spiga, A.; Le Mouélic, S.; Perret, L.; Smith, I. B.; Rodriguez, S.

    2015-10-01

    Mass and energy balance of ice sheets are driven by complex interactions between the atmosphere and the cryosphere. For instance, it has been demonstrated that feedbacks between katabatic winds and the cryosphere lead to the formation of sedimentation waves at the surface of Martian and terrestrial ice sheets [1, 2, 3 and 4]. Here we explore the role of sublimation and condensation of water vapor in the development of these sedimentation waves. We conduct this study by complementary observational and numerical investigations on the North Polar Cap of Mars.

  13. Mass changes in Arctic ice caps and glaciers: implications of regionalizing elevation changes

    NASA Astrophysics Data System (ADS)

    Nilsson, J.; Sandberg Sørensen, L.; Barletta, V. R.; Forsberg, R.

    2015-01-01

    The mass balance of glaciers and ice caps is sensitive to changing climate conditions. The mass changes derived in this study are determined from elevation changes derived measured by the Ice, Cloud, and land Elevation Satellite (ICESat) for the time period 2003-2009. Four methods, based on interpolation and extrapolation, are used to regionalize these elevation changes to areas without satellite coverage. A constant density assumption is then applied to estimate the mass change by integrating over the entire glaciated region. The main purpose of this study is to investigate the sensitivity of the regional mass balance of Arctic ice caps and glaciers to different regionalization schemes. The sensitivity analysis is based on studying the spread of mass changes and their associated errors, and the suitability of the different regionalization techniques is assessed through cross-validation. The cross-validation results shows comparable accuracies for all regionalization methods, but the inferred mass change in individual regions, such as Svalbard and Iceland, can vary up to 4 Gt a-1, which exceeds the estimated errors by roughly 50% for these regions. This study further finds that this spread in mass balance is connected to the magnitude of the elevation change variability. This indicates that care should be taken when choosing a regionalization method, especially for areas which exhibit large variability in elevation change.

  14. Regional modelling and mapping of the ionospheric characteristic parameters by spherical cap harmonic expansion

    NASA Astrophysics Data System (ADS)

    de Santis, A.; de Franceschi, G.; Zolesi, B.; Cander, Lj. R.

    1992-09-01

    The Haines et al. (1985) method of spherical cap harmonic (SCH) analysis has been applied to the critical frequency of the F2 layer observed at several European vertical incident ionospheric stations. The aim was the regional mapping and modeling of this parameter in Europe. To make it possible, a spherical cap including Europe, centered at 50 deg N, 14 deg E with the half-angle of 20 deg has been considered. The model is based on the expansion of Fourier longitudinal series and Legendre colatitudinal functions as the orthogonal basis functions over the caplike region of interest. It has been found that, for the modeling of the foF2, a SCH model with only 9 coefficients (K up to 2) well portrays its basic features.

  15. Biological Rhythms During Residence in Polar Regions

    PubMed Central

    2012-01-01

    At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms. Thus, the status of the circadian system is of interest. Moreover, the relatively controlled artificial light conditions in winter are conducive to experimentation with different types of light treatment. The hormone melatonin and/or its metabolite 6-sulfatoxymelatonin (aMT6s) provide probably the best index of circadian (and seasonal) timing. A frequent observation has been a delay of the circadian system in winter. A skeleton photoperiod (2 × 1-h, bright white light, morning and evening) can restore summer timing. A single 1-h pulse of light in the morning may be sufficient. A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h. With regard to general health in polar regions, intermittent reports describe abnormalities in various physiological processes from the point of view of daily and seasonal rhythms, but positive health outcomes are also published. True winter depression (SAD) appears to be rare, although subsyndromal SAD is reported. Probably of most concern are the numerous reports of sleep problems. These have prompted investigations of the underlying mechanisms and treatment interventions. A delay of the circadian system with “normal” working hours implies sleep is attempted at a suboptimal phase. Decrements in sleep efficiency, latency, duration, and quality are also seen in winter. Increasing the intensity of ambient light exposure throughout the day advanced circadian phase and was associated with benefits for sleep: blue-enriched light was slightly more effective than standard white light. Effects on performance remain to be fully investigated. At 75°S, base personnel adapt the circadian system to night work within

  16. Summer in Mars' North Polar Region

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Observations by NASA's 2001 Mars Odyssey spacecraft show a summertime view of the north polar region of Mars in intermediate-energy, or epithermal, neutrons. The map is based on data acquired by the high-energy neutron detector, one of the instruments in Odyssey's gamma-ray spectrometer suite. Soil enriched by hydrogen is indicated by the purple and deep blue colors on the map, which show a low intensity of epithermal neutrons. Progressively smaller amounts of hydrogen are shown in the colors light blue, green, yellow and red. The hydrogen is believed to be in the form of water ice. In some areas, the abundance of water ice is estimated to be up to 90 percent by volume. A shaded-relief rendition of topography is superimposed on this map for geographic reference.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson, and NASA's Johnson Space Center, Houston, operate the science instruments. The gamma-ray spectrometer was provided by the University of Arizona in collaboration with the Russian Aviation and Space Agency and Institute for Space Research (IKI), which provided the high-energy neutron detector, and the Los Alamos National Laboratory, New Mexico, which provided the neutron spectrometer. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. Winter in Mars' North Polar Region

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Observations by NASA's 2001 Mars Odyssey spacecraft show a wintertime view of the north polar region of Mars in intermediate-energy, or epithermal, neutrons. The map is based on data acquired by the high-energy neutron detector, one of the instruments in Odyssey's gamma-ray spectrometer suite. Soil enriched by hydrogen is indicated by the purple and deep blue colors on the map, which show a low intensity of epithermal neutrons. Progressively smaller amounts of hydrogen are shown in the colors light blue, green, yellow and red. The hydrogen is believed to be in the form of water ice. Much of the hydrogen is hidden at this time beneath a layer of carbon dioxide frost (dry ice). A shaded-relief rendition of topography is superimposed on this map for geographic reference.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson, and NASA's Johnson Space Center, Houston, operate the science instruments. The gamma-ray spectrometer was provided by the University of Arizona in collaboration with the Russian Aviation and Space Agency and Institute for Space Research (IKI), which provided the high-energy neutron detector, and the Los Alamos National Laboratory, New Mexico, which provided the neutron spectrometer. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  18. Dust aerosols above the south polar cap of Mars as seen by OMEGA

    NASA Astrophysics Data System (ADS)

    Vincendon, M.; Langevin, Y.; Poulet, F.; Bibring, J.-P.; Gondet, B.; Jouglet, D.; Omega Team

    2008-08-01

    The time evolution of atmospheric dust at high southern latitudes on Mars has been determined using observations of the south seasonal cap acquired in the near infrared (1-2.65 μm) by OMEGA/Mars Express in 2005. Observations at different solar zenith angles and one EPF sequence demonstrate that the reflectance in the 2.64 μm saturated absorption band of the surface CO 2 ice is mainly due to the light scattered by aerosols above most places of the seasonal cap. We have mapped the total optical depth of dust aerosols in the near-IR above the south seasonal cap of Mars from mid-spring to early summer with a time resolution ranging from one day to one week and a spatial resolution of a few kilometers. The optical depth above the south perennial cap is determined on a longer time range covering southern spring and summer. A constant set of optical properties of dust aerosols is consistent with OMEGA observations during the analyzed period. Strong variations of the optical depth are observed over small horizontal and temporal scales, corresponding in part to moving dust clouds. The late summer peak in dust opacity observed by Opportunity in 2005 propagated to the south pole contrarily to that observed in mid spring. This may be linked to evidence for dust scavenging by water ice-rich clouds circulating at high southern latitudes at this season.

  19. Polarized light from star forming regions

    NASA Technical Reports Server (NTRS)

    Weintraub, D.; Goodman, A.; Akeson, A.

    2000-01-01

    Studies of polarized radiation from molecular clouds and the environments of protostars are providing information about the orientations and strengths of magnetic fields and the sizes andcompositions of dust grains in these environments.

  20. Polarized Light From Star Forming Regions

    NASA Technical Reports Server (NTRS)

    Akeson, R.; Goodman, A.; Weintraub, D.

    1998-01-01

    Studies of polarized radiation from molecular clouds and the environments of protostars are providing information about the orientations and strengths of magnetic fields and the sizes and compositions of dust grains in these environments.

  1. Recent Geologic Mapping Results for the Polar Regions of Mars

    NASA Technical Reports Server (NTRS)

    tanaka, K. L.; Kolb, E. J.

    2008-01-01

    The polar regions of Mars include the densest data coverage for the planet because of the polar orbits of MGS, ODY, and MEX. Because the geology of the polar plateaus has been among the most dynamic on the planet in recent geologic time, the data enable the most detailed and complex geologic investigations of any regions on Mars, superseding previous, even recent, mapping efforts [e.g., 1-3]. Geologic mapping at regional and local scales is revealing that the stratigraphy and modificational histories of polar materials by various processes are highly complex at both poles. Here, we describe some of our recent results in polar geologic mapping and how they address the geologic processes involved and implications for polar climate history.

  2. ULF geomagnetic and polar cap potential signatures in the temperature and zonal wind reanalysis data in Antarctica

    NASA Astrophysics Data System (ADS)

    Regi, M.; De Lauretis, M.; Redaelli, G.; Francia, P.

    2016-01-01

    In the present study we investigated the possible coupling between geomagnetic activity and the low atmosphere dynamics in the polar cap. We compared daily values of the ERA-Interim temperature and zonal wind over Antarctica, with the daily geomagnetic ULF power, in the Pc5 (1-7 mHz), Pc1, and Pc2 (100 mHz-1 Hz) frequency ranges, at Terra Nova Bay (Antarctica, corrected geomagnetic latitude λ ~ 80°S) and with solar wind data during 2007, in correspondence to the last declining phase of the solar cycle 23. We found a high and statistically significant correspondence of temperature and zonal wind fluctuations in the stratosphere and troposphere with geomagnetic ULF power fluctuations at the ~27 day periodicity, with a substantial reduction at the tropopause height. A similar, clear relationship between the meteorological parameters and the polar cap potential difference was also observed. The results suggest that the changes in the atmospheric conductivity, due to energetic electrons precipitation driven by the ULF waves, as well as the high latitude potential variations, both associated to high geomagnetic activity, can affect the atmospheric dynamics.

  3. Aboveground activity rhythm in Arctic black-capped marmot ( Marmota camtschatica bungei Katschenko 1901) under polar day conditions

    NASA Astrophysics Data System (ADS)

    Semenov, Youri; Ramousse, Raymond; Le Berre, Michel; Vassiliev, Vladimir; Solomonov, Nikita

    2001-04-01

    Daily aboveground activity of wild black-capped marmots of Yakutia ( Marmota camtschatica bungei) was recorded under 'polar day' conditions at 71°56' N and 127°19' E (north of the Polar Circle). From the beginning of May until the end of August, the sun was permanently above or close to the horizon. However under this condition of continuous lighting, the aboveground activity of these arctic hibernating mammals was periodic. Onset and end of activity showed marked changes throughout the seasons. Activity time increased strongly from hibernation emergence until the end of July and then decreased slowly until onset of hibernation. Below daily mean temperatures of 5 °C, activity started when the sun was 35° above the horizon, and ended when it dropped below 28°. When daily mean temperatures were above 5 °C, activity onset was synchronised with a solar altitude around 17-18° and activity ended at 10°. Activity onset was more precise relative to the solar altitude than the end of activity. This may be explained by late feeding bouts, following a midday thermal stress. In absence of rapid natural light-dark (LD) transitions that occur at civil twilight, our results suggest that the activity pattern of black-capped marmots may be synchronised by the light cycle through the solar altitude and ambient temperature.

  4. Long-term variations in the intensity of polar cap plasma flows inferred from SuperDARN

    NASA Astrophysics Data System (ADS)

    Koustov, A. V.; Fiori, R. A. D.; Abooali zadeh, Z.

    2015-11-01

    Multiyear (1995-2013) velocity data collected by the Super Dual Auroral Network (SuperDARN) HF radars are considered to investigate the diurnal, seasonal, and solar cycle variation of the polar cap plasma flow speed. By considering monthly data sets, we show that the flows are systematically faster in the dawn/prenoon sector. The effect is particularly strong for interplanetary magnetic field (IMF) Bz < 0, By > 0 and in summer months. For Bz < 0, the flow speed increases with intensification of the IMF transverse component Bt at a rate of 20-30 m/s/nT during near noon summer hours. The dependence is weaker for other seasons and away from noon. For IMF Bz > 0, the flow speed response to the increase in Bt is weak. Despite the general sensitivity of the flow speed to Bt intensity and season, the speed for specific IMF bins and seasons or the speed averaged over a year does not change much over the solar cycle. Overall, the velocity is reduced during years of lowest solar activity, but a progression of the effect throughout the solar cycle was not observed. Inferred diurnal and seasonal trends of the polar cap flow speed are generally consistent with variations in the occurrence of VHF echoes whose onset depends on the strength of the ionospheric electric field or equivalently the magnitude of the plasma flow speed.

  5. A critical note on the IAGA-endorsed Polar Cap index procedure: effects of solar wind sector structure and reverse polar convection

    NASA Astrophysics Data System (ADS)

    Stauning, P.

    2015-11-01

    The International Association of Geomagnetism and Aeronomy (IAGA) has recently endorsed a new Polar Cap (PC) index version to supersede the previous seven different versions of the PCN (North) index and the five different PCS (South) index versions. However, the new PC index has some adverse features which should be known and taken into account by users of the index. It uses in its derivation procedure an "effective" quiet day level (QDC) composed of a "basic" QDC and an added solar wind sector term related to the azimuthal component (By) of the interplanetary magnetic field (IMF). The added IMF By-related terms may introduce unjustified contributions to the PC index of more than 2 index units (mV m-1). Furthermore, cases of reverse convection during strong northward IMF Bz (NBZ) conditions included in the database for calculation of index coefficients can cause unjustified index enhancements of 0.5-1 mV m-1 during calm conditions, reduction of index values by more than 20 % during disturbed conditions, and inconsistencies between index coefficients and index values for the northern and southern polar caps. The aim here is to specify these adverse features and quantify their effects, and to suggest alternative steps for future modifications of the index procedure.

  6. Observations of Doppler and delay spreads on HF signals received over polar cap and trough paths at various stages of the solar cycle

    NASA Astrophysics Data System (ADS)

    Stocker, A. J.; Warrington, E. M.; Siddle, D. R.

    2013-09-01

    Information on delay and Doppler spreading is of importance to designers and operators of digital communication systems within the HF band since modem performance rapidly deteriorates when delay and Doppler spreads exceed system dependent thresholds. The northerly ionosphere is a particularly challenging region in this regard as delay and Doppler spreads often significantly exceed those for similar length paths at midlatitudes. This paper presents results from an extensive set of measurements undertaken over three northerly paths: two subauroral paths aligned along the midlatitude trough (Uppsala to Bruntingthorpe and Nurmijärvi to Bruntingthorpe) and one path (Qaanaaq to Ny-Ålesund) contained entirely within the polar cap. Measurements span the period from the 2009 solar minimum to July 2012, close to solar maximum and 2001, close to the previous solar maximum.

  7. Mars residual north polar cap - Earth-based spectroscopic confirmation of water ice as a major constituent and evidence for hydrated minerals

    NASA Technical Reports Server (NTRS)

    Clark, R. N.; Mccord, T. B.

    1982-01-01

    A description is presented of new earth-based reflectance spectra of the Martian north residual polar cap. The spectra indicate that the composition is at least mostly water ice plus another component with a 'gray' reflectance. The other minerals in the ice cap appear to be hydrated. The data were obtained with a cooled circular variable filter spectrometer on February 20, 1978, using the 2.2-m telescope on Mauna Kea, Hawaii. It is pointed out that the identification of water ice in the north polar cap alone does not indicate that water makes up all or even most of the bulk of the cap. Kieffer (1970) has shown that a small amount of water will mask the spectral features of CO2.

  8. Analysis of vanillic acid in polar ice cores as a biomass burning proxy - preliminary results from the Akademii Nauk Ice Cap in Siberia

    NASA Astrophysics Data System (ADS)

    Grieman, M. M.; Jimenez, R.; McConnell, J. R.; Fritzsche, D.; Saltzman, E. S.

    2013-12-01

    Biomass burning influences global climate change and the composition of the atmosphere. The drivers, effects, and climate feedbacks related to fire are poorly understood. Many different proxies have been used to reconstruct past fire frequency from lake sediments and polar ice cores. Reconstruction of historical trends in biomass burning is challenging because of regional variability and the qualitative nature of various proxies. Vanillic acid (4-hydroxy-3-methoxybenzoic acid) is a product of the combustion of conifer lignin that is known to occur in biomass burning aerosols. Biomass burning is likely the only significant source of vanillic acid in polar ice. In this study we describe an analytical method for quantifying vanillic acid in polar ice using HPLC with electrospray ionization and tandem mass spectrometric detection. The method has a detection limit of 100 pM and a precision of × 10% at the 100 pM level for analysis of 100 μl of ice melt water. The method was used to analyze more than 1000 discrete samples from the Akademii Nauk ice cap on Severnaya Zemlya in the high Russia Arctic (79°30'N, 97°45'E) (Fritzsche et al., 2002; Fritzsche et al., 2005; Weiler et al., 2005). The samples range in age over the past 2,000 years. The results show a mean vanillic acid concentration of 440 × 710 pM (1σ), with elevated levels during the periods from 300-600 and 1450-1550 C.E.

  9. Keck adaptive optics images of Jupiter's north polar cap and Northern Red Oval

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Wong, Michael H.; de Kleer, Katherine; Hammel, Heidi B.; Ádámkovics, Máté; Conrad, Al

    2011-06-01

    We present observations at near-infrared wavelengths (1-5 μm) of Jupiter's north polar region and Northern Red Oval (NN-LRS-1). The observations were taken with the near-infrared camera NIRC2 coupled to the adaptive optics system on the 10-m W.M. Keck Telescope on UT 21 August 2010. At 5-μm Jupiter's disk reveals considerable structure, including small bright rings which appear to surround all small vortices. It is striking, though, that no such ring is seen around the Northern Red Oval. In de Pater et al. [2010a. Icarus 210, 742-762], we showed that such rings also exist around all small vortices in Jupiter's southern hemisphere, and are absent around the Great Red Spot and Red Oval BA. We show here that the vertical structure and extent of the Northern Red Oval is very similar to that of Jupiter's Red Oval BA. These new observations of the Northern Red Oval, therefore, support the idea of a dichotomy between small and large anticyclones, in which ovals larger than about two Rossby deformation radii do not have 5-μm bright rings. In de Pater et al. [2010a. Icarus 210, 742-762], we explained this difference in terms of the secondary circulations within the vortices. We further compare the brightness distribution of our new 5-μm images with previously published radio observations of Jupiter, highlighting the depletion of NH 3 gas over areas that are bright at 5 μm.

  10. Mapping the southern polar cap with a balloon-borne millimeter-wave telescope

    NASA Astrophysics Data System (ADS)

    Crawford, Thomas Mcfarland

    2003-10-01

    TopHat is a balloon-borne millimeter-wave telescope designed to make a map of a 48°-diameter region centered on the South Celestial Pole. The instrument consists of telescope optics, radiometer, rotational drive system, sun/earth shield, attitude and thermal sensors, and support electronics mounted on top of a 28-million cubic foot balloon, with a support gondola hanging below. The five-channel, single- pixel radiometer sits at the focus of an on-axis Cassegrain telescope with a 1-meter primary aperture. The detectors are monolithic, ion-implanted silicon bolometers, cooled to 265 mK by a sorption-pumped helium- 3 fridge. The five frequency bands have effective centers of 175, 245, 400, 460, and 630 GHz. The two lowest- frequency bands are designed to be sensitive to the 2.7 K Cosmic Microwave Background (CMB), while the three highest bands are designed to monitor thermal emission from interstellar dust grains. Together with a modified Winston cone at the Cassegrain focus, the telescope optics define a beam designed to be steeper than gaussian with a full-width at half-maximum of 20', rendering TopHat in principle sensitive to fluctuations in the CMB from scales of less than a degree up to the diameter of the map (6 ≤ ℓ ≤ 600). TopHat was launched on 4 January 2001 from McMurdo Station, Antarctica as part of the NASA National Scientific Balloon Facility (NSBF) Polar Long-Duration Balloon program and observed for four sidereal days until cryogens were exhausted. An unexpected ˜5° tilt in the mounting platform at the top of the balloon resulted in large scan-synchronous instrumental signals which were not removable at the level necessary to make an internally consistent measurement of the CMB power spectrum. Minimum-variance maps of the data in all five channels have been made and used to measure the integrated flux from three regions in the Magellanic Clouds, using a flux analysis technique that minimizes the aforementioned instrumental contamination. When

  11. The Polar Regions and Martian Climate: Studies with a Global Climate Model

    NASA Technical Reports Server (NTRS)

    Wilson, R. J.; Richardson, M. I.; Smith, M. D.

    2003-01-01

    Much of the interest in the polar regions centers on the fact that they likely contain the best record of Martian climate change on time scales from years to eons. This expectation is based upon the observed occurrence of weathering product deposits and volatile reservoirs that are coupled to the climate. Interpretation and understanding of these records requires understanding of the mechanisms that involve the exchange of dust, water, and carbon dioxide between the surface and atmosphere, and the atmospheric redistribution of these species. We will summarize our use of the GFDL Mars general circulation model (MGCM), to exploration aspects of the interaction between the global climate and the polar regions. For example, our studies have shown that while the northern polar cap is the dominant seasonal source for water, it can act as a net annual source or sink for water, depending upon the cap temperatures and the bulk humidity of the atmosphere. This behavior regulates the annual and global average humidity of the atmosphere, as the cap acts as a sink if the atmosphere is too wet and a source if it is too dry. We will then focus our presentation on the ability of the MGCM to simulate the observed diurnal variations of surface temperature. We are particularly interested in assessing the influence of dust aerosol and water ice clouds on simulated surface temperature and the comparison with observations. Surface thermal inertia and albedo are critical boundary inputs for MGCM simulations. Thermal inertia is also of intrinsic interest as it may be related to properties of the surface such as particle size and surface character.

  12. Ice in the lunar polar regions revisited

    NASA Astrophysics Data System (ADS)

    Hodges, R. Richard

    2002-02-01

    The common wisdom that water ice may exist in lunar polar cold traps has become a significant factor in the selection of space research objectives. The purpose of this paper is to address two topics that are missing from the discourse on lunar water: the effect that the pristine cleanliness of the regolith has on water transport on the moon, and the limits on water exposure implied by the extremely high adsorption potentials of the surfaces of soil grains. Water transport is characterized by chemisorption on soil grains and the mixing of ``wet'' grains into the regolith by meteoritic gardening. Ballistic lateral flow, which is generally thought to be an efficient conduit for moving water to the poles, is actually a secondary phenomenon that is facilitated by solar wind and micrometeor erosion but not by thermal desorption, as is the case for the dominant lunar exospheric gases, He and 40Ar. Simulation results show that even under the most optimistic conditions, less than 7% of the water accumulated in the regolith resides in the polar cold traps, where water concentrations cannot be greater than 350 ppm. More important, when realistic transport parameters are used in the simulator, the polar water concentration is reduced by almost 2 orders of magnitude. In a word, the concept of water ice at the lunar poles is insupportable.

  13. Seasonal and Annual Change in the Martian Polar Regions

    NASA Astrophysics Data System (ADS)

    Calvin, W. M.; James, P. B.

    2011-12-01

    The polar caps have a long established dichotomy in visual appearance, relative elevations, and surface composition. Observations using the Mars Reconnaissance Orbiter (MRO) instruments MARCI, CTX and CRISM have shown unique styles of seasonal frost retreat as well as fine scale variations in the composition of various units. With MRO we have observations for three Martian Years (MY) 28, 29 and 30 from November of 2006 to the present. We have observed the seasonal cap recessions in both the north and south using MARCI daily global images and have examined the composition of selected units of the polar layered deposits exposed in summer. Observation over multiple Mars years allows us to compare changes between years as well as longer term evolution of the high albedo deposits at the poles. North Cap Recession and Change: The northern seasonal cap recession was observed in both MY 29 and 30. Past work had noted large scale loss of bright deposits up to Ls 95 and the rugged terrain of the Gemini Scopuli darkens up to ~Ls 100 and then subsequently brightens. The patterns observed in MY 29 and 30 are similar. Significant variability in the early season is noted in both years and the retreating seasonal cap edge is extremely dynamic. Additional retreat of high albedo deposits are noted in MY 30. A new high albedo deposit appears off a reentrant in Olympia Planum in MY 29 and later disappears. In MY30, portions of Olympia Planitia have larger areas of high albedo. In both years sustained bright patches appear along the cap margins and while some are persistent between years, they are also variable over the northern summer. It is still uncertain if these albedo changes represent volatile "refrosting" or the removal of low albedo material to expose higher albedo material underneath and whether or not longer term loss of volatiles is implied. South Cap Recession and Change: The southern seasonal cap recession is fundamentally different than the north, and persistence of

  14. Three spacecraft observe Jupiter's glowing polar regions

    NASA Astrophysics Data System (ADS)

    1996-09-01

    with X ray observations by other spacecraft, have built up unprecedented albums of data from which astronomers can puzzle out the behaviour of these violent objects. After the termination of space operations, the IUE mission continues on the ground with the task of reprocessing all the raw data ever transmitted from the spacecraft, using the latest computational techniques. This will create the IUE archive of ultraviolet spectra, from which future generations of astronomers will continue to cull unique information on nearly 10,000 objects in the sky. Over the years, frequent international symposia have digested the results from IUE. At a special meeting of the European Astronomical Society next year November in Sevilla (Spain), astronomers will have the opportunity to put the latest findings in perspective, in relation to all the other observations since 1978. "When NASA decided last year to terminate its operations as the leading partner in IUE, we expanded our European operations at Villafranca" comments Roger Bonnet, ESA's Science Director. "Although we were unable to prolong the life of the spacecraft indefinitely, it is gratifying to see what excellent use the astronomers have made of this final phase of IUE's long career". An image illustrating IUE's last observations of the Jupiter Polar regions is available on request from ESA Public Relations, Paris (Tel : +33.1-53.69.7155 Fax : +33.1-53.69.76.90)

  15. Atmospheric Modeling of the Martian Polar Regions: CRISM EPF Coverage During the South Polar Spring Recession

    NASA Astrophysics Data System (ADS)

    Brown, A. J.; McGuire, P.; Wolff, M. J.

    2008-03-01

    We describe efforts to model dust and ice aerosols content and soils and icy surface reflectance in the Martian southern polar region during spring recession (Ls = 152-320) using CRISM emission phase function (EPF) observations.

  16. Dynamic microtubules: Experimental observation and computer simulation of polar microtubule behaviour with lateral cap model mechanisms

    NASA Astrophysics Data System (ADS)

    Bayley, P. M.; Martin, S. R.; Sharma, K. K.

    1991-05-01

    Microtubule dynamic instability involves the existence, within a population of microtubules, of sub-populations of growing and shrinking microtubules which interconvert apparently at random. We consider the scope and limitation of experimental observations of individual microtubules by video enhanced dark-field microscopy. This unique experimental phenomenon has been rationalized by the presence of a ``cap'' of tubulin-GTP which can stabilize the growing state. We have modelled this process quantitatively by numerical simulation and illustrate the basic principles by computer graphics. The inherent α-β asymmetry of the microtubule lattice determines that the relationship between the addition reaction of tubulin-GTP and the related hydrolysis of a polymer tubulin-GTP is different at the two ends of the microtubule. In the single layer, Lateral Cap model for microtubule dynamic instability, a plausible mechanism has been proposed for the dynamic properties at the ``active'' (presumed β-out) end in which the tubulin-GTP which is hydrolyzed is related longitudinally to the binding site by the 13-start protofilament helix. [1,2]. We now show a similar but distinct mechanism could hold for the ``inactive'' (presumed α-out) end of the microtubule. Lateral hydrolysis rules (related to 5- or 8- start helical contacts) predict that the α-end could in fact be less dynamic and cooperative in terms of reduced amplitudes of growth and shrinking. This would make a distinctive contribution to the J(c) plot of microtubule growth versus [tubulin-GTP]. These predictions are thus amenable to experimental verification. This approach illustrates how the helical lattice symmetry of the microtubule polymer can confer unique dynamic characteristics, which derive from the heterodimeric structure and guanine nucleotide binding properties of the component protein tubulin. It also provides a basis for the interpretation of the interactions of microtubules with anti-mitotic drugs used in

  17. PolarDARN Radar Observations of Plasma Flows Associated with Morning Polar Cap Forms Detaching from the Auroral Oval

    NASA Astrophysics Data System (ADS)

    Koustov, A. V.; Hosokawa, K.; Nishitani, N.; Ogawa, T.; Shiokawa, K.; Liu, H.

    2009-12-01

    OMTI all-sky camera at Resolute Bay (Canada) often detects optical forms detaching from the poleward edge of the dawnside auroral oval and moving toward dusk. Such forms typically consist of rayed arc-like fragments stretched toward the Sun. The two newly installed PolarDARN-SuperDARN HF radars at Rankin Inlet and Inuvik sometimes detect signatures of such forms. In this study, several events of joint radar-optical observations are presented to investigate features in the plasma flow patterns. We show that the forms typically occur within a band of anti-sunward flow. Strong sunward flow channels are sometimes seen between the form and auroral oval so that strong flow shears are formed. The data can be interpreted in terms of a mesoscale vortex embedded into a large-scale morning side convection cell. Other features are discussed.

  18. Statistical study of the effect of ULF fluctuations in the IMF on the cross polar cap potential drop for northward IMF

    NASA Astrophysics Data System (ADS)

    Kim, H.-J.; Lyons, L.; Boudouridis, A.; Pilipenko, V.; Ridley, A. J.; Weygand, J. M.

    2011-10-01

    Recent studies showed that, regardless of the orientation of the Interplanetary Magnetic Field (IMF), ULF wave activity in the solar wind can substantially enhance the convection in the high latitude ionosphere, suggesting that ULF fluctuations may also be an important contributor to the coupling of the solar wind to the magnetosphere-ionosphere system. We conduct a statistical study to understand the effect of ULF power in the IMF on the cross polar cap potential, primarily focusing on northward IMF. We have analyzed the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) calculations of the polar cap potential, a IMF ULF index that is defined as the logarithm of Pc5 ULF power in IMF, and solar wind velocity and dynamic pressure for 249 days in 2003. We find that, separated from the effects of solar wind speed and dynamic pressure, the average cross polar cap potentials show a roughly linear dependence on the ULF index, with a partial correlation coefficient of 0.19. Highly structured convection flow patterns with a number of localized vortices are often observed under fluctuating northward IMF. For such a convection configuration, it is hard to estimate properly the cross polar cap potential drop, as the enhanced flows around the vortices that may be associated with IMF fluctuations do not necessarily yield a large potential drop. Thus, despite the relatively small correlation coefficient, the linear trend we found gives support to the significant role of IMF ULF fluctuations on the coupling of the solar wind to the magnetosphere-ionosphere system.

  19. The Magnetic Landscape of the Sun's Polar Region

    NASA Astrophysics Data System (ADS)

    Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.; Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo, M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title, A. M.

    2008-12-01

    We present observations of the magnetic landscape of the polar region of the Sun that are unprecedented in terms of spatial resolution, field of view, and polarimetric precision. They were carried out with the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington inversion, we find many vertically oriented magnetic flux tubes with field strengths as strong as 1 kG scattered in latitude between 70° and 90°. They all have the same polarity, consistent with the global polarity of the polar region. The field vectors are observed to diverge from the centers of the flux elements, consistent with a view of magnetic fields that are expanding and fanning out with height. The polar region is also found to have ubiquitous horizontal fields. The polar regions are the source of the fast solar wind, which is channeled along unipolar coronal magnetic fields whose photospheric source is evidently rooted in the strong-field, vertical patches of flux. We conjecture that vertical flux tubes with large expansion around the photospheric-coronal boundary serve as efficient chimneys for Alfvén waves that accelerate the solar wind.

  20. Melting probes as a means to access the subsurface of Mars' polar caps and Jupiter's ice moons

    NASA Astrophysics Data System (ADS)

    Biele, J.; Ulamec, S.; Funke, O.; Engelhardt, M.

    There is a high scientific interest in exploring certain planetary icy environments in the solar system (Mars' polar caps, Europa and other icy satellites) motivated by the search for traces of life in these extreme environments as well as interest in planetary climate history as in the case of Mars. A promising technique to penetrate thick ice layers with small and reliable probes which do not require the heavy, complex and expensive equipment of a drilling rig is by melting. Contamination avoidance with respect to planetary protection requirements can be fulfilled using melting probes, since the melting channel refreezes behind the probe and shuts off the contact to the surface; also, in-situ decontamination of the probe is possible. Melting probes can be equipped with a suite of scientific instruments that are capable e.g. of determining the chemical and isotopic composition of the embedded or dissolved materials, of the ices themselves, of the dust content and possible traces of indigenous biological activity. Due to the still rather high energy demand to overcome the melting enthalpy, in case of extraterrestrial application (e.g. Europa or polar caps of Mars), only heating with radioactive isotopes seems feasible for reaching greater depths. The necessary power is driven by the desired penetration velocity (linearly) and the dimensions of the probe (proportional to the cross section). On Mars, however, solar cells could be used to power small tethered melting probes in polar summer. While such probes have successfully been used for terrestrial applications, e.g., in Antarctica in the 1990ies, the technology is not yet mature for space applications; for example, the behaviour in vacuum (below the triple point pressure of water, i.e., 611 Pa) needs to be assessed. We will report briefly on our laboratory tests with melting probes in vacuum and under very low temperatures to this end. Practical issues (impact of dust on the performance, gravity dependence

  1. The occurrence of polar cap patches in TEC fluctuations detected using GPS measurements in southern hemisphere

    NASA Astrophysics Data System (ADS)

    Krankowski, A.; Shagimuratov, I. I.; Baran, L. W.; Ephishov, I. I.; Tepenitzyna, N. J.

    2006-01-01

    GPS technique is widely used to study the global structure and dynamics of the ionosphere. This paper presents data on the occurrence of large-scale ionospheric irregularities observed at Antarctic stations McMurdo-MCM4 (-78N, 167E, Φ = 80°), Casey-CAS1 (-66N, 110E, Φ = 80°), Mawson-MAW1 (-68N, 63E, Φ = 71°), and Davis-DAV1 (-69N, 78E, Φ = 75°) in 2001. The irregularities caused strong Total Electron Content fluctuations. The intensity of TEC fluctuations was estimated with the ROT parameter and rate of TEC index (ROTI) expressed in TECU/min. Storm-time development of TEC fluctuations are presented for two geomagnetic active periods: June and September 2001. Data on temporal variations in TEC along individual satellites passes were also analyzed. Polar patches were associated with deep TEC fluctuations as the TEC enhancements were 2 10 times larger than the background, whereas the TEC increased by 10 50 TECU in about 5 10 min. The duration of such structures is 10 20 min. At 4 5 h interval, 3 5 strong and some weak patches were detected. The activity of patches depends to a low degree only on the magnetic activity index Kp. The intensity of TEC fluctuations increases during substorm activity. Diurnal, seasonal dependence, and longitudinal features of the occurrence of polar patches are also presented in the report.

  2. Comparisons of Na densities, Fe densities, and temperature measured over south polar cap with model predictions

    NASA Astrophysics Data System (ADS)

    Chu, X.; Gardner, C. S.; Vondrak, T.; Murray, B.; Plane, J. M.; Roble, R. G.; Espy, P. J.; Kawahara, T.

    Mesospheric Na and Fe layer densities and temperatures were measured by lidar systems at the South Pole, Syowa (69S, 39E), and Rothera (67.5S, 68.0W) during the past several years. Comparison of the wintertime temperatures measured above these sites with TIME-GCM predictions, suggests that the model over-estimates the compressional heating associated with downwelling. When simulating the winter Na and Fe densities at the pole using the UEA 1-D chemistry models, a 2-D general circulation model SOCRATES was used to predict the meridional and downward vertical transportation of O, H, etc. from the sunlit lower latitude into the polar vortex. However, the simulation indicates that the circulation, especially downward transport into the polar vortex, is overestimated by the general circulation model. Thus, the wintertime Na layer nearly disappears in the chemistry model, which does not agree with the maximum Na abundance observed in winter. In summer, the model correctly predicts the observed depletion of the metal atoms below 90 km. This results from the uptake of the metals onto ice particles, which seem to be a persistent feature of the summertime upper mesosphere at high latitudes. This paper will show that the observed seasonal behavior of the metal layers provides a rigorous test of general circulation models in the upper mesosphere.

  3. Extremely Low Ionospheric Peak Altitudes in the Polar-Hole Region

    NASA Technical Reports Server (NTRS)

    Benson, Robert F.; Grebowsky, Joseph M.

    1999-01-01

    Vertical electron-density (N (sub e)) profiles, deduced from newly-available ISIS-II digital ionospheric topside-sounder data, are used to investigate the "polar-hole" region within the winter, nighttime polar cap ionosphere during solar minimum. The hole region is located around 0200 MLT near the poleward side of the auroral oval. Earlier investigations had revealed very low N (sub e) values in this region (down to 200/cu cm near 300 km). In the present study, such low N, values (approx. 100/cu cm) were only found near the ISIS (International Satellite for Ionospheric Study)-II altitude of 1400 km. The peak ionospheric concentration below the spacecraft remained fairly constant (approx. 10 (exp 5)/cu cm across the hole region but the altitude of the peak dropped dramatically. This peak dropped, surprisingly, to the vicinity of 100 km. These observations suggest that the earlier satellite in situ measurements, interpreted as deep holes in the ionospheric F-region concentration, could have been made during conditions of an extreme decrease in the altitude of the ionospheric N (sub e) peak. The observations, in combination with other data, indicate that the absence of an F-layer peak may be a frequent occurrence at high latitudes.

  4. IRTM brightness temperature maps of the Martian south polar region during the polar night: The cold spots don't move

    NASA Technical Reports Server (NTRS)

    Paige, D. A.; Crisp, D.; Santee, M. L.; Richardson, M. I.

    1993-01-01

    A series of infrared thermal mapper (IRTM) south polar brightness temperature maps obtained by Viking Orbiter 2 during a 35-day period during the southern fall season in 1978 was examined. The maps show a number of phenomena that have been identified in previous studies, including day to day brightness temperature variations in individual low temperature regions and the tendency for IRTM 11-micron channel brightness temperatures to also decrease in regions where low 20-micron channel brightness temperatures are observed. The maps also show new phenomena, the most striking of which is a clear tendency for the low brightness temperature regions to occur at fixed geographic regions. During this season, the coldest low brightness temperatures appear to be concentrated in distinct regions, with spatial scales ranging from 50 to 300 km. There are approximately a dozen of these concentrations, with the largest centered near the location of the south residual polar cap. Other concentrations are located at Cavi Angusti and close to the craters Main, South, Lau, and Dana. Broader, less intense regions appear to be well correlated with the boundaries of the south polar layered deposits and the Mountains of Mitchell. No evidence for horizontal motion of any of these regions has been detected.

  5. Mesoscale variability of water vapor, surface ice aging and precipitation in the Martian polar regions

    NASA Astrophysics Data System (ADS)

    Evdokimova, Nadezda; Rodin, Alexander V.; Kuzmin, Ruslan; Fedorova, Anna

    We present the results of analysis of the H2 O and CO2 ices and the atmospheric water vapor distribution in the polar regions of Mars, based on the OMEGA C channel data obtained during the period of MY 26-27. We employ observations of the North polar cap (NPC) obtain during the aphelion campaigns of 26-27 MY, and corresponding South polar cap (SPC) observations obtained during the perihelion season. In both cases ices were mapped using spectral indices corresponding to specific adsorption bands. At the NPC where H2 O ices is presented during the spring-summer season we used square-based index of the 1.5 µm for estimation of the net ice content and one of the 1.25 µm band for the analysis of ice microstructure. At the SPC square indices are unreliable because of contamination of narrow CO2 absorption bands, so the relative depth of 1.5 µm was used for mapping of H2 O ice. CO2 ice was mapped using 1.57 µm band. In both hemispheres, wave-2 and wave-3 structures were observed in the circumpolar regions during limited period of time. At the NPC wave-2 pattern was found in the 1.25 µm index distribution during early aphelion season that presumably reflects enhanced aging rates of the NPC frost caused by cyclonic wind system in the circumpolar vortex, resulting in enlargement of grains in the optically active skin layer. Later in the aphelion season, wave-2 pattern is followed by wave-3 which is a consequence of change of the leading wavenumber in the polar vortex. At the SPC, wave-3 pattern is observed during the shot period when seasonal CO2 ice cap retreats. We interpret this structure as the outcropping of H2 O ice deposits accumulated during south hemisphere for autumn-winter season. Water vapor distribution inferred from OMEGA data also demonstrates zonal variations correlating with such wave structures. GCM simulations with comprehensive treatment of the water cycle reproduce stationary cyclonic eddies during the string-summer, and transient wave-3 system

  6. North polar region of Mars - Imaging results from Viking 2

    NASA Technical Reports Server (NTRS)

    Cutts, J. A.; Blasius, K. R.; Briggs, G. A.; Carr, M. H.; Masursky, H.; Greeley, R.

    1976-01-01

    During October 1976, the Viking 2 orbiter acquired approximately 700 high-resolution images of the north polar region of Mars. These images confirm the existence at the north pole of extensive layered deposits largely covered over with deposits of perennial ice. An unconformity within the layered deposits suggests a complex history of climate change during their time of deposition. A pole-girdling accumulation of dunes composed of very dark materials is revealed by the Viking cameras. The entire region is devoid of fresh impact craters. Rapid rates of erosion or deposition are implied. A scenario for polar geological evolution, involving two types of climate change, is proposed.

  7. Ice in the lunar polar regions

    NASA Technical Reports Server (NTRS)

    Arnold, J. R.

    1979-01-01

    The idea that ice and other trapped volatiles exist in permanently shadowed regions near the lunar poles was proposed by Watson, Murray, and Brown (1961). It is reexamined in the present paper, in the light of the vast increase of lunar knowledge. The stability of the traps and the trapping mechanism are verified. Four potential sources of lunar H2O, namely (1) solar wind reduction of Fe in the regolith, (2) H2O-containing meteoroids, (3) cometary impact, and (4) (the least certain) degassing of the interior, can supply amounts of trapped H2O estimated in the range of 10 to the 16th to 10 to the 17th g. Two important destructive mechanisms have been identified: photodissociation of H2O molecules adsorbed on the sunlit surface and sputtering or decomposition of trapped H2O by solar wind particles. The effect of impact gardening is mainly protective. The question of the presence of H2O in the traps remains open; it can be settled by experiment.

  8. Seasonal evolution of Titan's polar caps: interaction between atmospheric and subsurface processes

    NASA Astrophysics Data System (ADS)

    Sotin, C.

    2012-12-01

    Titan is the only satellite of the solar system with a dense atmosphere. It is also the only object, besides Earth, with stable liquid bodies at its surface. The (P,T) conditions at Titan's surface suggest that methane and ethane are liquid. Ethane has been detected in the lakes [1] whereas the signature of liquid methane is hidden by that of atmospheric methane which is the second most abundant atmospheric component. Methane is irreversibly transformed into ethane by photolysis. Titan's atmosphere contains very little ethane, which suggests that it is present in the surface (lakes) or/and the subsurface. Lakes are mostly located in the polar areas with many more lakes on the North Pole than on the South Pole. Ethane clouds above the North Pole have been identified during the winter when the atmospheric circulation leads to the formation of downwellings at the North Pole. Remote sensing instruments onboard the Cassini spacecraft have recently witnessed the formation of the South Polar vortex after the equinox in August 2009. Ethane rain may now happen over the South Pole. Laboratory experiments show that ethane and methane can react with ice to form clathrates that are denser and more stable than pure ice. Laboratory experiments also suggest that ethane clathrates are more stable than methane clathrates. The atmosphere can be replenished in methane through the substitution of methane by ethane that rains and percolates into the subsurface [2]. Because ethane clathrates are denser than methane clathrates, such a process would lead to significant subsidence on geological time scales. It may explain why Titan's flattening is larger than that due to spin rate only [2]. The amount of ethane required to explain Titan's shape is in agreement with the a global resurfacing event that would have occurred between a few hundreds of Myrs and 1 Gyr as suggested by the density of impact craters [3] and the age of the atmospheric methane [4]. The Cassini observations and results

  9. The relation between the azimuthal component of the interplanetary magnetic field and the geomagnetic field in the polar caps

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1973-01-01

    The recently discovered relation between the azimuthal component of the interplanetary magnetic field and magnetic variations in the earth's polar caps is reviewed. When the IMF azimuthal component is positive (typical of an interplanetary sector with magnetic field directed away from the sun) geomagnetic perturbations directed away from the earth are observed within 8 deg from the corrected geomagnetic pole. When the IMF azimuthal component is negative (typically within toward sectors) the geomagnetic perturbations are directed towards the earth at both poles. These perturbations can also be described by an equivalent current flowing at a constant magnetic latitude of 80 - 82 deg clockwise around the magnetic poles during toward sectors and counterclockwise during away sectors. This current fluctuates in magnitude and direction with the azimuthal component of the IMF, with a delay time of the order of 20 minutes. The importance of this effect for understanding of both solar magnetism and magnetospheric physics is stressed in view of the possibility for investigating the solar sector structure during the last five sunspot cycles.

  10. Total electron content and l-band amplitude and phase scintillation measurements in the polar-cap ionosphere

    SciTech Connect

    Klobuchar, J.A.; Bishop, G.J.; Doherty, P.H.

    1987-03-30

    The first measurements of absolute Total Electron Content (TEC) and L-band amplitude and phase scintillation was made from Thule, Greenland, a polar cap station, in early 1984. These measurements were made using signals transmitted from the Global Positioning System (GPS) satellites. The variability of the TEC, especially during the afternoon to pre-midnight hours, is large, with increases in TEC above the background values of greater than 100% not uncommon. During one disturbed time, quasi-periodic TEC enhancements having periods as short as ten minutes and amplitudes equal to the background TEC were observed for over two hours. The TEC during some of the disturbed periods in the dark Thule ionosphere exceeded mid-latitude daytime values. Amplitude scintillations were small, not exceeding 3 dB peak to peak during the entire observing period, but they were associated with the times of TEC enhancements, with some evidence for stronger scintillation occurring during the negative gradients of the TEC enhancements. Phase scintillations were highest during some of the times of enhanced TEC, and depend critically upon the phase detrend internal used.

  11. Mars: Stratigraphy of Western Highlands and Polar Regions

    NASA Technical Reports Server (NTRS)

    Tanaka, K. L.; Scott, D. H.; Tuesink, M. F.

    1985-01-01

    Geologic mapping and stratigraphic studies of Mars based on Viking images improved knowledge of the relative age and occurrence of geologic units on a global scale. Densities of geologic units or features during the Noarchian, Hesperian, and Amazonian periods are indicated for the North and South polar regions as well as the equatorial region of Mars. Cumulative counts of crater size frequencies for craters larger than 2 km in diameter on plateau units mapped in the western region of Mars counts indicate that the plateau terrain as a whole was thinly resurfaced during the Hesperian Period, and a large proportion of pre-existing craters less than 10 to 15 km in diameter was buried. The formation of northern plains, subpolar highlands, and both polar regions is also described.

  12. Statistical survey of pitch angle distributions in core (0-50 eV) ions from Dynamics Explorer 1: Outflow in the auroral zone, polar cap, and cusp

    NASA Technical Reports Server (NTRS)

    Giles, B. L.; Chappell, C. R.; Moore, T. E.; Comfort, R. H.; Waite, J. H., Jr.

    1994-01-01

    Core (0-50 eV) ion pitch angle measurements from the retarding ion mass spectrometer on Dynamics Explorer 1 are examined with respect to magnetic disturbance, invariant latitude, magnetic local time, and altitude for ions H(+), He(+), O(+), M/Z = 2 (D(+) or He(++)), and O(++). Included are outflow events in the auroral zone, polar cap, and cusp, separated into altitude regions below and above 3 R(sub E). In addition to the customary division into beam, conic, and upwelling distributions, the high-latitude observations fall into three categories corresponding to ion bulk speeds that are (1) less than, (2) comparable to, or (3) faster than that of the spacecraft. This separation, along with the altitude partition, serves to identify conditions under which ionospheric source ions are gravita- tionally bound and when they are more energetic and able to escape to the outer magnetosphere. Features of the cleft ion fountain inferred from single event studies are clearly identifiable in the statistical results. In addition, it is found that the dayside pre-noon cleft is a dayside afternoon cleft, or auroral zone, becomes an additional source for increased activity. The auroral oval as a whole appears to be a steady source of escape velocity H(+), a steady source of escape velocity He(+) ions for the dusk sector, and a source of escape velocity heavy ions for dusk local times primarily during increased activity. The polar cap above the auroral zone is a consistent source of low-energy ions, although only the lighter mass particles appear to have sufficient velocity, on average, to escape to higher altitudes. The observations support two concepts for outflow: (1) The cleft ion fountain consists of ionospheric plasma of 1-20 eV energy streaming upward into the magnetosphere where high-latitude convection electric fields cause poleward dispersion. (2) The auroral ion fountain involves field-aligned beams which flow out along auroral latitude field lines; and, in addition, for

  13. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    NASA Astrophysics Data System (ADS)

    Lühr, H.; Rentz, S.; Ritter, P.; Liu, H.; Häusler, K.

    2007-06-01

    Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4-) but moderate solar flux level (F10.7=124). Our analysis reveals clear wind features in the summer (Northern) Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern) Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00-18:00 MLT). In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  14. Partnerships in the Polar Regions: Climate to Classrooms

    NASA Astrophysics Data System (ADS)

    Warburton, J.; Bartholow, S.

    2013-12-01

    PolarTREC (Teachers and Researchers Exploring and Collaborating) is a program in which K-12 teachers spend 2-6 weeks participating in hands-on field research experiences in the polar regions which focus heavily on climate change and climate science. The goal of PolarTREC is to invigorate polar science education and understanding by bringing K-12 educators and polar researchers together. Through teachers, climate understanding can be shaped for the future by having scientifically literate students entering the workforce. Alone, PolarTREC reaches a myriad of classrooms throughout the country. With new partnerships of the National Park Service and Alaska Geographic, we developed additional field experiences in climate change education for teachers. Campaigns for climate literacy do impact students but are only effective with well-trained, experienced teachers. Our programmatic goal is to expand the opportunities for PolarTREC teachers to share their involvement in science with additional formal and informal educators. 'Teaching the teachers' will reach additional audiences in media, policy, and classrooms. Modeling this program, we designed and conducted teacher trainings on climate science in Denali National Park. Utilizing expert university faculty and park managers in climate science and PolarTREC alumni teachers, the program was touted as 'the best professional opportunity to date". This program gave new teachers the tools to adequately communicate climate science for a generation of scientifically literate students. This presentation will outline the practices used in creating and implementing a climate literacy program for teachers through partnerships that will effectively influence student learning.

  15. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Key, J. R.; Maslanik, J. A.

    1988-01-01

    The principal objectives of this project are: to develop suitable validation data sets to evaluate the effectiveness of the ISCCP operational algorithm for cloud retrieval in polar regions and to validate model simulations of polar cloud cover; to identify limitations of current procedures for varying atmospheric surface conditions, and to explore potential means to remedy them using textural classifiers: and to compare synoptic cloud data from a control run experiment of the Goddard Institute for Space Studies (GISS) climate model 2 with typical observed synoptic cloud patterns. Current investigations underway are listed and the progress made to date is summarized.

  16. Circular polarization in star- formation regions: implications for biomolecular homochirality

    PubMed

    Bailey; Chrysostomou; Hough; Gledhill; McCall; Clark; Menard; Tamura

    1998-07-31

    Strong infrared circular polarization resulting from dust scattering in reflection nebulae in the Orion OMC-1 star-formation region has been observed. Circular polarization at shorter wavelengths might have been important in inducing chiral asymmetry in interstellar organic molecules that could be subsequently delivered to the early Earth by comets, interplanetary dust particles, or meteors. This could account for the excess of L-amino acids found in the Murchison meteorite and could explain the origin of the homochirality of biological molecules. PMID:9685254

  17. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Key, J. R.; Maslanik, J. A.

    1988-01-01

    The principal objectives of this project are: (1) to develop suitable validation data sets to evaluate the effectiveness of the International Satellite Cloud Climatology Project (ISCCP) operational algorithm for cloud retrieval in polar regions and to validate model simulations of polar cloud cover; (2) to identify limitations of current procedures for varying atmospheric surface conditions, and to explore potential means to remedy them using textural classifiers; and (3) to compare synoptic cloud data from a control run experiment of the GISS climate model II with typical observed synoptic cloud patterns.

  18. The geologic setting of the Mars north polar cap's Basal Unit from the three dimensional analysis of MARSIS planetary radar sounder data

    NASA Astrophysics Data System (ADS)

    Frigeri, A.; Orosei, R.; Cartacci, M.; Cicchetti, A.; Giuppi, S.; Noschese, R.; Plaut, J.

    2012-12-01

    Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) is the orbital subsurface sounder aboard ESA's Mars Express spacecraft. It transmits a low-frequency radar pulse capable of penetrating below the surface, where subsurface dielectric discontinuities originate secondary echoes. MARSIS has been used to probe both the south and the north polar caps of Mars, revealing their thickness and structure. We report on the results of a campaign of observations of the north polar ice cap of Mars that took place between May and December 2011 in uniquely favorable conditions, and produced data of unprecedented quality. The focus of our work is the detection of signals from the Basal Unit, the dark, ice-rich, complexely layered geologic unit lying stratigraphically between the polar layered deposits and the Vastitas Borealis Formation, and extending beneath most of Planum Boreum and Olympia Planitia. The objective of this work is the study of the full three dimensional structure of the Northern Polar Deposit and in particular of the Basal Unit (BU). The analysis of signals in bi-dimensional radargrams sounding the BU reveal a layering of the unit, probably correlated with the Rupes Tenuis - Planum Boreum Cavi units' boundary. Using the density of data available from the 2011 polar campaign, we assembled radar observations into a three dimensional volume of data. The use of visualization techniques allow to explore these data interactively, identifying patterns that can be problematic to detect with unsupervised automatic methods. This way, specific areas, or sub-volumes, are being selected to be studied in detail. We will present MARSIS data from the Mars North Polar campaign, as well as the preliminary interpretation of these data in three dimensions, and the possible implications for the geologic history of the northern Martian ice-cap.

  19. The stratigraphic sequence of volcanic and sedimentary units in the north polar region of Mars

    NASA Technical Reports Server (NTRS)

    Botts, M. E.

    1980-01-01

    Based on photogeologic mapping of Viking orbiter images of Mars, four distinct informal stratigraphic units are defined for the region north of 70 degrees N latitude. They are: (a) bulbous plains, (b) mantled plains, (c) dune deposits, and (d) layered deposits/perennial ice. Background information on the Martian polar caps is provided from telescopic observation, Mariner mission results, and Viking mission results (August 1976-November 1978). A description, and an interpretation and distribution of the stratigraphic units are presented. Surface winds, which were determined from dune orientations, and discussed and implications for the source of circumpolar dune materials are delineated. A list of the Viking Orbiter imagery used in the research, the computer programs for crater size frequency distributions, and the crater size frequency data are presented.

  20. Stratigraphy of the south polar region of Ganymede

    NASA Technical Reports Server (NTRS)

    Dehon, R. A.

    1987-01-01

    A preliminary assessment is made of the stratigraphy and geology in the south polar region of the Jovian satellite, Ganymede. Geologic mapping is based on inspection of Voyager images and compilation on an airbrush base map at a scale of 1:5M. Illumination and resolution vary greatly in the region. Approximately half of the quadripole is beyond the terminator. Low angle illumination over a large part of the area precludes distinction of some units by albedo characteristics. Several types of grooved terrain and groove related terrain occur in the southern polar region. Grooves typically occur in straight to curvilinear sets or lanes. Bright lanes and grooved lanes intersect at high angles outlining polygons of dark cratered terrain. Groove sets exhibit a range of ages as shown by superposition or truncation and by crater superposition ages.

  1. Ephemeral liquid water at the surface of the martian North Polar Residual Cap: Results of numerical modelling

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Czechowski, Leszek; Velbel, Michael A.

    2015-12-01

    Gypsum, a mineral that requires water to form, is common on the surface of Mars. Most of it originated before 3.5 Gyr when the Red Planet was more humid than now. However, occurrences of gypsum dune deposits around the North Polar Residual Cap (NPRC) seem to be surprisingly young: late Amazonian in age. This shows that liquid water was present on Mars even at times when surface conditions were as cold and dry as the present-day. A recently proposed mechanism for gypsum formation involves weathering of dust within ice (e.g., Niles, P.B., Michalski, J. [2009]. Nat. Geosci. 2, 215-220.). However, none of the previous studies have determined if this process is possible under current martian conditions. Here, we use numerical modelling of heat transfer to show that during the warmest days of the summer, solar irradiation may be sufficient to melt pure water ice located below a layer of dark dust particles (albedo ⩽ 0.13) lying on the steepest sections of the equator-facing slopes of the spiral troughs within martian NPRC. During the times of high irradiance at the north pole (every 51 ka; caused by variation of orbital and rotational parameters of Mars e.g., Laskar, J. et al. [2002]. Nature 419, 375-377.) this process could have taken place over larger parts of the spiral troughs. The existence of small amounts of liquid water close to the surface, even under current martian conditions, fulfils one of the main requirements necessary to explain the formation of the extensive gypsum deposits around the NPRC. It also changes our understanding of the degree of current geological activity on Mars and has important implications for estimating the astrobiological potential of Mars.

  2. Pulsar Polar Cap Heating and Surface Thermal X-ray Emission. 2; Inverse Compton Radiation Pair Fronts

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alexander G.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We investigate the production of electron-positron pairs by inverse Compton scattered (ICS) photons above a pulsar polar cap (PC) and calculate surface heating by returning positrons. This paper is a continuation of our self-consistent treatment of acceleration, pair dynamics, and electric field screening above pulsar PCs. We calculate the altitude of the inverse Compton pair-formation fronts, the flux of returning positrons, and present the heating efficiencies and X-ray luminosities. We revise pulsar death lines implying cessation of pair formation, and present them in surface magnetic field-period space. We find that virtually all known radio pulsars are capable of producing pairs by resonant and nonresonant ICS photons radiated by particles accelerated above the PC in a pure star-centered dipole field, so that our ICS pair death line coincides with empirical radio pulsar death. Our calculations show that ICS pairs are able to screen the accelerating electric field only for high PC surface temperatures and magnetic fields. We argue that such screening at ICS pair fronts occurs locally, slowing but not turning off acceleration of particles until screening can occur at a curvature radiation (CR) pair front at higher altitude. In the case where no screening occurs above the PC surface, we anticipate that the pulsar gamma-ray luminosity will be a substantial fraction of its spin-down luminosity. The X-ray luminosity resulting from PC heating by ICS pair fronts is significantly lower than the PC heating luminosity from CR pair fronts, which dominates for most pulsars. PC heating from ICS pair fronts is highest in millisecond pulsars, which cannot produce CR pairs, and may account for observed thermal X-ray components in the spectra of these old pulsars.

  3. Regional Multi-Fluid-Based Geophysical Excitation of Polar Motion

    NASA Technical Reports Server (NTRS)

    Nastula, Jolanta; Salstein, David A.; Gross, Richard

    2011-01-01

    By analyzing geophysical fluids geographic distribution, we can isolate the regional provenance for some of the important signals in polar motion. An understanding of such will enable us to determine whether certain climate signals can have an impact on polar motion. Here we have compared regional patterns of three surficial fluids: the atmosphere, ocean and land-based hydrosphere. The oceanic excitation function of polar motion was estimated with the ECCO/JPL data - assimilating model, and the atmospheric excitation function was determined from NCEP/NCAR reanalyses. The excitation function due to land hydrology was estimated from the Gravity Recovery and Climate Experiment (GRACE) data by an indirect approach that determines water thickness. Our attention focuses on the regional distribution of atmospheric and oceanic excitation of the annual and Chandler wobbles during 1993-2010, and on hydrologic excitation of these wobbles during 2002.9-2011.5. It is found that the regions of maximum fractional covariance (those exceeding a value of 3 .10 -3) for the annual band are over south Asia, southeast Asia and south central Indian ocean, for hydrology, atmosphere and ocean respectively; and for the Chandler period, areas over North America, Asia, and South America; and scattered across the southern oceans for the atmosphere and oceans respectively

  4. North polar region of Mars: imaging results from viking 2.

    PubMed

    Cutts, J A; Blasius, K R; Briggs, G A; Carr, M H; Greeley, R; Masursky, H

    1976-12-11

    During October 1976, the Viking 2 orbiter acquired approximately 700 high-resolution images of the north polar region of Mars. These images confirm the existence at the north pole of extensive layered deposits largely covered over with deposits of perennial ice. An unconformity within the layered deposits suggests a complex history of climate change during their time of deposition. A pole-girdling accumulation of dunes composed of very dark materials is revealed for the first time by the Viking cameras. The entire region is devoid of fresh impact craters. Rapid rates of erosion or deposition are implied. A scenario for polar geological evolution, involving two types of climate change, is proposed. PMID:17797095

  5. Report on anisakid nematodes in polar regions - Preliminary results

    NASA Astrophysics Data System (ADS)

    Dzido, Joanna; Kijewska, Agnieszka; Rokicka, Magdalena; Świątalska-Koseda, Agnieszka; Rokicki, Jerzy

    2009-11-01

    The aim of this study is to extend our knowledge of the distribution of anisakid nematode parasites in Arctic and Antarctic polar regions. We examined vertebrate (fish) taxa characteristic of the faunas in both polar regions for the presence of parasitic nematodes. The material was collected from Svalbard (Arctic) between July and August 2008 and from King George Island (South Shetland Islands, Antarctic Peninsula) between November 2007 and January 2008. In addition, faecal, bird, and invertebrate samples were collected and examined for the presence of anisakid nematodes or eggs. Anisakis simplex s.s. was found in the body cavity of Arctic cod, and Contracaecum sp. and Pseudoterranova sp. were found in Antarctic notothenioids. Eggs of Anisakis sp. and Contracaecum sp. were recovered from the faeces of Mirounga leonina. We present the first record of the occurrence of A. simplex C in the Antarctic fishes Notothenia coriiceps and Notothenia rossii.

  6. Frontier Science in the Polar Regions: Current Activities of the Polar Research Board

    NASA Astrophysics Data System (ADS)

    Brown, L. M.

    2011-12-01

    The National Academies (the umbrella term for the National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council) is a private, nonprofit organization chartered by Congress in 1863. The Polar Research Board (PRB) is the focal point within the Academies for providing advice on issues related to the Arctic, Antarctic, and cold regions in general. Tasks within the PRB mission include: providing a forum for the polar science community to address research needs and policy issues; conducting studies and workshops on emerging scientific and policy issues in response to requests from federal agencies and others; providing program reviews, guidance, and assessments of priorities; and facilitating communication on polar issues among academia, industry, and government. The PRB also serves as the US National Committee to two international, nongovernmental polar science organizations: the Scientific Committee on Antarctic Research (SCAR) and the International Arctic Science Committee (IASC). The polar regions are experiencing rapid changes in environment and climate, and the PRB has a number of completed and ongoing studies that will enhance scientific understanding of these issues. This poster will illustrate current PRB activities as well as results from two recently released reports: Frontiers in Understanding Climate Change and Polar Ecosystems and Future Science Opportunities in Antarctica and the Southern Ocean. In the former, a set of frontier research questions are developed to help scientists understand the impacts of climate change on polar ecosystems. The report builds on existing knowledge of climate change impacts and highlights the next big topics to be addressed in the coming decades. In addition, a number of methods and technologies are identified that will be useful to advance future research in polar ecosystem science. In the latter, changes to important science conducted on Antarctica and the surrounding

  7. Illumination Conditions of the Lunar Polar Regions Using LOLA Topography

    NASA Technical Reports Server (NTRS)

    Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.; Torrence, M. H.

    2011-01-01

    We use high-resolution altimetry data obtained by the Lunar Orbiter Laser Altimeter instrument onboard the Lunar Reconnaissance Orbiter to characterize present illumination conditions in the polar regions of the Moon. Compared to previous studies, both the spatial and temporal extent of the simulations are increased significantly, as well as the coverage (fill ratio) of the topographic maps used, thanks to the 28 Hz firing rate of the five-beam instrument. We determine the horizon elevation in a number of directions based on 240 m-resolution polar digital elevation models reaching down to 75 latitude. The illumination of both polar regions extending to 80 can be calculated for any geometry from those horizon longitudinal profiles. We validated our modeling with recent Lunar Reconnaissance Orbiter Wide-Angle Camera images. We assessed the extent of permanently shadowed regions (PSRs, defined as areas that never receive direct solar illumination), and obtained total areas generally larger than previous studies (12,866 and 16,055 km2, in the north and south respectively). We extended our direct illumination model to account for singly-scattered light, and found that every PSR does receive some amount of scattered light during the year. We conducted simulations over long periods (several 18.6-years lunar precession cycles) with a high temporal resolution (6 h), and identified the most illuminated locations in the vicinity of both poles. Because of the importance of those sites for exploration and engineering considerations, we characterized their illumination more precisely over the near future. Every year, a location near the Shackleton crater rim in the south polar region is sunlit continuously for 240 days, and its longest continuous period in total darkness is about 1.5 days. For some locations small height gains ( 10 m) can dramatically improve their average illumination and reduce the night duration, rendering some of those particularly attractive energy-wise as

  8. The Discharging of Roving Objects in the Lunar Polar Regions

    NASA Technical Reports Server (NTRS)

    Jackson, T. L.; Farrell, W. M.; Killen, R. M.; Delory, G. T.; Halekas, J. S.; Stubbs, T. B.

    2012-01-01

    In 2007, the National Academy of Sciences identified the lunar polar regions as special environments: very cold locations where resources can be trapped and accumulated. These accumulated resources not only provide a natural reservoir for human explorers, but their very presence may provide a history of lunar impact events and possibly an indication of ongoing surface reactive chemistry. The recent LCROSS impacts confirm that polar crater floors are rich in material including approx 5%wt of water. An integral part of the special lunar polar environment is the solar wind plasma. Solar wind protons and electrons propagate outward from the Sun, and at the Moon's position have a nominal density of 5 el/cubic cm, flow speed of 400 km/sec, and temperature of 10 eV (approx. equal 116000K). At the sub-solar point, the flow of this plasma is effectively vertically incident at the surface. However, at the poles and along the lunar terminator region, the flow is effectively horizontal over the surface. As recently described, in these regions, local topography has a significant effect on the solar wind flow. Specifically, as the solar wind passes over topographic features like polar mountains and craters, the plasma flow is obstructed and creates a distinct plasma void in the downstream region behind the obstacle. An ion sonic wake structure forms behind the obstacle, not unlike that which forms behind a space shuttle. In the downstream region where flow is obstructed, the faster moving solar wind electrons move into the void region ahead of the more massive ions, thereby creating an ambipolar electric field pointing into the void region. This electric field then deflects ion trajectories into the void region by acting as a vertical inward force that draws ions to the surface. This solar wind 'orographic' effect is somewhat analogous to that occurring with terrestrial mountains. However, in the solar wind, the ambipolar E-field operating in the collision less plasma replaces

  9. In Brief: Mission to Mars's northern polar region

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2007-08-01

    NASA's Phoenix Mars Mission, which launched on 4 August, is scheduled to arrive at Mars on 25 May 2008 to examine the surface of the planet's northern polar region, study the formation and melting histories of ice, monitor weather, and investigate the subsurface environment. ``Our instruments are specially designed to find evidence for periodic melting of the ice and to assess whether this large region represents a habitable environment for Martian microbes,'' said Phoenix Principal Investigator Peter Smith of the University of Arizona, Tucson. For more information, visit the Web site: http://www.nasa.gov/phoenix.

  10. Srv2/CAP is required for polarized actin cable assembly and patch internalization during clathrin-mediated endocytosis.

    PubMed

    Toshima, Junko Y; Horikomi, Chika; Okada, Asuka; Hatori, Makiko N; Nagano, Makoto; Masuda, Atsushi; Yamamoto, Wataru; Siekhaus, Daria Elisabeth; Toshima, Jiro

    2016-01-15

    The dynamic assembly and disassembly of actin filaments is essential for the formation and transport of vesicles during endocytosis. In yeast, two types of actin structures, namely cortical patches and cytoplasmic cables, play a direct role in endocytosis, but how their interaction is regulated remains unclear. Here, we show that Srv2/CAP, an evolutionarily conserved actin regulator, is required for efficient endocytosis owing to its role in the formation of the actin patches that aid initial vesicle invagination and of the actin cables that these move along. Deletion of the SRV2 gene resulted in the appearance of aberrant fragmented actin cables that frequently moved past actin patches, the sites of endocytosis. We find that the C-terminal CARP domain of Srv2p is vitally important for the proper assembly of actin patches and cables; we also demonstrate that the N-terminal helical folded domain of Srv2 is required for its localization to actin patches, specifically to the ADP-actin rich region through an interaction with cofilin. These results demonstrate the in vivo roles of Srv2p in the regulation of the actin cytoskeleton during clathrin-mediated endocytosis. PMID:26604224

  11. Source-to-sink cycling of aeolian sediment in the north polar region of Mars

    NASA Astrophysics Data System (ADS)

    Ewing, R. C.; Kocurek, G.

    2012-12-01

    Aeolian sand dunes are prominent features on the landscapes of Earth, Mars, Venus and Titan and sedimentary deposits interpreted as aeolian in origin are found in the rock records of Earth and Mars. The widespread occurrence of aeolian dunes on the surface of these worlds and within their deep-time depositional records suggests that aeolian systems are and likely have been a default depositional environment for the Solar System. Within an aeolian source-to-sink context, we hypothesize that planet-specific boundary conditions strongly impact production, transport, accumulation and preservation of aeolian sediment, whereas dunes and dune-field patterns remain largely similar. This hypothesis is explored within the north polar region of Mars, which hosts the most extensive aeolian dune fields and aeolian sedimentary deposits yet recognized on Mars and appears to be a region of dynamic source-to-sink cycling of aeolian sediments. The Planum Boreum Cavi Unit rests beneath north polar ice cap of Mars and is composed of several hundred meters of niveo-aeolian dune cross-stratification. The overall architecture of the unit consists of sets of preserved dune topography with an upward increase in the abundance of ice. Dune sets are defined by stabilized, polygonally fractured bounding surfaces, erosional bounding surfaces and typical internal lee foresets made of sediment and ice. The accumulation of the Cavi Unit is interpreted as occurring through freezing and serves as an example of a cold temperature boundary condition on aeolian sediment accumulation. Preservation of the Cavi Unit arises because of deposition of the overlying ice cap and contrasts with preservation of aeolian sediment on Earth, which is largely driven by eustasy and tectonics. The Cavi Unit is thought to be one source of sediment for the north polar Olympia Undae Dune Field. The region of Olympia Undae near the Cavi Unit shows a reticulate dune field pattern composed of two sets of nearly orthogonal

  12. Extending the X/Ka Celestial Reference Frame over the South Polar Cap: Results from combined NASA-ESA Deep Space Network baselines to Malargüe, Argentina

    NASA Astrophysics Data System (ADS)

    Jacobs, Christopher S.; de Vicente, J.; Dugast, M.; García-Miró, C.; Goodhart, C. E.; Horiuchi, S.; Lowe, S. T.; Maddè, R.; Mercolino, M.; Naudet, C. J.; Snedeker, L. G.; Sotuela, I.; White, L. A.

    2013-03-01

    In order to extend the X/Ka-band (8.4/32 GHz) Celestial Reference Frame coverage over the south polar cap region of declinations -45 to -90 deg, we developed a collaboration between the NASA and ESA Deep Space Networks. In particular ESA's new 35-meter X/Ka-band antenna in Malargüe, Argentina which became operational in January 2013 is now available for X/Ka VLBI baselines to NASA's antennas in Tidbinbilla, Australia; Goldstone, California; and Robledo, Spain. We report first fringes on baselines from Malargüe to Tidbinbilla, Goldstone, and Robledo using a semi-portable digital backend recording at 256 Mbps. To the best of our knowledge the Giga-lambda Malargüe-Tidbinbilla baseline is producing the highest resolution interferometry ever achieved over the south polar cap. We will present the distribution of Ka-band sources detected on this all-southern baseline. Lastly, we will discuss the prospects for using these new baselines to improve the astrometric accuracy of the X/Ka frame in the southern hemisphere.

  13. Relief and geology of the north polar region of the planet Venus

    NASA Technical Reports Server (NTRS)

    Kuzmin, R. O.; Burba, G. A.; Shashkina, V. P.; Bogomolov, A. F.; Zherikhin, N. V.; Skrypnik, G. I.; Kudrin, L. V.; Bergman, M. Y.; Rzhiga, O. N.; Sidorenko, A. I.

    1986-01-01

    Description of topographic features is given for the North polar region of the planet Venus. Principal geomorphic types of terrain are characterized as well as their geologic relations. Relative ages of geologic units in Venus North polar region are discussed.

  14. Characterization of the Morphometry of Impact Craters Hosting Polar Deposits in Mercury's North Polar Region

    NASA Technical Reports Server (NTRS)

    Talpe, Matthieu, J.; Zuber, Maria T.; Neumann, Gregory A.; Mazarico, Erwan; Solomon, Sean C.; Vilas, Faith

    2012-01-01

    Earth-based radar images dating back two decades show that the floors of some polar craters on Mercury host radar-bright deposits that have been proposed to consist of frozen volatiles. Several hypotheses have been put forth to explain their source, including volcanic outgassing, chemical sputtering, and deposition of exogenous water ice. Calculations show that volatiles are thermally stable in permanently shadowed areas. An earlier study of the depths of north polar craters determined with photoclinometric techniques applied to Mariner 10 images yielded the conclusion that the mean ratio of crater depth d to rim-crest diameter D for craters hosting polar deposits is two-thirds that of the mean ratio for a comparable population of neighboring craters lacking such deposits. This result could be explained by (though doesn't require) the presence of a thick layer of volatiles within the polar deposit-hosting craters. Here we use altimetric profiles and topographic maps obtained by the Mercury Laser Altimeter (MLA) to revisit this analysis. MLA is an instrument on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which has been orbiting Mercury since March 2011. MLA transmits a 1064-nm laser pulse at 8 Hz during MESSENGER's trajectory over Mercury s surface. The MLA illuminates surface areas averaging between 15 m and 100 m in diameter, spaced approx 400 m apart along the spacecraft ground track. The radial precision of individual measurements is <1 m, and the current accuracy with respect to Mercury s center of mass is better than 20 m. As of mid-December 2011, MLA coverage had reached to 15 S and has yielded a comprehensive map of the topography of Mercury s northern hemisphere. The MLA data are used here to quantify the shapes of craters in the north polar region and to avoid the shadowing bias of photoclinometric techniques.

  15. North Polar Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    23 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. Surrounding much of the north polar ice cap are fields of sand dunes. In this case, the strongest winds responsible for the dunes blew off the polar cap (not seen here), from the north-northwest (upper left).

    Location near: 76.5oN, 63.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  16. Solar Wind Influence on the Oxygen Content of Ion Outflow in the High-Altitude Polar Cap During Solar Minimum Conditions

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    2001-01-01

    We correlate solar wind and interplanetary magnetic field (IMF) properties with the properties of O(+) and H(+) during early 1996 (solar minimum) at altitudes between 5.5 and 8.9 R(sub E) geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. Throughout the high-altitude polar cap we observe H(+) to be more abundant than O(+). O(+) is found to be more abundant at lower latitudes when the solar wind speed is low (and Kp is low), while at higher solar wind speeds (and high Kp), O(+) is observed across most of the polar cap. The O(+) density and parallel flux are well organized by solar wind dynamic pressure, both increasing with solar wind dynamic pressure. Both the O(+) density and parallel flux have positive correlations with both V(sub SW)B(sub IMF) and E(sub SW). No correlation is found between O(+) density and IMF Bz, although a nonlinear relationship with IMF By is observed, possibly due to a strong linear correlation with the dynamic pressure. H(+) is not as highly correlated with solar wind and IMF parameters, although H(+) density and parallel flux are negatively correlated with IMF By and positively correlated with both V(sub SW)B(sub IMF) and E(sub SW). In this solar minimum data set, H(+) is dominant, so that contributions of this plasma to the plasma sheet would have very low O(+) to H(+) ratios.

  17. Transient surface liquid in Titan's south polar region from Cassini

    USGS Publications Warehouse

    Hayes, A.G.; Aharonson, O.; Lunine, J.I.; Kirk, R.L.; Zebker, H.A.; Wye, L.C.; Lorenz, R.D.; Turtle, E.P.; Paillou, P.; Mitri, G.; Wall, S.D.; Stofan, E.R.; Mitchell, K.L.; Elachi, C.

    2011-01-01

    Cassini RADAR images of Titan's south polar region acquired during southern summer contain lake features which disappear between observations. These features show a tenfold increases in backscatter cross-section between images acquired one year apart, which is inconsistent with common scattering models without invoking temporal variability. The morphologic boundaries are transient, further supporting changes in lake level. These observations are consistent with the exposure of diffusely scattering lakebeds that were previously hidden by an attenuating liquid medium. We use a two-layer model to explain backscatter variations and estimate a drop in liquid depth of approximately 1-m-per-year. On larger scales, we observe shoreline recession between ISS and RADAR images of Ontario Lacus, the largest lake in Titan's south polar region. The recession, occurring between June 2005 and July 2009, is inversely proportional to slopes estimated from altimetric profiles and the exponential decay of near-shore backscatter, consistent with a uniform reduction of 4 ± 1.3 m in lake depth. Of the potential explanations for observed surface changes, we favor evaporation and infiltration. The disappearance of dark features and the recession of Ontario's shoreline represents volatile transport in an active methane-based hydrologic cycle. Observed loss rates are compared and shown to be consistent with available global circulation models. To date, no unambiguous changes in lake level have been observed between repeat images in the north polar region, although further investigation is warranted. These observations constrain volatile flux rates in Titan's hydrologic system and demonstrate that the surface plays an active role in its evolution. Constraining these seasonal changes represents the first step toward our understanding of longer climate cycles that may determine liquid distribution on Titan over orbital time periods.

  18. Writing About Polar Regions for the General Public

    NASA Astrophysics Data System (ADS)

    Walker, G.

    2003-12-01

    The Earth's polar regions hold an extraordinary attraction for members of the general public. In recent years, tales of polar exploration and derring-do have come to the public's attention through films, documentaries, novels and biographies of the early explorers. But the modern scientific exploration of Antarctica and the Arctic remains much less accessible to the lay public, and is often relegated by newspapers and magazines to disaster stories-for instance the discovery of a hole in the ozone layer over Antarctica, the disintegration of polar ice shelves because of global warming or even tragic accidents involving scientists themselves. As Features Editor of New Scientist, I visited Antarctica twice under the NSF science media program and made several research trips to the Arctic, each time writing magazine pieces about my experiences for the public. I have also recently published a popular book "Snowball Earth" about ancient ice, aimed at the intelligent lay person. I will discuss several different writing approaches for integrating descriptions of scientific research with the romance of Antarctica and the Arctic, in order to stimulate the imagination of lay people who are afraid of science, but ready to be captivated by ice.

  19. Stability within Jupiter's polar auroral 'Swirl region' over moderate timescales

    NASA Astrophysics Data System (ADS)

    Stallard, Tom S.; Clarke, John T.; Melin, Henrik; Miller, Steve; Nichols, Jon D.; O'Donoghue, James; Johnson, Rosie E.; Connerney, John E. P.; Satoh, Takehiko; Perry, Michael

    2016-04-01

    Jupiter's Swirl region, poleward of the main auroral emission, has been characterised in previous observations as having highly variable auroral emission, changing dramatically across the region on a two-minute timescale, the typical integration time for UV images. This variability has made comparisons with H3+ emission difficult. Here, we show that the Swirl region in H3+ images is characterised by relatively stable emission, often with an arc of emission on the boundary between the Swirl and Dark regions. Coadding multiple UV images taken over the approximate lifetime of the H3+ molecule in the ionosphere, show similar structures to those observed in the H3+ images. Our analysis shows that UV auroral morphology within Jupiter's Swirl region is only highly variable on short timescales of ∼100 s, an intrinsic property of the particle precipitation process, but this variability drops away on timescales of 5-15 min. On moderate timescales between 10 and 100 min, the Swirl region is stable, evolving through as yet unknown underlying magnetospheric interactions. This shows that observing the UV aurora over timescales 5-15 min resolves clear auroral structures that will help us understand the magnetospheric origin of these features, and that calculating the variability over different timescales, especially >15 min, provides a new and important new tool in our understanding of Jupiter's polar aurora.

  20. Spatial and Depth Distribution of Sub-surface Ice in the Polar Regions of Mars.

    NASA Astrophysics Data System (ADS)

    Boynton, W.; Kim, K.; Janes, D.; Kerry, K.; Williams, R.; Reedy, R.; Drake, D.

    The Mars Odyssey spacecraft has been in its mapping orbit for slightly over one Mars year. The Gamma-Ray Spectrometer (GRS) has been collecting data with the boom extended since June 2002 and has not quite collected a full Mars year of data in this configuration. Nevertheless, the statistical precision in the polar regions is such that the spatial resolution of the GRS maps are only slightly degraded by having to average over a larger region to improve the signal-to-noise ratio. Especially in the northern region, clear spatially resolved regions of different apparent ice contents can be resolved. For example in the region near 315E E. longitude, near the mouth of Chasma Boreale, has distinctly less ice (or deeper ice) than do the regions of similar latitude but at other longitudes. Although less easily resolved, it appears that the region around the Olympia Planitia also has less ice than regions surrounding it. In the case of Olympia Planitia, the hydrogen gamma ray signal is lower even than regions more equatorward at the same longitude. We have completed a detailed examination of the ground-truth calibration of the GRS by comparing the signal to that expected from a pure water ice northern residual cap. Doing so allows us to set accurate limits on the distribution of ice (really ice equivalent hydrogen) abundance with depth. Over much of the north polar region we can set limits that the distribution of ice with depth. If we assume the ice is buried beneath a hydrogen-poor dust layer, we can also set a limit on how deep the ice can be buried by assuming the lower ice-rich layer is pure ice. In this case the ice cannot be buried by more than 10 to 20 g/cm2 of hydrogen-poor dust, otherwise the gamma-ray flux would be too weak to account for the observed signal. If, on the other hand, we make the assumption that there is no dust layer to attenuate the gamma-ray signal, the ice content must be between 35% and 50% ice by mass. Because it is likely that there is at

  1. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Key, J.

    1989-01-01

    The objectives are to develop a suitable validation data set for evaluating the effectiveness of the International Satellite Cloud Climatology Project (ISCCP) algorithm for cloud retrieval in polar regions, to identify limitations of current procedures and to explore potential means to remedy them using textural classifiers, and to compare synoptic cloud data from model runs with observations. Toward the first goal, a polar data set consisting of visible, thermal, and passive microwave data was developed. The AVHRR and SMMR data were digitally merged to a polar stereographic projection with an effective pixel size of 5 sq km. With this data set, two unconventional methods of classifying the imagery for the analysis of polar clouds and surfaces were examined: one based on fuzzy sets theory and another based on a trained neural network. An algorithm for cloud detection was developed from an early test version of the ISCCP algorithm. This algorithm includes the identification of surface types with passive microwave, then temporal tests at each pixel location in the cloud detection phase. Cloud maps and clear sky radiance composites for 5 day periods are produced. Algorithm testing and validation was done with both actural AVHRR/SMMR data, and simulated imagery. From this point in the algorithm, groups of cloud pixels are examined for their spectral and textural characteristics, and a procedure is developed for the analysis of cloud patterns utilizing albedo, IR temperature, and texture. In a completion of earlier work, empirical analyses of arctic cloud cover were explored through manual interpretations of DMSP imagery and compared to U.S. Air Force 3D-nephanalysis. Comparisons of observed cloudiness from existing climatologies to patterns computed by the GISS climate model were also made.

  2. Cloud Statistics and Discrimination in the Polar Regions

    NASA Astrophysics Data System (ADS)

    Chan, M.; Comiso, J. C.

    2012-12-01

    Despite their important role in the climate system, cloud cover and their statistics are poorly known, especially in the polar regions, where clouds are difficult to discriminate from snow covered surfaces. The advent of the A-train, which included Aqua/MODIS, CALIPSO/CALIOP and CloudSat/CPR sensors has provided an opportunity to improve our ability to accurately characterize the cloud cover. MODIS provides global coverage at a relatively good temporal and spatial resolution while CALIOP and CPR provide limited nadir sampling but accurate characterization of the vertical structure and phase of the cloud cover. Over the polar regions, cloud detection from a passive sensors like MODIS is challenging because of the presence of cold and highly reflective surfaces such as snow, sea-ice, glaciers, and ice-sheet, which have surface signatures similar to those of clouds. On the other hand, active sensors such as CALIOP and CPR are not only very sensitive to the presence of clouds but can also provide information about its microphysical characteristics. However, these nadir-looking sensors have sparse spatial coverage and their global data can have data spatial gaps of up to 100 km. We developed a polar cloud detection system for MODIS that is trained using collocated data from CALIOP and CPR. In particular, we employ a machine learning system that reads the radiative profile observed by MODIS and determine whether the field of view is cloudy or clear. Results have shown that the improved cloud detection scheme performs better than typical cloud mask algorithms using a validation data set not used for training. A one-year data set was generated and results indicate that daytime cloud detection accuracies improved from 80.1% to 92.6% (over sea-ice) and 71.2% to 87.4% (over ice-sheet) with CALIOP data used as the baseline. Significant improvements are also observed during nighttime, where cloud detection accuracies increase by 19.8% (over sea-ice) and 11.6% (over ice

  3. Inhibition of translation by IFIT family members is determined by their ability to interact selectively with the 5′-terminal regions of cap0-, cap1- and 5′ppp- mRNAs

    PubMed Central

    Kumar, Parimal; Sweeney, Trevor R.; Skabkin, Maxim A.; Skabkina, Olga V.; Pestova, Tatyana V.

    2014-01-01

    Ribosomal recruitment of cellular mRNAs depends on binding of eIF4F to the mRNA’s 5′-terminal ‘cap’. The minimal ‘cap0’ consists of N7-methylguanosine linked to the first nucleotide via a 5′-5′ triphosphate (ppp) bridge. Cap0 is further modified by 2′-O-methylation of the next two riboses, yielding ‘cap1’ (m7GpppNmN) and ‘cap2’ (m7GpppNmNm). However, some viral RNAs lack 2′-O-methylation, whereas others contain only ppp- at their 5′-end. Interferon-induced proteins with tetratricopeptide repeats (IFITs) are highly expressed effectors of innate immunity that inhibit viral replication by incompletely understood mechanisms. Here, we investigated the ability of IFIT family members to interact with cap1-, cap0- and 5′ppp- mRNAs and inhibit their translation. IFIT1 and IFIT1B showed very high affinity to cap-proximal regions of cap0-mRNAs (K1/2,app ∼9 to 23 nM). The 2′-O-methylation abrogated IFIT1/mRNA interaction, whereas IFIT1B retained the ability to bind cap1-mRNA, albeit with reduced affinity (K1/2,app ∼450 nM). The 5′-terminal regions of 5′ppp-mRNAs were recognized by IFIT5 (K1/2,app ∼400 nM). The activity of individual IFITs in inhibiting initiation on a specific mRNA was determined by their ability to interact with its 5′-terminal region: IFIT1 and IFIT1B efficiently outcompeted eIF4F and abrogated initiation on cap0-mRNAs, whereas inhibition on cap1- and 5′ppp- mRNAs by IFIT1B and IFIT5 was weaker and required higher protein concentrations. PMID:24371270

  4. Mars' water isotope (D/H) history in the strata of the North Polar Cap: Inferences about the water cycle

    NASA Astrophysics Data System (ADS)

    Fisher, David Andrew

    2007-04-01

    A time varying stable isotope model for the D/H history of Mars water cycle is developed with variable atmosphere, space loss rate, ground and ice cap flux rates. It considers coupled ground reservoirs and traces D/H in the air and reservoirs secularly and over obliquity cycles. The various flux rates are prescribed time variables that simulate surface flux, and solar driven space loss rates. Predicted bulk averages for the ice cap, ground ice reservoirs and atmosphere span the observed ranges reported by Mumma et al. [Mumma, M.J., Novak, R.E., DiSanti, M.A., Bonev, B., Dello Russo, N., Magee-Sauer, K., 2003. The Martian Atmosphere. Conference Reports of "Sixth International Conference on Mars Atmosphere," No. 3186]. When the dominant obliquity cycle variations are scaled so that the model delivers present seasonal variations, the present long term bulk D/H average for the ice cap is ˜+2.7 (equivalent to +1700‰ in δ(D) wrt SMOW). The obliquity driven D/H cycle in the ice cap's layers varies between 3 and 6. The smaller more accessible reservoirs have larger bulk averages with the smallest being able to reach D/H values over 9 within ˜10 years. Small hypothetical solar activity driven variations in the escape rate to space and in the fractionation constant [Krasnopolsky, V.A., Feldman, P.D., 2001. Science 294, 1914-1917] for the escape process can produce a "solar wiggle" whose D/H amplitude can reach 0.1 ( δ(D) amplitude of 100‰). Because of the temporal variability, a single modern measured atmospheric D/H ratio at a particular Ls cannot tell very much about the total water inventory of Mars. A bulk average for the Northern Ice Cap and better still a dated vertical profile of D/H from the ice cap would, however, go a long way towards illuminating the "modern" water history of Mars. The age and stability of the Northern Ice Cap and the D/H history locked in the layering is discussed. An ice cap that is very young and exchanges its mass through the

  5. Characterizing the Oxidizing Properties of Mars' Polar Regions

    NASA Technical Reports Server (NTRS)

    Hendrix, A. R.; Simmons, K. E.; Mankoff, K. D.

    2003-01-01

    We investigate the oxidizing properties of Mars polar regions using disk-resolved ultraviolet spectra from the Ultraviolet Spectrometer (UVS) on Mariner 9. We detect the spectral characteristic of hydrogen peroxide (H2O2), which has already been found to exist on the icy galilean satellites. The Mariner 9 UVS data have been archived at NASA s Planetary Data System (PDS) Atmospheric Node and are also available at http://lasp.colorado.edu/Mariner_9_data/. A software visualization tool, Albatross, provides database access (http://lasp.colorado.edu/albatross/) and enables the user to view reflectance spectra for desired latitude/longitude regions and mission phases. It displays the UVS field-of-view (FOV) tracks along with the corresponding reflectance spectrum for a chosen FOV against a background showing the Mars surface image, or a user specified alternate dataset, such as a thermal, geologic or topographic map.

  6. Surface Texture Analysis of Enceladus' South Polar Region

    NASA Astrophysics Data System (ADS)

    Chang, J. P.; Buratti, B. J.; Hicks, M.; Mosher, J.; Landry, B.

    2009-12-01

    The Cassini spacecraft's discovery of active plumes at the south pole of Enceladus on its July 2006 flyby has sparked greater interest in both its internal and external physical and chemical properties. We choose to investigate the macroscopic surface texture of this active south polar region by implementing a surface roughness model developed by Buratti and Veverka (1985). The model requires intensity scans of Enceladus's surface and two unknown parameters: a scattering parameter A that indicates whether single or diffuse scattering is occurring, and a surface phase function f (α) that reflects changes in intensity due to various factors such as the single scattering albedo and the single particle phase function. The output is a quantitative description of surface roughness through a depth-to-radius ratio q. After fitting the model to the data, we find that plains north of the “tiger stripes” are fairly smooth, with preliminary values for q of around 0.08. Meanwhile, the stripes themselves are only slightly more rough, with preliminary values for q of around 0.10. These results strongly suggest in-filled coating of craters with water-ice throughout the entire south polar region of Enceladus. Furthermore, the model surface roughness of Enceladus does not appear to be sensitive to the choice of our photometric function, as changing A has little effect on q.

  7. North Polar Region of Mars: Topography of Circumpolar Deposits and Sediments Based on Mars Orbiter Laser Altimeter (MOLA) Data

    NASA Astrophysics Data System (ADS)

    Fishbaugh, K. E.; Head, J. W., III

    1999-03-01

    New topography data are interpreted to indicate that Olympia Planitia overlies ice, mantled cratered plains underlie mantled smooth plains, the cap was once larger, and significant circumpolar sediments originated from previous polar deposits.

  8. Evaporites on Ice: Experimental Assessment of Evaporites Formation on Antarctica (and on Martian North Polar Residual Cap)

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Derkowski, Arkadiusz; Skala, Aleksander; Trzcinski, Jerzy

    2016-04-01

    Evaporites are highly water soluble minerals, formed as a result of the evaporation or freezing of bodies of water. They are common weathering minerals found on rocks (including meteorites) on Antarctic ice sheet [1,2,3,4]. The water necessary for the reaction is produced by melting of ice below the dark-colored meteorites which can heat up to a few degrees above 0 °C due to insolation heating during wind-free summer days [5,6]. The Martian North Polar Residual Cap is surrounded by a young [7] dune field that is rich in evaporitic mineral: gypsum [8]. Its existence implies that relatively recently in the Martian history (in late Amazonian, when surface conditions were comparable to the current ones) there was a significant amount of liquid water present on the Mars surface. One of the proposed solutions to this problem is that gypsum is formed by weathering on/in ice [9,10,11,12,13], similarly to the process occurring on the Antarctic ice sheet. Recently, Losiak et al. 2015 showed that that during the warmest days of the Martian summer, solar irradiation may be sufficient to melt pure water ice located below a layer of dark dust particles lying on the steepest sections of the equator-facing slopes of the spiral troughs within Martian NPRC. Under the current irradiation conditions, melting is possible in very restricted areas of the NPRC and it lasts for up to couple of hours, but during the times of high irradiance at the north pole [15] this process could have been much more pronounced. Liquid water can be metastable at the NPRC because the pressure during the summer season is ~760-650 Pa [16] which is above the triple point of water. The rate of free-surface "clean" liquid water evaporation under average Martian conditions determined experimentally by [17] is comparable to the rate of melting determined by [21] (if there is no wind at the surface). In the current study we attempt to determine experimentally how many melting-freezing cycles are required to form

  9. Mars Global Digital Dune Database: Distribution in North Polar Region and Comparison to Equatorial Region

    NASA Astrophysics Data System (ADS)

    Hayward, R. K.; Fenton, L. K.; Tanaka, K. L.; Mullins, K. F.; Titus, T. N.; Bourke, M. C.; Hare, T. M.; Christensen, P. R.

    2008-03-01

    The north polar portion of the Mars Global Digital Dune Database (MGD3) extends coverage of medium to large-size dark dunes to include the region from 65°N to 90°N, building on the previously released equatorial portion that spans 65°S to 65°N.

  10. New Views of the Martian Polar Regions: The Latest Results from the Mars Odyssey THEMIS Investigation

    NASA Technical Reports Server (NTRS)

    Ivanov, A. B.; Byrne, S.

    2004-01-01

    One of the many questions of Martian exploration is to uncover the history of Mars, through analysis of the polar layered deposits (PLD). Martian polar ice caps hold most of the exposed water ice on the surface of Mars and yet their history and physical processes involved in their formation are unclear. In this work we present the latest imaging data acquired by the Mars Odyssey THermal EMission Imaging System (THEMIS) from the South Polar Residual Deposits (SPLD). We will concentrate our analysis on differences observed by THEMIS in winter/early spring and summer periods.

  11. Preserving Geological Samples and Metadata from Polar Regions

    NASA Astrophysics Data System (ADS)

    Grunow, A.; Sjunneskog, C. M.

    2011-12-01

    The Office of Polar Programs at the National Science Foundation (NSF-OPP) has long recognized the value of preserving earth science collections due to the inherent logistical challenges and financial costs of collecting geological samples from Polar Regions. NSF-OPP established two national facilities to make Antarctic geological samples and drill cores openly and freely available for research. The Antarctic Marine Geology Research Facility (AMGRF) at Florida State University was established in 1963 and archives Antarctic marine sediment cores, dredge samples and smear slides along with ship logs. The United States Polar Rock Repository (USPRR) at Ohio State University was established in 2003 and archives polar rock samples, marine dredges, unconsolidated materials and terrestrial cores, along with associated materials such as field notes, maps, raw analytical data, paleomagnetic cores, thin sections, microfossil mounts, microslides and residues. The existence of the AMGRF and USPRR helps to minimize redundant sample collecting, lessen the environmental impact of doing polar field work, facilitates field logistics planning and complies with the data sharing requirement of the Antarctic Treaty. USPRR acquires collections through donations from institutions and scientists and then makes these samples available as no-cost loans for research, education and museum exhibits. The AMGRF acquires sediment cores from US based and international collaboration drilling projects in Antarctica. Destructive research techniques are allowed on the loaned samples and loan requests are accepted from any accredited scientific institution in the world. Currently, the USPRR has more than 22,000 cataloged rock samples available to scientists from around the world. All cataloged samples are relabeled with a USPRR number, weighed, photographed and measured for magnetic susceptibility. Many aspects of the sample metadata are included in the database, e.g. geographical location, sample

  12. Plasma Conditions in Polar Plumes and Interplume Regions in Polar Coronal Holes

    NASA Astrophysics Data System (ADS)

    Cranmer, S. R.; Kohl, J. L.; Miralles, M.; Panasyuk, A. V.

    2001-05-01

    During times of low solar activity, large polar coronal holes are observed to contain bright raylike polar plumes that appear to follow open magnetic field lines. Plumes are believed to be flux tubes that are heated impulsively at their base, which leads to a higher density, a lower outflow speed, and a lower overall temperature in the extended corona, compared to the surrounding interplume regions. Despite years of white light and spectroscopic observations, though, the differences in mass, momentum, and energy flux in plumes and between plumes are not known precisely. This poster presents an updated survey of data from the Ultraviolet Coronagraph Spectrometer (UVCS), aboard SOHO, that attempts to sort out the local plume and interplume conditions. These results will be compared with previous analyses that characterized the ``mean'' plume/interplume coronal hole, averaged over many lines of sight through varying concentrations of plumes. Limits on the relative contributions of plumes and interplume regions to the high-speed solar wind will be determined, with emphasis on the proton outflow speed in the corona and at 1 AU. Implications for theoretical models of coronal heating and solar wind acceleration will be discussed. This work is supported by the National Aeronautics and Space Administration under grant NAG5-10093 to the Smithsonian Astrophysical Observatory, by Agenzia Spaziale Italiana, and by the Swiss contribution to the ESA PRODEX program.

  13. Exploring the origin of ice-filled craters in the north polar region of Mars

    NASA Astrophysics Data System (ADS)

    Hovius, Niels; Conway, Susan; Barnie, T.; Besserer, J.; Lemouelic, S.; Read, N.

    2010-05-01

    We investigate the origins of enigmatic ice-filled craters in the north polar region of Mars. We test several explanations for their origin, namely: (1) as polar cap remnants [1] (2) accumulation independently of the polar cap, and (3) upwelling of subsurface water, analogous to either aufice or pingo formation on Earth. Each of these hypotheses has a significant impact on our understanding of Mars' recent geological and climatic history and the behaviour of water and water ice at high latitudes. We used several lines of evidence to assess the most likely formation mechanism. We first performed a crater survey based on THEMIS visual data and MOLA elevation data to identify any craters that had domal central lumps which were different from normal central peaks. From this survey we identified 17 craters for further study. These include Louth, Korolev, Dokka and other unnamed craters. Using data from orbiting spectrometers; OMEGA on ESA's Mars Express and CRISM on NASA's Mars Reconnaissance Orbiter; we verified that the composition of the exposed central domes was predominantly water ice. We found the domes fell into three groups: (1) those completely covered by dunes, (2) those partially covered by dunes and (3) those with no dunes. We investigated the morphology and the relative position of the domes using MOLA elevation data. We found that the domes are always asymmetrically placed within the craters. However, this asymmetry could not easily be linked to wind directions as revealed by dune slip-faces [2]. The domes often have a moat-like structure and in some cases do not cover the entire crater floor, e.g. Louth Crater. From image data, we identified six craters which possessed internal stratigraphy, in the form of regularly spaced layers, and of these we have inspected three in detail. We found that the layers possess both strong sinuosity and high angle unconformities. We interpret the internal stratigraphy as representing a sequence of regular cyclic

  14. Polar Lunar Regions: Exploiting Natural and Augmented Thermal Environments

    NASA Technical Reports Server (NTRS)

    Brannon, David; Ryan, Robert E.; Underwood, Lauren W.; Russell, Kristen

    2010-01-01

    In the polar regions of the Moon, some areas within craters are permanently shadowed from solar illumination and can drop to temperatures of 100 K or lower. These sites may serve as cold traps, capturing ice and other volatile compounds, possibly for eons. Interestingly, ice stored in these locations could potentially alter how lunar exploration is conducted. Within craters inside craters (double-shaded craters) that are shaded from thermal re-radiation and from solar illuminated regions, even colder regions should exist and, in many cases, temperatures in these regions never exceed 50 K. Working in these harsh environments with existing conventional systems, exploration or mining activities could be quite daunting and challenging. However, if the unique characteristics of these environments were exploited, the power, weight, and total mass that is required to be carried from the Earth to the Moon for lunar exploration and research would be substantially reduced. In theory, by minimizing the heat transfer between an object and the lunar surface, temperatures near absolute zero can be produced. In a single or double-shaded crater, if the object was isolated from the variety of thermal sources and was allowed to radiatively cool to space, the achievable temperature would be limited by the 3 K cosmic background and the anomalous solar wind that can strike the object being cooled. Our analysis shows that under many circumstances, with some simple thermal radiation shielding, it is possible to establish environments with temperatures of several degrees Kelvin.

  15. An Overview of Observations of Mars' North Polar Region From the Mars Global Surveyor Laser Altimeter

    NASA Astrophysics Data System (ADS)

    Smith, D. E.; Zuber, M. T.

    1998-01-01

    Since its arrival at Mars on September l5, 1997, the Mars Global Surveyor (MGS) has been in a near-polar elliptical orbit, with the orbital eccentricity decreasing during orbital periapse passes where the spacecraft aerobrakes through the martian atmosphere. The Mars Orbiter Laser Altimeter (MOLA), an instrument on the MGS, has the ability to range to the martian surface during nonaerobraking passes. MOLA can operate whenever the range from the spacecraft to the surface is less than 786 km, with the limit determined by the number of bits encoded for the range measurement During the capture orbit, aerobraking hiatus, and science phasing orbit (SPO) mission phases, MOLA acquired approximately 200 profiles across the northern hemisphere of Mars and provided more than 2,000,000 measurements of the radius of the planet. These observations cover the region from the north pole to about 10 degrees S latitude with a precision of a few tens of centimeters and an accuracy (at present) of about 30 in. Absolute accuracy of the elevations is limited by the knowledge of the MGS orbits; these should improve later in the mission due to a more optimal tracking geometry, an improved gravitational field, and the use of the high-gain antenna once the spacecraft achieves its approximately 400-km-altitude circular mapping orbit. MOLA measurements so far show a planet with a low, flat high-latitude region in the north and a higher, topographically rougher terrain nearer the equator. The north polar cap stands approximately 2-3 km above the surrounding terrain and displays deep chasms and complex structure. MOLA measurements of elevation, 1064-nm reflectivity, and backscattered pulse width indicate that the layered terrains are composed mainly of ice.

  16. Horizontal velocity of Saturn's polar regions and Hexagon

    NASA Astrophysics Data System (ADS)

    Antuñano, A.; del Rio-Gaztelurrutia, T.; Sanchez-Lavega, A.; Hueso, R.

    2015-05-01

    We study the horizontal velocity and vorticity field of Saturn's polar regions (from 60° to 90° North and South) by analyzing data retrieved by Cassini's Imaging Science System instrument. We determine the zonal mean profiles for the North and South up to 89.5°S and 89.9°N and we also build two dimensional zonal and meridional velocity maps that allow to compute vorticity maps. The hexagonal feature encloses an eastward jet at 75.8°N that becomes non-zonal. The peak of this eastward jet lies closer to the pole than the eastward jet in the south, which is zonal. A similar anticyclone to the North Polar Spot (NPS) that was observed by the Voyagers in 1981 is observed in the South on 2008--2009 images impinging on the eastward jet. However, it seems that this vortex does not excite a wave on its closest jet stream. Finally, we study the stability of the zonal jets North and South, where we find potential instabilities at the flank of these jets.

  17. Quasistatic electric field structures and field-aligned currents in the polar cusp region

    NASA Astrophysics Data System (ADS)

    Jacobsen, K. S.; Moen, J. I.; Pedersen, A.

    2010-10-01

    Cluster data have been examined for quasi-stationary electric field structures and field-aligned currents (FACs) in the vicinity of the dayside cusp region. We have related the measurements to the Region 1/Region 2 (R1/R2) current system and the cusp current system. It has been theoretically proposed that the dayside R1 current may be located on open field lines, and experimental evidence has been shown for R1 currents partially on open field lines. We document that R1 currents may flow entirely on open field lines. The electric field structures are found to occur at plasma density gradients in the cusp. They are associated with strong FACs with current directions that are consistent with the cusp currents. This indicates that the electric field structures are closely coupled to the cusp current system. The electric equipotential structures linking the perpendicular electric fields seen at Cluster altitudes to field-aligned electric fields at lower altitudes fall into one of two categories: S shape or U shape. Both types are found at both the equatorward edge of the cusp ion dispersion and at the equatorward edge of injection events within the cusp. Previous studies in the nightside auroral region attributed the S-shaped potential structures to the boundary transition between the low-density polar cap and the high-density plasma sheet, concluding that the shape of the electric potential structure depends on whether the plasma populations on each side of the structure can support intense currents. This explanation is not applicable for the S-shaped structures observed in the dayside cusp region.

  18. Characterizing the Oxidizing Properties of Mars' Polar Regions

    NASA Technical Reports Server (NTRS)

    Hendrix, Amanda; Simmons, Karen

    2002-01-01

    This project had two primary goals. The first was to restore and archive the Ultraviolet Spectrometer (UVS) data from the 1971 Mariner 9 (MM71) mission to Mars. The second was to use this revised data set to analyze data of Mars' polar regions to look for and map out the ozone (03) and hydrogen peroxide (H2O2,) features. Data restoration and archiving activities for this project have resulted in the restoration of 100% of the original Mariner 9 raw data set as well as many of the secondary analysis data sets. These data sets have been submitted to the Planetary Data System (PDS) Atmospheric Node, long with their PDS labels and descriptive metadata.

  19. Preliminary albedo map of the south polar region

    NASA Technical Reports Server (NTRS)

    Devaucouleurs, G.; Roth, J.; Mulholand, C.

    1973-01-01

    A preliminary albedo map of the Martian south polar region in stereographic projection was prepared mainly from mission test video system (MTVS) prints before rectified and gridded prints were received, but some adjustments were made to conform with a semi-controlled photomosaic. Wherever possible, use also was made of crater coordinates. Two versions of the map are presented: one with a coordinate grid overlay and one without it. The precision of the coordinates is generally within 1 deg in latitude and the corresponding are in longitude. The maps show both the albedo markings and, with subdued contrast, the craters and topographic features that are necessary to locate the former. The map covers the range of latitudes from - 65 deg to the south pole.

  20. Cloud cover determination in polar regions from satellite imagery

    NASA Technical Reports Server (NTRS)

    Barry, R. G.; Maslanik, J. A.; Key, J. R.

    1987-01-01

    A definition is undertaken of the spectral and spatial characteristics of clouds and surface conditions in the polar regions, and to the creation of calibrated, geometrically correct data sets suitable for quantitative analysis. Ways are explored in which this information can be applied to cloud classifications as new methods or as extensions to existing classification schemes. A methodology is developed that uses automated techniques to merge Advanced Very High Resolution Radiometer (AVHRR) and Scanning Multichannel Microwave Radiometer (SMMR) data, and to apply first-order calibration and zenith angle corrections to the AVHRR imagery. Cloud cover and surface types are manually interpreted, and manual methods are used to define relatively pure training areas to describe the textural and multispectral characteristics of clouds over several surface conditions. The effects of viewing angle and bidirectional reflectance differences are studied for several classes, and the effectiveness of some key components of existing classification schemes is tested.

  1. HiRISE Monitoring of Ongoing Activity in the North Polar Region of Mars

    NASA Astrophysics Data System (ADS)

    Herkenhoff, K. E.; Russell, P. S.; Byrne, S.; Banks, M. E.; Hansen, C. J.; HiRISE Team

    2010-12-01

    The High Resolution Imaging Science Experiment (HiRISE) [1] on the Mars Reconnaissance Orbiter (MRO) has observed the north polar region during 3 summer seasons on Mars. Here we summarize analyses of the north polar data, focusing on active and recent processes including evolution of frost streaks, the north polar residual cap (NPRC), frost avalanches, and scarp erosion. Bright and dark streaks have been observed at the periphery of the NPRC by previous Mars orbiters and were the target of several HiRISE observations. Some of these HiRISE images indicate that formation of the streaks involves processes more complex than the emplacement of dark veneers proposed by Rodriguez et al. [2]. Bright and dark streaks are seen to evolve during the northern summer, evidence for active eolian redistribution of frost and perhaps darker (non-volatile) dust or sand. Based on MRO Context imager observations of craters on the NPRC, accumulation rates are estimated to be 4-5 mm/yr within these craters, with lower rates likely on the intracrater NPRC surface [3]. The observed crater population probably accumulated during the last 20 ka or less. It is likely that NPRC resurfacing is episodic rather than continuous, and that annual changes may be detectable at HiRISE image resolutions. Therefore, a campaign of HiRISE observations of four NPRC targets near 87°N latitude (the maximum latitude of the MRO ground track) was initiated during the Martian northern summer of 2008 and continued during the summer of 2010. The images acquired during this campaign, with nearly nadir viewing geometry and similar solar azimuth, are being searched for evidence for current redistribution of NPRC material. Analyses are ongoing; no changes have been detected to date. We also conducted an early- to mid-spring 2010 survey of circumpolar scarps to monitor for falls and avalanches of CO2 frost and dust, of the type discovered on a scarp in northern spring 2008 [4]. The results confirm the restriction of

  2. Imaging Enceladus' Exotic South Polar Regions: Imaging Science Team Results

    NASA Astrophysics Data System (ADS)

    Johnson, T.

    2005-12-01

    The Cassini spacecraft had a close (175 km altitute) encounter with Saturn's moon Enceladus on 14 July 2005, resulting in a major discovery: evidence from multiple experiments show that there is a large `plume' of water vapor and particles emanating from the satellite's south polar region. Infrared data from the CIRS instrument showed that this area is also anomalously warm, providing evidence for internal heat. High resolution images taken by the Imaging Science System during the encounter show that the warm region associated with water vapor venting is a unique area on this icy world. The region has very few if any detectable impact craters, making it the youngest surface seen on Enceladus, or any of the other icy Saturnian satellites; estimates from cratering models place its age at less than 10-100 million years. It is surrounded by tectonic features suggesting a global stress pattern that may be associated with a change in spin rate. Long, parallel fractures, informally dubbed `tiger stripes', cross the region and are correlated with at least some of the thermal anomalies, making them good candidates for the source regions of the water venting. Spectral data and photometric studies also show that the whole area and the tiger stripes in particular have fewer fine grained particles on the surface than most of the moon's surface, in agreement with a young surface and crystalinity and grain size interpretations of data from the Visual and Near Infrared Mapping Spectrometer experiment. Tidal forces and radioactive heating are probably responsible for the activity, although generating such intense internal heating is challenging for current models. Portions of this work were done at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

  3. Polar Lunar Regions: Exploiting Natural and Augmented Thermal Environments

    NASA Technical Reports Server (NTRS)

    Ryan, Robert E.; McKellip, Rodney; Brannon, David P.; Underwood, Lauren; Russell, Kristen J.

    2007-01-01

    In polar regions of the Moon, some areas within craters are permanently shadowed from solar illumination and can reach temperatures of 100 K or less. These regions could serve as cold traps, capturing ice and other volatile compounds. These potential ice stores have many applications for lunar exploration. Within double-shaded craters, even colder regions exist, with temperatures never exceeding 50 K in many cases. Observed temperatures suggest that these regions could enable equivalent liquid nitrogen cryogenic functions. These permanently shaded polar craters also offer unprecedented high-vacuum cryogenic environments, which in their current state could support cryogenic applications. Besides ice stores, the unique conditions at the lunar poles harbor an environment that provides an opportunity to reduce the power, weight, and total mass that needs to be carried from the Earth to the Moon for lunar exploration and research. Reducing the heat flux of geothermal, black body radiation can have significant impacts on the achievable temperature. With a few manmade augmentations, permanently shaded craters located near the lunar poles achieve temperatures even lower than those that naturally exist. Our analysis reveals that lightweight thermal shielding within shaded craters could create an environment several Kelvin above absolute zero. The temperature ranges of both naturally shaded and thermally augmented craters could enable the long-term storage of most gases, low-temperature superconductors for large magnetic fields, devices and advanced high-speed computing instruments. Augmenting thermal conditions in these craters could then be used as a basis for the development of an advanced thermal management architecture that would support a wide variety of cryogenically based applications. Lunar exploration and habitation capabilities would significantly benefit if permanently shaded craters, augmented with thermal shielding, were used to facilitate the operation of near

  4. Modeling the reflectance of CO2 frost with new optical constants: Application to Martian south polar cap spectra

    NASA Technical Reports Server (NTRS)

    Hansen, Gary B.; Martin, Terry Z.

    1993-01-01

    New measurements of the absorption coefficients of CO2 ice, in most of the spectral range 0.2 to 3.9 microns where absorption coefficients are below 1.5 per cm, have recently been made. Although these measurements are preliminary, they contain spectral detail not seen previously in the literature. Therefore, it is useful to combine these new data with older data from spectral regions of stronger absorption and reformulate models of the albedo or reflectance of CO2 frost. These models can then be adjusted in an attempt to match measurements of Martian polar deposits, such as the set of spectra returned by the IRS instrument on Mariner 7 (1969). The new absorption coefficients of CO2 ice were measured on several samples of 41-mm thickness at 150-155 K. A portion of the spectrum from 1.9 to 3.9 microns wavelength is shown in the form of imaginary coefficient of refraction ( = linear absorption x wavelength / 4 pi). The data above 3x10(exp -5) are obtained from, except for the absorption line at 3.32 micrometers, which is extrapolated in a way that is consistent with laboratory frost measurements, but the peak level is still highly uncertain. This new imagary coefficient, combined with the real coefficient, can be immediately applied to the models for hemispherical albedo, resulting in markedly different results from those in that study. The results for an infinite optical depth layer and solar incidence of 60 degrees are plotted for a range of mean particle radii from 0.03 to 3 mm.

  5. Proceedings of the Fourth International Conference on Mars Polar Science and Exploration

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Sessions in this conference include: Mars polar geology and glaciology; Mars and terrestrial radar investigations; Observations, nature, and evolution of the Martian seasonal polar caps; Mars' residual south polar cap; Climate change, ice core analysis, and the redistribution of volatiles on Mars; errestrial Mars analog environments; The Phoenix Scout mission and the nature of the near-polar environment; Moderated Discussion: Key Issues Regarding Phoenix Scout Mission and the nature of the near-polar environment; Panel Discussion: Key Issues in Mars Polar Science and Exploration; Mars Reconnaissance Orbiter investigations of the Martian polar regions and climate; Mars Polar Scout Mission concepts; and Panel Discussion: New perspectives on Mars polar science and exploration

  6. The evolution of dust deposits in the Martian north polar region

    NASA Technical Reports Server (NTRS)

    Squyres, S. W.

    1979-01-01

    The origin and evolution of two major eolian deposits of the Martian north polar region, the layered deposits and the debris mantle, are examined. Both apparently result from deposition of dust along with the seasonal CO2 frost cap. Dust deposited onto the perennial ice is incorporated into the layered deposits, while dust deposited directly onto the surface becomes part of the debris mantle. Climatically induced fluctuation of the perennial ice margin has influenced the evolution of both units. Periodic exposure to the atmosphere has allowed erosion of curvilinear troughs in the surface of the layered deposits. Intervening periods of deposition may have resulted in gradual poleward migration of the trough forms, leaving behind sets of low-amplitude surface undulations in former trough locations. Advance and retreat of the perennial ice margin has also probably resulted in a fine interfingering of the layered deposits-debris mantle contract. Limited post-depositional stripping of the debris mantle has been accomplished by intense winds blowing outward from the pole.

  7. High resolution spectroscopy of the Martian atmosphere - Study of seasonal variations of CO, O3, H2O, and T on the north polar cap and a search for SO2, H2O2, and H2CO

    NASA Technical Reports Server (NTRS)

    Krasnopolsky, V. A.; Chakrabarti, S.; Larson, H.; Sandel, B. R.

    1992-01-01

    An overview is presented of an observational campaign which will measure (1) the seasonal variations of the CO mixing ratio on the Martian polar cap due to accumulation and depletion of CO during the condensation and evaporation of CO2, as well as (2) the early spring ozone and water vapor of the Martian north polar cap, and (3) the presence of H2CO, H2O2, and SO2. The lines of these compounds will be measured by a combined 4-m telescope and Fourier-transform spectrometer 27097.

  8. A STATISTICAL STUDY OF CORONAL ACTIVE EVENTS IN THE NORTH POLAR REGION

    SciTech Connect

    Sako, Nobuharu; Shimojo, Masumi; Watanabe, Tetsuya; Sekii, Takashi

    2013-09-20

    In order to study the relationship between characteristics of polar coronal active events and the magnetic environment in which such events take place, we analyze 526 X-ray jets and 1256 transient brightenings in the polar regions and in regions around the equatorial limbs. We calculate the occurrence rates of these polar coronal active events as a function of distance from the boundary of coronal holes, and find that most events in the polar quiet regions occur adjacent to and equatorward of the coronal hole boundaries, while events in the polar coronal holes occur uniformly within them. Based primarily on the background intensity, we define three categories of regions that produce activity: polar coronal holes, coronal hole boundary regions, and polar quiet regions. We then investigate the properties of the events produced in these regions. We find no significant differences in their characteristics, for example, length and lifetime, but there are differences in the occurrence rates. The mean occurrence rate of X-ray jets around the boundaries of coronal holes is higher than that in the polar quiet regions, equatorial quiet regions, and polar coronal holes. Furthermore, the mean occurrence rate of transient brightenings is also higher in these regions. We make comparison with the occurrence rates of emerging and canceling magnetic fields in the photosphere reported in previous studies, and find that they do not agree with the occurrence rates of transient brightenings found in this study.

  9. Boundary layer polarization and voltage in the 14 MLT region

    NASA Astrophysics Data System (ADS)

    Lundin, R.; Yamauchi, M.; Woch, J.; Marklund, G.

    1995-05-01

    Viking midlatitude observations of ions and electrons in the postnoon auroral region show that field-aligned acceleration of electrons and ions with energies up to a few kiloelectron volts takes place. The characteristics of the upgoing ion beams and the local transverse electric field observed by Viking indicate that parallel ion acceleration is primarily due to a quasi-electrostatic field-aligned acceleration process below Viking altitudes, i.e., below 10,000-13,500 km. A good correlation is found between the maximum upgoing ion beam energy and the depth of the local potential well determined by the Viking electric field experiment within dayside 'ion inverted Vs.' The total transverse potential throughout the entire region near the ion inverted Vs. is generally much higher than the field-aligned potential and may reach well above 10 kV. However, the detailed mapping of the transverse potential out to the boundary layer, a fundamental issue which remains controversial, was not attempted here. An important finding in this study is the strong correlation between the maximum up going ion beam energy of dayside ion inverted Vs and the solar wind velocity. This suggests a direct coupling of the solar wind plasma dynamo/voltage generator to the region of field-aligned particle acceleration. The fact that the center of dayside ion inverted Vs coincide with convection reversals/flow stagnation and upward Birkeland currents on what appears to be closed field lines (Woch et al., 1993), suggests that field-aligned potential structures connect to the inner part of an MHD dyanmo in the low-latitude boundary layer. Thus the Viking observations substantiate the idea of a solar wind induced boundary layer polarization where negatively charged perturbations in the postnoon sector persistently develops along the magnetic field lines, establishing accelerating potential drops along the geomagnetic field lines in the 0.5-10 kV range.

  10. Residual Cap

    NASA Technical Reports Server (NTRS)

    2006-01-01

    10 May 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a summertime view of the south polar residual cap of Mars. In this image, mesas composed largely of solid carbon dioxide are separated from one another by irregularly-shaped depressions. The variation in brightness across this scene is a function of several factors including, but not limited to, varying proportions of dust and solid carbon dioxide, undulating topography, and differences in the roughness of the slopes versus the flat surfaces.

    Location near: 86.7oS, 343.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  11. Thermal and albedo mapping of the polar regions of Mars using Viking thermal mapper observations: 1. North polar region

    NASA Technical Reports Server (NTRS)

    Paige, David A.; Bachman, Jennifer E.; Keegan, Kenneth D.

    1994-01-01

    We present the first maps of the apparent thermal inertia and albedo of the north polar region of Mars. The observations used to create these maps were acquired by the infrared thermal mapper (IRTM) instruments on the two Viking orbiters over a 50-day period in 1978 during the Martian early northern summer season. The maps cover the region from 60 deg N to the north pole at a spatial resolution of 1/2 deg of latitude. The analysis and interpretation of these maps is aided by the results of a one-dimensional radiative convective model, which is used to calculate diurnal variations in surface and atmospheric temperatures, and brightness temperatures at the top of the atmospphere for a wide range of assumptions concerning aerosol optical properties and aerosol optical depths. The results of these calculations show that the effects of the Martian atmosphere on remote determinations of surface thermal inertia are more significant than have been indicated in previous studies. The maps of apparent thermal inertia and albedo show a great deal of spatial structure that is well correlated with surface features.

  12. The Need for System Scale Studies in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.; Newman, D.

    2010-12-01

    The understanding of polar regions has advanced tremendously in the past two decades and much of the improved insight into our knowledge of environmental dynamics is due to multidisciplinary and interdisciplinary studies conducted by coordinated and collaborative research programs supported by national funding agencies. Although much remains to be learned with respect to component processes, many of the most urgent scientific, engineering and social questions can only be addressed through the broader perspective of studies on system scales in which these components are coupled to each other. Questions such as quantifying feedbacks, understanding the implications of sea ice loss to adjacent land areas or society, resolving future predictions of ecosystem evolution or population dynamics all require consideration of complex interactions and interdependent linkages among system components. Research that has identified physical controls on biological processes, or quantified impact/response relationships in physical and biological systems is critically important, and must be continued; however we are approaching a limitation in our ability to accurately project how the Arctic and the Antarctic will respond to a continued warming climate. Complex issues, such as developing accurate model algorithms of feedback processes require higher level synthesis of multiple component interactions. Several examples of important questions that may only be addressed through coupled complex systems analyses will be addressed.

  13. Effects of climatic changes on anisakid nematodes in polar regions

    NASA Astrophysics Data System (ADS)

    Rokicki, Jerzy

    2009-11-01

    Anisakid nematodes are common in Antarctic, sub-Antarctic, and Arctic areas. Current distributional knowledge of anisakids in the polar regions is reviewed. Climatic variables influence the occurrence and abundance of anisakids, directly influencing their free-living larval stages and also indirectly influencing their predominantly invertebrate (but also vertebrate) hosts. As these parasites can also be pathogenic for humans, the paucity of information available is a source of additional hazard. As fish are a major human dietary component in Arctic and Antarctic areas, and are often eaten without heat processing, a high risk of infection by anisakid larvae might be expected. The present level of knowledge, particularly relating to anisakid larval stages present in fishes, is far from satisfactory. Preliminary molecular studies have revealed the presence of species complexes. Contemporary climate warming is modifying the marine environment and may result in an extension of time during which anisakid eggs can persist and hatch, and of the time period during which newly hatched larvae remain viable. As a result there may be an increase in the extent of anisakid distribution. Continued warming will modify the composition of the parasitic nematode fauna of marine animals, due to changes in feeding habits, as the warming of the sea and any localised reduction in salinity (from freshwater runoff) can be expected to bring about changes in the species composition of pelagic and benthic invertebrates.

  14. Energetics of the Thermosphere in Polar Regions Observed by SABER

    NASA Astrophysics Data System (ADS)

    Hunt, L. A.; Mlynczak, M. G.

    2015-12-01

    The Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on NASA's TIMED satellite has been measuring the vertical distribution of infrared radiation emitted by various atmospheric gases for nearly 14 years, providing important information about chemical species, including atomic oxygen, hydrogen, ozone and hydroxyl; temperature; and the radiation budget in the upper atmosphere. From these measurements, the infrared power and energy radiated by nitric oxide (NO) at 5.3 µm and carbon dioxide (CO2) at 15 µm have been computed. These infrared emissions have been shown to be a mechanism for the dissipation of the atmospheric heating that results from geoeffective solar storm energy, serving as a natural thermostat to cool the atmosphere to pre-storm conditions. We present the response in the polar region to several storm events that have occurred during the SABER mission, including the location of maximum response and a comparison of the relative NO and CO2 cooling that occurred, since they are each driven by different factors.

  15. Dynamic nuclear polarization in the hyperfine-field-dominant region

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

    2015-06-01

    Dynamic nuclear polarization (DNP) allows measuring enhanced nuclear magnetic resonance (NMR) signals. Though the efficiency of DNP has been known to increase at low fields, the usefulness of DNP has not been throughly investigated yet. Here, using a superconducting quantum interference device-based NMR system, we performed a series of DNP experiments with a nitroxide radical and measured DNP spectra at several magnetic fields down to sub-microtesla. In the DNP spectra, the large overlap of two peaks having opposite signs results in net enhancement factors, which are significantly lower than theoretical expectations [30] and nearly invariant with respect to magnetic fields below the Earth's field. The numerical analysis based on the radical's Hamiltonian provides qualitative explanations of such features. The net enhancement factor reached 325 at maximum experimentally, but our analysis reveals that the local enhancement factor at the center of the rf coil is 575, which is unaffected by detection schemes. We conclude that DNP in the hyperfine-field-dominant region yields sufficiently enhanced NMR signals at magnetic fields above 1 μ T.

  16. New space technology advances knowledge of the remote polar regions. [Arctic and Antarctic regions

    NASA Technical Reports Server (NTRS)

    Macdonald, W. R.

    1974-01-01

    The application of ERTS-1 imagery is rapidly increasing man's knowledge of polar regions. Products compiled from this imagery at scales of 1:250,000, 1:500,000 and 1:1,000,000 are already providing valuable information to earth scientists working in Antarctica. Significant finds detected by these bench mark products were glaciological changes, advancement in ice fronts, discovery of new geographic features, and the repositioning of nunataks, islands, and ice tongues. Tests conducted in Antarctica have proven the feasibility of tracking Navy navigation satellites to establish ground control for positioning ERTS-1 imagery in remote areas. ERTS imagery coupled with satellite geodesy shows great promise and may prove to be the most practical and cost effective way to meet the small-scale cartographic requirements of the polar science community.

  17. Multi-Year Monitoring of Ices, Frost and Dust in Mars Polar Caps from VIS-NIR Imaging Spectrometry

    NASA Astrophysics Data System (ADS)

    Langevin, Y.; Appéré, T.; Schmidt, F.; Douté, S.; Pilorget, C.; Vincendon, M.; Bibring, J.-P.; Schmitt, B.; Brown, A. J.; Herkenhoff, K. E.; Russell, P.; Titus, T. N.; Pommerol, A.; Gondet, B.; Seelos, K. D.

    2014-07-01

    Mex/OMEGA and MRO/CRISM, operating since 01/2004 and 11/2006, have played a major role in revealing the complexity and strong spatial variegation of polar processes on Mars, in relationship with seasonal and long term atmospheric evolution.

  18. The interannual variability of polar cap recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission

    NASA Technical Reports Server (NTRS)

    Martin, L. J.; James, P. B.

    1992-01-01

    The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets.

  19. The interannual variability of polar CAP recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission

    NASA Astrophysics Data System (ADS)

    Martin, L. J.; James, P. B.

    The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets.

  20. Modelling Sea Ice and Surface Wave Interactions in Polar Regions

    NASA Astrophysics Data System (ADS)

    Hosekova, L.; Aksenov, Y.; Coward, A.; Williams, T.; Bertino, L.; Nurser, A. J. G.

    2015-12-01

    seasonal variability. The study is part of the EU FP7 project 'Ships and Waves Reaching Polar Regions (SWARP)', aimed at developing techniques for sea ice and waves modelling and forecasting in the MIZ in the Arctic.

  1. Condensate phenomena in the polar regions of Mars

    NASA Technical Reports Server (NTRS)

    James, Philip B.

    1987-01-01

    Models used to study the changes in Martian climate must of necessity adequately describe the current volatile cycles. The focus is on mathematical modeling of current volatile cycles and modest extrapolation to past regimes. Water cycle, dust storms, polar variabilty, and north polar clouds data were compared to the model predictions.

  2. ICEPOD: A Multidisciplinary Imaging System for Application in Polar Regions

    NASA Astrophysics Data System (ADS)

    Zappa, C. J.; Frearson, N.

    2012-12-01

    The ICEPOD program is in it's third year of a five-year effort to develop a modular airborne ice imaging system mounted on New York Air National Guard (NYANG) LC-130 aircraft to map the surface and sub-surface topography of ice sheets, ice streams, outlet glaciers, ice-shelves and sea-ice for the NSF Major Research Instrumentation program. The project is funded by the American Recovery and Reinvestment Act. The fundamental goal of the ICEPOD program is to develop an instrumentation package that can capture the dynamics of the changing polar regions, focusing on ice, ice margins and ocean systems. To achieve this the instruments include a Scanning Lidar for precise measurements of the ice surface, Stereo photogrammetry from both a high sensitivity Infra-Red camera and a high resolution Visible Imaging camera to document the ice surface and temperature, sea-ice thickness imaging radar and a deep ice radar used to study interior and basal processes of glaciers, ice streams and ice-sheets. All instrument data sets will be time-tagged and geo-referenced by recording precision GPS satellite data. Aircraft orientation will be corrected using inertial measurement technology integrated into the pod. The vision is that this instrumentation will be operated both on routine flights of the NYANG in the polar regions, such as on missions between McMurdo and South Pole Station and on missions throughout Greenland, and on targeted science missions, from mapping sea ice in marginal ice zones and outlet glaciers such as those surrounding Ross Island or Greenland to quantifying large sub-glacial drainage systems in East Antarctica. Recent years have seen extreme changes in the Arctic. Particularly striking are changes within the Pacific sector of the Arctic Ocean, and especially in the seas north of the Alaskan coast. These areas have experienced record warming, reduced sea ice extent, and loss of ice in areas that had been ice-covered throughout human memory. Even the oldest and

  3. Mass Wasting Processes in Vesta's South Polar Region

    NASA Astrophysics Data System (ADS)

    Otto, K.; Jaumann, R.; Krohn, K.; Preusker, F.; Roatsch, T.; Stephan, K.; Sykes, M. V.; Schenk, P.; Raymond, C. A.; Russell, C. T.

    2012-12-01

    Images of Asteroid Vesta taken by the Dawn framing camera give insight to a wide range of geologic phenomena on Vesta's surface. In this abstract we focus on the evidence of different types of gravity-driven mass wasting that can be seen on Vesta with an emphasis on the south polar region where the formation of the giant impact basin of Rheasilvia (1, 2) caused significant mass movements and lateral displacement. During the formation of the impact basin various processes such as uplift and stretching moved material of the impact site (3). The remnant are fault scarps, ridges, and uplift features inside the Rheasilvia basin (2). Beside these mass movements, there are also three types of debris movement associated with the Rheasilvia impact basin: block slumping of solid material, granular landslides, and flow-like features. They all occur on the rim of the basin and the central peak with slopes varying from 10° to 40°. The movement, however, is in different directions. While the block slumping and landslides occur on the steep slopes of the crater wall facing inward, the flow-like movements go outward from the crater rim on less steep slopes. The block slumping is most prominent in the region between 80° and 120° east and 50° and 60° south (4). The slump blocks in a rotational movement showing multiple scarps and ridges. Landslides on the steep slopes inward of Rheasilvia have a length to height ratio of about 1. The flow-like features occur in the region between 50° and 90° east and 20° to 40° south. They are in a relatively young area and have a length to height ratio up to 35. Additionally, many small elongate depressions of about 1.5 km length can be found near the central peak of Rheasilvia. They are mainly arranged parallel to the slope with a slight curvature and are related to instability of granular material on a slope. References: (1) Jaumann et al., Science 336, 687 (2012); (2) Schenk et al., Science 336, 694 (2012); (3) Melosh, Impact Cratering

  4. Mapping of the water ice content within the Martian surficial soil on the periphery of the retreating seasonal northern polar cap based on the TES and the OMEGA data

    NASA Astrophysics Data System (ADS)

    Kuzmin, R. O.; Zabalueva, E. V.; Evdokimova, N. A.; Christensen, P. R.

    2012-11-01

    Analysis of seasonal data from the Mars Global Surveyor Thermal Emission Spectrometer (TES) shows a significant increase in thermal inertia during autumn, winter and spring in the middle and high latitudes of Mars. At each stage of the northern seasonal polar cap's recession in spring a distinct high thermal inertia (HTI) annulus arises around the cap's edge. Within this annulus, we estimated and mapped the springtime water ice content in the daily thermal skin depth layer using spring and summer values of the thermal inertia in TES surface footprints. The results show that the average water content in the surface soil within the HTI annulus varies from ˜5 vol % at the early stages of the seasonal polar cap retreating (Ls = 340°-360°) to ˜1 vol % at later stages (Ls = 60°-70°). Maximum values of water ice content within the HTI annulus occur at Ls = 0°-20° (2-6 vol %) and Ls = 20°-40° (4-10 vol %). We analyzed the temporal and spatial relationship between the HTI annuli and the water ice (WI) annuli at the edge of the northern seasonal polar cap. The water ice within the WI annuli was mapped using a water ice spectral index (the absorption band depth at the 1.5 μm wavelength) derived from the OMEGA (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité) imaging spectrometer aboard the Mars Express spacecraft. Recent OMEGA observations show that the WI annuli formation arises only around the retreating northern seasonal polar cap, never around the retreating southern seasonal cap. For this reason our study is confined only to the northern hemisphere. The observed relationship between the HTI and WI annuli in the northern hemisphere of Mars indicates a close physical interdependence between these two phenomena. Our results confirm that the seasonal permafrost exposed by the retreating northern polar cap (within the HTI annuli) is actively involved today in the condensation and sublimation processes in the modern water cycle on Mars. The water

  5. Saturnian north polar region: a triangle inside the hexagon?

    NASA Astrophysics Data System (ADS)

    Kochemasov, Gennady G.

    2010-05-01

    The famous and "mysterious" stable hexagon structure around the North Pole of Saturn was earlier interpreted as projections of faces of a structural tetrahedron [1]. This "hidden" simplest Plato's polyhedron is a result of an interference of four fundamental (wave 1) warping waves having in any rotating celestial body four directions: orthogonal and diagonal. Origin of the warping waves in any celestial body is due to their movements in elliptical keplerian orbits with periodically changing accelerations. The structural tetrahedron is an intrinsic geometric feature marking the celestial bodies ubiquitous tectonic dichotomy as in a tetrahedron always there is an opposition of a face (expansion) and a vertex (contraction). In the saturnian case the tetrahedron shows a face at the north and a vertex at the south. Morphologically this is manifested by the hexagon and opposing it in the south a vertex. Blue and pink hues of the northern and southern hemispheres also underline the tectonic dichotomy. These geometric expressions are enforced by a subtle dark equilateral triangle appearing in the image PIA11682 also around the north pole and inside the hexagon (the triangle side is about 15000 km long). One angle of the triangle is clearly visible, another one just shows itself and the third one is barely distinguished. The sides of the triangle are not strait lines but slightly broken amidst lines what makes the triangle appear a bit hexagonal (spherical) and the angle is a bit bigger than 60 degrees of a classical equilateral triangle (~70 degrees). The central part of the triangle is not imaged (a black hole in the PIA11682). This image also confirms that the wide northern polar region is also densely "peppered" with bright cloudy more or less isometric spots on average 400 to 800 km across as in other latitudinal belts of Saturn [2, 3, 4]. Earlier they were observed in IR wavelengths, now they show themselves in visible wavelengths. Their origin and size were

  6. Tuning polarization states and interface properties of BaTiO3/SrTiO3 heterostructure by metal capping layers

    NASA Astrophysics Data System (ADS)

    Zhou, Jun; Yang, Ming; Shen, Lei; Wu, Qing Yun; Xu, Lei; Feng, Yuan Ping; Rusydi, Andrivo

    2016-04-01

    How to tune two-dimensional electron gas at interface of heterostructures is becoming an important question for both fundamental physics and electronic applications. Here, using density functional theory calculations, we find that the polarization state of BaTiO3 in metal capped BaTiO3/SrTiO3 heterostructures changes dramatically, depending on the termination of BaTiO3 and the different metal layers (M =Al , Fe, Pt Au). Most interestingly, for Pt on the BaO-terminated BaTiO3/SrTiO3, interface conductivity can be tuned. With a paraelectric state in BaTiO3, Pt_BaTiO 3 /SrTiO3 remains insulating at interface, while when BaTiO3 is ferroelectric, a hole- or electron-conducting BaTiO3/SrTiO3 interface can be realized, depending on its polarization direction in BaTiO3. This conducting interface and the top Pt layer screen the depolarization field, and thus stabilize the ferroelectricity in BaTiO3. Our result provides important clues for the reversibly tunable conductivity at oxide interfaces.

  7. The ranging behavior of Lemur catta in the region of Cap Sainte-Marie, Madagascar.

    PubMed

    Kelley, Elizabeth A

    2013-01-01

    Large home ranges and extreme flexibility in ranging behaviors characterize most subarid dwelling haplorhines. However, the most comparable extant strepsirhine, Lemur catta, is characterized as having small home ranges with consistent boundaries. Since ranging studies on this species have been limited to gallery forest habitat, the author's goal is to identify ecological factors that affect range use of L. catta in one of the most resource-limited environments of its distribution. To conduct this study, ranging and behavioral data were collected on two nonoverlapping groups through all-day follows in the semidesert scrub environment of Cap Sainte-Marie (CSM), Madagascar. Data were collected from August 2007 through July 2008. Home range areas and day range lengths were generated using ArcGIS(®) 9.3. Other variables measured were habitat composition, diet richness, daily activity, and microclimate. Home range areas of CSM L. catta were very large relative to those of gallery forest L. catta, and there was great monthly variation. In contrast, day range lengths at CSM were either smaller than or approximated the size of comparative gallery forest groups. Temperature, sunning, and diet richness were associated with day range length for one but not for both groups and appear to be related to energy management needs. Based on these findings, the author suggests that L. catta is capable of extensive behavioral and ranging flexibility in the extremes of its environment. However, physiological constraints impose limitations that can interfere with its ability to adapt to even seemingly minor variations in microclimate and habitat structure within the same site. PMID:23180618

  8. Microstructural Considerations of Transporting Sea Ice Samples from Polar Regions

    NASA Astrophysics Data System (ADS)

    Lieb-Lappen, R.; Obbard, R. W.

    2012-12-01

    High latitude regions are at the forefront of climate change research as these regions have and will experience the greatest impact due to changing environmental conditions (e.g. Antarctic and recent Arctic stratospheric ozone holes, large temperature increases on the Antarctic Peninsula, changes in the extent and age of Arctic sea ice). One of the major challenges of polar scientific research is the preservation of frozen sea ice samples during their transport back to the laboratory and subsequent storage. Small fluctuations in temperature have been shown to have a significant effect on the microstructure of snow and ice samples. This is especially true for sea ice specimens where transport and storage temperatures are often only slightly below the eutectic point for its different constituents (i.e. salts). Furthermore, sea ice can have a 30 deg C in situ vertical temperature gradient that is lost during transport and storage. Sea ice plays a critical role in mediating the exchange of heat, gases, and chemical species across the ocean-atmosphere interface. The kinetics of these exchanges is highly dependent upon the brine channel microstructure, which is strongly coupled to temperature. To determine the degree of microstructural variation between samples shipped at different temperatures, ten samples of a single sea ice core collected in March 2012 were transported from Barrow, Alaska to Hanover, NH using two common techniques: with blue ice packs enclosed in a Styrofoam box (~ -25 deg C) and in a dry liquid nitrogen cryoshipper (~ -182 deg C). In addition, snow lying on the sea ice and blowing snow samples were collected and shipped via both techniques. All samples were then stored for analysis in a cold room maintained at ~ -33 deg C. The microstructure of both sets of samples was analyzed using x-ray micro-computed tomography (μ-CT), with samples on a Peltier cold stage to maintain a scanning temperature of -20 deg C. We compare sea ice porosity and brine

  9. Incorporating 3D-printing technology in the design of head-caps and electrode drives for recording neurons in multiple brain regions

    PubMed Central

    DeLucca, Michael V.; Haufler, Darrell; Paré, Denis

    2015-01-01

    Recent advances in recording and computing hardware have enabled laboratories to record the electrical activity of multiple brain regions simultaneously. Lagging behind these technical advances, however, are the methods needed to rapidly produce microdrives and head-caps that can flexibly accommodate different recording configurations. Indeed, most available designs target single or adjacent brain regions, and, if multiple sites are targeted, specially constructed head-caps are used. Here, we present a novel design style, for both microdrives and head-caps, which takes advantage of three-dimensional printing technology. This design facilitates targeting of multiple brain regions in various configurations. Moreover, the parts are easily fabricated in large quantities, with only minor hand-tooling and finishing required. PMID:25652930

  10. Incorporating 3D-printing technology in the design of head-caps and electrode drives for recording neurons in mult