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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. 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.

  4. Magnetospheric polar cap

    NASA Astrophysics Data System (ADS)

    Akasofu, S. I.; Kan, J. R.

    Mount Denali (McKinley), the Alaska Range, and countless glaciers welcomed all 86 participants of the Chapman Conference on the Magnetospheric Polar Cap, which was held on the University of Alaska, Fairbanks campus (UAF), on August 6-9, 1984. The magnetospheric polar cap is the highest latitude region of the earth which is surrounded by the ring of auroras (the auroral oval). This particular region of the earth has become a focus of magnetospheric physicists during the last several years. This is because a number of upper atmospheric phenomena in the polar cap are found to be crucial in understanding the solar wind—magnetosphere interaction. The conference was opened by J. G. Roederer, who was followed by the UAF Chancellor, P. J. O'Rourke, who officially welcomed the participants.

  5. Modeling polar cap F-region patches using time varying convection

    SciTech Connect

    Sojka, J.J.; Bowline, M.D.; Schunk, R.W.; Decker, D.T.; Valladares, C.E.; Sheehan, R.; Anderson, D.N.; Heelis, R.A.

    1993-09-03

    Here the authors present the results of computerized simulations of the polar cap regions which were able to model the formation of polar cap patches. They used the Utah State University Time-Dependent Ionospheric Model (TDIM) and the Phillips Laboratory (PL) F-region models in this work. By allowing a time varying magnetospheric electric field in the models, they were able to generate the patches. This time varying field generates a convection in the ionosphere. This convection is similar to convective changes observed in the ionosphere at times of southward pointing interplanetary magnetic field, due to changes in the B[sub y] component of the IMF.

  6. 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.

  7. Morphological characteristics of disturbances generated in the polar cap region of the upper thermosphere

    NASA Astrophysics Data System (ADS)

    Fujiwara, Hitoshi

    Recent radar and satellite observations have shown various disturbances in the polar cap region of the upper thermosphere. For example, the European incoherent scatter (EISCAT) radar, Super Dual Auroral Radar Network (SuperDARN), and CHAMP satellite observations have revealed ionospheric and thermospheric variations due to energy inputs from the magnetosphere. From the simultaneous observations with the EISCAT Svalbard radar and CUTLASS radar, Fujiwara et al. [2007] showed existence of significant heat source in the dayside polar cap/cusp region of the upper thermosphere in association with the dayside magnetospheric phenomena of reconnections and flux transfer events. Bruinsma and Forbes [2007] showed trans-polar propagation of the traveling atmospheric disturbances (TADs) in connection with three sudden injections of energy at high latitudes from the CHAMP mass density observations. In the present study, we focus our attention on both disturbances directly generated in the polar cap region of the upper thermosphere and those propagating from other regions. We perform numerical simulations with a general circulation model, which includes all the atmospheric regions, developed by Miyoshi and Fujiwara [2003]. The morphological characteristics of the disturbances due to auroral particle precipitation and electric field enhancement are investigated here. References: Bruinsma, S., and J. M. Forbes, Global observation of traveling atmospheric disturbances (TADs) in the thermosphere, Geophys. Res., Lett., 34, L14103, doi: 10.1029/2007GL030243, 2007. Fujiwara, H., R. Kataoka, M. Suzuki, S. Maeda, S. Nozawa, K. Hosokawa, H. Fukunishi, N. Sato, and M. Lester, Electromagnetic energy deposition rate in the polar upper thermosphere derived from the EISCAT Svalbard radar and CUTLASS Finland radar observations, Ann. Geophys., 25, 2393-2403, 2007. Miyoshi, Y., and H. Fujiwara, Day-to-day variations of migrating diurnal tide simulated by a GCM from the ground surface to the

  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. Polar Cap Patch Dynamics

    DTIC Science & Technology

    2013-04-25

    illustrate the concept with a sample model -run incorporating representative data. Title 12: Space weather challenges of the polar cap ionosphere ...located at Oslo and Ny-Ålesund. The primary objective has been to obtain a better understanding solar wind impacts on the polar ionosphere which are of...made no inventions, and Section 8 lists the core UiO personnel during this project. 15. SUBJECT TERMS EOARD, ionosphere (polar

  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. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    7 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.4 m/pixel (5 ft/pixel) view of a typical martian north polar ice cap texture. The surface is pitted and rough at the scale of several meters. The north polar residual cap of Mars consists mainly of water ice, while the south polar residual cap is mostly carbon dioxide. This picture is located near 85.2oN, 283.2oW. The image covers an area approximately 1 km wide by 1.4 km high (0.62 by 0.87 miles). Sunlight illuminates this scene from the lower left.

  13. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    7 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.4 m/pixel (5 ft/pixel) view of a typical martian north polar ice cap texture. The surface is pitted and rough at the scale of several meters. The north polar residual cap of Mars consists mainly of water ice, while the south polar residual cap is mostly carbon dioxide. This picture is located near 85.2oN, 283.2oW. The image covers an area approximately 1 km wide by 1.4 km high (0.62 by 0.87 miles). Sunlight illuminates this scene from the lower left.

  14. Midday auroral observations in the oval, cusp region, and polar cap.

    NASA Technical Reports Server (NTRS)

    Romick, G. J.; Brown, N. B.

    1971-01-01

    Evaluation of combined photographic and photometric measurements made on the 1969 NASA airborne expedition, yielding a description of the midday oval, cusp region, and polar cap auroral precipitation at low magnetic activity (Kp = 0, 1+). The observations delineate three regions through the description of the type of aurora observed and the photometrically inferred change in energy of the particles: (1) the region in and equatorward of the oval where greater than 3-keV electrons are associated with 6300 A/4278 A ratios less than or equal to 1 and with a diffuse glow or structured arcs; (2) the cusp region where electrons of several hundred electron volts and spikes of more energetic electrons are associated with 6300 A/4278 A ratios between 10 and 35 in broken, fragmented, rayed features and patches; (3) the polar cap where discrete earth-sun-aligned arcs have height luminosity profiles in 5577 A, 6300 A (forbidden O I), and 4278 A (N2(+)) that suggest incoming electrons with an energy spectrum of 2-keV characteristic energy above a low-energy (few hundred electron volts) background.

  15. Correlation between Poynting flux and soft electron precipitation in the dayside polar cap boundary regions.

    PubMed

    Deng, Yue; Sheng, Cheng; Su, Yi-Jiun; Hairston, Marc R; Knipp, Delores; Huang, Cheryl Y; Ober, Daniel; Redmon, Rob J; Coley, Robin

    2015-10-01

    Observations have revealed large Poynting flux and soft electron precipitation around the cusp region, which have strong impacts on the polar ionosphere/thermosphere. Simulations also confirmed that Poynting flux and soft electron precipitation significantly change the neutral density and dynamics around the dayside polar cap boundary regions. However, no detailed study has been conducted to show if they should coincide with each other or not. Our analysis of Defense Meteorological Satellite Program (DMSP) satellite data reveals a complex correlation between them. Poynting flux and soft particle precipitation are coincident in some cases (match cases), but a clear displacement between them can also be identified in others (nonmatch cases). In the 29 cusp crossings from F13 we investigated, the ratio between nonmatch and match cases is close to 1:4. In nonmatch cases, the displacement between the Poynting flux enhancement and soft particle precipitation enhancement can be as large as 1° in geomagnetic latitude.

  16. 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

  17. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2005-01-01

    8 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows landforms created by sublimation processes on the south polar residual cap of Mars. The bulk of the ice in the south polar residual cap is frozen carbon dioxide.

    Location near: 86.6oS, 342.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  18. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2005-01-01

    8 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows landforms created by sublimation processes on the south polar residual cap of Mars. The bulk of the ice in the south polar residual cap is frozen carbon dioxide.

    Location near: 86.6oS, 342.2oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  19. Polar Plasma Wave Observations in the Auroral Region and Polar Cap

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Averkamp, T. F.; Kirchner, D. L.; Pickett, J. S.; Persoon, A. M.; Gurnett, D. A.

    1998-01-01

    Auroral kilometric radiation (AKR), sometimes associated with auroral myriametric radiation (AMR), has been observed by the plasma wave instrument on board Polar on almost every northern hemisphere pass. High spectral resolution plots of the AKR obtained by the wide-band receiver of the plasma wave instrument on board the spacecraft often show discrete, negative-slope striations each extending over a period of several seconds. A preliminary survey of over 4000 spectrograms (each for 48 seconds of data) indicates that the striations are seen in the northern hemisphere near apogee about 5% of the time. The frequency range is 40 kHz less than f less than 100 kHz, but a few observations of signatures have been made at higher frequency (f less than 225 khz. The frequency drift rates R, are similar ranging from -9.0 kHz/sec less than R less than -1.0 kHz/sec. No data is currently available for perigee (southern hemisphere) passes. The paucity of positive-slope features may be due to the location of the satellite at altitudes well above the AKR source region. Past studies have suggested these features are due to AKR wave growth stimulated by the propagation of electromagnetic ion cyclotron waves travelling up (-R) or down (+R) the field line, through the source region. High-resolution waveform data from both Polar and FAST show the presence of solitary waves in the auroral region which may also be a source of these striations. AMR is seen as diffuse emission associated with, but at lower frequency than the lower AKR. Direction finding of these emissions is not conclusive, but for one case, they have a source region distinct from the magnetic field line containing the AKR source, but possibly associated with the auroral cavity density gradient.

  20. 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

  1. 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

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. Summer South Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    13 April 2004 The martian south polar residual ice cap is composed mainly of frozen carbon dioxide. Each summer, a little bit of this carbon dioxide sublimes away. Pits grow larger, and mesas get smaller, as this process continues from year to year. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of a small portion of the south polar cap as it appeared in mid-summer in January 2004. The dark areas may be places where the frozen carbon dioxide contains impurities, such as dust, or places where sublimation of ice has roughened the surface so that it appears darker because of small shadows cast by irregularities in the roughened surface. The image is located near 86.9oS, 7.6oW. The image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.

  9. Arecibo radar imagery of Mars: II. Chryse-Xanthe, polar caps, and other regions

    NASA Astrophysics Data System (ADS)

    Harmon, John K.; Nolan, Michael C.

    2017-01-01

    other ice processes in the dichotomy boundary region. The first delay-Doppler images of the radar-bright features from the north and south polar icecaps are presented. Both poles show the circular polarization inversion and high reflectivity characteristic of coherent volume backscatter from relatively clean ice. The south polar feature is primarily backscatter from the residual CO2 icecap (with a lesser contribution from the polar layered deposits), whose finite optical depth probably accounts for the feature's strong S/X-band wavelength dependence. Conversely, the north polar radar feature appears to be mostly backscatter from the H2O-ice-rich polar layered deposits rather than from the thin residual H2O cap. The north polar region shows additional radar-bright features from Korolev Crater and a few other outlying circumpolar ice deposits.

  10. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2005-01-01

    17 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows mesas and pits formed by sublimation of carbon dioxide of the south polar cap.

    Location near: 85.8oS, 351.5oW Image width: 2 km (1.2 mi) Illumination from: upper left Season: Southern Summer

  11. A model study of how electric field structures affect the polar cap F region

    SciTech Connect

    Sojka, J.J.; Schunk, R.W. )

    1988-02-01

    A three-dimensional time-dependent ionospheric model was used to study how electric field structures affect the polar F region. The electric field structures are represented by elongated Volland two-cell models whose dimensions range from tens to 1,000 km. These model structures are intended to represent the polar cap electric field for IMF B{sub z} northward conditions. A statistical method is used to generate a set of these structures. Their electric field strength and polarity are varied in order to study the F region's dependence on this magnetospheric input. For electric field structures whose size and electric field strengths are consistent with B{sub z} northward observations, several ionospheric dependencies were found. The n{sub m}F{sub 2} parameter, in general, decreased due to the presence of the higher electric fields associated with the structures. Decreases ranging from a few percent to a factor of 4 were obtained from the simulations. This decrease in N{sub m}F{sub 2} was further complicated by the initial N{sub m}F{sub 2} conditions, i.e., past history of the flux tube, being quite different when the structure is present. H{sub m}F{sub 2} in the vicinity of a structure can be raised or lowered by up to 100 km, however, this change is not uniquely dependent upon the vertical induced drift. The role of enhanced reaction rates due to elevated ion temperatures is very important. The F region becomes spatially very structured. The modulation of these structure in N{sub m}F{sub 2} is up to an order of magnitude in this study.

  12. Polar Cap Retreat

    NASA Technical Reports Server (NTRS)

    2004-01-01

    13 August 2004 This red wide angle Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a view of the retreating seasonal south polar cap in the most recent spring in late 2003. Bright areas are covered with frost, dark areas are those from which the solid carbon dioxide has sublimed away. The center of this image is located near 76.5oS, 28.2oW. The scene is large; it covers an area about 250 km (155 mi) across. The scene is illuminated by sunlight from the upper left.

  13. Extreme F-region gradients generated by patch-arc interactions in the polar cap

    NASA Astrophysics Data System (ADS)

    Semeter, J. L.; Dahlgren, H.; Zettergren, M. D.; Swoboda, J.; Perry, G. W.; St-Maurice, J. P.; Hosokawa, K.; Shiokawa, K.; Nicolls, M. J.

    2014-12-01

    We report observations of electrodyamic interactions between drifting F-region plasma structure and discrete polar cap arcs. Three-dimensional time-dependent images of ionospheric state variables (Ne, Te, Ti, Vi) are produced using multi-beam measurements by the Resolute Bay Incoherent Scatter Radar (RISR). The resulting parameter maps are registered with all-sky images of 630-nm and 557-nm emissions acquired by the collocated OMTI imager. The combined analysis allows us to disambiguate spatial and temporal effects, revealing the formation of a deep density depletion between the arc and the plasma patch, formed by the combined action of electrodynamic evacuation and enhanced chemical recombination in the auroral downward current region. This mechanism results in a steep density gradient (gradient scale length <5-km) extending for at least 800-km in a direction tangential to the arc. This region should be highly unstable to gradient drift instability, and a likely source of enhanced HF scatter. Interpretations are supported through three-dimensional transport modeling.

  14. Pits in Polar Cap

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This full-frame image from the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter shows faults and pits in Mars' north polar residual cap that have not been previously recognized.

    The faults and depressions between them are similar to features seen on Earth where the crust is being pulled apart. Such tectonic extension must have occurred very recently because the north polar residual cap is very young, as indicated by the paucity of impact craters on its surface. Alternatively, the faults and pits may be caused by collapse due to removal of material beneath the surface. The pits are aligned along the faults, either because material has drained into the subsurface along the faults or because gas has escaped from the subsurface through them.

    NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.

  15. Sunward convection in both polar caps

    SciTech Connect

    Reiff, P.H.

    1982-08-01

    The geomagnetic storm of July 29, 1977 has been the object of concentrated study. The latter part of the day (1800--2300 UT) is particularly interesting because it is a period of extremely strong, almost directly northward interplanetary magnetic fields (IMF). Such northward IMF's have been related to periods of reversed (i.e., sunward) convection in the polar cap, and this day is no exception. Zanetti et al. (1981), using Triad magnetometer data, show magnetic perturbations implying reversed convection in the northern polar cap, while the Birkeland currents in the southern polar cap are very weak. They give two possible interpretations: (1) merging occurs preferentially in the northern cusp region, and therefore reversed convection is restricted to the northern polar cap or (2) the currents flow predominantly in the sunlit northern polar cap because its conductivity is higher. This paper shows convection data from both the northern polar cap (S3-3) and the southern polar cap (AE-C). In both cases, regions of reversed convection are seen. Therefore the asymmetry of the Birkeland currents is more likely caused by a conductivity asymmetry than a convection asymmetry. It is likely that the low-energy ions seen deep in the polar cap may be traped on closed field lines after merging on both tail lobe boundaries.

  16. 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.

  17. 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

  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. 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.

  20. South Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 8 March 2004

    The Odyssey spacecraft has completed a full Mars year of observations of the red planet. For the next several weeks the Image of the Day will look back over this first mars year. It will focus on four themes: 1) the poles - with the seasonal changes seen in the retreat and expansion of the caps; 2) craters - with a variety of morphologies relating to impact materials and later alteration, both infilling and exhumation; 3) channels - the clues to liquid surface flow; and 4) volcanic flow features. While some images have helped answer questions about the history of Mars, many have raised new questions that are still being investigated as Odyssey continues collecting data as it orbits Mars.

    This image was collected March 5, 2002 during the southern summer season. Layering in the South polar cap interior is readily visible and may indicate yearly ice/dust deposition.

    Image information: VIS instrument. Latitude -86.6, Longitude 156.8 East (203.2 West). 19 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 led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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. 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

  4. 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

  5. North Polar Cap

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    This image shows clouds and one of the many storm fronts common in the north polar region during spring and early summer. Note the linear nature of the clouds towards the top of the image, and the appearance of a large crater barely visible beneath the cloud cover.

    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 is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey 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.

  6. South Polar Residual Ice Cap

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This mosaic is composed of 18 Viking Orbiter images (6 each in red, green, and violet filters), acquired on September 28, 1977, during revolution 407 of Viking Orbiter 2. The south pole is located just off the lower left edge of the polar cap, and the 0 degree longitude meridian extends toward the top of the mosaic. The large crater near the right edge (named 'South') is about 100 km in diameter. These images were acquired during southern summer on Mars (Ls = 341 degrees); the sub-solar declination was 8 degrees S., and the south polar cap was nearing its final stage of retreat just prior to vernal equinox. The south residual cap is approximately 400 km across, and the exposed surface is thought to consist dominantly of carbon-dioxide frost. This is in contrast to the water-ice surface of the north polar residual cap. It is likely that water ice is present in layers that underlie the south polar cap and that comprise the surrounding layered terrains. Near the top of this image, irregular pits with sharp-rimmed cliffs appear 'etched', presumably by wind. A series of rugged mountains (extending toward the upper right corner of the image) are of unknown origin.

  7. South Polar Residual Ice Cap

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This mosaic is composed of 18 Viking Orbiter images (6 each in red, green, and violet filters), acquired on September 28, 1977, during revolution 407 of Viking Orbiter 2. The south pole is located just off the lower left edge of the polar cap, and the 0 degree longitude meridian extends toward the top of the mosaic. The large crater near the right edge (named 'South') is about 100 km in diameter. These images were acquired during southern summer on Mars (Ls = 341 degrees); the sub-solar declination was 8 degrees S., and the south polar cap was nearing its final stage of retreat just prior to vernal equinox. The south residual cap is approximately 400 km across, and the exposed surface is thought to consist dominantly of carbon-dioxide frost. This is in contrast to the water-ice surface of the north polar residual cap. It is likely that water ice is present in layers that underlie the south polar cap and that comprise the surrounding layered terrains. Near the top of this image, irregular pits with sharp-rimmed cliffs appear 'etched', presumably by wind. A series of rugged mountains (extending toward the upper right corner of the image) are of unknown origin.

  8. No signature of clear CO2 ice from the 'cryptic' regions in Mars' south seasonal polar cap.

    PubMed

    Langevin, Yves; Douté, Sylvain; Vincendon, Mathieu; Poulet, François; Bibring, Jean-Pierre; Gondet, Brigitte; Schmitt, Bernard; Forget, F

    2006-08-17

    The seasonal polar ice caps of Mars are composed mainly of CO2 ice. A region of low (< 30%) albedo has been observed within the south seasonal cap during early to mid-spring. The low temperature of this 'cryptic region' has been attributed to a clear slab of nearly pure CO2 ice, with the low albedo resulting from absorption by the underlying surface. Here we report near-infrared imaging spectroscopy of the south seasonal cap. The deep and broad CO2 absorption bands that are expected in the near-infrared with a thick transparent slab of CO2 ice are not observed. Models of the observed spectra indicate that the low albedo results from extensive dust contamination close to the surface of a CO2 ice layer, which could be linked to atmospheric circulation patterns. The strength of the CO2 absorption increases after mid-spring, so part of the dust is either carried away or buried more deeply in the ice layer during the CO2 ice sublimation process.

  9. Martian north polar cap summer water cycle

    NASA Astrophysics Data System (ADS)

    Brown, Adrian J.; Calvin, Wendy M.; Becerra, Patricio; Byrne, Shane

    2016-10-01

    A key outstanding question in Martian science is "are the polar caps gaining or losing mass and what are the implications for past, current and future climate?" To address this question, we use observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) of the north polar cap during late summer for multiple Martian years, to monitor the summertime water cycle in order to place quantitative limits on the amount of water ice deposited and sublimed in late summer. We establish here for the first time the summer cycle of water ice absorption band signatures on the north polar cap. We show that in a key region in the interior of the north polar cap, the absorption band depths grow until Ls = 120, when they begin to shrink, until they are obscured at the end of summer by the north polar hood. This behavior is transferable over the entire north polar cap, where in late summer regions 'flip' from being net sublimating into net condensation mode. This transition or 'mode flip' happens earlier for regions closer to the pole, and later for regions close to the periphery of the cap. The observations and calculations presented herein estimate that on average a water ice layer ∼70 microns thick is deposited during the Ls = 135-164 period. This is far larger than the results of deposition on the south pole during summer, where an average layer 0.6-6 microns deep has been estimated by Brown et al. (2014) Earth Planet. Sci. Lett., 406, 102-109.

  10. 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.

  11. A statistical analysis of low frequency geomagnetic field pulsations at two Antarctic geomagnetic observatories in the polar cap region

    NASA Astrophysics Data System (ADS)

    Pietrolungo, M.; Lepidi, S.; Cafarella, L.; Di Mauro, D.

    2013-09-01

    The aim of this study is to investigate the characteristics of low frequency (˜0.5-5 mHz) geomagnetic field fluctuations as recorded at two Antarctic stations within the polar cap: the Italian observatory Mario Zucchelli Station (TNB) and the French-Italian observatory Dome C (DMC) in order to investigate the spatial extension and propagation characteristics of the phenomena observed at very high latitude. The stations have approximately the same geographic latitude, but a very different corrected geomagnetic latitude, being DMC close to the geomagnetic pole and TNB closer to the auroral oval. Our study focused on power spectra, coherence and phase difference between low frequency fluctuations analyzing the horizontal H component measured during the entire year 2006. The fluctuation power behavior during the day can be explained according to the positions of the stations with respect to the polar cap; indeed in the dayside sector it is higher in the cusp region, while in the nightside sector it is higher close to the geomagnetic pole. Furthermore the study of coherent fluctuations, focusing on their phase difference, indicated that the propagation direction within the cap is variable during the day: in the dayside and nightside regions it is from the auroral oval toward the geomagnetic pole, while in the magnetic local morning and afternoon sectors it is from the geomagnetic pole toward the dawn-dusk meridian. Finally the analysis of two individual pulsation events, consisting of short duration wave packets, is shown; it confirms the statistical considerations on the propagation direction and allows to estimate the wave number and apparent phase velocity, whose values are of the order of 3-4 and 30-15 km/s, respectively.

  12. Plasma Irregularity Production in the Polar Cap F-Region Ionosphere

    NASA Astrophysics Data System (ADS)

    Lamarche, Leslie

    Plasma in the Earth's ionosphere is highly irregular on scales ranging between a few centimeters and hundreds of kilometers. Small-scale irregularities or plasma waves can scatter radio waves resulting in a loss of signal for navigation and communication networks. The polar region is particularly susceptible to strong disturbances due to its direct connection with the Sun's magnetic field and energetic particles. In this thesis, factors that contribute to the production of decameter-scale plasma irregularities in the polar F region ionosphere are investigated. Both global and local control of irregularity production are studied, i.e. we consider global solar control through solar illumination and solar wind as well as much more local control by plasma density gradients and convection electric field. In the first experimental study, solar control of irregularity production is investigated using the Super Dual Auroral Radar Network (SuperDARN) radar at McMurdo, Antarctica. The occurrence trends for irregularities are analyzed statistically and a model is developed that describes the location of radar echoes within the radar's field-of-view. The trends are explained through variations in background plasma density with solar illumination affecting radar beam propagation. However, it is found that the irregularity occurrence during the night is higher than expected from ray tracing simulations based on a standard ionospheric density model. The high occurrence at night implies an additional source of plasma density and it is proposed that large-scale density enhancements called polar patches may be the source of this density. Additionally, occurrence maximizes around the terminator due to different competing irregularity production processes that favor a more or less sunlit ionosphere. The second study is concerned with modeling irregularity characteristics near a large-scale density gradient reversal, such as those expected near polar patches, with a particular focus on

  13. Deformation of Polar Cap Patches During Substorms

    NASA Astrophysics Data System (ADS)

    Zou, S.; Ridley, A. J.; Nicolls, M. J.; Coster, A. J.; Thomas, E. G.; Ruohoniemi, J. M.; Hampton, D.

    2015-12-01

    Polar cap patches refer to the islands of high F-region plasma density within the polar cap. Their formation on the dayside and deformation on the nightside are not well understood. The F-layer ionosphere density is strongly influenced by electric field, thermospheric wind as well as soft particle precipitation. This study combines observations from multiple instruments, including Poker Flat incoherent scatter radar, GPS TEC and optical instruments, as well as the Global Ionosphere and Thermosphere Model (GITM), to investigate the effects of highly structured electric fields and winds on the deformation of polar cap patches during substorms. We will also discuss variations of the auroral emissions associated with the patch evolution.

  14. 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.

  15. Mars South Polar Cap "Fingerprint" Terrain

    NASA Image and Video Library

    2000-04-24

    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 86.0°S, 53.9°W. http://photojournal.jpl.nasa.gov/catalog/PIA02373

  16. A technique for accurately determining the cusp-region polar cap boundary using SuperDARN HF radar measurements

    NASA Astrophysics Data System (ADS)

    Chisham, G.; Freeman, M. P.

    2003-04-01

    Accurately measuring the location and motion of the polar cap boundary (PCB) in the high-latitude ionosphere can be crucial for studies concerned with the dynamics of the polar cap, e.g. the measurement of reconnection rates. The Doppler spectral width characteristics of backscatter received by the SuperDARN HF radars have been previously used for locating and tracking the PCB in the cusp region. The boundary is generally observed in meridional beams of the SuperDARN radars and appears as a distinct change between low spectral width values observed equatorward of the cusp region, and high, but variable spectral width values observed within the cusp region. To identify the spectral width boundary (SWB) between these two regions, a simple algorithm employing a spectral width threshold has often been applied to the data. However, there is not, as yet, a standard algorithm, or spectral width threshold, which is universally applied. Nor has there been any rigorous assessment of the accuracy of this method of boundary determination. This study applies a series of threshold algorithms to a simulated cusp-region spectral width data set, to assess the accuracy of different algorithms. This shows that simple threshold algorithms correctly identify the boundary location in, at the most, 50% of the cases and that the average boundary error is at least ~ 1 2 range gates (~ 1° latitude). It transpires that spatial and temporal smoothing of the spectral width data (e.g. by median filtering), before application of a threshold algorithm can increase the boundary determination accuracy to over 95% and the average boundary error to much less than a range gate. However, this is sometimes at the cost of temporal resolution in the motion of the boundary location. The algorithms are also applied to a year’s worth of spectral width data from the cusp ionosphere, measured by the Halley SuperDARN radar in Antarctica. This analysis highlights the increased accuracy of the enhanced

  17. Polar Cap Area and Boundary Motion During Substorms

    NASA Technical Reports Server (NTRS)

    Brittnacher, M.; Germany, G. A.; Fillingim, M. O.; Parks, G. K.; Spann, James F., Jr.

    1998-01-01

    The area of the polar cap as a function of local time and substorm phase was measured using images from the Polar Ultraviolet Imager (UVI) for different interplanetary magnetic field (IMF) orientations during three substorms in January 1997. We measured changes in the polar cap area and motion of the poleward and equatorward boundary of the auroral oval as determined by UVI images. It was found that the polar cap boundary is strongly influenced by thinning of the oval, decrease in polar cap structures, the poleward expansion of the substorm at midnight and the fading of luminosity below the instrument sensitivity threshold. Generally these effects dominate over the latitudinal motion of the auroral oval at its equatorward edge. A new feature is that the polar cap region clears of precipitation during the substorm growth phase, which expands the size of the polar cap but may not necessarily be related to an expansion of the open flux. We present a new finding that the increase in polar cap area prior to onset and the decrease in the area following it are independent of the strength of the southward IMF component. For one case the polar cap area increased while the southward component of the IMF was no less than -0.5 nT. These observations have strong implications for models that use the polar cap area to estimate the magnitude of energy storage in the lobe magnetic field and loss during substorms.

  18. A model for polar cap electric fields

    NASA Technical Reports Server (NTRS)

    Dangelo, N.

    1976-01-01

    A model is proposed relating polar cap ionospheric electric fields to the parameters of the solar wind near the orbit of the earth. The model ignores the notion of field line merging. An essential feature is the role played by velocity shear instabilities in regions of the outer magnetosphere, in which mapping of the magnetosheath electric field would produce sunward convection. The anomalous resistivity which arises from velocity shear turbulence, suffices to essentially disconnect the magnetosphere from the magnetosheath, at any place where that resistivity is large enough. The magnetosheath-magnetosphere system, as a consequence, acts as a kind of diode or rectifier for the magnetosheath electric fields. Predictions of the model are compared with several observations related to polar cap convection.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Effective polar cap area and multi-station basis for Polar Cap (PC) indices

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2017-04-01

    The Polar Cap (PC) indices are useful indices for Space Weather forecasts and analyses. The PC indices have been used to monitor the interplanetary geoeffective electric field and solar wind pressure pulses, to analyze cross polar cap voltages, polar cap diameter, and general polar cap dynamics. Furthermore, the PC indices have been used to monitor auroral electrojet intensities, ionospheric Joule heating, and global auroral power, and to predict ring current intensities. For specific Space Weather warning forecasts the PC indices can be used to predict substorm development and the associated risk of power line disturbances in the subauroral regions. The PC indices, PCN (North) and PCS (South), are derived from geomagnetic observations at Thule in Greenland and Vostok in Antarctica, respectively. In order to provide reliable forecast services based on PC indices, it would be advantageous to have available back-up suppliers of index values. The presentation provides an analysis of the effective area for useful PC index derivation and suggests observatories that could provide back-up data for PC index calculations should the primary sources fail due to instrument or communication problems.

  4. Cold jets in the Martian polar caps

    NASA Astrophysics Data System (ADS)

    Kieffer, Hugh H.

    2007-08-01

    Mars seasonal polar caps display dark ice, local darker spots, aligned elongate patches, and radially dendritic forms that reverse albedo contrast. The unexpected variety and sequence of these features are explained on the basis of processes involving CO2, dust, sand, and H2O. These processes are largely related to the atmosphere being near its saturation temperature, and they have few terrestrial analogies. In the simplest case the ~1 m thick seasonal cap, initially dusty, cleans itself and becomes translucent after sunrise and is impermeable over extensive regions except for local vents. The slab ice sublimates at the base and is levitated on high-pressure gas, causing humidity exchange with deeper layers; subslab gas converging toward the vents erodes channels in the soil and ejects this material in high-velocity jets. Recent spectral observations indicate great variety in the details.

  5. 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.

  6. 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.

  7. 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.

  8. The nature of the residual Martian polar caps

    NASA Technical Reports Server (NTRS)

    Briggs, G. A.

    1974-01-01

    A model of the behavior of the Martian polar caps is described which incorporates the heating effects of the atmosphere, as well as insolation and conduction. This model is used to try to match the observed regression curves of the polar caps, and it predicts that all the seasonally condensed CO2 will be lost by around the summer solstice. The implication is that the residual caps are composed of water ice which, it is found by further modeling, should be stable during the Martian summers. However, it is also argued that this model may be too simplistic, and that the effects of wind in redistributing the seasonal condensate may lead to sufficient thicknesses of CO2 in the central polar region to allow the year-long existence of CO2 without significantly changing the retreat characteristics of the cap, and it is, therefore, concluded that at the present, the nature of the residual caps cannot be reliably determined.

  9. At the Edge of a Polar Cap

    NASA Image and Video Library

    2014-05-22

    The deep chasm that formed on the polar cap edge is identified as an area of strong down-slope winds and has a clear connection to Mars largest dune field, Olympia Undae as observed by NASA Mars Reconnaissance Orbiter.

  10. 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.

  11. 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.

  12. 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.

  13. O transport across the polar cap

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    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. We test the cleft ion fountain theory, which asserts that O ions escape from the cleft, cross the polar cap, and then enter the plasma sheet. Statistical studies of O density in the cleft, high-altitude polar cap, and plasma sheet all indicate that the O density increases with increasing solar wind dynamic pressure. In order to examine O transport more directly, we use polar cap ion outflow measurements and the 2001 Tsyganenko magnetic field model driven with advanced composition explorer (ACE) solar wind parameters. We calculate the distance between the cleft and the ionospheric footpoints of magnetic field lines mapped from the polar spacecraft along the noon midnight meridian. Using the observed outflow speed and the magnetic field line length we calculate the travel time for the ions. When we examine the distance from the cleft versus the O travel time for individual passes, the slope of the line is consistent with the measured ionospheric convection speed across the polar cap. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Pluto Insolation and the South Polar Cap

    NASA Astrophysics Data System (ADS)

    Rubincam, D. P.

    2009-05-01

    Pluto's south polar cap is a puzzle. The planet's southern cap may be brighter than the north, even though it was the south pole which faced the Sun on Pluto's recent approach to perihelion. One would think that the brighter pole would be the one which received less insolation: volatiles would be expected to sublimate from the sunny south and condense in the north, enlarging the north polar cap with fresh and bright frost. Thus the north pole should be brighter than the south. However, it may be the other way around, although the evidence is not entirely clear. One suggested explanation of the (possible) paradox is that the south polar cap has, over the last several million years, received less insolation than the north, accumulating a larger supply of volatiles. However, expressing the solar insolation in terms of Pluto's orbital elements clearly shows that both the north and south poles have received nearly the same amount of sunlight over the past several million years. Hence any difference between the polar caps cannot be ascribed to a difference in the amount of long-term insolation received at each pole. Thus any difference between the poles, if there is one, must invoke conditions peculiar to Pluto's climate system, rather than rely on insolation alone.

  18. 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.

  19. 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.

  20. Statistical relationships between enhanced polar cap flows and PBIs

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    boundary intensifications (PBIs) are auroral intensifications along the poleward boundary of the auroral oval and occur during all levels of geomagnetic activity. However, little is known about the triggering of PBIs. Recent case studies have indicated the existence of longitudinally localized flow channels in the polar cap near, and directed toward, the nightside open-closed field line boundary just before PBIs. Motivated by these studies, we analyze 115 events of coordinated observations by the Time History of Events and Macroscale Interactions during Substorms all-sky imager and Super Dual Auroral Radar Network HF radar at Rankin Inlet to determine if this polar cap flow-PBI relationship is commonly observed. We start with isolated and intense PBIs and examine the probability of them being associated with equatorward directed polar cap flows. Our results show the association to be frequent (90%), with one-to-one correlations occurring in ~50% of events. Considering the limitations of the radar observations, this result indicates that PBIs are commonly correlated with polar cap flow channels directed toward, and then traversing, the open-closed field line boundary. The flows statistically occur ~1-2 min before the PBI initiations, and the duration and width of the flows are comparable to those of the PBIs. We also perform a reverse study by starting with isolated polar cap flows and obtain similar results. The remarkably high occurrence of association between enhanced polar cap flows and PBIs indicates that enhanced mesoscale flows within the open field line region that traverse the open-closed field line boundary are an important driver of PBI formation.

  1. 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.

  2. 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.

  3. Mars' South Polar Cap in Summer

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Simultaneous infrared and visible images taken by the camera system on NASA's Mars Odyssey spacecraft show the martian south polar cap in late summer. The black areas in the infrared image are at a temperature near -125 degrees Celsius (-193 degrees Fahrenheit) and correspond to solid carbon dioxide ice. The purple regions are areas of exposed water ice at a temperature near -95 degrees Celsius (-139degrees Fahrenheit). The warmest (red) areas are classic 'dark lanes' of frost-free soil at a temperature near -55 degrees Celsius(-67 degrees Fahrenheit). The right panel shows the same infrared image with a visible image superimposed. The infrared image is approximately 32 kilometers (20 miles) wide.

    The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the 2001 Mars Odyssey mission for NASA's Office of Space Science in 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. Additional science partners are located at the Russian Aviation and Space Agency and at Los Alamos National Laboratories, New Mexico. 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.

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

    PubMed

    Duxbury, N S; Brown, R H

    1993-08-06

    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.

  5. 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.

  6. 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.

  7. Polar cap hot patches: Enhanced density structures different from the classical patches in the ionosphere

    NASA Astrophysics Data System (ADS)

    Zhang, Q.-H.; Ma, Y.-Z.; Jayachandran, P. T.; Moen, J.; Lockwood, M.; Zhang, Y.-L.; Foster, J. C.; Zhang, S.-R.; Wang, Y.; Themens, D. R.; Zhang, B.-C.; Xing, Z. Y.

    2017-08-01

    Based on in situ and ground-based observations, a new type of "polar cap hot patch" has been identified that is different from the classical polar cap enhanced density structure (cold patches). Comparing with the classical polar cap patches, which are transported from the dayside sunlit region with dense and cold plasma, the polar cap hot patches are associated with particle precipitations (therefore field-aligned currents), ion upflows, and flow shears. The hot patches may have the same order of density enhancement as classical patches in the topside ionosphere, suggesting that the hot patches may be produced by transported photoionization plasma into flow channels. Within the flow channels, the hot patches have low-energy particle precipitation and/or ion upflows associated with field-aligned currents and flow shears. Corresponding Global Navigation Satellite System (GNSS) signal scintillation measurements indicate that hot patches may produce slightly stronger radio signal scintillation in the polar cap region than classical patches. A new type of polar cap patches, "polar cap hot patches," is identified to differentiate enhanced density structures from classical patches. Hot patches are associated with particle precipitations, ion upflows, field-aligned currents, and shear flows in the polar cap. Hot patches may lead to slightly stronger ionospheric scintillations of GNSS signals in the polar cap region than classical patches.

  8. Quantifying Solar Wind-Polar Cap Interactions

    NASA Astrophysics Data System (ADS)

    Urban, K. D.; Gerrard, A. J.; Lanzerotti, L. J.; Weatherwax, A. T.; Huang, Y.

    2015-12-01

    It is well known that the solar wind is a major driver of ultra-low frequency [ULF] power at ground locations from low to high latitudes. However, due to the scarcity of deep polar cap magnetometer sites, it is not clear when, where, or if this is true deep inside the polar cap on open field lines where interplanetary magnetic field [IMF] ULF waves could possibly be directly detected. Given recent observations of very large Joule heating estimates from DMSP data, together with the large heating reported by the CHAMP satellite, it is important to understand the degree to which ULF waves in the solar wind can directly cause such heating. Using a time series of lagged correlation sequences ("dynamic correlograms") between GSM Bz ULF power (computed via data obtained from NASA's Advanced Composition Explorer [ACE] ahead of Earth in the solar wind) and the horizontal ULF power (H^2=N^2+E^2) from ground-based magnetometers in Earth's southern polar cap, we investigate the direct penetration of ULF waves from the solar wind into the polar ionosphere during a gamut of space weather conditions at a distributed network of Automated Geophysical Observatories [AGOs] in Antarctica. To infer causation, a predicted lag correlation maximum at each time step is computed by simply dividing the associated distance of ACE from Earth by the concurrent bulk solar wind speed. This technique helps parse out direct penetration of solar wind ULF waves from other sources (e.g., via leakage from closed field line resonances due to the bulk solar wind plasma viscously interacting at dawn/dusk flanks inducing Kelvin-Helmholtz instabilities [KHI] or compressional modes induced by impulses in solar wind dynamic pressure). The identified direct-penetrating ULF waves are related to the DMSP-derived Poynting fluxes by regression analysis, and conclusions are drawn for the importance of the ULF source for the measured heating.

  9. 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.

  10. Properties of electric turbulence in the polar cap ionosphere

    NASA Astrophysics Data System (ADS)

    Golovchanskaya, I. V.; Kozelov, B. V.

    2010-10-01

    Small-scale (scales of ˜0.5-256 km) electric fields in the polar cap ionosphere are studied on the basis of measurements of the Dynamics Explorer 2 (DE-2) low-altitude satellite with a polar orbit. Nineteen DE-2 passes through the high-latitude ionosphere from the morning side to the evening side are considered when the IMF z component was southward. A rather extensive polar cap, which could be identified using the ɛ- t spectrograms of precipitating particles with auroral energies, was formed during the analyzed events. It is shown that the logarithmic diagrams (LDs), constructed using the discrete wavelet transform of electric fields in the polar cap, are power law (μ ˜ s α). Here, μ is the variance of the detail coefficients of the signal discrete wavelet transform, s is the wavelet scale, and index α characterizes the LD slope. The probability density functions P(δ E, s) of the electric field fluctuations δ E observed on different scales s are non-Gaussian and have intensified wings. When the probability density functions are renormalized, that is constructed of δ E/ s γ, where γ is the scaling exponent, they lie near a single curve, which indicates that the studied fields are statistically self-similar. In spite of the fact that the amplitude of electric fluctuations in the polar cap is much smaller than in the auroral zone, the quantitative characteristics of field scaling in the two regions are similar. Two possible causes of the observed turbulent structure of the electric field in the polar cap are considered: (1) the structure is transferred from the solar wind, which is known to have turbulent properties, and (2) the structure is generated by convection velocity shears in the region of open magnetic field lines. The detected dependence of the characteristic distribution of turbulent electric fields over the polar cap region on IMF B y and the correlation of the rms amplitudes of δ E fluctuations with IMF B z and the solar wind transfer

  11. Martian South Polar Cap Close-Up

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This picture, illuminated by sunlight coming from the upper left, shows some of the variety of surface textures observed on the south polar residual cap. Here, the upper surface is dotted with a combination of polygonal patterns created by shallow troughs and large, almost circular pits formed by collapse. No one knows exactly how the large arcuate and circular pits are formed, but they appear to result from collapse which means that something underneath these pits has been removed. Alternatively, the ice that makes up much of the polar material has somehow become compacted, allowing the surface to sag and create pits.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of the south polar cap surface was obtained during southern spring on November 3, 1999. Located near 87.0oS, 5.9oW, this view covers 3 by 3 kilometers (1.9 x 1.9 miles) at 1.5 meters per pixel. The pits are only a few meters deep, at most, as determined by measuring shadows cast in them.

    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.

  12. Martian South Polar Cap Close-Up

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This picture, illuminated by sunlight coming from the upper left, shows some of the variety of surface textures observed on the south polar residual cap. Here, the upper surface is dotted with a combination of polygonal patterns created by shallow troughs and large, almost circular pits formed by collapse. No one knows exactly how the large arcuate and circular pits are formed, but they appear to result from collapse which means that something underneath these pits has been removed. Alternatively, the ice that makes up much of the polar material has somehow become compacted, allowing the surface to sag and create pits.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of the south polar cap surface was obtained during southern spring on November 3, 1999. Located near 87.0oS, 5.9oW, this view covers 3 by 3 kilometers (1.9 x 1.9 miles) at 1.5 meters per pixel. The pits are only a few meters deep, at most, as determined by measuring shadows cast in them.

    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.

  13. North Polar Cap Layers and Ledges

    NASA Image and Video Library

    2016-08-24

    At the edge of Mars' permanent North Polar cap, we see an exposure of the internal layers, each with a different mix of water ice, dust and dirt. These layers are believed to correspond to different climate conditions over the past tens of thousands of years. When we zoom in closer, we see that the distinct layers erode differently. Some are stronger and more resistant to erosion, others only weakly cemented. The strong layers form ledges. http://photojournal.jpl.nasa.gov/catalog/PIA21022

  14. 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

  15. Global Observation of Substorm Growth Phase Processes in the Polar Caps

    NASA Technical Reports Server (NTRS)

    Brittnacher, M.; OFillingim, M. O.; Chua, D.; Wilber, M.; Parks, G. K.; Germany, G. A.; Spann, J. F.

    1998-01-01

    Global images of the polar cap region during the substorm growth phase by the Polar Ultraviolet Imager reveals evidence of the processes which are not completely explained by current models. In particular, it was found that size of the polar cap region increases during the growth phase even if the interplanetary magnetic field has no southward component. Three phenomena were observed to produce an increase in the size of the polar cap: (1) motion of the auroral oval to lower latitude, (2) thinning of the auroral oval, and (3) reduction of intense aurora[ precipitation in the polar region. Correlation of image intensities with in situ particle measurements from the FAST satellite are being conducted to study the three growth phase phenomena; and to help identify the source regions of the particles, the mechanisms involved in producing the auroral structures and what may be reducing the polar cap precipitation during the substorm growth phase.

  16. 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.

  17. Simultaneous Two-Station Observation of Polar Cap Thermospheric Winds

    NASA Astrophysics Data System (ADS)

    Wu, Q.; Ward, W. E.

    2015-12-01

    Over the years, three different ground based stations inside the northern polar cap observed thermospheric winds, however, they did not overlap with each others. Consequently, the polar cap observations had only one station observation at a time. A single station observation is far from ideal to represent the thermospheric wind in the polar cap. In Nov 2014, for the first time, two Fabry-Perot interferometers started simultaneous observations in the polar cap. The Eureka (80N, 86W) and Resolute (75N, 95W) FPIs made near continuous observation during the winter season of the 2014. The observational results from these two instruments are compared. NCAR TIEGCM simulations with different polar cap ion convection drivers are used to examine the similarities and differences between the two stations. The results can provide more insight of the polar cap thermospheric dynamics and better interpretation of historical data for long-term trend studies.

  18. 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.

  19. Polar cap patch transportation beyond the classic scenario

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-He; Moen, Jøran; Lockwood, Michael; McCrea, Ian; Zhang, Bei-Chen; McWilliams, Kathryn A.; Zong, Qiu-Gang; Zhang, Shun-Rong; Ruohoniemi, J. Michael; Thomas, Evan G.; Dunlop, Malcolm W.; Liu, Rui-Yuan; Yang, Hui-Gen; Hu, Hong-Qiao; Lester, Mark

    2016-09-01

    We report the continuous monitoring of a polar cap patch, encompassing its creation, and a subsequent evolution that differs from the classic behavior. The patch was formed from the storm-enhanced density plume, by segmentation associated with a subauroral polarization stream generated by a substorm. Its initial antisunward motion was halted due to a rapidly changing of interplanetary magnetic field (IMF) conditions from strong southward to strong eastward with weaker northward components, and the patch subsequently very slowly evolved behind the duskside of a lobe reverse convection cell in afternoon sectors, associated with high-latitude lobe reconnection, much of it fading rapidly due to an enhancement of the ionization recombination rate. This differs from the classic scenario where polar cap patches are transported across the polar cap along the streamlines of twin-cell convection pattern from day to night. This observation provides us new important insights into patch formation and control by the IMF, which has to be taken into account in F region transport models and space weather forecasts.

  20. Ozone depletion over the polar caps caused by solar protons

    SciTech Connect

    Stephenson, J.A.E.; Scourfield, M.W.J. )

    1992-12-24

    Energetic solar protons are a natural source of ozone depletion due to nitric oxides they produce in the earth's atmosphere. In March 1989, following a period of intense solar activity, the TOMS instrument aboard the Nimbus 7 satellite recorded very similar ozone losses over both polar caps for areas extending from 90[degrees] to 70[degrees]. Ozone depletions of 7.4 [times] 10[sup 9] kg for the south polar cap and 8.0 [times] 10[sup 9] kg for the north polar cap indicate the degree of symmetry over the polar caps. 11 refs., 6 figs.

  1. Martian North Polar Cap on September 12, 1998 (color)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Mars Global Surveyor's Mars Orbiter Camera obtained its last SPO-2 images of Mars on September 12, 1998. SPO-2, or 'Science Phasing Orbit-2', took place between early June and mid-September 1998. Shown above are MOC wide angle (red and blue band) images of the martian north polar region obtained around 3:15 a.m. PDT on September 12, 1998. This color composite was made using red and blue wide angle MOC images 55001 and 55002--these were the last pictures taken of the planet until the camera resumes its work in late-March 1999.

    The north polar layered deposits, a terrain believed composed of ice and dust deposited over millions of years, dominates this view. The swirled pattern in the images above are channels eroded into this deposit. The pattern is accentuated by the illumination and seasonal frost differences that arise on sun-facing slopes during the summer. The permanent portion of the north polar cap covers most of the region with a layer of ice of unknown thickness.

    At the time this picture was obtained, the martian northern hemisphere was in the midst of the early Spring season. The margin of the seasonal carbon dioxide frost cap was at about 67o N, so the ground throughout this image is covered by frost. The frost appears pink rather than white; this may result from textural changes in the frost as it sublimes or because the frost is contaminated by a small amount of reddish martian dust. Please note that these pictures have not been 'calibrated' and so the colors are not necessarily accurately portrayed.

    In addition to the north polar cap, the pictures also show some clouds (bluish-white wisps). Some of the clouds on the right side of the images are long, linear features that cast similar long, dark shadows on the ground beneath them.

    When the MOC resumes imaging of Mars in March 1999, summer will have arrived in the north polar regions and the area surrounding the permanent polar cap will appear much darker than it does here. The dark features

  2. Simulations of the seasonal polar caps on Mars

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1992-01-01

    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 (Kieffer et al., Science, 194, 1341, 1976), but was primarily carbon dioxide ice in the Southern Hemisphere (Kieffer, J. Geophys. Res., 84, 8263, 1979). 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 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. It is shown here how the radiative effects of ozone, clouds, and 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. The combination of the effects of solar zenith angle on albedo and the radiative effects of clouds and dust act to extend the lifetime of CO2 ice on the south pole relatively more than on the north pole, possibly explaining the hemispherical asymmetry in the residual polar caps without the need of a hemispherical asymmetry in polar cap albedo. This does not imply

  3. 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

  4. 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.

  5. Wind erosion in the Martian polar regions.

    NASA Technical Reports Server (NTRS)

    Cutts, J. A.

    1973-01-01

    Wind erosion may have played a dominant role in sculpturing the terrains of the polar regions of Mars. Many topographic features of the pitted terrain and the laminated terrain are consistently aligned with wind directions inferred from albedo markings. Cold air outflow from the polar cap veering to the west as a result of the coriolis force may account for the observed alignments. The remarkable pseudocircular and spiral features that underlie the residual frost caps in both polar regions may have been formed by the more complex circulation patterns of the inner polar zone.

  6. Possible Composition of Martian Polar Caps and Controls on Ice-Cap Behavior

    NASA Astrophysics Data System (ADS)

    Kargel, J. S.

    1998-01-01

    David Fisher asked "if martian polar caps flow." Are martian polar caps akin to Earth's polar glacial ice sheets, or are they immobile? Though certain dynamical differences are obvious, it is unknown whether similarities in ice tectonics may also exist. The question bears not only on modem martian polar processes, but perhaps on hypothesized glacial processes elsewhere on Mars in the geologic past. The rheological properties and tectonics of martian polar caps also pertain to the possibility that liquids may have existed beneath the polar caps in the past, or even now, and to prospects for life in possible lakes beneath the ice caps. The cold martian polar surface temperatures and the lower martian gravity suggest a reduced propensity of martian polar ice deposits to deform under their own weight. The greater accumulation timescales of the martian polar caps compared to Earth's also mean that more time has been available for accumulated deformation, possibly offsetting the effects of colder temperatures and lower gravity on Mars. Further complicating our understanding is that the martian polar caps may not be made purely of ordinary water ice - CO2 is another possible major constituent; the rheological and melting behavior may be very different from what we are accustomed to dealing with on Earth.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. What the Polar Cap Tells Us about the Substorm Growth Phase

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    The polar cap region in the 30 to 60 minute period prior to the onset of the auroral substorm has been examined using global images from the Polar Ultraviolet Imager (UVI) to look for observational evidence of processes related to the substorm growth phase. In particular, the area of the polar cap has been measured to determine changes in its size in relation to the orientation of the interplanetary magnetic field (IMF). It was found that the size of the polar cap region increases during the growth phase even if the IMF has no southward component. Three phenomena have been observed to produce the increase in the size of the polar cap: (1) motion of the auroral oval to lower latitude, (2) thinning of the auroral oval, and (3) reduction of intense auroral precipitation in the polar cap region. The first phenomenon has been considered to be a result of the growth of the tail lobe magnetic field and the second is related to the thinning of the plasma sheet. Both of these have been supported by in situ observational evidence and are consistent with current models of substorm development. However, the third phenomenon appears to be unrelated to the first two and does not appear to be the result of opening of the polar cap flux tubes to the solar wind IMF. This reduction of auroral precipitation provides evidence of a growth phase process, or change in auroral precipitation processes, that is not explained by current substorm models.

  13. Dynamics of the Auroral Luminosity Boundary of the Polar Cap During Substorms

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The area of the polar cap during substorms has been measured using images from the Polar Ultraviolet Imager (UVI) for different interplanetary magnetic field (IMF) conditions. Changes in the poleward boundary of auroral luminosity have been analyzed in relation to substorm phase and IMF orientation. Reconnection models of flux transport into the polar cap during the substorm growth phase, and loss from the polar cap during the expansion phase, provide a framework by which these UVI observations can be analyzed. By comparison of the observations with the model predictions we can determine to what extent these models accurately predict the polar cap dynamics, and also where anomalous behavior calls for a new understanding of the dynamics beyond what these models provide. It was found that the polar cap boundary near noon and midnight usually shifted down in latitude by 1-2 degrees and 3-4 degrees respectively, increasing the area of the polar cap during the substorm growth phase as predicted. However, this growth phase phenomenon also unexpectedly occurs independently of the IMF Bz component, as shown for a substorm on January 9, 1997. The polar cap area also increased due to motion of the dawn and dusk aurora to lower latitudes, although the latitudinal shifts were asymmetric, not always concurrent, and continued well into the substorm expansion phase. The polar cap area decreased immediately following the expansion phase due to the poleward motion of the aurora on the nightside, consistent with the model prediction. What is not explained by the models is that the poleward auroral boundary in the nightside region sometimes reached very high latitudes (greater than 80 degrees MLat) greatly decreasing the polar cap area, independent of the magnitude of the substorm.

  14. Simultaneous polar cap and magnetotail observations of intense polar rain. [precipitation of low-energy electrons

    NASA Technical Reports Server (NTRS)

    Greenspan, M. E.; Meng, C.-I.; Fairfield, D. H.

    1986-01-01

    The significance of acceleration processes in accounting for the energies and temperatures of the electrons seen during periods of intense polar rain is investigated along with the role of the IMF and solar wind in controlling the polar rain. Evidence for an acceleration region is sought by comparing DMSP observations of the precipitating electrons over the polar cap with simultaneous ISEE 1 electron measurements in the conjugate tail lobe at distances between 10 and 22.6 earth radii. The second question is explored by examining the solar wind and IMF conditions during which the intense polar rain events occur. It is found that intense polar rain can pass through the tail lobes without undergoing acceleration between 22.6 earth radii and 800 km altitude.

  15. Solar wind control of the polar-cap voltage

    NASA Technical Reports Server (NTRS)

    Reiff, Patricia H.; Luhmann, Janet G.

    1986-01-01

    The results of using various models to predict polar-cap potentials are reviewed. Quantitative predictions of merging rate, and hence of polar-cap voltage, based on subsolar merging models are reviewed, and tests of dayside merging models and their results are reexamined. Predictions and tests of cusp merging models are discussed. Two new empirical formulas for the dependence of the asymptotic polar-cap potential on the IMF are presented, and predictions of the dependence of dayside and lobe merging voltages on the IMF are derived from the antiparallel merging hypothesis.

  16. 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.

  17. Polar cap electron densities from DE 1 plasma wave observations

    NASA Technical Reports Server (NTRS)

    Persoon, A. M.; Gurnett, D. A.; Shawhan, S. D.

    1983-01-01

    Electric-field-spectum measurements from the plasma-wave instrument on the Dynamics Explorer 1 spacecraft are used to study the local electron density at high altitudes in the northern polar-cap region. The electron density is determined from the upper cutoff of whistler-mode radiation at the electron plasma frequency. Median density values over the polar cap at L greater than 10 are found to vary from 35.2 + or - 8.5 cu cm at 2.1 earth radii to 0.99 + or - 0.51 cu cm at 4.66 earth radii. The steady-state radial-outflow model is examined for consistency with the observed density profile. A power-law fit to the radial variation of the electron density yields an exponent of - 3.85 + or - 0.32, which for the radial-outflow model implies a flow velocity increasing nearly linearly with incresing radial distance. Comparison of the observed electron densities with theoretical polar-wind densities yields consistent results up to 2.8 earth radii. A comparison of the observed electron densities with low-altitude density profiles from the Alouette II and ISIS 1 spacecraft illustrates transitions in the slope of the profile at 1.16 earth radii and between 1.55 and 2.0 earth radii. The changes in the density profile suggest that changes occur in the basic radial-transport processes at these altitudes.

  18. Response of polar cap to solar wind conditions

    NASA Astrophysics Data System (ADS)

    Liou, K.; Sotirelis, T.

    2014-12-01

    The ionospheric polar cap is an optically dark area encircled by the luminous auroral oval. It is created by solar wind-magnetospheric coupling, and its size is proportional to the open magnetic flux available for nightside reconnection. One of the difficulties in the study of solar wind-magnetosphere coupling is the large spatial domain it involves. Systematic studies of the polar cap dynamics are still rare. This study addresses this issue by utilizing global auroral images, from which the polar cap area can be extracted, acquired with the Ultraviolet Imager on board the Polar satellite. In particular, we quantify the area of polar cap and correlate it with solar wind parameters. Our preliminary results clearly demonstrate, as expected, a clear relationship between the dayside polar cap area and the north-south component of the interplanetary magnetic field. Other solar wind parameters also affect the polar cap size but with a lesser degree. We will present a detailed analysis and discuss the resulting implications.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. North-south geological differences between the residual polar caps on Mars

    USGS Publications Warehouse

    Thomas, P.C.; Malin, M.C.; Edgett, K.S.; Carr, M.H.; Hartmann, W.K.; Ingersoll, A.P.; James, P.B.; Soderblom, L.A.; Veverka, J.; Sullivan, R.

    2000-01-01

    Polar processes can be sensitive indicators of global climate, and the geological features associated with polar ice caps can therefore indicate evolution of climate with time. The polar regions on Mars have distinctive morphologic and climatologic features: thick layered deposits, seasonal CO2 frost caps extending to mid latitudes, and near-polar residual frost deposits that survive the summer. The relationship of the seasonal and residual frost caps to the layered deposits has been poorly constrained, mainly by the limited spatial resolution of the available data. In particular, it has not been known if the residual caps represent simple thin frost cover or substantial geologic features. Here we show that the residual cap on the south pole is a distinct geologic unit with striking collapse and erosional topography; this is very different from the residual cap on the north pole, which grades into the underlying layered materials. These findings indicate that the differences between the caps are substantial (rather than reflecting short-lived differences in frost cover), and so support the idea of long-term asymmetry in the polar climates of Mars.

  6. North-south geological differences between the residual polar caps on Mars.

    PubMed

    Thomas, P C; Malin, M C; Edgett, K S; Carr, M H; Hartmann, W K; Ingersoll, A P; James, P B; Soderblom, L A; Veverka, J; Sullivan, R

    2000-03-09

    Polar processes can be sensitive indicators of global climate, and the geological features associated with polar ice caps can therefore indicate evolution of climate with time. The polar regions on Mars have distinctive morphologic and climatologic features: thick layered deposits, seasonal CO2 frost caps extending to mid latitudes, and near-polar residual frost deposits that survive the summer. The relationship of the seasonal and residual frost caps to the layered deposits has been poorly constrained, mainly by the limited spatial resolution of the available data. In particular, it has not been known if the residual caps represent simple thin frost cover or substantial geologic features. Here we show that the residual cap on the south pole is a distinct geologic unit with striking collapse and erosional topography; this is very different from the residual cap on the north pole, which grades into the underlying layered materials. These findings indicate that the differences between the caps are substantial (rather than reflecting short-lived differences in frost cover), and so support the idea of long-term asymmetry in the polar climates of Mars.

  7. 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.

  8. 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).

  9. Mercury's South Polar Region

    NASA Image and Video Library

    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...

  10. Improving the twilight model for polar cap absorption nowcasts

    NASA Astrophysics Data System (ADS)

    Rogers, N. C.; Kero, A.; Honary, F.; Verronen, P. T.; Warrington, E. M.; Danskin, D. W.

    2016-11-01

    During solar proton events (SPE), energetic protons ionize the polar mesosphere causing HF radio wave attenuation, more strongly on the dayside where the effective recombination coefficient, αeff, is low. Polar cap absorption models predict the 30 MHz cosmic noise absorption, A, measured by riometers, based on real-time measurements of the integrated proton flux-energy spectrum, J. However, empirical models in common use cannot account for regional and day-to-day variations in the daytime and nighttime profiles of αeff(z) or the related sensitivity parameter, m=A>/&sqrt;J. Large prediction errors occur during twilight when m changes rapidly, and due to errors locating the rigidity cutoff latitude. Modeling the twilight change in m as a linear or Gauss error-function transition over a range of solar-zenith angles (χl < χ < χu) provides a better fit to measurements than selecting day or night αeff profiles based on the Earth-shadow height. Optimal model parameters were determined for several polar cap riometers for large SPEs in 1998-2005. The optimal χl parameter was found to be most variable, with smaller values (as low as 60°) postsunrise compared with presunset and with positive correlation between riometers over a wide area. Day and night values of m exhibited higher correlation for closely spaced riometers. A nowcast simulation is presented in which rigidity boundary latitude and twilight model parameters are optimized by assimilating age-weighted measurements from 25 riometers. The technique reduces model bias, and root-mean-square errors are reduced by up to 30% compared with a model employing no riometer data assimilation.

  11. Polar Cap Precursor of Nightside Meso-scale Auroral Enhancements

    NASA Astrophysics Data System (ADS)

    Zou, Ying

    2015-10-01

    Although the large-scale auroral oval has been well examined, what controls the occurrence of meso-scale enhanced auroras remains ambiguous. The answer is critical for forecasting ionospheric scintillation and remote-sensing magnetospheric disturbances. One important meso-scale auroral enhancement is poleward boundary intensifications (PBIs), which are intensifications along the poleward boundary of the nightside auroral oval and are produced by magnetic reconnection, a fundamental energy conversion process in the magnetosphere. This thesis is dedicated to understand when and where PBIs and the associated magnetotail reconnection occur, spontaneously or driven by external forcing, based on coordinated observations of all-sky imagers (ASIs) and radars. We found that the occurrence of PBIs is consistently accompanied with narrow and fast flows near the auroral poleward boundary in the polar cap. They occur simultaneously with or 1--2 min before PBIs near the PBI longitude, and direct equatorward toward the auroral poleward boundary. They have a duration and width comparable to those of PBIs. Although the prior flow evolution could not be obtained based on the limited radar field-of-view, a polar cap ASI can substantially expand our observing area by enabling flow tracing using airglow patches and polar cap arcs. It shows that deep in the polar cap, localized fast flows typically propagate at ˜600 m/s, persist tens of minutes to hours, and are of a few hundred km width. They appear as channels of flow enhancements that are elongated in the noon-midnight meridian, and significantly contribute to magnetic flux convection across the polar cap. The mosaic ASI images further show that as these fast flow propagate equatorward from the magnetic pole and impinge on the nightside auroral poleward boundary, they are followed by intensifications within the auroral oval that are spatially connected to them and occur within a few minutes and <˜10° longitudes. Such

  12. 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.

  13. Reverse Polar Cap convection and effects on PC indices

    NASA Astrophysics Data System (ADS)

    Stauning, Peter

    2017-04-01

    The convection of magnetospheric and ionospheric plasma across the polar caps relates to properties of the solar wind, primarily the velocity (Vsw) and the sign and magnitude of the Z-component, Bz, of the Interplanetary Magnetic Field (IMF). When Bz is negative (southward) or just small in magnitude, then the convection across the polar cap is antisunward with return flows in the morning and evening sectors of the auroral oval. When IMF Bz is strong and positive (northward) then strong sunward convection may develop in the central polar cap with return flows poleward of the usual auroral oval (NBZ conditions). In addition to depending on the strength of IMF Bz, the magnitude of the reverse convection relates to the ionospheric conditions varying with local time, season and solar cycle, and also to the geomagnetic field configuration. The ionospheric convection creates oppositely directed currents that generate the magnetic variations reflected in the Polar Cap (PC) indices. The immediate effect of reverse convection is to give negative values of the PC index. However, inclusion of reverse convection events in the data base used to derive the index coefficients has adverse consequences for the quality of the PC index. The presentation shall illustrate the properties of reverse polar cap convection and discuss the differing effects on the Northern (PCN) and Southern (PCS) indices.

  14. 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.

  15. Morphology of Mars North Polar Ice Cap

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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)(exp 2)/113.6] - [(Y-y)(exp 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.

  16. Morphology of Mars North Polar Ice Cap

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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)(exp 2)/113.6] - [(Y-y)(exp 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.

  17. 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'.

  18. 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'.

  19. Spatial Distribution of Pair Production Over the Pulsar Polar Cap

    NASA Astrophysics Data System (ADS)

    Belyaev, Mikhail A.; Parfrey, Kyle

    2016-10-01

    Using an analytic, axisymmetric approach that includes general relativity, coupled to a condition for pair production deduced from simulations, we derive general results about the spatial distribution of pair-producing field lines over the pulsar polar cap. In particular, we show that pair production on magnetic field lines operates over only a fraction of the polar cap for an aligned rotator for general magnetic field configurations, assuming the magnetic field varies spatially on a scale that is larger than the size of the polar cap. We compare our result to force-free simulations of a pulsar with a dipole surface field and find excellent agreement. Our work has implications for first-principles simulations of pulsar magnetospheres and for explaining observations of pulsed radio and high-energy emission.

  20. 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

  1. The hemispherical asymmetry in the Martian polar caps

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard L.

    1993-01-01

    An energy balance model is used to study the behavior of CO2 ice on Mars. The effect of the solar zenith angle dependence of albedo is to lengthen CO2 ice lifetimes at the poles. Hemispherical asymmetries in cloud and dust abundance could result in the survival of seasonal CO2 ice through summer in the south and not in the north, in agreement with observations. CO2 ice observed in the summertime polar cap in the south could be of recent origin, although a permanent CO2 polar cap cannot be ruled out.

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. Solar illumination control of ionospheric outflow above polar cap arcs

    NASA Astrophysics Data System (ADS)

    Maes, L.; Maggiolo, R.; De Keyser, J.; Dandouras, I.; Fear, R. C.; Fontaine, D.; Haaland, S.

    2015-03-01

    We measure the flux density, composition, and energy of outflowing ions above the polar cap, accelerated by quasi-static electric fields parallel to the magnetic field and associated with polar cap arcs, using Cluster. Mapping the spacecraft position to its ionospheric foot point, we analyze the dependence of these parameters on the solar zenith angle (SZA). We find a clear transition at SZA between ˜94° and ˜107°, with the O+ flux higher above the sunlit ionosphere. This dependence on the illumination of the local ionosphere indicates that significant O+ upflow occurs locally above the polar ionosphere. The same is found for H+, but to a lesser extent. This effect can result in a seasonal variation of the total ion upflow from the polar ionosphere. Furthermore, we show that low-magnitude field-aligned potential drops are preferentially observed above the sunlit ionosphere, suggesting a feedback effect of ionospheric conductivity.

  7. Neptune South Polar Region

    NASA Image and Video Library

    1999-07-25

    This image of Neptune south polar region was obtained by NASA Voyager on Aug. 23, 1989. The smallest cloud features are 45 kilometers 28 miles in diameter. The image shows the discovery of shadows in Neptune atmosphere, shadows cast onto a deep cl

  8. 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

    2004-04-08

    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.

  9. Localized field-aligned currents in the polar cap associated with airglow patches

    NASA Astrophysics Data System (ADS)

    Zou, Ying; Nishimura, Yukitoshi; Burchill, Johnathan K.; Knudsen, David J.; Lyons, Larry R.; Shiokawa, Kazuo; Buchert, Stephan; Chen, Steve; Nicolls, Michael J.; Ruohoniemi, J. Michael; McWilliams, Kathryn A.; Nishitani, Nozomu

    2016-10-01

    Airglow patches have been recently associated with channels of enhanced antisunward ionospheric flows propagating across the polar cap from the dayside to nightside auroral ovals. However, how these flows maintain their localized nature without diffusing away remains unsolved. We examine whether patches and collocated flows are associated with localized field-aligned currents (FACs) in the polar cap by using coordinated observations of the Swarm spacecraft, a polar cap all-sky imager, and Super Dual Auroral Radar Network (SuperDARN) radars. We commonly (66% of cases) identify substantial FAC enhancements around patches, particularly near the patches' leading edge and center, in contrast to what is seen in the otherwise quiet polar cap. These FACs have densities of 0.1-0.2 μA/m-2 and have a distribution of width peaking at 75 km. They can be approximated as infinite current sheets that are orientated roughly parallel to patches. They usually exhibit a Region 1 sense, i.e., a downward FAC lying eastward of an upward FAC. With the addition of Resolute Bay Incoherent Scatter radar data, we find that the FACs can close through Pedersen currents in the ionosphere, consistent with the locally enhanced dawn-dusk electric field across the patch. Our results suggest that ionospheric polar cap flow channels are imposed by structures in the magnetospheric lobe via FACs, and thus manifest mesoscale magnetosphere-ionosphere coupling embedded in large-scale convection.

  10. 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.

  11. Observations of polar cap flow channel and plasma sheet flow bursts during substorm expansion

    NASA Astrophysics Data System (ADS)

    PitkäNen, T.; Aikio, A. T.; Juusola, L.

    2013-02-01

    We present the first simultaneous observations of an enhanced polar cap flow impinging on the nightside polar cap boundary (PCB), two flow bursts in the plasma sheet and a conjugate ionospheric flow burst within the auroral oval. The ionospheric measurements on 3 September 2006 were made by the European Incoherent Scatter (EISCAT) radars and the magnetospheric measurements by the four Cluster spacecraft. In the end of a substorm growth phase, EISCAT measured a channel of enhanced equatorward plasma flow within the polar cap, which was about 1° wide in latitude and drifted slowly equatorward. During the substorm expansion phase, the PCB started to contract poleward. The interaction between the equatorward drifting polar cap flow channel and the poleward contracting PCB took 2-3 min. During this time, the F-region electron temperature was elevated at the PCB, which is interpreted as a possible signature of an auroral poleward boundary intensification (PBI). After that, enhanced equatorward flows were measured inside the auroral oval by EISCAT. During this period, the Cluster satellites measured two fast earthward flow bursts in the plasma sheet, which were associated with dipolarizations of the magnetic field, depletions in plasma density, and return flows. We suggest that the second flow burst in the plasma sheet represents the same flow burst that is seen in the ionosphere by EISCAT and propose that the plasma sheet flow bursts were triggered by the enhanced flow structure on open polar cap field lines. The suggestion is in line with Lyons et al. (2011).

  12. 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.

  13. Reconciling different observations of the CO2 ice mass loading of the Martian north polar cap

    USGS Publications Warehouse

    Haberle, R.M.; Mattingly, B.; Titus, T.N.

    2004-01-01

    The GRS measurements of the peak mass loading of the north polar CO2 ice cap on Mars are about 60% lower than those calculated from MGS TES radiation data and those inferred from the MOLA cap thicknesses. However, the GRS data provide the most accurate measurement of the mass loading. We show that the TES and MOLA data can be reconciled with the GRS data if (1) subsurface heat conduction and atmospheric heat transport are included in the TES mass budget calculations, and (2) the density of the polar deposits is ???600 kg m-3. The latter is much less than that expected for slab ice (???1600 kg m-3) and suggests that processes unique to the north polar region are responsible for the low cap density. Copyright 2004 by the American Geophysical Union.

  14. 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.

  15. 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.

  16. 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).

  17. Mass balance processes on the north polar cap on Mars

    NASA Astrophysics Data System (ADS)

    Hvidberg, C. S.

    2003-04-01

    The permanent north polar cap is thought to consist of H2O ice with some dust and CO2 ice. The cap has formed over millions of years, and its topography at present is a result of geologic and climatic processes. A characteristic feature of the cap is a spiraling pattern of scarps and troughs organized around the pole. Horizontal or north-facing areas appear white, while the scarps expose dark layers. The alternating white polar ice and exposed layers suggest that the cap interacts with the atmosphere through deposition and sublimation processes and plays an active role in the current water cycle on Mars. The spiraling scarps and troughs are thought to be formed in a combination of sublimation, wind effects, deposition and ice flow. We use an ice sheet model to study these mechanisms, their effects and relative importance under the present climatic conditions. The characteristics suggest that the spiraling structure is a result of sublimation combined with wind effects. Ice flow alone would close the troughs within 100-1000 kyrs. Sublimation rates must exceed the flow rates and be in the order of cm/year in order to keep troughs open. We estimate the total amount of sublimation to be in the order of 10^11 to 10^12 kg per Martian year. The result indicates that the cap accounts for the observed annual input of water vapor to the northern hemisphere atmosphere.

  18. Radar scattering from venus at large angles of incidence and the question of polar ice caps.

    PubMed

    Jurgens, R F

    1968-12-20

    Spectrum analysis of radar waves backscattered from an anulus near the limb of Venus shows that a uniform scattering model applies over regions extending from the equator to within approximately 15 degrees of the poles. These observations indicate that large polar ice caps extending to latitudes as low as 60 degrees are very unlikely.

  19. On the Symmetry of Ionospheric Polar Cap Patch Exits Around Magnetic Midnight

    NASA Astrophysics Data System (ADS)

    Moen, J. I.; Hosokawa, K.; Gulbrandsen, N.; Clausen, L.

    2014-12-01

    We present continuous observations of polar cap patches exiting the polar cap ionosphere into the night time auoral oval. Satellite images of the auroral oval and all-sky camera observations of 630.0 nm airglow patches superimposed onto SuperDARN convection maps, reveals a detailed picture on how patches exiting the polar cap and return to the dayside at night, on both the dusk convection cell and the dawn convection cell. We also present eight years of statistics demonstrating that the MLT distribution of patch exits are marginally affected by the IMF BY polarity 3-4 hours around midnight. Synthesizing our observations with previous results there are two, possibly related, explanations to why patches populate both convection cells almost symmetrically. i) Intake of patch material occur on both convection cells for both IMF BY polarities. ii) According to the patch formation model by Lockwood and Carlson et al. [1992] the excitation of flow associated with transient dayside reconnection produces cigar-shaped patches stretching across both the morning and the evening convection cells. Applying the dynamic polar cap flow model by Cowley and Lockwood [1992], we suggest that dawn-dusk elongated patches may be torn apart at night when they are grabbed by transient tail reconnection. The associated twin cell flow disturbance expanding from the reconnection region will divert plasma towards dawn and dusk. This may explain the observed exits on both convection cells.

  20. 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.

  1. F layer ionization patches in the polar cap

    NASA Technical Reports Server (NTRS)

    Weber, E. J.; Buchau, J.; Moore, J. G.; Sharber, J. R.; Livingston, R. C.; Winningham, J. D.; Reinisch, B. W.

    1984-01-01

    Ground-based optical and digital ionosonde measurements were conducted at Thule, Greenland to measure ionospheric structure and dynamics in the nighttime polar cap F layer. These observations showed the existence of large-scale (800-1000 km) plasma patches drifting in the antisunward direction during a moderately disturbed (Kp greater than or equal to 4) period. Simultaneous Dynamics Explorer (DE-B) low-altitude plasma instrument (LAPI) measurements show that these patches with peak densities of about 10 to the 6th el per cu cm are not locally produced by structured particle precipitation. The LAPI measurements show a uniform precipitation of polar rain electrons over the polar cap. The combined measurements provide a comprehensive description of patch structure and dynamics. They are produced near or equatorward of the dayside auroral zone and convect across the polar cap in the antisunward direction. Gradients within the large scale, drifting patches are subject to structuring by convective instabilities. UHF scintillation and spaced receiver measurements are used to map the resulting irregularity distribution within the patches.

  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. Rethinking the polar cap: Eccentric dipole structuring of ULF power at the highest corrected geomagnetic latitudes

    NASA Astrophysics Data System (ADS)

    Urban, Kevin D.; Gerrard, Andrew J.; Lanzerotti, Louis J.; Weatherwax, Allan T.

    2016-09-01

    The day-to-day evolution and statistical features of Pc3-Pc7 band ultralow frequency (ULF) power throughout the southern polar cap suggest that the corrected geomagnetic (CGM) coordinates do not adequately organize the observed hydromagnetic spatial structure. It is shown that that the local-time distribution of ULF power at sites along CGM latitudinal parallels exhibit fundamental differences and that the CGM latitude of a site in general is not indicative of the site's projection into the magnetosphere. Thus, ULF characteristics observed at a single site in the polar cap cannot be freely generalized to other sites of similar CGM latitude but separated in magnetic local time, and the inadequacy of CGM coordinates in the polar cap has implications for conjugacy/mapping studies in general. In seeking alternative, observationally motivated systems of "polar cap latitudes," it is found that eccentric dipole (ED) coordinates have several strengths in organizing the hydromagnetic spatial structure in the polar cap region. ED latitudes appear to better classify the local-time ULF power in both magnitude and morphology and better differentiate the "deep polar cap" (where the ULF power is largely UT dependent and nearly free of local-time structure) from the "peripheral polar cap" (where near-magnetic noon pulsations dominate at lower and lower frequencies as one increases in ED latitude). Eccentric local time is shown to better align the local-time profiles in the magnetic east component over several PcX bands but worsen in the magnetic north component. It is suggested that a hybrid ED-CGM coordinate system might capture the strengths of both CGM and ED coordinates. It is shown that the local-time morphology of median ULF power at high-latitude sites is dominantly driven by where they project into the magnetosphere, which is best quantified by their proximity to the low-altitude cusp on the dayside (which is not necessarily quantified by a site's CGM latitude), and that

  4. F-Layer Polar Cap Arcs.

    DTIC Science & Technology

    1987-09-01

    IONOSPHERE .... ......... 9 B. PRODUCTION AND LOSS IN THE D, E, AND Ft REGIONS 9 C. THE F2 LAYER ........ ................. I1 D. THE HIGH LATITUDE...1000" kilometers. Ionospheric behavior is governed by processes which result in the production /destruction and transport of ionization; different...radiation--a production mechanism--is deposited according to the absorption characteristics of the atmospheric constituents; (b) recombination--a

  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. Correlation of solar energetic protons and polar cap absorption

    NASA Astrophysics Data System (ADS)

    Patterson, J. D.; Armstrong, T. P.; Laird, C. M.; Detrick, D. L.; Weatherwax, A. T.

    2001-01-01

    This study shows the results of a model of polar cap absorption events (PCAs) using solar energetic proton flux as an input. The proton data are recorded by the Charged Particle Measurement Experiment (CPME) on board the IMP 8 satellite and are collected by the Applied Physics Laboratory at Johns Hopkins University. The IMP 8 satellite orbits the Earth at distances between 30 and 35 Earth radii, which places it in the solar energetic particle environment throughout most of its orbit. It has been shown in previous studies that these solar energetic particles have direct and immediate access to the polar atmosphere [Reid, 1970]. Our model shows that the majority of the ionization resulting from the influx of solar energetic protons occurs in the altitude range from ~50-90 km. Excess ionization at these altitudes causes enhanced absorption of cosmic HF radio waves. The levels of absorption used for comparison in this study were measured directly by the riometer at South Pole station, Antarctica. The results show a very strong correlation between the incident proton flux and measured path-integrated cosmic HF radio noise absorption for significant events, involving absorptions greater than 1.0 dB. For absorption levels lower than this it is obvious that other phenomena dominate. For HF radio waves the primary contributors to PCA are protons with energies near 20 MeV. This study extends the correlated observations of interplanetary particles and PCA throughout a 9-year period. The close quantitative agreement between the measured and calculated values of absorption supports the validity of the assumptions and suppositions made by this model. The data also suggest a method by which the path-integrated cosmic noise absorption may be used to probe the E and D layers of the ionosphere to determine the effective ion-electron recombination coefficients within these regions.

  7. Dependence of polar cap potential drop on interplanetary parameters

    NASA Technical Reports Server (NTRS)

    Reiff, P. H.; Spiro, R. W.; Hill, T. W.

    1981-01-01

    The convection potential drop across the polar cap is computed from data obtained on high-inclination low-altitude satellites. Potential measurements are correlated with various combinations of parameters measured simultaneously in the upstream solar wind. Most of the potential drop is successfully predicted by merging theory, although a significant background potential drop of 35 kV does not depend on IMF parameters and is attributed to a process other than merging. Results indicate that small values of the IMF are amplified by a factor of 5-10 at the dayside magnetopause, which, when taken into account, improves correlations between IMF parameters and polar cap potential drop. Potential drop is better correlated with IMF parameters than with geomagnetic indices, due to nonlinear response of the magnetosphere affecting geomagnetic activity indices.

  8. 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.

  9. Mars polar cap: a habitat for elementary life1

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    Ices in the Martian polar caps are potential habitats for various species of microorganisms. Salts in the ice and biological anti-freeze polymers maintain liquid in cracks in the ices far below 0°C, possibly down to the mean 220-240 K. Sub-surface microbial life is shielded from ultraviolet (UV) radiation, but could potentially be activated on south-facing slopes under the midday, midsummer Sun. Such life would be limited by low levels of vapour, little transport of nutrients, low light levels below a protective dirt-crust, frost accumulation at night and in shadows, and little if any active translocation of organisms. As in the Antarctic and in permafrost, movement to new habitats depends on geo-climatic changes, which for Mars's north polar cap occur on a 50 000 year scale, except for rare meteorite impacts.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. Patterning instability on the Mars polar ice caps

    NASA Astrophysics Data System (ADS)

    Ng, Felix S. L.; Zuber, Maria T.

    2006-02-01

    We present a mathematical theory to study the origin of large-scale spiral troughs on the Mars residual polar caps, starting with the hypothesis that atmospheric circulation governs the planform of the troughs via an instability that operates in the flow direction of surface winds. This concept can explain why the troughs spiral at each pole in an opposite sense to that expected for Coriolis-deflected winds. The instability arises from interactions on water ice, assumed to contain dust, and depends on how the exchange of atmospheric dust and moisture (H2O) with the polar cap surface controls its albedo and mass and energy balance. Our model predicts spatial patterns to form when moisture is carried by wind over the surface, owing to unstable coupling between the albedo and the H2O-vapor pressure. The resulting albedo pattern causes an alternating ``accumulation-ablation'' mass balance, so that an undulating topography develops which resembles the (dark) troughs and their adjacent (bright) smooth terrains on the polar caps. Because the albedo patterning process is fast, whereas topographic evolution is slow, we suggest that an ancient imprint in the surface albedo preconditions today's trough morphology.

  16. First simultaneous multistation observations of the polar cap thermospheric winds

    NASA Astrophysics Data System (ADS)

    Wu, Qian; Jee, Geonhwa; Lee, Changsup; Kim, Jeong-Han; Kim, Yong Ha; Ward, William; Varney, Roger H.

    2017-01-01

    Based on two northern (Eureka 80.0°N, 85.9°W, magnetic latitude (MLAT) 88, and Resolute 74.7°N, 94.8°W, MLAT 83) and one southern (Jang Bogo 74.7°S, 164.2°E, MLAT 77) polar cap stations, simultaneous thermospheric wind data during the northern (December) and southern (June) winter months were obtained and compared with the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM) simulations driven by the Weimer ion convection model. The TIEGCM simulation overestimates the thermospheric wind by 30 to 60%. The thermospheric winds at Eureka were larger than those at Resolute probably because Eureka is at high-geomagnetic latitude. The observed ion drifts observed by Resolute Incoherent Scatter Radar North face at Resolute also show that the Weimer ion convection model overestimates the ion drift. The observation and simulation also appear to suggest that the ion convection pattern in the Weimer model may be too large. The observed thermospheric winds at Jang Bogo are smaller than the TIEGCM but mostly in the zonal component. The thermospheric winds are smaller at Jang Bogo than the two northern stations which are likely due to their lower magnetic latitude. The results indicate the presence of internal structure in the thermospheric winds inside the polar cap and call for more observations in the polar cap to be undertaken.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. The Martian polar cap - Radiative effects of ozone, clouds, and airborne dust

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee

    1990-01-01

    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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. On the Polar Caps of the Three Musketeers

    NASA Astrophysics Data System (ADS)

    De Luca, A.; Caraveo, P. A.; Mereghetti, S.; Negroni, M.; Bignami, G. F.

    2005-04-01

    XMM-Newton EPIC observations of PSR B0656+14, PSR B1055-52, and Geminga have substantially increased the collection of statistics available for these three isolated neutron stars, so apparently similar to deserve the nickname of the Three Musketeers, given to them by Becker & Trümper. Here we take advantage of the EPIC statistics to perform phase-resolved spectroscopy for all three objects. The phase-averaged spectrum of the Three Musketeers is best described by a three-component model. This includes two blackbody components-a cooler one, possibly originating from the bulk of the star surface, and a hotter one, coming from a smaller portion of the star surface (a ``hot spot'')-plus a power law. The relative contributions of the three components are seen to vary as a function of phase, as the stars' rotation brings into view different emitting regions. The hot spots, which have very different apparent dimensions (in spite of the similarity of the three neutron stars polar cap radii) are responsible for the bulk of the phase variation. The amplitude of the observed phase modulation is also markedly different for the three sources. Another striking aspect of our phase-resolved phenomenology is the apparent lack of any common phase alignment between the observed modulation patterns for the two blackbody components. They are seen to vary in phase in the case of PSR B1055-52 but in antiphase in the case of PSR B0656+14. These findings do not support standard and simplistic models of neutron star magnetic field configuration and surface temperature distribution. Based on observations with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the US (NASA).

  8. GPS TEC variations in the polar cap ionosphere: Solar wind and IMF dependence

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    This statistical study examines the solar wind dependence of total electron content (TEC) variations arising from mesoscale (tens to hundreds of kilometers) structuring of the polar cap ionosphere. Six years of TEC measurements were collected from five high-data rate Global Positioning System (GPS) receivers of the Canadian High Arctic Ionospheric Network (CHAIN), from which high-resolution magnetic local time-latitude maps of TEC variation occurrence rate and amplitude were created. Ionosonde radars were used to identify TEC variations arising from ionization of the E and F region ionospheres. Statistical TEC maps were examined as a function of solar wind and interplanetary magnetic field (IMF) measurements. Statistical results showed that occurrence rate of TEC variations was highest in localized dayside regions, with exact local time and latitude of peak occurrence depending primarily on the dayside coupling rate of the solar wind and magnetosphere, as well as IMF orientation and magnitude in the Y-Z plane. Occurrence of TEC variations throughout the polar cap increased with solar wind-magnetosphere coupling rate and IMF magnitude. The solar wind dependence of occurrence rate largely reflected the location and rate of dayside magnetic reconnection and subsequent particle precipitation and polar cap convection. Amplitudes of TEC variations were largest around noon and increased throughout the polar cap with increased solar wind-magnetosphere coupling rate. These statistical results improve upon the existing observational picture of the polar ionosphere and will potentially facilitate development of models and techniques for mitigating impacts of the polar ionosphere on navigation signals and communication links.

  9. Understanding the solvent polarity effects on surfactant-capped nanoparticles.

    PubMed

    Leekumjorn, Sukit; Gullapalli, Sravani; Wong, Michael S

    2012-11-01

    Understanding the molecular interactions between suspended nanoparticles (NPs) and the suspending solvent fluid may provide a useful avenue to create and to study exotic NP ensembles. This study focused on using a coarse-grained computational model to investigate the molecular interactions between oleate-capped NPs in various solvents, and to relate the results to experimental features of solvent-suspended, oleate-capped CdSe quantum dots (QDs). The QDs were modeled as a closed-shell fullerene molecule with an oleate-like ligand attached to each vertex. Solvent polarity was found to correlate to the simulation and experimental results more strongly than either dielectric constant or dipole moment. Computational results showed that the nonpolar solvents of hexane, toluene, and benzene (polarity index E(T)(N) < 0.120) kept NPs in suspension and solvated the oleate chains such that the oleate layer swelled to full extension. In contrast, as the most polar solvent tested (E(T)(N) = 1.000), water caused NPs to aggregate and precipitate. It partially solvated the oleate chains and compressed the layer to 86% of full extension. For solvents of intermediate polarity like ethanol, acetone, and chloroform, the oleate layer swelled with decreasing polarity index values, with rapid swelling occurring close to E(T)(N) = 0.307 (~50:50 vol % chloroform/acetone) below which QDs were colloidally stable. This study represents the first attempt to delineate the solvent effect on surfactant-coated NP hydrodynamic size, colloidal stability, and aggregation behavior.

  10. 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.

  11. PLANETARY SCIENCE: 'Spiders' Channel Mars Polar Ice Cap.

    PubMed

    Lovett, R A

    2000-09-15

    Scientists studying the latest high-resolution photos of the martian south polar ice cap think they may have found additional clues to its ebb and flow. These hints of the planet's bizarre atmosphere come from a new class of dramatic-looking terrain features whose dark, multilimbed, vaguely radial designs have earned them the moniker "black spiders," and another group of dusky, spreading features called "dark fans." At a recent gathering here of Mars researchers, a planetary scientist proposed that the spiders might be subsurface gas channels, visible through an unusually transparent section of the martian ice.

  12. Polar cap potential saturation: An energy conservation perspective

    NASA Astrophysics Data System (ADS)

    Liu, W. William

    2007-07-01

    In the long run, energy entering the magnetosphere from the solar wind must be balanced by energy dissipation in or escape from the system. It then follows that the Joule heating rate in the ionosphere statistically should be bounded from the upside by the solar wind energy input function (e.g., the Perrault-Akasofu parameter). We show that this energy constraint, coupled with some observationally motivated assumptions about the behavior of the auroral oval under escalating solar wind conditions, leads to the prediction of polar cap potential saturation.

  13. 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.

  14. Neptune's south polar region

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This image of Neptune's south polar region was obtained by the NASA Voyager narrow-angle camera on Aug. 23, 1989, when it was at a distance of 25 million kilometers (1.6 million miles). The smallest cloud features are 45 kilometers (28 miles) in diameter. The image shows the discovery of shadows in Neptune's atmosphere, shadows cast onto a deep cloud bank by small elevated clouds. Located at about 68 degrees south latitude, they are the first cloud shadows ever seen by the Voyager on any planet. The dark regions adjacent to the small bright clouds are believed to be shadows, because they are on the side of the cloud that is opposite to the incoming sunlight and because they lengthen in places where the sun lies closer to the horizon. Estimates of the height of these discrete clouds above the underlying cloud bank can be obtained by careful analysis of this data. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

  15. The O+ Density Trough at 5000 km Altitude in the Polar Cap

    NASA Technical Reports Server (NTRS)

    Zeng, W.; Horowitz, J. L.; Cravens, P. D.; Rich, F. J.; Moore, T. E.

    2003-01-01

    At altitudes near 5000 km over the Southern polar cap region of the terrestrial magnetospherehonosphere, the Thermal Ion Dynamics Experiment (TIDE) onboard the Polar satellite has observed O+ ion density trough regions, in which the O+ densities were at least one order of magnitude lower than the surrounding O+ densities. In the O+ demify trough regions, the estimated O+ densities were generally lower than 0.01 per cc. The boundaries between normal density level regions and the trough density regions were usually abrupt transitions. From December 1, 1997 to November 30, 1998, polar cap O+ troughs in Polar/TIDE observations occurred at a frequency of about 48%. Statistical examination of the Polar perigee observations from December 1 , 1997 to November 30, 1998 shows that the Polar perigee passes evenly covered the southern polar cap region, while the O+ density trough was always located on the nightside portion of the polar cap magnetospherehonosphere, and that invariant latitude spans of such troughs could be as large as 230 in extent. The trough occurrence displayed strong seasonal dependence; in the winter season (e.g. for July in the southern hemisphere) the O+ ion density trough occurrence frequency ranged up to 92%, while in the summer season (e.g. for January in the southern hemisphere) it decreased to as infrequent as 15%. The O+ ion density trough occurrence appeared relatively independent of the geomagnetic Kp index, and IMF Bz, By conditions. However, as suggested by the seasonal dependence, the O+ ion density trough occurrence was strongly related to the solar zenith angle (SZA). In the SZA range 500 to 1250, the trough occurrence increased monotonically with SZA. Also, case-by-case examinations of near-simultaneous O+ densities and vertical velocities observed by the DMSP satellite group orbiting at 840 km altitude indicate that the O+ density troughs observed at 5000 km altitude exhibit moderate correlation or anti-correlation with topside ionosphere

  16. The O(+) Density Trough at 5000 km Altitude in the Polar Cap

    NASA Technical Reports Server (NTRS)

    Zeng, W.; Horwitz, J. L.; Craven, P. D.; Rich, F. J.; Moore, T. E.

    2004-01-01

    At altitudes near 5000 km over the southern polar cap region of the terrestrial magnetosphere/ionosphere, the Thermal Ion Dynamics Experiment (TIDE) on board the Polar satellite has observed O(+) ion density trough regions, in which the densities were at least one order of magnitude lower than the surrounding O(+) densities. In the 0" density trough regions, the estimated O+ densities were generally lower than 0.01 per cc. The boundaries between normal density level regions and the trough density regions were usually abrupt transitions. From 1 December 1997 to 30 November 1998, polar cap O(+) troughs in Polar/TIDE observations occurred at a frequency of about 48%. Statistical examination of the Polar perigee observations from 1 December 1997 to 30 November 1998 shows that the Polar perigee passes evenly covered the southern polar cap region, while the O(+) density trough was always located on the nightside portion of the polar cap magnetosphere/ionosphere, and that invariant latitude spans of such troughs could be as large as 23 deg. in extent. The trough occurrence displayed a strong seasonal dependence; in the winter season (e.g., for July in the Southern Hemisphere) the O(+) ion density trough occurrence frequency ranged up to 92%, while in the summer season (e.g., for January in the Southern Hemisphere) it decreased to as low as 15%. Our statistical results show that the trough occurrence was generally anticorrelated with solar wind dynamic pressure in the solar wind dynamic pressure range 0.8 - 2.6 nanopascal. The O(+) ion density trough occurrence appeared relatively independent of the geomagnetic Kp index, IMF Bz, and By conditions. However, as suggested by the seasonal dependence, the O(+) ion density trough occurrence was strongly related to the solar zenith angle (SZA). In the SZA range 50 deg. to 125 deg., the trough occurrence increased monotonically with SZA. In addition, we sought to determine consistent density and velocity signatures at lower

  17. CryoScout: A Descent Through the Mars Polar Cap

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Saunders, R. S.

    2003-01-01

    CryoScout was proposed as a subsurface investigation of the stratigraphic climate record embedded in Mars North Polar cap. After landing on a gentle landscape in the midst of the mild summer season, CryoScout was to use the continuous polar sunlight to power the descent of a cryobot, a thermal probe, into the ice at a rate of about 1 m per day. CryoScout would probe deep enough into this time capsule to see the effects of planetary obliquity variations and discrete events such as dust storms or volcanic eruptions. By penetrating tens of meters of ice, the mission would explore at least one of the dominant "MOC layers" observed in exposed layered terrain.

  18. CryoScout: A Descent Through the Mars Polar Cap

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.; Saunders, R. S.

    2003-01-01

    CryoScout was proposed as a subsurface investigation of the stratigraphic climate record embedded in Mars North Polar cap. After landing on a gentle landscape in the midst of the mild summer season, CryoScout was to use the continuous polar sunlight to power the descent of a cryobot, a thermal probe, into the ice at a rate of about 1 m per day. CryoScout would probe deep enough into this time capsule to see the effects of planetary obliquity variations and discrete events such as dust storms or volcanic eruptions. By penetrating tens of meters of ice, the mission would explore at least one of the dominant "MOC layers" observed in exposed layered terrain.

  19. 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

  20. 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

  1. 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.

  2. Mars secular obliquity change due to the seasonal polar caps

    NASA Technical Reports Server (NTRS)

    Rubincam, David P.

    1992-01-01

    There is a weak positive feedback mechanism between the astronomy and meteorology of Mars. The mechanism is this: the seasonal waxing and waning polar caps cause small changes in Mars' dynamical flattening. Because the changes in flattening are out of phase with the sun, there is a net annual solar torque on the planet which increases the angle between the equatorial and orbital phanes. On the basis of Viking observations of the present climate and simple atmospheric models of past climates, these seasonal shifts of mass between the atmosphere and polar caps are capable of secularly increasing Mars' obliquity by about 1 or 2 deg since the origin of the solar system. Thus, the climate, driven largely by the axial tilt, reacts back on the planet and slightly enhances the seasons on Mars as time progresses. More sophisticated models will probably not change this result much; therefore this mechanism probably produced only minor changes in Mars' climate. It causes negligible changes in the axial tilt and climate of the earth.

  3. Mars secular obliquity change due to the seasonal polar caps

    NASA Technical Reports Server (NTRS)

    Rubincam, David P.

    1992-01-01

    There is a weak positive feedback mechanism between the astronomy and meteorology of Mars. The mechanism is this: the seasonal waxing and waning polar caps cause small changes in Mars' dynamical flattening. Because the changes in flattening are out of phase with the sun, there is a net annual solar torque on the planet which increases the angle between the equatorial and orbital phanes. On the basis of Viking observations of the present climate and simple atmospheric models of past climates, these seasonal shifts of mass between the atmosphere and polar caps are capable of secularly increasing Mars' obliquity by about 1 or 2 deg since the origin of the solar system. Thus, the climate, driven largely by the axial tilt, reacts back on the planet and slightly enhances the seasons on Mars as time progresses. More sophisticated models will probably not change this result much; therefore this mechanism probably produced only minor changes in Mars' climate. It causes negligible changes in the axial tilt and climate of the earth.

  4. Possible contemporary evaporites formation at the Martian Northern Polar Cap

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Czechowski, Leszek

    Evaporitic minerals are abundant on the surface of Mars (e.g., Wentworth et al. 2005, Velbel 2012, Clark and Van Hart 1981, Wang et al. 2006, Kuzmin et al. 2009), especially within the Circumpolar Dune Field and on the Northern Ice Cap itself (e.g., Langevin et al., 2005, Roach et al. 2007, Horgan et al. 2009, Masse et al. 2010, 2012). Most of their proposed formation mechanisms require significant amounts of liquid water and are thus not possible under current Martian conditions (Arvidson et al. 2006, Andrews-Hanna et al. 2007, Fishbaugh et al. 2007, Szynkiewicz et al. 2010). Some authors have considered the potential role of ice and ice- or snowmelt-related alteration in the weathering of Martian materials (e.g., Catling et al. 2006, Zolotov and Mironenko 2007, Niles and Michalski 2009, Masse et al. 2010). However, none of those studies discussed details of the process leading to the formation of the evaporites or the timing of the processes. The aim of this paper is to model numerically if the current radiant heating is sufficient to melt a thin layer of ice surrounding a single dust grain exposed within the south facing side of the Martian North Polar Cap trench. The results of our initial study suggest that for dust grains with basaltic properties and ice with low values of coefficient of heat conduction, and solar constant = 492 W/m2 liquid water may exist below a dust grain for up to 4 hours a sol. This suggest that contemporary evaporites formation on Martian Polar Cap is possible.

  5. Mass Balance of Mars' South Polar Residual Cap

    NASA Astrophysics Data System (ADS)

    Thomas, Peter C.; Calvin, Wendy; Haberle, Robert; James, Philip; Lee, Steven

    2014-11-01

    The mass balance of the CO2 ice south polar residual cap (SPRC) of Mars is thought to be an indicator of Mars’ climate stability. Observations of eroding pits combined with year-to-year fluctuations in extent of the cap have inspired attempts to detect any changes in Mars’ atmospheric pressure that might arise from loss or gain of cap CO2 ice [1,2 ]. The results have been ambiguous. Attempts to use imaging to measure mass balance have been limited in scope, and yielded large negative values, -20 to -34 km3/Mars yr [3,4]. We have greatly expanded the mapping of types of features in the SPRC, their erosion rates, and detection of limitations on the vertical changes in the RSPC over the last 7 - 22 Mars yr. We find a net volume balance of -7 to +3 km3 /Mars yr ( ~-0.05% to +0.02% of atmospheric mass/Mars yr). Combined with the apparent relative ages of different units within the cap, the climate fluctuations over the last 20 Mars years probably are different from changes recorded in thick unit deposition probably >100 Mars yr before present. Modest changes of dust loading for extended periods of time (Mars decades) might be important in the different ice depositional regimes. [1] Haberle, R.M., Kahre, M.A. (2010) Int. Jour. Mars Science and Exploration 5, 68-75. [2] Haberle, R.M. et al. (2013) AGU Fall Meeting Abstracts, A1906. [3] Malin, M.C., et al. (2001) Science 294, 2146-2148. [4] Blackburn, D.G., et al. (2010) Planetary and Space Science 58, 780-791.

  6. An examination of Mars' north seasonal polar cap using MGS: Composition and infrared radiation balance

    NASA Astrophysics Data System (ADS)

    Hansen, Gary B.

    2013-08-01

    A detailed analysis of data from one revolution of the Mars Global Surveyor (MGS) is presented. Approximately 80% of this revolution observes the mid-winter northern seasonal polar cap, which covers the surface to <60°N, and which is predominantly within polar night. The surface composition and temperature are determined through analysis of 6-50 μm infrared spectra from the Thermal Emission Spectrometer (TES). The infrared radiative balance, which is the entire heat balance in the polar night except for small subsurface and atmospheric advection terms, is calculated for the surface and atmospheric column. The primary constituent, CO2 ice, also dominates the infrared spectral properties by variations in its grain size and by admixtures of dust and water ice, which cause large variations in the 20-50 μm emissivity. This is modified by incomplete areal coverage, and clouds or hazes. This quantitative analysis reveals CO2 grain radii ranging from ˜100 μm in isolated areas, to 1-5 mm in more widespread regions. The water ice content varies from none to about one part per thousand by mass, with a clear increase towards the periphery of the polar cap. The dust content is typically a few parts per thousand by mass, but is as much as an order of magnitude less abundant in "cold spot" regions, where the low emissivity of pure CO2 ice is revealed. This is the first quantitative analysis of thermal spectra of the seasonal polar cap and the first to estimate water ice content. Our models show that the cold spots represent cleaner, dust-free ice rather than finer grained ice than the background. Our guess is that the dust in cold spots is hidden in the center of the CO2 frost particles rather than not present. The fringes of the cap have more dust and water ice, and become patchy, with warmer water snow filling the gaps on the night side, and warmer bare soil on the day side. A low optical depth (<1 in the visible) water ice atmospheric haze is apparent on the night side

  7. 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

  8. Mapping TES Aerobreaking Data of The Martian Polar Caps

    NASA Astrophysics Data System (ADS)

    Altunaiji, E. S.; Edwards, C. S.; Smith, M. D.; AlShamsi, M. R.; AlJanaahi, A. A.

    2016-12-01

    The purpose of this paper is to create maps of the north and south Mars polar caps using Thermal Emission Spectrometer (TES) aerobreaking surface temperature data in south and north as well as Lambert albedo data in the south. TES is an instrument on board the Mars Global Surveyor (MGS) spacecraft. It has six detectors arranged in a 2x3 array with a nominal spot size of 3 × 6 km; however, given the elliptical nature of the orbit during aerobreaking the footprint can be significantly larger (10s of km), especially over the southern hemisphere. TES is a Fourier transform infrared spectrometer designed to study the Martian surface and atmosphere using thermal infrared emission spectroscopy. It is composed of 2 separate channels, a broadband visible/near-infrared bolometer and hyperspectral thermal infrared spectrometer with a broadband thermal infrared bolometer. TES aerobraking spectra were taken between Mars Year 23, Ls=180° and Mars Year 24, Ls=30°. To determine the footprint location on the surface, geometry is calculated using the Spacecraft Planet Instrument Camera Matrix and Event (SPICE) Toolkit. These data were then binned and mapped to surface in polar stereographic projection. While some early studies focused on these data, we have expanded upon the ranges, generated time-/seasonally-binned data, and re-examined this largely underutilized set of data from TES ultimately extending the record of polar science on Mars.

  9. Sublimation and transport of water from the north residual polar cap on Mars

    NASA Technical Reports Server (NTRS)

    Haberle, Robert M.; Jakosky, Bruce M.

    1990-01-01

    The possible role of the north residual cap in the current Martian water cycle was examined using models to assess the ability of the cap to supply water to the atmosphere and the ability of the atmospheric circulation to transport it out of the polar regions to low northern latitudes. Results indicate that rather extreme circumstances would be required for the cap to provide all of the observed increase in atmospheric water, such as a combination of high surface winds, low cap emissivities, or substantial evaporation from dark material. But even if these conditions could be met, the high-latitude circulation is too localized in scale to move much water vapor out of the polar environment. Both the present calculations and the data from the Viking's Mars Atmospheric Water Detection Experiment show that about two thirds of the water appearing in the Martian northern hemisphere during summer must be supplied by other sources. It is suggested that the additional source is water desorbing from the nonpolar regolith.

  10. 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.

  11. An unusual strolling motion of polar cap patches: an implication of the influence of tail reconnection on the nightside polar cap convection

    NASA Astrophysics Data System (ADS)

    Hosokawa, K.; Moen, J. I.; Jayachandran, P. T.; Shiokawa, K.; Otsuka, Y.

    2012-04-01

    On January 12, 2005, a successive appearance of polar cap patches on the nightside was observed in the image captured by an all-sky imager (ASI) at Resolute Bay, Canada (74.73°N, 265.07°E). During the interval, the patches showed an unusual strolling motion in which their moving direction was very drastically changed twice (antisunward-dawnward-duskward). One may suspect that such changes in motion were caused by the reconfiguration of the polar cap convection due to a change in the IMF By. However, there were no remarkable variations in the sign of the IMF By in the solar wind data, which indicates that the unusual behavior of the patches was independent of the IMF-driven polar cap convection changes. Before the first change in the motion occurred, a transient bright aurora appeared in the equatorward part of the field-of-view in the dawn side. Immediately after the appearance of the transient auroral feature, the direction of the motion of the patches changed from anti-sunward to dawnward as if the patches were drawn into the aurora. After the disappearance of the aurora, the patches once almost stagnated but subsequently started to move duskward and anti-sunward. We interpret the bright auroral feature as a signature of the poleward boundary intensification (PBI), which is an ionospheric manifestation of an enhanced reconnection in the magnetotail. Accordingly, we speculate that an excited flow across the open-closed field line boundary redirected the anti-sunward polar cap convection towards the PBI and then allowed the patches to be drawn into the aurora near the polar cap boundary. This study indicates the importance of the tail reconnection as a driver of the nightside polar cap convection, resulting in the dynamical characteristics of polar cap patches; this relation may enable us to monitor the activity of the tail reconnection by using the motion of polar cap patches as an indicator.

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Stability of the Early Mars Atmosphere to Collapse into Permanent Polar Caps

    NASA Astrophysics Data System (ADS)

    Haberle, R. M.; Kahre, M. A.; Wordsworth, R.; Forget, F.

    2016-09-01

    Snowfall from CO2 ice clouds on early Mars can affect the formation of permanent polar caps. We use a GCM to study the influence of CO2 cloud microphysics on the stability of thick CO2 atmospheres against collapse into permanent polar caps.

  18. 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.

  19. 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.

  20. Polar cap field-aligned currents for southward interplanetary magnetic fields

    SciTech Connect

    Xu, D.; Kivelson, M.G.

    1994-04-01

    It has been common to suppose that polar region field-aligned currents for southward interplanetary magnetic fields (IMF) consist of two parts: region 1 and region 2 currents. It is often suggested that both of these current systems flow on closed field lines. In this pilot study the limited data available from the ISIS 2 satellite are used to examine region 1 currents with the objective of establishing whether or not they can exist partially on open field lines (i.e., inside the polar caps) for southward IMF. Magnetic field perturbations were used to identify the field-aligned currents (FACs). The absence of {ge}keV electrons but the presence of {le}200 eV electrons in the polar cap or background polar rain is considered as the signature of open field lines. On some passes, region 1 sense FACs appear to be composed of two parts. The poleward part of the current signature is accompanied by electron fluxes at energies {le}200 eV or occasionally by fluxes at background levels while the equatorward part of the interval is accompanied by electron fluxes at energies both {le}200 eV and {ge}keV. On other passes, region 1 sense currents are accompanied by both {le}200 eV and {ge}keV electron fluxes during the entire pass. The authors propose that region 1 sense FACs flow on both closed and open field lines for the first situation and on closed field lines for the second situation. In seeking to understand why region 1 currents sometimes flow only on closed field lines and sometimes flow on open as well as closed field lines, the authors suggest a control by the IMF B{sub y}. The IMF B{sub y} may also shift the region 1 currents on open field lines to one side (dawn or dusk) of the polar cap like the convection cells. Such a shift provides a consistent model of the data taken on the dayside and the authors discuss why night side observations may be different. 47 refs., 6 figs., 1 tab.

  1. Monitoring of Polar Avalanche Region

    NASA Image and Video Library

    2010-03-03

    This image from NASA Mars Reconnaissance Orbiter shows the scarp that demarcates the boundary between layered deposits covering the north polar region and the lower surrounding terrain, which includes sand dunes. Original release date March 3, 2010.

  2. 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.

  3. 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.

  4. Pulsar bi-drifting: implications for polar cap geometry

    NASA Astrophysics Data System (ADS)

    Wright, Geoff; Weltevrede, Patrick

    2017-01-01

    For many years it has been considered puzzling how pulsar radio emission, supposedly created by a circulating carousel of sub-beams, can produce the drift bands demonstrated by PSR J0815+0939, and more recently PSR B1839-04, which simultaneously drifts in opposing directions. Here, we suggest that the carousels of these pulsars, and hence their beams, are not circular but elliptical with axes tilted with respect to the fiducial plane. We show that certain relatively unusual lines of sight can cause bi-drifting to be observed, and a simulation of the two known exemplars is presented. Although bi-drifting is rare, non-circular beams may be common among pulsars and reveal themselves by having profile centroids displaced from the fiducial plane identified by polarization position angle swings. They may also result in profiles with asymmetric- and frequency-dependent component evolution. It is further suggested that the carousels may change their tilt by specific amounts and later reverse them. This may occur suddenly, accompanying a mode change (e.g. PSR B0943+10), or more gradually and short lived as in `flare' pulsars (e.g. PSR B1859+07). A range of pulsar behaviour (e.g. the shifting drift patterns of PSRs B0818-41 and B0826-34) may also be the result of non-circular carousels with varying orientation. The underlying nature of these carousels - whether they are exclusively generated by polar cap physics or driven by magnetospheric effects - is briefly discussed.

  5. "Cottage Cheese" Texture on the Martian North Polar Cap in Summer

    NASA Image and Video Library

    2000-04-24

    This image is illuminated by sunlight from the upper left. Martian Dairy Products? If parts of the south polar cap can look like swiss cheese (see "Martian "Swiss Cheese""), then parts of the north polar cap might as well look like some kind of cheese, too. This picture shows a cottage cheese-like texture on the surface of a part of the residual--summertime--north polar cap. The north polar cap surface is mostly covered by pits, cracks, small bumps and knobs. In this image, the cap surface appears bright and the floors of pits look dark. Based upon observations made by the Mariner 9 and Viking orbiters in the 1970s, the north polar residual cap is thought to contain mostly water ice because its summertime temperature is usually near the freezing point of water and water vapor was observed by the Vikings to be coming off the cap during summer. The south residual cap is different--its temperatures in summer remain cold enough to freeze carbon dioxide, and very little to no water vapor has been observed to come off the south cap in summer. The pits that have developed on the north polar cap surface are closely-spaced relative to the very different depressions in the south polar cap. The pits are estimated from the length of shadows cast in them to be less than about 2 meters (5.5 feet) deep. These pits probably develop slowly over thousands of years of successive spring and summer seasons. This picture was taken by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) during northern summer on April 5, 1999. The picture is located near 82.1°N, 329.6°W and covers an area 1.5 km wide by 3 km long (0.9 x 1.8 miles) at a resolution of 3 meters (10 ft) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA02369

  6. 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.

  7. ON THE POLAR CAP CASCADE PAIR MULTIPLICITY OF YOUNG PULSARS

    SciTech Connect

    Timokhin, A. N.; Harding, A. K.

    2015-09-10

    We study the efficiency of pair production in polar caps of young pulsars under a variety of conditions to estimate the maximum possible multiplicity of pair plasma in pulsar magnetospheres. We develop a semi-analytic model for calculation of cascade multiplicity which allows efficient exploration of the parameter space and corroborate it with direct numerical simulations. Pair creation processes are considered separately from particle acceleration in order to assess different factors affecting cascade efficiency, with acceleration of primary particles described by recent self-consistent non-stationary model of pair cascades. We argue that the most efficient cascades operate in the curvature radiation/synchrotron regime, the maximum multiplicity of pair plasma in pulsar magnetospheres is ∼few × 10{sup 5}. The multiplicity of pair plasma in magnetospheres of young energetic pulsars weakly depends on the strength of the magnetic field and the radius of curvature of magnetic field lines and has a stronger dependence on pulsar inclination angle. This result questions assumptions about very high pair plasma multiplicity in theories of pulsar wind nebulae.

  8. Prediction filters for the Dst index and the polar cap potential

    NASA Technical Reports Server (NTRS)

    Fay, R. A.; Garrity, C. R.; Mcpherron, R. L.; Bargatze, L. F.

    1986-01-01

    The technique of linear prediction filtering is used to create filters relating solar wind parameters to the Dst index and to the polar cap potential. The square root of solar wind dynamic pressure and the solar wind electric field together are found to account for nearly 70 percent of the Dst variance. The prediction filter for the polar cap potential requires the square of the solar wind velocity and the solar wind electric field as inputs. The results suggest that both polar cap potential and ring current injection are primarily controlled by the solar wind, and that substorm expansions do not play a major role in ring current injection.

  9. 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

  10. 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

  11. Constraints on the composition of the Martian south polar cap from gravity and topography

    NASA Astrophysics Data System (ADS)

    Wieczorek, M. A.

    2007-12-01

    The polar caps of Mars have long been acknowledged to be composed of unknown proportions of water ice, solid CO2 (dry ice), and dust. Gravity and topography data are here analyzed over the southern cap to place constraints on its density, and hence composition. Using a localized spectral analysis and the assumption that the polar cap is uncompensated (as attested by data obtained from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) experiment), the density of the volatile-rich south polar layered deposits is constrained to be 1175±55~kg~m-3. A maximum of about 40% dry ice by volume could be sequestered in these deposits if they were completely dust free. Alternatively, if these deposits were completely free of solid CO2, the dust content would be constrained to lie between about 10 and 20% by volume. The bulk thermal conductivity of the polar cap is not significantly affected by these maximum allowable concentrations of dust. However, even if a moderate quantity of solid CO2 were present as horizontal layers, the bulk thermal conductivity of the polar cap would be significantly reduced. Reasonable estimates of the present day heat flow of Mars predict that dry ice beneath the thicker portions of the south polar cap would have melted. Depending on the quantity of solid CO2 in these deposits today, it is even possible that water ice could melt where the cap is thickest. If independent estimates for either the dust or CO2 content of the south polar cap could be obtained, and if MARSIS data could determine whether this polar cap is presently experiencing basal melting or not, it would be possible to use these observations to place tight constraints on the present day heat flow of Mars.

  12. 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 0o to 120o longitude sector was accelerated relative to the 1997 observations after LS = 240o; 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.

  13. 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.

  14. PULSAR PAIR CASCADES IN MAGNETIC FIELDS WITH OFFSET POLAR CAPS

    SciTech Connect

    Harding, Alice K.; Muslimov, Alex G.

    2011-12-20

    Neutron star magnetic fields may have polar caps (PCs) 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} {approx} 10{sup -3} L{sub sd} for normal pulsars and L{sub pair} {approx} 10{sup -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.

  15. Multi-instrument observation of simultaneous polar cap auroras on open and closed magnetic field lines

    NASA Astrophysics Data System (ADS)

    Reidy, J. A.; Fear, R. C.; Whiter, D. K.; Lanchester, B. S.; Kavanagh, A. J.; Paxton, L. J.; Zhang, Y.; Lester, M.

    2017-04-01

    This paper presents observations of polar cap auroral features on 19 January 2008, evaluated using multiple instruments with near-simultaneous observations in both hemispheres. Analysis of the features indicates that there are at least two formation mechanisms/types of polar cap aurora occurring simultaneously on different magnetic field topologies (one on open and the other on closed magnetospheric field lines). Two high-latitude structures were observed on opposing sides of the northern hemisphere polar cap in the same time interval. The structure on the duskside was formed on closed field lines that protruded into the polar cap and was generated by the precipitation of electrons with energies varying between 2 and 11 keV consistent with an identified mechanism for the formation of transpolar arcs. However, the structure did not extend fully across to the dayside of the auroral oval but rather stayed at ˜80° magnetic latitude for a minimum duration of 40 min. Thus, this structure is an example of a "failed" transpolar arc. The structure on the dawnside of the polar cap was associated with low-energy electron precipitation (less than 1 keV) and no associated ion signatures, which is consistent with it being a common low-intensity arc formed by accelerated polar rain on open field lines. The two separate types of polar cap auroras formed during the same interval, demonstrating the complexity of the solar wind-magnetosphere coupling during the interval.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  18. Formation and eruption of Sun-aligned arcs at the polar cap-auroral oval boundary

    SciTech Connect

    Berg, G.A.; Kelley, M.C.; Mendillo, M.

    1994-09-01

    This paper reports on results from a study of the poleward edge of the auroral oval in the morning sector using a comprehensive blend of in situ and ground-based measurements. Three rockets, equipped to measure electric and magnetic fields, energetic particles, and plasma density flew into an auroral display whose dynamical features were recorded with a digital image intensified all-sky camera as well as with an incoherent scatter radar. In addition, a number of DMSP satellite measurements bracketed that launch time. Evidence is presented here that in a condition of declining magnetic activity Sun-aligned arcs are injected into the polar cap at velocities {approximately}7 km/s from locations of periodic brightening along the morningside of the auroral oval. The multipoint in situ measurements allow some separation of temporal and spatial effects and strongly suggest a poleward contraction of the convection pattern of about 0.25{degrees} INVL in 70 s. The most equatorward of the two brightest arcs studied erupted into a region which already was characterized by strong sunward convection. The most poleward, however, pushed into a region that had been convecting in an antisunward direction at velocities exceeding 1 km/s less than 2 min earlier, and it is likely that sunward convection subsequently pertained poleward of that arc as well. The authors believe that these events mark the reconfiguration of the magnetosphere into a system characterized by a smaller polar cap. 34 refs., 14 figs.

  19. Io, the South Polar Region

    NASA Image and Video Library

    1998-06-04

    This archival image mosaic from NASA Voyager 1 shows Io south polar region. The South Pole is near the terminator line between daylight and night at right center. Haemus Mons, a 10-km high 32,000 foot mountain is at bottom. http://photojournal.jpl.nasa.gov/catalog/PIA00327

  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. 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.

  2. 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.

  3. 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.

  4. Multi-instrument observation of two different types of polar cap aurora occurring simultaneously during northward IMF

    NASA Astrophysics Data System (ADS)

    Reidy, J. A.; Fear, R. C.; Lanchester, B. S.; Whiter, D. K.; Kavanagh, A. J.; Paxton, L. J.; Zhang, Y.

    2016-12-01

    Polar cap aurora are a phenomena associated with periods of northwards IMF. By studying their appearance and formation, we can gain valuable information on the configuration of Earth's magnetosphere during the less understood `quiet' periods that occur approximately half of the time. Observations of high latitude aurora from multiple instruments on 19 January 2008 are presented, including almost simultaneous observations of the northern and southern auroral regions from the Special Sensor Ultra-violet Spectrographic Imager (SSUSI) instruments on board Defence Meteorological Satellite Programme (DMSP) spacecraft F16 and F17. SuperDARN flows are also explored in both hemispheres during the event. In the northern hemisphere, two high latitude structures were seen on opposite sides of the polar cap during the same interval. The energies of the precipitating electrons above the structure on the duskside was estimated to vary between 2-11 keV using the Auroral Structure and Kinetics (ASK) instrument in conjunction with the Southampton ion chemistry model. Further analysis of this structure revealed it to be formed on closed field lines that had protruded into the polar cap, consistent with the mechanism proposed for transpolar arcs. However this structure did not cross the entire polar cap but remained, in the northern hemisphere, at approximately 80° magnetic latitude for at least 40 minutes. This protrusion is hence suggested to be an example of a `failed transpolar arc'. The structure seen on the dawnside of the northern polar cap was analysed using DMSP particle spectrograph data. It was found to be associated with electron precipitation energies lower than 1 keV and no ion signature were present. Hence it is suggested that this sun-aligned structure is consistent with the common low intensity arcs formed by accelerated polar rain. The study shows there are at least two types of high latitude aurora occurring simultaneously during northwards IMF.

  5. Geological framework of the south polar region of Mars

    USGS Publications Warehouse

    Murray, B.C.; Soderblom, L.A.; Cutts, J.A.; Sharp, R.P.; Milton, D.J.; Leighton, R.B.

    1972-01-01

    The first 4 months of Mariner 9 photography of the south polar region are discussed. Three major geological units have been recognized, separated by erosional unconformities. From oldest to youngest they are: cratered terrain, pitted plains, and laminated terrain. The latter unit is unique in occurrence to the polar region, volatiles are probably involved in its origin, and may still be present within the laminated terrain as layered ice. The residual south polar cap has been observed to survive the disappearance of the thin annual CO2 frost deposit and to last virtually unchanged in outline through the southern summer. That exposed deposit is inferred to be composed of water-ice. The residual cap appears to lie at the apex of an unusual quasi-circular structure composed of laminated terrain; a similar structure also appears to exist near the north pole. ?? 1972.

  6. Interhemispheric study of polar cap patch occurrence based on Swarm in situ data

    NASA Astrophysics Data System (ADS)

    Spicher, A.; Clausen, L. B. N.; Miloch, W. J.; Lofstad, V.; Jin, Y.; Moen, J. I.

    2017-03-01

    The Swarm satellites offer an unprecedented opportunity for improving our knowledge about polar cap patches, which are regarded as the main space weather issue in the polar caps. We present a new robust algorithm that automatically detects polar cap patches using in situ plasma density data from Swarm. For both hemispheres, we compute the spatial and seasonal distributions of the patches identified separately by Swarm A and Swarm B between December 2013 and August 2016. We show a clear seasonal dependency of patch occurrence. In the Northern Hemisphere (NH), patches are essentially a winter phenomenon, as their occurrence rate is enhanced during local winter and very low during local summer. Although not as pronounced as in the NH, the same pattern is seen for the Southern Hemisphere (SH). Furthermore, the rate of polar cap patch detection is generally higher in the SH than in the NH, especially on the dayside at about 77° magnetic latitude. Additionally, we show that in the NH the number of patches is higher in the postnoon and prenoon sectors for interplanetary magnetic field (IMF) By<0 and IMF By>0, respectively, and that this trend is mirrored in the SH, consistent with the ionospheric flow convection. Overall, our results confirm previous studies in the NH, shed more light regarding the SH, and provide further insight into polar cap patch climatology. Along with this algorithm, we provide a large data set of patches automatically detected with in situ measurements, which opens new horizons in studies of polar cap phenomena.

  7. Nonequilibrium air clathrate hydrates in Antarctic ice: a paleopiezomdter for polar ice caps.

    PubMed

    Craig, H; Shoji, H; Langway, C C

    1993-12-01

    "Craigite," the mixed-air clathrate hydrate found in polar ice caps below the depth of air-bubble stability, is a clathrate mixed crystal of approximate composition (N2O2).6H2O. Recent observations on the Byrd Station Antarctic core show that the air hydrate is present at a depth of 727 m, well above the predicted depth for the onset of hydrate stability. We propose that the air hydrate occurs some 100 m above the equilibrium phase boundary at Byrd Station because of "piezometry"--i.e., that the anomalous depth of hydrate occurrence is a relic of a previous greater equilibrium depth along the flow trajectory, followed by vertical advection of ice through the local phase-boundary depth. Flowline trajectories in the ice based on numerical models show that the required vertical displacement does indeed occur just upstream of Byrd Station. Air-hydrate piezometry can thus be used as a general parameter to study the details of ice flow in polar ice caps and the metastable persistence of the clathrate phase in regions of upwelling blue ice.

  8. Nonequilibrium air clathrate hydrates in Antarctic ice: a paleopiezomdter for polar ice caps.

    PubMed Central

    Craig, H; Shoji, H; Langway, C C

    1993-01-01

    "Craigite," the mixed-air clathrate hydrate found in polar ice caps below the depth of air-bubble stability, is a clathrate mixed crystal of approximate composition (N2O2).6H2O. Recent observations on the Byrd Station Antarctic core show that the air hydrate is present at a depth of 727 m, well above the predicted depth for the onset of hydrate stability. We propose that the air hydrate occurs some 100 m above the equilibrium phase boundary at Byrd Station because of "piezometry"--i.e., that the anomalous depth of hydrate occurrence is a relic of a previous greater equilibrium depth along the flow trajectory, followed by vertical advection of ice through the local phase-boundary depth. Flowline trajectories in the ice based on numerical models show that the required vertical displacement does indeed occur just upstream of Byrd Station. Air-hydrate piezometry can thus be used as a general parameter to study the details of ice flow in polar ice caps and the metastable persistence of the clathrate phase in regions of upwelling blue ice. Images Fig. 2 PMID:11607442

  9. 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.

  10. 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.

  11. Black carbon aerosols and the third polar ice cap

    NASA Astrophysics Data System (ADS)

    Menon, S.; Koch, D.; Beig, G.; Sahu, S.; Fasullo, J.; Orlikowski, D.

    2009-12-01

    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 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 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 ~0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is ~30%, 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.

  12. Black carbon aerosols and the third polar ice cap

    NASA Astrophysics Data System (ADS)

    Menon, S.; Koch, D.; Beig, G.; Sahu, S.; Fasullo, J.; Orlikowski, D.

    2010-05-01

    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 ~0.9% due to aerosols. The contribution of the enhanced Indian BC to this decline is ~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. Summer evolution of the north polar cap of Mars as observed by OMEGA/Mars Express.

    PubMed

    Langevin, Y; Poulet, F; Bibring, J-P; Schmitt, B; Douté, S; Gondet, B

    2005-03-11

    The Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) visible-infrared imaging spectrometer extensively observed regions of Mars with latitudes above 70 degrees N in late 2004 (heliocentric longitude from Ls 93 degrees to Ls 127 degrees ). The extent of water ice at the surface and the size of ice grains were monitored as a function of time. Bright, small-grained frost, which initially covered a large fraction of the polar cap, waned in favor of large-grained ice. In outlying regions, dominated by large-grained ice, the albedo increased over the period. Evaluating the dust content was model dependent. However, contamination of ice by dust was low.

  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. 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.

  16. 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.

  17. A case-study of the evolution of polar-cap currents and auroral electrojets during polar geomagnetic disturbances with IMS magnetometer data

    NASA Technical Reports Server (NTRS)

    Iijima, T.; Kim, J. S.; Sugiura, M.

    1984-01-01

    The development of the polar cap current and the relationship of that development to the evolution of auroral electrojets during individual polar geomagnetic disturbances is studied using 1 min average data from US-Canada IMS network stations and standard magnetograms from sites on the polar cap and in the auroral zone. It is found that even when the auroral electrojet activity is weak, polar cap currents producing fields of magnitude approximately 100-200 nT almost always exist. A normal convection current system exists quasi-persistently in the polar cap during extended quiet or weakly disturbed periods of auroral electrojet activity. After one such period, some drastic changes occur in the polar cap currents, which are followed by phases of growth, expansion, and recovery. Polar cap currents cannot all be completely ascribed to a single source mechanism.

  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. 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

  2. A polar cap absorption model optimization based on the vertical ionograms analysis

    NASA Astrophysics Data System (ADS)

    Zaalov, N. Y.; Moskaleva, E. V.

    2016-11-01

    Space weather events significantly affect the high frequency (HF) radio wave propagation. The now-casting and forecasting of HF radio wave absorption is important for the HF communication industries. This paper assimilates vertical sounding data into an absorption model to improve its performance as a now-casting tool. The approach is a modification of the algorithm elaborated by Sauer and Wilkinson, which is based on the riometer data. The optimization is focused on accounting for short timescale variation of the absorption. It should be noted that the expression of the frequency dependence of absorption induced by the energetic particle precipitation employed in Sauer and Wilkinson model is based on the riometer data at frequencies of 20, 30, and 50 MHz. The approach suggested in this paper provides an opportunity for expanding the frequency dependence of the absorption for frequencies below 10 MHz. The simulation of the vertical ionograms in the polar cap region uses a computational model designed to overcome the high frequency wave propagation problem in high latitude of the Earth. HF radio wave absorption induced by solar UV illumination, X-ray flares and energetic particles precipitation is taken into consideration in our model. The absorption caused by the energetic particle precipitation is emphasized, because the study is focused on HF wave propagation in polar cap region. A comparison of observed and simulated vertical ionograms enables the coefficients, which relate absorption (day-time and night-time) to integral proton flux to be refined. The values of these coefficients determined from evaluation of the data recorded by any reliable ionosonde are valid for absorption calculation in high-latitude region.

  3. ''Electron Conic'' Signatures observed in the nightside auroral zone and over the polar cap

    SciTech Connect

    Menietti, J.D.; Burch, J.L.

    1985-06-01

    A preliminary search of the Dynamics Explorer 1 high-altitude plasma instrument data base has yielded examples of ''electron conic'' signatures. The three example passes show an association with regions of downward electron acceleration and upward ion beams, but this is not true of all the electron conic events. The electron conic signatures are clearly discernible on energy-flux-versus-time color spectrograms as pairs of discrete vertical bands which are symmetric about a pitch angle of approximately 180/sup 0/. One of the examples is a polar cap pass with electron conic signatures observed at invariant latitudes from 84/sup 0/ to 75/sup 0/. The other two cases are nightside auroral zone passes in which the regions of detectable electron conics are spatially more confined, covering only about 1/sup 0/ in invariant latitude. The conic signatures have been found at energies that range from 50 eVpolar cap. The distribution of the electrons about a pitch angle of 180/sup 0/ is larger than expected for a loss cone feature. If the electrons conserve the first adiabatic invariant in a dipole magnetic field, and in some cases a parallel electric field, the mirroring altitude varies between about 500 km and 8000 km, which is above the atmospheric loss region. For this reason, and in analogy with the formation of ion conics, we suggest that the conic signatures are produced by heating of the electrons perpendicular to the magnetic field.

  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. 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

  6. Seasat and polar ice. [instrument package for ice cap research

    NASA Technical Reports Server (NTRS)

    Campbell, W. J.

    1974-01-01

    The instrument package for SEASAT-A possesses three tools that could give data greatly needed in ice cap research: the Compressed Pulse Radar Altimeter (CPRA), the Coherent Imaging Radar (CIR), and the Scanning Multifrequency Microwave Radiometer (SMMR). Certain problems that can be studied with each sensor are discussed.

  7. Dont Get Lost in the North Polar Ice Cap

    NASA Image and Video Library

    2014-03-05

    A bright ice cap of frozen water covers the North Pole of Mars as seen by NASA Mars Reconnaissance Orbiter. In winter, thin coverings of carbon dioxide and water frost covers this area and frosts finally disappear at end of the Martian spring season.

  8. Seasat and polar ice. [instrument package for ice cap research

    NASA Technical Reports Server (NTRS)

    Campbell, W. J.

    1974-01-01

    The instrument package for SEASAT-A possesses three tools that could give data greatly needed in ice cap research: the Compressed Pulse Radar Altimeter (CPRA), the Coherent Imaging Radar (CIR), and the Scanning Multifrequency Microwave Radiometer (SMMR). Certain problems that can be studied with each sensor are discussed.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Recent ice mass loss of outlet glaciers and ice caps in the Qaanaaq region, northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Sugiyama, S.; Tsutaki, S.; Sakakibara, D.; Jun, S.; Yoshihiko, O.; Mihiro, M.; Naoki, K.; Podolskiy, E. A.; Minowa, M.; Satoshi, M.; Takanobu, S.; Matoba, S.; Martin, F.; Genco, R.; Enomoto, H.

    2016-12-01

    The Greenland ice sheet and peripheral ice caps are rapidly losing mass. Recently, ice mass loss is increasing particularly in northwestern Greenland (e.g. Enderlin et al., GRL 2014). It is urgently important to understand the ongoing changes in this region, but observational data are sparse in northern Greenland. To quantify current ice mass loss in northwestern Greenland and better understand processes driving the mass loss, we studied outlet glaciers and ice caps in the Qaanaaq region (Fig. 1). This was a part of a Japanese integrated Arctic research project, GRENE Arctic Climate Change Research Project. Field and satellite observations were performed to quantify ice surface elevation change of outlet glaciers and ice caps (Saito et al., Polar Science 2016; Tsutaki et al., J. Glaciol. in press). Frontal position and ice speed of outlet glaciers were mapped by satellite data. We also studied processes occurring near the front of outlet glaciers to investigate interaction of the glaciers and the ocean (Ohashi et al., Polar Science in press). Our field activities include mass balance monitoring on Qaanaaq Ice Cap since 2012 (Sugiyama et al., Ann. Glaciol. 2014), integrated field observations near the calving front of Bowdoin Glacier since 2013 (Sugiyama et al., J. Glaciol. 2015; Podolskiy et al., GRL 2016), and ocean measurements in front of the glaciers. In this contribution, we present the overview of the results obtained in the GRENE project, and introduce a new project established under the framework of ArCS (Arctic Challenge for Sustainability Project).

  18. 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

  19. Regression of Martian North Polar Cap: 1990-1997 Hubble Space Telescope Observations

    NASA Astrophysics Data System (ADS)

    Cantor, Bruce A.; Wolff, Michael J.; James, Philip B.; Higgs, Eric

    1998-12-01

    Hubble Space Telescope imaging of Mars from December 13, 1990, through April 17, 1997, has resulted in the synoptic monitoring of parts of four consecutive martian north polar cap regressional cycles spanningLs= 335.65° toLs= 144.56°. The 1990-1993 observations were obtained with the Wide Field Planetary Camera 1 (WFPC1) instrument while subsequent observations from 1994 to 1997 were obtained with the improved optics of the Wide Field Planetary Camera 2 (WFPC2). Mars observations were obtained from the ultraviolet (218 nm) to the near-infrared (1042 nm), which has allowed us to constrain the effects of clouds and dust particulates on cap edge measurements. HST observations of the polar cap regressions afterLs= 0° are fairly consistent from year to year with some variations possible beforeLs= 0°. The 1991 observations atLs= 35.25° andLs= 59.88° in the longitude range 270°-280° possibly support a standstill in cap retreat at a latitude 70°N. The standstill in cap retreat reported in previous years at a latitude 67°N was not observed in 1992-1997. Comparison with previous ground-based and spacecraft observations suggests that interannual variations may be significant; they may be due to interannual atmospheric changes such as global dust storm activity. Lambert albedos of the north polar cap in red and violet bandpasses are similar to those reported before.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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).

  5. Assimilation of real-time riometer measurements into models of 30 MHz polar cap absorption

    NASA Astrophysics Data System (ADS)

    Rogers, Neil Christopher; Honary, Farideh

    2015-04-01

    Space weather events may adversely affect high frequency (HF) radio propagation, hence the ability to provide nowcasting and forecasting of HF radio absorption is key for industries that rely on HF communications. This paper presents methods of assimilating 30 MHz radio absorption measurements into two types of ionospheric polar cap absorption (PCA) model to improve their performance as nowcasting tools. Type 1 models calculate absorption as m times the square root of the flux of solar protons above an energy threshold, Et. Measurements from 14 riometers during 94 solar proton events (1995-2010) are assimilated by optimising the day and night values of m by linear regression. Further non-linear optimisations are demonstrated in which parameters such as Et are also optimised and additional terms characterise local time and seasonal variations. These optimisations reduce RMS errors by up to 36%. Type 2 models incorporate altitude profiles of electron and neutral densities and electron temperatures. Here the scale height of the effective recombination coefficient profile in the D-region is optimised by regression. Furthermore, two published models of the rigidity cut-off latitude (CL) are assessed by comparison with riometer measurements. A small improvement in performance is observed by introducing a 3-h lag in the geomagnetic index Kp in the CL models. Assimilating data from a single riometer in the polar cap reduces RMS errors below 1 dB with less than 0.2 dB bias. However, many high-latitude riometers now provide absorption measurements in near-real time and we demonstrate how these data may be assimilated by fitting a low-order spherical harmonic function to both the measurements and a PCA model with optimised parameters.

  6. 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.

  7. 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.

  8. Comparison of the North and South Polar Caps of Mars: New Observations from MOLA Data and Discussion of Some Outstanding Questions

    NASA Astrophysics Data System (ADS)

    Fishbaugh, Kathryn E.; Head, James W.

    2001-11-01

    New high-resolution data from the Mars Orbiter Laser Altimeter (MOLA) have provided detailed topographic maps for the north and south polar regions. These new data allow one to compare the overall topography and geologic histories of the two polar regions and to highlight some specific outstanding questions in Mars polar studies, following earlier comparisons using Viking and Mars Global Surveyor data. The new data show that the centers of symmetry of the polar cap deposits in map view (which include both the layered terrain and residual ice) are offset from the current rotational pole in antipodal directions. Offset in the north appears to be due to retreat of the polar materials from predominantly one direction (180° W). Lines of evidence for movement and melting in different forms (e.g., lobes in young craters, kettle-like depressions, candidate residual mantles overlying polar layered terrain, and possible eskers) have been seen at both poles. The exact timing and causes of movement and melting is yet unknown. Differences in underlying topography (large, low, flat depression in the north; broad, cratered high and edge of a large impact basin in the south) may influence the accumulation, flow, and movement of polar material and the storage and movement of meltwater. The small number of superposed craters has been interpreted to indicate a Late Amazonian age for both caps, with the southern cap being somewhat older (7-15×10 6 years) than the northern cap (<100×10 3 years). The Late Amazonian-aged caps are surrounded and underlain by Hesperian-aged material, indicating an apparent hiatus almost 3-byr in duration. This apparent hiatus in the geologic record from the Late Hesperian to Late Amazonian at both poles may be accounted for in one of three ways. (1) Polar caps are recent events in the history of Mars: This scenario requires that conditions in the Late Amazonian changed to produce environments favorable for cap formation late in the history of Mars, or

  9. Climatic variations on Mars. II - Evolution of carbon dioxide atmosphere and polar caps

    NASA Technical Reports Server (NTRS)

    Ward, W. R.; Murray, B. C.; Malin, M. C.

    1974-01-01

    The long-term variations in the atmospheric pressure and the polar cap temperature of Mars resulting from the obliquity oscillations are discussed. In performing these calculations, the assumption is made that the atmosphere is in equilibrium with perennial CO2 ice deposits at the north pole, as is proposed by Leighton and Murray (1966). If heat transport by the atmosphere is neglected, the temperature of CO2 ice at the poles ranges from about 130 K to about 160 K, the corresponding atmospheric pressure rising from a few tenths of a millibar to about 30 mbar, respectively. The neglect of atmospheric heat transport probably underestimates the peak pressure. Because the altitude of the south cap is about 2 km higher than that of the north cap, CO2 ice is unstable there and will migrate to the north cap at a rate of about 10 g/sq cm yr, the implication being that the south residual cap is water ice. A simplified model of the annual polar caps and pressure fluctuations is also presented.

  10. Recent volcano ice interaction and outburst flooding in a Mars polar cap re-entrant

    NASA Astrophysics Data System (ADS)

    Hovius, Niels; Lea-Cox, Andrew; Turowski, Jens M.

    2008-09-01

    Formation of chasms in the polar ice caps of Mars has been attributed to meltwater outburst floods, but the cause of melting has remained uncertain. In a cap re-entrant enveloping Abalos Colles, west of Casma Boreale in the north polar cap, we have found possible evidence of recent volcano-ice interaction and outburst flooding. In this paper we demonstrate that these two mechanisms can have acted together to form or expand the Abalos re-entrant. Flat-topped ridges and circular rims protruding above the ice cap surface in the re-entrant apex may be lava ridges and volcano craters, and can have caused melting of 3.3 to 7.7×10 km of ice. The surrounding cap surface appears to have subsided and the likely volume of missing ice matches the melt estimate. Outburst flooding from this area may have reached peak discharges of 0.3 to 1.5×10 ms according to scour patterns in one of the re-entrant channels. This required ponding of melt water during lava eruption and catastrophic release through a sub- or englacial melt water tunnel, the collapse of which has left a chasm in the ice cap margin. The flood features are geologically recent, and volcano-ice interaction may have occurred within the last 20,000 years.

  11. Substorms and polar cap convection: the 10 January 2004 interplanetary CME case

    NASA Astrophysics Data System (ADS)

    Andalsvik, Y.; Sandholt, P. E.; Farrugia, C. J.

    2012-01-01

    The expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal variations in the winter polar cap convection structure during substorm activity under steady interplanetary conditions. Substorm activity (electrojets and particle precipitations) is monitored by excellent ground-satellite DMSP F15 conjunctions in the dusk-premidnight sector. We take advantage of the wide latitudinal coverage of the IMAGE chain of ground magnetometers in Svalbard - Scandinavia - Russia for the purpose of monitoring magnetic deflections associated with polar cap convection and substorm electrojets. These are augmented by direct observations of polar cap convection derived from SuperDARN radars and cross-track ion drift observations during traversals of polar cap along the dusk-dawn meridian by spacecraft DMSP F13. The interval we study is characterized by moderate, stable forcing of the magnetosphere-ionosphere system (EKL = 4.0-4.5 mV m-1; cross polar cap potential (CPCP), Φ (Boyle) = 115 kV) during Earth passage of an interplanetary CME (ICME), choosing an 4-h interval where the magnetic field pointed continuously south-west (Bz < 0; By < 0). The combination of continuous monitoring of ground magnetic deflections and the F13 cross-track ion drift observations in the polar cap allows us to infer the temporal CPCP structure on time scales less than the ~10 min duration of F13 polar cap transits. We arrived at the following estimates of the dayside and nightside contributions to the CPCP (CPCP = CPCP/day + CPCP/night) under two intervals of substorm activity: CPCP/day ~110 kV; CPCP/night ~50 kV (45% CPCP increase during substorms). The temporal CPCP structure during one of the substorm cases resulted in a dawn-dusk convection asymmetry measured by DMSP F13 which

  12. Field-calibrated model of melt, refreezing, and runoff for polar ice caps: Application to Devon Ice Cap

    NASA Astrophysics Data System (ADS)

    Morris, Richard M.; Mair, Douglas W. F.; Nienow, Peter W.; Bell, Christina; Burgess, David O.; Wright, Andrew P.

    2014-09-01

    Understanding the controls on the amount of surface meltwater that refreezes, rather than becoming runoff, over polar ice masses is necessary for modeling their surface mass balance and ultimately for predicting their future contributions to global sea level change. We present a modified version of a physically based model that includes an energy balance routine and explicit calculation of near-surface meltwater refreezing capacity, to simulate the evolution of near-surface density and temperature profiles across Devon Ice Cap in Arctic Canada. Uniquely, our model is initiated and calibrated using high spatial resolution measurements of snow and firn densities across almost the entire elevation range of the ice cap for the summer of 2004 and subsequently validated with the same type of measurements obtained during the very different meteorological conditions of summer 2006. The model captures the spatial variability across the transect in bulk snowpack properties although it slightly underestimates the flow of meltwater into the firn of previous years. The percentage of meltwater that becomes runoff is similar in both years; however, the spatial pattern of this melt-runoff relationship is different in the 2 years. The model is found to be insensitive to variation in the depth of impermeable layers within the firn but is very sensitive to variation in air temperature, since the refreezing capacity of firn decreases with increasing temperature. We highlight that the sensitivity of the ice cap's surface mass balance to air temperature is itself dependent on air temperature.

  13. A Detailed Study Of Polar Cap Ionospheric Dynamics By Multi-Instrument Techniques

    DTIC Science & Technology

    2006-05-05

    measurements with a 2-dimensional field of view above the Svalbard archipelago. The coherent scattered signals from the CUTLASS radar (part of SuperDARN ...combining data from the EISCAT Svalbard radar, SuperDARN HF radars, ground-based optics, and three low-altitude polar-orbiting spacecraft. During an...convection in the polar cap. SuperDARN convection maps were retrieved from JHU/APL and used to verify that the background flow in the radar field-of

  14. 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

  15. Two-dimensional direct imaging of structuring of polar cap patches

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    A highly sensitive all-sky electron multiplier charge-coupled device airglow imager has been operative in Longyearbyen, Norway (78.1°N, 15.5°E), since October 2011. The imager obtains the 630.0 nm all-sky images with an exposure time of 4 s, which is about 10 times shorter than the conventional cooled CCD airglow imagers. This new equipment allows us to image the ongoing structuring of polar cap patches in 2-D fashion. Here we report a case in which faint undulations appeared along the trailing edge of patches propagating in the central polar cap. The separation between the fingers in the undulations was about 50-100 km and the e-folding time of their growth was ˜5 min. We suggest that the gradient-drift instability (GDI) is one of the possible generation mechanisms of the undulating structures. The reasons for this interpretation are (1) the asymmetry in the preference of structuring between the leading and trailing edges is qualitatively consistent with the GDI mechanism and (2) the linear growth rate of GDI calculated by using electron density estimates from simultaneous European Incoherent Scatter Svalbard radar observations is roughly consistent with the observed growth time of the fingers. Such "unstable polar cap patches" could be important sources of seed irregularities, which would eventually be broken down to smaller-scale density perturbations affecting the transionospheric satellite communications in the central polar cap.

  16. How Thick is the North Polar Ice Cap on Mars?

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This map shows the thickness of the north polar layered deposits on Mars as measured by the Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter.

    The Shallow Radar instrument was provided by the Italian Space Agency. Its operations are led by the University of Rome and its data are analyzed by a joint U.S.-Italian science team. JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington

  17. How Thick is the North Polar Ice Cap on Mars?

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This map shows the thickness of the north polar layered deposits on Mars as measured by the Shallow Radar instrument on NASA's Mars Reconnaissance Orbiter.

    The Shallow Radar instrument was provided by the Italian Space Agency. Its operations are led by the University of Rome and its data are analyzed by a joint U.S.-Italian science team. JPL, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington

  18. 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.

  19. 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.

  20. Method to locate the polar cap boundary in the nightside ionosphere and application to a substorm event

    NASA Astrophysics Data System (ADS)

    Aikio, A. T.; Pitkänen, T.; Kozlovsky, A.; Amm, O.

    2006-08-01

    In this paper we describe a new method to be used for the polar cap boundary (PCB) determination in the nightside ionosphere by using the EISCAT Svalbard radar (ESR) field-aligned measurements by the 42-m antenna and southward directed low-elevation measurements by the ESR 32 m antenna or northward directed low-elevation measurements by the EISCAT VHF radar at Tromsø. The method is based on increased electron temperature (Te) caused by precipitating particles on closed field lines. Since the Svalbard field-aligned measurement provides the reference polar cap Te height profile, the method can be utilised only when the PCB is located between Svalbard and the mainland. Comparison with the Polar UVI images shows that the radar-based method is generally in agreement with the PAE (poleward auroral emission) boundary from Polar UVI.

    The new technique to map the polar cap boundary was applied to a substorm event on 6 November 2002. Simultaneous measurements by the MIRACLE magnetometers enabled us to put the PCB location in the framework of ionospheric electrojets. During the substorm growth phase, the polar cap expands and the region of the westward electrojet shifts gradually more apart from the PCB. The substorm onset takes place deep within the region of closed magnetic field region, separated by about 6-7° in latitude from the PCB in the ionosphere. We interpret the observations in the framework of the near-Earth neutral line (NENL) model of substorms. After the substorm onset, the reconnection at the NENL reaches within 3 min the open-closed field line boundary and then the PCB moves poleward together with the poleward boundary of the substorm current wedge. The poleward expansion occurs in the form of individual bursts, which are separated by 2-10 min, indicating that the reconnection in the magnetotail neutral line is impulsive. The poleward expansions of the PCB are followed by latitude dispersed intensifications in the westward

  1. Examination of the relationship between riometer-derived absorption and the integral proton flux in the context of modeling polar cap absorption

    NASA Astrophysics Data System (ADS)

    Fiori, R. A. D.; Danskin, D. W.

    2016-11-01

    Energetic protons can penetrate into the ionosphere increasing ionization in the D region causing polar cap absorption that may potentially block high-frequency radio communications for transpolar flights. The protons are guided by the geomagnetic field into the high-latitude polar cap region. Riometers monitor variations in ionospheric absorption by observing the level of background cosmic radio noise. Current polar cap absorption modeling techniques are based on the linear relationship between absorption and the square root of the integral proton flux, which has previously only been demonstrated using data from a single high-latitude polar station. The proportionality constant describing this relationship is evaluated for two different polar cap absorption events occurring 7-11 March 2012 and 23 January 2012 to 1 February 2012. Examination of the proportionality constant using data from riometers distributed between 60° and 90° magnetic latitude reveals a previously unreported latitudinal dependence for data at magnetic latitudes of ≤66.8° on the dayside and ≤70.8° on the nightside. Incorporating the latitudinal dependence into the current D Region Absorption Prediction absorption model improves the agreement between measurement-derived and modeled parameters by increasing the correlation coefficient between data sets, reducing the root-mean-square error, and reducing the bias.

  2. Statistical study of the relationship between enhanced polar cap flows and PBIs

    NASA Astrophysics Data System (ADS)

    Zou, Y.; Nishimura, T.; Lyons, L. R.; Donovan, E.; Ruohoniemi, J. M.; Nishitani, N.; Sofko, G. J.

    2012-12-01

    Poleward boundary intensifications (PBIs) are auroral disturbances along the poleward boundary of the auroral oval and occur during all levels of geomagnetic activity. Using radar and all-sky imager observations, previous case studies have given evidence that longitudinally localized flow bursts in the polar cap that are directed toward the open-closed field line boundary precede PBIs. The present study analyzes a larger number of events and examines if this polar cap flow-PBI relationship is commonly observed. We use coordinated observations of THEMIS all sky imagers and Super Dual Auroral Radar Network (SuperDARN) at Rankin Inlet and mainly focus on isolated PBIs with weak preceding auroral activity and a step-like change of intensity in time. From January to March 2012, we find 19 PBIs satisfying our criteria and 17 of them were preceded by longitudinally narrow, equatorward directed flow bursts within the nightside polar cap having line-of-sight velocity >~150 m/s above the background,. Such flow enhancements were not detected for the other two events, although the flow data indicate weak enhancements >100 m/s. The flow bursts statistically occurred simultaneously with or 1-2 min before the PBI initiations, and the duration of flow bursts was comparable with that of the PBIs. We also find cases when multiple PBIs are preceded by multiple enhanced flows in the polar cap. The remarkably high occurrence of the association between enhanced polar cap flows and PBIs indicates that enhanced meso-scale flows within the open field line that traverse the open-closed field line boundary may be responsible for the formation of PBIs.

  3. 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.

  4. 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.

  5. Modeling the Seasonal South Polar Cap Sublimation Rates at Dust Storm Conditions

    NASA Technical Reports Server (NTRS)

    Bonev, B. P.; James, P. B.; Wolff, M. J.; Bjorkman, J. E.; Hansen, G. B.; Benson, J. L.

    2003-01-01

    Carbon dioxide is the principal component of the Martian atmosphere and its interaction with the polar caps forms the CO2 seasonal cycle on the planet. A significant fraction of the atmospheric constituent condenses on the surface during the polar winter and sublimes back during spring. The basic aspects of the CO2 cycle have been outlined by Leighton and Murray and a number of follow-up theoretical models ranging from energy balance to general circulation models have been used to study the physical processes involved in the cycle. This paper presents a modeling study on the seasonal south polar cap subliminiation rate under dust storm conditions. Mars Global Surveyor observations are also presented.

  6. Gravitational separation of gases and isotopes in polar ice caps.

    PubMed

    Craig, H; Horibe, Y; Sowers, T

    1988-12-23

    Atmospheric gases trapped in polar ice at the firn to ice transition layer are enriched in heavy isotopes (nitrogen-15 and oxygen-18) and in heavy gases (O(2)/N(2) and Ar/N(2) ratios) relative to the free atmosphere. The maximum enrichments observed follow patterns predicted for gravitational equilibrium at the base of the firn layer, as calculated from the depth to the transition layer and the temperature in the firn. Gas ratios exhibit both positive and negative enrichments relative to air: the negative enrichments of heavy gases are consistent with observed artifacts of vacuum stripping of gases from fractured ice and with the relative values of molecular diameters that govern capillary transport. These two models for isotopic and elemental fractionation provide a basis for understanding the initial enrichments of carbon-13 and oxygen-18 in trapped CO(2), CH(4), and O(2) in ice cores, which must be known in order to decipher ancient atmospheric isotopic ratios.

  7. 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.

  8. 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

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

    USGS Publications Warehouse

    Bass, Deborah S.; Herkenhoff, Kenneth; Paige, David 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-μm-thick layer of 50-μm-sized ice particles with 10% dust or (2) a ~14-μm-thick layer of 10-μm-sized ice particles with 50% dust.

  10. Modeling the Stability of the Large CO2 Deposits on Mars South Polar Cap

    NASA Astrophysics Data System (ADS)

    Thomason, C.; Phillips, R. J.; Mellon, M. T.

    2013-12-01

    The Mars Reconnaissance Orbiter's Shallow Radar instrument (SHARAD) revealed that the geologic unit AA3 (Tanaka et al. 2007) in Mars' South Polar Layered Deposits is composed of CO2 ice (Phillips et al. 2011). This deposit is estimated to contain ~10,000 km3 of CO2 ice, making its stability an important consideration in understanding recent climate change, as the deposit mass approaches that of the present atmosphere. Such a large mass would likely be deposited during a period of low obliquity, however different values for the emissivity and albedo of the CO2 frost can dramatically change age estimates (Armstrong et al. 2004). Previous models have focused on the stability of the South Pole Residual Cap (SPRC) where the CO2 ice is exposed to the atmosphere. AA3 however, is largely covered by the SPRC and other thinner deposits. In this research we evaluate the age and long-term stability of the AA3 deposit using standard thermal and sublimation modeling techniques. Our model incorporates diurnal and annual thermal variations that are allowed to propagate into the subsurface. In order to address the effect of the overlying layers on AA3 we take account for both surface and subsurface sublimation. Any gas produced in the subsurface is then allowed to diffuse through the overlying material. Results are compared to a variety of spacecraft observations including visible imagery and thermal measurements. Additionally, these results should help guide interpretation of SHARAD data in the AA3 region and point to locales for new observations. References: Tanaka et al. 2007, 'Recent advances in the stratigraphy of the polar regions of Mars.' Paper presented at the Seventh International Conference on Mars, Pasadena, CA, 9 to 13 July 2007, 3276. Phillips et al. 2011, Massive CO2 Ice Deposits Sequestered in the South Polar Layered Deposits of Mars, Science 332: 838-841. Armstrong et al. 2004, A 1 Gyr climate model for Mars: new orbital statistics and the importance of seasonally

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. Interannual and seasonal changes in the south seasonal polar cap of Mars: Observations from MY 28-31 using MARCI

    NASA Astrophysics Data System (ADS)

    Calvin, W. M.; Cantor, B. A.; James, P. B.

    2017-08-01

    The Mars Color Imager (MARCI) camera on the Mars Reconnaissance Orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between Mars Years (MY) and over the southern summer. We present the first analysis of this data for the southern seasonal cap evolution observed in MY 28, 29, 30 and 31 (2/2007 to 07/2013). 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. Seasonal cap retreat is similar in all years and to retreats observed in other years by both optical and thermal instruments. The cryptic terrain has a fairly consistent boundary in each year, but numerous small-scale variations occur in each MY observed. Additionally, numerous small dark deposits are identified outside the classically identified cyptic region, including Inca City and other locations not previously noted. The large water ice outlier is observed to retain seasonal frost the longest (outside the polar dome) and is also highly variable in each MY. The development of the cryptic/anti-cryptic hemispheres is inferred to occur due to albedo variations that develop after dust venting starts and may be caused by recondensation of CO2 ice on the brightest and coldest regions controlled by topographic winds. Ground ice may play a role in which regions develop cryptic terrain, as there is no elevation control on either cryptic terrain or the late season brightest deposits.

  16. Electric Field Screening with Backflow at Pulsar Polar Cap

    NASA Astrophysics Data System (ADS)

    Kisaka, Shota; Asano, Katsuaki; Terasawa, Toshio

    2016-09-01

    Recent γ-ray observations suggest that particle acceleration occurs at the outer region of the pulsar magnetosphere. The magnetic field lines in the outer acceleration region (OAR) are connected to the neutron star surface (NSS). If copious electron-positron pairs are produced near the NSS, such pairs flow into the OAR and screen the electric field there. To activate the OAR, the electromagnetic cascade due to the electric field near the NSS should be suppressed. However, since a return current is expected along the field lines through the OAR, the outflow extracted from the NSS alone cannot screen the electric field just above the NSS. In this paper, we analytically and numerically study the electric field screening at the NSS, taking into account the effects of the backflowing particles from the OAR. In certain limited cases, the electric field is screened without significant pair cascade if only ultra-relativistic particles (γ \\gg 1) flow back to the NSS. On the other hand, if electron-positron pairs with a significant number density and mildly relativistic temperature, expected to distribute in a wide region of the magnetosphere, flow back to the NSS, these particles adjust the current and charge densities so that the electric field can be screened without pair cascade. We obtain the condition needed for the number density of particles to screen the electric field at the NSS. We also find that in the ion-extracted case from the NSS, bunches of particles are ejected to the outer region quasi-periodically, which is a possible mechanism of observed radio emission.

  17. Polar cap size during 14-16 July 2000 (Bastille Day) solar coronal mass ejection event: MHD modeling and satellite imager observations

    NASA Astrophysics Data System (ADS)

    RastäTter, L.; Hesse, M.; Kuznetsova, M.; Sigwarth, J. B.; Raeder, J.; Gombosi, T. I.

    2005-07-01

    This study investigates the development of the polar cap area as simulated by global magnetohydrodynamic models of the Earth's magnetosphere during the 14-16 July 2000 (Bastille Day) event. Around 1440 UT on 15 July, a magnetic cloud hit the magnetosphere and in the following hours high levels of activity in the magnetosphere and ionosphere were driven by the frequent changes in solar wind conditions. We compare the size of the polar cap (region of open magnetic field lines) as computed with two MHD models (UCLA-GGCM and BATSRUS) with observation data obtained from the IMAGE and Polar satellites. The two models in general reproduce the changes of the polar cap size that are seen by the satellite imagers. The range of modeled polar cap sizes, however, is limited to about 50-80% of the size range seen by the imagers and the shapes of the polar caps sometimes differ considerably among the models and compared to the observations. We found that a smoothing of solar wind parameters occurs, suggesting that solar wind inputs are stored in the magnetospheric system over a certain "memory" timescale. Cross-correlations are computed between smoothed solar wind input and the time history of the resulting polar cap size. Modeled magnetospheric "memory" timescales are estimated to be less than 12 min, whereas the satellite image data suggest a timescale of more than 20 min. The driver of magnetospheric activity in the models was found to be the Bz (north-south) component of the solar wind magnetic field and to a lesser degree, the Akasofu ɛ parameter which is closely related to Bz but is also influenced by the solar wind velocity Vx and magnetic field By. N, Vx, and Pdyn ∝ NVx2 show some degree of anticorrelation with observed polar cap sizes, but anticorrelations are barely significant for polar caps computed from either model. Memory timescales and reaction time delays could be derived from some of the parameters within the limits of statistical significance of the

  18. 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).

  19. Polar Field Reversals and Active Region Decay

    NASA Astrophysics Data System (ADS)

    Petrie, Gordon; Ettinger, Sophie

    2015-07-01

    We study the relationship between polar field reversals and decayed active region magnetic flux. Photospheric active region flux is dispersed by differential rotation and turbulent diffusion, and is transported poleward by meridional flows and diffusion. We summarize the published evidence from observation and modeling of the influence of meridional flow variations and decaying active region flux's spatial distribution, such as the Joy's law tilt angle. Using NSO Kitt Peak synoptic magnetograms covering cycles 21-24, we investigate in detail the relationship between the transport of decayed active region flux to high latitudes and changes in the polar field strength, including reversals in the magnetic polarity at the poles. By means of stack plots of low- and high-latitude slices of the synoptic magnetograms, the dispersal of flux from low to high latitudes is tracked, and the timing of this dispersal is compared to the polar field changes. In the most abrupt cases of polar field reversal, a few activity complexes (systems of active regions) are identified as the main cause. The poleward transport of large quantities of decayed trailing-polarity flux from these complexes is found to correlate well in time with the abrupt polar field changes. In each case, significant latitudinal displacements were found between the positive and negative flux centroids of the complexes, consistent with Joy's law bipole tilt with trailing-polarity flux located poleward of leading-polarity flux. The activity complexes of the cycle 21 and 22 maxima were larger and longer-lived than those of the cycle 23 and 24 maxima, and the poleward surges were stronger and more unipolar and the polar field changes larger and faster. The cycle 21 and 22 polar reversals were dominated by only a few long-lived complexes whereas the cycle 23 and 24 reversals were the cumulative effects of more numerous, shorter-lived regions. We conclude that sizes and lifetimes of activity complexes are key to

  20. Polar Field Reversals and Active Region Decay

    NASA Astrophysics Data System (ADS)

    Petrie, Gordon; Ettinger, Sophie

    2017-09-01

    We study the relationship between polar field reversals and decayed active region magnetic flux. Photospheric active region flux is dispersed by differential rotation and turbulent diffusion, and is transported poleward by meridional flows and diffusion. We summarize the published evidence from observation and modeling of the influence of meridional flow variations and decaying active region flux's spatial distribution, such as the Joy's law tilt angle. Using NSO Kitt Peak synoptic magnetograms covering cycles 21-24, we investigate in detail the relationship between the transport of decayed active region flux to high latitudes and changes in the polar field strength, including reversals in the magnetic polarity at the poles. By means of stack plots of low- and high-latitude slices of the synoptic magnetograms, the dispersal of flux from low to high latitudes is tracked, and the timing of this dispersal is compared to the polar field changes. In the most abrupt cases of polar field reversal, a few activity complexes (systems of active regions) are identified as the main cause. The poleward transport of large quantities of decayed trailing-polarity flux from these complexes is found to correlate well in time with the abrupt polar field changes. In each case, significant latitudinal displacements were found between the positive and negative flux centroids of the complexes, consistent with Joy's law bipole tilt with trailing-polarity flux located poleward of leading-polarity flux. The activity complexes of the cycle 21 and 22 maxima were larger and longer-lived than those of the cycle 23 and 24 maxima, and the poleward surges were stronger and more unipolar and the polar field changes larger and faster. The cycle 21 and 22 polar reversals were dominated by only a few long-lived complexes whereas the cycle 23 and 24 reversals were the cumulative effects of more numerous, shorter-lived regions. We conclude that sizes and lifetimes of activity complexes are key to

  1. Simulating Snowfall: Modeling Water Deposition on the Martian Northern Polar Ice Cap

    NASA Astrophysics Data System (ADS)

    Durbin, Allyn J.; Brown, A.; Hollingsworth, J. L.; Kahre, M. A.

    2013-01-01

    Every spring on the Martian northern ice cap, a retreat of the carbon dioxide ice reveals the permanent layer of water ice below. Data obtain by the Thermal Emission Spectrometer (TES) on the Mars Global Surveyor during this retreat detected the presence of both carbon dioxide and water ice. However, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard the Mars Reconnaissance Orbiter detected only water ice in the same location. It is theorized this discrepancy can be explained by the Houben process, first described in Houben, et al. (1997), which is a mechanism that provides the northward transfer of water ice onto the retreating carbon dioxide ice cap. In this project, we attempted to simulate Houben events using the NASA Ames Mars Climate Model. We have been able to replicate and verify some events indicative of the Houben process, providing a basis for the obscuration of carbon dioxide ice by water ice on Martian northern polar ice cap.

  2. Direct Measurements of the Plasma Velocity During Intervals of Reverse Convection in the Southern Polar Cap

    NASA Astrophysics Data System (ADS)

    Makarevich, R. A.

    2016-12-01

    Observations of the plasma convection near the dayside throat region, including resolution of reverse convection cells during intervals of northward interplanetary magnetic field (IMF), often involve assimilation of data from multiple sources such as the map potential technique utilized by the Super Dual Auroral Radar Network (SuperDARN). In this study, we also examine direct measurements of the plasma convection velocity by the SuperDARN Dome Concordia East and McMurdo radars which for >4 hours a day directly observe convection flows along the magnetic noon-midnight meridian. Solar wind control of these flows is examined by conducting a statistical analysis of the average and peak plasma velocities for various solar wind conditions. It is shown that signatures of reverse convection appear above a certain threshold in IMF Bz. The threshold appears to depend on IMF By and is, on average, 2 nT. Noticeable cross-polar-cap (CPC) convection asymmetry with respect to IMF By is also observed. The CPC convection dependence on IMF Bz or interplanetary electric field (IEF) is mostly linear, with some evidence of saturation for both northward and southward IMF at most extreme values. The implications for the high-altitude reconnection efficiency for different IMF conditions are discussed.

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

    SciTech Connect

    Benson, R.F.

    1985-06-01

    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. 15 references.

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

    NASA Astrophysics Data System (ADS)

    Benson, R. F.

    1985-06-01

    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.

  5. 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.

  6. Measurement of Polar Cap Ionospheric Velocities Using the RISR-C and SuperDARN Radars

    NASA Astrophysics Data System (ADS)

    Gillies, R. G.; Spanswick, E.; Varney, R. H.; Perry, G. W.; Koustov, A. V.; Donovan, E.

    2016-12-01

    The Canadian face of the Resolute Bay Incoherent Scatter Radar (RISR-C) began operations in 2015 and since then has been making highly detailed measurements of the polar ionosphere. The operations of RISR-C are often complemented by measurements from the co-located northward facing RISR-N radar which is operated by SRI International. RISR-C (and RISR-N), like other Advanced Modular Incoherent Scatter (AMISR) radars, are able to sample multiple look directions effectively simultaneously using electronic beam steering. Measurements of electron density, electron temperature, ion temperature, and line-of-sight (LOS) velocity are made along each of these beams in (typically) 1- or 5-minute intervals. Analysis of LOS velocity measurements in multiple directions allows estimation of full 3-D flow vectors assuming a mostly uniform velocity field exists in the field-of-view of the radar. In this study, these RISR velocity vectors are compared to conjugate measurements of ionospheric velocity from overlapping Super Dual Auroral Radar Network (SuperDARN) measurements at Rankin Inlet, Inuvik, and Clyde River. Accurate measurement of ionospheric velocities by the RISR and SuperDARN radars require several assumptions be made in analyzing both datasets. For example, measurement challenges for the SuperDARN radars include; E-region and groundscatter contamination, the non-unity refractive index in the scattering volume, and wave propagation effects. The overall goal of this study is to identify and solve possible issues in using the different techniques/instruments in order to produce the most accurate measurements of polar cap ionospheric velocities.

  7. Polar Field Reversals and Active Region Decay

    NASA Astrophysics Data System (ADS)

    Petrie, Gordon; Ettinger, Sophie

    2015-04-01

    We study the relationship between polar field reversals and decayed active region magnetic flux. Photospheric active region flux is dispersed by differential rotation and turbulent diffusion, and is transported poleward by meridional flows and diffusion. Using NSO Kitt Peak synoptic magnetograms, we investigate in detail the relationship between the transport of decayed active region flux to high latitudes and changes in the polar field strength, including reversals in the magnetic polarity at the poles. By means of stack plots of low- and high-latitude slices of the synoptic magnetograms, the dispersal of flux from low to high latitudes is tracked, and the timing of this dispersal is compared to the polar field changes. In the most abrupt cases of polar field reversal, a few activity complexes (systems of active regions) are identified as the main cause. The poleward transport of large quantities of decayed lagging-polarity flux from these complexes is found to correlate well in time with the abrupt polar field changes. In each case, significant latitudinal displacements were found between the positive and negative flux centroids of the complexes, consistent with Joy's law bipole tilt with lagging-polarity flux located poleward of leading-polarity flux. This work is carried out through the National Solar Observatory Summer Research Assistantship (SRA) Program. The National Solar Observatory is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

  8. 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.

  9. QED-PIC simulations of electromagnetic cascades at the surface of pulsar's polar cap

    NASA Astrophysics Data System (ADS)

    Grismayer, Thomas; Vranic, Marija; Fonseca, Ricardo; Silva, Luis

    2016-10-01

    The recent implementation of the QED module in the OSIRIS 3.0 framework has enabled to simulate various scenarios where pair production or gamma-rays emission can be produced with ultra-intense lasers and/or relativistic particles beams. In this study we leverage on these numerical tools to study extreme astrophysical scenarios where self-consistent produced electron-positron pair plasmas are of relevance such as in pulsar magnetospheres. The dynamics of pulsar's polar cap cascade, based on the Ruderman-Sutherland model, has been investigated for the first time numerically in one dimension by Timokhin. Including quantum synchrotron radiation additionally to curvature photon radiation for the possible processes responsible for photon emission, we present the results of one and two dimensional QED-PIC simulations of the development of electromagnetic cascades at the surface of the polar cap and the subsequent plasma discharges that are accompanied by strong electrostatic waves.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Production of polar cap electron density patches by transient magnetopause reconnection

    SciTech Connect

    Lockwood, M. ); Carlson, H.C. Jr. )

    1992-09-04

    Some implications are considered of recent theoretical work concerning the excitation of dayside ionospheric convection by magnetic reconnection at the dayside magnetopause. In particular, transient bursts of such reconnection ([open quote]flux transfer events[close quote]) are considered as a cause of polar cap [open quote]patches[close quote] of enhanced plasma density. Examples of such patches, as observed at European longitudes by the EISCAT radar, are presented and used to discuss the implications of the proposed mechanism.

  15. 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

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

    NASA Astrophysics Data System (ADS)

    van der 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.

  17. 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.

  18. Hemispheric Observations of Ionospheric Processes in the Polar Regions

    NASA Astrophysics Data System (ADS)

    Baker, J. B. H.; Ruohoniemi, J. M.; Maimaiti, M.; Thomas, E. G.

    2016-12-01

    Capabilities to monitor ionospheric processes in the polar regions have been significantly improved in recent years by expansion of ground-based instrument networks distributed over hemispheric spatial scales. For example, construction of several new radars at high latitudes (e.g. PolarDARN and RISR) are providing exciting new opportunities to monitor dayside magnetosphere-ionosphere coupling processes poleward of the cusp, particularly during extreme northward IMF conditions. Together with the increasingly dense coverage of GNSS receivers these new radars are also providing valuable new insights about the role of the convection electric field in shaping high latitude ionospheric density features such as polar cap patches and the Tongue of Ionization (TOI). In addition, AMPERE measurements of region-1 and region-2 field-aligned currents can be used to monitor coupled magnetosphere-ionosphere dynamics during storms and substorms, uninterrupted, and in both hemispheres simultaneously. In this presentation, we discuss several case study examples which illustrate how spatially distributed datasets are fundamentally changing our understanding of magnetosphere-ionosphere coupling processes in the polar regions.

  19. Thermal and albedo mapping of the north and south polar regions of Mars

    NASA Technical Reports Server (NTRS)

    Paige, D. A.; Keegan, K. D.

    1991-01-01

    The first maps of the thermal properties of the north and south polar region of Mars are presented. The maps complete the mapping of the entire planet. The maps for the north polar region were derived from Viking Infrared Thermal Mapper (IRTM) observations obtained from 10 Jun. to 30 Sep. 1978. This period corresponds to the early summer season in the north, when the north residual water ice cap was exposed, and the polar surface temperatures were near their maximum. The maps in the south were derived from observations obtained between 24 Aug. to 23 Sep. 1977. This period corresponds to the late summer season in the south, when the seasonal polar cap had retreated to close to its residual configuration, and the second global dust storm of 1977 had largely subsided. The major results concerning the following topics are summarized: (1) surface water ice; (2) polar dune material; and (3) dust deposits.

  20. 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.

  1. Effects of deliquescent salts in soils of polar Mars on the flow of the Northern Ice Cap

    NASA Astrophysics Data System (ADS)

    Fisher, D. A.; Hecht, M. H.; Kounaves, S.; Catling, D.

    2008-12-01

    The discovery of substantial amounts of magnesium and perchlorate by Phoenix' "Wet Chemistry Lab" (WCL) in the soil of Polar Mars suggests that magnesium perchlorate could be the dominant salt in the polar region's soils. This prospect opens some unexpected doors for moving liquid water around at temperatures as low as -68C. In its fully hydrated form ,this salt water mixture has a high density (~ 1700 kgm /cubic meter) (Besley and Bottomley,1969) and a freezing point of -68C (Pestova et al., 2005).This perchlorate is very deliquescent and gives off heat as it melts ice. About 1.8 gram of ice can be 'melted' by 1 gm of pure magnesium perchlorate . If the reported 1 percent perchlorate is typical of polar soils and if 5 percent of the Northern Permanent Ice Cap is soil then the perchorate , makes up about 0.0005 the of the ice cap. Given the average thickness of the ice cap is about 2000 meters,this suggests there enough perchorate in the ice cap to generate about 2m of salty water at the bed. Because of its density the perclorate salty water would pool over impervious layers and make the bed into a perchorate sludge that could be mobilized and deformed by the overburden of ice. The deformation of mobile beds is a well known phenomenon on some terrestrial glaciers presently and was thought to have played a major role during the Wisconsinan ice age (Fisher et al., 1985) . The perchorate sludge would be deformed and moved outwards possibly resulting its re-introduction to the polar environment. Having a deliquescent salt sludge at the bed whose melting point is -68C would mean that the ice cap could slide on its deformable bed while the ice itself was still very cold and stiff . This possibility has been modeled with a 2D time varying model . Adding the deformable bed material allows ice cap motion even at ice temperatures cold enough to generate and preserve the scarp/trough features. When the perchlorate formation mechanisms and rates are known the ultimate

  2. 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.

  3. Assessment of HRSC Digital Terrain Models Produced for the South Polar Residual Cap

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The current Digital Terrain Models available for Mars consist of NASA MOLA (Mars Orbital Laser Altimeter) Digital Terrain Models with an average resolution of 112 m/ pixel (512 pixels/degree) for the polar region. The ESA/DLR High Resolution Stereo Camera is currently orbiting Mars and mapping its surface, 98% with resolution of ≤100 m/pixel and better and 100% at lower resolution [1]. It is possible to produce Digital Terrain Models from HRSC images using various methods. In this study, the method developed on Kim and Muller [2] which uses the VICAR open source program together with photogrammetry sofrware from DLR (Deutschen Zentrums für Luft- und Raumfahrt) with image matching based on the GOTCHA (Gruen-Otto-Chau) algorithm [3]. Digital Terrain Models have been processed over the South Pole with emphasis on areas around South Polar Residual Cap from High Resolution Stereo Camera images [4]. Digital Terrain Models have been produced for 31 orbits out of 149 polar orbits available. This study analyses the quality of the DTMs including an assessment of accuracy of elevations using the MOLA MEGDR (Mission Experiment Gridded Data Records) which has roughly 42 million MOLA PEDR (Precision Experiment Data Records) points between latitudes of 78 o -90 o S. The issues encountered in the production of Digital Terrain Models will be described and the statistical results and assessment method will be presented. The resultant DTMs will be accessible via http://i-Mars.eu/web-GIS References: [1] Neukum, G. et. al, 2004. Mars Express: The Scientific Payload pp. 17-35. [2] Kim, J.-R. and J.-P. Muller. 2009. PSS vol. 57, pp. 2095-2112. [3] Shin, D. and J.-P. Muller. 2012. Pattern Recognition, 45(10), 3795 -3809. [4] Putri, A.R. D., et al., Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci., XLI-B4, 463-469 Acknowledgements: The research leading to these results has received partial funding from the STFC "MSSL Consolidated Grant" ST/K000977/1 and partial support from the

  4. 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.

  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. 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

  7. 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

  8. North Polar Cap Margin (natural color (top) and enhanced color (bottom))

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Water ice mixed with dust form the residual north polar ice cap (brown color). Seasonal frost of relatively pure ice (white color) partly blankets the polar deposits. A large trough, which is occupied by linear sand dunes (dark band), exposes polar layered deposits. The layered deposits hold a partial record of the history of atmospheric activity and climate of Mars. Center of picture is at latitude 82 degrees N., longitude 84 degrees W. Viking Orbiter Picture Numbers 82B11-12 (violet), 82B15-16 (green), and 82B17-18 (red) at 53 m/pixel resolution. Picture width is 106 km. North is 6 degrees counter-clockwise from top.

  9. Localized polar cap precipitation in association with nonstorm time airglow patches

    NASA Astrophysics Data System (ADS)

    Zou, Ying; Nishimura, Yukitoshi; Lyons, Larry R.; Shiokawa, Kazuo

    2017-01-01

    Although airglow patches are traditionally regarded as high-density ionospheric plasma unrelated to local precipitation, past observations were limited to disturbed conditions. Recent nonstorm time observations show patches to be associated with ionospheric flow channels and localized field-aligned currents. We examine whether nonstorm time patches are related also to polar cap precipitation using Fast Auroral Snapshot-imager conjunctions. We have identified localized precipitation that is enhanced within patches in comparison to the weak polar rain outside patches. The precipitation consists of structured or diffuse soft electron fluxes. While the latter resembles polar rain only with higher fluxes, the former consists of discrete fluxes enhanced by 1-2 orders of magnitude from several to several hundred eV. Therefore, patches should be regarded as part of a localized magnetosphere-ionosphere coupling system along open magnetic field lines and their transpolar evolution as a reflection of mesoscale magnetotail lobe processes. The precipitation a minor contributor to patch ionization.

  10. 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.

  11. H2O grain size and the amount of dust in Mars' residual North polar cap

    USGS Publications Warehouse

    Kieffer, H.H.

    1990-01-01

    In Mars' north polar cap the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 ??m or more. Ice of this granularity containing 30% fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be "old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain. -Author

  12. H2O grain size and the amount of dust in Mars' residual north polar cap

    NASA Technical Reports Server (NTRS)

    Kieffer, Hugh H.

    1990-01-01

    In Mars' north polar cap, the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 microns or more. Ice of this granularity containing 30 percent fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be 'old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain.

  13. CO2 Snowfalls, seasonal ice cap formations and baroclinic waves in the winter polar atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Kuroda, Takeshi; Kasaba, Yasumasa; Medvedev, Alexander S.; Hartogh, Paul

    The seasonal CO _{2} polar cap is formed from ice particles that have fallen from the atmosphere as well as those condensed directly on the surface. The possible occurrence of CO _{2} snowfall in the winter polar regions have been observed, and previous simulation studies have indicated that the longitudinal irregularities of CO _{2} ice clouds in the northern polar region seemed to be linked to local weather phenomena. Transient planetary waves are the prominent dynamical feature during northern winters in the martian atmosphere, and this study focuses on revealing the mechanism of how the dynamical influence of transient planetary waves affects the occurrences of CO _{2} ice clouds, snowfalls and formations of seasonal CO _{2} polar cap in high latitudes during northern winters. The DRAMATIC (Dynamics, RAdiation, MAterial Transport and their mutual InteraCtions) MGCM, which is used for this study, is based on a Japanese terrestrial model (CCSR/NIES/FRCGC MIROC) with a spectral solver for the three-dimensional primitive equations. A simple scheme representing the formation and transport of CO _{2} ice clouds has been implemented into the MGCM. The simulation results showed that the CO _{2} ice clouds are formed at altitudes of up to 40 km in the northern polar region (northward of 70(°) N) during winter, which is consistent with the observations by the Mars Climate Sounder onboard Mars Reconnaissance Orbiter. In addition, we found that the occurrence of the CO _{2} ice clouds correlated to a large degree with the cold phases of transient planetary waves. Ice particles formed up to 20 km can reach the surface in the form of snowfall in certain longitude regions (in 30(°) W-60(°) E), while in others these particles likely sublimate in the lower warmer atmospheric layers. Given the regular nature of such atmospheric waves on Mars, the results of this study suggest that the snowstorms may be predicted several weeks in advance. For missions to Mars aiming to explore

  14. Polar Lows: Mesocale Weather Systems in the Polar Regions

    NASA Astrophysics Data System (ADS)

    Bromwich, David H.

    2004-03-01

    Ten expert authors have combined to provide a comprehensive summary of the status of knowledge, circa 2000, about ``polar lows'' in both polar regions. The term ``polar low'' is normally reserved for small but fairly intense maritime cyclones that dominantly form in the northern oceans during winter, as cold air crosses regions of sharp sea surface temperature gradients. This synthesis covers the full spectrum of mesoscale lows with a diameter less than 1000 km that occur in the Arctic and Antarctic poleward of the main polar front. These features typically form and develop in data-sparse areas, so heavy reliance is placed on satellite remote sensing and numerical modeling to describe and understand these storms. Only a small number of systems have been directly sampled by aircraft. A particularly strong and attractive aspect of this book is the plethora of satellite images that illustrate the wide range of cloud signatures. In the introductory Chapter 1, J. Turner, E. Rasmussen, and A. Carleton give a brief history of research, and follow this with discussion of the vexing problem of labeling, for which many different descriptions have been used (polar low, mesoscale cyclone, Arctic instability low, polar air depression, etc.). Satellite images are then presented, showing comma cloud, spiraliform, merry-go-round, instant occlusion, baroclinic wave, and warm core types of mesoscale cyclones. Chapter 2, by Rasmussen, K. Ninomiya, and Carleton, addresses the climatology of mesoscale cyclones in the Arctic and the Antarctic in relation to the physical factors that occur in these regions. For example, the ubiquitous katabatic winds near the Antarctic coastal slopes play a central role in generating low-level frontal zones just offshore that are key to mesoscale cyclogenesis in that area. The spatial and temporal variations of mesoscale cyclones are then related to the large-scale modes of atmospheric variability, such as the North Atlantic Oscillation and the El Ni

  15. Automatic Extraction of Ice-Cap Layers from Radar Sounding Data over Greenland and the South Polar Residual Cap on Mars

    NASA Astrophysics Data System (ADS)

    Xiong, Siting; Muller, Jan-Peter

    2016-08-01

    Radar depth sounding employs low frequency radar operating at several hundreds of KiloHz to MegaHz frequencies and has been applied to the field of subsurface investigations on both the Earth and Mars.Over Antarctica and Greenland, the Multichannel Coherent Radar Depth Sounder (MCoRDS) onboard the NASA Operation IceBridge missions[1] has collected radar echograms since 2009 showing the subsurface ice layers caused by ice accumulation and interrupted by subsurface ice flow. Over the Martian polar regions, subsurface layers are also detected by low frequency radar systems, i.e. MARSIS (Mars Advanced Radar for Subsurface Ionosphere Sounding on board ESA's Mars Express) and SHARAD (SHAllow subsurface RADar on board NASA's Mars Reconnaissance Orbiter) [2]–[5].Although these subsurface layers are formed by different mechanisms, there is a need for fast and automatic information extraction from these subsurface radar reflectors with the larger and larger coverage acquired nowadays. The detection and automatic extraction of subsurface layers is very important preliminary work to future studies of surface evolution and past climate. This study presents a method based on the Radon Transform (RT) to automatically extract the subsurface layers over Greenland on Earth and South Polar Residual Cap on Mars.

  16. The hemispherical asymmetry of the residual polar caps on Mars. Semiannual progress report, 1 Sep. 1989 - 1 Mar. 1991

    SciTech Connect

    Lindner, B. L.

    1991-03-01

    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 CO{sub 2} frost at the south pole and reproduces the general trend in the Viking Lander pressure data.

  17. Influence of the interplanetary magnetic field orientation on polar cap ion trajectories - Energy gain and drift effects

    NASA Technical Reports Server (NTRS)

    Delcourt, D. C.; Horwitz, J. L.; Swinney, K. R.

    1988-01-01

    The influence of the interplanetary magnetic field (IMF) orientation on the transport of low-energy ions injected from the ionosphere is investigated using three-dimensional particle codes. It is shown that, unlike the auroral zone outflow, the ions originating from the polar cap region exhibit drastically different drift paths during southward and northward IMF. During southward IMF orientation, a 'two-cell' convection pattern prevails in the ionosphere, and three-dimensional simulations of ion trajectories indicate a preferential trapping of the light ions H(+) in the central plasma sheet, due to the wide azimuthal dispersion of the heavy ions, O(+). In contrast, for northward IMF orientation, the 'four-cell' potential distribution predicted in the ionosphere imposes a temporary ion drift toward higher L shells in the central polar cap. In this case, while the light ions can escape into the magnetotail, the heavy ions can remain trapped, featuring more intense acceleration (from a few electron volts up to the keV range) followed by precipitation at high invariant latitudes, as a consequence of their further travel into the tail.

  18. Warm O(+) polar wind and the DE-1 polar cap electron density profile

    NASA Technical Reports Server (NTRS)

    Ho, C. W.; Horwitz, J. L.

    1993-01-01

    Theoretical steady state semikinetic polar wind density profiles, based on DE1/RIMS polar wind data (up to 3700 km), were obtained which agree very well with the power law electron density profile measured by the DE1/PWI for high altitudes. The polar wind is found to be O(+) dominated for the full altitude range considered (up to 8 R(E)). Multiple solutions are obtained for various combinations of base altitude ion temperatures and electron temperatures, such that the densities fit the Persoon et al. (1983) profile. For example, good fits to measured density profile are found for low base ion temperatures (5000 K) and high electron temperatures (9000 K), and also for unheated H(+) and O(+)(3000 K) with electron temperatures of 11,000 K. Below 2.8 R(E) the theoretical polar wind density deviates somewhat from the r exp -3.85 power law. It is concluded that this theoretical polar wind density profile, with a sum of base electron and ion temperatures of 14,000 K, yields a close match with the measured DE-1 electron density profile.

  19. Ion Outflow and Convection in the Polar Cap and Cleft as Measured by Tide, EFI, MFE and Timas

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Craven, P. D.; Chandler, M. O.; Moore, T. E.; Maynard, N. C.; Peterson, W. K.; Lennartsson, O. W.; Shelley, E. G.; Mozer, F. S.; Russell, C. T.

    1997-01-01

    This study examines high-latitude ion outflows and velocities perpendicular to the magnetic field derived from moments of ion distributions measured by the TIDE (Thermal Ion Dynamics Experiment) instrument on the Polar satellite. Hydrogen and oxygen ions are shown to be E X B drifting in the polar cap and cleft regions with a speed of about 5-20 km/s at apogee (approximately 9 Re) and a speed of 1-2 km/s at perigee (approximately 1. 8 Re). E X B drifts are calculated from electric fields measured by EFI (Electric Field Instrument) and magnetic fields measured by MFE (Magnetic Field Experiment) both of which are also on Polar. How convection at Polar's perigee relates to potential patterns of the ionosphere will be discussed. In the cusp/cleft the distribution of hydrogen extends over a large enough range of energy to be measured by both TIDE and the Toroidal Imaging Mass-Angle Spectrograph (TIMAS). Such comparisons will be also be presented.

  20. Evidence of high densities and ion outflows in the polar cap during the recovery phase

    NASA Astrophysics Data System (ADS)

    Gallagher, D. L.; Waite, J. H., Jr.; Chappell, C. R.; Menietti, J. D.; Burch, J. L.

    1986-03-01

    The composition and characteristics of the polar cap plasma for an Oct. 14, 1981 outflow of polar wind ions are examined using data from the DE 1 satellite. The on-board instruments included a plasma wave instrument, a retarding ion mass spectrometer (RIMS) and a high altitude plasma instrument (HAPI). The outflow took place at an altitude of about 19,000 km at a magnetic local time of about midnight. The total plasma density measured was about 50/cu cm, which was an order of magnitude higher than normally recorded at that location and altitude. The background hydrogen plasma was disturbed by highly collimated flows of hydrogen and oxygen ions. The H(+) ions had a mean energy of 0.15 eV and a density of 6-10/cu cm. The O(+) ions had an average density of 20/cu cm and a temperature of 0.26 eV. The total flux of outflowing H(+) and O(+) was about 10 million/sq cm per sec. The HAPI data indicated that the O(+) ions appeared in the dayside ionosphere and the H(+) ions detected by the RIMS originated in the nightside polar cap.

  1. Evidence of high densities and ion outflows in the polar cap during the recovery phase

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Waite, J. H., Jr.; Chappell, C. R.; Menietti, J. D.; Burch, J. L.

    1986-01-01

    The composition and characteristics of the polar cap plasma for an Oct. 14, 1981 outflow of polar wind ions are examined using data from the DE 1 satellite. The on-board instruments included a plasma wave instrument, a retarding ion mass spectrometer (RIMS) and a high altitude plasma instrument (HAPI). The outflow took place at an altitude of about 19,000 km at a magnetic local time of about midnight. The total plasma density measured was about 50/cu cm, which was an order of magnitude higher than normally recorded at that location and altitude. The background hydrogen plasma was disturbed by highly collimated flows of hydrogen and oxygen ions. The H(+) ions had a mean energy of 0.15 eV and a density of 6-10/cu cm. The O(+) ions had an average density of 20/cu cm and a temperature of 0.26 eV. The total flux of outflowing H(+) and O(+) was about 10 million/sq cm per sec. The HAPI data indicated that the O(+) ions appeared in the dayside ionosphere and the H(+) ions detected by the RIMS originated in the nightside polar cap.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. Evidence of high densities and ion outflows in the polar cap during the recovery phase

    SciTech Connect

    Gallagher, D.L.; Menietti, J.D.; Burch, J.L.; Persoon, A.M.; Waite J.H. Jr.; Chappell, C.R.

    1986-03-01

    During the recovery phase of a large storm on October 14, 1981, instruments on board Dynamics Explorer 1 (DE 1) the Retarding Ion Mass Spectrometer (RIMS), the High Altitude Plasma Instrument (HAPI), and the Plasma Wave Instrument (PWI) detected unusually high plasma densities and ion flows in the polar cap. At the time of detection, DE 1 was located at a radial distance of about 3.5 earth radii, a magnetic local time near midnight, and between 70/sup 0/ and 80/sup 0/ invariant latitude. Total plasma density was found to be about 50 cm/sup -3/, an order of magnitude above median polar cap densities at the altitude of observation. In addition, highly collimated flows of hydrogen and oxygen are found flowing through a background hydrogen plasma. The O/sup +/ component of the plasma discussed is not directly identified but is inferred to be O/sup +/ through the combined analysis of data from three instruments. Results of the combined instrument analysis indicate that the detected plasma was composed of outflowing H/sup +/ with a density of 6-10 cm/sup -3/ with a temperature of about 0.15 eV; isotropic H/sup +/ with a density of about 15-20 cm/sup -3/; and outflowing and strongly convecting O/sup +/ with an average density of about 20 cm/sup -3/ and a temperature of about 0.26 eV. The flux of outflowing H/sup +/ and O/sup +/ are both about 10/sup 7/ cm/sup -2/ s/sup -1/. The data indicate that the O/sup +/ detected by HAPI seems to originate in the dayside ionosphere, while the H/sup +/ detected by RIMS has a source in the nightside polar cap.

  7. Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS Hi data

    NASA Astrophysics Data System (ADS)

    Ghosh, T.; Boulanger, F.; Martin, P. G.; Bracco, A.; Vansyngel, F.; Aumont, J.; Bock, J. J.; Doré, O.; Haud, U.; Kalberla, P. M. W.; Serra, P.

    2017-05-01

    The Planck survey has quantified polarized Galactic foregrounds and established that they are a main limiting factor in the quest for the cosmic microwave background B-mode signal induced by primordial gravitational waves during cosmic inflation. Accurate separation of the Galactic foregrounds therefore binds this quest to our understanding of the magnetized interstellar medium. The two most relevant empirical results from analysis of Planck data are line of sight depolarization arising from fluctuations of the Galactic magnetic field orientation and alignment of filamentary dust structures with the magnetic field at high Galactic latitude. Furthermore, Planck and H I emission data in combination indicate that most of the filamentary dust structures are in the cold neutral medium. The goal of this paper is to test whether these salient observational results, taken together, can account fully for the statistical properties of the dust polarization over a selected low column density region comprising 34% of the southern Galactic cap (b ≤ -30°). To do this, we construct a dust model that incorporates H I column density maps as tracers of the dust intensity structures and a phenomenological description of the Galactic magnetic field. By adjusting the parameters of the dust model, we were able to reproduce the Planck dust observations at 353GHz in the selected region. Realistic simulations of the polarized dust emission enabled by such a dust model are useful for testing the accuracy of component separation methods, studying non-Gaussianity, and constraining the amount of decorrelation with frequency.

  8. ULF/Lower-ELF Electromagnetic Field Measurements in the Polar Caps

    DTIC Science & Technology

    1980-12-01

    55 V . REFERENCES .......... ....................... 61 Iv 𔃾 , .. . KI.. ...n | - n m i Note: In this report the abbreviation...5 150-600 Pc 6 > 600 k I 12 , - V II. BACKGROUND ACTIVITY IN THE POLAR CAPS In an experimental study of geomagnetic activity in the 0.1-14 Hz band...poc. n te i 0.. The Office of Naval Research DS *under Contract No. N00014-79-C-0174 L-J 81 2 19 040 -- iS --n i - -. r Reproduction in whole or in

  9. 'Electron conic' signatures observed in the nightside auroral zone and over the polar cap

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Burch, J. L.

    1985-01-01

    The high altitude plasma instrument, i.e., five electrostatic analyzers, on board the DE 1 satellite obtained data on electron conical distributions during two nightside auroral zone passes and one polar cap pass. The southern orbit apogee was 675 km, the northern, 24,000 km. Electrons confined to the outside of the loss cone were the highest energy particles detected. The upward integrated flux was greater than the downward flux, indicating the presence of a heating process perpendicular to the geomagnetic field.

  10. 'Electron conic' signatures observed in the nightside auroral zone and over the polar cap

    NASA Astrophysics Data System (ADS)

    Menietti, J. D.; Burch, J. L.

    1985-06-01

    The high altitude plasma instrument, i.e., five electrostatic analyzers, on board the DE 1 satellite obtained data on electron conical distributions during two nightside auroral zone passes and one polar cap pass. The southern orbit apogee was 675 km, the northern, 24,000 km. Electrons confined to the outside of the loss cone were the highest energy particles detected. The upward integrated flux was greater than the downward flux, indicating the presence of a heating process perpendicular to the geomagnetic field.

  11. Pulsar magnetospheres, braking index, polar caps, and period-pulse-width distribution.

    NASA Technical Reports Server (NTRS)

    Roberts, D. H.; Sturrock, P. A.

    1973-01-01

    An investigation is conducted concerning the trapping of gas and its effect on the structure of the magnetic field. The aligned and orthogonal cases are discussed in detail. In each case, there are small collection zones which are both microscopically and macroscopically stable. By determining where macroscopic stability changes to instability, the separatrix between closed and open field lines is investigated together with the sizes and shapes of the polar caps. This information makes it possible to reexamine the period-pulse-width distribution and to compare it with observational data.

  12. 'Electron conic' signatures observed in the nightside auroral zone and over the polar cap

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Burch, J. L.

    1985-01-01

    The high altitude plasma instrument, i.e., five electrostatic analyzers, on board the DE 1 satellite obtained data on electron conical distributions during two nightside auroral zone passes and one polar cap pass. The southern orbit apogee was 675 km, the northern, 24,000 km. Electrons confined to the outside of the loss cone were the highest energy particles detected. The upward integrated flux was greater than the downward flux, indicating the presence of a heating process perpendicular to the geomagnetic field.

  13. 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.

  14. 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.

  15. 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.

  16. SWIR spectral mapping of the Martian South Polar Residual Cap using CRISM

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    The Martian South Polar Residual Cap (SPRC) exhibits unique CO2 ice sublimation features that cover the surface. These flat floored, circular depressions are highly dynamic, with scarp retreat rates of up to 8m per Martian Year. As the scarps sublimate in Martian Southern Hemisphere spring, they expose dust particles previously trapped within the ice during winter. This allows a window of opportunity to analyse the dust for fragile organic molecules that might otherwise be rapidly destroyed when subjected to ultraviolet radiation at the Martian surface. Polycyclic aromatic hydrocarbons (PAHs) are one such type of organic compound that have not yet been reported as detected on Mars. PAHs are considered to be important in astrobiology as they potentially play a role in abiogenesis, and are a biomarker for extant life. PAHs are abundant on Earth, in deep space and in recent years have been identified on the Saturnian moons Iapetus and Phoebe.Utilising data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter (MRO), SPRC features have been spectrally mapped, the effects of H2O and CO2 ice on infrared spectra eliminated, and regions with obvious dust particles analysed to establish their mineral composition, and signatures indicative of PAHs compared to Mars data.Spectral mapping has identified compositional differences between depression rims and the majority of the SPRC, allowing regions of spectral interest to be selected for in-depth analysis. CRISM spectra have been compared with known Martian mineralogy and PAH laboratory data, with results suggesting Magnesium Carbonate dust content in depression rims, and rims have been found to have higher water content than regions of featureless ice. CO2 ice has been found to be the most limiting factor in looking for PAH diagnostic signatures on the SPRC. Further work is being undertaken with more detailed results to be presented in the future.The research leading

  17. Polar Volatiles on Mars--Theory versus Observation: Excess solid carbon dioxide is probably present in the north residual cap.

    PubMed

    Murray, B C; Malin, M C

    1973-11-02

    The residual frost caps of Mars are probably water-ice. They may be the source of the water vapor associated with seasonal polar hoods. A permanent reservoir of solid CO(2) is also probably present within the north residual cap and may comprise a mass of CO(2) some two to five times that of the present atmosphere of Mars. The martian atmospheric pressure is probably regulated by the temperature of the reservoir and not by the annual heat balance of exposed solid CO(2) (37). The present reservoir temperature presumably reflects a long-term average of the polar heat balance. The question of a large permanent north polar cap is reexamined in light of the Mariner 9 data. The lower general elevation of the north polar region compared to the south and the resulting occurrence in the north of a permanent CO(2) deposit are probably responsible for the differences in size and shape of the two residual caps. The details of the processes involved are less apparent, however. It might be argued that the stability of water-ice deposits depends on both insolation and altitude. The present north and south residual caps should be symmetrically located with respect to such a hypothetical stability field. However, the offset of the south cap from the geometrical pole, the non-symmetrical outline of the north cap, and the apparently uniform thickness of the thin, widespread water-ice all argue against control by simple solid-vapor equilibrium of water under present environmental conditions. We think that the present location of the water-ice may reflect, in part, the past location of the permanent CO(2) reservoir. The extreme stability of polar water-ice deposits increases the likelihood that past environmental conditions may be recorded there. Detailed information on elevations in the vicinity of the residual caps is needed before we can further elucidate the nature and history of the residual caps. This, along with measurements of polar infrared emission, should be given high

  18. Large plasma density enhancements occurring in the northern polar region during the 6 April 2000 superstorm

    NASA Astrophysics Data System (ADS)

    Horvath, Ildiko; Lovell, Brian C.

    2014-06-01

    We focus on the ionospheric response of northern high-latitude region to the 6 April 2000 superstorm and aim to investigate how the storm-enhanced density (SED) plume plasma became distributed in the regions of auroral zone and polar cap plus to study the resultant ionospheric features and their development. Multi-instrument observational results combined with model-generated, two-cell convection maps permitted identifying the high-density plasma's origin and the underlying plasma transportation processes. Results show the plasma density feature of polar cap enhancement (PCE; ~600 × 103 i+/cm3) appearing for 7 h during the main phase and characterized by increases reaching up to 6 times of the quiet time values. Meanwhile, strong westward convections (~17,500 m/s) created low plasma densities in a wider region of the dusk cell. Oppositely, small (~750 m/s) but rigorous westward drifts drove the SED plume plasma through the auroral zone, wherein plasma densities doubled. As the SED plume plasma traveled along the convection streamlines and entered the polar cap, a continuous enhancement of the tongue of ionization (TOI) developed under steady convection conditions. However, convection changes caused slow convections and flow stagnations and thus segmented the TOI feature by locally depleting the plasma in the affected regions of the auroral zone and polar cap. From the strong correspondence of polar cap potential drop and subauroral polarization stream (SAPS), we conclude that the SAPS E-field strength remained strong, and under its prolonged influence, the SED plume provided a continuous supply of downward flowing high-density plasma for the development and maintenance of PCEs.

  19. 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.

  20. 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.

  1. 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.

  2. A new formulation for the ionospheric cross polar cap potential including saturation effects

    NASA Astrophysics Data System (ADS)

    Ridley, A. J.

    2005-12-01

    It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) Bz becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12mV/m at some time. When these events are examined as typically done in previous studies, all of them show some signs of saturation (i.e., over-prediction of the CPCP based on a linear relationship between the IMF and the CPCP). We show that by taking into account the size of the magnetosphere and the fact that the post-shock magnetic field strength is strongly dependent upon the solar wind Mach number, we can better specify the ionospheric CPCP. The CPCP (Φ) can be expressed as Φ=(10-4v2+11.7B(1-e-Ma/3)sin3(θ/2)) {rms/9 (where v is the solar wind velocity, B is the combined Y and Z components of the interplanetary magnetic field, Ma is the solar wind Mach number, θ=acos(Bz/B), and rms is the stand-off distance to the magnetopause, assuming pressure-balance between the solar wind and the magnetosphere). This is a simple modification of the original Boyle et al. (1997) formulation.

  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.

    2013-12-01

    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.

  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. Microorganisms on comets, Europa, and the polar ice caps of Mars

    NASA Astrophysics Data System (ADS)

    Hoover, Richard B.; Pikuta, Elena V.

    2004-02-01

    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.

  6. Optical and radar observations of small-scale polar cap auroral structures

    NASA Astrophysics Data System (ADS)

    Samara, M.; Michell, R. G.

    2013-12-01

    We present ground-based auroral observations from Resolute Bay, Nunavut, Canada (74.73°N, 94.9°W) during January 2011. Two electron-multiplying CCD (EMCCD) imagers were operated at 31 frames per second. One was equipped with an all-sky field of view (FOV) lens and the other with a narrow (19°) FOV lens, centered on the geographic zenith (0° Az., 90° El.), a few degrees away from magnetic zenith (315° Az., 88° El.). The Resolute Incoherent Scatter Radar (RISR) was operating in a mode that enabled common-volume observations with the imagers. Being well inside the polar cap, the magnetic field at Resolute Bay is considered ‘open’ and connects to the lobes of the magnetotail. However, there is no clear consensus on whether polar cap aurorae occur on open or closed field lines. The electron acceleration is likely driven by direct solar wind processes, distant tail lobe processes or plasma sheet processes. One possible mechanism for accelerating the precipitating electrons is the parallel electric field of inertial Alfvén waves. The dynamic nature of the small-scale auroral features, observed on several nights, and the altitude extent of the ionization observed with RISR provide support for this hypothesis.

  7. 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.

  8. Testing nowcasts of the ionospheric convection from the expanding and contracting polar cap model

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The expanding/contracting polar cap (ECPC) model, 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 or nowcasts 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 in situ by ion drift meters on board DMSP (Defense Meteorological Satellite Program) satellites and from the ground by SuperDARN (Super Dual Auroral Radar Network), with motions nowcasted by a theoretical model. 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, estimated using the OMNI data set. The results show that we can largely nowcast the magnitudes of ionospheric convection flows using the context of our understanding of magnetic reconnection at the magnetopause and in the magnetotail.

  9. 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.

  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. 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.

  12. 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.

  13. Oblique View of Vesta South Polar Region

    NASA Image and Video Library

    2011-10-10

    This image of asteroid Vesta, from NASA Dawn spacecraft, calculated from a shape model, shows a tilted view of the topography of the south polar region. This perspective removes the overall curvature of Vesta, as if the giant asteroid were flat and not

  14. Intensification and fading of auroral arcs in the dusk-midnight sector of the polar cap

    SciTech Connect

    Wu, Q.; Rosenberg, T.J. ); Berkey, F.T. ); Eather, R.H. )

    1991-05-01

    Observations of the aurora from South Pole station (magnetic latitude = {minus}74.2{degree}) have been used to study the intensification and fading of polar arcs observed near the dusk meridian. Most of the cases examined have the following features in common: (1) a preexisting auroral form intensifies for about 10 min; (2) this activation is followed by a pronounced decrease of luminosity; (3) the auroral fade terminates after 30-60 min with the onset of intense aurora which sweeps rapidly overhead. The availability of all-sky camera, auroral electrojet (AE) index and interplanetary magnetic field (IMF) data for some of the cases enables the following additional characterizations of these events. The preexisting form is a Sun- or oval-aligned arc (or part of a multiple arc system) which disappears following the activation; equatorward drift of the arc (or system) accompanies the luminosity change. There is some evidence to suggest that the arc is poleward of the auroral oval. The brief intensification and/or the onset of fading occurs during the growth phase or near the start of the expansive phase of a substorm; termination of the fade is near the maximum in AE and is probably indicative of the beginning of the recovery phase of the substorm. For all three cases for which IMF data were available the onset of fading occurred 20-30 min after B{sub z} turned southward. Sun-aligned arcs are a common feature of the polar cap during northward B{sub z} but disappear during the increasingly disturbed conditions that accompany southward B{sub z}. The present results suggest that brief intensifications of southern hemisphere polar cap arcs near dusk may be linked in part to the sunward orientation of the IMF which favors enhanced electron fluxes in the southern lobe of the magnetotail.

  15. Pegaso: Long durations balloons from polar regions

    NASA Astrophysics Data System (ADS)

    Romeo, G. R.; di Stefano, G. D. S.; di Felice, F. D. F.; Masi, S. M.; Cardillo, A. C.; Musso, I. M.; Ibba, R. I.; Palangio, P. P.; Caprara, F. C.; Peterzen, S. P.; Pegaso Group

    Launched from the Mario Zuccelli Station Baia Terra Nova in Antarctica during the 2005 06 austral summer the PEGASO-D payload lifted into the stratospheric anticyclone over the southern polar region This effort marks the first Long Duration Scientific payload to be launched from this location and is the fourth such payload launched in the polar regions Performing in the framework of the NOBILE AMUNDSEN collaborative LDB development between ASI-ARR The Italian Institute of Geophysics and Volcanology INGV with the sponsorship of the Italian Antarctic Program PNRA and the Italian Space Agency ASI designed and built the Ultra-Light system together with three Universities in Italy The Pegaso program has been created to investigate the Earth magnetic field and provide a precursor series of small payload launches for the bigger LDB program such as OLIMPO BOOMERanG and BArSPOrt through this collaboration between ASI and ARR The Italian scientific community aware of the big advantages that LDB balloons can offer to their experiments proposed to extend the LDB program to Southern polar regions besides performing launches from the newly initiated Nobile Amundsen Stratospheric Balloon Center in Svalbard Norway Three PEGASO Polar Explorer for Geomagnetics And other Scientific Observations payloads have been launched from the Svalbard No in collaboration with Andoya Rocket Range ASI and ISTAR Operations and logistics during the past two northern summers These stratospheric altitude m 35000 small 10kmc balloons have floated in the stratosphere between 14 to

  16. 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

  17. The initiation of the poleward boundary intensification of auroral emission by fast polar cap flows: A new interpretation based on ionospheric polarization

    NASA Astrophysics Data System (ADS)

    Ohtani, S.; Yoshikawa, A.

    2016-11-01

    The auroral intensification at the poleward boundary of the auroral oval is often considered to be the ionospheric manifestation of the distant reconnection. In the present study, however, we propose that the poleward boundary intensifications (PBIs) are initiated by ionospheric polarization due to fast polar cap flows, which are known to be well correlated with PBIs. The current continuity at the ionosphere can be described in two different ways, that is, the reflection of an Alfvén wave and the closure of Pedersen and Hall currents with field-aligned currents (FACs). The required consistency between the two approaches sets a framework for modeling the ionospheric polarization, and we numerically test the aforementioned idea focusing on an induced upward FAC as indicative of PBIs. The results show that in case the polar cap flow channel approaches the auroral oval perpendicularly from poleward, (i) upward and downward FACs are induced at the poleward boundary to the west and east of the longitudinal center of the flow channel, respectively; (ii) those induced FACs extend much wider in longitude than the flow channel; (iii) the peak densities of those induced FACs are significantly larger than those of the incident FACs; (iv) those induced FACs are distributed almost symmetrically in longitude, indicating that the Pedersen polarization dominates the Hall polarization; and (v) if the polar cap flow inclined dawnward (duskward), an upward (downward) FAC is induced first. These results are consistent with the reported characteristics of PBIs, which are rather difficult to explain otherwise.

  18. Northern Ice Cap of Mars

    NASA Image and Video Library

    2010-05-26

    This image, combining data from two instruments aboard NASA Mars Global Surveyor, depicts an orbital view of the north polar region of Mars. To the right of center, a large canyon, Chasma Boreale, almost bisects the white ice cap.

  19. Investigating the asymmetry of Mars’ South Polar Cap using the NASA Ames Mars General Circulation Model with a CO2 cloud microphysics scheme

    NASA Astrophysics Data System (ADS)

    Dequaire, Julie; Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; NASA Ames Global Climate Modelling Group

    2013-10-01

    One of the most intriguing and least understood climate phenomena on Mars is the existence of a high albedo perennial south polar CO2 ice cap that is offset from the pole in the western hemisphere (SPRC). Colaprete et al. (2005) hypothesize that since the process by which CO2 surface frost accumulates (i.e., precipitation or direct vapor deposition) affects the albedo of the ice, the atmosphere can play a role in the stability and asymmetry of the cap. They show that the basins of Hellas and Argyre force a stationary wave resulting in a colder western hemisphere in which atmospheric CO2 condensation and precipitation is favored. Because precipitated CO2 is brighter than directly deposited CO2, this could maintain the asymmetry of the southern ice cap. We build on their study with a version of the NASA Ames GCM that includes a newly incorporated CO2 cloud microphysics scheme. Simulated results compare well to observed temperatures, pressures and cap recession rates. Observed mesospheric and polar night clouds are well reproduced by the model, and a third unobserved type of cloud is predicted to form close to the surface of the subliming caps. As hypothesized by Colaprete et al. (2005), we find that the zonally asymmetric topography forces a stationary wave in the atmosphere resulting in an asymmetric cloud cover over the south pole during fall and winter and maximizing snowfall over a region encompassing the SPRC. These positive results open to further studies including a mesospheric simulation to refine the horizontal grid around the SPRC as well as the implementation of an ice albedo scheme dependent both on the amount and size of aerosols falling onto the cap during fall and winter (snow, frost and dust), and on surface metamorphism processes due to sintering and incoming solar radiation. The goal of this work is to develop a more complete understanding of the existence of the SPRC and of the Martian CO2 cycle.

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

    USGS Publications Warehouse

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

    2014-01-01

    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.

  1. 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.

  2. 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

  3. 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.

  4. The role of solar local time in polar cap magnetic variations

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Svalgaard, L.

    1974-01-01

    The role of the earth's main field in controlling the morphology of magnetic disturbance is usually accounted for by use of invariant latitude and MLT (magnetic local time) as a coordinate system. Magnetic disturbance from ionospheric currents is also controlled by ionospheric conductivity. At high latitudes, where SLT (solar local time) can be very different from MLT, the use of only MLT can give misleading results. In particular, those diurnal magnetic variations in the polar cap that change characteristics between interplanetary magnetic sectors have a tendency to peak near noon SLT rather than noon MLT at Alert, where noon MLT and noon SLT differ by more than 10 hours. Because of the sparsity of magnetic observatories it is not possible to completely separate SLT and MLT effects.

  5. Pitting within the Martian South Polar Residual Cap: Evidence for Pressurized Subsurface Carbon Dioxide

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    We present observations of small-scale pitting within the Swiss cheese terrain of the carbon dioxide South Polar Residual Cap (SPRC) and consider the implications of their rapid cascade-like evolution. We show that such pitting cascades: (1) only occur near the walls of thick Swiss cheese mesas; (2) rarely occur in polygonally-cracked mesas; and (3) occur far more often in Mars Global Surveyor (MGS) Years 2 and 3 than in MGS Year 1. We propose that pitting results from depressurization of a sealed layer, which requires subsurface heating that cannot be presently maintained by lateral heat conduction. Instead, we attribute the pressurization and heating implied by pitting to a solid state greenhouse initiated by the recent formation of slab CO2 ice during the southern spring and summer of MGS Year 1, which we show is consistent with Thermal Emission Spectrometer (TES) 25-micron band depth measurements of the SPRC over the last three Mars years.

  6. 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.

  7. IMF By effects in the plasma flow at the polar cap boundary

    NASA Astrophysics Data System (ADS)

    Kozlovsky, Alexander; Lukianova, Renata

    2010-05-01

    We used the dataset obtained from the EISCAT Svalbard Radar during 2000-2008 to study statistically the ionospheric convection as related to IMF By conditions, separately for northward and southward IMF. The effects of IMF By are manifested in the intensity and direction of the East-West component of ionospheric flow. The most significant effects are observed near noon and also in the early morning around 03 MLT, whereas in the evening (at 18 MLT) the effect is essentially less prominent. The other feature is an anti-sunward flow across the polar cap, which shows increasing with the magnitude of IMF By. Quantitative characteristics of the IMF By effects are presented and explained in frame of the magnetospheric electric fields generated due to the solar wind, with taking into account position of the open-closed boundary for different IMF conditions. This work was supported by the Academy of Finland.

  8. Seasonal effect for polar cap sunward plasma flows at strongly northward IMF Bz

    NASA Astrophysics Data System (ADS)

    Koustov, A. V.; Yakymenko, K. N.; Ponomarenko, P. V.

    2017-02-01

    We use Super Dual Auroral Radar Network data to study polar cap ionospheric flow under strongly dominant positive interplanetary magnetic field Bz component. We show that the near-noon flow along the magnetic meridian is predominantly sunward in summer. The sunward velocity increase with intensification of the external driver (the reverse convection electric field) is also faster in summer, and the rate of the increase is slightly larger for the Southern Hemisphere. The sunward flows simultaneously detected in both hemispheres are faster in the summer hemisphere. In addition, while sunward flows are aligned with the midnight-noon line in a winter hemisphere, they are oriented toward earlier magnetic local hours in a summer hemisphere.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. The melting sea ice of Arctic polar cap in the summer solstice month and the role of ocean

    NASA Astrophysics Data System (ADS)

    Lee, S.; Yi, Y.

    2014-12-01

    The Arctic sea ice is becoming smaller and thinner than climatological standard normal and more fragmented in the early summer. We investigated the widely changing Arctic sea ice using the daily sea ice concentration data. Sea ice data is generated from brightness temperature data derived from the sensors: Defense Meteorological Satellite Program (DMSP)-F13 Special Sensor Microwave/Imagers (SSM/Is), the DMSP-F17 Special Sensor Microwave Imager/Sounder (SSMIS) and the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument on the NASA Earth Observing System (EOS) Aqua satellite. We tried to figure out appearance of arctic sea ice melting region of polar cap from the data of passive microwave sensors. It is hard to explain polar sea ice melting only by atmosphere effects like surface air temperature or wind. Thus, our hypothesis explaining this phenomenon is that the heat from deep undersea in Arctic Ocean ridges and the hydrothermal vents might be contributing to the melting of Arctic sea ice.

  14. 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.

  15. Persistence of polar stratospheric clouds in the southern polar region

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Trepte, C. R.; Pitts, M. C.

    1989-01-01

    Observations of Antarctic polar stratospheric clouds (PSCs) were examined using the 1-micron aerosol extinction ratio data from the SAM II satellite experiment for the years 1979-1982 and 1984-1987. PSCs were sighted between 10 and 25 km and were usually first observed by mid-June. Clouds disappeared earlier at higher altitudes (late August near 24 km, in most cases) and later at lower altitudes (late September or October near 16 km). It was found that PSCs persisted longer in 1985 and 1987 at 18 km and were more frequently observed in September and October 1987 than the other years. Inference of likely PSC formation regions from National Meteorological Center temperature data indicated that clouds would begin forming in late May and usually disappear in September. This analysis confirmed the persistence of colder conditions during the spring of 1987.

  16. Column selectivity in reversed-phase liquid chromatography. VI. Columns with embedded or end-capping polar groups.

    PubMed

    Wilson, N S; Gilroy, J; Dolan, J W; Snyder, L R

    2004-02-13

    A previous model of column selectivity for reversed-phase liquid chromatography (RP-LC) has been applied to an additional 21 columns with embedded or end-capping polar groups (EPGs). Embedded-polar-group columns exhibit a significantly different selectivity vs. non-EPG, type-B columns, generally showing preferential retention of hydrogen-bond donors, as well as decreased retention for hydrogen-bond acceptors or ionized bases. EPG-columns are also generally less hydrophobic (more polar) than are non-EPG-columns. Interestingly, columns with polar end-capping tend to more closely resemble non-EPG columns, suggesting that the polar group has less effect on column selectivity when used to end-cap the column versus the case of an embedded polar group. Column selectivity data reported here for EPG-columns can be combined with previously reported values for non-EPG columns to provide a database of 154 different columns. This enables a comparison of any two of these columns in terms of selectivity. However, comparisons that involve EPG columns are more approximate.

  17. 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. .

  18. 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.

  19. 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.

  20. 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. .

  1. CO2-H2O Phase Equilibria: Residual Ice Layers and Basal Melting of the Martian Polar Ice Caps

    NASA Astrophysics Data System (ADS)

    Longhi, J.

    2004-03-01

    Shifts in saturation surfaces with pressure favor residual layers of solid CO_2 at the martian south pole. Basal melting of solid-CO_2 layers within polar ice caps during periods of low obliquity may lead to storage of liquid CO_2 in the Martian crust.

  2. Ice-Ripples on Martian Polar Caps: Exploration of Their Size and Dynamics by a Linear Instability Analysis

    NASA Astrophysics Data System (ADS)

    Carpy, S.; Bordiec, M.; Blanchard, C.; Perret, L.; Herny, C.; Massé, M.; Bourgeois, O.; Mathis, H.

    2016-09-01

    We have conducted a linear stability analysis of a coupled ice-airflow interface under turbulent boundary layer in order to evaluate whether ice-ripples similar to those observed in Antarctica can develop at the surface of the martian polar caps.

  3. Two models of cross polar cap potential saturation compared: Siscoe-Hill model versus Kivelson-Ridley model

    NASA Astrophysics Data System (ADS)

    Gao, Ye; Kivelson, Margaret G.; Walker, Raymond J.

    2013-02-01

    The cross polar cap potential is considered an instantaneous monitor of the rate at which magnetic flux couples the solar wind to the Earth's magnetosphere-ionosphere system. Studies have shown that the cross polar cap potential responds linearly to the solar wind electric field under nominal solar wind conditions but asymptotes to the order of 200 kV for large electric field. Saturation of the cross polar cap potential is also found to occur in MHD simulations. Several mechanisms have been proposed to explain this phenomenon. Two well-developed models are those of Siscoe et al. (2002), herein referred to as the Siscoe-Hill model, and of Kivelson and Ridley (2008), herein referred to as the Kivelson-Ridley model. In this study, we compare the mathematical formulas as well as the predictions of the two models with data. We find that the two models predict similar saturation limits. Their difference can be expressed in terms of a factor, which is close to unity during a saturation interval. A survey of the differences in the model predictions show that, on average, the potential of the Kivelson-Ridley model is smaller than that of the Siscoe-Hill model by 10 kV. Measurements of AMIE, DMSP, PC index, and SuperDARN are used to differentiate between the two models. However, given the uncertainties of the measurements, it is impossible to conclude that one model does a better job than the other of predicting the observed cross polar cap potentials.

  4. 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.

  5. 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.

  6. 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.

  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. 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.

  9. Comparison of polar cap electron density enhancement due to solar illumination and geomagnetic activity as measured by IMAGE/RPI

    NASA Astrophysics Data System (ADS)

    Nsumei, P.; Reinisch, B.; Song, P.; Tu, J.; Huang, X.

    2007-12-01

    Polar cap electron density (Ne) measurements made between the years 2000 - 2005 by the radio plasma imager (RPI) on board the IMAGE spacecraft are used to study the density enhancements resulting from changes in solar illumination and geomagnetic activity level. This study covers a geocentric distance, R = 1.4 - 5.0 RE and the polar cap is defined by an empirical boundary model that takes into account the dynamic nature of the location and size of the polar cap. The average polar cap electron density profile depends on geomagnetic activity level e.g., measured by the Kp index and solar illumination (solar zenith angle) at the footprints of the geomagnetic field lines. Our analysis of RPI Ne data shows that increase in geomagnetic activity leads to an enhancement in Ne. This enhancement in Ne is found to increase with altitude. At geocentric distance of R = 4.5 RE, an increase in the geomagnetic activity level from Kp < 2 to ~5 results in an Ne increase by a factor of ~5. On the other hand, a strong solar illumination control of Ne at lower altitudes, and not at higher is observed. At geocentric distance of ~ 2 RE, the average Ne is larger on the sunlit side than on the dark side by a factor of 3 - 4 both for quiet and disturbed conditions. At geocentric distance of about 2.5 RE the effects of these two factors on Ne appear to be comparable. Similar to previous polar cap density models, a functional representation of RPI Ne that takes the form of a power law is proposed. While in the previous Ne functional representations the power index is a constant, the power index in our representation of Ne distribution is found to correlate with (and hence is a function of) the Kp index and the solar zenith angle (SZA).

  10. Observational Evidence that Magnetosheath Plasma Parameters are Prominent in Determining Cross Polar Cap Potential Saturation

    NASA Astrophysics Data System (ADS)

    Clauer, Robert; Xu, Zhonghua; Hartinger, Michael; Ruohoniemi, Michael; Scales, Wayne; Maimaiti, Maimaitirebike; Nicolls, Michael; Wilder, Rick; Lopez, Ramon

    2016-04-01

    A variety of statistical studies have shown that the ionospheric polar potential produced by solar wind - magnetosphere - ionosphere coupling is linear for weak to moderate solar wind driving, but becomes non-linear during periods of very strong driving. It has been shown that this applies to the two-cell convection potential that develops during southward interplanetary magnetic field (IMF) and also to the reverse convection cells that develop during northward IMF. This has been described as polar potential saturation and it appears to begin when the driving solar wind electric field becomes greater than 3 mV/m. It has also been shown that the summer ionospheric electric field saturates at about the same value (20 mV/m) for both northward or southward IMF. Recent measurements of the high latitude convection on September 12 - 13, 2014 using the Resolute Incoherent Scatter Radar during periods of large northward IMF show ionospheric electric fields varying between 56 mV/m and 156 mV/m within the dayside reverse convection cells. There is no indication of saturation during these periods of very strong driving. We believe that the extremely rare conditions in the solar wind that produce extreme driving while also producing a high plasma beta in the magnetosheath provide the best explanation for the lack of potential saturation of the reverse convection cells. That is to say, the conditions in the magnetosheath that contribute to enhancing or limiting reconnection are most important in determining cross polar cap potential saturation. This research was supported at Virginia Tech by National Science Foundation Grant AGS-1216373.

  11. Investigating the asymmetry of Mars' South Polar Cap using the NASA Ames Mars General Circulation Model with a CO2 cloud microphysics scheme

    NASA Astrophysics Data System (ADS)

    Dequaire, J. M.; Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.

    2013-12-01

    One of the most intriguing and least understood climate phenomena on Mars is the existence of a high albedo perennial south polar CO2 ice cap that is offset from the pole in the western hemisphere (SPRC). Colaprete et al. (2005) hypothesize that since the process by which CO2 surface frost accumulates (i.e., precipitation or direct vapor deposition) affects the albedo of the ice, the atmosphere can play a role in the stability and asymmetry of the cap. They show that the basins of Hellas and Argyre force a stationary wave resulting in a colder western hemisphere in which atmospheric CO2 condensation and precipitation is favored. Because precipitated CO2 is brighter than directly deposited CO2, they suggest that this topography driven atmospheric circulation maintains the asymmetry of the southern ice cap. However, Colaprete et al (2005) do not explicitly model the albedo of the south cap to demonstrate the viability of their hypothesis. We build on their study with a version of the NASA Ames GCM that includes a newly incorporated CO2 cloud microphysics scheme. Simulated results compare well to observed temperatures, pressures, cap recession rates and cloud patterns (mesospheric and polar night clouds). Although mesospheric and polar night clouds are thoroughly documented in the literature, the model predicts a third type of cloud to form close to the surface of the subliming ice caps, which has not been observed. As hypothesized by Colaprete et al. (2005), we find that the zonally asymmetric topography forces a stationary wave in the atmosphere resulting in an asymmetric cloud cover over the south pole during fall and winter and enhanced snowfall over a region encompassing the SPRC. These positive results open to further studies including a mesospheric simulation to refine the horizontal grid around the SPRC as well as the implementation of an ice albedo scheme dependent both on the amount and size of aerosols falling onto the cap during fall and winter (snow

  12. 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.

  13. South Polar Residual Cap of Mars: Features Within, and Models of, MRO HiRISE Data

    NASA Astrophysics Data System (ADS)

    Byrne, S.; McEwen, A.; HiRISE Team

    2007-12-01

    We report on observations by the High Resolution Imaging Science Experiment (HiRISE) of the south polar residual CO2 cap of Mars and our related modeling efforts. HiRISE is currently acquiring continuous coverage of this deposit at spatial resolutions of up to 25 cm/px in three separate bands. Several previously undetected features in this CO2 landscape have been noted such as networks of linear ridges and some examples of mass wasting at the rims of pits within the ice. The thicker portions of the CO2 ice appear to be composed of roughly 10 layers. Previous MOC observations have shown that features within this landscape are evolving at meters per year. HiRISE observations will resolve the seasonal dependence of this expansion by the end of the Martian year. High resolution color data are currently showing that the seasonal frost is in the process of disappearing over exposures of the layers on the walls of the CO2 mesas. Although their ablation rates determine that they must be mostly composed of CO2 ice their color is much redder than expected which could possibly be due to dust contamination or grain-size effects. We have modeled the evolution of this CO2 landscape and reproduced its evolution as observed by previous spacecraft. These models have also successfully predicted some features visible at HiRISE resolution such as the linear ridges mentioned above. We report on these new observations and how they extend our current models. Model results have already suggested that the thick portions of this CO2 deposit are likely to be 50- 100 Martian year old, implying that the individual layers observed by HiRISE represent periods of time of order a few Martian years. Global dust storms occur with a similar frequency and may be modulating the behavior of the ice cap.

  14. Additions and corrections to the absorption coefficients of CO2 ice - Applications to the Martian south polar cap

    NASA Technical Reports Server (NTRS)

    Calvin, Wendy M.

    1990-01-01

    Reflectance spectra of carbon dioxide frosts were calculated using the optical constants provided by Warren (1986) for the wavelength region 2-6 microns. In comparing these calculated spectra to spectra of frosts observed in the laboratory and on the surface of Mars, problems in the optical constants presented by Warren (1986) became apparent. Absorption coefficients for CO2 ice have been derived using laboratory reflectance measurements and the Hapke (1981) model for calculating diffuse reflectance. This provides approximate values in regions where no data were previously available and indicates where corrections to the compilation by Warren (1986) are required. Using these coefficients to calculate the reflectance of CO2 ice at varying grain sizes indicates that a typical Mariner polar cap spectrum is dominated by absorptions due to CO2 frost or ice at grain sizes that are quite large, probably of the order of millimeters to centimeters. There are indications of contamination of water frost or dust, but confirmation will require more precise absorption coefficients for solid CO2 than can be obtained from the method used here.

  15. Mapping the open/closed boundary in Jupiter’s polar cap with a 2-D equatorial magnetic field model

    NASA Astrophysics Data System (ADS)

    Vogt, M. F.; Kivelson, M. G.; Khurana, K. K.; Walker, R. J.

    2009-12-01

    The main auroral oval emissions at Jupiter are not associated with the open/closed flux boundary in the polar cap as they are at the Earth, but with the breakdown of plasma corotation in the middle magnetosphere. As a result, the boundary between open and closed flux in the ionosphere is not well defined, though the region of open flux is generally thought to be small. We have mapped contours of constant radial distance from the magnetic equator to the ionosphere with the objective of understanding how auroral features relate to magnetospheric sources. Instead of following along a model field, we map equatorial field lines to the ionosphere by requiring that the magnetic flux in some specified region at the equator equal the magnetic flux in the area to which it maps in the ionosphere. We represent the north-south component of the measured magnetic field (Bθ) at the equator as a function of radial distance and local time by fitting equatorial field measurements to a two-dimensional functional form. From the equatorial field function, we calculate the flux through the equator in pixels of radial increment 5 RJ and a fixed longitudinal. We start by identifying the ionospheric footprint of an equatorial curve at 20 RJ where field models are reasonably accurate. The pixels at 20 RJ are traced to the ionosphere using the field bend back from Khurana and Schwarzl (2005) to determine the corresponding surface longitude. Using a version of the VIP4 model (Connerney et al., 1998) that has been modified to include the effects of the current sheet (Khurana, 1997) to estimate the internal Jovian field in the ionosphere, we then displace the auroral boundary poleward until the ionospheric flux equals the flux in the equatorial pixel. With iteration, we obtain the ionospheric mapping of the 25 RJ circle at the equator. Further iteration provides the mapping of successively distant circles. Equating the fluxes in this way allows us to link a given position in the magnetosphere

  16. 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

  17. Structures Within the South Polar Cap of Mars from Three-dimensional Radar Imaging

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    We used Shallow Radar (SHARAD) observations on 2093 orbital passes by the Mars Reconnaissance Orbiter over Planum Australe to construct a 3-D data volume encompassing the entirety of the Martian south polar layered deposits (SPLD) and their surroundings. Efforts are underway to apply 3-D migration processing, an imaging process that will correct off-nadir returns (clutter) and properly position internal structures while improving the overall signal-to-noise ratio (SNR). Clutter mitigation and the structural corrections that migration provides have been particularly effective for a 3-D SHARAD volume over Planum Boreum, notably supporting the mapping of a shallow unconformity linked to the most recent retreat of mid-latitude glaciation (Smith et al., 2016, Science 352) and revealing what appear to be impact craters fully buried within the ice (Putzig et al., 2015, AGU Fall Meeting, Abs. P53G-05). In the preliminary Planum Australe volume, many crater-like structures are also present, adding to the evidence from surface age dating that the SPLD may be an order of magnitude or more older that the 4-Ma-old north polar layered deposits. Migration processing will sharpen this view, and the expected improvement in SNR is likely to reveal structures that are missing or very faint in single-orbit 2-D profiles, such as the deeper sequences within the layered deposits that are often obfuscated by shallow or internal scattering. The clarified views of the polar-cap interiors emerging from each SHARAD 3-D volume advance our ability to map out the interior structures and infer the history of their emplacement. A full assessment of likely buried craters may provide a means to date the deposits that is independent of climate models and goes beyond estimating a surface age. Achieving these objectives would be a major advancement toward the overarching goal of linking the geologic history of the polar layered deposits to climate processes and their history. Figure provides a cut

  18. Thermal and albedo mapping of the polar regions of Mars using Viking thermal mapper observations: 2. South polar region

    NASA Technical Reports Server (NTRS)

    Paige, David A.; Keegan, Kenneth D.

    1994-01-01

    We present the first maps of the apparent thermal inertia and albedo of the south 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 30-day period in 1977 during the Martian late southern summer season. The maps cover the region from 60 deg S to the south pole at a spatial resolution of 1 deg of latitude, thus completing the initial thermal mapping of the entire planet. 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 atmosphere for a range of assumptions concerning dust optical properties and dust optical depths. The maps show that apparent thermal inertias of bare ground regions decrease systematically from 60 deg S to the south pole. In unfrosted regions close to the south pole, apparent thermal inertias are among the lowest observed anywhere on the planet. On the south residual cap, apparent thermal inertias are very high due to the presence of CO2 frost. In most other regions of Mars, best fit apparent albedos based on thermal emission measurements are generally in good agreement with actual surface albedos based on broadband solar reflectance measurements. The one-dimensional atmospheric model calculations also predict anomalously cold brightness temperatures close to the pole during late summer, and after considering a number of alternatives, it is concluded that the net surface cooling due to atmospheric dust is the best explanation for this phenomenon. The region of lowest apparent thermal inertia close to the pole, which includes the south polar layered deposits, is interpreted to be mantled by a continuous layer of aeolian material that must be at least a few millimeters thick. The low thermal inertias mapped in the south polar region imply an

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Polar cap potential saturation during the Bastille Day storm event using global MHD simulation

    NASA Astrophysics Data System (ADS)

    Kubota, Y.; Nagatsuma, T.; Den, M.; Tanaka, T.; Fujita, S.

    2017-04-01

    We investigated the temporal variations and saturation of the cross polar cap potential (CPCP) in the Bastille Day storm event (15 July 2000) by global magnetohydrodynamics (MHD) simulation. The CPCP is considered to depend on the electric field and dynamic pressure of the solar wind as well as on the ionospheric conductivity. Previous studies considered only the ionospheric conductivity due to solar extreme ultraviolet (EUV) variations. In this paper, we dealt with the changes in the CPCP attributable to auroral conductivity variations caused by pressure enhancement in the inner magnetosphere owing to energy injection from the magnetosphere because the energy injection is considerably enhanced in a severe magnetic storm event. Our simulation reveals that the auroral conductivity enhancement is significant for the CPCP variation in a severe magnetic storm event. The numerical results concerning the Bastille Day event show that the ionospheric conductivity averaged over the auroral oval is enhanced up to 18 mho in the case of Bz of less than -59 nT. On the other hand, the average conductivity without the auroral effect is almost 6 mho throughout the entire period. Resultantly, the saturated CPCP is about 240 kV in the former and 704 kV in the latter when Bz is -59 nT. This result indicates that the CPCP variations could be correctly reproduced when the time variation of auroral conductivity caused by pressure enhancement due to the energy injection from the magnetosphere is correctly considered in a severe magnetic storm event.

  4. 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.

  5. Simulation of the formation of O+ density troughs in the polar cap magnetosphere using the UT Arlington DyFK model

    NASA Astrophysics Data System (ADS)

    Jaafari, Fajer; Horwitz, James; Zeng, Wen

    2006-10-01

    Measurements of the O^+ densities in the polar cap near 5000 km altitude display normal and low density (trough) regions. In this presentation, we use the UTA Dynamic Fluid-Kinetic (DyFK) model to simulate such O^+ density profiles observed by the Thermal Ion Dynamics Experiment (TIDE) on the POLAR spacecraft. Using solar wind parameters and incorporating Cleft Ion Fountain effects for these events to drive a time-varying high-latitude convection model and auroral processes of soft electron precipitation, we simulate the evolving high-latitude ionospheric plasma transport and associated parameter profiles for several convecting flux tubes in the high-latitude ionosphere-magnetosphere system. For the convection patterns thus computed, these flux tubes nominally intersected the POLAR trajectory where the density measurements were made. It is found that, owing chiefly to F-region recombination processes during trajectory segments when the low altitude portions of such flux tubes in darkness, as well as incorporating CIF effects in the dayside auroral region, normal and low trough-like densities at higher altitudes developed along some of these flux tubes. The simulations of the density profiles for these flux tubes will be compared with measured POLAR/TIDE-measured O^+ densities for inside and outside of these regions. This work was completed under financial support by NASA grant NNG05GF67G and NSF grant ATM-0505918 to the University of Texas at Arlington.

  6. A Review of Laboratory Experiments in Support of Interpretation of Hyperspectral Data from the Mars South Polar Residual Cap

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The Martian South Polar Residual Cap (SPRC) is a permanent region of CO2 ice exhibiting unique, dynamic, flat floored, quasi-circular sublimation features known colloquially as Swiss Cheese Terrain (SCT). Sublimation processes can expose dust particles trapped within the ice during winter, which can be analysed using hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board NASA's Mars Reconnaissance Orbiter (MRO). Work is being carried out to establish the composition of these dust particles, and look for evidence of organic molecules that may have been afforded protection within the SPRC from the deleterious effects of ultraviolet radiation on the Martian surface. In this work we review laboratory experiments that have been carried out in order to better interpret CRISM spectra. In particular, SWIR (short-wave infrared) studies of CO2 and H2O ice/frost and dust mixtures, the behaviour of organic molecules in Martian conditions, and the angular reflectance measurements of such spectra. We will then briefly discuss what further work should be carried out to enable these measurements to be used to improve the interpretation of orbital hyperspectral data. Acknowledgements Part of the research leading to these results has received partial funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under iMars grant agreement n˚ 607379; MSSL STFC Consolidated grant no. ST/K000977/1 and the first author is supported by STFC under PhD studentship no. 526933.

  7. Solar wind density controlling penetration electric field at the equatorial ionosphere during a saturation of cross polar cap potential

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Wan, W.; Zhao, B.; Hong, M.; Ridley, A.; Ren, Z.; Fraenz, M.; Dubinin, E.; He, M.

    2012-09-01

    The most important source of electrodynamic disturbances in the equatorial ionosphere during the main phase of a storm is the prompt penetration electric field (PPEF) originating from the high-latitude region. It has been known that such an electric field is correlated with the magnetospheric convection or interplanetary electric field. Here we show a unique case, in which the electric field disturbance in the equatorial ionosphere cannot be interpreted by this concept. During the superstorm on Nov. 20-21, 2003, the cross polar cap potential (CPCP) saturated at least for 8.2 h. The CPCP reconstructed by Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure suggested that the PPEF at the equatorial ionosphere still correlated with the saturated CPCP, but the CPCP was controlled by the solar wind density instead of the interplanetary electric field. However, the predicted CPCPs by Hill-Siscoe-Ober (HSO) model and Boyle-Ridley (BR) model were not fully consistent with the AMIE result and PPEF. The PPEF also decoupled from the convection electric field in the magnetotail. Due to the decoupling, the electric field in the ring current was not able to comply with the variations of PPEF, and this resulted in a long-duration electric field penetration without shielding.

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

    NASA Astrophysics Data System (ADS)

    Benson, R. F.

    1984-04-01

    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.

  9. 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.

  10. 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.

  11. 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.

  12. Interplay of solar wind parameters and physical mechanisms producing the saturation of the cross polar cap potential

    NASA Astrophysics Data System (ADS)

    Myllys, M.; Kipua, E. K. J.; Lavraud, B.

    2017-04-01

    The nonlinear response of the cross polar cap potential (CPCP) to solar wind driving electric field is a well-known phenomenon. The reasons behind this saturation, however, are still under debate. We have performed a statistical study of the coupling efficiency between the solar wind and the northern polar cap index (PCN). PCN is used as a proxy for the CPCP. Our main focus is in quantifying how the solar wind dynamic pressure alters the efficiency. We show that the saturation of PCN occurs both during low and moderate upstream MA conditions. We also show that the increasing dynamic pressure is associated with increasing PCN. In addition, we find that the coupling is different depending on which parameter, the velocity or the magnetic field, increases the solar wind driving electric field: the higher the velocity the higher the coupling efficiency.

  13. Two-spacecraft charged particle observations interpreted in terms of electrostatic potential drops along polar cap field lines

    NASA Astrophysics Data System (ADS)

    Pollock, C. J.; Chappell, C. R.; Horwitz, J. L.; Winningham, J. D.

    We are studying the possible occurrence and magnitude of field-aligned electrostatic potential drops over the ionospheric polar caps. For this purpose, signatures in upgoing and downgoing photoelectrons, obtained in the topside ionosphere using the low altitude plasma instrument (LAPI) on the Dynamics Explorer 2 (DE 2), spacecraft are analyzed [Winningham and Gurgiolo, 1982]. These data are compared with positive ion data obtained at high altitude using the retarding ion mass spectrometer (RIMS) on the DE 1 spacecraft. Data were selected from intervals when DE 1 and DE 2 were approximately connected along polar cap magnetic field lines and when upflowing 0+ beams were observed in the RIMS data. We present here one case in which the comparison of data from the two DE spacecraft is quite favorable regarding its interpretation in terms of a field-aligned potential drop.

  14. 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.

  15. Mapping the open/closed boundary in Jupiter's polar cap with a 2-D equatorial magnetic field model

    NASA Astrophysics Data System (ADS)

    Vogt, Marissa; Kivelson, Margaret; Khurana, Krishan; Walker, Raymond

    2010-05-01

    How much of Jupiter's polar cap is open to the solar wind? Where do the auroral active, dark, and swirl regions map within (or outside) the magnetosphere? With a good global magnetic field model, one could map field lines from the equator to the ionosphere and answer these and similar questions. However, such a model does not exist for Jupiter, so we have taken a different approach in mapping magnetospheric sources to auroral features. Rather than following along a model field, we map equatorial field lines to the ionosphere by requiring that the magnetic flux in some specified region at the equator equal the magnetic flux in the area to which it maps in the ionosphere (flux conservation). The equatorial flux is calculated by using a two-dimensional fit to the north-south component of the measured magnetic field at the equator. This fit accounts for changes with radial distance and local time. To estimate the internal Jovian field in the ionosphere we use a version of the VIP4 model [Connerney et al., 1998] with magnetic anomaly [Grodent et al., 2008] that has been modified to include the effects of the current sheet [Khurana, 1997]. Equating the fluxes in this way allows us to link a given position in the magnetosphere to a position in the ionosphere and to gain insight into the source of different auroral features. We will discuss the results of our mapping in the northern and southern hemispheres, particularly the locations that map to beyond the dayside magnetopause and are likely regions of open flux. We will also compare our calculations to the available auroral observations.

  16. Longitudinal polarization of hyperons in the forward region in polarized pp collisions

    SciTech Connect

    Zhou Wei; Zhou Shanshan; Xu Qinghua

    2010-03-01

    We study the longitudinal polarization of hyperons and antihyperons at forward pseudorapidity, 2.5<{eta}<4, in singly polarized pp collisions at Relativistic Heavy Ion Collider energies by using different parametrizations of the polarized parton densities and different models for the polarized fragmentation functions. The results show that the {Sigma}{sup +} polarization is able to distinguish different pictures on spin transfer in high energy fragmentation processes; and the polarization of {Lambda} and {Lambda} hyperons can provide sensitivity to the helicity distribution of strange sea quarks. The influence from beam remnant to hyperon polarization in the forward region is also discussed.

  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. 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