Synergistic use of multitemporal RAMP,ICESat and GPS to construct an accurate DEM of the Larsemann Hills region,Antarctica

An enhanced digital elevation model (DEM) of the Larsemann Hills region, east Antarctica, is constructed synergistically by using highly accurate ground-based GPS measurements, satellite-derived laser altimetry (GLAS/ICESat) and Radarsat Antarctic Mapping Project (RAMPv2) DEM-based point elevation dataset. Our DEM has a vertical accuracy of about 1.5 times better than RAMPv2 DEM and seven times better than GLAS/ICESAT-based DEM. The accuracy is improved by validating the RAMPv2 DEM elevation by supplementing with GLAS/ICESat and DGPS survey data, when compared to that of DEM constructed by using GLAS/ICESat or RAMPv2 alone. With the use of accurate GPS data as ground control points reference elevations, the DEM extracted is much more accurate with least mean RMSE of 34.5 m than that constructed by using a combination of GLAS/ICESat and RAMPv2 as true reference. The newly constructed DEM 7 achieves highest accuracy with the least average elevation difference of 0.27 m calculated using 46 ground reference points. Available DEMs of Antarctic region generated by using radar altimetry and the Antarctic Digital Database indicate elevation variations in the range of 50–100 m, which necessitates the generation of local DEM and its validation by using ground truth. This is our first attempt of fusing multi-temporal, multi-sensor and multi-source elevation data to generate a DEM of any part of Antarctica, in order to address the ice elevation change to infer the ice mass balance. Our approach focuses on the strengths of each elevation data source to produce an accurate DEM.     

Searching for life in extreme environments relevant to Jovian’s Europa: Lessons from subglacial ice studies at Lake Vostok (East Antarctica)

The objective was to estimate the genuine microbial content of ice samples from refrozen water (accretion ice) from the subglacial Lake Vostok (Antarctica) buried beneath the 4-km thick East Antarctic ice sheet. The samples were extracted by heavy deep ice drilling from 3659 m below the surface. High pressure, a low carbon and chemical content, isolation, complete darkness and the probable excess of oxygen in water for millions of years characterize this extreme environment. A decontamination protocol was first applied to samples selected for the absence of cracks to remove the outer part contaminated by handling and drilling fluid. Preliminary indications showed the accretion ice samples to be almost gas free with a low impurity content. Flow cytometry showed the very low unevenly distributed biomass while repeated microscopic observations were unsuccessful.     

Temperature effects in the ATIC BGO calorimeter

The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment had a successful test flight and a science flight in 2000–01 and 2002–03 and an unsuccessful launch in 2005–06 from McMurdo, Antarctica, returning 16 and 19 days of flight data. ATIC is designed to measure the spectra of cosmic rays (protons to iron). The instrument is composed of a Silicon matrix detector followed by a carbon target interleaved with scintillator tracking layers and a segmented BGO calorimeter composed of 320 individual crystals totaling 18 radiation lengths to determine the particle energy. BGO (Bismuth Germanate) is an inorganic scintillation crystal and its light output depends not only on the energy deposited by particles but also on the temperature of the crystal. The temperature of balloon instruments during flight is not constant due to sun angle variations as well as differences in albedo from the ground. The change in output for a given energy deposit in the crystals in response to temperature variations was determined.     

Study of waves in the magnetotail region with cluster and DSP

The study of the neutral sheet is of fundamental importance in understanding the dynamics of the Earth’s magnetosphere. From the earliest observation of the magnetotail, it has been found that the neutral sheet frequently appears to be in motion due to changing solar wind conditions and geomagnetic activity. Multiple crossings of the neutral sheet by spacecraft have been attributed to a flapping motion of the neutral sheet in the north–south direction, a wavy profile either along the magnetotail or the dawn–dusk direction. Cluster observations have revealed that the flapping motions of the Earth’s magnetotail are of internal origin and that kink-like waves are emitted from the central part of the tail and propagate toward the tail flanks. This flapping motion is shown here to propagate at an angle of ∼45° with x_GSM. A possible assumption that the flapping could be created by a wake travelling away from a fast flow in the current sheet is rejected. Other waves in the magnetotail are found in the ULF range. One conjunction event between Cluster and DoubleStar TC1 is presented where all spacecraft show ULF wave activity at a period of approximately 5 min during fast Earthward flow. These waves are shown to be Kelvin–Helmholtz waves on the boundaries of the flow channel. Calculations show that the conversion of flow energy into magnetic energy through the Kelvin–Helmholtz instability can contribute to a significant part of flow breaking between Cluster and DoubleStar TC1.     

Multi- GNSS reflectometry performance evaluation for coastal sea level monitoring: A case study in Antarctic Peninsula

Antarctica is a continent that crucial for studying climate change and its progression across time, as well as analyzing and forecasting local and global change. In this environment, due to the challenges caused by sea-level rise, storm surges, and tsunamis, sustainability is a critical concern, particularly for coastal regions. As a result, the long-term observations that will be conducted in Antarctica are critical for monitoring the adverse impacts of climate change. In recent years, many monitoring approaches, both space, and ground-based are performed to monitor sea/ice level trends in space-based scientific investigations conducted in and around the region. In the study, based on one year of observations from the Palmer GNSS Station, the GNSS Reflectometry technique was used to measure the sea level on the Antarctic Peninsula (PALM). GNSS Station observations were analyzed with a Lomb-Scargle periodogram to monitor sea-level changes, and results were validated with data from a co-located tide gauge (TG). The results show that the correlation between GNSS-R sea-level changes and tidal sea-level changes is found as 0.91.     

Seasonal patterns of condensation and sublimation cycles in the cryptic and non-cryptic regions of the South Pole

The South Pole of Mars is characterized by an asymmetric residual ice cap composed of water ice and CO₂ ice. On the opposite side of the residual cap, there exists an area called cryptic region which is relatively free of ice during summer time. Many fan-shaped km-scale structures apparently caused by a wind-blown system of dust-laden gas jets occurred dozens degrees of Ls before the complete sublimation of the CO₂ frost layer. We have examined the seasonal cycles of condensation and sublimation in the cryptic and non-cryptic regions by using the topographic data from the MOLA/MGS measurements. Using the MOLA topography data collected over one Martian year (1999–2001), we have studied the temporal elevation change and the seasonal cycle of the carbon dioxide frost on the southern polar caps. We have produced mapping of the seasonal CO₂ frost thickness variation for seven Ls (30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°, 270° and 330°). It is found that the time variations of the CO₂ frost thickness in these two regions are quite similar. The greatest thickness of the CO₂ frost layer is about 0.76–0.78 m in both places occurs at Ls = 150°.     

Effective non-vertical and apparent cutoff rigidities for a cosmic ray latitude survey from Antarctica to Italy in minimum of solar activity

In this paper we will report the results of the computation of cutoff rigidities of vertical and non-vertical incident cosmic ray particles. Non-vertical effective cutoff rigidities have been computed by tracing particle trajectories through the “real” geomagnetic magnetic field comprising the International Geomagnetic Reference Field model (IGRF95, IAGA Division 5 Working Group 8, 1996: Sabaka, T.J., Langel, R.A., Baldwin, R.T., Conrad, J.A. The geomagnetic field, 1900–1995, including the large scale fields from magnetospheric sources and NASA candidate models for the 1995 IGRF revision. J. Geomag. Geoelect. 49, 157–206, 1997.) and the Tsyganenko [Tsyganenko, N.A. A magnetospheric magnetic field model with a warped tail current sheet. Planet. Space Sci. 37, 5–20, 1989.] magnetosphere model. The computation have been done for the backward route (from Antarctica to Italy) of the Italian Antarctic ship survey 1996–1997, for geographic points corresponding to the daily average coordinates of the ship; for zenith angles 15°, 30°, 45° and 60°, and azimuth angles from 0° to 360° in steps of 45°. By means of the obtained non-vertical cutoffs the apparent cutoff rigidities have been calculated. The information on integral multiplicities of secondary neutrons detected by the neutron monitor in dependence of the zenith angle of incoming primary cosmic ray particles have also been used. This information is based on the theoretical calculations of meson-nuclear cascades of primary protons with different rigidities arriving to the Earth’s atmosphere at the zenith angles of 0°, 15°, 30°, 45°, 60° and 75°. The difference between the computed apparent and vertical cutoff rigidities reaches ∼1 GV at rigidities >7–8 GV. At rigidities of 10–16 GV, the difference between the apparent and vertical cutoff rigidities is larger than that obtained earlier by Clem et al. [Clem, J.M., Bieber, J.W., Duldig, M., Evenson, P., Hall, D., Humble, J.E. Contribution of obliquely incident particles to neutron monitor counting rate. J. Geophys. Res. 102, 26919–26926, 1997.] and Dorman et al. [Dorman, L.I., Villoresi, G., Iucci, N., Parisi, M., Tyasto, M.I., Danilova, O.A., Ptitsyna, N.G. Cosmic ray survey to Antarctica and coupling functions for neutron component near solar minimum (1996–1997), 3. Geomagnetic effects and coupling functions. J. Geophys. Res. 105, 21047–21056, 2000.].     

Study of long path VLF signal propagation characteristics as observed from Indian Antarctic station,Maitri

To examine the quality and propagation characteristics of the Very Low Frequency (VLF) radio waves in a very long propagation path, Indian Centre for Space Physics, Kolkata, participated in the 27th Indian scientific expedition to Antarctica during 2007–2008. One Stanford University made AWESOME VLF receiving system was installed at the Indian Antarctic station Maitri and about five weeks of data were recorded successfully from the Indian transmitter VTX and several other transmitting stations worldwide. The quality of the signal from the VTX transmitter was found to be very good, consistent and highly stable in day and night. The signal shows the evidences of the presence of the 24 h solar radiation in the Antarctic region during local summer. Here we report the both narrow band and broadband VLF observations from this site. The diurnal variations of VTX signal (18.2 kHz) are presented systematically for Antarctica path and also compared the same with the variations for a short propagation path (VTX-Kolkata). We compute the spatial distribution of the VTX signal along the VTX-Antarctica path using the most well-known LWPC model for an all-day and all-night propagation conditions. The calculated signal amplitudes corresponding to those conditions relatively corroborate the observations. We also present the attenuation rate of the dominant waveguide modes corresponding to those propagation conditions where the effects of the Antarctic polar ice on the attenuation of different propagating waveguide modes are visible.     

Radar altimetry measurements over antarctic ice sheet: A focus on antenna polarization and change in backscatter problems

In this paper, we investigate the impact of the error due to the penetration of the altimetric wave within the snowpack. The phenomenon has two different impacts. The first one, due to temporal change in snow characteristics, affects the ice sheet volume trend as derived from altimetric series. The second one, because of both the anisotropy of the ice sheet surface properties and of the linear antenna polarization, introduces a difference in measurements at crossover points. These two phenomena are the cause of what are probably the most critical limitations to the interpretation of long-term altimetric series in term of mass balance and to the comparison between or data fusion of different missions. Moreover, they will lead to the largest error when comparing data from EnviSat with data from CryoSat, because of the different orbits, or with data from AltiKa, because of the different radar frequencies.     

Plasma sheet oscillations and their relation to substorm development: Cluster and double star TC1 case study

We examined two consecutive plasma sheet oscillation and dipolarization events observed by Cluster in the magnetotail, which are associated with a pseudo-breakup and a small substorm monitored by the IMAGE spacecraft. Energy input from the solar wind and an associated enhancement of the cross-tail current lead to current sheet thinning and plasma sheet oscillations of 3–5 min periods, while the pseudo-breakups occur during the loading phase within a spatially limited area, accompanied by a localized dipolarization observed by DSP TC1 or GOES 12. That is, the so-called “growth phase” is a preferable condition for both pseudo-breakup and plasma sheet oscillations in the near-Earth magnetotail. One of the plasma sheet oscillation events occurs before the pseudo-breakup, whereas the other takes place after pseudo-breakup. Thus there is no causal relationship between the plasma sheet oscillation events and pseudo-breakup. As for the contribution to the subsequent small substorm, the onset of the small substorm took place where the preceding plasma sheet oscillations can reach the region.     

On the transport of cosmic rays in the distant heliosheath

This paper discusses the transport of energetic charged particles through a sectored magnetic field in distant regions of the inner heliosheath. As the plasma flow slows down on approach to the stagnation point on the heliopause, the distance between the folds of the current sheet decreases to the point where it becomes comparable to the cyclotron radius of a cosmic ray particle. Under these conditions a particle can effectively drift across the stack of magnetic sectors with a speed comparable with the particle’s velocity. For a random distribution of current sheet separation distances, a diffusive transport across the stack of sectors occurs instead. The proposed mechanism could have contributed to unusually high intensities of galactic cosmic rays measured by Voyager 1 in the heliosheath during 2009–2010.     

A laboratory study on the thermally induced transformation of hydrogen cyanide (HCN) to the cyanogen anion (CN) in Solar System analog ices

Mixtures of molecular nitrogen and methane have been identified in numerous outer Solar Systemices including the icy surfaces of Pluto and Triton. We have simulated the interaction of ionizing radiation in the Solar System by carrying out a radiolysis experiment on a methane – molecular nitrogen ice mixture with energetic electrons. We have identified the hydrogen cyanide molecule as the most prominent carbon–nitrogen-bearing reaction product formed. Upon warming the irradiated sample, we followed for the first time the kinetics and temporal evolution of the underlying acid–base chemistry which resulted in the formation of the cyanide ion from hydrogen cyanide. On the surfaces of Triton and Pluto and on comets in Oort’s cloud this sort of complex chemistry is likely to occur. In particular, hydrogen cyanide can be produced in low temperature environments (Oort cloud comets) and may be converted into cyanide ions once the comets reach the warmer regions of the Solar System.     

Hydrocode modelling of hypervelocity impacts on ice

Experimental data are now widely available for the size of craters resulting from hypervelocity impacts of millimetre scale projectiles onto water ice targets. At such size scales the bowl shaped crater formed in ductile materials, or in larger scale impacts, is here surrounded by a large spallation zone due to the brittle nature of the ice. Modelling of these impacts therefore has to take account of this spallation. Here we used the iSALE2 hydrocode to simulate such impacts and compared the results to experimental data. We found that it was possible to reproduce the experimental data over a range of speeds (1–7 km s⁻¹) for aluminium and copper projectiles. Initially, to reproduce the large spallation regions around the craters it was assumed that above a certain degree of damage, material was removed by spallation. However this simple one-parameter model failed to model the crater depth adequately. Accordingly, to obtain the best agreement of the simulations with the experimental data, a two-step ice strength was introduced, whereby above a critical amount of damage (0.95), the yield strength reduced from 1 MPa (intact) to 70 kPa (damaged). As a result, experimental data for crater depth and diameter and the results of the simulations agree to within 6% for diameter and 5% for depth over the impact energy range used in the experiments (1–240 J).     

New evidence of solar variation in temperature proxies from Northern Fennoscandia

A new summer temperature proxy was built for northern Fennoscandia in AD 1000–2004 using parameters of tree growth from a large region, extending from the Swedish Scandes to the Kola Peninsula. It was found that century-scale (55–140 year) cyclicity is present in this series during the entire time interval. This periodicity is highly significant and has a bi-modal structure, i.e. it consists of two oscillation modes, 55–100 year and 100–140 year variations. A comparison of the century-long variation in the northern Fennoscandian temperature proxy with the corresponding variations in Wolf numbers and concentration of cosmogenic ¹⁰Be in glacial ice shows that a probable cause of this periodicity is the modulation of regional climate by the secular solar cycle of Gleissberg. This is in line with the results obtained previously for a more limited part of the region (Finnish Lapland: 68–70° N, 20–30° E). Thus the reality of a link between long-term changes in solar activity and climate in Fennoscandia has been confirmed. Possible mechanisms of solar influence on the lower troposphere are discussed.     

High resolution limb observations of clouds by the CRISTA-NF experiment during the SCOUT-O3 tropical aircraft campaign

The Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere – New Frontiers (CRISTA-NF) experiment on board the Russian research aircraft Geophysica measures limb emission spectra with an unprecedented vertical and horizontal resolution in the 4–15 μm wavelength region. The IR spectra measured during the SCOUT-O3 Tropical Aircraft Campaign have been analysed with respect of cloud occurrence, cloud vertical and horizontal extent, cloud spatial structures and their utilisation for trace gas retrievals. In addition indicators for ice water content and optical thickness of the clouds have been adopted. These new kinds of measurements in the upper troposphere/lower stratosphere region are especially valuable for the design and development of future space borne high resolution limb sounders.     

Kink-like mode of a double gradient instability in a compressible plasma current sheet

A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet.     

Ion-acoustic waves in unmagnetized collisionless weakly relativistic plasma of warm-ion and isothermal-electron using time-fractional KdV equation

Collisionless unmagnetized plasma consisting of a mixture of warm ion-fluid and isothermal-electron is considered, assuming that the ion flow velocity has a weak relativistic effect. The reductive perturbation method has been employed to derive the Korteweg–de Vries (KdV) equation for small – but finite-amplitude electrostatic ion-acoustic waves in this plasma. The semi-inverse method and Agrawal’s method lead to the Euler–Lagrange equation that leads to the time fractional KdV equation. The variational-iteration method given by He is used to solve the derived time fractional KdV equation. The calculations show that the fractional order may play the same rule of higher order dissipation in KdV equation to modulate the soliton wave amplitude in the plasma system. The results of the present investigation may be applicable to some plasma environments, such as space-plasmas, laser-plasma interaction, plasma sheet boundary layer of the earth’s magnetosphere, solar atmosphere and interplanetary space.     

Search for primordial antiparticles with BESS

The Balloon-borne Experiment with a Superconducting Spectrometer (BESS) has been carried out to search for primordial antiparticles in cosmic rays. In ten flights from 1993 to 2004, it measured the cosmic-ray antiproton spectrum in the energy range 0.1–4.2 GeV at various solar activity conditions. It also searched for antideuterons and antihelium nuclei, and it made precise measurement of cosmic-ray particle spectra. The BESS program has been extended to long duration balloon (LDB) flights in Antarctica (BESS-Polar) with the goal of achieving unprecedented sensitivity in the search for primordial antiparticles. This report describes recent results from BESS and progress of the BESS-Polar program.