The 16-day waves in the mesosphere and lower thermosphere over Wuhan (30.6°N, 114.5°E) and Adelaide (35°S, 138°E)

Winds from a meteor radar at Wuhan (30.6°N, 114.5°E) and a MF radar at Adelaide (35°S, 138°E) are used to study the 16-day waves in the mesosphere and lower thermosphere (MLT). The height range is 78–98 km at Wuhan and 70–98 km at Adelaide. By comparison, it is found that the zonal components at both sites are generally larger than the meridional ones, and eastward motion of the zonal background winds is favorable for the 16-day waves penetration to the MLT region. The zonal maximum amplitude appears in the autumn (September–October) around 86–98 km at Wuhan and in the winter months and early spring (July–October) around 72–82 km at Adelaide. Differences are found in wave amplitudes and time of appearance between the two years of 2002 and 2003. In 2003, the intensity of the wave amplitudes is relatively smaller than that for 2002 at both sites. The summer 16-day waves are comparatively weaker at Adelaide in both years, but stronger in 2002 at Wuhan near the mesopause and the lower thermosphere (86–98 km). The strong summer waves at Wuhan may come from the winter southern hemisphere.     

Low-frequency electric field and density fluctuation measurements on Solar Orbiter

Solar Orbiter will orbit the Sun down to a distance of 0.22 AU allowing detailed in situ studies of important but unexplored regions of the solar wind in combination with coordinated remote sensing of the Sun. In-situ measurements require high quality measurements of particle distributions and electric and magnetic fields. We show that such important scientific topics as the identification of coronal heating remnants, solar wind turbulence, magnetic reconnection and shock formation within coronal mass ejections all require electric field and plasma density measurements in the frequency range from DC up to about 100 Hz. We discuss how such measurements can be achieved using the double-probe technique. We sketch a few possible antenna design solutions.     

Characterization of the semi-annual-oscillation in mesospheric temperatures at low-latitudes

Novel measurements of the seasonal variability in mesospheric temperature at low-latitudes have been obtained from Maui, Hawaii (20.8°N, 156.2°W) during a 25-month period from October 2001 to January 2004. Independent observations of the OH (6, 2) Meinel band (peak height ∼87 km) and the O₂ (0–1) atmospheric band emission (∼94 km) were made using the CEDAR Mesospheric Temperature Mapper. The data revealed a coherent oscillation in emission intensity and rotational temperature with a well-defined periodicity of 181 ± 7 days. The amplitude of this oscillation was determined to be ∼5–6 K in temperature and ∼8–9% in intensity for both the OH and O₂ data sets. In addition, a strong asymmetry in the shape of the oscillation was also observed with the spring maximum significantly larger than the fall peak. These data provide new evidence in support of a semi-annual-oscillation in mesospheric temperature (and airglow emission intensities) and help quantify its seasonal characteristics.     

A new narrow beam Doppler radar at 3 MHz for studies of the high-latitude middle atmosphere

A Doppler radar at 3.17 MHz has been installed at Saura close to the Andøya Rocket Range as part of the ALOMAR observatory at Andenes, Norway in summer 2002 to improve the ground based capabilities for measurements of small scale features and turbulence in the mesosphere. The main feature of the new Saura MF radar is the transmitting/receiving antenna which is arranged as a Mills Cross of 29 crossed half-wave dipoles with a minimum beam width of about 7°. Each dipole is fed by its own transceiver, and the individual phase control of the 58 transceiver modules on transmission and reception provides high flexibility in beam forming and pointing as well as transmission switching between ordinary and extraordinary mode circular polarisation. In addition, beams with different widths at the same pointing angle can be formed. For multiple receiver applications (spaced antenna wind measurements, all-sky meteor detections) four independent receiving channels are available.     

Development of a 2.8 μm film for scientific balloons

Development of a balloon to fly at higher altitudes is one of the most attractive challenges in scientific balloon technologies. After reaching the highest record setting balloon altitude of 53.0 km using the 3.4 μm film in 2002, we tried to make a thinner balloon film. In 2003, we developed a forming die and an air-ring and succeeded in forming a film with a thickness of 3.0 μm and a width of 220 cm. Using this film, we manufactured a balloon with a volume of 5000 m³ and succeeded in flying the balloon up to an altitude of 46.0 km. We then searched for a good combination of resins to make a thinner and wider film and obtained films with widths of 280 cm, and a thickness of 3.0 μm at first, and then 2.8 μm. In 2004, we performed balloon experiments making a 30,000 m³ balloon with the 3.0 μm film and a 5000 m³ balloon with the 2.8 μm film. Both balloons were well manufactured and reached the highest altitudes of 50.7 and 42.6 km, respectively.     

The contribution of radar interferometry to the assessment of landslide hazards

Interferometric analysis of repeat pass radar images (InSAR) enables the mapping of slope movements with high accuracy, being of great relevance for the assessment of landslide risk. The InSAR method is briefly explained, with emphasis on data processing for landslide motion mapping. Constraints of the method are discussed, mainly resulting from temporal decorrelation of the radar signal in vegetated areas. Application examples for InSAR mapping of very slow slope movements, using SAR data of the European Earth Observation Satellite ERS, are shown for a mass waste above an alpine traffic route and for slope deformation in a mountain village. The comparison with GPS measurements of surface motion shows RMSE = 3.7 mm a⁻¹ between the InSAR and GPS retrieved motion, where part of this difference is attributed to the different observation periods. The investigations demonstrate the good capability of InSAR for detecting and monitoring surface deformation on mountain slopes, thus providing valuable support for landslide inventories and risk assessment.     

Ground-based measurement of strato–mesospheric CO by a FTIR spectrometer over Poker Flat,Alaska

Upper atmospheric CO above 24 km has been observed over Poker Flat (147°W, 65°N, altitude 0.61 km), Alaska using ground-based solar absorption infrared spectroscopy. This is the first reported detection of stratospheric–mesospheric CO using this method from the ground. The results clearly indicate that there is a seasonal variation of the CO profile with enhanced abundances in spring while remaining low from May onwards.The Poker Flat Research Range is one of the many measurement sites that constitute the Network for the Detection of Stratospheric Change (NDSC). The method used in this work, estimating the CO partial column abundances above the middle stratosphere, can be applied to spectra observed using FTIR spectrometry at many other NDSC sites. This suggests the availability of this established technique as a new method for CO measurements in the upper atmosphere.     

Giant radio pulses from the Crab pulsar

Individual giant radio pulses (GRPs) from the Crab pulsar last only a few microseconds. However, during that time they rank among the brightest objects in the radio sky reaching peak flux densities of up to 1500 Jy even at high radio frequencies. Our observations show that GRPs can be found in all phases of ordinary radio emission including the two high frequency components (HFCs) visible only between 5 and 9 GHz [Moffett, D.A., Hankins, T.H. Multifrequency radio observations of the Crab pulsar. Astrophys. J. 468, 779–783, 1996]. This leads us to believe that there is no difference in the emission mechanism of the main pulse (MP), inter pulse (IP) and HFCs. High resolution dynamic spectra from our recent observations of giant pulses with the Effelsberg telescope at a center frequency of 8.35 GHz show distinct spectral maxima within our observational bandwidth of 500 MHz for individual pulses. Their narrow band components appear to be brighter at higher frequencies (8.6 GHz) than at lower ones (8.1 GHz). Moreover, there is an evidence for spectral evolution within and between those structures. High frequency features occur earlier than low frequency ones. Strong plasma turbulence might be a feasible mechanism for the creation of the high energy densities of ∼6.7 × 10⁴ erg cm⁻³ and brightness temperatures of ∼10³¹ K.     

Airglow OH emission height inferred from the OH temperature and meteor trail diffusion coefficient

Simultaneous observations of the airglow OH(6,2) band rotational temperature, TOH, and meteor trail ambipolar diffusion coefficient, D, were carried out at Shigaraki (35°N, 136°E), during PSMOS 2003 Campaign, January 28 to February 8, 2003. The OH emission height was estimated by cross correlation analysis of the TOH and D nocturnal variations. A good correlation between TOH and D was obtained at 85 km of altitude. From the nocturnal variations of TOH and D, it is found that the OH emission peak height varied from 88 km before the midnight to 84 km in the early morning. The height variation could be caused by an atmospheric tidal effect in the emission height.     

Nonlinear processes in cosmic-ray precursor of strong supernova shock: Maximum energy and average energy spectrum of accelerated particles

The instability in the cosmic-ray precursor of a supernova shock is studied. The level of turbulence in this region determines the maximum energy of accelerated particles. The consideration is not limited by the case of weak turbulence. It is assumed that the Kolmogorov type nonlinear wave interactions together with the ion-neutral collisions restrict the amplitude of random magnetic field. As a result, the maximum energy of accelerated particles strongly depends on the age of a SNR. The average spectrum of cosmic rays injected in the interstellar medium in the course of adiabatic SNR evolution takes the approximate form E⁻² at energies larger than 10–30 GeV/nucleon with the maximum energy that is close to the position of the knee in cosmic-ray spectrum at 4 × 10¹⁵ eV. At an earlier stage of SNR evolution – the ejecta-dominated stage, the particles are accelerated to higher energies and have a rather steep power-law distribution. These results suggest that the knee may mark the transition from the ejecta-dominated to the adiabatic evolution of SNR shocks which accelerate cosmic rays.     

On the production of highest energy solar protons at 20 January 2005

On January 20, 2005, 7:02–7:05 UT the Aragats Multidirectional Muon Monitor (AMMM) located at 3200 m a.s.l. registered enhancement of the high energy secondary muon flux (threshold ∼5 GeV). The enhancement, lasting for 3 min, has statistical significance of ∼4σ and is related to the X7.1 flare seen by the GOES, and very fast (>2500 km/s) CME seen by SOHO, and the Ground Level Enhancements (GLE) #69 detected by the world-wide network of neutron monitors and muon detectors. The energetic and temporal characteristics of the muon signal from the AMMM are compared with the characteristics of other monitors located at the Aragats Space-Environmental Center (ASEC) and with other neutron and muon detectors. Since secondary muons with energies >5 GeV are corresponding to solar proton primaries with energies 20–30 GeV we conclude that in the episode of the particle acceleration at 7:02–7:05 UT 20 January 2005 solar protons were accelerated up to energies in excess of 20 GeV.     

Analysis of electromagnetic and electrostatic effects of particle impacts on spacecraft

Particle impacts on spacecraft can cause considerable damage, even leading to complete failure. A theory for the resulting vehicle potential changes and the electromagnetic radiation from impact-induced plasma has been published by Close et al. (2010). Here we compare this theory to impacts registered by the Radio and Plasma Wave Science instrumentation on the Cassini spacecraft. We study both low-velocity (16 km/s) large particles (2.6 μm radius) detected in Saturn’s rings and high-velocity (450 km/s) small particles (1 nm radius) in the solar wind. The agreement with the theory is quite good. We also apply these results to earth orbit and conclude that both Electrostatic Discharge and Electromagnetic Pulse radiation are likely and could lead to spacecraft failure.     

Velocity dependent response of a piezoelectric element to hypervelocity microparticles

Piezoelectric lead–zirconate–titanate (PZT) elements were studied by directly bombarding hypervelocity silver and iron particles in the velocity range of 2–63 km/s. This report focuses on the concept of “immediately after collision”. This concept was realized in the leading part of a pulsed signal that exhibited no effects due to reflection. The signal form was discussed from the viewpoint that information on impact was recorded by the waveform. The results indicated that the output amplitude was independent of the thickness of a PZT element, and that the waveform was explicitly related to the velocity at collision. Further, it appeared as an oscillating form at velocities less than 6 km/s. As the velocity increased, it gradually changed to a solitary pulse. The rise time of the single solitary waveform was linearly related to velocities above 6 km/s. The potential of a single PZT element is discussed as a real-time detector for hypervelocity microparticles.     

The high altitude student platform (HASP) for student-built payloads

An outstanding issue with aerospace workforce development is what should be done at the university level to attract and prepare undergraduates for an aerospace career. One approach adopted by many institutions is to lead students through the design and development of small payloads (less than about 500 grams) that can be carried up to high altitude (around 30 km) by a latex sounding balloon. This approach has been very successful in helping students to integrate their content knowledge with practical skills and to understand the end-to-end process of aerospace project development. Sounding balloons, however, are usually constrained in flight duration (∼30 min above 24 km) and payload weight, limiting the kinds investigations that are possible. Student built picosatellites, such as CubeSats, can be placed in low Earth orbit removing the flight duration constraint, but the delays between satellite development and launch can be years. Here, we present the inexpensive high altitude student platform (HASP) that is designed to carry at least eight student payloads at a time to an altitude of about 36 km with flight durations of 15–20 h using a small zero-pressure polyethylene film balloon. This platform provides a flight capability greater than sounding balloons and can be used to flight-test compact satellites, prototypes and other small payloads designed and built by students. The HASP includes a standard mechanical, power and communication interface for the student payload to simplify integration and allows the payloads to be fully exercised. HASP is lightweight, has simple mission requirements providing flexibility in the launch schedule, will provide a flight test opportunity at the end of each academic year.     

Energetic particle transport in anisotropic magnetic turbulence

We study energetic particle transport in a magnetic field configuration which models the solar wind magnetic turbulence plus the background field. A power-law Fourier amplitude is used for the fully 3D turbulence model, and in order to model anisotropic turbulence, the constant amplitude surfaces in k space are ellipsoids. The turbulence correlation lengths parallel (perpendicular) to the background magnetic field l_∥ (l_⊥) are varied in a wide range, and proton energies from 1 MeV to 10 GeV are assumed. Considering propagation on a distance corresponding to 1 AU, it is found that transport parallel and perpendicular to the background field heavily depends on the turbulence anisotropy, that is on the ratio l_∥/l_⊥. The spatial distribution of energetic particle follows the shape of magnetic flux tube up to about 10 MeV, while for larger energies the structure of the magnetic flux tube is progressively washed out. The scatterplots of particle distribution show intermittent, non Gaussian structures for l_∥ ≪ l_⊥ (quasi slab turbulence), while a more diffusive, Gaussian structure is obtained for l_∥ ≫ l_⊥ (quasi 2D turbulence). The long time behavior of transport shows that anomalous (subdiffusive perpendicular and superdiffusive parallel) transport regimes are obtained for l_∥ ≪ l_⊥, while Gaussian diffusive transport is obtained for both l_∥ ≫ l_⊥ and the isotropic turbulence case.     

Study of >100 GeV electrons with BETS detector using a long duration balloon flight in Antarctica

We have observed cosmic-ray electrons from 10 to 1000 GeV by a long duration balloon flight using Polar Patrol Balloon (PPB) in Antarctica. The observation was carried out for 13 days at an altitude of 35 km in January 2004. The detector is an imaging calorimeter composed of scintillating-fiber belts and plastic scintillators inserted between lead plates. The geometrical factor of detector is about 600 cm²sr and the total thickness of lead absorber is 9 radiation lengths. The performance of the detector has been confirmed by the CERN-SPS beam test and also investigated by Monte-Carlo simulations. New telemetry system using a commercial satellite of iridium, power supply by solar batteries, and automatic level control using CPU have successfully been developed and operated during the flight. We have collected 5.7 × 10³ events over 100 GeV including nearly 100 candidates of primary electrons.     

Detection of long-term trends in the mesosphere/lower thermosphere from ground-based radio propagation measurements

Mesospheric temperature trends can be derived from LF phase-height observations in mid-latitudes supported by ionospheric absorption and ionosonde observations. Analysing the full observation period from 1959 until 2003, a mean yearly temperature trend has been derived with −0.25 K/yr for the height interval from 48 to 82 km. Subdividing the whole observation interval in two parts before and after 1979, the trend is markedly stronger in the second period with −0.38 K/yr compared with −0.20 K/yr in the first part before 1979. These differences can at least partly be explained by a steeper CO₂ increase and ozone decrease in the second interval. The differences in the mesospheric temperature trends are most evidently expressed during winter months and are markedly smaller during summer season. The reason of this seasonal difference is not quite clear; it may be related with detected ozone trends which are clearly stronger during winter months on both hemispheres.     

USV test flight by stratospheric balloon: Preliminary mission analysis

The Unmanned Space Vehicle test flights will use a 7 m 1300 kg aircraft. The first three launches will take place at the Italian Space Agency ASI base in Trapani–Milo, Sicily, through a stratospheric balloon that will drop the aircraft at a predefined height. After free fall acceleration to transonic velocities, the parachute deployment will allow a safe splash down in the central Mediterranean Sea. The goal of this article is to show the preliminary analysis results for the first USV flight.We carried out a statistical study for the year 2000–2003, evaluating the typical summer and winter launch windows of the Trapani–Milo base.First, in the center Mediterranean, we define safe recovery areas. They cannot be reached during the balloon ascending phase so, after a sufficiently long floating part able to catch the open sea, the balloon will go down to the release height (24 km). The simulation foresees a 400,000 m³ balloon and 3 valves for the altitude transfer.A safe splash down must occur far enough from the nearest coast: the minimum distance is considered around 25 km. The vehicle should be released at a distance, from the nearest coast, greater than this minimum amount plus the USV model maximum horizontal translation, during its own trajectory from balloon separation to splash down. In this way we define safe release areas for some possible translations.Winter stratospheric winds are less stable. The winter average flight duration is 7 h and it is probably too long for the diurnal recovery requirement and its scheduled procedures.Comparing past stratospheric balloons flights and trajectories computed using measured meteorological data (analysis), with their predictions made using forecast models and soundings, we obtain the standard deviation of the trajectory forecast uncertainty at the balloon–aircraft separation. Two cases are taken into account: predictions made 24 and 6 h before the launch.Assuming a Gaussian latitudinal uncertainty distribution for the prediction 6 h before the launch, we are able to identify the forecast trajectories that have a probability greater than 97% to reach the safe release areas.Simulating the summer windows trajectories for the years from 2000 to 2003 and for the favorable ground wind days, we obtain the number of trajectories with the desired forecast probabilities.     

The role of drift and convection–diffusion mechanisms in small energy global cosmic ray modulation: Application to the hysteresis phenomenon of proton and alpha particle satellite data

The hysteresis effect for small energies of galactic cosmic rays is due to two effects. The first is the same as for neutron monitor energies – the delay of the interplanetary processes responsible for cosmic ray modulation with respect to the initiating solar processes, according to the effective velocity of solar wind and shock waves propagation. Then, the observed cosmic ray intensity is connected to the solar activity variations during many months before the time of cosmic ray measurement. The second is caused by the time delay of small energy cosmic ray diffusion from the boundary of modulation region to the Earth’s orbit. The model describing the connection between solar activity variation and cosmic ray convection–diffusion global modulation for neutron monitor energies is here developed by taking into account also the time-lag of the small energy particle diffusion in the Heliosphere. We use theoretical results on drifts and analytically approximate the dependences of drifts from tilt angle, and take into account the dependence from the sign of primary particles, and from the sign of polar magnetic field (A > 0 or A < 0). The obtained results are applied on proton and alpha-particle satellite data. We analyze satellite 5-min data of proton fluxes with energies >1 MeV, >2 MeV, >5 MeV, >10 MeV, >30 MeV, >50 MeV, >60 MeV, >100 MeV, and in intervals 10–30 MeV, 30–60 MeV, and 60–100 MeV during January 1986–December 1999. We exclude periods with great cosmic ray increases caused by particle acceleration in solar flare events. Then, we determine monthly averaged fluxes, as well as 5-month and 11-month smoothed data. We analyze also satellite 5-min data on alpha-particle fluxes in the energy intervals 60-160 MeV, 160–260 MeV and 330–500 MeV during January 1986–May 2000. We correct observation data for drifts and then compare with what is expected according to the convection–diffusion mechanism. We assume different dimensions of the modulation region (by the time propagation X₀ of solar wind from the Sun to the boundary of modulation region), for X₀ values from 1 to 60 average months, by one-month steps. For each value of X₀ we determine the correlation coefficient between variations of expected and observed cosmic ray intensities (the estimation of cosmic ray intensities values is given in Section 3 by Eq. (9), and the determination of correlation and regression coefficients in Section 3 by Eq. (8)). The dimension of modulation region is determined by the value of X_0 max, for which the correlation coefficient reaches the maximum value. Then the effective radial diffusion coefficient and residual modulation in small energy region can be estimated.     

The spatial distribution of galactic and anomalous cosmic rays in the heliosphere at solar minimum

The spatial distributions of galactic and anomalous cosmic rays in the heliosphere at the solar minima of Cycles 20/22 (qA > 0) and of Cycle 21 (qA < 0) are studied, using data from IMP 8, Voyagers 1/2 and Pioneer 10. It is found that the radial dependences of intensities J can be approximated by a power of radial distance r as J ∝ r^α with a different value of a constant in the inner and outer heliosphere with a transition at a radial distance of 10–15 AU. To study the physical meaning of these radial intensity profiles we examined the rigidity dependences of the intensity gradients by determining the particle mean free paths, using a simple one-dimensional modulation model. The particle mean free path λ was assumed to be a separable function of distance of the form r^γ and rigidity R of R^δ over the range of 0.5–3.0 GV in the inner and outer heliosphere. It was shown that λ of rigidity dependence of R^1.6 determined for Cycle 20/22 (qA > 0) with anomalous He is about 4–5 times larger than that of Cycle 21 (qA < 0) with R^0.9 at around 1 GV in the outer heliosphere, and that the radial dependences are r^1.4 and r^1.1, respectively, for Cycles 20/22 and for Cycle 21.