How much does weather control fire size and intensity in the Mediterranean region?
Ann. Geophys., 33, 931-939, doi:10.5194/angeo-33-931-2015, 2015
Several notes on the OH* layer
Summary: The expressions that determine the altitude and number density at peak of the OH* layer were derived. OH* number density in the vicinity of the OH* layer is directly proportional to the atomic oxygen concentration and inversely proportional to the power of temperature. The peak of the layer number density is anti-correlated with the height of the peak. Atomic oxygen is responsible for the vertical separation of sub-layers with different vibrational numbers, and for the distance between them.
Ann. Geophys., 33, 923-930, doi:10.5194/angeo-33-923-2015, 2015
Observations of thermosphere and ionosphere changes due to the dissipative 6.5-day wave in the lower thermosphere
Summary: The 6.5-day traveling planetary wave is able to impact the ionosphere/thermosphere via a dissipation mechanism. Ionospheric TEC and thermosphere O/N2 exhibit an apparent decrease as the result of extra meridional circulation induced by 6.5-day wave dissipation. Our work suggests that the modulation of E-dynamo is not the unique pathway through which planetary waves substantially influence the IT system.
Ann. Geophys., 33, 913-922, doi:10.5194/angeo-33-913-2015, 2015
Planetary period oscillations in Saturn's magnetosphere: comments on the relation between post-equinox periods determined from magnetic field and SKR emission data
Summary: We compare the reported properties of oscillations in Saturn's outer plasma environment near the ~10.6 hour planetary rotation period, as observed in magnetic field and radio emission data obtained by the Cassini spacecraft. We highlight similarities and differences, and suggest possible reasons for the latter.
Ann. Geophys., 33, 901-912, doi:10.5194/angeo-33-901-2015, 2015
Spectral properties of electrostatic drift wave turbulence in the laboratory and the ionosphere
Summary: The present review describes a number of laboratory studies of low-frequency electrostatic drift wave turbulence together with related results obtained by instrumented spacecraft in the Earth's near and distant ionospheres. The summary emphasizes readily measurable quantities, such as the turbulent power spectra for the fluctuations in plasma density, potential and electric fields. A number of future studies are suggested in order to resolve some outstanding issues.
Ann. Geophys., 33, 875-900, doi:10.5194/angeo-33-875-2015, 2015
WHU VHF radar observations of the diurnal tide and its variability in the lower atmosphere over Chongyang (114.14° E, 29.53° N), China
Summary: The diurnal tide and its variability in the lower atmosphere over Chongyang (114.14ºE，29.53ºN) were studied based on the newly established Wuhan University VHF radar observations in the whole year of 2012. We find that the diurnal tide was the dominant tidal component and showed remarkable height and season variations, as well as dramatic short-term variability.
Ann. Geophys., 33, 865-874, doi:10.5194/angeo-33-865-2015, 2015
Eddy diffusion coefficients and their upper limits based on application of the similarity theory
Summary: For the first time, the authors show that, by using the similarity theory, the same formula can be obtained for the eddy diffusion coefficient as the commonly used formula derived by J. Weinstock. Our results also explain the discrepancy between the large cooling rates calculated by the authors and the temperatures given by the MSIS-E-90 model.
Ann. Geophys., 33, 857-864, doi:10.5194/angeo-33-857-2015, 2015
Solar-wind control of plasma sheet dynamics
Ann. Geophys., 33, 845-855, doi:10.5194/angeo-33-845-2015, 2015
Auroral ion acoustic wave enhancement observed with a radar interferometer system
Summary: The high-latitude ionosphere is a dynamic region where particle precipitation leads to various phenomena including wave instability and turbulence. Anomalous echoes related to aurora are observed in ground-based radar observations of the ionosphere. These echoes indicate enhanced ion acoustic fluctuations. In this article, we show that the origin of the echo is located in or close to the region of particle precipitation and that the echo region itself is limited to hundreds of meters.
Ann. Geophys., 33, 837-844, doi:10.5194/angeo-33-837-2015, 2015
Estimating along-track plasma drift speed from electron density measurements by the three Swarm satellites
Summary: Though high-latitude plasma convection has been monitored with a number of methods, more independent measurements are still warranted. In this study we introduce an automatic method to estimate along-track plasma drift velocity in the high-latitude ionosphere using the Swarm constellation. The obtained velocity is in qualitative agreement with Super Dual Auroral Radar Network (SuperDARN) data. The method can be generalized to any satellite constellations in pearls-on-a-string configurations.
Ann. Geophys., 33, 829-835, doi:10.5194/angeo-33-829-2015, 2015
Impact of local data assimilation on tropical cyclone predictions over the Bay of Bengal using the ARW model
Ann. Geophys., 33, 805-828, doi:10.5194/angeo-33-805-2015, 2015
Investigation of weather anomalies in the low-latitude islands of the Indian Ocean in 1991
Summary: In December 1991, precipitation on the Glorieuses and Mayotte was more than 3 times the climatological mean and mean sunshine duration was less than 1.5h per day. The most likely explanation was low values of the Madden-Julian Oscillation index, which favours high rainfall. El Niño, eastward quasi-biennial oscillation and high solar activity may also have had an indirect effect. No effect of the Pinatubo volcanic eruption is indicated as the precipitation anomalies are only local.
Ann. Geophys., 33, 789-804, doi:10.5194/angeo-33-789-2015, 2015
Composite analysis of a major sudden stratospheric warming
Summary: The composite analysis of major sudden stratospheric warmings (SSW) showed changes in atmospheric parameters at mid-latitudes about 1-2 months before the central date of the SSW. Polar ozone is enhanced during the half year after the SSW event.
Ann. Geophys., 33, 783-788, doi:10.5194/angeo-33-783-2015, 2015
In situ magnetotail magnetic flux calculation
Summary: We explore two new modifications of the magnetotail magnetic flux calculation algorithm based on the pressure balance approach for the tail radius determination. The new modifications extend the scope of the algorithm to the inner magnetosphere, which is possible due to the approximate uniformity of the magnetic field of external sources. A new empirical formula for the tail radius at the terminator is also presented.
Ann. Geophys., 33, 769-781, doi:10.5194/angeo-33-769-2015, 2015
Hydroxyl layer: trend of number density and intra-annual variability
Ann. Geophys., 33, 749-767, doi:10.5194/angeo-33-749-2015, 2015
A comparison of overshoot modelling with observations of polar mesospheric summer echoes at radar frequencies of 56 and 224 MHz
Summary: Noctilucent clouds were observed by two radars at different wavelengths. Artificial electron heating was applied. As predicted by modelling, there is a general difference between the observations by the two radars. However, for some heater cycles we observed an exceptionally strong, rapid and similar increase in backscatter for both radars when the heater was on. Models predict a considerable difference in reaction. Our observation indicate that the charging models may not be complete.
Ann. Geophys., 33, 737-747, doi:10.5194/angeo-33-737-2015, 2015
The MAGIC of CINEMA: first in-flight science results from a miniaturised anisotropic magnetoresistive magnetometer
Summary: The first in-flight results from a new design of miniaturised magnetometer (MAGIC - MAGnetometer from Imperial College), aboard the first CINEMA (Cubesat for Ions, Neutrals, Electrons and MAgnetic fields) spacecraft in low Earth orbit, are presented. Not only can this sensor be used for determining attitude, but it is also able to detect the extremely small (20-40 nT) magnetic field signatures of field-aligned currents at the auroral oval. Thus, there are science capabilities with such sensors.
Ann. Geophys., 33, 725-735, doi:10.5194/angeo-33-725-2015, 2015
Electron-scale nested quadrupole Hall field in Cluster observations of magnetic reconnection
Summary: In magnetic reconnection in collisionless plasmas, a quadrupole structure of the magnetic field component in the direction of current supporting the reconnecting magnetic field is generated down to electron scales. This paper shows that the magnetic field can develop a "nested structure of quadrupoles" at the electron scales and identifies the nested structure in Cluster observations. Results are useful in interpreting the electron physics in observations, in particular by the NASA/MMS mission.
Ann. Geophys., 33, 719-724, doi:10.5194/angeo-33-719-2015, 2015
Dusk-to-nighttime enhancement of mid-latitude NmF2 in local summer: inter-hemispheric asymmetry and solar activity dependence
Ann. Geophys., 33, 711-718, doi:10.5194/angeo-33-711-2015, 2015
Equation of state for solar near-surface convection
Ann. Geophys., 33, 703-709, doi:10.5194/angeo-33-703-2015, 2015