Showing papers on "Longitude published in 2012"

Interstellar Gas Flow Parameters Derived from Interstellar Boundary Explorer-Lo Observations in 2009 and 2010: Analytical Analysis

Abstract: Neutral atom imaging of the interstellar gas flow in the inner heliosphere provides the most detailed information on physical conditions of the surrounding interstellar medium (ISM) and its interaction with the heliosphere. The Interstellar Boundary Explorer (IBEX) measured neutral H, He, O, and Ne for three years. We compare the He and combined O + Ne flow distributions for two interstellar flow passages in 2009 and 2010 with an analytical calculation, which is simplified because the IBEX orientation provides observations at almost exactly the perihelion of the gas trajectories. This method allows separate determination of the key ISM parameters: inflow speed, longitude, and latitude, as well as temperature. A combined optimization, as in complementary approaches, is thus not necessary. Based on the observed peak position and width in longitude and latitude, inflow speed, latitude, and temperature are found as a function of inflow longitude. The latter is then constrained by the variation of the observed flow latitude as a function of observer longitude and by the ratio of the widths of the distribution in longitude and latitude. Identical results are found for 2009 and 2010: an He flow vector somewhat outside previous determinations (λISM∞ = 79. ◦ 0+3 . 0(−3. ◦ 5), βISM∞ =− 4. 9 ± 0. 2, VISM∞ = 23.5 + 3.0(−2.0) km s −1 , THe = 5000–8200 K), suggesting a larger inflow longitude and lower speed. The O + Ne temperature range, T O+N e = 5300–9000 K, is found to be close to the upper range for He and consistent with an isothermal medium for all species within current uncertainties.

An analytical model of interstellar gas in the heliosphere tailored to interstellar boundary explorer observations

Abstract: The stationary distribution of interstellar neutral gas in the heliosphere subject to solar gravity, solar radiation pressure, photoionization, and charge exchange is investigated analytically assuming ionization rates and radiation pressure that are proportional to R –2, where R is the heliocentric radius. The collisionless hyperbolic trajectories of the individual atoms including ionization losses are combined with Liouville's Theorem to construct the heliospheric phase-space distribution function of an interstellar gas species in the solar reference frame under the assumption that the distribution is a drifting Maxwellian at large distances from the Sun. The distribution is transformed to the Earth (essentially Interstellar Boundary Explorer (IBEX)) frame as a function of solar longitude. The expression is then tailored to the latitudinal scan of IBEX as a function of longitude using the fact that IBEX detects each atom close to perihelion in its hyperbolic orbit. The distribution is further adapted to IBEX by integrating the differential intensity over the entrance aperture solid angle of the IBEX-Lo collimator, and over energy to predict the IBEX count rate of helium. The major features of the predicted count rate are described, including a peak in longitude, a peak in latitude at each longitude, and the widths of the major peak in both latitude and longitude. Analytical formulae for these features are derived for comparison with IBEX observations in order to determine the temperature and bulk velocity of the gas in interstellar space. Based in part on these formulae, the results for helium are presented in the companion paper by Mobius et al.

Observations of Stratocumulus Clouds and Their Effect on the Eastern Pacific Surface Heat Budget along 20°S

Abstract: Widespread stratocumulus clouds were observed on nine transects from seven research cruises to the southeastern tropical Pacific Ocean along 20°S, 75°–85°W in October–November of 2001–08. The nine transects sample a unique combination of synoptic and interannual variability affecting the clouds; their ensemble diagnoses longitude–vertical sections of the atmosphere, diurnal cycles of cloud properties and drizzle statistics, and the effect of stratocumulus clouds on surface radiation. Mean cloud fraction was 0.88, and 67% of 10-min overhead cloud fraction observations were overcast. Clouds cleared in the afternoon [1500 local time (LT)] to a minimum of fraction of 0.7. Precipitation radar found strong drizzle with reflectivity above 40 dBZ.Cloud-base (CB) heights rise with longitude from 1.0 km at 75°W to 1.2 km at 85°W in the mean, but the slope varies from cruise to cruise. CB–lifting condensation level (LCL) displacement, a measure of decoupling, increases westward. At night CB–LCL is 0–200 m an...

The comparative importance of DE3, SE2, and SPW4 on the generation of wavenumber‐4 longitude structures in the low‐latitude ionosphere during September equinox

Abstract: [1] Numerical simulations are performed to investigate the generation of the wave-4 longitude variation in the low-latitude ionosphere due to the diurnal eastward propagating nonmigrating tide with zonal wavenumber 3 (DE3), semidiurnal eastward propagating nonmigrating tide with zonal wavenumber 2 (SE2), and stationary planetary wave 4 (SPW4). From a fixed local time perspective, the DE3, SE2, and SPW4 all appear as wave-4 structures in longitude, and thus each of these waves must be considered as a potential source of the wave-4 variation in the ionosphere. Both theDE3 and SPW4 are found to produce significant wave-4 variations in the equatorial verticalE × Bdrift velocity, and in the ionospheric peak density (NmF2) at 15°N magnetic latitude. The daytime wave-4 variation in NmF2 is driven by the combination of verticalE × Bdrift variability and in-situ effects due largely to meridional neutral winds. The simulation results indicate that theSE2 is not a contributor to the wave-4 longitude variation. Our results further demonstrate that the actual wave-4 longitude variation is due to a combination of theDE3 and SPW4. We therefore conclude that, in addition to the DE3, the SPW4 also needs to be considered as an important driver of the wave-4 longitude variation in the low-latitude ionosphere. We additionally present evidence for the generation of theSPW4 due to the nonlinear interaction between the migrating diurnal tide and the DE3, and demonstrate the impact of DE3 variability on the amplitude of the SPW4.

Precursory effects in the nighttime VLF signal amplitude for the 18th January, 2011 Pakistan earthquake

Abstract: We have presented the result of the analysis of the nighttime VLF signals transmitted from the Indian Navy station VTX (latitude 8.43°N, longitude 77.73°E) at 19.2 kHz and received at Kolkata (latitude 22.57°N, longitude 88.24°E). On 18th January, 2011 an earthquake of magnitude 7.4 occurred at Southwestern Pakistan (latitude 28.9°N, longitude 64°E). We have analyzed the nighttime VLF signals for 2 weeks around 18th of January, 2011 to see if there have been any precursory effects of this earthquake. We have found that the amplitude of the nighttime VLF signals anomalously fluctuated 4 days before the earthquake. This agrees well with our previous findings based on the analysis of 1 year of earthquake data.

Spatial distribution of Kelvin-Helmholtz instability at low-latitude boundary layer under different solar wind speed conditions

Abstract: Using the PPMLR-MHD global simulation model, we examined the Kelvin-Helmholtz (K-H) instability at the low-latitude boundary layer (LLBL) under northward interplanetary magnetic field (IMF) conditions with various solar wind speeds (400, 600, and 800 km/s). The spatial distribution of the K-H wave power in the equatorial plane shows two distinct power populations, referring to the two modes of K-H surface waves. The spatial evolution of K-H instability at the boundary layer is classified into four phases: quasi-stable, exponential growth, linear growth, and nonlinear phases. The boundary layer is quasi-stable near the subsolar point region. The K-H instability starts at about 30 degrees longitude, and grows exponentially with a spatial growth rate of 0.28 similar to 0.87 R-E(-1) until similar to 45 degrees longitude where the vortices fully develop. At larger longitudes, the instability grows linearly, while the vortices grow in size. From similar to 80 degrees longitude to the distant magnetotail, the K-H instability develops nonlinearly and the vortices roll up. The wave frequency, wavelength, and phase speed are given at various spatial points. Model results show that the higher solar wind speed generates K-H waves with higher frequency under the northward IMF, and the wavelengths and the phase speeds increase with the increase of the longitude. Moreover, we made a comparison of the K-H wave periods on Earth's, Mercury's and Saturn's magnetopauses by a proposed prediction method.

GPS-TEC variations during low solar activity period (2007–2009) at Indian low latitude stations

Abstract: The paper is based on the ionospheric variations in terms of vertical total electron content (VTEC) for the low solar activity period from May 2007 to April 2009 based on the analysis of dual frequency signals from the Global Positioning System (GPS) satellites recorded at ground stations Varanasi (Geographic latitude 25°16′ N, Longitude 82°59′ E), situated near the equatorial ionization anomaly crest and other two International GNSS Service (IGS) stations Hyderabad (Geographic latitude 17°20′ N, longitude 78°30′ E) and Bangalore (Geographic latitude 12°58′ N, longitude 77°33′ E) in India. We describe the diurnal and seasonal variations of total electron content (TEC), and the effects of a space weather related event i.e. a geomagnetic storm on TEC. The mean diurnal variation during different seasons is brought out. It is found that TEC at all the three stations is maximum during equinoctial months (March, April, September and October), and minimum during the winter months (November, December, January and February), while obtaining intermediate values during summer months (May, June, July and August). TEC shows a semi-annual variation. TEC variation during geomagnetic quiet as well as disturbed days of each month and hence for each season from May 2007 to April 2008 at Varanasi is examined and is found to be more during disturbed period compared to that in the quiet period. Monthly, seasonal and annual variability of GPS-TEC has been compared with those derived from International Reference Ionosphere (IRI)-2007 with three different options of topside electron density, NeQuick, IRI01-corr and IRI 2001. A good agreement is found between the GPS-TEC and IRI model TEC at all the three stations.

Photometric variability of the disk-integrated thermal emission of the earth

Abstract: Here we present an analysis of the global-integrated mid-infrared emission flux of the Earth based on data derived from satellite measurements. We have studied the photometric annual, seasonal, and rotational variability of the thermal emission of the Earth to determine which properties can be inferred from the point-like signal. We find that the analysis of the time series allows us to determine the 24 hr rotational period of the planet for most observing geometries, due to large warm and cold areas, identified with geographic features, which appear consecutively in the observer's planetary view. However, the effects of global-scale meteorology can effectively mask the rotation for several days at a time. We also find that orbital time series exhibit a seasonal modulation, whose amplitude depends strongly on the latitude of the observer but weakly on its ecliptic longitude. As no systematic difference of brightness temperature is found between the dayside and the nightside, the phase variations of the Earth in the infrared range are negligible. Finally, we also conclude that the phase variation of a spatially unresolved Earth-Moon system is dominated by the lunar signal.

Positive ionospheric storm effects at Latin America longitude during the superstorm of 20–22 November 2003: revisit

Abstract: . Positive ionospheric storm effects that occurred during the superstorm on 20 November 2003 are investigated using a combination of ground-based Global Positioning System (GPS) total electron content (TEC), and the meridian chain of ionosondes distributed along the Latin America longitude of ~280° E. Both the ground-based GPS TEC and ionosonde electron density profile data reveal significant enhancements at mid-low latitudes over the 280° E region during the main phase of the November 2003 superstorm. The maximum enhancement of the topside ionospheric electron content is 3.2–7.7 times of the bottomside ionosphere at the locations of the ionosondes distributed around the mid- and low latitudes. Moreover, the height of maximum electron density exceeds 400 km and increases by 100 km compared with the quiet day over the South American area from middle to low latitudes, which might have resulted from a continuous eastward penetration electric field and storm-generated equatorward winds. Our results do not support the conclusions of Yizengaw et al. (2006), who suggested that the observed positive storm over the South American sector was mainly the consequence of the changes of the bottomside ionosphere. The so-called "unusual" responses of the topside ionosphere for the November 2003 storm in Yizengaw et al. (2006) are likely associated with the erroneous usage of magnetometer and incomplete data.

Photometric Variability of the Disk Integrated Infrared Emission of the Earth

Abstract: We present an analysis of the global-integrated mid-infrared emission flux of the Earth based on data derived from satellite measurements. We have studied the photometric annual, seasonal, and rotational variability of the thermal emission of the Earth to determine which properties can be inferred from the point-like signal. We find that the analysis of the time series allows us to determine the 24 hr rotational period of the planet for most observing geometries, due to large warm and cold areas, identified with geographic features, which appear consecutively in the observer's planetary view. However, the effects of global-scale meteorology can effectively mask the rotation for several days at a time. We also find that orbital time series exhibit a seasonal modulation, whose amplitude depends strongly on the latitude of the observer but weakly on its ecliptic longitude. As no systematic difference of brightness temperature is found between the dayside and nightside, the phase variations of the Earth in the infrared range are negligible. Finally, we also conclude that the phase variation of a spatially unresolved Earth-Moon system is dominated by the lunar signal.

The characteristics of temperature variability with terrain, latitude and longitude in Sichuan-Chongqing Region

Abstract: Using the daily temperature data of 95 meteorological stations from Sichuan-Chongqing Region and its surrounding areas, this paper adopted these methods (e.g., linear regression, trend coefficient, geographical statistics, gray relational analysis and spatial analysis functions of GIS) to analyze the relations of temperature variability with topography, latitude and longitude. Moreover, the rank of gray correlation between temperature variability and elevation, longitude, latitude, topographic position and surface roughness also was measured. These results indicated: (1) The elevation affected temperature variability most obviously, followed by latitude, and longitude. The slope of the linear regression between temperature change rate and elevation, latitude and longitude was 0.4142, 0.0293 and −0.3270, respectively. (2) The rank of gray correlation between temperature change rate and geographic factors was elevation > latitude > surface roughness > topographic position > longitude. The gray correlation degree between temperature change rate and elevation was 0.865, followed by latitude with 0.796, and longitude with 0.671. (3) The rate of temperature change enhanced with the increase of elevation. Especially, the warming trend was significant in the plateau and mountain areas of western Sichuan, and mountain and valley areas of southwestern Sichuan (with the warming rate of 0.74°C/10a during the 1990s). However, there was a weak warming trend in Sichuan Basin and its surrounding low mountain and hilly areas. (4) The effects of latitude on temperature change rate presented the specific regulation, which the warming rate of low-latitude areas was more significant than that of high-latitude areas. However, they were consistent with the regulation that the increasing of low temperature controlled most of the warming trend, due to the effects of terrain and elevation on annual mean temperature. (5) Basically, temperature variability along longitude direction resulted from the regular change of elevation along longitude. It was suggested that, in Sichuan-Chongqing Region, special features of temperature variability largely depended on the terrain complexity (e.g., undulations, mutations and roughness). The elevation level controlled only high or low annual mean temperature and the range of temperature change rate in the macro sense.

Ionospheric longitudinal variations at midlatitudes: Incoherent scatter radar observation at Millstone Hill

Abstract: Incoherent scatter radar (ISR) extra-wide coverage experiments during the period of 1978–2011 at Millstone Hill are used to investigate longitudinal differences in electron density. This work is motivated by a recent finding of the US east-west coast difference in TEC suggesting a combined effect of changing geomagnetic declination and zonal winds. The current study provides strong supporting evidence of the longitudinal change and the plausible mechanism by examining the climatology of electron density Ne on both east and west sides of the radar with a longitude separation of up to 40o for different heights within 300–450 km. Main findings include: 1) The east-west difference can be up to 60% and varies over the course of the day, being positive (East side Ne > West side Ne) in the late evening, and negative (West side Ne > East side Ne) in the pre-noon. 2) The east-west difference exists throughout the year. The positive (relative) difference is most pronounced in winter; the negative (relative) difference is most pronounced in early spring and later summer. 3) The east-west difference tends to enhance toward decreasing solar activity, however, with some seasonal dependence; the enhancements in the positive and negative differences do not take place simultaneously. 4) Both times of largest positive and largest negative east-west differences in Ne are earlier in summer and later in winter. The two times differ by 12–13 h, which remains constant throughout the year. 5) Variations at different heights from 300–450 km are similar. Zonal wind climatology above Millstone Hill is found to be perfectly consistent with what is expected based on the electron density difference between the east and west sides of the site. The magnetic declination-zonal wind mechanism is true for other longitude sectors as well, and may be used to understand longitudinal variations elsewhere. It may also be used to derive thermospheric zonal winds.

The annual and longitudinal variations in plasmaspheric ion density

Abstract: [1] This paper shows that at solar maximum, equatorial ion densities at L = 2.5 are substantially higher at American longitudes in the December months than in the June months. This arises because the configuration of the geomagnetic field causes a longitude-dependent asymmetry in ionospheric solar illumination at conjugate points that is greatest at American longitudes. For example, at −60°E geographic longitude the L = 2.5 field line has its foot point near 65° geographic latitude in the Southern Hemisphere but near 42° latitude in the Northern Hemisphere. We investigated the consequent effects on equatorial electron and ion densities by comparing ground-based observations of ULF field line eigenoscillations with in situ measurements of electron densities (from the CRRES and IMAGE spacecraft) and He+ densities (IMAGE) for L = 2.5 at solar maximum. Near −60°E longitude the electron and ion mass densities are about 1.5 and 2.2 times larger, respectively, in the December months than in the June months. Over the Asia-Pacific region there is little difference between summer and winter densities. Plasmaspheric empirical density models should be modified accordingly. By comparing the electron, helium, and mass densities, we estimate the annual variation in H+, He+, and O+ concentrations near −3°E longitude and −74°E longitude. In each case the He+ concentration is about 5% by number, but O+ concentrations are substantially higher at −3°E longitude compared with −74° E. We speculate that this may be related to enhanced ionospheric temperatures associated with the South Atlantic anomaly.

Equatorial longitude and local time variations of topside magnetic field‐aligned ion drifts at solar minimum

Abstract: [1] In the topside ionosphere, the high mobility of the plasma along the magnetic field allows field-aligned ion drifts to occur readily as a result of field-aligned gravitational forces, collisional forces, or pressure gradients. Therefore, variations in the field-aligned ion drifts can be used to explore the influence of thermospheric, electrodynamic, and chemical processes on the ionosphere. Longitude and local time variations in the field-aligned ion drifts near the magnetic equator are presented using observations from the Coupled Ion Neutral Dynamics Investigation on board the Communications/Navigation Outage Forecast System satellite. These observations were obtained during the period of extremely low solar activity present in 2008 and 2009, allowing the seasonal, local time, and longitudinal variations to reveal the relative importance of the processes responsible for topside field-aligned plasma drifts during solar minimum. This investigation found that the low-altitude winds and tides, the net ionization or loss, and the meridional E×B drift were all influential in creating longitudinal and local time variations in the field-aligned drift, though the strength of the influence seen by each driver was found to vary with season, local time, and longitude.

Assessing and Forecasting Atmospheric Outflow of α-HCH from China on Intra-, Inter-, and Decadal Time Scales

Abstract: Atmospheric outflow of alpha-HCH-HCH from China from 1952 to 2009 was investigated using Chinese Gridded Pesticide Emission and Residue Model (ChnGPERM). The model results show that the outflows via the northeast boundary (NEB, longitude 115-135 degrees E along 55 degrees N and latitude 37-55 degrees N along 135 degrees E) and the mid-south boundary (MSB, longitude 100-120 degrees E along 17 degrees N) of China account for 47% and 35% of the total outflow, respectively. Two climate indices based on the statistical association between the time series of modeled alpha-HCH outflow and atmospheric sea-level pressure were developed to predict the outflow on different time scales. The first index explains 70/83% and 10/46% of the intra-annual variability of the outflow via the NEB and MSB during the periods of 1952-1984 and 1985-2009, respectively. The second index explains 16% and 19% of the interannual and longer time scale variability in the outflow through the NEB during June-August and via the MSB during October December for 1991-2009, respectively. Results also revealed that climate warming may potentially result in stronger outflow via the NEB than the MSB. The linkage between the outflow with large scale atmospheric circulation patterns and climate warming trend over China was also discussed.

Study of dust storm synoptical patterns in southwest of Iran.

Abstract: As widespread deserts is located in west and southwest of Iran plateau, dust storms form due to west andsouthwest systems over Syria or Iraq as well as Arabian Peninsula. These systems severely affect west and southwestregions. Sometimes the fine dusts transmit to central, north east, and east regions. In this study for investigating dustysynoptical patterns, meteorological data at 5 synoptic stations were studied during recent ten years. Mean daily sealevel pressure data were selected from the NCEP reanalysis data encompassing the region from 20°-60°N latitude by20°-80°E longitude, with a 2.5 spatial resolution and for the 10 year period 1961-2003 in dusty days. Selectedterritory is located in a geographical situation that covers all the effecting systems on Iran. For classification anddelineate synoptical patterns Principal Component Analysis (PCA) and clustering method were used. Results showedthat in this region, days with dust have three general circulation patterns. Analyzing these patterns show that there isa trough which restricted to 30-45°E longitude in 850 hPa chart, and at least one relatively strong low pressure overArabian Peninsula in sea level pressure extending to the west, south west and the study region. This study shows thatabove aspects are the major specifications of dusty days.

Long-term variations in the flux of cosmogenic isotope 10 Be over the last 10000 years: Variations in the geomagnetic field and climate

Abstract: A spectral analysis of data on the flux of cosmogenic 10Be in ice core samples from the Central Greenland (project GRIP) over the last 10 thousand years have been carried out. It has been shown that the 10Be flux varies cyclically; the most significant cycle is of about 2300 years. Variations in the position of the virtual geomagnetic pole over 8000 years have been analyzed. Significant components, pointing to the cyclic variation in the position of the geomagnetic pole with a period of about 2300 years, have been revealed in a periodogram of the virtual geomagnetic pole longitude. In addition to the nearly 2300-year-long cycle, some lines are observable in the 10Be flux periodogram, which can be considered as a manifestation of the 1000-year-long cycle of the 10Be deposition rate on the ice surface. The relationship between the cyclicity of the geomagnetic pole position and the 10Be flux is discussed.

Response of low latitude ionosphere to the geomagnetic storm of May 30

Abstract: Response of low latitude ionosphere to the geomagnetic storm of May 30, 2005 in the Indian longitude sector has been investigated by using the GPS data recorded at three stations namely, Udaipur, Hyderabad and Bengaluru. The event is noteworthy due to the fact that the Z component of interplanetary magnetic field (IMF Bz) remained southward for about 10 hours, coincident with the local day time for the Indian longitude sector, along with significantly higher values of AE and ASY-H indices. However, we neither found any evidence for the presence of long lasting storm time electric fields nor could we infer episodes of eastward-westward penetration of electric fields under steady southward IMF Bz and unsteady ring current conditions. On the storm day, the maximum enhancement in the total electron content has been found to be about 60%. The ionosonde observations also showed increased critical frequency (foF2) and the height (hPF2) of the F layer. The foF2 was enhanced by ∼60% which is consistent with the enhancement in total electron content. The slow rise and long duration enhancement of hPF2 and foF2 have been attributed to the upwelling by the meridional neutral winds, caused by continuous energy inputs at higher latitudes. The poleward expansion of the equatorial ionization anomaly has also been observed on May 30. On May 31, the following day of the storm, significantly suppressed anomaly with near absence of its northern crest in the Indian longitude sector, revealed the effect of storm induced disturbance dynamo electric fields.

Heat center of the western Pacific warm pool

Abstract: A heat center (HC) of the western Pacific warm pool (WPWP) is defined, its variability is examined, and a possible mechanism is discussed. Analysis and calculation of a temperature dataset from 1945–2006 show that the mean position of the HC during this period was near 0.4°S/169.0°E, at 38.0 m depth. From a time series of the HC, remarkable seasonal variability was found, mainly in the meridional and vertical directions. Interannual variabilities were dominant in the zonal and vertical directions. In addition, semiannual variation in the HC depth was discovered. The longitude of the HC varies with ENSO events, and its latitude is weakly related to ENSO on time scales shorter than a decade. The variation of the HC longitude leads the Nino-3 index by about 3–4 months, and its depth lags the index for approximately 3 months. It is concluded that the HC depth results from a combination of its longitudinal and latitudinal variations. Low-pass-filtered time series reveal that the HC has moved eastward since the mid 1980s.

Modeling the daytime, equatorial ionospheric ion densities associated with the observed, four‐cell longitude patterns in E × B drift velocities

Abstract: [1] Previous studies have quantified the longitude gradients in E × Bdrift associated with the four-cell tidal structures and have confirmed that these sharp gradients exist on a day-to-day basis. For this paper, we incorporate the Ion Velocity Meter (IVM) sensor on the Communications/Navigation Outage Forecasting System satellite to obtain the daytime, verticalE × B drift velocities at the magnetic equator as a function of longitude, local time, and season and to theoretically calculate the F region ion densities as a function of altitude, latitude, longitude, and local time using the Global Ionosphere Plasmasphere model. We compare calculated ion densities assuming no longitude gradients in E × Bdrift velocities with calculated ion densities incorporating the IVM-observedE × Bdrift at the boundaries of the four-cell tidal structures in the Peruvian and the Atlantic longitude sectors. Incorporating the IVM-observedE × B drift velocities, the ion density crests rapidly converge to the magnetic equator between 285 and 300°E geographic longitude, are absent between 300° and 305°, and move away from the magnetic equator between 305° and 340°. In essence, the steeper the longitude gradient in E × B drifts, the steeper the longitude gradient in the equatorial anomaly crest location.

Polynomial modelling of CHAMP satellite data to investigate rapid secular variation fluctuations over southern Africa during 2003 and 2004

Abstract: Polynomial surface modelling is one of several useful methods to represent the geomagnetic field over a restricted area. This technique was applied to CHAMP satellite data for the period 2001–2005 to investigate rapid secular variation fluctuations at 400 km altitude over southern Africa region between 10° and 40° South in latitude and between 10° and 40° East in longitude. The results are compared with an analysis of monthly time series data of 2 magnetic observatories in the region, namely, Hermanus (HER) in South Africa and Tsumeb (TSU) in Namibia. Consequently 2 rapid secular variation fluctuations are identified around 2003.0 and 2004.0 respectively.

Propagation in longitude and altitude of wave 4 thermospheric perturbations from WINDII data at low and high latitudes

Abstract: [1] The diurnal eastward propagating nonmigrating tide of wave number 3 (DE3) has been observed as wave 4 from slowly precessing satellites, for both the ionized and neutral atmospheres. This tide has been identified as arising from deep tropical convection, propagating into the thermosphere and ionosphere, where it has been observed at equatorial latitudes. This feature was previously identified in the Wind Imaging Interferometer (WINDII) O(1S) 557.7 nm emission rate measurements at 250 km in the high-latitude region as well as the equatorial region. The WINDII wind measurements presented here provide detailed vertical structure from the MLT (Mesosphere and Lower Thermosphere) region to the thermosphere, 100 km to 250 km altitude, the first time that the DE3 winds have been measured over this vertical range. In the present work, the longitudinal propagation of wave 4 at different altitudes is discussed for the daytime and nighttime. The seasonal variations of wave 4 amplitude are compared for different altitudes and latitude regions.

Southward surface flow in the central South Pacific

Abstract: A large-scale surface flow with a southward component is proposed for the central South Pacific Ocean based on an interpretation of existing closely spaced and accurately measured temperatures and salinities along two latitudes in two different southern hemisphere winters: 28o S (Scorpio) and five degrees south of that (WOCE). Such a southward flow is not predicted from theory nor is it shown on current charts and globes. The observed longitudinal maximum in surface temperature along 28o S is centered around 130o W and has an amplitude of at least 5o C and an east/west range of about 60o of longitude. This striking feature is most easily explained by horizontal transport from latitudes closer to the equator. Since temperature atlases show that equatorial surface temperatures are always highest in the west, the origin of the warm water probably is toward the western side of the ocean as well. Thus the surface flow surrounding the longitudinal temperature maximum should be directed to the southeast. Where the surface temperatures are maximum the mixed layer depths are relatively large in a convex downward lens with maximum depths of 100 m; a correlation that is consistent with warm water moving south and being cooled from above. Salinities are maximum near the temperature maximum, also suggesting that the source of the surface flow is at low latitudes, where evaporation is usually expected to exceed precipitation. It is conjectured that the large-scale southeastward flow of the South Pacific is the analogue of the northeastward wide warm current off California documented over 30 years ago.

The dynamics of solar activity and anomalous weather of summer 2010: 2. Relationship with the active longitude zone; effects in the west and east

Abstract: We confirm the close synoptic relationship of the sectoral structure of the Sun’s magnetic field of the with the near-Earth tropospheric pressure with a case study of three European points (Troitsk, Rome, Jungfrau) in the period of the anomalously hot summer of June–August 2010. We substantiate the position that such a relationship was fostered by the anomalously low solar activity as a result of superposition of the minima of the 22- and 180-year cycles. Sectoral analysis of the solar-tropospheric relationships has shown that the appearance of a blocking anticyclone in the Moscow suburbs, its expansion to Rome and Jungfrau, and subsequent retreat at first from these points, and then from the Moscow suburbs was closely related to solar activity phenomena producing, according to contemporary notions, cyclonic activity, shown by simulation of the Earth’s electric field.