Morning polar substorms and variations in the atmospheric electric field

The effects of morning magnetospheric substorms in the variations in near-Earth atmospheric electricity according to the observations of the electric field vertical component (E _z ), at Hornsund polar observatory (Spitsbergen). The E _z, data, obtained under the conditions of fair weather (i.e., in the absence of a strong wind, precipitation, and fog), are analyzed. An analysis of the observations indicated that the development of a magnetospheric substorm in the Earth’s morning sector is as a rule accompanied by positive deviations in E _z, independently of the Hornsund location: in the polar cap or at its boundary. In all considered events, Hornsund was located near the center of the morning convection vortex. In the evening sector, when Hornsund fell in the region of evening convection vortex, the development of a geomagnetic substorm was accompanied by negative deviations in E _z., It has been concluded that the variations in the atmospheric electric field E _z), at polar latitudes, observed during the development of magnetospheric substorms, result from the penetration of electric fields of polar ionospheric convection (which are intensified during a substorm) to the Earth’s surface.     

Effect of magnetic storms in variations in the atmospheric electric field at midlatitudes

The observations of the variations in the vertical component of the atmospheric electric field (E _z ) at Swider midlatitude Poland observatory (geomagnetic latitude 47.8°) under the conditions of fair weather during 14 magnetic storms have been analyzed. The effect of the magnetic storm main phase in the daytime midlatitude variations in E _z in the absence of local geomagnetic disturbances has been detected for the first time. Considerable (～100–300 V m^?1) decreases in the electric field strength (E _z ) at Swider observatory were observed in daytime simultaneously with the substorm onset in the nighttime sector of auroral latitudes (College observatory). The detected effects indicate that an intensification of the interplanetary electric field during the magnetic storm main phase, the development of magnetospheric substorms, and precipitation of energetic electrons into the nighttime auroral ionosphere can result in considerable disturbances in the midlatitude atmospheric electric field.     

Simulation of variations in the polar atmospheric electric field related to the magnetospheric field-aligned currents

The distribution of the electric potential, generated by the magnetospheric field-aligned currents flowing along the auroral oval and in the dayside cusp region at the upper atmospheric boundary in the polar ionosphere, is calculated. The obtained electric potential distributions are used to calculate the electric field strength near the Earth’s surface. The results of the model calculations are in good agreement with the electric field measurements at Vostok Antarctic station. It has been indicated that large-scale magnetospheric fieldaligned currents, related to IMF variations, can affect variations in the electric field strength in the polar regions via changes in the electric potential in the polar ionosphere, associated with these currents.     

Effects of geomagnetic disturbances in daytime variations of the atmospheric electric field in polar regions

We have studied the influence of daytime polar substorms (geomagnetic bays under the IMF Bz > 0) on variations of the vertical gradient of the atmospheric electric field potential (Ez) observed at the Polish Hornsund Station (Svalbard, Norway). Only the observations of Ez under “fair weather” conditions were used, i.e. in the absence of strong wind, precipitations, low cloud cover, etc. We studied more than 20 events of daytime polar substorms registered by the Scandinavian chain of IMAGE magnetometers in 2010–2014 during the “fair weather” periods at the Hornsund Station. Analysis of the observations showed that Ez significantly deviates from the its background variations during daytime, as a rule, when the Hornsund Station is in the region of projection of the daytime auroral oval, the position of which was determined from OVATION data. It was shown that the development of a daytime polar substorm leads to fluctuating enhance of Ez values. It was found that Ez surges are accompanied by intensification of field-aligned electric currents outflowing from the ionosphere, which were calculated from the data of low-orbit communication satellites of the AMPERE project.     

A seasonal effect in diurnal variation of the atmospheric electric field on the Pacific coast of Japan

The measurement of the atmospheric electric field was carried out with a field mill at a small island in a bay on the Pacific coast of Japan. The data obtained during 80 months from 1971 to 1977 were analysed. It was found that characteristically the diurnal variation regularly alters with the seasons. Whereas the electric field in winter has the same diurnal pattern as that observed at globally representative stations, it exhibits in summer a pattern depending on the variation of the local electric conductivity. The alteration is inferred to be associated with regional atmospheric conditions surrounding the observation site.     

On the seasonal effect of orbital variations on the climates of the next 4000 years

A northern hemisphere thermodynamic climate model is used to compute the effect of the insolation anomalies due to orbital variations in the climates for the next 4000 years. Bergers mean monthly anomalies of insolation are used in the computations, which are carried out for 1000, 2000, 3000 and 4000 years after present (kyears AP). The numerical simulations show that in the climates of the next 4000 years, due to the effect of the orbital variations, springs and summers will be increasingly dryer and falls and winters wetter than the present climate.     

Global variation in the atmospheric electric field

Summary An analysis of the global nature of the atmospheric electric field is presented on the basis of comparison of measurements on the research vessel, Hakuho-Maru, on the Mid- and South-Pacific Ocean, with those at Syowa Station in Antartica and on two vessels on the Mid-Atlantic Ocean. The comparison of daily averages gave a different type of latitude dependence, which was characterized by a gradual decrease toward the antarctic region. Diurnal variations at these globally representative stations on the same day were checked with each other for the first time, and the correlation between them was found much higher than that between land stations. The regional effect, which might depend on the distance from the thunderstorm area, was not evidently detected. So the influence of the generator area was considered to propagate over the entire globe without significant attenuation.

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Zusammenfassung Auf der Grundlage von Vergleichen zwischen Messungen an Bord des Forschungsschiffes Hakohu-Maru im mittleren und südlichen Pazifischen Ozean, an der antarktischen Forschungsstation Syowa und an Bord von zwei Forschungsschiffen im mittleren Atlantik wird eine Analyse der weltweiten Natur des luftelektrischen Feldes vorgelegt. Der Vergleich von Tagesmitteln ergab eine spezielle Abhängigkeit von der geographischen Breite, gekennzeichnet durch eine allmähliche Abnahme in Richtung auf den antarktischen Bereich. Die Tagesgänge an diesen weltweitrepräsentativen Stationen wurden zum ersten Mal untereinander für jeweils die gleichen Tage verglichen. Es wurde gefunden, dass die Korrelation zwischen ihnen weitaus grösser war als sie zwischen Landstationen ist. Ein regionaler Effekt, vermutbar in der Form einer Abhängigkeit von der Entfernung zur Gewitterzone, wurde nicht sicher gefunden. Deswegen wird angenommen, dass die Auswirkungen des Generatorbereichs sich über die gesamte Erde ohne merkliche Verminderung erstrecken.

     

On the connection between the atmospheric electric field measured at the surface and the ionospheric electric field in the Central Antarctica

Regular measurements of the atmospheric electric field made at Vostok Station (φ=78.45°S; λ=106.87°E, elevation 3500 m) in Antarctica demonstrate that extremely intense electric fields (1000–5000 V/m) can be observed during snow storms. Usually the measured value of the atmospheric electric field at Vostok is about 100–250 V/m during periods with “fair weather” conditions. Actual relation between near-surface electric fields and ionospheric electric fields remain to be a controversial problem. Some people claimed that these intense electric fields produced by snowstorms or appearing before strong earthquakes can re-distribute electric potential in the ionosphere at the heights up to 300 km. We investigated interrelation between the atmospheric and ionospheric electric fields by both experimental and theoretical methods. Our conclusion is that increased near-surface atmospheric electric fields do not contribute notably to distribution of ionospheric electric potential.     

Annual and seasonal variations in the low-latitude topside ionosphere

Annual and seasonal variations in the low-latitude topside ionosphere are investigated using observations made by the Hinotori satellite and the Sheffield University Plasmasphere Ionosphere Model (SUPIM). The observed electron densities at 600 km altitude show a strong annual anomaly at all longitudes. The average electron densities of conjugate latitudes within the latitude range ±25° are higher at the December solstice than at the June solstice by about 100% during daytime and 30% during night-time. Model calculations show that the annual variations in the neutral gas densities play important roles. The model values obtained from calculations with inputs for the neutral densities obtained from MSIS86 reproduce the general behaviour of the observed annual anomaly. However, the differences in the modelled electron densities at the two solstices are only about 30% of that seen in the observed values. The model calculations suggest that while the differences between the solstice values of neutral wind, resulting from the coupling of the neutral gas and plasma, may also make a significant contribution to the daytime annual anomaly, the E × B drift velocity may slightly weaken the annual anomaly during daytime and strengthen the anomaly during the post-sunset period. It is suggested that energy sources, other than those arising from the 6% difference in the solar EUV fluxes at the two solstices due to the change in the Sun-Earth distance, may contribute to the annual anomaly. Observations show strong seasonal variations at the solstices, with the electron density at 600 km altitude being higher in the summer hemisphere than in the winter hemisphere, contrary to the behaviour in NmF2. Model calculations confirm that the seasonal behaviour results from effects caused by transequatorial component of the neutral wind in the direction summer hemisphere to winter hemisphere.     

Synoptic variations in the chemical composition of atmospheric precipitation

Summary A study of the chemical composition of monthly precipitation samples from a number of stations in Sweden brings out the existence of significant variations in the relative proportions of chlorides and sodium depending upon the general character of the prevailing circulation. In maritime westerly flows the weight ratio of chloride to sodium decreases eastward to values which lie far below that value characteristic of sea water. In precipitation falling from arctic or polar continental air masses the chloride component is almost completely absent. The highest amounts of chlorides relative to sodium are observed in precipitation from warm and most air masses reaching Sweden from the south or southeast.Significant variations are observed also in the yearly means of the chloride to sodium ratio depending upon the dominance of maritime or continental air currents.A sketch map of the «average» chloride concentration in European precipitation prepared from miscellaneous older data lends support to the results of the analysis of the monthly data. The separation of the chemical components indicated by this study would seem to be of considerable geochemical interest since it would permit different maritime salts to be deposited in widely separated parts of the continents.The full paper will be published in «Tellus», VII (1955), 1.

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Zusammenfassung Ein Studium der chemischen Zusammensetzung von Proben des monatlichen Niederschlages einer Anzahl von Beobachtungsstationen in Schweden deckt die Existenz von deutlichen Schwankungen im relativen Verhältnis von Chlor und Natrium auf, welche vom allgemeinen Charakter der vorherrschenden Zirkulation abhängen. In maritimen westlichen Strömungen nimmt das Gewichtsverhältnis von Chlor zu Natrium gegen Osten zu auf Werte, welche weit unterhalb des charakteristischen Betrages für Meerwasser liegen, ab. Im Niederschlag, welcher aus arktischen oder polar-kontinentalen Luftmassen stammt, fehlt die Chlor-Komponente beinahe vollständig. Der höchste Betrag von Chlor relativ zu Natrium wurde im Niederschlag aus warmen und den meisten Luftmassen, welche Schweden vom Süden und Südosten erreichen, gefunden.Deutliche Schwankungen wurden auch in den Jahresmitteln des Verhältnisses Chlor zu Natrium beobachtet, welche von der Vorherrschaft der maritimen oder kontinentalen Luftströmungen abhängen.Eine schematische Karte der «mittleren» Chlor-Konzentration im Europäischen Niederschlag, welche mit Hilfe von verschiedenen älteren Daten entworfen wurde, unterstützt die Resultate der Analyse der Monatswerte. Die Trennung der chemischen Komponenten, welche durch diese Untersuchung angedeutet wird, scheint von beträchtlichem Interesse für die Erdchemie zu sein, da auf diese Weise verschiedene maritime Salze in weit auseinander liegenden Teilen der Kontinente abgelagert würden.Die ausführliche Arbeit wird in der Zeitschrift «Tellus», VII (1955), 1 veröffentlicht werden.

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Presented by Mr. ClaesRooth, Institute of Meteorology, University of Stockholm, Lindhagensgatan 124v,Stockholm (Sweden).     

Diurnal periodicity of earthquakes and its seasonal variations

Analysis of earthquake catalogues on 14 world regions has revealed a distinct diurnal periodicity of seismic events in all of them. The amplitude of the diurnal variations usually decreases with an increase in earthquake energy, although in some regions, the time series of strong earthquakes also demonstrate diurnal periodicity. Earthquakes are more frequent at night. The acrophase of the course of diurnal seismicity correlates with geographic longitude. The Rayleigh — Schuster hodographs of diurnal periodicity demonstrate sharp changes (kinks) in the vicinity of the equinox and solstice moments. The annual hodograph of the diurnal periodicity of earthquakes is distinctly divided by the equinox moments into segments with different slopes. The defined segments differ in the amplitude and acrophase of the course of diurnal seismicity. The data imply influence of the mutual positions of the Sun and Earth on seismicity in different world regions. Possible mechanisms responsible for such influence are discussed.     

Calculation of atmospheric electric fields penetrating from the ionosphere

The spatial distributions of electric fields and currents in the Earth’s atmosphere are calculated. Electric potential distributions typical of substorms and quiet geomagnetic conditions are specified in the ionosphere. The Earth is treated as a perfect conductor. The atmosphere is considered as a spherical layer with a given height dependence of electrical conductivity. With the chosen conductivity model and an ionospheric potential of 300 kV with respect to the Earth, the electric field near the ground is vertical and reaches 110 Vm⁻¹. With the 60-kV potential difference in the polar cap of the ionosphere, the electric field disturbances with a vertical component of up to 13 V m⁻¹ can occur in the atmosphere. These disturbances are maximal near the ground. If the horizontal scales of field nonuniformity are over 100 km, the vertical component of the electric field near the ground can be calculated with the one-dimensional model. The field and current distributions in the upper atmosphere can be obtained only from the three-dimensional model. The numerical method for solving electrical conductivity problems makes it possible to take into account conductivity inhomogeneities and the ground relief.     

Variation of atmospheric electric field during aurorae

Summary The measured data of the atmospheric potential gradientE during aurorae are summarized. It is shown that aurorae in the northern hemisphere decreaseE, and aurorae in the southern hemisphere increaseE. Depending on aurorae intensities, variations ofE reach 30–35% from the mean.Deviations ofE from normal values, on the average, begin 3.5 hours before aurora occurrence and end 3 hours after that.

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Zusammenfassung Messdaten des luftelektrischen Feldes (Potentialgefälles)E während des Auftretens von Polarlichtern werden zusammengefasst. Es wird gezeigt, dassE bei Nordlicht abgeschwächt, bei Südlicht verstärkt wird. Die Änderungen vonE erreichen 30–35% des Mittelwerts und hängen von der Stärke des Polarlichts ab. Im Mittel beginnen die Abweichungen desE von seinem normalen Wert 3.5 Stunden vor, und enden 3 Stunden nach dem Auftreten des Polarlichts.

     

Formation of a local atmospheric electric field

We have estimated the variations in the atmospheric electrostatic field (AEF, E _Z(0)) strength in the surface layer caused by variations in conductivity due to radon influences, cosmic ray intensity, changes in the balance of light and heavy ions during sunset and sunrise, and under the effect of the ionospheric electric current potential on the AEF potential. It is shown that the air conductivity varies due to ionization under the effect of radon emanations and is determined by the radon exhalation and turbulent diffusion of the surface air layer, while the cosmic ray intensity affects the surface air conductivity through changes in the ion recombination conditions. A decrease in the air conductivity due to a decrease in the cosmic ray intensity (Forbush decrease) also decreases E _Z(0), while a decrease in radon fluxes results in an increase in E _Z(0). We have estimated the effect of illumination conditions on the AEF due to variations in the relative concentration of heavy and light ions under the influence of photodetachment and photoattachment processes. The work has been done on the basis of data received from the Paratunka observatory (Kamchatka).     

Global methane flux into the atmosphere and its seasonal variations

We have analyzed the regularities in the spatiotemporal behavior of the methane concentration and mass, recorded in different regions of the globe. In the southern hemisphere (SH), the methane concentration does not depend on latitude. In the northern hemisphere (NH), the methane concentration increases towards the Arctic zone. The maximum CH₄ concentration in the fall is due to the action of the additional methane sources in the NH Arctic region. The methane flux calculations showed that in the SH the methane flux into the Earth’s atmosphere is barely season dependent. In the NH during the fall season, the methane flux considerably increases, and the difference between the maximum flux in August-September and the flux in December-January reaches three. The additional, still disregarded sources, sustaining high methane emission in the spring season at high SH latitudes are estimated to be as strong as 100–120 Tg per year. To equilibrate the methane supply to the atmosphere and methane sink in SH, additional, yet unidentified sources of over 300 Tg/yr are required. The global methane flux into the Earth’s atmosphere should be no less than 1050–1100 Tg yearly.     

临近空间大气扰动变化特性的定量研究

本文利用TIMED/SABER 2002年1月至2013年1月共11年的卫星温度探测数据,通过全球网格化及在网格内作数学统计的方法,得到了20~100 km高度上全球网格点上温度的平均值和标准差,实现了对临近空间全球大气扰动进行定量刻画的目的.通过定量分析温度标准差的分布特性,文中得到了临近空间大气扰动的全球分布规律,并讨论了与这些分布规律相关的物理过程.结果表明,在20~70 km高度上,温度标准差为1~10 K,有显著的冬季/夏季的差异,冬季的温度标准差比夏季大;大气重力波扰动是最主要来源,同时大气传播性行星波引起的扰动也是来源之一.在70~100 km高度上,温度标准差常年较强,量值为10~30 K,冬季/夏季的差异小,低纬地区的温度标准差高于中高纬度地区,呈现许多局地化的小结构.大气重力波是引起该区域大气总扰动量的主要扰动来源,大气潮汐波、传播性行星波(准2天、准6.5天)也有重要贡献.     

Correlated seasonal and climatic variations of trace constituents in the stratosphere

Summary Spectrometric experiments performed, in November 1976, within the framework of the Latitude Survey Mission on board the NASA Convair 990 from Ames Research Center are briefly deseribed. The results presented concern odd nitrogen molecules, HCl and water vapor. In terms of vertical column density, HNO₃ is predominant over NO+NO₂ at all latitudes higher than 40 degrees. A seasonal variation of NO₂ abundance is observed, with larger values in the summer hemisphere at high latitude. The mean zenith column density of HCl above 11 km is 1.5×10¹⁵ mol.cm^–2, with no evidence for any seasonal or climatic variation. Local number densities as high as 1.4×10¹⁰ mol.cm^–3 for HNO₃ and 5.4×10¹⁴ mol.cm^–3 for water vapor have been measured during the same flight near 11 km.     

The atmospheric electric ring current in the higher atmosphere

Summary The atmospheric electric current flow in the ionosphere was discussed in a qualitative way at the UGGI General Assembly at Berkeley, California in 1963. The following picture emerged: The atmospheric electric fair weather current leaves the earth in a radially outward direction. As it enters the higher regions of the atmosphere and the ionospheric it is increasingly influenced by the earth's magnetic field. Because the main part of the current is crowded into the polar regions, the current density over the equatorial belt is small. A circular movement around the earth's axis results in an overall flow pattern tentatively termed, the atmospheric electric ring current. An attempt to calculate this current flow soon made it clear that the generally used simplification of the one-dimensional case with slanted magnetic field lines is not adequate—not even as a first approximation. The same is true for the assumption usually made in magnetohydrodynamics that the current follows approximately the magnetic field lines. An essential feature of the atmospheric electric ring current is that in equatorial regions the flow is forced across the magnetic field lines, the component along the lines being zero. A calculation is discussed that treats the magnetic field lines as those of a true dipole field with the corresponding tensor character of conductivity. The results of the calculation are presented as graphs of the density distribution of the ring current, the space charge distribution, the current flow, and equipotential lines.

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Zusammenfassung Der luftelektrische Stromfluss in der Ionosphäre ist in qualitativer Weise während der UGGI Tagung in Berkeley California, 1963 diskutiert worden. Hierbei hat sich das folgende Bild ergeben: Der luftelektrische Schönwetterstrom fliesst von der Erdoberfläche nach ausswärts in radialer Richtung. Sobald er in die höheren Atmosphärenschichten und dann in die Ionosphäre kommt wird er in zunehmendem Masse vom erdmagnetischen Feld beeinflusst. Der Hauptteil des Stromes wird in die Polarzonen abgedrängt, wodurch die Stromdichte über dem Äquatorgürtel verhältnismässig klein wird. Zu gleicher Zeit wird eine kreisförmige Bewegung um die Erdachse ausgelöst, was ein Strombild ergibt, das versuchsweise der luftelektrische Ringstrom genannt wird.—Bei der Berechnung dieses Stromflusses ergab sich bald, dass die allgemein üblichen Vereinfachungen des eindimensionalen Falles mit homogenem, schräg einfallendem Magnetfeld nicht brauchbar sind, nicht einmal in erster Näherung. Dasselbe gilt für die Annahme, die gewöhnlich in der Magnetohydrodynamik gemacht wird, nämlich dass der Stromfluss angenähert dem magnetischen Felde folgt. Eine wichtige Eigenschaft des luftelektrischen Ringstromes ist es, dass der Strom über dem Äquatorgürtel gezwungen ist quer über die magnetischen Feldlinien zu fliessen, wobei die Stromkomponente in Richtung der Feldlinien gleich 0 ist. In der hier durchgeführten Rechnung wird das magnetische Feld als wahres Dipolfeld behandelt mit dem einer solchen Feldverteilung entsprechenden Tensorcharakter der Leitfähigkeit. Die Ergebnisse der Rechnung werden an Hand von graphischen darstellungen der Ringstrom- und Raumladungsdichte und der Strom- und Äquipotentiallinien diskutiert.

     

Short-period fluctuations in the atmospheric electric field over the ocean

Fluctuations of short period in the atmospheric electric field were studied through the measurements of electric field and space charge density on the Mid-Pacific Ocean. The amplitude of fluctuation is about one third of the mean electric field, and the period mainly ranges from 2 to 5 min. The fluctuations are considered to be under the influence of spatial and temporal variation of space charge layer that possibly originates from the electrode effect above the sea surface. The unit of electrical irregularities in the atmosphere above the ocean has horizontal scale of the order of 1.5 km and indicates a tendency to become large as the wind speed increases. The vertical scale of space charge layer is estimated at several tens meters.