Variations In Ion Composition Research Articles

The Middle and Low Latitude Ion Composition Variations Observed by the DMSP Satellites on 20–31 August 2018

AbstractThe coupling between the ionosphere and plasmasphere is not known well during the quiet and storm times. The topside ionosphere ion composition reflects the exchange between the ionosphere and plasmasphere. We used the DMSP satellite observations to show the changes of the 840 km altitude H+ and O+ ions at ∼3–6 LT in the mid‐ and low‐latitudes on 20–31 August 2018 where a storm occurred on 25 August. The H+ was the main ion at 3–4 LT, and its concentration presented two peaks around 40°N/S magnetic latitudes on 20–24 August. The H+ concentration strongly lessened for more than five days around 40°N/S magnetic latitudes in the recovery phase of the storm on 26–30 August. Further, the enhancement and reduction of the H+ concentration persisted mainly in the Pacific and Asian sectors. The O+ density increased in Northern Hemisphere at 6:36 LT, and the H+ concentration showed the maximum around the magnetic equator during the quiet times, while the H+ concentration still mainly reduced around 40°N/S and stronger at 40°S in the recovery phase. The plasmaspheric total electron content showed a peak around the magnetic equator on 20–24 August, and the peak was weakened or disappeared on 26–30 August. The plasmasphere might be the principal sources for the mid‐latitude H+ enhancement along the geomagnetic field lines during the quite times and the storm‐time suppressed plasmasphere plasma density would weaken the supply of the H+ at 840 km altitude.

Ionospheric effects of the August 11, 2018, solar eclipse over the People’s Republic of China

The purpose of the work is to describe the ionospheric effects of the August 11, 2018 partial solar eclipse (SE) that occurred over the People’s Republic of China, as observed via GPS technology. SEs present rare phenomena of nature. In the course of 2 to 3 hours, the rearrangement of processes acting at the Earth’s surface, in the atmosphere, geospace, i.e., in the Earth — atmosphere — ionosphere — magnetosphere system (EAIMS), occurs. The response of this system depends on the solar activity, season, time of day, and on the state of atmospheric and space weather. Therefore, the study of the EAIMS response to SEs remains an urgent need. The response is accompanied by controllable dynamic processes, the study of which improves our understanding of the near-Earth environment. The study of the EAIMS response to SEs is of fundamental importance to science. Its practical applications include the following. The SE give rise to significant perturbations in the EAIMS, which affect the propagation of radio waves virtually in all frequency bands, and consequently deteriorate the operation of radar, radio astronomy, and radio navigation systems, as well as the instruments for remotely sensing the medium. The SE effects have been studied for over more than about 100 years. Thus far, the following regular effects have been quite well studied: decreases in the electron density, electron and ion temperatures, variations in ion composition, and plasma vertical movements. The irregular effects have been studied to a significantly smaller degree, and they can vary from one solar eclipse to another. The main feature of the SE over the PRC was the fact that it was observed during before local time sunset period. The maximum phase of the eclipse within the PRC area varied from 0.07 to 0.52, while the Sun’s surface area occulted by the moon was observed to be 0.02—0.42. The beginning of the eclipse over the PRC was observed to occur in the 09:54—10:05 UT period, and the end varied from 10:07 UT to 11:10 UT. The SE duration varied from a few minutes to approximately 67 min. The insignificant duration of the eclipse and the dusk terminator affected the SE effects. The state of space weather during the solar eclipse was conducive to observing the SE effects occurring in the ionosphere. To reveal the ionospheric response to the August 11, 2018, SE, the global navigation satellite system data were processed. The ionospheric time delay and, respectively, the vertical total electron content (TEC), were calculated combining the pseudo range and integrated phase data at two frequencies. Regardless of the dusk terminator influence, we have managed to confidently detect the ionospheric SE effects, which proved to be sufficiently small because of small values of the SE phase. Over the People’s Republic of China area, a funnel-shaped decrease in TEC was observed to occur approximately 1,300 km in latitude and 2,000 km in longitude. The TEC decrease was observed to be 7 %. The solar eclipse was accompanied by the generation of aperiodic TEC disturbances at a rate of 0.4—0.8 TEC unit/h and 105-min in duration. Wave disturbances caused by the SE were not observed confidently, which is due to the small value of the SE phase and insignificant disturbances in the electron density.

Solar cycle variations in ion composition in the dayside ionosphere of Titan

AbstractOne Titanian year spans over two complete solar cycles, and the solar irradiance has a significant effect on ionospheric densities. Solar cycle 24 has been one of the quietest cycles on record. In this paper we show data from the Cassini ion and neutral mass spectrometer (INMS) and the radio and plasma wave science Langmuir probe spanning the time period from early 2005, at the declining phase of solar cycle 23, to late 2015 at the declining phase of solar cycle 24. Densities of different ion species measured by the INMS show a consistent enhancement for high solar activity, particularly near the ionospheric peak. The density enhancement is best seen in primary ion species such as CH3+ rather than heavier ion species such as HCNH+. Unlike at Earth, where the ionosphere and atmosphere thermally expand at high solar activity, at Titan the altitude of the ionospheric peak decreases, indicating that the underlying neutral atmosphere was less extensive. Among the major ion species, CH5+ shows the largest decrease in peak altitude, whereas heavy ions such as C3H5+ show very little decrease. We also calculate the ion production rates using a theoretical model and a simple empirical model using INMS data and show that these effectively predict the increased ion production rates at high solar activity.

Spatial-temporal patterns of major ion chemistry and its controlling factors in the Manasarovar Basin, Tibet

The Manasarovar Basin in southern Tibet, which is considered a holy land in Buddhism, has drawn international academic attention because of its unique geographical environment. In this study, based on actual measurements of major ion concentrations in 43 water samples collected during the years 2005 and 2012, we analyzed systemically the spatial-temporal patterns of water chemistry and its controlling factors in the lake and inflowing rivers. The results reveal that the water in the Manasarovar Basin is slightly alkaline, with a pH ranging between 7.4–7.9. The amounts of total dissolved solids (TDS) in lake and river waters are approximately 325.4 and 88.7 mg/l, respectively, lower than that in most of the surface waters in the Tibetan Plateau. Because of the long-term effect of evaporative crystallization, in the lake, Na+ and HCO3 − have the highest concentrations, accounting for 46.8% and 86.8% of the total cation and anion content. However, in the inflowing rivers, the dominant ions are Ca2+ and HCO3 −, accounting for 59.6% and 75.4% of the total cation and anion content. The water exchange is insufficient for such a large lake, resulting in a remarkable spatial variation of ion composition. There are several large inflowing rivers on the north side of the lake, in which the ion concentrations are significantly higher than that on the other side of the lake, with a TDS of 468.9 and 254.9 mg/l, respectively. Under the influence of complicated surroundings, the spatial variations in water chemistry are even more significant in the rivers, with upstreams exhibiting a higher ionic content. The molar ratio between (Ca2++Mg2+) and (Na++K+) is much higher than 1.0, revealing that the main source of ions in the waters is carbonate weathering. Although natural processes, such as rock weathering, are the major factors controlling main ion chemistry in the basin, in the future we need to pay more attention to the anthropogenic influence.

M/Q = 2 ion distribution in the inner magnetosphere estimated from ion cyclotron whistler waves observed by the Akebono satellite

AbstractIn this study, we examine the spatial occurrence distributions of H+, He+, and M/Q = 2 ion band ion cyclotron whistler waves observed by the Akebono satellite below an altitude of 10,500 km. These ion cyclotron whistler waves are categorized as electromagnetic ion cyclotron mode waves with characteristic spectrum properties that depend on the ion composition in the plasma. Statistical research is particularly important for clarifying the variation of ion composition in a plasmaspheric ion environment. In this study, essential differences are noted among the observed regions of each ion cyclotron whistler wave band. Our statistical analysis showed that the generation of H+ band ion cyclotron whistlers in the equatorial region is difficult, while M/Q = 2 ion band ion cyclotron whistlers are frequently observed near this region. Thus, a certain amount of M/Q = 2 ions is evident. To explain these statistical results, we propose a model for generation of several bands of ion cyclotron whistlers along a propagation path. In addition, we examine the magnetic local time dependence of the observed ion cyclotron whistlers. The spatial occurrence distribution of the M/Q = 2 ion cyclotron whistler waves is greatest inward of L ∼ 2.4 in the local dayside; however, they extend to L ∼ 3.0 in the local nightside. Our results suggest a density enhancement process of M/Q = 2 ions in the nightside plasmasphere, which is consistent with previous satellite observations. Thus, this study presents important knowledge on the effects of minor ion population on wave propagation and generation.

Model Organisms Retain an “Ecological Memory” of Complex Ecologically Relevant Environmental Variation

Although tractable model organisms are essential to characterize the molecular mechanisms of evolution and adaptation, the ecological relevance of their behavior is not always clear because certain traits are easily lost during long-term laboratory culturing. Here, we demonstrate that despite their long tenure in the laboratory, model organisms retain "ecological memory" of complex environmental changes. We have discovered that Halobacterium salinarum NRC-1, a halophilic archaeon that dominates microbial communities in a dynamically changing hypersaline environment, simultaneously optimizes fitness to total salinity, NaCl concentration, and the [K]/[Mg] ratio. Despite being maintained under controlled conditions over the last 50 years, peaks in the three-dimensional fitness landscape occur in salinity and ionic compositions that are not replicated in laboratory culturing but are routinely observed in the natural hypersaline environment of this organism. Intriguingly, adaptation to variations in ion composition was associated with differential regulation of anaerobic metabolism genes, suggesting an intertwined relationship between responses to oxygen and salinity. Our results suggest that the ecological memory of complex environmental variations is imprinted in the networks for coordinating multiple cellular processes. These coordination networks are also essential for dealing with changes in other physicochemically linked factors present during routine laboratory culturing and, hence, retained in model organisms.

Impact of tecnogenic halogenesis on water catchment landscapes of river valleys and water systems: Case study of the south of Tyumen province

The article gives the analysis of the impact of artesian mineralized water flowing from old prospecting wells on water catchment landscapes of river valleys and small watercourses. The processes related to the variation in ion composition of water and chemical composition of bottom sediments of small watercourses under the impact of the technogenic halogenesis are discussed.

Modeling of properties of the plasmasphere under quiet and disturbed conditions

Based on theoretical models of the ionosphere and the plasmasphere, the ion composition variations in the plasmasphere and the plasmapause structure were studied depending on the choice of the distribution model of the magnetospheric convection electric field at low and high geomagnetic activity at the equinox and the December solstice. Based on the model calculations performed, the plasmapause shape and size during an increase and decrease in geomagnetic activity were studied. It was revealed that the size of the plasmasphere mainly depends on the magnetic local time (MLT) sector and the level of geomagnetic activity, and it greatly depends on the maximum universal time during the equinox. The Earth’s plasmasphere asymmetry is manifested in the noon-midnight and morning-evening directions. The analysis results of daily and seasonal variations in the ionic composition of the Earth’s plasmasphere at a moderate solar activity level show that there is a certain increase in the ion concentrations of H+ and He+ in the winter period probably due to an increase in the exospheric density at the summer to winter transition. The data obtained are in good agreement with satellite observations which makes it possible to use the model proposed to study the plasmasphere under different geophysical conditions.

Impacts of the Osmolality and the Lumenal Ionic Strength on Osmosensory Transporter ProP in Proteoliposomes

H(+) symporter ProP serves as a paradigm for the study of osmosensing. ProP attains the same activity at the same osmolality when the medium outside cells or proteoliposomes is supplemented with diverse, membrane-impermeant solutes. The osmosensory mechanism of ProP has been probed by varying the solvent within membrane vesicles and proteoliposomes. ProP activation was not ion specific, did not require K(+), and could be elicited by large, uncharged solutes polyethylene glycols (PEGS). We hypothesized that ProP is an ionic strength sensor and lumenal macromolecules activate ProP by altering ion activities. The attainable range of lumenal ionic strength was expanded by lowering the phosphate concentration within proteoliposomes. ProP activity at high osmolality, but not the osmolality, yielding half-maximal activity (Π(1/2)/RT), decreased with the lumenal phosphate concentration. This was attributed to acidification of the proteoliposome lumen due to H(+)-proline symport. The ionic strength yielding half-maximal ProP activity was more anion-dependent than Π(1/2)/RT for proteoliposomes loaded with citrate, sulfate, phosphate, chloride, or iodide. The anion effects followed the Hofmeister series. Lumenal bovine serum albumin (BSA) lowered the lumenal ionic strength at which ProP became active. Osmolality measurements documented the non-idealities of solutions including potassium phosphate and other solutes. The impacts of PEGS and BSA on ion activities did not account for their impacts on ProP activity. The effects of the tested solutes on ProP appear to be non-coulombic in nature. They may arise from effects of preferential interactions and macromolecular crowding on the membrane or on ProP.

A sensitivity study of the Enceladus torus

We have developed a homogeneous model of physical chemistry to investigate the neutral‐dominated, water‐based Enceladus torus. Electrons are treated as the summation of two isotropic Maxwellian distributions: a thermal component and a hot component. The effects of electron impact, electron recombination, charge exchange, and photochemistry are included. The mass source is neutral H2O, and a rigidly corotating magnetosphere introduces energy via pickup of freshly ionized neutrals. A small fraction of energy is also input by Coulomb collisions with a small population (<1%) of suprathermal electrons. Mass and energy are lost due to radial diffusion, escaping fast neutrals produced by charge exchange and recombination, and a small amount of radiative cooling. We explore a constrained parameter space spanned by water source rate, ion radial diffusion, hot electron temperature, and hot electron density. The key findings are as follows: (1) radial transport must take longer than 12 days; (2) water is input at a rate of 100–180 kg s−1; (3) hot electrons have energies between 100 and 250 eV; (4) neutrals dominate ions by a ratio of 40:1 and continue to dominate even when thermal electrons have temperatures as high as ≈5 eV; (5) hot electrons do not exceed 1% of the total electron population within the torus; (6) if hot electrons alone drive the observed longitudinal variation in thermal electron density, then they also drive a significant variation in ion composition.

WN4 effect on longitudinal distribution of different ion species in the topside ionosphere at low latitudes by means of DEMETER, DMSP-F13 and DMSP-F15 data

Abstract. Plasma probe data from DMSP-F13, DMSP-F15 and DEMETER satellites were used to examine longitudinal structures in the topside equatorial ionosphere during fall equinox conditions of 2004 year. Since the launch of DEMETER satellite on 29 June 2004, all these satellites operate close together in the topside ionosphere. Here, data taken from Special Sensor-Ion, Electron and Scintillations (SSIES) instruments on board DMSP-F13, F15 and Instrument Analyser de Plasma (IAP) on DEMETER, are used. Longitudinal variations in the major ions at two altitudes (~730 km for DEMETER and ~840 km for DMSP) are studied to further describe the recently observed "wavenumber-four" (WN4) structures in the equatorial topside ionosphere. Different ion species H+, He+ and O+ have a rather complex longitudinal behavior. It is shown that WN4 is almost a regular feature in O+ the density distribution over all local times covered by these satellites. In the evening local time sector, H+ ions follow the O+ behavior within WN4 structures up to the pre-midnight hours. Near sunrise H+ and later in the daytime, He+ longitudinal variations are out of phase with respect to O+ ions and effectively reduce the effect of WN4 on total ion density distribution at altitudes 730–840 km. It is shown that both a WN4 E×B drift driver and local F-region winds must be considered to explain the observed ion composition variations.

Geotail observations of plasma sheet ion composition over 16 years: On variations of average plasma ion mass and O+ triggering substorm model

We examined long‐term variations of ion composition in the plasma sheet, using energetic (9.4–212.1 keV/e) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. EPIC/STICS observations are available from 17 October 1992 for more than 16 years, covering the declining phase of solar cycle 22, all of solar cycle 23, and the early phase of solar cycle 24. This unprecedented long‐term data set revealed that (1) the He+/H+ and O+/H+ flux ratios in the plasma sheet were dependent on the F10.7 index; (2) the F10.7 index dependence is stronger for O+/H+ than He+/H+; (3) the O+/H+ flux ratio is also weakly correlated with the ΣKp index; and (4) the He2+/H+ flux ratio in the plasma sheet appeared to show no long‐term trend. From these results, we derived empirical equations related to plasma sheet ion composition and the F10.7 index and estimated that the average plasma ion mass changes from ∼1.1 amu during solar minimum to ∼2.8 amu during solar maximum. In such a case, the Alfvén velocity during solar maximum decreases to ∼60% of the solar minimum value. Thus, physical processes in the plasma sheet are considered to be much different between solar minimum and solar maximum. We also compared long‐term variation of the plasma sheet ion composition with that of the substorm occurrence rate, which is evaluated by the number of Pi2 pulsations. No correlation or negative correlation was found between them. This result contradicts the O+ triggering substorm model, in which heavy ions in the plasma sheet increase the growth rate of the linear ion tearing mode and play an important role in localization and initiation of substorms. In contrast, O+ ions in the plasma sheet may prevent occurrence of substorms.

Cassini UVIS observations of the Io plasma torus: III. Observations of temporal and azimuthal variability

In this third paper in a series presenting observations by the Cassini Ultraviolet Imaging Spectrometer (UVIS) of the Io plasma torus, we show remarkable, though subtle, spatio-temporal variations in torus properties. The Io torus is found to exhibit significant, near-sinusoidal variations in ion composition as a function of azimuthal position. The azimuthal variation in composition is such that the mixing ratio of S II is strongly correlated with the mixing ratio of S III and the equatorial electron density and strongly anti-correlated with the mixing ratios of both S IV and O II and the equatorial electron temperature. Surprisingly, the azimuthal variation in ion composition is observed to have a period of 10.07 h—1.5% longer than the System III rotation period of Jupiter, yet 1.3% shorter than the System IV period defined by [Brown, M.E., 1995. J. Geophys. Res. 100, 21683–21696]. Although the amplitude of the azimuthal variation of S III and O II remained in the range of 2–5%, the amplitude of the S II and S IV compositional variation ranged between 5 and 25% during the UVIS observations. Furthermore, the amplitude of the azimuthal variations of S II and S IV appears to be modulated by its location in System III longitude, such that when the region of maximum S II mixing ratio (minimum S IV mixing ratio) is aligned with a System III longitude of ∼ 200 ° ± 15 ° , the amplitude is a factor of ∼4 greater than when the variation is anti-aligned. This behavior can explain numerous, often apparently contradictory, observations of variations in the properties of the Io plasma torus with the System III and System IV coordinate systems.

Ion composition variations in the plasma sheet observed by Cluster/RAPID

Based on the energetic particle measurements obtained by Cluster/RAPID (Research with Adaptive Particle Imaging Detectors), ion composition variations in the plasma sheet have been investigated. By comparing observations during quiet and storm intervals, it is found that, in addition to the enhanced energy density for all ion species, the ratio of energetic O+ ions to protons shows an increase during geomagnetic active periods in the near‐Earth plasma sheet (−15 RE < X < −12 RE). However, the ratio shows a decrease in the middle plasma sheet (−19 RE < X < −15 RE). These observation results have been further confirmed by a statistical study of all the plasma sheet crossing events from 2001 to 2003. Observations also show that energetic particles embedded in the earthward high‐speed streams observed in the plasma sheet have an obvious low abundance of heavy ions compared with surrounding plasmas. It is implied that energetic O+ ions could be distributed in a limited region in the plasma sheet and much less ionosphere origin particles could reach the region beyond X = −15 RE. Bursty Bulk Flows (BBFs) could not supply more energetic O+ ions to the near‐Earth plasma sheet, whereas the ionospheric supplement, together with local acceleration processes, leads to an enhanced oxygen abundance during active times.

TEMPORAL VARIATIONS OF POLLUTANT LOADS DURING STORM EVENTS IN A SMALL RIVER BASIN

Not only to estimate the impact of storm water on receiving waters but also to deduce the origin of the pollutants, it is important to analyze the runoff characteristics of pollutants during storm events. We conducted seven surveys during storm events to clarify the runoff characteristics of various pollutants and relationships between pollutant loads and runoff patterns. In addition, origins of various ions were deduced by examining the temporal variations of ion composition. Typical first flush effects in VSS and T-BOD concentrations were observed, and it was estimated that river sediments deposited in fine days strongly affect the runoff of VSS during a storm event. NO3--N concentration decreased by the early runoff, but kept up higher level at the recession stage, while ion concentrations decreased during the rising stage and increased again at the recession stage, indicating that ions were diluted by the major runoff. Relationships between pollutant loads and runoff were examined by the empirical equation “L/A = a (Q/A)n”. Judging from the n values, ash, SS, VSS, NH4+-N and TP were easily flushed out during storm events, while TN, DN, NO3--N, K+ and DOC kept almost constant concentration during a storm event. Most ions seemed to be diluted by storm water. It was indicated that NO3-, SO42- and K+ were mainly originated from diffuse sources during storm events in the surveyed watershed, while Mg2+ and Na+ was from the same source as Cl-. Most of the nitrate and sulfate loads seemed to be drained out from the surface soil layer of river basins and carried by subsurface runoff.

The Generation of a Dense Hot Plasma by Intense Subpicosecond Laser Pulses

A simple model is developed for describing the interaction of intense femtosecond laser pulses with solid-state targets which is based on a set of equations of two-temperature hydrodynamics for electrons and ions of a plasma formed upon ionization of the target matter, equations describing the variation of ion composition of plasma upon ionization and the heat energy expenditure on thermal ionization, and equations defining the energy contribution by laser radiation to the target matter. A self-similar solution is suggested which well describes the heating of plasma electrons during the time of effect of a femtosecond laser pulse in a wide range of its parameters. Lagrangian computer codes developed for this purpose are used to derive, in a one-dimensional approximation, a numerical solution for the set of equations for the parameters corresponding to femtosecond experimental facilities under development in Germany and Russia. Profiles of hydrodynamic quantities (electron and ion temperature, plasma pressure and density, mean ion charge) obtained in the numerical solution at different moments of time may be used for preliminary assessment of the results of future experiments with a view to optimizing their parameters.

Ion composition variations in the inner magnetosphere: Individual and collective storm effects in 1991

Ion composition variations in the inner magnetosphere during storm times are studied by using data sets obtained from the magnetospheric ion composition spectrometer (MICS) on board the Combined Release and Radiation Effects Satellite (CURES). The observations were made during the second half of the CRRES mission, which was near the maximum of solar cycle 22. Four selected storms are subjects of detailed case studies; statistical results are based on a group of moderate (50 < |Dst| < 100 nT) and large storms (|Dst| > 100 nT) storms observed in 1991. The case studies show that energetic particle enhancements occur at very low equatorial altitudes (L = 3∼4) during large storms with significant delays relative to the storm sudden commencement times (of about 20 hours). The average time duration of the particle enhancements is about 47 hours. By studying the time variation of energy spectrograms of H+, it is found that low‐energy (E < 100 keV) and high‐energy (E > 100 keV) protons show different time profiles during the development and decay of the ring current. The low‐energy part shows a dramatic intensification and a rapid decay. However, its relative contribution to the ring current defined by the density ratio N(HL+)/N during the storm maximum is almost constant. On the other hand, high‐energy protons first exhibit a flux decrease followed by a delayed increase. The density ratio shows an anticorrelation with the storm intensity. It is confirmed that the ionospheric origin particles (e.g., O+) are important constituents of the storm time ring current. The fractional number density of O+ ions increases with the intensity of the storm. The statistical results demonstrate that the energy density of O+ is a steep function of Dst for moderate storms. However, it seems to increase very slowly with Dst, or even to be almost independent of Dst for large storms (|Dst| ≥ 120 nT). The ratios of solar wind origin He++ density to the total density show no obvious difference among large storms. The same appears for He+ ions.

Ion Composition Variations in Intense Magnetic Storms and their Relation to Storm Evolution

AbstractIon composition variations in the inner magnetosphere during storm times are investigated using data set obtained from CRRES/ MICS. Case study of the twin storms in July, 1991 and statistical study of 12 intense storms from February to October, 1991 both indicate that the storm time ring current ions can be divided into two groups: one consists of O+, low energy H+ and He+, which are originated from the ionosphere (IOP); the other is composed of high energy H+ and He++ , which are mainly originated from the solar wind (SOP). It is shown that in quiet times the major ions of the ring current are SOPs, whereas during the main phase of large storms the major component of ring current particles is the IOP. Ring current ions of intense storms can be injected into low L‐altitudes (2 − 4). It is confirmed that the contribution of IOPs to the ring current increases with increasing L value. IOP is the major constituent of the ring current, even up to 80% of the total number density, at the Dst minimum of large storms. There is clear evidence showing that it is the rapid enhancement and reduction of the O+ flux of the ring current that leads the Dstindex to rapidly decrease during the second stage of the main phase and to quickly recover in the early recovery phase. Further analyses indicate that in weak storms (Dst >‐50 nT) the contribution of O+ ions to the ring current is negligible.

Chemical composition of precipitation and wet deposition of major ions on the Korean peninsula

Daily wet precipitations were collected at nine stations in South Korea from May 1996 to April 1998 and analyzed for pH, electrical conductivity and major ions; SO 4 2−, NO 3 −, Cl −, NH 4 +, Ca 2+, Na +, Mg 2+ and K +. The volume-weighted mean concentrations of NO 3 − and non-seasalt SO 4 2− were 19.3 and 43.0 μeq l −1, respectively, which were comparable to Northeast America and Central Europe. However, the level of H + was found to be significantly lower as a result of neutralization by ammonia and calcium containing compounds. Although the pH of individual precipitations fluctuated excessively with a wide range from 3.4 to 8.0, the annual mean value ranged from 4.6 to 4.8 without area variation. With the exception of the seasalt ions, no distinct spacial variations in ion composition were observed. On the other hand, seasonal variations were evident. Annual wet deposition was estimated and compared to that in East Asian countries and other continents.

Longitude variations in ion composition in the morning and evening topside equatorial ionosphere near solar minimum

Ion composition data from the Defense Meteorological Satellite Program (DMSP) F10 have been averaged by geographic longitude and dip latitude for the months of June, September, and December 1993. The data were taken under near solar minimum conditions. Near 800 km at two fixed local times near 0920 hours and 2120 hours, and at all longitudes, significant variation in local time and season are found. Longitude variations are consistent with modulation of the F peak height by meridional and zonal neutral winds. The components of these winds parallel to the magnetic field lines act to raise and lower the height of the F peak and, additionally, at night, to modulate the plasma decay rate. Zonal winds were found to have significant effects in the longitude regions 150°E to 270°E and 300°E to 360°E, where the magnetic declination is significant. Under solstice conditions, the summer to winter meridional winds play a dominant role in regulating the F peak height, with the zonal winds enhancing or opposing the effects of the meridional winds at longitudes with significant magnetic declination. Zonal winds dominate the regulation of the F peak height near equinox, when the meridional winds are fairly symmetric about the dip equator. The longitude variations are most clearly seen in the O+ and H+ concentrations when O+ is the dominant ion and is in equilibrium with H+. These conditions were found during the daytime during all seasons. H+ is frequently the dominant ion near 800 km, and at night, the longitudinal variations clearly seen in the O+ concentrations were not as easily seen in the H+ concentrations due to the larger scale height of H+.